Bending die

Abstract

To provide a bending die that can be further downsized.SOLUTION: A bending die comprises a punch 1 that is relatively moved toward a surface of a tabular workpiece W and abutted on the workpiece W. The punch 1 includes: a punch body 10; and a punch tip 11 that is held by the punch body 10 linearly slidably relative to the punch body 10, and that is abutted on the surface of the workpiece W. A tip edge 11c of the punch tip 11 can be switched between a position of coinciding with a bending line BL on the workpiece W, and a position of separating from a bending reference plane RP including the bending line BL, according to linear slide movement of the punch tip 11 relative to the punch body 10 that is generated by abutting on the workpiece W. The bending reference plane RP is a plane parallel to a movement direction including the bending line BL.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a bending die. [Background technology]

[0002] Patent Document 1 below discloses a bending die used in a punch press. The bending die in Patent Document 1 includes a pair of upper and lower dies (punch and die) that bend a plate-shaped workpiece. The upper die has a swingable presser die (punch tip) that presses the workpiece from above during bending (see, for example,

[0030] of Patent Document 1). Meanwhile, the lower die has a vertically movable upward punch (die tip) (see, for example,

[0033] to

[0034] of Patent Document 1).

[0003] By raising the upward punch of the lower die against the workpiece held down from above by the presser die of the upper die, the workpiece can be bent by 90 degrees or more (see

[0037] and [Fig. 8] of Patent Document 1, etc.). When the bending process is completed, the upward punch of the lower die is lowered, and the upper die with the presser die is raised. When the tip of the horizontally arranged presser die comes into contact with the bent part of the workpiece as the upper die rises, the presser die is swung downward around the swing center provided at its base end. This prevents the workpiece from being caught by the presser die and lifted up when the upper die rises. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3946564 Summary of the Invention [Problem to be solved by the invention]

[0005] In the invention disclosed in Patent Document 1, the horizontally arranged pressure die of the upper die is swung to separate its tip from the bent portion of the workpiece. Therefore, a certain distance must be secured between the center of oscillation of the base end of the pressure die and its tip, which increases the horizontal size of the upper die. Furthermore, if it is necessary to secure space for the pressure die to oscillate on the side of the pressure die, this also increases the horizontal size of the upper die. Large bending dies require a large space when mounted on a punch press or the like, making them difficult to use and hindering improvements in operating rates. Further miniaturization of bending dies is desired. [Means for solving the problem]

[0006] One aspect of one or more embodiments provides a bending die comprising a punch that is moved relatively toward the surface of a plate-shaped workpiece and abuts against the workpiece, the punch having a punch body and a punch tip that is held by the punch body so as to be linearly slidable relative to the punch body and abuts against the surface of the workpiece, and the leading edge of the punch tip is switched between a position that is aligned with a bend line on the workpiece and a position that is away from a bending reference plane that includes the bend line and is parallel to the direction of movement of the punch during relative movement relative to the workpiece by the linear sliding movement of the punch tip relative to the punch body that occurs when the punch tip abuts against the workpiece. [Effects of the Invention]

[0007] Further miniaturization is possible with one or more embodiments of the bending tool. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view showing a bending mold (punch and die) according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a bending process (first process) using the bending die shown in FIG. [Figure 3] 1. FIG. 4 is a cross-sectional view showing a bending step (second step) using the bending die shown in FIG. [Figure 4] 1. FIG. 4 is a cross-sectional view showing a bending step (third step) using the bending die shown in FIG. [Figure 5] 1. FIG. 4 is a cross-sectional view showing a bending step (fourth step) using the bending die shown in FIG. [Figure 6] 1. FIG. 4 is a cross-sectional view showing a bending step (fifth step) using the bending die shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] A bending die according to an embodiment will be described with reference to the drawings. The bending die according to the embodiment is used in a numerically controlled turret punch press (hereinafter referred to as NCT, not shown). The NCT is a machine that performs punching and bending of a plate-shaped workpiece W, and its operation is numerically controlled.

[0010] As shown in FIG. 1, the bending die of this embodiment includes a punch 1 and a die 2. The punch 1 is also called the upper die and is attached to the upper turret of a pair of upper and lower turrets of the NCT. The die 2 is also called the lower die and is attached to the lower turret of the NCT. The turret is provided with multiple stations, each of which has a station hole for attaching a punch or die. During bending, the punch 1 is moved relatively toward the workpiece W placed on the die 2. In this embodiment, during bending, the workpiece W and die 2 are not moved toward the punch 1, but the punch 1 is moved downward toward the workpiece W. After bending, the punch 1 is moved upward so as to move away from the workpiece W.

