US20130276505A1

US20130276505A1 - Press

Info

Publication number: US20130276505A1
Application number: US13/990,325
Authority: US
Inventors: Eiji Kitai
Original assignee: Kojima Press Industry Co Ltd
Current assignee: Kojima Industries Corp
Priority date: 2010-11-30
Filing date: 2010-11-30
Publication date: 2013-10-24
Also published as: JP5808755B2; WO2012073337A1; CN103328198A; TW201221346A; JPWO2012073337A1; CN103328198B

Abstract

A press including a number of pairs of dies each clamped by a driving source to press set work pieces in a vertical direction, and a revolver holding the pairs of dies and rotatable around a vertical axis, wherein the revolver by rotating moves any pair of dies to a pressing position where pressing process is performed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. §371 national stage application of PCT/JP2010/071391 filed Nov. 30, 2010, which is hereby incorporated herein by reference in its entireties for all purposes.

TECHNICAL FIELD

The present invention relates to a press. More particularly, the present invention relates to a press clamping a pair of dies in the vertical direction by a drive source and pressing process a workpiece set in the dies.

BACKGROUND ART

Japanese Laid-Open Patent Publication No. 2001-300780 discloses a currently known press. This press clamps a pair of dies in the vertical direction by means of a driving source to press a workpiece set in the dies.

SUMMARY OF THE INVENTION

In the prior art described above, however, in order to perform another processing step using a single press, dies must be removed from the press for exchange, which takes some time and trouble. An object of the present invention is to provide a press in which the dies can be exchanged without removing them from the press in order to perform a number of processing steps.
Embodiments of the present invention include a press including a number of pairs of dies each clamped by a driving source to press a set workpiece in a vertical direction, and a revolver holding the pairs of dies and rotatable around a vertical axis, wherein the revolver by rotating moves any pair of dies to a pressing position where pressing process is performed.
This structure allows the press to hold in advance a numbers of pairs of dies, to move any pair of dies to a position where pressing process is performed simply by rotating the revolver. The dies may be thus changed without removing them from the press in order to perform a number of processing steps.
Further, in the present invention, each time a pressing process is completed in one of the pairs of dies, the revolver rotates so that the pair of dies holding a processed workpiece is moved to a position different from the pressing position, and that another pair of dies is moved to the pressing position.
This structure allows to perform processing using other pairs of dies without waiting for completion of transfer of processed workpieces. Therefore, it is possible to reduce time required for production and thus to provide a press with good production efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of the press.

FIG. 2 is a plan view of the press.

FIG. 3 is a side view of the press.

FIG. 4 is a schematic diagram with the transfer arms holding a workpiece.

FIG. 5 is a schematic diagram with the transfer arm lifting up the workpiece.

FIG. 6 is a schematic diagram with the workpiece taken out of the holder by the transfer arm.

FIG. 7 is a schematic diagram with the transfer arm placing the workpiece in a pair of dies one stage above.

FIG. 8 is a block diagram showing a control system of the press.

FIG. 9 is a sectional view of the press taken along the line V-V of FIG. 2 with dies (a) opened and (b) clamped.

FIG. 10 is a schematic plan view showing a part of the workpiece transfer step of the first embodiment.

FIG. 11 is a diagram showing the flow of a workpiece transfer and assignment of the processing steps of the first embodiment.

FIG. 12 is a schematic plan view showing a part of the workpiece transfer step of the second embodiment.

FIG. 13 is a diagram showing the flow of a workpiece transfer and assignment of the processing steps of the second embodiment.

FIG. 14 is a schematic plan view showing a part of the workpiece transfer step of the third embodiment.

FIG. 15 is a diagram showing the flow of a workpiece transfer and assignment of the processing steps of the third embodiment.

