Patent Publication Number: US-2002000359-A1

Title: Circuit-substrate-related-operation performing system

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a system for performing an operation related to a circuit substrate such as a printed circuit board, for example, mounting circuit components such as electric-circuit or electronic-circuit components on the circuit substrate, or applying an adhesive to the circuit substrate.  
       [0003] 2. Related Art Statement  
       [0004] There is known a circuit-substrate-related-operation performing system which includes a conveyor for conveying a circuit substrate (“CS”) and positioning and supporting the CS, and an operation performing device for performing an operation related to the CS positioned and supported by the conveyor. For example, there is known a system of this sort which includes (a) a main conveyor which conveys a CS and positions and supports the CS, (b) an operation performing device which performs an operation for the CS positioned and supported by the conveyor, (c) a carry-in conveyor which conveys the CS toward the main conveyor and hands over it thereto, and (d) a carry-out conveyor which receives the CS from the main conveyor and conveys it away from therefrom.  
       [0005] As a system of this sort, there is known a circuit-component (“CC”) mounting system for mounting CCs on a CS. This system includes (a) two CS conveying lines which are arranged in parallel with each other and each of which includes a carry-in conveyor, a main conveyor, and a carry-out conveyor arranged in series with one another, and (b) a CC mounting device which mounts CCs on a CS positioned and supported by each of the two main conveyors. More specifically described, while the CC mounting device mounts CCs on a CS positioned and supported by one of the main conveyors, a CS which is positioned and supported by the other main conveyor and on which CCs have been mounted is carried out therefrom by the carry-out conveyor, and another CS is carried in onto the other main conveyor and is positioned and supported thereby.  
       [0006] In the above CC mounting system, the CC mounting device can start mounting the CCs on the CS positioned and supported by the other main conveyor, immediately after it finishes mounting the CCs on the CS positioned and supported by the one main conveyor. Thus, it needs substantially no time to change two CSs with each other, which leads to improving the efficiency of mounting of CCs.  
       [0007] However, the above CC mounting system has the two carry-in conveyors and the two carry-out conveyors. Meanwhile, an upstream-side device is provided on an upstream side of the CC mounting system in a direction of conveying of CSs, and a downstream-side device is provided on a downstream side of the CC mounting system. The upstream-side device hands over a CS to the CC mounting system, and the downstream-side device receives the CS from the CC mounting system. The upstream-side device may be a CS supplying device, another CC mounting system, or an applying system which applies an adhesive or a solder paste to CSs. The downstream-side device may be another CC mounting system, an adhesive curing furnace which cures or hardens the adhesive temporarily fixing the CCs to the CS, a solder reflowing furnace which reflows or melts the solder for electrically connecting the CCs to the CS. Generally, the upstream-side device has only a single CS-hand-over portion, and the downstream-side device has only a single CS-receive portion. Accordingly, a CS receiving and distributing device is needed which receives CSs from the CS-hand-over portion of the upstream-side device and distributes the CS to the two carry-in conveyors, and a CS collecting and handing-over device is needed which collects the CS from the two carry-out conveyors and hands over the CS to the CS-receive portion of the downstream-side device. This leads to complicating the construction of the CC mounting system, thereby increasing the production cost of the same. This problem will also occur to other systems which include operation performing devices other than the CC mounting device.  
       SUMMARY OF THE INVENTION  
       [0008] It is therefore an object of the present invention to provide a circuit-substrate-related-operation performing system which includes a plurality of main conveyors, performs a circuit-substrate-related operation with improved efficiency, and enjoys a simple construction.  
       [0009] The present invention provides a circuit-substrate-related-operation performing system which has one or more of the technical features which are described below in respective paragraphs given parenthesized sequential numbers (1) to (28). Any technical feature which includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to that technical feature. Thus, two or more of the following technical features may be combined, if appropriate. Each technical feature may be accompanied by a supplemental explanation, as needed.  
       [0010] (1) According to a first feature of the present invention, there is provided a system for performing an operation for a circuit substrate, comprising a plurality of main conveyors each of which conveys, positions, and supports a circuit substrate, the plurality of main conveyors being arranged in a direction perpendicular to a circuit-substrate conveying direction in which the each main conveyor conveys the circuit substrate; an operation performing device which performs at least one operation for the circuit substrate positioned and supported by the each main conveyor; at least one of (a) a carry-in conveyor which conveys the circuit substrate to the each main conveyor and loads the circuit substrate thereon, and (b) a carry-out conveyor which loads the circuit substrate off the each main conveyor and conveys the circuit substrate away therefrom; and a conveyor shifting device which selectively shifts the at least one of the carry-in conveyor and the carry-out conveyor to one of a plurality of shift positions at each of which the one conveyor is aligned with a corresponding one of the main conveyors. In the case where the present operation performing system includes the carry-in conveyor and the conveyor shifting device shifts the carry-in conveyor, the carry-in conveyor can receive a CS at a desired one of the plurality of shift positions thereof, and can hand over the CS to a desired one of the main conveyors at a corresponding one of the shift positions which may be the same as, or different from, the desired shift position. Since the carry-in conveyor is shifted by the conveyor shifting device, it can receive a CS at each of its shift positions and can hand over the CS to each of the main conveyors at a corresponding one of the shift positions. Meanwhile, in the case where the present operation performing system includes the carry-out conveyor and the conveyor shifting device shifts the carry-out conveyor, the carry-out conveyor can receive a CS from each of the main conveyors at a corresponding one of the plurality of shift positions thereof, and can carry out the CS at a desired one of the shift positions which may be the same as, or different from, the one shift position where the carry-out conveyor receives the CS from the each main conveyor. Thus, the present system does not need more than one carry-in conveyor or more than one carry-out conveyor in contrast to the conventional system. In addition, the present system does not need any device for distributing CSs to the plurality of main conveyors, or any device for collecting CSs from the plurality of main conveyors. Thus, the present system includes the plurality of main conveyors, needs substantially no time for changing CSs with each other, performs the operation with high efficiency, and enjoys a simple construction. In the case where the present system includes the carry-in conveyor and an upstream-side device for handing over CSs to the carry-in conveyor, the carry-in conveyor can receive the CSs at a desired one of the plurality of shift positions thereof. Therefore, even in the case where the upstream-side device is designed such that it can hand over CSs at a single predetermined position only, the upstream-side device can easily connected to the present system. This is also true with the case where the present system includes the carry-out conveyor and a downstream-side device for receiving CSs from the carry-out conveyor, and the case where the present system includes both the carry-in conveyor and the carry-out conveyor and both an upstream-side device for handing over CSs to the carry-in conveyor and a downstream-side device for receiving CSs from the carry-out conveyor. The main conveyors may not be so long because they are just required to have a length sufficient to position and support a CS, whereas the distance by which a CS is conveyed by the carry-in conveyor or the carry-out conveyor for being carried in onto, or carried out from, each main conveyor may be considerably long. Accordingly, the carry-in conveyor and/or the carry-out conveyor may be considerably long. However, since the present system employs the single carry-in conveyor and/or the single carry-out conveyor, it can be produced at reduced cost, as compared with the case where the same number of carry-in and/or carry-out conveyors as that of the main conveyors are employed, though the present system additionally includes the conveyor shifting device or devices for shifting the carry-in conveyor and/or the carry-out conveyor. In the case where each CS has its identification such as a bar code, the present system is equipped with just a single CS identifying device which identifies the sort of each CS by recognizing the identification thereof and which is provided on the single carry-in conveyor. In this case, the present system does not need more than one CS identifying device, which leads to reducing the cost of CS identification. If the carry-in conveyor is designed such that it can receive CSs at a single predetermined shift position only, the single CS identifying device may be provided at that shift position. The operation performing device may be one of various devices including a CC mounting device, a CS processing device, a circuit testing device, and a high-viscosity-fluid applying device such as a screen printing machine and an adhesive dispenser. In any case, the present system can enjoy the above-indicated advantages. The shorter the cycle time between the beginning and the end of one operation or a series of operations which is or are performed for each CS is, the greater the ratio of the time needed for changing CSs with each other to the cycle time is, that is, the greater the advantage that the plurality of main conveyors are employed for reducing the time needed for changing CSs with each other to substantially zero is. Thus, the present invention is very advantageous for the devices, such as the circuit testing device and the high-viscosity-fluid applying device, which have a considerably short operation-cycle time. In particular, the high-viscosity-fluid applying device can store a high-viscosity fluid in an amount that can be successively applied to a plurality of CSs, and can successively apply the fluid to CSs except each time period during which it is supplied with the fluid from a fluid supplying device. That is, the operation of the fluid applying device is not interrupted by the changing of CSs and accordingly can be done with high efficiency. Even in the case where the present system employs an operation performing device which has a long operation-cycle time and therefore has a small ratio of the CS-changing time to the operation-cycle time, the present system can enjoy a great advantage that the CS-changing time is reduced to substantially zero and accordingly its substantial availability factor is improved, if the operation performing device is an expensive device such as a CC mounting device. The present system may employ one, two, or more CC mounting devices. The or each CC mounting device may hold one or more component holders. The present system may employ one, two, or more operation performing devices other than the CC mounting device or devices. The present system may employ a plurality of operation performing devices of a same sort or of different sorts. The present operation performing system can enjoy the above-indicated advantages not only in the case where it employs both the carry-in and carry-out conveyors but also in the case where it employs either the carry-in or carry-out conveyor. For example, the present system may be a “line” system which includes a plurality of operation performing devices each of which performs a certain operation for a CS and which are arranged in series with each other. In this case, at the downstream-side end of the line system, a robot or an operator can take the CSs directly from the main conveyors to store them in a storing device such as a stocking device. Thus, the line system does not need any carry-out conveyor, and employs a carry-in conveyor only. However, since the single carry-in conveyor can selectively hand over a CS to each of the plurality of main conveyors, the line system can enjoy the above-indicated advantages of the present invention. Also, at the upstream-side end of the line system, a robot or an operator can place the CSs directly on the main conveyors, or a CS supplying device may be provided which has a plurality of CS-hand-over portions for handing over the CSs to the plurality of main conveyors, respectively. In this case, the line system does not need any carry-in conveyor, and employs a carry-out conveyor only. However, since the single carry-out conveyor can selectively receive a CS from each of the plurality of main conveyors, the line system can enjoys the above-indicated advantages of the present invention. The present system may include two, three, or more main conveyors. In the case where the present system employs three or more main conveyors, the carry-in and/ or carry-out conveyors have three or more shift positions. In the latter case, the conveyor shifting device may comprise, as a drive source thereof, a combination of a plurality of fluid-pressure-operated cylinder devices, or an electric motor such as a servomotor, which selectively shifts the carry-in or carry-out conveyor to one of the three or more shift positions thereof. The servomotor as the drive source of the conveyor shifting device can easily move and stop the carry-in or carry-out conveyor to and at a position or positions different from the three or more shift positions thereof.  
       [0011] (2) According to a second feature of the present invention which includes the first feature (1), the operation performing device comprises at least one circuit-component mounting device which mounts at least one circuit component on the circuit substrate positioned and supported by the each main conveyor. Immediately after the CC mounting device finishes mounting CCs on a CS positioned and supported by one of the plurality of main conveyors, the CC mounting device can start mounting CCs on a waiting CS positioned and supported by another or the other main conveyor. Thus, the CC mounting device can mount CCs with high efficiency. Since the single CC mounting device can mount CCs on a CS on each of the main conveyors, the present system does not need another CC mounting device. However, the present system may employ a plurality of CC mounting devices. In the latter case, while one CC mounting device takes CCs from a CC supplying device, the other CC mounting device can mount CCs on a CS. Thus, the CC mounting operation is not interrupted by the CC taking operation, which leads to improving the efficiency of mounting of CCs. The CC mounting device may be one of various devices. For example, the CC mounting device may be provided by a device including a plurality of component holders which is revolved around a common axis line and is sequentially positioned at a predetermined operative position and which is moved between a CC supplying device and the main conveyors, for receiving CCs from the supplying device and mounting the CCs on CSs on the main conveyors; or a device including a single component holder which is moved to desired positions in a component-holder moving plane facing a CC supplying device and CSs, for receiving CCs from the supplying device and mounting the CCs on the CSs.  
       [0012] (3) According to a third feature of the present invention which includes the first feature (1), the plurality of main conveyors comprises two main conveyors, wherein the system further comprises two circuit-component supplying devices which are provided outside the two main conveyors such that the two main conveyors are positioned between the two circuit-component supplying devices, and wherein the operation performing device comprises two circuit-component mounting devices each of which receives at least one circuit component from a corresponding one of the two circuit-component supplying devices, conveys the one circuit component to above each of the two main conveyors, and mounts the one circuit component on the circuit substrate positioned and supported by the each of the two main conveyors. In the present system, the two CC mounting devices cooperate with each other to mount CCs on a CS positioned and supported by each of the two main conveyors, for providing a circuit on the CS. It is particularly preferred that the present system be operated such that while one CC mounting device mounts CCs on a CS, the other CC mounting device receives CCs from a corresponding one of the two CC supplying devices and such that after the one CC mounting device finishes mounting the CCs on the CS, the other CC mounting device starts mounting the CCs on the CS in place of the one CC mounting device. If the present system employs a single CC mounting device only, no CC can be mounted on a CS after the single mounting device finishes mounting all CCs on the CS and before it starts mounting CCs on the CS after receiving the CCs from a CC supplying device. This is a waste of time. On the other hand, if the present system employs the two CC mounting devices which alternately mount CCs on a CS, it can mount the CCs on the CS without any waste of time. Thus, the present system can mount CCs on CSs with improved efficiency owing to not only the advantage that substantially no time is needed for changing two CSs with each other but also the advantage that the two CC mounting devices alternately mount CCs on each CS. However, it is not essentially required that the two CC mounting devices alternately mount CCs on each CS. For example, in the case where the present system employs a single CC mounting device only, the present system may employ two CC supplying devices each of which is of a considerably small size and supplies various sorts of CCs to the CC mounting device. In the last case, the present system can provide a circuit which needs various sorts of CCs, while preventing an excessive increase of the distance of movement of the CC mounting device.  
       [0013] (4) According to a fourth feature of the present invention which includes the third feature (3), the each circuit-component mounting device comprises a mounting head which includes a plurality of component holders which are revolvable around a common axis line, and a component-holder positioning device which sequentially positions the component holders at at least one operative position predetermined on a locus of the revolution of the component holders; and a mounting-head moving device which moves the mounting head to a desired position in a mounting-head moving plane which faces the one circuit-component supplying device and the two main conveyors. In the present system, each of the CC mounting devices receives, each time, a plurality of CCs from a corresponding one of the CC supplying devices, and mounts all the CCs on a CS. In contrast, if each CC mounting device includes a single component holder only, the CC mounting device is moved between the corresponding CC supplying device and the CS each time the single component holder receives and mounts a single CC. Thus, the present system can mount CCs on a CS with a reduced number of movements of each CC mounting device between the corresponding CC supplying device and the CS, which leads to improving the efficiency of mounting of CCs. When the plurality of component holders are sequentially positioned at the operative position predetermined on the locus of revolution thereof, each for receiving a CC, each of the component holders is positioned at the operative position by a small angle of revolution thereof. In addition, the positioning of each mounting head relative to the corresponding CC supplying device can easily be done by aligning the operative position of the mounting head with a portion of the CC supplying device which supplies the next CC to the mounting head. Thus, if CCs are provided at appropriate positions on each CC supplying device, the amount of relative movement between the CC supplying device and the corresponding mounting head can be very small, and accordingly the time needed for revolving each component holder and moving each mounting head can be significantly shorter than the time needed for moving each component holder between the corresponding CC supplying device and the CS. Thus, the present system can receive CCs with high efficiency. This is also true when CCs are mounted on a CS, and accordingly the present system can mount CCs with high efficiency. The component-holder positioning device also functions as a component-holder revolving device which revolves the plurality of component holders for sequentially positioning them at the operative position. Each of the CC mounting devices may be one which includes (a) an X-Y robot and (b) an index-type CC mounting head which is conventionally employed in an index-type CC mounting device and which is moved by the X-Y robot. Thus, each CC mounting device enjoys the same CC-mounting efficiency as that of the index-type CC mounting device. In addition, in the case where two CC mounting devices alternately receive CCs, and alternately mount the CCs on a CS, the CC-mounting-operation cycle time of the present system at which each CC is mounted on a CS can be shortened to the same degree as that to which the index-type CC mounting device shortens its CC-mounting-operation cycle time. However, since the index-type CC mounting head transfers, by the rotation thereof, a CC from a CC supplying device to above a CS, it is difficult to decrease the diameter of locus of revolution of the component holders held by the index-type mounting head and accordingly it is difficult to increase the speed of rotation of the index-type mounting head. Contrary to that, the present system need not revolve the component holders along so great a circle and accordingly can revolve them at high speed. In addition, since each mounting head can be positioned, by the movement thereof, relative to the corresponding CC supplying device or the CS, the CC supplying device may not be a CC supplying table including a number of component feeders and a movable table which is movable while supporting the feeders. In addition, the present system does not need any CS supporting device which is movable, while supporting a CS, for moving each of CC-mount places on the CS to a component mounting position of each CC mounting device. A large space would be needed to allow the CC supplying table and the CC supporting device to move relative to each CC mounting device. In particular, in the case where large-size CSs are employed, or in the case where various sorts of CCs are mounted on a CS, a large-size CC supplying table and a large-size CS supporting device would be needed, but a larger space would be needed to allow the respective movements of those elements. In contrast, the present system can be provided in a small space. Moreover, since the index-type CC mounting device cannot quickly accelerate or decelerate a large-size CC supplying table and a large-size CS supporting device, it cannot reduce the CC-mounting-operation cycle time. In contrast, the present system is free from this problem. Each CC mounting device is operated such that the plurality of component holders are sequentially positioned at the operative position by the revolution thereof and the mounting head is moved to desired positions in the mounting-head moving plane by the mounting-head moving device. This CC mounting device enjoys a high CC-mounting efficiency, but is somewhat expensive. Thus, if the CS-changing time of the present system is reduced to substantially zero, so that the CC mounting devices can be operated without needing any pause or break, the present system can be highly cost-effective and can particularly effectively enjoy the above-indicated advantages of the operation performing system according to the first feature (1). The mounting-head moving plane may be a horizontal plane or a plane inclined with respect to a horizontal plane, and may be defined in one of various manners, e.g., may be defined by an X-Y coordinate system, a polar coordinate system, or the like. In the case where the CS and the CC supplying devices are provided while taking respective attitudes inclined with respect to a horizontal plane, each of the mounting heads is moved in the mounting-head moving plane which is inclined with respect to the horizontal plane, for taking CCs from the inclined CC supplying devices and mounting the CCs on the inclined CS. In the case where the moving plane is defined by the X-Y coordinate system, the mounting-head moving device may be provided by, e.g., an X-Y robot. An operative position where each component holder receives a CC may be the same as, or be different from, an operative position where the component holder mounts the CC on the CS. Each component holder may be provided by one of various holders such as a component sucker which sucks and holds a CC by applying a negative pressure thereto, or a component chuck including a plurality of grasping members and a grasping-member opening and closing device for symmetrically opening and closing the grasping members with each other.  
       [0014] (5) According to a fifth feature of the present invention which includes any one of the first to fourth features (1) to (4), the operation performing system comprises both (a) the carry-in conveyor provided on an upstream side of the main conveyors in the circuit-substrate conveying direction and (b) the carry-out conveyor provided on a downstream side of the main conveyors in the circuit-substrate conveying direction, wherein the system further comprises an upstream-side device which is provided in alignment with a reference position as one of the plurality of shift positions of the carry-in conveyor and which hands over the circuit substrate to the carry-in conveyor, and a downstream-side device which is provided in alignment with a reference position as one of the plurality of shift positions of the carry-out conveyor and which receives the circuit substrate from the carry-out conveyor. The upstream-side or downstream-side device may be one which just hands over a CS to the carry-in conveyor or one which just receives a CS from the carry-out conveyor, or one which performs some operation for a CS, e.g., applies an adhesive to a CS or hardens an adhesive on a CS. The carry-in conveyor can receive a CS at any one of the plurality of shift positions thereof, and the carry-out conveyor can hand over a CS at any one of the plurality of shift positions thereof. Thus, even in the case where the upstream-side and downstream-side devices have only a single CS-hand-over position and only a single CS-receive position in the directions of shifting of the carry-in and carry-out conveyors, respectively, the carry-in and carry-out conveyors can receive, without any problems, CSs from the upstream-side device and hand over CSs to the downstream-side device, respectively, if the upstream-side and downstream-side devices are connected to the carry-in and carry-out conveyors and the main conveyors, such that the CS-hand-over position of the upstream-side device is aligned with a reference position as one of the shift positions of the carry-in conveyor and the CS-receive position of the downstream-side device is aligned with a reference position as one of the shift positions of the carry-out conveyor.  
       [0015] (6) According to a sixth feature of the present invention which includes any one of the first to fifth features (1) to (5), the at least one of the carry-in conveyor and the carry-out conveyor comprises a pair of side frames including at least one movable side frame which is movable toward, and away from, the other side frame, wherein the system further comprises a width changing device which changes a circuit- substrate conveying width defined by the pair of side frames of the at least one conveyor, by moving the movable side frame thereof relative to the other side frame thereof, and wherein the width changing device comprises a drive shaft which is provided corresponding to the at least one conveyor and which extends over the plurality of shift positions thereof; a driven rotatable member which is held by the at least one conveyor such that the driven rotatable member is rotatable about an axis line thereof, and is not movable in an axial direction thereof, relative to the at least one conveyor and which is engaged with the drive shaft such that the driven rotatable member is not rotatable about the axis line thereof, and is movable in the axial direction thereof, relative to the drive shaft; and a motion converting device which converts the rotation of the driven rotatable member into the movement of the movable side frame of the at least one conveyor. In the present system, even if a shiftable conveyor as one of the carry-in and carry-out conveyors is shifted, the drive shaft cannot be moved in the axial direction thereof. In addition, the driven rotatable member provided for the shiftable conveyor can be rotated irrespective of the current shift position of the shiftable conveyor. Thus, a handle which is manually rotatable by an operator for applying its rotary drive force to the drive shaft directly or indirectly via a rotation transmitting device, may be provided at a fixed position, which leads to facilitating the CS-conveying-width-changing operation. In addition, in the case where the drive shaft is driven by a drive source such as an electric motor, the drive source may be provided at a fixed position where the rotation of the drive source may be transmitted to the drive shaft via a simple rotation transmitting device, which leads to reducing the production cost of the present system. In the case where the present system comprises both the carry-in and carry-out conveyors and the two side frames of each of the carry-in and carry-out conveyors comprise at least one movable frame, the respective CS conveying widths of the carry-in and carry-out conveyors can simultaneously be changed by transmitting the rotary drive force of the handle or the drive source to respective drive shafts provided for the carry-in conveyor and the carry-out conveyor, via a common rotation transmitting device or respective exclusive rotation transmitting devices.  
       [0016] (7) According to a seventh feature of the present invention which includes any one of the first to fourth and sixth features (1) to (4) and (6), the operation performing system comprises both (a) the carry-in conveyor provided on an upstream side of the main conveyors in the circuit-substrate conveying direction and (b) the carry-out conveyor provided on a downstream side of the main conveyors in the circuit-substrate conveying direction. If the respective CS-conveying directions of the carry-in and carry-out conveyors are reversed in addition to those of the main conveyors, then they function as the carry-out and carry-in conveyors, respectively.  
       [0017] (8) According to an eighth feature of the present invention, there is provided a system comprising at least two subsystems, each according to the seventh feature (7), which are arranged in series with each other, wherein the at least two subsystems comprise a first subsystem comprising the main conveyors as first main conveyors, the operation performing device as a first operation performing device, the carry-in conveyor as a first carry-in conveyor, the carry-out conveyor as a first carry-out conveyor, and the conveyor shifting device as a first conveyor shifting device, and a second subsystem comprising a plurality of second main conveyors each of which conveys, positions, and supports a circuit substrate, the plurality of second main conveyors being arranged in the direction perpendicular to the circuit-substrate conveying direction; a second operation performing device which performs at least one operation for the circuit substrate positioned and supported by the each second main conveyor; a second carry-in conveyor which is provided on an upstream side of the second main conveyors in the circuit-substrate conveying direction and which conveys the circuit substrate to the each second main conveyor and loads the circuit substrate thereon; a second carry-out conveyor which is provided on a downstream side of the second main conveyors in the circuit-substrate conveying direction and which loads the circuit substrate off the each second main conveyor and conveys the circuit substrate away therefrom; and a second conveyor shifting device which selectively shifts each of the carry-in conveyor and the carry-out conveyor to one of a plurality of shift positions at each of which the each conveyor is aligned with a corresponding one of the second main conveyors. In the present system, the carry-out conveyor of the upstream-side subsystem hands over CSs to the carry-in conveyor of the downstream-side subsystem. Each of the carry-out conveyor and the carry-in conveyor can be selectively shifted to one of the plurality of shift positions thereof, so that the carry-out conveyor being positioned at a desired one of its shift positions can hand over a CS to the carry-in conveyor being positioned at a desired one of its shift positions. Thus, it is not required that the carry-out conveyor be positioned at a predetermined one of its shift positions for handing over a CS or that the carry-in conveyor be positioned at a predetermined one of its shift positions for receiving the CS. That is, the carry-out conveyor can hand over a CS at one of its shift positions, and/or the carry-in conveyor can receive the CS at one of its shift positions, which position or positions can be selected depending upon the sorts of the respective operations performed by the first and second operation performing devices and/or the degree of progress of those operations. Thus, the present system enjoys improved degree of freedom.  
       [0018] (9) According to a ninth feature of the present invention which includes any one of the first to fourth and sixth features (1) to (4) and (6), the operation performing system comprises (a) the carry-in conveyor and (b) the carry-out conveyor which comprise a carry-in and carry-out conveyor which is provided on an upstream side of the main conveyors in the circuit-substrate conveying direction. The carry-in and carry-out conveyor can convey CSs in both a forward direction and a backward direction. When it conveys CSs in the forward direction, it functions as a carry-in conveyor; and when it conveys CSs in the backward direction, it functions as a carry-out conveyor. Each of the main conveyors convey CSs in both a forward direction and a backward direction. The present system is particularly advantageous in a special case where a CS must be carried out to the same side as that from which the CS is carried in.  
       [0019] (10) According to a tenth feature of the present invention which includes any one of the first to eighth features (1) to (8), the operation performing system comprises both (a) the carry-in conveyor provided on an upstream side of the main conveyors in the circuit-substrate conveying direction and (b) the carry-out conveyor provided on a downstream side of the main conveyors in the circuit-substrate conveying direction, wherein the conveyor shifting device comprises a carry-in-conveyor shifting device which shifts the carry-in conveyor, independent of the carry-out conveyor, and a carry-out-conveyor shifting device which shifts the carry-out conveyor, independent of the carry-in conveyor. Alternatively, it is possible to employ the conveyor shifting device which simultaneously shifts both the carry-in and carry-out conveyors. However, if the carry-in and carry-out conveyors can be shifted independent of each other, the present system can enjoy improved degree of freedom.  
       [0020] (11) According to an eleventh feature of the present invention which includes any one of the first to tenth features (1) to (10), the conveyor shifting device comprises a conveyor support member which supports the at least one of the carry-in conveyor and the carry-out conveyor, and a fluid-pressure-operated cylinder device which shifts the conveyor support member. Since the fluid-pressure-operated cylinder device is employed, the conveyor shifting device which can quickly shift the carry-in and/or carry-out conveyors can be produced at low cost.  
       [0021] (12) According to a twelfth feature of the present invention which includes the eleventh feature (11), the fluid-pressure-operated cylinder device comprises a rodless cylinder device which extends over the shift positions of the at least one of the carry-in conveyor and the carry-out conveyor. The conveyor shifting device which employs the rodless cylinder device enjoys a simpler construction than a conveyor shifting device which employs a fluid-pressure-operated cylinder having a piston rod.  
       [0022] (13) According to a thirteenth feature of the present invention which includes any one of the first to tenth features (1) to (10), the conveyor shifting device comprises a conveyor support member which supports the at least one of the carry-in conveyor and the carry-out conveyor, and a drive device including an electric motor which shifts the conveyor support member. The electric motor may be a rotary motor, or a linear motor. The rotary motor may be a servomotor or a stepper motor which can be accurately controlled with respect to its rotation angle or position. The rotary motor linear moves the conveyor support member via, e.g., a motion converting device including a threaded shaft and a nut.  
       [0023] (14) According to a fourteenth feature of the present invention which includes any one of the first to thirteenth features (1) to (13), the conveyor shifting device comprises a wide-range conveyor shifting device which moves the at least one of the carry-in conveyor and the carry-out conveyor within a range wider than a range whose opposite ends correspond to two end shift positions of the at least one conveyor, respectively, which correspond to two end main conveyors, respectively. In the case where a shiftable conveyor as at least one of the carry-in and carry-out conveyors is just required to be aligned with each of the plurality of main conveyors, it is only required that the shiftable conveyor be moved within the first range whose opposite ends correspond to the two end shift positions out of all the shift positions of the shiftable conveyor, respectively, which correspond to the two end main conveyors out of all the main conveyors, respectively. However, in the case where the shiftable conveyor is movable within a second range wider than the first range, a device which is arranged in series with the present system can enjoy improved degree of freedom with respect to the position of provision of its CS-hand-over position or CS-receive position, and a “line” system including the present system and the above device can enjoy improved degree of freedom of its construction. For example, the present system can employ a plurality of devices such that those devices are arranged in parallel with each other on at least one of the upstream and downstream sides of the carry-in and carry-out conveyors and the main conveyors, and are connected to those conveyors.  
       [0024] (15) According to a fifteenth feature of the present invention which includes any one of the first to fourteenth features (1) to (14), each of the main conveyors comprises a circuit-substrate positioning and supporting device which positions and supports the circuit substrate at a position away from a circuit-substrate conveying plane in which the each main conveyor conveys the circuit substrate. The circuit-substrate positioning and supporting device can surely position and support the CS.  
       [0025] (16) According to a sixteenth feature of the present invention which includes the fifteenth feature (15), each of the main conveyors comprises at least one conveyor belt which supports and conveys the circuit substrate, and the main conveyors comprise a common belt-driving device which simultaneously moves the conveyor belts of the main conveyors. Since the circuit-substrate positioning and supporting device positions and supports the CS at a position away from the CS conveying plane, the CS for which the operation is being performed is not moved even if the respective conveyor belts of the main conveyors are simultaneously moved. In addition, since the common belt-driving device is employed, the present system can be produced at low cost.  
       [0026] (17) According to a seventeenth feature of the present invention which includes any one of the fifth, seventh, eighth, and tenth to sixteenth features (5), (7), (8), and (10) to (16), each of the main conveyors, the carry-in conveyor, and the carry-out conveyors comprises a pair of side frames including at least one movable side frame which is movable toward, and away from, the other side frame, and wherein the system further comprises a width changing device which simultaneously changes a circuit-substrate conveying width defined by the pair of side frames of the each of the main conveyors, the carry-in conveyor, and the carry-out conveyor, by moving the movable side frame of the each conveyor relative to the other side frame thereof.  
       [0027] (18) According to an eighteenth feature of the present invention which includes the seventeenth feature (17), the width changing device comprises a carry-in-conveyor-side drive shaft which is provided corresponding to the carry-in conveyor and which extends over at least the shift positions thereof; a carry-out-conveyor-side drive shaft which is provided corresponding to the carry-out conveyor and which extends over at least the shift positions thereof; a carry-in-conveyor-side driven rotatable member which is held by the carry-in conveyor such that the carry-in-conveyor-side driven rotatable member is rotatable about an axis line thereof, and is not movable in an axial direction thereof, relative to the carry-in conveyor and which is engaged with the carry-in-conveyor-side drive shaft such that the carry-in-conveyor-side driven rotatable member is not rotatable about the axis line thereof, and is movable in the axial direction thereof, relative to the carry-in-conveyor-side drive shaft; a carry-out-conveyor-side driven rotatable member which is held by the carry-out conveyor such that the carry-out-conveyor-side driven rotatable member is rotatable about an axis line thereof, and is not movable in an axial direction thereof, relative to the carry-out conveyor and which is engaged with the carry-out-conveyor-side drive shaft such that the carry-out-conveyor-side driven rotatable member is not rotatable about the axis line thereof, and is movable in the axial direction thereof, relative to the carry-out-conveyor-side drive shaft; a carry-in-conveyor-side motion converting device which converts the rotation of the carry-in-conveyor-side driven rotatable member into the movement of the movable side frame of the carry-in conveyor; and a carry-out-conveyor-side motion converting device which converts the rotation of the carry-out-conveyor-side driven rotatable member into the movement of the movable side frame of the carry-out conveyor. Even if the carry-in or carry-out conveyor is shifted, the driven rotatable member of the carry-in or carry-out conveyor remains engaged with the corresponding drive shaft. Thus, the CS conveying widths of the carry-in and carry-out conveyors can be changed by the rotation of the driven rotatable members thereof, irrespective of which shift positions are currently taken by the conveyors, respectively, or irrespective of whether the respective current shift positions of the conveyors are aligned with each other or not. That is, the carry-in and carry-out conveyors can be shifted independent of each other, although their CS conveying widths are changed simultaneously with each other. Since the carry-in and carry-out conveyors are not required to be moved to any positions for changing their CS conveying widths, the CS-conveying-width changing operation can be more easily done in a shorter time. Each of the two motion converting devices may be provided by (a) a threaded shaft which is supported by a member supporting the corresponding movable side frame such that the movable side frame is movable and which is rotatable about an axis line thereof parallel to a direction in which the movable side frame is moved relative to the other side frame, and is not movable in the axial direction thereof, and (b) a nut which is attached to the movable side frame such that the nut is not rotatable about an axis line thereof, and is not movable in the axial direction thereof, relative to the movable side frame, and which is threadedly engaged with the threaded shaft. In the case where the two side frames of each of the carry-in and carry-out conveyors are movable relative to each other, the threaded shaft of each of the two motion converting devices may be one which includes a first and a second threaded portion which are threaded in different or opposite directions, respectively. In the latter case, if the first threaded portion is threadedly engaged with a first nut fixed to one of the movable side frames, and the second threaded portion is threadedly engaged with a second nut fixed to the other movable side frame, the pair of movable side frames are symmetrically moved toward, and away from, each other, by the rotation of the threaded shaft, for changing the CS conveying width of a corresponding one of the carry-in and carry-out conveyors.  
       [0028] (19) According to a nineteenth feature of the present invention which includes the eighteenth feature (18), the width changing device further comprises a width-changing-rotation producing device; and a rotation transmitting device which transmits the rotation of the width-changing-rotation producing device to the carry-in-conveyor-side drive shaft and the carry-out-conveyor-side drive shaft. In the present system, the changing of the CS conveying widths of the carry-in and carry-out conveyors is done using the width changing rotation produced by the width-changing-rotation producing device. If the present system further comprises a control device for automatically controlling the producing device, the present system can automatically change the CS conveying widths of the conveyors. It is possible to employ two exclusive width-changing-rotation producing devices for driving the two drive shafts, respectively, and a control device for controlling the two producing devices such that the two driven shafts are rotated in synchronism with each other. In the latter case, the CS conveying widths of the carry-in and carry-out conveyors are simultaneously changed. However, since the present system employs the single width-changing-rotation producing device and the rotation transmitting device transmits the rotation of the producing device to both the two drive shafts, the present system can be produced at low cost. The width-changing-rotation producing device may be replaced by a manually operable member such as a handle. In the last case, the drive force produced by the manually operable member may be transmitted by a drive-force transmitting device to both the two drive shafts. In the present system, the single width-changing-rotation producing device is commonly used by the carry-in and carry-out conveyors, and the CS conveying widths of the two conveyors are simultaneously changed.  
       [0029] (20) According to a twentieth feature of the present invention which includes any one of the seventeenth to nineteenth features (17) to (19), the width changing device further comprises a main-conveyor-side driven rotatable member which is provided for at least one of the main conveyors such that the main-conveyor-side driven rotatable member is rotatable about an axis line thereof, and is not movable in an axial direction thereof, relative to the at least one main conveyor; and a motion converting device which converts the rotation of the main-conveyor-side driven rotatable member into the movement of the movable side frame of the at least one main conveyor. It is possible to employ a driven rotatable member and a motion converting device for each of the main conveyors, and operate the respective motion converting devices in synchronism with each other for simultaneously moving the respective movable side frames of the main conveyors. Alternatively, it is possible to employ no driven rotatable member or no motion converting device for at least one of the main conveyors, and employ a connection member for connecting the movable side frame of the one main conveyor to that of another or the other main conveyor which has its driven rotatable member and motion converting device. The respective motion converting devices provided for the plurality of main conveyors may be synchronized with each other by controlling respective width-changing-rotation producing devices exclusively provided for the main conveyors, respectively, or by transmitting the motion of one of the motion converting devices to the other motion converting device or devices.  