[0011] In this embodiment, the punch and die have a cylindrical shape and their basic cross section is circular. The cross section of the station hole is also circular. Multiple types of stations are prepared according to the basic outer diameter of the punch and die. Usually, the number of small-diameter station holes provided in one turret is greater than the number of large-diameter station holes. In other words, large-diameter punches and dies cannot be used if the few large-diameter station holes are filled. On the other hand, small-diameter punches and dies that can be attached to the many small-diameter station holes have fewer restrictions on their use. In this embodiment, the basic outer diameter of punch 1 and die 2 is [1 + (1 / 4)] inches, and they can be attached to relatively small-diameter station holes.

[0012] The punch 1 has a punch body 10 and a punch tip 11. The punch body 10 is configured to be mountable in a station hole formed in the upper turret of the NCT. The punch body 10 is assembled by fastening a head 10a, a punch body 10b, and a tip holder 10c together with bolts. The punch tip 11 is held by the tip holder 10c so that it can slide linearly. This holding structure will be described in detail later, along with details of the punch tip 11, with reference to FIG. 2. A coil spring 10d is interposed between the punch body 10b and the punch tip 11 inside the punch 1. Note that the shape of the coil spring 10d is shown simplified in FIG. 1. The coil spring 10d biases the punch tip 11 diagonally downward.

[0013] The die 2 has a die body 20 and a die tip 21. The die body 20 is configured to be mountable in a station hole formed in the lower turret of the NCT. The die body 20 is assembled by connecting a lower body 20a and an upper body 20b with a coil spring 20c interposed therebetween. Note that the shape of the coil spring 20c is shown simplified in FIG. 1. The lower body 20a and the upper body 20b are slidable relative to each other but are connected to each other so that they do not separate more than a maximum distance. When compressed during bending, the coil spring 20c generates an elastic restoring force that separates the lower body 20a and the upper body 20b from each other. Note that a spring seat 20h fixed to the lower body 20a is also provided between the lower body 20a and the lower end of the coil spring 20c.

[0014] The die body 20 also has an upper plate 20d attached to the upper body 20b and a rod 20e whose lower end is joined to the lower body 20a. The upper plate 20d will be described later. The upper part of the rod 20e is slidably held by the upper body 20b. The central axis of the rod 20e coincides with a reference axis X1 passing through the center of the circular reference cross section of the die 2. During bending, the punch 1 and die 2 are positioned so that the reference axis X1 of the die 2 attached to the lower turret coincides with the reference axis X1 passing through the center of the circular reference cross section of the punch 1 attached to the upper turret (as shown in Figure 1). The reference axis X1 is parallel to the direction of relative movement of the punch 1 described above (hereinafter, this direction of relative movement will be simply referred to as the movement direction).

[0015] A tip storage section 20e1 for storing the die tip 21 is provided at the upper end of the rod 20e. As shown in FIG. 4, the tip storage section 20e1 is formed like a slide rail, and the die tip 21 can be inserted into the tip storage section 20e1 from the side. The die tip 21 is slidably stored in the tip storage section 20e1, and the lower bottom surface of the die tip 21 contacts the inner bottom surface of the tip storage section 20e1. A pair of flanges 20e2 (see FIG. 2) extend from the upper edges of a pair of side walls of the tip storage section 20e1 toward each other, restricting displacement of the die tip 21 in the direction of the reference axis X1, i.e., in the vertical direction, relative to the tip storage section 20e1. The die tip 21 can slide vertically to the reference axis X1, i.e., horizontally, within the tip storage section 20e1, but the sliding distance is very short.

[0016] A recess is formed in the inner bottom surface of the tip storage section 20e1 and the lower bottom surface of the die tip 21, and a gap is formed between the rod 20e and the die tip 21. A coil spring 20f is stored in this gap formed between the rod 20e and the die tip 21. Note that the coil shape of the coil spring 20f is not shown in the figure. The coil spring 20f is interposed between a wall 20e3 erected from the bottom surface of the tip storage section 20e1 and a wall 21a1 hanging down from the bottom surface of the die tip 21. The central axis of the coil spring 20f is horizontal and perpendicular to the wall 20e3 and the wall 21a1.

[0017] The die tip 21 has a base 21a and a die indenter 21b protruding from the base 21a along the reference axis X1. The base 21a is a portion slidably held by the tip storage section 20e1 described above. The die indenter 21b is a portion that protrudes from the die body 20 (upper plate 20d) during bending. The cross section of the die indenter 21b perpendicular to the reference axis X1 is rectangular. The inner surface 21b1 of the die indenter 21b is formed as a negatively inclined plane so that bending can be performed at an angle of 90 degrees or more. Meanwhile, a first cam inclined surface 21b2 for sliding the die tip 21 is formed on a part of the outer surface of the die indenter 21b.

