Die changing device for bending machine, and die changing method for bending machine

Abstract

A die storage drum (60) is provided with a plurality of storage slots (63) capable of respectively storing a plurality of center dies (32) having different lengths. A center mold unit (70) is provided with a center arm (72) to which a center mold (32) can be mounted, and can be switched, by rotation of the center arm (72) about a rotation axis (A1) extending in the left-right direction, to a sprung-up state in which the center mold (32) can be replaced. A transfer unit (80) is provided with left and right hands (81L, 81R) that are arranged side by side in the left-right direction and that move in the left-right direction while maintaining the distance therebetween. The transfer unit (80) transfers a center mold (32) between the center arm and a storage slot disposed on an extension line of the direction of movement of the left and right hands (81L, 81R). The direction of movement of the left and right hands (81L, 81R) corresponds to the direction in which a center die (32) is inserted / removed into / from the storage slot (63) and the center arm (72).

Description

Die changing device for bending machine and die changing method for bending machine

[0001] The present disclosure relates to a die changing device for a bending machine and a die changing method for a bending machine.

[0002] A bending machine is known that includes a top die including a center die and multiple reference dies provided on the left and right of the center die, and a bottom die facing the top die. The bending machine further includes a bend beam that is provided behind the top die and the bottom die and is configured to be able to swing freely up and down.

[0003] With the workpiece fixed between the top and bottom dies, the bend beam is swung upward or downward. The end of the workpiece protruding rearward from the top and bottom dies is bent (ironing) by a bending die attached to the front upper or lower part of the bend beam. Prior to bending, the size of the center die (the die length in the left-right direction) and the number of left and right reference dies are selected according to the bending length of the workpiece.

[0004] Patent Document 1 discloses a die changing device for changing a center die. This die changing device includes a die magazine and a center die unit. The die magazine includes left and right die storage drums provided on the front side of an upper frame. Each die storage drum stores multiple center dies. The center die unit is mounted on a die support beam provided at the lower end of the upper frame so as to be movable left and right and rotatable.

[0005] Patent No. 3268909

[0006] However, the die changing device disclosed in Patent Document 1 has a problem in that machining cannot be performed for a long period of time because, after storing the used center die set in the top die in the die storage drum, the center die unit must wait until the die storage drum rotates and the desired center die reaches the center die unit.

[0007] One aspect of one or more embodiments relates to a die exchange device mounted on a bending machine that includes an upper frame that is vertically movable and that is provided with a top die including a center die, and a lower frame that is provided with a bottom die facing the top die. The die exchange device is configured to bend a workpiece while the workpiece is fixed between the top die and the bottom die. The die exchange device includes: a die storage device with multiple storage slots that can store multiple center dies of different lengths, a center arm to which the center dies can be attached, and a center die unit that is switchable between a reference state in which the center die is aligned as part of the top die and a lifted state for center die exchange by rotating the center arm about a rotation axis extending in the left-right direction; and a transfer unit that includes left and right hands that are arranged side by side in the left-right direction and move in the left-right direction while maintaining a distance from each other, and that transfers the center die between the storage slots located on an extension of the movement direction of the left and right hands and the center arm. The movement direction of the left and right hands corresponds to the insertion and removal direction of the center die relative to the storage slots and the center arm.

[0008] According to this mold changing device, the storage slot and center arm are arranged on an extension of the movement direction of the left and right hands, and the movement direction of the left and right hands corresponds to the insertion and removal direction of the center mold relative to the storage slot and center arm.

[0009] Therefore, the left and right hands can hold the used center die and the center die to be used, respectively, so there is no need to wait for the operation of the die storage device as in the case where one hand is used to change the center die.In addition, by moving the left and right hands left and right, one hand can remove the used center die from the center arm while the other hand can attach the center die to the center arm.

[0010] According to one or more embodiments of the die changing device, the center die can be efficiently changed relative to the center arm, thereby preventing a prolonged period during which machining cannot be performed.

[0011] FIG. 1 is a diagram showing a main part of a mold changing device according to this embodiment. FIG. 2 is a front view showing a bending machine according to this embodiment. FIG. 3 is a side view showing a bending machine according to this embodiment. FIG. 4 is a front view showing a main part of a mold changing device according to this embodiment. FIG. 5 is a diagram showing a pivoting operation of a center mold unit provided in the mold changing device according to this embodiment. FIG. 6 is a perspective view showing a main part of a mold changing device according to this embodiment. FIG. 7 is a side view showing a state in which a center arm according to this embodiment is jumped up. FIG. 8 is a diagram showing a main part of a mold changing device according to this embodiment. FIG. 9 is a diagram showing a main part of a mold changing device according to this embodiment. FIG. 10 is a diagram showing a mold changing method according to the first embodiment. FIG. 11 is a diagram showing a mold changing method according to the first embodiment. FIG. 12 is a diagram showing a mold changing method according to the second embodiment. FIG. 13 is a diagram showing a mold changing method according to the third embodiment. FIG. 14 is a diagram showing a mold changing method according to the third embodiment.

[0012] Hereinafter, a die changing device and die changing method for a bending machine according to this embodiment will be described with reference to the drawings.

[0013] First Embodiment First, with reference to FIGS. 1 to 3, an overview of a bending machine 1 according to a first embodiment will be described. FIG. 1 is a diagram illustrating a main portion of a die exchange device according to this embodiment. FIG. 2 is a front view illustrating the bending machine according to this embodiment. FIG. 3 is a side view illustrating the bending machine according to this embodiment. In describing the configuration of the bending machine 1, directions are defined as left-right, front-rear, and up-down. The left-right and front-rear directions correspond to two directions that are orthogonal to the horizontal direction, and the up-down direction corresponds to the vertical direction. In the drawings, the right direction, left direction, up direction, down direction, front direction, and rear direction are indicated by RT, LT, UP, DN, FR, and RR, respectively. However, these directions are merely defined for convenience in describing the bending machine according to this embodiment.

[0014] The die exchange device 50 according to this embodiment is mounted on a bending machine 1. The bending machine 1 includes an upper frame 20 that is provided with a top die 30 including a center die 32 and that is movable in the vertical direction, and a lower frame 10 that is provided with a bottom die 14 that faces the top die 30. The bending machine 1 performs bending processing on the workpiece W while the workpiece W is fixed between the top die 30 and the bottom die 14. The die exchange device 50 includes a die storage drum 60 having a plurality of storage slots 63 capable of storing a plurality of center dies 32 of different lengths, a center die unit 70 having a center arm 72 to which the center dies 32 can be attached, and which can be switched between a reference state in which the center dies 32 are aligned as part of the top die 30 and a lifted state in which the center dies 32 can be exchanged by rotating the center arm 72 about a rotation axis A1 extending in the left-right direction, and a transfer unit 80 having left and right hands 81L, 81R arranged side by side in the left-right direction and moving in the left-right direction while maintaining a distance between them, which transfers the center die 32 between the center arm 72 and the storage slots 63 arranged on an extension line of the movement direction of the left and right hands 81L, 81R. The movement direction of the left and right hands 81L, 81R corresponds to the insertion / removal direction of the center die 32 with respect to the storage slot 63 and the center arm 72.