FIG. 16 is a diagram showing the flow of a workpiece transfer and assignment of the processing steps of the fourth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of the present invention will be described with reference to the drawings. FIGS. 1 to 3 respectively show a front view, a plan view and a side view of a press 10. As shown in FIG. 1, the press 10 has a table 11 at the bottom, and a crown 12, an upper plate, at the top. A crown 12 and the table 11 are tied with two vertical struts 13 fastened by bolts. A rotation shaft 23, which will be described later, also functions as a strut, so that the crown 12 is virtually supported by the rotation shaft 23 and the struts 13.
In the center of the press 10 is provided a revolver 20 rotatable about a vertical axis. The revolver 20 has four holders 30 suspended from it. Each of the holders 30 supports three pairs of forming dies 40 a, 40 b and 40 c in series. As shown in FIG. 3, below the top plate 111 of the table 11, there is provided with a hydraulic cylinder 50 as a driving source of press, and a servo motor 60 as a driving source for rotating the revolver 20. As shown in FIGS. 4 to 7, the press 10 is provided with, in addition to the above, a transfer device 70 as means of transferring raw or processed materials (hereinafter collectively referred to as workpiece W), hydraulic cylinder 50, and a control device 80 which controls the servo motor 60 and the transport device 70.
Firstly the revolver 20 will be described in detail. In the top and bottom of the revolver 20 there is respectively provided with a disc-shaped upper plate 21 and lower plate 22, and in the center of the revolver 20 the rotation shaft 23 penetrating the center of the lower plate 22 and upper plate 21. As shown in FIG. 3, above the upper plate 21 a bearing 121 provided in the crown 12 receives a length of the rotation shaft 23. Below the lower plate 22 a bearing 112 provided on the top plate 111 of the table 11 receives a length of the rotation shaft 23. A pulley 231 is fixed on the lower end of the rotation shaft 23. The whole revolver 20 is rotatable by a pulley 231 on the rotation shaft 23 driven by the servo motor 60. The lower plate 22 and top plate 21 are supported by struts 24 near the periphery, away from the positions of the holder 30.
The lower plate 22 has a number of cam followers 25 for the revolver 20 to smoothly rotate on the top plate 111 of the table 11. Only four of the cam followers are seen in FIGS. 1 and 3. A spacer 232 is provided around the rotation shaft 23 to secure such an amount of gap between the top plate 111 and lower plate 22 of the table 11 that the cam follower 25 may function. Portions of the lower plate 22 that are immediately below each of the holders 30 suspended are separate lifting blocks 26, which may be lifted up when the cylinder rod 51 pushes up. As shown in FIG. 3, on the lower face of each lifting block 26 is provided a pair of receiving hook 261 having an inwardly bent L-shaped cross section. The receiving hook 261 on the lifting block 26 is configured to embrace from around the head 52 of the cylinder rod 51 when it rotates together with the revolver 20 to come just above the cylinder rod 51 by.
The lower plate 22 is provided with foot receivers 27 fixed on the upper side, and each receiving a foot 341 provided at the lower end of each tie rod 34 of each holder 30. Each foot receiver 27 is shaped so as to support the tie rod 34 to prevent it from any horizontal swing, but not to prevent its slight vertical movement during clamping as will described below.
The upper plate 21 is provided with pairs of suspending hooks 28 fixed on the lower side at four positions in every 90 degrees, with two pairs for hanging each holder 30. Each holder 30 has two pairs of T-bars 32 fixed on the upper face, which are horizontally inserted in the suspending hooks 28 on the revolver 20 so that the holder 30 is suspended. This structure makes the holders 30 exchangeable.
The dies 40 a, 40 b and 40 c and the holders 30 are now described. Each holder 30 includes four die plates 31 a, 31 b, 31 c and 31 d. The T-bars 32 mentioned above are formed on the upper side of the uppermost die plate 31 a. As shown in FIG. 2, the die plates 31 a, 31 b, 31 c and 31 d each have two guide holes 33 in opposite ends, into which the tie rods 34 are inserted through the four die plates 31 a, 31 b, 31 c and 31 d. The die plates 31 b, 31 c and 31 d, except the uppermost one 31 a, which is fixed to the upper plate 21 of the revolver 20, may be slid up and down while being guided by the tie rods 34. The die plates 31 a, 31 b, 31 c and 31 d support separately the upper and lower dies of three pairs of dies 40 a, 40 b and 40 c as shown in FIG. 1. Each of the dies 40 a, 40 b and 40 c may be exchanged by sliding horizontally.
