US2867276A

US2867276A - Self-contained perforating implement

Info

Publication number: US2867276A
Application number: US501274A
Authority: US
Inventors: Paul H Taylor
Original assignee: WALES STRIPPITE CORP
Current assignee: WALES STRIPPITE CORP; WALES-STRIPPITE Corp
Priority date: 1955-04-14
Filing date: 1955-04-14
Publication date: 1959-01-06
Anticipated expiration: 1976-01-06

Description

Jan. 6, 1959 P. H. TAYLOR ,3

SELF-CONTAINED PERFORATING iMPLEMENT Filed April 14, 1955 2 Sheets-Sheet 2 775 77 I 7 WE? 77;? 92 7 V 7 t Z 00 g i 720 5; i5; 415% 93 gg W" "6 702-0!) 1 I A q A z I! IN V EN TOR.

SELF-CONTAINED PERFORATING IMPLEMENT Paul H. Taylor, Grand Island, N. Y., assignor to Wales- Strippite Corporation, North Tonawanda, N. Y., a corporation of New York Application April 14, 1955, Serial No. 501,274

19 Claims. (Cl. 164-110) The present invention relates to perforating apparatus and more particularly to self-contained perforating implements.

Self-contained perforating implements are widely used in the sheet metal industry. A conventional self-contained implement comprises a C-frame, a punch stripper combination mounted on the upper arm of the O-frame, and a die mounted in the lower arm of the G-frame in axial alignment with the punch. The stripper of the conven tional unit comprises a wound steel wire stripping spring, and a sleeve or guide which is reciprocable in the upper arm of the C-frame, and in which the punch is reciprocable. The punch and the'strippe'r move as a unit until they contact the workpiece. Then the punch is forced through the workpiece while the stripping spring is compressed between the punch and the guide member. Upon release of the punching forces, the compressed stripping spring expands and withdraws the punch from the work.

Self-contained perforating implements are particularly useful where it is desired to punch a number of holes simultaneously in a workpiece because a plurality of these implements can be mounted on the bed-of a punch press to be actuated simultaneously by the descending ram of the press, and because extremely rapid set-ups are possible, since the implements have to be locatedonly in the required relation on the bed of the press. The punch and die are already accurately aligned with one another in the punch unit itself, and do not have'to be aligned as in the case where the punch and die are separate; and the base of the O-frame of each implement can be provided with a pilot-pin, in accurate alignment with the punch and the die, for engagement in a hole in a pattern or template to quickly position the unit in proper position relative to the work. Self-contained perforating implements also are quickly .interchangeable for the reasons noted. Thus, the down-time of presses in which these devices are used is reduced to a minimum.

The wound steel spring used to provide stripping force in self-contained perforating implements of the type described, has been the'most serious drawback to the In such an implement efliciency of such implements. the stripping spring surrounds the punch; and the thicker the material which is to be punched, the larger the stripping spring must be. The spring greatly adds to the bulk of the perforating unit and thus limits the center distance at which holes can be punched simultaneously in a workpiece.

In my pending U. S. Patent application Serial No.

464,722, filed October 26, 1954, now Patent 2,805,717

granted September 10, 1957, there is described perforat-- ing apparatus of the self-contained type which employs a resilient plastic member to provide the stripping force instead of a mechanical stripping spring. This plastic member is in the form of an elongate tube which surrounds the punch and is adapted to reciprocate therewith. On a working stroke the plastic-member, which may be made, for instance, of nylon, is compressed and elastically distorted between the workpiece and a head 7' tates atent 2 on the punch. The recoil or expansion of the plastic member to its original form upon releaseof the working force serves to extract or strip the punch from the workpiece.

The plastic stripping member described in the appli cation mentioned, out-performs the mechanical coil springs heretofore used and enables the perforating implement to be made in a much narrower width for agiv'en thickness of sheet metal workpiece. However, to produce the necessary amount of stripping force, the plastic member must be of considerable length and the workin stroke must be sufficiently long to properly compress and distort the plastic. This means, however, that such a perforating implement can be used only in a punch press of large shut=height. If there is' insu'fiicient shutheight, the nylon will not 'be distorted properly, and-will fail.

