US2612951A - Pneumatic press - Google Patents

Description

.@f j M 1 0% T w, m Z j? w m 2, m Uw m il 2 n d d e UM ,mf/M w e W 6 Pr w AE 7 ER 79m LP J Mm m. 1 H /5 Pm w swg Hm H 1 j M0 7 2 M @Mtv sa a 1 a 7, .w u F Oct. 7, 1952 H. PALMLEF 2,612,951

PN'EUMATIC PRESS Filed Aug. e, 1947 2 SHEETS- SHEET 2 Patented Oct. 7, 1952 UNITED-STATES PATENT OFFICE Herbert Palmleaf, Chicago, Ill., assignor to AMI,

Gerrard &v Company, Chicago, Ill., a corporation of Illinois y Applicaties August 6,1947, serialNo. 766,721

19 claims. (01.164-95) The invention relates generally to power presses and more particularly to a pneumatically operated press such as a punch press, or the like.

The invention has among its objects the production of such a pneumaticpress which is so constructed that a relatively small aircylinder may be employed, at the same time producing a blow of maximum powenand which press due to its novel construction will occupya relatively small space. 1

Another object of the invention is the production of such a press in which the stroke may be readily and easily adjusted from zero.1 to the full length of travel of the pneumatic actuating unit. 1 1

Another object of the invention is the production of such a press in which the effective pressure may be varied to `meet the particular operating requirements, and in which a very sharp blow may be obtained with relatively low air pressures. f -1 A A further object of the invention is the production of such a device in whichthe power unit may be mounted lfiorizontally,1 vertically, or diagonally, as required. w 1

A further object` of the invention is the production of such a pneumatic press wherein the reciprocable member may be cushioned as it approaches the end of a power stroke.

A further object of the inventionis the production of novel means for momentarily retard-` ing the travel of the reciprocal membenwhereby a sharp blow `may be obtained lwithirelatively low air pressures. 1 1

Many other objects and advantages 'of the construction herein shown and described will be obvious to those skilled in the artfrom the disclosure herein given. l 1 j U To this end my invention consists inthe novel construction, arrangement andcombination of parts herein shown and described and moreparf ticularly pointed out in the appendedclaims.

In the drawings wherein like reference characters indicate like or correspondingparts:

Fig. 1 is a front elevational viewcf a press.

embodying the present invention with portions broken away to show the details thereof;

Fig. 2 is a sectional viewqtaken approximately on the line 2-2 of Fig. l;

Fig. 3 is a sectional view through one of the,

retarding elements taken approximately onY the line 3-3 of Fig. 2;

Fig. l is a sectional viewof the retarding ele` ment taken approximately on" the line lf-4 of Fig. 3; and l Fig. 5 is a schematic diagram of one pneumatic and electrical circuit that may be employed with the device. 1

In the past, pneumatic punch presses and similar equipment have not been satisfactory as relatively large air cylinders and extremely high air pressures were required to produce a blow comparable to a mechanically actuated press, inasmuch as the pressure exerted would be dependent upon the area of the piston employed and the air line pressure. For example, employing a pressure of 1100 lbs. per square inch on a piston 8 inches in'diameter would result in a total pressure vof approximately 5,500 lbs., which is insuliicient for the operation of a large die or tool. However, bythe use of the present invention a sharp blow may be obtained with approximately ten times the effective force than that previously obtained while employing the same size air cylinder and same air line pressures.

This resultis 'accomplished in the present invention by employing means for momentarily interrupting the power stroke of the reciprocable memberof the device after such stroke has been partially completed, and then suddenly releasing the reciprocal member at substantially the peak of the additional force built up in the air cylinder, resulting in a very sharp impact on the punching die, or the like. 1

