PUNCH DIE SET

Abstract: A punch die set capable of easily making changes of a punch, a die and the like and improving a working precision. In this punch die set, a stripper inserted so as to be vertically slidable on the inner peripheral surface of a hollow sleeve (5) solidly secured to a set holder (4) through a bonding agent includes a hollow stripper body (6) and a stripper plate (7) provided with a punch through hole (8) and detachably mounted to the bottom open end of the stripper body (6). A die (2) is detachably mounted onto a die holder (20) solidly secured to the set holder (4) through a bonding agent. Positioning means are provided between the stripper body (6) and the stripper plate (7) and between the die (2) and the die holder (20), respectively.

Description: The invention is related a punch-die set according to the preamble of claim 1. Such a punch-die set is disclosed in the US-A-3,296,905 which specifies a turret type press punch having a punch mounted for vertical movement relative to the surface of a workpiece and a compressive type stripping unit mounted for partial movement with the punch. A sleeve is surrounding the punch and is attached to the punch so that the sleeve moves partially with the punch but is free to move within defined limits in vertical directions relative to the punch. A stripper has a flat disk supported by the sleeve on its downwardly directed surface by a plurality of magnets located within this surface. Compression spring means urge the sleeve in the direction of the work surface and are mounted concentrically to a portion of the press and are bearing on an upwardly directed surface of the sleeve. In the WO-A-89 119 32 is disclosed a composite punching tool which can be dismantled in three parts to make it possible to exchange the cutting part. The tool consists of the punching or cutting part, a guiding part and a shank part, which can all be separated from each other. The cutting part has a form disclosure which fits into a recess in the guiding part by means of which the cutting part can be centred and the cutting part can be immobilized in a given angle position of the cutting part which has a polygonal tenon with a threaded hole in which the shank part is threaded into with a thread bolt. It is an object of the invention to provide a punch-die set that facilitates the replacement of the punches and the dies without the necessity to take precautions for the automatic positioning of these parts and maintains the machining accuracy, the accurate positioning in the circumferential direction and the easy carrying-out of the replacement also after a change of different parts of the press punch. In accordance with the present invention, a punch-die set is provided with a stripper means which comprises a stripper plate holder formed into a hollow shape and a stripper plate detachably installed on the lower open end of said stripper plate holder; said stripper plate having a punch passing hole through which said punch is passed; said stripper plate holder and said stripper plate have first positioning means for positioning said stripper plate holder and said stripper plate in the circumferential direction; said stripper plate is detachably fitted to said stripper plate holder via said positioning means, said first positioning means in the circumferential direction comprises a plurality of positioning protrusions formed on the surface of said stripper plate and a plurality of positioning recesses formed on the the lower end face of said stripper plate holder corresponding to said protrusions and in that a die holder on which said die is placed is provided under a location at which said die is installed; said die and said die holder have second positioning means for positioning said die and said die holder in the circumeferential direction; and said die is detachably fitted to said die holder via said second positioning means. The invention will now be described by way of examples with reference to the followings drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram illustrating the construction of an embodiment of this invention. Fig. 2 is a cross-sectional view taken along line A-A shown in Fig. 1. Fig. 3 is a cross-sectional view taken along line B-B shown in Fig. 1. Fig. 4 is a perspective view of assistance in explaining the positioning means of this invention. Fig. 5 is a diagram illustrating the construction of a punch-die set of a conventional type. BACKGROUND OF THE INVENTION A punch-die set for piercing and blanking sheet metal (hereinafter referred to as a workpiece), such as sheet steel, as shown in Fig. 5 is well known. Fig. 5 is a longitudinal sectional view illustrating the essential part of a punch-die set of a conventional type. Reference