US2756825A

US2756825A - Die set leader pins and leader pin bushings

Info

Publication number: US2756825A
Application number: US262815A
Authority: US
Inventors: Janiszewski Kasimir
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-12-21
Filing date: 1951-12-21
Publication date: 1956-07-31
Anticipated expiration: 1973-07-31

Description

July 31, 1956 K. JANlszEwsKl 2,756,825

DIE SET LEADER PINS AND LEADER PIN BUSHINGS Filed Dec. 2l. 1951 2 Sheets-Sheet l July 31, 1956 K. JANlszEwsKl DIE SET LEADER PINS AND LEADER PIN BUSHINGS 2 Sheets-Sheet 2 Filed Dec. 2l, 1951 United States qPat-ern:

DIE SET LEADER rINs AND LEADER PIN BUSHINGS Kasimir Janiszewski, Hales Corners, Wis. Application December 21, 1951, Serial No. V262,815 Claims. (Cl. 164-;1'1'8) This invention relates to improvements in die set leader '.'pins and l*leader pin bushings having clearances variable in the course of their relative movement.

One of the objects of the invention is to facilitate separation of the platens of a die set without cramping the leader pins in their respective bushings. For this purpose, leader pin and bushing assemblies having variable 'clearance between the respective leader pins and bushings are provided.

The problem of die set leader .pins `cramping in their 'punch holder bushings is particularly noteworthy whenever the punch holder of the die set is removed for punch changing or other purposes. The punch holder is conventionally guided by a plurality of leader pins, varying'in number, but frequently four, one at each corner of the punch holder. As the punch holder is lifted from the die set, by a crane or the like, it may, 'as it is about to clear the top ends of the leader pins, tilt or cant to withdraw completely-from one pin before clearing the 'remaining pins, and thus cramp or seize and even bend the other leader pins, or break or crack 'the bushings. Even if the punch holder does not prematurely clear one pin, the gradual reduction in bearing surface 'may permit the ,punch holder to tilt and 'cramp or bend one or all 'of the pins.

Accordingly, it is one object of the present invention to obviate this diiculty by providing the leader pins with immediately available clearance during the course of vplaten separation either between the bushings and the leader pins, or between the leader pin cores yand separable sleeve portions thereof, or both, thereby eliminating the ,possibility of cramping.

Another important object of the invention Vis to provide leader pins and bushings having variable clearance to -slidably engage with precision t only during that critical portion of the punch holder stroke when the punch is engaging the work, and are relatively yfree of close contact during other and less critical portions of the punch holder stroke.

Forthese purposes a leader pin and'bushing sleeve assembly is provided with complementary mating surfaces which provide close guidance at axially remote points but afford increased clearance immediately as Ithe platens separate. In preferred embodiments of the i`nvention, the tapered surfaces comprise stepped cylindrical surfaces rather than surfaces of 'frusto-.conical form. In all embodiments, however, the leader pin and bushing sleeve have complementary surfaces which have clearance progressively increasing in the direction of withdrawal of 'the punch holder from the die shoe and decreasing in the direction of work engagement.

A specific object is to provide, in V'one vembodiment of the invention, a sectional leader pin having internally tapered complementary-'cored 'and socketed sections with coupling means therebetween.

Other objects and advantages of the invention will be 'more apparent to one skilled in the art upon an exarn'iiiation Yof the following disclosure.

2,756,825 Patented July 31, 1956 In the drawings:

Fig. 1 is a'p'erspective view of a die set having separable platens and leader pin and bushing sleeve assemblies embodying the invention.

Fig. 2 is an enlarged vertical cross section through a portion of the die set and one embodiment of a sectional leader pin and bushing sleeve assembly, portions of the leader pin being shown in elevation and other portions being shown in section to expose details of construction.

Fig. 3 is an aXial cross section through the leader pin only of Fig. 2, ythe respective leader pin sections being shown in separated position.

Fig. 4 is a view partly in elevation and partly in cross section of a modiiication of the sectional leader pin shown in Figs. 2 and'3.

Fig. 5 is a lfragmentary view of a still further modification of a sectional 'leader pin embodying the invention.

Fig. 6 4is a vertical cross section through a portion of a die set having a leader pin and bushing Vsleeve assembly with ycomplementary stepped cylindrical bearing surfaces, the leader pin being shown in elevation.

Fig. 7 is a view similar to that of Fig. 6 showing a modieation in the lbushing sleeve.

Fig. 8 is a further modification ofthe device ofV Fig. 6.