Referring to the drawings and more particularly to Figs. r1 `and 2, l indicates generally a supporting frame or structure, comprising in the embodiment of the invention illustrated, four vertical corner members 2 connected by an upper plate 3, a lower plate 4 and intermediate side members 5, the latter in the present instance, as well as the uprights 2, being formed from angle iron. The various elements thus far described are suitably fastened together, as for example, by welding, and if desired, the `plate 4 may be suitably reinforced by cross members B.. Also 'secured to the uprights `2 and extending between the front` and rear cross members 5 are a pair of spaced members l illustrated in the present instance as being formed frein angle iron, and similarly secured by welding, or the like, to the respective crossmembers 5. The twomembers l are likewise connected by cross members 8. formed from the same size stock as the members 1, and are rigidly connected to the latter by welding, or the like to deiine a square opening in which is positioned a guide sleeve 9, the latter being secured in position by welding, or if desired, may be removably mounted by means of bolts, or the likepassing through the adjacent frame members 1 and Y Slidably positioned in the sleeve 9 is a reciprocable work member I I, corresponding to the usual extension of the common punch press, which is cylindrical in shape and connected to the piston rod I2 by a screw I3 having a shank i4 threaded into the work member II, the opthe upper plate 3 of the supporting structure, and is provided with air ports I8 and I9 com# municating respectively with the air cylinder above and below the piston I6. The `air cylinder I'I may be of any suitable type and readily procured on the open market, consequently the details thereof form no part of the present invention. The work member II is securely held in position relative to the screw I3 by any suitable means such as a lock nut 2|.

For the purposes of illustration, a die set, indicated generally by the numeral 22, is illustrated in Fig. 1 and comprises a lower die element 23 mounted on the bedplate 24 carried by the plate 4, and an upper die element 25 operatively connected to the ram 26 carried by the lower end ofv the extension member Il. The lower die element 23 may be provided with the usual leader pins 21 passing through bores in the i upper die element for maintaining the same in alignment throughout the punching operation. Likewise, the lower die element 23 may be provided with a bore 28 through which punched articles may pass, in which case the bed member 24 and plate 4 likewise may be provided with openings for permittingthe stamping to pass therethrough. Obviously, these details of construction will depend to a great extent on the character of the operations to be performed on the machine.

Carried by the members 'i and S are a plurality of retard members, each indicated generally by the numeral 3I. Each member comprises a stationary base 32 having ,a base portion formed by the block 32a, side walls formed by the blocks 32h, .an end wall formed by the block 32e, and opposed ange or shoulder portions 33 formed by the blocks 32d positioned on the blocks 32o. In the embodiment of the invention illustrated, the members 32a, b, c and d, are secured together by `screws 34 connecting the respective members. It will be apparent, however, that the base member 32 may be constructed from va single piece of material if desired, rather than in the assembled .form .asillustrated rThe members 3l are secured to the respective cross members 'i and 3 by 'screws 35 extending through the base portion 32a into the respective member 'I lor 8, as the case may be.

Slidably positioned between .the blocks 32h and 32d is aretard block v33, the lower portion of the block 36 being provided with shoulders 31 slidably engaging the adjacent overhangi-ng surfaces of the shoulders 33 formed by the blocks 32d, thereby restricting the movement .of the block 33, other than in a longitudinal direction; riilhreaded into the -end wall formed by the block 32e is a sleeve 38 adapted to beheld in position 'by a lock nut 39, and threaded into the block 33 and "extending through the sleeve 38 is 'an adjusting stud 43, having lock nuts 4I threaded on the free end thereof and engageable with the free end of the sleeve 38 lto limit movement of the block 36 in a direction away from the end ywall formed by the member 32e. The block 36 is urged in the latter direction by a spring 42 encircling the stud 43 and seated at its respective ends on the block 35 and the inner end of the sleeve 38. Thus, by adjusting the sleeve 33 relative to the base 32, and the nuts 4I on the stud 43, the outward travel of the block 33 may be limited and the biasing pressure exerted by the spring 42 on the block 36 may be readily varied as required.

The blocks 33, are each provided with a small bore 43 opening on the exposed end 44 of the block, the axis of the respective bores extending at an angle of approximately 30 with respect to the axis of the extension II, which in the construction illustrated is vertical. As clearly illustrated in Fig. 3, the lower surface of the bore 43 adjacent the mouth 45 of the bore is iiat, as indicated at 46. Positioned in the bore 43 is a ball 4l adapted to rest `upon the flat surface 43 and partially extend through the mouth 45 of the bore 43,`the ball being biased in this position by a suitable spring 4S, seated at one end upon the ball and at the other end upon a cap member 49 threaded or otherwise secured to the block 33.

