US2586695A

US2586695A - Hydraulic punch and stripping device

Info

Publication number: US2586695A
Application number: US767963A
Authority: US
Inventors: Mueller Otto
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-08-11
Filing date: 1947-08-11
Publication date: 1952-02-19
Anticipated expiration: 1969-02-19

Description

Feb. 19, 1952 Y o. MUELLER 2,586,695

HYDRAULIC PUNCH AND STRIPPING DEVICE Filed Aug. 11, 1947 3 Sheets-Sheet l \waa.

INVENTOR.

Ozfa Mueller Feb. 19, 1 952 o. MUELLER ,69

HYDRAULIC PUNCH AND STRIPPING DEVICE Filed Aug. 11, 1947 3 Sheets-Sheet 2 IN VEN TOR.

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Feb. 19, 1952 o. MUELLER HYDRAULIC PUNCH AND STRIPPING DEV-ICE 3 Sheets-Sheet'fi Filed Aug. 11, 1947 INVENTOR. 02 2 0 Mveller.

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Patented Feb. 19, 1952 HYDRAULIC PUNCH STRIYPING DEVICE OttdMueller, Dearborn Mich. Application August 11, 1947; serial-No. 7672963 17 Claims. 1

This invention relates topunchingand stripping devices andpar-ticularly to a device-for op erating a pressure plate-to hold the work-during theadvancing and-withdrawing operations of the punch by hydraulic pressure.

In Patent No. 2,353,488", issued July- 11, 1944; a

device is illustrated having amoving cylinder for producing the punching and stripping operations when the cylinderisutilized as a slide" and perated over a stationary piston.

The present device is structurally different from that of the patent and embodies a stal-- tionary or movable frame having a cylinder' mounted on on'e'end and a die-supporting standard on the other end" in alignment with the cylinder. A slide operates on the frame and carries the punches and" the pressure plate along with rods in engagement therewith. On thecylinder side of the slide,. a piston rod. is mounted having a piston which operates in the cylinder. A telescoping piston is mounted'on the piston'rod in the cylinder for engaging a plate which contacts the ends of the rods for applying apressure to the pressure plate.

The two pistons may be moved in unison and may be actuated relative to each other. An aperture is provided in the main piston and rod into which a tubular element extends through which fluid is introduced into the main piston rod from which it is conducted between the two pistons. Fluid is first introduced into the piston rod and between the pistonsfor producing the advancement of the telescoping'piston, the pressure plate rods and the pressure plate so that the front face of the latter extends beyondthe forward ends of the punches. Fluid is then introduced into the main cylinder for moving the main piston, the rod, the telescoped piston, the slide, punches and pressure-plate forwardly toward the work to be punched. Upon engagement with the work, resistance is offered to the movement by the fluid between-the telescoped and main pistons, the pressure exerted thereby'on'the pressure plate and work beingcontrolled by apressure regulating valvewhich bleeds off the fluid between the pistons at a desired pressure as the main piston continues to advanceto move the punch or punches through the work. Pressure ismaintained on the workpiece by the pressure of the fluid between the telescoping and main pistons. After the punching operation, fluid is again directed between the telescoping and main pistons; whilethe fiuid backof the main piston inthe main cylinder is directed to tank. The

2., building up of pressure lrietween' the pistons causes=the main pistemto b'eretraeted withii'a tlie main cylinder. while the telescoping" piston applies the pressure te the pressure plate for re taining the work in clamped position as thee nds of the punches are withdraw-1t therefrom.- Afterthe withdrawingoperation, fluid is then introdue'ed into the" forward end" of thecylinder engagement witlithe" forwardend of the new scoping piston for producing the retra'ctive move: ment'of botlr of the pistons? the'slide,-.punehes and pressure plate tothei ri hi tial po's'itiens,-=w h the press-urepla-testillirradvanced position ahead' of the-punch,- ready for a subsequent operation:

Accordingly; the main object's of tr-reinventionare: to provid aipnnchifig-afid strippingde'vice having one piston teles'copedonWhepistdn rod of the main piston for applying pressure" to 'the pressur'e'plate 'ast'lie punchesa're retracted when a fluid is admitted between the pistons; tom-o: videapunch'a-nd" strippingj device embodying a fixed cylinder having a pistorr and piston" rod extending therefrom? along with a telescoping piston and' rod which-operate relative to} eachother in 'un-isorr'on the wall of thef'fix'eiic'ylind"er; toprovid'e a' punching. and stripping" device new ing' a pair of telescoping pistons whic'h"riiay" on er'ate inunison orrelativetoeachotherfoif pro": viding pressure on a pressure plate while the punch is advanced and retracted from the work to construct punching and stripping devitesof narrow widthso tfiat tlfiey ni'ay'be nestedf about a Wheel tb' puiICTl? dlosli adjacfitf' Hares therein? and} general; liiiftYi/iif, a puiiiflfi'hg: and" stripping devieef which simple in? con struction, positive in operation and economical" of manufacture;

Other objectsand featuresof novelty of the invention will be specifically pointedout' or will become apparent when referring-for a better' understanding of the invention, to the following. description-takenin conjunction? with the accompanying drawings, wherein:

Figure 1 is a sectional view of a punching. and

stripping device-embodying features-ot this invention," with parts shown in position after a punching operation has; been performed;

Fig. 2- is a sectional view of; the-structure illus tratedcin Fig. 1-; taken on the 1ine-2-+2 thereof Fig. 3 isa broken viewof;the structure illus trated in Fig. -1,'with:the partsshown at the be ginning or endof the punching and stripping operations;

Fig. 4:-'-is"=a-sectiona1 ViBW- o the+strueture illus trated in Fig. 1, taken on the line 4-4 thereof;

Fig. 5 is a view of a machine for punching holes in tne rim of a wheel, showing a further form of the invention;

Fig. 6 is an enlarged sectional view of the structure illustrated in Big. 5, taken along the line 65 thereof, with the punch in retracted position, and

Fig. '7 is a sectional view of the structure illustrated in Fig. 6, taken along the line 1-! thereof.

In Figs. 1 to 4, a base H is illustrated, having ways l2, a standard l3 at one end, and a collar H3 at the other for receiving and supporting a cylinder thereon. The cylinder has an enlarged end 16 and is provided with a thread H on the opposite end on which a nut I8 is threaded for securing the cylinder to the collar. The standard I3 is provided with a work plate l9 containing one or more dies 2!. Apertures 22 are provided in the plate l9 and standard l3, permitting the punched slugs passing through the dies 2i to be advanced in the apertures and finally ejected from the device.

The ways I2 support a slide 23 on the base ll, having a punch supporting plate 24 to which the punch holders 25 are secured for supporting the punches 2G aligned with the dies 2i. A pressure plate 21 is provided with apertures through which the punches extend. The plate is mounted by means of a collar 28 secured over a sleeve 29 which is attached to the forward face of the plate 24 by a screw 3!. A shoulder 32 on the sleeve 29 limits the outward movement of the collar 28 plurality of rods 34 extend through the slide 23 and plate 24 in engagement with the pressure plate 21.

Rearwardly of the slide, a piston rod 35 is secured thereto by a screw 35. The opposite end of the rod is provided with a main piston 31 which operates on the internal wall of the cylinder [5. A piston 38 and piston rod 39 are telescoped over the main piston rod 45, with the piston 38 contacting the wall of the cylinder I5, while the rod 39 contacts the wall of the main piston rod 35. The forward end of the piston rod 38 is secured to a plate 4| which abuts the rear ends of the rods 34.

A cap 42 is secured to the left-hand end of the cylinder l5, as viewed in the figure, by a plurality of screws 43, the cap being sealed to the outer surface of the auxiliary piston rod 39 by suitable O-rings 44. Similarly, the inner surface of the auxiliary piston rod 39 is sealed to the surface of the main piston rod 35 by an O-ring 45. Metal sealing rings 45 seal the main piston 3! and the telescoping piston 38 to the inner wall of the main cylinder 15. An O-ring 41 may be employed between the cap 42 and the end of the cylinder i5 to form a seal therewith.