numeral 41 in the figure refers to a punch; 42 to a die; 43 to a die fixing screw; 44 to a die locking pin; 45 to a workpiece; 46 to a set holder; 47 to a sleeve; 48 to a stripper; 49 to a punch passing hole; 50 to a stripper spring; 51 to a punch holder; 52 to a punch support; 53 to a parallelism reference plane; 54 to a punch-holder threaded portion; 55 to a parallelism reference jig plate; 56 to a punch pusher; 57 to a punch-pusher threaded portion; 58 to a punch head; 59 to a punch pad; and 60 to a punch-holder spring, respectively. In Fig. 5, the stripper 48 is formed into a bottomed hollow cylindrical shape, and supported on the set holder 46 via the stripper spring 50 in such a manner as to be vertically slidable in the sleeve 47 fixedly fitted to the set holder 46 via adhesive. On the bottom of the stripper 48 formed is a punch passing hole 49 through which the punch 41 is passed. The punch holder 51 is formed into a bottomed hollow cylindrical shape, and constructed so as to be vertically slidably inserted into the stripper 48. On the bottom of the punch holder 51 formed is the punch support 52 to which the punch 41 is fixedly fitted by bonding, crimping or other means. The punch holder 51 has the parallelism reference plane 53 formed by machining part of the outer circumferential surface thereof so as to ensure that the parallelism reference plane 53 slidably comes in contact with the end face of the parallelism reference jig plate 55 provided on the set holder 46. With this arrangement, the rotation of the punch holder 51, that is, the punch 41 is controlled. Furthermore, the punch-holder threaded portion 54 is provided in the form of female threads on the inner circumferential surface at the upper end of the punch holder 51, and engaged with the punch-pusher threaded portion 57, which is provided in the form of male threads on the punch pusher 56. Thus, the punch pusher 56 is integrally connected to the punch holder 51 by screwing the punch pusher threaded portion 57 to the punch-holder threaded portion 54. The punch pusher 56 is connected to the punch holder 51 in such a manner as to push the punch pad 59. The punch pad 59 prevents the punch 41 from coming off upwards, and adjusts the punching stroke by adjusting the thickness thereof properly. In addition, the punch-holder spring 60 is provided between the punch pusher 56 and the stripper 48. The die 42 is installed at a location facing the punch 41 of the set holder 46. The die 42 is fixedly fitted to the set holder 46 by the die fixing screw 43, and is prevented from being rotated by the die locking pin 44. In the foregoing, the construction of the conventional type of punch-die set as shown in Fig. 5 has been described. In the following, the operation of the punch-die set of the conventional type will be described. The punch-die set is set an a press table, for example, and the punch head 58 is pushed downwards by a press or cylinder ram (not shown). As the punch head 58 is pushed downwards, the stripper spring 50 is first deflected and the stripper 48 is pushed down until the bottom surface of the stripper 48 comes in contact with the workpiece 55 because the resiliency of the stripper spring 50 is smaller than the resiliency of the punch-holder spring 60. Then, the punch-holder spring 60 is deflected, and thereby the punch pusher 56 and the punch holder 51 are pushed down to a predetermined stroke. Thus, the workpiece 45 placed on the die 42 is pierced or blanked by the punch 41. In general, the shape of piercing or blanking with a punch-die set is not always kept constant, but may usually be varied as necessary. In such a case, the punch and die used in the punch-die set have to be changed to a shape corresponding to the required piercing or blanking shape. At the same time, the shape of the punch passing hole provided on the stripper also has to be changed. In the prior art shown in Fig. 5, not only the punch 41 and the die 42 but also the stripper 48 having the punch passing hole 49 have to be changed to cope with changes in the piercing or blanking shape. Although the replacement of the punch 41 and the die 42 is not so difficult, the replacement of the stripper 48 is extremely difficult, increasing the required manhours for the replacement. The stripper 48 not only requires large manhours for the replacement, but also is difficult to manufacture, requiring considerable manufacturing manhours. Furthermore, since the punch passing hole 49 provided on the bottom of the stripper 48 has to be formed in accordance with the location and shape of the punch 41, it is not easy to machine the punch passing hole 49, Moreover, the vertical positions of the punch 41, the punch passing hole 49 and the die 42 and the horizontal angular