Transfer driver device for pressing machine

Abstract: A transfer device for a pressing machine includes the following components: a feed cylinder device (30) with an absolute encoder (33) for applying force to feed bars (10F,10B) for advance or return operation; a pair of left and right clamp cylinder devices (20L,20R), each having an absolute encoder (23L,23R), for applying force to the feed bars for clamp or unclamp operation; hydraulic pressure supplier means (50) common to the cylinder devices for supplying hydraulic pressure to each of the cylinder devices for motion generation; hydraulic valve means (60), having a plurality of servo valves (61) directly controlling each cylinder device in response to feedback signal (f) from the absolute encoder of each cylinder device, for supplying hydraulic pressure from the hydraulic pressure supplier means to each of the cylinder devices so that each cylinder device is driven by a predetermined stroke at a predetermined speed; and driver control means (70) for selecting between the hydraulic valve means for control according to a predetermined switching sequence, whereby the feed bars are directly actuated for linear motions with minimum energy.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer driver device for a pressing machine, and particularly to the transfer driver device which employs a plurality of precision positioning cylinder devices and a common minimum capacity hydraulic supplier means. 2. Description of the Related Art Transfer pressing machines are provided with transfer driver devices, and they transfer mold materials (semi-finished products) through multiple stages in a sequential and automated manner. Included in these transfer pressing machines are two types: one is a two-dimensional type which allows feed bars to move in an advance/return mode and a clamp/unclamp mode and the other is a three-dimensional type which allows feed bars to move in the above two modes plus a lift/down mode. In both types, since the motion of the feed bars must be in cooperation with the up and down stroke of a slide, the feed bars are driven by a link mechanism, a rack and pinion mechanism, a planetary gear mechanism or the like through a crank mechanism and rotating cams which rotate in synchronism with a crank shaft. From US-A-4 462 521 a transfer mechanism for transferring articles one by one from one position to another position in a forging press having a plurality of molds arranged in series is known in which a pair of parallel feedbars provided on their opposing surfaces with plural pairs of clamping jaws are moved by three separate sets of hydraulic cylinders in three orthogonal directions. Said hydraulic cylinders are supplied with hydraulic fluid by cam-operated hydraulic pumps operated with cams mounted in different phases on a drive shaft rotated in timed relation with the forging press, each cam-operated hydraulic pump being hydraulically connected to one of working chambers of each hydraulic cylinder and the other chamber of each hydraulic cylinder being connected to an accumulator for accumulating working oil at a predetermined pressure created by a hydraulic pump so that the feedbars effect cyclic movement to clamp, lift up, carry ahead, lift down and unclamp blanks and return to an original position. From US-A-4 356 763 a control circuit for controlling either the position and the speed of travel of a press table or the hydraulic pressure acting on the press table, or both, in a hydraulic press is known, comprising an actual-value transmitter for the position of the press table, a pressure transmitter for the hydraulic pressure in the hydraulic press cylinder, a set point transmitter, and a control valve, actuated by the deviation of the actual value from the set point value, for the hydraulic cylinder by means of which the pres table is moved. The control valve is a pressure controlling proportional valve, and the circuit can be designed to provide an arbitrary control curve during at least the high-pressure part of the closing sequence of the press. US-A-4 721 028 describes a control system for controlling the movement of the slide of a hydraulic press having a main cylinder containing a piston mounting the slide. The control system comprises an electronic processor, a pressure transducer to measure the pressure of hydraulic fluid applied to the piston to move the slide downwardly, a position encoder coupled to the slide to determine the vertical position of the slide, and a hydraulic circuit to supply hydraulic fluid under pressure to the cylinder to move the piston upwardly and downwardly. The hydraulic circuit comprises a plurality of cartridge valves having controls actuable by outputs from the processor. Mechanical transfer driver devices of the above kind are also disclosed in Japanese Utility Model Laid Open No.61-122028, Japanese Utility Model Application Publication