[0018] A disk-shaped upper plate 20d is attached to the upper surface of the upper body 20b so as to cover the die tip 21 stored in the tip storage section 20e1. The upper plate 20d of the die body 20 supports the back surface of the workpiece W from below during bending. The upper body 20b is also provided with a key block 20g (see FIG. 1) that restricts displacement of the die 2 relative to the lower turret in the direction of the reference axis X1, i.e., vertical displacement and rotation of the die 2 relative to the lower turret. A through hole 20d1 is formed in the upper plate 20d to accommodate the die indenter 21b of the die tip 21. The through hole 20d1 has a rectangular shape that matches the upper end surface of the die indenter 21b. A second cam inclined surface 20d2 for sliding the die tip 21 is formed on the inner surface of the through hole 20d1 opposite the above-mentioned first cam inclined surface 21b2.

[0019] The structure for holding the punch tip 11 by the punch body 10 will be described with reference to FIG. 2. Note that the depiction of the details of the punch 1 is slightly different between FIG. 1 and FIG. 2 to FIG. 6, but this does not hinder understanding of the embodiment. Also, in FIG. 2 to FIG. 6, the coil spring 10d (see FIG. 1) that biases the punch tip 11 is omitted. As described above, the punch tip 11 is held by the punch body 10 so as to be linearly slidable relative to the punch body 10. The slide axis X2 of this linear slide of the punch tip 11 is inclined with respect to the reference axis X1 described above.

[0020] The punch tip 11 is slidable between a standby position where it protrudes most from the punch body 10 and a bending position where it bottoms out against the punch body 10. The standby position is the position of the punch tip 11 relative to the punch body 10 when the punch 1 is waiting before bending, and is shown in FIG. 2. The bending position is the position of the punch tip 11 relative to the punch body 10 when the punch tip 11 and die tip 21 bend the workpiece W, and is shown in FIGS. 3 to 5. After bending, when the punch 1 is released from the bent workpiece W and die 2 as shown in FIG. 6, the elastic restoring force of the coil spring 10d returns the punch tip 11 to the standby position relative to the punch body 10.

[0021] As shown in FIG. 2, the punch tip 11 has a punch indenter 11b and a guide neck 11a that protrudes from the punch indenter 11b along the slide axis X2. The guide neck 11a is slidably held in the tip holder 10c. The upper surface 11b1 and the lower surface 11b2 of the punch indenter 11b are perpendicular to the reference axis X1, i.e., horizontal surfaces. The inner surface 11b3 of the punch indenter 11b is formed as a negatively inclined plane so that bending at angles of 90 degrees or more can be performed. The linear edge formed by the lower surface 11b2 and the inner surface 11b3, i.e., the leading edge 11c of the punch tip 11, is horizontal and is aligned with the bend line BL of the workpiece W during bending.

[0022] In this embodiment, the outer surface 11b4 of the punch indenter 11b is formed as a vertically curved surface that matches the circular cross section of the punch 1. That is, the cross section of the punch indenter 11b perpendicular to the reference axis X1 is D-shaped. Four key grooves 10b1 parallel to the reference axis X1 are formed evenly around the circumference on the outer peripheral surface of the punch body 10b to regulate the rotation of the punch 1 relative to the upper turret. One key (not shown) that engages with one of the four key grooves 10b1 protrudes inward from the inner peripheral surface of the station hole of the upper turret. (Four key grooves are also formed on the inner peripheral surface of the station hole of the lower turret, and the key block 20g of the die 2 described above engages with one of the four key grooves.) When the punch 1 is inserted into the station hole, the key is accommodated in the key groove 10b1, regulating the rotation of the punch 1. A key avoidance groove 11b5 is formed on the outer surface 11b4 of the punch indenter 11b in accordance with the key groove 10b1 to avoid interference with the key of the upper turret.

[0023] An accommodation hole 11a1 for the coil spring 10d is formed inside the guide neck 11a along the slide axis X2. A flange 11a2 is formed at the upper end of the guide neck 11a, extending perpendicular to the reference axis X1, i.e., horizontally outward. The basic cross-sectional shape of the guide neck 11a perpendicular to the reference axis X1 is rectangular. The guide neck 11a and the punch indenter 11b partially overlap along the reference axis X1, ensuring the strength and rigidity of the punch tip 11.

[0024] A guide hole 10c1 that guides the sliding of the guide neck 11a is formed inside the tip holder 10c along the slide axis X2. The rectangular shape of the guide hole 10c1 in a cross section perpendicular to the slide axis X2 is slightly larger than the rectangular shape of the guide neck 11a in a cross section perpendicular to the slide axis X2 to allow the sliding of the punch tip 11. A flange accommodating chamber 10c2 that communicates with the guide hole 10c1 and accommodates the flange 11a2 is formed above the guide hole 10c1 along the reference axis X1. The flange accommodating chamber 10c2 is formed to be larger than the range of movement of the flange 11a2 that accompanies the sliding movement of the punch tip 11.

