US2378069A - Hydraulic stripping mechanism - Google Patents

Description

June 12, 1945. c. M 'EASQN 2,378,069

HYDRAULIC S TRIPPING MECHANISM Filed April 7, 1944 4 Sheets-Sheet l I INEENTOR. Clarencemfi'won,

/ may 7 I I jad 4 Sheets-Sheet 2 INVENTOR.

I Clarence Mlaaari HYDRAULIC STRIPPING MECHANISM June 12, 1945.

June 12, 1945. c, EA-SON 2,378,069

nynmumc STRIPPING MECHANISM Filed April 7; 1944 4 Sheets-Sheet 4 I N V EN 7 0R. 84 I I Manse/45:15am,

Patented June 12, 1945 OFFICE r 2,378,069 HYDRAULIC STRIPPING MECHANISM Clarence M. Eason, Waukesha, Wis. ApplicationApril '7, 1944, Serial No. 529,992

Claims.

The present invention relates to hydraulic stripping mechanism for punch presses and the like. The present invention embodies improvements upon the construction of hydraulic stripping mechanism disclosed in my copending-application Serial No. 446,311, filed June 8, 1942.

In performing deep drawing operations on a hydraulic press, punch press or other like ma, chine, it is frequently difiicult to effect release of the drawn blank from the punch upon the completion of the drawing operation when relying upon mechanical stripping devices of the prior art. These mechanical stripping devices frequently cause excessive mutilation of the upper edge of the blank where the mechanical stripper engages the blank. This is particularly true when performing deep drawing operations on tubular shells, such as steel cartridge cases, where the punches used in the last one or two draws have only a very slight taper and hence have a tighter binding action. Steel shells appear" to be more difficult to strip from the punches than brass shells, and it may require the exertion of several thousand pounds pressure ongthe steel shell to strip it from the last punch in the series of v drawing operations. When the stock has been drawndown to a shell of relatively thin wall, the exertion of a high stripping pressure as a mechanical force against the upper edge of this'thin walled shell is veryllkely to multilate the upper imposed upon this trapped liquid become sufficiently high, there is the possibility that such trapped liquid will distort the shell. This possibility is completely avoided by an improvedv venting arrangement which I have embodied in the hydraulic stripping mechanism herein disclosed. Such venting arrangement enables any This automatic venting at the start of the drawing operation, without interferin with the high stripping pressures at the conclusion of the drawing operation, is preferably accomplished by venting the trapped liquid back through the very same cylinder or cylinders'which later transedge of the shell so badly as to require that a considerable portion of the upper edge of the shell be cut off as waste scrap. Such difficulties in mechanical stripping, with the resultant mutilation of the shells, are entirely avoided by the improved hydraulic stripping mechanism disclosed in my aforesaid copending application Serial No. 446,311, and also disclosed in my present appli-cation.

One of the general objects of the present invention is to provide improved hydraulic stripping mechanism which will strip the, shell from the punch by the exertion of a hydraulic pressure between the lower end of the-shell and the punch. More specifically, it is one of the principal objects of the embodiment shown in this application to provide means for automatically releasingany liquid which may be trapped between the punch and the shell at the time that the punch is becoming seated in the shell and is starting to force the shell down through the die; This liquid is the liquid which is used to lubricate and cool the bottom of the shell at the start of the seating and drawing operation, and if the pressures the punch and die surfaces and the blank, such mit the extremely high hydraulic pressures to the space between the-punch and shell. Because of this venting back through the cylinders, I term this function a back-venting function, such being one of the distinctive featuresof the present invention.

Other objects, features and advantages of the invention will be apparent from the following detail description of a preferred embodiment thereof. In the accompanying drawingsillustrating such embodiments:

Figure 1 is a fragmentary elevationalview show ing my improved hydraulic stripping mechanism applied to a hydraulic press;

Figure 2 is a fragmentar sectional view showing how liquid may become trapped between the lower end of the punchrand the lower end of the shell;

Figure 3 is a perspective view of one of the hydraulic cylinders of the stripping mechanism;

Figure 4 is a fragmentary horizontalsectional view through the head block of the pressure cyl- Figure 5 is a fragmentary vertical sectional view through the hydraulic cylinder of the stripping mechanism, showing the piston or ram element of this device in its lower position, with the controlled back venting valve open; v

Figure 6 is a similar fragmentary sectional view showing the piston or ram element in its raised position with the controlled back-venting valve closed; and

Figure 7 is a fragmentary detail viewof the back-venting valve, drawn on a larger scale.

