US2605731A - Apparatus for forming sheet material under controled pressure - Google Patents

Description

g 5, 1952 R. B. SCHULZE ETAL 2,605,731

APPARATUS FOR FORMING SHEET MATERIAL UNDER CONTROLLED PRESSURE 2 SHEETS-SHEET 1 a M) em Io m RICH/7R0 5. SCAM/L 2E, hf/V/FY Rf-IESSAEA,

Filed Dec. 16, 1948 Guava- Aug. 5, 1952 R. B. scHuLzE ET AL APPARATUS FOR FORMING SHEET MATERIAL UNDER CONTROLLED PRESSURE Filed Dec. 16. 1948 2 SHEETS-SHEET 2 W W w/W M X L k 32? 561 1 2& m Ra my 15 n 5;

. 1 v, E E .w

w/ J m w m IIWWWW N n p 4, A & y .Ffli N N....W\ 7 mm "H .l I 1 a I b M y? E g g nu E wg Patented Aug. 5, 1952 APPARATUS FOR FORMING SHEET MATE- RIAL UN DERCONTROLLED PRESSURE" Richard-B. Sichulze, Henry P. Hessler, Clarence- M. Davison, and Mahlon A. Winter, Baltimore, Md., assignors to The Glenn L..Martin Com-. pany, Middle River, Md a corporation. of.

Maryland Application December 16, 1948, .SerialNoeGSjSZ 4 Claims.

This application is acontinuation-in-part of our co-pending application S. N. 30,766,.filed June,3, 1948, and entitled Method and Apparatus for Controlled Pressure Forming of Sheet Material.

This invention relates to an apparatus to be used in conjunction with a conventional hydraulic press for the purpose of shaping parts of sheetmetaLor similar material, over a .form block or die. The invention relates to improved structure and techniques involving the rubber forming process for metal which has been previously used with some success in limited applications. The inherent disadvantage of known rubber pressure pad forming operations is that the parts formed, are limited tolarge radius curvatures and shallow depths ofform. It is possible by known apparatus ,to form reinforcing ribs and beads, and punch out lightening holes from plane.area, but where it is required to make a deep flange or draw, the sheet metal wrinkles so badly that hand operations are usually required if the part is to be used at all. I

It is" an object of this invention to provide apparatus for forming sheet metal to compound curvatures andwith deep drawnflanges by the use of a rubber pressure pad'and a form block, and wherein means is provided for maintaining the. pressure pad under predetermined back pressure throughout the forming operationto preclude wrinkling or tearing of .the metal being formed.v

A further object of this invention is to provide, in-apparatus of the above-mentioned type, means for automatically, variably controlling the back pressure in a predetermined manner in accordance with'the progress of the forming operation.

Another object is to provide in such forming apparatus means for producing a back pressure against'said rubber, pressure pad'by fluid pressure derived from the downward movement of the forming head. the pressure being automati cally regulated bya single cam-controlled, variable pressure-relief valve in accordance withthe progress of the forming operation.

Another object of this invention is to provide in a forming machine of the above mentioned type, a pressure control"cammounted to move in accordance with the progress of the forming operation and comprising a plurality of individually'adjustable cam elements which together form the effective contour of said cam, whereby the cam shape, and henceithe'back-pressures controlled thereby, can be readily varied, to facilitate setting up; the machine for any-particular. forming operation.

A still further object isto'provide a cam-controlled, variable pres-sure-relief valve wherein a relatively. light camstructure can be employed to positively control highpressures overa relatively wide range. a

Another object is to provide hydraulically actuated'means for stripping the formed article fromthe die, the stripping means.being controlled by the. position of the forming head so as to delay the stripping'action until after the rubber pad in the-head hasbeen raised outof contact with the-formed article.

A still further object is to providea templet surrounding; the die block and depressable against the-action of fluid pressure means in the base for-applying back-pressure to the rubber padin thehead during the forming operation, and means-for supplying fluid to said fluid pressure means after said forming operation is completed to again raise said templet,- whereby said templet also serves to strip the formed article from the die block.

Further and other objects of this invention will become apparent from the description of the accompanying drawings which form a part of this disclosure and wherein like numerals refer-to like parts.