No.63-17540, Japanese utility Model Application Publication No.63-24776 and Japanese Utility Model Laid Open No.2-93030. A motor-driven transfer driver device, as opposed to the above mechanical transfer driver devices, is proposed, for example, in Japanese Patent Application Publication No.63-22895. In such motor-driven transfer driver device, a reversible variable-speed motor is used as a mover. To drive feed bars, the rotary motion by the motor is converted into linear motion by means of a rack and pinion mechanism, ball screw, splined shaft or the like. The conventional mechanical transfer driver devices described above need a number of parts, and are bulky and complex in construction and thus costly to manufacture. Furthermore, the switching of feed stroke and feed rate is normally difficult. In the conventional mechanical transfer driver devices, no sufficient room is allowed in achieving compact and low cost design and adaptability to diversity of application. In contrast, the motor-driven transfer driver devices are more flexibly adapted to compact and low cost design. From the viewpoint of cost, however, the motor-driven transfer driver devices do not necessarily satisfy low cost design requirements because the rack and pinion mechanism for converting the rotary motion into the linear motion remains costly. Furthermore, each of the feed, clamp and lift modes needs its dedicated motor and associated driver control device, requiring a large scale power supply system. This leads to a poor operating efficiency, jeopardizing power saving efforts. Proposed as another mover is a hydraulic generator device which uses cylinder mechanisms on each of which a plurality of cams are coaxially disposed. The rotation of the cams drives a corresponding cylinder mechanism. The use of such a device is not widespread, because the construction of the device except the mover portion needs a number of parts and thus the device itself becomes costly. SUMMARY OF THE INVENTION It is an object of the present invention to provide the transfer driver device of a pressing machine which is easy to handle, compact, and low cost while saving power and widening adaptability to diversity of application. Recognizing that the above described problems are attributable to the conversion of the rotary motion of a crank shaft or a motor, and recognizing the basic technical logic of transfer driving that feed bars are not allowed to move both in advance/return mode and clamp/unclamp mode at a time, the present invention is characterized by cylinder devices which directly drive the feed bars in a linear motion, and common minimum capacity hydraulic supplier means which switches between the cylinder devices to drive, in order to achieve the above described object. The transfer driver device of pressing machine according to the present invention comprises a feed cylinder device with an absolute encoder for applying force of advance/return mode to feed bars, a pair of left and right clamp cylinder devices with absolute encoders for applying force of clamp/unclasp mode to the feed bars, common hydraulic pressure supplier means for supplying hydraulic pressure for motion activation to each of the cylinder devices, hydraulic valve means, having a plurality of servo valves directly controlling each cylinder device in response to feedback signal from the absolute encoder of each cylinder device, for supplying hydraulic pressure from the hydraulic pressure supplier means to each of the cylinder devices so that each cylinder device is driven at a predetermined stroke and speed, and driver control means for selecting between the hydraulic valve means according to a predetermined sequence. In the operation of the pressing machine according to the present invention, the driver control means switches and controls each of the hydraulic valve means in accordance with the predetermined sequence. Each cylinder device is directly driven to move linearly according to the predetermined stroke at the predetermined speed each time the servo valves making up the hydraulic pressure supplier means are switched on. The advance, unclamp, return and clamp motions of the feed bars may be performed in a smooth manner. Since the conversion mechanism of rotary motion to linear motion is dispensed with, every motion is performed precisely and quickly. This also permits compact design to be incorporated. Since the motions are performed in a sequential manner, operating efficiency is enhanced, power saving is achieved, and the device is easy to handle. For example, in accordance with the advance/return motions, minimum hydraulic pressure supplier means may be continuously operated at the highest efficiency possible. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a general block diagram showing an embodiment of the present invention. Fig.2 is a plan view showing linkage between cylinder devices and feed bars. Fig.3 is a cross-sectional side view showing linkage between the cylinder devices and the feed bars. Fig.4 illustrates the switching sequence of operations. DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, an embodiment of the present invention is discussed below. As seen from the drawings, the transfer driver device comprises a feed cylinder device 30, a pair of left and right clamp cylinder devices 20L, 20R, a pair of left and right lift cylinder devices 40L, 40R, common hydraulic pressure supplier means 50, hydraulic valve means 60 including a plurality of servo valves, and driver control means 70, whereby the cylinder devices performing linear motion directly move linearly feed bars 10F, 10B accomplishing a three-dimensional transfer function. Each cylinder device may be directly coupled to the feed bars 10F, 10B. In this embodiment, however, each cylinder device is coupled to the feed bars 10F, 10B via a coupling mechanism such as the one consisting of a pinion 28, clamp driver shafts 26C, 26D, lift pins 45F, 45B as shown in Fig.1 and Fig.2, mainly for the purpose of minimizing the number of cylinder devices and hydraulic valve means for compact and low cost design. The coupling mechanism is of a type which allows the linear motions of the feed bars 10F, 10B by the linear motions of the cylinder devices 20L, 20R, 30, 40L, 40R, rather than a type which converts rotary motion into linear motion. Unlike the conventional device which uses planetary gear mechanism, crank mechanism and the like, neither cost increase nor bulky construction may result. Fig.2 and Fig.3 show left hand side views of the pressing machine. X direction (fore-aft direction) is the clamp/unclamp direction of the feed bars 10F, 10B, and Y direction (left-right direction) is the advance/return direction and Z direction (up-down direction) is the lift/down direction. Each of the cylinder devices (20L, 20R, 30, 40L and 40R) is an intelligent cylinder device, for example, one manufactured by Horiuchi Machinery Corporation, which is capable of reciprocating linear motion accurate to a predetermined stroke at a predetermined speed. Each of them is provided with a respective absolute encoder (23L, 23R, 33, 43L and 43R) which transmits feedback signals f. The cylinder devices are of a hydraulically driven type. As shown in Fig.2, the feed cylinder device 30 is coupled to a pair of fore and aft feed bars 10F, 10B, via a slider 35 which is slidably supported by a coupling mechanism made up of a pair of guide rods 37F, 37B. Linear motion for advance operation (in the direction from bottom to top in Fig.2) or for return operation acts on the feed bars 10F, 10B. The end of the piston 32 of the feed cylinder device 30 is rigidly attached to the slider 35, and the feed bars 10F, 10B are coupled to feed blocks 36F, 36B on the slider 35 by fixing pins 36Fa, 36Ba, respectively. The linear motion of the piston 32 is translated into the linear motion of the feed bars 10F, 10B. As is evident from the above description, dramatically simplified and low cost design thus results, compared to the mechanical transfer driver devices in the above quoted disclosures. Furthermore, the above arrangement minimizes risk of feeding error. Next, the clamp cylinder device 20L allows the feed bars 10F, 10B to mutually approach or separate from each other along the X direction. Approach motion means clamp operation, and separation motion means unclamp operation. A coupling mechanism is formed of a pair of clamp driver shafts 26C, 26D functioning as guide rods as well, slidably supported on a frame 1, clamp blocks 25F, 25B, feed bar guides 24F, 24B, and the like. The feed bar guides 24F, 24B allow the feed bars 10F, 10B to move in advance or return operation. Namely, the feed bars 10F, 10B are slid along the feed guides 24F, 24B in the Y direction. The feed bar guides 24F, 24B are coupled to the clamp blocks 25F, 25B respectively by lift pins 45F, 45B which make up the lift/down coupling mechanism described later, in such a manner that the feed bar guides 24F, 24B are slidable in the Z direction along with the clamp blocks 25F, 25B, but are not displaceable in the X direction. As seen from Fig.2, the clamp block 25F (25B) is coupled to the clamp driver shaft 26D (26C) by the fixing pin 25Fa (25Ba), and both clamp driver shafts 26D, 26c are reversibly movable in the X direction via a rack member 27C, a pinion 28, and a rack member 27D. When the clamp cylinder device 20L is driven pushing both the piston 22L and the clamp driver shaft 26C to the right in Fig.2, the rear (left hand in Fig.2) feed bar 10B is moved to the right via the clamp block 25B and the lift pin 45B. The clamp driver shaft 26D is then moved to the left by the rack members 27C, 27D and the pinion 28, and the front feed bar 10F is moved to the left by the clamp block 25F, and the lift pin 45F. Both feed bars 10F, 10B thus perform the