Press working apparatus

Abstract

[Problem] To provide a press working apparatus that has a structure which does not deteriorate over time, and that is capable of obtaining a pressing force of a holding part with sufficient leeway in regard to a damage limit of an elastic body, while also maintaining the necessary clearance for ordinary pressing. [Solution] A press working apparatus in which a vibrator is mounted on an upper part of a punch, and a flange-shaped holding part is provided to an outside surface of the punch, wherein: an upper surface of the holding part abuts a backing plate; a lower surface of the holding part abuts a clamping part of a punch retainer; the apparatus has a structure in which the holding part is held clamped by the backing plate and the punch retainer; a groove having a shape following a side-surface shape of the holding part is formed in the clamping part; an elastic body having the same shape as the groove is provided in the groove; and an upper surface of the elastic body abuts the lower surface of the holding part.

Description

Pressing machine

[0001] The present invention relates to a press working apparatus in which a vibrator is mounted on the upper part of a punch and a flange-shaped holding portion is provided on the outer surface of the punch. More particularly, the present invention relates to a press working apparatus in which a groove is provided in the clamping portion of a punch retainer that clamps the holding portion, and an elastic body of a predetermined height is installed in the groove to obtain the expected punch holding force and to improve resistance to deterioration over time.

[0002] Generally, press working includes processes such as separation and forming, and the equipment used for these processes is generally called a press working machine. A press working machine places a workpiece, such as sheet metal or laminated board, between two dies, an upper die (also called a "punch") and a lower die (also called a "die"). The workpiece is then clamped and pressed between the upper and lower dies to process it into the desired shape.

[0003] Separation processing involves shaping a workpiece by cutting it; for example, punching is a known process where the workpiece is placed on a lower die and the shape is cut out by an upper die. Forming processes include bending, which involves bending the workpiece, and drawing, which involves stretching the workpiece to form the shape. However, in separation processing, burrs and sagging occur at the beginning and end of the sheared surface, and the state of these burrs and sagging varies depending on the thickness and type of the workpiece plate, processing speed, clearance, etc. If a lot of sagging occurs, the flatness of the sheared surface is impaired, which becomes a problem when flatness of the sheared surface is required. Also, because burrs have sharp edges, they can cause injuries to people or lead to defective or flawed products.

[0004] Furthermore, in forming processes, there is a risk of quality degradation due to the occurrence of "scratches" or "cracks" during bending, depending on the thickness and type of the workpiece, processing speed, clearance, etc. Also, in drawing processes, there is a risk of "wrinkles" or "cracks" occurring, depending on the thickness and type of the workpiece, processing speed, clearance, etc.

[0005] As a solution to the above-mentioned problems, for example, a press working apparatus shown in Japanese Patent No. 6427438 (Patent Document 1) is known. Specifically, as shown in Figure 1, the press working apparatus 1 has a movable side portion (upper die) 2 having a punch 10 and a fixed side portion 3 having a lower die 30. The movable side portion 2 has a punch 10, a punch retainer 21A and a backing plate 21B that fix the punch 10, and a support 23 that fixes the punch retainer 21A and the backing plate 21B to the upper die holder 22. The upper die holder 22 and the support 23 are fixed with bolts 24A, and similarly the support 23 and the punch retainer 21A and backing plate 21B are fixed with bolts 24B. The punch 10 is fixed by being clamped by the punch retainer 21A and the backing plate 21B at a flange-shaped holding portion 11 provided in the middle, and other parts are not fixed. In other words, when the punch 10 is vibrated by the vibrator 50, that vibration is not transmitted to the stripper 25 or the support 23.

[0006] Furthermore, the movable part 2 includes a stripper 25 for removing the workpiece W when it adheres to the punch 10, a spring 26 for biasing the stripper 25 toward the lower die 30, and a guide pin 27 for stabilizing the position of the stripper 25. In addition, a vibrator 50 made of a piezoelectric element driven by the drive unit is attached to the upper surface of the punch 10.