I In the drawings:

Figure-lis a somewhat diagrammatic view of the forming machine together with its associated pressure. regulating equipment.

Figure 2 is a sectional view of a stripper control valve used therewith.

Figure 3' isian end view of the machine with certain parts... omitted, showing the manner in which thecontrol cam is mounted thereon.

Figure ,4 is. a sectional view of the cam-actuated backepressure control-valve unit used with the machine.

In Figures 1" to 4 is shown a forming machine using a single, cam-controlled, back-pressure *valve to vary the'forming pressure as desired and incorporating ,means for-automatically stripping the-fi'nished work from the die block.

Referringhrst to Figure 1, which is a diagrammatic showing of the device,.there is shown the head 1 with its rubber pad 2. Base assembly 4 includes the cylinders ll with mating pistons l4 supporting on their'upper ends movable platform 19. Platform l9 carries a templet 26 by means of posts 25 slidable through suitable openings in the upper portion of base A. Templet 26'- closely surrounds die block 21, rigidly supportedby. the base, the upper surfaces of the die block and of the templet normally lying in substantially the same plane. Filler block 29,

. conduit 60 leading to the cylinders ll.

described elements, the corresponding parts therein having similar reference numerals to those in the instant application.

A conduit 60 carries hydraulic fluid to or from the cylinders II as controlled by the cam-controlled, back-pressure valve unit 30l and the stripper control valve 366. Conduit 60 is connected to back-pressure valve 39! by conduit 306. An exhaust line 392 runs from the valve unit 30l to a, reservoir 393. A pump 394 is adapted to draw fluid from this reservoir and discharge it at relatively low pressure into low pressure line 305 leading to the stripper control valve 396. A manually operable shut-off valve 365' is provided in line 305 to cut out the automatic stripping operation when desired. A pressure relief valve 301 in by-pass line 398 limits the pressure that can obtain in line 305. Stripper control valve 396 communicates directly with A suitable pressure gage 6! is provided on conduit 69.

Also, as in the earlier device, a pointer 44, pivoted at 43 to the base 4, is provided to indicate the extent of movement of templet 26 relative to the die block. The pointer is actuated by a stud 41 carried by platform I9 and extending outwardly through a slot 49 in the front side of the base 4 and into engagement with the offset bifurcated end of pointer 44.

The stripper control valve (see Figures 1 and 2) consists of a body 399 suitably rigidly supported from the base 4 and having a vertical bore 3m extending therethrough and communicating at its lower end with low pressure line 305. Conduit 60 terminates in a port 316 opening into the side of the bore 3I9. A plunger 3 slidable in bore 310, is connected by links 3l2 to a lever 3l3 pivotally supported as at 3M from the base 4. Lever 3l3 carries a roller 314' adapted to be engaged by an actuator 3l5 rigidly carried by the head I. The actuator is so adjusted relative to the head and the roller 3l4' as to move plunger 3 downwardly to close off port 3l6 just before the head engages the piece to be formed, and to maintain this' position of the plunger until the head moves away from the die-block after the forming operation has been completed. Thus during the forming operation, the flow of fluid from the cylinders H is under the sole control of the cam-controlled, back-pressure Valve unit 30!. The cam-controlled, back-pressure valve unit 3! consists essentially of a cam-controlled, follow-up type of air booster for applyin variable loading to the compression spring of a ball-type pressure relief valve. This valve unit 39! is controlled by a'roller 325'riding on a cam 3|! carried in a slotted holder 3I8. The cam and its holder are mounted for movement proportional to the downward movement of the templet 26 relative to the die block, bythe means shown in Figure 3.

A lever arm 3|9, rigidly carrying the cam holder 3l8 at its outer end, is pivotally mounted as at 320 on the left hand side of the base 4. The inner end of this lever is bifurcated and engages the outer end of a stud 32l mounted in movable platform I9 and extending outwardly through a slot 322 in the side of base member 4. Thus, as the platform and templet move downwardly during the forming operation, the cam will move upwardly, its profile determining the position of the roller 325 at any particular time.