[0015] 2 and 3, the detailed configuration of the bending machine 1 according to the first embodiment will be described. The bending machine 1 according to this embodiment is a machine that bends the edge portion of a plate-shaped workpiece W (ironing bending) to bend the workpiece W into a desired shape, and is also called a panel bender. A manipulator (not shown) that supplies and positions the workpiece W is disposed in front of the bending machine 1.

[0016] The bending machine 1 includes a lower frame 10 , an upper frame 20 , a bottom die 14 , a top die 30 , a bend beam 40 , a die exchange device 50 , and a control device 100 .

[0017] The lower frame 10 is formed horizontally long along the left-right direction and is fixed to the front part of the fixed frame 12. A bottom die 14 serving as a fixed mold is provided on the upper part of the lower frame 10 and extends in the left-right direction.

[0018] The upper frame 20 is formed horizontally long along the left-right direction and is fixed to the front part of the movable frame 22. The movable frame 22 is provided above the fixed frame 12 and is configured to be able to swing freely in the up-down direction around a rotation shaft 24. A top die 30 serving as a movable mold facing the bottom die 14 is provided below the upper frame 20.

[0019] The movable frame 22 is provided with a frame drive mechanism (not shown). When the frame drive mechanism is driven and the movable frame 22 swings upward around the rotation shaft 24, the bottom die 14 and the top die 30 release the pressure on the workpiece W. Conversely, when the movable frame 22 swings downward around the rotation shaft 24, the bottom die 14 and the top die 30 press the workpiece W. This pressure allows the workpiece W to be firmly fixed in place.

[0020] The top die 30 is composed of a center die 32 and a plurality of reference dies 34 .

[0021] A mold support beam 26 is provided below the upper frame 20. A center mold 32 held by a center mold unit 70 (described later) is provided approximately in the center in the left-right direction of the mold support beam 26. One or more reference molds 34 are provided to the left of the center mold 32 on the mold support beam 26, and one or more reference molds 34 are provided to the right of the center mold 32 on the mold support beam 26.

[0022] This bending machine 1 is provided with a plurality of center dies 32 of different sizes (die lengths in the left-right direction). For example, 14 types of center dies 32 are provided in increments of 7.5 mm from 100 mm to 197.5 mm. The center die unit 70 holds center dies 32 of any size selected from the plurality of center dies 32. The remaining center dies 32 are stored in a die storage drum 60, which will be described later. Note that the center dies 32 stored in the die storage drum 60 are not shown in the drawings. Note that the plurality of center dies 32 are not limited to the above-described configuration. For example, it is also possible to provide 20 types of center dies 32 in increments of 5.0 mm from 100 mm to 195 mm.

[0023] A die selection cylinder 28 is provided above each reference die 34. In addition, an opening / closing cylinder 36 is provided on the upper frame 20. By operating the selected die selection cylinder 28, the required reference die 34 can be selected from the left and right reference die 34. This allows the reference die 34 that constitutes the top die 30 to be moved closer to or away from the center die 32.

[0024] The size of the center die 32 and the number of left and right reference dies 34 are determined according to the bending length of the workpiece W. The center die 32 is replaced by a die replacement device 50.

[0025] The bend beam 40 is disposed behind the bottom die 14 and the top die 30. The bend beam 40 extends in the left-right direction. The bend beam 40 is configured to be movable in the front-rear direction and swingable in the up-down direction around a connecting shaft 42, and is driven by a bend beam drive mechanism (not shown). The up-down and front-rear movement of the bend beam 40 causes the front end of the bend beam 40 to move in an arc. A forward bending die 44 for performing forward bending is provided below the front end of the bend beam 40. A reverse bending die 46 for performing reverse bending is provided above the front end of the bend beam 40.

[0026] The die exchanging device 50 is a device that exchanges the center die 32 that forms part of the top die 30. The die exchanging device 50 will be described in detail later.

[0027] The control device 100 is configured by a computer having a hardware processor such as a CPU (Central Processing Unit), a memory, and various interfaces. The memory and various interfaces are connected to the hardware processor via a bus. The various functions of the control device 100 are realized by having the hardware processor execute programs stored in the memory.

[0028] The control device 100 controls the operation of the bending machine 1. In addition, the control device 100 also controls the operation of the die changing device 50.

[0029] In the bending machine 1, bending of the workpiece W is performed as follows. That is, the control device 100 drives the frame drive mechanism to lower the movable frame 22 relative to the workpiece W positioned by the manipulator. When the movable frame 22 lowers, the bottom die 14 and the top die 30 press against the workpiece W, fixing the workpiece W in place. The control device 100 drives the bend beam drive mechanism to swing the bend beam upward or downward. When the bend beam is swung upward, a forward bending is performed by the forward bending die 44, and when the bend beam is swung downward, a reverse bending is performed by the reverse bending die 46.

[0030] The mold exchanging device 50, which is one of the features of this embodiment, will be described below with reference to Figs. 2 to 7. Fig. 4 is a front view showing the main parts of the mold exchanging device according to this embodiment. Fig. 5 is a diagram showing the turning operation of the center mold unit provided in the mold exchanging device according to this embodiment. Fig. 6 is a perspective view showing the main parts of the mold exchanging device according to this embodiment. Fig. 7 is a side view showing the center arm according to this embodiment in a jumped-up state.

[0031] 2 and 3, the die exchanging device 50 includes a die storing drum 60, a center die unit 70, and a transfer unit 80. The center die 32 is replaced by the center die unit 70 and the transfer unit 80. The replaceable center die 32 is stored in the die storing drum 60.

[0032] The mold storage drum 60 is attached to the front side of the upper frame 20 and is positioned above the center mold unit 70, which will be described later. The mold storage drum 60 is a rotary mold storage device that stores a plurality of center molds 32. Note that the mold storage device applicable to the mold changing device 50 may be a rotary type, an elevating type that moves up and down, or another type. The mold storage drum 60 includes a chain 61, a drum drive mechanism 62, and a plurality of storage slots 63.

[0033] The chain 61 is stretched over a pair of sprockets (not shown). The pair of sprockets are rotatable about a pair of rotation shafts A21, A22 extending in the left-right direction, and the pair of rotation shafts A21, A22 are spaced apart in the up-down direction. The chain 61 is provided with a plurality of storage slots 63 arranged at regular intervals along the running direction of the chain 61. Note that a belt may be used instead of the chain 61.

[0034] The drum drive mechanism 62 includes, for example, a drive motor, gears, etc., and rotates one of the sprockets. When the one sprocket is rotated, the chain 61 rotates and travels.

