US2807323A - Self-contained perforating unit - Google Patents

Description

Sept. 24, 1957 PQ H. TAYLOR 2,807,323

sELE CONTAINED PERFORMING UNIT Filed April 14, 195s K 2 sheetsheet 1 Sept. 24, 1957 P. H. TAYLOR 2,807,323

SELF CONTAINED PERFORMING UNIT y Filed April 14, 1955 2 Sheets-Sheet 2 A S'/ Z0' JNVENToR. 20 y Ruz/lf 233107,. I.

United States Patent SELF-CONTAINED PERFORATING UNIT Paul H. Taylor, Grand Island, N. Y., assignor to Wales- Strippit Corporation, North Tonawanda, N. Y., a corporation of New York Application April 14, 1955, Serial No. 501,275

v 15 Claims. (Cl. 1644-94) The present invention relates to perforating apparatus `and more particularly to self-contained perforating implements. In a still more specific aspect, the invention constitutes an improvement on the invention disclosed in my pending U. S. patent application, Serial No. 464,722, iled October 26, 1954.

The ordinary self-contained perforating unit comprises a C-frame, a punch-stripper assembly mounted on the upper arm of the C-frame, and a die mounted in the lower arm of the C-frame in axial alignment with the punch. The stripper of such a conventional unit comprises a wound steel wire 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 stripper move as a unit until they contact the workpiece. Then theA punch is kforced through they workpiece, while the stripping spring is compressed between the punch and the stripper sleeve. Upon release of the punching force, the compressed stripping spring expands and withdraws the punch from the work.

Such conventional self-contained'perforating units have the ldisadvantage that it is impossible with them to punch simultaneously a plurality of holes on close centers. This is because of the stripping spring. The stripping spring surrounds the punch; and the thicker the material which is to be punched, the larger the stripping springs must be. Different perforating units cannot be placed any closer together kthan their strippingsprings will allow.

In the perforating unit disclosed in my U. S. patent application above-mentioned, both the stripper guide and the stripper spring of conventional perforating units are eliminated; and a single tubular, plastic, stripping sleeve is substituted therefor. This stripping sleeve reciprocates in a'bore in the upper arm of the C-frame. When the punch is forced through a workpiece, the stripping sleeve is compressed between the punch and the workpiece. Upon release of the punching force, Vthe stripping sleeve expands' to its original size and form, and, in so doing, strips the punch from the workpiece.

A perforating implement, such as disclosed in my application above mentioned, operates with great e'iciency but is limited as to the-sizeof workpiecewhich it can perforate. When the workpiece is of substantial thickness, the plasticstripping sleeve may become overloaded and rupture., g y; I

One' object ofthe present invention is to'provide aV selfcontained perforating unit employing resilient, plastic means as a combination stripper sleeve and stripping spring, but which is capable of perforating thicker workpieces without fatigue than has heretofore been possible where such a combination resilient plastic stripper sleeve and stripping spring has been employed.

Another object of the invention is to provide a selfcontained perforating unit of the character described in which the combination stripperv and stripping spring is a plastic sleeve.

Another object of this invention is to provide a selfcontainedr perforating unit which lis, capable of a longer Patented Sept. 24, 1957 working stroke without increasing the width of the unit, thus enabling a number of such units to be used to punch simultaneously a plurality of closely-spaced holes through a metal sheet of substantial thickness.

. Another object of this invention is to provide perforating apparatus of the character described in which a single member may still lserve as a bearing and guide for the punch and to provide at least part of the stripping force.

