US2805717A - Self-contained perforating implement - Google Patents

Description

Sept. 10, 1957 P. H. TAYLOR SELF-CONTAINED PERFORATING IMPLEMENT Filed Oct. 26, 1954 3 6 3 wwwiw (w fvv. vm v INVENTOR.

QZ1 o7'ne United States Patent SELF-CONTAINED PERFORATING IMPLEMENT Paul H. Taylor, Grand Island, N. Ya, assignor to Wales- Strippit Corporation, North Tonawanda, N. Y., a corporation of New York Application October 26, 1954, Serial No. 464,722 18 Claims. (Cl; 164-110) The present invention relates to perforating apparatus and more particularly :to self-contained perforating implements.

Self-contained perforating units have been Widely adopted by industry for use where it is desired to punch a number of holes simultaneously in a workpiece, such as a sheet metal plate. A conventional self-contained perforating unit comprises a C-frame, a punch-stripper com bination mounted on the upper arm of the C-frame, and a die mounted on the lower arm of the C-frame in axial alignment with the punch. The stripper of the 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 the stripper 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 force, the compressed stripping spring expands and withdraws the punch from the work.

Self-contained perforating implements of conventional construction have the disadvantage that it is impossible with them to punch a pattern of h-Oles on centers as close together. as can be punched where a die separate from the punch, and positive stripping are employed. In the conventional self-contained perforating implement, the stripping spring surrounds the punch; and the thicker the material which is to be punched, the larger the stripping springs must be. As the stripping springs get larger, the widths of the units increase; and the closeness of holes which can be punched in one operation correspondingly decreases. This has limited the market for conventional perforating units to jobs where the hole spacing can be fabricated conveniently with self-contained units of a size sufiicient to provide a rugged enough structure to withstand normal operating conditions in a tool room.

To achieve narrower widths of self-contained perfo rating implements, the punch-stripper assembly of the Wales U. 8. Patent No. 2,355,344, issued August 8, 1944, was devised. In this implement three, small stripping springs are mounted in tandem to provide the required stripping force. With this construction, a narrower implement width results; and consequently closer center to center hole spacing may be obtained in the workpiece. However, with this implement difiiculty was sometimes experienced in that the stripping guide assembly, which had to be made comparatively hard to carry the stripping loads, would sometimes mark the workpiece. When the punch tip was withdrawn from the work against the stripper guide, moreover, very often a small upward burr was raised in the workpiece, because the normal clearance be tween the punch bit and the stripping guide permitted the soft metal of the workpiece to be drawn up slightly into the stripping guide. This was often objectionable; and in some cases burnishing had to be resorted to to eliminate these burrs.

Another disadvantage of this tandem stripping spring type perforating implement has been its high cost due to the cost of its three springs, base, and cap member.

While the present invention has particular application in self-contained perforating units, it is by no means limited to use in such units. -It may be employed, also, where a plurality of punches are mounted in a common supporting plate, asis shown, for instance, in the Wales U. S. Patents Nos. 1,964,752 and 2,355,765, granted July 3, 1934, and August 15, 1944, respectively.

One object of the present invention is to provide a selfcontained perforating implement of great simplicity which is of reduced size and cost as compared with previously known self-contained perforating units, and which has greater resilient capacity for stripping.

Another object of this invention is to provide a selfcontained perforating unit of very narrow width so that a plurality of units may be mounted side by side in a punch press to punch, simultaneously, holes on closer centers than has heretofore been possible using self-contained perforating units.

Another object of this invention is to provide in a unit of the character described a punch-stripper assembly in which the stripper member will not mark soft workpieces when it comes into contact with them. Another object of this invention is to provide a unit of the character described in which a single member serves as a punch guide, as a punch stiffener, as an assembly guide, and as a resilient device for providing the stripping force, and yet this member will not mark the work.

Another object of this invention is to provide in perforating apparatus a punch-stripper assembly which provides means for stiffening and supporting the punch in its perforating stroke to thereby protect it from the stresses to which it is subjected.

Another object of the invention is to provide a stripping assembly which during its approach to the workpiece, on the working stroke of the unit, travels freely in the supporting plate or frame, and upon engagement with the workpiece expands to eliminate all clearance between the punch and holder, whereby the hole is more accurately centered, and the slender punch is stiffened against the side loads to which it is subjected.