The main piston 31 and its associated rod 35 are provided with a cavity 48 and an aperture 49. The aperture 49 has its wall in engagement with the outer surface of a sleeve 5| having a passageway 52 therein which communicates with the cavity. A sealing ring 53 seals the surface of the sleeve 5| with the wall of the aperture 49. The head 54 of the cylinder has a central aperture 55 through which the end of the tubular element extends and is clamped in fixed relation thereto by a nut 58. A shoulder 51 on the interior of the cylinder is sealed to the inner face of the head 54 by a sealing ring 58. An annular groove 59 is provided about the sleeve 51 which is connected by the engagement of its shoulder 33 thereof. A 9.

by a passageway 6| to the passageway 52 within the element. A passageway 62 in the head conducts a fluid into the cavity 48 of the main piston rod 35. A passageway 53 is also provided in the head for conducting fluid to and from the cylinder 15. A passageway 64 is provided between the cavity 48 and an annular recess 65 provided in the inner wall of the encompassing piston 38. An annular passageway 55 is provided about the inner wall of the annular piston 38 having adjacent to the bottom thereof a passageway 61 through the wall of the annular piston 39. An annular slot 68 is provided about the main piston rod 35 of a width to span the bottom of the passageway 58 and the passageway 61.

With the device in the position illustrated in Fig. 3, a workpiece 59 is placed in the space between the work plate l9 and the pressure plate 21 and fluid is introduced into the passageway 63 to move the main piston 31 toward the workpiece. This advances the main piston rod 35, the slide 23, along with the punch supporting plate 24, elements 25 and punches 26. The telescoping piston 38 and rod 39 are maintained in fixed position ahead of the piston 31 on the main piston rod 35 to maintain therods 34 and pressure plate 21 also in advanced position. The pressure plate forces the workpiece 69 against the work plate (9, and as the piston 31 continues to advance the slide 23, pressure will build up between the pistons 31 and 38 until a predetermined pressure is applied by the pressure plate 21 to the work 59. Thereafter, a pressure regulating valve in the fluid system (not illustrated) will open to hold the pressure between the two pistons constant as the piston 31 continues to advance the slide, the supporting plate 24 and punch holders 25 to move the punches through the apertures in the pressure plate 21 and thereafter to perform the punching operation on the workpiece 69.

After the completion of the power stroke by the main piston to perform the punching operation, the flow of fluid is reversed, that within the cylinder l5 being directed from the passageway 53 to tank. Fluid under pressure is admitted to the passageways 52 and 52, to the cavity 48 where it passes from the passageway 54 into the recesses 55 and 55. This fluid pressure applies a holding force to the pressure plate 21 and a force to the adjacent side of the piston 31, to thereby retract the piston 3'! in the cylinder l5 and withdraw the punches from the work 59 into the aperture in the pressure plate 21. Thereafter, the passageway 86 is joined to the passageway 67 through the annular groove 68 in the main piston rod 35. This fluid is delivered to the space between the cylinder cap 42 and the telescoping piston 38 to an additional slight passageway ll to move the two pistons while in separated position to the rearmost position in the cylinder [5 to have all of the elements of the device in the same position and relationship had at the beginning of the operation.

The device is believed to be novel in providing the main and telescoping pistons which operate in the same cylinder l5 relative to each other during the punching and stripping operations. The telescoping piston 38 is maintained in advancement of the piston 31 prior to the punching operation, and during the punching operation the fluid therebetween is by-passed to tank through a pressure regulating valve, to thereby maintain a predetermined pressure on the workpiece during the punching operation. The retraction of the punches to the position had prior thereto is accomplished by-theadmission of fluid pressure between the pistons which provides a holding pressure for the piston 38 and pressure plate 2'! and a retracting pressure for main piston 3'! and the punches. After the two pistons 3! and 38 have assumed the initial separated relationship, the fluid then returns both pistons as a unit to their initial positions in the cylinder I5 ready for another punching operation.

It will be noted that both pistons are moved together and that only a small relative movement is provided therebetween so that only a minimum quantity of fluid is required for producing the holding and punching pressures.

While the cylinder I5 is illustrated as a'-sep arate element, it is to be understood that it could 'be part of the base'casting. It is believed, however, that the sleeve arrangement is preferable because of leakage which may occur caused by porosity and blow holes in cast materials. It will be noted further from Fig. 3 that the fluid in the area 73 ahead-of the encompassing piston 38 is free to pass to the other side of the piston and out through the passageway 52 through the pressure relief valve to tank during the initial rapid advancement of the slide. As soon as the pressure plate engages the work, the passageway 61 is cut off from the passageway 66, and the further advancement of the piston 3! relative to piston 38 causes the fluid therebetween to be forced past the pressure regulating valve into tank, thereby maintaining a set pressure on the workpiece during the punching operation.