positions thereof must be accurately aligned to improve machining accuracy. In the Prior art shown in Fig. 5, however, the die 42 is fixedly fitted in such a manner that the die 42 is forced onto the set holder 46 by the die fixing screw 43 while setting the angular position thereof in the horizontal direction by the die locking pin 44. Although it is seemed that this accurately positions vertical and horizontal angular positions of these components, it is in fact difficult to accurately position them vertically or in horizontal angular direction by merely pushing the die 42 by the die fixing screw 43 to the set holder 46 because of the presence of small gaps among the die 42, the die fixing screw 43 and the set holder 46. Additional fine adjustment is therefore required, leading to increased replacement operations. PREFERRED EMBODIMENTS OF THIS INVENTION Fig. 1 is a diagram illustrating the construction of an embodiment of this invention. Fig. 2 is a cross-sectional view taken along line A-A shown in Fig. 1. Fig. 3 is a cross-sectional view taken along line B-B in Fig. 1. Fig. 4 is a perspective view of assistance in explaining the positioning means of this invention. In Fig. 1, reference numeral 1 refers to a punch; 2 to a die; 3 to a workpiece; 4 to a set holder; 5 to a sleeve; 6 to a stripper plate holder; 7 to a stripper plate; 8 to a punch passing hole; 9 to a stripper parallelism reference plane; 10 and 11 to springs; 12 to a punch holder, 13 to a punch support; 14 to punch plate; 15 to a punch parallelism reference plane; 16 to a punch head; 17 and 18 to a stroke adjusting screw; 19 to a parallelism reference jig plate; 20 to a die holder; and 21 to a die pad, respectively. In the embodiment shown in Fig. 1, the stripper plate holder 6 is formed into a hollow cylindrical shape, and adapted to be vertically slidable in the sleeve 5 that is fixedly fitted to the set holder 4 by means of adhesive. The stripper plate 7 having the punch passing hole 8 through which the punch 1 is passed is detachably installed on the lower open end of the stripper plate holder 6. The stripper plate holder 6 has the stripper parallelism reference plane 9 formed by machining part of the stripper plate holder 6 to match with the parallelism reference jig plate 19, which will be described later, and is constructed so that the stripper parallelism reference plane 9 slidably comes in contact with the end face of the parallelism reference jig plate 19 provided on the set holder 4 to control the rotation of the stripper plate holder 6. The manner in which the rotation of the stripper plate holder 6 is controlled will be described in more detail later, referring to Fig. 3, and the manner in which the stripper plate 7 is installed will be described in detail, referring to Figs. 2 and 4. The stripper plate holder 6 is supported on the set holder via the stripper springs 10. The punch holder 12 is constructed so that the punch holder 12 is vertically slidably inserted in the stripper plate holder 6, and incorporates the punch support 13 on the bottom of which the punch 1 is detachably installed by adhesive or crimping or other means. The punch support 13 is detachably supported by being pushed by the punch plate 14. The punch holder 12 has the punch parallelism reference plane 15 formed by machining part of the outer circumferential surface thereof; the punch parallelism reference plane 15 being constructed so as to vertically slidably come in contact with the end face of the parallelism reference jig plate 19 to control the rotation of the punch holder 12, that is, the punch 1. The manner in which the rotation of the punch holder 12 is controlled will be in detail later, referring to Fig. 3. Furthermore, the punch holder 12 has the punch head 16 formed by protruding on the upper end thereof, to which the stroke adjusting screws 17 and 18 for adjusting the punching stroke are screwed. The punch-holder spring 11 is interposed between the punch holder 12 and the stripper plate holder 6. The die 2 is detachably installed on the die holder 20 embedded in the set holder 4 via the die pad 21 in such a manner as to face the punch 1 and the stripper plate 7. The manner in which the die 2 is installed will be described in detail later. In the foregoing, the construction of the punch-die set of this invention shown in Fig. 1 has been described. Now, the construction of the essential part characterizing this invention will be described in detail in the following, referring to Figs. 2 through 4. Fig. 2 is a cross-sectional view taken along line A-A shown in Fig. 1, which is of assistance in explaining the manner in which the stripper plate 7 is installed. Fig. 4 is a perspective view of assistance in explaining the positioning means (positioning protrusions and positioning recesses, which will be described later). Numeral 22 in the figure refers to positioning protrusions; 23 to positioning recesses; 24 to a fixing screws; 25 to fixing screw holes, respectively. Other numerals correspond to like numerals in Fig. 1. In Fig. 2, the positioning protrusions 22 is formed by providing protrusions on the surface of the stripper plate 7 mating with the stripper proper 6. The positioning recesses 23 are formed on the lower end face of the stripper plate holder 6 corresponding to the positioning protrusions 22. These positioning protrusions 22 and the positioning recesses 23 are formed by using as references the Y axis parallel with the aforementioned stripper parallelism reference plane 9 and the punch parallelism reference plane 15 (shown in Fig. 3), and the X axis orthogonally intersecting with the Y axis. The punch passing hole 8 formed on the stripper plate 7 is machined using as references the X and Y axes. The stripper plate 7 is installed on the stripper plate holder 6 by the fixing screws 24 after the positioning protrusions 22 are engaged with the positioning recesses 23. In this way, the punch passing hole 8, the positioning protrusions 22, the positioning recesses 23 are machined using as references the X and Y axes. Consequently, when changing the stripper plate 7 with a new one, the punch passing hole 8 corresponding to the punch 1 is automatically positioned. In Figs. 2 and 4, the positioning protrusions are provided on the stripper plate 7, and the positioning recesses are provided on the stripper plate holder 6. Needles to say, the positioning protrusions may be provided on the stripper plate holder 6 and the positioning recesses on the stripper plate 7. In the following, these positioning protrusions and the positioning recesses are called positioning means. Though not shown in the figure, the positioning means are provided between the die 2 and the die holder 20, and between the lower end face of the punch holder 12 and the punch plate 14. As a result, the die 2 and the punch plate 14 can also be replaced easily and with high accuracy, as noted above. Fig. 3 is a cross-sectional view taken along line B-B shown in Fig. 1 of assistance in explaining the manner in which the rotation of the stripper plate holder 6 and the punch holder 12 is controlled. Like numerals in the figure correspond to those used in Fig. 1. In Fig. 3, the stripper parallelism reference plane 9 formed on the stripper plate holder 6 and the punch parallelism reference plane 15 formed on the punch holder 12 are constructed so as to slidably come in contact with the end face of the parallelism reference jig plate 19 provided on the set holder 4. As a result, the stripper plate holder 6 or the punch holder 12 is prevented from being rotated even during its vertical movement. Now, the method of fixing the sleeve 5 and the die holder 20 will be described. The sleeve 5 and the die holder 20 are fixedly fitted to the sot holder 4. If the fixing positions of the sleeve 5 and the die holder 20 are not accurate, high-precision machining is not possible. In this invention, therefore, the sleeve 5 and the die holder 20 are accurately positioned using a fixing jig (not shown) in the following manner. The fixing jig has such an outside diameter that the jig is vertically slidable with the inner circumferential surface of the sleeve 5, and is of a cylindrical or columnar shape having on the lower end face thereof a positioning means corresponding to the positioning means provided on the die holder 20. The fixing jig is inserted into the sleeve 5 downwards from above until the jig reaches the die holder 20 in the state where those other than the sleeve 5 and the die holder 20 are not installed, causing the positioning means of the fixing jig to match with the positioning means of the die holder 20. The sleeve 5 and the die holder 20 are fixed at accurate positions by filling and curing adhesive in the gap provided in advance between the sleeve 5 and the outer circumferential surface of the die holder 20 and the set holder 4. In the foregoing, description has been made about the construction of the punch-die set of this invention. Now, the operation of the embodiment shown in Fig. 1 will be described in the following. The punch-die set is set on a press table, for example, and the punch holder 12 is pushed downwards by exerting a pushing force to the stroke adjusting screws 17 and 18 by a press or cylinder ram (not shown). As the punch holder 12 is pushed downwards, the stripper spring 10 is first deflected, and then the entire punch mechanism is pushed down until the stripper plate 7 comes in contact with the workpiece 3 because the resiliency of the stripper