A further object of this invention is to provide in perforating apparatus a punch-stripper assembly which is self-centering and self-expanding in operation from the punching loads imposed therein, and which thus requires less accuracy in its fabrication, and is, therefore, of reduced cost.

Another object of the invention is to provide a homogeneous stripping-lifting assemblage for a perforating implement comprising a single, simple tubular member which serves the three-fold purpose of guide member, stripping spring member, and lifting spring member.

Another object of this invention is to provide a stripping assemblage for a perforating implement comprising a single piece which is adapted to constitute a guide member, a stripping member, and a countersink forming member.

Still another object of this invention is to provide perforating apparatus having a punch-stripper assembly which is self-lubricating.

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

In the drawing:

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 the punch in withdrawn, non-working position;

Fig. 2 is a fragmentary section on an enlarged scale taken on line 22 of Fig. 1 and looking in the direction 3 of the arrows, illustrating particularly the structure of the punch-stripper assembly;

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

Fig. 4 is a fragmentary section, similar to Fig. 2, of a perforating implement constructed according to another embodiment of this invention, the parts of the punchstripper assembly being shown in withdrawn, non-working position;

Fig. 5 is a fragmentary section, similar to Fig. 3, of the modification shown in Fig. 4, but showing the parts of the punch-stripper assembly at the end of a working stroke;

Fig. 6 is a fragmentary section of the punch-stripper assembly of a perforating implement constructed according to a still further embodiment of the invention and suitable for use where countersinking is desired simultaneously with the punching of a hole; and

Fig. 7 is a fragmentary sectionshowing a modified form of head construction for the punch of a perforating implement built according to the present invention.

Referring first to the embodiment of the invention shown in Figs. 1-3 inclusive, 10 denotes a self-contained perforating unit comprising a C-frame 11,.a die member 12, and a. punch-stripper assembly 15.. The C-frame has an upper arm 22, in which the punch-stripper assembly is mounted, and a lower arm 21, on which the die is mounted. The lower arm 21 has a channel or cutout 24 in its under side which is adapted to engage a key 25 on the bed 26 of the press to locate the perforating unit on the bed. Pilot pins may also be used to locate the perforating unit on the bed as well known in the art.

The die 12 has a centralbore 29 communicating with a discharge chute 30 through which slugs S punched from a workpiece W may pass. The die is provided with a pilot-pin 31 at itsbottom end which is coaxial with opening 29 and which fits into an accurately placed hole in lower arm 21 of the. C-frame to align the die accurately with the punch stripper assembly 15. The punch-stripper assembly 15 comprises a cylindrical punch 35, and a resilient tubular member 37. The punch 35 is in axial alignment with the die opening 29 in die 12. The tubular member 37 surrounds the punch. It is adapted to slide in a bore 39 in upper arm 22 of the C-frame. The punch 351's formed with an enlarged head portion 38 which engages the upper end of this tubular member 37.

The tubular member 37 is made of a plastic-like material such as nylon, Kel-F, Teflon, polystyrene, or the like. By far the superior material for most applications, at present, is material of the nylon family, though the other materials suggested, as well as some of the silicone solids may be employed. The rigid nylon, or plastic-like member 37 is by its nature suitable as a guiding member for guiding the punch 35; and it provides a bearinglike support for the punch 35 in the bore 39 of the upper arm 22 of the C-frame.

A light, mechanical, coil spring 40 serves as a lifter spring for the punch-stripper unit. This spring 40 seats at its lower end on the upper surface 41 of arm 22 and engages at its upper end against a split-ring 42. Splitring 42 may be of nylon or steel. It is made to frictionally hold firmly to the periphery of tubular member 37, yet be able to expand with expansion of the member 37. Spring 40 serves to hold punch 35 and elastic, tubular member 37 normally in lifted position (Figs. 1 and 2) to provide clearance between the lower end of stripper-punch unit 15 and the top of die 12 so that a sheet metal plate or other workpiece W may be readily inserted between them.