[0007] On the other hand, the fixed side portion 3 includes a lower die 30 and a lower die holder 32 for fixing the lower die 30. The lower die 30 is a metal member having a predetermined thickness and is stacked on the lower die holder 32 and fixed by bolts 34. The lower die 30 also has a hole 31 with a shape corresponding to the shape of the punch 10 and a hole 33 for receiving the guide pin 27. The press working apparatus 1 is equipped with a drive mechanism (not shown) for applying the force necessary for processing to the die, a control device (not shown) for controlling the drive mechanism (not shown), a safety device (not shown), and the like.

[0008] Figure 2 shows an example of the structure of the punch 10, which has a barrel-shaped horizontal cross section, with flange-shaped holding parts 11 on the flat surfaces on both sides, and a vertically oriented and elongated through hole 12 drilled in the center of the barrel-shaped section, the through hole 12 drilled in the vertical direction of the holding part 11, that is, straddling the position of the holding part 11. In addition, a screw hole 13 for fixing the vibrator 50 with a screw is provided on the upper surface of the punch 10.

[0009] Furthermore, Figure 3(A) is a perspective view showing an example of the structure of a punch 10A with a circular horizontal cross-section. A flange-shaped retaining portion 11A is provided around the outer circumferential surface of the middle part of the punch 10A, and a through hole 12A with an elliptical to elongated cross-section is drilled across the retaining portion 11A from above and below. The retaining portion 11A at the position intersecting the through hole 12A is notched, and a screw hole 13A for fixing the vibrator 50 with a screw is provided on the upper surface of the punch 10A. Furthermore, Figure 3(B) is a perspective view showing an example of the structure of a punch 10B with a rectangular horizontal cross-section. Flange-shaped retaining portions 11B are provided on both outer ends of the middle part of the punch 10B, and a through hole 12B with an elliptical to elongated cross-section is drilled across the retaining portions 11B at both ends. The holding portion 11B at the position where it intersects with the through hole 12B is notched, and a screw hole 13B for fixing the vibrator 50 with a screw is provided on the upper surface of the punch 10B.

[0010] Figure 4 is a perspective view showing the detailed structure of a punch 40 with a circular cross-section and no through holes. The overall structure is a cylindrical stepped structure, with a relatively small diameter body 46 between the upper transmission section 44 and the lower pressing section 45, and a flange-shaped holding section 41 is provided around the periphery of the body 46. A screw hole 43 for attaching the vibrator 50 is drilled in the center of the upper surface of the transmission section 44, and the bottom surface of the pressing section 45 is a cutting edge 45A.

[0011] Figure 5 shows a cross-sectional view of the punch 40 shown in Figure 4 mounted on a press working machine. The transmission part 44 of the punch 40 is housed in the base plate 60, and the holding part 41 is held and fixed by the backing plate 61 and the punch retainer 62 (clamping part). The vibrator 50 is screwed into the screw hole 43 of the punch 40 with a threaded rod 51 and fixed so that the vibration pressure of the vibrator 50 is applied to the punch 40. The threaded rod 51 is also screwed into the screw hole 52 of the vibrator 50.

[0012] Patent No. 6427438

[0013] As described above, in conventional press working machines, the punch 40 is held and fixed by clamping the holding part 41, which is provided on the outer surface of the punch 40, between the backing plate 61 and the punch retainer 62, and holding it with pressing force from both sides. During pressing, vibration is applied from the vibrator 50 to the upper surface of the punch 40, and the holding part 41 is adjusted to act as a node in the vibration. Furthermore, since the holding part 41 has a thickness H4 to support the punching load of the punch 40, the upper and lower surfaces of the holding part 41 move up and down very slightly. In addition, although the vibration mode by the vibrator 50 is vertical expansion and contraction, there is also a small amount of lateral distortion associated with this, and it is not possible to completely eliminate the vibration of the holding part 41. If this is gripped too tightly, it will act in a direction that inhibits vibration, and if the grip is loose or there is a gap between the holding part and the punch, it will cause noise due to rattling (forging) and affect the amount of punching (stroke amount of the punch 40), which will negatively affect product quality.

