Punch and die set having improved slug management system

Abstract: A system for controlling slugs (10) in a stamping and forming machine has a slug stripper (32) for stripping slugs from the end (13) of the punch (11) and slug supporting bars (78, 80) which support slugs at their edges as they move through a passageway (82). The slug stripper (32) is mounted in the facial surface (18) of the die plate (14) and has an end portion (56) which extends partially over the die opening (44). When the punch (11) descends and punches a notch in the strip material (2), the slug (10) which is produced moves the stripper (32) to a retracted position. When the slug (10) is moved past the end of the slug stripper (32), the slug stripper returns to its normal position so that on the return stroke of the punch the slug will be removed by the end portion (58) of the stripper. The slugs are maintained in a stack in the slug passageway (82) by the opposed supporting bars (78,80) which are resiliently biased against opposite edges of the slugs.

Description: This invention relates to a punch assembly and to a die assembly according to the preamble of claim 1. U.S. Patents 4,497,196 on which the preamble of claim 1 is based, 4,819,476, and 4,809,576 show features of a type of stamping and forming machine in which the present invention can be used. These U.S. patents are hereby incorporated by reference. When an opening is formed in a strip of material by a conventional punch press, a slug of scrap material which conforms in shape to the shape of the opening is produced during each operating cycle and these slugs must be removed from the vicinity of the punch and die as they are produced. When the punching operation is carried out with a conventional press having a punch on a reciprocable ram and a fixed die, with the punch and die extending vertically, the slugs produced are pushed into a passageway from the die opening and the passageway extends vertically to a suitable receptacle for the scrap slugs. If the slugs are relatively heavy, they will fall by gravity through the passageway, which can be made oversized relative to the slugs, and disposal of the slugs does not present any serious problems. However, if the slugs are relatively small and have a very slight mass, they will have a tendency to adhere to the sides of the passageway and bridge across the passageway thereby blocking it against the passage of additional slugs. As a result, a large number of compacted slugs will build up in the passageway beneath the die opening. This condition can result in the entire passageway being filled with slugs so that at some point, the punch may be broken as it attempts to push a recently-produced slug onto the compacted mass of slugs in the passageway and in the die opening. The problem of compacting of the slugs is complicated if the opening in the strip material is formed as a notch in the edge of the material rather than as a centrally located hole in the material. When the strip is notched in a punching operation, the slugs will be of varying size from one reel of coiled strip material to another for the reason that the width of the strip will vary from one reel to another within the tolerance limits which are set for a particular strip specification. For example, the width of metal strip used in a stamping operation may vary as much as ± 0.002 inches (0.O51mm) so that the overall variation in width as between the narrowest and the widest strips will be 0.004 inches (0.101mm). Since the slugs are produced from the edge of the strip, the size of the slugs will similarly vary from one reel of material to another. The passageway must be large enough to accommodate the largest slugs which will be produced plus a slight clearance so that the largest slugs can move freely through the passageway. If, however, relatively small slugs are being produced from relatively narrow strip material, the possibility of jamming or packing of the slugs in the passageway is increased. In the discussion presented above, it is assumed that the press is vertically mounted and that the slugs will fall under the influence of gravity. U.S. Patent 4,497,196 shows a stamping and forming machine in which the punch and die assemblies are mounted horizontally for a relative movement toward and away from each other. In machines of this type, the slug passageway must extend horizontally through the die assembly and the influence of gravity is not available for slug removal purposes. A further problem which is sometimes encountered in punching operations is that of adherence of a slug to the punch when the punch returns to its normal position after carrying out a punching operation. If the slugs are of small mass and have a thin film of lubricant on them, the lubricant on the slugs and on the punch may cause the slugs to adhere to the punch due to surface tension effects. If such adherence occurs, during the next operation cycle, the punch will move the adhered slug against the stock material and encounter increased forces as it moves downwardly and pushes the slug against the stock which is positioned over the die opening. This condition can cause breakage of the punch and in any event, requires that the press be stopped and the jam in the punch be cleared. The problems