US2971557A - Sheet and plate stretching apparatus - Google Patents

Description

Feb. 14, 1961 M. D. STONE HAL 2,971,557

SHEET AND PLATE: STRETCHING APPARATUS Filed Sept. 23 1957 5 Sheets-Sheet 1 .h ,.N @E I Wn INVENTORS MORRIS D. STONE' Ho WAR 171.3 A TTORNEY Feb. 14, 1961 M. D. STONE ErAL SHEET AND PLATE STRETCHING APPARATUS Filed Sept. 25. 1957 3 sheets-sheet 2 s T n mw n. N m n M man. W M7 A u @WH .Y am muznow MN umamwuf. .525m nzxw u 3 UGM )Gm No8 m no3 53 vu mm mu 5% vm Feb. 14, 1961 M, D, STONE ErAL 2,971,557

SHEET AND PLATE STRETCHING APPARATUS Filed Sept. 23, 1957 5 Sheets-Sheet 5 INVENTORS /t/oQ/s D. S70/VE 755/@ ,4free/ver United States Patent O 'i SHEET AND PLATE STRETCHING APPARATUS Morris D. Stone and Howard H. Talbot, Pittsburgh, Pa.,

assignors to United Engineering and Foundry Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Sept. 23, 1957, Ser. No. 685,490

2 Claims. (Cl. 153-35) This invention relates to apparatus for processing elongated metal workpieces such as sheets and plates and in particular relates to apparatus for stretching aluminum alloy sheets and plates by securing them at their ends between two elements and then moving the elements relative to one another to cause the plates to be elongated to the extent desired, a safety feature being included in the apparatus for protecting the apparatus and the foundation upon which it is mounted.

There are many types of sheet and plate stretching apparatus presently in use for processing relatively light gauge strip, where the total forces required to accomplish the particular stretching operation is relatively low, so that in the event a workpiece breaks while the operation is in progress, the shock imposed upon the elements making up the apparatus as well as upon the foundation to which the apparatus framework is secured is not too serious. However, for stretching relatively heavy gauge sheets and plates, unless precautions are taken for absorbing the shocks incident to the failure of certain op erating elements or to the breakage of the workpieces themselves while being stretched, serious damage to the apparatus as well as to the foundation upon which the apparatus is mounted will result. Moreover, in eX- tremely large capacity stretching apparatus as presently employed, even under normal operating conditions eX tremely large and objectionable forces are imposed upon the foundation.

1t is an object of this invention to provide in a plate and sheet stretching apparatus means for absorbing the shock, due to the energy suddenly released, upon the apparatus such as that incident to the breakage of a workpiece while undergoing a stretching operation.

It is another object of this invention to provide in a workpiece stretching apparatus a base so constructed and arranged with respect to the remaining portion of the apparatus as to permit shocks to be absorbed in motion rather than by being transmitted from the apparatus directly to a foundation rigidly connected thereto.

1t is still another object of this invention to provide a plate and sheet stretching apparatus for stretching relatively heavy sheets and plates which is rugged of construction and capable of absorbing effectively any shocks which may be imposed thereon without causing any damage to be suffered by the elements or the supporting foundation.

A further object of this invention is to provide a plate and sheet stretching apparatus which is economical to construct as well as relatively inexpensive to maintain under service conditions.

These objects as well as the various other novel features of this invention will become apparent from the description and accompanying drawings of which:

Fig. 1 is a sectional elevation of a stretching apparatus embodying the features of this invention;

Fig. 2 is a partial sectional View taken at II-II of Fig.

2,971,557 Patented Feb. 14, 1961 Fig. 3 is a front' elevation view taken at III-III of Fig.

Fig. 4 is an enlarged end elevation view taken from the right of Fig. 1;

Fig. 5 is a schematic diagram of the hydraulic control system for the workpiece gripping elements of the stretching apparatus;

Fig. 6 is a partial side elevation taken at the right of the apparatus shown in Fig. l but embodying a modification of the invention herein disclosed;

Fig. 7 is a plan view of the apparatus shown in Fig. 1; and

Fig. 8 is an enlarged side elevation view of the pinch rolls associated with one of the jaw heads.