Tubular member 37 is formed with a bore 43 (Fig. 2) which, when the member is in its normal, at-rest position, has a diameter slightly greater than the diameter of the shank 36 of the punch 35 to provide some clearance relative to the punch shank. Further, the outside diameter of the tubular member 37 is considerably less than the diameter of the bore 39 in the upper arm 22 of the C-frame, thereby providing relatively a considerable initial clearance between the tubular member 37 and the bore 39 of the C-frame. For precision machine tool components, the outside diameter of the tubular member 37 may be, for instance, .002" to .004 less than the diameter of the bore 39, where normally that is with conventional construction, such parts would have to be held to a tolerance of at least .0005 fit.

The operation of the perforating unit 10 can be seen from Figs. 2 and 3. When the punch press ram R (shown only in Fig. 3) is driven downwardly, it forces punch 35 and tubular member 37 to move downwardly also as a unit until the stripper member 37 contacts the work. In this downward movement of the punch and stripper sleeve, the lifter-spring 40 is compressed between the top surface 41 of arm 22 and split-ring 42. When the member 37 strikes the upper surface of the workpiece W, its downward movement stops. Thereafter, the punch 35 moves relative to member 37, being forced through workpiece W, while member 37 is compressed between the head 38 of the punch and the workpiece W. This compression of member 37 causes it to distort elastically, thereby eliminating all clearance between its bore 43 and the shank 36 of punch 35, and at the same time, eliminating all clearance between it and the bore 39 in arm 22 of the C-frame. The elimination of these clearances causes punch 35 to be accurately centered and positively guided in its working stroke. Furthermore, the elimination of these clearances causes the punch 35 to be supported and stiffened as it moves downwardly to perforate the workpiece W. When the force applied by ram R is removed, the compressed member 37 expands to its normal size and form, thereby stripping punch 35 from workpiece W. Then coil spring 40 raises the assembly to its starting position.

The unit above described punches holes in a workpiece with a degree of accuracy heretofore practically impossible to obtain. This results from the action of member 37 which serves many purposes. Its resiliency provides the stripping force required to withdraw punch 35 from workpiece W after a perforating stroke. At the same time it provides an accurate guide for guiding the punch into the work; in fact, it provides a more accurate guide for this purpose than has heretofore been attainable in a selfcontained perforating implement. It also in expanding serves to center and stiffen the punch, augmenting the strength of the small-diameter punch shank by the added strength of the expanded stripper sleeve which, upon expansion, intimately embraces the punch shank around its whole periphery. Thus in the single tubular member 37 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 39 of the 0- frame 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 tight, yet, because of the nature of plastics such as nylon, Kel-F, Teflon, etc., lubricated embrace, and guides the punch very accurately. The expansion of the tubular member 37 on the working stroke, moreover, prevents upward extrusion of the metal of the workpiece into the bore 43 of the tubular member when thin gauge stock is punched. Being made of nylon, or similar material, the tubular member 37 is self-lubricating, thereby eliminating all lubricating normally associated with perforating apparatus. Furthermore, since member 37 is made of plastic it is softer than the workpiece being perforated, even when the workpiece is aluminum or some other soft metal. Thus, when it engages the workpiece on a downward stroke, it will not mar or mark the work.

The use of a resilient, plastic, tubular stripper member 37 greatly reduces the cost of the perforating implement 20. Since tubular member 37 expands elastically under compression and firmly engages the bore 39 in arm 22 of the C-frame it need not be manufactured with an outside diameter held to very close tolerance. Likewise, because the tubular member 37, when expanded, tightly embraces the shank of the punch 35, its bore 43 and the punch shank 36 do not have to be made to close tolerances. Therefore, member 37 can be made of commercial, extruded plastic tubing having the approximate inside and outside diameters desired. By contrast, the punch-stripping assemblies heretofore used in self-contained perforating units had to be carefully manufactured with minimum practical clearances between the parts so that the stripper sleeve would properly support and guide the punch and so that formation of burrs would be eliminated.