       [0030] (21) According to a twenty-first feature of the present invention which includes the twentieth feature (20), the width changing device further comprises a connecting member which connects the respective movable side frames of the main conveyors to each other so that the respective movable side frames of the main conveyors are movable as a unit.  
       [0031] (22) According to a twenty-second feature of the present invention which includes the twentieth or twenty-first feature (20) or (21), the rotation transmitting device transmits the rotation of the width-changing-rotation producing device to the main-conveyor-side driven rotatable member provided for the at least one main conveyor, in addition to the carry-in-conveyor-side drive shaft and the carry-out-conveyor-side drive shaft. It is possible to employ an exclusive width-changing-rotation producing device for rotating the driven rotatable member provided for at least one of the main conveyors, and employ a control device for automatically controlling, in addition to the common width-changing-rotation producing device for the carry-in and carry-out conveyors, the exclusive width-changing-rotation producing device for the one main conveyor, such that the CS conveying widths of the carry-in and carry-out conveyors and the main conveyor are simultaneously changed. However, since the present system uses the single width-changing-rotation producing device commonly for the carry-in and carry-out conveyors and the main conveyor, it can be produced at reduced cost. The present system may employ a single width-changing-rotation producing device commonly for all the main conveyors, or a plurality of width-changing-rotation producing devices for the plurality of main conveyors, respectively. In the case where the width-changing-rotation producing device provided for the carry-in and carry-out conveyors is replaced by a manually operable member such as a handle, the rotation transmitting device transmits the rotation produced by the manually operable member, to the driven rotatable member provided for at least one main conveyor, in addition to the two drive shafts provided for the carry-in and carry-out conveyors.  
       [0032] (23) According to a twenty-third feature of the present invention which includes any one of the fifth, seventh, eighth, and tenth to nineteenth features (5), (7), (8), and (10) to (19), each of the main conveyors, the carry-in conveyor, and the carry-out conveyors comprises a pair of side frames including at least one movable side frame which is movable toward, and away from, the other side frame, and wherein the system further comprises a width changing device which simultaneously changes a circuit-substrate conveying width defined by the pair of side frames of each of the carry-in conveyor and the carry-out conveyors, by moving the movable side frame of the each conveyor relative to the other side frame thereof; and a frame connecting device which connects, when the width changing device changes the respective circuit-substrate conveying widths of the carry-in and carry-out conveyors, the respective movable side frames of the main conveyors to the respective movable side frames of the carry-in and carry-out conveyors so that the respective movable side frames of the main conveyors and the carry-in and carry-out conveyors are movable as a unit. The frame connecting device may include a connection member which selectively takes one of an operative position where the connection member connects the respective movable side frames of the main conveyors to the respective movable side frames of the carry-in and carry-out conveyors, and an inoperative position where the connection member does not. The connection member may be one which is manually operable by an operator for being positioned at operator&#39;s selected one of the operative and inoperative positions, or one which is driven by a connection-member driving device for being automatically positioned at one of the two positions.  
       [0033] (24) According to a twenty-fourth feature of the present invention which includes any one of the first to twenty-third features (1) to (23), each of the main conveyors and the at least one of the carry-in and carry-out conveyors comprises at least one conveyor belt which supports and conveys the circuit substrate, and where the main conveyors comprise a first belt-driving device which simultaneously drives the conveyor belts of the main conveyors, independent of the conveyor belt of the at least one of the carry-in and carry-out conveyors, and the at least one of the carry-in and carry-out conveyors comprises a second belt-driving device which drives the conveyor belt of the at least one of the carry-in and carry-out conveyors, independent of the conveyor belts of the main conveyors. Since the present system employs the exclusive belt-driving device for the main conveyors, and the exclusive belt-driving device for the at least one of the carry-in and carry-out conveyors, the conveyor belts of the main conveyors can be driven independent of the conveyor belts or belt of the carry-in and/or carry-out conveyors. Thus, the present system enjoys improved degree of freedom.  
       [0034] (25) According to a twenty-fifth feature of the present invention which includes any one of the fourth to twenty-fourth features (4) to (24), the component-holder positioning device comprises a plurality of rotary members which are rotatable about the common axis line of the component holders, independent of each other; and a rotary-motion applying device which applies a rotary motion to each of the rotary members such that the each rotary member is rotated while having a predetermined time difference from the preceding rotary member and that while the each rotary member is rotated by 360 degrees about the common axis line, the each rotary member is stopped at least one time, the rotary members having, at a common distance from the common axis line, respective holding portions each of which holds a corresponding one of the component holders such that the one component holder is movable in an axial direction thereof. Each of the rotary members may be equipped with a movable member which holds a corresponding one of the component holders and which is supported by the each rotary member such that the movable member is movable in a direction parallel to the axis line of the one component holder. In this case, each component holder is moved in the direction parallel to the axis line thereof, by the movement of the corresponding movable member. The holding portions may comprise respective holding holes in which the component holders are fitted such that the holders are rotatable about their axis lines. In this case, the current rotation position of the CC held by each holder can be changed, or the rotation-position error of the CC can be corrected. A holder revolving device including a plurality of rotary members which are rotatable about a common axis line, independent of each other, and which hold a plurality of component holders, respectively, is disclosed in U.S. patent application Ser. No. 08/769,700 assigned to the Assignee of the present U.S. patent application. The rotary-motion applying device may be one which includes a plurality of cam followers which are provided on the plurality of rotary members, respectively, and a rotary-motion applying cam device which sequentially engages the cam followers and moves them for rotating the corresponding rotary members about the common axis line. It is preferred that the rotary-motion applying cam device include a plurality of concave globoidal cams which are disposed at respective positions axis-symmetric with each other with respect to the common axis line such that lines of intersection of respective outer circumferential surfaces of the concave globoidal cams with a plane including respective axis lines of the concave globoidal cams and perpendicular to the common axis line cooperate to define a substantially continuous circle which has a center at the common axis line.  
       [0035] (26) According to a twenty-sixth feature of the present invention which includes any one of the fourth to twenty-fourth features (4) to (24), the component-holder positioning device comprises a rotatable body which is rotatable about the common axis line of the component holders and which has, at a common distance from the common axis line, a plurality of holding portions each of which holds a corresponding one of the component holders such that the one component holder is movable in an axial direction thereof. In this apparatus, too, the holding portions may comprise respective holding holes in which the component holders are fitted such that each of the component holders is rotatable about its axis line for changing the current rotation position of the CC held thereby, or correcting the rotation-position error of the CC. The rotatable body may be one which is rotatable by any desired angle in a positive direction or a reverse direction, or an intermittently rotatable body which is intermittently rotated by an intermittent-rotation angle which is equal to a regularly spacing angle at which the component holders are equiangularly spaced from each other about the common axis line. A drive source which rotates the rotatable body may be an exclusive one, or a common one which is shared by, e.g. an elevating and lowering device for elevating and lowering one or each component holder. In the case where the rotatable body is rotated by an exclusive drive source, the rotatable body can be rotated by any angle in either direction, which leads to improving the efficiency of transferring of CCs. In the case where the rotatable body is rotated by the common drive source, it is preferred to employ a motion converting device including a cam, a cam follower, etc., for transmitting the rotation of the drive source to the rotatable body. In this case, the total number of drive sources is decreased and accordingly the production cost of the present apparatus is reduced.  
       [0036] (27) According to a twenty-seventh feature of the present invention which includes the twenty-fifth or twenty-sixth feature (25) or (26), the common axis line of revolution of the component holders is perpendicular to the mounting-head moving plane, and wherein an axis line of each of the component holders extends parallel to the common axis line. The mounting-head moving plane in which the mounting head is moved may be either a horizontal plane, or a plane which is inclined with respect to a horizontal plane. In the case where the moving plane is inclined with respect to a horizontal plane, the respective axis lines of the component holders are inclined with respect to a vertical direction. Meanwhile, there is known a CC mounting system in which a CC supplying device which supplies CC, and/or a CS on which CCs are mounted are inclined with respect to a horizontal plane. In the latter case, the component holders inclined with respect to the vertical direction can receive the CCs from the CC supplying device and/or mount the CCs on the CS, while taking their attitudes perpendicular to the inclined CC supplying device and/or the inclined CS.  
       [0037] (28) According to a twenty-eighth feature of the present invention which includes the twenty-fifth or twenty-sixth feature (25) or (26), respective axis lines of the component holders are defined by a plurality of generators of a circular cone whose center line is defined by the common axis line of revolution of the component holders, and wherein the common axis line is inclined with respect to a perpendicular of the mounting-head moving plane, by an angle at which one of the generators is perpendicular to the mounting-head moving plane. In the case where the mounting-head moving plane is a horizontal plane, each of the component holders can take a vertical attitude at one of stop positions, and can be moved downward and upward at the one stop position. In the present system, the height position of each of the component holders in a direction parallel to the axis line of the each component holder can be changed as the rotatable body is rotated. Accordingly, an image pick-up device may be disposed in a space which is created below the component holders. The present system in which the axis line of the rotatable body is inclined can easily change the respective height positions of the component holders with a smaller number of parts than the case where each of the component holders is moved downward and upward by using a cam member which is provided above the locus of revolution of the holders and which has a lower cam surface including a height-changing portion, and cam followers which follows the cam surface of the cam member. Thus, the rotatable body enjoys a small mass, and can be rotated at high speed. In the case where the rotatable body is moved by a rotatable-body moving device, it can be moved at high speed. Thus, the efficiency of transferring of CCs can be improved. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0038] The above and optional objects, features, and advantages of the present invention will be better understood by reading the following detailed description of the preferred embodiments of the invention when considered in conjunction with the accompanying drawings, in which:  
     [0039]FIG. 1 is a plan view of a circuit-component (“CC”) mounting system to which the present invention is applied;  
     [0040]FIG. 2 is a front elevation view of a circuit-substrate (“CS”) conveyor device which provides part of the CC mounting system of FIG. 1;  
     [0041]FIG. 3 is a side elevation view of the CS conveyor device and two CC mounting devices each of which provides part of the CC mounting system of FIG. 1;  
     [0042]FIG. 4 is a plan view of the CS conveyor device;  
     [0043]FIG. 5 is a side elevation view of two main conveyors which provide part of the CS conveyor device;  
     [0044]FIG. 6 is a view showing chains and sprockets for adjusting respective CS conveying widths of a carry-in conveyor, two main conveyors, and a carry-out conveyor of the CS conveyor device;  
     [0045]FIG. 7 is a side elevation view of a CC supplying device which provides part of the CC mounting system of FIG. 1;  
     [0046]FIG. 8 is a partly cross-section, side elevation view illustrating the manner in which the CC supplying device is combined with a base of the CC mounting system;  
     [0047]FIG. 9 is a side elevation view of a CC feeder which provides part of the CC supplying device;  
     [0048]FIG. 10 is an enlarged, side elevation view of a CC-carrier-tape feeding section of the CC feeder;  
     [0049]FIG. 11 is a partly cross-section, front elevation view of a CC mounting head and an X-direction slide of the CC mounting device;  
     [0050]FIG. 12 is a cross-section, front elevation view of a CC suction shaft which is provided on the CC mounting head;  
     [0051]FIG. 13 is a plan view of a portion of the CC mounting head in which a CC-image pick-up device is provided;  
     [0052]FIG. 14 is a plan view of the CC mounting head;  
     [0053]FIG. 15 is a front elevation view of the CC mounting head and the X-direction slide;  
     [0054]FIG. 16 is a view showing the CC suction shafts of the CC mounting head;  
     [0055]FIG. 17 is a plan view of a mechanical section of a switch-valve control device of the CC mounting head;  
     [0056]FIG. 18 is a front elevation view of the mechanical section of the switch-valve control device;  
     [0057]FIG. 19 is a side elevation view of the mechanical section of the switch-valve control device;  
     [0058]FIG. 20 is a front elevation view of a portion of the switch-valve control device which switches a pressure switch valve to its negative-pressure (“NP”) supply state;  
     [0059]FIG. 21 is a side elevation view of the portion of the switch-valve control device which switches the pressure switch valve to its NP supply state;  
     [0060]FIG. 22 is a cross-section view taken along line  22 - 22  in FIG. 20;  
     [0061]FIG. 23 is a cross-section, front elevation view of an operative member of the portion of the switch-valve control device which switches the pressure switch valve to its NP supply state;  
     [0062]FIG. 24 is a diagrammatic view of a control device of the CC mounting system of FIG. 1;  
     [0063]FIG. 25 is a time chart indicating timings at which the movement of an X-Y robot, the rotation of an intermittent-rotation body, the rotation and upward and downward movements of a CC suction shaft, the feeding of CC-carrier tapes by feeders, and the CC-image taking of a CC-image pick-up device are carried out by the CC mounting system of FIG. 1 for sucking CCs, taking the images of the CCs, transferring the CCs, and mounting the CCs on a CS;  
     [0064]FIG. 26 is a table indicating respective operation states of a main air cylinder  930 , a main air cylinder  974 , and an auxiliary air cylinder  984  of the switch-valve control device which are selected in response to respective drive commands supplied to the cylinders  930 ,  974 ,  984  for carrying out a CC sucking operation and two sorts of CC mounting operations;  
     [0065]FIG. 27 is a side elevation view showing the operation state of the switch-valve control device for carrying out the CC sucking operation;  
     [0066] FIGS.  28 (A) and  28 (B) are side elevation views respectively showing two steps of the operation of the switch-valve control device for carrying out the first sort of CC mounting operation in which small-size CCs are mounted;  
     [0067] FIGS.  29 (A) and  29 (B) are side elevation views respectively showing two steps of the operation of the switch-valve control device for carrying out the second sort of CC mounting operation in which large-size CCs are mounted;  
     [0068]FIG. 30 is a table indicating respective rotation-position error angles, image-based recognized angles, rotation-position-error correcting angles, rotation-position changing angles, and summed CC-suction-shaft rotating angles for the manner in which the mounting of some of the twenty CCs held by the CC mounting head and the taking of images of other CCs are concurrently carried out;  
     [0069]FIG. 31 is a table indicating respective rotation-position error angles, image-based recognized angles, rotation-position-error correcting angles, rotation-position changing angles, and summed CC-suction-shaft rotating angles for the manner in which the mounting of the twenty CCs is carried out after the taking of images of all the CCs are finished;  
     [0070]FIG. 32 is a table indicating respective rotation-position error angles, image-based recognized angles, rotation-position-error correcting angles, rotation-position changing angles, and summed CC-suction-shaft rotating angles for the manner in which the mounting of some of the seventeen CCs held by the CC mounting head and the taking of images of other CCs are concurrently carried out;  
     [0071]FIG. 33 is a partly cross-section, front elevation view of a CC mounting head and an X-direction slide of a CC mounting device of a CC mounting system as a second embodiment of the present invention;  
     [0072]FIG. 34 is a left-hand side elevation view of the CC mounting head and the X-direction slide of FIG. 33;  
     [0073]FIG. 35 is a plan view of an upper portion of an intermittent-rotation body of the CC mounting head of FIG. 33;  
     [0074]FIG. 36 is a plan view of a lower portion of the intermittent-rotation body of the CC mounting head of FIG. 33;  
     [0075]FIG. 37 is a cross section, front elevation view of a CC suction shaft and a CC-suction-shaft holding member of the CC mounting head of FIG. 33;  
     [0076]FIG. 38 is an illustrative view of a CC mounting head of a CC mounting device of a CC mounting system as a third embodiment of the invention, the CC mounting head holding two sorts of CC suction nozzles;  
     [0077]FIG. 39 is an illustrative view of a CC mounting head of a CC mounting device of a CC mounting system as a fourth embodiment of the invention, the CC mounting head holding two sorts of CC suction nozzles in a manner different from that in which the CC mounting head of FIG. 38 does;  
     [0078]FIG. 40 is an illustrative view of a CC mounting head of a CC mounting device of a CC mounting system as a fifth embodiment of the invention, the CC mounting head holding three sorts of CC suction nozzles;  
     [0079]FIG. 41 is an illustrative bottom view of a CC mounting head of a CC mounting device of a CC mounting system as a sixth embodiment of the invention;  
     [0080]FIG. 42 is a front elevation view of the CC mounting head of FIG. 41;  
     [0081]FIG. 43 is an illustrative bottom view of a CC mounting head of a CC mounting device of a CC mounting system as a seventh embodiment of the invention;  
     [0082]FIG. 44 is a front elevation view of the CC mounting head of FIG. 43;  
     [0083]FIG. 45 is an illustrative bottom view of a CC mounting head of a CC mounting device of a CC mounting system as an eighth embodiment of the invention;  
     [0084]FIG. 46 is a diagrammatic view of an air-supply control circuit of a switch-valve control device of a CC mounting device of a CC mounting system as a ninth embodiment of the invention;  
     [0085]FIG. 47 is a schematic view of an electronic-circuit assembly line including the CC mounting system of FIG. 1;  
     [0086]FIG. 48 is a schematic view of another electronic-circuit assembly line including a CC mounting system, as a tenth embodiment of the present invention;  
     [0087]FIG. 49 is a plan view of a CS conveyor of the CC mounting system of FIG. 48;  
     [0088]FIG. 50 is a view showing a CS-conveying-width changing device of a CS conveyor of a CC mounting system as an eleventh embodiment of the present invention wherein a servomotor is used as a drive source of the width changing device;  
     [0089]FIG. 51 is a schematic view of another electronic-circuit assembly line including a CC mounting system, as a twelfth embodiment of the present invention wherein respective movable side frames of a carry-in conveyor and a carry-out conveyor of a CS conveyor are connectable to respective movable side frames of main conveyors with the help of connection members;  
     [0090]FIG. 52 is a schematic view of another electronic-circuit assembly line including two CC mounting systems arranged in series with each other, as a thirteenth embodiment of the present invention;  
     [0091]FIG. 53 is a schematic view of another electronic-circuit assembly line including a CC mounting system and a CS carry-in and carry-out device, as a fourteenth embodiment of the present invention; and  
     [0092]FIG. 54 is a plan view of a CC mounting head of a CC mounting device of a CC mounting system providing part of another electronic-circuit assembly line as a fifteenth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0093] Referring first to FIGS.  1  to  32  and  47 , there will be described a circuit component (“CC”) mounting system  8  which is, as shown in FIG. 47, part of an electronic-circuit (“EC”) assembly line  6  to which the present invention is applied. The CC mounting system  8  or the EC assembly line  6  is a printed-circuit-board-related-operation performing system as a sort of circuit-substrate-related-operation performing system.  
     [0094] The EC assembly line  6  includes, in addition to the CC mounting system  8 , a screen printing system  2  as an upstream-side device provided upstream of the CC mounting system  8  in a direction, indicated at arrow, in which circuit substrates (“CS”) are conveyed, and a solder reflowing system  4  as a downstream-side device provided downstream of the CC mounting system  8 . The screen printing system  2  is a sort of solder-paste applying system which applies solder paste to each CS, that is, prints the solder paste on the CS, for providing a printed circuit board (“PCB”) on which CCs are mounted by the CC mounting system  8 . The solder reflowing system  4  includes a reflowing furnace, and reflows or melts the solder paste on the PCB, for electrically connecting the CCs to the PCB.  
     [0095] The CC mounting system  8  will be described below.  
     [0096] In FIG. 1, reference numeral  10  designates a base  10 . On the base  10 , a PCB conveying device  12 , two CC supplying devices  14 ,  16 , and two CC mounting devices  18 ,  20  are provided. The PCB conveying device  12  includes two main conveyors  400 ,  402 , a single carry-in conveyor  404 , and a single carry-out conveyor  406 . The two main conveyors  400 ,  402  are juxtaposed, that is, provided side by side, in a direction (Y direction) perpendicular to a direction (X direction) in which PCBs  408  (FIG. 3) as CSs are conveyed. The X direction, that is, the PCB conveying direction is the direction from the left-hand side to the right-hand side in FIG. 1.  
     [0097] The carry-in conveyor  404  will be described below.  
     [0098] As shown in FIG. 2, the carry-in conveyor  404  includes a guide support table  420  as a stationary member which is provided on the base  10  such that the height position of the support table  420  can be adjusted by a plurality of adjustor bolts  422  as height-position adjusting members. As shown in FIG. 4, the support table  420  is a frame-like member having a rectangular shape and a central opening, and has a length sufficient to be adjacent to both the two main conveyors  400 ,  402 . Two straight guide rails  424  as guide members are fixed to a pair of opposite sides of the support table  420 , respectively, such that the guide rails  424  extend parallel to the Y direction. As shown in FIGS. 2 and 4, a conveyor support table  426  is fit on the two guide rails  424  via four guide blocks  428  as guided members. The guide rails  424  and the guide blocks  428  cooperate with each other to provide a guiding device. The carry-in conveyor  404  is provided on the support table  426 .  
     [0099] The conveyor support table  426  has a frame-like shape having a rectangular shape and a central opening. As shown in FIG. 4, the support table  426  includes a pair of side portions  430  which are parallel to the Y direction, and a connection member  432  which connects the two side portions  430 . The support table  426  is fixed, at a longitudinally middle portion of the connection member  432  thereof, to a movable member (not shown) of a rodless cylinder  436  that is an air-pressure-operated cylinder having no piston rod. The movable member of the rodless cylinder  436  that is integral with a piston thereof airtightly projects outward from a housing thereof, and the connection member  432  is fixed to the movable member. The rodless cylinder  436  is provided on the guide support table  420  such that the cylinder  436  extends parallel to the Y direction. When the conveyor support table  426  is moved by the rodless cylinder  436 , the carry-in conveyor  404  is moved to a first shift position where the conveyor  404  is aligned with the first main conveyor  400  and to a second shift position where the conveyor  404  is aligned with the second main conveyor  402 . The conveyor support table  426  and the rodless cylinder  436  cooperate with each other to provide a carry-in-conveyor shifting device  438 . A stroke-end sensor (not shown) identifies which position the carry-in conveyor  404  is taking, the first or second shift position, by detecting the current position of the piston of the rodless cylinder  436 , i.e., identifying whether the piston has been moved to its stroke end.  
     [0100] As shown in FIG. 4, the carry-in conveyor  404  includes a fixed frame  440  and a movable frame  442  each as a side frame. The two side frames  440 ,  442  have an elongate shape longer than the dimension of the conveyor support table  426  in the PCB conveying direction. The fixed frame  440  is fixed to one end portion of the support table  426  which portion extends parallel to the PCB conveying direction, so that the fixed frame  440  extends parallel to the PCB conveying direction. The movable frame  442  is so provided as to extend parallel to the PCB conveying direction, and is attached to the support table  426  such that the movable frame  442  is movable in the Y direction perpendicular to the PCB conveying direction, toward, and away from, the fixed frame  440 .  
     [0101] The conveyor support table  426  includes another or second end portion opposite to its one end portion to which the fixed frame  440  is fixed. The second end portion provides a support portion  444  which extends parallel to the PCB conveying direction. Opposite ends of each of a pair of straight guide rails  446  as guide members are fixed to the fixed frame  440  and the support portion  444 , respectively. In addition, opposite ends of a threaded shaft  448  are rotatably supported by the two members  440 ,  444 , respectively. The two guide rails  446  and the threaded shaft  448  extend parallel to the direction of movement of the movable frame  442 , which fits on the two guide rails  446  via respective guide blocks  450  fixed thereto as guided members and fits on the threaded shaft  448  via a nut  452  fixed thereto. The threaded shaft  448  and the nut  452  cooperate with steel balls (not shown) to provide a ball screw. Therefore, when the threaded shaft  448  is rotated, the movable frame  442  is moved toward, or away from, the fixed frame  440  by being guided by the guide rails  446 .  
     [0102] As shown in FIG. 4, the guide support table  420  supports a spline shaft  456  such that the spline shaft  456  is rotatable about an axis line parallel to the Y direction. As shown in FIGS. 2 and 4, the spline shaft  456  extends over the first and second shift positions of the carry-in conveyor  404 , and is positioned below the fixed and movable frames  400 ,  442 . A spline tube or a spline member  458  which is attached via a bracket  457  (FIG. 2) to the fixed frame  440  such that the spline member  458  is rotatable relative thereto and is not axially movable relative thereto, fits on the spline shaft  456  such that the spline member  458  is not rotatable relative thereto and is axially movable relative thereto. The spline member  458  has a spline hole which spline-fits on the spline shaft  456 , and is meshed with the spline shaft  456  via balls. The spline member  458  and the spline shaft  456  cooperate with each other to provide a ball spline. A sprocket  460  is provided as an integral part of the spline member  458 . A chain  464  (shown in FIG. 2 but not shown in FIG. 4) is wound on the sprocket  460  and another sprocket  462  fixed to the threaded shaft  448 , so that the rotation of the spline shaft  456  is transmitted to the threaded shaft  448 . Reference numeral  466  designates a tension sprocket.  
     [0103] As shown in FIGS. 2 and 4, a sprocket  468  is fixed to an end portion of the spline shaft  456  which portion projects outward from the fixed frame  440  in a direction away from the movable frame  442 . When a chain  470  wound on the sprocket  468  is moved, the spline shaft  456  is rotated, so that the threaded shaft  448  is rotated and the movable frame  442  is moved. Thus, the Y-direction width (hereinafter, referred to as the “PCB conveying width”) of the carry-in conveyor  404  is adjustable to that of the PCB  408 . When the carry-in conveyor  404  is shifted by the movement of the conveyor support table  426 , the sprocket  460  fixed to the spline member  458  is moved with the fixed frame  440  relative to the spline shaft  456 , in the axial direction of the shaft  456 , in such a manner that the sprocket  460  remains spline-fit on the shaft  456  and accordingly the rotation of the sprocket  460  can be transmitted to the threaded shaft  448 . Therefore, whether the carry-in conveyor  404  may take the first or second shift position, the rotation of the sprocket  460  can be transmitted to the threaded shaft  448 , so that the PCB conveying width of the carry-in conveyor  404  can be adjusted.  
     [0104] The adjusting of PCB conveying width of the carry-in conveyor  404  is carried out simultaneously with the adjusting of PCB conveying width of the main conveyors  400 ,  402  and the carry-out conveyor  406 . The chain  470  and its drive source will be described later.  
     [0105] As shown in FIG. 4, the fixed frame  440  and the support portion  444  of the conveyor support table  426  respectively support opposite end portions of a spline shaft  480  as a rotation transmitting shaft which extends parallel to the Y direction, such that the spline shaft  480  is rotatable about an axis line thereof. One of the two end portions of the spline shaft  480  which is nearer to the movable frame  442  fits in a spline tube or a spline member  482  such that the spline shaft  480  is not rotatable relative to the spline member  482  and is movable relative to the member  482  in the axial direction of the shaft  480 . The spline member  482  is attached to the movable frame  442  such that the spline member  482  is rotatable relative to the frame  442  and is not movable relative to the frame  442  in the axial direction of the shaft  480 . The spline member  482  and the spline shaft  480  cooperate with each other to provide a ball spline. A sprocket  484  is fixed to an end portion of the spline shaft  480  which portion projects outward from the fixed frame  440  in a direction away from the movable frame  442 . As shown in FIG. 2, the sprocket  484  is connected via a chain  490  to a sprocket  488  fixed to an output shaft of a PCB conveying motor  486  as a belt driving device. The PCB conveying motor  486  as an electric rotary motor as a sort of an electric motor is an induction motor as a sort of AC three-phase motor.  
     [0106] A conveyor belt (not shown) is wound on a pulley  492  (FIG. 2) provided as a part integral with one of the two end portions of the spline shaft  480  which is nearer to the fixed frame  440 , and a plurality of pulleys  494  (only two pulleys  494  are shown in FIG. 4) attached to the fixed frame  440 . Another conveyor belt (not shown) is wound on a pulley (not shown) provided as a part integral with the spline member  482 , and a plurality of pulleys  496  (only two pulleys  496  are shown in FIG. 4) attached to the movable frame  442 . Therefore, when the PCB conveying motor  486  is actuated, the spline shaft  480  is rotated and accordingly the pulleys  492 ,  494 ,  496 , etc. are rotated, so that the pair of conveyor belts are moved and the PCB  408  supported on the belts is conveyed or fed forward. The PCB conveying motor  486  which is attached to the conveyor support table  426  is moved with the carry-in conveyor  404 , so that whether the carry-in conveyor  404  may take the first or second shift position, the motor  486  can function as the drive source which conveys the PCB  408 .  
     [0107] When the PCB  408  is conveyed, opposite end faces of the PCB  408  in the Y direction, i.e., in the widthwise direction thereof are guided by respective vertical guide surfaces of elongate guide members  498 ,  500  (FIG. 4) which are fixed to the fixed and movable frames  440 ,  442 , respectively. Each of the guide members  498 ,  500  includes a hold-down portion which projects over the corresponding conveyor belt and prevents the PCB  408  from jumping off the belt.  
     [0108] As shown in FIG. 4, a PCB-arrival sensor  504  which detects the PCB  408  being conveyed is attached to a downstream-side portion of the fixed frame  440  in the PCB conveying direction. The PCB-arrival sensor  504  is a reflection-type photoelectric sensor including a light emitter and a light detector. However, the sensor  504  may be provided by a transmission-type photoelectric sensor including a light emitter and a light detector, a limit switch, a proximity switch, or the like.  
     [0109] The carry-out conveyor  406  has the same construction as that of the carry-in conveyor  404 , and accordingly the same reference numerals as used for the carry-in conveyor  404  are used to designate the corresponding elements or parts of the carry-out conveyor  406  and the description thereof is omitted. It is noted that the conveyor support table  426  and the rodless cylinder  438  of the carry-out conveyor  406  cooperate with each other to provide a carry-out-conveyor shifting device  508  which shifts the carry-out conveyor  406  between its first and second shift positions. Thus, each one of the carry-in and carry-out conveyors  404 ,  406  can be shifted by a corresponding one of the carry-in-conveyor and carry-out-conveyor shifting devices  438 ,  508 , independent of the other conveyor.  
     [0110] As shown in FIG. 1, a handle  510  as a PCB-conveying-width adjusting member is provided near to the carry-out conveyor  406 . A rotatable shaft  514  is attached via a bracket  512  to the base  10  such that the shaft  514  is rotatable about an axis line parallel to the Y direction. The handle  510  is fixed to one end portion of the rotatable shaft  514 , and a sprocket  516  on which the chain  470  is wound is fixed to the other end portion of the shaft  514 . The chain  470  is also wound on a sprocket  518  which is attached to the bracket  512  such that the sprocket  518  is rotatable about an axis line.  
     [0111] Next, there will be described the main conveyors  400 ,  402 . Since the two main conveyors  400 ,  402  have substantially the same construction, the first main conveyor  400  will be mainly described below.  
     [0112] As shown in FIGS. 2 and 4, a conveyor support table  520  as a stationary member is fixed to the base  10  at a position between the carry-in and carry-out conveyors  404 ,  406 . The conveyor support table  520  has a Y-direction dimension corresponding to the two main conveyors  400 ,  402 , and two straight guide rails  522  (FIG. 2) as guide members are fixed to respective end portions of the support table  520 , such that the guide rails  522  extend parallel to the Y direction.  
     [0113] The main conveyor  400  includes, as side frames, a fixed frame  524  and a movable frame  526 . The fixed frame  524  shown in FIG. 2 as a representative of the two frames  524 ,  526  has a gate-like shape including a pair of leg portions  528  and a connection portion  530 , and is fixed via the leg portions  528  to the support table  520 . Two guide blocks  532  as guided members are fixed to the two leg portions  528  of the movable frame  526 , respectively, and fit on the two guide rails  522 , respectively, such that the movable frame  526  is movable relative to the fixed frame  524 . The guide blocks  532  and the guide rails  522  cooperate with each other to provide a guiding device.  
     [0114] As shown in FIGS. 4 and 5, the two leg portions  528  of the fixed frame  524  of the main conveyor  400  support respective threaded shafts  536  (only one  536  is shown in FIG. 4) such that the threaded shafts  536  are rotatable relative to the fixed frame  524  and is not movable relative to the same  524  in the axial direction of the shafts  536 . As shown in FIG. 5, the threaded shafts  536  are threadedly engaged with respective nuts  538  which are fixed to opposite end portions of the movable frame  526  of the first main conveyor  400  in the PCB conveying direction. Respective end portions of the threaded shafts  536  which project from the movable frame  526  of the first main conveyor  400  are rotatably supported by the fixed frame  524  of the second main conveyor  402 . Each of the threaded shafts  536  cooperates with a corresponding one of the nuts  538  to provide a ball screw. The respective movable frames  526  of the two main conveyors  400 ,  402  are connected to each other by a connection member  540 , so that the two movable frames  526  are moved with each other as a unit.  
     [0115] As shown in FIGS. 2 and 5, two sprockets  542  are fixed to respective end portions of the threaded shafts  536  which project outward from the fixed frame  524  of the main conveyor  400 . As shown in FIGS. 2 and 6, the chain  470  are wound on the sprockets  542 , and a plurality of sprockets  544  which are attached to the conveyor support table  520  and the fixed frame  524 . Therefore, when the handle  510  is rotated by an operator, the chain  470  is moved and the two threaded shafts  536  of the main conveyor  400  are rotated, and simultaneously the respective spline shafts  456  of the carry-in and carry-out conveyors  404 ,  406  are rotated and accordingly the respective threaded shafts  448  are rotated. Consequently the respective movable frames  442 ,  526  of the four conveyors  400 ,  402 ,  404 ,  406  are moved by the same distance in the same direction. Thus, the four conveyors  400 - 406  are simultaneously adjusted to the same PCB conveying width. Since the respective movable frames  526  of the two main conveyors  400 ,  402  are connected to each other by the connection member  540 , the movable frame  526  of the second main conveyor  402  is also moved when the movable frame  526  of the first main conveyor  400  is moved by the rotation of the threaded shafts  536 .  
     [0116] An endless conveyor belt  546  (FIG. 5) is wound on a plurality of pulleys (not shown) which are attached to opposite end portions of an inner vertical surface of the connection portion  530  of the fixed frame  524  in the PCB conveying direction, and another endless conveyor belt  546  is wound on a plurality of pulleys (not shown) which are attached to opposite end portions of an inner vertical surface of the connection portion  530  of the movable frame  526  in the PCB conveying direction. The respective inner vertical surfaces of the connection portions  530  of the fixed and movable frames  524 ,  526  are opposed to each other. The conveyor belts  546  are moved when a spline shaft  548  which is rotatably supported by the fixed and movable frames  524 ,  526  is rotated.  
     [0117] As shown in FIG. 5, the spline shaft  548  of the first main conveyor  400  is rotatably supported by the fixed frame  524  of the same  400 . A spline tube or a spline member  550  is attached to the movable frame  526  such that the spline member  550  is rotatable relative to the frame  526  and is not movable relative to the same  526  in the axial direction of the shaft  548 . The spline member  550  fits on the spline shaft  548  such that the spline member  550  is not rotatable relative to the shaft  548  and is movable relative to the same  548  in the axial direction of the same  548 . The spline member  550  and the spline shaft  548  cooperate with each other to provide a ball spline. A pulley  553  is provided as a part integral with one end portion of the spline shaft  548  which is nearer to the fixed frame  524 , and another pulley  553  is provided as a part integral with the spline member  550 . One conveyor belt  546  is wound on one pulley  553 , and the other conveyor belt  546  is wound on the other pulley  553 . The spline shaft  548  projects from the movable frame  526  of the first main conveyor  400 , and is rotatably supported by the fixed frame  524  of the second main conveyor  402 . A first pulley  553  of the second main conveyor  402  is provided as a part integral with the projecting end portion of the spline shaft  548 , and a first conveyor belt  546  of the second main conveyor  402  is wound on the first pulley  553 . The spline shaft  548  of the first main conveyor  400  is connected to a spline shaft  548  of the second main conveyor  402  by a coupling member  552 , so that the two spline shafts  548  are rotated as a unit.  