In Figurel I have shown my improved hydraulic stripping mechanism applied to a, conventional construction of hydraulic press comprising the usual bedor base structure It) formed with upwardly extending sides between which reciprocates a vertically moving cross-head |2. In a hydraulic press the cross-head |2 is reciprocated by an overhead hydraulic cylinder (not shown), and in a crank type of punch press this cross-head or ram is reciprocated through a conventional pitman connecting to a crankshaft, as is well known. Y

The punch or male die which moves down inside of the shell is indicated at Hi, this punch being detachably secured to the underside of the reciprocating ram or cross-head l2. die through which the shell case is drawn is indicated at l5, this die being detachably secured to the stationary bolster or bed plate Hi. The drawn tubular shell is indicated in its entirety at ll. In the illustrated arrangement, this tubular shell I! may be considered as typical of a cartridge case for guns ranging as large as 75, 90 or 105 mm. or larger. The tubular shell ll may also be regarded'as composed of steel, which rep- The female resents a more difiicult'stripping problem than a 'ner, and this mounting block 2| is secured to the underside of the reciprocating cross-head l2. An'axial passageway 24 extends down through the punch to its lower end, a flow controlling plug 25 being preferably seated in the lower end of the bore 24. Two high pressure passageways 2'] extend outwardly in diametrically opposite directions from the upper end of the punch I4, these passageways bein either formed as short sections of high pressure tubing, or as passageways cored out in the mounting block 2|. Ihese passageways 37 communicate through high pressure connections 28, 28 with the upper end of the bore 34 in the punch.

Each passageway 27, 21 extends to a hydraulic cylinder 3|, there being two of these cylinders at diametrically opposite sides of the punch so as to equalize the stresses imposed on the ram and its guideways when the high stripping pressures are created inthese hydraulic cylinders. As shown in Figures 4 and 5, the outer end of each high pressure tube 21 enters'a tapped bore 32 in a head casting 33 which constitutes the upper closure head of each high pressure cylinder 3|. A depending annular skirt or flange 34 extending downwardly from the head 33 is formed with an external groove 35 in which is mounted an .expansible ring 36 composed of rubber, Neoprene or the like. A bottom stop ring 31 having an inwardly extending stop shoulder 38 is bolted to the lower end of the cylinder 3| by long cap screws or stud bolts 39 which have their upper ends anchored in the head block 33. Reciprocating in each high pressure cylinder 3| is a piston or ram 4| which is formed with a reduced lower portion 4| adapted to pass down through the lower stop ring 31, an outwardly extending shoulder 42 on the piston being adapted to strike the shoulder 38 of the ring 31 for limiting the downward movement of the piston. The upper portion of the piston 4| is formed with a reduced neck around which are assembled an upper sealing ring 44 and a lower sealing ring 45. These two rings are preferably constructed in the form of cup leathers of U-shaped cross-section which are held in the Spaced apart relation illustrated by an intermeditributing pressures from the outside to the inside of the ring. A retaining member 48 holds the assembly in place, and this retaining member is secured to the piston by a locking ring 49 which snaps into an annular groove in the reduced neck portion of the piston. The upper cup leather 44 functions as the suction sealing leather for the purpose of preventing the entrance of air into the cylinder on the down stroke of the piston 4|, and the lower cup leather functions as the pressure sealing leather for preventing oil leakage past the piston when the piston is forced upwardly in the cylinder in the hydraulic stripping operation. The oil pressures within the cylinder 3| may rise to approximately 10,000 lbs. per square inch in the hydraulic stripping operation. The tapered edges of the -U-shaped cup leathers augment the ability of these leathers to maintain an effective seal under these pressures.

