US2378413A - Device for shaping metal sheets - Google Patents

Description

June 19, 1945. i B. LERMONT ETAL 2,378,413

, DEVICE FOR SHAPING METAL SHEETS Filed Sept. 24, 1942 2 Sheets-Sheet 1 IN V EN TOR. '5ms/z. ER/WONT .By ARNOLD /7. WWF

June 19, 1945- B'. LERMONT'ETAL 2,373,413

, DEVICE FOR SHAPING' METAL SHEETS l Filed sept. 24, 1942 2 sheets-sheet 2 HHHHHW lt MIII! y VEN TOR. .5ms/.1. HMa/vr By /R/vozo /7. h/alF md Tramways Patented June 19, 1945 UNITE-D STATES PATENT OFFICE Basil Lermont, New York, and Arnold M. Wolf,

Brooklyn, N. Y., assignors to Cairns Corporation, Brooklyn, N. Y., a corporation of Delaware Application September 24, 1942, Serial No. 459,496

' for. 153-48) a sheet metal shaping device in which the sheet 2 Claims.

This invention lrelates to devices for shaping metal and relates more particularly to devices for stretching, working and forming metal sheets into transversely and longitudinally curved shapes suitable for use in the construction of fuselages for aircraft, boat hulls and other structures having curved portions,

Many different types of devices have been used heretofore to convert initiallyriiat sheets of metal into curved and angular shapes. The most widely used metal-shaping devices are die presses involving the use of accuratelydesigned and fitted cooperating male and female die members. Such die presses are admirably suited for mass production operations, where great numbers of identical articles are to be produced. However, they have vthe disadvantages of being extremely expensive and diiiicult to manufacture, they require presses of great weight and size in order to apply the' necessary pressure to deform the sheets into the desired shape, and because of the diiculty of manufacturing the die elements and replacing them in the presses, such die `presses lack versatility in the manufacture of parts of varying shape.

It has been suggested that a. single die member may be used to shape sheets into complemental forms. Such devices usually include mechanisms for gripping the edges of a sheet and a hydraulic ram or similar device which forces the die member against one side of the sheet to stretch the sheet beyond its yield point and cause it to conform to the contour of the die. Such single die presses have not been entirely satisfactory for the reason that a considerable wasteof material results due to the edges of the sheet being retained in a plane while the remainder of the sheet is deflected from the plane, thereby necessitating extensive trimming away of the edges to produce the desired curvature of the edges of the sheet. Moreover, uncontrollable stresses and buckling of the sheets result from the differences in shape of the die and the retaining means. Nevertheless, the use of a single die would have marked advantages in the production of compound-curved sheets, if it were possible to control more closely the amount the sheets are stretched, the nal shape of the sheets and the stresses exerted on the sheets. i

An object of the present invention is to pro- -vide a device for shaping sheet metal into curved forms over a single or'multiple diemember or form with a minimum waste of material.

Another object of the invention is to provide a device for shaping sheet metal in which the metal is stretched under controlled conditions to correspond to the shape ofthe diemember, members or form.

A further object of the invention is to provide forms or die members may be easily interchanged and the means for gripping the sheets of metal are arranged in relation to the forms or die members to provide a predetermined allocation of the metal, thereby increasing the extent to which the sheet may be worked before reaching its critical point and resultingin fracture. Y

A further object `of this invention is to provide a flexible device for shaping sheet metal in whichthe gripping means may be adjusted to vary the angles of pull in order to provide a predetermined allocation of draw radii thereby reducing the concentration of stresses at the draw radii and more uniformly Idistributing the elongation of the metal through the sheet.

Other objects of the invention will become apparent from the following description of typical forms of devices embodying the present invention. G

In accordance with the present invention, a

device is provided which includes opposed pairs of jaws for gripping the opposite edges of a sheet of metal and tensioning the sheet over an interposed form of predetermined contour to stretch the sheet intol a shape corresponding to the contourv of the form. More particularly, the device includes gripping jaws that are moved individually 'or in unison to stretch and pull the sheet into tight engagement with a iixed or movable form or forms and therebystretch the sheet beyond its yield point to cause it to become curved and form-retaining in a permanent set. The jaws are of such shape that they correspond substantially to the desired curvature of the sheet, thereby avoiding the introduction of stresses at angles to the direction of stretching of the sheets and rendering substantially the entire sheet usable. The gripping and stretching means may be utilized in combination with a ram t0 provide increased flexibility of operation.

