US2776540A

US2776540A - Hydraulic punching apparatus

Info

Publication number: US2776540A
Authority: US
Inventors: Felix S Kraujalis
Original assignee: HANNIFIN CORP
Current assignee: HANNIFIN Corp
Priority date: 1955-01-06
Filing date: 1955-01-06
Publication date: 1957-01-08
Anticipated expiration: 1974-01-08

Description

Jan. 8, 1957 F. s. KRAUJAUS 2,776,540

HYDRAULIC PUNCHING APPARATUS INVENTOR.

FELX S. KRAUJAL/S A 7' TORNEVS Jan. 8, 1957 F. s. KRAUJALls 2,776,540

HYDRAULIC PUNCHING APPARATUS Filed Jan. 6, 1955 2 Sheets-Sheet 2 rif (M Q LA f 93 INVENTOR Qj v FEL/x s. KRAUJAL/s x Q BY ATTORNEYS United States Patent Office 2,776,540 Patented Jan. 8, 1957 HYDRAULIC PUNCHING APPARATUS Felix S. Kraujalis, Western Springs, Ill., assiguor to Hanniiin Corporation, Des Plaines, Ill., a corporation of Illinois Application January 6, 1955, Serial No. 480,189

22 Claims. (Cl. 60-97) This invention relates to apparatus for actuating a punch or the like and a stripper therefor.

One principal object of the invention is to provide an improved hydraulic cylinder for actuating a punchtype tool and a stripper or pressure plate therefor, together with an improved hydraulic circuit for controlling the cylinder. It will be understood that the term punch is intended to include rivet heading tools and the like, as well as hole punches.

A further object is to provide apparatus for hydraulically advancing andretracting a tool and a pressure member therefor in a definite predetermined sequence of operations.

It is another object of the invention to provide an improved punch and stripper actuating cylinder which is simple, rugged, and inexpensive in construction, while being highly effective and dependable in operation.

A further object is to provide a cylinder of the foregoing character, together with an automatic hydraulic circuit for carrying out a predetermined sequence of punching and stripping operations.

Further objects and advantages of the invention will appear from the following description, taken with the accompanying drawings, in which:

Figure lis a diagrammatic partly sectional elevational view of a punch and stripper actuating apparatus constituting an illustrative embodiment of the invention;

Fig. 2 is an elevational sectional View taken longitudinally through a hydraulic cylinder and a sequence valve embodied in the apparatus of Fig. l;

Fig. 3 is a cross-sectional view taken through the cylinder along a line 3--3 in Fig. 2; and

Fig. 4 is an elevational view of the rod end of the cylinder shown in Figs. l and 2.

Fig. 5 is a fragmentary, diagrammatic sectional View of a modified embodiment.

If the drawings are considered in greater detail, it will be seen that they illustrate a hydraulic cylinder 10 adapted to actuate a punch 12, or some other tool such as a rivet heading tool, for example. The cylinder 10 is also adapted to actuate a stripper or pressure plate 14. The illustrated tool 12 is a punch adapted to form holes in a workpiece 16. The punch 12 acts in opposition to a die 18 having a bore 20 for receiving the punchings from the workpiece 16. It will be seen that the die 18 is mounted in a xed abutment 22. Those skilled in the art will understand that the stripper or pressure plate 14 is adapted to clamp the workpiece 16 against the abutment 22 while the punch 12 is being advanced through the workpiece 16. When the punch 12 is being retracted, the stripper 14 is adapted to maintain pressure against the workpiece 16 so as to strip the workpiece from the punch. Finally, the stripper 14 is adapted to he retracted to release the workpiece and permit the insertion of a new workpiece.

The hydraulic cylinder 10 is constructed in a novel and advantageous manner to accomplish the general sequence of operations outlined above. In the embodiment of 2 Fig. l, the stripper 14 is operated by a irst piston 24 movable in the cylinder 10, the illustrated piston being hollow or annular in form. However, the hollow piston 24 may be employed to operate a punch or other tool, as will be explained in connection with Fig. 5. A cylinder bore 26 is provided in a casing 2S for slidably receiving the hollow piston 24. An external cylindrical surface 3@ is formed on the piston 24 for sliding engagement with the cylinder bore 26. Sealing rings 32 are disposed in grooves 34 formed in the surface 30. A hollow piston rod 36 extends from one end of the piston 24 and is slidably received in a piston rod bore 33 formed in the casing 2S. The piston rod 36 is sealed by annular packing rings 4l) which are compressed by a packing gland 42 mounted on the rod end of the casing 28.

ln the embodiment of Fig. l, the punch 12 is operated by a second piston 44 which is arranged coaxially relative lto the stripper actuating piston 24. However, as will be explained in connection with Fig. 5, the second piston may be employed to operate the stripper instead of the tool. A piston rod 46 extends axially from the second piston 44 and is slidably received in an internal axial bore 4S formed in the hollow stripper actuating piston rod 36. The rod 46 is sealed by a ring Si! mounted in a groove 52 which is formed at the outer end of the bore 48. The second actuating piston 44 is slidably received in a bore 54 formed axially in a cylinder member 56. In this instance, the cylinder member 56 is formed integrally with a head 58 which closes the outer cylinder bore 26 and is secured to 4the casing 23. Sealing rings 60 are disposed in grooves 62 formed in the piston 44. It will be seen that the cylinder member 56 is provided with a cylindrical outer surface 64 which is slidably received within a cylinder bore 66 formed in the hollow piston 24. Sealing lings 6@ are disposed in grooves '70 formed along the external surface 66. Stops 72 are formed on the head of the piston 44 to maintain spacing between the piston and the head member 58.

Fluid ports 74 and 75 are provided to carry liuid to and from the head ends of the outer and

inner cylinder bores

26 and 54. A cylinder port 76 communicates with Ithe rod end of the outer cylinder bore 26. Communication is established between the rod ends of the outer and

inner cylinder bores

26 and 54 by means of one or more ports 78 extending through the rod end of the outer hollow piston 24.