One object of this invention" is to provide a selfcontained perforated implement, having a resilient,pla's'tic stripping medium, which can be used in presses having a short shut-height.

Another object of this invention is to provide a selfcontained perforating implement of the character described which is of much reduced height as compared with piror' perforating implements of this type.

Another object of this invention is to provide aper'f'o'ra'ting implement of the character described which has greater stripping capacity than prior such implements.

Another object of this invention is to providea perforating implement of the character describedha'ving improved means for stiffening and supporting the punch in its perforating stroke to thereby protect it from the stresses to which it is subjected.

A further objectof this invention is to rovide perforating apparatus of the character described in which the punch is accurately centered and guided in its working and return strokes.

Another object of this invention is to provide a perforating implement of the type 'desc'ribed in which the resilient, plastic, stripping medium also serves as a bearing and guide for the punchin operation.

A still further object of this invention is.to;provide perforating apparatus of the character described having a stripper assembly which during its approach to a workpiece, on a working stroke of the unit, travels freely in its supporting holder, but which upon engagement with a workpiece expands to eliminate all clearance between the working member and its holder, whereby the whole punch is more accurately centered and the Working mem her is stiifened againstthe side loads'to which it is subjected.

A still further object of this invention is to provide a perforating implement of the character described having a punch stripper assembly which is self-lubricating.

Other objects of this invention willbe apparent hereinafter from the specification and from the recital of the appended claims.

In the drawings:

Fig. 1 is a side elevation of a self-contained perforating unit constructed according to one embodiment of this invention, the unit being shown with" its punchin withdrawn, non-Working position;

Fig. 2 is a fragmentary section on an enlarged scale taken on line 22 of Fig. 1 and looking inthe direction of the arrows, and illustrating particularly the structure of the punch stripper assembly; 7

Fig. 3 is a fragmentary section similar to Fig. 2 but showing the punch stripper assembly at thelend of a working stroke;

Fig. 4 is a section takenon line 44 of Fig. 2 and lookingin the direction of the arrows;

Fig. 5 is a fragmentary section, similar to Fig. 3, of a i this. invention, the unit being shown with its punch in withdrawn, non-working position;

Fig. 8 is a fragmentary section on an enlarged scale taken on line 88 of Fig. 7 and looking in the direction of the arrows, illustrating particularly the structure of the punch stripper assembly;

Fig. 9 is a fragmentary section similar to Fig. 8 but showing the punch stripper assembly at the end of a working stroke;

Fig. 10 is a section taken on the line 1010 of Fig. 7 and looking in the direction of the arrows; and

Fig. 11 is a fragmentary section, similar to Fig. 9, of a perforating unit constructed according to still another embodiment of this invention, the parts of the punch stripper assembly being again shown at the end of a working stroke.

Referring now to the drawings by numerals of reference and first to the embodiment of the invention shown in Figs. 1-4 inclusive, 10 denotes the C-frame of the perforating unit; and 11 and 12 designate, respectively, the upper and lower arms of this C-frame. The die;14 of the unit is mounted in the lower arm 12 of the C-frame; and the punch stripper assembly 15 is mounted in the upper arm 11 of the C-frame. Lower arm 12 has a pilot pin 16 projecting downwardly from its underside which is adapted to engage in a hole in the bed B of apress, thereby to locate the perforating unit on the bed.

7 Die 14 is a tubular member having a central bore 18 communicating at one side of the die. with a discharge chute 19 (Fig. 1) through which slugs punched from a workpiece W may pass.

Punch stripper assembly 15 comprises a stepped, cylindrical punch .20, a stripper sleeve 21', and two telescoping, resilient plastic, solid tubular, stripping

springs

22 and 24. Stripper sleeve 21 is reciprocable in the bore 23 of upperarm 11 of the C-frame, and is normally held in its upper position, shown in Figs. 1 and 2 by a coil lifter spring 25 which surrounds sleeve 21 and which is interposed between the upperarm 11 of the C-frame and a flange, or collar, 26 on the stripper sleeve. The lifter spring may be secured at one end to arm '11 by a screw 27 (Fig. 1). At its other end it may be inserted in a hole (not shown) in flange 26, or otherwise suitably secured thereto. Spring 25 serves to hold the assembly 15 in a raised position (Figs. 1 and 2) to thereby provide space for insertion of a workpiece W between the top of die 14 and the bottom of assembly 15. Spring 25 further serves to lift assembly 15 back to its starting position after a working stroke of the perforating unit.