With reference to the drawings, the workpiece stretching apparatus consists of a normally stationary gripper head 11, a movable workpiece gripper head 12, two compression bars 13 having openings 14 therein along their length into which there are extended suitable pins 11a secured to the normally stationary workpiece gripper head 11 for securing the head at a desired location along the bars 13, and a piston-cylinder assembly 15 of which piston 16 is secured at its outer end to a crosshead 17 which in turn is connected by two links 1S to the movable gripper head 12. The piston-cylinder assembly 15 is secured within an entablature 19 having secured to its under portion a platform 21 which is slidably mounted upon a base 22. To the two sides of the entablature, one end of each of the bars 13 is rigidly secured thereby connecting the entablature to the stationary gripper head. in this arrangement under stretching operation the entablature, bars and stationery gripper head are mechanically connected together as a unit. Attached to the front end of the base 22 there are two relatively small pistoncylinder assemblies 23, the pistons 24 ot which are constantly urged in contact with the front portion of the platform 21 thereby maintaining the entablature 19 and piston-cylinder assembly 15 in their most extreme left hand position as shown in Fig. 1 so that the opposite ends of the platform 21 abut against suitable stops 25 which are also secured to the base 22. It is to be appreciated that the capacity of the piston-cylinder assemblies 23 is such that under normal operation of the stretcher, the assemblies 23 will prevent any longitudinal movement of the entablature in the direction toward the cylinders. However, the assemblies 23 are so designed as to permit the entablature to move a slight amount when abnormal horizontal forces are encountered such as those caused when sudden breakage of a workpiece occurs and are of su'cient capacity to return .the assembly to its original position. Although piston-cylinder assemblies 23 have been shown for purposes of illustration, any type of yieldable means may be employed for the purpose such as springs, for example.

Extending through the entablature 19 and at op-positely disposed points with respect to one another, there are two pull back piston-cylinder assemblies 26 of which the pistons 27 are secured at their ends to the crosshead 17, the crosshead being slidably mounted upon a suitable .platform 23.

With particular reference to Fig. 3, it is noted that the entablature 19 is rigidly secured to the ends of the compression bars 13 whereas the links 18 are attached to the movable gripper head 12 and pass along suitable guiding surfaces 29 in the side of entablature 19, and extend to a point adjacent to the crosshead 17 to which they are secured by suitable pins 31. In order to prevent the entablature 19 from being displaced sideways with respect to the base 22, suitable side plates 32 are welded to the base 22 at spaced points on either side thereof. Similar plates 3v 33 are secured to the platform 28 for preventing sideways displacement of the crosshe'ad 17. Y

For securing a plate atV its ends between the gripper heads, each head vis'provided with a tapered opening 34 within which a plurality of pairs of suitable gripper jaws 35 are slidable received, being mov-able into and out of their gripping positions by push rods 36 and 35a secured at their outer ends to levers 37 and 35 respectively acuatable by a plurality of piston-cylinder assemblies connected thereto and to the top of each head.

4Between the two gripper heads there are shown two longitudinal support carriages 4,1 which are spaced apart from one another and vsupported by the compression bars 13 and serve to support the workpiece along its length. Each of these carriages isV provided with rollers 41h andy transversely movable side guards 4117 which, through the individual frame work supporting each one, are` connected to a right and left 'hand threaded screw 41e. The guards 41b are arranged t'o be moved transversely relative to the longitudinal center of the stretcher on rotation of the screw 41C, by means of a hand wrench or the like, in order to center the workpiece prior to the gripping and subsequent stretching operations.