1t will be observed that lthe forward or outer end of the piston rod 46 is adapted to be connected to the punch 12 0r other tool and, to this end, is formed with a diametrical aperture Si) for receiving a pin S2 which will retain the punch on the piston rod. Tapped holes 84 are formed in the face of the 'hollow piston rod 36 to receive cap screws 86 or `the like, which will secure the stripper 14 to the hollow piston rod.

When the workpiece 16 is in place against the abutment 22 and is ready to be punched, the stripper 14 and stripper piston 24 are advanced by applying hydraulic pressure to the port 74. The stripper 14 is advanced by the resulting Huid pressure on the head end of the piston 24. At the same time, the port 76 is vented to the tank or sump so that hydraulic iluid will pass freely out of the rod end of the cylinder bore 26. After the stripper 14 has clamped the workpiece 16 against the abutment 22, the punch 12 and punch piston 44 are advanced by applying iluid pressure to the port 75. The fluid pressure thus supplied to the head end of the piston 44 is usually considerably greater than that applied to the head end ofthe stripper piston 24. The punch 12 is thereby forced through the work 16. As the piston 44 advances, hydraulic uid in the rod end of the inner cylinder bore 54 escapes freely through the port 78 in the outer piston 24, and thence into the port 76.

After the punching Operation has been completed, the punch 12 and punch piston 44 are retracted by applying Huid pressure to the port 76, while relieving the fluid pressure" at ,the port 75. The fluid under pressure is `trans.- mitted to the rod end of .the punch Pistn`44 through the ports .78 in the stripper piston 24 and the punch piston is thereby retracted. To prevent immediate retraction of the stripper piston 24, fluid pressure is maintained at the port 74 communicating with the head end of the stripper piston. This preferably is accomplished by the provision of a sequence valve 88 (Figs. "1 and 2). As illustrated, the sequence Valve 88 includes an outlet port 90 and an inlet port V92. A pipe 94 is employed to connect the outlet port 90 to the port 74. To provide for free iow of hydraulic iiuid from the inlet port 92 to the outlet port 9,0, ,the sequence valve 88 is equipped with a check valve 95. More specifically, a passage 96 extends between the outlet and inlet ports 90 and 9,2 and is formed with a reduced portion 9&8 adjacent the inlet port so as to dene a shoulder 100 facing toward the outlet port 90.

A ball 102 or other movable valve element is disposed in the passage 96 and is adapted to seat on the shoulder 100 over the reduced passage or port 98. A light spring 104 is provided to bias the ball 102 onto its seat. It will be understood that the ball 102 prevents reverse ow of hydraulic iuid through the passage 9 6 and thereby traps hydraulic iluidin the head end of the cylinder bore 26.

Atter the piston 44 has been retracted and the die 12 has been withdrawn from the work 16, pressure is allowed to build up in the port 76. As a result, corresponding hydraulic pressure is built up in the head end of the cylinder bore 26. To provide for return of the stripper piston 24 at a predetermined pressure, the sequence valve 88 is equipped with a spring loaded pressure relief valve 106 arranged in a passage 108 extending between the outlet and

inlet ports

90 and 92. As shown, a reduced portion or port 110 is formed in the passage 108 adjacent the outlet port 90 so as to define a shoulder 112 facing toward the inlet port 92. A ball 114 or other valve member is movable into engagement with the shoulder 112 so as to close the port 110.l The ball 114 is normally held over the port 110 by means of a loading spring 116 acting between the ball and an adjustable screw threaded abutment 118, whereby the force exerted by the spring may beadjusted. `In this way, the pressure at which thefval've 106 opens may be varied. .When the pressure in the head end of ythe stripper cylinder 26 builds toY a'predetermined value, the relief valve 106 opens and permits flow of hydraulic iluid to the tank through the port 92.` Y As a result, the stripper `1,4 and the stripper piston 24 are remmd. .Y

In the exemplary apparatus of Fig. 1, the flow of hydraulic iluid under pressure to the cylinder is controlled by a pressure generator 120, which may be of the general type disclosed and claimed in United States Patents Nos. 2,163,627, 2,308,712, 2,348,439, and 2,612,756, assigned to the same assignee as thepresent application. Briey the illustrated pressure generator 120 comprises a pump 122 operated by a motor 124. .The pump may be capable of developing a hydraulic pressure on lthe order of 1000 pounds per square'inch (p. s. i.). An' outlet pipe 126 is connected between the pump and a passage 128 formed in the valve body 130. The passage 126 leads to a reversing valve 132 adapted to control the advance and retraction of the stripper and punch

pistons

24 and 44. It will be seen that the reversingvalve 132 comprises a valve spool 134 adapted toV direct hydraulic fluid from the passage 128 into either of two passages 136 and 138,-the other of these two passages being'connected through the valve 132 and passages '140 to the tank. A pipe 142 is connected between the passage 136 and the inlet port 92 of the sequence valve 88, while a pipe 144 extends between the passage 13:8 and the cylinder port-76. Accordingly,-

the pipes 142 and'144 are adaptedto carry'iuidtoand from the head land `rod ends ,of the 'stripper' cylinder bore 26.

