US2928450A - Self-contained perforating and countersinking unit - Google Patents

Description

-w t t. 4- s March 15, 1960 F. M. BELDING 2,928,450

SELF-CONTAINED PERFORATING AND COUNTERSINKING UNIT Filed Feb. 7, 1955 VENTOR.

Franu's M fi m-n BY M afi orng /J i United States Patent SELF-CONTAINED PERFORATING AND COUNTERSINKING UNIT Francis M. Belding, Kenmore, N.Y., assignor to Wales- Strippit Corporation, North Tonawanda, N.Y., a corporation of New York Application February 7, 1955, Serial No. 486,425

' 1 Claim. (Cl. 153-21 The present invention relates generally to self-contained perforating units, and more particularly to a selfcontained perforating unit adapted to punch and countersink a hole simultaneously.

Devices of the type disclosed herein have been needed for some time by the sheet metal industry where it is often desirable to punch a hole and countersink simultaneously; for with a self-contained perforating unit that will punch and countersink a hole simultaneously need for composite or progressive dies will be avoided. With these dies the holes must first be punched and then these holes must be accurately registered with the countersinking unit in order to countersink the holes. Heretofore, however, where attempts have been made to use a self-contained unit for simultaneously punching and countersinking a sheet metal piece, the punch has had to be solid enough to perforate the workpiece, which has meant a substantial column. This, in turn, has meant that when the countersinking portion of the punch is bottomed, the punch itself seats against solid metal; and the pressure of the press ram on the punch is transmitted directly through the punch to the die of the unit and to the bed of the press. As a result, extremely high stress levels are produced in the punch, with consequent failure of the mechanism, and in particular of the punch. Generally, the life of conventional self-contained perforating units for punching and countersinking a hole simultaneously, has been extremely short.

In some instances, stop-blocks have been used on the press to prevent overloading the punch members. When stop-blocks are used, however, the high forces developed are usually transmitted to the press itself because a press by nature is a piece of heavy equipment and cannot be accurately set to stop on its downward stroke within precise limits.

' Despite their short life and other disadvantages the use of conventional perforating units for punching and countersinking has been justifie d because of thereduction in overall cost as compared with the cost of the complex dies required where punching and countersinking are used for perforating in a countersinking application, for,

in many instances it is possible to do the countersinking without failure of the unit, because the spring-stripper provides the unit with the required compensating resiliency. Since it is difficult, however, to hold a tool, which has to both perforate and countersink, very accurate in length, that is, to an accuracy of less than .001, and

since it is also extremely difficult to adjust the shut height of the press close enough so that simultaneous perforatice ing and countersinking can be done without a high rate of failure of the punches, the problem is presented of achieving resiliency in such way that suflicient force can be transmitted to the punch member to enable it to per:

forate and countersink a workpiece, while preventinga buildup in stress levels to a point where, because of overtravel-of the press ram, inaccuracy in the length of the punch, or the like, the punch will be fractured. In the past all attempts to use, for this purpose, rubber or other resilient devices have failed. This is because such high forces must be transmitted through the resilient medium, that the resilient member had to be so large that it has rendered the unit itself impractical. Moreover, none of the resilient mediums heretofore available were suitable for the purpose. As a result, in most instances it has been preferred to overload the punch or the stop blocks, and to replace these parts when they failed.

When stop blocks are used, however, extreme accuracy in manufacture of the punching units is still required to control the distance from the head to the countersink very accurately, as well as the height of the die member, and of the holder to which the unit is attached. Tolerances in the neighborhood of .0002" are necessary on these parts of the unit to prevent excessive buildup'in stress levels with resultant early failure of the units. Even when such close tolerances are maintained, poor countersinking by some of the units, where a multiple unit set-up is used, sometimes occurs because of this .0002" tolerance.

An alternative, when a number of perforating and countersinking units are to be used for simultaneous operation on a workpiece, is to take the units after they have all been assembled and to grind the punches to the same identical lengths, when closed. This is time-consuming and costly, and prevents the interchangeability of punches and other parts, normally associated with a mass pro-' duction operation.

One object of this invention is to provide a nonbottoming perforating-oountersinking unit.

Another object of this invention is to provide in a countersink type of perforating unit means for compensating for a buildup in tolerances in the several parts of the unit.

Another object of this invention is to provide perforat-' ing-countersinking apparatus in which commercial parts may be used to provide a non-bottoming perforating unit.

Another object of the invention is to provide a counter sink type of perforating unit, which will eliminate failure of punches when a plurality of them are used simultaneously for multiple punching-countersinkirig operations on a workpiece.