It is a feature of the gripper heads that the push rods 3,6 thereof are relatively thin compared to their lengths, thereby being rather limber, so that when compressive Yforces are imposed thereon in a longitudinal direction on breakage of a workpiece during a stretching operation, the rods will immediately elastically buckle and consequently draw open the jaws and release the ends of the workpiece held therebetween. Then, too, in order to prevent exceptionally high pressures from being built up instantane- A,ously in the piston-cylinder assemblies 39' should a yworkpiece break during a stretching operation, the pistoncylinder assemblies 39 'are opened to exhaust soon after a stretching operation begins so that there will be no pushing action imposed upon the rods in opposition to the forces which will be encountered bythe rods when breakage of a workpiece occurs. By this'construction, the jaws, their cylinders and the elements associated therewith are automatically relieved o f the full impact forces incident to the breakage of a workpiece. lFurthermore, the end of the plate is quickly released and is permitted to pass through the jaws and strike'against the gripper head itself so that a considerablepart of the impact energy of the broken plate is absorbed by the head rather than by the jaw assembly itself-` Spaced along the length of the two bars lnthererare several pairs of frames 42, the details of which are shown in Fig. 4, which are provided with shoulders 43 for engaging with and supporting the bars 13` at spaced points along their lengths. The bars 13 are rigidly connected tothe frames 42 by means of suitable bolts which pass through openings in the frames and the bars, each of frames 42 being slidably supported upon a base 44. So that the frames 42 will be prevented from being displaced transversely with respect to the base 44, there are provided for each assembly a central guide key 45 between the frame 42 and the base 44 and a pair of C clamps 46 whiich are secured to the frames 42 by means of suitable stu s.

Also as shown in Fig. 4, there is attached to the adjustable gripper head 11 a frame 47 extending downwardly therefrom and upon which there are rotatably mounted reels 48, 49 andV 51 which serve to retrieve and pay out the electrical wires connected topa power source and to the head adjusting motor 52 and other electrical equipment associated with the heads. The motor 52 as well as the adjustable gripper head 1l and its related parts are mountedpuponra carriage'SS, the wheels 4 of which ride along the upper surface'of the bars 13. Stops S Yareprovided at the ends'of suitable track extensions '552; which are secured to the ends of bars 13 and sup-A ported from beneath "by struts SSb: `A cross "brace '55C is connected to the track extensions at their outer ends.

einen 4 The motor 52 is connected in driving relationship to a worm gear drive 56 which, in turn, through shafts 57, is connected to a pair of bevel gear drives 58, the output shafts S9 of which extend vertically downward therefrom and upon the lower ends of each shaft there is mounted a pinion 61 which engages with a rack 62 secured to each bar 13 at its inner, face.

'lust forward of each'of thel gripper heads 11 andv 12 there is a pairY of pinch rols 63`and 6.3, the lower one 63 being driven bymeansof a suitableA motor, not shown', and adjustable vertically by means of a jack screw 64 threadably attached to the carriage53. The upper pinch roll 63a is mounted upon Van arm 65 which is pivotally supported upon Ythe carriage 53A and movable into and out of engagement with the lower roll by means of suitable piston-cylinder assemblies, not shown, connected to the arm 65 and to the carriage S3. Thus, by means of the vertically adjustable lower pinch rolls, it is possible to compensate for dierent plate thicknesses 'so as to maintain the workpiece at theproper level and in align ment with the gripper heads.

ln Fig. 5 there is shown a schematic diagram of the hydraulic control system employed in conjunction with the piston cylinder assemblies 39, push rods 36 and 36a and jaws 35, which they actuate, of the stationary gripper head 11, the same control arrangement being employed for the various elements of the gripper head 1?.. In this particular arrangement, five sets or pairs of assemblies are employed, beginning with a central pair 39C1 and continuing in an outward transverse direction through pairs 39C2, 39C3, 39.; and 39C5. As noted in Fig. 5, each assembly of each pair is disposed an equal distance on either side of the center line of the apparatus.'Y For controlling the movement of each pair of gripper push rods 36 and 36a, a system of controls is provided for causing the` separate pairs ofprods, and consequently the jaws actuated thereby, to beoperated in sequence so that the central pairs Vof. jaws will first grip "the workpiece and Vthen at Vintervals determined by the build up of pressure in piston-cylinder assembly 3 C1, working pressure. Vis introduced into the next adjacent piston-cylinder 39C2 to cause the jaws controlled thereby to vclose until finally all of the gripper jaws will be'clamped across one end of the workpiece. This same action will also take place at the gripper head 1,2.

