WORKPIECE TRANSFER METHOD, WORKPIECE TRANSFER DEVICE, AND WORKPIECE TRANSFER PROGRAM

A workpiece transfer method is for transferring a workpiece when bending of the workpiece is performed by a press brake including a die and a punch, the workpiece transfer method including, before or after the bending: moving an upstream transferer in a transfer direction of the workpiece while pushing the upstream transferer against an end of the workpiece, the upstream transferer being located on an upstream side with respect to the press brake in the transfer direction, the end of the workpiece being an upstream end in the transfer direction; and supporting the workpiece from below by a support in conformity with a shape of the workpiece after pressing of the workpiece by the punch, and intermittently transferring the workpiece in the transfer direction, the support being located on a downstream side with respect to the press brake in the transfer direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a workpiece transfer method, a workpiece transfer device, and a workpiece transfer program.

2. Description of the Related Art

Conventionally, bending devices are known which perform bending of sheet materials. For example, Japanese Laid-Open Patent Application Publication No. H3-297516 discloses a bending device that uses a workpiece pusher to push a workpiece against a back gauge when transferring the workpiece to a given position. Japanese Laid-Open Patent Application Publication No. 2019-081184 discloses a bending device that secures supports to upstream and downstream ends of a workpiece in a transfer direction, that hooks a holder of an upstream mover on one of the supports, and that hooks a holder of a downstream mover on the other support. In this bending device, the workpiece is transferred by moving the movers with the holders hooked on the supports.

The bending device of Japanese Laid-Open Patent Application Publication No. H3-297516, which pushes a workpiece by the workpiece pusher until the workpiece reaches a given position, is disadvantageous in that when the bending device is used for incremental forming where transfer and pressing are repeated to form the workpiece into a desired shape, the accuracy of transfer to a given position decreases as the amount of bending increases with the progress of the forming process. The use of the bending device of Japanese Laid-Open Patent Application Publication No. 2019-081184 involves the step of securing the supports to a workpiece and the step of hooking the holders of the movers on the supports. There has been a demand for a simpler way of workpiece transfer.

SUMMARY OF THE INVENTION

A workpiece transfer method of the present disclosure is a workpiece transfer method for transferring a workpiece when bending of the workpiece is performed by a press brake including a die that supports the workpiece and a punch that is located above the die and presses the workpiece supported by the die, the workpiece transfer method including, before or after the bending: moving an upstream transferer in a transfer direction of the workpiece while pushing the upstream transferer against an end of the workpiece, the upstream transferer being located on an upstream side with respect to the press brake in the transfer direction, the end of the workpiece being an upstream end in the transfer direction; and supporting the workpiece from below by a support in conformity with a shape of the workpiece after pressing of the workpiece by the punch, and intermittently transferring the workpiece in the transfer direction, the support being located on a downstream side with respect to the press brake in the transfer direction.

A workpiece transfer device of the present disclosure is a workpiece transfer device that transfers a workpiece when bending of the workpiece is performed by a press brake including a die that supports the workpiece and a punch that is located above the die and presses the workpiece, the workpiece transfer device including: an upstream transferer that is located on an upstream side with respect to the press brake in a transfer direction of the workpiece; a transfer driver that moves the upstream transferer in the transfer direction; a support that is located on a downstream side with respect to the press brake in the transfer direction and that supports the workpiece from below in conformity with a shape of the workpiece after pressing of the workpiece by the punch; and control circuitry configure to, before or after the bending, control the transfer driver to intermittently transfer the workpiece in the transfer direction by moving the upstream transferer in the transfer direction while pushing the upstream transferer against an upstream end of the workpiece.

A workpiece transfer program of the present disclosure is a workpiece transfer program that runs on a computer in a workpiece transfer device that transfers a workpiece when bending of the workpiece is performed by a press brake including a die that supports the workpiece and a punch that is located above the die and presses the workpiece supported by the die, the workpiece transfer program being configured to allow the computer to function as transfer control means that, before or after the bending: moves an upstream transferer in a transfer direction of the workpiece while pushing the upstream transferer against an end of the workpiece, the upstream transferer being located on an upstream side with respect to the press brake in the transfer direction, the end of the workpiece being an upstream end in the transfer direction; and causes a support to support the workpiece from below in conformity with a shape of the workpiece after pressing of the workpiece by the punch, and intermittently transfers the workpiece in the transfer direction, the support being located on a downstream side with respect to the press brake in the transfer direction.

DETAILED DESCRIPTION

Hereinafter, a workpiece transfer method, a workpiece transfer device, and a workpiece transfer program according to one embodiment of the present disclosure will be described with reference to the drawings. The workpiece transfer method, workpiece transfer device, and workpiece transfer program described below are merely an exemplary embodiment of the present disclosure. The present disclosure is not limited to the embodiment described below, and additions, deletions, and changes may be made without departing from the gist of the present disclosure.

FIG.1is a plan view showing a bending system200including workpiece transfer devices100according to one embodiment of the present disclosure.FIG.2is a perspective view showing the workpiece transfer device100ofFIG.1as viewed from the downstream side in the transfer direction, andFIG.3is a perspective view showing the workpiece transfer device100ofFIG.1as viewed from the upstream side in the transfer direction. In the following description, the transfer direction in which a workpiece W is transferred by the workpiece transfer device100is denoted by D1, and two directions perpendicular to the transfer direction D1are referred to as a first perpendicular direction D2and a second perpendicular direction D3, respectively. The second perpendicular direction D3is, for example, an up-down direction, and the workpiece W is pressed in the second perpendicular direction D3. The first perpendicular direction D2corresponds to a transverse direction.

The bending system200bends the flat sheet-shaped workpiece W into a given shape by repeating the step of transferring the workpiece W by a pitch in the transfer direction D1and the step of pressing the workpiece W in the second perpendicular direction D3. As shown inFIG.1, the bending system200includes: a press brake1including a die2as a lower mold and a punch3as an upper mold; and the workpiece transfer devices100. AlthoughFIG.1illustrates four workpiece transfer devices100arranged in the first perpendicular direction D2, only one workpiece transfer device100may be used, or five or more workpiece transfer devices100may be used.

The die2extends in the first perpendicular direction D2. The upper edge of the die2is chamfered. At the top of the die2there is a groove2a, and a backup plate BP is disposed to fill the groove2a. The backup plate BP supports the workpiece W. The backup plate BP is designed not to be plastically deformed when pressed by the punch3with the workpiece W interposed between the backup plate BP and the punch3. The die2supports the workpiece W. The punch3is located above the die2. The punch3presses the workpiece W supported by the die2. The punch3extends in the first perpendicular direction D2. InFIG.4and the subsequent figures, the groove2aand the backup plate BP are omitted for the sake of simplicity.

The workpiece transfer devices100will be described. The workpiece transfer devices100all have the same configuration. Each of the workpiece transfer devices100includes: an upstream transferer15aincluding a contact structure4aand a holder5; a downstream transferer15bincluding a contact structure4band a holder5; a support6; a roller guide7; a guide rail8; and a guide rail9.

The upstream transferer15ais located on the upstream side with respect to the press brake1in the transfer direction D1. Each of the contact structures4aand4bis shaped as a block and made of, for example, a resin. The contact structure4acontacts an upstream end Wz of the workpiece W. The contact structure4apushes the end Wz without gripping the end Wz. The contact structure4ais held by the holder5. The holder5is connected to a transfer driver26shown inFIG.4. The holder5corresponds to a connector between the contact structure4aand the transfer driver26and is made of, for example, a metal. The holder5rotates about an axis parallel to the first perpendicular direction D2. The side where there is the contact structure4aor4b, whichever is at a greater distance from the die2at the start of transfer toward the die2of the flat sheet-shaped workpiece W that has yet to be subjected to bending, is defined as the upstream side with respect to the press brake1in the transfer direction D1, and the opposite side is defined as the downstream side with respect to the press brake1in the transfer direction D1.

