Patent Publication Number: US-9422118-B2

Title: Transport unit and transport apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of U.S. patent application Ser. No. 13/787,930 filed on Mar. 7, 2013, and claims the benefit of Japanese Patent Application No. 2012-077770, filed Mar. 29, 2012, the entire content of each of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a technique of transporting an object to be transported. 
     2. Description of the Related Art 
     When an object to be transported is transferred to a predetermined position, it must often be positioned with high accuracy. Hence, an apparatus including a transport mechanism and positioning mechanism has been proposed. Japanese Patent Laid-Open No. 2000-258497, for example, discloses an apparatus including a belt conveyor which transports a pallet on which a plurality of chips are mounted, and a mechanism which positions the pallet. Japanese Utility Model Laid-Open No. 5-82939 discloses a conveyor including a pallet positioning device. Moreover, Japanese Utility Model Laid-Open No. 7-29484 discloses a conveyor including a tray positioning mechanism. 
     The transport mechanism and positioning mechanism require periodical maintenance. Also, when these mechanisms have broken down, they require repair and replacement. Since such maintenance and other operations must be done while the system is kept stopped, they preferably take only a short period of time. Furthermore, when a broken transport mechanism or positioning mechanism is replaced, it requires position adjustment relative to other system components. This position adjustment operation prolongs the system downtime. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a transport unit and transport apparatus which can prevent prolongation of the system downtime. 
     According to an aspect of the present invention, there is provided a transport unit comprising: a base member including a bottom wall extending in a transport direction, and a pair of side walls standing upright from two side portions, respectively, of the bottom wall; a transport mechanism which is supported by the base member, and transports an object to be transported; and a positioning mechanism which is supported by the base member, and positions the object, transported by the transport mechanism, relative to the base member. 
     According to another aspect of the present invention, there is provided a transport apparatus including a transport unit, and a mount table on which the transport unit is mounted, the transport unit including a base member including a bottom wall extending in a transport direction, and a pair of side walls standing upright from two side portions, respectively, of the bottom wall, a transport mechanism which is supported by the base member, and transports an object to be transported, and a positioning mechanism which is supported by the base member, and positions the object, transported by the transport mechanism, relative to the base member, and the mount table including a positioning reference portion against which the object abuts, and a press mechanism which presses the object toward the positioning reference portion. 
     According to still another aspect of the present invention, there is provided a transport apparatus including a transport unit, and a mount table on which the transport unit is mounted, the transport unit including a base member including a bottom wall extending in a transport direction, and a pair of side walls standing upright from two side portions, respectively, of the bottom wall, a transport mechanism which is supported by the base member, and transports an object to be transported, a positioning mechanism which is supported by the base member, and positions the object, transported by the transport mechanism, relative to the base member, and a reference member fixed to the base member, and the mount table including an engaging member which defines a mount position of the transport unit, the reference member including a positioning reference portion against which the object abuts, and a portion to be engaged, with which the engaging member engages, and the positioning mechanism including a press mechanism which presses the object toward the positioning reference portion. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing the layout of a work system as an application example of the present invention; 
         FIG. 2  is a perspective view showing a transport apparatus according to an embodiment of the present invention; 
         FIG. 3  is a perspective view showing a transport unit according to the embodiment of the present invention; 
         FIG. 4  is a partially exploded perspective view of the transport unit shown in  FIG. 3 ; 
         FIGS. 5A and 5B  are perspective views showing a positioning mechanism; 
         FIGS. 6A and 6B  are views for explaining the operation of the positioning mechanism shown in  FIGS. 5A and 5B ; 
         FIGS. 7A and 7B  are views for explaining the operation of the positioning mechanism shown in  FIGS. 5A and 5B ; 
         FIGS. 8A and 8B  are views for explaining the operation of the positioning mechanism shown in  FIGS. 5A and 5B ; 
         FIG. 9  is a perspective view showing a mode in which an old transport unit is replaced in the transport apparatus shown in  FIG. 2 ; 
         FIG. 10  is a block diagram showing a control device for the work system shown in  FIG. 1 ; 
         FIG. 11  is a perspective view for explaining another example of the positioning mechanism; 
         FIG. 12  is a perspective view for explaining still another example of the positioning mechanism; and 
         FIG. 13  is a perspective view for explaining still another example of the positioning mechanism. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     Work System 
       FIG. 1  is a diagram showing the layout of a work system A as an application example of the present invention. The work system A performs a predetermined work and inspection for components (not shown) on a tray T, and includes transport apparatuses  1  and transport units  10  according to an embodiment of the present invention. The components are, for example, IC chips. The operation of the work system A will briefly be described below. Note that in the accompanying drawings, the X- and Y-directions are orthogonal horizontal directions, and the Z-direction is the vertical direction. 
     A transport device  2   a  is, for example, a belt conveyor, and transports, in the Y-direction, the tray T on which a plurality of components are mounted. A work device  3  is disposed in the middle of the transport path of the transport device  2   a . The work device  3  picks up the components on the tray T which is positioned in the transport path and stopped in transport, performs a predetermined work, and returns them onto the tray T. Examples of the operation details include heating and cleaning of the components. 