Since the control for each pair of assemblies is practically the same, and, further, since the actuation of each pair of succeeding assemblies depends upon actuation of the pair preceding, it is considered to be sufficient to describe only the controls for the irst two pairsof assemblies 39C1 and 39C2 and the push rods and jaws operated thereby. To the assemblies 39C1 there are connected two hydraulic lines which merge into one and to which there is connected a balance piston type relief valve 39V1 which communicates with the main pressure line PLp a right angle type check valve 39CV1, which also is connected to the main pressure line, and a balance piston type relief valve 39V2, which valve is, in turn, connected to the second pair of piston-cylinder assemblies 39C2, as shown in Fig. 5. The next succeeding pairs of piston-cylinder assemblies 39C3, 39C.,E and 39C5 are connected together to the main pressure source in a fashion similar to that in which piston cylinder assemblies 39C1 and 39C2 are interconnected, valves 39V3 and39V4 being connected rto assemblies 39C3 and 39C4 respectively. VSince vthe assemblies 39C5 are the last in the group, it is not necessary to provide a separatek piston type relief valve therefor. From the opposite end of each of the piston-cylinder assemblies, separate lines extend and they are directly connected to a second hy draulic line 'PL2 which communicates with a reversing valve and to which line PL1 is v.also connected through balanced .piston type relief valves BRV1 and BRVZ, the purpose of the reversing valve being to introduce uid under pressure to either end of the piston-cylinder assemsemblies 39C1, thereby to cause the push rods 36 and `36a to close the jaws 35 to grip the end of the workpiece. As soon as gripping of the workpiece by the first set of jaws takes place, due to the build up of pressure 1n the rst piston-cylinder assembly 39C1, the valve 39V1 i opens at the top thereby permitting uid under pressure to pass to the second valve 39V2 and consequently therethrough and to the pair of piston-cylinder assemblies '93C2. As soon as the jaws actuated by piston-cylinder .assemblies 39C2 grip the workpiece, the next succeeding assemblies 39C3 are actuated on suicient build-up 'of pressure within the assemblies 39C2 to cause uid to flow from the upper portion of the valve 39V2 to the valve 39V3 and consequently to the piston cylinder aszsemblies 39C3. This sequence of operation continues `until all of the jaws 35 are clamped upon the workpiece. Y-By this arrangement, ironing out or attening of the `workpiece at the ends `is quite readily accomplished. For 'releasing the workpiece from the jaws, it is merely neces- :sary to reverse valve RV to cause lluid to liow into line VPL2 to the opposite ends of the piston cylinder assemblies thereby to actuate all of the push rods at Ithe same time and to open the jaws.

At times, it may be desirable to close all of the workpiece gripping jaws 35 simultaneously rather than in sequence. This is accomplished by locking together all of the links 37 by passing a key 40a, as shown in Fig. 6, through suitable transversely in line openings 40 provided in each of the links 37. The valves 39V1, 39V2, 39V3, 39V4 and 39V5 are, of course, adjusted so as to permit the high pressure fluid from line PLI to llow directly and simultaneously to all of the piston-cylinder assemblies 3901, 39C2, 39GB, 39C., and 39C5. Should ere be any irregularities such as high spots along the width of the workpiece, then the jaws adjacent thereto will first make contact with the workpiece and consequently the pressure coming to bear upon the workpiece at that instant will be the total pressure of all of the piston-cylinder assemblies so that flattening of the workpiece at that point will be readily accomplished. Flattening of the workpiece will continue across its width and iinally all of the jaws will be in gripping relationship therewith. A