For a Ibetter understanding of the present invention, reference may be had to the accompanying drawings in which:

Figure l is a View in side elevation of a typical form of device embodying the invention;

Figure 2 is a top plan view of the device;

Figure 3 is a viewin section of one of the clamping jaws, taken on line 3-3 of Figure 2; and l form I5 has a fiat base Ita, and an upper surface Ib of a shape corresponding to the shape of the sheet to be produced. As illustrated, the upper surface Ilb of the form I9 may have transverse and longitudinal curvatures, thereby providing a compound curved surface. It will be understood that the shape of the surface I5b may be varied widely and may consist of any desired combination of curvatures. The form I5 may be made of wood, concrete, plastics, metal or combinations of the same, or any other type of material that is capable of withstanding high compressive stresses, without appreciable distortion. Hard wood is entirely suitable for the reason` that it will not scratch the sheets, is easily worked into the desired shape and is capable of withstanding the stresses applied thereto during the shaping operation. o

At opposite ends of the basemember III are mounted adjustable gripping and stretching' members I9 that are adapted to grip the ends of a sheet S of metal and stretch it over the form I5. Each of the gripping and stretching members I6 includes a pair of levers I1 and I8 connected to opposite ends of a shaft I9 that is journaled in suitable bearings adjacent each end of the base vmember I0. The upper ends of the levers I1 and I3 are connected to a rigid boxlike member 2I that is formed of an upper plate 2Ia, a lower plate 2lb and interposed partitions or braces 2Ic'. The member 2I is also provided with a front wall 2 Id that is spaced inwardly from the front edge of the plate 2 I-b and has a plurality of upwardly projecting. spaced-apart hinge elements 2Ie thereon that extend above the upper plate 2Ia.

In front of. the wall 2Id is detachably mounted a lower jaw member I22 for gripping the end of` the sheet S. The lower jaw 22 may be secured to the bottom plate 2lb and the front wall 2Id by means ofA any suitable sturdy detachable fastening means such as, for example, bolts.

A cooperating gripping jaw member 23 is detachably mounted on a plate 24 that is provided with hinge elements 24a adapted to be received between the hinge elements 2Ie and retained in pivotal relationship thereto by means of a hinge pin 25. The jaw 23 is also detachably connected to the plate 24 by means of detachable fastenings such as, for example, bolts.

Themechanism for opening and closing the jaws may consist of the toggles 26 having their outer ends pivotally connected to the plates 2lb and 24 and their inner ends pivotally connected to a plunger 21 of a hydraulic rain 28. The hydraulic rams 28 may be supported on the front wall 2Id and are connected to a suitable source of fluid pressure. When the plunger 21 is projected, the toggles 29 are straightened, thereby forcing the jaws 22 and 23 together to firmly grip the ends of the sheet S. When the plunger 21 is retracted. the toggles 29 are collapsed, thereby causing thejaws 22 and 23 to separate.

Figure 4 is a view in section taken on line 4-4 The jaws 22 and 23, illustrated, are curved from end to end, the lower jaw being convex and the upper jaw being concave. These curvatures are substantially the same as the curvatures of the adjacent ends of the form I5 so that there will be no tendency of the sheet to buckle adjacent the ends of the form during the stretching operation.

In order to stretch the sheet of metal over the form I5, means is provided for moving the clamping and gripping elements I6 pivotally with relation to the base member. The means for -moving the jaws, illustrated in the drawings, may consist ofsuitable pairs of hydraulic rams including cylinders 29 pivotally connected to the base member III. The cylinders 29 are provide'd with pistons having piston rods 30 thereon that are provided with bifurcated end portions 3| that straddle the levers I1 and I9 and are secured thereto by suitable pivot pins 32. The hydraulic rams 29 are connected to a suitable source of liquid under pressure so that the piston rods 30 may ybe projected into the positions shown in Figure 1 with the clamping and gripping elements in their innermost position, or retracted to move the clamping and gripping velements I8 apart in order to stretch the sheet of metal gripped therebetween. It will be understood that the liquid in the cylinders 29 may be controlled by suitable valves so that gripping and stretching elements I6 may be moved selectively.