Another object of this invention is to provide perforating apparatus of the character described in which the combination spring and guide is so constructed that its manufacture is simple and of loW cost.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

In the drawings: Y

Fig. l is a side elevation, with parts broken away, of a self-contained perforating unit constructed according to one embodiment of this invention, the unit being shown with the punch withdrawn;

Fig. 2 is a fragmentary section, taken at right angles to Fig. l, showing the punch-stripper assembly and a portion of the die, the parts being illustrated with the punch at the end of a working stroke;

Fig. 3 is a fragmentary section taken on the line 3--3 of Fig. 2, `and looking in the direction of the arrows;

Fig. 4 is a view, similar to Fig. l, showing a further embodiment of the invention;

Fig. 5 is a fragmentary section, similar to Fig. 2, taken at right angles to Fig.V 4 and showing the punch-stripper assembly of the unit-ofFig. 4 at the end of a working stroke; and

Fig. 6 is a fragmentary section on the line 6 6 of Fig. 4 looking in the direction of the arrows.

Referring now to the drawings by numerals of reference and iirst to the embodiment of the invention shown in Figs. 1 to 3 inclusive, 10 denotes a self-contained perforating implement which comprises, generally, a C-frame 11, a punch-stripper assembly 12, and a die 13 in axial alignment with assembly 12. The C-frame 11 has an upper arm 16, in which the punch-'stripper assembly 12 is reciprocably mounted, and a lower arm 17 on which die 13 is mounted. On the underside of the lower arm 17 is a conventional pilot pin 18 which is adapted to t into a suitable hole in the bed B of the press, on which the implement is used, to properly locate the implement on the bed.

Die 13 comprises a cylindrical body 20 having a central bore 21 communicating with an angular discharge chute 22 through which slugs S (Fig. 2) punched from a workpiece W may pass. 4 The punch stripper assembly 12 comprises a punch 23, and a pair of resilient, plastic, tubular members 26 and 27, in which the shank of the punch is mounted and is reciprocable. The tubular member 27 is mounted on top of the tubular member 26. Punch 23 has an enlarged head portion 28 ber 27. Member 26 is mounted to reciprocate in a bore 30 in the upper arm 16 of the C-frame. Y -V A light, wire, coil spring 31 serves as a lifter for the punch stripper assembly 12. Spring 31 surrounds the upper end of lower stripper member 26.. The upper end of this spring is secured in a hole 33 in resilient, stripper member 26-and the lower end of the spring seats on the upper arm 16 of the C-frame 11 and is fastened thereto by a screw 32. Spring 31 normally holds yassembly 12 in a raised position, as sho-Wn in Fig l, to provide clearance between the lower end of the assembly and the top of die 13 so that a workpiece may be readily inserted therebetween.

which engages the upper end of memo u than the `diameter of -the shank of punch 23.` Tubular stripping member 26 may also have normal clearance with reference `to punch 23, also, have a tight fit around the shank of the punch at alltimes. j The'outside diameter of tubular member 26, however, ispreferably made less than the diameter of bore 30 in .the upper arm 16 .of C-frame 11, thereby providing relatively, an initial` clearance between member 26 and the bore 30. For precision machine tool components, the outside diameter of member 26 may be, for instance, .002 inch to .004 inch less than the diameter of bore 30, Where normally, that is, with conventional construction, such parts would have to be held to a tolerance of at least .0005 inch.

Tubular stripper members 26 and 27 are both made of a suitable plastic such as nylon. Howeventhey are made of different types of nylon. Upper tubular member 27 is made of a nylon, such as nylon 7001, having greater compressibility `and elasticity than lower member 26, which is made of a more rigid, less compressible nylon, suchV as nylon 10,001. Member 27 is adapted to be highly compressed on actuation rof the unit to store a large amount of energyy for stripping punch 23 from a workpiece upon completion of a working stroke. Member 26 is adapted to be compressedy to a lesser degree, storing energy for use in stripping the punch from a workpiece, but more important, for guiding punch 23 in its reciprocating movement and providing a bearing-like support for the punch in bore 30 of upper arm 16.