The downstream transferer15bis located on the downstream side with respect to the press brake1in the transfer direction D1. The contact structure4bcontacts a downstream end Wk of the workpiece W. The contact structure4bpushes the end Wk without gripping the end Wk. The contact structure4bis held by the holder5of the downstream transferer15b. The holder5is connected to the transfer driver26.

The workpiece W is in the shape of a flat sheet before being pressed by the punch3. Thus, when the flat sheet-shaped workpiece W is transferred by pushing it with the contact structure4a, the contact structure4ais in surface contact with the upstream end Wz of the workpiece W. During this transfer, the contact structure4ais in surface contact with that upstream end face of the flat sheet-shaped workpiece W which crosses the workpiece W's surface that is to be pressed by the punch3. Thus, in the present disclosure, the end Wz includes the upstream end face of the workpiece W.

In case that the workpiece W bent in an arc by pressing the workpiece W with the punch3(this bending may be referred to as “first bending” hereinafter) fails to attain a desired shape, additional bending (which may be referred to as “re-bending” hereinafter) may be performed by pressing the arc-shaped workpiece W again with the punch3. In this case, the workpiece W having undergone the first bending is transferred by pushing it with the contact structures4aand4b. During this transfer, since the workpiece W having undergone the first bending is arc-shaped, the contact structure4ais in surface contact with the upstream end face of the workpiece W which crosses the workpiece W's flat surface that is to be pressed by the punch3or in line contact with an edge constituting a part of the upstream end face. The contact structure4bis in surface contact with the downstream end face of the workpiece W which crosses the workpiece W's flat surface that is to be pressed by the punch3or in line contact with an edge constituting a part of the downstream end face. Thus, in the present disclosure, the end Wz further includes the edge constituting a part of the upstream end face of the workpiece W. The end Wk includes the downstream end face of the workpiece W and the edge constituting a part of the downstream end face.

The support6supports the workpiece W while the workpiece W is being pressed or while the shape of the workpiece W is being measured. For example, two supports6are located on the upstream side in the transfer direction D1, and two supports6are located on the downstream side in the transfer direction D1. Alternatively, one support6or three or more supports6may be located on each of the upstream and downstream sides. The upstream supports6are spaced at a given distance from each other in the first perpendicular direction D2, and the downstream supports6are spaced at a given distance from each other in the first perpendicular direction D2.

Each support6includes rollers6r. The upper edge of the support6is arc-shaped. The rollers6rare arranged in an arc at the upper edge of the support6and spaced at a given distance from one another in the transfer direction D1. The rollers6rare rotatably supported between two sheet materials that constitute the support6and that are spaced at a given distance from each other in the first perpendicular direction D2. Each of the rollers6ris rotatable about an axis parallel to the first perpendicular direction D2. The rollers6rrotate when contacted by the workpiece W. Preferably, a line connecting the upper edges of the rollers6rto one another coincides with the contour shape of the workpiece W having undergone bending. The support6moves in a direction, such as the second perpendicular direction D3, toward or away from the workpiece W. The support6may pivot about a given pivot shaft parallel to the first perpendicular direction D2instead of moving in a direction toward or away from the workpiece W. In the support6, each of the rollers6rmay be movable by a motor or the like in the second perpendicular direction D3instead of being rotatably supported between two sheet materials.

The roller guide7supports the workpiece W during transfer of the workpiece W. For example, two roller guides7are located on the upstream side in the transfer direction D1, and two roller guides7are located on the downstream side in the transfer direction D1. Alternatively, one roller guide7or three or more roller guides7may be located on each of the upstream and downstream sides. The downstream ends of the upstream roller guides7are located downstream of the downstream ends of the upstream supports6. The upstream ends of the downstream roller guides7are located upstream of the upstream ends of the downstream supports6. The upstream roller guides7are spaced at a given distance from each other in the first perpendicular direction D2, and the downstream roller guides7are spaced at a given distance from each other in the first perpendicular direction D2.

Each roller guide7extends in the transfer direction D1. The roller guide7includes rollers7r. The rollers7rare rotatably supported between two sheet materials that constitute the roller guide7and that are spaced at a given distance from each other in the first perpendicular direction D2. Each of the rollers7ris rotatable about an axis parallel to the first perpendicular direction D2. The rollers7rrotate when contacted by the workpiece W. The roller guide7pivots about a given pivot shaft parallel to the first perpendicular direction D2. The roller guide may be in any shape but is preferably flat.

The guide rail9is located on each of the upstream and downstream sides in the transfer direction D1. The guide rail9extends in the transfer direction D1. The guide rail9supports the holder5from below and guides the holder5in the transfer direction D1and a direction opposite to the transfer direction D1. Thus, the contact structures4aand4bmove in the transfer direction D1and the direction opposite to the transfer direction D1.

The guide rail8is located on each of the upstream and downstream sides in the transfer direction D1. The guide rail8extends in the first perpendicular direction D2. The guide rail8supports the guide rail9from below and guides the guide rail9and the holder5supported by the guide rail9in the first perpendicular direction D2. Thus, the contact structure4aand4bmove in the first perpendicular direction D2.

As shown inFIGS.2and3, a distance sensor10is mounted on the contact structure4a. The distance sensor10detects the distance between the contact structure4aand the upstream end Wz of the workpiece W. If the distance detected by the distance sensor10is 0, this means that the contact structure4ais in contact with the end Wz. The distance sensor10is, for example, a proximity sensor, a laser range sensor, or an image sensor. In the case where an image sensor is used as the distance sensor10, the size of the end Wz or Wk of the workpiece W in the image captured by the image sensor can be acquired as distance-related information (without calculating the distance directly). Thus, the distance-related information is not limited to distance information directly acquired but includes information from which the distance can be estimated indirectly.

A distance sensor10is mounted on the contact structure4b. The distance sensor10mounted on the contact structure4bdetects the distance between the contact structure4band the downstream end Wk of the workpiece W. InFIG.3, the workpiece W is shown by a dashed-double dotted line to clearly show the constituent elements of the transfer device100.

The workpiece transfer device100includes shape sensors11. The shape sensors11are located in proximity to the die2. Specifically, the shape sensors11are located below the workpiece W supported by the die2. Some of the shape sensors11are located on the upstream side in the transfer direction D1and spaced at a given distance from one another in the first perpendicular direction D2. The other shape sensors11are located on the downstream side in the transfer direction D1and spaced at a given distance from one another in the first perpendicular direction D2. Each of the shape sensors11is, for example, a proximity sensor, a laser range sensor, a contact sensor, or an image sensor. Each of the shape sensors11acquires a parameter related to the shape of the workpiece W. Specifically, each of the shape sensors11acquires an angle (e.g., an angle relative to a horizontal plane) or a curvature of that portion of the workpiece W which has been pressed by the punch3.

A sucker12is mounted on each of the upstream and downstream transferers15aand15b. The sucker12sucks and holds the workpiece W. Examples of the way of suction by the sucker12include air or electromagnetic suction using a suction cup.

FIG.4is a block diagram showing a control system in the workpiece transfer device100. As shown inFIG.4, the workpiece transfer device100includes a control unit20, a press driver25, a transfer driver26, a roller driver35, a support driver36, and a roller guide driver38.