spring 10 is smaller than the resiliency of the punch-holder spring 11. Then, the punch-holder sprint 11 is deflected, and the punch 1, together with the punch holder 12, is pushed down by a predetermined stroke. As a result, the workpiece 3 placed on the die 2 is pierced or blanked by the punch 1. Moreover, if a change has to be made in the machining shape, etc. high-precision machining can be maintained merely by changing the punch 1, the stripper plate 7 and the die 2, together with the punch support 13, the punch plate 14, as noted earlier. Needless to say, the punching stroke can be adjusted by the stroke adjusting screws 17 and 18 as necessary. In this invention, since the stripper means comprises a stripper plate holder formed into a hollow cylindrical shape, and a stripper plate detachably installed on the lower open end of the stripper plate holder and having a punch passing hole through which the punch is passed, the stripper plate holder need not be replaced during the replacement of the punch. This makes the replacement of the punch easy. Furthermore, since positioning means are provided between the stripper plate holder and the stripper plate between the die and the die holder, and between the punch holder and the punch plate, positioning in the circumferential direction can be accurately and easily carried out during the replacement of punches and dies, and machining accuracy can also be improved. As set forth above, this invention makes it possible to provide a punch-die set, in which punches and dies can be easily changed with changes in machining shape, etc., and machining accuracy can be improved. As described above, the punch-die set according to this invention is useful as a punch-die set used for piercing and blanking sheet metal by installing on a punching press, etc., and is particularly suitable as a punch-die set in which punches and dies can be easily changed and accurately positioned.

Claims: A punch-die set comprising at least a stripper means of cylindrical shape and adapted so as to be vertically slidable with respect to a sleeve (5); a punch holder (12) adapted so as to be vertically slidable with respect to the inside surface of said sleeve, a punch (1) installed on the lower end of said punch holder (12) by a punch plate (14) and a die (2) disposed in such a manner as to face said punch via a gap for inserting a workpiece (3), said stripper means comprises a stripper plate holder (6) formed into a hollow shape and a stripper plate (7) detachably installed on the lower open end of said stripper plate holder (6); said stripper plate (7) having a punch passing hole (8) through which said punch (1) is passed; said stripper plate holder (6) and said stripper plate (7) have first positioning means (22, 23) for positioning said stripper plate holder (6) and said stripper plate (7) in the circumferential direction; said stripper plate is detachably fitted to said stripper plate holder via said first positioning means, characterized in that said first positioning means in the circumferential direction comprises a plurality of positioning protrusions (22) formed on the surface of said stripper plate (7) and a plurality of positioning recesses (23) formed on the lower end face of said stripper plate holder (6) corresponding to said protrusions (22) and in that a die holder (20) on which said die (2) is placed is provided under a location at which said die (2) is installed; said die and said die holder have second positioning means for positioning said die and said die holder in the circumferential direction; and said die is detachably fitted to said die holder via said second positioning means. A punch-die set according to Claim 1 wherein said second positioning means for positioning said die (2) and said die holder (20) comprises a plurality of positioning protrusions and a plurality of positioning recesses corresponding to said protrusions. A punch-die set as set forth in Claim 1 or 2 wherein said punch holder (12) and said punch plate (14) provided at the lower end face of said punch holder have third positioning means for positioning said punch holder and said punch plate (14) in the circumferential direction; and said punch plate is detachably fitted to said punch holder via said positioning means. A punch-die set according to Claim 3 wherein said third positioning means for positioning said punch holder (12) and said punch plate (14) comprises a plurality of positioning protrusions and a plurality of positioning recesses corresponding to said protrusions.

Inventors: FUTAMURA SHOJI, FUTAMURA, SHOJI
Applicants: INST TECH PRECISION ENG, INSTITUTE OF TECHNOLOGY PRECISION ELECTRICAL DISCHARGE WORK'S
Application year: 1992
Main classification: B21D28
IPC codes: B21D28, B21D45