Another object of this invention is to provide perforat ing-countersinking apparatus of the character described which has incorporated therein resilient means for preventing excessive buildup in stress levels.

Another object of this invention is to provide perforating-countersinking apparatus which will have a vastly longer life than similar units of prior design, but which at the same time will be reasonable in cost.

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

In the drawing:

Fig. l is a side elevation of a perforating. unit constructed according to one embodiment of this invention, the unit being shown with the tool in withdrawn, nonworking position;

Fig. 2 is a fragmentary section taken on line 2-2 of Fig. 1 looking in the direction of the arrows, illustrating on an, enlarged scale the'structure of the punching, countersinking assembly and showing a workpiece'disposed on the die in position to be punched and countersunk, the punch and the parts associated therewith being shown in withdrawn, non-working position; and

Fig 3. is a section similar,tQ FigMZ, .buttshowin'g the.

positions of the: parts Ton completion of a Working stroke ofthe punch. Q I j e W Q Referring-nowto the drawing by numerals of reference,

20 denotes generally a self-contained perforating-counter:

sinking unit constructed according to one embodiment of this invention. The unit comprises, generally; a Q-frame Die member 22 has a central bore 32; formed withv a conical portion 33 at its'upp'er end, and communicating with a discharge chute 34 through which slugs punched from a workpiece W may be discharged. i

The punch-countersink-stripper assembly 23 comprises escapee to accurately adjust the stroke of the ram of a heavy I punch press, capable of producing say a two hundred toir force, within a few thousandths of an inch. That is why,

as stated above, it has been necessary in the past to put heavy stop blocks in the'press to prevent the ram from overloading the. perforating units. However, as also stated, this'simply transfers the stress from the punch member-to the. bed and rain of the press, often causing failure of the press.

The diificulties and disadvantages of previous apparatus may be avoided in the perforatorcountersinker of the present invention byprovidingpunch-stripper assembly 23.

t with. a cap member 65 which is adapted to be engaged by ram R (Figs. 2' and 3) of the press; Cap 65 ismade of a resilient materiaLpreferably nylon. It is formed with a skirt portion 66, which nests over the punch head 41 and the upper end of stripper-spring 55. v Skirt 66 has an inside diameter equal to or even slightly less than the i outside diameter of head 41 and ofspring 55. Thus,

the tool 40, the tubular, combined stripper and guide mem- 1 her 50, a coil spring 55; and a secondary lifter. spring 60.

,Member 5ii-is reciprocable in bore 37 of theupper arm of holder 21. Coil spring 55 surrounds the tool 40 and theupper, neck portion 52 of stripper 50, and is interposed between the head. 41 of the tool and the upper f-ace51 of a collar 53* formed on the stripper 50. Lifter spring 60 surrounds xthelstripper sleeve 50 and is interposed betweentthe lower. face 54 of this collar and the upper surface of arm 25. 'Lifter spring 60 acts to hold the assembly- 23 in raised position. (Figs. 1 and 2.) to provide clearance for the insertion of workpiece W between the tooland die.

Referring now to Fig. 3 it will be noted thatthe tool or punch member 40, instead of having just a punch tip 42 on it, has also a conical countersink portion 43 formed thereon. above; punch tip 42. Countersink portion 43 is complementary to the mating countersink portion 33 formed in the die member 22. Countersink portion 43 connects the tip 42 of the tool with the shank 44- ofthe tool. The shank 44 is mounted to reciprocate in and to be guided, by the bore of stripper sleeve 50; Above the stripper sleeve the tool shank is of increased diameter when it is pressed onto the head 41 and spring 55 it will grip the peripheries of these parts and stay in place. .As a result, whenthe implement is transported there is no danger of cap 65 falling off.

.On punching andcountersinking operations, the elastic member 65'serves to transmit the force of the ram R to the punch head 41; and. at the same time it provides resiliency. between the ram and the punch. If the stroke of the ramis in excess of that proper for the length of the.

punch," or if. a punch inla multiple perforating tool set-up as denoted at 45. Portion 45 of the 'tool'shank connects V with. thetool head 41.

In operation, the ,tool 40 descends and its part 42 punches a slug; out of the workpiece into the die; after whichcontinued downward movement of the tool causes the tapered countersink portion 43 of the tool, in cooperation with..the conical recess 33 in the die, to' form a countersink Cain workpiece W. This latter is the operation that has caused the difficulties heretofore in achieving a practical tool for simultaneously punching and countersinking a workpiece.