Each of the die plates 31 a, 31 b, 31 c and 31 d has holes in the four corners, into each of which a suspension strut 35 composed of a long bolt is inserted. Each of the hanging struts 35 has four nuts (not shown) screwed thereon, which serve as stoppers defining the falling end of the die plates 31 b, 31 c and 31 d. The uppermost stoppers are screwed at positions above the uppermost die plate 31 a so that the suspension struts 35 are hung down from the uppermost die plate 31 a. The other stoppers are screwed at positions below the other die plates 31 b, 31 c and 31 d to define the most lowered positions of the die plates 31 b, 31 c and 31 d. For each holder 30, the position of the stopper can be adjusted to change the opening distance of a pair of dies 40 a, 40 b and 40 c as desired, while the positions of the lowest stoppers should be unified for all holders 30. Each of the dies 40 a, 40 b and 40 c may be provided with the guide pins 41 on the lower die and as many opposed guide bushings 42 on the upper die, which may be used to align the pair of dies when mounting.
Now the servo motor 60 and the hydraulic cylinder 50 will be described. As shown in FIG. 3, the hydraulic cylinder 50 is fixed on the lower surface of the top plate 111 of the table 11. A cylinder rod 51 is positioned upwardly from the hydraulic cylinder 50 through the top plate 111 of the table 11 in order to transmit power of the hydraulic cylinder 50. The cylinder rod 51 has a head 52 with an outwardly extending flange formed at the end. A pulley 61 is fixed on the shaft of the servo motor 60. The pulley 61 on the servo motor 60 is connected via a belt 62 to the pulley 231 of the rotation shaft 23, so as to transmit rotational force to the rotation shaft 23.
Now the transfer device 70 will be described. As shown in the schematic diagrams of FIGS. 4 to 7, the transfer device 70 includes four transfer arms 71 provided at different levels, and each transfer arm 71 has a holder 72 at the end, which can hold a workpiece by suction. As shown in FIGS. 4 to 7, the transfer arms 71 are provided to allow to stretch or move independently in the direction required of the front and back, up and down, and left and right. FIG. 4 shows the transfer arms 71 holding the workpieces W0, W1, W2 and W3. FIG. 5 shows the transfer arms 71 lifting up the workpieces W0, W1, W2 and W3. FIG. 6 shows the transfer arms 71 taking the workpieces W0, W1, W2 and W3 out of the holder 30 a. FIG. 7 shows the transfer arms 71 placing the workpieces W0, W1 and W2 into the dies 40 a, 40 b and 40 c one stage above.
The control system of the press 10 will next be described. FIG. 8 is a block diagram showing a control system of the press 10. The press 10 includes a controller 80 as shown in FIG. 8. The control device 80 controls hydraulic pressure in the hydraulic cylinder 50, rotation of the servo motor 60, and various movements such as listed above of the transfer arm 71 of the transfer device 70.
A single pressing operation will next be described. FIGS. 9( a) and 9(b) is sectional views of the press 10 at the plane V-V of FIG. 2, with pairs of dies opened and clamped, respectively. As shown in FIG. 2, out of the four holders, one that has come just above the hydraulic cylinder 50 at the time (hereinafter referred to as pressing position) is the target holder 30 for which a pressing operation is carried out. First, starting with the condition of FIG. 9( a), the hydraulic cylinder 50 is controlled by controller 80 to start pushing up the cylinder rod 51. The lifting block 26 in the lower plate 22 of the revolver 20 is lifted up by the cylinder rod 51 rising, and then the lowermost die plate 31 d is lifted up. The lifting block 26 has a wider upper surface than the cylinder rod 51, and thus allow a more stable lift as compared with the case where the cylinder rod 51 directly raises the die plate 31 d. Then, the die plates 31 b and 31 c rise in turn, and each pair of dies 40 a, 40 b and 40 c sandwiches respective workpieces W.
As shown in FIG. 9( a), there may be some play in the vertical direction in the hanging structure with the T-shaped bar 32 on the holder 30 and the hanging hook 28 on the upper plate 21 of the revolver 20. In addition, there may be a gap of about 1 mm between the upper plate 21 of the revolver 20 and crown 12, when the dies are opened. With such conditions, after all the workpieces W are sandwiched in the dies 40 a, 40 b and 40 c, all the holder 30 are raised slightly and then the whole revolver 20 is also lifted slightly. Accordingly, the dies 40 a, 40 b and 40 c bear the load of the revolver 20 and all the holders 30, and this weight thus presses to process the workpieces W. However, in case that the largest processing weight required for pairs of dies 40 a, 40 b and 40 c that is supported on the target holder 30 for press is greater than that total weight which the dies 40 a, 40 b and 40 c bear as mentioned above, the revolver 20 will rise into close contact with the crown 12 and then the workpieces W will be pressed with an additional reaction force applied from the crown 12.
In the condition of FIG. 9( b), the cylinder rod 51 next starts to draw back. The revolver 20 and the holder 30 fall by their own weight as the cylinder rod 51 goes lower. The die plates 31 b, 31 c and 31 d also go down in turn, and stop at the level where each gets in contact with the respective stopper on the hanging rod. Each pair of dies 40 a, 40 b and 40 c opens to a preset distance when a single pressing operation for this holder 30 is completed.
