US2437092A - Metal-stretching press - Google Patents

Description

March 2, 1948. P A. M. GREENE, JR, Er AL 2,

METAL STRETCHING PRESS Filed Sept. "22, 1944 3 Sheets-Sheet I CIZIZZ' I INVENTORS ARTHUR H. GREENE- JR. WALTER ER NST ATTORNEYS March 2, 1.948- A. M. GREENE, JR, ET AL ,4

- mam. s'rjnmcame mass 7 Filed Sept. 22, 1944 s Sheets-Sheet? ll INVENTORS- ARTHUR M. GREENE JR.

WALTER ERNST BY ATTORN EYS March 2, 1948.

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A. M. GREENE, JR, ET AL METAL STRETCHING PRESS Filed Sept. 22,- 1944 a Sheets-Sheet 3 INVENTORS ARTHUR M. GREENE JR. WA LTER ERNST ATTORNEYS Patented Mar. 2, 1948 UNITED'STATES PATENT OFFICE BIETAL-STRETCHING PRESS Arthur M. Greene, Jr., Princeton, N. J., and Walter Ernst, Mount Gilead, Ohio, assignors to H-P-M Development Corporation, Wilmington, Del., a corporation of Delaware Application September 22, 1944, Serial No. 555,238

11 Claims. 1

This invention relates to method and apparatus for stretching sheets of material into predetermined configurations.

In the art of metal stretching it is customary to grip a sheet of metal along the edge thereof and to advance a single die or forming member into the said sheet so as to stretch the material into the desired configuration. Ordinarily, the gripping jaws are manually manipulated to be moved closer to the stretching member as the operation progresses so that the sheet does not rupture or so that the sheet may be more completely formed around the punch or die member.

It will be apparent that the manual manipulation of the gripping members requires a highly skilled operator and, at best, can only approach the most desirable conditions for a stretching operation.

It is a primary object of the present invention to provide a stretching press which will produce superior workpieces.

It is another object to provide a stretching press in which the tension in the sheet being stretched is automatically controlled.

It i another object of the present invention to provide automatic means for moving the gripping members during the stretching operation,

It is another object to provide a stretching press in which any predetermined tension may be maintained on the sheet, or in any portion thereof during the stretching operation.

It is another object to provide a method and apparatus for stretching sheets into more or less complex configurations. I

These and other objects and advantages will become more apparent upon reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic view of a metal stretching press constructed according to this invention;

Figure 2 is an enlargement of a portion of Figure 1 showing in greater detail the swivelled laws and the valve arrangementassociated with the jaw reciprocating motor;

Figures 3, 4 and 5 are diagrammatic views showing diiferent stages of a stretching cycle;

Figure 6 is a modification showing a plurality of gripping members attached to a crosshead and a single jaw reciprocating motor;

Figure 7 is a view showing a plurality of jaws and jaw reciprocating motors in association with a pressing member of irregular shape; and

Figure 8 is a View of a modified arrangement for the jaw and slide reciprocating motor showpower means for moving thesame; v

2 General arrangement In general, a stretching press constructed according to this invention comprises a frame having suitably mounted therein, in any desirable manner, a die carrying reciprocable platen. Motor means, preferably fluid operable, are provided for reciprocating the platen thereby to advance the die or punch into the work. The workpiece is adapted to be gripped by a pair of g ipp members mounted on the press frame on either side of the said platen. According to this invention, the jaws are swivelled to crossheads which latter are automatically reciprocated during the stretching operation. The movement of the crossheads or jaw carrying slides is automatically controlled so that a predetermined and substantially constant tension is maintained in the sheet throughout the stretching operation. The jaws and slides to which they are attached are preferably reciprocated by a fluid motor which has associated therewith suitabl valving means for initially positioning the said jaws and for thereafter eiiecting the aforementioned automatic control.

The valve which automatically controls the motor connected with the slide comprises a pilot operated valve which is hydraulically connected with a plunger associated with the gripping jaws, In response to a predetermined tension on the sheet, a predetermined pressure is developed by the said plunger and i transmitted to the pilot operated valve. The pilot operated valve is adapted to respond to a predetermined pressure to permit the exhaust of fluid from one side of the slide motor thereby permitting the latter to move. I

According to one modification the pilot operated valve is-connected with a source of fluid pressure so that the slide is positively moved by fluid pressure rather than by the tension in the sheet.