     [0118] As shown in FIG. 5, an end portion of the spline shaft  548  of the second main conveyor  402  projects outward from the movable frame  526 , and the projecting end portion of the spline shaft  548  is rotatably supported by a support member  554  fixed to the conveyor support table  520 . A sprocket  556  is fixed to the projecting end portion of the spline shaft  548 , and is connected via a chain  562  to a sprocket  560  (FIG. 4) fixed to an output shaft of a PCB conveying motor  558  attached to the support member  554 . The PCB conveying motor  558  as an electric rotary motor as a sort of electric motor is a speed-controllable motor as a sort of AC three-phase motor. A second pulley  553  of the second main conveyor  402  is provided as a part integral with a spline member  550  which fits on the spline shaft  548 , and a second conveyor belt of the second main conveyor  402  is wound on the second pulley  553 .  
     [0119] Therefore, when the PCB conveying motor  558  is actuated, the two spline shafts  548  are rotated as a unit, and the pulleys  553  of the first main conveyor  400  are rotated, so that the conveyor belts  546  of the first main conveyor  400  are moved and the PCB  408  supported there on is conveyed. When the conveyor belts  546  are moved, the belts  546  are guided by two belt guides  564  (FIG. 5) which are fixed to the fixed and movable frame  524 ,  526 , respectively. When the PCB  408  is conveyed, opposite ends of the PCB  408  in the Y direction are guided by respective vertical guide surfaces of two guide members  566 ,  568  which are fixed to the fixed and movable frames  524 ,  526 , respectively. The two guide members  566 ,  568  include two hold-down portions  570 ,  572 , respectively, which cooperate with each other to prevent the PCB  408  from jumping off the conveyor belts  546 . A space which has a dimension greater than the thickness of the PCB  408  is provided between each of the two hold-down portions  570 ,  572  and a corresponding one of the two conveyor belts  546 . Therefore, a small clearance remains between each hold-down portion  570 ,  572  and the upper surface of the PCB  408  placed on the corresponding conveyor belt  546 . When the PCB conveying width of the conveyors  400 - 406  is adjusted, the spline members  550  are moved relative to the spline shafts  548  in the axial direction of the shafts  548 , in such a manner that the spline members  550  remain spline-fit on the spline shafts  548 . Thus, even if the PCB conveying width may be adjusted or changed, the rotation of the PCB conveying motor  558  can be transmitted to the pulleys  553 , so that the PCB  408  can be conveyed on the conveyor belts  546 .  
     [0120] As shown in FIG. 5, two thrust-up members  580  are attached to respective inner surfaces of the fixed and movable frames  524 ,  526  which are opposed to each other, such that each thrust-up member  580  is movable up and down. Each thrust-up member  580  has a thin plate-like shape, and has substantially the same length as that of the fixed or movable frame  524 ,  526 . The two thrust-up members  580  are fixed to two holder members  582 , respectively, which are attached to the fixed and movable frames  524 ,  526 , respectively, such that each holder member  582  is movable up and down. Each thrust-up member  580  is provided inside the corresponding conveyor belt  546 .  
     [0121] Two engagement members  584  (only one  584  is shown in FIG. 2) project downward from opposite end portions of a lower surface of each of the holder members  582  in the longitudinal direction of the holder  582 . Each holder member  582  is biased downward by a compression coil spring  586  (FIG. 2) as an elastic member as a sort of biasing device which is provided between the holder member  582  and the connection portion  530 , so that the corresponding thrust-up member  580  normally takes a retracted position in which the upper surface of the member  580  is below the PCB conveying level including the upper surfaces of upper horizontal portions of the conveyor belts  546  and accordingly the member  580  does not interfere with the movement of the PCB  408 .  
     [0122] As shown in FIG. 5, the conveyor support table  520  supports two elevator tables  598  and two elevating and lowering devices  600 . Each elevator table  598  has dimensions greater than those of the greatest PCBs  408  that are conveyed by the main conveyors  400 ,  402 . The distance between the two leg portions  528  of each movable frame  526  is greater than the X-direction dimension of each elevator table  598 . Therefore, when the PCB conveying width is adjusted, each movable frame  526  does not collide with the corresponding elevator table  598 . On each elevator table  598 , there is provided a plurality of PCB suction devices  602  as PCB support devices (only one  602  is shown in FIGS. 2, 4, and  5 ). Each PCB suction device  602  utilizes a negative pressure or a vacuum supplied from a vacuum source (not shown), for sucking the PCB  408 .  
     [0123] Each elevating and lowering device  600  includes a pair of rotatable axis members  608  which are attached to the conveyor support table  520  such that the axis members  608  are rotatable about respective axis lines parallel to the X direction. Two levers  610  (FIG. 5) are attached, at one end portions thereof, to opposite end portions of each of the rotatable axis members  608 , such that each lever  610  is not rotatable relative to a corresponding one of the axis members  608 . Four rollers  612  which are rotatably attached to respective free end portions of the four levers  610 , rotatably fit in respective engagement recesses  614  formed in the lower surface of the elevator table  598 . The two axis members  608  are connected to each other so that they are rotatable as a unit. Therefore, when one of the two axis members  608  is rotated by a drive air cylinder (not shown), the four levers  610  are simultaneously rotated, so that the elevator table  598  is moved upward and downward while maintaining its horizontal attitude. As shown in FIG. 5, the upward and downward movements of the elevator table  598  are guided by a guide rod  616  fixed to the elevator table  598 , and a guide cylinder  618  which is fixed to the support table  520  and in which the guide rod  616  fits.  
     [0124] When the elevator table  598  is moved upward, the PCB suction devices  602  suck the PCB  408  by applying the negative pressure thereto, so that respective support surfaces of support portions of the suction devices  602  which are covered by rubber-based suction cups, respectively, support the lower surface of the PCB  408 . In addition, the elevator table  598  engages the engagement members  584 , and moves up the holder members  582 , i..e, the thrust-up members  580  against the biasing forces of the compression coil springs  586 , so that the PCB  408  is thrusted up off the conveyor belts  546 . Thus, the PCB  408  is sucked and supported by the PCB suction devices  602 , and is thrusted up off the conveyor belts  546  so as to be sandwiched between the thrust-up members  580  and the hold-down portions  570 ,  572  of the guide members  566 ,  568 . In this way, the PCB  408  is fixed by one main conveyor  400 ,  402  such that a possible warpage of the PCB  408  is corrected. The positions where the PCB suction devices  602  are provided on the elevator table  598  can be adjusted depending upon the dimensions of the PCB  408  and, in the case where small-size PCBs  408  are used, the suction devices  602  may be omitted.  
     [0125] As shown in FIG. 4, each main conveyor  400 ,  402  is equipped with a deceleration-start-position sensor  620 , a PCB-arrival sensor  622 , and a PCB stopping device  624  in a downstream-side end portion thereof. Each of the sensors  620 ,  622  is provided by a reflection-type photoelectric sensor including a light emitter which emits a light toward the PCB  408  and a light detector which detects the light reflected from the PCB  408 , and the former sensor  620  detects that the PCB  408  has reached the position where the deceleration of the movement of the PCB  408  should be started, and the latter sensor  622  detects that the PCB  408  has reached the position where the arrival of the PCB  408  should be recognized. Each elevator table  598  has a cutout  626  which permits the light emitted from each sensor  620 ,  622  to impinge on the PCB  408 . However, each of the sensors  620 ,  622  may be provided by a transmission-type photoelectric sensor including a light emitter which emits a light toward the PCBs  408  and a light detector which detects the light transmitted through a space present between each pair of successive PCBs  408 ; a proximity switch; a limit switch; or the like.  
     [0126] The PCB stopping device  624  is provided on the downstream side of the two sensors  620 ,  622 , and includes a stopper member  630  and an elevating and lowering device  632  which elevates and lowers the stopper member  630 . As shown in FIG. 2, the elevating and lowering device  632  includes, as a drive source thereof, an air cylinder  634  as a sort of fluid-pressure-operated cylinder, and utilizes the air cylinder  634  for thrusting up the stopper member  630  to an operative position thereof at the PCB conveying level where the stopper  630  stops the movement of the PCB  408  and retracting the stopper  630  to an inoperative position thereof below the PCB conveying level where the stopper  630  permits the PCB  408  to be moved thereover.  
     [0127] Thus, the PCB conveyor device  12  includes the two main conveyors  400 ,  402  whose respective PCB conveying routes are arranged side by side and both extend in the X direction. However, in the present EC assembly line  6 , the screen printing system  2  and the solder reflowing system  4  provided on the upstream and downstream sides of the CC mounting system  8 , respectively, are aligned with the first main conveyor  400  of the CC mounting system  8 . Therefore, the carry-in conveyor  404  receives the PCB  408  from the printing system  2  when the conveyor  404  is at its first shift position, and the carry-out conveyor  406  hands over the PCB  408  to the reflowing system  4  when the conveyor  406  is at its first shift position. In the present embodiment, the operator is required to perform his or her work on the side of not the second main conveyor  402  but the first main conveyor  400  which is aligned with the printing and reflowing systems  2 ,  4  in the EC assembly line  6 .  
     [0128] Next, there will be described the CC supplying devices  14 ,  16 . As shown in FIG. 1, the two CC supplying devices  14 ,  16  are provided outside the two main conveyors  400 ,  402  such that the main conveyors  400 ,  402  are positioned between the two CC supplying devices  14 ,  16 . The two CC supplying devices  14 ,  16  have the same construction, and supply the same sorts of CCs. There will be described the CC supplying device  14  as a representative of the two CC supplying devices  14 ,  16 .  
     [0129] As shown in FIG. 7, the CC supplying device  14  includes a support car  52  as a main member thereof, and a plurality of feeders  54  which are supported on the support car  52  and which cooperate with the support car  52  to provide the CC supplying device  14 . In FIG. 7, the feeders  54  are indicated at phantom lines (i.e., two-dot chain lines). The support car  52  includes a base member  60 , a handle  61 , a frame  62  supported by the base member  60 , a frame plate  63  attached to the frame  62 , a feeder holding device  64  provided on the frame  62 , and two engaging portions  66  provided on the frame  62  (only one  66  is shown in FIG. 7). FIG. 3 is the left side elevation view of the supplying apparatus  8 , and FIG. 4 is the right side elevation view of the same  8 .  
     [0130] As shown in FIG. 8, the two engaging portions  66  are engaged by two engaging devices  68 , respectively, which are provided on the base  10 , so that the support car  52  is combined with the base  10 . Each engaging device  68  is equipped with an engaging projection  70  which has a petal-like shape and which is movable in a direction in which the support car  52  and the base  10  are arranged (i.e., the left-right direction in FIG. 8) and is rotatable about an axis line parallel to the moving direction. The above movement of the engaging projection  70  is caused by a double-action air cylinder (not shown) which is incorporated in the engaging device  68 . During this movement, the projection  70  is rotated by a predetermined angle (e.g., 90 degrees) about the axis line parallel to the moving direction by a cam mechanism (not shown).  
     [0131] In a non-combined state in which the support car  52  is not combined with the base  10 , the engaging projection  70  of each engaging device  68  projects freely in the space and takes an angular or rotational phase at which the projection  70  can fit, in an axial direction thereof, in one of the two engaging portions  66  of the support car  52 . Each engaging portion  66  has an opening consisting of a circular hole  71  and a pair of side recesses  72  laterally extending from the circular hole  71  in opposite directions, respectively. When the support car  52  is moved toward the base  10  so as to be combined with the same  10 , each of the two projections  70  enters the circular hole  71  and the side recesses  72  of a corresponding one of the two engaging portions  66 . In this state, if air is supplied to one of two pressure chambers of the air cylinder of each engaging device  68  and air is permitted to flow out of the other pressure chamber, each projection  70  is retracted, during an initial period, while being rotated in a positive direction, so that the projection  70  engages the corresponding engaging portion  66  such that the two elements  70 ,  66  cannot be disengaged from each other in the axial direction of the projection  70 . After this rotation, each projection  70  is moved back or retracted over a predetermined distance, so that the support car  52  is strongly combined with the base  10 . If the direction of flow of air is reversed in the air cylinder, each projection  70  is moved out or advanced, during an initial period, while being not rotated, so that the support car  52  is permitted to separate from the base  10 , and then each projection  70  is further advanced while being rotated in the opposite direction, so that each projection  70  is placed in a state in which it can be separated from the corresponding engaging portion  66 .  
     [0132] Two tapered guide sleeves  74  (only one  74  is shown in FIG. 8) are provided on the base  10 . The guide sleeves  74  can fit in the corresponding engaging portions  66  in such a manner that the guide sleeves  74  do not interfere with the engagement of the engaging projections  70  and the engaging portions  66 . More specifically described, the guide sleeves  74  fit in the respective circular holes  71  of the engaging portions  66 . Since the right-hand end of each engaging projection  70  is positioned nearer to the support car  52  than that of the corresponding guide sleeve  74  as seen in FIG. 8, the guide sleeve  74  does not interfere with the engagement of the projection  70  and the corresponding engaging portion  66 . Since the two guide sleeves  74  fit in the respective circular holes  71  of the two engaging portions  66 , the support car  52  is accurately positioned relative to the base  10  in all directions parallel to a vertical plane parallel to the X direction.  
     [0133] As shown in FIG. 7, there are provided a pair of guide mechanisms  80  each of which is associated with the base  10  and the support car  52 . Each guide mechanism  80  is provided by a guide member  82  which is attached to the base  10  and a roller  84  which is attached to the base member  60  of the support car  52  (only one guide member  82  and only one roller  84  are shown in FIG. 7). FIG. 7 shows the relative position of one guide member  82  and the support car  52  in a combined state in which the car  52  is combined with the base  10 . In this state, two fixed wheels  86  and two pivotal wheels  88  which are provided on the base member  60  are separate from the floor. Also, the two rollers  84  are slightly separate from the two guide members  82 , respectively. In the non-combined state, the support car  52  is supported on the floor via the two fixed wheels  86  and the two pivotal wheels  88 , so that the car  52  can easily be moved on the floor.  
     [0134] When the support car  52  is moved toward the base  10  so as to be combined therewith, the rollers  84  roll up to respective inclined surfaces  90  of the guide members  82 , while being separated from the floor. When the car  52  further approaches the base  10 , the two rollers  84  roll onto two guide rails  92 , respectively, which are provided on the two guide members  82 , respectively. The engagement of the rollers  84  with the guide rails  92  results in adjusting the position of the car  52  relative to the base  10  in the X direction so that the car  52  can easily be combined with the base  10 , that is, so that the tapered guide sleeves  74  can easily fit in the circular holes  71  of the engaging portions  66 , respectively. The base  10  is equipped with a combined-state detector (not shown). In the combined state in which the guide sleeves  74  have fit in the circular holes  71  and contact members  94  have contacted projections (not shown) projecting from the base  10 , the combined-state detector detects an exclusive projection (not shown) provided on the car  52 . When the detector detects the projection  95 , the respective air cylinders of the engaging devices  68  are operated so that the projections  70  are engaged with the engaging portions  66 , such that the projections  70  cannot be disengaged from the portions  66  in the axial direction of the projections  70 , and the car  52  is pulled and combined with the base  10 , as described above.  
     [0135] As shown in FIG. 8, when the support car  52  is pulled toward the base  10 , respective contact surfaces  96  of the engaging portions  66  contact respective contact surfaces  97  of the engaging devices  68 , and the contact members  94  of the car  52  contact respective projections (not shown) formed on the base  10 . Thus, the car  52  is accurately positioned relative to the base  10  in the Y direction in which the car  52  is moved relative to the base  10  so as to be combined therewith. Hereinafter, a vertical plane which is defined by the contact surfaces  97  and the respective contact surfaces of the above-indicated projections (not shown) will be referred as the “combining plane”, and a direction normal to the combining plane will be referred to as the “combining direction”, when appropriate. The engaging devices  68  pull the engaging projections  70  toward the base  10 , with a force greater than a force which is needed to move up the car  52  such that the pivotal wheels  88  are separated from the floor and the rollers  84  are separated from the guide rails  92 . Accordingly, the car  52  is strongly combined with the base  10 . For example, each engaging device  68  pulls the corresponding projection  70  with a force of about 250 kgf (i.e., about 2,450 N).  
     [0136] The feeders  54  are held by a plurality of feeder holding units  100  of the feeder holding device  64 , respectively, on the support car  52 . The feeder holding device  64  includes, as a main body member thereof, a base plate  106  (described below). In the present embodiment, the feeder holding device  64  has four feeder-holding-unit groups  102  each group of which consists of six successive feeder holding units  100  (only one feeder holding unit  100  of only one feeder-holding-unit group  102  is shown in FIG. 7). Accordingly, the feeder holding device  64  can hold at most twenty-four feeders  54 .  
     [0137] As shown in FIG. 7, each feeder holding unit (“FHU”)  100  includes a base plate  106 , an engaging member  108  and a guide plate  110  which are supported by the base plate  106 , an air supply section  112  which supplies pressurized air to the feeder  54 , and an electric-power supply section  114  which supplies electric power to the feeder  54 . The base plate  106  and the guide plate  110  are shared by all the FHUs  100 , and the engaging member  108  is shared by the six FHUs  100  of each of the four FHU groups  102 .  
     [0138] The base plate  106  has a plurality of engaging grooves (not shown) which correspond to the FHUs  100 , respectively, and which extend in the Y direction in which the base  10  and the support car  52  are arranged. Each feeder  54  has an engaging projection  122  which is engageable with one of the engaging grooves and one of the engaging members  108 . When each feeder  54  is held by one FHU  100 , the feeder  54  is moved in the direction from the right-hand side toward the left-hand side in FIG. 7, so that finally the feeder  54  is held at a position shown in FIG. 7. Since the engaging projection  122  of the feeder  54  held by the FHU  100  is engaged with the engaging groove  120  of the base plate  106 , the feeder  54  is inhibited from moving relative to the FHU  100  in the X direction. In addition, the guide plate  110  which is attached to the base plate  106  via a plurality of columns  124  permits only slight movements of the feeder  54  in a vertical direction in a plane normal to the X direction. These features enable an operator to attach or detach easily each feeder  54  to or from one FHU  100  by engaging or disengaging smoothly the engaging projection  122  with or from the engaging member  108 . In the attached state shown in FIG. 7, the engaging projection  122  is engaged with the engaging member  108  and accordingly the feeder  54  is inhibited from moving relative to the base plate  106  in the Z direction.  
     [0139] Each feeder  54  is equipped with a generally U-shaped engaging member  126  (FIG. 10) which is engageable with an engaging groove  125  formed in the base plate  106  so as to bias the feeder  54  toward the frame  62  (i.e., leftward in FIG. 7). While a lever  128  is not operated, the engaging member  126  projects outward from the feeder  54 , as shown in FIG. 7. On the other hand, while the lever  128  is operated, the member  126  is retracted into an internal space of the feeder  54 . A mechanism for retracting the member  126  into the feeder  54  will be described later by reference to FIG. 10. In the process in which each feeder  54  is held by one FHU  100 , the lever  128  is operated so that the engaging member  126  is retracted into the feeder  54 . However, if the lever  128  is released for stopping the operation thereof, the feeder  54  is firmly held by the FHU  100 . Each feeder  54  can easily be removed from the FHU  100  by first operating the lever  128  for retracting the engaging member  126  into the feeder  54  and then moving the feeder  54  rightward in FIG. 7.  
     [0140] The support car  52  is equipped with an electric-power receiving section (not shown) for receiving electric power from the base  10 , and an air receiving section (not shown) for receiving pressurized air from the same  10 .  
     [0141] As shown in FIG. 7, each feeder  54  can hold at most two CC tape reels  150  each of which stores a CC carrier tape  156  which carries a plurality of CCs (circuit components) of a same sort. The CC carrier tape  156 , which is wound around the tape reel  150 , includes a CC accommodating tape  152  having a plurality of CC accommodating pockets each for accommodating a CC, and a cover tape  154  for covering the respective upper openings of the accommodating pockets. The CC carrier tape  156  is of an emboss-type tape wherein the CC accommodating tape  152  includes a pair of opposite side portions which extend parallel to each other in the longitudinal direction of the tape  152 , and the CC accommodating pockets which project downward from, and between, the two side portions such that the pockets are provided at a regular interval of distance in the longitudinal direction. The cover tape  154  is adhered to the accommodating tape  152  for preventing the CCs from coming out of the accommodating pockets. The cover tape  154  is peeled from the accommodating tape  152  at a position which is adjacent to a CC sucking position where the CCs are sucked by suction nozzles  784 , that is, position where one nozzle  784  is shown in FIG. 8 and which is on the side of the tape reel  150  with respect to the nozzle  784  (i.e., on the right-hand side of the nozzle  784  in FIG. 8). The CC sucking position can also be said as a CC supplying position or a CC taking position. Hereinafter, it will be referred as the CC taking position, if appropriate. The accommodating tape  152  from which the CCs have been sucked up by the suction nozzles  784  is fed toward the side of the base  10  (i.e., leftward in FIG. 7), at a feeding pitch which is equal to a CC-accommodating pitch at which the CCs are accommodated by the tape  152  in the longitudinal direction thereof.  
     [0142] More specifically described, the tape  152  from which the CCs have been taken is fed to a cutting machine  162  while being guided by a tape guide  160 . The tape guide  160  and the cutting machine  162  are supported by the frame  62 . The cutting machine  162  cuts the tape  152  into small pieces which are collected in a container  164  provided below the frame  62 . The manner in which the cover tape  154  peeled from the accommodating tape  152  is dealt with will be described later. In FIG. 7, the tape guide  160  and the cutting machine  162  are indicated at phantom lines (two-dot chain lines).  
     [0143] Next, the construction of each feeder  54  employed in the CC supplying device  14  will be described in detail.  
     [0144]FIG. 9 is a front elevation view of each feeder  54 . As described above, each feeder  54  can support at most two CC tape holders  150  each of which holds a plurality of CCs of a same sort. Each feeder  54  can feed, based on a supply command or commands from a control device  1050  (FIG. 24), CCs of a first sort one by one from one of the two reels  150  and CCs of a second sort one by one from the other reel  150 , such that the feeding of CCs from the one reel  150  is independent of that from the other reel  150 . The first and second sorts may be the same as each other, or may be different from each other. Therefore, each feeder  54  can simultaneously feed the CCs from both of the two reels  150 . However, though the CC mounting device  18  or  20  has a plurality of suction nozzles  784  as described later, the control device  1050  does not generate, under normal conditions, any supply command that the feeder  54  should simultaneously supply the CCs from both the two reels  150 . Similarly, the control device  1050  does not simultaneously send a plurality of supply commands to a plurality of feeders  54 , respectively.  
     [0145]FIG. 10 is a front elevation view of a part of one of the feeders  54 , with a first, a second, and a third cover member  192 ,  194 ,  196  shown in FIG. 9 being removed for easier understanding purposes only. Each feeder  54  includes two drive devices  200 ,  201 , each attached to a side plate  198 , for feeding the two CC carrier tapes  156  from the two tape reels  150 , respectively.  
     [0146] The first drive device  200  includes an electric motor  202 , a drive gear  204  which is fixed to an output shaft of the motor  202 , a driven gear  206  which is meshed with the drive gear  204  and has more teeth than those of the drive gear  204 , a drive pulley  208  which is formed integrally with the driven gear  206 , a drive belt  210  which transmits the rotation force of the drive pulley  208 , a driven pulley  212  which is driven by the drive belt  210 , and a sprocket  214  which is formed integrally with the driven pulley  212 . In addition, the first drive device  200  includes a drive belt  216  which transmits the rotation of the drive pulley  208 , a driven pulley  218  which is driven by the driven belt  216 , a drive pinch roller  220  which is formed integrally with the driven pulley  218 , and a driven pinch  222  which is held in pressed contact with an outer circumferential surface of the driven pinch  220  with a predetermined pressure. Thus, the rotation of the motor  202  is transmitted to the sprocket  214  and the two pinches  220 ,  222 .  
     [0147] The drive belt  210  circulates along a route defined by a plurality of guide rollers  224 . Since the electric motor  202  is a stepper motor, the amount or angle of rotation of the sprocket  214  can be controlled by changing a number of pulse signals which are supplied to the motor  202 . The ratio of a rotation angle of the motor  202  to a corresponding rotation angle of the sprocket  214  is equal to the product of a gear ratio of the drive gear  204  and the driven gear  206  and a ratio of the radius of the drive pulley  208  to the radius of the driven pulley  212 . The CC accommodating tape  152  has perforations which are successive at a regular interval of distance in the longitudinal direction thereof and which are engageable with projections which are formed at a regular interval of distance on an outer circumference of the sprocket  214 . A cover member  225  is provided for preventing the accommodating tape  152  from moving up away from the sprocket  214  and thereby surely engaging the tape  152  with the sprocket  214 .  
     [0148] When the sprocket  214  is rotated, the CC carrier tape  156  is subjected to a tension caused by, e.g., frictional resistance produced when the corresponding tape reel  150  is rotated. In addition, the drive belt  210  is subjected to a tension caused by, e.g., the friction produced when the guide rollers  224  are rotated. However, in the present embodiment, each feeder  54  can easily feed the carrier tape  156  at any desired feeding pitch, by changing the number of pulse signals supplied to the electric motor  202 , irrespective of whether those disturbances may be small or large. Therefore, even if a first CC carrier tape  156  may be replaced with a second CC carrier tape  156  whose CC-accommodating pitch (i.e., regular interval at which CCs are accommodated by its CC-accommodating tape  152  in the longitudinal direction thereof) is different from that of the first tape  156 , each feeder  54  can easily adapt itself to that occasion. The pinches  220 ,  222  are held in pressed contact with each other under a predetermined pressure, and the cover tape  154  peeled from the CC accommodating tape  152  is pinched by the two pinch rollers  220 ,  222 , as shown in FIG. 9.  
     [0149] When the CC carrier tape  156  is fed forward by the sprocket  214 , the rollers  220 ,  222  cooperate with each other to send the peeled cover film  154  rearward to the side of the corresponding reel  150 , so that the cover tape  154  is further peeled little by little from the accommodating tape  152 . The cover-tape sending pitch at which the cover tape  154  is sent back by the pinches  220 ,  222  is larger than the carrier-tape feeding pitch at which the CC carrier tape  156  is fed by the sprocket  214 . Since the position where the cover tape  154  is peeled from the accommodating tape  152  is defined and fixed by a cover-tape drawing slit which is formed through the thickness of the cover member  225 , an excessive length of the cover-tape sending pitch is absorbed or accommodated by the sliding of the pinch rollers  220 ,  222  on the cover tape  154 . Thus, the length of the cover tape  154  between the cover member  225  and the rollers  220 ,  222  is held stretched out.  
     [0150] Like the first drive device  200 , the second drive device  201  includes an electric motor  226 , a drive gear  228 , a driven gear  230 , a drive pulley  232 , driven belts  234 ,  236 , a driven pulley  238 , pinch rollers  240 ,  242 , and guide rollers  244 . The second drive device  201  additionally includes a sprocket (not shown) similar to the sprocket  214 , and a driven pulley (not shown) similar to the driven pulley  212 . The sprocket and driven pulley of the second drive device  201  are aligned with the sprocket  214  and driven pulley  212  of the first drive device  200 , and are not shown in FIG. 10.  
     [0151] The cover tape  154  sent back by the pinch rollers  220 ,  222  and the cover tape  154  sent back by the pinch rollers  240 ,  242  are passed through a pipe  246  whose axis line is vertical, as shown in FIG. 9, so that the cover tapes  154  fall down onto the base  60 . Accordingly, in the attached state in which each feeder  54  is attached to one FHU  100 , the waste cover tapes  154  are collected on the base  60  of the support car  52 . An air nozzle  248  is provided for passing smoothly the cover tapes  154  through the pipe  246 . When at least one of the electric motors  202 ,  226  is driven or rotated, pressurized air is supplied to the air nozzle  248  which in turn supplies the air to the pipe  246  from the top inlet thereof. A solenoid-operated valve  250  is opened to supply the pressurized air to the air nozzle  248 .  
     [0152] Each feeder  54  is equipped with some manually operable switches (not shown). Those switches include ones for rotating each one of the electric motors  202 ,  226  in opposite directions, independent of the other motor; ones for selecting a speed at which each one of the motors  202 ,  226  is rotated for supplying CCs; ones for selecting a rotation angle of each one of the motors  202 ,  226  for supply each one of CCs; and ones for selecting each one of the drive devices  200 ,  201  for being operated.  
     [0153] As shown in FIG. 10, the lever  128  of each feeder  54  is biased by a biasing member in the form of a spring  252  in a direction in which the lever  128  is rotated counterclockwise about an axis member  254 . This biasing force is transmitted to the engaging member  126  via a link mechanism  256 , so that while the lever  128  is not operated, the engaging member  126  projects outward from the feeder  54 . The engaging member  126  can be retracted into the feeder  54 , by rotating the lever  128  clockwise about the axis member  254 .  
     [0154] Each feeder  54  is equipped with an air receiving section  272  which fits on the air supply section  112  for receiving pressurized air therefrom, so that the pressurized air is supplied to the above-described solenoid valve  250 . In addition, the feeder  54  is equipped with an electric-power receiving section  274  which is electrically connected to the electric-power supply section  114  for receiving electric power therefrom, so that the electric power is supplied to the electric motors  202 ,  226 , etc. The electric power is supplied from the base  10  to the support car  52 . The car  52  has a second electric-power receiving section (not shown) for receiving electric power in the non-combined state in which the car  52  is not combined with the base  10 , e.g., during a preparing operation prior to the CC mounting operation.  
     [0155] Next, there will be described the CC mounting devices  18 ,  20 . As shown in FIG. 1, the first CC mounting device  18  includes a CC mounting head  650 , and an X-Y robot  662  which includes an X-direction slide  654  and a Y-direction slide  658  (hereinafter, referred to as the X slide  654  and the Y slide  658 ) and which moves the CC mounting head  650  to any position in a horizontal plane. Similarly, the second CC mounting device  20  includes a CC mounting head  652 , and an X-Y robot  664  which includes an X-direction slide  656  and a Y-direction slide  660  and which moves the CC mounting head  652  to any position in a horizontal plane. Since the two CC mounting devices  18 ,  20  have the same construction and the X-Y robots  662 ,  664  have the same construction, there will be described the first CC mounting device  18  and the X-Y robot  662  thereof as a representative of the two CC mounting devices  18 ,  20  and a representative of the two X-Y robots  662 ,  664 .  
     [0156] As shown in FIGS. 2 and 3, two straight guide rails  666  as guide members are provided at two locations on the base  10  which are distant from each other in the PCB conveying direction (i.e., the X direction), such that the guide rails  666  extend parallel to the Y direction. The Y slide  658  fits on the two guide rails  666  such that the Y slide  658  is movable in the Y direction. The Y slide  658  has an X-direction dimension greater than that of the CC support car  52  to which the feeders  54  are attached. Two guide blocks  668  (FIGS. 2 and 3) as guided members are fixed to opposite end portions of the Y slide  658  which are opposite to each other in the longitudinal direction thereof, and fit on the two guide rails  666 , respectively. Thus, the Y slide  658  is movable on the guide rails  666  in the Y direction.  
     [0157] As shown in FIGS. 2 and 3, two nuts  670  are fixed to respective portions of the Y slide  658  which are above the two lower end portions thereof which fit on the two guide rails  666 , respectively, such that the two nuts  670  are oriented parallel to the Y direction. An upper and a lower threaded shaft  672  are provided at each of two locations on the base  10  which are distant from each other in the X direction, such that the two threaded shafts  672  are rotatable about respective axis lines thereof parallel to the Y direction. One of the two nuts  670  is threadedly engaged with the upper one of the two threaded shafts  672  provided at a corresponding one of the two locations, and the other nut  670  is threadedly engaged with the lower one of the two threaded shafts  672  provided at the other location. Each nut  670  and the threaded shaft  672  threaded with the nut  670  cooperate with each other to provide a ball screw. One of the upper and lower threaded shafts  672  at each location which is not threadedly engaged with the corresponding nut  670 , can enter a through-hole (not shown) formed in the corresponding end portion of the Y slide  658 . Thus, the movement of the Y slide  658  is not interfered with by that threaded shaft  672 .  
     [0158] The four threaded shafts  672  are rotated by four Y-direction servomotors  674  (“Y motors  674 ”) as drive sources which are provided on the base  10 . The Y motors  674  are AC (alternating current) servomotors. The Y slide  658  is driven by the corresponding two Y motors  674  which are connected to a common drive circuit (not shown) and are rotated in synchronism with each other. Therefore, the Y slide  658  which has an elongate shape can be smoothly moved at high speed, without vibration which would otherwise result from the inertias of the Y slide  658  itself, the X slide  654 , and the CC mounting head  650  mounted on the X slide  654 . The pair of guide rails  666  are commonly used for the respective Y slides  658 ,  660  of the two CC mounting devices  18 ,  20 . The two Y slides  658 ,  660  are individually driven such that they do not interfere with each other.  
     [0159] As shown in FIGS. 1 and 3, two straight guide rails  676  as guide members are fixed to a lower surface of the Y slide  658 , such that the two guide rails  676  extend in the X direction. Two guide blocks  680  as guided members are fixed to the X slide  654  and fit on the guide rails  676 , respectively, so that the X slide  654  is movable in the X direction. As shown in FIG. 3, a nut  684  is fixed via a bracket  682  to an upper surface of the X slide  654 , and is threadedly engaged with a threaded shaft  686  which is provided on the Y slide  658  such that the threaded shaft  686  extends in the X direction, is rotatable relative to the Y slide  658 , and is not movable in an axial direction thereof. When the threaded shaft  686  is rotated by an X-direction servomotor  688  (“X motor  688 ”, FIG. 2) as a drive-source device, the X slide  654  is moved in the X direction. The nut  684  and the threaded shaft  686  cooperate with each other to provide a ball screw. In FIG. 1, reference numeral  690  designates a flexible protector which protects flexible wires and pipes, such as signal transmitting lines, electricity supplying lines, pressurized-air supplying hoses, vacuum supplying hoses, and the like, which are provided between the base  10  and the Y slide  658 . In FIG. 2, reference numeral  692  designates a flexible protector which protects flexible wires and pipes, such as signal transmitting lines, which are provided between the Y slide  658  and the X slide  654 .  
     [0160] The CC mounting head  650  is mounted on the X slide  654 . As shown in FIG. 11, the X slide  654  includes a pendent portion  700  to which the guide blocks  680  are fixed and which is supported by the Y slide  658  such that the pendent portion  700  is pendent from the Y slide  658 . The X slide  654  additionally includes a connection portion  702  which extends downward from one of opposite end portions of the pendent portion  700  which are opposite to each other in the X direction. As shown in FIGS. 11 and 13, a lower end portion of the pendent portion  700  includes a horizontal portion  704  which horizontally extends toward the other end portion of the pendent portion  700 . A support portion  706  horizontally extends from an intermediate portion of the horizontal portion  704  as viewed in the Y direction, toward the other end portion of the pendent portion  700 .  
     [0161] As shown in FIG. 11, the support portion  706  supports a lower end portion of a rotation shaft  708  via a bearing  710  such that the shaft  708  is rotatable about an axis line thereof, and an upper end portion of the shaft  708  is supported by the pendent portion  700  such that the shaft  708  is rotatable. A stationary cam  712  is fixed to the pendent portion  700 . The cam  712  has a receiving hole  713  which is formed therethrough such that the hole  713  is concentric with the shaft  708 . A fitting portion  718  of a drive gear  716  fits in the receiving hole  713  via bearings  714 . A driven pulley  722  is fixed to an upper end portion of the fitting portion  718  which projects upward from the cam  712 , such that the driven pulley  722  is concentric with the drive gear  716  and is rotatable as a unit with the same  716 . The driven pulley  722  and the drive gear  716  cooperate with each other to support the rotation shaft  708  via bearings  720 ,  721  such that the shaft  708  is rotatable about its axis line that is a vertical line parallel to a perpendicular of the horizontal PCB conveying plane. Thus, the drive gear  716  and the driven pulley  722  are concentric with the rotatable shaft  708 .  
     [0162] As shown in FIG. 14, the rotation of a rotation-position correcting and changing servomotor  724  as a drive source is transmitted to the driven pulley  722  via a drive pulley  726  and a timing (cog) belt  728  as a wound-on member, so that the drive gear  716  is rotated by any desired angle in each of opposite directions. As shown in FIG. 11, a plate-like detectable member  730  is fixed to the driven pulley  722  such that the detectable member  730  is oriented radially outwardly of the pulley  722 . When the detectable member  730  is detected by a drive-gear initial-position sensor  732  (FIG. 24) which is fixed to the X slide  654 , the initial position of the drive gear  716  is detected. The detection of the initial position of the drive gear  716  is carried out when an electric power is initially applied to the present CC mounting system  8 , and the current angular or rotation position of the drive gear  716  is calculated based on the detected initial position.  