[0025] A through hole 10c3 for passing the coil spring 10d therethrough is formed above the flange accommodating chamber 10c2 of the tip holder 10c. A seating hole 10b2 is formed in the punch body 10b in alignment with the through hole 10c3. The bottom surface of the seating hole 10b2 is formed perpendicular to the slide axis X2 and functions as a seating surface for the coil spring 10d. The bottom surface of the accommodation hole 11a1 of the punch tip 11 is also formed perpendicular to the slide axis X2 and functions as the other seating surface for the coil spring 10d.

[0026] 3 to 5, when the punch tip 11 bottoms out during bending, the upper surface 11b1 of the punch indenter 11b comes into contact with the punch body 10b and the lower end surface 10c4 of the tip holder 10c. In other words, the lower end surface 10c4 of the punch body 10 is a body abutment surface that comes into contact with the punch tip 11 as the punch tip 11 linearly slides relative to the punch body 10 (i.e., during bending). On the other hand, the upper surface 11b1 of the punch indenter 11b is a tip abutment surface that comes into contact with the lower end surface 10c4, which is the body abutment surface, as the punch tip 11 linearly slides relative to the punch body 10 (i.e., during bending).

[0027] Furthermore, when punch tip 11 bottoms out during bending, inclined outer surface 11a3 of guide neck 11a, which faces slightly upward, comes into contact with inclined inner surface 10c5 of tip holder 10c, which faces slightly downward. During bending, the contact area between punch body 10 and punch tip 11 increases due to the contact between the body contact surface (lower end surface 10c4) and the tip contact surface (upper surface 11b1), which do not come into contact when bending is not being performed, and the area that receives the load during bending increases.

[0028] In particular, the lower end surface 10c4, which is the body abutment surface, is a plane perpendicular to the movement direction (reference axis X1) of the punch 1, and the upper surface 11b1, which is the tip abutment surface that comes into contact with this lower end surface 10c4 during bending, is also a plane perpendicular to the movement direction (reference axis X1). Furthermore, the lower surface 11b2 of the punch tip 11 (punch indenter 11b), which comes into contact with the workpiece W during bending, is also a plane perpendicular to the movement direction (reference axis X1). Therefore, the punch indenter 11b is firmly clamped from above and below during bending, so the punch tip 11 can firmly withstand the load during bending.

[0029] Here, the bending reference plane RP will be defined. In this embodiment, the punch 1 is moved toward the die 2 during bending, and after bending, the punch 1 is moved away from the die 2. That is, before and after bending, the punch 1 is moved relative to the die 2 in the movement direction described above, which is parallel to the reference axis X1 described above. Here, the bending reference plane RP is a plane that is parallel to the movement direction, i.e., the reference axis X1, and includes the bend line BL of the workpiece W. In this embodiment, the reference axis X1 intersects the bend line BL at a right angle, so the reference axis X1 also lies on the bending reference plane RP. During bending, the leading edge 11c of the punch tip 11 is aligned with the bend line BL, so during bending, the leading edge 11c of the punch tip 11 is located on the bending reference plane RP.

[0030] In this embodiment, the reference axis X1 passes through the center of the leading edge 11c of the punch tip 11 (see Figures 3 to 5) at the bending position. As described above, the reference axis X1 is inclined with respect to the slide axis X2 of the punch tip 11. That is, the slide axis X2 is inclined with respect to the bending reference plane RP (the angle α between the plane and the line is defined as 0<α≦90 degrees). In order to smoothly slide the punch tip 11 linearly relative to the punch body 10, the angle of the slide axis X2 with respect to the bending reference plane RP is preferably 45 degrees or less. In this embodiment, the angle of the slide axis X2 with respect to the bending reference plane RP is 10 degrees.

[0031] Next, the bending process will be described with reference to Fig. 2 to Fig. 6. Fig. 1 to Fig. 6, including Fig. 1 described above, are cross-sectional views of a cross section perpendicular to a bending reference plane RP, which includes the reference axis X1 and the slide axis X2.

[0032] As shown in FIG. 2, before bending, the workpiece W is set so that the bend line BL of the workpiece W coincides with the bending reference plane RP. The workpiece W is gripped and moved by the clamp 4 of the NCT and remains gripped by the clamp 4 during bending. The punch tip 11 is protruded downward relative to the punch body 10 by the coil spring 10d. The flange 11a2 of the punch tip 11 abuts against the inner lower surface of the flange accommodating chamber 10c2. The punch 1 is separated from the die 2, and the punch tip 11 is positioned in a standby position relative to the punch body 10 by the coil spring 10d. At this time, the leading edge 11c of the punch tip 11 is positioned away from the bending reference plane RP. In the state shown in FIG. 2, the coil spring 20f biases the die tip 21.