     A transport device  4  includes a transport section  4   a  which transports the tray T in the Y-direction, and a driving unit  4   b  which reciprocally moves the transport section  4   a  in the X-direction. The transport section  4   a  is, for example, a belt conveyor. The transport section  4   a  receives the tray T from the transport device  2   a , and supplies it to a standby device  5 . Further, the transport section  4   a  receives the tray T from the standby device  5 , and transfers it to a transport device  2   b . The transport device  2   b  is, for example, a belt conveyor, and transports, in the Y-direction, an empty tray T and a tray T on which defective components are mounted. 
     The standby device  5  includes, for example, a belt conveyor, and allows the tray T supplied from the transport device  4  to stand by on itself. A transfer device  6  transports the components on the tray T standing by on the standby device  5  to an inspection device  7 . The transfer device  6  serves as a gantry robot, and includes a transfer mechanism  6   b  which ascends/descends in the Z-direction and reciprocally moves a hand portion  6   a  in the Y-direction, and a pair of transfer mechanisms  6   c  which move the transfer mechanism  6   b  in the X-direction. 
     The inspection device  7  inspects and measures the components. The transfer device  6  returns components, determined to be unfit upon inspection by the inspection device  7 , onto the tray T on the standby device  5  as unfit components. The transfer device  6  transports fit components onto the trays T positioned on the transport units  10 . 
     After inspection operations of all components mounted on the tray T on the standby device  5  are completed, the standby device  5  returns the tray T to the transport device  4 . The transport device  4  transports and transfers the tray T returned from the standby device  5  to the transport device  2   b.    
     A transport device  2   c  is, for example, a belt conveyor, and transports an empty tray T from a stocker (not shown) to a transport device  8 . The transport device  8  includes a transport section  8   a  which transports the tray T in the Y-direction, and a driving unit  8   b  which reciprocally moves the transport section  4   a  in the X-direction. The transport section  8   a  supplies the empty tray T to each transport unit  10 . 
     Each transport apparatus  1  includes a plurality of transport units  10 . In this embodiment, two transport apparatuses  1  are arranged on the two sides of the driving unit  8   b  in the Y-direction, and each transport apparatus  1  includes five transport units  10  arrayed in the X-direction. 
     Each transport unit  10  positions an empty tray T first as it is supplied from the transport device  8 . Then, the transfer device  6  transports components onto the tray T. When a predetermined number of components are stacked on the tray T, the tray T is transported to a succeeding device  9  (in the Y-direction). The device  9  is, for example, a stocker for the tray T. 
     In this way, the work system A can automate a predetermined work and inspection of the components, and accommodation of the components on the tray T. 
     &lt;Transport Apparatus&gt; 
       FIG. 2  is a perspective view showing the transport apparatus  1 . The transport apparatus  1  includes a plurality of transport units  10 , and a mount table  20  on which the transport units  10  are mounted. The mount table  20  has an upper surface which serves as a flat mount surface, and the transport units  10  are mounted on the mount surface. Each transport unit  10  is removably fixed to the mount table  20  by a fixing structure such as a screw. 
     The mount table  20  includes engaging members  21 . In this embodiment, two engaging members  21  are used for one transport unit  10 . Again in this embodiment, the engaging members  21  are circular cylinders standing upright on the mount surface. The engaging members  21  define the mount positions of the transport units  10  on the mount table  20 . In other words, the engaging members  21  serve to position the transport units  10 . Also, by positioning each transport unit  10  on the mount table  20 , the tray T to be positioned on this transport unit  10  is also positioned relative to the mount table  20 . 
     In a configuration in which each transport unit  10  is fixed to the mount table  20  using a screw, the rough position of the transport unit  10  relative to the mount table  20  can be defined by a hole into which a screw is inserted. However, the accuracies of the position and size of a hole into which a screw is inserted are relatively low. Hence, providing the engaging members  21  makes it possible to improve the positioning accuracy of the tray T. Details of this mechanism will be described later. 
     &lt;Transport Unit&gt; 
     The configuration of the transport unit  10  will be described with reference to  FIGS. 3 to 5B .  FIG. 3  is a perspective view showing the transport unit  10  and tray T.  FIG. 4  is a partially exploded perspective view of the transport unit  10 , and mainly shows a base member  11  and a transport mechanism  12 .  FIGS. 5A and 5B  are perspective views showing a positioning mechanism  13 , in which  FIG. 5A  is a perspective view as viewed from above; and  FIG. 5B  is a perspective view as viewed from below. 
     The transport unit  10  includes the base member  11 , the transport mechanism  12 , the positioning mechanism  13 , and guide members  14  and  15 . 
     The base member  11  includes a bottom wall  111  which extends in the transport direction (Y-direction), a pair of side walls  112  which stand upright from the two side portions of the bottom wall  111  in the X-direction, and edge portions  113  which project to the interior of the base member  11  (toward the opposed side walls  112 ) in the upper portions of the side walls  112 . The base member  11  has a C cross-sectional shape that opens on its upper portion, and has a cylindrical shape with its two ends in the Y-direction opening as a whole. Hence, an internal space is formed inside the base member  11 . The base member  11  can be formed by, for example, bending a metal plate by, for example, press working, and integrally molding the bent portions. 