clamp operation. The left clamp cylinder device 20L in Fig.2 applies the clamp/unclamp motion to each left end of the feed bars 10F, 10B, while the right cylinder device 20R in Fig. 1 applies the clamp/unclamp motion in synchronism with each right end of the feed bars 10F, 10B. Namely, a pair of clamp cylinder devices 20L, 20R operating in synchronism apply the clamp/unclamp motion to both left and right ends of the feed bars 10F, 10B. In Japanese Utility Model Laid open No. 2-93030 (Fig.14), left and right clamp/unclamp mechanisms are linked for synchronism by the conventional link mechanism (70). No such link is required in the present invention. From this point of view, simple construction, low cost and compact design may be achieved. The lift cylinder device 40L provided to perform a three dimensional transfer function is means for applying force onto both feed bars 10F, 10B for lift/down motion (in the Z direction). As seen from Fig.3, the lift cylinder device 40L is coupled to the feed bars 10F, 10B via a lift/down coupling mechanism made of a lift bar 44, a pair of lift pins 45F, 45B, a pair of links 47F, 47B and the like. Specifically, in Fig.3, the lift bar 44 penetrates through the lift pins 45F, 45B at their lower end portions 45Fa, 45Ba in a manner that allows the lift bar 44 to slidably move in the X direction. Both ends of the lift bar 44 are rotatably supported by links 47F, 47B via pins 46F, 46B. The links 47F, 47B are rotatably supported by support pins 48F, 48B which are at the same level. The above arrangement allows the lift bar 44 to lift or lower the lift bar 44 level. A cylinder device 4, consisting of a piston 5L, a cylinder 6L and a cylinder chamber 7L, shown in Fig.3 resists the link 47F so that the overall weight of the feed bars 10F, 10B, the clamp blocks 25F, 25B, the lift pins 45F, 45B, the lift bar 44 and the like may not directly act on the lift cylinder device 40L. The cylinder 41L of the lift cylinder device 40L is rotatably supported at a pin 2P by a bracket 2 which is integral part of the frame 1. The end portion of the piston 42L which penetrates through a hole 1H is rotatably supported at the pin 46F by the lift bar 44 in Fig.3. Namely, when the link 47 is rotated clockwise (counterclockwise) to lift (lower) the lift bar 44, no undue force is applied to the cylinder device 40L. The lift cylinder 40R disposed on the right hand side of the pressing machine is operable in synchronism with the left cylinder device 40L illustrated in Fig.2 and Fig.3 in a manner similar to the operational relationship between the left clamp cylinder device 20L and the right clamp cylinder device 20R. The conventional link mechanism (70) is dispensed with. Hydraulic pressure supplier means 50 is common to all the cylinder devices, and supplies hydraulic pressure to each of the cylinder devices 20L, 20R, 30, 40L and 40R for mechanical power generation. In this embodiment, a hydraulic pump 51 is included. Since the hydraulic pressure supplier means 50 is common to all the cylinder devices, each cylinder device dose not have its own dedicated hydraulic pump. The hydraulic pump 51, driven by the rotation of a motor 52 (and a driver 53), pressurizes hydraulic oil inside an oil tank 54. In this embodiment, an accumulator 57 is provided to prevent pulsating oil flow. Signal DRV represents motor driving signal in Fig.1. Although the hydraulic pump 51 is common to the cylinder devices 20L, 20R, 30, 40L and 40R, its capacity is no larger than the capacity capable of driving only the largest cylinder device (feed cylinder device 30 in this embodiment). Of advantage is its small capacity, substantially smaller than the overall capacity required to drive all the cylinder devices (20L, 20R, 30, 40L and 40R) combined. The present invention does not limit the number of pumps in use to a single hydraulic pump 51 only. The arrangement may be changed for convenience; for example, two half-capacity pumps may replace one full capacity pump. It should be understood that the implementation of compact power supply system, the reduction of power consumption and the enhancement of operating efficiency are simultaneously achieved by selectively driving the cylinder devices by means of the hydraulic pressure supplier means 50 capable of driving the largest cylinder device 30 only. This arrangement is opposed to the conventional system in which each of the feed, left clamp, right clamp, left lift and right lift functions needs independently its own motor. In this embodiment, the use of the accumulator 57 allows the capacity of the hydraulic pump 51 to be set smaller than the pump capacity required to drive the largest feed cylinder device 30. Also, the hydraulic pressure supplier means 50 (51, 52, 53, 54, 57) is installed at a remote location distanced from the pressing machine. As seen from Fig.1, hydraulic valve means 60 comprises regulating valves 61AR, 61CAL, 