In Fig. 6 there is shown a modification of the invention herein disclosed in which therev are provided pistoncylinder assemblies 66, secured to the foundation, which .engage with the ends of the bars 13 and serve the same purpose as the piston-cylinder assemblies 23 as shown and described in the preferred form of invention. As .in the case of the piston-cylinder assemblies 23, the as- -semblies 66 serve to oppose movement of the entablature- ;side bar-stationary gripper head-combination to the right ,at the time a stretching operation is being carried out vand yet will yield suflciently to permit this assembly to move to the right in the event breakage of a workpiece occurs during a stretching operation, thereby preventing damage to the apparatus. As in the case of the piston-cylinder assemblies 23, the piston-cylinder assem- In operation, the apparatus embodying the features of the invention in preferred form as herein disclosed may 1 be briey summarized as follows:

Depending upon the initial length of workpiece upon 1 which a stretching operation is to be performed, the

normally stationary gripper head 11 is moved along the compression bars 13 to the desired position depending upon the length of workpiece to be stretched and then secured in place by extending the pins 11a, which are connected to the head 11, through the adjacent openings 14 in the bars 13. Depending upon the thickness of the workpiece to be processed, the lower pinch rolls 63 are either raised or lowered in order that the centerline of the workpiece supported thereby will be in alignment with the jaws. By means of a crane or the like, a workpiece is deposited upon the pinch rolls 63 and the support carriages 41, and pinch rolls 63 rotated to feed one end of the workpiece into the jaws of the gripper head 11 and then the movable head 12 moved into position for gripping the opposite end of the workpiece. Pressure is applied to the piston-cylinder assemblies 39C1, 39C2, 39C3, 39C4 and 39C5 either in sequence or simultaneously and the workpiece ends gripped by jaws 35. Pressure is then introduced into the piston-cylinder assembly 15 causing the crosshead 17 to move to the left, as viewed in Fig. 1, thereby to pull the gripper head 12 in the same direction causing the .workpiece to be stretched. As soon as stretching begins, pressure is cut od from the piston-cylinder assemblies 39C1 through 39C5 and the valves 39V1, 39V2, 39V3 and 39V4, for example, opened to exhaust. Fluid in the two small piston-cylinder assemblies 23 is maintained under suicient pressure during a stretching operation so that the resistance otered thereby together with the friction between the platform 21 and the base 22 prevents the entablature and the elements attached thereto from inadvertently sliding along the base 22. Due to the slight change in length of the bars 13 caused by the compression loads imposed thereon, the frames 42 will move a. slight distance along their bases 44.