     [0163] A driven pulley  740  as a driven rotation member is fixed to an upper end portion of the rotation shaft  708  such that the driven pulley  740  is concentric with the shaft  708 . As shown in FIG. 14, the rotation of a rotatable-body rotating servomotor  742  as a drive source is transmitted to the driven pulley  740  via a drive pulley  744  and a timing belt  746  as a wound-on member, so that the rotation shaft  708  is rotated by any desired angle in each of opposite directions. As shown in FIG. 11, a plate-like detectable member  748  is fixed to the driven pulley  740  such that the detectable member  748  is oriented radially outwardly of the pulley  740 . When the detectable member  748  is detected by a rotation-shaft initial-position sensor  750  (FIG. 14) which is fixed to the X slide  654 , the initial position of the shaft  708  is detected. The detection of the initial position of the shaft  708  is carried out when an electric power is initially applied to the present CC mounting system  8 , and the current rotation position of the shaft  708  is calculated based on the detected initial position thereof.  
     [0164] A CC-suction-shaft holding member  760  is fixed to a lower portion of the rotation shaft  708  which is lower than the portion of the same  708  supported by the drive gear  716 , such that the holding member  760  is concentric with the shaft  708 . The holding member  760  cooperates with the shaft  708  to provide an intermittent-rotation member  762 . The holding member  760  has a generally cylindrical shape, and the cylindrical wall thereof has twenty holding holes  764  which are located on a circle whose center rides on the axis line of rotation thereof and are equiangularly spaced from one another about the axis line and each of which is formed through the thickness thereof in a direction parallel to the axis line. A shaft member  768  as an axial portion of a CC suction shaft  766  is fitted in each holding hole  764  via a bearing  770  and a fitter member  772 . When the intermittent-rotation member  762  is intermittently rotated, the twenty CC suction shafts  766  are rotated around the axis line of rotation of the rotation member  762 .  
     [0165] The diameter of each holding hole  764  is greater than that of each shaft member  768  and, as shown in FIG. 12, the shaft member  768  is fitted in the holding hole  764  such that the air tightness of the shaft member  768  is maintained by two sealing members  774 ,  776 . Thus, an annular passage  780  is provided in the holding hole  764 . The fitter member  772  is fitted in a lower opening end of the holding hole  764  and is fixed to the CC-suction-shaft holding member  760  with a bolt (not shown) as a fixing member. A lower one  776  of the two sealing members  774 ,  776  is held by the fitter member  772 . The bearing  770  and the fitter member  772  are attached to the holding member  760  such that the former two members  770 ,  772  are not movable relative to the latter member  760 . Thus, the two members  770 ,  772  provide part of the intermittent-rotation member  762 . A portion of the holding hole  764  to which the bearing  770  is attached, and a hole of the fitter member  772  in which the shaft member  768  is fitted cooperate with each other to provide a holding hole in which the shaft member  768  is fitted such that the member  768  is rotatable about an axis line thereof and is movable in an axial direction thereof.  
     [0166] A lower end portion of the shaft member  768  of each CC suction shaft  766  projects downward from the CC-suction-shaft holding member  760 , and has a nozzle holding hole  782  which is concentric with the axis line of the shaft member  768 . A CC suction nozzle  784  is fitted in the hole  782  such that the nozzle  784  is movable in an axial direction thereof relative to the hole  782 . Each CC suction nozzle  784  includes a suction-pipe holding member  786 , and a suction pipe  788  which is held by the holding member  786 , and is biased by a compression coil spring  790  as a sort of elastic member as a sort of biasing device, in a direction in which the nozzle  784  is moved downward in the nozzle holding hole  782 . Since a pin  792  as an engagement member which is fitted in the suction-pipe holding member  786  is engaged with a recess  794  as an engagement portion which is formed in a wall defining the hole  782 , the nozzle  784  is prevented from coming off the hole  782  and rotating relative to the shaft member  768 . Reference numeral  796  designates a reflector plate which is provided on the suction-pipe holding member  786 . Here, for the purpose of easier understanding only, it is assumed that the twenty CC suction nozzles  784  are of the same sort and therefore the respective suction pipes  788  thereof have the same diameter. The nozzles  784  can be selected from various sorts of nozzles which are suitable for sucking various sorts of CCs, so that the selected nozzles  784  are attached to the shaft members  768 , respectively. However, each sort of nozzles can suck and hold different sorts of CCs having different sizes.  
     [0167] An upper end portion of each shaft member  768  projects upward from the CC-suction-shaft holding member  760 , and a driven gear  800  and a cam-follower holding member  802  are fixed to the upper end portion of the shaft member  768  such that the former members  800 ,  802  are concentric with the latter member  768 . The diameter of the driven gear  800  is smaller than that of the drive gear  716 , and is meshed with the drive gear  716 . When the drive gear  716  is rotated, all the driven gears  800  meshed with the drive gear  716  are concurrently rotated, so that the twenty CC suction shafts  766  are concurrently rotated by the same angle in the same direction.  
     [0168] Each cam-follower holding member  802  holds a ball-like cam follower  804  therein, such that the cam follower  804  is rotatable in all directions and is prevented from coming thereoff and such that a portion of the cam follower  804  projects outward therefrom. Each CC suction shaft  766  is biased upward by a compression coil spring  806  as a sort of an elastic member as a sort of a biasing device which is provided in the annular passage  780 , so that the cam follower  804  is held in pressed contact with a cam surface  808  of the stationary cam  712 . One end portion of the spring  806  rests on a spring seat  810  which is fixed to the shaft member  768 , and the other end portion of the same  806  is held by a retainer (not shown) which is supported by a bearing  812  attached to the fitter member  772  such that the spring  806  is rotatable relative to the member  772 . Therefore, when each CC suction shaft  766  is rotated about an axis line thereof, the spring  806  is rotated together with the shaft  766  without being distorted or twisted. The shaft member  768  of the CC suction shaft  766  extends through the bearing  812  such that the shaft member  768  is rotatable relative to the bearing  812  and is movable in the axial direction thereof relative to the same  812 .  
     [0169] As shown in FIGS. 11 and 12, the stationary cam  712  includes a cam-surface defining cylindrical portion  814  which is concentric with the rotation shaft  708 , and a lower surface of the cylindrical portion  814  defines the cam surface  808 . The cam surface  808  is provided above the locus of revolution of the CC suction shafts  766  and, as shown in FIGS. 11 and 15, includes a portion whose height level or position continuously changes. Therefore, when the intermittent-rotation member  762  is rotated, each cam follower  804  is moved while rolling on the cam surface  808 . Thus, the twenty CC suction shafts  766  are sequentially moved upward and downward while being revolved around the axis line of the rotation shaft  708 .  
     [0170] When the intermittent-rotation member  762  is rotated and the CC suction shafts  766  are moved up and down while being revolved, the respective driven gears  800  fixed to the respective upper end portions of the respective shaft members  768  of the CC suction shafts  766  are moved up and down while being meshed with the drive gear  716 . The width of the drive bear  716  is greater than those of the driven gears  800 . That is, the dimension of the drive bear  716  as measured in a direction parallel to the axis line of rotation of the intermittent-rotation member  762  and parallel to the CC suction shafts  766 , is greater than those of the driven gears  800 . Therefore, even if the suction shafts  766  are moved up and down, the gears  800  remain meshed with the drive gear  716 .  
     [0171] The horizontal portion  704  of the X slide  654  has a recess  816  (FIGS. 11 and 13) formed along a part-cylindrical surface whose center rides on the axis line of rotation of the intermittent-rotation member  762 . Thus, the horizontal portion  704  does not interfere with the CC suction shafts  766  or the CCs  842  held by the shafts  766 .  
     [0172] The height of the cam surface  808  continuously increases from the lowest point thereof toward the diametrically opposite point thereof, in each of opposite directions, such that the cam surface  808  has the highest level at a point distant by 90 degrees from the lowest point in each direction. The rotation shaft  708  is intermittently rotated, that is, rotated by an angle equal to that at which the twenty CC suction shafts  766  are equiangularly spaced from one another, and then stopped for a suitable time. Thus, while the shaft  708  is intermittently rotated by 360 degrees, each of the suction shafts  766  is stopped at twenty stop positions. In the present embodiment, one of the twenty stop positions which corresponds to the lowest point of the cam surface  808  is utilized as a CC suck-and-mount position which can be called as a CC receive-and-mount position or a CC suck-and-release position, and another stop position which corresponds to the point which is distant by 90 degrees from the lowest point in one direction and has the highest level is utilized as a CC-image pick-up position. The cam surface  808  is so formed as to ensure that each suction shaft  766  is moved in a horizontal direction in the vicinity of each of the CC suck-and-mount position and the CC-image pick-up position. FIG. 16 shows the CC suck-and-mount position and the CC-image pick-up position. In this figure, white circles represent the respective reflector plates  796  of the CC suction nozzles  784 .  
     [0173] A CC-image pick-up device  820  is provided on the X slide  654 , at a position corresponding to the CC-image pick-up position. As shown in FIGS. 13 and 15, the pick-up device  820  is attached to one end portion of the horizontal portion  704  of the X slide  654  as viewed in the Y direction via brackets  824 ,  826 . The first bracket  824  is attached to the horizontal portion  704  by the engagement of screw members  828  with elongate holes  830 , so that the position of the bracket  824  is adjustable in the X direction, and the second bracket  826  is attached to the first bracket  824  by the engagement of screw members  832  with elongate holes  834 , so that the position of the bracket  826  is adjustable in the Y direction.  
     [0174] The CC-image pick-up device  820  includes a lighting device  836 , a reflecting device  838 , and a CCD (charge-coupled device) camera  840 . As shown in FIG. 13, the lighting device  836  and the reflecting device  838  are provided below the CC suction shaft  766  being stopped at the CC-image pick-up position and the CC  842  held by the suction shaft  766 , are oriented in a direction perpendicular to both a tangential line with respect to the locus of revolution of each suction shaft  766  at the CC-image pick-up position and the axis line of rotation of the intermittent-rotation member  762 , and are opposed to the CC  842 . The reflecting device  838  includes, e.g., a prism or a plurality of mirrors, and deflects the direction of propagation of an image forming light so that the deflected light is incident to the CCD camera  840 . The lighting device  838  includes two lighting sections  848  provided on both sides of the reflecting device  838 , respectively, and which emit lights toward the reflector plate  796  of each CC suction nozzle  784 . The positions of the CC-image pick-up device  820  in the X and Y directions can be adjusted by changing the positions where the two brackets  824 ,  826  are attached to the horizontal portion  704 . The lighting device  836  can be detached from the X slide  654 , by operating a manually operable member  850 .  
     [0175] Thus, the height level of the CC-image pick-up position is higher than that of the CC suck-and-mount position. The CC-image pick-up device  820  is provided in a space over which each CC suction shaft  766  is moved up by the cooperation of the stationary cam  712  and the cam follower  804 . Thus, the pick-up device  820  does not interfere with each CC suction nozzle  784  and the CC  842  held thereby, and does not interfere with the CC supplying device  14  and the PCB  408 . In addition, the distance over which each CC suction nozzle  784  is moved up and down for sucking or mounting the CC  842  at the CC suck and mount position, is reduced.  
     [0176] In the case where each CC suction shaft  766  takes the same height level at each of the CC suck and mount position and the CC-image pick-up position, it goes without saying that the pick-up device  820  must not interfere with each CC suction nozzle  784  and the CC  842  held thereby, and must not interfere with the CC supplying device  14  and the PCB  408 . In this case, however, the distance over which each CC suction nozzle  784  is moved up and down for sucking or mounting the CC  842  at the CC suck-and-mount position, is increased.  
     [0177] As shown in FIG. 11, the X slide  654  supports a reference mark image pick-up device  854  which picks up images of reference marks provided on each PCB  408 . More specifically described, the pick-up device  854  is attached to a lower portion of the pendent portion  702  which is opposite to the CC image pick-up device  820  as viewed in the Y direction, such that the pick-up device  854  is oriented downward.  
     [0178] Each CC suction nozzle  784  sucks the CC  842  by applying a negative pressure or vacuum to the same  842 . Respective pressure switch valves  860  for the twenty CC suction shafts  766  are fixed to the outer surface of the CC-suction-shaft holding member  760  such that the switch valves  860  are equiangularly spaced from one another (only two valves  860  are shown in FIG. 15). As shown in FIG. 12, each CC suction shaft  766  has a passage  862  which extends in the axial direction of the shaft  766  and which communicates with the nozzle holding hole  782 . The passage  862  also communicates with the switch valve  860  via the passage  780  provided between the holding hole  764  and the suction shaft  766  and a passage (not shown) formed in the CC-suction-shaft holding member  760 .  
     [0179] As shown in FIG. 11, the negative pressure is supplied to a passage  866  and an annular passage  868  which are formed in the horizontal portion  704  and the support portion  706  of the X slide  654 , and a passage  870  which is formed in the rotation shaft  708 , and finally to the twenty pressure switch valves  860  via hoses (not shown). The passage  866  is connected to a vacuum source via a hose (not shown) which is attached to the X slide  654  with a joint member. The communication of the passage  870  with the passage  866  via the annular passage  868  is maintained while the rotation shaft  708  is rotated.  
     [0180] As shown in FIG. 12, each pressure switch valve  860  includes a housing  872  and a movable switch member  874  which is provided in the housing  872  such that the switch member  874  is linearly movable up and down so as to selectively supply the CC suction nozzle  784  with a negative pressure or a pressure not lower than the atmospheric pressure. When the switch member  874  is moved down to its negative-pressure (“NP”) supply position, the pressure switch valve  860  changes the pressure in the nozzle  784  from the pressure not lower than the atmospheric pressure, to the negative pressure, so that the nozzle  784  can suck and hold the CC  842 . The state in which the switch member  874  is at its NP supply position, will be referred to as the “NP supply state” of the switch valve  860 . Meanwhile, when the switch member  874  is moved up to its NP remove position, the pressure switch valve  860  changes the pressure in the nozzle  784  from the negative pressure to the pressure not lower than the atmospheric pressure, so that the nozzle  784  can release the CC  842 . The state in which the switch member  874  is at its NP remove position, will be referred to as the “NP remove state” of the switch valve  860 . The switch member  874  has, at its axially opposite ends thereof, two large-diameter stopper portions  876 ,  878 , respectively, which stop the movement of the switch member  874  in its axial direction at its NP supply and remove positions, respectively. The switch member  874  is adapted such that once it is moved to each of the NP supply and remove positions, it is held at that position.  
     [0181] As shown in FIGS. 17, 18, and  19 , there are provided, on the X slide  654  and in the vicinity of the CC suck-and-mount position, an individual-CC-suction-shaft elevating and lowering device  880  which elevates and lowers each CC suction shaft  766 , and a mechanical portion of a switch-valve control device  882 .  
     [0182] As shown in FIGS. 17 and 19, a linear motor  886  as a drive-source device is fixed to a portion of the X slide  654  which corresponds to the CC suck-and-mount position. The linear motor  886  includes an output member  888  which projects vertically downward from a housing of the motor  886  and to which a movable member  890  is fixed.  
     [0183] As shown in FIGS. 20 and 22, the movable member  890  has a recess  891  formed through the thickness thereof in a direction parallel to a tangential line with respect to the locus of revolution of each CC suction shaft  766  at the CC suck and mount position. An axis member  894  is fixed to the movable member  890  at a position laterally offset from the locus of revolution of the CC suction shaft  766  (indicated at one-dot chain line in FIG. 22), and a drive member  892  is attached to the axis member  894  such that the drive member  892  is rotatable about a vertical axis line, i.e., the axis member  894 . As shown in FIG. 18, an end portion of the drive member  892  which projects from the axis member  894  toward the stationary cam  712  provides a thin-plate-like drive portion  896  which can fit in a recess  898  (FIGS. 18 and 21) which is formed in a portion of the cam  712  which corresponds to the CC suck-and-mount position, such that the drive portion  896  is movable downward, and upward, out of, and into, the recess  898 . The recess  898  has a width (i.e, dimension in the circumferential direction of the cam  712 ) which allows the drive portion  896  to be fitted therein without any clearance and be released therefrom, and a depth (i.e., dimension in a direction parallel to the center line of the cam  712 ) which is slightly greater than the thickness of the drive portion  896  and which allows each cam follower  804  to continue moving while rolling thereover.  
     [0184] When the movable member  890  is elevated and lowered by the linear motor  886 , the drive member  892  is elevated and lowered between an upper position where the drive portion  896  is fitted in the recess  898  such that the drive portion  896  can be elevated and lowered and where the lower surface of the drive portion  896  is flush with the cam surface  808  of the stationary cam  712 , and a lower position where the drive portion  896  is released from the recess  898  and where the lower surface of the drive portion  896  is below the cam surface  808 . The upper surface of the drive portion  896  has a pair of obliquely cut end portions (not shown) which are opposite to each other in the direction of revolution of each CC suction shaft  766  and which function as guide portions for guiding the drive portion  896  when the portion  896  is fitted in the recess  898 .  
     [0185] As shown in FIG. 20, the drive member  892  has a notch  900  which is formed in the lower surface of the other end portion thereof opposite to the drive portion  896  and which extends in a longitudinal direction thereof perpendicular to the axis line of rotation thereof and functions as a positioning recess. A positioning device  902  which is called as a “ball springe” is attached to the movable member  890 . The positioning device  902  includes a casing  906  which is screwed in the movable member  890 , and a ball  908  as a positioning member which is accommodated in the casing  906  such that the ball  908  is movable therein and is prevented from coming thereoff. The ball  908  is biased by a spring (not shown) as a sort of elastic member as a sort of biasing member which is accommodated in the casing  906 , in a direction in which the ball  908  projects outward from the casing  906 .  
     [0186] As shown in FIGS. 21 and 22, a bracket  912  is fixed to the movable member  890 , and an adjustor bolt  914  as a stopper member whose position is adjustable is screwed in the bracket  912 . The adjustor bolt  914  is provided adjacent to the other end portion of the drive member  892  which is opposite to the drive portion  896  thereof, and on the downstream side of the drive member  892  in the direction of revolution of each CC suction shaft  766  indicated at arrow in FIG. 22. The adjustor bolt  914  is screwed in the bracket  912  such that the bolt  914  extends perpendicular to the axis line of revolution of the movable member  892  and in a direction parallel to the tangential line with respect to the locus of rotation of the CC suction shaft  766  at the CC suck-and-mount position. The adjustor bolt  914  stops the rotation of the drive member  892  being positioned at its lower position due to its malfunction, in a direction opposite to a direction in which the drive member  892  is rotated by the CC suction shaft  766 .  
     [0187] The position of a free end of the adjustor bolt  914  is so adjusted that with the drive member  892  being in contact with the bolt  914 , the ball  908  fits in the notch  900  such that the ball  908  engages one of a pair of opposite inner oblique surfaces of the notch  900  which is nearer to the bolt  914 , and separates from the other inner oblique surface, so that the ball  908  presses the drive member  892  against the bolt  914  and thereby accurately positions the drive portion  896  at its operative position (indicated at solid line in FIG. 22) where the drive portion  896  can fit in the recess  898  formed in the stationary cam  712 . Thus, the notch  900  and the positioning device  902  cooperate with each other to provide a biasing device, which cooperates with the adjustor bolt  914  to provide a positioning device as a sort of clip-stop device.  
     [0188] There is provided, on the X slide  654 , a drive-member retraction sensor  920  (FIG. 24) which detects that the drive member  892  has been rotated to its retracted position indicated at two-dot chain line in FIG. 22. The retraction sensor  920  is provided by a transmission-type photoelectric sensor including a light emitter and a light detector, and detects that the drive member  892  has been rotated to its retracted position, when the drive portion  896  of the drive member  892  interrupts the light emitted by the light emitter, i.e., when the light detector fails to detect the light emitted by the light emitter. However, the retraction sensor  920  may be provided by a reflection-type photoelectric sensor, a proximity switch, a limit switch, or the like.  
     [0189] As shown in FIGS. 19, 20, and  21 , a main air cylinder  930  is attached to the movable member  890  such that the height position of the cylinder  930  is adjustable. The height position of the main air cylinder  930  relative to the movable member  890  is defined by the contact thereof with an adjustor bolt  932  which is screwed in the movable member  890  and, in this state, the cylinder  930  is fixed to the movable member  890  by screwing bolts  940  in the member  890  through elongate holes  938  of an attachment portion  936  (FIG. 21) which is integral with a cylinder tube  934  (FIG. 23).  
     [0190] The main air cylinder  930  is provided by an air cylinder as a sort of fluid-pressure-operated cylinder device. The cylinder  930  is of a double-action type and, as shown in FIG. 23, includes a piston  944  which is airtightly fitted in the cylinder tube  934  such that the piston  944  is movable in the axial direction of the tube  934 , and a piston rod  946  which projects downward from the tube  934 . A stepped through-hole  948  is formed in the piston  944  and the piston rod  946 , such that the hole  948  extends through the members  944 ,  946  in the axial direction of the tube  934 . The through-hole  948  includes a large-diameter portion  950  in which a fitting portion  954  of an operative member  952  fits such that the portion  954  is movable in the axial direction.  
     [0191] The operative member  952  includes a shaft portion  956  which extends from the fitting portion  954  and projects downward from the piston rod  946  through a small-diameter portion  958  of the through-hole  948 , and which includes an operative portion  960 . The operative member  952  is biased by a compression coil spring  962  as a sort of elastic member as a sort of biasing member which is provided in the large-diameter portion  950 , in a downward direction in which the piston rod  946  projects from the cylinder tube  934 . The downward movement of the operative member  952  due to the biasing force of the spring  962  is stopped or limited by the engagement of the fitting portion  954  with the bottom wall of the piston rod  946 . One end of the spring  962  is seated on a plug  964  which is screwed in an opening of the piston  944 . The main air cylinder  930  is provided at a position right above the switch member  874  of the pressure switch valve  860  associated with the CC suction shaft  766  being stopped at the CC suck-and-mount position. Thus, the operative member  952  is positioned right above the switch member  874 .  
     [0192] As shown in FIGS.  17  to  19 , a bracket  970  is fixed to a portion of the X slide  654  which is near to the CC suck-and-mount position, such that the bracket  970  extends downward from the X slide  654 . A straight guide rail  972  as a guide member is fixed to a vertical side surface of the bracket  970 , such that the guide rail  972  vertically extends. A cylinder tube  976  of a main air cylinder  974  as a sort of fluid-pressure-operated cylinder device fits on the guide rail  972  via a guide block  978  as a guided member.  
     [0193] The main air cylinder  974  is of a double-action type and, as shown in FIG. 19, includes a piston  980  which is airtightly accommodated in the cylinder tube  976  such that the piston  980  is movable in the tube  976 . A piston rod  982  which extends from the piston  980  projects downward from the tube  976 , and an auxiliary air cylinder  984  as another fluid-pressure-operated cylinder device is attached to an externally threaded lower end portion  986  of the rod  982 . The threaded portion  986  is screwed in a cylinder tube  988  of the auxiliary air cylinder  984 . The height position of the auxiliary air cylinder  984  relative to the main air cylinder  974  can be adjusted by changing the amount of threaded engagement of the threaded portion  986  with the cylinder tube  988 .  
     [0194] The auxiliary air cylinder  984  is of a double-action type, and the cylinder tube  988  fits on the guide rail  972  via a guide block  990  as a guided member such that the tube  988  is movable on the rail  972 . The air cylinder  984  includes a piston  992  which is airtightly fitted in the cylinder tube  988  such that the piston  992  is movable in the tube  988 . A piston rod  994  which is integral with the piston  992  projects downward from the tube  988 , and has an externally threaded lower end portion  996  with which a support member  998  is threadedly engaged. The support member  998  fits on the guide rail  972  via a guide block  1000  as a guided member, such that the support member  998  is movable on the rail  972 . The height position of the support member  998  relative to the auxiliary air cylinder  984  can be adjusted by changing the amount of threaded engagement of the threaded portion  996  with the support member  998 .  
     [0195] An operative member  1002  fits, via a guide block  1004  as a guided member, on a lower end portion of the guide rail  972  which is below the support member  998 , such that the operative member  1002  is movable on the rail  972 . A tension coil spring  1006  as a sort of elastic member as a sort of biasing member is provided between the operative member  1002  and the support member  998 , so that the operative member  1002  is biased in a direction toward the support member  998 . A cushion member  1008  which is formed of an elastic material (e.g., rubber) is fixed to the lower surface of the support member  998 , and is fitted in a blind hole  1010  which is formed in the operative member  1002  such that the cushion member  1008  is movable relative to the hole  1010 . The upward movement of the operative member  1002  due to the biasing force of the spring  1006  is stopped or limited by the contact of the cushion member  1008  with the bottom of the blind hole  1010 . The cushion member  1008  absorbs the impact which is produced when the operative member  1002  is moved upward by the biasing force of the spring  1006  and is stopped at its upper position.  
     [0196] As shown in FIG. 17, the operative member  1002  projects horizontally toward the intermittent-rotation member  762  from a base portion of the member  1002  which fits on the guide rail  972 , and an end portion of the member  1002  is positioned below the switch member  874  of the pressure switch valve  860  of the CC suction shaft  766  being stopped at the CC suck-and-mount position. Thus, the operative member  1002  has a generally L-shaped configuration as shown in FIG. 18. A contact member  1014  which is screwed in the end portion of the operative member  1002  provides an operative portion of the operative member  1002 . The contact member  1014  has a groove  1016  which is formed through an upper portion thereof in a diametrical direction thereof.  
     [0197] As shown in FIGS. 18 and 19, the operative member  1002  is connected to an air-supply device (not shown) via a joint member  1018  and an air supply hose (not shown). The air (pressurized air) supplied from the air supply device is conducted through a passage  1020  formed in the operative member  1002  and a passage  1022  formed in the contact member  1016 , so that the air blows upward. A solenoid-operated shut-off valve  1024  (FIG. 24) which is provided between the joint member  1018  and the air supply device, permits the air to be supplied to the operative member  1002  and inhibits the air from being supplied to the same  1002 . The joint member  1018  is equipped with a variable throttle valve  1026  which is operable for changing the amount of air supplied from the air supply device to the operative member  1002 .  
     [0198] As shown in FIGS. 18 and 19, a link  1030  is attached via an axis member  1032  to the bracket  970  such that the link  1030  is rotatable about an axis line parallel to a tangential line with respect to the locus of revolution of the pressure switch valve  860  of the CC suction shaft  766  being stopped at the CC suck-and-mount position. A movable member  1034  is provided as an integral part of the cylinder tube  976  of the main air cylinder  974 , and a roller  1036  is attached to the movable member  1034  such that the roller  1036  is rotatable. The roller  1036  fits in a recess  1038  (FIG. 18) formed through one end portion of the link  1030 , such that the roller  1036  is rotatable.  
     [0199] The link  1030  has another recess  1040  (FIG. 18) formed through the other end portion thereof. A roller  1042  (FIG. 21) is attached to the movable member  890  which is moved up and down by the linear motor  886 , such that the roller  1042  is rotatable. The roller  1042  fits in the recess  1040  such that the roller  1042  is rotatable. Therefore, when the movable member  890  is moved upward and downward by the linear motor  886 , the link  1030  is rotated, so that the movable member  1034  is moved downward and upward in synchronism with the upward and downward movements of the movable member  890 , respectively. Thus, the two operative members  952 ,  1002  simultaneously move toward, and away from, the switch member  874  of the pressure switch valve  860 . That is, when the operative member  952  moves toward, and away from, the switch member  874 , the operative member  1002  also moves toward, away from, the same  874 .  
     [0200] The present CC mounting system  8  includes a control device  1050  which is provided by a computer  1052  as shown in FIG. 24. The computer  1052  includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), an input interface, an output interface, and a bus which connects those elements. To the computer  1052 , are connected the PCB-arrival sensor  504 , the deceleration-start-position sensor  620 , the PCB-arrival sensor  622 , the drive-gear initial-position sensor  732 , the rotation-shaft initial-position sensor  750 , the CC-image pick-up device  820 , the reference-mark image pick-up device  854 , and the drive-member retraction sensor  920 . The computer  1052  is connected via respective drive circuits (not shown) to an air-cylinder-control solenoid-operated valve  1058  which controls the air cylinder of the engaging device  68 ; the electric motors  202 ,  226 ; a rodless-cylinder control solenoid-operated valve  1060  which controls the rodless cylinder  436 ; the PCB conveying motors  486 ,  558 ; an air-cylinder-control solenoid-operated valve  1062  which controls the air cylinder  634 ; the Y-direction servomotor  674 ; the X-direction servomotor  688 ; the rotation-position correcting and changing servomotor  724 ; the rotation-body rotating servomotor  742 ; the linear motor  886 ; main-air-cylinder-control solenoid-operated valves  1064 ,  1066  which control the main air cylinders  930 ,  974 , respectively; an auxiliary-air-cylinder-control solenoid-operated valve  1068  which controls the auxiliary air cylinder  984 ; and the solenoid-operated shut-off valve  1024 . The linear motor  886  which linearly moves the movable member  890  and thereby elevates and lowers the drive member  892 , can be feed-back controlled to accurately position each CC suction shaft  766  and accurately decelerate and accelerate the same  766  via the movable member  890  and the drive member  892 . The ROM stores various control programs which are needed for supplying, sucking, and mounting the CCs  842  and carrying in and out the PCBs  408 .  
     [0201] Next, there will be described the operation of the present CC mounting system  8 .  
     [0202] The first and second CC mounting devices  18 ,  20  alternately mount the CCs  842  on the PCB  408  which is positioned and supported by either one of the first and second main conveyors  400 ,  402 . That is, the two CC mounting devices  18 ,  20  cooperate with each other to mount all the CCs  842  that are to be mounted on each PCB  408 . While the two CC mounting devices  18 ,  20  mount the CCs  842  on one PCB  408  positioned and supported by one of the two main conveyors  400 ,  402 , another PCB  408  is carried in onto the other main conveyor, and positioned and supported thereby, so that the PCB  408  waits for the CC mounting devices  18 ,  20  to mount the CCs  842  thereon. After the CC mounting devices  18 ,  20  finish mounting the CCs  842  on one PCB  408  on one main conveyor  400  or  402 , then the devices  18 ,  20  start mounting the CCs  842  on another PCB  408  on the other main conveyor  402  or  400 .  
     [0203] First, there will be described the manner in which the PCB  408  is carried in onto, positioned and supported by, and carried out from, the main conveyor  400 ,  402 . The following description is made on the assumption that the CC mounting devices  18 ,  20  have already started their operations and are now in their steady operating state.  
     [0204] The PCB  408  is conveyed onto the carry-in conveyor  404  from the screen printing system  2  which is provided on the upstream side of the present CC mounting system  8 , while the carry-in conveyor  404  is positioned at its first shift position. When the carry-in conveyor  404  is moved to its first shift position, the PCB conveying motor  486  is started, and the PCB  408  is received from the screen printing system  2  by the carry-in conveyor  404 . The control device  1050  can identify which position the carry-in conveyor  404  is taking, the first or second shift position, based on the detection signal supplied from the stroke-end sensor (not shown) which detects that the piston of the rodless cylinder  436  has been moved to its stroke end. When the PCB  408  which has been conveyed onto the carry-in conveyor  404  is detected by the PCB-arrival sensor  504 , the PCB conveying motor  486  is stopped, so that the PCB  408  is stopped on the carry-in conveyor  404 . In the case where the carry-in conveyor  404  carries in the PCB  408  onto the first main conveyor  400 , the carry-in conveyor  404  is kept at its first shift position.  
     [0205] However, the control device  1050  judges that an abnormality has occurred, if the PCB-arrival sensor  504  does not detect the PCB  408  even though more than a predetermined time has passed after the conveying of the PCB  408  from the screen printing system  2  has started. In this case, the control device  1050  automatically interrupts the CC mounting operations of the CC mounting devices  18 ,  20 , and informs an operator of the occurrence of the abnormality. This interruption means that even after the devices  18 ,  20  have finished mounting all the CCs  842  on the current PCB  408  and then the PCB  408  has been carried out off the current main conveyor, the devices  18 ,  20  do not start mounting the CCs  842  on the next PCB  408  on the other main conveyor.  
     [0206] If, because a PCB  408  has been carried out from the first main conveyor  400  onto the carry-out conveyor  406  (the PCB carrying-out operation will be described later), another PCB  408  can be carried in onto the main conveyor  400 , the carry-in conveyor  404  carries in another PCB  408  onto the main conveyor  400 . The control device  1050  judges whether a PCB  408  can be carried in onto the first main conveyor  400 , by judging whether the PCB-arrival sensor  622  as a CS detecting device is detecting the preceding PCB  408 . In a step where a PCB  408  is carried in onto the main conveyor  400 , the control device  1050  judges whether the PCB  408  has been carried in and placed on the main conveyor  400 , based on the detection signal supplied from the PCB-arrival sensor  622 . In other steps, the control device  1050  judges that there is no PCB  408  on the main conveyor  400  and accordingly a PCB  408  can be supplied to the main conveyor  400 , if the PCB-arrival sensor  622  does not detect any PCB  408 .  
     [0207] When a PCB  408  is carried in, the PCB conveying motor  486  of the carry-in conveyor  404  and the PCB conveying motor  558  of the main conveyors  400 ,  402  are started, so that the conveyor belts  546  are moved. Thus, the PCB  408  is placed onto the main conveyor  400 . In this state, the stopper member  630  of the PCB stopping device  624  of the main conveyor  400  has been moved to its operative position. Subsequently, when the deceleration-start-position sensor  620  detects the PCB  408 , the control device  1050  controls the PCB conveying motor  558  to start decelerating the speed of movement of the conveyor belts  546 . Then, when the PCB-arrival sensor  622  detects the PCB  408 , the control device  1050  stops the PCB conveying motor  558 . At this moment, the PCB  408  has been stopped by the stopper member  630 , while being held in butting contact with the same  630 . Since the speed of movement of the PCB  408  has been decreased, the PCB  408  butts against the stopper  630  while producing only reduced impact.  
     [0208] However, if the PCB-arrival sensor  622  does not detect any PCB  408  even though more than a predetermined time has passed after the PCB conveying motor  558  has been started, the control device  1050  judges that an abnormality has occurred. Hence, the control device  1050  interrupts the current CC mounting operation and informs the operator of the occurrence of the abnormality.  
     [0209] After the PCB conveying motor  558  is stopped, the elevator table  598  is moved up, so that the PCB suction devices  602  suck and support the PCB  408  and simultaneously the thrust-up members  580  thrust up the PCB  408  and press the same  408  against the hold-down portions  570 ,  572 . Thus, the PCB  408  being positioned and supported by the first main conveyor  400  waits for the CC mounting devices  18 ,  20  to mount the CCs  842  thereon. Therefore, after one of the two CC mounting devices  18 ,  20  mounts the last CC  842  on the PCB  408  positioned and supported by the second main conveyor  402 , the one CC mounting device is moved away from the second main conveyor  402  to the corresponding CC supplying device  14 ,  16  and simultaneously the other CC mounting device is moved to the first main conveyor  400  to start mounting the CCs  842  on the waiting PCB  408 . Thus, it needs substantially no time after the CC mounting devices  18 ,  20  finish the CC mounting operation on one PCB  408  and before the same  18 ,  20  start the same operation on another PCB  408 . Accordingly, the present CC mounting system  8  can mount the CCs  842  on the PCBs  408  with high efficiency. The manner in which the CCs  842  are mounted on the PCBs  408  will be described later.  
     [0210] The PCB conveying motor  558  is common to the two main conveyors  400 ,  402 . Accordingly, when the motor  558  is started, the conveyor belts  546  of both the two main conveyors  400 ,  402  are moved. However, while the CCs  842  are mounted on the PCB  408 , the PCB  408  is thrusted up away from the conveyor belts  546 . Therefore, the PCB  408  is not moved even if the conveyor belts  546  are moved. Thus, the CCs  842  can be mounted on one PCB  408  positioned and supported by one main conveyor, while concurrently another PCB  408  is carried in onto the other main conveyor or carried out from the same.  