Now a flow of producing parts according to the first embodiment will be described. FIG. 10 is a schematic plan view showing a part of the workpiece transfer step according to the first embodiment. The transfer device 70 is positioned in front of the press 10 as shown in FIG. 10 (a) to (d). This means that the position where transferring operations are performed on the holder 30 (hereinafter referred to as transferring position) is the same as the pressing position. FIG. 11 is a process diagram showing flow of workpiece transfer and assignment of processing steps according to the first embodiment. Plate materials such as aluminum plates or the like usually undergoes several processing steps, such as drawing, forming, punching and trimming, in sequence to produce a specific kind of parts. In FIG. 11, symbols A1, A2, etc. appended to each pair of dies represent different kinds of processing steps assigned to those pairs of dies. For example, A1 represents the first processing step to produce a part A. The arrows drawn to the right of the holder 30 a represents flow of workpieces W0, W1, W2 and W3. For example, W1 represents a workpiece after completion of the first processing step for producing parts A. Note that the W0 is a raw material before any processing.
A flow of producing parts A using the press 10 will be described below. FIG. 10 (a) shows a condition in which the holder 30 a in pressing position, the holder 30 b, the holder 30 c and the holder 30 d arranged counterclockwise in this order. Parts A requires three processing steps A1, A2 and A3 to produce, which are assigned to the pairs of dies in the holder 30 a from bottom up in that order, as shown in FIG. 11. First, the hydraulic cylinder is controlled by a control device to perform a pressing operation described above on the holder 30 a in the pressing position as in FIG. 10( a). The workpieces W0, W1 and W2 respectively becomes workpieces W1, W2 and W3 via processing steps A1, A2 and A3, as shown in FIG. 11. The control device then drives the transfer arms 71 into movement as follows. First, as shown in FIG. 4 and FIG. 10 (b), the upper three transfer arms 71 are inserted into the holder 30 a and take hold of the processed workpieces W 1, W2 and W3. At the same time, the lowermost transfer arm 71 takes hold of a raw material workpiece W0 piled in the material storage M. The transfer arms 71 then lift up the workpieces W0, W1, W2 and W3 and temporarily go back out of the holder 30 a, as shown in FIGS. 6 and 10 (c). Next, as shown in FIG. 7 and FIG. 10 (d), the lower three transfer arms 71 are inserted again into the holder 30 a and place the workpieces W0, W1 and W2 in the pairs of dies 40 a, 40 b and 40 c. At the same time, the uppermost transfer arm 71 takes the workpiece W3, which has gone through all the processing steps, to the outside of the press. An operational cycle for producing parts A has thus been completed. This cycle is repeated to produce parts A in succession by the single holder 30 a.
Next, the flow for the production of parts B, C, and D will be described. Parts B, C and D each require three steps to produce, like Part A. The production process for parts B, C and D are respectively and independently assigned to the die holders 30 b, 30 c and 30 d that are not in the pressing position, as shown in FIG. 10( a) to (d). The pairs of dies are arranged in the holders 30 b, 30 c and 30 d in such a way that the three steps proceed from bottom up as shown in FIG. 11, like the holder 30 a. A desired holder 30 b, 30 c or 30 d may be moved to the pressing position by the controller controlling the servo motor to rotate the revolver 20. The holder 30 b, 30 c or 30 d that has been moved to the pressing position may be controlled in the same way as described above for production of parts A, in order to produce parts B, C or D corresponding to that holder.
The first embodiment of the present invention has been described above. According to this embodiment, the four holders 30 a, 30 b, 30 c and 30 d are supported in advance on the rotatable revolver and arranged in the rotational direction, any holder can be moved to the pressing position simply by rotating the revolver. The dies 40 may be easily exchanged by simply rotating the revolver 20 without removing them from the press 10, in order to carry out multiple processes, and thus the press 10 is suitable for multi-production.
According to this embodiment, in each holder three pairs of dies are lined in series in the pressing direction. Therefore, it is possible to carry out three pressing steps in a single operation at the same time. This allows to integrate a process for producing parts consisting of three steps in a single press 10.