[0035] As shown in Fig. 6, the multiple storage slots 63 rotate as the chain 61 rotates. Under the control of the control device 100, the chain 61 rotates to position any one of the multiple storage slots 63 relative to the drum's lowest position. The drum's lowest position is the lowest position in the orbit of the storage slots 63, and is a position where the center die 32 can be inserted and removed by the transfer unit 80. In the following description, the rotation of the chain 61 and the movement of the multiple storage slots 63 along the chain 61 will be expressed as rotating the die storage drum 60.

[0036] The storage slot 63 stores the center die 32. The storage slot 63 is composed of a pair of holding members 63a, 63b that hold the center die 32. The pair of holding members 63a, 63b face each other so as to sandwich the center die 32 from both sides.

[0037] Taking the storage slot 63 located at the lowest position of the drum as an example, one holding member 63a is located on the front side, and the other holding member 63b is located on the rear side. The front holding member 63a has a flange shape that protrudes rearward, and the rear holding member 63b has a flange shape that protrudes forward. The flange length in the front-to-rear direction of the rear holding member 63b is set to be shorter than the flange length in the front-to-rear direction of the front holding member 63a.

[0038] The front holding member 63a and the rear holding member 63b are arranged at a fixed distance apart, and a space extends in the left-right direction between the pair of holding members 63a, 63b. This space allows the center die 32 to be inserted into and removed from the storage slot 63. The insertion and removal direction of the center die 32 into and from the storage slot 63 corresponds to the left-right direction.

[0039] A plunger 63c is provided at the flange tip of the rear holding member 63b to position and fix the stored center die 32. A plunger 63c is also provided on the front holding member 63a. The plunger 63c may be provided on only one of the front holding member 63a and the rear holding member 63b.

[0040] 2, the center die unit 70 is attached to the front side of the upper frame 20 and is disposed below the die storage drum 60. The center die unit 70 is a unit for holding the center die 32 so that it is aligned as part of the top die 30, and for replacing the center die 32.

[0041] As shown in FIG. 4, the center mold unit 70 is mainly composed of a unit base 71, a center arm 72, an arm rotating mechanism 73, and an arm moving mechanism 74.

[0042] The unit base 71 is a member that supports the center arm 72. A guide member (not shown) extending in the left-right direction is provided on the upper frame 20, and the unit base 71 is configured to be movable in the left-right direction via the guide member.

[0043] The center arm 72 is attached to the unit base 71. The center arm 72 is configured to be rotatable about a rotation axis A1 extending in the left-right direction. The center die 32 is attached to the tip of the center arm 72. The center arm 72 can rotate between a downward state (hereinafter referred to as the "reference state") in which the center die 32 is aligned as part of the top die 30, as shown by the solid line in Fig. 5, and an upward state (hereinafter referred to as the "flip-up state") in which the center die 32 is positioned above, as shown by the two-dot chain line in Fig. 5. This flip-up state is a state in which the center die 32 can be replaced, i.e., the center die 32 can be inserted into or removed from the center arm 72 by the transfer unit 80.

[0044] 5 and 7, the center arm 72 includes an arm body 72a, a holder 72b, and a piston 72c. The center die 32 attached to the center arm 72 is composed of a die body 32a, a holding block 32b that holds the die body 32a, and a holding piece 32c with a T-shaped cross section that is provided at the tip of the holding block 32b.

[0045] The base end of the arm body 72a is rotatably attached to the unit base 71, and a holder 72b for holding the center die 32 is attached to the tip end of the arm body 72a. A space extending in the left-right direction is provided in the holder 72b. This space is formed to be one size or larger than the holding piece 32c of the center die 32, and a piston 72c is provided in this space.

[0046] The piston 72c is provided with a slot 72c1 extending in the left-right direction. The slot 72c1 is designed to be slightly larger than the holding piece 32c of the center die 32, and the holding piece 32c of the center die 32 can be inserted into and removed from the holder 72b via this slot 72c1. In other words, the insertion and removal direction of the center die 32 with respect to the center arm 72 corresponds to the left-right direction.

[0047] As shown in Figure 7, a vertical gap is provided between the space in the holder 72b and the piston 72c, and the piston 72c can be moved vertically by an air cylinder built into the arm body 72a. When the piston 72c is pulled downward by the air cylinder, the connection between the center arm 72 and the center die 32 is tightly attached. This allows the center die 32 to be fixed to the center arm 72. On the other hand, when the piston 72c is pushed upward by the air cylinder, clearance is created in the connection between the center arm 72 and the center die 32. This allows the center die 32 to be inserted into or removed from the center arm. The air cylinder operates in conjunction with the replacement operation of the center die 32 under the control of the control device 100.

[0048] 4, the arm rotation mechanism 73 includes, for example, a drive motor, gears, etc., and rotates the center arm 72. Operation of the arm rotation mechanism 73 allows the center arm 72 to be switched between a reference state and a jumped-up state.

[0049] The arm movement mechanism 74 includes, for example, an air cylinder and is capable of moving the unit base 71, i.e., the center arm 72, in the left-right direction. Operation of the arm movement mechanism 74 enables the center arm 72 to be moved left-right and positioned.

[0050] The center arm 72 is positioned so that the center of the center arm 72 in the left-right direction coincides with the mechanical center of the bending machine 1 in the left-right direction. At this time, the center die 32 is positioned at the mechanical center of the bending machine 1. Meanwhile, as necessary, the center arm 72 can be positioned at a position shifted to the left or right from the mechanical center by operating the arm moving mechanism 74. This allows the center die 32 to be positioned at a position shifted to the left or right from the mechanical center.

[0051] 2, the transfer unit 80 is attached to the front side of the upper frame 20, and is disposed below the mold storage drum 60 and above the center mold unit 70. The transfer unit 80 transfers the center mold 32 between the mold storage drum 60 and the center mold unit 70. Specifically, the transfer unit 80 transfers the center mold 32 stored in the storage slot 63 located at the lowest position of the drum and attaches it to the center arm 72 located at the flip-up position. The transfer unit 80 also transfers the center mold 32 attached to the center arm 72 located at the flip-up position and stores it in the storage slot 63 located at the lowest position of the drum.

[0052] As shown in FIG. 4, the transfer unit 80 is mainly composed of left and right hands 81L and 81R, a guide rail 82, and a hand moving mechanism 83.

[0053] The left hand 81L and the right hand 81R are arranged side by side in the left-right direction with a certain distance between them, and hold the center die 32 from both the left and right sides.