     The guide members  14  and  15  are fixed onto the edge portions  113  with spacers  14   a  and  15   a  sandwiched between them. The guide members  14  and  15  guide movement of the tray T to prevent the tray T from meandering during transport. 
     Note that the tray T has a square plate shape as a whole, and integrally includes a square bottom plate portion Ta, and a square stage portion Tb higher than the bottom plate portion Ta by one step, as shown in  FIG. 3 . Recessed portions Tc which receive components are formed in the upper surface of the stage portion Tb in a matrix. The distance across which the inner side surfaces of the guide members  14  and  15  are spaced apart from each other is set slightly larger than the side of the stage portion Tb. The guide members  14  and  15  guide the stage portion Tb (its side surfaces) to prevent the tray T from meandering. 
     Note that the guide members  14  and  15  can also guide the bottom plate portion Ta instead of the stage portion Tb. 
     The spacers  14   a  and  15   a  are members for position adjustment of the guide members  14  and  15 , respectively, in the Z-direction. The spacers  14   a  and  15   a  adjust the positions of the guide members  14  and  15  in the Z-direction so that the position (level), in the Z-direction, of the stage portion Tb of the tray T transported by the transport mechanism  12  becomes level with that of the guide members  14  and  15 . The guide members  14  and  15  include guide portions which project from the spacers  14   a  and  15   a  to which they are respectively fixed, and guide the tray T, and are removably fixed to the edge portions  113  by a fixing structure such as a screw. The bottom plate portion Ta is positioned on the lower side of each of the guide members  14  and  15  to allow transport movement. 
     In this embodiment, the guide member  14  includes two portions to be engaged  142  which engage with the two engaging members  21 , respectively, of the mount table  20 , and a positioning reference portion  141  which serves as a reference for positioning by the positioning mechanism  13 . Hence, the guide member  14  is a reference member that serves as a reference for the position of the tray T relative to the mount table  20 . 
     The portions to be engaged  142  are semicircular notches, which engage with the circumferential surfaces of the engaging members  21  as circular cylinders. The position of the transport unit  10  in the X- and Y-directions can be defined by forming the portions to be engaged  142  into a semicircular shape, while the orientation (direction) of the transport unit  10  in the horizontal plane can be defined by providing the two portions to be engaged  142 . This facilitates an operation of replacing an old transport unit  10 .  FIG. 9  shows a mode in which an old transport unit  10  is replaced. As shown in  FIG. 9 , in mounting a new transport unit  10  on the mount table  20 , alignment of the transport unit  10  relative to the mount table  20  is completed as the engaging members  21  and the portions to be engaged  142  engage with each other. As a result, alignment of the tray T, positioned on the transport unit  10 , relative to the mount table  20  is also completed. This facilitates an operation of replacing an old transport unit  10 , and aligning the tray T in the X-direction. Although the portions to be engaged  142  are semicircular notches, they may have a circular shape or a shape with two lines forming a vertex (V groove shape). 
     The positioning reference portion  141  uses the positioning mechanism  13  (to be described later) to position the tray T (in the X-direction) as one end edge of the stage portion Tb of the tray T abuts against it. In other words, the positioning reference portion  141  guides transport of the tray T, and constitutes part of the positioning mechanism  13 . 
     The positioning reference portion  141  and portions to be engaged  142  can be provided as independent members. However, as in this embodiment, since one guide member  14  includes the positioning reference portion  141  and portions to be engaged  142 , it is possible to simultaneously perform alignment of the transport unit  10  relative to the mount table  20 , and adjustment of the position at which the tray T is to be positioned. 
     &lt;Transport Mechanism&gt; 
     The transport mechanism  12  is supported by the base member  11 , and transports the tray T as an object to be transported. In this embodiment, the transport mechanism  12  includes a pair of belt transmission mechanisms  12   a  supported on the inner sides of the side walls  112 . Supporting the belt transmission mechanisms  12   a  on the inner sides of the side walls  112  makes it possible to accommodate the transport mechanism  12  in the internal space of the base member  11 , thus downsizing and integrating the transport unit  10 . 
     Each belt transmission mechanism  12   a  includes a drive source  121  such as a motor, a drive pulley  122  which is supported and rotated by the drive source  121 , a driven pulley  123 , and an endless belt  124  looped around the drive pulley  122  and driven pulley  123 . The endless belt  124  travels upon rotation of the drive pulley  122 . The tray T is suspended across the endless belts  124 , and transported in the Y-direction as the endless belts  124  travel. 
     Each drive source  121  is supported by a support member  125 . Each support member  125  includes an attachment portion  125   a . Each attachment portion  125   a  has, for example, screw holes. Holes  112   b  are formed in the side walls  112  of the base member  11 , and the support members  125  can be fastened to the side walls  112  by inserting bolts (not shown) into the holes  112   b  so that the bolts threadably engage with the attachment portions  125   a . With this configuration, the side walls  112  can support the drive sources  121  and drive pulleys  122 . 