Now a second embodiment of the present invention will be described. The elements shown in FIGS. 1 to 8 are common to the first embodiment, and thus the description of them will be omitted. The flow of producing parts according to the second embodiment will be described. FIG. 12 is a schematic plan view showing a part of the workpiece transfer process according to the second embodiment. As shown in FIGS. 12( a) to (d), the transfer device 70 is positioned on the left side of the press 10. That is, the transferring positions and the pressing position are different from each other. FIG. 13 is a process diagram showing assignment of the processing steps and flow of workpiece transfer, according to the second embodiment. W, X, Y and Z represent a workpiece in process of producing parts A, B, C and D, respectively.
A flow of producing parts A, B, C and D by using the press 10 will be described. In FIG. 12 (a), the holder 30 a in the pressing position, the holder 30 b, the holder 30 c and the holder 30 d are arranged counterclockwise in that order. Parts A, B, C and D each require three steps to produce. Production processes for these kinds of parts are assigned to different holders, as shown in FIG. 11. Steps A1, A2 and A3 are assigned to the dies of the holder 30 a from bottom up in that order, and likewise processing steps for parts B, C, and D are assigned to the pairs of dies in the other holders 30 b, 30 c and 30 d from bottom up in order.
First, the hydraulic cylinder is controlled by a control device to carry out a pressing operation described above on the holder 30 a in the pressing position as in FIG. 12( a). The workpieces W0, W1 and W2 respectively becomes workpieces W1, W2 and W3 via the processing steps A1, A2 and A3, as shown in FIG. 11. During this pressing operation, a transferring operation is carried out on the holder 30 d as in FIG. 12( a). The holder 30 d holds workpieces Z1, Z2, Z3 which have gone through steps D1, D2, D3. At this time, the workpieces Z1 and Z2 for which not all processing steps are completed is transferred one stage up into dies 40 b and 40 a, the workpiece Z3 for which all processing steps have been completed are taken out of the holder 30 d to the outside of the press 10, and the workpiece Z0 which is a raw material before any processing is brought from a material storage M outside the press 10 into the lowermost pair of dies 40 c in the holder 30 d. During this, the control device drives the transfer arm 71 in the same movement as the transfer arm according to the first embodiment described above. The servo motor is then controlled by the control device to rotate the revolver 20 clockwise by 90 degrees. One operational cycle for production of parts A, B, C, and D has thus been completed.
Parts A, B, C and D may be produced in this order by repeating the cycle in which, as described above, a processing process is performed at the pressing position while a transferring process is carried out at another position, and then the revolver rotates by 90 degrees. This cycle is repeated to produce parts A, B, C and D in succession, by all the holders 30 a, 30 b, 30 c and 30 d.
The second embodiment of the present invention has been described above. According to this embodiment, after each pressing operation is completed, the revolver 20 is rotated, the dies holding the workpieces that has been pressing process is moved to a position different from the pressing position while another holder is moved to the press position. Therefore, it is possible to carry out processing steps in the dies of another holder, without waiting for the completion of transfer of processed workpieces. Therefore, it is possible to provide a press with good production efficiency and can reduce the time required for production. According to this embodiment, processes of processing parts A, B, C and D are completed in turn one by one. Assembly process of parts may be started as soon as all kinds of parts are collected by one piece for each kind, and this can contribute to an improved efficiency in production process.
A third embodiment of the present invention will be described with reference to the drawings. The elements shown in FIGS. 1 to 8 are common to the first embodiment, and thus the description of them will be omitted. FIG. 14 is a schematic plan view showing a part of workpiece transferring process according to the third embodiment. As in FIG. 14( a) to (d), the transfer device 70 is arranged on the left side of the press 10. Further, the transfer device 70 has transfer arms similar to those shown in FIGS. 4 to 7. Unlike the first embodiment, however, the transfer device 70 has two, left and right transfer arms 71 a and 71 b at each of three levels, as shown in FIG. 14( a) to (d). The total six transfer arms can independently hold a workpiece by a holder 72 provided on their end. FIG. 15 is a process diagram showing the flow of workpiece transfer and assignment of processing steps according to the third embodiment. W, X and Y represent a workpiece during processing parts A, B and C, respectively.
A flow of producing parts A, B and C of the third embodiment will be described. For FIG. 14 (a) shows a condition in which the holder 30 a in the pressing position, the holder 30 b, the holder 30 c, the holder 30 d are arranged counterclockwise in this order. The kinds of parts A, B and C each requires four steps to produce. The production processes for these kinds of parts are assigned to the lower, middle and upper rows of dies respectively so that their final processing step belong to different holders. As shown in FIG. 15, the final steps for each part A, B and C fall in the holders b, c and d, respectively.