The punch is mounted to reciprocate in the stripper sleeve 21. It has an enlarged head 28 at its upper end which bears directly on the upper face of the plastic, tubular spring member 22. Its shank is reciprocable in plastic, tubular spring member 24.

Spring members

22 and 24 are preferably both made of nylon but the other tubular spring member 22 is preferably made of a softer, more pliable nylon than the inner tubular spring member 24 which is preferably made of a harder, stiffer nylon.

The two

nylon spring members

22 and 24 are, in effect, mounted in series or tandem with each other. The outer spring'member 22 is connected to the inner spring member 24 by a thin, steel sleeve 30 which has an inturned flange 31 at its upper .end that seats on the top face of 1111161 spring member 24. This sleeve 30 also has an outwardly-directed flange 32 at its lower end on WhiQh tubular spring member 22 seats.

The inner tubular spring member'2'4 seats at its lower end on stripper sleeve When the press ram R (Fig. 3) moves downwardly, it

forces assembly 15 to move downwardly with it. Lifter spring is compressed between the top of C-frame arm 11 and flange 26 of stripper sleeve 21. When stripper sleeve 21 engages the workpiece, its downward movement is arrested. Punch 20, then moves relative to the stripper sleeve, perforating the workpiece. As this occurs, the softer, more pliable, outside tubular spring member 22 is first compressed between head 28 of the punch and flange 32 of steel sleeve 30. Thereafter, as the pressure increases, the force is transmitted from outer spring sleeve 22 through steel sleeve to innerplastic stripping spring member 24. This member is then compressed between flanged end 31 of steel sleeve 30 and stripper sleeve 21, and elastically distorted. .In its 1 elastic distortion, nylon sleeve 24 takes up the clearance between it and the shank of punch 20; so that the punch is strongly supported and guided as it effects the perforating operation.

Upon release of the working force, the tubular, spring forms thereby stripping the punch from the workpiece. Lifter spring 25 then lifts assembly 15 back to its starting position. v

The series mounting of

tubular spring members

22 and 24 provides a great stripping force in a very compact space. Substantially twice as much distortion is obtained for a given length of ram travel by using the two telescoping plastic tubular spring members than when a single sleeve is used. Furthermore, when the two nylon sleeves reach a point where they act in parallel,

as shown in Fig. 3, there is a sudden, tremendous surge load. A perforating unit can be built according to the present invention, then, which is very powerful but which can readily be used in presses having a very short shut height. H

Figs. 5 and 6 show a perforating unit made according to this invention having a somewhat modified stripper assembly construction. The punch 20 and lifter spring 25 may be identical with those previously described. The stripper sleeve 41, telescoping, tubular, plastic, stripping

spring members

42 and 44; and the rigid sleeve 50 connecting them are of slightly different construction from corresponding

parts

22,24 and 30 of the previouslydescribed embodiment of the invention. Tubular spring member 44, like spring member 24, is interposed between head 28 on the punch and the upper surfaceof a flange 46 on stripper sleeve 41. Flange 46 is of greater diameter than flange 26 of stripper sleeve 21, however; and tubular spring member 42 bears at all times on this flange, also. The perforating unit of Fig. 5 is intended for perforating thicker worksheets W than the unit of Figs. 1 to 4 inclusive.

Inner spring member 44 has three equi-angularly spaced recesses 51 cut-in it at its top thereby forming a scalloped upper end. The outer spring member 42 is formed at its bottom with three similar recesses 52. Interposed between the two

plastic spring members

42 and 44 is rigid sleeve 50, which has three equi-angularly spaced in-turned flange fingers 61 at its upper end which engage in the recesses 51 in tubular spring member 44 and seat 6 operates in a somewhat dilferent manner from the unit shown in Figs. 1 to 4, inclusive. Here the inner sleeve 44 may be the softer, more pliable spring member; and the outer sleeve 42 may be the harder. Inner spring member 44 distorts first, therefore, but when the outer tubular spring member 42 bottoms, as shown in Fig. 5, the compressive force is applied to both

nylon members

42 and 44. When the ram is withdrawn, it is this force which overcomes the static, at-restposition of the ram at the bottom of its stroke and effects initial stripping of the punch from the Work.