In a conventional perforating unit, for instance, the clearance between the stripper sleeve and the bore of the upper arm of the C-frame has to be extremely small because the clearance between the punch and the die in the punching operation must be extremely small to prevent formation of a downwardly extending burr on the part being punched. In some instances, for light aircraft stock, for example, the normal clearance between the stripper sleeve and the bore of the upper arm of the C-frame is less than .002". This requires that conventional stripperpunch assemblies be made extremely accurate to permit the tight sliding fit required. In contrast with conventional construction, in the perforating implement of the present invention, the only dimension, that requires to be held accurately, is the clearance between the punch and die for the working stroke. This must be held to a tight clearance to avoid formation of undesirable burrs in the punching operation. However, this tight clearance accuracy need only be maintained at the punch tip, and the punch does not have to be made to fit the stripper sleeve tightly for its whole length, as is required with conventional perforating implement construction.

A unit, such as shown in Figs. 1-3, can produce stripping loads of a magnitude of 1400 lbs., whereas an otherwise identical perforating device of the type shown in Patent 2,355,344, previously mentioned, with a threespring stripping assemblage, can only provide 320 lbs. of stripping force. Thus, it is clear that the device of this invention can punch much thicker stock than has heretofore been possible with a self-contained perforating implement; or conversely, the width of the holder or C-frame can be reduced by reduction in the width of the stripping assemblage, thereby enabling punching of holes on closer centers than is possible with conventional implements.

Figs. 4 and 5 illustrate an embodiment of the invention in which a tubular stripper member 50 similar to tubular member 37 is employed except that it has an integral lifting spring element molded or machined thereon. The resilient, molded or machined integral side lifting member 51 joins member 5%) adjacent its upper end; and, at its lower end engages in a depression 54 in the upper arm 22 of the C-frame of the implement. In this device, when the punch-stripper assembly is forced downwardly by press ram R (Fig. 5), side member 511 is deflected as shown. After the perforating force is removed and the punch is stripped from the workpiece, member 51 springs back to its original position thereby raising the punch-stripper assembly to normal, starting position. In regard to guiding of the assembly, guiding the punch and stripping the punch from the workpiece, tubular member 54 operates in exactly the same manner as the tubular member 37 previously described. In member 50, however, there is provided a lifter-stripping combination in one molded or machined piece.

It will be obvious, that instead of a single side member 51, a pair of side members 51 can be molded or machined integral with sleeve 50 at diametrically opposite sides of member 50 to provide a balanced lifting force should such be desired. Member 51 can also be formed to. straddle the punching assembly in a forked arrangement to apply a stripping or lifting force along the axis of the punch.

In a normal, at-rest position, shown in Fig. 4, the punch 35 is elevated at its cutting end slightly above the stripping guide 50. Actually in all embodiments of the invention the punch will preferably be withdrawn slightly into the stripping guide sleeve when at rest. This is to assure that the expansion of the plastic guide sleeve will take place before the sharp punch engages the workpiece. Otherwise, the guide sleeve would not expand to center the punch properly at the moment of entry of the punch into the work.

Fig. 6 shows a punch-stripper assembly constructed according to another embodiment of the invention and adapted to countersink or dimple the Worksheet simultaneously with the punching operation. Here, the punch 55 has a working end 56 of reduced diameter. Here, also, the resilient, tubular stripping member 57 is closed at its lower end 58 except for a central hole through which end 56 of the punch passes. Here, also, the tubular stripping member has the portion of it, which in the at-rest position extends above upper arm 22 of the 0- frame, tapering in thickness upwardly. The tapering thickness of the stripper member reduces the stripping loads. This taper in thickness also induces the plastic deformation of the stripper member, when it is compressed, to take place above the upper arm 22.

The lower end 58 of tubular member 57 is formed with a conical surface 59 adapted to countersink or dimple a workpiece simultaneously with the stripping of the punch. The conical surface 59 is adapted to cooperate with a complementary internal conical surface 60 on the die 12' of the perforating unit. Since it is not desired to have the lower end 58 of the stripper sleeve distort too much, otherwise it would not be able to effect the dimpling or countersinking operation, the lower section of the tubular member is thickened as contrasted with the upper section thereof. This reduces the plastic deformation locally to provide a forming (dimpling or countersinking) operation.