     [0211] After the last CC  842  is mounted on the PCB  408 , the PCB suction devices  602  are communicated with the atmosphere, so that the PCB  408  is released from the suction devices  602 . Subsequently, the elevator table  598  is moved down, so that the PCB  408  is placed again on the conveyor belts  546 . The PCB conveying motors  486 ,  558  of the carry-out conveyor  406  and the main conveyors  400 ,  402  are started, so that the PCB  408  is placed onto the carry-out conveyor  406 . In the case where the PCB  408  is carried out from the first main conveyor  400 , the carry-out conveyor  406  has already been shifted to its first shift position, and the stopper member  630  has already been moved to its inoperative position.  
     [0212] When the PCB-arrival sensor  504  of the carry-out conveyor  406  detects the PCB  408 , the control device  1050  stops the PCB conveying motors  486 ,  558 , so that the PCB  408  waits on the carry-out conveyor  406  for being fed to the solder reflowing system  4  provided on the downstream side of the CC mounting system  8 . However, the PCB  408  may be immediately fed to the solder reflowing system  4 , if possible, without stopping of the PCB conveying motor  486  of the carry-out conveyor  406 . In the PCB carrying-out step, too, the control device  1050  judges that an abnormality has occurred, if the PCB-arrival sensor  504  does not detect any PCB  408  even though more than a predetermined time has passed after the PCB conveying motors  486 ,  558  have been started. Then, the control device  1050  interrupts the current CC mounting operation and informs the operator of the occurrence of the abnormality.  
     [0213] After the carry-in conveyor  404  hands over one PCB  408  to the first main conveyor  400 , it receives another PCB  408  from the screen printing system. Then, the carry-in conveyor  404  is shifted to its second shift position, by the movement of its conveyor support table  426 . Thus, the carry-in conveyor  404  waits for handing over the PCB  408  to the second main conveyor  402 . After the last CC  842  is mounted on the preceding PCB  408  on the second main conveyor  402  and that PCB  408  is carried out therefrom, the carry-in conveyor  404  hands over the PCB  408  to the second main conveyor  402 .  
     [0214] After the carry-out conveyor  406  hands over one PCB  408  received from the first main conveyor  400 , to the solder reflowing system provided on the downstream side of the CC mounting system  8 , it is shifted, by the movement of its conveyor support table  426 , to its second shift position where it waits for receiving another PCB  408  from the second main conveyor  402 . After the carry-out conveyor  406  receives the PCB  408  from the second main conveyor  402 , it is shifted to its first shift position where it hands over the PCB  408  to the solder reflowing system.  
     [0215] After one PCB  408  is carried in from the carry-in conveyor  404  onto the second main conveyor  402 , the PCB  408  is positioned and supported by the second main conveyor  402 , in the same manner in which a PCB  408  is positioned and supported by the first main conveyor  400 . Thus, the PCB  408  waits on the second main conveyor  402  for the CC mounting devices  18 ,  20  to mount the CCs  842  on the PCB  408 . After the last CC  842  is mounted on the PCB  408  positioned and supported by the first main conveyor  400 , the CC mounting devices  18 ,  20  start mounting the CCs  842  on the PCB  408  positioned and supported by the second main conveyor  402 . After the last CC  842  is mounted on the PCB  408  on the second main conveyor  402 , the PCB  408  is moved onto the carry-out conveyor  406 .  
     [0216] When, in place of the current sort of PCBs  408  having a certain width, another sort of PCBs  408  having a different width are used, it is needed to change the current PCB conveying width of the main conveyors  400 ,  402 , the carry-in conveyor  404 , and the carry-out conveyor  406 . To this end, the operator rotates the handle  510  to move the chain  470 , under the state in which no PCB  408  is supported on the conveyors  400 ,  402 ,  404 ,  406 . Thus, the respective movable frames  442 ,  526  of the conveyors  400  to  406  are simultaneously moved in the same direction and by the same distance, and the PCB conveying width of the conveyors  400  to  406  is changed to a new value.  
     [0217] Next, there will be described the manner in which CCs  842  are mounted on each PCB  408 .  
     [0218] The two CC mounting devices  18 ,  20  alternately mount CCs  842  on one PCB  408 . The first CC mounting device  18  is supplied with CCs  842  from the first CC supplying device  14  only, and the second CC mounting device  20  is supplied with CCs  842  from the second CC supplying device  16  only. The first CC mounting and supplying devices  18 ,  14  are provided on the same, one side of the conveyors  400  to  406 , and the second CC mounting and supplying devices  20 ,  16  are provided on the same, other side of the conveyors  400  to  406 . Therefore, when the respective CC mounting heads  650 ,  652  of the two CC mounting devices  18 ,  20  receive and mount the CCs  842 , the respective Y slides  658 ,  660  of the two devices  18 ,  20  do not interfere with each other.  
     [0219] Before the CC mounting operation is started, the image of the reference marks of each PCB  408  are taken by the reference-mark-image pick-up device  854 . This is done while the PCB  408  waits for the CC mounting operation after having been carried in onto the main conveyor  400  (or  402 ) and positioned and supported thereon. This is done by the reference-mark-image pick-up device  854  of one  18  (or  20 ) of the CC mounting devices which corresponds to the main conveyor  400  (or  402 ) supporting the waiting PCB  408 . While the CC mounting operation is carried out on one PCB  408  positioned and supported on one main conveyor  400  (or  402 ), another PCB  408  is carried in onto the other main conveyor  402  (or  400 ) and is positioned and supported by the same. The CC mounting device  20  (or  18 ) corresponding to the other main conveyor  402  (or  400 ) takes the image of the reference marks of the PCB  408  on the other main conveyor, midway when it goes and fetches CCs  842  from the corresponding CC supplying device  16  (or  14 ) after it has mounted, on the PCB  408  on the one main conveyor  400  (or  402 ), all the CCs being currently held thereby. Even at a timing at which all the CCs that should be mounted on one PCB  408  have not been mounted on the PCB  408  yet, the image of the reference marks of the next PCB  408  may be taken, if the next PCB  408  has been carried in. Each PCB  408  has two reference marks on a diagonal line thereof. While the control device  1050  controls the CC mounting devices  18 ,  20  to suck and mount the CCs  842 , the computer  1052  calculates, based on the image data representative of the taken image of the reference marks, an X-direction and a Y-direction position error of each of predetermined CC-mount places on the PCB  408 , and stores the calculated errors in the RAM thereof.  
     [0220] There will be described the operation of the CC mounting head  650  as a representative of the two CC mounting heads  650 ,  652 .  
     [0221] First, the CC mounting head  650  is moved to the CC supplying device  14 , to take a predetermined number of CCs  842  from the supplying device  14 . Here it is assumed that the mounting head  650  continuously mounts twenty CCs  842  on the PCB  408 , each time, and accordingly each of the twenty CC suction shafts  766  of the head  650  takes one CC  842 . In addition, for the purpose of easier understanding only, it is assumed that the feeders  54  which feed the respective sorts of CCs  842  to the head  650  are arranged in the same order in which the head  650  mounts the respective sorts of CCs  842  on the PCB  408 . Each time the intermittent-rotation body  762  is rotated by one angular pitch (i.e., 360°/20=18°) and then stopped, and is linearly moved in the X direction by one pitch (i.e., pitch at which the feeders  54  are provided), each one of the twenty CC suction nozzles  784  is rotated to the CC suck-and-take position where the one nozzle  784  sucks a CC  842  from a corresponding feeder  54  being positioned thereunder.  
     [0222] More specifically described, the CCs  842  are taken from the feeders  54 , while the intermittent-rotation body  762  is intermittently rotated and accordingly the twenty CC suction shafts  766  are sequentially positioned at the CC suck-and-mount position and while the body  762  is sequentially moved by the X-Y robot  662  to respective CC taking positions of the feeders  54  which feed the respective sorts of CCs  842 . When the body  762  is intermittently rotated, the drive gear  716  is also rotated in the same direction at the same angular velocity. Thus, the CC suction shafts  766  are not rotated relative to the body  762 .  
     [0223] Before each CC suction shaft  766  reaches the CC suck-and-mount position, the cam follower  804  of the suction shaft  766  engages the lower surface of the drive portion  896  of the drive member  892 . Following this engagement, the linear motor  886  is started to lower the movable member  890 , so that the drive member  892  is lowered and the shaft  766  is also lowered. Thus, the CC suction shaft  766  is lowered while being revolved. Before the nozzle  784  contacts the CC  842 , the shaft  766  reaches the CC suck-and-mount position and stops thereat. Thus, the nozzle  784  can contact the CC  842  with high accuracy. While the shaft  766  is lowered at the CC suck-and-mount position by the drive member  892 , the driven gear  800  remains meshed with the drive gear  716 .  
     [0224] The CC carrier tapes  156  fed by the feeders  54  are emboss-type carrier tapes in which the respective upper surfaces of the CCs  842  accommodated in the respective embossed CC pockets of the tape take a predetermined height position in a vertical direction parallel to the direction of movement of the CC suction shafts  766 , even though the respective sorts of CCs  842  carried by the CC carrier tapes  156  may have different height dimensions. The twenty nozzles  784  are of the same sort, and accordingly the lower end surface (i.e., suction surface) of the suction pipe  788  of each nozzle  784  being positioned at the CC suck-and-mount position takes a predetermined height position. Therefore, the distance between the lower end surface of the suction pipe  788  of each nozzle  784  being positioned at the CC suck-and-mount position, and the upper surface of the CC  842  being positioned at the CC taking position on each feeder  54 , is constant even though the respective sorts of CCs  842  fed by the feeders  54  may have different height dimensions. Thus, the drive member  892  is moved down and up by a predetermined distance which is slightly greater than the distance between the lower surface of the suction pipe  788  and the upper surface of the CC  842 . After the suction pipe  788  contacts the CC  842 , the drive member  892  is further lowered by a small distance, so that the suction pipe  788  can surely suck the CC  842 . An excessive downward movement of the nozzle  784  is accommodated or absorbed by the compression of the compression coil spring  790 . The control device  1050  controls the linear motor  886  to lower each CC suction shaft  766  such that the shaft  766  is initially accelerated smoothly and then is decelerated smoothly. Thus, the suction pipe  788  can butt on the CC  842  with reduced impact only. The drive member  892  is decelerated smoothly, also when it is additionally lowered after the suction pipe  788  has contacted the CC  842 . Since the linear motor  886  is used as the drive source for moving up and down each CC suction shaft  766 , the control device  1050  can be programmed to move the shaft  766  at any desired speed or by any desired distance. Thus, the CCs  842  can be sucked or mounted in a shorter time.  
     [0225]FIG. 25 shows a time chart representing a relationship among the operation of the X-Y robot  662  (i.e., the movements of the CC mounting head  650 ), the intermittent rotations of the intermittent-rotation body  762 , and the upward and downward movements of the CC suction shaft  766  being positioned at the CC suck-and-mount position. The curve associated with the X-Y robot  662  represents the time-wise change of speed of movement of the robot  662 ; the curve associated with the intermittent-rotation body  762  represents the time-wise change of speed of rotation of the body  762 ; and the curve associated with the CC suction shaft  766  represents the time-wise change of speed of upward and downward movements of the shaft  766 . An increasing and a decreasing portion of each of the above three curves represent an increasing and a decreasing speed, respectively. In FIG. 25, CORRECTING AND CHANGING OF ROTATION POSITION OF CC means, as described later, that a possible rotation-position error of the CC  842  held by each CC suction shaft  766  is corrected, or the current rotation position of the CC is changed to its predetermined rotation position at which the CC is mounted on the PCB  408 . This operation is effected by rotating the drive gear  716  and thereby rotating the shaft  766 . The curve associated with CORRECTING AND CHANGING OF ROTATION POSITION OF CC represents the time-wise change of speed of rotation of the shaft  766 . The curve associated with FEEDERS  54  represents the time-wise change of speed of feeding of the CC carrier tapes  156  by the feeders  54 . The curve associated with CC-IMAGE PICK-UP DEVICE  820  represents the times of occurrence of events that the CC-image pick-up device  820  takes the images of the CCs  842  held by the CC suction shafts  766 .  
     [0226] As the movable member  890  is lowered, the main air cylinder  930  is lowered, so that the operative member  952  is lowered. In addition, the link  1030  is rotated, so that the movable member  1034  is elevated and the operative member  1002  is elevated. When the CCs  842  are sucked or mounted, the control device  1050  outputs, as shown in FIG. 26, drive commands to the main air cylinders  930 ,  974  and the auxiliary air cylinder  984 , so that the main-air-cylinder control valves  1064 ,  1066  and the auxiliary-air-cylinder control valve  1068  are switched. More specifically described, the control device  1050  outputs “ON” commands to those air cylinders which are required to operate for moving the operative members  952 ,  1002  to their operative positions, and outputs “OFF” commands to those air cylinders which are required to operate for moving the operative members  952 ,  1002  to their inoperative positions. When the CCs  842  are sucked, the piston rod  946  of the main air cylinder  930  is advanced from the cylinder tube  934 , so that the operative member  952  is positioned at its operative position where the operative member  952  is distant from the cylinder tube  934 . Simultaneously, the piston rod  982  of the main air cylinder  974  is advanced from the cylinder tube  976  and the piston rod  994  of the auxiliary air cylinder  984  is retracted into the cylinder tube  988 , so that the operative member  1002  is positioned at its inoperative position. The table of FIG. 26 indicates that the respective piston rods  946 ,  982 ,  994  of the air cylinders  930 ,  974 ,  984  take their advanced or retracted positions, such that the air cylinders  930 ,  974 ,  984  take their advanced or retracted positions, for easier understanding purposes only.  
     [0227] As shown in FIG. 27, as the movable member  890  is moved downward, the operative member  952  engages the switch member  874  of the pressure switch valve  860 , so that the switch member  874  is moved downward. Simultaneously, the operative member  1002  is moved upward, but does not engage the switch member  874 . Thus, the switch member  874  is moved to its NP (negative-pressure) supply position, and the switch valve  860  is switched to its NP supply state. As a result, the CC suction nozzle  784  is supplied with the negative pressure. In this state, the upper stopper portion  876  is held in contact with the housing  872 . As the drive member  892  is lowered, the two movable members  890 ,  1034  are moved in opposite directions, respectively, so as to act on the switch member  874  on opposite sides thereof. However, since the two movable members  890 ,  1034  are moved in mechanical synchronism with each other, there is no possibility that the two operative members  950 ,  1002  simultaneously act on the switch member  874  because of their malfunction or that either one of the two operative members  950 ,  1002  acts on the switch member  874  at an inappropriate timing because of, e.g., its delayed movement. This is also true when the CCs  842  are mounted on the PCB  408 .  
     [0228] The pressure switch valve  860  is switched to its NP supply state at such a timing that the negative pressure is supplied to the lower opening of the suction pipe  788  shortly before the suction pipe  788  contacts the CC  842 . Shortly after the suction pipe  788  contacts the CC  842 , the suction pipe  788  can apply a sufficiently high negative pressure to the CC  842  and thereby quickly suck and hold the same  842 . The timing at which the switch valve  860  is switched can be adjusted by adjusting the height position of the main air cylinder  930  relative to the movable member  890 . Since the downward movement of the CC suction nozzle  784  and the switching of the pressure switch valve  860  are performed in mechanical synchronism with each other, the negative pressure can be supplied to the suction pipe  788  at an accurate timing. Thus, the CC mounting head  650  is free from the problem of failing to suck and hold the CCs  842 . This is also true when the CCs  842  are mounted on the PCB  408 . That is, the negative pressure can be removed or cut from the suction pipe  788  at an accurate timing, and accordingly the CC mounting head  650  is free from the problem of failing to mount the CCs  842  on the PCB  408 .  
     [0229] As described above, the movable member  890  or the drive member  892  is further moved downward by a small distance after the suction pipe  788  contacts the CC  842 . During this downward movement, the switch member  874  is moved to its NP supply position where the upper stopper portion  876  is held in contact with the housing  872 . An excessive downward movement of the movable member  890  is accommodated or absorbed by the compression coil spring  962  being compressed by the operative member  952  being moved relative to the movable member  890 .  
     [0230] After the suction pipe  788  sucks and holds the CC  842 , the movable member  890  or the drive member  892  is moved upward. During this upward movement, the CC suction shaft  766  is moved upward by the biasing force of the compression coil spring  806 , to follow the drive member  892 . Thus, the CC  842  is taken from the CC carrier tape  152 . As the movable member  890  is moved up, the main air cylinder  930  is moved up, so that the operative member  952  is moved up away from the switch member  874 . However, the switch member  874  remains held at its NP supply position and accordingly the CC  842  remains held by the suction nozzle  784 . Since the movable member  1034  is moved downward, the operative member  1002  is also moved downward.  
     [0231] Before the movable member  890  reaches its upper stroke-end position and accordingly the drive portion  896  fits in the recess  898  of the stationary cam  712 , the intermittent-rotation body  762  is caused to start rotating, so that the cam follower  804  is moved along the lower surface of the drive portion  896 . That is, the CC suction shaft  766  is revolved around the axis line of the rotation body  762 , while simultaneously being moved upward. Since each of the twenty CC suction shafts  766  is revolved while being moved up or down, for the sucking or mounting of CC  842 , the shafts  766  can sequentially reach the CC suck-and-mount position at a shortened time interval or pitch. Thus, the efficiency of mounting of CCs  842  is improved. After the movable member  890  reaches its upper stroke-end position and the drive portion  896  fits in the recess  898 , the cam follower  804  is moved onto the cam surface  808  of the stationary cam  712 , so that the current CC suction shaft  766  holding the CC  842  is moved away from the CC suck-and-mount position and the following suction shaft  766  is quickly moved to the CC suck-and-mount position to suck and hold another CC  842 .  
     [0232] During the intermittent rotation of the rotation body  762 , the CC mounting head  650  is moved by the X-Y robot  662  in the X direction, so that the following suction shaft  766  is moved to right above the CC taking position of the following feeder  54 . However, in the case where the following shaft  766  takes another CC  842  from the same feeder  54  as that from which the preceding shaft  766  has taken one CC  842 , the head  650  is not moved in the X direction while the rotation member  762  is rotated by one angular pitch. After one CC  842  is taken from each feeder  54 , the feeder  54  feeds the CC carrier tape by one pitch so that another CC  842  is positioned at the CC taking position.  
     [0233] When the intermittent-rotation body  762  is rotated and accordingly one CC suction shaft  766  is moved to the CC suck-and-mount position, the control device  1050  or the linear motor  886  may malfunction such that the drive member  892  starts moving downward, before the cam follower  804  engages the lower surface of the drive portion  896 , and accordingly is positioned below the cam follower  804 . In this case, the driven gear  800  and/or the shaft member  768  of the CC suction shaft  766  collide with the drive portion  896 . However, when more than a predetermined force is exerted to the drive member  892  by the CC suction shaft  766  being rotated, the drive member  892  is rotated to its retracted position indicated at two-dot chain line in FIG. 22. Thus, the drive member  892  and/or each CC suction shaft  766  is prevented from being damaged. The drive-member retraction sensor  920  detects that the drive member  892  has been rotated to its retracted position and supplies a detection signal indicative of that situation to the control device  1050 , which interrupts the current CC sucking operation. If the cause of the malfunction is removed by the operator, the CC sucking operation is resumed after the drive member  892  is returned to its operative position, the drive portion  896  is fitted in the recess  898 , and the cam follower  804  of the suction shaft  766  is engaged with the lower surface of the drive portion  896 . This is also true when the CCs  842  are mounted on the PCB  408 .  
     [0234] Even if the linear motor  886  or a portion of the control device  1050  for controlling the motor  886  may so malfunction, and simultaneously the rotation-body rotating servomotor  742  or a portion of the control device  1050  for controlling the motor  742  may so malfunction, that one CC suction shaft  766  fails to stop at the CC suck-and-mount position and the drive member  892  takes its lower position away from its upper stroke-end position when the shaft  766  passes through the CC suck-and-mount position, the shaft  766  can be revolved while rotating the drive member  892  to its retracted position and the cam follower  804  can go on over the recess  898 . Thus, the shaft  766  and the drive member  892  are prevented from being damaged.  
     [0235] After the CCs  842  are taken by the CC suction shafts  766  from the feeders  54 , the CC-image pick-up device  820  takes the images of the CCs  842  held by the shafts  766 , before the CCs  842  are mounted on the PCB  408 . As shown in FIG. 16, the CC-image pick-up position is distant from the CC suck-and-mount position by 5 angular pitches (one angular pitch is equal to the angle contained by adjacent two CC suction shafts  766  held by the intermittent-rotation body  762 ). Each CC suction shaft  766  which has sucked and held one CC  842  at the CC suck-and-mount position, is moved to the CC- image pick-up position while other suction shafts  766  are sequentially moved to the CC suck-and-mount position one by one by the intermittent rotations of the rotation body  762 . The image of the CC  842  held by each CC suction shaft  766  is taken by the pick-up device  820 . Based on the image data indicative of the taken image, the control device  1050  calculates an X-direction and a Y-direction position error and an angular or rotation position error of the CC  842  held by the shaft  766 . At the CC-image pick-up position, the pick-up device  820  may sequentially take, depending upon the number of the CCs  842  to be held, the respective images of CCs  842  while other CCs  842  are sequentially sucked or mounted at the CC suck-and-mount position. However, the pick-up device  820  may take the respective images of CCs  842  after the CCs  842  are sequentially sucked, or before the CCs  842  are sequentially mounted on the PCB  408 . Those optional operations of the pick-up device  820  will be described later. In the present embodiment, the respective images of the CCs  842  held by some CC suction shafts  766  can be taken at the CC-image pick-up position, while the other shafts  766  which may, or may not, hold the CCs  842  are moved to the CC suck and mount position. Thus, the sucking of CCs  842  and the taking of CC images may be carried out concurrently, or the mounting of CCs  842  and the taking of CC images may be carried out concurrently. Thus, the control device  1050  does not need any exclusive time for calculating the respective X-direction and Y-direction position errors and the rotation position error of the CC  842  held by each shaft  766 . Thus, the present CC mounting system  8  can mount the CCs  842  on the PCBs  408  with improved accuracy, while maintaining the efficiency of mounting of CCs  842 .  
     [0236] After all of the twenty CC suction shafts  766  have sucked the CCs  842 , the CC mounting head  650  is moved to above the PCB  408  by the X-Y robot  662 , so that the suction shafts  766  mount the CCs  842  on the PCB  408 . The position on the X slide  654  where the mounting of CCs  842  is carried out is the same as that where the sucking of CCs  842  is carried out. In order to mount the CC  842  on the PCB  408 , each CC suction shaft  766  is revolved to, and positioned at, the CC suck-and-mount position by the intermittent rotation of the intermittent-rotation body  762 , and the CC mounting head  650  is moved to above a CC-mount place on the PCB  408  by the X-Y robot  662 . Since the sucking and mounting of CCs  842  are carried at the same position, i.e., the CC suck-and-mount position on the X slide  654 , the single drive source, i.e, linear motor  886  suffices for moving each suction shaft  766  up and down for sucking and mounting the CCs  842 . Thus, the present system  8  can be produced at low cost. In addition, the inertia of the X-Y robot  662  that is moved in use can be decreased, and accordingly the mounting head  650  can be moved at high speed.  
     [0237] While each CC suction shaft  766  is positioned at the CC suck-and-mount position by the rotation of the intermittent-rotation member  762 , the rotation-position error of the CC  842  held by the shaft  766  is corrected and additionally the shaft  766  is rotated about its axis line so that the CC  842  held thereby takes a correct rotation position prescribed by the control program pre-stored in the ROM of the computer  1052 . More specifically described, the drive gear  716  is rotated relative to the rotation member  762 , so that the suction shaft  766  is rotated about its axis line.  
     [0238] The drive gear  716  is meshed with all the driven gears  800  which are fixed to the CC suction shafts  766 , respectively. Accordingly, when one suction shaft  766  is rotated for correcting the rotation-position error of the CC  842  held thereby, all the other suction shafts  766  are also rotated about their axis lines. Therefore, each of the second and following suction shafts  766  is rotated based on not only its rotation-position error and its prescribed rotation position but also the rotation-position error(s) and prescribed rotation position(s) of the preceding suction shaft(s)  766 . In addition, the X-direction and Y-direction distances of movement of the X-Y robot  662  are so determined as to eliminate the X-direction and Y-direction position errors of the center of the CC  842  held by each CC suction shaft  766  and the X-direction and Y-direction position errors of the corresponding CC-mount place on the PCB  408 . The X-direction and Y-direction position errors of the center of the CC  842  are the sum of the position errors of the center thereof which may be produced when the CC  842  is sucked by the suction shaft  766  and the amounts of movement of the center thereof when the rotation-position error of the CC  842  is corrected and/or the rotation position of the same  842  is changed.  
     [0239] Like the sucking of CCs  842 , the mounting of CCs  842  are carried out such that before each CC suction shaft  766  reaches the CC suck-and-mount position and after the cam follower  804  engages the lower surface of the drive portion  896  of the drive member  892 , the movable member  890  is lowered and accordingly the suction shaft  766  is lowered. Before each CC suction shaft  766  actually mounts the CC  842  on the PCB  408 , the shaft  766  reaches the CC suck-and-mount position. Thus, the suction shaft  766  can mount the CC  842  on the PCB  408  with accuracy.  
     [0240] As the movable member  890  is lowered, the operative member  952  is lowered and the operative member  1002  is elevated. When the CC suction shaft  766  mounts the CC  842 , the main air cylinder  930  (i.e., piston rod  946 ) takes its retracted position and the operative member  952  takes its inoperative position. However, the operative member  1002  takes its operative position that is higher than the inoperative position taken thereby when the suction shaft  766  sucks the CC  842  and accordingly is nearer to the switch member  874  of the pressure switch valve  860 , so that the contact member  1014  engages the switch member  874  and moves the same  874  upward. Thus, the switch member  874  is moved to its NP remove position and the switch valve  860  is switched to its NP remove state. At the NP remove position, the lower stopper portion  878  of the switch member  874  is held in contact with the housing  872 .  
     [0241] The operative member  1002  can selectively take, as described later, a first operative position which is established when the main air cylinder  974  takes its retracted position and the auxiliary air cylinder  984  takes its advanced position as indicated in FIG. 26, and a second operative position which is established when both the main and auxiliary air cylinders  974 ,  984  take their retracted positions and which is higher than the first operative position.  
     [0242] The solenoid-operated shut-off valve  1024  which controls the supply and cut-off of air to and from the pressure switch valve  860  is opened before the contact member  1014  contacts the switch member  874 . Immediately after the switch valve  860  is switched to its NP remove state, the valve  860  starts the supplying of air to the CC suction nozzle  784 , thereby quickly releasing the CC  842 .  
     [0243] When the contact member  1014  contacts the switch member  874 , the air pressure in the passages  780 ,  862  connecting between the pressure switch valve  860  and the CC suction nozzle  784  is negative. It needs a certain time for the air supplied to the switch valve  860  to reach the lower end opening of the suction pipe  788  after the switch  860  is switched to its NP remove position. In order to release quickly the CC  842 , this time should be shortened. If a greater amount of air is supplied to the valve  860 , the time can be shortened. However, if an excessive amount of air is supplied, the air might move the CC  842  on the PCB  408  or even blow the same  842  off the PCB  408 .  
     [0244] This is why the groove  1016  that permits leakage of the air is formed in the contact member  1014 . While the air flows from the pressure switch valve  860  to the lower end opening of the suction pipe  788  immediately after the switch valve  860  is switched to its NP remove state, the air leaks through the groove  1016 . In addition, in a time duration immediately after the switch valve  860  is switched to its NP remove state, the air pressure in the passage  780  and others connecting between the switch valve  860  and the CC suction nozzle  784  is negative. Therefore, even if the air leaks through the groove  1016  in this time duration, a major portion of the air supplied to the valve  860  flows into the nozzle  784 , so that the air is quickly supplied to the lower end opening of the suction pipe  788 . When the air pressure in the nozzle  784  increases up to, or exceeds, the atmospheric pressure, the air pressure in the passage  780  and others connecting the valve  860  and the nozzle  784  also increases. Thus, the amount of air leaking through the groove  1016  increases, whereas the amount of air flowing into the nozzle  784  decreases. Thus, the suction nozzle  784  is supplied with an appropriate amount of air for releasing the CC  842  off the suction pipe  788 .  
     [0245] The degree of opening of the variable throttle valve  1026  can be adjusted to such a value which enables the air to be quickly supplied to the CC suction nozzle  784  and enables the CC  842  to be released from the suction pipe  788  because of the supplying thereto of appropriate amount of air as a result of leaking of excessive amount of air through the groove  1016  after the pressure in the nozzle  784  has increased. The total amount of the air supplied to the nozzle  784  and the air leaking into the atmosphere can be controlled by changing the degree of opening of the throttle valve  1026 . Consequently the ratio of the amount of air flowing into the nozzle  784  immediately after the pressure switch valve  860  is switched to its NP remove state, to the amount of air flowing into the same  784  after the pressure in the nozzle  784  has sufficiently increased, can be controlled. In the case where the CC mounting head  650  is equipped with plural sorts of CC suction nozzles  784  having different sizes, the degree of opening of the valve  1026  may be adjusted to a value corresponding to the nozzles  784  of a middle size.  
     [0246] Immediately after the contact member  1014  contacts the switch valve  874 , the pressure switch valve  860  has not been switched to its NP remove state yet and accordingly the passage  1022  remains closed by the switch member  874  and disconnected from the CC suction nozzle  784 . Therefore, if the groove  1006  were not provided, the flowing of the air would be stopped for a while. However, since the groove  1006  is provided, the air leaks through the groove  1006 , so that the air continues to flow. Thus, as soon as the switch member  874  is switched to its NP remove position and accordingly the supplying of the negative pressure is stopped, the air is supplied to the nozzle  784  without any delay and with reduced air pulsation.  
     [0247] In this way, the CC  842  is quickly released from the suction pipe  788  due to the air supplied thereto. Therefore, the switching of the pressure switch valve  860  to the NP remove state is carried out at such a timing that after the CC  842  contacts the PCB  408 , the air reaches the lower end opening of the suction pipe  788 . If the air reaches the lower end opening of the pipe  788  before the CC  842  contacts the PCB  408 , the CC  842  might be placed at an incorrect position on the PCB  408 .  
     [0248] The greater heights the CCs  842  have, the shorter distances the CC suction nozzles  784  are lowered before the CCs  842  contact the PCB  408 , and the sooner the pressure switch valves  860  are switched to their NP remove positions, i.e., the sooner the CCs  842  are released from the nozzles  784 . Thus, it is desirable that the timing at which each switch valve  860  is switched to its NP remove state be continuously or stepwise changed depending upon the heights of the CCs  842 . In the present embodiment, the operative member  1002  can selectively take one of the first and second operative positions corresponding to two different timings of switching of the switch valves  860 . Thus, different sorts of CCs  842  having different heights are grouped into two groups, a large-size group and a small-size group. For the large-size CCs  842 , the movable member  890  is lowered by the shorter distance, and the operative member  1002  is moved to the second (higher) operative position, so that the switch valve  860  is switched at an earlier timing. On the other hand, for the small-size CCs  842 , the movable member  890  is lowered by the longer distance, and the operative member  1002  is moved to the first (lower) operative position, so that the switch valve  860  is switched at a later timing.  
     [0249] More specifically described, the CCs  842  whose heights are up to 3 mm are grouped into the small-size group, and the CCs  842  whose heights are from 3 mm to 6 mm are grouped into the large-size group. For each of the two groups, the distance or stroke of downward movement of the movable member  890  is set, on the CC mounting head  650 , based on the smallest one of the heights of the CCs  842  belonging to that group. As shown in FIGS. 28 and 29, assuming that the distance between the lower surface of the suction pipe  788  of the CC suction shaft  766  being positioned at the CC suck-and-mount position, and the upper surface of the PCB  408 , is 14 mm, each small-size CC  842  is lowered by 14 mm+α (α is a predetermined distance), and each large-size CC  842  is lowered by 11 mm+α. Thus, even the smallest CCs  842  can surely contact the PCB  408 . The vertical distance between the first and second operative positions of the operative member  1002  is 3 mm (=14 mm−11 mm).  
     [0250] The timing of switching of the pressure switch valve  860  can be changed by changing the height position of the operative member  1002  relative to the movable member  1034 , that is, changing the height position of the auxiliary air cylinder  984  relative to the main air cylinder  974  and/or the height position of the support member  998  relative to the auxiliary air cylinder  984 . For each of the small-size and large-size CC groups, the switch valve  860  is adapted such that the valve  860  is switched at such a timing that the air is supplied to the lower end opening of the suction pipe  788  after the CC  842  which may be the smallest in each group is placed on the PCB  408 . Therefore, the timing of supplying of air to the pipe  788  differs for CCs  842  having different sizes in each group. However, for every size of CC  842 , it is assured that the air is supplied to the pipe  788  after the CC  842  is placed on the PCB  408 . The stroke of downward movement of the movable member  890  can be adjusted to a value which enables the CCs  842  to be surely placed on the PCB  408  and which enables the switch valve  860  to be switched at the above-defined timing, that is, enables the switch member  874  to be held at its NP remove position where the lower stopper portion  878  is held in contact with the housing  872 .  
     [0251] When the CCs  842  whose heights are greater than zero and not higher than 3 mm are mounted on the PCB  408 , the main air cylinders  930 ,  974  and the auxiliary air cylinder  984  are driven according to the drive commands indicated in the table of FIG. 26. That is, as shown in FIG. 28(A), the main air cylinder  974  is switched to its retracted position, and the auxiliary air cylinder  984  is switched to its advanced position, so that the operative member  1002  is moved to its first (lower) operative position. Thus, the timing of switching of the pressure switch valve  860  is delayed. Simultaneously, the main air cylinder  930  is switched to its retracted position, so that the operative member  952  is moved to its inoperative position where it cannot contact the switch member  874 .  
     [0252] When the movable member  890  is lowered, the CC  842  contacts the PCB  408 , as shown in FIG. 28(B), and then the movable member  890  is additionally moved downward by a small distance. This additional downward movement is allowed by the compression of the compression coil spring  790  of the CC suction nozzle  784 .  
     [0253] In addition, the contact member  1014  moves the switch member  874  upward, thereby switching the pressure switch valve  860  to its NP remove position. After this switching, the movable member  890  is further moved downward, and the movable member  1034  is moved upward. This downward movement of the movable member  890  is allowed by the extension of the tension coil spring  1006  caused by the upward movement of the support member  998  relative to the operative member  1002 . Thus, the contact member  1014  and the switch valve  890  are prevented from being damaged. After the air is supplied to the lower end opening of the suction pipe  788  for a predetermined time duration which is sufficient for releasing the CC  842  from the pipe  788 , the solenoid-operated shut-off valve  1024  is closed, so as to cut the supplying of the air to the pipe  788 .  
     [0254] Also when the CCs  842  are mounted on the PCB  408 , the linear motor  886  is controlled such that the downward movement of the movable member  890  is accelerated and decelerated, so that each CC  842  contacts the PCB  408  with minimized impact. All the CCs  842 , large or small, that belong to each one of the large- and small-size CC groups are moved downward by the same distance. However, the greater heights the CCs  842  have, the earlier they contact the PCB  408 . Accordingly, the greater heights the CCs  842  which may belong to the same CC group have, the earlier they are decelerated.  
     [0255] When the CCs  842  which belong to the large-size CC group are mounted on the PCB  408 , both the main air cylinder  974  and the auxiliary air cylinder  984  are switched to their retracted positions, as shown in FIG. 29(A), so that the timing of switching of the pressure switch valve  860  becomes earlier. When the movable member  890  is moved downward, the operative member  1002  is moved upward, as shown in FIG. 29(B), so that the contact member  1014  contacts the switch member  874 , thereby moving it to its NP remove position. After each CC  842  is mounted on the PCB  408 , the air is supplied to the lower end opening of the suction pipe  788 , so that the CC  842  is released from the pipe  788 .  
     [0256] After each CC  842  is mounted on the PCB  408 , the movable body  890  is moved upward, and the intermittent-rotation member  762  is rotated, so that the next CC suction shaft  766  is moved to, and positioned at, the CC suck-and-mount position where the next shaft  766  mounts the CC  842  on the PCB  408 . Simultaneously, the CC mounting head  650  is moved by the X-Y robot  662 , so that the CC suck-and-mount position of the head  650  is moved to above another CC-mount place on the PCB  408 . Also when the CCs  842  are mounted on the PCB  408 , the upward movement of the suction shaft  766  and the intermittent rotation of the body  762  are simultaneously carried out, so that the next suction shaft  766  is quickly moved to, and positioned at, the CC suck-and-mount position for mounting another CC  842  on the PCB  408 .  