Figs. 710 inclusive, show a self-contained perforating unit constructed according to another embodiment of this invention. In this embodiment, an implement of even smaller shut height is provided. 'Here, telescoping tubular stripping spring members are provided which are compressed and elastically distorted during the perforating operation between a punch and a workpiece, instead of between a punch and a stripper sleeve.

The perforating unit here comprises a C-frame 70, which has a lower arm 72 in which die 74 is mounted, and an upper arm 71 in which the punch stripper assembly 75 is mounted. Lower arm 72 has a pilot pin 76 projecting downwardly from its underside which is adapted to engage in a hole in the bed B of the press in which the implement is mounted to thereby locate the unit on the bed. Die 74, assembly 75 and pin 76 are coaxial.

The die is a cylindrical member which is secured in a suitable bore 77 in the lower arm 72 of the C-frame. It has a central bore 78, and a communicating counterbore 79. The counterbore communicates with a discharge passage or chute (not shown) in arm 72 through which slugs punched from a workpiece W may pass.

Punch assembly 75 comprises a stepped, cylindrical punch 90, an outer tubular, resilient, solid, plastic spring member 92, an inner, tubular, resilient, solid plastic, spring member 94, and a rigid connecting tubular member 100. The punch 90 reciprocates in spring member 94; and the enlarged head 98 of the punch engages the upper end of spring member 92. Tubular spring member 94 is mounted withinconnecting member 100; and connecting member 100 has an upper inwardly turned flange 101 which seats on member 94. Tubular spring member 92 seats at its lower end on outwardly directed flange 102 at the lower end of connecting member 100. The punch-stripper assembly 75 reciprocates as a whole in a bore 93 in upper arm 71, the outer spring member 92 having a slight clearance with reference to'this bore. The lower end of inner spring member 94 projects below the lower end of outer spring member 92.

The punch-stripper assembly is constantly urged to its upper, at-rest position by two coiled lifter springs 104 which are positioned in two recesses 105 that are at diametrically opposite sides of the bore 93. The lifter springs 104 engage the upper-ends 107 of two Z -shaped strap members 106, which have lower end portions 108 on which the bottom of tubular stripping spring member 94 seats. A plate 110, which is secured to the top of C-frame arm 71 by screws 111 (Fig. serves to hold the lifting springs 104 in place.

The operation of perforating unit '70 is illustrated in Figs. 8 and 9. When the punch press ram R (Fig. 9) descends, it engages the head% of punch 90, first compressing nylon spring member 92 which is the softer, more pliable member. The pressure of the ram is transmitted from this nylon sleeve 92 through rigid sleeve 100 to nylon sleeve 94. Thus, as the punch-stripper unit descends, the straps 106, move downwardly compressing lifter springs 104. When the combined spring and stripping member 94 strikes the workpiece W, its downward movement is arrested. But as the punch 90 is forced through the workpiece W,

members

94 and 92 are compressed and elastically distorted. The compression of the stripping members and their elastic distortions eliminates all clearance between the bore 93 in upper arm '71 of the C-frame and tubular spring member 92. At the same time, any clearance between the punch and the bore of tubular spring member 94 is eliminated. Thus the punch 90 is accurately centered and positively guided in its perforating operation. Furthermore, the elimination of these clearances supports and stiffens' the punch as it perforates the workpiece W.

When the ram R is withdrawn, the compressed stripping

members

92 and 94 expand to their normal size and form, thereby stripping punch 90 from workpiece W. The expansion of lifter springs 104 then serves to raise punch-stripper assembly 75 to its starting position.

Perforating unit 70 has relatively a very small height. Therefore, it may be used in punch presses having an extremely short shut height. Further, it will punch holes' in a workpiece with a degree of accuracy heretofore practically impossible to obtain. This results from the action of the telescoped

tubular spring members

92 and 94 which serve many purposes. Their resiliency provides the stripping force required to withdraw punch 90 from workpiece W after a perforating stroke. At the same time, they serve to center and to stiffen and to guide the punch in its perforating operation.