According to another modification a plurality of gripping means are provided on either side of the platen and the tension in the sheet may be varied from place to place as required by the shape of the pressing member.

According to still another modification a plurality of jaws is provided on either side of the the other.

Detailed description Referring to Figure 1, the press according to this invention comprises a frame I!) having mounted therein, or integral therewith, a main cylinder H within which is reciprocable the ram l2 which carries a platen 13. A die or punch IA is attached to the platen l3 in any suitable manner.

Arranged on either side of the platen I3 are the gripping or jaw structures [5 and I6. Each of the jaw structures comprises a slide or cross-- head ll which is slidably mounted on the press piston-cylinder-arrangement at 20 so that movement to the left by the jaw I9 is effective to create a pressure which, when conducted to the cylinder 42, actuates the plunger 4| and the valve member 38.

Connected with the discharge side of the pump 29 by means of the conduit 45 is a distributing valve 46 which also has connected therewith the exhaust conduit 41, the conduit 48 which leads to the upper end of the cylinder l l and, the con- I duit 49 which leads to the lower end of the cylinframe 10 such as by the way and gib arrange-e ment indicated at I3. Swivelly attached .tothe slide member ll are jaw units comprising a gripping member l3 and a, piston and cylinder arrangement it. The piston-cylinder arrangement. 1

is connected by the trunnion 2| to the slide mem.- ber ll. Since the jaw structures at each side of the platen are identical, a description of the one at the right of the platen, as seen in Figure 1, will sufiice for both.

Affixed to the side of the slide member I"! opposite the platen I5 is a plunger 22 which extends into a cylinder 23 mounted on the bed ill. The plunger 22 extends completely through the said cylinder and has a piston 24 thereon within the cylinder so as to form a fluid operable motor having advancing and retracting areas which are equal.

Connected with the right end of the cylinder 23 is a conduit 25 which leads to a four-way valve 26. Connected to the left end of the cylinder 23 is a conduit 2i also leading to the valve 26. The valve 26 is supplied with pressure fluid by a conduit 23 from the pump 29 which is connected by a conduit 36 with a reservoir 3|. The valve 2% also has connected thereto an exhaust conduit 32 which leads directly to the reservoir 3 I. The

valve 26 is movable into a first end position tointerconnect the conduits 28 and 35 while simultaneously connecting the conduits 21 and 32 and, into a second end position to interconnect the conduits 2'? and 23 and the conduits 25 and 32.

The valve 26 is also movable into an intermediate position wherein the fluid communication between the said conduits in interrupted.

Also connected with the left end of the cylinder 23 is a conduit 33 which leads to a valve. 34, the valve also being connected by the conduit 35 with the right end of the cylinder 23. The conduit 35 comprises the check valve 36 which permits the fluid flow from the valve to the cylinder but not vice-versa.

The valve 34, more clearly shown in Figure Z, comprises a valve casing 31 within which is reciprocable a valve member 33. The valve member 36 is urged into its right hand end position by a spring 3.9, the thrust of which may be varied by adjusting the hand wheel and screw arrangement at it. In its right hand position, the valve member 38 interrupts fluid communication between the conduits 33 and 35. Opposite the spring 39 is a plunger M which is reciprocable in the cylinder Q2. The plunger 4! is operable, when pressure fluid is supplied to the cylinder 42 from the conduit 43, to move the valve member 38 leitwardly so as to interconnect the conduits 33 and 35.

The conduit 63 is connected with the pistoncylinder arrangement at 29 associated with the jaw I3. Preferably the conduit 43 comprises a flexible portion M which permits the free movement of the slide ll relative to-the valve am The conduit 43 is connected into the left end of the der H. The valve it is movable into position to interconnect the conduits 48 and 5 and the conduits 49 and t! or into position to connect the conduits 48 and 4'! and the conduits l9 and 45.