The control unit20includes control circuitry21embodied as a CPU (Central Processing Unit), a ROM (Read Only Memory)22, a RAM (Random Access Memory)23, and an HDD (Hard Disk Drive)24. The ROM22stores various pieces of information such as target positions to which the contact structures4aand4bare moved at the time of transfer of the workpiece W. The target positons are those defined based on information about the contour R of the workpiece W to be shaped by bending and include different positions of the workpiece W in the transfer direction D1and heights associated with the different positions. The RAM23is used as a processing region for the control circuitry21. The control circuitry21corresponds to transfer control means, and the ROM22, RAM23, and HDD24together correspond to a storage.

The HDD24stores a workpiece transfer program for operating the workpiece transfer device100of the present disclosure. The workpiece transfer program may be received from an external device and stored into the HDD24or may be retrieved from a computer-readable recording medium (such as a DVD-ROM or USB flash memory) recording the workpiece transfer program and stored into the HDD24.

The control circuitry21controls the operation of the press driver25to press the punch3against the workpiece W by a given stroke. After the pressing of the workpiece W, the control circuitry21controls the operation of the press driver25to move the punch3away from the workpiece W. The press driver25includes, for example, a motor and a hydraulic cylinder.

The control circuitry21controls the operation of the transfer driver26to move the contact structure4aor4bin the transfer direction D1, the first perpendicular direction D2, and the second perpendicular direction D3based on the target position. The details of the transfer driver26will be described later. The control circuitry21controls the operation of the suckers12to suck and hold the workpiece W.

The control circuitry21controls the operation of the roller driver35to move the roller6rof the support6in a direction toward or away from the workpiece W. The control circuitry21controls the operation of the support driver36to cause the support6to pivot about a given pivot shaft. The control circuitry21controls the operation of the roller guide driver38to cause the roller guide7to pivot about a given pivot shaft. The workpiece transfer device100may include either or both of the roller driver35and the support driver36.

The control circuitry21receives information on the distance between the contact structure4aand the upstream end Wz of the workpiece W from the distance sensor10located on the upstream side in the transfer direction D1. The control circuitry21receives information on the distance between the contact structure4band the downstream end Wk of the workpiece W from the distance sensor10located on the downstream side in the transfer direction D1. The control circuitry21changes the operation of the punch3and the operation of the transfer driver26in accordance with the distance detected by each distance sensor10. Specifically, for example, the control circuitry21stops the operation of the punch3and the operation of the transfer driver26in case that the distance detected by the distance sensor10is greater than an acceptable limit, namely in case that there is an unacceptably large gap between the workpiece W and the contact structure4aor4b.

The control circuitry21receives information on the angle or curvature of the pressed portion of the workpiece W from each of the shape sensors11. For example, in an abnormal situation where the angle or curvature of the pressed portion of the workpiece W is outside a given range, the control circuitry21may stop the operation of the punch3and the operation of the transfer driver26.

FIG.5is a schematic diagram showing the upstream transferer15apushing the workpiece W in the first bending.FIG.6is a schematic diagram showing the upstream and downstream transferers15aand15bas viewed immediately before or after the upstream and downstream transferers15aand15bpush the workpiece W in the re-bending. InFIG.5, the downstream transferer15band the transfer driver26that drives the downstream transferer15bare omitted.

The transfer driver26that drives the upstream transferer15aand the transfer driver26that drives the downstream transferer15bhave the same configuration. The configuration of the transfer driver26that drives the upstream transferer15awill be described below as a representative. The transfer driver26includes a first driver26a, a second driver26b, a third driver26c, and a fourth driver26d. A slide structure31and a raising/lowering structure32are coupled to the holder5. The raising/lowering structure32is, for example, a ball screw and driven by the first driver26awhich is a drive source such as a motor. The raising/lowering structure32is raised or lowered by the first driver26a. Thus, the holder5is raised or lowered, and accordingly the contact structure4ais also raised or lowered.

The slide structure31is, for example, a ball screw and driven by the second driver26bwhich is a drive source such as a motor. The second driver26bcauses the slide structure31to slide along the guide rail9. Thus, the holder5slides along the guide rail9, and accordingly the contact structure4amoves in the transfer direction D1or in the direction opposite to the transfer direction D1. The third driver26cis, for example, a drive source such as a motor and causes the slide structure31and the guide rail9to slide along the guide rail8. Thus, the holder5slides along the guide rail8, and accordingly the contact structure4amoves in the first perpendicular direction D2.

The fourth driver26dis, for example, a drive source such as a motor and causes a rotational shaft included in the holder5to rotate about an axis parallel to the first perpendicular direction D2. Thus, the sucker12rotates about an axis parallel to the first perpendicular direction D2. The sucker12is rotated in accordance with the shape of the workpiece W and sucks the workpiece W.

When starting transfer of the workpiece W for the first bending, the first, second, and third drivers26a,26b, and26cmove the contact structure4ato a given position in accordance with instructions from the control circuitry21. Thus, the contact structure4ais placed away from and facing the end Wz of the workpiece W in the transfer direction D1. After this state is established, the second driver26bmoves the contact structure4ain the transfer direction D1in accordance with an instruction from the control circuitry21to bring the contact structure4ainto contact with the end Wz of the workpiece W. Subsequently, the second driver26bcauses the contact structure4ato push the end Wz of the workpiece W and move the workpiece W to a position defined by the workpiece transfer program. In this manner, the workpiece W is transferred in the transfer direction D1.

When starting transfer of the workpiece W for the re-bending, the first, second, and third drivers26a,26b, and26cmove the contact structures4aand4bto given positions in accordance with instructions from the control circuitry21. In the re-bending, the contact structures4aand4bmove also in the second perpendicular direction D3since the workpiece W has the contour R. Tus, the contact structure4ais placed away from and facing the end Wz of the workpiece W in the transfer direction D1, and the contact structure4bis placed away from and facing the end Wk of the workpiece W in the transfer direction D1. After this state is established, the second driver26bmoves the contact structure4ain the transfer direction D1in accordance with an instruction from the control circuitry21to bring the contact structure4ainto contact with the end Wz of the workpiece W. Subsequently, the second driver26bcauses the contact structure4ato push the end Wz of the workpiece W and move the workpiece W to a position defined by the workpiece transfer program. Next, the second driver26bmoves the contact structure4bin the direction opposite to the transfer direction D1in accordance with an instruction from the control circuitry21to bring the contact structure4binto contact with the end Wk of the workpiece W located at the position defined by the workpiece transfer program. In this manner, the end Wz of the workpiece W is pushed by the contact structure4a, and the end Wk of the workpiece W is contacted by the contact structure4b. Thus, the workpiece W can be accurately positioned by the contact structures4aand4bwhile being transferred.

FIG.7shows a state where positioning locks4iof the contact structures4aand4bare in engagement with lock receivers Wh of the workpiece W.

As shown inFIG.7, lock receivers Wh may be located at both the upstream and downstream ends Wz and Wk of the workpiece W in the transfer direction D1. Two or more lock receivers Wh may be located at each of the ends Wz and Wk of the workpiece W. For example, the lock receivers Wh are shaped as protrusions extending outward from the ends Wz and Wk.

A positioning lock4iis located on each of the contact structures4aand4b. The engagement of the positioning locks4iwith the lock receivers Wh can ensure accurate positioning of the workpiece W in the first perpendicular direction D2.