     Each driven pulley  123  is rotatably supported by a shaft member  126 . Each shaft member  126  has, for example, a screw hole. Holes  112   c  are formed in the side walls  112  of the base member  11 . The shaft members  126  can be fastened to the side walls  112  by inserting bolts (not shown) into the holes  112   c  so that the bolts threadably engage with the shaft member  126 . With this configuration, the side walls  112  can support the driven pulleys  123 . 
     In this embodiment, the drive sources  121  and drive pulleys  122  are disposed on the side of one end of the base member  11  in the Y-direction, while the driven pulleys  123  are disposed on the side of the other end of the base member  11  in the Y-direction. With this configuration, the traveling range of the endless belts  124  can be set wide, thereby transporting the tray T from one end to the other end of the transport unit  10  in the Y-direction. 
     Also, the drive sources  121  such as motors generally occupy a large space. In this embodiment, the drive sources  121  are disposed on the side of one end of the base member  11  in the Y-direction, while the positioning mechanism  13  is disposed on the side of the other end of the base member  11  in the Y-direction with respect to the side walls  112 . This makes it possible to efficiently use the space inside the base member  11 , thus downsizing the transport unit  10 . 
     In this embodiment, since the driven pulleys  123  have a diameter smaller than the drive pulleys  122 , a larger number of other constituent elements can be arranged in the space inside the base member  11  on the side of the driven pulleys  123 . In other words, a wider installation space can be ensured for the positioning mechanism  13 . On the other hand, to horizontally transport the tray T, the positions of the shaft centers of the driven pulleys  123  shift to the side above that of the shaft centers of the drive pulleys  122  so that the endless belt  124  has a horizontally set, upper traveling portion  124   a , and an obliquely set, lower traveling portion  124   b.    
     Although the transport mechanism  12  is a belt transmission mechanism in this embodiment, it may be other types of transport mechanisms. 
     &lt;Positioning Mechanism&gt; 
     The positioning mechanism  13  is supported by the base member  11 , and positions the tray T, transported by the transport mechanism  12 , relative to the base member  11 . In this embodiment, the positioning mechanism  13  positions the tray T in both the X- and Y-directions. However, the positioning mechanism  13  may position the tray T in one of the X- and Y-directions. 
     In this embodiment, the positioning mechanism  13  includes, as a configuration which positions the tray T in the Y-direction, a positioning reference portion  134 , and a press mechanism  131  which presses the tray T so as to move the tray T toward the positioning reference portion  134 . The positioning reference portion  134  and press mechanism  131  are used for the transport direction. 
     The positioning mechanism  13  also includes, as a configuration which positions the tray T in the X-direction, the positioning reference portion  141  arranged on the guide member  14 , and a press mechanism  132  which presses the tray T so as to move the tray T toward the positioning reference portion  141 . The positioning reference portion  141  and press mechanism  132  are used for a direction perpendicular to the transport direction. 
     In this embodiment, the positioning mechanism  13  includes a driving unit  133  common to the press mechanisms  131  and  132 . Although a configuration in which the press mechanisms  131  and  132  include individual drive sources can also be adopted, the use of a common drive source allows space and cost saving corresponding to one drive source. 
     The positioning reference portion  134  and press mechanism  131  will be described first. Since the Y-direction for positioning coincides with the transport direction of the tray T, it is necessary to prevent interference with the tray T during transport. 
     The positioning reference portion  134  positions the tray T as one end of the bottom plate portion Ta of the tray T abuts against it from the Y-direction. In this embodiment, the positioning reference portion  134  has a circular cylindrical shape. The positioning reference portion  134  is moved in the Z-direction by a moving mechanism  134   a . The moving mechanism  134   a  lifts/lowers the positioning reference portion  134  between a retreat position at which the tray T does not abut against it, and a positioning or butting position at which the tray T abuts against it. The retreat position is lower than the position (height) to which the tray T is transported by the transport mechanism  12 , and the positioning position is a position at which the positioning reference portion  134  traverses the position to which the tray T is transported. 
     The moving mechanism  134   a  is an actuator such as a solenoid, and is supported by the bottom wall  111  of the base member  11 . The positioning reference portion  134  is set at the positioning position in positioning the tray T, while it is set at the retreat position in other cases. 
     The press mechanism  131  includes a butting member  1312  which presses the tray T against the positioning reference portion  134  as the other end of the bottom plate portion Ta abuts against it from the Y-direction. The butting member  1312  includes a butting surface  1312   a  which abuts against the bottom plate portion Ta of the tray T. When the butting member  1312  is in an orientation shown in  FIG. 5A , its butting surface  1312   a  abuts against a stopper  1315 , that is, faces down. When the butting surface  1312   a  faces down, it is in a retracted state in which transport movement of the tray T is not hindered. 