61CAR, 61LDL and 61LDR disposed correspondingly to cylinder devices 30, 20L, 20R, 40L and 40R, and valve controllers 62AR, 62CA and 62LD and the like. The regulating valve 61AR is a control servo valve which is provided with ports A, B communicating with the feed cylinder device 30 via pipings 65, 66, port I communicating with the accumulator 57 (hydraulic pump 51) via piping 64, and port O communicating with the oil tank 54 via piping 67. This control servo valve 61AR directly controls the cylinder device 30. The valve controller 62AR outputs a control signal CNT to activate the servo valve 61AR for advance operation or return operation. Provided further in this embodiment are a position setter 63P and a speed setter 63S for setting or modifying stroke (ending point and starting point) and speed. Receiving the feedback signal f from the feed cylinder device 30 (33), the valve controller 62AR controls speed and position. These constitute a closed control system. Each of regulating valves 61CAL, 61CAR, 61LDL and 61LDR is structurally and functionally equivalent to the regulating valve 61AR, and each of valve controllers 62CA and 62LD is structurally and functionally equivalent to the valve controller 62AR. No description about them is thus repeated. For left and right synchronizing operation, however, regulating valves 62CA and 62LD are coupled to the pair of 61CAL and 61CAR and the pair of 61LDL and 61LDR, respectively. The valve controller 62LD has arc orbit motion compensation. It should be noted that the motion of the link 47F (47B) rotating in a semi-circular orbit with its center on the pin 48F (48B) causes the lift bar 44 to linearly move in the Z direction. Driver control means 70, made up of logic circuits and computers, switches and controls hydraulic valve means 60 (62AR, 62CA, 62LD) according to a predetermined sequence. Indicated at 75 is an angle detector for detecting the angle of the crank shaft, for example, an absolute encoder with a resolution of 0.1 to 0.5 degree. The pressing machine in this embodiment is designed to perform each motion according to crank angle as shown in Fig.4. The driver control means 70 sends down signal Sd shown in Fig.1 to the valve controller 62LD when the crank angle detected by the angle detector 75 is within predetermined range of 55 to 85 degrees. Similarly, the driver control means 70 sends unclamp signal Sac to the valve controller 62CA when the detected signal is within the range of 85 to 125 degrees, return signal Sr to the valve controller 62AR when the detected signal is within the range of 125 to 235 degrees, clamp signal Sc when the detected signal is within the range of 235 to 275 degrees, lift signal Sl when the detected signal is within the range of 275 to 305 degrees, and advance signal Sa when the detected signal is within the range of 305 to 355 degrees. Settings of crank angles corresponding to the starting and ending points of each motion may be modified. The operation of the device is described below. For convenience of description, it is assumed that the pressing machine is at the initial state in which the crank angle is at 235 degrees in Fig.4 and the feed bars 10F, 10B take the state as shown in Fig.2 and Fig.3 with a return operation just completed. Also assumed is that the driver control means 70 has already output the motor driving signal DRV shown in Fig.1 to the driver 53 before the pressing machine is started, that hydraulic pressure of the accumulator 57 is set to a predetermined one with the motor 52 and the hydraulic pump 51 operating, and that the setters 63P, 63S are set to respective predetermined values. When the pressing machine is switched on, the driver control means 70 sends the clamp signal Sc to the valve controller 62CA. The valve controller 62CA, in turn, outputs control signals CNT to regulating valves 61CAL, 61CAR functioning as servo valves. Hydraulic pressure is applied by ports A via pipings 65 shown in Fig.1 to the clamp cylinders 20L, 20R, and then pistons 22L, 22R are simultaneously pushed out to the left in Fig.1. Namely, on the left hand side of the pressing machine, the clamp driver shaft 26C is moved to the right in Fig.2, and the clamp driver shaft 26D is moved to the left by the rack member 27c, the pinion 28 and the rack member 27D. As a result, both feed bars 10F, 10B mutually approach to the center in Fig.1 and Fig.2 by the clamp blocks 25F, 25B, thereby clamping material. This clamp motion is performed at a predetermined speed according to a predetermined stroke. When a crank angle of 275 degrees is reached, the clamp motion is terminated. In the meantime, the accumulator 57 supplies hydraulic pressure for clamp motion to the port I (port I) of the regulating valve 61CAL (61CAR) via piping 64. At the same time, hydraulic pressure for unclamp motion inside the cylinder device 20L (20R) is discharged from the port O (port O) via pipings 