Processing machine including noise-reducing structure

Abstract: It is an object of the present invention to provide a silent structure of a drawing die capable of reducing, as small as possible, a noise generated when a die abuts against a thin plate on a blank holder of the drawing die. A silent structure of a drawing die comprising a punch, a blank holder fitted around the punch and vertically movably supported by a cushion pin, and a vertically movable die disposed such as to face the punch, a thin plate being placed on a blank holder which is moved up by the cushion pin, the die being lowered, thereby sandwiching the thin plate between the blank holder and the die for drawing the thin plate by the punch, wherein a lower die base plate is rotatably provided with a run-up lever for pushing the blank holder for allowing the latter to run up before the die collides against the thin plate, an operation cam for driving the run-up lever is disposed at a position on the die facing the run-up lever, and the die collides against the thin plate on the blank holder after the blank holder runs up.

Description: BACKGROUND OF THE INVENTION The present invention relates to a processing machine, including a noise-reducing structure used when a metal plate part such as an automobile or an electric home appliance is subjected to a drawing working. The background of the present invention will be explained based on the drawing die as an example. Fig.9 shows one example of a drawing die. The drawing die comprises a punch 101 located at a central position of the drawing die, a blank holder 103 fitted around the punch 101 and vertically movably supported by a cushion pin 102, and a die 104 disposed such as to oppose the punch 101 for vertical movement. The reference number 105 represents an air vent. A lower die 109 comprising the punch 101 and the blank holder 103 is fixed to a bolster 106 of a pressing machine, and an upper die 110 comprising the die 104 is fixed to a ram 107 of the pressing machine. The upper die 110 moves vertically by driving the pressing machine. The blank holder 103 is supported by the cushion pin 102, the cushion pin 102 is moved vertically by a cushion device of the pressing machine and with this movement, the blank holder 103 is also moved vertically. A drawing processing will be explained. First, the blank holder 103 is moved up to a position shown with phantom lines by the cushion pin 102. Next, a thin plate 108 is placed on the blank holder 103 and the punch 101 as shown with the phantom lines. Then, if the upper die 110 is lowered, the die 104 collides against the thin plate 108 on the blank holder 103 around the entire outer periphery of the punch 101 so that the thin plate 108 is sandwiched between the blank holder 103 and the die 104. Subsequently, if the upper die 110 is lowered, the thin plate 108 sandwiched between the blank holder 103 and the die 104 is drawn by the punch 101, and when the upper die 110 reaches the bottom dead center, the thin plate 108 is drawn into a work W. If the upper die 110 moves up, the blank holder 103 is moved up to the position shown with the phantom lines by the ascending force of the cushion pin 102, and the work W is removed from the punch 101. The die 104 of the upper die 110 is provided with the air vent 105 so that the negative pressure is prevented from being generated between the work W and the die 104 when the work W is dropped by its own weight. Alternatively, the work W may be moved downward by a push pin (not shown) biased by a spring, thereby removing the work W from the die 104. The work W removed from the pressing machine is transferred to the next step. In the above described drawing working, when the die 104 collides against the thin plate 108 placed on the blank holder 103, die 104 and the thin plate 108 over the entire outer peripheral surface of the punch 101 (i.e., the thin plate 108 on the blank holder 103) are directly contacted with each other concurrently and since the upward biasing pressure of the cushion 102 may be about 60 to 100 tons in some cases, a great noise of 110dB or higher is generated. Since a quiet environment is required in recent years, the noise of the drawing die is a social problem. In order to prevent the noise generated when the die collides against the thin plate on the blank holder of the drawing die, an attempt was made to provide an urethane rubber or a gas spring on the blank holder so that the die collided against the urethane rubber or the gas spring before colliding against the thin plate, thereby absorbing the impact force to reduce the noise. However, a sufficient effect could not be obtained. Further, so as to prevent the noise from being generated outside, there is an example that the pressing machine is surrounded by a soundproof wall. However, an opening must be formed in the soundproof wall for bringing in and out the work from and to the pressing machine and thus, the noise leaks from the opening. On the other hand, an operator working in the vicinity of the pressing machine surrounded by the soundproof