     The butting member  1312  is pivotally supported by a support member  1314 . More specifically, the support member  1314  includes a pair of shaft support members  1313 , which support a shaft  1313   a . The shaft  1313   a  extends through the butting member  1312 , which can pivot about the shaft  1313   a.    
     A slit  1314   b  is formed in the support member  1314 , and the butting member  1312  can pass through the slit  1314   b  as it pivots about the shaft  1313   a.    
     The stopper  1315  is fitted in the slit  1314   b . The stopper  1315  abuts against the butting member  1312  to regulate its pivot operation. 
     An elastic member  1317  is disposed on the lower surface of the support member  1314 . In this embodiment, the elastic member  1317  is a coil spring. The elastic member  1317  has its one end fixed to a fixing member  1317   a , and its other end fixed to a fixing member  1317   b . The fixing member  1317   a  is fixed to the support member  1314 , while the fixing member  1317   b  is fixed to the butting member  1312 . Therefore, the elastic member  1317  extends between the support member  1314  and the butting member  1312 . Also, one side surface of the support member  1314  in the X-direction includes an engaging portion  1314   a  to serve as a cam surface. The engaging portion  1314   a  includes a linear portion which positions a butting member  1321  in a retracted state, and a recessed portion (a portion notched on the side of the guide member  14  (see  FIG. 3 ) with respect to the linear portion) which positions the butting member  1321  in a positioned state. The linear portion and recessed portion continuously communicate with each other via a sloped portion. 
     A regulating member  1311  has its one end supported by the bottom wall  111  of the base member  11 , and its other end including a butting portion  1311   a . The butting portion  1311   a  abuts against the butting member  1312  to regulate its pivot operation. 
     The driving unit  133  is an actuator which advances/retreats an L-shaped movable portion  133   a  in the Y-direction while its main body portion is fixed to the bottom wall  111  of the base member  11 , and is, for example, an electric cylinder. The support member  1314  is fixed to the movable portion  133   a , and movably supported by the bottom wall  111  of the base member  11  through the driving unit  133 . As the movable portion  133   a  advances/retreats in the Y-direction, the support member  1314  also advances/retreats. As a result, the butting member  1312  also advances/retreats in the Y-direction. 
     The press mechanism  132  will be described below. The press mechanism  132  includes a pair of butting members  1321  spaced apart from each other in the Y-direction. Each butting member  1321  includes a butting portion  1321   a  at its upper end (one end). The butting portion  1321   a  has a distal end surface curved in an arc as viewed from the top. The butting portion  1321   a  abuts against the end edge (side surface) of the stage portion Tb of the tray T from the X-direction. In this embodiment, the butting portion  1321   a  abuts against one side surface of the stage portion Tb of the tray T, while the positioning reference portion  141  abuts against the other side surface of the stage portion Tb of the tray T, thereby positioning the tray T in the X-direction while it is sandwiched between the butting portion  1321   a  and the positioning reference portion  141 . 
     Each butting member  1321  is supported by a support mechanism  1322 , supported by the bottom wall  111  of the base member  11 , to be movable in the X-direction. The support mechanism  1322  is fixed to the bottom wall  111  of the base member  11 , and includes a rail member  1322   a  extending in the X-direction, and a slide member  1322   b  slidable on the rail member  1322   a . The lower end (other end) of the butting members  1321  is fixed to the slide member  1322   b , and can reciprocally move in the X-direction together with the slide member  1322   b.    
     In this embodiment, each butting member  1321  extends to the exterior of the base member  11  upon passing through the side walls  112  of the base member  11 , and is curved in a C shape so as to return onto the base member  11 . More specifically, opening portions  112   a  through which the butting members  1321  can pass are formed in one of the pair of side walls  112  of the base member  11 , as shown in  FIG. 3 . The lower end of each butting member  1321  extends through the opening portion  112   a  from the exterior of the base member  11 , and is connected to the slide member  1322   b , as shown in  FIG. 4 . 
     Forming each butting member  1321  in the above-mentioned shape makes it possible to downsize the transport unit  10  while positioning the tray T in the X-direction. In addition, except the butting members  1321 , the transport mechanism  12  and positioning mechanism  13  can be accommodated in the internal space of the base member  11  to integrate them with the transport unit  10 . This facilitates handling of the transport unit  10 . 
     Referring to  FIGS. 5A and 5B , a support member  1323  which supports a cam follower  1323   a  is fixed to each butting member  1321 , so the cam follower  1323   a  substantially constitutes part of the butting member  1321 . The cam follower  1323   a  engages with the engaging portion  1314   a  of the support member  1314 . 
     Each butting member  1321  is always biased against the positioning reference portion  141  (the support member  1314  in  FIGS. 5A and 5B ) by a corresponding biasing mechanism  1324 . In this embodiment, the biasing mechanism  1324  is a spring plunger, and is supported by the bottom wall  111  of the base member  11  through a support member  1325 . The biasing mechanism  1324  has a cylinder portion fixed to the support member  1325 , and a plunger portion which abuts against the support member  1323  to press it against the positioning reference portion  141 . Hence, each butting member  1321  can independently abut against one side portion of the stage portion Tb of the tray T to make the tray T abut against the positioning reference portion  141  by an appropriate biasing force. Although the biasing mechanism  1324  is a spring plunger in this embodiment, it may be formed by rubber or a spring alone, which extends between the butting member  1321  and the base member  11 . 