[0033] Next, the punch 1 is lowered, and as shown in FIG. 3, the punch tip 11 slides linearly relative to the punch body 10 by contacting the workpiece W and is positioned at the bending position. The workpiece W is pressed down by the punch tip 11 from above. The workpiece W is supported from below by the die 2. The punch tip 11 shown in FIG. 3 is in a bottomed state, and the punch indenter 11b of the punch tip 11 is clamped between the surface of the workpiece W and the lower end surface 10c4 of the punch body 10. In the first half of the descent of the punch 1, that is, until the lower surface 11b2 of the punch indenter 11b comes into contact with the surface of the workpiece W, the punch tip 11 does not displace horizontally.

[0034] However, during the latter half of the descent of the punch 1, i.e., after the lower surface 11b2 of the punch indenter 11b contacts the surface of the workpiece W, the guide neck 11a of the punch tip 11 begins to linearly slide within the guide hole 10c1 as the punch 1 continues to descend. Because the slide axis X2 is inclined with respect to the reference axis X1 (the direction of movement of the punch 1), the punch indenter 11b is displaced vertically, i.e., horizontally, relative to the bending reference plane RP on the surface of the workpiece W so as to approach the bending reference plane RP. Therefore, the punch indenter 11b does not displace vertically, but only horizontally while sliding against the surface of the workpiece W. This horizontal displacement of the punch indenter 11b ends when the upper surface 11b1 of the punch indenter 11b contacts the lower end surface 10c4 of the punch body 10 and the punch tip 11 bottoms out. At this time, the leading edge 11c reaches the bending reference plane RP and coincides with the bending line BL. In this way, the punch tip 11 is also displaced horizontally by utilizing the vertical relative movement of the punch 1 toward the die 2 due to the cam structure formed within the punch 1 by its guide neck 11a and the guide hole 10c1 of the tip holder 10c.

[0035] Next, as shown in Fig. 4, the die tip 21 is raised and the die indenter 21b protrudes upward from the die body 20. This raising of the die tip 21 is achieved by the lower end of the rod 20e being pushed upward from below by the piston 3 (see Fig. 1) of the NCT. As the die indenter 21b protrudes from the die body 20 (upper plate 20d), the workpiece W is bent at the bending line BL by cooperation between the leading edge 11c of the punch indenter 11b and the leading edge of the die indenter 21b.

[0036] During the first half of the rise of the die tip 21, the die tip 21 rises vertically and does not displace horizontally. However, during the second half of the rise of the die tip 21, the first cam inclined surface 21b2 of the die tip 21 abuts against the second cam inclined surface 20d2 of the upper plate 20d, causing the die tip 21 to be displaced vertically, i.e., horizontally, relative to the bending reference plane RP as it rises. During this horizontal displacement, the die tip 21 slides slightly horizontally within the tip storage section 20e1. At this time, because the inner surface 11b3 of the punch indenter 11b and the inner surface 21b1 of the die indenter 21b are formed as negatively inclined surfaces as described above, the bent portion Wa of the workpiece W can be bent by 90 degrees or more. In this embodiment, the workpiece W can be bent up to 94 degrees.

[0037] Furthermore, the leading edge 11c of the punch tip 11 is aligned with the bending line BL of the workpiece W, and the area near the bending line BL is firmly pressed from above by the underside 11b2 of the punch tip 11. The workpiece W is also firmly supported by the die 2 from below. As a result, the workpiece W is bent neatly along the bending line BL. In the state shown in FIG. 4, the die tip 21 is slightly displaced horizontally, so the coil spring 20f is compressed between the wall portion 20e3 of the rod 20e and the wall portion 21a1 of the die tip 21, and exerts a horizontal elastic restoring force.

[0038] During the bending process, the workpiece W bends in such a way that the vicinity of the bend line BL is wrapped around the leading edge 11c. At this time, a load from below is applied to the punch tip 11 via the workpiece W, mainly as the die indenter 21b rises. In addition, in the latter half of the bending process, a horizontal load is also applied to the punch tip 11 via the workpiece W due to the horizontal displacement of the die indenter 21b. These loads applied to the punch tip 11 are firmly absorbed by the punch body 10 through the contact surfaces between the upper surface 11b1 and the lower end surface 10c4, and between the inclined outer surface 11a3 and the inclined inner surface 10c5. As a result, the workpiece W is bent cleanly along the bend line BL.

[0039] In the structure of Patent Document 1 described above, a load acts on the pivot axis of the pivotable presser die (punch tip) during bending, leaving concerns about strength and rigidity. In the present embodiment, there is no pivot axis or rotation axis, which makes it difficult to ensure strength and rigidity, so there are no such concerns. Furthermore, in the structure of Patent Document 1 described above, the area over which the punch body to which the presser die (punch tip) is attached receives the load applied to the presser die (punch tip) is small, which also leaves concerns about strength and rigidity. In the present embodiment, the load is received by punch tip 11, which is a monoblock that slides linearly, and the load is further received over a wide area by punch body 10, so there are no such concerns.