The introduction of fiuid between the -two pistons produces a holding pressure for the work and the withdrawal of the punches therefrom as the piston 37 is moved away from the piston 38. Thereafter, the fluid being admitted between the two pistons is again free to pass ahead of the piston 38 and retract the two pistons, slide, pressure plate and punches to their initial positions. Therefore, a free passage of fluid to and from the area 13 is provided during the approach and return cycles which occur in a rapid manner.

It is further to be understood that while a single screw 3| is illustrated for holding the pressure .plate 21 in position, that additional screws may be provided, located in different points of the plate depending on the position of the punches. If a central punch is being employed, then a pair of the holding elements embodying thesleeves 28'and 2t and screw 3i would be utilized.

In the device herein illustrated thepower piston has an efiective area of 7.85 square inches. The stripping piston has an efiective area of 5.45 square inches and the return piston has an effective area of 1.91 square inches. The cylinder has a 3 bore, providing a device having substantial power for performing the punching and stripping operations and requiring only approximately 28 cubic inches of oil per cycle to operate.

Referring to Fig. 5, a further form of the invention is illustrated, that wherein a machine is provided embodying a bed l5 having four fixtures 16 mounted thereon spaced 90 apart. Each fixture is provided with three punching and stripping devices TI so that four groups of three holes may be punched through the web of a wheel rim E8 in a single operation. The

"-rim is dropped into a fixture (not illustrated) and the fluid isdirec'ted into the devi'ces 'I'I simul- 3 taneou' sly -01 seriatim to produce the punching operations. *Eachof the' punches l-l is the same *andthisis shown-insection in "Figs.'6 and '7. Rererringto Figs. 13 and 7, the punching and r stripping-device ll "comprises a yoke 19 having *themai-n body-portion'mounted on a slide 8| 'of t'he fixture 16. A block-82 extends through *a'slot"83-'on the projecting end-84- of the yoke 19, having=-a-screw 85 therein projecting ina thread-pf -=a'-lock block '86 and adjustable in a T 'slotwi. rod--88 extnds'forwardly from the block' 82" abo-utwhich a spr'ing 89 is disposed ina, *slot*9 I "in *the-base-of the yoke I9. The sprin urges the yoke J 19 toward the center-of the rim fFBun-til the rearfaceof the "slot 83 strikes the "block 82. in the forward end the-yoke I 9 has *a -proj ecting 92 carrying the punch die 93. The opposite end-of'ithe yoke-l9 carries a boss 94 having -a-sleeve 2O 95 "machined thereon for receiving the cylinder "96 of "the punching and stripping device. The "cylinder 96 has a slot 97 medially of itsends 'i'hwhi'cha split'ri-n'g 98 may "be disposed. -"I-he cylinder*96 is disposed in-the sleeve 95 from the forward side, after which the two lralves of the ring "9-8 are applied to the slot '91 "and move into the shoulder -99 in the forward end f the cylinder 95. Thereafter, --a clamping ring IM is screwed upon-the rear'end'of'the'cylinder toclamp "the cylinder fltwithinthe -sleeve 95. Thereafter, the "stripping'p'iston 1M is-inserted within the "cylinder 93, being sealed thereto by a plurality T01 piston rings W 3, Forwardly-ofthe-cylinder ollow piston rod W4 is providedfhaving splines thereon mating'with theareas between splines T66 within the 'forwardend I O-I-of the cylinder 96. The-forwardend of the cylinderis sealed to the sleeve Illdbyan O-rin'g 108 disposed within the slot provided on the inward-wall thereof. The splihesdildand I06=prevent the rotation of the sleevelfl'd with the "cylinder 96 inorder to align "the'punchwi-th the "die 93 if "a hole other than circular is 'tob'e punched. Otherwise the splines ma be omittedfrom the device.