[0014] A conventional solution to this problem involves sandwiching a thin film of rubber between the holding part and the retaining part. Figure 6 shows the detailed structure, where the upper surface of the holding part 41 abuts against the bottom surface of the backing plate 61, and a thin film of rubber 70 is interposed between the lower surface of the holding part 41 and the upper surface of the punch retainer 62. In other words, the thin film of rubber 70 is sandwiched in a minute clearance (the clearance usually set in a press is about 0.1 mm) that does not affect the press stroke of the punch 40 and does not cause rattling. However, the deformation of the holding part 41 due to vibration is 1 to 3 μm, and combined with the amount of initial compression caused by sandwiching the thin film of rubber 70, a compression of about 20% is applied. Therefore, if subjected to vibration and fluctuations in the amount of compression due to the press stroke over a long period of time, there is a problem of significant deterioration over time.

[0015] The present invention has been made in accordance with the circumstances described above, and the object of the present invention is to provide a press working apparatus that can obtain the pressing force of the holding part with sufficient margin over the damage limit of the elastic body while maintaining the clearance normally required for pressing, and has a structure that does not deteriorate over time in a way that adversely affects product quality within the mold maintenance cycle.

[0016] The present invention relates to a press working apparatus in which a vibrator is mounted on the upper part of a punch and a flange-shaped holding portion is provided on the outer surface of the punch. The above object of the present invention is a structure in which the upper surface of the holding portion abuts against a backing plate, the lower surface of the holding portion abuts against a clamping portion of a punch retainer, and the holding portion is held by being clamped between the backing plate and the punch retainer. This is achieved by having a groove formed in the clamping portion that conforms to the side shape of the holding portion, an elastic body having the same shape as the groove installed in the groove, and the upper surface of the elastic body abutting against the lower surface of the holding portion.

[0017] According to the press working apparatus of the present invention, by reducing the initial compression amount and the compression change amount due to vibration of the elastic body sandwiched between the holding part and the punch retainer, the progression of deterioration of the elastic body over time, which is correlated in magnitude, can be slowed down. Furthermore, the amount of variation in the initial compression amount can be reduced, and the risk of premature deterioration due to excessive compression can be avoided.

[0018] FIG. 1 is a configuration diagram showing an example of a general press working apparatus. FIG. 2 is a perspective view showing an example of a punch. FIG. 3 is a perspective view showing another example of a punch. FIG. 4 is a perspective view showing an example of a punch. FIG. 5 is a cross-sectional view showing an example of a conventional structure in which a punch is mounted on a press working apparatus. FIG. 6 is a cross-sectional view showing a partial detailed structure of a mounting portion. FIG. 7 is a cross-sectional view showing an example of a press working apparatus according to the present invention. FIG. 8 is a cross-sectional view showing a partial detailed structure of a mounting portion in the present invention. FIG. 9 is a perspective view showing a structural example of a punch retainer according to the present invention. FIG. 10 is the X １ -X ２ line and Y １ -Y ２ cross-sectional view of the line. FIG. 11 is a perspective view showing an example of an elastic body used in the present invention. FIG. 12 is a cross-sectional view showing a modified example of a groove. FIG. 13 is a perspective view and a side view showing another example of a punch to which the present invention can be applied. FIG. 14 shows an example in which a plurality of cylindrical elastic bodies are arranged at equal intervals along a circle formed by a clamping portion of a punch retainer and erected. FIG. 14(A) is a top view thereof, FIG. 14(B) is a cross-sectional view of the C １ -C ２ line portion of FIG. 14(A), and FIG. 14(C) is a semi-cross-sectional perspective view of the D １ -D ２ line portion of FIG. 14(A). FIG. 15 is a top view showing an example in which a plurality of arc-shaped elastic bodies are arranged at equal intervals along a circle formed by a clamping portion and erected. FIG. 16 shows an example in which a thick rectangular elastic body is arranged along a rectangle formed by a clamping portion. FIG. 16(A) is a top view thereof, and FIG. 16(B) is the E １ -E ２Figure 16(C) is a perspective view showing an example of the arrangement of these components around a rectangular punch (shown by a dotted line). Figure 17 is a top view showing an example in which a thick rectangular elastic body is divided into multiple sections along the rectangular shape formed by the upper surface of the clamping section and erected. Figure 18 is a cross-sectional view following the example in Figure 8, showing an example in which a protective part made of a different material is used on the upper surface of the elastic body. Figure 18(A) is a cross-sectional view showing the structure around the holding part of the punch, Figure 18(B) is a cross-sectional view showing an example in which an uneven structure is provided between the elastic body and the protective part, and Figure 18(C) is a cross-sectional view showing an example in which a dovetail joint structure is provided between the elastic body and the protective part. Figure 19 is a cross-sectional view following the example in Figure 8, showing an example in which a graded functional material is used as the elastic body.