Fig. 9 shows a modification of the device of Fig. 2, showing a `different form of sectional leader pin.

Fig. ll0 is a different aXial cross sectional view of the device-of Fig. 9, showing 'the respective leader pin -sections in the course of separation.

Fig. /ll is a cross sectionalvview through a modied form yof the device shown in Fig. 9.

Fig. 12 is a vertical cross section 4through a portion of a die set fitted with a vmodified form of a tapered leader pin and bushing embodying -the invention.

Fig. 13 'is a cross sectional View Vtaken along the lines 13-13 of Fig. 12.

A die set having separable platens comprising a die shoe 20 and punch holder 21 is diagrammatically shown in Fig. l. As best indicated in Fig. 2, the die shoe normally carries Ia die, illustrated diagrammatically 'at 22, and has at least i-one upstanding leader pin 2S. The punch holder carries a punch, illustrated diagrammatically at 23, Vand is provided with a bushing in which the leader pin is slidable 'to guide the punch as it reciprocates with the punch holder to coact with the die 22 upon the work 'illustrated diagrammatically at 24.

Individual leader pin assemblies, usually two, three 'or four in number, are normally provided at each corner of the die set, as best shown in Fig. l. Prior to the present invention, the respective leader pins and punch holder bushings were made with complementary precision fitted bearing-surfaces extending for substantially the full height of the punch holder and full length of the leader pins.

The improved leader pin and bushing assemblies yillustrated in the accompanying drawings, and which are hereinafter described, all are structurally designed to provide for lateral clear-ance between the leader pin and bushing when the punch holder is -separated from the die shoe. Several embodiments of leader pin and bushing taper will be hereinafter described. Some of these embodiments comprise complementary frus'to-conical mating surfaces, and other embodiments comprise stepped complementary cylindrical surfaces. I choose' to denominate the configuration of thesevar'ious modifications by a generic term taper, and such term will be understood as used throughout the specication and claims, except as otherwise indicated, to mean compl'ernentary mating surfaces of progressively smaller diameter in the direction 4of punch holder Withdrawal. A

In 'the preferred construction shown in Figs. 2 and 3, a sectional leader pin having-acore section l2-5 is provided with la head l26 having discontinuous upwardly `tapered 3 frusto-

conical surfaces

27 and 28. Sleeve section 31 is provided with a cylindrical bore 3.3 and a communicating tapered bore or inner surface 32 complementary with the head surfaces 27 and 2S.

At the junction of the cylindrical bore 33 and tapered bore 32, an apertured and countersunk plug 3d is inserted to serve as a seat for the head of a screw 35 which couples the sleeve section 31 and the core section 25 of the leader pin. Plug 34 is rotatably keyed to sleeve 31 by means of a snap expansion ring 3S which fits within the annular space provided by aligned

peripheral grooves

36 and 37 in the plug and sleeve, respectively.

Head 26 of the leader pin section 25 is axially tapped at 41 to receive the threads of coupling screw 35, the head of which is seated in the countersunlc aperture 4f?. in the plug 34. The head of screw 35 is provided with a socket 43 to receive a socket wrench such as the wrench la shown in Fig. 3. ln order to develop axial thrust between the sleeve and the head. sections to separate these sections,

plug 34- may be shouldered above the head of the screw,

whereby turning the screw in a direction to remove it from tap 41 will exert thrust against the plug to separate the sections. In the embodiment of Figs. 2 and 3, the shoulder is provided by upsetting portion 46 of the plug near its top surface over the counterbore, an apertured washer being first positioned over the screw head and below the top surface of the plug.

ln the embodiment of Fig. 5, a welsh plug 43 may be used to provide the shoulder in lieu of upsetting the plug.

Plug 34 is provided, in its counterbore 42, with an under- A cut peripheral groove 47 within which the centrally apertured welsh plug 48 may be driven to substitute for the washer 4S of Figs. 2 and 3 and to provide the shoulder against which the head of the bolt 35 acts. The function of the shoulder is best illustrated in Fig. 3, where the i sleeve section 31 has been partially lifted from the core section 26, thus laterally as well as axially clearing the complementary tapered frusto-

conical surfaces

32 and 27, 28.

A somewhat modified form of the sectional leader pin is shown in Fig. 4 wherein the sleeve 51 of the sectional leader pin is internally threaded at 52, and is provided with a plug 53 complementarily threaded at 54. The threads hold the parts together, as compared to the snap ring arrangement of the embodiments of Figs. 2 and 3. ln the embodiment of Fig. 4, however, plug 53 may be advanced axially on its threads toward the top of the leader pin core 55. Upon contact of the downwardly projecting boss 56 of the plug with the core top, axial thrust is developed to separate the sleeve and core sections.