The piston 4| is cored out with a relatively long central bore or well 5| therein into which extends a heavy compression spring 52 normally tending to hold the stop shoulder 42 of the piston down against the lower stop ring 31. As the high pressure cylinder 3| moves down with the crosshead |2 in the operation of forcing the tubular shell down through the female die l5, the lower end of the piston 4| engages the top of a striker post 54 at just about the time that the tubular shell has been forced completely through the female die l5 and is ready to be stripped from the punch I4. From this point on the piston 4| has relative movement within the cylinder 3 i. e. the piston stands stationary and the cylinder moves down over the piston in the continued downward movement of the cross-head. It will be understood that this same operation is, of course, also occurring in thecase of the other high pressure cylinder 3| mounted on the other side of the cross-head. The spring 52 is compressed in this movement of the cylinder 3| down'over the pis- .tom of the central bore 5| in the piston 4|.

ton 4|. The lower end of the spring 52 seats on a ring 56 which bears constantly against the bot- This ring 56 has a peened or other suitable connection with a long guide sleeve 58 which extends up axially within the spring 52. A bore 59 in the lower portion of the sleeve 58 is provided with outwardly radiating vent holes 5| near its upper end, and above these vent holes is formed an inwardly extending shoulder 62. A counterbore 63 extends upwardly above the shoulder 62, and extending down through this counterbore and into the lower bore 59 is a valve actuating rod 64 which serves to actuate a ball valve 65 at its upper end. Disposed within the counterbore 53 and surrounding the rod 64 are two friction grip washers 56 and 5'! which exert a slidable clutching action on the rod. Above and below the Washers 66 and 57 are supplementary clutching washers 6B and 69. These several washers may be composed of different materials suitable for obtaining a friction gripping. action on the surface of the rod 64; in the preferred construction I have made the two intermediate washers 66 and 61 of Neoprene and the two outer washers 68 and 69 of leather. The washer assembly is held in place by a threaded gland ring or bushing 1| which screws down into the threaded upper end of the counterbore 63. Confined within this threaded bushing is a compression spring 12 which also serves to keep the friction washers compressed into firm frictional contact with the surface of the rod 54. In the operation of this friction clutch mechanism 66-59, the friction washers exert upward force through the valve 'rod 64 to force the ball valve 65 to its seat'when the 64 to pull the ball valve 65 ofiof its seat when the.

piston 4| has relativemovement downwardly within the cylinder. v

The ball valve 65 is operative to control a port "I5 which functions as an inlet port whenliquid is entering the cylinder 3| from the liquid circulating system, and whichalso functions as the backventing port for back-venting trapped liquid out of the tubular shell and out of" the cylinder 3| in the operation of seating the punch in the shell and forcing the shelldown through the female die. The valve port '|5 isformed intermediate the ends of a valve cage which is pressed up into a central bore 'I'l formed in the head block 33. valve cage opens laterally into .an inlet bore I9 which has-connection with the pump of the circulating system, and which may alsohave con nection with the coolant nozzle at the stationary die, as I shall presently describe' A sealing ring 8| composed of Neoprene or like material may be set into an annular groove in the valve cage'IB to prevent any possibility of leakage of the high pressures up along the outer side of the valve cage.

The ball valve 65 is mounted in a confiningring or sleeve 8| which has an inwardly turned upper lip embracing the ball above its horizontal diametric plane, whereby the confining ring is oper ative to pull the valve 65 forcibly downwardly A threaded guide bushing 85 screws into the 'internally threaded lower end of the valve cage ,16 and serves to limit thedownward movement of the valve 65 in'a direction away from the seat I5.

These is suflicient-lateral play in the vertical movement of the ring 8| within the valve cage or of the sleeve 83 within the bushing 85 to insure that the ball valve will be self-centering when it The fluid passageway I8 of this I engages the-valve port 15. Ports 86 open outwardly through the wall of the valve cage immediately below the valve portl5. The upper end P .of the compression spring 52 can bear against either the head block 33 or against the valve cage I6. The latter arrangement is preferable, and is obtained by. having the spring bear against a thrust ring 81 which abuts against a suitable shoulder or stop ring carried by thevalve cage.