Referring nowto Figure 6, a modification is shown wherein the pressing member 50 is of an irregular shape; being larger at the one end than at the other. The press shown in Figure 6 comprises a plurality of jaw members 5| which are connected with a plurality of piston-cylinder arrangements at 52 the latter being universally connected with a crosshead or slide 53 by the pivotal connections 52a and 52b. ihe slide 53 is pivoted as at 54 to a plunger 55 of the motor 55. As in the case of the motor 23, the motor 55 has equal advancing and retracting areas.

A valve 5'! similar to the valve 34 is connected with the opposite ends of the motor 58 and is piloted by fluid conducted thereto to the conduit 58. The conduit 58- is connected with the several piston-cylinders 52 so that the average pressure in the said piston-cylinderarrangement is conducted to the valve 57. It will be apparent that the arrangement in Figure 6 is such that a predetermined tension may be maintained across a sheet which is being drawn by an irregularly shaped pressing member.

Referring to Figure '7, there is shown a modified arrangement of this invention wherein the pressing member til is of relatively complexvconfiguration. A plurality'of jaws 6i grip the workpiece along the margin thereof, each of the jaws ill having associated therewith a piston-cylinder arrangement $2M Each of the piston-cylinder arrangements 62'isipivotallyconnectedwith an individual'slide '63 at 63c, and each of the latter has associated therewith the motor 6 3.

Eachof the motors 64xhas connected thereto a valvetfi similar .to the valves 3t and 51 and each valve' is actuated by fluid 'pressure conducted thereto from the associated piston-cylinder 62 by a conduit 66;.

It will be apparentthat'any desired tension may .be'maintained inany portionofthe sheet merely by adjusting the individual valves 65. Accordingly, it is possible to form a workpiece of relatively complex configuration without overstressingorrupturing or underforming any of the various portions thereof. It will be noted that the jaws at are pivoted attwo points so that they may:follow the outline of the work-piece as it is being formed.

Referring now toFigure 8, there is shown a modified arrangement wherein the jaw and slide reciprocating motor is positively moved during the stretching operation. In this figure the jaw and slide reciprocating motor it. has therein the double acting piston H to which is attached the plunger .12 which is, in turn, connected with the slidemember of the jaw structure.

Connected with the right end of the cylinder lii is'a conduit 73 which connects with the valve l4 arid,- connectedwiththe left end of the cylinder it is a conduit lfial's'o leadingtothe valve i l.

The valve 14 is supplied with pressure fluid by a conduit 16 which connects with the discharge side of the pump 11. The pump 1! and the valve 14 are also connected with a reservoir 18 by the conduits l9 and 80, respectively.

p The valve 14 is movable into position to directpressure fluid either to the right or to the left end of the cylinder in while simultaneously exhausting the other end or, into an intermediate position for interrupting said fluid connections.

Connected with the conduits 13 and 75 are a pair'of conduits 8| and 82 which lead to a valve 83. The valve 83 also has connected therewith the conduit 84 which is connected with the discharge side of the pump 1'! and a conduit 85 which is connected with the reservoir I8. The

valve 83 comprises a valve member 86 which is normally positioned to interrupt fluid communication between the various valve conduits. An adjustable spring 81 at the right endof the valve urges the valve member 86 leftwardly until the collar 88 engages the end of the valve casing.

A spring 89 at the left end of the valve urges the valve member 86 rightwardly until the collar 90 engages the end of the valve casing. A conduit 9| is connected into the spring casing 92 and is also connected with the piston-cylinder arrangement associated with the jaw and slide structure attached to the plunger 12.

Itwill be apparent that a predetermined pressure within the spring chamber 92 conducted thereto by the conduit 9| is effective to move the valve member 86 rightwardly thus establishing fluid communication between the pump 11 and the right end of the cylinder while simultaneously connecting the left end of the cylinder 10 with exhaust. The plunger 12 is thus positively moved toward the platen of the press.

Operation position so that the fluid in the opposite ends of the motors 23 is trapped.

The operator then shifts the valve 46 to move the plunger I 2 and the punch or die member [4 upwardly. The condition prior to the stretching operation is shown in Figures 1 and 3.