66 (66) and port B (port B), and then circulated back to the oil tank 54 via pipings 67. For unclamp motion, hydraulic pressure for unclamp motion is supplied to the cylinder device 20L (20R) via ports I and B while hydraulic pressure is discharged into the oil tank 54 via ports A and O. When the crank angle reaches 275 degrees, the driver control means 70 outputs the lift signal Sl to the valve controller 62LD. The valve controller 62LD sends the control signals CNT simultaneously to the regulating valves 61LDL, 61LDR, causing the pistons 42L, 42R of respective cylinder devices 40L, 40R to be retracted to the right in Fig.1. When the piston 42L is retracted in Fig.3, the links 47F, 47B clockwise rotate respectively around the support pins 48F, 48B from their position illustrated by solid line to the position illustrated by phantom line. The lift bar 44 shifts upwards in the Z direction with its position kept level. Both feed bars 10F, 10B, with material clamped, are lifted by the lift pins 45F, 45B. This lift operation is terminated when a crank angle of 305 degrees is reached. Since the link 47F is urged at a constant force by the cylinder device 4, no undue force is applied to the lift cylinder 40L (40R). The lift cylinder 40L (40R) is rotatably supported at the pin 2P by the frame 1, and thus the rotational movement of the lift bar 44 is smoothly absorbed. When the crank angle reaches 305 degrees, the driver control means 70 outputs the advance signal Sa to the valve controller 62AR. The valve controller 62AR sends the control signals CNT to the regulating valve 61AR to supply hydraulic pressure to the feed cylinder device 30 via port B. The piston 32 is thus retracted to the right in Fig.1. In Fig.2, when the piston 32 is retracted downward moving the slider 35 from its position illustrated by solid line to the position illustrated by phantom line, the feed bars 10F, 10B operate in advance motion. The feed bars 10F, 10B thus slide downward on respective feed bar guides 24F, 24B for advance motion. In this case, since both feed bars 10F, 10B keep clamping material as a result of previous clamping operation, and remain elevated as a result of previous lift operation, the feed bars may transfer the material to a succeeding mold by clamping it from previous mold without interference from other machines. To set the material to the next mold, the down operation at a crank angle range from 55 to 85 degrees and the unclamp operation at a crank angle range from 85 to 125 degrees should be completed. After setting the material, the return operation at a crank angle range from 125 to 235 degrees may be performed to proceed to the next step. These operations, however, are similar to the above described operations except that the feed bars 10F, 10B are operated in a reverse manner, and thus no description will be provided herein. The embodiment according to the present invention comprises the feed cylinder device 30, the pair of clamp cylinder devices 20L, 20R, the common hydraulic pressure supplier means 50, the hydraulic valve means including a plurality of servo valves, and the driver control means 70, whereby hydraulic pressure is selectively supplied to the cylinder devices to drive them into linear motion by the hydraulic pressure supplier means 50, common to all the cylinder devices and having a minimum possible capacity, and the feed bars 10F, 10B are directly driven in a linear motion. The embodiment according to the present invention thus achieves simple construction, power saving design, compactness, low-cost, while being easy to handle and flexibly adaptable to application, compared to conventional mechanical or motor-driven device in which rotary motion is converted into linear motion. Compared to the conventional hydraulic generator, the substantial cost decrease may be achieved in the embodiment. Cylinder devices (20L, 20R, 30) are precision positioning cylinder devices having a respective absolute encoder (23L, 23R, 33) for generating a feedback signal f, and are operable at a predetermined stroke at a predetermined speed. Thus, material may be clamped in a assured manner and fed to a next mold. Three dimensional transfer is achieved by allowing lift/down operation by means of the cylinders 40L, 40R. Thus, the feeding of material is carried out in a smooth manner, increasing adaptability to application. Cylinder devices 20L, 30, 40L are coupled to the feed bars 10F, 10B via a simple structured coupling mechanism including 26C, 26D, 24F, 24B, 35, 37F, 37B, 44, 45F, 45B, 47F, 47B. Thus, the number of cylinder devices are minimized, reducing manufacturing cost, allowing easy assembly and reducing installation space. The hydraulic pressure supplier means 50 comprises a single hydraulic pump 51 of which capacity is no greater than the capacity capable of driving the largest feed cylinder device 30. The hydraulic pump 51 is commonly used to