By reason of the threaded connection of the sleeve section 51 and plug 53, the coupling screw 57 need not be used to separate these parts. Accordingly, the plug counterbore 5b is smooth-walled and not provided with a shoulder. The plug 53 is, however, provided with sockets 59 to receive a wrench to turn the plug respecting the sleeve section 51.

A still further sectional leader pin modification is shown in Figs. 9, l0 and ll wherein the leader pin comprises an anchorage section 61 having a head 62 with a continuous frusto-conical tapered surface 63 mating with the cornplementary frusto-conical tapered bored surface 64 of sleeve section 65 of the pin. Sleeve section 65 has an integrally formed transverse web 66, as distinguished from .A

the separate plug 34 in the embodiment of Fig. 2, and which constitutes the base of the socket 64. Web 66 is provided with a central aperture 67 and a counterbore 72 through which a screw 68 extends to threaded engagement with tap 71 of core 62. Counterbore 72 is threaded at '73 for a purpose to be hereinafter described in more detail.

Screw 68 has a socketed head 74, of less outer diameter than the web counterbore 72. Accordingly, axial movement and rotation of the head 74 is not interfered with by l the thread 73. Screw 68 serves to couple the complementary tapered socketed and cored sections of the lleader pin. A transverse aligning pin 75 may be provided at the junction of the socketed and cored leader pin sections to assure uniform registration of the sectional parts.

At such times as it is desired to clear the socketed and cored sections of the leader pin, as incident to withdrawal of the punch holder 21 from the die shoe 20, screw 68 may be removed and replaced by a jack stud 76 (Fig. l0) having an enlarged head 77 with threads '73 engaging the threads 73 of the counterbore 72. Head 77 is provided with a central socket 31 to receive a soclret Wrench 82 whereby separating thrust may be developed between the threads 73 in the socketed section 65 of the leader pin and the cored section 61 of the leader pin through the unthreaded jack stud 76. As clearly shown in Fig. 10, separation of the mating leader pin sections will result in lateral as well as axial clearance between the frusto-conical surface 63 on the core 62, and the mating frusto-conical surface 64 on the socketed section 65 of leader pin.

if, during use of a die set, the leader pin section 65 seizes in bushing 91, the screw 68 will break to permit leader pin section 61 to withdraw, with constantly increasing clearance, from the tapered socket in section 65, thus precluding damage.

Screws

35, 57 and 88 may be frangible for the same purpose.

A somewhat moditied form of the device shown in Figs. 9 and lO is shown in Fig. ll. In this modification, the head section 83 of the leader pin is provided with a smooth wall counterbore S4 having an internally facing groove 35 near its top end to receive a snap ring 86 which provides an upper shoulder against which the socketed head S7 of screw S8 may act. In this manner the same screw 88 accomplishes the function of the threaded screw 63 in Fig. 9 and the jack screw 76 in Fig. 10.

In the embodiments of the invention shown in Figs. 9, l0 and 1l, the punch holder 21 is provided with a conventional continuously cylindrically walled bushing 91 complementary with the cylindrical outer wall or surface 92 of the socketed portion of the sectional leader pin. Accordingly in these embodiments the leader pin and bushing are in bearing relation throughout the normal range of such holder reciprocation.

In the embodiment of Fig. 2, however, provision is made to permit the leader pin to ride free in the bushing except at the critical point in the stroke where the dies coact upon the Work. The punch holder bushing comprises axially spaced cylindrically

walled collars

93 and 94, the collar 93 having an inner cylindrical surface 95 of smaller diameter than the inner cylindrical surface 96 of the collar 94. A spacer 97, of greater internal diameter than the collars, separates the

collars

93 and 94. An external washer 98, of still greater internal diameter, holds the collars and spacer assembled against the annular shoulder 99 of the punch holder. The washer 9S is held against the under surface of the punch holder 2.1 and against the under surface of the collar 94 by one or more screws 101. The external surface of the socketed portion 31 of the leader pin is stepped to provide

cylindrical surfaces

102 and 103, said surfaces being complementary with the cylindrical surfaces and 96 of

collars

93 and 94, respectively.