wall is bothered by the great noise. Further, when the die collides against the thin plate on the blank holder, an attempt was made to reduce the cushion pressure only during a certain time period of initially lowering movement of the cushion pin. However, the cushion device of the pressing machine must be improved, which costs too expensive. Although the above description has been made based on the drawing die of the pressing die as the example, not only the noise of the drawing die, but also a noise of a pressing die sandwiching a thin plate or a work for machining or working is also a social problem. Further, in relation to the pressing die, a noise of a pressing machine having a pressing die, and noises of other processing machine for metal or resin are also regarded as a social problem. Since a quiet environment is required in recent years, it is required to reduce the noise generated by a processing machine, a pressing machine and a pressing die as small as possible. Especially in the drawing die, a great noise is generated when a die collides against a thin plate on a blank holder, and it is required to reduce this noise as small as possible. DE 36 23 188 C1 discloses a drawing press including a noise-reducing structure, the press comprising a punch, a blank holder fitted around the punch and vertically movably supported by cushion pins so as to face the punch between the stationary die supporting the punch and a vertically movable upper die. Lever arms are pivotally attached to the punch and extend through holes provided in the blank holder. Protruding arms attached to the upper die are adapted to engage with ends of the lever arms protruding from the blank holder when the upper die descends on the punch before the remainder of the upper die contacts the blank holder or the workpiece placed thereon. Upon contact of the protrusions of the upper die with the ends of the lever arms, the lever arms are pivoted to contact stoppers on the blank holder, thereby moving the blank holder before the upper die contacts the workpiece. EP-A-0 074 421 discloses a cushioning device for vertically biasing a blank holder which hydraulically accelerates the blank holder in the drawing direction, thereby reducing a relative velocity between the blank holder and the upper die descending on the blank holder. It is the object of the present invention to provide a processing machine including a noise-reducing structure and which has a cushioning device for vertically biasing the holder member, which processing machine provides noise-reduction by mechanical means. According to the present invention there is provided a processing machine including a noise-reducing structure as defined in claim 1. Preferred embodiments of the processing machine are defined in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS Figures 1 to 4 are provided for a better understanding of the functioning of a noise-reducing structure, and figures 6 to 8 show a concrete embodiment of the processing machine according to the invention. FIG. 1 is a vertical sectional view of an essential portion showing a state in which a run-up lever starts operating; FIG. 2 is a vertical sectional view of an essential portion showing a state in which a blank holder runs up and an upper die abuts against a thin plate on the blank holder; FIG. 3 is a vertical sectional view of an essential portion showing a state of the bottom dead center in which an upper die further lowered from the state shown in FIG. 2 and the drawing is completed; FIG. 4 is a vertical sectional view of a pressing die comprising a lower die provided with an operation cam, and the upper die provided with the run-up lever and a bracket; FIG. 5 is a graph comparing a case in which a silent structure is not mounted to the drawing die and a case in which a silent structure is mounted to the drawing die; FIG. 6 is a schematic view of an essential portion of an embodiment of the invention showing the state in which the run-up lever starts operating; FIG. 7 is a schematic view of an essential portion of an embodiment of the invention showing the state in which the blank holder runs up and abuts against the thin plate on the blank holder; FIG. 8 is a schematic view of an essential portion of an embodiment of the invention showing the state of the bottom dead center in which the upper die further lowered from the state shown in FIG. 7 and the drawing is completed; and FIG. 9 is a vertical sectional view of a conventional drawing die. EXAMPLES AND EMBODIMENT The present invention will be described in detail below based on examples and a concrete embodiment shown in the accompanying drawings. To facilitate the understanding, a noise-reducing structure of a drawing die will be explained first. Referring to FIG. 1, a lower die 1 comprises a punch 2, and a blank holder 4 vertically movably fitted around the punch 2 and supported by a cushion pin 3. The reference number 7 represents a lower die base plate integrally formed with an outer periphery of the punch 2. An upper die 5 comprises a die 6 disposed such as to