[0019] The present invention relates to a press working apparatus in which a vibrator is mounted on the upper part of a punch and a flange-shaped retaining portion is provided on the outer surface of the punch. A groove is provided in the clamping portion of the punch retainer that clamps the retaining portion, and an elastic material such as urethane is placed in the groove to clamp the retaining portion.

[0020] The groove shape follows the side shape of the holding part. If the punch cross-section is circular and the holding part is circular, the groove is circular. If the punch cross-section is rectangular or barrel-shaped and the holding part is straight, the groove is also straight. The height of the elastic body is such that it has the necessary clearance for pressing and can press the holding part with sufficient margin over the damage limit. The horizontal cross-sectional shape of the punch can be circular, rectangular, or barrel-shaped. The punch may have one through-hole spanning the holding part, or two through-holes above and below the holding part, and it can also be applied to punches without through-holes.

[0021] According to the present invention, the amount of compression of the elastic body sandwiched between the holding part and the punch retainer can be reduced, improving resistance to deterioration over time. This reduces the influence of variations in the initial compression amount on the compression amount, thereby improving resistance to deterioration over time.

[0022] Embodiments of the present invention will be described below with reference to the drawings.

[0023] Figure 7 shows a cross-section of a press working apparatus according to an example of the present invention, corresponding to Figure 5, and Figure 8 shows in detail the holding structure around the holding portion 41 of the punch 40. As shown in Figures 7 and 8, in the present invention, a groove 64 with a depth H1 and a width W1 is formed in a stepped concave clamping portion 65 (as shown in Figure 10) provided along the periphery of the round hole 63 that accommodates the punch 60 of the punch retainer 62, and an elastic body 80 with a height (H1 + H3) is installed in the groove 64 (as shown in Figure 8). The shape of the groove 64 is a shape that follows the side shape of the holding portion of the punch, that is, a shape that corresponds to the shape of the round hole 63. If the cross-section of the punch is circular, the holding portion is also circular as shown in Figures 3(A) and 4, and the groove 64 is also circular. Also, if the cross-section of the punch is a barrel drum as shown in Figure 2, or if the cross-section of the punch is rectangular as shown in Figure 3(B), the holding portion is provided in a straight line at both ends, so the groove is also straight.

[0024] The elastic body 80 is made of, for example, urethane, and its upper surface, when placed in the groove 64, abuts against the bottom surface of the holding part 41 and presses against it, with the backing plate 61 and punch retainer 62 holding the holding part 41 by the pressing force. The height of the elastic body 80 (H1 + H3) is slightly greater than the depth of the groove 64 (H1), so that when the elastic body 80 is placed in the groove 64, the elastic body 80 protrudes from the top surface of the punch retainer 62 by a small height H3. The height of the elastic body 80 (H1 + H3) is such that it maintains the clearance necessary for press working and also has a margin of safety regarding the damage limit of the elastic body 80. For example, height H1 is 2 [mm], height H2 is 8.1 [mm], height H3 is 0.1 [mm], and height H4 is 8 [mm].