'A *punh operatingpiston I 09 is then inserted "within .the cylinder :96, the piston havinga piston "rod II'I 'extendingforwardlythereof. The piston rodiis solid the greater part of its length and "carrieson the end thereof apunch II'-2 secured finpo'sitionb'yaiclampingicollar II3. The inner wan of the sleeve T942213 the forward end is'pro- 'v-ided with keywaysl.l4 in whichkeys H5 in Tthe'pistonrodl'll operate "to prevent the piston rod IiI'IYfrom turning "relativeto the sleeve I04. 5 iniilarlyfithe pun'ohltll is provided with one or .moreflatjfaces II6 whichposition' the punch relative" to-the .pistonirod II I The .pistonf 02 is hollow. to permit the piston rod III to project 'therethrough, and the piston 60 1-09 is also provided with a central opening I'II through which a conduitl'ldpas's'es into a recess WIS-intherearerid of thepiston rod 1 I I. The

conduit I I8 is supported by theend cap IZI which=is threaded .or otherwise secured to the 65 :endof the cylinder96 and sealed thereto by an o ri-ng l22. The conduitI I8Thas abo'ss I23 which extends-through the .end cap to be secured in -position 'thereonrbyawasher T24 and nut I and 'se'aled thereto by O-ringsHG. The passageway 70121 in the-conduit -I-I'8- communicates through an aperture 12-8 'inthe cap I2.I, witha supply coned'uit (not shown) --connected thereto through a threaded port I29. The cap also-is-provided with a passageway I3I extending from a threaded .75 ort I 32 to the interior of the cap to communicate 7 with fluid at the rear end of the punch piston I09. The fluid introduced into the passageway I21 passes into the recess II9 of the piston rod II I from which it is directed between the pistons I02 and I09 through an aperture I38.

An annular passageway I34 is provided between the piston rod III and the piston I02. A similar annular passageway I35, in the nature of a recess, is provided in the wall of the piston rod III. The sleeve I04 is provided with'a passageway I36 for the passage of a fluid to and from the area ahead of the pressure plate piston I02. The sleeve I04 has a pressure applying plate. I31 in the nature of a cap which is threaded to the end of the sleeve and provided with a central aperture I38 through which the punch II2 may be relatively advanced and retracted. In the position illustrated in Fig. 6, the punch is in retracted position, with the piston I02 advanced forwardly from the piston I09 to have the pressure plate I31 extend forwardly of the end of the punch. This provides a space between the pressure plate and the die 93 which permits the machine to be loaded with the rim 18 and the dished hub portion I39.

Fluid is introduced through the passageway I3I to the rear of the piston I09 to advance the pistons I09 and I02 simultaneously toward the die 93. Fluid between the pistons is prevented from passing out of the passageay I28 and port I29 by a pressure relief valve (not illustrated) in the conduit connected to the port I29. When the pressure plate I31 strikes the rim 18, the reaction thereto causes the yoke 19 to be moved to the left, as viewed in the figure, to advance the die 93 into engagement with the disk I39 so that the disk and rim are clamped between the die 93 and pressure plate I31. The further application of fluid in the rear of the piston I09 causes the piston to advance and the fluid between the piston I09 and I02 to be forced out through the port I29, past the pressure relief valve, so that the plate I31 will always maintain engagement with the workpiece and die 93 at the predetermined set pressure of the relief valve.

This differential movement between the pistons I02 and I09 causes the die I I2 to advance through the workpieces and to perform the desired punching operation thereon. The relationship of the two pistons at the end of the punching operation is illustrated in Fig. '7. It will be noted that the pressure plate is still exerting pressure on the workpieces against the die 93 and that the die is advanced to completed punching position. The flow of fluids is then reversed in the ports I32 and I29 so that fluid is introduced into the port 77 I29 and conducted to tank from port I32, as viewed in Fig. 7. The fluid passing into-the passageways I29 and I21 into the recess II9, through the passageway I38 into the annular passageway I34, causes the piston I09 to be moved to the left relative to the piston I02. This retracts the punch' I I2 with relation to the pressure plate I31 to a position as illustrated in Fig. 6. In this position fluid may pass to the recess I35 and the wall of the piston rod I I I, through the passageway I39 ahead of the piston I02 to cause the piston to be moved to the left, carrying the piston I09 along therewith spaced from the piston I02. This relationship maintains until the piston I09 reaches the end of the cylinder 96 and all parts are in the position as shown in Fig. 6 which is the position had at the beginning or end of the punching operation.