The number and arrangement of the positioning locks4iare determined in accordance with the number and arrangement of the lock receivers Wh of the workpiece W. The positioning locks4iare shaped, for example, to have a recess. Although in the shown example the lock receivers Wh are shaped as protrusions and the positioning locks4iare shaped to have a recess, this is not limiting. The lock receivers Wh may be shaped as recesses, and the positioning locks4imay be shaped to have a protrusion. Each of the positioning locks4imay be shaped to have two or more recesses, and each of the lock receivers Wh may include two or more protrusions. Each of the positioning locks4imay be shaped to have two or more protrusions, and each of the lock receivers Wh may include two or more recesses.

FIG.8Ais a side view showing the arrangement of the distance sensors10, andFIG.8Bis a front view showing the arrangement of the distance sensors10.FIG.9is a front view showing the arrangement of distance sensors10aaccording to another example.

As shown inFIGS.8A and8B, one or more distance sensors10are mounted on the contact structure4a. The distance sensors10are mounted on those surfaces of the contact structure4awhich cross the contact structure4a's surface that faces the end Wz of the workpiece W. That is, the distance sensors10are mounted on both of the side surfaces of the contact structure4a. The same is true of the distance sensors10mounted on the contact structure4b. Examples of the distance sensors10include proximity sensors and laser range sensors. In the case where the distance sensors10are proximity sensors, the distance sensors10are arranged at different heights so that the range over which the point of contact of the end Wz of the workpiece W with the contact structure4ais detectable may be broadened in the height direction. If one distance sensor10is sufficient to cover the necessary detection range in the height direction, only one distance sensor10may be used. If the detection range covered by two or more distance sensors10arranged in the height direction is free of any zone where the workpiece W is undetectable, the distance sensors10need not be mounted on both of the side surfaces of the contact structure4a.

In another example, the distance sensor10used may be a distance sensor10athat is a laser range sensor. As shown inFIG.9, two or more distance sensors10aare mounted on the contact structure4a. The distance sensors10aare mounted on those surfaces of the contact structure4awhich cross the contact structure4a's surface that faces the end Wz of the workpiece W. That is, the distance sensors10aare mounted on both of the side surfaces of the contact structure4a. The same is true of the distance sensors10amounted on the contact structure4b. The distance sensors10aare arranged to let their light sources emit lasers at different heights so that the range over which the point of contact of the end Wz of the workpiece W with the contact structure4ais detectable may be broadened in the height direction. By virtue of the above-described arrangement of the distance sensors10, the distance between the contact structure4aor4band the end Wz or Wk of the workpiece W or information on the distance between the contact structure4aor4band the end Wz or Wk of the workpiece W can be detected regardless of which portion of the contact structure4aor4bthe end Wz or Wk of the workpiece W comes close to. If one distance sensor10is sufficient to cover the necessary detection range in the height direction, only one distance sensor10may be used. If the detection range covered by two or more distance sensors10arranged in the height direction is free of any zone where the workpiece W is undetectable, the distance sensors10need not be mounted on both of the side surfaces of the contact structure4a.

FIGS.10and11are flowcharts showing the flow of the process of bending. As shown inFIG.10, the flat sheet-shaped workpiece W that has yet to be shaped by bending is pushed by the contact structure4aof the upstream transferer15ato transfer the workpiece W from the upstream side toward the downstream side such that a downstream surface end portion Ws of the workpiece W is placed at a given position on the die2(step S1). In this transfer, the control circuitry21moves the downstream supports6to positions where the downstream supports6support the workpiece W, and moves the upstream supports6to positions where the upstream supports6do not support the workpiece W. During transfer and bending of the workpiece W, the control circuitry21may change the operation of the punch3and the operation of the transfer drivers26in accordance with the distances detected by the distance sensors10; for example, the control circuitry21may stop the operation of the punch3and the operation of the transfer drivers26.

The control circuitry21causes the punch3to press the downstream surface end portion Ws of the workpiece W while keeping the upstream end Wz of the workpiece W in contact with the contact structure4aof the upstream transferer15a(step S2). In the present disclosure, the “surface end portion Ws” refers to that upstream or downstream region of the surface of the workpiece W where the punch3and the contact structure4aor4bcould interfere with each other during pressing by the punch3.

Next, the control circuitry21causes the contact structure4aof the upstream transferer15ato push the end Wz of the workpiece W and transfer the workpiece W to a given measurement position to measure the shape of the pressed downstream surface end portion Ws and, after that, calculates parameters related to the shape of the pressed portion of the workpiece W based on results of detection by the shape sensors11(step S3). Subsequently, the control circuitry21causes the contact structure4ato push the end Wz of the workpiece W and transfer the workpiece W to a given position (step S4). The control circuitry21causes the punch3to press the workpiece W (step S5). The control circuitry21then causes the contact structure4aof the upstream transferer15ato push the end Wz of the workpiece W and transfer the workpiece W to a given measurement position and, after that, calculates parameters related to the shape of the pressed portion of the workpiece W based on results of detection by the shape sensors11(step S6).

In case that the portion to be subsequently pressed by the punch3is determined not to be the upstream surface end portion Ws based on the workpiece transfer program (NO in step S7), the control circuitry21returns to step S4and repeats the subsequent steps. In case that the portion to be subsequently pressed by the punch3is determined to be the upstream surface end portion Ws based on the workpiece transfer program (YES in step S7), the control circuitry21causes the contact structure4ato push the end Wz of the workpiece W and transfer the workpiece W such that the upstream surface end portion Ws of the workpiece W is placed at a given position on the die2(step S8).

The control circuitry21causes the contact structure4ato withdraw from the workpiece W while causing the sucker12of the downstream transferer15bto suck and hold the workpiece W and, after that, causes the punch3to press the upstream surface end portion Ws of the workpiece W (step S9). Next, the control circuitry21causes the workpiece W to be transferred to a given measurement position in the direction opposite to the transfer direction D1, and then calculates parameters related to the shape of the pressed portion of the workpiece W based on results of detection by the shape sensors11located upstream of the die2(step S10).

Subsequently, the control circuitry21determines whether the workpiece W has a given shape (step S11). The control circuitry21can make the determination of whether the workpiece W has the given shape based on the calculated parameters related to the pressed portions of the workpiece W. In case that the workpiece W has the given shape (YES in step S11), the control circuitry21ends the process of bending.

In case that the workpiece W does not have the given shape (NO in step S11), the control circuitry21carries out re-bending of the workpiece W as described below. The process described below is one where the downstream surface end portion Ws of the workpiece W, the upstream surface end portion Ws of the workpiece W, and the rest of the surface of the workpiece W (the region of the surface that is other than the downstream and upstream surface end portions Ws) are all subjected to re-bending. Depending on the shape measurement results, re-bending of the downstream or upstream surface end portion Ws or the rest of the surface of the workpiece W may be skipped.

First, the control circuitry21causes the contact structure4bto push the end Wk of the workpiece W formed in an arch shape by the first bending and transfer the workpiece W to a given position in the direction opposite to the transfer direction D1and, after that, causes the contact structure4aof the upstream transferer15ato transfer the workpiece W from the upstream side toward the downstream side such that the downstream surface end portion Ws of the workpiece W is placed at a given position on the die2(step S12). During transfer and bending of the workpiece W, the control circuitry21may change the operation of the punch3and the operation of the transfer drivers26in accordance with the distances detected by the distance sensors10; for example, the control circuitry21may stop the operation of the punch3and the operation of the transfer drivers26.