[0054] As shown in FIG. 6 , the left hand 81L includes a housing 81a and left and right fingers 81b and 81c mounted on the housing 81a. The left and right fingers 81b and 81c are arranged side by side in the left-right direction. The left and right fingers 81b and 81c are driven by a finger drive mechanism (not shown) housed in the housing 81a and can move toward and away from each other. When the left and right fingers 81b and 81c move toward each other, the left and right fingers 81b and 81c close and can hold the center die 32. On the other hand, when the left and right fingers 81b and 81c move away from each other, the left and right fingers 81b and 81c open and can release the center die 32. The housing 81a may be the finger drive mechanism itself.

[0055] The left finger 81b is mainly composed of a finger base 81b1 and a finger body 81b2. The finger base 81b1 is a member that connects the finger drive mechanism and the finger body 81b2. The finger base 81b1 of the left finger 81b extends diagonally upward and leftward, away from the center of the hand. The finger body 81b2 is provided at the tip of the finger base 81b1 and extends forward.

[0056] Like the left finger 81b, the right finger 81c is primarily composed of a finger base 81c1 and a finger body 81c2. The finger base 81c1 of the right finger 81c extends diagonally upward, away from the upper right and center of the hand. The finger body 81c2 is attached to the tip of the finger base 81c1 and extends forward.

[0057] In this manner, the left and right finger bodies 81b2, 81c2 are attached to the housing 81a via the finger base 81b1. The left finger body 81b2 is disposed above and to the left of the housing 81a, and the right finger body 81c2 is disposed above and to the right of the housing 81a. In other words, the left and right finger bodies 81b2, 81c2 are disposed far from the housing 81a. As a result, the housing 81a is disposed relatively lower than the left and right finger bodies 81b2, 81c2.

[0058] The right hand 81R is composed of a housing 81a and left and right fingers 81b, 81c mounted on the housing 81a, and its configuration is similar to that of the left hand 81L.

[0059] As shown in Fig. 2, the guide rail 82 is attached to the front side of the upper frame 20 and extends in the left-right direction. As shown in Fig. 4, the left and right hands 81L, 81R are slidably attached to the guide rail 82 and can move along the guide rail 82. The left and right hands 81L, 81R are attached to the guide rail 82 in an integrated state. Therefore, the left and right hands 81L, 81R move in the left-right direction while maintaining a distance between them.

[0060] The storage slot 63 and center arm 72 are disposed on an extension of the movement direction of the left and right hands 81L, 81R. In this embodiment, the storage slot 63 is located on the left side of the center arm 72. The left and right hands 81L, 81R can transfer the center die 32 between the storage slot 63 and the center arm 72.

[0061] The hand movement mechanism 83 is configured by, for example, an electric actuator, and moves the left and right hands 81L, 81R in the left and right direction. Under the control of the control device 100, the hand movement mechanism 83 can move the left and right hands 81L, 81R in the left and right direction and position them to predetermined positions.

[0062] Next, the relative relationships between the tool storage drum 60, the center tool unit 70, and the transfer unit 80 will be described with reference to Figures 1, 8, and 9. Figures 8 and 9 are diagrams showing the main parts of the tool changing device according to this embodiment. Figures 1, 8, and 9 show the storage slot 63 at the lowest position of the drum, the center arm 72 in a lifted-up state, and the left and right hands 81L, 81R. The center arm 72 of the center tool unit 70 is positioned so that the center of the center arm 72 in the left-right direction coincides with the center of the bending machine 1 in the left-right direction (machine center).

[0063] 1, the distance between the left and right hands 81L and 81R is set to a distance Da. As described above, the left and right hands 81L and 81R move in the left-right direction while maintaining the distance between them, so the distance between the left and right hands 81L and 81R remains the distance Da regardless of their positions in the left-right direction.

[0064] The mold storage drum 60 is disposed at a position offset to the left from the center mold unit 70, and the storage slot 63 is also disposed at a position offset to the left from the center arm 72. The distance between the mechanical center of the storage slot 63 and the mechanical center of the center arm 72 is set to a distance Db.

[0065] These distances Da and Db are set to the same value. Based on these distances Da and Db, four positions are set for the left and right hands 81L and 81R to operate: a storage position Pc1, an exchange position Pc2, a left standby position Pc3, and a right standby position Pc4.

[0066] 1 and 8, the storage position Pc1 is a position where the left and right hands 81L, 81R are located below the storage slot 63 and their mechanical centers are aligned. As shown in Figures 8 and 9, the exchange position Pc2 is a position where the left and right hands 81L, 81R are located above the center arm 72 and their mechanical centers are aligned. The exchange position Pc2 is also a position separated by a distance Dm to the right from the storage position Pc1.

[0067] The left standby position Pc3 is a position separated by a distance Dm to the left from the storage position Pc1, and the right standby position Pc4 is a position separated by a distance Dm to the right from the exchange position Pc2.

[0068] The distance Dm is the same as the distance Da and the distance Db. Therefore, the left and right hands 81L and 81R are located at two adjacent positions among the four positions Pc1 to Pc4.

[0069] That is, as shown in Fig. 1, when the left hand 81L is in the left standby position Pc3, the right hand 81R is in the storage position Pc1. As shown in Fig. 8, when the left hand 81L is in the storage position Pc1, the right hand 81R is in the exchange position Pc2. As shown in Fig. 9, when the left hand 81L is in the exchange position Pc2, the right hand 81R is in the right standby position Pc4.

[0070] Based on this relationship, the control device 100 controls the hand movement mechanism 83 to position the left and right hands 81L, 81R at the four positions Pc1 to Pc4, or to move them by a distance Dm in the left-right direction. In this way, the control device 100 controls the left and right hands 81L, 81R to transition between the three states.

[0071] 1, the first state is a state in which one hand 81R (81L) of the left and right hands 81L, 81R is in a position (storage position Pc1) corresponding to the storage slot 63. In the mechanical configuration of this embodiment, this corresponds to a state in which the right hand 81R is in the storage position Pc1, and at this time, the left hand 81L is in the left standby position Pc3.

[0072] 8, the second state is a state in which one hand 81R (81L) is in a position corresponding to the center arm 72 (exchange position Pc2), and the other hand 81L (81R) is in a position corresponding to the storage slot 63 (storage position Pc1). In the mechanical configuration of this embodiment, this corresponds to a state in which the right hand 81R is in the exchange position Pc2 and the left hand 81L is in the storage position Pc1.

[0073] 9, the third state is a state in which only one hand 81L (81R) of the left and right hands 81L, 81R is in a position (exchange position Pc2) corresponding to the center arm 72. In the mechanical configuration of this embodiment, this corresponds to a state in which the left hand 81L is in the exchange position Pc2, and at this time, the right hand 81R is in the right standby position Pc4.

[0074] Next, a mold changing method using the mold changing device 50 will be described with reference to Figures 10 and 11. Figures 10 and 11 are diagrams showing the mold changing method according to the first embodiment. This mold changing method is executed under the control of the control device 100.

[0075] In the following explanation, the center die 32 to be newly attached to the center arm 72 will be referred to as the "center die 32A to be used," and the center die 32 already attached to the center arm 72 will be referred to as the "used center die 32B."