It will be noted that the pressure employed for withdrawing the punch from the workpieces after the punching operation is applying at the same time an equal amount of pressure forwardly on the pressure plate I31 to hold the workpieces in position against the punch 93 during the with drawal of the punch therefrom. The rearward movement of the piston I99 relative to the piston I02 is prevented beyond the amount to retract the punch H2 by the cap II3 which holds the punch II2 on the end of the piston rod III engaging a shoulder I4I on the inner wall of the sleeve I04. This occurs after a passageway has been completed from the recess I34- to the recess I35 in the inner wall of the piston I02 and the outer wall of the piston rod III, respectively. After the pressure plate I31 is retracted from the workpieces, the spring 89 moves the yoke 19 to the right, thereby moving the die 93 away from the workpiece so that it may be removed and a new set of elements to be punched inserted in the machine. It will be noted that the forward end 92 of the yoke 19 is tapered so that the three devices grouped together to produce three punch holes at the 90 points on the wheel may be nested close together so that closely spaced holes may be punched by the devices. While the punching device only is claimed in the present application, the arrangement of the plurality of devices for punching apertures in a wheel rim is claimed in the copending application, Serial No. 226,431, filed May 15, 1951.

What is claimed is:

1. In a device for performing a punching and stripping operation, a punch carrying piston and piston rod, a stripper carrying piston and rod telescoped over said first rod, with the pistons having the same diameter, a cylinder in which the pistons operate in unison and relative to each other, said device incorporating means for conducting a fluid to the working end of the punch carrying piston, means for conducting a fluid between the pistons, and means for conducting a fluid from between the pistons to the retracting end of the stripper carrying piston after the pistons have been separated a predetermined amount to thereafter move both pistons simultaneously within the cylinder while maintained in separated relation.

2. In a device for performing a punching and stripping operation, a punch carrying piston and piston rod, a stripper carrying piston and rod telescoped over said first rod, with the pistons having the same diameter, a cylinder in which the pistons operate in unis-on and relative to each other, a slide carried by the punch carrying piston rod, a pressure plate mounted ahead of said slide, means operatively connecting the pressure plate to said telescoping piston rod, said device incorporating means for conducting a fluid to the working end of the punch carrying piston, means for conducting a fluid between the pistons, and means for conducting a fluid from between the pistons to the retracting end of the stripper carrying piston after the pistons have been separated a predetermined amount to thereafter move both pistons simultaneously within the cylinder while maintained in separated relation.

3. In a device for performing a punching and stripping operation, a punch carrying piston and piston rod, a stripper carrying piston and rod telescoped over said first rod, with the pistons having the same diameter, a cylinder in which the pistons operate in unison and relative to each other, a slide carried by the punch carrying piston rod, a pressure plate mounted ahead of said 75 slide, means operatively connecting the pressure 9. p a e to-sa d elescoping s o r a Pa e n. which said slide operates, means on one end of the base for supporting the, cylinder, means on the opposite end of the base for supportin a work plate, punches carried by said slide pro: jecting through apertures in said pressure plate, dies carried by said work plate in alignment with said punches, said device incorporating means for conducting a fluid to the working end of the punch carrying piston, means for conducting a fluid between the pistons, and means for conducting a fluid from between the pistons to the retracting end of the stripper carrying piston after the pistons havebeen separated a predetermined amount to thereafter move both pistons simultaneously within the cylinder whilejmain:

tained in separated relation.

4. In a device for punching and, stripping a workpiece comprising a cylinder, a pair of pistc'ns. in engagement with the wall of the cylinder and having rods disposed in telescoped relation to each other, a slide operated by one of said rods, a punch on said slide, a pressure plate operated by the other of said rods, and means for trapping fluid under pressure between said pistons. for applying a holding force to the pressure plate by one of said pistons to. retain it in advance of said punch when the other piston is initially moved to advance both pistons together.

5. In a device for performing a punching and stripping operation comprising a cylinder, a pair of pistons and rods disposed in telescoped relation in the cylinder, a slide secured to one rod, a punch on said slide, a pressure plate carried by said slide having an aperture through which said punch may extend and having connection with said other rod, said cylinder and rods haying fluid passageways for fluid for producing relative movement between the pair of pistons in the cylinder for advancing the pressure plate ahead of the slide and punch for producing movement of the spaced pistons as a unit when the slide piston has fluid applied thereto for advancing the pressure plate into engagement with the work for maintaining pressure on the other piston and pressure plate as the slide is further advanced to perform the punching operation and for producing a relative movement between the two pistons for holding the pressure plate in position as the punch and slide are retracted and fcr moving both pistons when in spaced relation as a unit to return all parts to initial position.