Although it has been found that nylon is preferable for most applications, members 26 and 27 maybe made instead of other plastic materials such as Kel-F, Teflon, polystyrene or the like,

I'he manner in which perforating implement 10 operates is illustrated in Figs. l and 2. When the punch press ram R (Fig. 2) is driven downwardly, it forces punch 23 and tubular plastic members 26 and 27 to move downwardly as a unit untilY member 26 contacts the workpiece W. In this downward movement of the punch and plastic members, lifter spring 31 is compressed. When member 26 strikes the surface of the workpiece W its downward movement is arrested. Thereafter, punch 23 moves relative to plastic members 26 and 27, being forced through workpiece W, whilel members 26 and 27 are compressed between the workpiece and the head 28 of the punch. Since members 26 and 27 are made of different densities of nylon, the amount which they are compressed differs. As shown in Fig. 2, member 27 is highly compressed while member 26 is compressed to a much lesser degree. The compression of member 26 causes it to distort elastically, thereby eliminating all clearance, if any, between its `bore 36 and the shank of` the punch 23, and at the same time eliminating all clearance between it and the bore 30 of arm 16. The elimination of these clearances causes the punch 23 to be accurately centered and positively `guided in its working stroke. Moreover, by elirnf inating these clearances, punch`23 issupportedand stiffened as it moves downwardly 4to perforate workpiece W. The compression of upper member 27, onthe other hand, permits of a much longer stroke of the punch than would be possible if the shankof the punch were sur- Irounded for its full length lby a single sleeve of the density of sleeve 26.

vWhen the force applied to the ram R is removed, compressed members .26 and 27 expand lhack to their original 'sizes and shapes, thereby stripping punch 23 from workpiece W.` Then lifter spring .31 raises assembly 12 back to its starting` position.

The unit above described punches holes in a workpiece with a degree of accuracy heretofore practically impossible to attain. This results from the action of the member `26 "which serves many purposes. n member 27` to provide the stripping force to withdraw Its resiliency helps punch `23 from the workpiece W after a perforating stroke. At thc same time it provides an accurate guide for guidbut because of` its resilience may,v

ing the punch as it penforates the workpiece; in fact it provides a more accurate guide for this purpose than has heretofore been attainable in a self-contained perfo rating implement of conventional construction. In expanding, it also serves to center and stiften the punch, augmenting the strength of the smallediameter punch shank by the added strength of the expanded stripper sleeve 26 which, upon` expansion, intimately embraces the punch shank around its whole periphery.` Thus in the single tubular member 26 there is provided not only a spring but also a guide, and a centering `and stiffening agent, with excellent bearing surfaces. This tubular member is loose enough to resiliently slide up and down, in the bore 30 of the arm 16 during the initial part of the working stroke and during the return stroke. During the actual punching operation, however, it holds the punch in a tightyet, because of the nature `tof plastics such as nylon, Kel-F, Teflon," etc., lubricated embrace, and guides the punch very accurately. The expansion of the member 26 on the working stroke, more over, prevents upward extension of the metal of the workpiece into the bore 36 of the tubular member when thin gauge stock is punched. Being made of nylon, or similar material, the tubular member 26 is self-lubricating, thereby eliminating all lubricating normally associated with conventional perforating apparatus. Further, since member 26 is made of plastic, it is softer than the workpiece being perforated, even when the workpiece is aluminum or some other soft metal. Therefore, when it engages the workpiece on a working stroke, it will not mar or mark the workpiece.

The greater compressibility of member 27 allows the punch 23 to have a greater stroke.` Therefore, work-` pieces W of substantial thickness can be perforated. If member 27 was made of the same nylon as member 26, the stroke of the punch would 'be limited, and any attempt to drive punch 23 through a thick workpiece would cause `the plastic' members to be overloaded and ruptured. Therefore, by using a dense nylon in member 26 and a highly compressible nylon in member 27, punch 23 is properly guided and stifened in its reciprocating stroke, its working stroke can be extended, and, at the same time, a sutiicient stripping force is developed in the plastic members to strip the punch from the workpiece.