of slug adherence to the punch and compacting of the slugs in the slug passageway can be obviated in a conventional press by providing a suction system in the slug passageway so that the slugs will be drawn by a flow of air through the slug passageway to the outlet of the slug passageway. These suctions systems are effective; however, they occupy space in the die assembly and require compressed air lines in regions of the press where compressed air is otherwise not required. Also, it is impractical to provide suction systems in stamping and forming machines of the type described in U.S. Patent 4,497,196. The present invention is directed to the achievement of an improved slug removal and controlling system which obviates the above problems encountered in the management of control of slugs in a stamping and forming machine. The present invention consists in a punch assembly and a die assembly as defined in claim 1. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which:- Figure 1 is a perspective view of the parts exploded from each other of a punch and die set in accordance with the embodiment of the invention. Figure 2 is a view similar to Figure 1 but with the parts partially assembled. Figure 3 is a view showing the die assembly fully assembled. Figure 4 is an exploded perspective view showing the die insert of the die assembly. Figure 5 is a sectional view looking in the direction of arrows 5-5 of Figure 3. Figures 6 and 7 are views similar to Figure 5 showing the positions of the punch at different stages of the operating cycle. Figure 8 is a sectional view looking in the direction of the arrows 8-8 of Figure 6. Figure 9 is a view looking in the direction of the arrows 9-9 of Figure 6. Figure 10 is a plan view of a strip of material having notches punched in one side edge thereof. Figures 11 and 12 show the slugs which are produced from the strip as a result of the punching operation. Figures 10-12 illustrate the conditions which can give rise to serious problems of slug packing or slug jamming in the slug passageway of a stamping and forming machine. Figure 10 shows a strip 2 of material having parallel side edges 4, 6. Notches 8 have been punched from the side edge 6 and each notch, when formed, produces a slug 10 which is sheared from the side edge and pushed from the material through the die opening to the slug passageway. The strip material 2 will have a nominal width between the edges 4 and 6; however, from one reel of material to another, the actual width will vary within the tolerance limits which are specified for the particular strip material being used. For example, a specification will require that a strip be of the nominal width ± 0.002 inches (0.O51mm). If the side edge 6 is taken as a side edge of a strip of minimum width, then the side edge 6′ can be assumed to be the side edge of a maximum width strip. When the side edge is at 6′ rather than at 6, the slug 10′ shown in Figure 12 will be considerably larger than the slug 10 shown in Figure 11. The relative width of the strip and sizes of the slugs 10, 10′ are greatly exaggerated in Figures 10-12 for purposes of illustration. However, a difference of even 0.004 inches (0.1O1mm) or less between the smallest and the largest of the slugs produced gives rise to vexatious problems of die design. The passageway through which the slugs must pass must be large enough to accommodate the largest slug produced, the slug 10′ with a slight clearance; as a result, the smallest slug produced, the slug 10, will have a relatively generous clearance in the passageway. The smaller slugs particularly may tumble and become compacted in the passageway and damage to the press can result as explained above. The practice of the present invention avoids compacting of slugs in the passageway of the die assembly as well as the adherence of slugs to the end of the punch. A punch 11 and die assembly 12 are shown in Figures 1-3. The punch 11 will extend from a punch assembly which is not specifically shown but which may be of the type described in detail in the above-identified U.S. Patent 4,819,476. A triangular groove or recess 15 extends from the end 13 of the punch partially along its length for the reception of a portion of the slug stripper as described below. The die assembly 12 comprises a die plate 14 and a die backup plate 16. The die plate has a facial surface 18 which is opposed to the punch and a reverse surface 20 which is against the upper surface 22, as viewed in Figure 1, of the backup plate 16. A square hole 24 (Figure 4) extends through the die plate and an irregularly shaped hole 26 extends through the backup plate 16. A die insert assembly 28 shown in Figure 4 is mounted in the square hole 24 and comprises a die insert block 30, a slug stripper 32, and a retaining block 34. The insert 30 has an upwardly facing surface 36 and a surface 38 which is below the upper surface 36, a side surface 37, and a projecting lip 42. The die opening 44 extends downwardly from the surface 36 and a slot 46 is provided which opens into the die opening from the side surface 37, the side walls 48 of this slot being convergent. The slug stripper 32 is a machined block having a top surface 52, sides 54, and a triangular projection 56 having convergent side surfaces 58. The edge