By reason of the spacing of

collars

93 and 94, bearing engagement of their

inner surfaces

95 and 96 with leader pin surfaces 102, 103 occurs in only a short range of punch holder reciprocation. The leader pin 25 is so positioned in die shoe Ztl that these bearing surfaces do not come into engagement until the dies are about to coact upon the work.y Accordingly, the leader pin acts as a guide only during the short period of the stroke of the punch holder when accurate guiding is of utmost importance. At all other times, th punch holder is relatively free and clear of Vthe leader pin. Inthis manner l cylindrical bushing sleeve surfaces.

of Fig. 6, the bushing bearing surfaces comprise the bottom collar 125 seats.

lshoulder l128.

aduanas wear on the pin and bushing .is greatly reduced and'crfamp- .ing becomes virtually impossible because Vthe Icomple- -mentary bearing surfaces at opposite endsof the leader 4pin clear simultaneously in response to the lirstwithdrawal movement.

In the embodiments of the invention shown in Pigs. 6 and 7 the leader pin is a vone piece construction, the conical tapers and screw being omitted. Instead, `the upward taper on the leader pin 104 is in the form o'fstepped

cylindrical surfaces

105, 106 and 107, the respective surfaces being of .progressively smaller diameter in the direction of -punch holder Withdrawal. These stepped vleader pins surfaces4 mate with complementary stepped In the -embodiment stepped surfaces 10S, 109., 110. These surfaces are inwardly embossed on common sleeve 113: to progressively .smaller diameters in the ldirection of `punch holder Withdrawal. Common sleeve 1.13 ris further provided with an outturned bottom flange 114 which abuts the bottom surface of the punch holder l21 to position the sleeve respecting the punch holder. Sleeve 113 is .norm-allyheld .within the punch holder aperture 11.2 by a press it.

In the embodiment of Fig. 7, the stepped complevmentary cylindrical bushing surfaces 115, 1.16 and )117 comprise the vinner annular peripheries of raxially .spaced Acollars or rings which are separate from, but .axially .spaced by, spacer sleeves 118 and 119. The sleeves and collars are held in assembly against the shoulder r120 "of the punch vholder by an annular washer 121, similar to washer 98 in Fig. 2.

vIn either of the embodiments of Figs. -6 and 7, the bearing surfaces of thev punch holder bushing .or sleeve comprising the respective collars 4or embossmen'ts .are substantially spaced axially. The lleader .pin is also .so positioned that these bearing surfaces do not contact the leader pin surface until near the end of the downward stroke of the punch holder. Accordingly, :almost immediate lateral, as well as axial, disengagement -of the leader .pin cylindrical bearing surfaces from the punch `holder bushing or sleeve cylindrical.bearingvrsurfaces will occur after upward movement Ao'f the punch vholder has been initiated. In this manner, lateral clearance between the .leader pin and .punch holderbushing is developed by reason of the stepped complementary.

surfaces and smooth withdrawal of the Apunch holder Vfrom the die shoe Without cramping or seizing of the bushing against the leader pin is facilitated.

The embodiments of Figs. 6-and 7 are also characterized by cam action between the respective bearing surfaces on .the punch holder bushing and leader pin during the portions of punch stroke when leader pin .guidanceis most necessary. At all other times, the leader pin is free andl clear of bearing contact with the punch holder bushing.

In the embodiment yof Fig.. 8, the vleader pin v.124 is pro- .i

vided with stepped cylindrical surfaces of different diameters which comprise axially spaced '

annu'l'ar collars

125 and 126 which are slipped over 'a central core `127 of the leader pin. The leader pin is 'provided at 'thelower base of the core 127 with a shoulder'1'28 againstwhichthe Spacer sleeve 129 axially separates the respective collars 125 and 1'2'6. Top wa'sherlor ,plate 132, held to the leader pin by 'screw l133', holds the collars fand spacer in unitary assembly against the In this embodiment, the punch lholder bushing also comprises axially spaced collars 13'4 and 135 having stepped cylindrical surfaces `complernenta'ry'with the stepped cylindrical surfaces of the

leader pin collars

125 and 126.

Collars

134 and 135 are axially spaced by the spacer 136. The

respective collars

134 and 135 and spacer 136 are held against punch holder shoulder 137 by means of an external washer 138, which bears against the under surface of the punch holder 21.