The cam itself is made up of a plurality of relatively thin, slotted plates 323 stacked within the slot 318' of holder 318 and clamped therein by wing bolt 324 which extends through the slots 323' in the plates 323 and into threaded engagement with clamping block 324. Plates 323 have their end edges in position to engage the valve actuating roller 325. By loosening Wing bolt 324 and sliding the individual plates 325 toward or away from the roller, the shape of the cam can be readily varied to control the back pressure in the manner desired for any particular formin operation.

The back-pressure control valve itself comprises a valve housing 325 threaded into the end of booster cylinder 326, both being rigidly carried by a bracket 32! bolted to the front face of base 4 by bolts 328 passing through the bracket and suitable spacer sleeves (not shown). Housing 325' is closed at the end opposite cylinder 326 by a cap 329 having a longitudinally extending bore 330 therethrough to which conduit 399 is connected. The inner end of bore 339 is adapted to be closed by a ball valve 33| urged thereagainst by compression spring 332 acting between plugs 333 and 334 slidable within housing 325'. An opening 33! through the lower wall of the housing and the bracket 321 connects the space between plug 333 and cap 329 to the exhaust line 392.

Booster cylinder 326 carries therein a piston 335 having a hollow piston rod 335' extending oppositely from the valve housing, out through a suitable seal in cap 336. The piston 335 also threadedly carries a stud 33! extending into engagement with plug 334. A nut 338 serves to lock the stud in the desired position of extension from the piston 335.

The hollow interior 340 of the piston rod 335 communicates with the interior of the cylinder 326 by means of ports 340 adjacent the piston.

Slidable within the outer enlarged portion 356 of the piston rod is a valve stem 339 having a longitudinally extending passageway 34l communicating with the interior 349 of the piston rod and connected by suitable cross ports to a circumferential groove or necked portion 343 in the outer periphery of the stern. Exhaust port 345 and inlet port 35!, in opposite walls of the piston rod, are arranged so that the spacing therebetween longitudinally of the stem is just greater than the width of the groove 343. The side of the stem facing the inlet port 35| has a flat 344 formed therein to effectively increase the width of the groove 343 on that side. Flexible air line 352 supplied compressed air to inlet port 35L The outer end 346 of the valve stem threadedly carried a bifurcated roller bracket 34! carrying the roller 325 onv pin 348 in position .to ride on the ends of the cam plates 323. Bracket 34! is locked in desired position on the stem by lock nut 349.

With this construction, it can be seen that as cam 3" moves roller 325 and valve stem 339 to the right, annular groove 343 will be moved opposlte inlet port 351 with theresult that air wm be. forced into cylinder 326throughpassages 3M 343.; and 340.. This will cause piston 335 to similarly move. to the right to increase the compression of, spring 332. also act against the inner end of the stem to maintain the roller in constant'engagement with the. cam. As the piston moves to the right, it, of course, moves the piston rod also to the right until.ports..35.l and 345. are again both closed as the-rodreaches anew position, spaced'to the right from the Figure 4 position an amount equal to the initial movement of stem 346. and roller 325., The compression of the spring will have, therefore, been increased by an amount proportional tow the original. movement ofthe'cam roller.

If, on the other hand,,the cam shape at a particularplaceis. such asto tend tomove awayfrom the, roller, thestem will be forced. to follow the cam by the air under pressure in the 1 cylinder, thus causing groove 343. to move opposits the exhaust port 3 55. Air will thenbe exhausted from within the cylinder andthe piston will .move to the left under the action of It can thus be seen thatthe spring tension against ball valve 33! will be automatically varied in direct relation to. the shape of the cam and that, since the valve port 330 isin direct communication with the fluid in the base cylinders .H, the back pressure of the fluid resisting downward movement of the templet can be positively and continuously controlled to follow any desiredpressure' curve as the forming proceeds.

The fluid, after passing through the back-pressure valve, is conducted throughpassage 33! and exhaust line 302 to the reservoir.