be opposed to the punch 2. A run-up unit is mounted to the lower die base plate 7 and the die 6 for allowing the blank holder 4 to run up. One example thereof is illustrated. A substantially triangle run-up lever 11 for pushing the blank holder 4 for allowing the latter to run up is rotatably provided around a center shaft 13 of a bracket 12. The bracket 12 is fixed to the lower die base plate 7 by a bolt 14. The run-up lever 11 is rotatably provided around the center shaft 13 provided on the bracket 12 such that the run-up lever 11 pushes a flange 15 of the blank holder 4. A roller 16 is rotatably provided around a supporting shaft 17 on an upper portion of the run-up lever 11, and another roller 18 is rotatably provided around a supporting shaft 19 on the bracket 12 at a position opposed to the roller 16. An operation cam 20 is provided on the die 6 at a position between the rollers 16 and 18. This operation cam 20 is mounted to the die 6 through a supporting mount 21. The supporting mount 21 is fixed to the die 6 by a bolt 22, and the operation cam 20 is fixed to the supporting mount 21 by a bolt 23. The operation cam 20 and the supporting mount 21 may integrally be formed as one unit. The operation cam 20 has a cam surface 26. A portion of the cam surface 26 which first contacts with the roller 16 when the upper die 5 moves downward is formed with a low speed tilt angle α. The cam surface 26 is also formed with an intermediate speed tilt angle β which is continuously formed with the low speed tilt angle α. A connecting portion of the cam surface 26 connecting the low speed tilt angle α and the intermediate speed tilt angle β is arced for smoothly connecting both the angles α and β. Because of the difference in angle between the low speed tilt angle α and the intermediate speed tilt angle β of the operation cam 20, the lowering speeds of both the run-up lever 11 and the blank holder 4 can be controlled. Although the run-up unit having the run-up lever 11 and the operation cam 20 has been described above, the present invention should not be limited to this only, and the run-up unit may be mounted to the lower die base plate 7 and the die 6 for allowing the blank holder 4 to run up. For example, a push-down rod may be fixed to the die, and the blank holder may run up by the push-down rod. Next, the operation of this drawing die will be explained. A thin plate 24 is placed on the punch 2 and the blank holder 4. FIG. 1 shows a state in which the upper die 5 is lowered and the run-up lever 11 starts abutting against the flange 15 of the blank holder 4 by the operation cam 20. A run-up clearance H between the blank holder 4 and the die 6 shown in FIG. 1 is set to such a value that the blank holder 4 collides against the die 6 after run-up and a noise-reducing effect can sufficiently be obtained. FIG. 2 shows a state in which the run-up lever 11 allows the blank holder 4 to run up and the die 6 abuts against the thin plate 24 on the blank holder 4. The die 6 abuts against the thin plate 24 on the running blank holder 4 not against the thin plate 24 on the stationary blank holder 4. Since the die 6 does not collide against the stationary thin plate 24 but collides against the running thin plate 24, little noise is generated. Then, the upper die 5 is subsequently lowered and the drawing is completed at the bottom dead center shown in FIG.3, thereby forming the work W. When the upper die 5 moves upward, the work W is removed from the punch 2 by the blank holder 4. The die 6 is provided with an air vent 25 so that the negative pressure is prevented from being generated between the work W and the die 6 when the work W is dropped by its own weight. Alternatively, the work W may be moved out from the die 6 by a push-out pin (not shown) biased by a spring. If various parts having different size such as the run-up lever 11, the bracket 12, the operation cam 20 and the like (including the roller 16, the roller 18, the supporting shafts 17, 19 and the supporting mount 21) are prepared as standard parts, the existing drawing die can easily be changed to a drawing die having the noise-reducing structure. Although the run-up lever 11 and the bracket 12 are mounted to the lower die 1 and the operation cam 20 is mounted to the upper die 5 in the above-described example, even if the run-up lever 11 and the bracket 12 are mounted to the upper die 5 and the operation cam 20 is mounted to the lower die 1 as shown in FIG.4, the noise-reducing effect can be obtained. In this case, although a pad 31 is biased by a spring 32, since the pad collides against the work W after the pad runs up by the run-up lever 11 and the operation cam 20, the noise-reducing effect can be obtained. Further, in the present invention, when the thin plate is bent or is bent twice, i.e., when one end thereof is bent downward and the other end is bent upward, the pad runs up first and then the thin plate or the work is sandwiched, thereby obtaining the noise-reducing effect. With reference to FIG. 5, description will be made concerning an example comparing a case