The use of resilient, plastic, tubular stripping members 26 and 27 greatly reduces the cost of the perforating implement. Since the member 26 expands elastically when compressed and rmly engages the bore 30 `in arm 16, `it need not be manufactured with an outside diameter to a very close tolerance. Likewise because the member 26, when expanded, tightly embraces the shank of punch 23, its bore 36 and the punch shank need not be manufactui-ed to very close tolerances. Since member 27 serves only to provide additional stripping force for a long punch stroke, it also need not be made to close tolerances. Members 26 and 27 can, therefore, be made of commercial, extruded plastic tubing having the approximate inside and outside diameters desired. By contrast, the punch stripping assembly `in conventional, self-contained perforating units have had to be` carefully manufactured with minimum. practical clearances between the parts so that the stripper sleeve will properly support and guide the punch and the formation of burrs will be avoided.

In conventional perforating units, the clearance between the stripper sleeve and the bore of the upper arm of the G-frame has to be' extremely small because the clear-ance between the punch and the die in the punching operation must be extremely small to preventformation of `a downwardlyr extending burr on the part being punched. In some instances, for light aircraft stock, for example, the normal clearance Abetween the stripper sleeve and the bore of the upper arm of the C-frame is less than .002 inch. This requires that conventional punch-stripper assemblies be made extremely accurate to permit the tight sliding t required. In contrast with The perforating implement of the present invention, I

furthermore, can produce a stripping force of great magnitude and the punch is able to travel a considerable distance without rupturing the plastic stripping members because of the high compressibility of Vupper member 27. Thus, implement 10 can punch much thicker workpieces thanhas `been possible with a conventional self-contained perforatingfunit; or conversely, the Width of the holder or C-frame can be reduced by reduction in the Width of the vstripping assemblage, thereby enabling-punching of holes'on closer centers than is possible with'conventional implements. i

The embodiment of the invention shown in Figs. 4 to 46has alllthe advantages of the embodiment of Figsfl to 3and the additional advantages of simplicity and lower cost so far-as the plastic stripper-spring members are concerned. Here, as before, a C-frame 11 may beemployed with the die 13 mounted in its lower arm 17 and the punch-stripper assembly, here designated 42, mounted in its upper arm 16. Identical parts are designated by the same reference numbers in all figures. Here, however, the combination guide Iand stripping means comprises a plurality of nylon or other resilient, plastic washers, which lit on the shank of the punch 23. l Alternate washers 44 and 45 may be made of a soft, pliable plastic and of a thick, dense plastic, respectively. Thus, washers 44 may be made of nylon 7001, while washers 45 maybe made of nylon 10,001. The latter is thicker-and denser lthan the former.

v'The washers may be hot-punched to tit the punch 23 closely. in fact, the lowermost, denoted 44', may be shrunk on the shank of the punch so that it resiliently grips the shank of the punch and will not fall off. Thereby it will retain all the other washers` on the shank of the punch.

' The washers may be all molded together so that in effect they form one single part. lt is preferable, however, to make them separate since in this way they can be slipped on and off the punch shank readily.

The soft pliabie washers 44 in their normal, at rest, positions have considerable clearance with reference to the bore Sii of the arm 16 of the C-frame, Whereas the hard dense washers 45 in their normal, at-rest positions have Vless clearance with reference to this bore, and in fact may have an interference fit therewith. lAll the washers may also have clearance with reference to the shank of the punch 23 if they are molded together. If they are separate from one another and are retained on the punch by lowermost washer 44then all except this iowermost washer may have considerable clearance with reference to the shank of the punch.

A ltlat, leaf spring 47, which is secured at one end on top of arm 16 of the T-frame and which engages at itg'opposite end between two adjacent washers 44 and 45, -serves as a lifter-spring for the punch-stripper assembly 42. This spring has an elongate slot 49 (Fig. 6) in it through which the shank of the punch passes. This siot permits of relative movement between the punch and the spring during perforation and during stripping. Spring 47 normally holds the assembly 4Z in raised p0- sition, as shown in Fig. 4, to provide clearance between ,the lower end of the punch-stripper assembly and the top oftdie `13 so that a workpiece may readily beinserted therebetween.