Since the member 94 is made of nylon, or similar flexible, plastic material, the workpiece is not damaged in any way through contact of it with the stripping member 94. This is true, even when the workpiece is aluminum or some other soft metal. Further, nylon is self-lubricating and, therefore, the necessity for periodic lubricating, normally associated with perforated units, is eliminated.

Since the clearances between the parts of assembly 75, and between the assembly 75 and bore 93 of arm 71, are eliminated during a working stroke, the components of a perforating unit made according to the present invention need not be manufactured with the precision normally required in perforating units. For example, the outside diameter of punch 90 may be .002 inch to .004 inch less than the diameter of the bore of member 94; and likewise, the outside diameter of nylon sleeve 92 may be .002 inch to .004 inch less than the diameter of the bore 93. In conventional perforating units punch 90, for instance, would have to be held to a tolerance of at least .0005 inch for the unit to operate properly.

Fig. 11 shows a further modification of the invention. Here the punch-stripper assembly is denoted at 115. In this figure, parts identical with those of Figs. 7 to 10 inclusive are indicated by like reference numerals. The difference in construction is in the telescoped tubular spring members 112 and 114, and the rigid connecting sleeve 120.

The telescoped tubular stripping, spring members 112 and 114 are of equal length. Inner member 114 is castellated at its upper end being provided with three equiangularly-spaced axially-extending recesses, one of which is shown at 125. The outer tubular spring member 112 has three similar recesses at its bottom, one of which is denoted at 127.

Interposed between the tubular plastic stripping members 112 and 114 is a thin steel sleeve provided at both its top and bottom with three equiangularly-spaced fingers 131 and 132, respectively, which extend inwardly and outwardly, respectively, to engage in the slots and 127, respectively, in the nylon sleeves 114 and-112, respectively.

The embodiment of the invention shown in Fig. 11 operates .in a manner similar to that of the unit of Fig. 5. In the perforating unit of Fig. 11, as in the perforating unit of Fig. 5, the outside nylon sleeve 112, as well as the inside nylon sleeve 114, bottoms on the work as the punch 90 effects the perforating operation. The compressive force is applied directly, therefore, to both nylon sleeves; and both nylon sleeves, operate together, therefore, to strip the punch 90 from the work W". The unit of Fig. 11, like the unit of Fig. 5, is for'punchin'g thick sheets.

While reference has been made throughout to use of nylon stripping springs and nylon stripper-spring members, it will be understood that resilient, plastic, solid materials, other than nylon might be used instead. Thus, Teflon (tetrafluoroethylene resin), Kel-F, polystyrene, and the like, could also be used.

While this invention has been described in connection with several different embodiments thereof, it will be understood that it is capable of further modifications, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention what I claim is:

1. Apparatus for perforating a workpiece comprising a punch, a first resilient, compressible, plastic, tubular member surrounding said punch and in which said punch reciprocates, a second resilient, plastic, tubular member surrounding said first plastic member, one of said plastic, tubular members being of greater compressibility than the other, and means connecting said plastic members to said punch for compressing and elastically distorting said second plastic member and then said first plastic member serially on a working stroke of said punch to thereby store energy in said members for stripping said punch from said workpiece.

2. Apparatus for perforating a workpiece comprising a holder, a tubular stripper member reciprocable in said holder, a punch reciprocable in said stripper member, said punch having an enlarged head at its upper end, resilient means surrounding said punch and interposed between said head and said stripper member for stripping said punch from a workpiece, said means comprising a first resilient, compressible, plastic, tubular member surrounding said punch and in which said punch reciprocates, a second resilient, plastic, tubular member surrounding said first plastic member, said plastic second member being more compressible than said first plastic member and having its upper end positioned above the upper end of said first plastic member and engaging said head, said first plastic member having its lower end positioned below the lower end of said second member and engaging said stripper member, means for connecting the upper end of said. first plastic member to the lower end of said second plastic member to transmit a compressive force between them, said punch, stripper member and plastic members moving together on a working stroke until said stripper member engages the workpiece, after which, said plastic members are compressed and distorted serially and said punch moves relative to said stripper member and said plastic members.