Where no expansion of the tubular guide at its lower end is desired, as is the case with guide sleeve 57, the punch 55 can be flush with the stripper sleeve at its lower end in normal, at-rest position, as shown in Fig. 6. However, even in this case it is preferred to have the bottom of the punch in its at-rest position a few thousandths of an inch above the bottom of the sleeve to insure that it will be properly stripped from the work.

Fig. 7 illustrates a modification in the construction of the punch member for use in the above described units. Here instead of making the punch with an enlarged head, such as head 38, the punch is made as a straight, cylindrical punch having a threaded upper extremity 68 to threadedly engage the resilient, tubular, stripping member 67. In this instance, the plastic member transmits its stripping loads directly to the punch through the threaded extremity 68 of the punch. This type of punch eliminates the necessity of costly machining an enlarged head on the punch as required in the previously described embodiments of the invention. It also permits straight, cylindrical pieces of tool steel to be utilized for punches instead of having to use large diameter stock and to turn that stock down with attendant great waste of expensive material. This particular construction is suitable where the stripping loads are relatively light, for example, in perforating light sheet metal for aircraft. However, if a steel insert member is placed inside the bore of member 67, heavy stripping loads can be carried.

As already pointed out the present invention is not limited to use in self-contained perforating implements. It may be employed in other types of perforating apparatus, also, with advantages such as those attained in a self-contained perforating implement. Thus fthe invention may beemployed-for instance, where a plurality of punches are mounted in a single supporting plate, as is the case in the apparatus shown intlie Wales Patents Nos. 1,964,752 and 2,355,765 referred to above. The plastic guide sleeves will be mounted reciprocably, loosely in the supporting plate, and normally held in upper position by either. a separate or an integral lifter spring device; and the punch will be mounted reciprocably, loosely in the plastic guide sleeve'but will be connected thereto by its head, or other means, so that punching and stripping forces may be transmitted between the punch and sleeve. When the ram descends, the several punches will be engaged and will transmit the motion of the ram to the tubular guide sleeves, at the sam'c time compressing the lifter springs, until the guide sleeves engage the work. Then the guide sleeves will be expanded in the bores of the plate and center the punches; as in the illustrated embodiments of the invention. When the ram returns, the sleeves will strip the punches from the work, and the lifter springs will return the punches and the sleeves to upper, at-rest position as in the illustrated embodiments of the invention.

While the invention has been described in connection with several different embodiments thereof, it will be understood that it is capable of further modification, 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 de partures 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. Perforating apparatus comprising a punch, a distortable, resilient, plastic tubular member in the bore of which said punch reciprocates, said tubular member constituting a combined guide and resilient stripping element, a holder having a bore in which said tubular member is reciprocably mounted, means connecting said punch to said tubular member so that they move together when a punching force is applied to said punch until said tubular member engages the workpiece, said tubular member being adapted thereafter to distort elastically when said punch is forced through a workpiece and to return to its original form on removal of the punching force to thereby strip the punch from the workpiece.

2. Perforating apparatus comprising a punch, a resilient, distortable, plastic tubular member surrounding said punch, said tubular member constituting a combined guide and resilient stripping element for the punch and having a bore the diameter of which is slightly larger than the diameter of the portion of said punch which is mounted in said tubular member, thereby providing normally a clearance between said punch and said tubular member, a holder, said holder having a bore in which said tubular member is reciprocably mounted, means for transmitting force between said punch and one end of said tubular member, saidtubular member being adapted to engage a workpiece to be punched on the punching stroke and thereafter being adapted to distort elastically as said punch is forced through a workpiece and to return to its original form on removal of the punching force to thereby strip the punch from the workpiece, the difference in diameters of said tubular member and of the portion of said punch mounted therein being such that when said tubular member is distorted the clearance between its bore and the periphery of the punchris eliminated.

3. Perforating apparatus comprising a punch, a resilient, distortable, plastic tubular member surrounding said punch, said tubular member constituting a combined guide and resilient stripping element for the punch, a holder, said holder having a bore in which said tubular member is reciprocably mounted, said tubular memher having a normal outside diameter less than the diameter of said bore to thereby provide clearance normally between said punch and said tubular member, means for transmitting force between said punch and one end of said tubular member, said tubular member being adapted to engage a workpiece to be punched on the punching stroke and thereafter being adapted to distort elastically when said punch is forced through a workpiece and to return to its original form on removal of the punching force to thereby strip the punch from the workpiece, the diiference in diameters of said tubular member and of the portion of said punch mounted therein being such that when said tubular member is distorted the clearance between its periphery and the bore of said holder is eliminated.