- The perforating unit of Figs. 4 to 6 inclusive operates in a manner similar to the perforating unit of Figs. 1 to 3 inclusive. When the punch press ram R descends it forces punch 23 and washers 44, 45 downwardly as a unit until washer 44 contacts the workvW. In this downward movement, lifter spring 47 is loaded. When washer 44 engages the work, downward movement of the washers is arrested, but punch 23 continues on to perforate the work under pressure of ram R. During perforation of the work, the washers 44 `and 45 are compressed between the sheet metal plate W and the head 28 of the punch. Since washers 44 and 45 are nylon parts of different densities, they are differently compressed. The softer, more pliable nylon washers 44 will be highly compressed, while the denser, harder nylon washers 45 will be compressed to ya much lesser degree. Moreover, the softer, more pliable nylon washers 44 will be compressed first and elastically distorted. Then the harder, nylon washers 45 will be compressed.r v'

lf there is any clearance between the washers 45 and the bore 30 and between them and punch 23, the com` pression of these washers will also cause them toV distort elastically, eliminatingall clearance between them and bore 30 and between them and the punch 23.Y -The elim-` ination of these clearances causes the punch to be accurately centered and positively guided in its working stroke. Moreover, by eliminating these clearances the punch is supported and stiffened as it perforates the work. Y When the ram is reversed, the compressed washers 44 and 45 expand to their original sizesr and return to their original shapes, thereby stripping the punch 23 from the workpiece W. Then lifter spring 47raises assembly 42 back to its starting position; The soft, pliable washers 44 permitrof a much longer stroke of the punch, that is,v perforation of thicker ma# terial, than would be possible if hard dense Washers, or a hard dense nylon sleeve, only were used. The use of washers generally has the yadvantage, that ythey can be molded more easily than a sleeve and at `less cost. ,v Y While it is preferred to make thewashers 4.4.and 45 both of a resilient, plasticcmateriaL such as nylon, it is possible to make either set of ,washers of anotherrmaterial such as steel. VFor instance, if washers 45 are, made of steel, they will have a sliding lit in -bore 30, and will act as the guiding and supporting members for the punch. The stripping force will then depend wholly on the degree of compression of the washers 44. Y

It will be apparent, that the present invention islnot limited to self-contained perforating implements. It may also be used in other types of perforating apparatus, with advantages such as those attained in a self-contained perforating implement. Thus, the invention may be ernployed, for instance, where a plurality of punchesare mounted in a single supporting plate, as in the case of the apparatus shown in Wales Patents Nos. 1,964,752 and 2,355,765, grantedk July 3, 1935 and August 151944, respectively. The denser kplastic guide sleeves will kbe mounted, reciprocablyloosely `in the supporting plate, and bothk the denser and the more compressible Vsleeves will normally be held in their upper positions bylifter springs; and the punch will be mounted reciprocably loosely in the plastic sleeves being'connected with theupper, more compressible, sleeve by Vits head, orrother means so ythat punch kand stripping forces may be transmitted `be'- l tween the punch and sleeves as in the illustrated embodiments of the invention. l Y

While the invention has been described in connection with particular embodiments thereof, then it will be understood that it is Capable of further modification, and this applicationis 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 lcustomary practice in the art'to which the invention pertains 7 l and as fall within the scope of the invention or the limits ofthe appended claims.

Having `thus described my invention what I claim is:

l. Perforating apparatus comprising a punch, a pair of resilient plastic tubular members mounted one on top of the other and surrounding said punch, at least one of said tubular members having `a bore the normal diameter of which is slightly larger than the outside diameter of the portionofsaid punch which is mounted in the tubular member,` thereby providing a normal clearance between the periphery of the punch and said one tubular member, the upper tubular member of said pair of members having a `greater compressibility than the lower member, a holder having abore in which the lower tubular member is reciprocably mounted,` said lower tubular member constituting a `combined guide sleeveand stripping spring for said punch, means connecting said punch to said upper member so that said members move with said punch on a working lstroke until said lower member engages a workpiece, said tubular members being thereafter compressed as said punch passes through said workpiece so that the normal clearance between said one tubular member and said punch is taken up, and said tubular members expanding to their original forms on removal of the punching force thereby to strip said punch from the workpiece. 2. Perforating apparatus comprising a punch, a plurality of bored, resilient, plastic members mounted one on top of the other and surrounding said punch, at least one of` said bored membershaving a bore the normal diameter of which is slightly larger than the outside diameter of the portion of said punch which is mounted in said one bored member, thereby `providing a normal clearancebetween the periphery of the punch and said one bored member, said members having different degrees of compressibility, `a holder having `a bore in which at least one of said bored members is reciprocably mounted, said last-named one bored member, at least, constituting a combined guide sleeve `and stripping spring for said punch, means connecting. said punch to said bored members so that said bored members move with said punch on a working stroke until the lowermost of said members engages a workpiece,said bored members being thereafter compressed and distorted elastically as said punch passes through said workpiece so that the normal clearance between the first-namedrone bored member and said punch is taken up, and said bored members expanding to their original forms on removal of the punching force thereby to strip said punchfrom the workpiece.

3. Perforating apparatus comprising a punch, a pair of resilient plastic tubular members mounted one on top of the other and surrounding said punch, at least one of said tubular members having a bore, the normal diameter of which is slightly larger than the outside* diameter of the portion of said punch which is mounted therein, thereby normally providing clearance between the periphery of the punch and said one tubular member, the upper tubular member of` said pair of members having a greater compressibility-than the lower member, a holder having a bore in which the lower tubular member is reciprocably mounted"said lower tubular member constituting a combined guide sleeve and stripping spring for said punch, said lower member having a normal outside diameter which is slightly smaller `than the diameter of said bore of said holder, means connecting said punch to said upper member so that said members move with said punch on a working stroke until said lower member engages a workpiece, said tubular members `being thereafter compressed `as said punch passes through said workpiece; and said tubular members expanding to their original form on removal of the :punching force tottherebytstrip said punch from the workpiece, the di'erence in diameters of said one tubular member and the portion of the punch which is reciprocable therein and the diierence in diameters betweenthe peripheryhoftsaid lower tubular member and said `bore of Said holder being such that the clearance between the periphery of said punch and the bores of said one member and between Ythe periphery of said lower member and the bore of said holder are eliminated when said members are elastically distorted.

lljlerforating apparatus comprising a punch, a pair of resilient plastic tubular members mounted one on top of `the other and surrounding said punch, the upper tubular member having greater resiliency and compressibility than the lower member, said punch having an enlarged head at its upper end, which abuts against said upper tubular member, a holder having a bore in which the lower tubular member is reciprocably mounted, said punch and tubular members being adapted to move together on a working stroke until said lower member engages the workpiece, said tubular members being compressed between said head and said workpiece and elastically distorted as said punch passes through the workpiece, said tubular members expanding to their original form on removal of the punching force to strip said punch from the workpiece.

5. Perforating apparatus comprising a punch, a pair of resilient plastic tubular members mounted one on top of the other and surrounding sai-d punch, at least one of said tubular members having a -bore the normal diameter of which is slightly larger than the diameter of said punch, the upper. tubular member having greater resiliency and compressibility than the lower member, said punch having an enlarged head at its upper end, which abuts against said upper tubular member, a holder having a bore in which the lower tubular member is reciprocably mounted, said lower tubular member constituting a combined guide sleeve and stripping spring for said punch, the lower tubular member having a normal outside diameter which is slightly smaller than said bore, said punch and tubular members being adapted to move together on a working stroke until said lower member engages the workpiece. said tubular members being compressed between said head and said workpiece and elastically distorted as said Vpunch passes through the workpiece, said tubular members expanding to their original forms on removal of the punching force to strip said punch from the workpiece, the differences in diameters of the bore of said one tubular member and of the Iportion of the punch which is reciprocable therein and the difference in diameters between the periphery of said lower tubular member and the bore of said holder being such that the clearances between the periphery of said punch and the bore of said one tubular member and between the periphery of said lower member and the bore of said holder are eliminated when said members are elastically distorted.