Referring to Fig. 3, it will be apparent that a downward force applied to the portion of the ball 47 extending from the mouth 45 of the bore 43 will lock the ball in position so that it is in effect a rigid part of the block 36 while such force is so applied thereto. On the other hand, if an upward force is applied to the `extending portion of the ball, such force, upon .overcoming the biasing pressure of the spring 48 will move the ball upwardly into the bore 43.

As illustrated in Fig. l, the work member or extension II, is provided with a .shoulder or cam surface 5i. By. adjusting the blocks 3,5, the latter may be so positioned with respect to the path of the shoulder 5I, that the latter will engage the portions of the respective balls 4i extending from the blocks 35, as the member II is moved downwardly in a power stroke. This engagement of the shoulder 5I with the balls 4l will momentarily retard or impede the downward movement of the work member I! and piston iB until the force exerted on the member H is sufficient to retract the pressure exerted .on the blocks 35 by 'their respective springs 4.2, the pressure required being dependent .upon the adjustment of the sleeve 38. Obviously, as soon as the blocks 36 have moved outward Aor rearward ysufficiently to permit the cylindrical sur.- face 52 of the member II to pass between the balls 41, the member II will be free to conti-nue its downward movement to the end of its stroke, and by varying the relationship between the member II and screw I3, the point along the powerstroke at which the shoulder 5I vwill engage the balls 4l may likewise 'be vvaried lso that this point of engagement may occur anywhere along the power stroke.

Fig. 5 illustrates one form of Vcircuit that may be employed to control vthe device, in which the ports I3 and I9 of the air cylinder I? vare operativelyconnected to a'pressure airline v53 and an exhaust line 54, through a four way uvalve `indicated generally by the 4numeral 55, the latter being of common construction .and readily procurable onthe open market. The valve 55 is connected to the port lI8 through a conduit 5B and to the port I9 by a conduit '57, a three way valve indicated generally by the numeral 59 being interposed in the line 51, if desired, for'purboses which will hereinafter be described. In'theconstruction illustrated in Fig. 5, the'valve 55 is of theelectrically operated type, being actuated from one. position to another bysolerioids 6| and 62, 'diagrammaticallyillustrated.. The construe-- tion is such thatxwhen the solenoid 6I is energized, port. I8 and the upper end of the air cylinder I1 will be connected to the pressure air line 53, iwhileport I9 and thelower end of the air cylinder` |1. will be operatively connected to the exhaustgline, thus driving the piston I6 downwardly. l Similarly, when the solenoid 62 is energizedjihwill reverse the valve 55 to connect theport` I il` with the exhaust line 54 and air pressure line53 thereby `reversing the travel of the piston 16. "'lheiparticular valve 55 illustrated, is iof thef-typelin which the energization of the solenoids 6I and 62 are required only in actuating the'valve, andthe latter will remain in either position when `the solenoids are de-energized until the valve mechanism is reversed by theaction of ,theproper solenoid. Obviously, if another form of valve is employed, the electrical circuit could be varied' accordingly to provide proper operation thereof. One side of each solenoid is connected by a conductor 63 to one side 64 of a power line, the other side of the solenoid 6| being connectedl by a yconductor 65 to the stationary contact 66 of a single pole single throw switch indicated generally by the numeral 61, the mov- -able contact 680i the switch 61 being connected by a conductor 69 through a master switch 1I to the other side of the power line, so that when the contacts 66 and 68 are closed, and the master switch 1I is closed, the solenoid 6| will beenergized. In like manner, the other end of the sole noid 62 is connected by a conductor 13 tothe stationary `contact 14 of a single pole double throw switch indicated generally by the numeral 15, the movable contact 16 of the switch 15 being connectedA to the? conductor 69. As illustrated in Fig. 1, `the switches 61` and 15 are rigidly supported relative to the frame structure I by any suitable means, as for example, a bracket 11, rigidly connected to the air cylinder I1. The switches 61 and 15 are adapted to be actuated by a.. projection 19 rigidly mounted, in the present instance, on the head I4 of the screw I3, the projection19 `being engageable with the actuating levers L of the respective switches during reciprocationof the piston I6. The switches 61 and 15V are` preferably adjustably mounted on the bracket '11,whereby the switches may be moved vertically along the bracket and securely locked in any 1desiredvertical position, the adjustable mounting of the switches being accomplished by any suitable means such as providing slots in the bracket through which the mounting screws 18 of the respective switches may extend, so that by loosening the screws 18 the switches may be moved vertically up and down and locked in place by retightening the screws.