First, the hydraulic cylinder is controlled by the control device to carry out a pressing operation described above on the holder 30 a in the pressing position as in FIG. 14( a). The workpieces Y0, X1, W2 becomes workpieces Y1, X2, W3 through the processing steps C1, B2, A3, respectively, as shown in FIG. 14 (c). During this pressing operation, the transfer device is controlled by the control device to carry out a transferring operation on the holder 30 d. As shown in FIG. 14( a), the holder 30 d holds workpieces Y4, X1, W2 which has just gone through the steps C4, B1, A2. The transfer arms 71 b on one side in the transfer device 70 hold workpieces Y3, X0, W1 which are to be placed next. Out of these workpieces, the workpiece X0 is a raw material that was brought from a material storage outside the press 10. The transfer device 70 inserts the transfer arms 71 a into the revolver 20, as shown in FIG. 14( b), and the transfer arms 71 a hold and lift up the workpieces Y4, X1, W2 in the dies of the holder 30 d. The transfer arms 71 b then place and set the workpieces Y3, X0, W1 in the dies of the holder 30 d, as shown in FIG. 14( c). In condition shown in FIG. 14( c), transfer arms 71 a are temporarily moved out of the revolver 20 while holding the workpieces Y4, X1, W2. At the same time, the revolver 20 is rotated clockwise by 90 degrees by the control device, reaching the condition shown in FIG. 14( d). The workpiece Y4, as all the processing steps are completed, is transferred out of the press 10 by the transfer arm. One operational cycle for producing parts A, B and C has thus been completed.
The above is a part of the production flow. The transfer device basically repeats a behavior in which it removes workpieces from pairs of dies by its transfer arms on one side, and place on the same pairs of dies workpieces that has been held in the transfer arms on the other side. The role of the transfer arms will alternate for every cycle between the left and right side. The workpieces are thus transferred in turn to neighboring die holders, as shown in FIG. 15. Some transfer arms are, though, differently moved when they remove the completely processed workpieces W4, X4, Y4 to the outside of the press, or bring the raw workpieces W0, X0, Y0 from a material storage outside the press. Parts A, B and C are produced in turn by repeating a cycle in which, as described above, a processing operation is performed in the pressing position, while a transferring operation is performed in another position, and then the revolver is rotated by 90 degrees.
The third embodiment of the present invention has been described above. According to this embodiment, since the final steps of processing each kind of parts A, B, and C are assigned to different die holders 30 b, 30 c and 30 d, processes of processing parts A, B, and C are completed in turn one by one. Therefore, assembly process of parts may be started as soon as all kinds of parts are collected by one piece for each kind, and this can contribute to an improved efficiency in production process. Further, according to this embodiment, there is no need of transferring workpieces between upper and lower rows of dies. This allows transfer arms to remain in the holder after they have removed the processed workpieces until they place those workpieces to be processed next.
A fourth embodiment of the present invention will be described with reference to the drawings. The elements shown in FIGS. 1 to 8 are common to the first embodiment, and thus the description of them will be omitted. As in the third embodiment, the transfer device 70 is disposed on the left side of the press 10. The transfer device 70, by two left and right in each height of the four-stage, and has transfer arm 71 a of eight books, 71 b. FIG. 16 is a process diagram showing the flow of the workpiece transfer and assignment of the processing steps according to the fourth embodiment. Workpiece W represent what in the processing step of the component A.
A flow of producing parts A according to the fourth embodiment will be described. Parts A require twelve steps to produce, and these steps are assigned to the pairs of dies from bottom up in order, four steps for each row, as shown in FIG. 16. In the same manner as in the third embodiment, the press repeats the cycle in which a processing operation is carried out in the pressing position while a transferring operation is performed in another position and then the revolver rotates by 90 degrees. The transfer device repeats a behavior that is basically similar to the third embodiment in which it removes a workpiece from the dies by its one transfer arm while it places the workpieces held by another transfer arm into the same dies. The transfer device, however, operates with an upward movement one stage above as in the first embodiment, when it brings a raw workpiece W0 from outside of the press into the bottom stage of the holder 30 a and takes a workpiece W12 for which all processing steps are completed out of the top stage of the holder 30 d to the outside of the press. The workpieces W4 and W8 in the holder 30 d is replaced in the dies one stage above in the holder 30 a. Parts A are produced through the above process.