A Salemi@ .146 is previste@ te Statt f1.1@ Operation 0f the generator 120. When actuated, the solenoid`146 swings a lever 148 clockwise. The lever 148 is pivoted at an intermediate point on a rod 150 biased downwardly by a spring 152. A spring biased latch 154 is provided to retain the rod 150 against upward movement. The lever 148 has a pivotal operating connection to a rod 156 connected to the spool 134 of the reversing valve. Thus, actuation of the solenoid'and resulting clockwise movement of the lever 148 lowers the rod 156 and the valve spool 134 so as to direct hydraulic fluid under pressure to the passage 136. The downward movement of the valve operating rod 156 compresses a spring '158 acting between the rod 156 and the upper face of a movable abutment 160 which is secured to a rod 162. A rocker 164 has its ends pivoted to the rods 156 and 162 and has its lower edge supported on a pivot 166 intermediate the rods. Thus, when the rod 156 is pushed downwardly, the rod 162 is raised a corresponding amount, with the result that the abutment V160 compresses a spring 168. A spring biased latch 170 is provided to retain the rod 162 in its raised position. i

To supply hydraulic iluid under high pressure to the punch cylinder 54, the generator 120 is provided with an intensifier 172, whichis illustrated as comprising aplunger 174 movable through a plunger bore 176 into a plunger chamber 1778. A piston 180, slidable in a cylinder 182, is connected to the lower end of the plunger 174. It will be seen that a passage 183 extends between the passage 136 'and a port 184 communicating with an intermediate point along the plunger bore 176. A pipe 186 is con nected between the ripper end of the plungei chamber 175 andthe punch cylinder port 75. Thus, hydraulic fluid passes 'under pressure l'from the passage 136 throughthe plunger chamber 178 to the punch cylinder 54. The pressure thus'derived directly from the pump 122 is sufcient to advance'the punch againstthe work but not to complete the punching operation.

To bring the intensifier 172 into play after the stripper and punch pistons 2.4 and 44 have been fully advanced, the generator 120 is provided with an intensifier control valve 18S, which includes a valve spool 190 having an axial bore 192 connected at its upper end to a radial passage 194. The lower end of Vthe bore 192 is closed by a stationary pin 196 slidably received in the bore. Hydraul lic fluid is supplied to the radial passage 194 through a port 19Sl connected to the passage 136. A pipe 200 is connected between the lower end of the piston cylinder 182 and a port 202, which normally is in communication through a groove 204 in Vthe valve spool 190 with a port 206 leading to the'tank. lt will be recognized that fluid pressure in the axial bore 192 tends toraise the valve spool 190 and thereby place the port 202 in communication, through the groove 204, with a port 208 connected to the passage 136. Such raising movement of thc valve spool 1.90 will supply hydraulic fluid from the pump 1.22 to the lower end of Ythe piston cylinder 182 and thus 4.raise the piston and the plunger 174. it will be understood that the pressure applied to `the piston 180 isrnultiplied or intensified in ythe plunger chamber 170. in this way, a pressure on the order of 5000 p. s. i. may be obtained in the punch cylinder' 54 with e. pump pressure of 1000 p. s. i.

The operation of the intensifier actuating valve 188 is retarded, however, until the pump pressure has risen to a value sufficient to insure initial advancement of the stripper 14 andthe punch 12. To this end, a retarding plunger 210 is connected to the upper end of the valve spool 1920 and is slidably disposed in a chamber 212. A spring loaded relief valve 214'is provided to trap hydraulic `huid inv the cliamber'2ll2' until the' plunger 210 exerts a predetermined pressure. This p ressn'rcnivill'be achieved Wh'en' the' pump pressure, lacting von the 'valve spool 19,0,has reached'a level sufficient tos-'eat the'strip'pe'r 14 and the punch 12 againstl the work 16. Then" the .5 relief valve 2.14 opens and allows hydraulic fluid to pass `from the chamber into a pipe 215leadin'g to the passage 138 which at this stage is connected to the tank through the reversing valve 132. With the escape of fluid from the chamber 212, the plunger 210 and the valve spool 190 are permitted to rise and to establish communication between the passage 136 and the lower end of the intensier piston cylinder 182.

After the pressure in the punch cylinder 54 has risen to a predetermined value suiiicient to accomplish the punching operation, the generator 120 reverses the how of hydraulic iiuid to the stripper and punch

cylinders

24 and 54. To this end, the pressure in the intensifier plunger chamber 178 is transmitted through a pipe 216 to the lower end of a plunger 218 which is biased downwardly by a spring 220. Formed on the plunger 218 is a cam 222 which is effective to unlatch the latch 154 when the intensifier pressure reaches a predetermined value. Accordingly, the rod 150 is released for upward movement under the force of th spring 158, which acts on the rod 150 through the lever 148. The valve operating rod 156 moves upwardly with the rod 150 and is effective to raise the valve spool 134 so as to direct hydraulic liuid from the pump 122 through the passage 138. At the same time, the passage 136 is connected to the tank. Accordingly, the intensifier valve spool 190 descends to its normal position to re-establish communication between the lower end of the intensifier cylinder 182 and the tank. As a result, the head end of the punch cylinder 54 is vented to the tank through the plunger chamber 178 and the reversing valve 132. Hydraulic fluid under pressure passes through the

passages

138 and 144 to the rod end of the stripper cylinder 24. As already explained, hydraulic pressure is transmitted through -the ports 78 to the rod end of the punch cylinder 54, with the result that the punch piston 44 is retracted. The lsequence valve 8S retains hydraulic liuid in the head end of the stripper cylinder 26 until the punch piston 44 has been retracted. Then the hydraulic pressure builds up in the head end of the cylinder 26 until the relief valve 106 opens, whereupon the stripper piston 24 is retracted.

As the pump pressure builds up in the passage 138, lluid is forced into the retarder chamber 212 through a check valve 224. At the salme time, the rising pressure in the passage 138 is transmitted through a passage `226 to the lower lend of a plunger 228. A regulating valve 236 may be disposed in the passage 226. l When the pressure on the lower end of the plunger 228 reaches a pre determined value suliicient to insure retraction ofthe stripper piston 24, the plunger 228 rises against the biasing action of a spring 232. As a result, a `cam 234, formed on therplunger 228, unlatches the latch 170 and thereby releases the rod 162 for downward movement. The rocker 164 thereupon raises the valve spool 134 to its neutral position so as to bypass the pump outlet 126 to the tank andterminate the cycle of the generator 120. The downward movement of the rod 162 permits the spring 152 to move the rod 150 downwardly and relatch the latch 154. lt will be seen that a pressure relief or safety valve 236 is connected to the pump outlet 126 as an added safety feature.