or apex 61 of the projection 56 slopes rightwardly as viewed in Figures 5-7 for reasons explained below. The top surface 60 of this triangular portion is normally above the facial surface 18 of the die block 14 as shown in Figure 5 and the underside 62 of the triangular projection is against the upper end of a projection 118 of a slug support 78. A transverse recess 64 extends across the slug stripper and receives the connecting neck 72 which extends between two sections of the retainer 34. The two sections of the retaining block 34 define a gap 70 on the underside of this retaining block in which the slug stripper 32 is contained. As shown in Figure 5, the neck 72 has a width which is narrower than the width of the recess 64 so that the slug stripper 32 can move horizontally leftwardly from the position shown in Figure 5. Slug stripper 32 is resiliently biased to the position shown in Figure 5 by a coil spring 76 which is contained in a bore 74 that extends inwardly from the lefthand surface of the slug stripper. The block 34 is held in position on the die block by means of a fastener which extends through a threaded opening 66 in the retaining block and into an opening 68 in the die insert block. A recess is provided as shown at 77, Figure 5, for the ledge 42 of the die block and in cooperation with the ledge 42, retains the die block securely in its position on the backup plate 16. The slugs are supported in parallel planes in an orderly stack in the slug passageway 82 by first and second slug supporting bars 78, 80, Figures 1, 5, and 8. The first slug supporting bar 78 has a generally rectangular cross-section having one surface 84 which is opposed to a first surface 86 of the opening 26 that extends through the backup plate 16. The second slug supporting bar 80 is contained in the opposite or second surface 87 as will be described below. The first slug supporting bar 78 is pivotally supported for limited arcuate movement at its lower end by the edge of a triangular projection 88 which bears against the surface 86. The first slug support bar is resiliently biased in a clockwise direction as viewed in Figure 5 by a spring 92 which extends through a bore 94 in the backup plate, the end of the spring being received in a recess 90 in the surface 84. Spring 92 is retained in position by a plug 96. An additional bore 98 extends through the backup plate to the opening 26 and is counterbored to provide a shoulder as shown at 100. A fastener having an enlarged head 102 is positioned in the counter bore and the shank portion of the fastener 104 extends through the reduced diameter bore section 98. The end of this fastener is threaded as shown at 106 into the first slug supporting bar 78. The arcuate movement of the first slug supporting bar is limited by the enlarged head 102 of this fastener. The first slug supporting bar can be swung leftwardly by a slight distance from the position of Figure 5 but cannot move rightwardly or clockwise beyond the position of Figure 5. The slugs are supported in the passageway by a triangular projection 108, Figure 8, which extends from the rightwardly facing surface 109 of the slug supporting bar. The edge 110 of this projection bears against the edges of the slugs 10 contained in the passageway and urges the slugs against the surfaces 114, 112 and the inner surface 116 of the passageway 82. The triangular projection 108 of the first slug supporting bar projects above the upper end 117 of the rectangular portion as shown at and into the die opening 44. This projection 118 serves to engage the edge portions of slugs which are in the die opening and which have not yet entered the passageway 82. The slugs in the die opening are pushed against the opposite surface 119 of the opening and are thereby maintained in an orderly stack. The second slug supporting bar 80 is generally channel-shaped having a web 122 and sides 124. A rib 120 extends from the web for engagement with the edges of the slugs which are on the opposite sides of the slugs as those edges which are engaged by the edge 110. The channel-shaped portion of the second slug supporting bar is received in a rectangular opening 126 which is adjacent to the passageway 82 and the rib 120 projects through a slot 121 which extends from the side surface 116 of the passageway to the opening 126. A sinuous spring 130 is positioned in the opening 126 and biases the slug supporting bar 80 leftwardly as viewed in Figures 8 so that it will normally project beyond the surface 116 in Figure 8. The function of the second slug supporting bar 80 is shown in Figures 8 and 9. Since the first slug supporting bar 78 is pivoted at its lower end as viewed in the drawing, the apex 110 will not always be vertical but will depart from a vertical orientation by an amount which will depend upon the size of the slugs in the passageway. If small slugs are being produced as shown at 10, the first slug supporting bar will be at the limit of its clockwise travel as viewed in Figure 5. The passageway 82 will, as a result, be relatively wider in its lower portions than in its upper portions. In other words, because of the fact that the first slug supporting bar is slanted to the right in Figure 5, the apex 110 will be closer to the side 87 at the upper end of bar 78 