in which this noise-reducing structure is not mounted to the drawing die and a case in which the noise-reducing structure is mounted to the drawing die. In FIG. 5, the axis of abscissas shows time, and the axis of ordinates shows noise level (dB). A noise meter is disposed in front of a front surface of the pressing machine and the noise is continuously recorded in a recorder. In FIG. 5, a region A shows a case in which the noise-reducing structure was not mounted, and a region B shows a case in which the noise-reducing structure was mounted. When the noise-reducing structure was not mounted, the maximum noise level was 110dB. Although the maximum noise level is set at 110dB as shown in FIG. 5, since the noise meter was off-scale, it is estimated that the actual maximum noise level was 115 to 120dB. When the noise-reducing structure was mounted, the maximum noise level was about 95dB. In the illustrated example, the reduced amount of the noise level was 15dB, and it is estimated that the actual reduced amount was 20 to 25dB. FIG. 5 shows only one experiment result, but the experiment was repeated and the same data were obtained. Next, an embodiment in which the noise-reducing structure is mounted to a pressing machine is described with reference to the schematic views of FIGs. 6 to 8. The pressing machine comprises a stationary bed 41, a ram 42 which is vertically moved with respect to the bed 41, and a pad 44 of a cushion device 43 located below the bed 41 for biasing a cushion pin 3 upward. The ram 42 is vertically moved through a connecting rod 45, and an upper die 5 of a drawing die is fixed to a lower surface of the ram 42. The drawing die is the same as that described with reference to FIGs. 1 to 3. A lower die 1 is fixed to an upper surface of the stationary bed 41, a blank holder 4 fitted around a punch 2 is supported by the cushion pin 3, and a die 6 of the upper die 5 is disposed such as to oppose to the punch. The pad 44 is connected to a tip end of a piston rod 47 of a hydraulic pressure cylinder 46 of a cushion device 43. The cushion pin 3 is inserted to a guide hole 48 of the bed 41 and is positioned between the upper surface of the pad 44 and the lower surface of the blank holder 4, the pressure of the cushion device 43 is transmitted to the blank holder 4, a thin plate 24 placed on the blank holder 4 and the punch 2 is sandwiched between the blank holder 4 and the die 6 and is lowered and drawn by the punch 2. Length of the cushion pin 3 is determined in correspondence with the drawn depth of the work W. The reference number 49 represents a hollow columnar standing at the side of the pressing machine. An essential portion of the noise-reducing structure can be accommodated in the hollow columnar 49. It is needless to say that the noise-reducing structure can be provided outside the hollow columnar. A stationary member 50 is fixed in the hollow columnar 49 in the vicinity of the side portion of the pad 44. The pad 44 of the stationary member 50 is provided with a pressure-receiving portion 51. The ram is also formed at its side with a supporting portion 52 at a position facing the pressure-receiving portion and the stationary member 50. The pressure-receiving portion 51 and the pad 44 may be integrally formed, and other members may be fixed. The supporting member 52 and the ram 42 may be integrally formed, and other members may be fixed. The noise-reducing structure is provided with the supporting portion 52 and the stationary member 50, the pressure-receiving portion 51. This noise-reducing structure is the same as that described with reference to FIGs. 1 to 3 except that the length of an operation cam 20' is longer. The bracket 12 is fixed to the stationary member 50 by a bolt 14, the run-up lever 11 is rotatably provided around the center shaft 13, the run-up lever 11 can abut against an upper surface of the pressure-receiving portion 51, and the rollers 16, 18 are rotatably provided around the supporting shafts 17, 19 at the upper portions of the run-up lever 11 and the bracket 12, respectively. The operation cam 20' is disposed at position facing the rollers 16, 18, and is mounted to a supporting portion 52 through the supporting mount 21. The operation cam 20' is fixed to the supporting mount 21 by the bolt 23, and the supporting mount 21 is fixed to the supporting portion 52 by the bolt 24. The operation of the pressing machine will be explained next. The thin plate 24 is placed on the punch 2 and the blank holder 4. FIG. 6 shows a state in which the ram 42 is lowered and the run-up lever 11 starts abutting against the pressure-receiving portion 51 by the operation cam 20'. A run-up clearance H between the blank holder 4 and the die 6 shown in FIG. 6 is set to such a value that the blank holder 4 collides against the die 6 after run-up and a noise-reducing effect can sufficiently be obtained. The run-up lever 11 pushes the upper surface of the pressure-receiving portion 51 downward, thereby lowering the pad 44. With this movement, the cushion pin 3 and the blank holder 4 are moved