While the operation of the apparatus will be clear from the foregoing, it may be helpful to offer a brief rsum. With the work 16 in place in front of the punch abutment 22, the cycle of operations is initiated by energizing the solenoid 146. This shifts the reversing valve spool 134 downwardly and directs hydraulic fluid from the pump 122 to the passage 136. initially, hydraulic fluid ows from the passage 136 through the pipe 142 and sequence valve 83 to the head end of the stripper cylinder 26. As

After the

pistons

24 and 44 have been fully advanced against the work 16, the pump pressure builds up in the passage 136 until the pressure is suicient to raise the valve spool 190 of the intensifier valve 188. As the valve spool 194B is raised, the plunger 210 forces hydraulic uid out of the retarder chamber 212 through the relief valve 214. With the valve spool 190 raised, hydraulic fluid passes from the pump into the lower end of the intensifier piston cylinder 182 so as to raise the piston 180. The pressure on the piston 180 is multiplied in the plunger chamber 178 to a value suicient to push the punch 12 through the workpiece 16. When the maximum desired operating pressure has been reached in the intensifier plunger chamber 178, the control plunger 218 is raised so as to unlatch the latch 154 and permit the valve spool 134 to shift upwardly under the biasing v action of the spring 158. As a result, the reversing valve a result, the stripper piston 24 is advanced' to move the 132 directs hydraulic liuid from the pump to the passage 138 and thence to the rod end of the stripper cylinder 26. The port 78 in the stripper piston 24 transmits the fluid pressure to the rod end of the punch cylinder 54. At the same time, the head end of the punch cylinder 54 is vented to the tank through the intensifier chamber 178 and the passage 136. Accordingly, the punch piston 44 and the punch 12 are retracted. tion of the stripper piston 24 is prevented by the sequence valve 88 which retains iiuid in the head end of the stripper cylinder 26 until the pump pressure builds up sufficiently to open the relief valve 106. After the stripper piston 24 has been retracted, the pump pressure builds up until it is suiiicient to raisethe control plunger 228, whereupon the latch 170 is unlatched to release the rod 162 for downward movement and thereby permit the valve spool 134 to shift to its neutral position.`

lt will be recognized that the operation of the apparatus as a whole is automatic once the solenoid has been actuated. The apparatus carries out a sequence of operations in which the stripper and punch are advanced initially, the punch is forced through the work, the work is stripped from the punch, and the stripper is retracted to permit removal of the workpiece. The arrangement of the apparatus is such `that the sequence of operations is positively maintained, each operation being completed before the following operation is initiated.

The construction of the hydraulic cylinder 10 will be seen to be surprisingly simple, rugged, and inexpensive. Nevertheless, the cylinder carries out its various functions more effectively and dependably than heretofore.

The modified embodiment of Fig. 5 is the same as that of Fig. l, except that the high pressure line 186, leading from the intensifier' 172, is connected to the cylinder port 74, while the low pressure line 142 is connected through the sequence valve 88 to the cylinder port 75; A line 240 is connected between the sequence valve 88 and the cylinder port 75. Moreover, the hollow piston 24 is fitted with a plurality of tools in the form of punches 12a acting in opposition to dies 18a. Furthermore, the axial piston 44 is equipped with a stripper member or plate 14a adapted to hold the workpiece 16 against an abutment 22a.

With the arrangement illustrated in Fig. 5, the hydraulic'pressure initially generated in line 142 advances the axial or inner piston 44, with the result that the stripper 14a clamps the work 16 against the abutmenty l actuate the punches 12a.

WhenV the valve 134 is reversed to vent the

lines

142 and 186, while supplying uid under pressure to the line 144, the hollow piston 24 is immediately retracted, so as to withdraw the punches 12a from the workpiece 16. 'Howevery immediate retraction ofthe axial piston 44 is prevented by the sequence valve 88. When the hollow piston 24 has been fully retracted, pressure -builds up in the rod end of the piston cylinder 26 and is trans- Immediate retrac- 7 ed thrqush .the 'passages .7.8 t0 the rQd @ad .of the p iswn ,C'y nder .Exelitaal'lythe pressure iS silcient t0 .Open tll spring loaded v alvedhf and permit movement of'the axiall piston 44 to its retracted position.

I t will thus vbe clear, from a comparison of Figs. l

and 5, that either of the

pistons

24 and 44, embodied in the cylinder 1 0 may be employed to operate the punching or other tool, the other piston then being employed to operate the stripper. No modification of the cylinder 10 is necessary to accommodate these alternative modes of operation; Various other modifications, alternative constructions and equivalents may beemployed without departing from thetrue spirit and scope of the invention as exemplified in the foregoing description and defined in the following claims. i

I claim:

l. .A dual hydraulic cylinder for actuating a tool element and a stripper element therefor, .said cylinder cornprising a casing having a cylinder bore therein, a first piston reciprocable insaid cylinder bore for advancing and vretracting one of s aid elements, a first piston rod extending in one direction from said first piston, a guide bore insaid casing extending coaxially from one end of said cylinder bore and 'slidably receiving said first piston rod, a head member enclosing the opposite cnd of said cylinder bore, said first piston having an axial cylinder bore therein opening toward said 'head member, said head member having a cylinder member thereon extending into said cylinder bore in said first piston and in slidable sealing relation thereto, said cylinder member having a third cylinder bore formed axially therein, a second piston slidably disposed in said third cylinder bore for advancing and retracting the other of said elements, a second piston rod extending in said one direction from said second piston, said first piston and said first piston rod having a second guide bore extending axially therein in said one direction from said second cylinder bore therein, saidsecond piston rod being slidably'received in said second guide bore in coaxial relation to said first piston rod, first and second fiuid ports communicatingwith opposite ends of said first cylinder bore, and a third fluid lport extending through said head member into said third cylinder bore on the side of said second piston opposite from said second piston rod, said first piston having a port extending therethrough to convey fiuidin either direction between the rod end of said second cylinder bore and the rod end of said first cylinder bore.