drive the cylinder devices 30, 20L, 20R, 40L and 40R by switching properly from one cylinder device to another. Compared to the conventional motor-driven device in which for each operation its own dedicated motor is provided, capacity of the power supply system may be reduced. From this point of view, even more compact and low cost design may be achieved. Since the hydraulic pressure supplier means 50 is associated with the accumulator 57, accumulation of energy of hydraulic pressure is possible. The capacities of the driving motor 52 of the hydraulic pump 51 and its driver 53 may be reduced in the sense that no electric energy is accumulated in the conventional motor-driven device. Since the motor 52 may be left run in a continuous operation, maximum operating efficiency and thus power saving may be achieved. Hydraulic pressure output by the hydraulic pump 51 is subjected to variations as a result of voltage variations, and such hydraulic pressure variations cause pulsating oil flow. The accumulator 57 regulates pulsating oil flow, providing stable hydraulic pressure. Thus, each operation of the device may be performed in a precise and smooth manner. The hydraulic pressure supplier means 50 may be installed in a remote location, separate from the location of the cylinder devices 20L, 20R, 30, 40L and 40R. This allows easiness in planning the layout of the pressing machine at installation, and saves space left available for other machines. The hydraulic valve means 60 comprises regulating valves 61AR, 61CAL and other valves, each functioning as a control servo valve, corresponding to cylinder devices 30, 20L, and other cylinder devices, and valve controllers 62AR, 62CA and other valve controllers. These components form closed loop control systems which work in response to feedback signals f output by encoders 33, 33L and other encoders. Thus, each cylinder device exactly performs its own assigned operation (advance, return, clamp or unclamp) moving by a predetermined stroke for a predetermined duration. Each of the valve controllers 62AR, 62CA and 62LD is provided with the position setter 63P and the speed setter 63S. This allows feed pitch and feed rate of material to be selected or modified in a timely manner. Thus, this makes the transfer device easy to handle and adaptive to a variety of application. Valve controllers 62CA and 62LD are, respectively, common to the pair of left and right cylinder devices 20L and 20R and to the pair of left and right cylinder device 40L and 40R. Thus, the device suffer neither looseness in mechanical parts due to wear which would be encountered in the conventional mechanical device nor performance variations due to slip of motors which would be encountered in the conventional motor-driven device. This allows the feed bars 10F, 10B to perform, on their both left and right side ends, accurate and completely synchronized clamp/unclamp and lift/down operations. Thus, the unsuccessful gripping of material may be avoided, and precision transfer of material is assured. In response to low level control signals CNT, the valve controllers 62AR, 62CA and 62LD control respective control servo valves (61AR, 61CAL, 61CAR, 61LDL and 61LDR) for regulating powerful hydraulic pressure. Small capacity of control system and compact design are achieved, compared to the conventional motor-driven device in which large driving power fed to motors is directly controlled. This substantially simplifies internal wiring operation for the pressing machine. In response to an accurate crank angle detected by the angle detector 75, the driver control means 70 outputs the advance signal Sc, down signal Sd, unclamp signal Sac and other signals. This allows the slide to perform up and down stroke motion in a completely synchronized manner. Thus, material is transferred without any interference in a smooth manner. Starting and ending crank angles for each operation may be set or modified in the driver control means 70, and thus transfer function is performed in a timely manner in accordance with slide and stroke motion of the pressing machine. Maximum acceleration for each operation is thus reduced, and rigidity requirements for coupling mechanisms may be lowered. Installation of conventional rotary motion to linear motion converter mechanisms or heat emitting rotary motors is not required. Instead, installed in the pressing machine are linear motion cylinder devices 30, 20L and the like. Thus, safety installation is assured. No particular steps to control heat radiation is required. Since expansion and contraction of components due to heat emission do not take place, accuracy degradation associated with them will not occur. In the above embodiment, each cylinder is coupled to the feed bars 10F, 10B via coupling mechanisms. Alternatively, each cylinder may be directly coupled to the feed bars 10F, 10B. The use of simple structured coupling