' The operation of the` pneumatic and electrical circuit thus far described is as follows:

Assuming the valve 55 is set to admit air into the upper end ofthe air cylinder I1 and exhaust it from the lower end thereof, the piston I6 and associated elements will move downwardly until the projection 19 closes the contacts 14 and 16 of the switch 15, thereby energizing the solenoid 62, reversing` the Valve 55 to admit air into the lower end ofthe cylinder I1 and exhaust air from the topend thereof, whereby the piston I6 and associated elements `will move upwardly. This upwardmovement will continue until the projectionw19f`closes the contacts 66 and 68 of the switch 61, energizing the solenoid4 6I to 'reverse the cycle ofoperation.. The device may be con trolled` bythe' master switch `1I `as well as by a master valve 8| in the air line 53.

It may oftentimes be desirable toprovide a cushioning effect at the lower or terminating end of the powerlstrokepand this can be accomplished, for` exampleby, inserting the three way valve 59 inseries with the` conductor 51 into theport I9 and lower end off-the air cylinder I1. Thethird side of the valve 59 is connected tothe pressure air line V53 through a conduit 82, avalve 83 being interposed in the latter line.- For illustrative purposes, it will be assumed that the three way valve 59 is of the spring biased single solenoid. type, commerciallyprocurable andadapted to be actuatedby thesolenoid winding 84, the valve being so connected that when the solenoid winding 84 is `de-energized-the `port I9 is directly connected with the valve 55andair from the pressure line 53 is cut oil.` However, when the solenoid winding 84 is energized, the port `I9 `is cut off from the valve `55 and connected through `the conduit 82 and valve 83 to thepressure' line 53.

4The electrical wiring iorthe valve 59 is as follows: n i

One side of the solenoid winding 84 is connected bya conductor 85 to the side 64 of the power line, and the other side of the winding 84 is connected by a conductor `86v to the stationary contact 81 or the normally open relay, indicated generally by thenumeral 88, thelatter having an actuating winding 89, one side of which is connected by the conductorl tothe side 64 of the power line, and the other side of thewinding 89 connected to the contact 92.` Contact 921s `also connected by a conductor-93 `to contact `91| of the switch 95, the other `contact 96 ofthe switch 95 being connected by conductor 91 to the contacts 98 and 99 of the relay 88 and tothe otherstationary contact I6! of the switch 15. The contacts 92 and 99of the relay 88 are lock-in `contacts serving to maintain thewrelay 88 energized4 until the circuit is broken elsewhere. VIt will be noted that when the contacts 16 and IDI oftheswit'ch 15 are closed, contacts 98 and 99 of therelay 88 are connected to the side 12 of the power line, and when the contacts 94 and 96 of the switch 95 are closed under such conditions, the relay 88 will be energized and locked in `by the contacts 92 and 99 so that it will remain energized untilpthe contacts 16 and I8| are broken, following which the relay 88 will not be energized untllcontacts 16 and IUI of the switch 15 andcontacts 94 and 98 of the switch 95 are bothclosed Obviously, when the relay 88 is energized contacts 81 and 98 will be closed, energizing solenoid winding 84 of the valve 59.

In the circuit illustrated in Fig. 5, the switch 95 may be actuated by any suitable means, as for example, one of the blocks 36, as illustrated in Fig. 3, wherein the switch 95 may be mounted on the blocks 32d by the same screws 34 that secure the latter'to'the blocks 32h, the switch 95 being preferably slidably mounted so that it may be longitudinally adjusted. Rigidly carried by the cooperating block 36 is a projection |02 adapted to engage the actuating pin or member |03 of the switch 95 to actuate the switch 95 when the block 3 6 is moved toward the same. Thus, the switch `95 may be so adjusted, with respect to the block 36, that the valve 519 will be actuated at substantially the same time the work member II begins its accelerated downward movement after Shaving been retarded by engagement of the shoulder 5I with the balls 41 carried-by the blocks 36. The amount of air adthe valve 55 to its original position and `repeat 7s mittedtO-the lower end 0f the cylinder when the valve 59 is factuated may .be controlled by the valve 83, thus controlling the cushioning eect tobe achieved.