4. Perforating apparatus comprising a punch, a resilient, distortable, tubular member surrounding said punch, said tubular member constituting a combined guide and resilient stripping element for the punch and having a bore the diameter of which normally is slightly larger than the diameter of said punch thereby providing normally clearance between its bore and said punch, a holder, said holder having a bore in which said tubular member is reciprocably mounted, said tubular member having an outside diameter normally less than the diameter of the bore of said holder thereby providing normally clearance between said tubular member and the bore of said holder, means yieldably urging said tubular member to its normal, at-rest position in said holder, means for transmitting force between said punch and one end of said tubular member, said tubuiar member being adapted to engage a workpiece to be punched on the working stroke and thereafter being adapted to distort elastically when said punch is forced through a workpiece andto return to its original form on removal of the punching force to thereby strip the punch from the workpiece, said tubular member when distorted eliminating the clearances between its bore and the periphery of the punch and between its periphery and the bore of said holder.

5. Perforating apparatus comprising a punch, a resilient, distortable, plastic, tubular member surrounding said punch, said tubular member constituting a combined guide and resilient stripping element for the punch, a holder, said holder having a bore in which said tubular member is reciprocably mounted, a resilient arm extending from said tubular member to said holder to yieldably hold said tubular member in normal; at-rest position, means for transmitting a punching force between said punch and said tubular member when said punch is moved in one direction, said tubular member being adapted to distort elastically when said tubular member engages a workpiece and said punch is forced in said one direction through the workpiece and said tubular member beingad'apted to return to its original form on removal of the punching force to thereby strip the punch from the workpiece by movement of said punch in the opposite direction.

6. Perforating apparatus comprising a cylindrical punch, a resilient, distortable, plastic, tubular member surrounding said punch, said tubular member constituting a combined guide and resilient stripping element for the punch and having a bore the diameter of which is slightly larger than the diameter of said punch thereby providing a clearance between said tubular member and said punch, a holder, said holder having a bore in which said tubular member is reciprocably mounted, said punch having a head portion at its upper end which engages the upper end of said tubular member so that, when said tubular member engages a workpiece and the lower end of the punch is forced through the workpiece, said tubular member will be compressed and distorted elastically between the workpiece and said punch head and so that on removal of the punching force said tubular member will expand to its original form to strip the workpiece from the punch, said tubular member when distorted elim- 9 inating the clearance between its bore and the periphery of the punch.

7. Perforating apparatus comprising a cylindrical punch, a resilient, distortable, plastic, tubular member surrounding said punch,- said tubular member constituting a combined guide and resilient stripping element for the punch, a holder, said holder having a bore in which said tubular member is reciprocably mounted, said tubular member having an outside diameter less than the diameter of the bore of said holder thereby providing a clearance between said tubular member and said bore, said punch having a head portion at its upper end which engages the upper end ,of said tubular member so that, when said tubular member engages a workpiece and the lower end of the punch is forced through the workpiece, said tubular member will be compressedtand distorted elastically between the workpiece and said head, and so that on removal of the punching force said tubular member will expand to its original form to strip the workpiece from the punch, said tubular member when distorted eliminating the clearance between its periphery and the bore of said holder.

8. Perforating apparatus comprising a cylindrical punch, a resilient, distortable, plastic, tubular member surrounding said punch, said tubular member constituting a combined guide and resilient stripping element for the punch and having a bore the diameter of which is slightly larger than the diameter of said punch thereby providing a clearance between said punch and bore, a holder, said holder having a bore in which said tubular member is reciprocably mounted, said tubular member having an outside diameter less than the diameter of the second bore thereby providing clearance between said tubular member and said second bore, means yieldably holding said tubular member in normal, at-rest position, said punch having a head portion at its upper end which engages the upper end of said tubular member so that, when said tubular member engages a workpiece and the lower end of the punch is forced through the workpiece, said tubular member will be compressed and distorted elastically between the workpiece and said head, and so that on removal of the punching force said tubular member will expand to its original form to strip the workpiece from the punch, said tubular member when distorted eliminating the clearances between its bore and the periphery of the punch and between its periphery and said second bore.