The high pressure conduit 2|'opens into passageways 9| (Figure 6) which communicate with vertical bores or cavities 92'communicatingwith the chambered upper portion of the head block 33.. A suitable high pressure coupling 93 screws into the threaded counterbore 32 ofthe h'ead block for establishing a high pressure seal around the conduit 21, this coupling comprising a Neoprene sealing ring 94 functioning substantially the same as described of the highpressure couplings disclosed in my prior application Serial No. 446,311. The high pressure couplings 28 which join the inner ends of the tubes 21 to the bore 24 of the punch I4 may also be of the Neoprene ring type disclosed in said copending application.

Screwing into the threaded outer end of the inlet bore 19 (Figure5) is any suitable pipe fitting or coupling 96 which has connection through a flexible conduit 91 with the source of liquid supply. It is customary to supply a liquid coolant to the dieparts during the drawing'oper'ation, and in the preferred embodiment of my invention this liquid coolant is used as the hydraulic stripping medium for stripping the shell from the punch l4. This-liquid coolant, which has 'anoil-ba'se 'or other'suitable base appropriate for lubricating and cooling purposes, is circulated-through a circulating system which is shown in Figure 1 as comprising a motor driven pump 93- which" draws the liquid from a suitable sump 99 dis-posed beneath the press. The liquid is forced upwardly at a relatively moderate pressure of 15 or 20 pounds or'so to a four-wayfitting 1I0|.' Leading from one branch of this fitting-is a discharge nozzle I02 which discharges coolant around the female die I5 and the exterior of the tubularshell ll. Leading from other branches of said fitting IOI are pipes I03 which extend to'filters I04 feed-' ing liquid to the flexible conduits il'l. Valves |05 may be provided in the nozzle line I02 and in the pipe lines I03'for shutting off flow or for regulating the pressure of the flow. If desired; a branch passageway I06 may be formed in each head block 33, leading from the inlet chamber "I9, for con-' ducting coolant to a pressure' release by-pass valve,- thereby providing a ready avenueof discharge through which back-vented coolant can be quickly vented from each cylinder 3| without having to be forced back through the filters I04.

Referring now to the operation of the apparatus, in the normal position of the parts, the crosshead I2 stands in its raised position with the punch I4 entirely clear of the female die '|5,'and with the two' high pressure cylinders 3| raised a substantial distance above the striker posts 54'. At this time the circulating pump is forcing coolant liquid through the high pressure cylinders 3| and through the passageways 2|:for discharging some of the coolant down through the axial bore 24 in the punch I 4. Someof the coolant is of course also flowing through the discharge nozzle I02 to the female die. In this condition of the parts, the pistons 4| of the two high pressure cylinders are in their lower positions under the action of the springs 52' and under the pressure of the coolant liquid, in which position the valves 65 of each cylinder are heldofi their valve seats I5; as shown in Figure 5. As soonas the tubular shell H which is to be drawn is placed-under the punch I4 the flow of coolant issuing from the lower end of the punch collects in this tubular shell. In the operation offorcing the shell and the punch downwardly through the female die I5 the shell is forced downwardly into a closer and closer fit with the punch so that there is an increasing likelihood of the liquid confined in the lower end of the shell becoming these two cylinders. Hence, the maximum pressure which can be created in this trapped liquid is merely the pressure of thepump 98,-which is usually in the neighborhood from to lbs.

per square inch. The back-vented liquid can be forced back through the pump 98, or it may be discharged through passageways I06 or through other corresponding channels leading either to the discharge nozzle I02 or back to the sump 99. This back-venting connection remains open during substantially the entire drawing operation performed in the tubular shell, or until the lower ends of the high pressure pistons 41 engagethe striker posts 54, This does not usually occur until after the tubular shell ha been forced down completely through the female die l5, corresponding to the completion of the drawing operation- As soon as the lower ends of the two pistons 4-! engage their respective striker posts their further downward; movement is stopped, i. e. they have relative upward movement within their respective cylinders 3|. The very first part of this relative upward movement acts through the friction clutching washers 68-69 to exert an. upward force through rod 64 for pressing the ball valve 65' up against its seat 15. 'I'hereupon, the back-venting connection through the high pressure cylinder is closed.