     [0257] It emerges from the foregoing description that when the CC  842  is sucked, the negative pressure is supplied to the lower end opening of the suction pipe  788  before the pipe  788  contacts the CC  842 , so that the pipe  788  can quickly suck the CC  842  and that when the CC  842  is mounted, the movable member  890  is moved downward by an appropriate one of the two distances corresponding to the two CC groups, and the pressure switch valve  860  is switched to its NP remove state at an appropriate one of the two timings corresponding to the two CC groups. Thus, the CC mounting device  18 ,  20  effectively reduces useless downward movements of the movable member  890 , and quickly releases the CC  842  from the suction pipe  788  after the CC  842  is placed on the PCB  408 . That is, the mounting device  18 ,  20  can suck the CC  842  in a shortened time and mount the CC  842  in a shortened time, thereby improving the efficiency of mounting of CCs  842  on PCBs  408 .  
     [0258] As shown in the time chart of FIG. 25, the CC mounting head  650  is horizontally moved by the X-Y robot  662 , the intermittent-rotation body  762  is intermittently rotated, the rotation position of the CC  842  is corrected and changed, and the CC suction shaft  766  is moved downward and upward for mounting the CC  842 . Those operations are repeated for mounting all the CCs  842  held by the mounting head  650 , on the PCB  408 . After all the CCs  842  held by the mounting head  650  are mounted on the PCB  408 , the mounting head  650  is moved to the CC supplying device  14  for taking additional CCs  842  therefrom. While the first CC mounting device  18  mounts CCs  842  on a PCB  408 , the second CC mounting device  20  takes CCs  842  from the second CC supplying device  16 . Immediately after the first CC mounting device  18  has finished mounting the CCs  842  on the PCB  408 , the second CC mounting device  20  starts, in place of the first device  18 , mounting the CCs  842  on the same PCB  408 . Thus, the two devices  18 ,  20  can continue mounting the CCs  842  on the PCB  408  without any interruptions. This leads to improving the efficiency of mounting of CCs  842  on PCBs  408 .  
     [0259] If any sucking error occurs, for example, if the CC  842  sucked by one CC suction shaft  766  is not of a correct sort, or if the rotation-position error of the CC  842  held by one shaft  766  is too large, the CC  842  is not mounted on the PCB  408 . In this case, if the suction shaft  766  is positioned at the CC suck-and-mount position, the linear motor  886  is not started, and the shaft  766  is not lowered. After the CC mounting head  650  mounts all the CCs (except for the “error” CC  842 ) held thereby, on the PCB  408 , the head  650  is moved to above a CC collecting container (not shown) which is provided midway between the main conveyors  400 ,  402  and the CC supplying device  14 , while the head  650  is moved toward the supplying device  14 . The head  650  discards the “error” CC  842  into the container. In this case, the CC suction shaft  766  holding the “error” CC  842  is positioned at the CC suck-and-mount position. After the shaft  766  reaches the container, or immediately before the shaft  766  reaches the container, the linear motor  886  is started. Since the operative member  952  is at its inoperative position and the operative member  1002  is at its first or second operative position, the downward movement of the movable member  890  causes the operative member  1002  to engage the switch member  874  and move it to its NP remove position. Thus, the pressure switch valve  860  is switched to its NP remove state, and the CC  842  is released into the container. In the case where the operative member  1002  is at its second (upper) operative position, the CC  842  can be released in a shorter time after the linear motor  886  is started, than the case where it is at its first (lower) position. The head  650  being stopped above the container discards the CC  842  into the container. However, in the case where the container has an elongate shape, it is possible that the head  650  be adapted to discard a CC  842  into the container without being stopped above the container, i.e., while being moved.  
     [0260] As described above, after each CC suction shaft  766  sucks and holds a CC  842 , the shaft  766  is moved toward the CC-image pick-up position while simultaneously the following shaft  766  is moved to the CC suck-and-mount position, as the intermittent-rotation body  762  is rotated. At the CC-image pick-up position, the image of the CC  842  held by the shaft  766  is picked up or taken by the CC- image pick-up device  820 . However, the CC-image pick-up position is distant from the CC suck-and-mount position by five angular pitches. Therefore, when the CC mounting head  650  finishes sucking and holding a predetermined number of CCs  842 , there may be one or more CCs  842  whose images have not been taken yet. If the predetermined number is not greater than five, there is no CC  842  whose image has already been taken when the CC mounting head  650  finishes sucking and holding the predetermined number of CCs  842 .  
     [0261] Therefore, after the CC mounting head  650  finishes sucking and holding the predetermined number of CCs  842 , the CC-image pick-up device  820  takes the image or images of the CC or CCs  842  which has or have not been taken, in an appropriate one of the following three different manners corresponding to three cases, i.e., (1) the first case where each CC mounting device  18 ,  20  sucks twenty CCs  842  each time, that is, all the twenty CC suction shafts  766  are used to suck the CCs  842 , and the rotation-position changing angle of each of the five CCs  842  which are sucked first, second, third, fourth, and fifth falls within the ranges of 0±15 degrees (i.e., from −15 degrees to +15 degrees), 90±15 degrees, 180±15 degrees, and 270±15 degrees; (2) the second case where each CC mounting device  18 ,  20  sucks twenty CCs  842  each time, that is, all the twenty CC suction shafts  766  are used to suck the CCs  842 , and the rotation-position changing angle of at least one of the five CCs  842  which are sucked first, second, third, fourth, and fifth does not fall within the ranges of 0±15 degrees, 90±15 degrees, 180±15 degrees, and 270±15 degrees; and (3) the third case where each CC mounting device  18 ,  20  sucks smaller than twenty CCs  842  each time.  
     [0262] The CC  842  held by each CC suction shaft  766  may be mounted on the PCB  408 , while having a rotation position different from the rotation position thereof at the time when the CC  842  is supplied from the CC supplying device  14 ,  16 . The rotation-position changing angle of each CC  842  is defined as an angle by which the CC  842  should be rotated for changing the current rotation position of the CC  842  (which is assumed to have no rotation-position error) when the CC  842  is supplied to the shaft  766 , to that of the CC  842  when the CC  842  is mounted on the PCB  408 . The respective rotation-position changing angles of the CCs  842  are prescribed by the CC mounting control program, depending upon the sorts of the CCs  842 , the CC-mount places where the CCs  842  are mounted on the PCB  408 , etc. The rotation-position changing angle of each CC  842  is defined in terms of an angle by which the CC  842  should be rotated in a predetermined direction. However, in an actual operation, each CC  842  is rotated in an appropriate one of opposite directions in which the rotation position of the CC  842  at which the CC  842  is supplied is changed, by the rotation of the CC  842  over the smallest angle, to the rotation position at which the CC  842  is mounted.  
     [0263] In the above-indicated first case (1), the present CC mounting system  8  is operated as follows:  
     [0264] In the case where twenty CCs  842  are sucked each time (No.  1  to No.  20  in FIG. 30), the respective images of the first to fifteenth CCs  842  are taken while concurrently the sixth to twentieth CCs  842  are sucked (No.  6  to No.  20 ), as indicated in the table of FIG. 30. Thus, the respective rotation-position error angles, φ 1   a  to φ 15   a,  of the first to fifteenth CCs  842  are obtained as respective image-based recognized angles. When the intermittent-rotation body  762  is rotated by one angular pitch after the last shaft  766  sucks the twentieth CC  842  (No.  20 ), the first shaft  766  holding the first CC  842  is returned to the CC suck-and-mount position where the shaft  766  can mount the first CC  842  on the PCB  408  (No.  21 ).  
     [0265] However, when the sucking of all the CCs  842  is finished, the respective images of the sixteenth to twentieth CCs  842  have not been taken yet. Therefore, if the rotation-position changing angle of each of the first to fifth CCs  842  falls within the ranges of 0±15 degrees, 90±15 degrees, 180±15 degrees, and 270±15 degrees, the respective images of the sixteenth to twentieth CCs  842  are taken while the first to fifth CCs  842  are mounted on the PCB  408 .  
     [0266] Meanwhile, when the image taken from each CC  842  indicates that the rotation position of the CC  842  does not fall within the ranges of 0±30 degrees, 90±30 degrees, 180±30 degrees, and 270±30 degrees, the present CC mounting system  8  judges that a sucking error has occurred to the CC  842 , and does not mount the CC  842  on the PCB  408 . The reason for this is as follows: In the present CC mounting system  8 , the respective driven gears  800  fixed to the twenty CC suction shafts  766  are meshed with the common drive gear  716 . Therefore, when the CC  842  held by one CC suction shaft  766  is rotated, all the other shafts  766  are rotated by the same angle in the same direction. Thus, in the case where the mounting of some CCs  842  and the taking of images of other CCs  842  are concurrently carried out, the rotation position of each CC  842  whose image is being taken contains not only its own rotation-position error angle but also the rotation-position error correcting angle and rotation-position changing angle of another CC  842  being concurrently mounted. Therefore, in the case where whether the CC  842  whose image is being taken has an excessive rotation-position error or not is judged using a simple rule which does not take into account the rotation-position error correcting angle and rotation-position changing angle of the CC  842  being concurrently mounted, it is needed to judge that an excessive rotation-position error has occurred to the CC  842 , if the position angle of the CC  842  does not fall with in the ranges of 0±α degrees, 90±α degrees, 180±α degrees, and 270±α degrees, and it is needed to determine the reference value, α (&gt;0), by taking into account not only the rotation-position error angle of the CC  842  whose image is being taken but also the rotation-position error correcting angle and rotation-position changing angle of the CC  842  being concurrently mounted. In an extreme case where it is assumed that each of the CCs  842  does not have any rotation-position error angle, i.e., does not need any rotation-position-error correcting angle, the reference value α may take any value other than 45 (degrees). However, in fact, each CC  842  has some rotation-position error angle and needs some rotation-position-error correcting angle. Therefore, it is needed to employ the value α which is not greater than 45−β (degrees, β&gt;0).  
     [0267] In the present CC mounting system  8 , the rotation-position error angles fall within the ranges of ±5 degrees in almost all cases, and do not go beyond the ranges of ±10 degrees unless an abnormality occurs. Therefore, the ranges of ±α are determined as the ranges of ±30 degrees as indicated above. In the case where the respective rotation-position changing angles of the first to fifth CCs  842  fall within the ranges of 0±15 degrees, 90±15 degrees, 180±15 degrees, and 270±15 degrees, then the angle by which each of the first to fifth CCs  842  is rotated when being mounted on the PCB  408  is not greater than 20 degrees in almost all cases. For example, if the rotation-position error angle of one CC  842  is +5 degrees and the rotation-position changing angle of the same is −15 degrees, the angle of rotation of the CC  842  is 20 degrees. Therefore, the angle of rotation of each CC  842  does not go beyond the range of ±30, because the angle of rotation of each CC  842  is at most 25 degrees even if the rotation-position error angle of the CC  842  whose image is taken may be +5 degrees and the CC  842  may be additionally rotated by the 20 degrees. In the case where the rotation-position error angle of each of the first to fifth CCs  842  is +10 degrees and the rotation-position error angle of the CC  842  whose image is taken is +10 degrees, the angle of rotation of the CC  842  whose image is taken is at most 35 degrees. However, this case is very rare to occur. Accordingly, the possibility that a CC  842  which is actually a normal one is discarded as an “error” one is very low. Thus, the mounting of some CCs  842  and the taking of images of other CCs  842  can be concurrently carried out without raising any practical problems.  
     [0268] In the case where the first to fifth CCs  842  are mounted on the PCB  408  and concurrently the images of the sixteenth to twentieth CCs  842  are taken (No.  21  to No.  25 ), the intermittent-rotation body  762  is horizontally moved by the X-Y robot  662 , after the twenty CCs  842  are sucked (No.  1  to No.  20 ), so that the CC suck-and-mount position is moved to above the first CC-mount place on the PCB  408 . During this horizontal movement of the body  762 , the member  762  is rotated by one angular pitch while the CC suction shaft  766  being positioned at the CC suck-and-mount position is rotated about its axis line as needed. Thus, the shaft  766  holding the first CC  842  is moved to the CC suck-and-mount position (No.  21 ), and the rotation-position error angle the first CC  842  is corrected and/or the rotation position of the same  842  is changed by its rotation-position changing angle. Immediately after the first CC  842  reaches the first CC-mount place on the PCB  408 , the CC  842  is placed there on the PCB  408 .  
     [0269] As indicated in the table of FIG. 30, the angle by which the CC suction shaft  766  holding the first CC  842  is rotated when the CC  842  is mounted on the PCB  408 , is the sum of −φ 1   a  and φ 1   b  (No.  21 ). Thus, the CC-image-based recognized angle of the sixteenth CC  842  contains the summed rotation angle, (−φ 1   a +φ 1   b ), of the first CC  842 . Therefore, the angle by which the shaft  766  holding the sixteenth CC  842  is rotated when the CC  842  is mounted on the PCB  408 , is equal to (−φ 16   a +φ 1   a −φ 1   b )+φ 16   b  that is obtained by adding its rotation-position changing angle, φ 16   b,  to an angle for eliminating its rotation-position error angle, (φ 16   a −φ 1   a +φ 1   b ). The respective summed rotation angles of the shafts  766  holding the seventeenth to twentieth CCs  842  (No.  22  to No.  25 ) can be calculated in a similar manner. Each of the second and following CCs  842  is rotated each time its preceding CC or CCs  842  are rotated. Therefore, the rotation angle and direction of each of the second and following CCs  842  are determined based on not only the rotation-position error angle and changing angle of each CC  842  but also the respective rotation-position error angle(s) and changing angle(s) of its preceding CC or CCs  842 . In an actual operation, each CC  842  is rotated in an appropriate one of opposite directions in which the current rotation position of each CC  842  is changed, by the rotation thereof over the smallest angle, to the predetermined rotation position thereof at which it is to be mounted on the PCB  408 .  
     [0270] Next, there will be described the manner in which the CC mounting system  8  is operated in the above-indicated second case (2).  
     [0271] In the case where the rotation-position changing angle of at least one of the first to fifth CCs  842  does not fall within the ranges of 0±15 degrees, 90±15 degrees, 180±15 degrees, and 270±15 degrees, then the respective images of the sixteen to twentieth CCs  842  are taken (No.  21  to No.  25 ) before the first to fifth CCs  842  are mounted on the PCB  408  (No.  26  to No.  30 ). Since in the above case there is some possibility that at least one CC  842  go beyond the permission ranges of ±30 and be judged as an “error” CC, the mounting of those CCs  842  is not carried out while the images of other CCs  842  are taken.  
     [0272] As indicated in the time chart of FIG. 25, the images of the sixteen to twentieth CCs  842  are taken while the CC mounting head  650  is horizontally moved by the X-Y robot  662  and accordingly the CC suck-and-mount position is moved to above the first CC-mount place on the PCB  408 . Concurrently, the intermittent-rotation body  762  is intermittently rotated by five angular pitches, i.e., 90 degrees in total. Thus, the CC suction shaft  766  holding the first CC  842  is revolved from the CC suck-and-mount position toward the CC-image pick-up position by four angular pitches. Accordingly, after the image of the twentieth CC  842  is taken (No.  25 ), the body  762  is rotated by four angular pitches in the reverse direction, so that the shaft  766  holding the first CC  842  is moved to the CC suck-and-mount position. Simultaneously, the shaft  766  holding the first CC  842  is rotated about its axis line as needed for correcting the rotation-position error angle of the first CC  842  and changing the rotation position of the first CC  842  by its rotation-position changing angle.  
     [0273] In the case where the time needed for taking the images of the sixteenth to twentieth CCs  842  is longer than that needed for horizontally moving the CC mounting head  650 , the rotation of the intermittent-rotation body  762  and the rotation of the CC suction shaft  766  are completed in a time duration in which the head  650  is horizontally moved, as indicated in the time chart of FIG. 25. On the other hand, if not, the body  762  and the shaft  766  continue their rotations after the horizontal movement of the head  650 .  
     [0274] As indicated in the table of FIG. 31, the rotation-position error angle of the first CC  842  is φ 1   a  (No.  6 ), and this error is corrected by rotating the first CC  842  by −φ 1   a  (No.  26 ). If it is assumed that the rotation-position changing angle of the first CC  842  is φ 1   b,  the angle by which the first CC  842  is rotated when the CC  842  is mounted on the PCB  408 , is the sum of −φ 1   a  and φ 1   b  (degrees). The respective summed angles of the second and following CCs  842 , by which the CCs  842  are rotated for being mounted on the PCB  408 , are calculated in a similar manner. Each CC suction shaft  766  is rotated about its axis line while it is moved to the CC suck-and-mount position by a single intermittent rotation of the intermittent-rotation body  762 . Like in the first case (1), the rotation angle and direction of each of the second and following CCs  842  are determined based on not only its rotation-position error angle and changing angle but also the respective rotation-position error angle(s) and changing angle(s) of its preceding CC or CCs  842 .  
     [0275] Next, there will be described the manner in which the CC mounting system  8  is operated in the above-indicated third case (3).  
     [0276] This manner relates to the cases where the CC mounting head  650 ,  652  takes a predetermined number, N (N=a natural number of from 16 to 19) of CCs  842 , each time, from the CC supplying device  14 ,  16 . If the rotation-position changing angle of at least one of the first to (N−15)-th CC or CCs  842  does not fall within any of the ranges of 0±15 degrees, 90±15 degrees, 180±15 degrees, and 270±15 degrees, then the CC suction shaft  766  holding the first CC  842  is returned, like in the above-described second case (2), to the CC suck-and-mount position where the first CC  842  is mounted on the PCB  408 , after all the CCs  842  are sucked and held by the CC suction shafts  766  and the images of all the CCs  842  are taken.  
     [0277] In the case where the predetermined number N is fifteen, the number, (N−15), is zero. Accordingly, there is no case where one CC  842  reaches the CC-image pick-up position and simultaneously another CC  842  reaches the CC suck-and-mount position. Therefore, after the sucking of the CCs is finished, five intermittent rotations of the intermittent-rotation body  762  occur without any CC mounting, so that the taking of images of all the CCs  842  is finished.  
     [0278] On the other hand, if the rotation-position changing angle of each of the first to (N−15)-th CC or CCs  842  falls within the ranges of 0±15 degrees, 90±15 degrees, 180±15 degrees, and 270±15 degrees, only the taking of an image or images of a CC or CCs  842  held by the CC suction shaft or shafts  766  which reaches or reach the CC-image pick-up position as the body  762  is intermittently rotated, occurs (No.  18  to No.  20 ) before the CC suction shaft  766  holding the first CC  842  reaches the CC suck-and-mount position. After the first CC  842  reaches the CC suck-and-mount position, the CC mounting and CC-image taking operations simultaneously occur (No.  21  and No.  22 ). In other words, (20−N) times intermittent rotations of the body  762  occur without any CC mounting.  
     [0279] For example, in the case where the predetermined number, N, is seventeen (N=17), three intermittent rotations of the body  762  occur without any CCs  842  being mounted on the PCB  408  after all the CCs  842  are sucked and held by the CC suction shafts  766 , as indicated in the table of FIG. 32. Thus, the first CC  842  is moved toward the CC suck-and-mount position, while the images of the thirteenth to fifteenth CCs  842  are sequentially taken (No.  18  to No.  20 ). During the fourth intermittent rotation of the body  762 , the shaft  766  holding the first CC  842  is moved or revolved to the CC suck-and-mount position, while it is rotated about its axis line for correcting its rotation-position error angle and changing its current rotation position by its rotation-position changing angle. The taking of images of the sixteenth and seventeenth CCs  842  occur concurrently with the mounting of the first and second CCs  842  (No.  21  and No.  22 ). Thus, the image-based recognized angles of the sixteenth and seventeenth CCs  842  reflect the summed rotation angles of the first and second CCs  842 , respectively.  
     [0280] After the seventeen CCs  842  are sucked by the CC mounting head  650 ,  652 , the head  650 ,  652  is horizontally moved to above the PCB  408 . During this horizontal movement, the images of the thirteenth to fifteenth CCs  842  are sequentially taken. If the taking of those images is finished before the horizontal movement is finished, then the shaft  766  holding the first CC  842  is moved to the CC suck-and-mount position while being rotated about its axis line as needed. On the other hand, if not, the taking of those images is finished after the horizontal movement, and then the shaft  766  holding the first CC  842  is moved to the CC suck-and-mount position while being rotated about its axis line as needed.  
     [0281] In the case where the predetermined number, N, is not greater than fourteen (N≦14), there is no case where one CC  842  reaches the CC-image pick-up position and simultaneously another CC  842  reaches the CC suck-and-mount position. Particularly, in the case where the predetermined number, N, is not greater than fourteen and not smaller than six (6≦N≦14), after the sucking of all the CCs  842  is finished, five intermittent rotations of the intermittently rotatable body  762  occur, so that the taking of the images of all the CCs  842  is finished. In the case where the predetermined number, N, is not greater than five (N≦5), the body  762  is intermittently rotated by the same number of times as the predetermined number, N. In this case, however, the shaft  766  holding the first CC  842  has not reached the CC-image pick-up position yet when the sucking of all the CCs  842  is finished. Hence, in order to move the shaft  766  holding the first CC  842  to the CC-image pick-up position, the body  762  is continuously rotated by an angle equal to the angle between the current angular position of the first CC  842  and the pick-up position, after the sucking of all the CCs  842  is finished.  
     [0282] Also in the case where the predetermined number, N, is not greater than fourteen (N≦14), the CC-image taking operation occurs concurrently with the horizontal movement of the intermittent-rotation body  762 . If the CC-image taking operation is finished before the horizontal movement is finished, the body  762  is rotated with the horizontal movement, so that the shaft  766  holding the first CC  842  is moved to the CC suck-and-mount position while being rotated about its axis line as needed. On the other hand, if not, the image taking operation is finished after the horizontal movement, and then the shaft  766  holding the first CC  842  is moved to the CC suck-and-mount position while being rotated about its axis line as needed. When the body  762  is rotated to revolve the shaft  766  holding the first CC  842  to the CC suck-and-mount position, the body  762  is rotated in an appropriate one of opposite directions in which the first CC  842  reaches the CC suck-and-mount position by the rotation thereof over the smallest angle.  
     [0283] As is apparent from the foregoing description, in the present embodiment, each of the CC suction shafts  766  provides a CC sucker as a sort of CC holder, or a CC holding shaft as a sort of CC holder; and each of the CC suction nozzles  784  provides a CC sucking portion as a CC holding portion of each CC suction shaft  766 . The rotation-body rotating servomotor  742  and a portion of the control device  1050  which controls the servomotor  742  to intermittently rotate the intermittent-rotation body  762  cooperate with each other to provide a holder positioning device which sequentially positions each of the CC suction shafts  766  at each of the CC suck-and-mount position and the CC-image pick-up position; and each of the X-Y robots  662 ,  664  including a corresponding one of the X slides  654 ,  656  as a holder-revolving-device supporting movable member, provides a holder-revolving-device moving device.  
     [0284] The elevator table  598 , the elevator-table elevating and lowering device  600 , the PCB suction devices  602 , and the hold-down portions  570 ,  572  of the guide members  566 ,  568 , of each of the main conveyors  400 ,  402  cooperate with one another to provide a CS supporting device. The intermittent-rotation body  762 , the driven pulley  740 , the drive pulley  744 , and others cooperate with the holder positioning device to provide a sucker revolving device as a sort of a holder revolving device. The holder-revolving-device supporting movable member is moved while supporting the holder revolving device. The sucker revolving device cooperates with each of the X-Y robots  662 ,  664  to provide a sucker moving device.  
     [0285] The linear motor  886  provides a drive device which elevates and lowers the drive member  892 ; and the linear motor  886  cooperates with the drive member  892  to provide the individual-CC-suction-shaft elevating and lowering device  880  which elevates and lowers each one of the CC suction shafts  766  which is positioned in the vicinity of the CC suck-and-mount position as a CC receiving and mounting position. The stationary cam  712  as a cam member cooperates with the cam followers  804  and the compression coil springs  806  to provide an elevating and lowering device which sequentially elevates and lowers the CC suction shafts  766  (i.e., the CC holders) along the cam surface  808  of the cam  712 . A portion of the control device  1050  which controls the CC suction shafts  766  to receive, at the CC suck-and-mount position, the CCs  842  supplied from the CC supplying device  14 ,  16 , and mount the CCs  842  on the PCB  408 , provides a CC receiving and mounting control device. That is, the control device  1050  controls the holder revolving device, the holder-revolving-device moving device, the individual-CC-suction-shaft elevating and lowering device, and the CC receiving and mounting control device. The CC suction shafts  766 , the holder revolving device, the holder-revolving-device moving device, the individual-CC-suction-shaft elevating and lowering device, and the CC receiving and mounting control device cooperate with one another to provide a CC mounting unit. In the present embodiment, two mounting units are employed.  
     [0286] A portion of the control device  1050  which controls the two mounting units to alternately receive or mount the CCs  842 , provides an alternate-CC-mounting control device. A portion of the control device  1050  which corrects the distance of movement of the holder-revolving-device moving device based on the X-direction and/or Y-direction position error of the CC  842  held by each CC suction shaft  766 , and thereby corrects the position of the shaft  766  (i.e., the CC holder) established by the holder revolving device relative to the CS supporting device, provides a CC-suction-shaft position error correcting device. The drive gear  716  cooperates with each of the driven gears  800  and the rotation-position correcting and changing servomotor  724  as a drive device, to provide a holder rotating device; and a portion of the control device  1050  which controls the holder rotating device based on the rotation-position error of the CC  842  held by each CC suction shaft  766  and thereby eliminating the error, provides a rotation-position error correcting device. As described above by reference to FIGS. 30 and 32, a portion of the control device  1050  which controls the CC suction shafts  766  to mount the CCs  842  and concurrently controlling the CC-image pick-up device  820  to take the respective images of the CCs  842  held by the shafts  766 , provides a concurrent-image-taking control device.  
     [0287] The intermittent-rotation body  762  provides a movable member which holds the CC holders such that the respective shaft portions of the CC holders are rotatable about their axis lines and are movable in their axial directions, and which is movable in a direction intersecting those axis lines. The intermittent-rotation body  762  also provides part of a CC transferring device which transfers the CCs  842  by the intermittent rotations thereof.  
     [0288] A portion of the control device  1050  which controls the main air cylinders  930 ,  974  and the auxiliary air cylinders  984  provides an actuator control device, which cooperates with the air cylinders  930 ,  974 ,  984  to provide the switch-valve control device  882  which moves, when the drive member  892  lowers the CC suction nozzle  784 , the switch member  874  to its NP supply position and thereby switches the pressure switch valve  860  to its NP supply state in which the nozzle  784  is supplied with the negative pressure in place of the air pressure not lower than the atmospheric pressure, and which alternatively moves, when the drive member  892  lowers the CC suction nozzle  784 , the switch member  874  to its NP remove position and thereby switches the pressure switch valve  860  to its NP remove state in which the nozzle  784  is supplied with the air pressure not lower than the atmospheric pressure, in place of the negative pressure. The link  1030  and the rollers  1036 ,  1042  cooperate with each other to provide a coupling device which converts the upward and downward movements of the drive member  892  to the downward and upward movements of the movable member  1034 ; the tension coil spring  1006  biasing the operative member  1002  provides a relative-movement permitting device which applies an elastic force to the operative member  1002  and permits the same  1002  to be moved relative to the air cylinders  974 ,  984 , when the force applied thereto by the air cylinders  974 ,  984  exceeds a predetermined value; and the compression coil spring  962  biasing the operative member  952  provides another relative-movement permitting device. The passages  1020 ,  1022  provide a positive-pressure supply passage which is formed in the operative member  1002 ; and the passage (not shown) which is formed in the switch member  874  and which is supplied with air from the passages  1020 ,  1022 , cooperates with the passages  1020 ,  1022  to provide a positive-pressure supply passage.  
     [0289] A width changing device which changes the PCB conveying width of the carry-in and carry-out conveyors  404 ,  406  is provided by the spline shaft  456  as a carry-in-conveyor-side drive shaft, the spline shaft  456  as a carry-out-conveyor-side drive shaft, the spline tube  458  as a driven rotatable member, a motion converting device including the screw shaft  448 , the nut  452 , the sprockets  460 ,  462 , and the chain  464 , and a rotation transmitting device including the sprockets  468 ,  516 ,  518 ,  542 ,  544  and the chain  470 .  
     [0290] Referring next to FIGS.  33  to  37 , there will be described a second embodiment of the present invention, which also relates to a CC (circuit component) mounting system but includes two CC mounting heads  1100  in place of the CC mounting heads  650 ,  652  of the CC mounting system  8  as the first embodiment. The second embodiment is different from the first embodiment in that a plurality of CC suction shafts  1170  are supported by an intermittent-rotation body  1164  such that the suction shafts  1170  have, as respective axis lines thereof, a plurality of generators of a circular cone whose center line is defined by an axis line of the rotation body  1164 , i.e., a common axis line around which the suction shafts  1170  are revolved, and that the common axis line is inclined with respect to a perpendicular of a rotation-body moving plane in which the rotation body  1164  is moved by an X-Y robot  1102 , by an angle at which one of the generators is perpendicular to the rotation-body moving plane. The following description addresses only the differences between the first and second embodiments.  
     [0291] Like the CC mounting heads  650 ,  652 , each CC mounting head  1100  is horizontally moved by an X-Y robot  1102  including an X-direction slide  1104 . As shown in FIG. 33, the X-direction slide  1104  is provided by a plurality of members which are fixed to one another. One of those members is a connection member  1106  to which a pair of block members  1108  as guided members are fixed. The connection member  1106  fits via the block members  1108  on a pair of guide rails  1110  as guide members which are provided on a Y-direction slide (not shown), such that the connection member  1106  is movable relative to the guide rails  1110  in the X direction. A nut  1112  is fixed to the connection member  1106  on one hand, and is threadedly engaged with a screw shaft  1114  which is attached to the Y-direction slide such that the screw shaft  1114  is rotatable about its axis line. The nut  1112  and the screw shaft  1114  cooperate with each other to provide a ball screw. The rotation of an X-direction servomotor  1116  is transmitted to the screw shaft  1114  via a coupling  1118  so that the screw shaft  1114  is rotated and the X-direction slide  1104  is moved in the X direction. The coupling  1118  can transmit the rotation of the servomotor  1116  to the shaft  1114 , even if an output shaft  1120  of the motor  1116  may be offset from the axis line of the shaft  1114 .  
     [0292] As shown in FIGS. 33 and 35, a pair of support portions  1124  (only one  1124  is shown in FIG. 33) project downward from one of two end portions of the connection member  1106  which are opposite to each other in the X direction, and extend toward the other end portion of the same  1106 . A support member  1126  is fixed to the two support portions  1124 . As shown in FIGS. 33 and 34, the support member  1126  has a pair of arm portions  1127  which are also fixed to the connection member  1106 . Another support member  1128  is fixed to the other end portion of the connection member  1106  such that the support member  1128  extends downward.  
     [0293] As shown in FIG. 33, the first support member  1126  supports a rotatable axis member  1132  via a plurality of bearings  1134  such that the axis member  1132  is rotatable about its axis line. For easier assembling, the support member  1126  is provided by a plurality of portions which are fixed to each other. One of those portions which supports an upper portion of the axis member  1132  is detachably attached to another portion of the support member  1126  which is fixed to the connection member  1106 .  
     [0294] A driven pulley  1136  is fixed to a lower portion of the axis member  1132 . The rotation of a rotation-body rotating servomotor  1138  as a drive source which is attached to the support member  1126  via a bracket  1137 , is transmitted to the driven pulley  1136  via a drive pulley  1140  and a transmission belt  1142 . Thus, the axis member  1132  can be rotated by any desired angle in each of opposite directions.  
     [0295] A hollow shaft member  1148  fits on the rotatable shaft member  1132  via bearings  1146  such that the hollow shaft member  1148  is rotatable about its axis line. A drive bevel gear  1150  as a drive gear is fixed to a lower end portion of the hollow shaft member  1148 , and a driven pulley  1152  is fixed to an upper end portion of the shaft member  1148 . The rotation of a rotation-position correcting and changing servomotor  1154  as a drive source which is attached to the support member  1126  is transmitted to the driven pulley  1152  via a drive pulley  1156  and a timing belt  1158 . Thus, the drive bevel gear  1150  can be rotated by any desired angle in each of opposite directions.  
     [0296] A CC-suction-shaft holding member  1162  is fixed to a projecting end portion of the rotatable shaft  1132  which projects downward from the hollow shaft  1148 , and cooperates with the rotatable shaft  1132  to provide the intermittent-rotation body  1164 . The holding member  1162  has sixteen holding holes  1166  (only two holes  1166  are shown in FIG. 33). The holding holes  1166  have, as their center lines, sixteen generators of a circular cone whose center line is defined by the axis line of rotation of the rotatable shaft  1132 , and the rotatable shaft  1132  is attached to the support member  1126  such that the axis line of the shaft  1132  is inclined with respect to a perpendicular of the horizontal rotation-body moving plane in which the rotation body  1164  is moved by the X-Y robot  1102 , by an angle at which one of the generators is perpendicular to the rotation-body moving plane. The two servomotors  1138 ,  1154  are attached to the support member  1126  such that respective output shafts of the motors  1138 ,  1154  are so inclined as to be parallel to the axis line of the rotatable shaft  1132 .  
     [0297] As shown in FIG. 37, a sleeve  1168  is fitted and fixed in each of the sixteen holding holes  1166 . Each sleeve  1168  includes a fixed portion which is fixed with a bolt (not shown) as a fixing member to a corresponding one of sixteen outer surfaces of the holding member  1162  which define respective portions of the sixteen outer surfaces of a 16-pyramid.  
     [0298] A rotatable member  1178  is fitted in each sleeve  1168  via a pair of bearings  1176  such that the member  1178  is rotatable about its axis line. Each rotatable member  1178  includes a lower end portion providing a large-diameter contact portion  1180 , an upper end portion on which a driven bevel gear  1182  as a driven gear fits, and an externally threaded portion  1184  with which a nut  1186  is threadedly engaged. Thus, the driven bevel gear  1182  is fixed to the rotatable member  1178  such that the pair of bearings  1176  are provided between the bevel gear  1182  and the contact portion  1180  and such that the bevel gear  1182  is meshed with the drive bevel gear  1150 .  
     [0299] A CC suction shaft  1170  is fitted in each rotatable member  1178 . Each CC suction shaft  1170  includes a shaft member  1190 , and a CC suction nozzle  1194  which is attached to the shaft member  1190  with an adaptor  1192 . The shaft member  1190  is fitted in the rotatable member  1178  such that the shaft member  1190  is movable relative to the rotatable member  1178  in an axial direction of the shaft member  1190 . A projecting lower end portion of the shaft member  1190  which projects downward from the rotatable member  1178  provides a large-diameter nozzle holding portion  1196 . A bearing  1200  is attached with an attaching member  1198  to a projecting upper end portion of the shaft member  1190  which projects upward from the rotatable member  1178 . A compression coil spring  1202  as an elastic member as a sort of biasing member is provided between the bearing  1200  and the nut  1186 , for biasing the CC suction shaft  1170  upward. The limit of the upward movement of the suction shaft  1170  due to the biasing force of the spring  1202  is defined by the contact of the nozzle holding portion  1196  with a friction ring  1204  fixed to a lower surface of the contact portion  1180  of the rotatable member  1178 . The friction ring  1204  is formed of a material having a high friction factor (e.g., rubber). The rotation of the rotatable member  1178  is transmitted to the shaft member  1190  by the frictional engagement of the ring  1204  and the holding portion  1196 .  
     [0300] The nozzle holding portion  1196  has a stepped hole  1210  which opens downward, and the adaptor  1192  is fitted in the stepped hole  1210  such that the adaptor  1192  is movable in an axial direction of the holding portion  1196 . The adaptor  1192  is held by a plurality of holding members  1212  which are attached to the nozzle holding portion  1196  such that the holding members  1212  are equiangularly spaced from each other about the axis line of the holding portion  1196 . A compression coil spring  1214  as an elastic member as a sort of biasing member biases the adaptor  1192  in a downward direction in which the adaptor  1192  advances out of the stepped hole  1210  of the nozzle holding portion  1196 .  