6. Perforating apparatus comprising a punch, a pair of resilient plastic tubular members mounted one on top of the other and surrounding said punch, at least one of said tubular members having a bore the normal diameter of which is slightly larger than the diameter of said punch, the upper tubular member having greater resiliency and compressibility than the lower member, said punch having an enlarged head at its upper end, which abuts against said upper tubular member, a holder having a bore in which the lower tubular `member is reciprocably mounted, said lower tubular member constituting a combined guide sleeve and stripping spring for said punch, the lower tubular member having a normal outside diameter which is slightly smaller than the bore of said holder, said punch and tubular members being adapted to move together yon a working stroke until said lower member engages the workpiece, said tubular members being compressed between said head and said workpiece and elastically distorted as said punch passes through the workpiece, said tubular members expanding to their original forms on removal of the punching force to strip said punch from the workpiece, the diterence in diameters of the bore of said one tubular member and the portion of the punch which is reciprocable therein and the difference in diameters between the periphery of said lower tubular member and the bore of said holder being such that the clearances between the periphery of said punch and the bore of said one tubular member and between the periphery of said lower member and the bore of said holder are eliminated when said members are elastically distorted, and a coil spring interposed between said lower tubular member and said holder which constantly urges said tubular members to their normal, at-rest positions, said spring having its lower end connected to said holder and its upper end connected to the upper end of said lower tubular member.

7. Perforating apparatus comprising a punch having an enlarged head at oneV end and a' cutting face at its opposite end, a'holder having a'b'ore therethrough, a plurality of bored, resilient, plastic members surrounding said punch and reciprocable in said bore, said members having different degrees of compressibility, the less compressible of said members having an outside diameter normally slightly less than the diameter of the bore of said holder, whereby when a punching force is applied to said punch, the punch and plastic members move together until the plastic member which is disposed adjacent the cutting face of the punch engages the workpiece and thereafter the less compressible of said members is compressed and distorted elastically, as the punch passes through the workpiece, to take up the clearance between said less compressible member and the bore of said holder, whereby said less compressible member acts as a support and guide for the punch as it perforates the workpiece.

8. Perforating apparatus comprising a punch, a holder having a bore therethrough, a plurality of bored, resilient, plastic members surrounding said punch and mounted on top of one another, means connecting said punch to said members so that they move together when a punching force is applied to said punch, alternate plastic members having greater and lesser degrees of compressibility, respectively, at least one of said members being reciprocable in the bore of said holder, said one member being of lesser compressibility, said one member having an outside diameter normally slightly less than the diameter of the bore of said holder, whereby when a punching force is applied to force said punch through a workpiece said plastic members are compressed and said one member, at least, is elastically distorted to take up the clearance between said one member and said holder whereby said one member acts as a guide forthe punch as the punch perforates the workpiece, said plastic members expanding upon release of said punching force to strip the punch from the workpiece.

9. Perforating apparatus comprising a holder having a bore therethrough, at least two contiguous, resilient, bored, plastic members, one of said plastic members being more dense and less elastic than the other, said one plastic member, at least, being reciprocable in the bore of Said holder, a punch reciprocable in the bores of said plastic members, means connecting said punch to said plastic members so that upon application of a punching' force to said punch the plastic members are moved with the punch until the plastic member, which is nearest the workpiece, engages the workpiece, and thereafter the plastic members are compressed as the punch perforates the workpiece, said plastic members expanding upon release of the punching force to strip the punch from the workpiece.