The fourth embodiment of the present invention has been described above. According to this embodiment, since all the twelve steps are assigned to the twelve pairs of dies, a production process with twelve steps can be integrated to a single press.
The embodiments of the present invention described above are for exemplary purpose only, and it should be meant that the present invention is not limited to that description. The number of holders 30 hung on the revolver 20 is not limited to four and may be any plurality. Further, the number of pair of dies 40 held in one holder 30 is not limited to three, but may be at least one. The number of dies held in each holder 30 may be different from each other. Further, how to assign processing steps into pairs of dies is not limited to the embodiments described above, and a variety of arrangements may be envisaged. Behavior of the transfer device and the revolver may be appropriately controlled by the control device 80 according to those arrangements. With this system, it is possible to integrate any production process including a number of processing steps within a single press 10.
In particular, the holder 30 that holds a number of pairs of dies 40, the stoppers may be adjusted on the suspension struts so that the dies 40 held in that holder 30 have different opening amounts. Therefore, it is possible to effectively use the limited vertical space to assign processing steps, even if the heights of the workpieces W are different with each other. Furthermore, for the holder 30 for holding the dies 40 a plurality of pairs, the weight required for a single pressing operation may be suppressed to the largest processing weight that is required to pairs of dies. It is thus possible to save required energy as compared to clamping each pair of dies separately.
The number of the hydraulic cylinder 50 may be any plurality, while it was one in the first to fourth exemplary embodiments. This means that there may be a number of pressing positions where pressing operations are performed. With this arrangement, pressing operations can be performed in parallel at a number of positions, which allows an increased productivity. It should be noted that, when this configuration is applied to the first to fourth embodiments, control by the control device 80 and assignment of pressing positions are appropriately designed so that the holder 30 which has gone through a pressing operation at one press position may not undergo a further pressing operation at another pressing position before any transferring process. For example, one more hydraulic cylinder may be provided in the opposite of the hydraulic cylinder 50 shown in FIG. 2. Transferring operations are performed at two positions other than a pressing position, and every time the revolver 20 is rotated by 90 degree by the control device, transfer and press steps are alternately performed for each holder 30.
In the second to fourth embodiments, the position for transferring workpieces W is not limited to the left side of the pressing position, but may be the right or opposite side. Alternatively, a number of transfer devices 70 may be provided in some of those positions in order to take partial charge of transferring process. This latter embodiment can simplify the operation of each transfer arm 71 of the transfer device 70. In addition, the number, shape and possible movement of the transfer arms may be altered in accordance with the purpose of the embodiment. Transporting process may be manually performed by workers, while in the first to fourth exemplary embodiment it is done by the transfer device controlled by the controller.
The hydraulic cylinder 50 may be arranged to downwardly clamps dies, while in the first to fourth embodiments it upwardly clamp dies 40. In this embodiment with downward clamping, it is required to provide members such as springs which exhibits a restoring force to make the upper die to open. Further, the cam follower 25 may be provided on the top plate 111 of the table 11, instead of the revolver 20.

Claims

1. A press comprising a number of pairs of dies each clamped by a driving source to press set workpieces in a vertical direction, and

a revolver holding the pairs of dies and rotatable around a vertical axis, wherein the revolver by rotating moves any pair of dies to a pressing position where pressing process is performed.

2. A press according to claim 1, wherein each time a pressing process is completed in one of the pairs of dies, the revolver rotates so that the pair of dies holding a processed workpiece is moved to a position different from the pressing position, and that another pair of dies is moved to the pressing position.