Operation Figure 1 shows the-parts ofthe machine in position to start a forming-operation; Valves 395 and 336 are open at this time and cylinders Hare filled with low pressure fluid thus supporting pistons [4, platform l9, posts and templet 26 in their uppermost positions, with the upper surface of templet 26 substantially flush withthe top of die block 27. Ball valve 33I is held against its seat at the inner end of passage 33!] by a spring force proportional to the position of the cam roller, 325 as determined by the upper portion of the cam 3 I I. A blank to be formed is placed in proper position-on the die clock and templet and the press is actuated to lower the head. Justbefore the head engages the blank, actuator 3l5 engages roller 3 Hi to rock lever3l3 so as to force plunger 3 H downwardlyagainst the low pressure fluid to a position cutting 01f port 3H5 as indicated by dotted lines in Figure 2. Thus the only path of escape for the fluid in cylinders H is through conduits 60 and d and past the spring loaded back-pressure control valve 30 I As the rubber block 2 inthe head engages the blank and templet, the pressure of the trapped fluid incylinders I I will build up to a' valve proportional to the loading of the valve spring 332- which in. turn is determined by the portion of. the .cam 3|! then engaging theroller 325. This backpressure results in placing-;theyrubberpad The air pressure will undera: corresponding pressure before any-actual,

formingof theblank begins. When this initial desired, pressure is reached, the back pressure valve will open to let fluid flow'from cylinders II to the reservoir by way of conduits 60, 303, 332 33! and 302. The templet together with platform 19, pistons l4 and posts 25, will then gradually be depressed as the form temand the pointer 44 will show the distancethat the templet has been depressed.

Thus throughout the forming operation the blankbeing formed ,will be subject to a predeterm-inedpressure applied between the rubber block and the, templet or the die blockas the case may be, causing; the metal to flow smoothly, without,

wrinkling or cracking as it assumes the desired shape;

When-the reached, the head is startedp-upwardlyin the 1 usual fashion to prepare for another cycle.

Meanwhile, the pistons, l4; together with platform l9 and templet 26, will remain in lowered position since stripper valve 306 will still beheld closed by the actuator3l5 and no pressure fluid can enter the cylinders. However, just after the head clears the top of the die block, actuator 3l5 will move away from the roller 3W on lever 313, permitting the plunger 3 to return to its upper position shown in Figures 1 and 2 and to open port 318 to the low pressure line 385. Fluid will,

therefore, flow into the cylinders, moving the templet upwardly tostrip the formed piece from the die and to prepare for another cycle of operation. a

The use of the .air booster cylinder to control the spring pressure on the ball valve makes it possible to automaticallycontrol the extremely high back-pressure, essential for satisfactory forming, by a relatively simple and light-weight camexerting but a relativel light pressure against its roller follower. Yet, extreme smoothness of control over a rather wide range of pressures is readily obtainable. 7

Moreover, with this arrangement the problem ofsetting up the machine for any particular job is materially simplified. In setting up the machine fo r anew job, shut-off valve 305 is manuandeven when the cycle is stopped and again started, the pressure at a particular point in the cyclewill always be substantially the same. If cracks or wrinkles are found to be starting at any point in the operation, the cam plate or plates 323, corresponding to that point in the.

end'of the forming stroke has been 7 checking the article being formed and making any indicated correction in the cam shape at the end of each step, the proper cam shape for any particular job can be quickly determined. Once determined for a particular job, the cam shape can be recorded or a templet made to facilitate setting up the same or similar jobs in the future. However, even without such a templet, an operator soon learns, from having previously observed the eifect of changes in backpressure on the forming of particular sizes and shapes of articles, to initially set the cam plates for any particular job so that no further adjustment of the cam, or, at the most, but relatively slight adjustment thereof will be necessary to produce formed articles completely free of cracks, wrinkles, or other flaws. Once the cam is properly adjusted for a particular job, valve 305 is of course again opened to restore the automatic stripping action and the machine is ready for use.

While but a single embodiment is specifically shown and described in this specification, it is believed obvious that many changes may be made in the arrangement of parts without departing from the principle and spirit of this invention as set forth in the appended claims and the claims are not therefore to be unnecessarily restricted in scope.