[0040] Next, as shown in FIG. 5, after the bending process is completed, the die tip 21 is first lowered. As the die tip 21 lowers, the bending force applied to the workpiece W is released, and the bend angle of the bent portion Wa of the workpiece W returns slightly to 90 degrees due to springback. In this way, a 90-degree bend that takes springback into account can be achieved by bending the workpiece W by more than 90 degrees. In the first half of the lowering of the die tip 21, the die tip 21 is subjected to the elastic restoring force of the coil spring 20f, and therefore displaces horizontally as it descends. This displacement ends when the die tip 21 abuts against the upper plate 20d. Therefore, in the second half of the subsequent lowering of the die tip 21, the die tip 21 descends vertically and does not displace horizontally.

[0041] In this way, the die tip 21 is also displaced horizontally by utilizing the vertical descent of the die tip 21 and the elastic restoring force of the coil spring 20f due to the cam structure formed within the die 2 by the first cam inclined surface 21b2 and the second cam inclined surface 20d2. This horizontal displacement separates the die tip 21 from the bending reference plane RP, i.e., separates it from the bent portion Wa. This prevents scratches from being formed on the bent portion Wa due to interference with the die tip 21. Furthermore, since interference between the bent portion Wa and the die tip 21 can be avoided, the die tip 21 can be smoothly lowered.

[0042] Next, as shown in Figure 6, the punch 1 is raised. During the first half of the raising of the punch 1, the punch tip 11 is urged downward relative to the punch body 10 by the coil spring 10d. For this reason, the lower surface 11b2 of the punch indenter 11b is in contact with the surface of the workpiece W until the flange 11a2 abuts against the inner lower surface of the flange accommodating chamber 10c2. However, even if the lower surface 11b2 is in contact with the surface of the workpiece W, the moment the upper surface 11b1 of the punch indenter 11b separates from the lower end surface 10c4 of the punch body 10, a cam mechanism inside the punch 1 begins to horizontally displace the punch indenter 11b away from the bending reference plane RP.

[0043] The horizontal displacement of the punch indenter ends when the flange 11a2 abuts against the inner lower surface of the flange accommodating chamber 10c2. At this time, the punch tip 11 has returned to its standby position relative to the punch body 10. In the latter half of the subsequent ascent of the punch 1, the punch 1 is raised to its initial position as shown in FIG. 6. Therefore, as the punch 1 begins to rise, the punch indenter 11b displaces only horizontally while sliding against the surface of the workpiece W, moving away from the bending line BL, i.e., the bending reference plane RP. This prevents scratches from being formed in the bent portion Wa due to interference with the punch tip 11. Furthermore, because interference with the bent portion Wa by the punch tip 11 can be avoided, the die tip 21 can be smoothly raised.

[0044] As described above, when bending the workpiece W along the bend line BL, the workpiece W bends in such a way that the portion of the workpiece W near the bend line BL is wrapped around the leading edge 11c, and the leading edge 11c of the punch tip 11 bites into the bend line BL. Therefore, if the punch indenter 11b is raised before or simultaneously with the horizontal displacement of the leading edge 11c, the workpiece W into which the leading edge 11c is biting will also be lifted. However, in this embodiment, the punch indenter 11b is first horizontally displaced to release the biting of the leading edge 11c, effectively preventing the workpiece W from being lifted.

[0045] This tendency is particularly pronounced when bending at angles greater than 90 degrees, taking springback into consideration. However, even when bending at angles greater than 90 degrees is not performed, the workpiece W still bends around the acute leading edge 11c, resulting in biting. Furthermore, depending on the material and thickness of the workpiece W, bending at angles greater than 90 degrees, taking springback into consideration, may not be necessary. In such cases, 90-degree bending is possible even if the inner surface 11b3 of the punch indenter 11b is made vertical rather than inclined. If the inner surface 11b3 is made vertical, the leading edge 11c will not be an acute edge as described above, but will be a right-angled edge. However, even in this case, the bending behavior is still similar to that of wrapping around the workpiece W, resulting in biting. These negative effects of biting can be avoided by first horizontally displacing the punch indenter 11b.

[0046] Furthermore, as shown in FIG. 2, the workpiece W is gripped by the clamp 4. Therefore, if the workpiece W is bent in a wrapping manner, the clamp 4 and the leading edge 11c of the workpiece W will mutually pull on the workpiece W after bending. Therefore, the bend line BL of the workpiece W is pulled toward the leading edge 11c by the clamp 4. However, as in this embodiment, by first horizontally displacing the punch indenter 11b, the workpiece W can be reliably prevented from lifting up.