[0025] The perspective view structure of the punch retainer 62 is such that, when the horizontal cross-section of the punch 40 is circular, a circular groove 64 is provided in the clamping portion 65 around the round hole 63 that accommodates the punch 40, as shown in Figure 9. １ -X ２ The cross-sectional structure of the line is as shown in Figure 10(A), Y １ -Y ２The cross-sectional structure of the wire is as shown in Figure 10(B). Specifically, a groove 64 with a depth H1 and a width W1 is formed in a circular shape in the clamping portion, which is the part that contacts and holds the holding portion 41 of the punch retainer 62, and an annular elastic body 80 as shown in Figure 11 is inserted and installed into this groove 64. The elastic body 80 can be installed in the groove 64 by fitting, applying adhesive, or screwing it in.

[0026] The bottom of the groove 64 may be flat as shown in Figure 10, triangular as shown in Figure 12(A), or round as shown in Figure 12(B).

[0027] After the elastic body 80 is placed in the groove 64 of the punch retainer 62, the upper surface of the elastic body 80 is brought into contact with the lower surface of the holding part 41, as shown in Figure 8, and a pressing force is applied to hold it in place.

[0028] The punch of the present invention can also be applied to those having two through holes 153 and 154 as shown in Figures 13(A) and 13(B). Specifically, a flange-shaped holding portion 151 is provided around the middle of the side surface of the cylindrical punch 150, a screw hole 152 for attaching the vibrator 160 is provided on the upper surface, and a cutting edge 155 is attached to the lower surface. Furthermore, the punch 150 is provided with through holes 153 and 154 for adjusting the vibration resonance of the vibrator 160.

[0029] In this example, a cylindrical punch with a through-hole was shown, but a punch without a through-hole, as shown in Figure 4, may also be used.

[0030] Furthermore, the above examples illustrate the configuration of the present invention, and within the scope of the spirit of the present invention, the above configuration can be modified as appropriate.

[0031] Therefore, for example, in the above example, as shown in Figures 7 to 11, an annular elastic body 80 was exemplified as an elastic body to be placed in the punch retainer 62 corresponding to the cylindrical punch 40.

[0032] However, when using a cylindrical punch, the shape of the elastic body can be different from that of an annular shape, as illustrated in Figures 14 and 15.

[0033] Among these, FIG. 14 shows an example in which a plurality of cylindrical elastic bodies 80A are arranged at equal intervals along a circle formed by the clamping portion of the punch retainer and erected. FIG. 14(A) is a top view thereof, and FIG. 14(B) is a C １ - C ２ sectional view of the C-C line portion, and FIG. 14(C) shows an arrangement example around the punch 40 with a circular cross section (shown by a dotted line) in FIG. 14(A) at the D １ - D ２ half-sectional perspective view of the line portion.

[0034] And in the configuration example shown in FIG. 14, on the upper surface of the clamping portion 65 of the punch retainer 62, a plurality of cylindrical holes are provided along a circle facing the annulus formed by the upper surface, and the elastic body 80A arranged therein has the same upper surface shape as the holes provided on the upper surface of the clamping portion when viewed from the upper surface, and when viewed from the side, it protrudes from the upper surface of the clamping portion and is generally formed in a cylindrical shape.

[0035] Further, FIG. 15 shows an example in which a plurality of arc-shaped elastic bodies 80B are arranged at equal intervals along a circle formed by the clamping portion 65 of the punch retainer 62 and erected in the same manner as in the case of FIG. 14(A). And also in this case, on the upper surface of the clamping portion 65 of the punch retainer 62, a plurality of arc-shaped holes are provided along the annulus formed by the upper surface, and the elastic body 80B arranged therein has the same shape as the holes provided on the upper surface of the clamping portion when viewed from the upper surface side, and when viewed from the side surface side, it is formed so as to protrude from the upper surface of the clamping portion.

[0036] And the degree of such protrusion (height) is set to maintain the clearance required for press working as described above and to have a dimension with a margin with respect to the damage limit of the elastic body. Therefore, such a height is set so that there is no loose holding state or a gap between the holding portion, so that rattling does not occur, and at the same time, the elastic body is not damaged or prematurely deteriorated due to excessive pressing, according to the properties and durability of the material of the elastic body.