[0076] 10, the left hand 81L is in the left standby position Pc3, and the right hand 81R is in the storage position Pc1, which is the initial state of the left and right hands 81L and 81R (S10). At this time, the left and right hands 81L and 81R are in an open state. In addition, an empty storage slot 63 in which no center die 32 is stored is located at the lowest position of the drum.

[0077] In step S11, the control device 100 moves the left and right hands 81L, 81R to the right and positions them at the storage position Pc1 and the exchange position Pc2, respectively. Then, the control device 100 rotates the mold storage drum 60 and positions the storage slot 63 storing the center mold 32A to be used at the lowest position of the drum. The control device 100 closes the left hand 81L to hold the center mold 32A to be used with the left hand 81L.

[0078] In step S12, the control device 100 rotates the center arm 72, to which the used center die 32B is attached, to a jumped-up state. After the center arm 72 rotates, the control device 100 closes the right hand 81R to hold the used center die 32B with the right hand 81R. The control device 100 pulls the piston 72c (see FIG. 7) upward to release the used center die 32B from the center arm 72.

[0079] In step S13, the control device 100 moves the left and right hands 81L, 81R to the right. At this time, the center die 32A to be used is withdrawn from the storage slot 63, and the used center die 32B is withdrawn from the center arm 72. The control device 100 positions the left and right hands 81L, 81R at the exchange position Pc2 and the right standby position Pc4, respectively. In the process of positioning the left hand 81L at the exchange position Pc2, the center die 32A to be used is inserted into the center arm 72. The control device 100 pulls the piston 72c (see FIG. 7) downward to fix the center die 32A to be used relative to the center arm 72.

[0080] 11, the control device 100 opens the left hand 81L and transfers the center die 32A to be used of the left hand 81L to the center arm 72. When the center die 32A to be used is transferred, the control device 100 rotates the center arm 72 to which the center die 32A to be used is attached to the reference state.

[0081] In step S15, the control device 100 moves the left and right hands 81L and 81R to the left, and positions the left and right hands 81L and 81R at the left standby position Pc3 and the storage position Pc1, respectively. During the process of positioning the right hand 81R at the storage position Pc1, the used center die 32B is inserted into the storage slot 63.

[0082] In step S16, the control device 100 opens the right hand 81R and transfers the used center die 32B to the storage slot 63. When the used center die 32B is transferred, the control device 100 rotates the die storage drum 60 to place an empty storage slot 63 in which no center die 32 is stored at the lowest position of the drum.

[0083] In step S17, the control device 100 moves the left and right hands 81L and 81R to the right and positions them at the storage position Pc1 and the exchange position Pc2, respectively. When a new mold exchange operation is to be performed, the operations from step S11 onwards are repeated.

[0084] Of the above-described series of operations, steps S10 to S11 and S15 to S17 are performed when the bending machine 1 is in processing operation, and steps S12 to S14 are performed when the bending machine 1 is not in processing operation.

[0085] Thus, according to the mold exchange device 50 of this embodiment, the storage slot 63 and the center arm 72 are positioned on an extension line of the movement direction of the left and right hands 81L, 81R, and the movement direction of the left and right hands 81L, 81R corresponds to the insertion / removal direction of the center mold 32 relative to the storage slot 63 and the center arm 72.

[0086] Therefore, the left and right hands 81L, 81R can hold the used center die 32B and the center die to be used 32A, respectively, so there is no need to wait for the rotation of the die storage drum 60, as is the case when one hand is used to change the center die 32. In addition, by moving the left and right hands 81L, 81R in the left-right direction, one hand 81R (81L) can remove the used center die 32B from the center arm 72, while the other hand 81L (81R) can attach the center die to the center arm 72.

[0087] Therefore, according to the die exchanging device 50 of this embodiment, the center die 32 can be efficiently exchanged with respect to the center arm 72. This makes it possible to prevent the time during which machining cannot be performed from becoming long.

[0088] In this embodiment, the distance Db in the left-right direction between the storage slot 63 and the center arm 72 is the same as the distance Da in the left-right direction between the left and right hands 81L, 81R.

[0089] According to this configuration, when the other hand 81L (81R) is in the storage position Pc1, one hand 81R (81L) is in the exchange position Pc2. As a result, by moving the left and right hands 81L and 81R a certain distance in the left-right direction, the other hand 81L (81R) can remove the center die 32A to be used from the storage slot 63, while the one hand 81R (81L) can remove the used center die 32B from the center arm 72. In addition, the other hand 81L (81R) can attach the center die 32A to be used that was removed from the storage slot 63 to the center arm 72 from which the used center die 32B has been removed by the one hand 81R (81L). This allows the center die 32 to be exchanged efficiently with respect to the center arm 72, thereby preventing a prolonged period of time during which machining cannot be performed.

[0090] In this embodiment, the left and right hands 81L, 81R are configured to be movable toward and away from each other, and each include left and right fingers 81b, 81c that hold the center die 32 from both the left and right sides, and a housing 81a on which the left and right fingers 81b, 81c are mounted. Each of the left and right fingers includes a finger base 81b1, 81c1 that extends obliquely upward away from the center of the hand, and a finger body 81b2, 81c2 that extends forward from the finger base 81b1, 81c1 and holds the center die 32.

[0091] According to this configuration, the housing 81a is disposed at a position relatively lower than the left and right finger bodies 81b2, 81c2, which makes it possible to prevent the center die 32 stored in the storage slot 63 from interfering with the housing 81a when the die storage drum 60 rotates.

[0092] In this embodiment, the mold changing device 50 further includes a control device that controls the left and right hands.

[0093] According to this configuration, the control device 100 controls the left and right hands 81L and 81R, so that the center die 32 can be replaced appropriately.

[0094] In this embodiment, the control device 100 controls the left-right movement and positioning of the left and right hands 81L, 81R so as to transition between three states. The three states include a state in which one of the left and right hands 81L, 81R is in a storage position corresponding to the storage slot, a state in which one hand 81R (81L) is in an exchange position Pc2 corresponding to the center arm 72 and the other hand 81L (81R) of the left and right hands 81L, 81R is in the storage position Pc1, and a state in which the other hand 81L (81R) is in the exchange position Pc2.

[0095] According to this configuration, by simply transitioning the states of the left and right hands 81L, 81R once, one hand 81R (81L) can remove the used center die 32B from the center arm 72 while the other hand 81L (81R) can attach the center die 32A to be used to the center arm 72. This allows the center die 32 to be replaced with a new one on the center arm 72 efficiently, thereby preventing the time during which machining cannot be performed from becoming too long.