After the die has moved upwardly a short distance, the conditions existing are illustrated in Figure 4. In this figure .the movement of the die member has created a predetermined tension in the portion of the sheet between the die and the jaw members on either side thereof. The tension in the sheet creates apredeterm-inedprese sure in the piston-cylinder arrangement which, when conducted through the conduit 43 to the cylinder 42 actuates the plunger 4| to move the valve member 38 leftwardly against the thrust of the spring 39 thus interconnecting the conduits. 33 and 35. After the valve member 38 has been shifted to interconnect the opposite ends of the ,motor 23, the tension on the sheet is efiective to move the slide l1 and plunger 22 leftwardly until the valve 34 again closes.

In this manner the piston-cylinder arrangement 20 acts as a signal cylinder for the main arrangement 20 which moves in response to the tension created in the work piece, but it is the signal cylinder 20 carried by it, which moves in response to said tension. It is to be further noted that the pivot points of the pivotal connections at 2| of the gripping arrangements 20 are moved automatically in response to a. predetermined tension in the sheet in a direction at right angles to the upward movement of the pressing member,

As the stretching cycle continues the parts move from their Figure 4 position into the position indicated in Figure 5 where the workpiece is substantially completed. It will be apparent that throughout the stretching operation a substantially constant and predetermined tension has been maintained in the portions of the sheet between the pressing and the edges thereof which are gripped by the jaws.

It should be noted that as the work piece is formed, as shown in Figures 3, 4, and 5, the gripped edges of the sheet material have moved towards the forming member substantially at right angles to it, subject only to a slight angular deflection caused by the tilting of the member 28 about the pivot 2|. Thus, said gripped edges are automatically paid out towards said forming member in a substantially right angular relation to it, said paying out of said edges being in response to a predetermined tension in said sheet material.

Should it be desired to move the jaws even closer to the platen than their Figure 5 position, the operator may shift the valves 26 while permitting the die M to continue its advancing movement.

The operation of the embodiment shown in Figure 6 is similar to the operation of the embodiment of Figure 1 except that the slide 53 is free to assume an angular position relative to the press frame thus permitting a workpiece to be stretched which is substantially wider at one end than the other. It will be apparent that the modification of Figure 6 also provides for a substantially constant and predetermined tension to be maintained in the sheet at all times.

The modification illustrated in Figure 7 operates in a manner substantially identical with the modification of Figure 1 except that each gripping member or jaw is separately moved so that a workpiece of complex configuration may be formed. It will be noted that the pressure which 'is maintained on the portion of the sheet associated with each jaw is individually adjustable so that one portion of the sheet may be stretched a great deal more than another portion without in any way detracting from the quality of the finished workpiece.

The modification shown in Figure 8 provides power means for moving the jaws and thereby eliminates the possibility that the inward movement of the jaws may be halted before the forming operation is completed. In fact, with the arrangement shown in Figure 8, the margins of the workpiece may be formed even beyond the limits of the die member thus providing means for eliminating spring-back should it be desired parallel side portions thereon.

It will be apparent that various modifications may be made in the structure of this invention without in any way departing from the spirit thereof. For example, the motors 23 could be contained within the bed 20 if so desired thereby rangement. Also, the jaws l9 could be replaced It will be obvious that the piston-cylinder-arrangements at 20 provide means for directly measuring the tension in: the .sheet .-l;llflthusinsuring that the valve 35 311111 be actuated at-the proper time. V'Also, it will be obvious-that;the valve 34 will, in most instances, operate to throttle the flow of fluid from the left end -of- -the motor 23 rather than intermittently exhaustingthe same.

It i will also be apparent, upon reference to Figures 6 and 7,- that tlie worksheets-could' be slit between-the jaw membersin order to; facilisired.

It will be understood; thatwe desire-topomprehendwithin our inventionsuch modifications as may come withinthe scope ofthe invention and the claims.

Having thus fully described our invention,what we claim as new and desireto secure by Letters Patent, is: l

1. A method of forming workpieces from ductile sheet material with a single forming member "which comprises, rigidly gripping the said sheet at, a plurality of l points on either side. of said forming member and, advancing said forming member into said sheet While automatically. positively, paying out saiclrigidly gripped points sub- 'stantiallyatright angles-to said forming member in response to a substantially constant-and predetermined unit stress in said materia1 between each of said gripped pointsand said forming member.

.2. A method of forming: workpieces from ductile sheet material which comprises,-;rigi dly.gripping apair of opposite edges of said sheetby a betweeneach of said grippingmembers and said forming member.