downward, the blank holder 4 is allowed to run up downward, and the die 6 abuts against the thin plate 24 on the blank holder 4. FIG. 7 shows this state. A clearance exists between the upper surface of the pad 44 and the lower surface of the bed 41, the cushion pin 3 is moved downward by the distance of this clearance, and the blank holder 4 is also moved downward. The die 6 abuts against the thin plate 24 on the running blank holder 4 not against the thin plate 24 on the stationary blank holder 4. Since the die 6 does not collide against the stationary thin plate 24 but collides against the running thin plate 24, little noise is generated. Then, the upper die 5 is subsequently lowered and the drawing is completed at the bottom dead center shown in FIG. 8, thereby forming the work W. When the upper die 5 moves upward, the work W is removed from the punch 2 by the blank holder 4. The die 6 is provided with an air vent 25 so that the negative pressure is prevented from being generated between the work W and the die 6 when the work W is dropped by its own weight. Alternatively, the work W may be moved out from the die 6 by a push-out pin (not shown) biased by a spring. Since the operation cam 20' becomes long, it is preferable to provide a guide, and the length thereof must be determined in accordance with the height of the pressing die. It is preferable to prepare some operation cams having different length or to prepare an operation cam which is extendable mechanically or by air pressure or hydraulically. Although the noise-reducing structure of the pressing machine has been described above, the noise-reducing structure can also be applied to a processing machine of metal or resin.

Claims: A processing machine including a noise-reducing structure comprising: a stationary structure (2,41,50); a movable structure (6,42) vertically movable with respect to said stationary structure (2,41,50); a holder member (4) for supporting a workpiece (W), said holder member (4) being disposed vertically between said stationary structure (2,41,50) and said movable structure (6,42) and being vertically movable with respect to said stationary structure (2,41,50); a cushioning device (43,44,3) for vertically biasing said holder member (4) in a direction toward said movable structure (6,42), said cushioning device (43,44,3) including a cushioning pad (44) supporting said holder member (4); a run-up lever (11) pivotally attached to said stationary structure (2,41,50), said run-up lever (11) being engagable with a portion (51) of said cushioning pad (44); and an operation cam (20') fixed to said movable structure (6,42) so as to be engagable with said run-up lever (11) upon movement of said movable structure (6,42), thereby pivoting said run-up lever (11) into engagement with said portion (51) of said cushioning pad (44) and driving the same, thereby allowing said holder member (4) to run up before said movable structure (6,42) collides against said holder member (4) and/or the workpiece (W) on said holder member (4). The processing machine according to claim 1, wherein said processing machine is a pressing machine including a drawing die, said stationary structure (2,41,50) includes a bed (41) supporting a lower die (1) including punch (2), and said movable structure (6,42) includes an upper die (6) opposing said punch (2). The processing machine according to claim 2, wherein said holder member comprises a blank holder (4) fitted around said punch (2). The processing machine according to claim 2 or 3, wherein said cushioning pad (44) is located below said bed (41) and said cushioning device includes a cushion pin (3) passing through an aperture (48) in said bed (41) and extending between said holder member (4) and said cushion pad (44). The processing machine according to any one of claims 1 to 4, wherein said cushion pad (44) includes a pressure-receiving portion (51), said run-up lever (11) engaging said pressure-receiving portion (51) of said cushion pad (44). The processing machine according to any one of claims 1 to 5, wherein said operation cam (20') includes a cam surface (26) having a varying inclination angle for varying a speed of movement of said run-up lever (11) and said holder member (4). The processing machine according to claim 6, wherein said run-up lever (11) is pivotally supported by a support member (12) which includes a first roller (18), said run-up lever (11) includes a second roller (16), and said operation cam (20') is insertable between said first roller (18) and said second roller (16) such that said cam surface engages said second roller (16). The processing machine according to claim 7, wherein said support member comprises a bracket (12) attached to said stationary structure, said bracket (12) supporting a shaft (13) for providing pivotal movement of said run-up lever (11) with respect to said bracket (12).

Inventors: MATSUOKA MITSUO, MATSUOKA, MITSUO, Matsuoka, Mitsuo c/o JCM Co., Ltd.
Applicants: UMIX CO LTD, UMIX CO., LTD.
Application year: 1999
Main classification: B21D22
IPC codes: B21D24, B30B15, B21D22