3. Apparatus for perforating a workpiece comprising a holder, a punch stripper assembly reciprocable in said holder, said assembly comprising a tubular stripper member reciprocable in said holder, a punch reciprocable in said stripper member, said punch having an enlarged head at its upper end, resilient means interposed between said punch head and said stripper member for stripping said punch from a workpiece, said means comprising a first resilient, compressible, plastic, tubular member surrounding said punch and in which said punch reciprocates, a second resilient, compressible, plastic, tubular member surrounding said first member, the head of said punch seating on said two plastic members and said two plastic members seating on said stripper member, means connecting said tubular plastic members to transmit a compressive force between them, said punch, stripper member and plastic members moving together on a working stroke until said stripper member engages the workpiece, after which, said punch moves relative to said stripper mem ber and said plastic members.

4. Apparatus for perforating a workpiece comprising a holder, a tubular stripper memberreciprocable in said holder, a punch reciprocable in said stripper member, resilient means surrounding said punch andinterposed between said punch and said stripper member for stripping said punch from a workpiece, said means comprising a first resilient compressible, plastic tubular member surrounding said punch and in which said punch reciprocates, a second resilient compressible, plastic tubular member surrounding said first member, said plastic members being of equal length, said first plastic member being scalloped at its upper end, said second plastic member being scalloped at its lower end, means for engaging in the scallops of the upper scalloped end of said first plastic member and in the scallops of the lower scalloped end of said second plastic member to connect said plastic members together to transmit pressure between them, said punch member, stripper member and plastic members moving together on a working stroke until said stripper member engages the workpiece after which said. punch moves relative to said stripper member and said plastic members.

5. Apparatus for perforating a workpiece comprising a punch having an enlarged head at its upper end, a first resilient, compressible, plastic, tubular member in which said punch reciprocates, a second resilient, compressible, plastic, tubular member surrounding said first member, a holder having a bore in which said second plastic member reciprocates, said second plastic member being more compressible than said first plastic member and having its upper end positioned above the upper end of said first plastic member, said first plastic member having its lower end positioned below the lower end of said second plastic member, and means connecting said plastic members to each other and to said punch so that they move together on a working stroke until said first plastic member engages the workpiece, after which, said plastic members are compressed serially and elastically distorted as said punch moves relative to said plastic members.

6. Apparatus for perforating a workpiece comprisinga punch, said punch having an enlarged head at its upper end, a first resilient, compressible, plastic, tubular member in which said punch reciprocates, a second resilient, compressible, plastic, tubular member surrounding said first member, a holder having a bore in which said second plastic member reciprocates, said second plastic member being more compressible than said first plastic member and having its upper end positioned above the upper end of said first plastic memberand engaging said head, said first plastic member having its lower end positioned below the lower end of said second plasticmember and being adapted to engage the workpiece, and means connecting the upper end of said first plastic member to the lower end of said second plastic member, said punch and plastic members being adapted to move together on a working stroke, until said first member engages said workpiece, after which, said plastic members are compressed serially and elastically distorted between the workpiece and said head.

7. Apparatus for perforating a workpiece comprising a punch, a first resilient, compressible, plastic, tubular member in which said punch reciprocates, a second resilient, compressible, plastic, tubular member surrounding said first member, said plastic members being of equal length, said first member being scalloped at its upper end, said second plastic member being scalloped at its lower end, means for connecting the upper scalloped end of said first member to the lower scalloped end of said second member to transmit a compressive force between the two plastic members, a holder having a bore in which said second plastic member reciprocates, and means for connecting said plastic members to said punch sothat they move with the punch on a workingstroke until. the plastic members engage the workpiece, after which, said punch moves relative to said plastic members,

.-v App at s f r pe f rat ng, awo piece comprisin a punch, said punch having an enlarged head at its upper end, a first resilient, compressible, plastic, tubular member in which said punch reciprocates, a second resilient, compressible,'plastic, tubular member surrounding said first member, said plastic members being of equal length, a holder having a bore in which said second plastic member reciprocates, said plastic members engaging said head at their upper ends, said first member being scalloped at its upper end, said second member being scalloped at its lower end, means for connecting the upper scalloped end of said first member to the lower scalloped end of said second member to transmit a compressive force between said members, said punch member and said plastic members moving together on a working stroke until said plastic members engage the workpiece after which said punchmoves relative to said plastic members. i

9. Apparatus for perforating a workpiece comprising a support, a pair of resilient, compressible, plastic, tubular members mounted one within the other and reciprocable in said support, a punch reciprocable in the inner of said plastic members, meansconnecting said punch to at least one of said tubular member to transmit pressure from said punch to said one tubular member, and means connecting said tubular members to one another to transmit pressure between them, one of said tubular members being made of a softer, more pliable plastic than the other.