2. A dual hydraulic cylinder for actuating a punch and a stripper therefor, said cylinder comprising a casing h'aving a cylinder bore therein, a first piston reciprocable in said cylinder bore, a first piston rod extending in one direction from said first piston, a guide bore in one end of said casing for slidably receiving said first piston rod said'frst piston having a second cylinder bore therein, a cylinder member on said casing extending into said second cylinder-bore in saidfirst piston, said cylinder member h-aving a third cylinder bore therein, a second .piston sli-dably disposed in said .third `cylinder bore, a second piston rod extending in lsaid one direction from said second piston, said 'first piston yand said first piston rod having a second jguideboreextending axially therein for 4slidably receiving said second piston rod, first and second fiuid ports-communicating with opposite ends of said first cylinder bore, and a third fluid port communicating with the head end of said .third cylinder bore, said first piston having a founth port extending therethrough between the rod ends of said 4first and second cylinder bores.

3. A dual hydraulic cylinder for actuating a punch and a stripper therefor, said cylinder comprising a casing haying la cylinder bore therein, a first pis-ton reciprocable insaid 'cylinder bore, a first piston rod extending in one direction from said first piston, a guide b ore in one -end ofsad casing for slidably receiving said first piston rod piston rod extending in said one direction from said second pis-ton, said first piston land said rst piston rod having a second ygui-de bore extending axially therein for slidably receiving said second piston rod.

4. A dual hydraulic cylinder for actuating a punch and a stripwr therefor, said cylinder comprising a casing having a cylinder bore therein, a first pist-on relciprocable in said cylinder bore, a first piston rod extending in one direction from said first piston, a guide bore in one end of said casing for slidably receiving said first piston rod said first piston having a second cylinder bore therein, a-

cylinder member onsaid casing and extending into said second cylinder bore in said first piston, said cylinder member having la third cylinder bore `therein, a second piston slidably disposed in said third cylinder bore, a second piston rod extending in said one direction from said second piston, said fir-st piston and said first piston rod having a second yguide bore extending axially therein for slidably receiving said second piston rod, first and second fluid ports communicating with `opposite ends of said first cylinder bore, and third and fourth ports communicating with `the head and rod ends of said third cylinder bore.

5. A dual hydraulic `cylinder for actuating a punch and a stripper therefor, said cylinder comprising a casing having a cylinder bore therein, a first piston lrcciprocable in said cylinder bore, a -first piston rod extending in one direction from said first piston, a guide bore in said casing extending coaxially from one end of said cylinder bore and slidably receiving said first piston rod, a head member closing .the opposite end of said cylinder bore, said first piston having an axial cylinder bore therein opening tcward said head member, said head member having a cylinder member thereon extending into said cylinder bore in said first piston and in slidable sealing Irelation thereto, said cylinder member having a third cylinder bore formed .axially therein, a second piston slidably disposed in said third cylinder bore, a second piston rod extending in said one direction from s-ai-d second piston, said first piston and said first piston rod having a second guide bore extending axially therein in said Ione direction from said second cylinder bore therein, said second piston rod being slidably received in said second guide bore in coaxial relation fto said first piston rod, first and second fluid ports communicating with opposite ends of said first cylinder bore, a third fiuid port extending through said head member into the head end of said thi-rd cylinder bore, and a fourth port extending through said first piston between the rod end of said first and second cylinder bores.

6. A dual hydraulic cylinder, comprising a firs-t hollow piston having a first cylinder bore therein, a lfirst hollow piston `rod on said piston land :having a first axial guide bore therein, a casing having second interconnected cylinder and guide bores slidably receiving said piston and piston rod, said casing having a lthird cylinder bore therein yalined-vvith said first vcylinder bore, a second piston movably'disposed in vsaid first and third cylinder boresI and having a second piston `rod extending therefrom through said first guide bore in said first piston rod, said rst piston having a -rst port extending therethrough between the nod ends of said first and second cylinder bores, second and third fin-id ponts in said casing communicating with the head yand rod ends of said second cylinder bore, and a fourth port in 'said casing communicating with the head end of said third cylinder bore.

7. A dual hydraulic cylinder, comprising a hollow piston having a'first cylinder bore therein, a hollow piston mod =on said piston `and having a first axial guide bore therein, a casing having second interconnected cylinder and guide bores slidably receiving said piston and piston rod, sa-id .casing having athird cylinder bore therein alined with said first cylinder bore, a second .piston movably disposed in said first and third cylinder bores and having a second amarlo piston rod extending therefrom through lsaid rst guide bore in said hollow piston rod, iirst and second duid port-s communicating with opposite ends of said second cylinder borre, and third `and fourth 1in-id ports communicating with said iirst and lthird cylinder bores.