3. A press for shapingmetal sheets comprising a frame, a reclprocable pressinga ember carried there a p r 10f gri in "mea slidablv mounted on said irame cn 'oppos1tesldes;- of said pressing member, eachot said.- gripping'mean ,in-

cluding jaw members.,;swivelled thereto, ,fluid'voperable .motor means for reciprocatingsaid-pressing member relative to saidgripping means, fluid operable motor means for initially 1i positioning said gripping means relative-to said pressing member, and fluidpressure vcontrol means for l said gripping means automatically operable in response tov a predetermined tensi-onin said sheet to cause said second mentioned motorqmeansto -move said grippingmeans toward-each-ptherin a plane vwhich is substantially at right angles to said pressing member.

4. A press fOY'ShalJingIllBtdl sheets; comprising a frame,a press platen reciprocable-relative to said frame and adapted to mount adiemember,

c slide means arranged on. saidframe on either side-oi said pressplaten and movable relative thereto, eachofsaid slidetmeans includinga :jaw

member having associated therewith a;-pist oncylinder arran ementppivotallysecured to;.;said

slide-means; first motor; means for; reciprocating e-said, presssplaten; relativatq a: she tgri pe by and said slide means,-- valve Ineansconnected with -;--.said :fluidsourcaand vsaid second motor means 'iandlmovable intoia position to interrupt fluid =communioation between said-motormeans and tsaidqfluid:source'for maintaining said slide means imanyi predetermined position,. and fluid control means associatedwith said second motor means l-responsiveto a, predetermined pressure in said .piston-cylinder arr,ange,ment to .by-pass fluid aroundsaid valve means to-cause said slide means to move relative to said platen. tate the shaping of complex workpieces if ,s0 de-' 5.. 1A presslfor shapingmetaLisheets comprising-ca frame,aplaten adapted to mounta die zmember reciprocable relativeto said frame, slide imeansqslidable, 1011 @said. frame on. either. side of ssaid -platen jawmeansztassociated with each of saidislide means. and including 7 a piston-cylinder arrangement pivotally connected with said slide means, reciprocable fluid operable motor. means coi1nected :vvith said slide means for. reciprocating v-the-sam e,- .-valve means operable to connect said .-motor-i.means with a source ofifluid pressure or to disconnect said gmotor means i from said fluid sourceand'f-rom exhaust, othervvalve meansoperable to simultaneously.connectsaid motor means awithesaidsource of fluid pressure and with exahaustsandfluidpressure actuated means responsiverto apredetermined pressure in said pistoniacylinder arrangement for operating said other valve ameans.

.- 6..:A pressfor shaping ductile sheet material into-workpieces comprising a frame, a vertically reciprocable press platen carriedby said frame, a pair of transversely-slidable crossheads slidably carried on said frame on either side of said 140 platen, each of saidcrossheads having pivoted thereto cylinder means, each of said cylinder means having a, piston therein and each of said 1 pistons having connected therewith a jaw member adapted togrip a marginal portion of said 5 sheet, fluid operable motor means mounted on said; frame having plungers reciprocable therein and connected with said crossheads, said plungers havingequal, opposed areas thereon, agfluid source for supplying actuating fluid to said areas,

; .valve means movable to connect one or the other of said areas with said source, said valve also being movable to interrupt fluid communication 1 between said areas and said source, other valve vmeans interconnecting said areas and normally positioned toprevent fluid'flowtherebetween, and

[fluid pressure responsive control means for said other valve operable in response toa predetermined fl-uid ,.pressure in said I cylinder means to causeisaid other valve to move into position to hydraulically interconnect said. areas, andmeans for, adjusting the pressure at which said control .-means is responsive to maintain any .desired .-predetermined. constant tension in fsaidv sheet duringreci rocation of said platen.