than at the bottom of bar 78. The slugs, however, will be of uniform size during a particular run of the press. The slugs would therefore be loosely received in passageway at the lower end thereof if the second slug supporting bar were not provided. The second bar compensates for the slope of the first supporting bar and the distance between the apex 110 and the rib will remain constant along the length of the passageway. As shown in Figure 9, the rib projects past surface 116 in the lower end of passageway 82 and does not project past surface 116 in Figure 8. During continuous operation of a stamping and forming machine in which the invention is installed, the slugs produced are controlled and managed as follows. At the beginning of an operating cycle, the end 13 of the punch 11 will be spaced from the facial surface of the die plate as shown in Figure 5 and strip material, which has been recently fed, will be positioned as shown partially extending over the die opening. The strip material 2 will have its edge adjacent the sloping apex 61 of the triangular projection 56 of the slug stripper. As the punch descends to the position of Figure 6, a slug 10 is punched from the edge portion of the material 2 and pushed into the die opening. As the slug moves downwardly, it engages the inclined apex 61 on the triangular projection of the slug stripper and moves the slug stripper a slight distance to the left as viewed in Figure 5. The slug is thereby permitted to pass the underside 62 of the slug stripper and move into the die opening. After the slug has been moved past the surface 62, the slug stripper returns to its normal position under the influence of spring 76 and a portion of the apex enters the V-slot 15. If, by any chance, the slug should adhere to the end of the punch, the underside 62 of the apex will engage the slug as it is pulled upwardly and strip it from the end 13 of the punch 11 so that it will remain in the die opening. The slugs which are in the die opening will be maintained in a neat, orderly stack in planes which are substantially parallel to the facial surface of the die plate. Such maintenance of the slugs is achieved by virtue of the fact that the first slug support bar 78 is biased in a slight clockwise direction as viewed in Figures 6 and 8 so that the apex of the extension 118 bears against the edges of the slugs and confines them thereby preventing them from assuming any orientation other than that shown in the drawing. During successive operating cycles, the stack of slugs is built up and moves into the passageway 82. The upper end of the rib of the second slug supporting bar is slightly chamfered as shown in Figure 5 so that no difficulty will be encountered when the slugs pass from the die opening into passageway 82. During passage through the passageway 82, the slugs are urged rightwardly by the apex 110 of the triangular projection of the first slug supporting bar and against the surface of the rib 120 of the second slug supporting bar 80. The second slug supporting bar is biased lightly leftwardly, as viewed in Figure 5, so that if the slugs are stacked entirely through the passageway, the edges will always be engaged by the rib of the second slug supporting bar. The second slug supporting bar is desirable for the reason that the upper portion 118 of the triangular projection pushes the edges of the slugs in the die opening against a fixed wall, the wall 119 of the die opening as shown in Figure 6. The upper portion 118 will support the slugs against the wall of the die opening regardless of whether the slugs are of minimum size as shown in Figure 11 or of maximum size as shown in Figure 12. The portion of the triangular projection which extends through the passageway 82 must also accommodate slugs of the varying sizes shown in Figures 11 and 12 and the apex of the triangular projection will not always be perfectly vertical; in other words, the first slug supporting bar will be moved arcuately to a slight extent if the slugs are relatively small as shown in Figure 12 and its normal position will be displaced in a counter-clockwise direction for relatively large slugs. The passageway 82 must accommodate slugs at both extremes of the dimensional range and this is accomplished by the resiliently biased second slug supporting bar. This bar will yield for relatively larger slugs more than will be the case for smaller slugs. This embodiment can be incorporated into a wide variety of stamping and forming machines, including machines of the conventional type in which the die assembly is fixed and the punch assembly reciprocates vertically towards and away from the die assembly. The invention is particularly useful in stamping and forming machines of the type shown in the above-identified U.S. Patent 4,497,196 for the reason that machines of this type have very compact die assemblies and it is impractical to provide suction systems for removing the slugs. Furthermore, since these machines are horizontal rather than vertical, the forces of gravity are not present to assist in slug removal. In the accompanying drawing, the punch is shown as being reciprocable in a vertical direction; however, it is to be understood that the punch in a machine of the type referred to above will be moving horizontally.