     &lt;Operation of Positioning Mechanism&gt; 
     The positioning operation of the tray T by the positioning mechanism  13  will be described with reference to  FIGS. 6A to 8B . Of  FIGS. 6A to 8B ,  FIGS. 6A, 7A, and 8A  are views showing the positioning mechanism  13  as viewed from the side, and  FIGS. 6B, 7B, and 8B  are views showing the positioning mechanism  13  as viewed from the top. Note that the positioning reference portion  141  is not shown in  FIGS. 6A to 8B . The tray T is not shown in  FIGS. 6B, 7B, and 8B , either. 
       FIGS. 6A and 6B  show a state before positioning, that is, a state in which a new tray T is transported. Note that during positioning, the transport mechanism  12  is kept stopped, and the tray T is mounted on the endless belts  124 . 
     First, referring mainly to  FIG. 6A , attention will be paid to the press mechanism  131  and positioning reference portion  134  which position the tray T in the Y-direction. 
     The positioning reference portion  134  is at a retreat position, at which it does not interfere with the tray T. The support member  1314  is at the retreat position on the right side of  FIG. 6A . The butting member  1312  is always biased by the elastic member  1317  with a pivot force acting clockwise in  FIG. 6A . However, the regulating member  1311  regulates the pivot operation of the butting member  1312 , and the butting surface  1312   a  is at a retreat position (in a horizontal orientation) at which it abuts against the stopper  1315 . The retreat position is a position (on the side of the bottom wall  111 ) lower than a tray transport plane in which the butting member  1312  does not interfere with the tray T. 
     Next, referring mainly to  FIG. 6B , attention will be paid to the press mechanism  132  which positions the tray T in the X-direction. Each butting member  1321  is biased against the lower side (the side of the X positioning reference portion) in  FIG. 6B  by the corresponding biasing mechanism  1324 . However, since each cam follower  1323   a  engages with the linear portion of the engaging portion  1314   a , each butting member  1321  is not movable and is at the retreat position. At the retreat position, the tray T cannot be pressed against the positioning reference portion  141 . 
       FIGS. 7A and 7B  show a state at the start of positioning. First, referring mainly to  FIG. 7A , attention will be paid to the press mechanism  131  and positioning reference portion  134  which position the tray T in the Y-direction. 
     Upon actuation of the moving mechanism  134   a , the positioning reference portion  134  moves to a positioning position, at which it interferes with the tray T. Upon driving of the driving unit  133 , the movable portion  133   a  starts to extend (to the left in  FIG. 7A ) in the Y-direction (to the side of the positioning reference portion  134 ). Hence, the support member  1314  also advances to the left in  FIG. 7A  from the retreat position. As the support member  1314  advances, the butting member  1312  also advances to the left in  FIG. 7A . On the other hand, the regulating member  1311  stays in position without advancing, so the butting member  1312  and regulating member  1311  start to separate from each other. As a result, upon biasing of the elastic member  1317 , the butting member  1312  starts to pivot clockwise in  FIG. 7A . 
     Next, referring mainly to  FIG. 7B , attention will be paid to the press mechanism  132  which positions the tray T in the X-direction. Upon movement of the support member  1314 , each cam follower  1323   a  still engages with the linear portion of the engaging portion  1314   a  and does not reach the recessed portion in the engaging portion  1314   a , despite a change in position at which the cam follower  1323   a  engages with the engaging portion  1314   a . Therefore, each butting member  1321  stays at the retreat position. 
       FIGS. 8A and 8B  show a state after positioning. First, referring mainly to  FIG. 8A , attention will be paid to the press mechanism  131  and positioning reference portion  134  which position the tray T in the Y-direction. 
     The positioning reference portion  134  stays at the positioning position. Upon driving of the driving unit  133 , the movable portion  133   a  further moves in the Y-direction from the state shown in  FIGS. 7A and 7B . In other words, the driving unit  133  further extends as a whole. Hence, the support member  1314  also further advances to the left in  FIG. 8A  from the retreat position. Upon further advancing of the support member  1314 , the butting member  1312  also further advances to the left in  FIG. 8A . The butting member  1312  and regulating member  1311  sufficiently separate from each other. As a result, upon biasing of the elastic member  1317 , the butting member  1312  completes its clockwise pivot operation in  FIG. 8A  and is positioned at the positioning position. At this time, the butting member  1312  is in an upright orientation. The butting surface  1312   a  abuts against the tray T to press it against the positioning reference portion  134 . As a result, the positioning operation of the tray T in the Y-direction is completed. 