'10. Apparatus for perforating a workpiece comprising a support, a pair of resilient, compressible, plastic, tubular members mounted one within the other and reciprocable in said support, a punch reciprocable in the inner of said tubular members, means'connecting said punch to at least one of said tubular members to transmit pressure from said punch to said one tubular member, and means connecting said tubular members to one another to transmit pressure between them, one of said tubular members being made of a softer, more pliable plastic than the other, the inner of said tubular members normally having clearance with reference to said punch but being distorted upon compression to eliminate said clearance and to guide and support said punch during its perforating operation.

11. Apparatus for perforating a workpiece comprising a support, a stripper reciprocably mounted in said support, a punch reciprocable in said stripper and having an enlarged head at its upper end, a pair of resilient, compressible, plastic, tubular members surrounding said punch and mounted one within the other, the inner of said plastic members being mounted on the top of said stripper, the upper end of the outer of said plastic members, at least, serving as a seat for said head, and a rigid sleeve disposed within said outer plastic member and surrounding said inner plastic member, said sleeve having an inwardly directed flange at its upper end which seats on the top of said inner plastic member, and said sleeve having an outwardly directed flange at its lower end on which said outer plastic member seats.

12. Apparatus for perforating a workpiece comprising a support, a stripper reciprocably mounted in said support, a punch reciprocable in said stripper and having an enlarged head at its upper end, a pair of resilient, compressible, plastic, tubular members surrounding said punch and mounted one within the other, the inner of said plastic members being mounted on the top of said stripper, the upper end of the outer of said plastic members, at least, serving as a seat for said head, and arigid sleeve disposed within said outer plastic member and surrounding said inner plastic member, said sleeve having an inwardly directed flange at its upper end which seats on the top of said inner plastic member, and said sleeve having an outwardly directed flange at it lower .end on which said outer plastic member seats, one of said plastic members beingmade of a softer,more.plia ble1 plastic than the other.

13. Apparatus for perforating a workpiece comprising a punch, a pair of telescoping resilient, compressible, plastic, tubular members surrounding said punch and conected to said punch in series so that pressure is transmitted from said punch serially tosaid plastic members, as the punch perforates the work, whereby to compress said members so that upon release of the pressure said plastic members expand to strip the punch from the work, the outer of said plastic members being made of a softer, more pliable plastic than the other, and the inner of said plastic members normally having clearance with reference to said punch, said inner plastic member being elastically distorted, as well as compressed, as the punch perforates the work, thereby to eliminate this clearance and to guide and support the punch.

14. Apparatus for perforating a workpiece comprising a support, a stripper reciprocably mounted in said support, a punch reciprocable in said stripper and having an enlarged head at its upper end, a pair of resilient, compressible, plastic, tubular members surrounding said punch and mounted one within the other, the inner of said plastic members, at least, being mounted on the stripper, said head being seated on the upper ends of both said plastic members, and a rigid sleeve disposed within said outer plastic member and surrounding said inner plastic member, saidsleeve having an inward-lydirected flange at its upper end which seats on the top of said inner plastic member, and said sleeve having an outwardly-directed flange at its lower end on which said outer plastic member seats, said stripper being disposed to engage the work on a working stroke of said punch as the punch perforates the work, whereby said plastic members are compressed so that upon release of the punching pressure they will expand to strip the punch from the work, said outer plastic member being shaped to have clearance relative to said outwardly-directed flange when said plastic members engage the work.