As in the embodiments of Figs. 6 and 7, the Fig. 8 embodiment comprises leader pin and punch holder bearfno -positions'other :than the immediate proximity to .itsrlower- `most position -of the punchholder.. 4As aforesaid, this Vrelation of lparts prevents punch -holder cramping and lprovides cam act-ion only when accurate leader -,pin guidance t.isrequired In allappropriate embodimentsyby formi-ng the respective bearing surfaces on removable collars, :as distinguished from forming 'them integrally with the bushing sleeve for .leader pinl propenrready replacement -of individual worn collars is made possible, thus reducing maintenance costs.

.'In the embodiment of the-:invention Ashown inFigs. l2 .and i3, the leader pin 1-41 is provided-with an upwardly frusto-conical tapering surface 142, and the punch holder bushing 143vis provided withfa complementary vtapering bore 144. Accordingly, .movement of -"the `punch holder .21 from the die set 'will cl'ea'r thepunchn'holder bushing and mating leader .pin surfaces .in the :manner y'aforesaid :to prevent seizing. -.=As :the "tapers mate ronly lat one point in .punch 'holder stroke this arrangement of parts precisely valigns the punch holder 'and die .shoe lat the bottom ofthe `punch .holderstroke when .Iac'curacy fis desired, but' permit the `leader pinto separate from -its punch holder bushing at all other times.

:Inorder to adjust the moment at which the fcomple- :mentary tapers mate, in'accordance with theeheight of the 'work .inthe die shoe, the :leader pin :in the embodiment Vof Figs. `l2 and .i3 fprovided "with a clamp mounting in -which the pin is vertically. adjustable.

Theaclamp mounting @comprises a sleeve 145 'Smoun'ted .in the 'punch holder bore 140: The sleeve '145 :is .split along yone side margin at146 and isprovidedfwith-an encircling @collar 147 having a clamp zarrangementcomprising a nut 148 and bolt 149. The rdiarnet'er of 7the sleeve 145 may thus tbe fchanged whereby to act as aclamp .for theieader pin 141. In this manner l'ead'er'pin 1-41 may be raised or-lowered in its mounting, and Vtheheight v'of the ,'pin .adjusted so that the .taperron its upper surface will fmatewith thepunchl holder Vbush-ing vtaper fat the precisemoment that the punch `is -at its lowermost position in its stroke. In the other embodiment k.of the invention, th'e vleader pin 'need not be adjustably langle .of the tapered :sides with the .leader -pin axis is thus vthree f degrees, .thirty-four minutes, yand thirtyve seconds; the included yangle l:of `:the .tapered .sides lbeing seven -de- Vgrecs, nine vminutes and -ten seconds. Such yan angular relationship will y.permit th'e vrespective ifrusto-corrioal tapered parts to adhere under -all normal circumstances but tto separateea'isily lupon the exertion of v axial thrust -between the mated parts. While other tapers would provide satisfactory clearances upon withdrawal .of the punch holder,-the`stated taper is .preferred because 7of .its particular -aforenoted characteristic.

.Pro-m the foregoing description, ytaken .in` connection v'with fthe accompanying drawings,.it is ,clear that 4a novel form of leader gpin fand punch .holder bushing having complementary tapered'surfaees, .which may either :be of :truste-conical or of .stepped cylindrical .form,fhas .been provided whereby .later-al as well as axial clearance between the ,partsfisf-developed .upon separation. thereof. The particular structures of the devices .shownuinfFigsr-Z, 3., 4, "6, 7, 8, l2 and 13 also provide for cam action of the leader pin bearing surfaces with the punch holder bushing bearing surfaces in a narrow range of punch holder movement.

I claim:

1. In a die set having separable platens, the combination with a leader pin fixed to one of said platens, of a sleeve movable respecting said leader pinwith the other of said platens, said pin'and sleeve having complementary mating surfaces which are of slightly smaller diameter adjacent their respective upper ends than adjacent their lower ends, whereby separation of said platens will cause lateral disengagement of said surfaces, the said surfaces being in suicient proximity for effective pin guidance at all points of pin movement within the sleeve and having close working t throughout said surfaces solely adjacent the point of die operation.

2. The combination of claim 1 in which the mating surfaces of the pin and sleeve comprise frusto-conical surfaces.

3. The combination of claim 1 in which the mating surfaces of the pin and sleeve comprise stepped cylindrical surfaces.

4. The combination of claim 1 wherein the sleeve cornprises a bushing fast to said other platen. v

5. The combination of claim l wherein said leader pin comprises a mounting part and a separable terminal sleeve part, said parts being provided with a coupling uniting said parts during normal leader pin action, said coupling being disengageable to permit the sleeve part to move with the said other platen during the course of separation of the platens, said terminal sleeve and first mentioned sleeve having said complementary surfaces.