The automatic operation 'of the is as follows:

Assuming the valve 55 is .in a position to A'actuate the piston I6 in a .power stroke, the work member I I will move downwardly until the shoulder I engages the balls '47, thus momentarily retarding the downward movement of the member, and blocks 3S, and as they are spread, fas a result of the additional force by 'the continued downward 'movement foi `the member il, switch S5 will be closed, and as contacts IIJ'I and 16 'of the switch 'I5 'are closed, -c'l'o's'ing of 'the vswitch 95 will actuate relay 88, energizing tlie winding 8d to actuate 'the valve 59, the amount/affair jadmitted to the lower end of the piston -I6 being dependent upon the setting of the valli/'e433I -to achieve the desired cushioning effect. vAs the member I I nears the end of its downward travel, switch 'I5 will be actuated by 'engagement 'of 'the projection I9 with the lactuating lever L Vof the switch closing contacts 'I4 vand T6 lto reverse the valve 55, at the same time breaking the 'contacts lt and IBI, thereby de-energizing relay 88 and the winding 8l of the valve 59 to vreverse the same. Full air pressure is 'thereby applied to the lower end 'of the cylinder I'I reversing 'the travel of the piston I6 and w'ork 'member II 'to move the same through a return stroke, 'which will continue 'until the projection 'I9 engages 'the actuating arm L of the switch 61 closing 'the contacts 66 and '68 'to actuate the windingVIiI, reverse valve 55 and ythe fflow of air to the .air cylinder I1, and initiate another powerstroke.

It will be 'apparentthat whileflhavelilllus'trated the cushioning laction as Abeing controlledy yby movement of one of `the blocks Jt6, obviously-the actuation of the switch A95 maybe synchronized with the movement of Athe work member III by other suitable means, asl-for example, by -di-rect actuation by means carried by the work vmember I I, or associated elements.

It will be noted from the abo-ve description thatI have produced a'novel punch press, or ithe like, which may -be relatively Vsmall in -size .and at the same time very efficient for the lpurposes intended.

Having thus described -my invention, itis obvious that various immaterial vmodifications may be made in the same without `departing `from the spirit of my invention; hence, Ido 'not `wish to be understood as limiting myself to 4the exact form, construction, arrangement and ycombination of parts herein shown and ide'soribedfor uses mentioned. l

What I claim `as new and l:desire to secure rby Letters Patent is:

1. In a pneumatic punch presa. the combination of an adjustable reciprocab'le work :member of the punch press, a pneumatic 'actuating unit including an Vair cylinder `and a cooper'able ,piston, means operatively connecting said .piston and member for transmitting motion :from theA former to the latter, valve means for controlling the flow of air to and .from said-cylinder., means responsive to movement of said member vfor actuating said lvalve means to -reciprocate said member through a power stroke Vof 'a predetermined length and a return stroke, `said `adjustable reciprocable work member having a cam surface thereon permitting adjustment thereof with -respect to the length of the :stroke vci* the 'reciprocable workrmembe'r, 'a vretard member movable entire circuit with respectto vsaid cam surface and having a yieldable element thereon, and means for urging said retard member toward and the yieldable element into the path of the cam surface on said reciprocable member, .said yieldable element being temporarily .rigid lrelative to said retard 'member and momentarily retarding movement of the work member dur-ing an -intermediate fraction of a power stroke for increasing the eifec-tive impact 'force of the work member, and yieldable relative rto said retard member Vduring a return stroke to permit unrestricted return movement of 'said r'eciprocable work member.