6. In a device'for performing a punching and strip-ping operation on a workpiece comprising a base, a cylinder on one end of the base, a standard on the opposite end of the base, a slide mounted on the base for movement between said cylinder and standard, a piston Within the Cylinder having a rod connected to said slide, a second piston within the cylinder having a rod, said second piston and cylinder telescoping over said first rod, a pressure plate carried by said slide in advance thereof for reciprocal movement relative thereto, and means connecting the pressureplate to said telescoping piston rod t produce a movement thereof relative to said slide conforming to the movement of said last rod;

7. In a device for performing a punching and stripping operation on a workpiece comprisinga base, a cylinder on one end of thejbase, an andard on the opposite end of the base, 'a slide mounted on the base for movement between said cylinder and standard, a piston within the cyinder havirn a rod connected to said slide, a second piston within the cylinder having a rod,

said second piston and cylinder telescoping over.

said first rod, a pressure plate carried by said slide in advance thereof for reciprocal movement relative thereto, means connecting the pressure plate to said telescoping piston rod to produce a movement thereof relative to said slide, and means for introducing fluid to said first piston for advancing the slide, second piston and pres-, sure platev as a unit with said second piston disposed in advance of said first piston.

8. In a device for performing a punching and stripping operation on a workpiece comprising a base, a cylinder on one end of the base, a stand ard on the opposite end of the base, a slide mounted on the base for movement between said cylinder and standard, a piston within the cylin der having a rod connected to said slide, a second piston within the cylinder having a rod, said second piston and cylinder telescoping over said first rod, a pressure plate carried in advanceof said slide, means connecting the pressure plate to said telescoping piston rod'to produce a nove ment thereof relative to said slide, means for introducing fluid to said first piston for advancing the slide, second piston and pressure plate as a unit, and means for trapping fluid between said two pistons for maintaining said second piston in advance of the first piston during the advancement of both pistons.

9. In a device for performing a punching and stripping operation on a workpiece comprisinga base, a cylinder on one end of the base, a stands ard on the opposite end of the base, a slide mounted on the base for movement between said cylinder and standard, a piston within the cylinder having av rcd connected to said slide, a se,cond piston within the cylinder having a rod, said second piston and cylinder telescoping over said first rod, a pressure plate carried in advance of said slide, meansconnecting the pressure plate to said telescoping piston rod to prod ce a moves ment thereof relative to said slide, means for intro cin 1111.1 1 sa d, fir t Piston f dv nc ingthe slide, second piston and pressure plate as a unit, means for conducting fluid to an area between said two pistons for producing relative movement thereioetween, and additional means for directing fluid from between said piston to a point ahead of said telescoping piston for producing the retraction of the pistons in separated relation within the cylinder after performing the punching and stripping operations.

10, In a device for performing a punching and stripping operation in a workpiece, a base, a cylinder on said base, a slide on said base, a piston in said cylinder, a piston rod connecting said, piston to said slide, a telescoping piston mounted on said piston rod, said device incorporating means for conducting a fluid to the working end of the one piston, means for conducting, a fluid between the pistons, and means for conducting a fluid from between the pistons to the. retracting end of the other piston after the pistons have been separated a predetermined amount to thereafter move both pistons simultaneously within the cylinder while maintained in separated relation.

11 In a device fer performing a punching and stripping operation in a workpiece, a base, a cylinder on said base, a slide on said base, a piston in said cylinder, a piston rod connecting said piston to said slide, and a telescoping piston mountedon said piston rod, said telescoping piston being disposed within said cylinder in position to operate with and independently of said first cylinder, means for preventing relative r tation between said second piston and cylinder, and means for preventing relative rotation between said first piston and said second piston.