l0. Perforating apparatus comprising a holder having a bore therethrough, at least two contiguous, resilient, bored, nylon members, one of said members being made of more dense, less elastic nylon than the other, said one member, at least, being reciprocable in the bore of said holder and normally having clearance with reference to the bore of said holder, a punch reciprocable in the bores ot' said members, said punch normally having clearance with reference to the bore of at least one of said members, said punch having an enlarged head at its end remote from its cutting tace which engages the uppermost of said members so that upon application of a punching A10 force to said punch. said kmembers are movedlwith the punch until the member, which is nearest the workpiece, engages the workpiece, and thereafter said members are compressed and elastically distorted as the punch perforates the' workpiece, the normal clearances being such that said irst-named one member in its elastic distortion takes up the normal clearance between it and the bore of said holder to support and guide the punch as it perforates the workpiece, said members expanding upon reipunch from the bored members move with saild punch on a workingv stroke until the lowermost of said members engages a workpiece, said bored members being thereafter compressed and elastically distorted as said punch passes through said workpiece whereby said one member fills the bore of said holder to support and guide the punch, and said bored members expanding to their original forms on removal of the punching force thereby to strip said punch from the workpiece.

l2. Perforating apparatus comprising a bored holder, a plurality of axially-aligned bored members mounted one on top of the other, one of said members being more compressible than another of said members and at least one of said members being reciprocable in the bore of Isaid holder, a punch mounted in the bores of said members to be reciprocable therein, and means connecting said punch to said bored members so that said bored members move with said punch on a working stroke until the lowermost of said members engages a workpiece, the first-named one member being thereupon compressed as said punch passes through the workpiece, said first-named one member expanding on removal of the punching force thereby to strip said punch from the workpiece.

13. Perforating apparatus comprising a bored holder, a plurality of axially-aligned, plastic, compressible, bored members, a plurality of second bored members alternating with the first-named members, the bores of the second bored members being aligned axially 'with the bores of the first-named members, at least one of eadh of said members being reciprocable in the bore of said holder, a punch mounted in the bores of said members to reciprocate therein, and means connecting said punch to said bored members so that said bored members move with said punch on a working stroke of the punch until the lowermost of said members engages a workpiece, the first-named bored members being thereupon compressed as said punch perforates the workpiece, said first-named bored members expanding on removal of the punching force thereby to istrip the punch from the workpiece.

14. Perforating apparatus comprising a bored holder, compressible means comprising a plurality of axiallyaligned, plastic, compressible, bored members, a plurality of second bored members axially aligned with and alternating with the first-named bored members, the second bored members being less compressible than the irstnamed bored members and being normally of larger diameter than said first-named bored members, at least one of each of said members being reciprocable in the bore of said holder, a punch mounted in the bores of said members to reciprocate therein, and means connecting said punch to said bored members so that said bored members move with said punch on a working stroke of the punch until the lowermost of said members engages a workpiece, the compressible bored members being thereupon compressed as said punch perforates the workpiece, `said compressible bored members expanding on 11 released the punching force,k thereby to strip the punch from sthe, workpiece.

15.* Performing; apparatus Comprising a bored holder, comprcssible means [comprising a` plurality of axiallyaligned plastic, compressible, bored members, a plurality of second bored members axially valigned with and alternating with therst-namedibored members, the second bored, members `being alsoicompressible but less comprcssiblel than the-rst-named bored members and being normally of larger diameter than said first-named bored members, at least one of each of said members being reciprocable in the bore of said holder, a punch mounted in the bores of said members to `reciprocate therein, and means connecting said punch to said bored members so that said bored members move with said punch on a working stroke of the punch until the lowermost of said members engages a workpiece, the bored members being thereupon compressed as said punch perforates the workpiece, said bored members expanding on release of the punching iforce thereby to strip the punch from the `workpiece.

References Cited in the le of this patent UNITED STATES PATENTS 2,355,765 Wales Aug. 15, 1944 2,373,844 Norsen Apr.17, 1945 2,380,485 Wales July 31, 1945 2,419,862 Wales` Apr. 29, 1947 V2,597,976 Cousins May 27, 1952 OTHER REFERENCES Article entitled Teflon, in Product Engineering, of September1952, pages 149 et seq.

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