2. In a pneumatic punch press, the combination of lareciprocable work member of the punch press, a vpneumatic actuating unit including an air cylinder land a 'cooperable piston, 'adjustable means operatively connecting said piston and member for transmitting motion from the Sformer to the latter, valve means fork controlling the flow 'of air to and from said -Vcylinder to reciprocate said member through la power stroke of a predetermined length and a return stroke. said member having a cam surface thereon and said adjustable means `permitting adjustment of the ,position of the cam with respect to the 'length of the stroke of the reciprocable work member, a retard member Vmovable with .respect to Vsaid cam surface and having a yieldable element carried thereby, and means for `urging Asaid retard member Vtoward and the yieldable element into lthepath of the cam surface on said reciprocable member, said yieldable element being temporarily rigid relative to said retard member and momentarily retarding movement of Asaid reciprocable workmember during` an intermediate fraction of the power stroke prior to the workengaging positioning of said member for increasing the effective impact force of the work member-and yieldable relative to said .retard member during a return stroke to permit unrestricted return movement of said reciprocable work member.

:3. In a device of the kind described, the 'combination of 'a supporting structure, a recprocable work'member slidably mounted in saidstructure, apneumatic actuating unit including .-'aniair cylinder and` a cooperable 'piston 'carried by said structure, means operatively connecting said piston and member for transmitting motion from the former to the latter, electrically operable valve means for controlling the flowof air to and from said cylinder, switch means responsive to predetermined movement oi'sa'idmember for actuating said valve means to reciprocate said member through a power stroke of a predetermined length and a return stroke, said `member having a camsurface thereon, 'a retard member supported by said structure Vand movable transversely with respect Ato the path of said member, said retard member 'having'a ball carried thereby, vmeans for urgingsaid retard member toward and said ball into the path of vthe cam surface on said reciprocable member, and a spring for biasing said ball in'a position to Vmaintain vthe same rigid relative to'said retard member, and momentarily retard movement of the reciprocable work member 'during a power stroke, said spring being yieldable to yallow movement of said ball relative to said retard member during a return stroke and permit unrestricted return movement of said reciprocable work member.

4. In a pneumatic punch press, the combination of areciprocable work member, a pneumatic actuating unit :including an air cylinder vand a 9, cooperable piston, means operatively connecting said piston and member for transmitting motion from the former to the latter, electrically op-` erable valve means for controlling the ow of air to and from said cylinder, switch means responsive to movement of said member for actuating said valve means, to reciprocate said member through a power stroke of a predetermined length and a return stroke, said` member having a cam surface thereon, a retard member movable with respect tosaid cam surface, and spring means forfurging said retard member into the path of the cam surface on said reciprocable member for momentarily retarding movement of the latter during a predetermined intermediate fraction of the power stroke thereof prior to the work engaging positioning of said member for increasing the effective impact force of the work member.

5. In a pneumatic punch press, the combination of a reciprocable work member, apneumatic actuating unit including an air cylinder and a cooperable piston, means operatively connecting said piston and member for transmitting motion from the former to the latter, electrically operable valve means for controlling the flow of air to and from said cylinder, switch means respon sive to movement of said member for actuating said valve means to reciprocate said member through a power stroke of a predetermined length and a return stroke, and means for momentarily retarding said member during an intermediate fraction of the power stroke prior to the work engaging positioning of said memben 6. In a pneumatic punchpress, the combination of a reciprocable work member ofthe punch press, a pneumatic actuating unit including an air cylinder and a cooperable piston, adjustable means operatively connecting saldi piston and member for transmitting motion from the former to the latter, valve means for controlling the flow of air to and from said cylinder,l means responsive to movement of said member for actuating said valve means to reciprocate said member through a power stroke of a predetermined length and a return stroke, said member having a cam surface thereon, a retard member movable with` respect .to said cam surface, and means for urging` said retard member into the path ofthe cam surface on said reciprocable member to momentarily retard movement of the latterfor an intermediate fraction of a power stroke thereof prior to the work engaging positioning of said member to increase the effective impact force of the work member. i i i i 7. In a device of the kind described, the combination of a supporting structure with a reciprocable work member slidably mounted in said structure, a pneumatic actuating unitincluding an air cylinder and a cooperable piston carried by said structure, means operatively connecting said piston and member for transmitting motion from the former to the latter, electrically operable valve means for controlling the flow of air to and from said cylinder, switch means responsive to predetermined movement of said member for actuating said valve means to reciprocate said member through a power stroke of Va` predetermined length and a return stroke,.said member having a transversely extending cam surface thereon, a plurality of retard memberseach supported by said structure and movable transversely with respect to the path of said member. i