15. Apparatus for perforating a workpiece comprising a holder having a bore therethrough, a punch, a pair of resilient compressible, plastic, tubular members surrounding said punch and mounted one within the other and reciprocable in said bore, said punch being reciprocable in the inner of said plastic members, the outer of said plastic members normally having clearance with reference to said bore, means connecting said punch to at least one of said plastic members to transmit pressure from said punch to said one plastic member, and means connecting said plastic members to one another to transmit pressure between them, at least one of said plastic members being positioned to engage the work as said punch perforates the work, whereby to compress said plastic members during perforation of the work so that when the punching pressure is relieved said plastic members expand to strip the punch from the work, said outer plastic member distorting during perforation of the Work to eliminate said clearance.

16. Apparatus for perforating a workpiece comprising a holder having a bore therethrough, a punch, a pair of resilient, compressible, plastic, tubular members surrounding said punch and mounted one within the other and reciprocable in said bore, said punch being reciprocable in the inner of said plastic members, the inner of said plastic members normally having clearance with reference to said punch, means connecting said punch to at least one of said plastic members to transmit presssure from said punch to said one plastic member, and means connecting said plastic members to one another to transmit pressure between them, at least one of said plastic member being positioned to engage the work as said punch perforates the work, whereby to compress said plastic members during perforation of the work so that when the punching pressure is relieved said plastic members expand to strip the punch from the work, said inner plastic member distorting during perforation of the work to eliminate said clearance. j

l7. Apparatus for perforating a workpiece comprising a holder having a bore therethrough, a punch, a pair of resilient, compressible, plastic, tubular members surrounding said punch and mounted one Within the other and reciprocable in said here, said punch being reciprocable in the inner of said plastic members, the inner of said plastic members normally having clearance with reference to said punch, the outer of said plastic members normally having clearance with reference to said bore, means connecting said punch to at least one of said plastic members to transmit pressure from said punch to said one plastic member, and means connecting said plastic members to one another to transmit pressure between them, at least one of said plastic members being positioned to engage the work as said punch perforates the work, whereby to compress said plastic members during perforation of the Work so that When the punching pressure is relieved said plastic members expand to strip the punch from the work, said plastic members distorting during perforation of the work to eliminate said clearance.

18. Apparatus for perforating a workpiece comprising a holder having a bore therethrough, a punch, a pair of resilient, compressible, plastic, tubular members surrounding said punch and mounted one within the other and reciprocable in said bore, said punch being reciprocable inthe inner of said plastic members, a rigid sleeve surrounding said inner plastic member and mounted Within said outer plastic member, said sleeve having an inwardly-extending flange at its top seating on said inner plastic member, said sleeve having an outwardly-directed flange at its bottom on which said outer plastic member isseated, lifter spring means interposed between said outer plastic member and said holder for resiliently suspending said outer plastic member in said bore, means connecting said punch to at least one of said plastic members to transmit pressure from said punch to said one plastic member, and means connecting said plastic a 12 members to one'another to transmit pressure between them, at leastone of said plastic'members being positioned to engage the work asthe punch perforates the work, whereby to compress said plastic members during perforation of the work so that when the punching pres sure is relieved said plastic members expand to strip the punch from the work.

19. Apparatus for perforating a workpiece comprising a support, stripping means reciprocable on said support and comprising two resilient, compressible, plastic tubular members, one of which is mounted in the other, a punch reciprocable in the inner of said two tubular members, said punch being connected directly at least to one of said tubular members so that upon application of a punching force said force is transmitted to said directly connected tubular member, means connecting said tubu lar members together so'that said punching force is transmitted between them, said'tubular members-being adapted to be compressed and distorted when said punch moves relative to said tubular members in perforating a workpiece, and said tubular members being adpated to expand upon release of the punching force to strip the punch from the workpiece, and resilient means interposed between said stripping means and said support for lifting said stripping means and said punch as an assembly to return said assembly to initial position after completion of the perforating operation.

References Cited in the file of this patent UNITED STATES PATENTS 2,117,264 Workman May 10, 1938 2,334,011 Wales Nov. 28, 1944 2,427,409 Kirsch Sept. 16, 1947 2,597,976 Cousins ,May 27, 1952 2,649,157 Weisbeck Aug. 18, 1953 2,650,663 Wales et al. Sept. 1, 1953 2,702,703 Franceschetti Feb. 22, 1955' 2.708,970 Taylor May 24, 1955