It willibe obvious that, if

the ram 'R of a'press. engages directly with the head 41 of the punch, the height of thearm 26, the height of the die 22 above its seat on arm 26, the height or, length of the tool" 40, and the height of the stripper 50 must be held to absolute accuracy to avoid a buildup in tolerance from one part to the other under the ram. Obviously this is a physical impossibility and variations in total height as' high as .005" occur even with the most accuratemanu facture.

Wherethere are a plurality of holes to be punched and countersunk simultaneously in a workpiece by a plurality of perforating units, it may become necessary even to grind the headsof the punches so that they are all engaged simultaneously by the ram, but this renders the punches no longer interchangeable. Even grinding of the heads of the punches may be of no avail ifthe ram of the press has a taper or belly in iton its lower-face. Moreover, as previously} stated, itis extremely 'difiicult happens: to bemore: than the. desired.1ength,.the cap:

is reduced in thickness and its skirt portion 66 is ex panded so thatit no longer hugs tool head 41 and;

'spring 55, The plastic cap 65 will therefore transmit the. pressure" required to press the countersink 43 of the 1 tool into the work piece whileat the same time providing sufficient elasticity to insure that a safe limit stress i on the machine tool elements will not be exceeded. In

other words, the plastic cap 65 is, in effect, a safety valve preventing overload of the tool 40, or of the press from the' perforating forces.

When the ram R is retractedupon completion of its working stroke, the stripper spring 55 expands in the usual fashion to strip the tool from the work; and then the lifter spring 60 lifts the wholetool-stripper assembly 23 back to the position shown in Figs. .1 and2.

cap 65 returns to its normal shape, skirt 66 againgiipping headf41 and spring 55.

The apparatus described W111 perforate. and cotmtersink a workpiece, simultaneously, with a degree of accuracy and efficiency heretofore unattainable. The resilient member 65 in the implement transmits the working force and at the same time positively prevents excessive build up in stress'levels in the punch-countersink member. This'means that: the implement will have a long life. The use of stop-blocks on the press is no,

longer retiuired. Also, any necessity for grinding in dividual punches in an assembly operation is likewise eliminated, thus permitting interchangeability of parts.

Further, the cost of manufacturing the implements greatly reduced because extremely close tolerances need not be maintained. Nylon member 65 need not be pre cision' made. A commercial part constructed with ap; proximatelythe desired length and diameter is-suflicient, as is apparent from the foregoing description.

While the invention has been described in connection with a'specific embodiment thereof, it will be understood that it is capable of modification, and this application is i'ntenderl'to cover any variations, uses or adaptationshf the invention following, in general, the principles of the invention and including such departures from the present disclosure as come withinknown or customary practice in? the art to which the invention pertains and as maybe applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claim.

Having thus described my invention what I claim is:

A self-contained implement for use in a press for simultaneously punching and countersinking a workpiece, comprising a C-frame having upper and lower arms, a die mounted on said lower arm, a stripper sleeve reciprocably mounted in a bore in said upper arm in axial alignment with said die, a tool reciprocable in said sleeve, said tool having a shank portion of one diameter slidably guided in said sleeve, a punch bit of reduced diameter at its lower end, a conical countersink portion connecting said punch bit with said shank portion, and an enlarged head at its upper end, said die having a bore, to receive said punch bit, which has a conical portion at its upper end to cooperate with the conical countersink portion of said tool, a coil stripper-spring interposed between said stripper sleeve and said head, and a compressible, distortable, resilient plastic cap mounted on top of said head, said cap having a depending skirt which surrounds the periphery of said head and the upper end ,of said spring, and which resiliently embraces said spring in the normal position of said cap but which is free thereof, said cap being adapted to transmit the working force of the press to said tool, said cap being distortable and deflectable to protect the tool from being over-stressed,

said skirt expanding away from said headand from said spring when said cap is distorted. p 7

References Cited in the tile of this patent. UNITED STATES PATENTS 59,823 Crate Nov. 20, 1 866 78,947 Fansworth June 16, 1868 392,957 Latulip Nov. 13, 1888 768,126 Huber Aug. 23, 1904 939,324 Robinson Nov. 9, 1909 1,008,226 Wanlin Nov. 7, 1911 1,150,484 Bechman Aug. 17, 1915 1,409,638 Zetterman Mar. 14, 1922 1,726,219 Gammeter Aug. 27, 1929 1,911,108 Coyle May 23. 1933 2,122,316 Ganio June 28, 1938 2,123,393 Windsor vl'uly 12, 1938 2,134,815 Elliott Nov. 1, 1938 2,600,843 Bush June 17, 1952 2,685,928 Bergh 'Aug.'10, 1954 2,708,288 Fuller et al. May 17, '1955 OTHER REFERENCES Modern Plastics, disclosure on page 114, November 1946.

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