[0096] In this embodiment, the mold storage drum 60 is positioned at a position shifted to the left of the center mold unit 70. The control device 100 performs the following steps (1a) to (8a). (1a) The left and right hands 81L and 81R are moved rightward, transitioning the left and right hands 81L and 81R from a state in which the right hand 81R is in the storage position Pc1 to a state in which the right hand 81R is in the exchange position Pc2 and the left hand 81L is in the storage position Pc1. (2a) The left hand 81L is closed to hold the center mold 32A to be used that is stored in the storage slot 63 with the left hand 81L. (3a) The right hand 81R is closed to hold the used center mold 32B that is attached to the center arm 72 in the lifted-up state with the right hand 81R. (4a) The left and right hands 81L, 81R are moved to the right, and the left and right hands 81L, 81R are transitioned to a state where the left hand 81L is in the exchange position Pc2. (5a) The left hand 81L is opened and the center die 32A to be used is transferred to the center arm 72. (6a) The left and right hands 81L, 81R are moved to the left, and the left and right hands 81L, 81R are transitioned to a state where the right hand 81R is in the storage position Pc1. (7a) The right hand 81R is opened and the used center die 32B is transferred to the storage slot 63. (8a) The left and right hands 81L, 81R are moved to the right, and the left and right hands 81L, 81R are transitioned to a state where the right hand 81R is in the exchange position Pc2 and the left hand 81L is in the storage position Pc1.

[0097] According to this configuration, the left hand 81L handles the center die 32A to be used, and the right hand 81R handles the used center die 32B. As a result, while the left and right hands 81L and 81R move to the right, the right hand 81R can remove the used center die 32B from the center arm 72, while the left hand 81L can attach the center die 32A to be used to the center arm 72. This allows the center die 32 to be replaced efficiently on the center arm 72, thereby preventing the time during which machining cannot be performed from becoming prolonged.

[0098] Second Embodiment A die changing device 50 for a bending machine 1 and a die changing method thereof according to a second embodiment will be described below. The configurations of the bending machine 1 and the die changing device 50 according to the second embodiment are the same as those of the first embodiment, but the flow of the die changing method is different. The following description will focus on the differences from the first embodiment.

[0099] 12 is a diagram showing a mold changing method according to the second embodiment. In the mold changing method according to the second embodiment, the processes from step S10 to step S14 are the same as those in the first embodiment, so the description will start from step S15a following step S14.

[0100] In step S15a, the control device 100 moves the left and right hands 81L and 81R leftward and positions the left and right hands 81L and 81R at the storage position Pc1 and the exchange position Pc2, respectively.

[0101] In step S16a, the control device 100 rotates the mold storage drum 60 to position the storage slot 63 storing the new center mold 32C to be used at the lowest position of the drum. The control device 100 closes the left hand 81L to hold the new center mold 32C to be used with the left hand 81L.

[0102] In step S17a, the control device 100 moves the left and right hands 81L, 81R to the left and positions the left and right hands 81L, 81R at the left standby position Pc3 and the storage position Pc1, respectively. During the process of positioning the left and right hands 81L, 81R, the new center die 32C to be used is pulled out from the storage slot 63, and the used center die 32B is inserted into the storage slot 63.

[0103] In step S18a, the control device 100 opens the right hand 81R and delivers the used center die 32B to the storage slot 63. When the used center die 32B is delivered, the control device 100 operates the die storage drum 60 to place an empty storage slot 63 in which no center die 32 is stored at the lowest position of the drum.

[0104] In step S19a, the control device 100 moves the left and right hands 81L, 81R to the right and positions the left and right hands 81L, 81R at the storage position Pc1 and the exchange position Pc2, respectively. During the process of positioning the left hand 81L at the storage position Pc1, a new center die 32C to be used is temporarily inserted into the storage slot 63. Then, in order to perform the die exchange operation for the new center die 32C to be used, the operations from step S12 onward shown in the first embodiment are performed.

[0105] In this embodiment, the mold storage drum 60 is positioned at a position shifted to the left of the center mold unit 70. The control device 100 performs the following steps (1b) to (10b). (1b) Move the left and right hands 81L and 81R to the right, transitioning the left and right hands 81L and 81R from a state in which the right hand 81R is in the storage position Pc1 to a state in which the right hand 81R is in the exchange position Pc2 and the left hand 81L is in the storage position Pc1. (2b) Close the left hand 81L to hold the center mold 32A to be used that is stored in the storage slot 63 with the left hand 81L. (3b) Close the right hand 81R to hold the used center mold 32B that is attached to the center arm 72 in the lifted-up state with the right hand 81R. (4b) The left and right hands 81L, 81R are moved to the right, and the left and right hands 81L, 81R are transitioned to a state where the left hand 81L is in the exchange position Pc2. (5b) The left hand 81L is opened and the center die 32A to be used is transferred to the center arm 72. (6b) The left and right hands 81L, 81R are moved to the left, and the left and right hands 81L, 81R are transitioned to a state where the right hand 81R is in the exchange position Pc2 and the left hand 81L is in the storage position Pc1. (7b) The left hand 81L is closed and the left hand 81L holds the new center die 32C to be used in the storage slot 63. (8b) The left and right hands 81L, 81R are moved to the left, and the left and right hands 81L, 81R are transitioned to a state where the right hand 81R is in the storage position Pc1. (9b) The right hand 81R is opened to transfer the used center die 32B to the storage slot 63. (10b) The left and right hands 81L, 81R are moved to the right, and the left and right hands 81L, 81R are transitioned to a state in which the right hand 81R is in the exchange position Pc2 and the left hand 81L is in the storage position Pc1.

[0106] According to this configuration, similar to the first embodiment, the left hand 81L handles the center die 32A to be used, and the right hand 81R handles the used center die 32B. As a result, while the left and right hands 81L and 81R move rightward, the right hand 81R can remove the used center die 32B from the center arm 72, while the left hand 81L can attach the center die 32A to be used to the center arm 72. This allows the center die 32 to be replaced efficiently on the center arm 72, thereby preventing a prolonged period of time during which machining cannot be performed.

[0107] In addition, the left hand 81L can hold the new center die 32C to be used before the right hand 81R stores the used center die 32B in the storage slot 63. This allows the left hand 81L to smoothly receive the new center die 32C to be used.

[0108] (Third embodiment) Hereinafter, a die exchanging device 50 of a bending machine 1 and its die exchanging method according to a third embodiment will be described. The configurations of the bending machine 1 and the die exchanging device 50 according to the third embodiment are the same as those of the first embodiment, but the flow of the die exchanging method is different. Specifically, in the first embodiment, the center die 32A to be used is handled with the left hand 81L, whereas in the third embodiment, the center die 32A to be used is handled with the right hand 81R. The following description will focus on the differences from the first embodiment.

[0109] A mold changing method using the mold changing device 50 will be described with reference to Figures 13 and 14. Figures 13 and 14 are diagrams showing a mold changing method according to a third embodiment. This mold changing method is executed under the control of the control device 100.