     [0301] The nozzle holding portion  1196  has a plurality of recesses  1216  which extend parallel to the axis line of the shaft member  1190  and which are equiangularly spaced from each other about the axis line of the holding portion  1196 . The holding members  1212  are fitted in the recesses  1216 , respectively, such that each holding member  1212  is rotatable, and are held on the holding portion  1196  with a ring-like spring member  1218  which is wound around the holding portion  1196 . Each holding member  1212  includes a projecting portion  1220  which is located above a portion thereof being fitted in the recess  1216 , which projects toward the center axis line of the holding portion  1196 , and which is fitted in a recess  1222  which is formed in the holding portion  1196 . Thus, each holding member  1212  is rotatable about its axis line which passes through the projecting portion  1220  being fitted in the recess  1222 , which is perpendicular to a lengthwise direction thereof and which is parallel to a tangent of an outer circumferential surface of the holding portion  1196  at a position where the holding member  1212  is attached to the holding portion  1196 . The holding member  1212  further includes an operative portion  1224  which projects upward from the projecting portion  1222  and which fits in a recess  1226  formed in the holding portion  1196 . Since the holding member  1212  fits in the recess  1216  and the operative portion  1224  thereof fits in the recess  1226 , the holding member  1212  is prevented from rotating about an axis line perpendicular to the axis line of the CC suction shaft  1170 .  
     [0302] A lower end portion of each holding member  1212  is fitted in a recess  1232  which is formed in a large-diameter engagement portion  1230  of the adaptor  1192 . Thus, the adaptor  1192  is prevented from being rotated relative to the holding portion  1196 . Each holding member  1212  includes an engagement projection  1234  which projects from the lower end portion thereof toward the adaptor  1192  and which engages a lower surface of the engagement portion  1230 , thereby preventing the adaptor  1192  from coming off the stepped hole  1210 . In this state, the adaptor  1192  can be removed from the holding portion  1196 , by pushing the respective operative portions  1224  of the holding members  1212  against the biasing force of the spring member  1218 , rotating the holding members  1212  about their axis lines, respectively, and thereby disengaging the engagement projections  1234  of the holding members  1212  from the engagement portion  1230  of the adaptor  1192 .  
     [0303] Each CC suction nozzle  1194  includes a suction-pipe holding member  1240 , and a suction pipe  1242  which is held by the holding member  1240 . The holding member  1240  includes a tapered portion  1244  which is fitted in a tapered hole  1246  formed in the adaptor  1192  and is held by the adaptor  1192  with the help of a spring member  1248 . The spring member  1248  has a generally U-shaped configuration including a pair of arms which are fitted in a pair of recesses  1252  formed in the adaptor  1192 , respectively. The distance between the two arms gradually decreases in a direction toward respective free end portions thereof. The free end portions of the two arms are bent toward each other, so that the spring member  1248  is prevented from coming off the adaptor  1192 .  
     [0304] When the tapered portion  1244  is fitted in the tapered hole  1246 , the spring member  1248  is fitted in an annular groove  1254  which is formed in the tapered portion  1244 , so that the spring member  1248  engages the tapered portion  1244 , thereby holding the holding member  1240 , and drags the tapered portion  1244  into the tapered hole  1246 , thereby positioning the holding member  1240  in the tapered portion  1244 . In a state in which the tapered portion  1244  is naturally fitted in the tapered hole  1246  of the adaptor  1192 , the center of the semi-circular cross section of the annular groove  1254  of the tapered portion  1244  is slightly upward offset from the center of the circular cross section of the spring member  1248  attached to the adaptor  1192 . Therefore, the spring member  1248  engages an upper portion of the annular groove  1254 , thereby pulling the holding member  1240  into the tapered hole  1246 . Reference numeral  1256  designates a reflector plate associated with the nozzle  1194 . Thus, the nozzle  1194  and the adaptor  1192  which holds the nozzle  1194  are detachably attached as a unit to the shaft member  1190 .  
     [0305] Sixteen pressure switch valves  1260  are fixed to the outer surface of the CC-suction-shaft holding member  1162 , such that the sixteen valves  1260  correspond to the sixteen CC suction shafts  1170 , respectively. Each switch valve  1260  includes a switch member  1261 , and is fixed to the holding member  1162  such that the switch valve  1260  extends parallel to the axis line of the corresponding suction shaft  1170 . As shown in FIGS. 33 and 37, the switch valve  1260  is connected to a vacuum device (not shown) via a passage  1262  formed in the holding member  1162 , passages  1264 ,  1266  formed in the rotatable shaft  1132 , and an annular passage  1268  formed in the support member  1126 .  
     [0306] As shown in FIG. 37, each pressure switch valve  1260  is connected to a passage  1282  formed in the shaft member  1190  of the corresponding CC suction shaft  1170  via another passage  1270  formed in the CC-suction-shaft holding member  1162 , a passage  1272  formed in the sleeve  1168 , a passage  1276  formed in a sealing member  1274 , and an annular passage  1280  formed in the rotatable member  1178 . The annular passage  1280  is elongate in the axial direction of the shaft member  1290 . Therefore, even when the suction shaft  1170  is rotated, or axially moved, relative to the rotatable member  1178 , the communication between the two passages  1280 ,  1282  is maintained.  
     [0307] Each CC suction shaft  1170  is sequentially stopped at sixteen stop positions while it is intermittently revolved by the intermittent-rotation body  1164 . One of the sixteen stop positions where the axis line of each CC suction shaft  1170  perpendicularly intersects the horizontal rotation-body moving plane is a CC suck-and-mount position, and another stop position angularly distant from the CC suck-and-mount position by 90 degrees is a CC-image pick-up position. At the CC suck-and-mount position, each CC suction shaft  1170  takes its lowest position, while it is intermittently revolved by the rotation body  1164 , and the CC-image pick-up position is higher than the CC suck-and-mount position. As shown in FIG. 36, a CC-image pick-up device  1290  is fixed via a bracket  1288  to a portion of the support member  1126  which corresponds to the CC-image pick-up position. The CC-image pick-up device  1290  has a construction similar to that of the CC-image pick-up device  820 , that is, includes a lighting device (not shown), a reflecting device  1294 , and a CCD camera  1296 . At the CC-image pick-up position, the axis line of each CC suction shaft  1170  is inclined with respect to a perpendicular of the horizontal rotation-body moving plane. The CC-image pick-up device  1290  is fixed to the support member  1126  such that the optical axis of the pick-up device  1290  is perpendicular to the axis line of each CC suction shaft  1170  being stopped at the pick-up position. As shown in FIG. 33, the optical axis of the pick-up device  1290  is inclined with respect to the horizontal rotation-body moving plane.  
     [0308] As shown in FIG. 34, a reference-mark-image pick-up device  1300  is supported by the second support member  1128  which provides part of the X-direction slide  1104 . As shown in FIG. 33, respective mechanical parts of an individual-CC-suction-shaft elevating and lowering device  1302  and a switch-valve control device  1304  are supported by a portion of the support member  1128  which corresponds to the CC suck-and-mount position. A linear motor  1310  is attached to the support member  1128 , and a drive member  1316  is fixed to a movable member  1314  which is fixed to a movable element  1312  of the linear motor  1310 . The drive member  1314  includes an engagement portion  1318  as a drive portion which extends to above the CC suction shaft  1170  being positioned at the CC suck-and-mount position.  
     [0309] The switch-valve control device  1304  has a construction similar to that of the switch-valve control device  882 . The movable member  1314  supports a main air cylinder  1320  as a main actuator, and an operative member  1322  which is moved by the main air cylinder  1320  to its operative and inoperative positions for switching the pressure switch valve  1260  to its negative-pressure (“NP”) supply position. Additionally, the support member  1128  supports a second main air cylinder as a main actuator, an auxiliary air cylinder as an auxiliary actuator, a second movable member, and a second operative member (all not shown) which cooperate with one another to switch the switch valve  1260  to its NP remove position. When the first movable member  1314  is moved by the linear motor  1310 , the first and second movable members are moved in opposite directions, respectively, in mechanical synchronism with each other, so that the first and second operative members are moved in opposite directions, respectively, so as to selectively act on the switch member  1261 . Thus, the switch valve  1260  is switched between its NP supply and remove states.  
     [0310] The second CC mounting system constructed as described above operates for mounting CCs  842  on a PCB  408 , in a manner similar to that in which the first CC mounting system  8  does. That is, each X-Y robot  1102  is operated and the corresponding intermittent-rotation body  1164  is intermittently rotated, so that the CC suction shafts  1170  are sequentially moved to the CC suck-and-mount position where the suction shafts  1170  suck the CCs  842  and subsequently are moved to above the PCB  408  for mounting the CCs  842  on the PCB  408 .  
     [0311] When the CCs  842  are sucked, the sixteen CC suction shafts  1170  are sequentially moved to the CC suck-and-mount position while the intermittent-rotation body  1164  is intermittently rotated. Since the drive bevel gear  1150  is rotated in the same direction and at the same angular velocity as those of the rotation body  1164 , each CC suction shaft  1170  is prevented from being rotated about its axis line. After each CC suction shaft  1170  reaches the CC suck-and-mount position, the movable member  1314  is lowered and accordingly the drive member  1316  and the suction shaft  1170  are lowered. When the suction shaft  1170  is lowered, the nozzle holding portion  1196  of the shaft member  1190  is separated from the friction ring  1204 . However, the suction shaft  1170  is not rotated relative to the rotatable member  1178 . For example, if a torsion is produced in the compression coil spring  1202 , a torque is produced which rotates the suction shaft  1170  relative to the rotatable member  1178 . However, since one end of the spring  1202  is supported by the suction shaft  1170  via the bearing  1200 , the spring  1202  is rotated relative to the suction shaft  1170  and accordingly the suction shaft  1170  is not rotated.  
     [0312] At a timing during the downward movement of the CC suction shaft  1170 , the pressure switch valve  1260  is switched to its NP supply state so that the NP (negative pressure) is supplied to the CC suction nozzle  1194  to suck and hold the CC  842 . After the sucking of the CC  842 , the drive member  1316  is elevated. Then, the suction shaft  1170  is elevated due to the biasing force of the compression coil spring  1202 . Thus, the CC  842  is taken from a feeder  54 .  
     [0313] When the CC suction shaft  1170  holding the CC  842  is moved to the CC-image pick-up position due to the rotation of the intermittent-rotation body  1164 , the image of the CC  842  held by the suction shaft  1170  is taken by the CC-image pick-up device  1290 . Like in the first embodiment, the image or images of one or more CCs  842  may be taken concurrently with, or prior to, the mounting of the first to fifth CCs  842  on the PCB  408 , depending upon the total number of the CCs  842  held by the sixteen suction shafts  1170  each time and the magnitudes of the rotation-position changing angles of the first to fourth CCs  842 .  
     [0314] When the CCs  842  are mounted on the PCB  408 , the CC suction shafts  1170  are sequentially positioned at the CC suck-and-mount position. While the CC suction shaft  1170  holding the CC  842  is moved to the CC suck-and-mount position for mounting the CC  842  on the PCB  408 , as the intermittent-rotation body  1164  is rotated by one angular pitch, the drive bevel gear  1150  is rotated relative to the rotation body  1164 , so that the suction shaft  1170  is rotated about its axis line for correcting its rotation-position error and changing its current rotation position by its rotation-position changing angle. The rotation of the drive bevel gear  1150  is transmitted to the CC suction nozzle  1194  via the driven bevel gear  1182 , the rotatable member  1178 , the friction ring  1204 , the nozzle holding portion  1196 , the holding members  1212 , and the adaptor  1192 . Thus, the CC  842  is rotated about the axis line of the nozzle  1194 . After the suction shaft  1170  reaches the CC suck-and-mount position, the drive member  1316  is lowered and accordingly the suction shaft  1170  is lowered for mounting the CC  842  on the PCB  408 . In addition, since the movable member  1314  is lowered, the pressure switch valve  1260  is switched to its NP remove state, so that after the CC  842  contacts the PCB  408 , air is supplied to the CC suction nozzle  1194  for releasing the CC  842  from the nozzle  1194 . Like in the first embodiment, the distance or stroke of upward and downward movements of each CC suction shaft  1170  and the timing at which each pressure switch valve  1260  is switched to its NP remove state can be selected from two different strokes and two different timings, respectively, depending upon the heights of the CCs  842 .  
     [0315] In the second CC mounting system, the common axis line around which the CC suction shafts  1170  are revolved is inclined with respect to the horizontal rotation-body moving plane. Accordingly, when the intermittent-rotation body  1164  is rotated, each suction shaft  1170  is moved up and down (i.e., moved toward, and away from, the horizontal rotation-body moving plane) while it is revolved. Each suction shaft  1170  takes the lowest position at the CC suck-and-mount position, and the CC-image pick-up position is higher than the CC suck-and-mount position. Thus, the CC-image pick-up device  1290  may be provided in a space between the CC suck-and-mount position and the CC-image-pick-up position. Therefore, the CC-image pick-up device  1290  is effectively prevented from interfering with each suction shaft  1170 , the CC  842  held by the shaft  1170 , or the corresponding CC supplying device  14 ,  16 . In addition, this arrangement contributes to reducing the distance or stroke of upward and downward movements of each CC suction shaft  1170  at the CC suck-and-mount position. Moreover, the optical axis of the CC-image pick-up device  1290  is also inclined with respect to the horizontal rotation-body moving plane. Accordingly, the dimension of the pick-up device  1290  in a direction perpendicular to the rotation-body moving plane is smaller than that of the same  1290  which would be provided at a stop position where each suction shaft  1170  takes a horizontal attitude and the optical axis of the device  1290  is perpendicular to the rotation-body moving plane. Thus, the X-direction slide  1104  can enjoy a compact construction and can move the intermittent-rotation body  1164  at high speed.  
     [0316] In the first or second embodiment shown in FIGS.  1  to  32  or FIGS.  33  to  37 , it is assumed that the twenty or sixteen CC suction nozzles  784 ,  1194  are of the same sort, that the respective suction pipes  788 ,  1242  thereof have the same diameter, and that the suction nozzles  784 ,  1194  are equiangularly spaced from one another as illustratively shown in FIG. 16 or FIG. 35. However, in a third embodiment shown in FIG. 38, ten first CC suction nozzles  1330  whose suction pipes have a large diameter and ten second CC suction nozzles  1332  whose suction pipes have a small diameter are alternately provided, and the twenty nozzles  1330 ,  1332  in total are equiangularly spaced from each other. In this figure, the nozzles  1330 ,  1332  are represented by their reflector plates.  
     [0317] In a fourth embodiment shown in FIG. 39, the ten first CC suction nozzles  1330  are provided adjacent to one another, and the ten second CC suction nozzles  1332  are provided adjacent to one another and are separated from the first nozzles  1330 .  
     [0318] In a fifth embodiment shown in FIG. 40, three sorts of CC suction nozzles  1340 ,  1342 ,  1344  whose suction pipes have different diameters are provided. In the case where the three sorts of nozzles  1340 ,  1342 ,  1344  are supported by respective CC suction shafts whose shaft portions have the same diameter irrespective of the different diameters of their suction pipes and accordingly each of the shaft portions can be freely fitted in any of twenty holding holes of the intermittent-rotation body  762 ,  1164 , the suction shafts supporting the nozzles whose pipes have the largest diameter may be fitted in every second or third holes. On the other hand, in the case where the three sorts of nozzles  1340 ,  1342 ,  1344  are supported by respective CC suction shafts whose shaft portions have different diameters corresponding to the different diameters of their suction pipes, respectively, the rotation body  762 ,  1164  may have holding holes which have different diameters corresponding to the different diameters of the shaft portions of the suction shafts, respectively.  
     [0319] In a modified form of the fifth embodiment, all the CC suction shafts held by the intermittent-rotation body  762 ,  1164  are provided by those which support the CC suction nozzles  1344  whose pipes have the largest diameter of the three sorts of nozzles  1340 ,  1342 ,  1344 . In this case, the rotation body  762 ,  1164  may hold ten CC suction shafts which are equiangularly spaced from one another. Otherwise, the rotation body  762 ,  1164  may hold CC suction shafts which support CC suction nozzles whose suction pipes have a diameter larger than that of the suction pipes of the CC suction nozzles  1344 . Moreover, the rotation body  762 ,  1164  may be adapted to support four or more sorts of CC suction nozzles.  
     [0320] In the case where the intermittent-rotation body  762 ,  1164  is equipped with CC suction nozzles whose suction pipes have a diameter or diameters corresponding to the size or sizes of CCs  842 , the rotatable body  762 ,  1164  can surely suck and hold the CCs  842 . Therefore, while the suction nozzles are intermittently revolved by the rotation body  762 ,  1164 , the CCs  842  are effectively prevented from being moved relative to the suction pipes, without having to lowering the speed of rotation of the rotation body  762 ,  1164 . Thus, the efficiency of mounting of CCs  842  can be maintained.  
     [0321] In each of the first to fifth embodiments, the CC mounting head  650 ,  652 ,  1100  is equipped with the intermittent-rotation body  762 ,  1164  which is rotatable about its axis line, and the CC suction shafts  766 ,  1170 , which are held by the rotation body  762 ,  1164 . However, in a sixth embodiment shown in FIGS. 41 and 42, a plurality of CC suction shafts  1352  are mounted on an X-Y robot  1350  as a CC transferring device, and the CC suction shafts  1352  are moved by the movement of the X-Y robot  1350  to a CC taking position where each suction shaft  1352  takes a CC  842  from the CC supplying device  14 ,  16 , and to above CC-mount places on a PCB  408 . The X-Y robot  1350  is equipped with a CC-suction-shaft selecting device  1354  which selects one of the CC suction shafts  1352  which is to suck or mount a CC  842 , and with an elevating and lowering device  1356  which simultaneously elevates or lowers all the CC suction shafts  1352 . While the elevating and lowering device  1356  simultaneously elevates or lowers all the CC suction shafts  1352 , the CC-suction-shaft selecting device  1354  selects one of the suction shafts  1352  such that the selected shaft  1352  projects downward from the other suction shafts  1352 . Thus, only the selected shaft  1352  can suck or mount the CC  842 .  
     [0322] In a seventh embodiment shown in FIGS. 43 and 44, an X-Y robot  1360  as a CC transferring device supports a movable member  1362  which is movable relative to the X-Y robot  1360  in one direction (e.g., X direction), and the movable member  1362  supports a plurality of CC suction shafts  1364  which are arranged in an array in the same direction. The X-Y robot  1360  is equipped with a movable-member moving device (not shown) which moves the movable member  1362  and which cooperates with the movable member to provide a CC-holder moving device which linearly moves the CC suction shafts  1364  as CC holders so that the suction shafts  1364  are sequentially positioned at a CC suck-and-mount position. Thus, the X-Y robot  1360  as the CC transferring device also functions as a CC-holder-moving-device supporting member. At the CC taking position on the CC supplying device  14 ,  16 , or at the CC-mount places on the PCB  408 , the CC suction shafts  1364  are sequentially moved by the movement of the movable member  1362  to the CC suck-and-mount position where each suction shaft  1364  sucks a CC  842  from the CC supplying device  14 ,  16  or mounts the CC  842  at the corresponding CC-mount place on the PCB  408 . The X-Y robot  1366  is additionally equipped with a CC-suction-shaft moving device  1366  (e.g., an elevating and lowering device) which moves each suction shaft  1364  in an axial direction thereof, and with a switch-valve control device (not shown). The CC-suction-shaft moving device  1366  and the switch-valve control device are mounted on a portion of the X-Y robot  1360  in the vicinity of the CC suck-and-mount position. The CC-suction-shaft moving device  1366  moves the CC suction shaft  1364  being positioned at the CC suck-and-mount position, in its axial direction, and the switch-valve control device switches one of a plurality of pressure switch valves which are provided for the plurality of CC suction shafts  1364 , respectively, the one switch valve being provided for the CC suction shaft  1364  being positioned at the CC suck-and-mount position. Thus, the CC suction shaft  1364  being positioned at the CC suck-and-mount position sucks the CC  842 , or mounts the CC  842  on the PCB  408 .  
     [0323] In the seventh embodiment of FIGS. 43 and 44, the movable member  1362  is movable in one direction only. However, in an eighth embodiment shown in FIG. 45, an X-Y robot  1370  as a CC transferring device is equipped with a movable member  1372  which is movable in both an X direction and a Y direction, and with a movable-member moving device (not shown) which moves the movable member in both the X and Y directions. The movable member  1372  supports a plurality of CC suction shafts  1374  which are arranged to form a matrix, i.e., arranged in a plurality of arrays in each of the X and Y directions. In this case, the movable member  1372  cooperates with the movable-member moving device to provide a CC-holder moving device which linearly moves the CC suction shafts  1374  as CC holders.  
     [0324] In the seventh embodiment of FIGS. 43 and 44 or the eighth embodiment of FIG. 45, the X-Y robot  1360  or  1370  may be equipped with a cam surface including a curved or inclined portion having changing height positions in a direction parallel to the respective axis lines of the CC suction shafts  1364 ,  1374 , and each of the CC suction shafts  1364 ,  1374  may be equipped with a cam follower which follows the cam surface. In this case, while the movable member  1362 ,  1372  is movable relative to the X-Y robot  1360 ,  1370  in the X and Y directions, each suction shaft  1362 ,  1372  is movable in the axial direction thereof due to the engagement of the cam follower thereof with the curved or inclined portion of the cam surface of the X-Y robot  1360 ,  1370 .  
     [0325] In each of the sixth to eighth embodiments shown in FIGS.  41  to  45 , the CC-suction-shaft moving plane in which the CC suction shafts are moved is horizontal. However, the horizontal moving plane may be replaced by an inclined moving plane which is inclined with respect to a horizontal plane.  
     [0326] In each of the illustrated embodiments, the variable throttle valve  1026  adjusts the amount of air flowing from the CC suction nozzle  784 ,  1194  as the CC holding portion after the air pressure in the suction nozzle  784 ,  1194  has been increased, and the throttle valve  1026  is connected in series with the pressure switch valve  860  associated with the suction nozzle  784 . However, in a ninth embodiment shown in FIG. 46, a variable throttle valve  1402  as a variable restrictor device is provided in parallel with a pressure switch valve  1400  which is in communication with the atmosphere. In this case, before an operative member (not shown) contacts and pushes a movable switch member (not shown) of the switch valve  1400 , a solenoid-operated shut-off valve  1404  is opened, so that the switch valve  1400  is supplied with air from an air supplying device  1406  via a restrictor  1408 . The symbol “o” (white circle) represents the state in which the operative member contacts the switch member. If the switch valve  1400  is switched to its NP remove position, a suction pipe  1410  is supplied with the air. Till the air pressure in the suction pipe  1410  increases up to, or exceeds, the atmospheric pressure, a major portion of the air is supplied to the suction pipe  1410 . After this pressure increase, the amount of air flowing into the atmosphere through the variable throttle valve  1402  increases. Thus, the suction pipe  1410  is supplied with an appropriate amount of air for releasing the CC  842  therefrom.  
     [0327] As the degree of opening of the variable throttle valve  1402  decreases, i.e., as the amount of air leaking into the atmosphere decreases, the amount of air supplied to the suction pipe  1410  after the air pressure in the pipe  1410  has increased up to, or exceeded, the atmospheric pressure increases, and vice versa. The twenty or sixteen CC suction shafts  766 ,  1170  have their pressure switch valves  860 ,  1400 . When the current sort of CC suction nozzles  784 ,  1194  for mounting the current sort of CCs  842 ,  1194  are replaced with another sort of nozzles  784 ,  1194  for mounting another sort of CCs  842 , the degree of opening of the variable throttle valve  1402  is adjusted corresponding to the diameter of the suction pipes  788 ,  1242  of the new sort of nozzles  784 . Thus, each suction pipe  788 ,  1242  is supplied with an appropriate amount of air corresponding to the diameter thereof, and the CC  842  held by the suction pipe  788 ,  1242  is effectively prevented from being blown off due to the supplying thereto of an excessive amount of air. That is, the CC  842  is quickly and surely released from the suction pipe  788 ,  1242 .  
     [0328] In the ninth embodiment of FIG. 46, the restrictor  1408  may be provided by a variable restrictor which adjusts the amount of air supplied to the pressure switch valve  1400  from the air supplying device  1406 . In this case, the ratio of the amount of air flowing into the CC suction nozzle  784 ,  1194  immediately after the switching of the pressure switch valve  1400  to its NP remove position, to the amount of air flowing into the CC suction nozzle  784 ,  1194  after the increase of air pressure in the nozzle  784 , can be adjusted with higher accuracy.  
     [0329] In the first embodiment shown in FIGS.  1  to  32 , the carry-in conveyor  404  and the carry-out conveyor  406  are shifted to their first and second shift positions by the carry-in-conveyor shifting device  438  and the carry-out-conveyor shifting device  508 , respectively, which include the respective rodless cylinders  436  as their drive sources. In contrast, in a CC mounting system  1444  as a tenth embodiment shown in FIGS. 48 and 49, a PCB conveyor  1446  includes a carry-in conveyor  1454  and a carry-out conveyor  1456 , and a carry-in-conveyor shifting device  1450  and a carry-out-conveyor shifting device  1452  for shifting the carry-in conveyor  1454  and the carry-out conveyor  1456 , respectively, by using, as their drive sources, respective servomotors  1448  each as an electric rotary motor as a sort of electric motor. A servomotor is accurately controllable with respect to its angular or rotation position.  
     [0330] First, the carry-in-conveyor shifting device  1450  will be described. The present CC mounting system  1444  includes a guide support table  1458  on which an externally threaded shaft  1464  is provided such that the threaded shaft  1464  is rotatable about its axis line parallel to a Y direction in which two main conveyors  1460 ,  1462  are arranged, and such that the threaded shaft  1464  is not movable in its axial direction. The threaded shaft  1464  has a length greater than the respective dimensions of the main conveyors  1460 ,  1462  in the Y direction in which they are arranged, and is provided on the guide support table  1458  such that the threaded shaft  1464  extends over the summed lengths of the two main conveyors in the Y direction. An internally threaded nut  1468  fixed to a conveyor support table  1466  is threadedly engaged with the threaded shaft  1464  via steel balls (not shown). The threaded shaft  1464 , the nut  1468 , and the steel balls cooperate with one another to provide a ball screw.  
     [0331] When the threaded shaft  1464  is rotated by the servomotor  1448 , the conveyor support table  1466  is moved by being guided by a pair of straight guide rails  1470  as guide members, so that the carry-in conveyor  1454  is shifted to not only its first and second shift positions where the carry-in conveyor  1454  is aligned with the first and second main conveyors  1460 ,  1462 , respectively, but also one or more desired shift positions which are different from the first and second shift positions and are within a widened range wider than the range whose opposite ends correspond to the first and second shift positions, respectively. The pair of guide rails  1470  which extend, like the threaded shaft  1464 , over the summed lengths of the two main conveyors  1460 ,  1462 , cooperate with guide blocks  1472  as guided members which are attached to the conveyor support table  1466 , to provide a guiding device  1474 . The guide blocks  1472  are fitted on the guide rails  1470  such that the conveyor support table  1466  is movable relative to the guide rails  1470 . The threaded shaft  1464  cooperates with the nut  1468  to provide a motion converting device, which cooperates with the servomotor  1448  to provide a drive device, which cooperates with the conveyor support table  1466  and the guiding device  1474  to provide the carry-in-conveyor shifting device  1450 . The servomotor  1448  is controlled by the control device  1050 , employed in the first embodiment, via a drive circuit (not shown).  
     [0332] The carry-in conveyor  1454  includes two side frames, that is, a fixed side frame  1476  and a movable side frame  1478 . A spline shaft  1480  is provided on the guide support table  1458  such that the spline shaft  1480  is rotatable about its axis line, and is not movable in its axial direction, relative to the table  1458 . A spline tube  1482  is attached to the conveyor support table  1466  such that the spline tube  1482  is rotatable about its axis line, and is not movable in its axial direction, relative to the table  1466 . The spline tube  1482  is fitted on the spline shaft  1480  such that the tube  1482  is movable in its axial direction, and is not rotatable about its axis line, relative to the shaft  1480 . Thus, the rotation of the spline shaft  1480  is converted into the linear movement of the movable side frame  1478  by a threaded shaft  1484  and a nut  1486 , so that the CS conveying width of the carry-in conveyor  1454  is changed, in the same manner as that described for the first embodiment. The spline shaft  1480  and the spline tube  1482  cooperate with each other to provide a ball spline. The spline shaft  1480  extends, like the threaded shaft  1464 , over the summed lengths of the two main conveyors  1460 ,  1462 . Thus, when the carry-in conveyor  1454  is shifted, the spline tube  1482  remains engaged with the spline shaft  1480 . Two cylindrical guide blocks  1487  as guided members which are fixed to the movable side frame  1478  are respectively fitted, via balls (not shown), on two straight guide rails  1488  as guide members which are provided on the conveyor support table  1466 . Thus, the movable side frame  1478  is movable relative to the conveyor support table  1466 . The guide blocks  1487  and the guide rails  1488  cooperate with each other to provide a linear ball guide  1489  as a sort of guiding device for guiding the linear movement of the movable side frame  1478 .  
     [0333] The carry-out-conveyor shifting device  1452  and the carry-out conveyor  1456  have the same constructions as those of the carry-in-conveyor shifting device  1450  and the carry-in conveyor  1454 , respectively. The same reference numerals as used for the carry-in-conveyor shifting device  1450  and the carry-in conveyor  1454  are used for designating the corresponding elements or parts of the carry-out-conveyor shifting device  1452  and the carry-out conveyor  1456 , respectively, and the description thereof is omitted. However, the shift range within which the carry-out conveyor  1456  is shiftable is wider than that of the carry-in conveyor  1454 , and accordingly the threaded shaft  1464 , guide rails  1470 , and spline shaft  1480  of the carry-out-conveyor shifting device  1452  have longer lengths than those of the counterparts of the carry-in-conveyor shifting device  1450 .  
     [0334] A handle  1490  is manually operable or rotatable by an operator. The driving or rotating force produced by the operator&#39;s manual rotation of the handle  1490  is transmitted to the respective spline shafts  1480  of the carry-in and carry-out conveyors  1454 ,  1456  by a rotation transmitting device including a plurality of sprockets  1492  each as a sort of rotatable member and a plurality of chains  1494  each as a sort of wound-on member. Each of the chains  1494  is wound on two or more sprockets  1492 .  
     [0335] Each of the two main conveyors  1460 ,  1462  includes two side frames, that is, a fixed side frame  1498  and a movable side frame  1500 . Two nuts (not shown) which are fixed to the movable side frame  1500  of the first main conveyor  1460  are threaded engaged with two threaded shafts  1502  (only one shaft  1502  is shown in FIG. 49), respectively. Two sprockets  1492  which provide part of the above-indicated rotation transmitting device are fixed to the two threaded shafts  1502 , respectively. Thus, the rotation transmitting device transmits the rotating force produced by the operator&#39;s manual rotation of the handle  1490  to the threaded shafts  1502 . The sprockets  1492  provide driven rotatable members, and the nuts and the threaded shafts  1502  cooperate with each other to provide a motion converting device. The movement of the movable side frame  1500  is guided by a linear ball guide  1503  as a sort of guiding device which is provided by straight guide rails  1506  and cylindrical guide blocks  1504  which are fitted on the guide rails  1506  via balls (not shown) such that the guide blocks  1504  is movable in their axial direction relative to the guide rails  1506 .  
     [0336] The movable side frame  1500  of the second main conveyor  1462  is integrally connected to the movable side frame  1500  of the first main conveyor  1460  by two connection members  1508 . Like the movable side frame  1500  of the first main conveyor  1460 , the movable side frame  1500  of the second main conveyor  1462  is guided, when being moved, by another linear ball guide  1503  including straight guide rails  1506  and cylindrical guide blocks  1504  which are fitted on the guide rails  1506  via balls (not shown) such that the guide blocks  1504  is movable in their axial direction relative to the guide rails  1506 .  
     [0337] The CC mounting system  1544  provide part of an electronic-circuit assembly line  1522  which additionally includes a screen printing system  1512  as an upstream-side device which is disposed on an upstream side of the CC mounting system  1444  in a PCB conveying direction in which PCBs are conveyed. As shown in FIG. 48, the printing system  1512  has a carry-out conveyor  1514  which carries out PCBs one by one and which is aligned with a portion of the shift range of the carry-in conveyor  1454  of the CC mounting system  1444  which portion is offset from the first main conveyor  1460  in a direction away from the second main conveyor  1462 . Additionally, the assembly line  1522  includes two solder reflowing systems  1516 ,  1518  each as a downstream-side device which are disposed on a downstream side of the CC mounting system  1444  in the PCB conveying direction. The two reflowing systems  1516 ,  1518  are arranged in a direction parallel to a shifting direction in which the carry-out conveyor  1456  is shifted. The two reflowing systems  1516 ,  1518  include respective carry-in conveyors  1520 ,  1520  which are aligned with opposite end portions of the shift range of the carry-out conveyor  1456  in its shifting direction.  
     [0338] The carry-in conveyor  1454  of the CC mounting system  1444  is moved to one of its shift positions where the conveyor  1454  is aligned with the carry-out conveyor  1514  of the screen printing system  1512 , for receiving a PCB  408  on which a screen printing has been finished, and then is moved to its first or second shift position where it hands over the PCB  408  to the first or second main conveyor  1460  or  1462 . The carry-out conveyor  1456  of the CC mounting system  1444  is moved to its first or second shift position where it receives the PCB  408  from the first or second main conveyor  1460  or  1462 , and then is moved to one of its shift positions which is aligned with the first or second solder reflowing systems  1516  or  1518 , for handing over the PCB  408  to the same  1516  or  1518 . The carry-in or carry-out conveyor  1454  or  1456  can be shifted to any desired position within its shift range, owing to the use of the servomotor  1448  as the drive motor. Therefore, the carry-in or carry-out conveyor  1454 ,  1456  can receive, without any problems, the PCB  408  from the screen printing system  1512 , or hand over the PCB  408  to the first or second solder reflowing system  1516  or  1518 , at its shift position different from its shift position where the carry-in or carry-out conveyor  1454 ,  1456  hands over the PCB  408  to, or receives the PCB  408  from, the first or second main conveyor  1460  or  1462 . Accordingly, the printing system  1512  or the reflowing systems  1516 ,  1518  enjoys or enjoy improved degree of freedom with respect to the manner in which it or they are laid out relative to the CC mounting system  1444 . This is also true with the carry-out conveyor  1514  or the carry-in conveyors  1452 ,  1456  which is or are provided between the CC mounting system  1444  and the printing system  1512  or the reflowing systems  1516 ,  1518  for handing over or receiving the PCB  408 . Consequently, the electronic-circuit assembly line  1522 , or a CS-related-operation performing line including the assembly line  1522 , enjoys improved degree of design.  
     [0339] The respective spline shafts  1480  of the carry-in and carry-out conveyors  1454 ,  1456  extend over the summed lengths of the two main conveyors  1460 ,  1462  in the Y direction. Thus, whichever position the carry-in or carry-out conveyor  1454  or  1456  may be shifted to, the spline tube  1486  of the carry-in or carry-out conveyor  1454  or  1456  remains engaged with the spline shaft  1480 . Thus, whenever the operator rotates the handle  1490 , the respective threaded shafts  1484 ,  1502  of the carry-in and carry-out conveyors  1454 ,  1456  and the first main conveyor  1460  are concurrently rotated, so that the PCB conveying widths of the carry-in and carry-out conveyors  1454 ,  1456  and the first main conveyor  1460  are concurrently changed by the same value. Since the movable side frame  1500  of the first main conveyor  1460  is integrally connected to that  1500  of the second main conveyor  1462  via the connection members  1508 , the two movable side frames  1500  are moved as a unit, so that the PCB conveying widths of the two main conveyors  1460 ,  1462  are simultaneously changed by the same value.  
     [0340] The two downstream-side devices  1516 ,  1518  may be replaced by a single downstream-side device, and the single upstream-side device  1512  may be replaced by a plurality of upstream-side devices which are arranged in the shifting direction of the carry-in conveyor  1454 . Alternatively, the present assembly line  1522  may comprise a plurality of upstream-side devices which are arranged in the shifting direction of the carry-in conveyor  1454 , and a plurality of downstream-side devices which are arranged in the shifting direction of the carry-out conveyor  1456 .  
     [0341] At least one of at least one upstream-side device  1512  and at least one downstream-side device  1516 ,  1518  of the assembly line  1522  may be provided at at least one position which is aligned with at least one of the main conveyors  1460 ,  1462  of the CC mounting system  1444 .  