In case that the region of the workpiece W that is to be pressed in the re-bending is the downstream surface end portion Ws of the workpiece W, the control circuitry21causes the sucker12of the upstream transferer15ato suck and hold the workpiece W and causes the contact structure4bto withdraw from the workpiece W and, after that, causes the punch3to press the downstream surface end portion Ws of the workpiece W (step S13). Next, the control circuitry21causes the contact structure4ato transfer the workpiece W to a given measurement position and then calculates parameters related to the shape of the pressed portion of the workpiece W based on results of detection by the shape sensors11(step S14).

Subsequently, the control circuitry21determines whether the workpiece W has a given shape (step S15). In case that the workpiece W does not have the given shape (NO in step S15), the control circuitry21causes the contact structure4bto push back the workpiece W (step S12) and then repeats step S13and the subsequent steps.

In case that the workpiece W has the given shape (YES in step S15) and the region of the workpiece W that is to be subsequently pressed in the re-bending is between the downstream and upstream surface end portions Ws of the workpiece W, the control circuitry21causes the contact structure4bto move in the transfer direction D1and be on standby at a given position. Next, the control circuitry21causes the contact structure4ato push the end Wz of the workpiece W and transfer the workpiece W such that the workpiece W is placed at a given position on the die2. Subsequently, the control circuitry21causes the contact structure4bto move in the direction opposite to the transfer direction D1and come into contact with the end Wk of the workpiece W (step S16). The control circuitry21then causes the punch3to press the workpiece W with its end faces held between the contact structures4aand4b(step S17). The control circuitry21causes the workpiece W to be transferred to a given measurement position and then calculates parameters related to the shape of the pressed portion of the workpiece W based on results of detection by the shape sensors11(step S18).

Subsequently, the control circuitry21determines whether the workpiece W has a given shape (step S19). In case that the workpiece W does not have the given shape (NO in step S19), the control circuitry21causes the contact structure4ato move in the direction opposite to the transfer direction D1and be on standby at a given position. Next, the control circuitry21causes the contact structure4bto push the end face Wk of the workpiece W and push back the workpiece W. The control circuitry21then causes the contact structure4ato move in the transfer direction D1and come into contact with the end Wz of the workpiece W (step S16) and, after that, repeats step S17and the subsequent steps.

In case that the workpiece W has the given shape (YES in step S19) and the portion to be subsequently pressed by the punch3is determined not to be the upstream surface end portion Ws based on the workpiece transfer program (NO in step S20), the control circuitry21returns to step S16and repeats the subsequent steps.

In case that the workpiece W has the given shape (YES in step S19) and the portion to be subsequently pressed by the punch3is determined to be the upstream surface end portion Ws based on the workpiece transfer program (YES in step S20), the control circuitry21causes the contact structure4ato transfer the workpiece W such that the upstream surface end portion Ws of the workpiece W is placed at a given position on the die2(step S21).

The control circuitry21causes the sucker12of the downstream transferer15bto suck and hold the workpiece W and causes the contact structure4ato withdraw from the workpiece W and, after that, causes the punch3to press the upstream surface end portion Ws of the workpiece W (step S22). Next, the control circuitry21causes the workpiece W to be transferred to a given measurement position in the direction opposite to the transfer direction D1and then calculates parameters related to the shape of the pressed portion of the workpiece W based on results of detection by the shape sensors11located upstream of the die2(step S23).

Subsequently, the control circuitry21determines whether the workpiece W has a given shape (step S24). In case that the workpiece W does not have the given shape (NO in step S24), the control circuitry21causes the contact structure4ato push the end Wz of the workpiece W and transfer the workpiece W in the transfer direction D1(step S21) and, after that, repeats step S22and the subsequent steps. In case that the workpiece W has the given shape (YES in step S24), the control circuitry21ends the process of bending.

FIG.12is a diagram for explaining how to press the upstream surface end portion Ws of the workpiece W by the punch3in steps S8and S9ofFIG.10described above. When pressing the surface end portion Ws of the workpiece W by the punch3, it is necessary to prevent interference between the punch3and the contact structure4apushing the end Wz.

As shown inFIG.12, the contact structure4apushing the end Wz of the workpiece W is moved onto the die2, and then the workpiece W is sucked and held by the sucker12of the downstream transferer15b. The contact structure4ais then moved in the direction opposite to the transfer direction D1and withdrawn to a given position. Despite this withdrawal of the contact structure4a, the workpiece W can be held in a stable position by the sucker12.

After the contact structure4ais withdrawn from the position on the die2in the direction opposite to the transfer direction D1, the surface end portion Ws of the workpiece W is pressed by the punch3. Thus, the surface end portion Ws of the workpiece W can be pressed by the punch3without interference between the contact structure4aand the punch3. As shown in steps S1and S2or in steps S12and S13, the surface end portion Ws of the workpiece W is also pressed by the punch3in a similar manner where the workpiece W is sucked and held by the sucker12of the upstream transferer15a.

FIG.13is a diagram for explaining how to acquire parameters related to the shape of the surface end portion Ws of the workpiece W in step S10ofFIG.10described above or step S23ofFIG.11described above. As shown inFIG.13, the surface end portion Ws of the workpiece W is pressed by the punch3. The parameters related to the shape of the surface end portion Ws cannot be acquired by the downstream shape sensors11because the surface end portion Ws is on the die2and because if the workpiece W is transferred downstream, the surface end portion Ws will fall off the die2and become unstable. Thus, the workpiece W having undergone the pressing is pushed back in the direction opposite to the transfer direction D1by the contact structure4aor by the contact structures4aand4band then sucked and held by the sucker12of the downstream transferer15b, and the contact structure4ais withdrawn in the direction opposite to the transfer direction D1. In this state, the parameters related to the shape of the surface end portion Ws are acquired by the shape sensors11located on the upstream side. In this case, the acquisition of the parameters by the shape sensors11can be performed for the workpiece W supported by the die2. Thus, the shape of the workpiece W can be accurately determined. Although in the description ofFIG.13the workpiece W is pushed back in the direction opposite to the transfer direction D1by the contact structure4aor by the contact structures4aand4b, the workpiece W may be pushed back in the direction opposite to the transfer direction D1while being sucked by the sucker12of the downstream transferer15b.

FIG.14is a diagram showing an example which concerns step S10ofFIG.10described above or step S23ofFIG.11described above and which is different from the example ofFIG.13or showing the details of the shape-related parameter measurement shown in step S3ofFIG.10or step S14ofFIG.11.FIG.14depicts a situation where the parameters related to the shape of the workpiece W are acquired for the workpiece W held by the sucker12.

As shown inFIG.14, the parameters related to the shape of the workpiece W may be acquired by the shape sensors11for the workpiece W held by the sucker12. Since the workpiece W supported by the sucker12and the die2are held in a stable position, displacement of the workpiece W can be prevented during the acquisition of the parameters. Thus, the shape of the workpiece W can be accurately determined. Although in the example ofFIG.14the workpiece W is sucked by only the sucker12of the upstream transferer15a, the workpiece W may be sucked by the suckers12of both the upstream and downstream transferers15aand15b.

FIG.15is a diagram for explaining deforming structures4hincluded in the upstream and downstream transferers15aand15b.FIGS.16A to16Eare diagrams showing the flow of the process of transfer of the workpiece W by the upstream and downstream transferers15aand15bincluding the deforming structures4hand the flow of the process of bending the upstream surface end portion Ws.FIGS.16A to16Ecorrespond to steps S8and S9ofFIG.10or steps S21and S22ofFIG.11. The supports6are omitted inFIGS.16A to16E.