[0110] 13, the left hand 81L is in the left standby position Pc3, and the right hand 81R is in the exchange position Pc2, which is the initial state of the left and right hands 81L and 81R (S20). At this time, the left and right hands 81L and 81R are in an open state. In addition, an empty storage slot 63 in which no center die 32 is stored is located at the lowest position of the drum.

[0111] In step S21, the control device 100 rotates the mold storage drum 60 to position the storage slot 63 storing the center mold 32A to be used at the lowest position of the drum. The control device 100 closes the right hand 81R to hold the center mold 32A to be used with the right hand 81R.

[0112] In step S22, the control device 100 moves the left and right hands 81L and 81R to the right, and positions the left and right hands 81L and 81R at the exchange position Pc2 and the right standby position Pc4, respectively.

[0113] In step S23, the control device 100 rotates the center arm 72, to which the used center die 32B is attached, to a jumped-up state. After the center arm 72 rotates, the control device 100 closes the left hand 81L to hold the used center die 32B with the left hand 81L. The control device 100 pulls the piston 72c (see FIG. 7) upward to release the used center die 32B from the center arm 72.

[0114] In step S24 of Fig. 14, the control device 100 moves the left and right hands 81L and 81R to the left. At this time, the used center die 32B is withdrawn from the center arm 72. The control device 100 positions the left and right hands 81L and 81R at the storage position Pc1 and the replacement position Pc2, respectively. During the process of positioning the left and right hands 81L and 81R at the storage position Pc1 and the replacement position Pc2, respectively, the center die 32A to be used is inserted into the center arm 72, and the used center die 32B is inserted into the storage slot 63. The control device 100 pulls the piston 72c (see Fig. 7) downward to fix the center die 32A to be used relative to the center arm 72.

[0115] In step S25, the control device 100 opens the right hand 81R and hands over the center die 32A to be used to the center arm 72. When the center die 32A to be used is handed over, the control device 100 rotates the center arm 72 to which the center die 32A to be used is attached to the reference state.

[0116] In step S26, the control device 100 opens the left hand 81L and transfers the used center die 32B to the storage slot 63. When the used center die 32B is transferred, the control device 100 operates the die storage drum 60 to place an empty storage slot 63 in which no center die 32 is stored at the lowest position of the drum. The processing of step S26 may be performed simultaneously with the processing of step S25.

[0117] In step S27, the control device 100 moves the left and right hands 81L and 81R to the left, and positions the left and right hands 81L and 81R at the left standby position Pc3 and the storage position Pc1, respectively. When a new mold exchange operation is to be performed, the operations from step S21 onwards are repeated.

[0118] Of the above-described series of operations, steps S20 to S22 and S26 to S27 are performed when the bending machine 1 is in processing operation. On the other hand, steps S23 to S25 are performed when the bending machine 1 is not in processing operation.

[0119] As described above, in this embodiment, the mold storage drum 60 is positioned at a position shifted to the left of the center mold unit 70. The control device 100 performs the following steps (1c) to (7c). (1c) When the right hand 81R is in the storage position Pc1, the right hand 81R closes to hold the center mold 32A to be used in the storage slot 63 with the right hand 81R. (2c) The left and right hands 81L, 81R are moved rightward to transition the left and right hands 81L, 81R to a state where the left hand 81L is in the exchange position Pc2. (3c) The left hand 81L closes to hold the used center mold 32B attached to the center arm 72 in the raised state with the left hand 81L. (4c) The left and right hands 81L, 81R are moved leftward, transitioning the left and right hands 81L, 81R to a state where the right hand 81R is in the exchange position Pc2 and the left hand 81L is in the storage position Pc1. (5c) The right hand 81R is opened and the center die 32A to be used is transferred to the center arm 72. (6c) The left hand 81L is opened and the used center die 32B is transferred to the storage slot 63. (7c) The left and right hands 81L, 81R are moved leftward, transitioning the left and right hands 81L, 81R to a state where the right hand 81R is in the storage position Pc1.

[0120] According to this configuration, the right hand 81R can handle the center die 32A to be used, and the left hand 81L can handle the used center die 32B. As a result, it is not necessary to wait for the die storage drum 60 to rotate, as is the case when one hand is used to change the center die 32. In addition, while the left and right hands 81L and 81R are moving leftward, the left hand 81L can remove the used center die 32B from the center arm 72, while the right hand 81R can attach the center die 32A to be used to the center arm 72. This allows the center die 32 to be replaced efficiently on the center arm 72, thereby preventing a prolonged period of time during which machining cannot be performed.

[0121] As described above, the die exchanging device 50 for the bending machine 1 according to the first to third embodiments has been described. The die exchanging method for the bending machine 1 also functions as part of this embodiment. That is, the die exchanging device 50 for the bending machine 1 includes: a die storage drum 60 having a plurality of storage slots 63 capable of storing a plurality of center dies 32 of different lengths, a center arm 72 to which the center dies 32 can be attached, and a center die unit 70 that can be switched between a reference state in which the center dies 32 are aligned as part of the top die 30 and a lifted state in which the center dies 32 can be replaced by rotating the center arm 72 about a rotation axis A1 extending in the left-right direction; and a transfer unit that includes left and right hands 81L, 81R that are arranged side by side in the left-right direction and move in the left-right direction while maintaining a distance from each other, and that transfers the center die between the center arm and the storage slots that are arranged on an extension line of the movement direction of the left and right hands 81L, 81R. In this die exchange method, the left and right hands 81L, 81R exchange the center die between the storage slot 63 and the center arm 72 while transitioning between three states, including a state in which one hand 81R (81L) of the left and right hands 81L, 81R is in a storage position Pc1 corresponding to the storage slot 63, a state in which one hand 81R (81L) is in an exchange position Pc2 corresponding to the center arm 72 and the other hand 81L (81R) of the left and right hands 81L, 81R is in the storage position Pc1, and a state in which the other hand 81L (81R) is in the exchange position Pc2.

[0122] According to the die changing method of this embodiment, the storage slot 63 and the center arm 72 are arranged on an extension line of the movement direction of the left and right hands 81L, 81R. Therefore, the left and right hands 81L, 81R can hold the used center die 32B and the center die to be used 32A, respectively, so there is no need to wait for the die storage drum 60 to rotate.

[0123] In addition, by simply transitioning the states of the left and right hands 81L, 81R once, it is possible to remove the used center die 32B from the center arm 72 with one hand 81R (81L) while attaching the center die 32A to be used to the center arm 72 with the other hand 81L (81R).

[0124] Therefore, according to the die changing method of this embodiment, the center die 32 can be efficiently changed relative to the center arm 72. This makes it possible to prevent the time during which machining cannot be performed from becoming long.