7.. A press for shaping. ductilev sheet material intosworlzpieces.comprisinga frame, a die carrying platen reciprocable relative to said frame, a cro'sshead slidablymounted .on ,said frame on either side of saidplaten, said crossheads and said frame having cooperating guidingmeans to cause saidgcrossheads toamove transversely. of said frameand also .to, swing in said frame, .each of 1 ?'-.l -i f05 1 hav n p v iel e r thereto .pl raliir ,aden ne-m b s l a h twli has x-v a s d te t erewi h-a lrif scvllnqen area ment, fluid operable motor means pivotally secured to said crossheads for initially positioning t latter relative to said press platen, means for ac rating said motor means for accomplishing initial positioning and for thereafter trapping the fluid in said motor means, valve means connected with said motor means for bypassing the same to allow yielding movement of said crosshead, and fluid pressure responsive hydraulic control means interconnected with said valve means and with said piston-cylinder arrangement operable by pressure variations in said piston cylinder arrangement to cause said valve means to regulate the yielding movement of said crosshead in response to a predetermined average tension in said sheet.

8. The combination in a metal stretching press having a frame and a pressing member reciprocable relative thereto, of means slidably mounted on said frame on either side of said pressing member for gripping opposite marginal portions of said sheet, each of said gripping means comprising a jaw member universally pivoted to a plunger, a cylinder within which said plunger is reciprocable, a slide to which said cylinder is pivotally connected, and motor means connected with said slide for reciprocating the same so as to initially position said jaw members; and fluid control means operable by pressure created in said cylinder by the pull of said jaw member on said plunger to cause said motor means to move said jaw member toward said pressing member as the latter advances into said sheet.

9. A press for shaping ductile sheet material comprising a frame; a pressing member. reciprocable relative to said frame; workpiece gripping means slidably mounted on said frame on either side of said pressing member, said workpiece gripping means comprising a jaw member, a piston-cylinder arrangement, a slide member and a fluid operable motor, said jaw member being pivotally connected to said piston-cylinder arrangement and said piston-cylinder arrangement beil'lg pivotally connected to said slide member; means connecting said slide member with said fluid operable motor; valve means operable to entrap fluid in said fluid operable motor; and fluid pressure control means for said valve means interconnected between said fluid operable motor and said piston-cylinder arrangement, said fluid pressure control means being responsive to a predetermined pressure in said piston-cylinder arrangement so as to release said entrapped fluid by controlling said valve means.

10. A method of forming workpieces from sheet material which comprises, rigidly gripping a sheet of material along at least two edges thereof, effectingrelative movement between said sheet and a forming member so as to form the Workpiece, and automatically maintaining a positively controlled tension in said sheet at a substantial- 1y predetermined constant amount throughout the whole of said relative movement and the en tire formation of said workpiece by automatically positively paying out said rigidly gripped edges of said sheet at substantially right angles to the plane of said forming member in response to said tension.

11. The combination in a metal stretching press having a frame and a die carrying platen reciprocable relative to said frame, of workpiece gripping means slidabiy mounted on said frame on either side of said platen, said workpiece gripping means comprising slide means, jaw members pivotally connected with said slide means, and motor means selectively operable for reciprocating said slide means to initially position said jaw members; and control means connected with said motor means so that said motor means may cause further automatic movement of said slide means and the pivot points of said pivotal connections, said control means being automatically operable in response to a predetermined tension applied to oppose the pull of said jaw members in the workpiece to thus cause said motor means to move said slides and said pivot points relative to each other in timed relationship with the reciprocation of said platen, said relative movement of said slides and said pivot points being at right angles to the reciprocation of said platen.

WALTER ERNST. ARTHUR M. GREENE, Js.

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

UNITED STATES PATENTS Number Name Date 1,461,471 Bancroft July 10, 1923 1,622,590 Jolstad Mar. 29, 1927 1,710,261 Kellogg Apr. 23, 1929 2,006,468 Longren July 2, 1935 2,129,774 Kohner Sept. 13, 1938 2,245,723 Salzmann June 17, 1941 2,279,964 Berliner Apr. 14, 1942 2,279,965 Berliner et al Apr. 14, 1942 2,289,584 MacMillin et a1. July 14, 1942 2,301,960 Lermont et al Nov. 17, 1942 2,302,953 Pocock Nov. 24, 1942 2,326,470 Lermont et al Aug. 10, 1943 2,342,437 Summers Feb. 22, 1944 2,346,213 Flowers Apr. 11, 1944 2,349,520 Ripley May 23, 1944 2,371,587 Seifried Mar. 13, 1945 2,378,413 Lermont et a1 June 19, 1945

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