     [0342] In the case where the assembly line  1522  includes a single upstream-side device, or a single downstream-side device, the single upstream-side device or the single downstream-side device may have a plurality of carry-out conveyors each for carrying out CSs, or a plurality of carry-in conveyors each for carrying in CSs, respectively. Those carry-out conveyors or those carry-in conveyors may include at least one conveyor which is not aligned with any main conveyors  1460 ,  1462  of the CC mounting system  1444 . In those cases, however, the carry-in conveyor  1454  or the carry-out conveyor  1456  of the CC mounting system  1444  can be shifted to a position aligned with each one of the carry-out conveyors of the upstream-side device, or each one of the carry-in conveyors of the downstream-side device. Thus, the carry-in conveyor  1454  or the carry-out conveyor  1456  can surely receive the PCB  408  from the upstream-side device, or hand over the PCB  408  to the downstream-side device.  
     [0343] The shift range of the carry-in conveyor  1454  may be wider than, or equal to, that of the carry-out conveyor  1456 . In the last case, the upstream-side device  1512  and the downstream-side devices  1516 ,  1518  may be disposed relative to the main conveyors  1460 ,  1462  of the CC mounting system  1444 , such that at least one of the carry-out conveyor  1514  of the upstream-side device  1512  and the carry-in conveyors  1520  the downstream-side devices  1516 ,  1518  is not aligned with any main conveyors  1460 ,  1462 .  
     [0344] The two threaded shafts  1502 , the nuts threadedly engaged with the shafts  1502 , and the two connection members  1508  may be replaced by two motion converting devices which are provided for the two main conveyors  1460 ,  1462 , respectively, and each of which includes a threaded shaft and a nut threadedly engaged with the shaft. In the latter case, the two threaded shafts are connected to each other such that the two shafts are not rotatable, and is not movable in their axial directions, relative to each other. The two threaded shafts may be replaced by a single shaft including two threaded portions. When the two or single threaded shafts or shaft are or is rotated, the respective movable side frames  1500  of the two main conveyors  1460 ,  1462  are concurrently moved relative to the respective fixed frames  1498  of the same  1460 ,  1462 .  
     [0345]FIG. 50 shows an eleventh embodiment of the present invention in which the PCB conveying widths of the main conveyors  400 ,  402 ,  1460 ,  1462 , the carry-in conveyor  404 ,  1454 , and the carry-out conveyor  406 ,  1456  of the first or tenth embodiment are automatically changed by using, as a drive source, a servomotor  1540  as an electric rotary motor as a sort of electric motor. The servomotor  1540  is controlled by the control device  1050  of the first embodiment via a drive circuit (not shown). Thus, the respective PCB conveying widths of the above-indicated conveyors are changed all at once by the same amount. All the other elements or parts of the eleventh embodiment are the same as the corresponding elements or parts of the tenth embodiment shown in FIGS. 48 and 49, and the description thereof is omitted.  
     [0346] In the first or tenth embodiment, the respective PCB conveying widths of the main conveyors  400 ,  402 ,  1460 ,  1462 , the carry-in conveyor  404 ,  1454 , and the carry-out conveyor  406 ,  1456  of the PCB conveyor device  12 ,  1446  are simultaneously changed by rotating altogether the respective threaded shafts  448 ,  536 ,  1484 ,  1502  of those conveyors  400 ,  402 ,  1460 ,  1462 ,  404 ,  1454 ,  406 ,  1456 . In contrast, FIG. 51 shows a twelfth embodiment of the present invention in which respective movable side frames  1554  of a carry-in conveyor  1550  and a carry-out conveyor  1552  are connectable to a movable side frame  1558  of a desired one of two main conveyors  1556  (only one conveyor  1556  is shown in the figure) with the help of two separable connection members  1560 . Thus, when the movable side frames  1554  are moved, the respective movable side frames  1558  of the two main conveyors  1556  which are integrally connected to each other with the help of two connection members  1566  fixed thereto are moved, so that the PCB conveying widths of those conveyors  1550 ,  1552 ,  1556  are simultaneously changed. Each of the conveyors  1550 ,  1552 ,  1556  includes, in addition to a corresponding one of the movable side frames  1554 ,  1556 , a fixed side frame (not shown).  
     [0347] Each of the respective movable side frames  1554  of the carry-in and carry-out conveyors  1550 ,  1552  has a groove  1562  formed in an end portion thereof on the side of the main conveyors  1556 . The two grooves  1562  function as engageable portions which are engageable with the two connection members  1560 , respectively. Each of the grooves  1562  opens in an upper surface of a corresponding one of the movable side frames  1554 , and in an end surface of the same facing the main conveyors  1556 . The carry-in and carry-out conveyors  1550 ,  1552  have the same constructions as those of the carry-in and carry-out conveyors  404 ,  406  of the first embodiment shown in FIGS.  1  to  32 , except that the movable side frames  1554  of the former conveyors  1550 ,  1552  have the grooves  1562 , respectively. Thus, when an operator rotates the handle  510 , the threaded shafts of the carry-in and carry-out conveyors  1550 ,  1552  are simultaneously rotated, so that the respective movable side frames  1554  thereof are simultaneously moved. Thus, the PCB conveying widths of the two conveyors  1550 ,  1554  are simultaneously changed.  
     [0348] The movable side frame  1558  of each of the two main conveyors  1556  has a groove  1564  formed in one end portion thereof on the side of the carry-in conveyor  1550 , and another groove  1564  formed in the other end portion thereof on the side of the carry-out conveyor  1552 . The two grooves  1564  also function as engageable portions which are engageable with the two connection members  1560 . One of the two grooves  1564  opens in an upper surface of the movable side frame  1558  of each main conveyor  1556 , and in an end surface of the same facing the carry-in conveyor  1550 , and the other groove  1564  opens in the upper surface of the movable side frame  1558  of each main conveyor  1556 , and in an end surface of the same facing the carry-out conveyor  1552 . Each of the two main conveyors  1556  is not equipped with any threaded shafts or nuts for changing its PCB conveying width, unlike the main conveyors  400 ,  402  of the first embodiment.  
     [0349] When the PCB conveying widths of the conveyors  1550 ,  1552 ,  1556  are changed, first, the carry-in and carry-out conveyors  1550 ,  1552  are moved to their shift positions where those conveyors are aligned with an appropriate one of the two main conveyors  1556 . In this state, an operator fits the first connection member  1560  in the groove  1562  of the carry-in conveyor  1550  and a corresponding one of the two grooves  1564  of the one main conveyor  1556 , and fits the second connection member  1560  in the groove  1562  of the carry-out conveyor  1552  and the other groove  1564  of the one main conveyor  1556 . Thus, the two movable side frames  1554  are connected to the two movable side frames  1558 . Subsequently, if the operator rotates the handle  510 , the two movable side frames  1554  are simultaneously moved, so that the two movable side frames  1558  which are integrally connected to each other by the connection members  1566  are simultaneously moved by being guided by a guiding device (not shown). Since the respective movable side frames  1558  of the two main conveyors  1556  are integrally connected to each each other by the connection members  1566 , the movement of one of the movable side frames  1558  which is directly connected to the movable side frames  1554  causes the movement of the other movable side frame  1558  connected to the one movable side frame  1558  by the connection members  1566 , while those movements are guided by the guiding device. Thus, the PCB conveying widths of the two main conveyors  1556  are simultaneously changed. Then, the operator removes the connection members  1560  from the grooves  1562 ,  1564 , so that the carry-in and carry-out conveyors  1550 ,  1552  can be shifted relative to the main conveyors  1556 . The connection members  1560  and the grooves  1562 ,  1564  cooperate with each other to provide a frame connecting device  1568 .  
     [0350] The operator selects, based on, e.g., the respective current shift positions of the carry-in and carry-out conveyors  1550 ,  1552  at the time when the PCB conveying widths thereof are changed, an appropriate one of the two main conveyors  1556  to which the carry-in and carry-out conveyors  1550 ,  1552  are connected by the frame connecting device  1568 . For example, in the case where both the carry-in and carry-out conveyors  1550 ,  1552  are at that time at respective positions aligned with one of the two main conveyors  1556 , the operator can easily select the one main conveyor  1556 . In the case where the carry-in and carry-out conveyors  1550 ,  1552  are at that time at respective positions aligned with the two main conveyors  1556 , respectively, an appropriate one of the carry-in and carry-out conveyors  1550 ,  1552  is moved to a position aligned with the other of the carry-in and carry-out conveyors  1550 ,  1552 , so that both the carry-in and carry-out conveyors  1550 ,  1552  are aligned with one of the two main conveyors.  
     [0351] In the case where at least one of the carry-in and carry-out conveyors  1550 ,  1552  are at that time at a position aligned with neither of the two main conveyors  1556 , the operator selects one of the two main conveyors  1556  such that the sum of the distance between the one main conveyor  1556  and the carry-in conveyor  1550  and the distance between the one main conveyor  1556  and the carry-out conveyor  1552  is shorter than that of the distance between the other main conveyor  1556  and the carry-in conveyor  1550  and the distance between the other main conveyor  1556  and the carry-out conveyor  1552 , and moves the carry-in and/or carry-out conveyors  1550 ,  1552  to respective positions aligned with the one main conveyor  1556 .  
     [0352] However, the respective movable side frames  1554  of the carry-in and carry-out conveyors  1550  may be connected to the two main conveyors  1556 , respectively, because the two movable side frames  1558  are permanently connected to each other by the connection members  1566 . Thus, the operator enjoys improved degree of freedom of selection of the respective shift positions of the carry-in and carry-out conveyors  1550 ,  1552  at the time when the PCB conveying widths of the conveyors  1550 ,  1552 ,  1556  are changed.  
     [0353] In the first or tenth embodiment, the EC (electronic-circuit) assembly line  6 ,  1522  includes the single CC mounting system  8 ,  1444  in addition to the screen printing system  2 ,  1512  and the solder reflowing system or systems  4 ,  1516 ,  1518 . In contrast, FIG. 52 shows a thirteenth embodiment of the present invention relating to an EC assembly line  1578  which includes, in addition to a screen printing system  1574  and a solder reflowing system  1576 , two CC mounting systems  1570 ,  1572  which are arranged in series with each other in a PCB conveying direction indicated at arrow in the figure in which the PCB  408  is conveyed. Each of the two CC mounting systems  1570 ,  1572  includes a PCB conveyor device  1580  which includes two main conveyors  1582 ,  1584 , a single carry-in conveyor  1586 , and a single carry-out conveyor  1588 . The carry-out conveyor  1588  of the upstream-side CC mounting system  1570  can hand over each PCB  408  to the carry-in conveyor  1586  of the downstream-side CC mounting system  1578  at a desired one of the two shift positions of each of the two conveyors  1588 ,  1586 .  
     [0354]FIG. 53 shows a fourteenth embodiment of the present invention relating to a CS-related-operation performing line  1610  including a PCB-related-operation performing system  1600  which includes two main conveyors  1602 ,  1604  and a single carry-in and carry-out conveyor  1606  which is provided on an upstream (or downstream) side of the main conveyors  1602 ,  1604  and which functions as both a carry-in conveyor and a carry-out conveyor. The carry-in and carry-out conveyor  1606  can convey the PCB  408  in both a forward direction and a backward direction. When the conveyor  1606  conveys each PCB  408  in the forward direction, it functions as a carry-in conveyor; and when it conveys each PCB  408  in the backward direction, it functions as a carry-out conveyor. Each of the two main conveyors  1602 ,  1604  can also convey the PCB  408  in both the forward and backward directions. The carry-in and carry-out conveyor  1606  is selectively shifted, by a carry-in-and-carry-out-conveyor shifting device (not shown), to one of its first and second shift positions where the conveyor  1606  is aligned with a corresponding one of the two main conveyors  1602 ,  1604 . The carry-in-and-carry-out-conveyor shifting device includes, as a drive source thereof, a rodless cylinder device similar to that  436  of the conveyor shifting device  438  of the first embodiment. However, the shifting device may include, as the drive source thereof, a servomotor similar to that  1488  of the conveyor shifting device  1450  of the tenth embodiment. In the latter case, the shifting device can move the conveyor  1606  to any position within its shift range.  
     [0355] The operation performing line  1610  additionally includes a PCB carry-in and carry-out device  1608  on an “upstream” side of the operation performing system  1600 , assuming that the carry-in and carry-out conveyor  1606  is operating as the carry-in conveyor, that is, on a “downstream” side of the same  1600  assuming that the carry-in and carry-out conveyor  1606  is operating as the carry-out conveyor. The PCB carry-in and carry-out device  1608  has the function of supplying a plurality of PCBs  408  one by one to the operation performing system  1600 , and the function of receiving the PCBs  408  one by one from the system  1600  and temporarily storing them. The PCB-related-operation performing system  1600  discharges the PCBs  408  to the same side as that from which it receives the PCBs  408 . The PCB carry-in and carry-out device  1608  supplies PCBs  408  one by one to the carry-in and carry-out conveyor  1606  and receives the PCBs  408  one by one on which CCs have been mounted. Thus, the PCB carry-in and carry-out device  1608  functions as both an upstream-side device and a downstream-side device with respect to the operation performing system  1600  functioning as a CC mounting system.  
     [0356] The shift range within which the carry-in and carry-out conveyor  1606  is shiftable may be wider than a range whose opposite ends are defined by its two shift positions, respectively, which are aligned with the two main conveyors  1602 ,  1604 , respectively.  
     [0357]FIG. 54 shows a CC mounting head  1620  of a CC mounting device of a CC mounting system as an eighth embodiment of the present invention. The CC mounting head  1620  includes a vertical axis member  1624  which is supported by an X-direction movable slide  1622  of an X-Y robot (not shown), and a plurality of rotary plates  1626  (twelve rotary plates  1626  in the present embodiment) as a plurality of rotary members which are attached to the axis member  1624  such that the rotary plates  1626  are rotatable about the axis member, independent of each other. Each of the rotary plates  1626  includes a holding portion which holds a CC suction head (not shown) such that the CC suction head is movable in an axial direction thereof, i.e., movable up and down. When the rotary plates  1626  are rotated by a rotary-plate rotating device  1628  as a rotary-motion applying device, the twelve CC suction heads are revolved around the vertical axis member  1624 , i.e., a vertical axis line thereof. Each of the twelve CC suction heads includes a CC suction nozzle which is rotatable about an axis line thereof.  
     [0358] The rotary-plate rotating device  1628  includes twelve cam-follower rollers  1632  attached to the twelve rotary plates  1626 , respectively, and four concave globoidal cams  1634   a,    1634   b,    1634   c,    1634   d  as rotary-motion applying cams which sequentially engage each of the cam-follower rollers  1632  for moving the roller  1632  and thereby rotating the corresponding rotary plate  1626 . The four concave globoidal cams  1634   a - 1634   d  are disposed at respective positions which are axial-symmetric with one another with respect to the vertical axis member  1624 , such that the inner lines of intersection of respective outer circumferential surfaces of the concave globoidal cams  1634  with a plane including respective axis lines of the globoidal cams and perpendicular to the axis member  1624  cooperate with each other to define a substantially continuous circle whose center rides on the axis member  1624 .  
     [0359] The four cams  1634   a,    1634   b,    1634   c,    1634   d  have respective bevel gears  1636   a,    1636   b,    1636   c,    1636   d  at their one axial ends, and respective bevel gears  1638   a,    1638   b,    1638   c,    1638   d  at their other axial ends. The bevel gears  1636   a,    1638   d  are meshed with each other; the bevel gears  1636   b,    1638   a  are meshed with each other; the bevel gears  1636   c,    1638   b  are meshed with each other; and the bevel gears  1636   d,    1638   c  are meshed with each other. When the first cam  1634   a  is rotated by a drive source in the form of a drive servomotor  1640  as a sort of electric motor, the four cams  1634   a - 1634   d  are contemporaneously rotated in synchronism with one another. The cam-follower roller  1632  of each of the rotary plates  1626  engages respective cam grooves  1642   a,    1642   b,    1642   c,    1642   d  of the four cams  1634   a,    1634   b,    1634   c,    1634   d,  in the order of description. Thus, the twelve rotary plates  1626  are rotated while being sequentially stopped at each of a CC suck-and-mount position where the CC suction head of each rotary plate  1626  sucks a CC  842  from the CC supplying device  14 ,  16 , or mounts the CC  842  on a PCB  408 , and a CC-image pick-up position where the image of the CC  842  held by each CC suction head is taken by a CC-image pick-up device (not shown). More specifically described, while one or two of the rotary plates  1626  is or are stopped at the CC suck-and-mount position or/and the CC-image pick-up position, the other rotary plates  1626  are rotated. Thus, it can be said that the rotary plates  1626  are rotated independent of one another. The cam grooves  1642   a - 1642   d  are designed such that while the rotary plates  1626  are rotated, each of the rotary plates  1626  has a predetermined time difference from its preceding rotary plate  1626 . In the present embodiment, the CC suction heads held by the rotary plates  1626  can be sequentially moved to the CC suck-and-mount position at a short time of interval. Thus, the present CC mounting system enjoys improved CC-sucking and CC-mounting efficiencies.  
     [0360] Like the CC mounting heads  650 ,  652  of the CC mounting system  8 , the CC mounting head  1620  of the present CC mounting system includes a stationary cam member (not shown) which is fixed to the X-direction slide  1622  and which has a cam surface including a position-changing portion whose height position in a vertical direction changes along the locus of revolution of the CC suction heads held by the rotary plates  1626 . Each of the CC suction heads has a spherical cam follower (not shown) and is biased by a biasing device (not shown) toward the cam surface. When the rotary plates  1626  are rotated about the axis member  1624 , the CC suction head held by each rotary plate  1626  is revolved while being moved up and down due to the rolling engagement of its cam follower with the position-changing portion of the cam surface. A portion of the X-direction slide  1622  in the vicinity of the CC suck-and-mount position supports an individual-CC-suction-head elevating and lowering device (not shown), and a switch- valve control device (not shown) for switching each of a plurality of pressure switch valves which are provided for the plurality of CC suction heads, respectively. The elevating and lowering device lowers and elevates the CC suction head being positioned at the CC suck-and-mount position, and the switch-valve control device switches the pressure switch valve provided for the CC suction head being positioned at the CC suck-and-mount position, so that a negative pressure is supplied to, and cut off from, a CC suction nozzle of the CC suction head. A CC-suction-nozzle rotating device which is provided for each of the CC suction heads corrects a possible rotation-position error of the CC held by the each CC suction head and/or changes the current rotation position of the CC to a desired rotation position.  
     [0361] In the first embodiment, the contact member  1014  has the groove  1016  and, even in the state in which the contact member  1014  is held in contact with the switch member  874 , the passage  1022  remains communicated with the atmosphere. However, the contact member  1014  may have a through-hole in place of the groove  1016 . The through-hole is formed through the contact member  1014  such that the through-hole intersects the passage  1022  which opens in the upper surface of the contact member  1014 . The through-hole permits air to flow from the passage  1022  into the atmosphere.  
     [0362] In the first embodiment, the feeders  54  which feed respective sorts of CCs  842  are arranged in the same order as that in which those sorts of CCs  842  are mounted on each PCB  408 , and the twenty CC suction nozzles  784  of the intermittent-rotation body  762  suck or mount the CCs  842  in the same order as that in which the nozzles  784  are held by the rotation body  762  in one of opposite circumferential directions of the same  762 . This arrangement leads to minimizing the total distance of movement of the rotation body  762  needed for sucking and mounting the CCs  842 . However, for example, in the case where the feeders  54  which feed the respective sorts of CCs  842  are used for mounting CCs  842  on two or more sorts of PCBs  408 , it is impossible to arrange the feeders  54  in the same order as the order of mounting of those sorts of CCs  842  on every sort of PCB  408 .  
     [0363] In the above case, if the twenty CC suction nozzles  784  suck respective sorts of CCs  842  from feeders  54  which are not arranged in any orders, in the same order as the order of mounting of those sorts of CCs  842  on each sort of PCB  408  while the intermittent-rotation body  762  is intermittently rotated at a regular angular pitch, it is needed to move the rotation body  762  in the X direction to each position where a corresponding one of the feeders  54  is located which feeds the CC of the sort to be next sucked. This operation mode leads to increasing the total distance of movement of the rotation body  762  needed for sucking the CCs  842 . Meanwhile, the suction nozzles  784  may be adapted to suck respective sorts of CCs  842  from feeders  54 , in the same order as the order of arrangement of the feeders  54  on the rotation body  762 , while the rotation body  762  is intermittently rotated at a regular angular pitch. The second operation mode leads to minimizing the total distance of movement of the rotation body  762  needed for sucking the CCs  842 . The distance of movement of the rotation body  762  is increased if the rotation body  762  passes by one or more feeders  54  which feeds or feed one or more sorts of CCs  842  which is or are not mounted on the PCB  408 . This increase cannot be avoided. However, it is more important that the second manner leads to increasing the total distance of X-direction and Y-direction movements of the rotation body  762  needed for mounting the CCs  842  on the PCB  408 . The CC mounting system  8  may be adapted to be operated in only a pre-selected one of the two operation modes. However, from the standpoint of improvement of the CC mounting efficiency, it is preferred to employ a third operation mode in which a CC sucking order and a CC mounting order are so determined as to minimize the sum of the respective distances of movement of the rotation body  762  needed for sucking CCs  842  and mounting the CCs  842  on a PCB  408 . In addition to, or in place of, this measure employed for minimizing the summed distances, it is possible to adapt, for improving the CC mounting efficiency, the rotation body  762  such that the rotation body  762  can be continuously rotated by an angle equal to two or more angular pitches and/or can be rotated in the reserve direction.  
     [0364] The first embodiment has been described on the assumption that the intermittent-rotation body  762  holds the single sort of CC suction shafts  766 , however, for easier understanding purposes only. Therefore, the rotation body  762  may be adapted to hold two or more sorts of CC suction shafts  766 . In the latter case, it is preferred that taking the sorts of the suction shafts  766  and the order of arrangement of the same  766  on the rotation body  762  into account, the orders of sucking and mounting of CCs  842  be so determined as to improve the efficiency of sucking and mounting of CCs  842 . For example, in the case where two sorts of CC suction shafts  766  is alternately held by the rotation body  762 , the rotation body  766  may be rotated in the forward direction, and/or in the reverse direction, by an angle different from the regular angular pitch at which the suction shafts  766  are equiangularly spaced from each other about the axis line of the rotation body  762 , so that the suction shafts  766  suck and/or mount CCs  842  in an order different from the order of arrangement of the suction shafts  766  on the rotation body  762 . Thus, the sucking and/or mounting of CCs  842  can be carried out with improved efficiency.  
     [0365] In the first embodiment, the two main conveyors  400 ,  402  are employed. However, three or more main conveyors may be employed. In the latter case, a plurality of fluid-pressure-operated cylinders may be employed and combined as a drive source for shifting the carry-in and carry-out conveyors  404 ,  406  to three or more shift positions at each of which the conveyors  404 ,  406  are aligned with a corresponding one of the three or more main conveyors. Alternatively, a servomotor may be employed as a drive source for the same purpose. In the last case, for example, a screw shaft is provided on the guide support table  420  such that the screw shaft extends over the range of movement of the carry-in conveyor  404 , and a nut which is fixed to the conveyor support table  426  is threadedly engaged with the screw shaft, which is rotated by the servomotor for selectively moving the carry-in conveyor  404  to one of the three or more shift positions.  
     [0366] In the case where the carry-in and carry-out conveyors  404 ,  406  are moved by a servomotor, those conveyors can be stopped at any desired position that may be different from the shift positions. For example, in the case where the upstream-side device provided on the upstream side of the CC mounting system  8  including the carry-in and carry-out conveyors  404 ,  406  and the two main conveyors  400 ,  402 , is a fluid applying system which includes a high-viscosity-fluid applying device such as a screen printing machine or an adhesive applying device, and two hand-over conveyors which are provided in parallel with each other for handing over CSs to the main conveyors, the distance between the two hand-over conveyors may be different from that between the two main conveyors. In this case, the carry-in conveyor should be moved to the two shift positions where the carry-in conveyor is aligned with the two main conveyors, respectively, and also to two CS-receive positions where the carry-in conveyor receives CSs from the two hand-over conveyors, respectively. The servomotor as the drive source may be controlled according to a predetermined control program for moving and stopping the carry-in conveyor to and at the two CS-receive positions as well as the two shift positions.  
     [0367] The screen printing system  2  as the upstream-side device provided on the upstream side of the CC mounting system  8  is a sort of fluid applying system which includes a screen printing machine as a sort of high-viscosity-fluid applying device and which prints a solder cream as a sort of high-viscosity fluid, on a CS such as a PCB. However, the upstream-side device may be provided by a different fluid applying system such as an adhesive applying system which includes an adhesive applying device and which applies an adhesive to a CS.  
     [0368] The solder reflowing system  4  as the downstream-side device provided on the downstream side of the CC mounting system  8  may be replaced by a CC mounting system including a device which mounts such a sort of CCs (e.g., capacitors) that are mounted in a small number only on each PCB  408 .  
     [0369] In the first embodiment, if the rotation-position changing angle of at least one of the first to fifth CCs  842  does not fall within the angular ranges of 0±15, 90±15, 180±15, and 270±15, the respective images of the sixteenth to twentieth CCs  842  are taken while the CC mounting head  650 ,  562  is moved to the PCB  408  after the head  650 ,  652  has taken all the CCs  842  from the CC supplying device  14 ,  16 , so that after the movement to the PCB  408 , the head  650 ,  562  can quickly start mounting the CCs  842  on the PCB  408 . However, the head  650 ,  652  may be moved to the PCB  408  after the images of the sixteenth to twentieth CCs  842  have been taken. This is also true with the cases where the CC mounting head  650 ,  652  holds not more than nineteen CCs  842  and the image or images of one or more CCs  842  are taken after the head  650 ,  652  has sucked and held all the CCs  842 .  
     [0370] In the first embodiment, the CC carrier tapes  156  are employed which are the emboss-type tapes that hold different sorts of CCs  842  such that the respective upper surfaces of the different sorts of CCs  842  take the same height position, i.e., position in the direction parallel to the respective axis lines of the CC suction shafts  766 . However, the CC mounting system  8  may use CC carrier tapes of a different type. For example, a CC carrier tape may be one which includes a paper-based tape having a number of through-holes which are formed at a regular interval of distance in a longitudinal direction thereof; a bottom tape which is adhered to the bottom surface of the paper tape for closing the respective lower openings of the through-holes and thereby providing a number of CC accommodating pockets in which CCs are accommodated, respectively; and a cover tape which covers the respective upper openings of the CC accommodating pockets. In the latter case, the respective upper surfaces of different sorts of CCs  842  accommodated in the CC accommodating pockets may take different height positions. Accordingly, the timing at which the negative pressure is supplied to each suction shaft  766  for sucking a CC  842 , and the distance by which the suction shaft  766  is moved down and up for the same purpose should be changed depending upon the different heights of CCs  842 . For example, like the manner in which the timing at which each pressure switch valve  860  is switched to its NP remove state for mounting a CC  842  can be changed depending upon the different sizes of CCs  842 , a main and an auxiliary air cylinder may be employed as a main and an auxiliary actuator for moving the operative member  1002  to its two different operative positions corresponding to the different height positions of respective upper surfaces of two sorts of CCs  842 . In addition, the drive member  892  is moved down and up by a shorter distance for sucking a taller CC  842  than a distance for sucking a smaller CC  842 .  
     [0371] The timing at which each pressure switch valve  860  is switched from its NP supply state to its NP remove state, or vice versa, may be changed among three or more timings. In the latter case, two or more auxiliary actuators may be provided in series.  
     [0372] The images of the reference marks of each PCB  408  may be taken during a time duration different from the time duration in which the CCs  842  are mounted on the PCB  408 . For example, those images may be taken when, or immediately before, the mounting of CCs  842  on the PCB  408  ends. The control device  1050  can know, from the CC mounting control program, the timing at which one of the CC mounting devices  18 ,  20  which corresponds to one of the main conveyors  400 ,  402  which supports the current PCB  408  mounts its last CC  842  on the PCB  408 . Therefore, when the one mounting device  18 ,  20  mounts its last CC  842 , the control device  1050  can control its reference-mark pick-up device  854  to take the images of the reference marks while the one mounting device  18 ,  20  is moved to the corresponding CC supplying device  14 ,  16  for taking CCs  842  therefrom. If the mounting of all CCs  842  on the PCB  408  ends with the mounting of the last CC  842  of the one mounting device  18 ,  20 , then it can be said that the images are taken when the mounting of CCs  842  on the PCB  408  ends. On the other hand, if the mounting of all CCs  842  on the PCB  408  ends with the mounting of the last CC  842  of the other mounting device  18 ,  20 , then it can be said that the images are taken immediately before the mounting of CCs  842  on the PCB  408  ends. The computer  1052  calculates position errors of the CC-mount places on the PCB  408  based on the image data indicative of the taken images, while simultaneously controlling the mounting of CCs  842  and the carrying-in and carrying-out of PCBs  408 . The computer  1052  stores the calculated errors in its RAM. However, it is not essentially required that before the mounting of CCs  842  on the PCB  404  is started, the calculation of position errors of all the CC-mount places on the PCB  408  be finished. The position errors of the CC-mount places may be calculated concurrently with the mounting of CCs  842  on the PCB  404 . In the last case, the computer  1052  can employ a memory whose capacity is small, for storing the rotation-position errors and the X-direction and Y-direction position errors.  
     [0373] In the first embodiment, if a CC  842  has a rotation-position error greater than +30 degrees or smaller than −30 degrees, the CC mounting system  8  does not mount the CC  842  on a PCB  408 . However, the reference angle range used for identifying the sucking errors may be widened to, e.g., ±40 degrees. In the latter case, even if a CC  842  may have a rotation-position error which is greater than +30 degrees and smaller than +40 degrees, or smaller than −30 degrees and greater than −40 degrees, the CC mounting system  8  does not identify the rotation-position error as a CC sucking error and accordingly can carry out the mounting of CCs  842  and the taking of images of other CCs  842  concurrently with each other.  
     [0374] In the case where the mounting of CCs  842  and the taking of images of other CCs  842  may be carried out concurrently with each other, the rotation-position changing angle of each CC  842  may be so selected as to fall in an angle range different from the range of from −15 degrees to +15 degrees. For example, if in almost all cases the rotation-position errors of CCs  842  fall in the range of −5 degrees to +5 degrees, the rotation-position changing angles of the CCs  842  may be so selected as to fall in the range of −30 degrees to +30 degrees, by employing the range of −40 degrees to +40 degrees as the reference angle range.  
     [0375] In the first embodiment, the respective rotation-position errors of the CCs  842  are corrected by rotating the suction shafts  766  as the CC holders by using the common drive gear  716  and the common drive source  724 , and the respective rotation positions of the CCs  842  are changed by using the same  716 ,  724 . However, a CC-holder rotating device which rotates each CC suction shaft  766  may be provided at one of the stop positions of the CC holders, or between adjacent two stops positions. In this case, each CC holder includes an engagement portion which is engageable with an engagement member of the CC-holder rotating device. The engagement member is engaged with the engagement portion of each CC holder, at a position where the engagement member is engageable with the engagement portion. Then, each CC holder is rotated about its axis line, so that the rotation-position error of the CC holder is corrected and the rotation position of the same is changed.  
     [0376] In the first embodiment, the CC suction shafts  766  as the CC holders are moved down and up while being revolved, on both the prior and subsequent sides of each of the stop positions. However, it is possible that the CC suction shafts  766  be moved down and up while being revolved, on only one of the two sides of each stop position.  
     [0377] Each of the CC suction shafts  766  as the CC holders may be moved down and up while it is revolved around the axis line of the rotation table  762 , if the lower surface of the drive member  892  has, in the direction of revolution of each suction shaft  766 , a length greater than the distance of revolution of the suction shaft  766  during the downward and upward movements of the same  766 . In this case, each CC suction shaft  766  may be revolved at a constant speed, or may be decelerated and then accelerated around the CC suck-and-mount position where each suction shaft  766  is moved down and up. In the last case, each suction shaft  766  is revolved at a low speed around the CC suck-and-mount position.  
     [0378] In the above case, too, if the drive member  892  takes its low position due to its malfunction or the like though no CC suction shaft  766  should be moved down or up, the drive member  892  is retracted to its retracted position as one suction shaft  766  is revolved. Thus, the drive member  892  is prevented from being damaged. In addition, since the recess  898  is shallow, the cam follower  804  can roll over the recess  898 . Thus, the cam follower  804  is not forcedly moved while being fitted in the recess  898 , and is prevented from being damaged. When the retracting rotation of the drive member  892  is detected by the drive-member retraction sensor  920 , the control device  1050  stops the CC suction shafts  766  based on the detection signal supplied from the retraction sensor  920 . Even though the suction shafts  766  may be revolved before being stopped by the control device  1050 , the cam followers  804  can roll over the recess  898  and accordingly are not damaged. Even if no retraction sensor  920  is employed and therefore the suction shafts  766  cannot be stopped based on the detection signal supplied from the retraction sensor  920 , the suction shafts  766  are prevented from being damaged.  
     [0379] In the case where the CC suction shafts  766  as the CC holders can be stopped by the control device  1050 , even though the revolution of the suction shafts  766  may be started for some reason with the cam follower  804  of one suction shaft  766  being fitted in the recess  898 , the cam follower  804  is prevented from being damaged because it can roll over the recess  898 .  
     [0380] In the first embodiment, the drive member  892  is rotated to its retracted position by one suction shaft  766 , if it takes its low position due to, e.g., the malfunction of the linear motor  886  while the CC suction shafts  766  are revolved for sucking or mounting the CCs  842 . The drive member  892  may be adapted such that it is rotated to its retracted position by one suction shaft  766 , if it takes its low position due to, e.g., the malfunction of the linear motor  886  also while the suction shafts  766  are rotated in the reverse direction.  
     [0381] In the first embodiment, the speed of downward movement of the movable member  890  which is driven by the linear motor  886  for mounting the CC  842 , is accelerated and then decelerated, so that the CC  842  can contact the PCB  408  with reduced impact. That is, the deceleration of the movable member  890  is continued till the movable member  890  reaches its lower stroke end. However, after the CC  842  contacts the PCB  408 , the movable member  890  may be accelerated so as to quickly reach its stroke end.  
     [0382] In the first embodiment shown in FIGS.  1  to  32 , the width of the drive gear  716  is wider than that of each driven gear  800 . However, the width of the drive gear  716  may be smaller than that of each driven gear  800 .  
     [0383] In the first embodiment, the CC-image pick-up device  820  may be adapted to take a front elevation image of the CC  842  held by each CC suction shaft  766  as the CC holder.  
     [0384] In the first or second embodiment, the rotation-position error of each CC  842  is corrected, and the rotation position of the CC  842  is changed, by rotating the CC suction shaft  766  holding the CC  842 , about the axis line of the same  766 . However, the CCs  842  may be mounted on the PCB  408 , without any change of the rotation positions of the CCs  842 , and with only correction of the rotation-position errors of the CCs  842 .  
     [0385] In each of the first and second embodiments, the CC mounting heads  650 ,  652  are moved by the servomotors  674 ,  688  each of which is an electric rotary motor as a sort of electric motor. However, each of the servomotors  674 ,  688  may be replaced by a different sort of electric rotary motor whose rotation angle or position is accurately controllable, such as a stepper motor. Alternatively, each servomotor  674 ,  688  may be replaced by a linear motor as a sort of electric motor. A linear motor which linearly moves a movable element thereof may be provided by a servomotor which is so controllable as to accurately position the movable element and accurately accelerate and decelerate the speed of the movable element; or a stepper motor.  
     [0386] In each of the first and second embodiments, the individual-CC-suction-shaft elevating and lowering device  880 ,  1302  includes the feedback-controlled linear motor  886 ,  1310  as the drive source for elevating and lowering each CC suction shaft  766 ,  1170  at the CC suck-and-mount position. However, the feedback-controlled linear motor  886 ,  1310  may be replaced by a linear stepper motor. The drive source is not limited to a linear motor but may be a rotary motor such as a servomotor or a stepper motor.  
     [0387] One or more members of each one of the illustrated embodiments may be replaced by one or more members of another or other embodiments.  
     [0388] It is to be understood that the present invention may be embodied with other changes, improvements, and modifications that may occur to those skilled in the art without departing from the scope and spirit of the invention defined in the appended claims.