     Next, referring mainly to  FIG. 8B , attention will be paid to the press mechanism  132  which positions the tray T in the X-direction. Upon movement of the support member  1314 , the position at which each cam follower  1323   a  engages with the engaging portion  1314   a  further changes, and reaches the recessed portion in the engaging portion  1314   a . Upon biasing of each biasing mechanism  1324 , each butting member  1321  moves to the positioning position on the lower side in  FIG. 8B . At this time, the butting portion  1321   a  abuts against the stage portion Tb of the tray T to press the tray T against the positioning reference portion  141 . As a result, the positioning operation of the tray T in the X-direction is also completed. 
     In this embodiment, the positioning operations of the tray T in the X- and Y-directions are thus completed (positioning ON state). Hence, the transfer device  6  shown in  FIG. 1  can prevent a position shift of each component when this component is transported to each recessed portion Tc in the tray T. Then, when the movable portion  133   a  is retreated by driving the driving unit  133 , the entire driving unit  133  contracts, so the positioning mechanism  13  returns to the state shown in  FIGS. 6A and 6B , in which the transport mechanism  12  is ready to transport the tray T. That is, upon retreat of the support member  1314 , each cam follower  1323   a  separates from the recessed portion in the engaging portion  1314   a  and engages with the linear portion, so each butting member  1321  moves in the direction, opposite to the biasing direction of the biasing mechanism  1324 , from the engaging portion  1314   a , and returns to the retreat position. Also, the butting member  1312  returns to the retreat position as the regulating member  1311  abuts against it (positioning OFF state). 
     In this embodiment, with the advancing/retreating operation of the support member  1314 , the butting member  1312  advances/retreats in the Y-direction, and the butting member  1312  interlocks with this advancing/retreating operation to move (pivot) between a retreat position at which it does not abut against the tray T, and a positioning position at which it abuts against the tray T, so as not to hinder transport of the tray T by the butting member  1312  during transport of the tray T. The support member  1314 , elastic member  1317 , and regulating member  1311  constitute a driving mechanism (or actuating mechanism) which interlocks with the advancing/retreating operation of the butting member  1312  to move (pivot) the butting member  1312  between the retreat position and the positioning position. 
     &lt;Maintenance and Other Operations of Transport Unit  10 &gt; 
     In this embodiment, the transport unit  10  includes constituent elements such as the transport mechanism  12  and positioning mechanism  13 , but can be integrally accommodated in the base member  11  in a small space and is easy to handle. When the transport mechanism  12  or positioning mechanism  13  of a given transport unit  10  requires maintenance, the transport unit  10  need only be replaced with a new transport unit  10  as a whole. Since both the transport mechanism  12  and positioning mechanism  13  are supported by the base member  11 , their position adjustment is completed when the transport unit  10  has been assembled. 
     Hence, in an operation of replacing an old transport unit  10 , it is unnecessary to adjust the positions of the transport mechanism  12  and the positioning mechanism  13  relative to each other. This makes it possible to prevent prolongation of the downtime of the work system A. 
     Also, in an operation of replacing an old transport unit  10 , an operation of finely adjusting the position of the tray T relative to the mount table  20  is necessary, but can be easily performed (is made substantially unnecessary) by providing the engaging members  21  and portions to be engaged  142  on the guide member  14 , as shown in  FIG. 9 . Therefore, in a configuration equipped with the engaging members  21  and portions to be engaged  142 , there is no need to perform a position designation operation of recognizing the positions of the recessed portions Tc relative to the transfer device  6  for every replacement of the transport unit  10 . This makes it possible to more reliably prevent prolongation of the downtime of the work system A. 
     &lt;Control Device&gt; 
       FIG. 10  is a block diagram showing a control device  200  of the work system A. The control device  200  controls the overall work system A in accordance with instructions from a host computer  210 . The control device  200  outputs control commands to controllers individually provided to the work device  3 , standby device  5 , inspection device  7 , device  9 , and each transport apparatus  220  to control them. Each transport apparatus  220  includes the transport devices described with reference to  FIG. 1 , and includes the transport units  10 . The controller of the transport unit  10  may be provided for each transport unit  10  or each transport apparatus  1 . 
     The control device  200  includes a processing unit  201 , storage unit  202 , and interface unit  203 , and are connected to each other via a bus (not shown). The processing unit  201  executes a program stored in the storage unit  202 . The processing unit  201  is, for example, a CPU. The storage unit  202  is, for example, a RAM, a ROM, or a hard disk. The interface unit  203  includes, for example, a communication interface which allows communication between the processing unit  201  and the host computer  210 , and that which allows communication between the processing unit  201  and each controller. 
     The storage unit  202  may store the arrangement information and ON/OFF information of each transport unit  10 . The ON/OFF information can include information indicating the enabling/disabling of each transport unit  10 . Control preferably is done so as to prevent an empty tray T from being transported to a disabled transport unit  10  due, for example, to a breakdown or requirement of a replacement operation. Hence, even while some transport units  10  are replaced, it is unnecessary to stop the overall work system A. Also, as the positions of the recessed portions Tc in the tray T in the positioning ON state set by each transport unit  10  transported by the transfer device  6  are designated in advance and stored in the storage unit  202 , IC chips inspected by the inspection device  7  can be accommodated in the recessed portions Tc in the tray T based on the inspection result. 