8. Fluid actuated apparatus comprising a casing having a rst cylinder bore and a communicating piston rod bore therein, an annular iirst piston slidably disposed in said cylinder bore and having a hollow piston rod thereon extending slidably through said piston rod bore, said piston having an internal cylindrical surface therein, said casing having a head closing said cylinder bore and provided with a cylinder member having' an external surface slidably received in said internal surface in said piston, said cylinder member having a second cylinder bore therein communicating with the interior of said piston, a second piston slidably disposed in said second cylinder bore and having a second piston rod thereon extending slidably through said hollow piston rod, a first port extending through said first piston between the rod ends of said iirst and second cylinder bores, second and third ports communicating with the head and rod ends of said tirst cylinder bore, a fourth port communicating with the head end of said second cylinder bore, a sequence valve having inlet and outlet ports, means connecting said outlet port to said second port, said sequence valve including a check valve lfor freely conveying iluid between said inlet and outlet ports while preventing return ow of iiuid through said check valve, means for applying tluid pressure to said inlet port while relieving fluid pressure at said third port for advancing said first piston, means for applying fluid under pressure to said fourth port for advancing said second piston, means for applying iiuid under pressure to said third port while relieving fluid pressure at said fourth port to retract said second piston, said rst port in said first piston being eiiective to applyy iluid pressure to the rod end of said second piston,` said check valve retaining iiuid in the head end of said iirst cylinder bore and thereby preventing retraction of saidv nrst piston while said second piston is beingV retracted, said sequence valve including a pressure relief valve for conveying iiuid in excess of a predetermined pressure between said outlet and inlet ports and thereby providing for return of said iirst piston by the iiuid pressureat said third port after the return of said second piston.

9. Fluid actuated apparatus comprising a casing having a rst cylinder bore and a communicating piston rod bore therein, an annular iirst piston slidably disposed in said cylinder bore and having a hollow piston rod thereon extending slidably through said piston rod bore, said piston having a second cylinder bore therein, said casing having a cylinder member slidably received in said second cylinder bore in said piston, said cylinder member having a third cylinder bore therein, a second piston slidably disposed in said third cylinder bore and having a second piston rod thereon extending slidably through said hollow piston rod, a first port extending through said tirst piston between the rod ends of said rst and second cylinder bores, second and third ports communicating with the head and rod ends of said iirst cylinder bore, a fourth port communicating with the head end of said third cylinder bore, a sequence valve connected to said second port and including a check valve for freely conveying uid to said second port while preventing return ow of fluid through said check valve, means for applying iluid pressure to said check valve while relieving tiuid pressure at said third port for advancing said first piston, means for applying fluid under pressure to said fourth port for advancing said second piston, means for applying iluid under pressure to said third port while relieving iluid pressure at said fourth port to retract second piston, said rst port in said rst piston being effective to apply uid pressure to the rod end of said second piston, said check valve retaining fluid in the head end of said rst cylinder bore and thereby preventing retraction of said first piston while said second piston is being retracted, said sequence valve including a pressure relief Valve for conveying fluid in excess of` a predetermined pressure away from said second port and thereby providing for return of said rst piston by the iiuid` pressure at said third port after the return of said second piston l0. Fluid actuated apparatus comprising a casing having a first cylinder bore and a communicating piston rod bore therein, an annular first piston slidably disposed in said cylinder bore and having a hollow piston rod thereon extending slidably through said piston rod bore, said piston having a second cylinder bore therein, said casing having a third cylinder bore therein alined with said second cylinder bore, a second piston movably disposed in said second and third cylinder bores and having a second piston rod thereon extending slidably through said hollow piston rod, a ilrst port extending through said rst piston between the rod ends of said rst and second cylinder bores, second and third ports communicating with the head and rod ends of said iirst cylinder bore, a fourth port communicating with the head end of said third cylinder bore, a check valve for freely conveying luid to said second port while preventing return iiow of fluid through said check valve, means for applying iiuid pressure to said check valve while relieving uid pressure at said third port for advancing said iirst piston, means for applying fluid under pressure to said fourth port for advancing said second piston, means for applying iiuid under pressure to said third port while relieving fluid pressure at said fourth port to retract said second piston,k

said first port in said tirst piston being eiective to apply tluid pressure to the rod end ot' said second piston, said check valve retaining fluid in the head end of said first cylinder bore and thereby preventing retraction of said iirst. piston while said second piston is being retracted, and a. pressure relief valve for conveying uid in excess of a predetermined pressure away from said second port toprovide for return of said rst piston by the duid pressure: at said third port after the return of said second piston.

ll. Fluid actuated apparatus comprising a casing-hawin-g :a first cylinder Ib-ore and a communie-ating piston rod bore therein, `an annular tirst piston slidably disposed in said cylinder lbore and having ia hollow piston rod thereon extending slidably through said pis-ton rod bore, said piston having a second cylinder bore therein, said casing having a cylinder member slidably received in said second cylinder here in said piston, said cylinder Inember lhaving ya thimd cylinder bore therein, a second piston slid- Iably disposed in sai-d third cylinder bore and having :a second piston r-od thereon extending slidably through said hollow piston rod, a iirst port extending through said iirst piston between the rod ends of said iirst and second -cyIlinder bores, second and third ports .communicating with thel head and trod ends yof said iirst cylinder ^bore, a fourth port communicating with the head end of said third cylinder ibore, means for applying huid pressure to said second port while relieving pressure at said third port and thereby .advancing said first piston, means for applying iluid pressure 'to said fourth portto advance sai-d second piston, means `for :applying iiuid pressure to sai-d third port while relieving flu-id pressure at said fourth port to retract said second piston, and means for retaining huid pressure lat said second port to prevent immediate retnaction of said iirst piston, said last mentioned means lbeing adapted to be overcome -by predetermined pressure :at said third port. i

12. Fluid :actuated apparatus comprising a casing having ra iirst cylinder lbore and a communicating piston rod bore therein, an annular iirst .piston slidably disposed in said cylinder bore iand having a hollow piston rod thereon extending slidaibly through :said piston rod bore, said piston having a second cylinder bore therein, said cas-ing having -a third cylinder bore therein alined with said second cylinder bore, a second piston movably disposed in said second and third cylinder bores and having a sec- @adriaan rod thema' extending slidably through Said hollo'wpiston rod, a rst port extending through said rst piston between the rod ends of said first and second cylinder bores, second and third ports communicating with the head land rod ends of said first cylinder |bore, a fourth port communicating with the head end of said third cylinder bore, means -for applying iiuid pressure -to said .second port `while relieving pressure at sai-d third port and thereby `advancing said first piston, means for applying fluid pressure to said fourth port to ladvance said second piston, lmeans for applying iiuid pressure to said third .port while relieving fiuid pressure at said fourth port to retract said second piston, and means for retaining fluid pressure at said vsecond port to prevent immedi- -ate retraction of said first piston, said last mentioned means 4being adapted to be overcome by predetermined pressure at said third port.