9. Perforating apparatus comprising a punch, a resilient, distortable, plastic, tubular member surrounding said punch, said tubular member constituting a combined guide and resilient stripping element for the punch, said tubular member being tapered toward its upper end for the greater portion of its length and having a convex face at its lower end, a holder, said holder having a bore in which said tubular member is reciprocably mounted, said punch having a head portion at its upper end which engages the upper end of said tubular member so that when said tubular member engages a workpiece and the lower end of the punch is driven through the workpiece said tubular member will be compressed and elastically distorted between the workpiece and said head, said tubular member on its expansion after a perforating stroke stripping said punch from the workpiece.

l0. Perforating apparatus comprising a holder, a die mounted in said holder, a tubular, resilient, distortable, plastic member reciprocably mounted in a bore in said holder in axial alignment with said die, the diameter of said bore being greater than the normal diameter of the portion of said tubular member which reciprocates in said bore, a punch reciprocably mounted in the bore of said tubular member, the diameter of said punch being less than the normal diameter of the second-named bore, and means for transmitting movement between said punch and said tubular member, said tubular member being adapted to engage a workpiece on a working stroke of the punch while the punch is being forced through the workpiece,

vwhereby said tubular member is elastically distorted to eliminate the clearances between said tubular member and the first-named bore and between the tubular member and said punch as said punch is forced through the workpiece on said working stroke, and said tubular member operat ing on release of the punching force to strip said punch from the workpiece, said plastic member having a convex end confronting said die, and said die having a concave recess confronting the convex end of said plastic member and complementary thereto. v

11. Perforating apparatus comprising a holder, a tubular, resilient, distortable, plastic member reciprocably mounted in a bore in said holder, the diameter of said bore being greater than the normal diameter of the portion of said tubular member which reciprocates in said bore, a punch reciprocably mounted in the bore of said tubular member, the diameter of said punch being less than the normal diameter of the second-named bore, said punch having threaded engagement with said tubular member so that movement is transmitted between said punch and said tubular member, said tubular member constituting a combined guide and resilient stripping element for the punch and being adapted to engage a workpiece on a working stroke of the punch while the punch is being forced through the workpiece, whereby said tubular member is elastically distorted to eliminate the clearances between said tubular member and the first-named bore and between the tubular member and said punch, and saidtubular member operating on release of the punching force to strip said punch from the workpiece.

l2. Perforating apparatus comprising a holder, a tubular, resilient, distortable, plastic member reciprocably mounted in a bore in said holder, the diameter of said bore being greater than the normal diameter of the portion of said tubular member which reciprocates in said bore, a' punch reciprocably mounted in the bore of said tubular member, the diameter of said punch being less than thenor'm'al diameter of the second-named bore, and means for transmitting movement between said punch and said tubular member, said tubular member constituting a combined guide and resilient stripping element for the punch and being adapted to engage a workpiece on a working stroke of the punch while the punch is being forced through the workpiece, whereby said tubular member is elastically distorted to eliminate the clearances between said tubular member and the first-named bore and between the tubular member and said punch, and said tubular member operating on release of the punching force to strip said punch from the workpiece, and a lifting member integral with said tubular member and engaging said holder to be compressed on the working stroke of the punch, and to return the tubular member'to its normal, at-rest position on release of the punching force.

13. Perforating apparatus comprising a holder, a tubular resilient, distortable, plastic member having a portion of uniform outside diameter reciprocably mounted in a bore in said holder and having a portion of gradually decreasing outside diameter extending above said holder, the diameter of said bore being greater than the normal diameter of said portion of uniform outside diameter, a punch reciprocably mounted in the bore of said tubular member, the diameter of said punch being less than the normal diameter of the second-named bore, means for transmitting movement between said punch and said tubular member, said tubular member constituting a combined guide and resilient stripping element for the punch and being adapted to engage a workpiece on a working stroke of the punch while the punch is being forced through the workpiece, whereby said tubular member is elastically distorted to eliminate the clearances between said tubular member and the first-named bore and between said tubular member and said punch, and said tubular member operating on release of the punching force to strip said punch from said workpiece.