each retard member having a ball carried thereby, means for urging the respective retard members toward and their corresponding balls into the path of the cam surface on said reciprocable l member, and springs for biasing the respective balls in a position tomaintain the samerigid relative to their respective retard members, and simultaneously momentarily retard movement of the reciprocable work member` during a power stroke, said springs being yieldable to allow movement of said balls relative to their respective retard members during a return stroke and per.n mitunrestricted return movement of said` re ciprocable work member. i

i 8. In a pneumatic punch press, a reciprocable work member, means including a pneumatic actuating element for reciprocating said member through a power stroke and a return stroke. pressure biased means forretarding movement of said member for a predetermined intermediate fraction of the power stroke thereof until the actuating element overcomes said biasing pressure to increase the eifective impact force of the work member, and means for applying a counter pneumatic force on said memberto cushion th same at the end of a, power stroke.

9. In a pneumatic punch press, a reciprocable work member of the punch press, means including a pneumatic actuating .element for recipro cating said member through a power stroke and a return stroke, adjustable means operatively connected to said work member to momentarily retard movement of said member for a predetermined fraction of the power stroke to increase the effective impact force of said member, and means for applying a counterpneumatic force on said member to `cushion the same at the end of a power stroke. i

10. In a pneumatic punch press, a'reoiprocable Work member of the punch press, means including a pneumatic actuating element for reciprocating said member through a power stroke and a return stroke, adjustable pressure-biased means operatively connected to said reciprocable work member to retard movement of said member during the power stroke of said pneumatic actuating element until the actuating element overcomes said biasing pressure to increase the effective im pact force of the work member, and means for applying a counterpneumatic force on said member to cushion the same at the end of a. power stroke controlled by said adjustable pressure# biased means. i l l 11. In a pneumatic punch press, the combination of a pneumatic cylinder, including a1 piston and having a pair of ports communicating with respective opposite sides of said piston, electrically energized valve means for controlling the admission of air into the cylinder, switch means responsive to movement of said piston for actuating said valve to effect reciprocation of said piston through a power stroke and a return stroke and means operatively connected to the piston to momentarily retard movement of the piston as the latter moves in a power stroke to increase the impact force of the work member. i i

l2. `In a pneumatic punch press, the combina tion of a reciprocable work member of the punch press, a pneumatic actuating unit including an air cylinder and a cooperable piston, means operatively connecting said piston and member for transmitting motion from the former to the 1atv ter, solenoid operated valve means for controlling the flow of air to and from said cylinder, switch means operatively connected to said valve means and responsive to movement of said member for actuating said valve means to reciprocate said l l member through a power stroke of a predetermined length and a return stroke, `and means operatively connected to said reciprocable work member to. momentarily retard said member during a fraction of the power stroke prior to the work engaging positioning of said member` 13. In a pneumatic punch press, a reciprocable work member of the punch press, means ineluding a pneumatic actuating element for reciprocating said member through a power stroke and a return stroke, adjustable, spring biased means operatively connected to said reciprocable work member during a predetermined part, of the power stroke to momentarily retard movement of said member during the power stroke thereof to increase the effective impact force of the work member, and means for applying a counter-force to said member as the latter approaches the end of a desired power strokeA operatively controlled by said adjustable spring biased means.

14,. In a pneumatic punch press, a reciprocable work member of the punch press, means including a pneumatic actuating element for reciprocating said member through a power stroke and a. return stroke, spring biased means operatively connected to said reciprocable work member during a predetermined part of the power stroke to momentarily retard movement ci said member during the power stroke thereof to increase the effective impact force of the work member, and means comprising electrically energized valve means and switch means therefor controlled by movement of said retarding means for applying a. counter-force to said member as the latter approaches the end of a desired power stroke.

15. In a pneumatic punch press, the combination of a reciprocable workmember, a pneumatic actuating unit including an air cylinder and a cooperable piston, means operatively connecting said piston and member for transmitting motion from the former to the latter, valve means for controlling the ilow of air to and from said cylinder, means responsive to movement oi said member for actuating said valve means to reciprocate said member through a power stroke of a predetermined length and a return stroke, said member having a cam surface thereon, a retard member movable with respect to said cam surface and having a yieldable element thereon, means for urging said retard member toward the yieldable element into the path of the cam surface on said reciprocable member,y said yieldable element being rigid 'relative to said retard member for momentarily retarding movement of the latter during a power stroke to increase the effective impact force. of said workl member, and yieldable relative to said retard member during a return stroke to permit unrestricted return movement of said reciprocable work memben and means for admitting a counter-flow of air to said cylinder as the reciprocable arm approaches the end of a power stroke.