However, should the workpiece be ruptured during a stretching operation, a tremendous amount of energy will suddenly be released thereby imposing upon the structure exceptionally large forces which must be properly absorbed in order to prevent damage to the apparatus. As mentioned above, during a stretching operation, the bars 13 areV placed under compression and actually becorne elastically shortened. When a workpiece breaks, the push rods 36 and 36a, being limber, are caused to buckle elastically by the longitudinal shock forces imposed thereon so that the jaws are pulled open immediately, thereby releasing the ends of the broken plate held therebetween and avoiding damage to the jaws. Then, too, the piston cylinder assemblies 39C1, 39C2, 39C3, 39C.,L and 39C5, having been previously exhausted, offer very little, if any, resistance to outward movement of the rods 36 and 36a. Furthermore, when breakage occurs, the hydraulic pressure within the piston-cylinder assembly 15 is reduced rapidly and the crosshead 17 moves immediately outward to the left, the movement being resisted, however, by the action of the pull back v piston-cylinder assemblies 26. Of utmost importance, also, is the behavior of the two bars 13 at the time a workpiece breaks. Immediately on relief of the compression load upon the bars 13, the bars are caused to extend Very rapidly, i.e. more rapidly than the hydraulic pressure decreases in the-main cylinder, the net result of which is to cause the entablature 19 together with the platform 21 connected thereto to tend to be moved to the right. This tendency is resisted by the frictional forces oEered by the platform 21 and base 22 at their points of support and by the hydraulic pressure of the pull back cylinders 26 and the piston-cylinder assemblies 23. The total released energy when a plate breaks is absorbed by the permitted motion of the assembly against the resistive forces-the forces being reduced in proportion as the permitted motion is increased. When, on breakage of the workpiece, displacement of the platform 21 to the right takes place, the piston-cylinder assemblies of both the preferred form as well as of the 7 icidfiedvpfrm of invention are ofsuticient capacity to rfefv "tlieappa'ratusto Vits original Positionen Then, too, th 'capacity' ofy the pull back piston-cylinder assemblies 26 1s' siuflicientlygreat to return the crosshead 17 and the movable head 12 connected thereto to their original positions to the right, Figure V1,'after displacement to the left has occurred on breakage of a workpiece. Of course, under many conditions of operation, the frictional resistance to movement between the entablature and the platform will, at times, be of sufficient magnitude to prevent any movement of the entablature relative to the base, whereas the resistance to movement offered by the frictional resistance as well as either the piston cylinder assemblies` 23 or 66 will be overcome primarily under those conditions of operation where the shock lenergy of,V such intensity that damage to the foundation and possibly-to other parts of the apparatus would result if the entablature were trmlyaixed to the foundation.

lIn accordance with the provision kof the patent statutes, 'We have explained the principle and operation of our invention and have illustrated and described what we consider to represent the best embodiment thereof. However, we desire to have it understood4 that within the scope of the appended claims, the invention may be practiced otherwise'than as specically illustrated and described.

l We claim:

l. Apparatus for performing a stretching operation upon elongated workpieces comprising a normally stationary workpiece gripper head, a movable workpiece gripper head, av pair of carriages interposed between said heads` adapted toy support a workpiece thereon, transverselymovable side'guards mounted upon said carriages en'gageab'le with and for centering a workpieceton said carriages, means foradjusting said stationary head inra direction toward and 'away from said movable head, a pair of longitudinally extending parallel bars having spaced transversely opposite openings in the sides thereof, pins carried by said stationary head adapted to be inserted in said openings'therebyl to secure said normally stationaryV head ina selected position along said bars, an lentablature Vrigidly secured to saidbars, a cross head, afpairof'links connected to said movable head and to saidcross head, power means operatively connected to said 'cross headv and to saidvv entablature, adaptedtol die; place said cross` head in a direction away from said enfL tablature and said normally stationary head, guides, e,

cured to said ent'ablature and in slidable engagement with 'said links, a baseupon which said entablatupe is slidabl'ymounted, yieldable means in` engagement: @19 normally restrainingimovement of' said entablatureS/upon said base during a stretching operation and operatively arranged Yto permit relative movement betweenjsaid` entablature and said base in the event breakage of awor-kfY piece occurs during a stretching operation thereby to prevent damage to said apparatusfrom sudden shock forces incident to such breakage and to return said entablature to its original position after such relativernpvement takes place.

2. Apparatus for performing a stretching operation upon elongated workpieces according to claim 1 in which said.-gripper heads include a plurality of pairsv of workpiece gripper jaws positioned transverseiy across said apparatus, push rods operably connected to each pair of said jaws and means operably secured toyand for simultaneously actuating said. rods thereby to close said jaws simultaneously in gripping relationship with the work` piece, said rods being adapted to buckle elasticallywhen forces are imposed thereon by the sudden release of energy in the event of breakage Ofva workpiece during a 'stretching operationithus to withdraw said jaws andto release the portions of a workpiece engaged therebetween.

References Cited in the ileof this patent

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