In operation, a form I5 of the desired contour is positioned on top of the base member, the jaws 22 and 23 of each of the gripping members I6 are separated and the ends of a sheet of metal are inserted therebetween. The jaws 22 and 23 are then forced together by means of the rams 28 to rmly grip the ends of the' sheet of metal.

When the sheet is gripped by the gripping members I6, fluid under pressure is delivered into the hydraulic rams 29 and the gripping members I6 are moved apart, thereby stretching the sheet and as the jaws move apart and downwardly, pulling the sheet rmly into contact with at least a portion of the surface I5b of the form I5. The ram I3 may then be operated to force the form I5 against the sheet S until the sheet has been stretched sufciently to be form-retaining and to flt closely 'over the form. Inasmuch as the stretching operation stretches the sheet beyond its yield point, there is no tendency for the sheet S to coil or spring back upon itself or to return to its initially flat shape. The sequence of operations can be varied widely depending upon the shape of the form I5 and the amount a sheet of metal must be stretched to shape it to the contour of the form. In some cases, the entire stretching operation may be conducted fby movement of the gripping elements I6 while in others sheet buckle at the uncontacted region when the ram is forced into contact with the sheet. Through a choice of the proper hydraulic circuits the action of the gripping jaws may be synchr'onized to feed the metal at a desired tension in accordance with the elevation ofthe form or die members placed on the platen of the ram in properjfeeding of the metal to and 23 of the gripping devices I6 with other jaws' of different curvature in order to correspond to the curvatures of the ends of the form. Inasmuch as ythe jaws are detachable, this change is readily made, thereby permitting the` device to be used in producing sheets of varying contour.

While the preferred form of the device has been described above, it will be understood thatthe device is susceptible to considerable modification without departing from the invention. For example, the actuating means for the jaws 22 and 23 and the gripping memlbers I6, as a whole, may be any equivalent of the hydraulic rams disclosed, such as, for example, electrically operated jacks or the like. Additional adjustments may be provided for the clamping and stretching devices, for example, the levers II and I8 may be made extensible in order to adjust the ends of the sheets with relation to the ends of the form. l The base member need not be a unitary construction, but may be made up of a plurality of parts mounted upon a suitable foundation, as maybe desired and the entire device may be inverted, if desired.

Therefore, the form of the invention disclosed, should be considered as illustrative only, and not as limiting the scope of the following claims.

We claim:

l. An apparatus for shaping sheets of metal into transversely and longitudinally curved form comprising a base member, a form having a convex surface supported adjacent to said base memfrom said base member, a pair of levers at each end of said form, means pivotally connecting the lower ends of said levers to said base member, a pair of pivotally connected jaw members supported at the upper ends of each pair of levers for gripping an edge portion of a sheet of metal, said jaw members being complementally curved to conform substantially to the curvature of the ends of said form adjacent thereto, and means for rocking said pairs of levers about said pivot means for moving each pair of jaw members relatively tosaid form to stretch said sheet over said form and into engagement with said convex surface.

2.An apparatus for shaping sheets of `metal into transversely and longitudinally curved form comprising a base member, a form having a con- A vex surface supported adjacent to said base member. means for moving said form toward and away ber, a hydraulic ram supportingl said form forv movement toward and away from said base member, a pair of pivotally connected jaw members adjacent opposite ends of said form for gripping an dge portion of a sheet of metal, said jaw..A

members being complementally curved to conform substantially to the curvature of the ends of saidform adjacent thereto, arms pivotally mounted on said base member and extending upward therefrom above said form, said jaw members bef ing carried by said arms and pivotally movable with respect thereto on movement of said arms, and means connected to said base and arms for moving said arms in lopposite directions outwardly and downwardly with respect to said form whereby said jaw members are moved relative to` said form to stretch said sheet over said form and into engagement with said convex surface.

BASIL LERMONT.l ARNOLD M. WOLF.

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