As shown inFIG.15, each of the upstream and downstream transferers15aand15bmay include the deforming structure4hthat deforms to permit displacement of the contact structure4aor4bonly when the contact structure4aor4bis subjected to a pressure equal to or higher than a predefined level or a pressure acting in a direction that is not along the transfer direction D1of the workpiece W. The deforming structure4hmay be any structure that deforms when the contact structure4aor4bis subjected to a pressure from the workpiece W, and examples of the deforming structure4hinclude a hinge, a spring, and an elastic material.FIG.15shows hinges as the deforming structures4h.

The deforming structures4hare located between one of the holders5and the contact structure4aand between the other holder5and the contact structure4b. Each of the deforming structures4hdeforms to permit displacement of the contact structure4aor4bonly when the contact structure4aor4bis subjected to a pressure equal to or higher than a predefined level or a pressure acting in a direction that is not along the transfer direction D1of the workpiece W. Thus, when the workpiece W is pushed and held between the contact structures4aand4b, the contact structure4aor4bis displaced only in case that the contact structure4aor4bis subjected to a pressure equal to or higher than a predefined level or a pressure acting in a direction that is not along the transfer direction D1of the workpiece W. As such, overloads on the workpiece W and the contact structures4aand4bcan be prevented without reducing the positioning accuracy of the workpiece W.

As shown inFIG.16A, the upstream end face Wz of the workpiece W is pushed by the contact structure4ato transfer the workpiece W to a given position, where the workpiece W is supported by the downstream support6. In this transfer, the control circuitry21causes the contact structure4ato be positioned such that the lower surface of the contact structure4ais below the upper surface of the die2. The downstream transferer15bis kept on standby at a given position in the transfer direction D1.

Next, as shown inFIG.16B, the control circuitry21causes the contact structure4ato move in the transfer direction D1, and upon contact of the contact structure4awith the die2, the deforming structure4hembodied as a hinge opens to displace the contact structure4a. As a result, the contact structure4ais placed on top of the die2. Thus, the upstream surface end portion Ws of the workpiece W, which is to be pressed by the punch3, is supported by the die2. After the surface end portion Ws of the workpiece W is supported by the die2, as shown inFIG.16C, the workpiece W is sucked and held by the sucker12of the downstream transferer15b.

After the workpiece W is sucked by the sucker12, as shown inFIG.16D, the contact structure4ais moved in the direction opposite to the transfer direction D1and withdrawn to a given position. Despite the withdrawal of the contact structure4a, the workpiece W is held in a stable position by the sucker12. After the withdrawal of the contact structure4a, as shown inFIG.16E, the upstream surface end portion Ws of the workpiece W is pressed by the punch3. In the case where, as in steps S12and S13ofFIG.11, the workpiece W is transferred in the direction opposite to the transfer direction D1and then the downstream surface end portion Ws of the workpiece W is subjected to bending, the operations performed on the upstream side inFIGS.16A to16Emay be performed on the downstream side, and the operations performed on the downstream side inFIGS.16A to16Emay be performed on the upstream side.

FIG.17is a diagram showing a situation where the support drivers36cause the supports6to pivot about given pivot shafts.FIG.18is a diagram showing a situation where support drivers37raise or lower the supports6. The rollers6rare omitted inFIG.17andFIG.18.

As shown inFIG.17, each of the supports6located on the upstream and downstream sides in the transfer direction D1includes a pivot shaft6kat the end of the support6that faces toward the die2. The pivot shaft6kis parallel to the direction in which the die2extends. The support drivers36are connected to the supports6, respectively. Each of the support drivers36includes an actuator such as any type of cylinder and pushes or pulls the corresponding support6to cause the support6to pivot about the pivot shaft6k. Although the support drivers36are provided for both the upstream and downstream supports6, this is not limiting and the support driver36may be provided only for either the upstream or downstream support6.

When parameters related to the shape of the pressed portion of the workpiece W are acquired in step S3, S6, S10, S14, S18, or S23, either of the upstream and downstream supports6supporting the workpiece W is caused to pivot, i.e., is moved, to stop the support6from supporting the workpiece W. Specifically, in the case where the pressed portion of the workpiece W, for which the shape-related parameters are to be acquired, is located on the upstream side in the transfer direction D1, the upstream support6is moved by the support driver36to stop the support6from supporting the workpiece W. In the case where the pressed portion of the workpiece W, for which the shape-related parameters are to be acquired, is located on the downstream side in the transfer direction D1, the downstream support6is moved by the support driver36to stop the support6from supporting the workpiece W. After that, the shape-related parameters are acquired by the shape sensors11for the pressed portion of the workpiece W which was supported by the moved support6. Thus, the acquisition of the shape-related parameters can be accomplished without any pressure applied by the support6to the pressed portion subject to the acquisition, and this leads to accurate determination of the shape of the workpiece W.

When the first bending is performed on the workpiece W by the punch3, the downstream support6is moved to a position where the downstream support6supports the workpiece W, the upstream support6is moved to a position where the upstream support6does not support the workpiece W, and then the workpiece W is pressed by the punch3.

Instead of the configuration ofFIG.17where the supports6are caused to pivot, a configuration may be employed where the supports6are raised or lowered by support drivers37as shown inFIG.18. Each of the support drivers37includes an actuator such as any type of cylinder or a motor and pushes or pulls a corresponding one of the supports6or rotates a ball screw to raise or lower the corresponding support6. When parameters related to the shape of the pressed portion of the workpiece W are acquired in step S3, S6, S10, S14, S18, or S23, either of the upstream and downstream supports6supporting the workpiece W is lowered to stop the support6from supporting the workpiece W.

FIG.19Ais a diagram showing the rollers6rsupporting the workpiece W from below, andFIG.19Bis a diagram showing a situation where the rollers6rhave been moved. Instead of the configuration ofFIG.17where the supports6are caused to pivot or the configuration ofFIG.18where the supports6are raised or lowered by the support drivers37, a configuration may be employed where the rollers6rare raised or lowered by the roller drivers35as shown inFIGS.19A and19B. In this case, the rollers6rfunction as the supports.

As shown inFIG.19A, the roller drivers35are in one-to-one correspondence with the rollers6r. Each of the roller drivers35includes an actuator such as a hydraulic cylinder, a pneumatic cylinder, an electric cylinder, a rack and pinion, or a motor and moves a corresponding one of the rollers6rin a direction toward or away from the workpiece W. Each of the rollers6ris independently movable to a desired position by the corresponding roller driver35. Thus, as shown inFIG.19B, the rollers6rcan be moved in accordance with the shape of the workpiece W to cause the rollers6rto support the workpiece W. In the case where the arc-shaped workpiece W is supported as shown inFIG.19B, the amount of movement of each roller6rfrom the initial position increases as the roller6ris located farther from the die2supporting the workpiece W in the transfer direction D1or the direction opposite to the transfer direction D1.

FIG.20is a diagram showing a situation where the downstream roller guide7is caused to pivot in the first bending.FIG.21is a diagram showing a situation where the upstream and downstream roller guides7are caused to pivot.

As shown inFIG.20, each of the roller guides7located on the upstream and downstream sides in the transfer direction D1includes a pivot shaft7kat the end of the roller guide7that faces away from the die2. The pivot shaft7kis parallel to the direction in which the die2extends. The roller guide drivers38are connected to the roller guides7, respectively. Each of the roller guide driver38includes an actuator such as any type of cylinder and pushes or pulls a corresponding one of the roller guides7to cause the corresponding roller guide7to pivot about the pivot shaft7k. Instead of being located at the end of the roller guide7that faces away from the die2as mentioned above, the pivot shaft7kmay be located at any point in a direction along the transfer direction D1.