[0037] Therefore, in the present invention, it is possible to arbitrarily set the form of the elastic body corresponding to the form of the holding part of the punch and the retainer facing it. Also in the present invention, with such a configuration of the elastic body, it is possible to secure the pressing force in the holding part according to the purpose of the present invention and reduce the deterioration over time that adversely affects the target quality of the product.

[0038] Furthermore, in the above example, a cylindrical punch was used, but the present invention is not limited to such a form. For example, as shown in FIGS. 2 and 3(B), when the holding part of the punch is configured in a rectangular shape in a top view, correspondingly, as shown in FIGS. 16 and 17, it is also possible to use a thick rectangular elastic body 80C.

[0039] Here, the example shown in FIG. 16 is a case where the horizontal cross-sectional shape of the punch 10B is rectangular, or a barrel drum shape in which two opposite sides (on the side without the holding part) of the horizontal cross-sectional shape of the punch 10 form a rectangle and are smoothly constricted at the central part. Corresponding to the holding part (11B, 11) becoming rectangular, an example using a thick rectangular elastic body 80C as the elastic body arranged in the punch retainer 62 is shown.

[0040] More specifically, FIG. 16 shows an example in which a thick rectangular elastic body 80C is arranged along the rectangular shape formed by the sandwiching part 65 of the punch retainer 62. FIG. 16(A) is a top view thereof, and FIG. 16(B) is a cross-sectional view of the E １ -E ２ -E line part, and FIG. 16(C) is a perspective view showing an example of the arrangement around the punch 10B with a rectangular cross-section (shown by a dotted line) for such a sandwiching part.

[0041] In the configuration example shown in FIG. 16, on the upper surface of the sandwiching part 65 of the punch retainer 62, a rectangular hole substantially similar to the rectangular shape formed by the upper surface is provided along the rectangular shape. The elastic body 80C arranged there has the same shape as the hole provided on the upper surface of the sandwiching part when viewed from above, and when viewed from the side, it is formed in a generally thick rectangular shape so as to protrude from the upper surface of the sandwiching part.

[0042] Furthermore, Figure 17 shows an example in which a thick, rectangular elastic body 80D, as shown in Figure 16, is divided into multiple sections and erected along the rectangular shape formed by the upper surface of the clamping portion of the punch retainer, similar to the case in Figure 16(A). In this case as well, the upper surface of the clamping portion 65 of the punch retainer 62 is provided with multiple rectangular holes along the rectangular shape formed by the upper surface, and the elastic body 80D placed therein has the same shape as the holes provided on the upper surface of the clamping portion 65 when viewed from the top side, and is formed to protrude from the upper surface of the clamping portion when viewed from the side side.

[0043] Therefore, in this invention, the shape of the elastic body can be arbitrarily set in accordance with the shape of the punch holding portion and the retainer facing it. In this invention, even with such an elastic body configuration, it is possible to ensure the pressing force in the holding portion according to the purpose of the present invention and to reduce deterioration over time that adversely affects the target quality of the product.

[0044] Furthermore, in the example described above, the individual elastic bodies were constructed as a single unit, but it is also acceptable to use a protective part 90 on the upper part of the elastic body, as shown in Figure 18.

[0045] Here, Figure 18 is a cross-sectional view showing an example in which a protective part 90 made of a different material is used on the upper surface of the elastic body 80E, following the example in Figure 8. Figure 18(A) is a cross-sectional view showing the structure around the punch holding part, following the example in Figure 8. Figure 18(B) is a cross-sectional view showing an example in which an uneven structure is provided between the elastic body 80E and the protective part 90. Figure 18(C) is a cross-sectional view showing an example in which a "dovetail joint" structure is provided between the elastic body and the protective part.

[0046] Therefore, in this invention, by arranging a protective part on the upper surface of the elastic body in this manner, it is possible to prevent the vibrating punch from directly contacting the elastic body, thereby reducing the risk of extreme wear and deterioration of the elastic body.