Claims: A punch assembly and a die assembly (12) which are intended for mounting in a press for punching notches (8) in one edge (6) of a strip (2) of material which is intermittently fed along a strip feed path, the die assembly (12) having a facial surface (18) and having a die opening (44) extending into the facial surface (18), a slug receiving passageway (82) extending through the die assembly (12) from the die opening (44) to a slug outlet, the passageway (82) being in alignment with the die opening (44), the punch assembly having a punch (11) extending therefrom, the punch (11) having a free end (13) which is dimensioned to be received in the die opening (44), the punch (11) and the die assembly (12) being relatively movable towards and away from each other, the strip feed path extending between the punch and die assemblies (11,12) and partially over the die opening (44) whereby upon relative movement of the punch (11) and the die assembly (12) towards and away from each other during a non-feeding interval of the strip material (2), a slug (10,10') will be punched from the one edge (6,6') of the strip (2) by the free end (13) of the punch (11) and will be pushed into and through the die opening (44) and through the passageway (82) to the outlet, and wherein a slug stripper (32) is provided for ensuring that a slug (10,10') does not adhere to the free end (13) of the punch (11), characterised in that: the punch assembly is arranged in opposed relationship to the die assembly (12), the punch and die assemblies (11,12) being reciprocable towards and away from each other between open and closed positions, the slug stripper (32) being mounted in the facial surface (18) of the die assembly (12) and being resiliently biased to a normal position in which an end portion (56) of the slug stripper (32) extends partially across the die opening (44), the slug stripper (32) being retractable to a retracted position and the punch (11) having a recess (15) therein which is located and dimensioned to receive the end portion (56) of the slug stripper (32), whereby the slug stripper (32) serves to strip from the free end (13) of the punch (11) any, slugs (10,10') which may adhere thereto when the punch assembly returns to its open position during continuous operation of the press; and in that slug supporting means (78,80) provided in the passageway (82) and extending from a location adjacent to the die opening (44) through the passageway (82) towards the slug outlet, comprise a first slug supporting bar (78) extending along a first side (86) of the passageway (82) to the outlet and being resiliently biased towards a second side (87) of the passageway (82) and having an extension (118) which extends into the die opening (44), for supporting each slug (10,10') in the die opening (44); and a second slug supporting bar (80) extending axially along the passageway (82) along said second side (87) thereof and being biased towards said first bar (78), so that slugs (10,10') in the passageway (82) are supported between said bars (78,80); whereby during continuous operation of the press slugs (10,10') in the passageway (82) will be maintained in parallel planes in an orderly stack. A punch assembly and a die assembly (12) as claimed in claim 1, characterised in that the die opening (44) overlaps the strip feed path. A punch assembly and a die assembly (12) as claimed in claim 1, characterised in that the die opening (44) overlaps the strip feed path so that the die opening (44) and the passageway (82) have one side (86) which is beside, and spaced from, the strip feed path and have a second side (87) which is on the strip feed path, the die assembly (12) comprising a die plate (14) and a die backup plate (16), the facial surface (18) being one surface of the die plate (14), the die backup plate (16) being against the other surface (20) of the die plate (14), the die opening (44) extending through the die plate (14) and the passageway (82) extending through the backup plate (16), the second slug supporting bar (80) being entirely contained in the passageway (82) and the first slug supporting bar (78) being pivoted at a location (88) spaced from the die opening (44) for arcuate movement towards the second slug supporting bar (80). A punch assembly and a die assembly (12) as claimed in claim 1, 2 or 3, characterised in that the die assembly (12) has a recess (74) in the facial surface (18) thereof, the recess (74) extending from a location beside the die opening (44) to the die opening (44), the slug stripper (32) being contained in the recess (74), and a spring (76) being provided in the recess (74) which biases the slug stripper (32) towards its normal position. A punch assembly and a die assembly (12) as claimed in any one of the preceding claims, characterised in that said recess (15) in the punch (11) extends from the free end (13) of the punch (11) partially along its length. A punch assembly and a die assembly (12) as claimed in any one of the preceding claims, characterised in that the slug stripper (32) has a triangular projection (56,58) extending towards the die opening (44), said end portion of the slug stripper (32) being the end portion (56) of the projection including the apex (61) thereof, the recess (15) in the punch (11) comprising a V-shaped groove, the triangular projection having a top surface (60) which is parallel to, and above, the facial surface (18), said apex (61) extending downwardly towards the facial surface (18) and being inclined towards the strip feed path. A punch assembly and a die assembly (12) as claimed in any one of the preceding claims, characterised in that the punch assembly and the die assembly (12) are movable horizontally towards and away from each other.

Inventors: BAKERMANS JOHANNES CORNELIS WI, DEIMLER JOHN DAVID, REAVIS RONNIE WAYNE, BAKERMANS, JOHANNES CORNELIS WILHELMUS, DEIMLER, JOHN DAVID, REAVIS, RONNIE WAYNE
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1990
Main classification: B21D45
IPC codes: B26F1, B26D7, B21D45, B21D28