After starting transfer of the workpiece W by the contact structure4afor the first bending, the downstream roller guide7is caused to pivot as shown inFIG.20to push the workpiece W from below until the workpiece W is supported by the downstream support6. This can prevent the workpiece W from contacting the die2during transfer of the workpiece W. In addition, the workpiece W having its end Wz pushed by the contact structure4ais prevented from moving inertially, and the workpiece W can be pressed against the contact structure4aby means of the weight of the workpiece W itself. Thus, detachment of the workpiece W from the contact structure4acan be prevented during transfer of the workpiece W, and the transfer accuracy can be further improved.

When the workpiece W is being transferred after the workpiece W has become supported by the downstream support6, each of the upstream and downstream roller guides7is caused to pivot as shown inFIG.21such that the end of each roller guide7that faces toward the die2is above the opposite end of the roller guide7. This can prevent the workpiece W from contacting the die2during transfer of the workpiece W.

According to the present embodiment, as described above, the workpiece W is transferred in the transfer direction D1while pushing the contact structure4aof the upstream transferer against the upstream end Wz of the workpiece W and, after being pressed by the punch3, the workpiece W is supported from below in conformity with the shape of the workpiece W by the support6located on the downstream side in the transfer direction D1. Thus, in incremental forming where transfer and pressing are repeated to form the workpiece W into a desired shape, the accuracy of transfer of the workpiece W to a given position does not decrease even though the amount of bending increases with the progress of the forming process. As such, the accuracy of transfer to a position where the workpiece W is pressed by the punch3is higher than in a conventional configuration where the workpiece is pushed by a workpiece pusher located only on the upstream side in the transfer direction D1. Additionally, since there is no need for the step of securing supports (attachments) to the workpiece W and the step of hooking holders of movers on the supports, the workpiece W can be transferred in a simpler way than ever before.

The present disclosure is not limited to the above embodiment, and various modifications as described below may be made without departing from the gist of the present disclosure.

Although the above embodiment is configured such that the roller guide7pivots about the pivot shaft7k, this is not limiting. For example, the roller guide7may be raised or lowered by means of a motor and a ball screw or may be moved in the transfer direction D1or the opposite direction.

Although the above embodiment is configured such that the support6pivots about the pivot shaft6k, the support6is raised or lowered, or the rollers6rare raised or lowered, this is not limiting. For example, the support6may be moved by means of a motor and a ball screw in the transfer direction D1or the opposite direction toward or away from the workpiece. In the configuration where the support6is moved in the transfer direction D1or the opposite direction, parameters related to the shape of the pressed portion of the workpiece W are acquired after the support6is moved away from the die2.

Although in the above embodiment the support6includes two or more rollers6r, this is not limiting and the support6may include only one roller6r.

Although in the above embodiment the upstream and downstream transferers15aand15bof the workpiece transfer device100have the same configuration, this is not limiting and the upstream and downstream transferers15aand15bmay have different configurations.

In the above embodiment, proximity sensors or laser range sensors are used as the distance sensors10for detecting the distance between the contact structure4aand the upstream end Wz of the workpiece W and the distance between the contact structure4band the downstream end Wk of the workpiece W. However, this is not limiting and different types of distance sensors10may be arranged in combination.

Although in the above embodiment the support drivers36are connected to the upstream and downstream supports6, respectively, this is not limiting and the support driver36may be connected only to either the upstream or downstream support6.

Although in the above embodiment the roller guide drivers38are connected to the upstream and downstream roller guides7, respectively, this is not limiting and the roller guide driver38may be connected only to either the upstream or downstream roller guide7.

Although in the above embodiment the holder5is moved by the guide rails8and9, this is not limiting and any structure that can move the holder5in the first perpendicular direction D2and the second perpendicular direction D3may be used. For example, a conveyor may be used, or a robot such as an articulated robot may be used.

Although in the above embodiment the third driver26cis a drive source such as a motor, the slide structure31may be slid manually along the guide rail8.

Although in the above embodiment the first, second, and third drivers26a,26b, and26care motors and the slide structure31and raising/lowering structure32are ball screws, each of these drivers or structures may be any other known drive structure such as a hydraulic cylinder, a pneumatic cylinder, an electric cylinder, or a rack and pinion.

Although inFIGS.19A and19Bdescribed above the workpiece W is supported by the rollers6rdriven by the roller drivers35, this is not limiting. A support6may be used which is caused to pivot by the support driver36and which further incorporates the rollers6rdriven by the roller drivers35. Alternatively, a support6may be used which is raised or lowered by the support driver37and which further incorporates the rollers6rdriven by the roller drivers35.

The configuration for implementing the control by the control circuitry21is not limited to that illustrated above. The functionality of the elements disclosed herein may be implemented using circuitry or processing circuitry which includes general purpose processors, special purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuitry and/or combinations thereof which are configured or programmed to perform the disclosed functionality. Processors are considered processing circuitry or circuitry as they include transistors and other circuitry therein. In the disclosure, the circuitry, units, or means are hardware that carry out or are programmed to perform the recited functionality. The hardware may be any hardware disclosed herein or otherwise known which is programmed or configured to carry out the recited functionality. When the hardware is a processor which may be considered a type of circuitry, the circuitry, means, or units are a combination of hardware and software, the software being used to configure the hardware and/or processor.

According to the present disclosure, the workpiece is transferred in the transfer direction while pushing the upstream transferer against the upstream end of the workpiece and, after being pressed by the punch, the workpiece is supported from below in conformity with the shape of the workpiece by the support located on the downstream side in the transfer direction. Thus, in incremental forming where transfer and pressing are repeated to form the workpiece into a desired shape, the accuracy of transfer of the workpiece to a given position does not decrease even though the amount of bending increases with the progress of the forming process. As such, the accuracy of transfer to a position where the workpiece is pressed by the punch is higher than in a conventional configuration where the workpiece is pushed by a workpiece pusher located only on the upstream side in the transfer direction. Additionally, since there is no need for the step of securing supports (attachments) to the workpiece and the step of hooking holders of movers on the supports, the workpiece can be transferred in a simpler way than ever before.

In the above disclosure, a downstream transferer located on the downstream side in the transfer direction of the workpiece may be moved in the transfer direction; the upstream transferer may be moved in the transfer direction while pushing the upstream transferer against the upstream end of the workpiece; and the downstream transferer may be moved into contact with the downstream end of the workpiece, and the workpiece may be intermittently transferred in the transfer direction.

According to the above configuration, a decrease in transfer accuracy can be avoided even during re-bending of the workpiece.

In the above disclosure, a target position to which the upstream transferer is moved may be stored into a storage; the target position of the upstream transferer may be acquired from the storage; and the upstream transferer may be moved based on the target position of the upstream transferer, and the workpiece may be transferred in the transfer direction.

According to the above configuration, the workpiece can be reliably transferred by a predefined amount.

In the above disclosure, distance-related information related to a distance between the upstream transferer and the end of the workpiece may be detected; and operation of the press brake and operation of the upstream transferer may be changed in accordance with the distance-related information.

According to the above configuration, forming failure can be avoided which is due to the presence of a gap between the upstream transferer and the workpiece being transferred.

In the above disclosure, one of the upstream transferer and a downstream transferer located on the downstream side with respect to the press brake in the transfer direction may include a sucker that sucks the workpiece; the workpiece may be sucked and held by the sucker of the one of the upstream and downstream transferers; and the other of the upstream and downstream transferers may be moved away from the press brake to stop the other of the upstream and downstream transferers from pushing an end of the workpiece.

According to the above configuration, interference between the punch and the transferer that pushes the end of the workpiece can be prevented.