     Second Embodiment 
     Although two sets of a butting member  1321  and a support mechanism  1322  are provided so that each butting member  1321  is independently movable in the above-mentioned first embodiment, one set of a butting member  1321  and a support mechanism  1322  may be provided.  FIG. 11  illustrates an example of the latter configuration. 
     In an example shown in  FIG. 11 , a positioning mechanism  13 A includes one set of a butting member  1321 ′ and a support mechanism  1322 . Because one butting member  1321 ′ is used, one cam follower  1323   a , one support member  1323  which supports the cam follower  1323   a , and one biasing mechanism  1324  are used. Also, because one cam follower  1323   a  is used, an engaging portion  1314   a ′ of a support member  1314  has a shape different from that of the engaging portion  1314   a  in the above-mentioned first embodiment. 
     The butting member  1321 ′ includes an L-shaped main body portion  1321   b , an arm portion  1321   c  which is connected to the main body portion  1321   b  via a shaft  1321   d  and is pivotally movable about the shaft  1321   d , and butting portion forming members  1321   e  fixed to the two ends, respectively, of the arm portion  1321   c . Butting portions  1321   a  are the distal ends of the butting portion forming members  1321   e , and these distal end portions (butting portions) are formed in a curved shape. Other constituent elements of the positioning mechanism  13 A are the same as in the positioning mechanism  13  according to the above-mentioned first embodiment. 
     In this embodiment, one set of a butting member  1321 ′ and a support mechanism  1322  is used, while two butting portions  1321   a  are used, as in the above-mentioned first embodiment. Unlike the above-mentioned first embodiment, each butting portion  1321   a  does not independently move, but the arm portion  1321   c  is pivotally movable about the shaft  1321   d , so the relative position of each butting portion  1321   a  can change. Hence, each butting portion  1321   a  can abut against a stage portion Tb of a tray T to the same degree despite a simple configuration. 
     Third Embodiment 
     Although the positioning reference portion  134  and moving mechanism  134   a  are arranged on the transport unit  10  in the above-mentioned first embodiment, they may be arranged at predetermined positions on the mount table  20  on which the transport units  10  are mounted.  FIG. 12  illustrates an example of the latter configuration. 
     In an example shown in  FIG. 12 , a notch-shaped opening portion  111   a  is formed in a bottom wall  111  of a base member  11 . A positioning mechanism  13 B is the same as the positioning mechanism  13 , except for a positioning reference portion  134 ′ and a moving mechanism  134   a ′. The positioning reference portion  134 ′ and moving mechanism  134   a ′ have the same configurations as the positioning reference portion  134  and moving mechanism  134   a , respectively, and they are different only in their arrangements from the latter in which the moving mechanism  134   a ′ is fixed to the mount table  20  in the opening portion  111   a . This makes it possible to form a simpler configuration of a transport unit  10 . It is also possible to facilitate re-positioning of a tray T. 
     Fourth Embodiment 
     Although the positioning reference portion  134  can be moved by the moving mechanism  134   a  in the above-mentioned first embodiment, it may be fixed in position.  FIG. 13  illustrates an example of the position of the positioning reference portion  134 . 
     In an example shown in  FIG. 13 , a guide member  14  includes a positioning reference portion  143 , in addition to a positioning reference portion  141 . The positioning reference portion  143  substitutes for the positioning reference portion  134 , and a positioning mechanism  13 C according to this embodiment includes no moving mechanism  134   a.    
     Although the positioning operation by the positioning mechanism  13 C is the same as in the above-mentioned first embodiment, the positioning reference portion  143  stays in position, so a tray T cannot be transported past the positioning reference portion  143 . Therefore, the tray T is transported while turning back from the positioning reference portion  143 , as indicated by a line L1. With such a configuration, the relationship between reference positions in the X- and Y-directions is set by one member, so it is possible to form a simpler configuration of a transport unit  10 . It is also possible to facilitate re-alignment of the tray T. 
     Other Embodiments 
     In the above-mentioned first to third embodiments, in positioning the tray T in the Y-direction, a reference position is defined by disposing the positioning reference portion  134  and moving mechanism  134   a  at positions below the transport surface of the tray T, and extending the positioning reference portion  134  on the transport track so as to make it abut against one end of the bottom plate portion Ta of the tray T. However, the positioning reference portion  134  and moving mechanism  134   a  may be disposed at positions to the side of or above the tray T to extend the positioning reference portion  134  on the transport track. By disposing the positioning reference portion  134  and moving mechanism  134   a  at positions to the side of or above the tray T, the positioning reference portion  134  can abut against one end, in the Y-direction, of the stage portion Tb of the tray T. Similarly, in the above-mentioned first to fourth embodiments, the butting member  1312  of the press mechanism  131  on the biasing side in positioning the tray T in the Y-direction may be disposed to the side of or above the tray T to extend it on the transport track. 
     Although an example in which the transport apparatus  1  and transport unit  10  are applied to the work system A has been exemplified in the above-mentioned embodiments, the present invention is applicable to various systems. The tray T is merely an example of the object to be transported. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.