11 V 14. Perforating apparatus comprising a holder, a tubular, resilient, distortable, plastic member having a portion of uniform outside diameter reciprocably mounted in a bore in said holder and having a portion of gradually decreasing outside diameter extending above said holder, the diameter of said bore being greater than the normal diameter of said portion of uniform outside diameter, a punch reciprocably mounted in the bore of said tubular member, the diameter of said punch being less than the normal diameter of the second-named bore, means for transmitting movement between said punch and said tubular member, said tubular member constituting a combined guide and resilient stripping element for the punch and being adapted to engage a workpiece on a working stroke of the punch While the punch is being forced through the workpiece, whereby said tubular member is elastically distorted to eliminate the clearances between said tubular member and the first-named bore and between said tubular member and said punch, and said tubular member operating on release of the punching force to strip said punch from said workpiece, said tubular member having its workpiece-engaging end shaped to form said workpiece.

15. In a perforating assemblage, a holder, a punch while the punch is being forced through the workpiece,-

and at least one plastic member being secured to and offset from said tubular member and adapted to bear against said holder, said one plastic member permitting the resilient compression of. said tubular member for engagement of the work piece on said working stroke and elevating said tubular member for feed clearance when the punching force is released on completion of said working stroke.

16. In perforating apparatus, a C-frame member having upper and lower arms, said arms having bores in coaxial alignment, a die fixed in the bore of one of said arms, a punch-stripping assemblage slidably engaging the bore in said other arm, said assemblage comprising a headed punch, a semi-rigid plastic, distortable, member associated with said punch and in sliding contact with the second-named bore, and resilient lifting means associated with said assemblage to normally provide feed clearance between said die member and said assemblage, whereby upon compression of said assemblage between the bed and ram of a press, said assemblage is first depressed against said lifting means until said plastic member engages the work piece, after which said plastic member is distorted elastically as said punch perforates the workpiece, whereby said plastic member is first centered in the bore of .said other arm, and then under continued distortion centers said punch in said plastic member, whereby said punch is guided in accurate coaxial movement with said die during the punching operation.

17. In a punch-stripping assemblage, punch member having a head at one end and an operating portion at its opposite end, a resilient, distortable, semi-rigid, tubular plastic member in whichsaid punch member is reciprocable, the head of said punch seating against the adjacent end of said tubular member to connect said punch to said tubular member for transmission of punching and stripping forces therebetween, and guide means in which said plastic member is reciprocably mounted, whereby upon movement of the assemblage toward a workpiece,

said tubular member will engage the workpiece and then said plastic member will be compressed axially and will expand radially, storing energy and simultaneously centering said plastic member with regard to its guide means and said punch with respect to said plastic member.

18. In perforating apparatus, a holder, a die mounted in said holder, and a punch-stripping assemblage mounted in said holder in axial alignment with said die, said assemblage comprising a tubular, semi-rigid, plastic member reciprocably mounted in a bore in said holder, and a punch reciprocably mounted in the bore of said plastic member, said punch being connected to said plastic memher so that movement will be transmitted therebetween, said plastic member having a convex end confronting said die and being of uniform thickness for a portion of its length above said end and then tapering in thickness to ward its other end, and said die having a concave recess confronting the convex end of said plastic member and complementary thereto, the normal outside diameter of said punch being less than the diameter of the bore of said plastic member, and the normal outside diameter of the plastic member being less than the diameter of the bore of said holder, whereby upon engagement of said plastic member with a workpiece in a perforating operation said plastic member will be compressed axially and will expand radially to center said punch in said holder and with respect to said die and to hold the punch centered during its operation, said plastic member serving to strip said punch from the workpiece upon completion of the perforating operation.

References Cited in the tile of this patent UNITED STATES PATENTS 928,258 Grissom July 20, 1909 2,230,043 Moran Jan. 28, 1941 2,355,765 Wales Aug. 15, 1944 2,650,663 Wales Sept. 1, 1953

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