l3. Fluid actuated apparatus comprising `a 4casing having ya first cylinder bore and ya communicating piston rod bore therein, `an annular first piston slidably disposed in said cylinder bore and having a hollow piston rod `thereon extending slidably through said piston rod here, said piston having a second cylinder bore therein, said casing having -a cylinder member slidably received in said second cylinder bore in said piston, said cylinder member having a third cylinder bore therein, .a second piston slidalb'ly disposed in said third cylinder bore and having a second piston rod thereon extending slid-ably through said hollow piston rod, a first port extending through vsaid first piston between the nod ends of said first and second cylinder bores, second tand .third ports communieating with the head and .rod ends of :said first cylinder bore, a `fourth port communicating with thehead end of said third cylinder bore, means for applying relatively low iiui-d .pressure to .said second port while relieving pressure at said :third port and thereby advancing said first piston, means for applying rela-tively high fluid pressure to said fourth port to .advance said second piston, means responsive to predetermined pressure at said fourth port for applying iiuid pressure to said-'third port while relieving uid pressure at said fourth port tto retra-ct said second piston, and means for retaining fluid pressure at said second port` to prevent immediate ret-naction of sai-d first piston, said last mentioned means being adapted to be overcome by predetermined pressure `at said third port.

14. Fluid .actu-ated apparatus comprising a casing having a first cylinder borre and a communicating piston rod -bore therein, an annular first piston slidably disposed in said cylinder bore and having a hollow piston rod .thereon extending slidably through said piston rod bore, said piston having -a second cylinder bore therein, said casing having a third cylinder bore itherein tal-ined withsaid second cylinder bore, a second piston movably .dis-

posed lin said second and third cylinder bores and having i a second piston rod thereon extending vsl-idably through said hollow .piston rod, :a first port extending 'through said 4first .pist-on between the rod ends of said first .and-

second cylinder bores, second and third ports communieating with fthe head and rod ends of said first cylinder bore, a fourth port communicating with the head end of said third cylinder bore, means for applying relatively low duid pressure to said second port while relieving pressure tat sai-d third port and thereby ladvancing said 'lirst piston, means VJor applying relatively 'high fiuid pres` sure .to said fourth port to advance said second piston, means responsive to predetermined pressure at said Vfourth port for applying fiuid pressure :to said third port While relieving ii-uid pressure .at said fourth port to lretract said second piston, and means for retaining fluid pressure at said second port to prevent immediate retraction .of said first piston, said last `mentioned means *boing adapted to be overcome by predetermined pressure at said third port.

15, Fluid actuated apparatus` comprising an annular first piston having external and internal cylindrical sur- 12 fases, an annular ,first piston rod on Said piston au. extending ,in one direction therefrom.' Said piston vrad having an axial bore therein, a casing having interconnected cylinder and 'guide bores slidably receiving the external surfaces of Said pistonV and piston rod, a head member closing said cylinder bore and having a cylinder member slidably' received in the internal cylindrical surface in'said piston, said cylinder member having a second cylinder bore therein cooperating with said internal surface of said piston t'ofor'm a second piston chamber, a second piston slidably disposed in said second cylinder bore and having fa second piston rod thereon and extending in saidl one direction therefrom through said bore insaid rstpiston rod, said first piston having a first port extending through the end thereof adjacent said piston rod thereof and connecting the rod end of said first cylinder bore with the rod end of said second piston chamber, a second fiuid 'port communicating with the end of said rs't cylinder bore opposite from'said first piston rod, meanslv for applying uid under pressure to said second port for advancing -said first piston, a third uid port extending through said head member and communicating with they head end of said second cylinder bore, means for applying f iuid under pressure to said third uid port for advancing said second piston, a fourth fiuid port communicating with the rod end of said first cylinder bore, means for relieving fiuid pressure at said third duid port while'applying fluid pressure at said fourth fluid port for retracting said Second piston, fiuid pressure being applied to the rod end of said second piston through said first port in said first piston, means for retaining fiuid in the head end of said first cylinder bore and thereby preventing retraction of said first piston while said second piston is being retracted, the fiuid under pressure applied to said fourth fluid port being effective to retract said first piston after said second'piston has been retracted.

16. Fluid actuated apparatus comprising a casing having a first cylinder bore and a communicating piston rod bore therein, afhollow piston slidably disposed in said cylinder bore and having a hollow piston rod thereon extending slidably through said piston rod bore, said pistonl'havillg a Second cylinder bore therein, said casing having a cylinder member slidably received in said secondv cylinder bore in said piston, said cylinder member having a third cylinder bore therein, a second piston slidably disposed in said third cylinder bore and having a second piston rod thereon extending slidably through said hollow piston rod, a first port extending through said hollow piston between the rod ends of said first and second cylinder bores, second and third ports communicating with thehead and rod ends of said first cylinder bore, a fourth'po'rt communicating with the head end of said third cylinder bore, means for applying fiuid pressure to one of said second and fourth ports while` relieving pressure at said thildiport andv thereby advancing one of said pistons, means 4for applying fluid pressure to the other of said second and fourth ports to advance the other of said pistons,y means for applying` fluid pressure to said third port While relieving uid pressure at one of said second and 'fourth ports to retract said other piston, and means for retaining` fiuid pressure at the other of said second and fourth ports to prevent immediate retraction of said one piston, said last mentioned means being adapted to be overcome by predetermined pressure at said third port.