We claim as our invention:

1. In an apparatus for forming a metal blank, and including a base member, a die block adapted to be supported from said base member, and a power actuated head member movable toward said base member throughout the forming operation for forming said blank over said die block, said head member comprising a rigid box-like housing of constant predetermined volume, the side thereof facing said base being open, and a pad of rubber-like, resilient material substantially filling said housing, and means carried by said base and adapted to mate with and form a movable wall for the open side of said housing to completely confine said resilient material throughout the forming operation and including said die block and a templet closely surrounding said die block and adapted to support a blank to be formed over said die block and mounted for movement relative to said die block in accordance with the progress of the forming, said resilient pad beingcoextensive with said die block and said templet and constituting the sole medium for forming said blank over and around said die block, fluid pressure means for opposing movement of said templet as said head moves toward said base during the forming operation whereby to produce corresponding forming pressure throughout said pad, a variable pressure relief valve for regulating the fluid pressure within said pressure means, said valve being selectively operable to either increase or decrease the pressure to any predetermined value at any stage of the forming operation and control means including an element movable with the templet for continuously controlling the pressure setting of said valve in a predetermined manner throughout the forming operation, whereby the forming pressure of said pad against said blank may be accordingly controlled, said movable element comprising a cam, and said variable pressure-control valve including a housing having a pressure port connected to the fluid pressure means and an exhaust port, means resiliently opposing the flow of fluid from said pressure port to said exhaust port and including a loading spring means within said housing, a booster cylinder rigid with said housing having a piston axially movable therein and engaging said spring means for controlling the loading thereof, a piston rod for said piston having a hollow interior communicating with the inside of said booster cylinder and having axially spaced inlet and exhaust ports in the outer portions thereof, means for connecting said inlet port to a source of pressure fluid, a valve stem axially slidable in the hollow interior of said piston rod and having portions adapted to block off communication between both of said ports and said hollow interior or selectively to block either port while providing communication between the other port and the hollow interior, and means on said valve stem for engaging said cam means whereby the position of said piston and the loading of said spring will vary in accordance with the contour of said cam to correspondingly vary the pressure of said pad against said blank.

2. In an apparatus for forming a metal blank, and including a base member, a die block adapted to be supported from said base member, and a power actuated head member movable toward said base member throughout the forming operation for forming said blankover said die block, said head member comprising a rigid box-like housing of constant predetermined volume, the side thereof facing said base being open, and a pad of rubber-like, resilient material substantially filling said housing, and means carried by said base and adapted to mate with and form a movable Wall for the open side of said housing to completely confine said resilient material throughout the forming operation and including said die block and a templet surrounding said die block and adapted to support a blank to be formed over said die block and mounted for movement relative to said die block in accordance with the progress of the forming, said resilient pad being co-extensive with said die block and said templet and constituting the sole medium for forming said blank over and around said die block, fluid pressure means for resisting movement of said templet as said head moves toward said base during the forming operation whereby to produce corresponding forming pressure throughout said pad, a variable pressure relief valve for regulating the fluid pressure within said pressure means, said valve being selectively operable to either increase or decrease the pressure to any predetermined value at any stage of the forming operation and including a seat, and a valve member adapted to coact with said seat to resist the flow of fluid from said pressure means, and a fluid pressure booster chamber having a movable wall thereof acting against said valve member and urging it toward said seat in accordance with the pressure in said chamber, and control means for continuously controlling the pressure setting of said valve in a predetermined manner throughout the forming operation, whereby the forming pressure of said pad against said blank may be accordingly controlled and comprising a manually adjustable, variable contour cam movable with said templet, a booster pressure control valve in fluid communication with said booster chamber and with a source of fluid pressure and including a movable control member for regulating the flow of pressure fluid to and from said chamber in accordance with the position of said control member and the pressure in said chamber whereby to cause the pressure in said-chamber to correspond to the position of said control member, and a cam follower contacting said cam and operatively connected to said'control member for controlling the position of said control member in accordance with the contour of said cam throughout the forming operation.