[0047] Furthermore, the material used for such protective parts 90 can be, for example, so-called SK material (carbon tool steel). Also, when connecting such protective parts 90 to the upper surface of the elastic body 80F, an adhesive may be used, or, as illustrated in Figure 18(B), a mutually interlocking protrusion-and-recess structure 90J may be provided, or an engaging part using a dovetail joint structure 90d as illustrated in Figure 18(C) may be provided.

[0048] Furthermore, for reasons such as improved durability, the elastic body 80F itself may be constructed using functionally graded materials (FGMs), as schematically shown in Figure 19. In this case, by adjusting the type and density of the constituent material of the elastic body on the upper and lower sides, it is possible to use a material in which the strength and elasticity are optimally varied between the upper and lower sides.

[0049] Therefore, even with the elastic body configuration described above, the present invention makes it possible to secure the pressing force in the holding portion according to the purpose of the present invention and to reduce deterioration over time that adversely affects the target quality of the product.

[0050] 1 Pressing machine 2 Movable side part (upper die) 3 Fixed side part 10, 40 Punch 11, 11A, 11B, 41 Holding member 12, 12A, 12B Through hole 21A, 62 Punch retainer 21B, 61 Backing plate 22 Upper die holder 23 Support 25 Stripper 26 Spring 30 Lower die 32 Lower die holder 44 Transmission part 45 Press part 46 Body part 50 Vibrator 60 Base plate 64 Groove 65 Clamping part 70 Thin film rubber 80, 80A, 80B, 80C, 80D, 80E, 80F Elastic body 90 Protective part 90J Uneven structure part 90D Dovetail joint structure part

Claims

1. A press working apparatus in which a vibrator is mounted on the upper part of a punch and a flange-shaped holding portion is provided on the outer surface of the punch, wherein the upper surface of the holding portion abuts against a backing plate, the lower surface of the holding portion abuts against a clamping portion of a punch retainer, and the holding portion is held by being clamped between the backing plate and the punch retainer, wherein a groove is formed in the clamping portion that conforms to the side shape of the holding portion, and an elastic body having the same shape as the groove is installed in the groove, and the upper surface of the elastic body abuts against the lower surface of the holding portion.

2. The press working apparatus according to claim 1, wherein the height of the elastic body is such that it maintains the clearance necessary for pressing and allows for pressing with sufficient margin over the damage limit of the elastic body.

3. The press working apparatus according to claim 2, wherein the horizontal cross-sectional shape of the punch is circular.

4. The press working apparatus according to claim 3, wherein the grooves formed in the clamping portion and shaped to conform to the side shape of the holding portion are a plurality of cylindrical holes provided along a circle opposite to the annular ring formed by the bottom surface of the holding portion, and the elastic bodies arranged in the plurality of cylindrical holes are cylindrical in shape and have the same top surface shape as the holes provided on the top surface of the clamping portion when viewed from above.

5. The press working apparatus according to claim 2, wherein the horizontal cross-sectional shape of the punch is rectangular or barrel-shaped.

6. The press working apparatus according to claim 5, wherein the groove formed in the clamping portion is shaped in accordance with the side shape of the holding portion, and is a rectangular hole provided opposite to the rectangular shape formed by the bottom surface of the holding portion, and the elastic body placed in the rectangular hole is rectangular in shape and has the same top surface shape as the hole provided on the top surface of the clamping portion when viewed from above.

7. The press working apparatus according to any one of claims 1 to 6, wherein a protective part is provided on the upper surface side of the elastic body.

8. The press working apparatus according to any one of claims 1 to 6, wherein the elastic body is urethane.

9. The press working apparatus according to any one of claims 1 to 6, wherein the punch is provided with a through hole that spans the holding portion.

10. The press working apparatus according to any one of claims 1 to 6, wherein the punch is provided with two through holes above and below so as to sandwich the holding portion.

11. The press working apparatus according to any one of claims 1 to 6, wherein the punch is not provided with a through hole.

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