12. In a device for performing a punching and stripping operation in a workpiece, a base, a cylinder on said base, a slide on said base, a piston in said cylinder, a piston rod connecting said piston to said slide, a telescoping piston mounted on said piston rod, said telescoping piston being disposed within said cylinder in position to operate with and independently of said first cylinder, a sleeve within said cylinder over which said first piston operates having a passageway communicating with the outside of the cylinder for directing fluid to an area between said two pistons, said telescoping piston having passageways which conduct fiuid to the slide side of said telescoping piston for retracting both pistons when separated a predetermined dis tance by fluid conducted therebetween, and a piston stop for regulating the degree of separation of said pistons.

13. In a device for performing a punching and stripping operation in a workpiece, a base, a cylinder on said base, a slide on said base, a piston in said cylinder, a piston rod connecting said piston to said slide, a telescoping piston mounted on said piston rod, said telescoping piston being disposed within said cylinder in position to operate with and independently of said first cylinder, a sleeve Within said cylinder over which said first piston operates having a passageway communicating with the outside of the cylinder for directing fluid to an area between said two pistons, and means operative when said pistons are moved to separated position for connecting the area between said pistons to a passageway ahead of the telescoping piston for moving both pistons as a unit within the cylinder.

14. In a device for performing a punching and stripping operation, a main piston and piston rod, a second piston and rod telescoped over said first rod, said pistons having the same diameter, a cylinder in which said pistons operate in unison and relative to each other, a punch carried by said main piston rod, a pressure plate carried by said telescoping piston rod and encompassing said punch when the latter is retracted, a base on which said device is slidable,

and means for urging said device to one position on said base, said device incorporating means for conducting a fluid to the working end of one piston, means for conducting a fluid between the pistons, and means for conducting fluid from between the pistons to the retracting end of the other piston after the pistons have been separated a predetermined amount to thereafter move both pistons simultaneously within the cylinder while maintained in separated relation, said device being moved from said one position by the action of said one piston when the punch is advanced to perform the punching operation.

15. In a device for performing a punching and stripping operation, a G-shaped frame, a cylinder carried by one end of said frame, a die carried by the other end of said frame, a piston in said cylinder, a rod extending from said cylinder aligned with said die, a second piston and rod in said cylinder telescoped over said first rod and operable in said cylinder with and independently of said first piston, a punch carried by said first rod, a pressure element carried by said telescoping rod through which said punch operates, a slide on which said 6 frame is supported, said device incorporating means for conducting a fiuid to the working end of the one piston, means for conducting a fluid between the pistons, and means for conducting a fluid from between the pistons to the retracting end of the other piston after the pistons have been separated a predetermined amount to thereafter move both pistons simultaneously within the cylinder while maintained in separated relation.

16. In a device for performing a punching and stripping operation, a C-shaped frame, a cylinder carried by one end of said frame, a die carried by the other end of said frame, a piston in said cylinder, a rod extending from said cylinder aligned with said die, a second piston and rod in said cylinder telescoped over said first rod and operable in said cylinder with and independently of said first piston, a punch carried by said first rod, a pressure element carried by said telescoping rod through which said punch operates, a slide on which said C frame is supported, means for moving said frame on said slide, said device incorporating means for conducting a fluid to the working end of the one piston, means for conducting a fluid between the pistons, and means for conducting a fluid from between the pistons to the retracting end of the other piston after the pistons have been separated a predetermined amount to thereafter move both pistons simultaneously within the cylinder while maintained in separated relation.

17 In a device for performing a punching and stripping operation, a C-shaped frame, a cylinder carried by one end of said frame, a die carried by the other end of said frame, a piston in said cylinder, a rod extending from. said cylinder aligned with said die, a second piston and rod in said cylinder telescoped over said first rod and operable in said cylinder with and independently of said first piston, a punch carried by said first rod, a pressure element carried by said telescoping rod through which said punch operates, a slide on which said 0 frame is supported, a spring urging said frame toward one end of said slide, said device incorporating means for conducting a fluid to the working end of the one piston, means for conducting 'a fluid between the pistons, and means for conducting a fluid from between the pistons to the retracting end of the other piston after the pistons have been separated a predetermined amount to thereafter move both pistons simultaneously within the cylinder while maintained in separated relation.

OTTO MUELLER.

REFERENCES CITED The following references are of record in the file of this patent.

UNITED STATES PATENTS Number Name Date 612,507 ROthe Oct. 18, 1878 2,112,153 Gorham Mar. 22, 1938 2,202,894 Bihler June 4, 1940 2,215,643 Gorham Sept. 24, 1940