Upon the engagement of the valve 65 with the.

seat 15 this valve becomes an intake check valve, and thereafter all hydraulic pressure created within the cylinder 3! is transmitted through the high pressure connection 21 to the axial bore 24 extending down through the punch l4. With the. continued downward movement of the crosshead 42 the friction washers Git-69: slide along the rod 64 for continuously maintaining the valve 65 against the seat '15, aided by the high pressure which is continuingto rise in the cylinder 3!. When the pressurein these two cylinders. reaches a point capable of stripping the tubular shell from the punch the shell moves downwardly. along the punch, thereupon quickly releasing the high stripping pressure. The entire stripping operation can be performed hydraulically, or it may be initiated hydraulically and completed mechanically. On the return strokeof the cross-head l2 the first relative movement of each piston 4| in a downward direction: operates through the friction washers (SB-69 to exert a downward pull on the valve rod 64 for pulling the ball: valve 65 ofi its seat 15. The pressure continuously transmitted through the liquid coolant from the pump 98 also assists. in forcing the While I have illustrated and described what I regard to be the preferred embodiment of my invention, nevertheless it will be understood that such is merely exemplary and that numerous modifications and rearrangements may be made therein without departing from the essence of the invention.

I claim:

1.v In a press comprising a reciprocating ram, the combination of punch and die members adapted to be moved toward and from each other by the reciprocation of said rain for drawing a tubular shell, a hydraulic cylinder and coopcrating piston having relative motion therein responsive to the motion of said ram for creating a hydraulic. stripping pressure between said punch member and said tubular shell, and valve means automatically responsive to relative motion between said hydraulic cylinder and piston for preventing the creation of high liquid pressures between said punch member and said tubular shell prior to the hydraulic stripping operation.

2. In a press comprising a reciprocating ram, the combination of punch and die members adapted to be moved toward and from each other by the reciprocation of said ram for drawing a tubular shell, a hydraulic cylinder and piston adapted by relative converging movement therebetween to create hydraulic stripping pressures between the shell and the punch at the end of the drawing operation, valve means for preventing liquid from becoming trapped between the shell and the punch in the drawing operation, and means responsive to the initial converging movement between said cylinder and said piston for closing said valve means.

3. In a press including a reciprocating ram together with punch and die members adapted to be moved toward and away from each other by the reciprocation of said ram for drawing a tubular shell, the combination therewith of a hydraulic cylinder and piston operative by relative converging movement therebetween to create hydraulic stripping pressures between the shell and the punch at the end of the drawing operation, valve means for venting liquid trapped between the shell and the punch in the drawing operation, and mechanically acting means responsive to the initial converging movement between said cylinder and piston for closing said valve means.

4. In apparatus of the class described including punch and die members having relative movement therebetweento effect a drawing operation ontubular shells, the combination of a hydraulic cylinder and piston adapatedby relative converging movement therebetween to create hydraulic stripping pressures between the shell and the punch at the end of the drawing operation, valve means for venting liquid trapped. between the shell and the punch in the drawing operation,

and friction. clutch means operative to close said valve response to the initial converging movement between said cylinder and piston.

5-. In apparatus of the class described including punch and: die members cooperating with each other to produce a drawing operation on a metallic blank, the combination therewith of a hydraulic cylinder and piston adapted by relative converging movement'therebetween. to create hydraulic stripping pressures between the blank andthe punch at the end ofthe drawing operation, a valve for venting fluid trapped between the blank and the punch in the drawing operation, a stem extending from said valve, and frictio'n slippage clutch means carried by said piston and movable along said valve stem for im-' parting up. and down movement to said valve.

- CLARENCE EASON.

Images