6. In a die set having platens movable toward and away from each other, the combination with a leader pin fixed to one of said platens and a bearing bushing fixed to the other said platen, said bushing and pin having complementary stepped cylindrical bearing surfaces concurrently slidably engageable with close tit in the relatively proximate position of the platens in which the die is operative, and laterally free of engagement and in loose guiding tit in relatively separated positions of the platens.

7. The device of claim 6 wherein the cylindrical surfaces on the bushing are axially spaced.

8. The device of claim 6 wherein the bushing comprises a unitary sleeve fitting the punch holder, said sleeve having stepped bearing surfaces embossed inwardly to progressively smaller diameters in the direction of platen separation.

9. The device of claim 6 wherein the bushing comprises a plurality of axially spaced bearing sleeves extending inwardly to progressively smaller diameters in the direction of platen separation and corresponding to the respective pin diameters, and spacers between said sleeves.

l0. The device of claim 6 wherein said pin comprises separable sections and frangible connecting means.

11. In a die set comprising relatively movable platens having coacting leader pin and bushing means, the combination with a leader pin, of a terminal cap sleeve ernbracing an end portion of the pin and externally provided with a bearing surface for bushing engagement, and means detachably connecting said sleeve to the pin, whereby the pin may be freed in the event the cap sleeve sticks in the bushing.

12. The device of claim 11 in which the pin and sleeve have mutually engaged bearing surfaces relatively smaller in diameter near the end of the pin than remote from said end, whereby to give immediate increase in radial clearance upon axial relative movement in a direction of sleeve removal upon detachment of said connection.

13. The device of claim 11 in which the detachable connecting means comprises a screw in the endof the pin, said sleeve having abutment and retainer means spanning the end of the pin in xed connection with the sleeve and engaged by the screw.

' 14. The device of` claim 13 in'which the sleeve has a groove in its inner periphery and said retainer means comprises a circular member marginally engaged in the groove and with which the abutment means is fastened to be positioned in the sleeve. y

15. The device of claim 13 in which the screw is headed and is frangible for the detachment'of said connection to release the pin from the sleeve when tension is excessive.

16. The device of claim 13 in which the screw is headed and the abutment and retainer means comprise a thrust surface overlying the screw head to detach the sleeve and pin positively by effecting relative axial movement in a releasing direction when the screw is unscrewed from the pin. v

17. The device of claim l1 in which the pin and sleeve have mutually engaged bearing surfaces relatively Vsmaller in diameter near the end of the pin than remote from said end, whereby to give immediate increase in radial clearancel upon axial relative movement in a direction of sleeve removal upon detachment of said connection, the bearing surfaces including axially spaced portions between Which there is clearance between the sleeve and pin.

18. The device of claim 11 in which the pin and sleeve have mutually engaged bearing surfaces relatively smaller in diameter near the end of the pin than remote from said end, whereby to give immediate increase in radial clearance upon axial relative movement in a direction of sleeve removal upon detachment vof said connection, the said surfaces being frusto-conical.

19. In a die set comprising relatively movable platens having coacting leader pin and bushing means, the combination with a leader pin, of a terminal cap sleeve embracing an end portion of the pin and externally provided with a bearing surface for bushing engagement, and means detachably connecting said sleeve to the pin, whereby the pin may be freed in the event the cap sleeve sticks in the bushing, together with a bushing complementary to the sleeve, the sleeve and bushing having mating bearing surfaces of slightly smaller diameter at the outer end of the sleeve than adjacent the pin to provide a close bushing and sleeve t at both ends of the sleeve during die action and increased radial clearance but effective guidance in relative movement to and from the point of die action.

20. The device of claim 19 in which the sleeve and pin also have complementary and normally engaged bearing surfaces of smaller diameter at the end of the pin than the diameter remote therefrom to provide increased radial clearance between the cap sleeve and pin upon relative pin withdrawal consequent upon detachment of said connection.

References Cited in the tile of this patent UNITED STATES PATENTS 629,429 Corscaden July 25, 1899 789,021 Hartman May 2, 1905 1,543,010 Johnson June 23, 1925 1,875,930 Martin Sept. 6, 1932 2,205,731 Olsen June 25, 1940 2,236,221 Schwayder Mar. 25, 1941 2,433,617 Marsilius Dec. 30, 1947 2,504,642 Burgess Apr. 18, 1950 2,523,358 Conner Sept. 26, 1950 Ianiszewslci Sept. 22, 1953