16. In a device of the. kindA described, the combination of a reciprocable work member, a. pneumatic. actuating unit including an, air cylinder and a cooperable piston, means operatively connecting said piston and member for transmitting motion from the former to the latter, valve means for controlling the :dow `of air to and from said cylinder, means responsive to movement of said member for actuating said valve means to reciprocate said member through a pQwer stroke of a predetermined length and a return stroke, said member having a cam surface thereon, a retard member movable with respect to said cam surface and having a yieldable element thereon, means. for urging said retard member toward the yieldable element into the path of the cam surface on said reciprocable member, said yieldable element being rigid relative to said retard member for momentarily retarding movement of the latterduring a power stroke, and yieldable relative to said retard member during a return stroke to permit lunrestricted return movement oi said reciprocable work member, and means controlled by movement of said retard member for admitting a counter-flow of air to said cylinder as the reciprocable arm approaches the end of a power stroke.

17'. In a device of the kind described, the combination of a reciprocable work member, a pneumatic actuating unit including an air cylinder and a cooperable piston, means operatively connecting said piston and member for transmitting motion from the former to the latter, valve means for controlling the flow of air to and from said cylinder, means responsive to movement of said member for actuating said valve means to reciprecateV said member through a power stroke of a predetermined length and a return stroke, means for momentarily retarding said member during the power stroke prior to the work engaging positioning of said member, a second valve means for admitting a counter-flow of air to saidcylinder, and means coordinated with the movement of said retarding means for actuating said second valve, and means to admit such counter-flow of air to said cylinder as the iatter approaches the end of a power stroke.

18.` In a device of the kind described, the combination vof a supporting structure, a reciprocable work member slidably mounted in said structure, a pneumatic actuating unit including an air cylinder and a cooperable piston carried by said structure, means operatively connecting said piston and member for transmitting motion from the former to the latter, electrically operable valve means for controlling the ilow of air to and from said cylinder, switch means responsive to predetermined movement of said member for actuating vsaid valve means to reciprocate said member through a power stroke of a predetermined length and a return stroke, said member having a camsurface thereon, a retard member supported by said structure and movable transversely with respect to the path of said member, said retard member having a bore therein` extending at an angle of approximately 30 to the axis of said reciprocable member in the general direction of return movement of the latter, a ball positioned in' said bore, means for urging said retard member toward, and said ball into the path of the camV surface on said reciprocable member, and a spring for biasing said ball in a directiontoward said reciprocable member to maintain the. ball rigid relative to said retard member, andV momentarily retard movement of the reciprocable. work member during a power stroke, said spring being yieldable to allow movementv of said ball relative to said retard member during areturn stroke and permit unrestricted return .movement of said reciprocable work member. I

19. A compressible-uid punch press including in combination a reciprocable work member of the, punch, press', a compressible-iiuid actuated unitl including a cylinder and co-operable piston, means operatively and adjustably connecting said piston and' member for transmitting motion from the former to the latter, and spring-biased means operatively connected to said recprocable Work member to momentarily retard said mem` power stroke thereof. 5

HERBERT PALMLEAF. i

REFERENCES CITED The following references are of record in the lle of this patent: 10

UNITED STATES PATENTS Number Name Date 635,848 Dutton Oct.- 31, 1899 1,326,228 Turner Dec. 30, 1919 15 1,508,580 Schoelkopf Sept. 16, 1924 Number Number Name Date Bath Aug. 13, 1929 Wiegner Feb. 14, 1933 Stratton Feb. 28, 1933 Cardwell July 17, 1934 Rippl Apr. 23, 1940 Clark May 6, 1941 Rippl June 1, 1943 Shendrek Nov'. 6, 1945 Banning July 2, 1946 Kovach Sept. l, 1947 Mead Dec. 26, 1950 FOREIGN PATENTS Country Date Sweden July 30, 1910

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