[0047] Next, the miniaturization of the above-mentioned bending dies (punch 1 and die 2) will be described. As described above, the bending dies (punch 1 and die 2) of this embodiment have a relatively small basic outer diameter due to miniaturization. The adoption of the above-mentioned cam mechanism is a major factor in enabling the punch 1 and die 2 to be miniaturized while still retaining the function of horizontally displacing the punch indenter 11b and the die indenter 21b.

[0048] The punch 1 is provided with the above-described cam structure, which utilizes a stroke of the punch 1 in the direction of the reference axis X1, i.e., a vertical stroke. More specifically, the vertical stroke of the punch 1 is used to stroke the punch tip 11 obliquely relative to the punch body 10, thereby displacing the punch indenter 11b of the punch tip 11 horizontally. The punch tip 11 is also displaced vertically relative to the punch body 10, but because the punch 1 itself strokes vertically, there is ample room to ensure a vertical range of movement for the punch tip 11. Meanwhile, this cam structure effectively reduces the radial size of the reference radius of the punch 1, i.e., the size in the direction perpendicular to the reference axis X1.

[0049] For example, in the above-mentioned Patent Document 1, the leading edge of the punch can be moved away from the bend line by swinging the pressing die (punch tip). However, to do so, a certain distance must be secured between the center of swing and the leading edge. This necessitates increasing the size of the punch in the direction perpendicular to the direction of punch movement, i.e., in the radial direction of the reference radius. Furthermore, if the orientation of the swingable pressing die (punch tip) is to be maintained horizontal in the standby state, the mechanism for this would be provided to the side of the pressing die (punch tip), which also necessitates increasing the size of the punch 1 in the radial direction of the reference radius. Patent Document 1 also provides such a mechanism (see paragraph

[0030] of Patent Document 1).

[0050] The same applies to the miniaturization of the die 2. As described above, a cam mechanism is also constructed inside the die 2, and this mechanism contributes to the miniaturization. The cam structure utilizes the stroke of the rod 20e in the direction of the reference axis X1, i.e., the vertical stroke. More specifically, the vertical stroke of the rod 20e is used to horizontally displace the die indenter 21b of the die tip 21 relative to the die body 20. However, the horizontal displacement of the die indenter 21b here is slight, and it is technically more difficult to miniaturize the punch 1, which does not have a moving part such as the rod 20e inside.

[0051] In particular, in this embodiment, the punch 1 and die 2 are bending dies used in NCT. As described above, the punch 1 and die 2 are attached to circular station holes provided in the turret. A variety of station hole sizes are available, but if the punch 1 and die 2 are made smaller, they can be attached to the many small-diameter station holes provided in the turret, making them easier to use. Furthermore, if the punch 1 and die 2 are made smaller, the amount of material used can be reduced, which also reduces the manufacturing costs of the bending dies.

[0052] The effects of the above embodiment will be described below.

[0053] The bending die according to the above embodiment includes a punch 1 that is moved relatively toward the surface of a plate-shaped workpiece W and brought into contact with the workpiece W. The punch 1 has a punch body 10 and a punch tip 11 that is held by the punch body 10 so as to be linearly slidable relative to the punch body 10 and that comes into contact with the surface of the workpiece W. A leading edge 11c of the punch tip 11 is switched between a position that is aligned with a bend line BL on the workpiece W and a position that is away from a bending reference plane RP that includes the bend line BL, by a linear sliding movement relative to the punch body 10 that occurs when the punch tip 11 comes into contact with the workpiece W. The bending reference plane RP is a plane that includes the bend line BL and is parallel to the movement direction (reference axis X1).

[0054] Therefore, according to the bending die of the above embodiment, the leading edge 11c can be aligned with the bending line BL during bending by the linear sliding movement of the punch tip 11 relative to the punch body 10 of the workpiece W. Furthermore, when the punch 1 moves relative to the workpiece W (die 2) before and after bending, the leading edge 11c can be moved away from the bending reference plane RP by the linear sliding movement described above. Since the leading edge 11c is displaced by utilizing the linear sliding movement of the punch tip 11 relative to the punch body 10, the punch 1 can be made more compact. In particular, the size in the direction perpendicular to the movement direction (reference axis X1) of the punch 1 can be made more compact. This miniaturization allows for a reduction in the amount of raw material used for the punch 1, thereby lowering manufacturing costs.

[0055] Furthermore, according to the bending die of the above embodiment, the punch tip 11 has a guide neck 11a inclined with respect to the movement direction (reference axis X1), and the punch body 10 has a guide hole 10c1 that slidably accommodates the guide neck 11a. During the relative movement described above, the punch tip 11, which abuts against the workpiece W, is displaced in a direction perpendicular to the bending reference plane RP as its guide neck 11a is guided by the guide hole 10c1. The guide neck 11a and the guide hole 10c1 form a cam structure within the punch 1 that utilizes the relative movement along the movement direction (reference axis X1) of the punch 1. This cam mechanism can align the leading edge 11c with the bend line BL or move the leading edge 11c away from the bending reference plane RP that includes the bend line BL. The displacement of the leading edge 11c perpendicular to the movement direction (reference axis X1) can be achieved by a simple cam structure within the punch 1.