In the above disclosure, each of the upstream transferer and a downstream transferer located on the downstream side with respect to the press brake in the transfer direction may include a contact structure that contacts an end face of the workpiece and a deforming structure that deforms to permit displacement of the contact structure when the contact structure is subjected to a pressure equal to or higher than a predefined level or a pressure acting in a direction that is not along the transfer direction of the workpiece. Before a surface end portion of the workpiece that is on the upstream side or the downstream side in the transfer direction is pressed by the punch, the workpiece may be transferred by bringing the contact structure of one of the upstream and downstream transferers into contact with the workpiece and moving the one of the upstream and downstream transferers toward the press brake while keeping a lower surface of the contact structure below an upper surface of the die; the contact structure may be displaced onto the die by deformation of the deforming structure upon contact of the contact structure with the die; the workpiece may be sucked and held by a sucker included in the other of the upstream and downstream transferers; and the one of the upstream and downstream transferers may be withdrawn away from the press brake.

According to the above configuration, displacing the contact structure by deformation of the deforming structure upon contact of the contact structure with the die allows the end of the workpiece to be transferred to a position on the die. Additionally, sucking and holding the workpiece by the sucker enables withdrawal of one of the transferers, thus making it possible to prevent interference between the one of the transferers and the punch.

In the above disclosure, after a surface end portion of the workpiece that is on one of the upstream and downstream sides in the transfer direction is pressed by the punch, the workpiece may be moved toward the one of the upstream and downstream sides in the transfer direction by a transferer located on the one of the upstream and downstream sides or by transferers located on both the upstream and downstream sides, and a shape of the surface end portion of the workpiece that was pressed by the punch may be measured.

According to the above configuration, the measurement can be performed for the workpiece supported stably by the die.

In the above disclosure, after a surface end portion of the workpiece that is on one of the upstream and downstream sides in the transfer direction is pressed by the punch, the workpiece may be sucked by a sucker included in a transferer located on the other of the upstream and downstream sides and moved toward the one of the upstream and downstream sides in the transfer direction; and the workpiece may be sucked and held by the sucker included in the transferer located on the other of the upstream and downstream sides, and a shape of the surface end portion of the workpiece that was pressed by the punch may be measured.

According to the above configuration, forming failure of the workpiece can be detected.

In the above disclosure, the support, which is located on the downstream side in the transfer direction, may be moved toward or away from the workpiece in accordance with the shape of the workpiece, and another support may be moved toward or away from the workpiece in accordance with the shape of the workpiece, the other support being a support that is located on the upstream side in the transfer direction and that supports the workpiece from below in conformity with the shape of the workpiece after pressing of the workpiece by the punch.

According to the above disclosure, the workpiece can be supported in accordance with the varying shape of the workpiece.

In the above disclosure, one of the supports on the upstream and downstream sides may be moved to stop the one of the supports from supporting the workpiece, and a shape of a portion of the workpiece that was supported by the moved support and that was pressed by the punch may be measured.

According to the above configuration, the portion of the workpiece, whose shape is to be measured, can avoid being subjected to a moment applied by the support. This can prevent the workpiece from being pressed and bent by the support, thus ensuring accurate measurement of parameters related to the shape of the workpiece.

In the above disclosure, the support on the downstream side may be moved to a position where the support supports the workpiece, the other support on the upstream side may be moved to a position where the other support does not support the workpiece, and the workpiece may be transferred.

According to the above configuration, the withdrawal of the upstream support can prevent the upstream support from interfering with the flat sheet-shaped portion (portion yet to be pressed by the punch) of the workpiece that is on the upstream side in the transfer direction.

In the above disclosure, a roller guide may be moved or caused to pivot to push the workpiece from below with the roller guide, the roller guide being a roller guide that is located on the downstream side with respect to the press brake in the transfer direction, that supports the workpiece from below, and that moves upward and downward, pivots about an axis parallel to a direction in which the die extends, or moves in the transfer direction and a direction opposite to the transfer direction; and the end of the workpiece may be brought into contact with the upstream transferer, and the workpiece may be transferred.

According to the above configuration, after the start of transfer of the workpiece by the upstream and downstream transferers, the downstream roller guide can be moved to push the workpiece from below until the workpiece is supported by the downstream support. This can prevent the workpiece from contacting the die during transfer of the workpiece. In addition, the workpiece can be pressed against the upstream transferer and prevented from being released from pushing by the upstream transferer.

In the above disclosure, roller guides may be moved or caused to pivot to position one end of each of the roller guides above an opposite end of each of the roller guides, and the workpiece may be transferred, the roller guides being roller guides that are located on the upstream and downstream sides with respect to the press brake in the transfer direction, that support the workpiece from below, and each of which moves upward and downward, pivots about an axis parallel to a direction in which the die extends, or moves in the transfer direction and a direction opposite to the transfer direction, the one end of each of the roller guides being an end facing toward the press brake.

According to the above configuration, after the workpiece is supported by the downstream support, each of the upstream and downstream roller guides is caused to pivot to position the press brake-facing end of each roller guide above the opposite end of the roller guide. This can prevent the workpiece from contacting the die during transfer of the workpiece.

In the above disclosure, the workpiece transfer device may further include a storage storing a target position to which the upstream transferer is moved, and the control circuitry may be configured to: acquire the target position of the upstream transferer from the storage; and control the transfer driver to move the upstream transferer based on the target position of the upstream transferer.

In the above disclosure, the workpiece transfer device may further include a distance sensor that detects distance-related information related to a distance between the upstream transferer and the end of the workpiece, and the control circuitry may be configured to change operation of the press brake and operation of the upstream transferer in accordance with the distance-related information detected by the distance sensor.

In the above disclosure, the workpiece transfer device may further include a downstream transferer that is located on the downstream side with respect to the press brake in the transfer direction of the workpiece, each of the upstream and downstream transferers may include: a contact structure that contacts an end face of the workpiece; a deforming structure that deforms to permit displacement of the contact structure when the contact structure is subjected to a pressure equal to or higher than a predefined level or a pressure acting in a direction that is not along the transfer direction of the workpiece; and a connector that holds the deforming structure and that is connected to the transfer driver.

In the above disclosure, the contact structure of the upstream transferer may include a positioning lock shaped to conform to a lock receiver located at the upstream end of the workpiece in the transfer direction.

According to the above configuration, the engagement of the positioning lock with the lock receiver allows for accurate positioning of the workpiece in a transverse direction crossing the transfer direction.

In the above disclosure, the workpiece transfer device may further include: a downstream transferer that is located on the downstream side with respect to the press brake in the transfer direction of the workpiece; and a sucker that is included in the upstream transferer or the downstream transferer and that sucks and holds the workpiece.

In the above disclosure, the workpiece transfer device may further include arc-shaped supports that are located on the upstream and downstream sides with respect to the press brake in the transfer direction and that support the workpiece from below.

In the above disclosure, each of the supports may include rollers that move toward and away from the workpiece, and the workpiece transfer device may further include roller drivers that are in one-to-one correspondence with the rollers and each of which moves a corresponding one of the rollers.

In the above disclosure, the workpiece transfer device may further include support drivers each of which causes a corresponding one of the supports to pivot about a given pivot shaft.

In the above disclosure, the workpiece transfer device may further include transverse-direction support drivers each of which moves a corresponding one of the supports in the transfer direction or a transverse direction crossing the transfer direction.

In the above disclosure, the workpiece transfer device may further include roller guides that are located on the upstream and downstream sides with respect to the press brake in the transfer direction, that support the workpiece, and each of which pivots about a given pivot shaft, moves in the transverse direction, or moves in the transfer direction.