- 3. In an apparatus for forming a metal blank, and including a base member, a die block adapted to be supported from said base member, and a power actuated head member movable toward said base member throughout the forming operation for forming said blank over said die block, said head member comprising a rigid box-like housing of constant predeterminedvolume, the side thereof facing said base being open, and a pad of rubber-like, resilient material substantially filling said housing, and means carried by said base and adapted to mate with and form a movable wall for the open side of said housing to completely confine said resilient material throughout the forming operation and including said die block and a templet surrounding said die block and adapted to support a blank to be formed over said die block and mounted for movement relative to said die block in accordance with the progress of the forming, said'resilient pad being co-extensive with said die block and said templet and constituting the sole medium for forming said blank over and around said die block, fluid pressure means for resisting movement of said templet as said head moves toward said base during the forming operation whereby to produce corresponding forming pressure throughout said pad, a variable pressure relief valve for regulating the fluid pressure within said pressure means, said valve being selectively operable to either increase or decrease the pressure to any predetermined value at any stage of the forming operation and including a seat, and a valve member adapted to coact with said seat to resist the flow of fluid from said pressure means, and a fluid pressure booster chamber having a movable wall thereof acting against said valve member and urging it toward said seat in accordance with the pressure in said chamber, and control means for continuously controlling the pressure setting of said valve in a predetermined manner throughout the forming operation, whereby the forming pressure of said pad against said blank may be accordingly controlled and comprising a manually adjustable, variable contour cam movable with said templet, a booster pressure control valve in fluid communication with such booster chamber and with a source of fluid pressure and including a movable control member for regulating the flow of pressure fluid to and from said chamber in accordance with the position of said control member and the pressure in said chamber whereby to cause the pressure in said chamber to correspond to the position of said control member, and a cam follower contacting said cam and operatively connected to said control member for controlling the position of said control member in accordance with the contour of said cam throughout the forming operation, the fluid communication between said chamber and said booster control valve being so arranged that the chamber pressure reacts against said control member so as to urge said follower against said cam.

4. In an apparatus for forming a metal blank, and including a base member, a die block adapted to be supported from said base member, and a power actuated head member movable toward said base member throughout the forming operation for forming said blank over said die block, said head member comprising a rigid box-like housing of constant predetermined volume, the side thereof facing said base being open, and a pad of rubber-like, resilient material substantially 10 filling said housing, and means carried by said base and adapted to mate with and form a movable wall for the open side of said housing to completely confine said resilient material throughout the forming operation and including said die block and a templet surrounding said die block and adapted to support a blank to be formed over said die block and mounted for movement relative to said die block in accordance with the progress of the forming, said resilient pad being co-extensive with said die block and said templet and constituting the sole medium for forming said blank over and around said die block, fluid pressure means for resisting movement of said templet as said head moves toward said base during the forming operation whereby to produce corresponding forming pressure throughout said pad, a variable pressure relief valve for regulating the fluid pressure within said pressure means, said valve being selectively operable to either increase or decrease the pressure to any predetermined value at any stage of the forming operation and including a seat, and a valve member adapted to coact with said seat to resist the flow of fluid from said pressure means, and a fluid pressure booster chamber having a movable wall thereof acting against said valve member and urging it toward said seat in accordance with the pressure in said chamber, and control means for continuously controlling the pressure setting of said valve in a predetermined manner throughout the forming operation, whereby the forming pressure of said pad against said blank may be accordingly, controlled and comprising a cam movable with said templet, and means for controlling the pressure in said chamber in accordance with the contour of said cam and including a cam follower engaging said cam and a booster control valve connected to said chamber and to a source of fluid pressure, said booster control valve having a stem member operatively connected to said follower for movement therewith and a valve member coacting with said stem member to control the flow of pressure fluid to and from said chamber, said last mentioned valve member being movable relative to said stem member in response to the pressure in said chamber whereby to maintain said pressure at a value corresponding to the position of said stem.

RICHARD B. SCI-IULZE. HENRY P. HESSLER. CLARENCE M. DAVISON. MAHLON A. WINTER.

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

UNITED STATES PATENTS Number Name Date 633,187 Smith July 3, 1900 1,131,953 Pilkington Mar. 16, 1915 1,745,549 Marghitan Feb. 4, 1930 1,757,738 Rode May 6, 1930 1,777,130 Rode Sept. 30, 1930 1,968,701 Miner July 31, 1934 1,976,820 Wettstein Oct. 16, 1934 2,172,853 Rode Sept. 12, 1939 2,317,745 Duckstein Apr. 27, 1943 2,333,529 Ernst Nov. 2, 1943 2,342,858 Hansen Feb. 29, 1944 2,375,599 Walton May 8, 1945 2,400,004 Jager May 7, 1946 2,434,538 Baston Jan. 13, 1948 2,507,194 Chyba May 9, 1950

Images