[0125] In each of the above-described embodiments, the mold storage drum 60 is disposed at a position shifted to the left of the center mold unit 70. However, the mold storage drum 60 may be disposed at a position shifted to the right of the center mold unit 70. In this case, the mold changing method can be considered by interchanging the movements of the left and right hands 81L, 81R described in the first to third embodiments.

[0126] Although the present embodiment has been described above, the description and drawings forming a part of this embodiment should not be understood as limiting this embodiment. From this embodiment, various alternative embodiments, examples and operation techniques will become apparent to those skilled in the art.

[0127] The disclosure of this application is related to the subject matter described in Japanese Patent Application No. 2023-097656, filed with the Japan Patent Office on June 14, 2023, the entire disclosure of which is incorporated herein by reference.

Claims

1. A die exchange device to be mounted on a bending machine comprising an upper frame having a top die including a center die and movable in the vertical direction, and a lower frame having a bottom die facing the top die, the bending machine bending a workpiece while the workpiece is fixed between the top die and the bottom die, the die exchange device comprising: a die storage device having a plurality of storage slots capable of storing a plurality of center dies of different lengths, a center die unit having a center arm to which the center die can be attached, the center arm rotating about a rotation axis extending in the left-right direction, and switchable between a reference state in which the center die is aligned as part of the top die, and a lifted state in which the center die can be exchanged, and a transfer unit having left and right hands arranged side by side in the left-right direction and moving in the left-right direction while maintaining a distance between them, the transfer unit transferring the center die between the center arm and the storage slot arranged on an extension line of the movement direction of the left and right hands, the movement direction of the left and right hands corresponding to the insertion and removal direction of the center die with respect to the storage slot and the center arm. Die changing device for a bending machine.

2. A die changing device for a bending machine as set forth in claim 1, wherein the distance in the left-right direction between said storage slot and said center arm is the same as the distance in the left-right direction between said left and right hands.

3. A die changing device for a bending machine as described in claim 1, wherein each of the left and right hands is configured to be freely movable in directions approaching and separating from each other, and has left and right fingers that hold the center die from both the left and right sides, and a housing on which the left and right fingers are mounted, and each of the left and right fingers includes a finger base that extends diagonally upward away from the center of the hand, and a finger body that extends forward from the finger base and holds the center die.

4. The die changing device for a bending machine according to claim 1, further comprising a control device for controlling the left and right hands.

5. A die exchange device for a bending machine as described in claim 4, wherein the control device controls the left and right movement and positioning of the left and right hands to transition between three states, the three states including: a state in which one of the left and right hands is in a storage position corresponding to the storage slot; a state in which the one hand is in an exchange position corresponding to the center arm and the other of the left and right hands is in the storage position; and a state in which the other hand is in the exchange position.

6. The die storage device is disposed at a position shifted to the left of the center die unit, and the control device: moves the left and right hands rightward to transition the left and right hands from a state in which the right hand is in the storage position to a state in which the right hand is in the exchange position and the left hand is in the storage position; closes the left hand to hold the center die to be used that is stored in the storage slot with the left hand; closes the right hand to hold the used center die attached to the center arm in the lifted up position with the right hand; moves the left and right hands rightward to transition the left and right hands to a state in which the left hand is in the exchange position; opens the left hand to deliver the center die to be used to the center arm; moves the left and right hands leftward to transition the left and right hands to a state in which the right hand is in the storage position; opens the right hand to deliver the used center die to the storage slot; The die changing device for a bending machine according to claim 5, wherein the left and right hands are moved rightward to transition the left and right hands to a state in which the right hand is in the changing position and the left hand is in the storage position.

7. The die storage device is disposed at a position shifted to the left of the center die unit, and the control device: moves the left and right hands rightward to transition the left and right hands from a state in which the right hand is in the storage position to a state in which the right hand is in the exchange position and the left hand is in the storage position; closes the left hand to hold the center die to be used that is stored in the storage slot with the left hand; closes the right hand to hold the used center die attached to the center arm in the lifted up position with the right hand; moves the left and right hands rightward to transition the left and right hands to a state in which the left hand is in the exchange position; opens the left hand to deliver the center die to be used to the center arm; moves the left and right hands leftward to transition the left and right hands to a state in which the right hand is in the exchange position and the left hand is in the storage position; closes the left hand to hold a new center die to be used in the storage slot with the left hand; 6. The die exchange device for a bending machine according to claim 5, further comprising: moving the left and right hands in a left direction, transitioning the left and right hands to a state in which the right hand is in the storage position; opening the right hand to deliver the used center die to the storage slot; and moving the left and right hands in a right direction, transitioning the left and right hands to a state in which the right hand is in the exchange position and the left hand is in the storage position.

8. The die storage device is disposed at a position shifted to the left of the center die unit, and the control device: closes the right hand when the right hand is in the storage position to hold the center die to be used in the storage slot with the right hand; moves the left and right hands in a rightward direction to transition the left and right hands to a state where the left hand is in the exchange position; closes the left hand to hold the used center die attached to the center arm in the lifted position with the left hand; moves the left and right hands in a leftward direction to transition the left and right hands to a state where the right hand is in the exchange position and the left hand is in the storage position; opens the right hand to deliver the center die to be used to the center arm; opens the left hand to deliver the used center die to the storage slot; moves the left and right hands in a leftward direction to transition the left and right hands to a state where the right hand is in the storage position. A die exchange device for a bending machine as described in claim 5.

9. A method for changing dies of a bending machine comprising an upper frame having a top die including a center die and movable in the vertical direction, and a lower frame having a bottom die opposed to the top die, wherein the bending machine performs bending of a workpiece while the workpiece is fixed between the top die and the bottom die, the die changing device of the bending machine comprising: a die storage device having a plurality of storage slots capable of storing a plurality of center dies of different lengths, a center die unit having a center arm to which the center die can be attached, the center arm rotating about a rotation axis extending in the left-right direction, thereby being switchable between a reference state in which the center die is aligned as part of the top die, and a lifted-up state in which the center die can be replaced, and a transport unit having left and right hands arranged side by side in the left-right direction and moving in the left-right direction while maintaining a distance between each other, the center die being transported between the storage slot arranged on an extension line of the movement direction of the left and right hands and the center arm, the left and right hands being arranged side by side in the left-right direction and moving in the left-right direction while maintaining a distance between each other, the center die being transported between the center arm and the storage slot, the center die being transported between the center arm and the left and right hands ... left and right hands, the left and right hands being arranged side by side in the left-right direction and moving in the left-right direction while maintaining a distance between each other, the center die being transported between the center arm and the left and right hands, the left and right hands being arranged side by side in the left-right direction and moving in the left-right direction while maintaining a distance between each other, the center die being transported between the center arm and the A die changing method for a bending machine, which changes the center die between the storage slot and the center arm while transitioning between three states including a state in which the one hand is in an exchange position corresponding to the center arm and the other of the left and right hands is in the storage position, and a state in which the other hand is in the exchange position.

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