[0056] Furthermore, according to the bending die of the above embodiment, the punch body 10 has a body contact surface (lower end surface 10c4) that comes into contact with the punch tip 11 as the punch tip 11 linearly slides. Meanwhile, the punch tip 11 has a tip contact surface (upper surface 11b1) that comes into contact with the body contact surface (lower end surface 10c4) as the punch tip 11 linearly slides. During bending, the contact area between the punch body 10 and the punch tip 11 increases due to the contact between the body contact surface (lower end surface 10c4) and the tip contact surface (upper surface 11b1). Therefore, the load applied to the punch tip 11 via the workpiece W during bending is firmly received by the punch body 10 due to the contact between the body contact surface (lower end surface 10c4) and the tip contact surface (upper surface 11b1). As a result, reliable bending is possible, and the durability of the punch 1 is improved.

[0057] Furthermore, the bending die according to the above embodiment further includes, in addition to the punch 1, a die 2 that cooperates with the punch 1 to bend the workpiece W during bending. The die 2 includes a die body 20 that supports the back surface of the workpiece W and a die tip 21 that protrudes from the die body 20 during bending and cooperates with the punch tip 11 to bend the workpiece W held by the punch tip 11. The punch body 10 is configured to be mountable in a station hole formed in the upper turret of a turret punch press, and the die body 20 is configured to be mountable in a station hole formed in the lower turret of the turret punch press. That is, the bending die includes a punch 1 and a die 2 used for NCT. As described above, the number of station holes for NCT is limited, and the smaller the diameter, the more holes can be mounted. The miniaturized (smaller diameter) punch 1 and die 2 of this embodiment are easier to use, improving the operating rate of the bending die and turret punch press.

[0058] Although the above-described embodiments have been described, the present invention is not limited thereto, and various modifications are possible within the scope of the present embodiments. For example, the cam structure of the die 2 in the above-described embodiments includes the first cam inclined surface 21b2 and the second cam inclined surface 20d2. However, the cam structure of the die 2 may include a cam pin and a cam groove for guiding the cam pin. Furthermore, in the above-described embodiments, the punch tip 11 is raised after the die tip 21 is lowered. However, the die tip 21 may be lowered after the punch tip 11 is raised. In this case, even if the bent portion Wa of the workpiece W is bent by the die tip 21 by 90 degrees or more, the punch indenter 11b is displaced horizontally, thereby avoiding interference with the bent portion Wa bent by 90 degrees or more. Furthermore, although the turret punch press in the above-described embodiments is a numerically controlled turret punch press, it may also be a punch press without numerical control. Furthermore, even in a numerically controlled turret punch press, bending using the bending die of the above-described embodiments may be performed without numerical control. [Explanation of symbols]

[0059] 1 punch 10 Punch body 10c1 Guide hole 10c4 Lower end surface (body contact surface) 11 Punch Tip 11a Guide neck 11b1 Top surface (chip contact surface) 11c Tip edge 2 Die 20 Die body 21 Die Chip RP bending reference plane double work X1 Reference axis (movement direction) X2 slide axis

Claims

1. A bending die, The punch is moved relatively toward the surface of a plate-shaped workpiece and is brought into contact with the workpiece, The punch has a punch body and a punch tip that is held by the punch body so as to be linearly slidable relative to the punch body and that abuts against the surface of the workpiece, A bending die in which the leading edge of the punch tip is switched between a position aligned with a bending line on the workpiece and a position away from a bending reference plane including the bending line, which is parallel to the direction of relative movement of the punch with respect to the workpiece, by a linear sliding movement relative to the punch body caused by the punch tip abutting against the workpiece.

2. The bending die according to claim 1, the punch tip has a guide neck portion inclined with respect to the moving direction, and the punch body has a guide hole that slidably accommodates the guide neck portion, During the relative movement, the punch tip that contacts the workpiece is displaced in a direction perpendicular to the bending reference plane as its guide neck portion is guided by the guide hole, a bending die.

3. The bending die according to claim 2, the punch body has a body contact surface that contacts the punch tip as the punch body moves linearly, The punch tip has a tip abutment surface that comes into contact with the body abutment surface as the punch tip linearly slides.

4. The bending die according to claim 3, Further provided is a die that cooperates with the punch during bending to perform bending of the workpiece, The die has a die body that supports the back surface of the workpiece, and a die tip that protrudes from the die body during bending and bends the workpiece held by the punch tip in cooperation with the punch tip, The punch body is configured to be mountable in a station hole formed in an upper turret of a turret punch press, The bending die is configured so that the die body can be attached to a station hole formed in a lower turret of the turret punch press.

Images