17. Fluid actuated apparatus comprising a casing having a first cylinder bere and a communicating piston rod bore therein, a hollow first piston slidably disposed in said cylind'erhore and having a hollow piston rod thereon extending slidably through said piston rod bore, said piston having a second cylinder bore therein, said casing having a third cylinder bore therein alined with said secondy cylinder bore, a-second piston movably disposed in Said *Se-cortili and. third cylinder bores and having, a Second. piston rod thereon extending slidably through said hollow 13 piston rod, a first port extending through said rst piston between the rod ends of said first and second cylinder bores, second and third ports communicating with the head and rod ends of said first cylinder bore, a fourth port communicating with the head end of said third cylinder bore, means for applying liuid pressure to said fourth port while relieving pressure at said third port and thereby advancing said second piston, means for applying Huid pressure to said second port to advance said first piston, means for applying fluid pressure to said third port while relieving fluid pressure at said second port to retract said first piston, and means for retaining fluid pressure at said fourth port to prevent immediate retraction of said second piston, said last mentioned means being adapted to be overcome by predetermined pressure at said third port.

18. Fluid actuated apparatus comprising a casing having a rst cylinder bore and a communicating piston rod bore therein, a hollow first piston slidably disposed in said cylinder bore and having a hollow piston rod thereon extending slidably through said piston rod bore, said piston having a second cylinder bore therein, said casing having a third cylinder bore therein alined with said second cylinder bore, a second piston movably disposed in said second and third cylinder bores and having a second piston rod thereon extending slidably through said hollow piston rod, a first port extending through said first piston between the rod ends of said first and second cylinder bores, s'econd and third ports communicating with the head and rod ends of said first cylinder bore, a fourth port communicating with the head end of said third cylinder bore, a check valve for freely conveying uid to one of said second and fourth ports while preventing return flow of fluid through said check valve, means for applying iiuid pressure to said check valve while relieving fluid pressure at said third port for advancing one of said pistons, means for applying uid under pressure to the other of said second and fourth ports for advancing the other of said pistons, means for applying fluid under pressure to said third port while relieving uid pressure at said other port to retract said other piston, said rst port in said hollow piston being effective to apply fluid pressure to the rod end of said second piston, said check valve retaining fluid in said one port and thereby preventing retraction of said one piston while said other piston is being retracted, and a pressure relief valve for conveying fluid in excess of a predetermined pressure away from said one port to provide for return of said one piston by the uid pressure at said third port after the return of said other piston.

19. Fluid actuated apparatus comprising a casing having a first cylinder bore and a communicating piston rod bore therein, a hollow first piston slidably disposed in said cylinder bore and having a hollow piston rod thereon extending slidably through said piston rod bore, said piston having a second cylinder bore therein, said casing having a third cylinder bore therein alined with said second cylinder bore, a second piston movably disposed in said second and third cylinder bores and having a second piston rod thereon extending slidably through said hollow piston rod, a first port extending through said first piston between the rod ends of said first and second cylinder bores, second and third ports communicating with the head and rod ends of said first cylinder bore, a fourth port communicating with the head end of said third cylinder bore, a check valve for freely conveying liuid to said fourth port while preventing return flow of uid through said check valve, means for applying uid pressure to said check valve while relieving fluid pressure at said third port for advancing said second piston, means for applying fluid under pressure to said second port for advancing said first piston, means for applying iiuid under pressure to said third port while relieving fluid pressure at said second port to retract said first piston, said first port in said first piston being effective to apply fluid pressure to the rod end of said second piston, said check valve retaining liuid in the head end of said third cylinder bore and thereby preventing retraction of said second piston, while said first piston is being retracted, and a pressure relief valve for conveying iiuid in excess of a predetermined pressure away from said second port to provide for return of said second piston by the uid pressure at said third port after the return of said first piston.

20. A dual fluid actuated cylinder, comprising a hollow first piston element having a first piston rod thereon, a casing element having rst interconnected cylinder and guide bores slidably receiving said piston element and piston rod, second and third aligned axial bores in said casing element and said piston element, a hollow cylindrical member fixed on one of said elements, said cylindrical member having one of said second and third bores therein and being slidably received in the other of said second and third bores, said first piston rod having a guide bore therein, and a second piston slidably received in one of said second and third bores and having a second piston rod received in said last mentioned guide bore.

21. A dual uid actuated cylinder, comprising a hollow rst piston element having a first piston rod thereon, a casing element having first interconnected cylinder and guide bores slidably receiving said piston element and piston rod, second and third aligned axial bores in said casing element and said piston element, a hollow cylindrical member fixed on one of said elements, said cylindrical member having one of said second and third bores therein and being slidably received in the other of said second and third bores, said first piston rod having a guide bore therein, first and second port means communicating with opposite ends of said first piston element, and third and fourth port means communicating with opposite ends of said second piston.

22. A dual fluid actuated cylinder, comprising a hollow first piston element having a first piston rod thereon, a casing element having first interconnected cylinder and guide bores slidably receiving said piston element and piston rod, second and third aligned axial bores in said casing element and said piston element, a hollow cylindrical member fixed on one of said elements, said cylindrical member having one of said second and third bores therein and being slidably received in the other of said second and third bores, said first piston rod having a guide bore therein, first and second port means in said casing and communicating with the head and rod ends of said first piston element, third port means in said casing and communicating with the head end of said second piston, and fourth port means in said first piston and communicating with the rod end of said second piston.

References Cited in the file of this patent UNITED STATES PATENTS 2,215,643 Gorham Sept. 24, 1940 2,513,192 McFarland June 27, 1950 2,534,292 Mueller Dec. 19, 1950 2,586,695 Mueller Feb. 19; 1952 2,612,756 Peterson et al. Oct. 7, 1952 FOREIGN PATENTS 521,980 Great Britain June 5, 1940