mechanisms allows the number of cylinder devices to be minimized without pushing up manufacturing cost and thus allows space to be left available inside the pressing machine, compared to the conventional rotary motion to linear motion converter mechanism. Although the valve controllers 62AR, 62CA and 62CD are separately disposed in the embodiment, they may be integrated into a single unit. Or, alternatively, they may be integrated with the driver control means 70. For example, they may be integrated with pressing machine control panel (including CPU, ROM, RAM and the like) which controls the entire pressing machine so that components of the panel may function as a valve controller in addition to their own function in the panel. The driver control means 70 carries out each operation sequentially in a continual and step-by-step manner as shown in Fig.4. Alternatively, however, the end portion of advance operation and the start portion of down operation may partly overlap. The hydraulic pressure supplier means 50 is formed of a single hydraulic pump 51 capable of driving the largest feed cylinder 30. When two successive operations partly overlap as described above, the capacity of the hydraulic pump 51 is set to equal to the sum of capacity which allows two cylinders to perform simultaneously two overlap operations. As described above, the present invention comprises linear motion feed and clamp cylinder devices, hydraulic pressure supplier means common to all the cylinder devices, hydraulic valve means including a plurality of servo valves, and driver control means, whereby hydraulic pressure by minimum capacity hydraulic pressure supplier means is swichably supplied to each of the cylinder means according a predetermined sequence. The above arrangement eliminates disadvantages of the conventional devices such complex and costly construction, and narrow adaptability to application, all these resulting from the use of rotary motion to linear motion converter mechanism. The above arrangement further achieves power saving, widening adaptability to diversity of application, simple and compact structure and low cost design. Easy-to-handle, high-speed and precision transfer operation is thus achieved.

Claims: A transfer driver device for a pressing machine comprising: a feed cylinder device (30) for applying force to feed bars (10F, 10B) for advance or return operation, a pair of left and right clamp cylinder devices (20L, 20R) for applying force to the feed bars (10F, 10B) for clamp and unclamp operation, eventually a pair of left and right lift cylinder devices (40L, 40R) for applying force to the feed bars (10F, 10B) for lifting and lowering operation, hydraulic pressure supplier means (50) common to said cylinder devices and having a hydraulic pump (51) for supplying hydraulic pressure to each of said cylinder devices for motion generation, and driver control means (70) for selectively controlling the hydraulic pressure supply to said cylinder devices, characterized in that each of said cylinder devices (30, 20L, 20R, 40L, 40R) is provided with an absolute encoder (33, 23L, 23R, 43L, 43R) for detecting a respective feedbar position, said hydraulic pressure supplier means (50) has a capacity of driving at a time only the cylinder device or pair of cylinder devices affording the largest amount of hydraulic supply, hydraulic valve means (60) are provided having a plurality of servo valves (61AR, 61CAL, 61CAR, 61LDL, 61LDA) directly controlling each cylinder device in response to a feedback signal from the absolute encoder of each cylinder device for supplying hydraulic pressure from the hydraulic pressure supplier means (50) to each of said cylidner devices so that each cylinder device is driven by a predetermined stroke at a predetermined speed in accordance with a predetermined switching sequence controlled by said driver control means (70) by selecting between the servo valves (61AR, 61CAL, 61CAR, 61LDL, 61LDR) of the hydraulic valve means (60) in a manner that only one or only one pair of said cylinder devices is activated at a time. A transfer driver device as set forth in claim 1, wherein said hydraulic pressure supplier means (50) comprises a plurality of hydraulic pumps each having a partial amount of the total pump capacity of said hydraulic pressure supplier means (50). A transfer driver device as set forth in claims 1 or 2, wherein said hydraulic pressure supplier means (50) comprises an accomulator (57) allowing the capacity of the pump(s) supplying said accumulator (57) with hydraulic pressure to be set smaller than the pump capacity required to drive the largest cylinder device or pair of cylinder devices if no such accumulator was present.

Inventors: ARAI TOSHIHIKO, IMANISHI SHOZO, ARAI, TOSHIHIKO, IMANISHI, SHOZO
Applicants: AIDA ENG LTD, AIDA ENGINEERING LTD.
Application year: 1992
Main classification: G05B19
IPC codes: G05B19, B21D43