US3113607A

US3113607A - Prestretch forming fixture for drawing die press

Info

Publication number: US3113607A
Application number: US76806A
Authority: US
Inventors: Paul F Maize
Original assignee: Cyril Bath Co
Current assignee: Cyril Bath Co
Priority date: 1960-12-19
Filing date: 1960-12-19
Publication date: 1963-12-10
Anticipated expiration: 1980-12-10
Also published as: ES273061A1; LU40983A1; BE611641A; CH382095A

Description

Dec. 10, 1963 P. F. MAIZE 3, 07

PRESTRETCH FORMING FIXTURE FOR DRAWING DIE PRESS Filed Dec. 19. 1960 5 Sheets-Sheet 1 PAUL /T MA/ZE BY r y Dec. 10, 1963 P. F. MAlZE I 3,113,607

PRESTRETCH FORMING FIXTURE FOR DRAWING DIE PRESS Filed Dec. 19, 1960 5 Sheets-Sheet 2 PAUL M/I/ZE BY W ATTORNEY Dec. 10, 1963 P. F.

MAIZE

3, 7

PRESTRETCH FORMING FIXTURE FOR DRAWING DIE PRESS Filed Dec. 19. 1960 s Sheets-Sheet s Fzy J? PAUL FT MA /Z 4 rme/vi K P. F. MAIZE Dec. 10, 1963 PRESTRETCH FORMING FIXTURE FOR DRAWING DIE PRESS Filed Dec. 19, 1960 5 Sheets-Sheet 4 INVENTOR. PAUL MA/ZE Dec. 10, 1963 P. F. MAIZE 3,113,607

PRESTRETCH FORMING FIXTURE FOR DRAWING DIE PRESS Filed Dec. 19,' 1960 5 Sheets-Sheet 5 INVENTOR. PA UL E M/l/ZE BY q w- ATTOE/VEK Unite This invention relates to a prestretch die drawing fixture for drawing die presses by which sheet and strip metal stock can be prestretched by tensioning it into a range above its elastic limit while it is disposed between the open drawing dies of the press and, while it is held prestretched under tension by the fixture, drawn to the shape of the die cavity by closure of the drawing dies by the press, in accordance with the inventions of Cyril 3'. Bath, disclosed in 11.8. Patent No. 2,961,028, issued November 22, 1969, and entitled Method and Apparatus for Combined Stretch and Die Forming of Metal Stock.

More specifically, the present invention relates to a fixture which may be used in conventional drawing die presses for performing some of the methods described in said above patent.

As therein more fully described, many advantages are obtained by preconditioning metal stock preparatory to drawing it in dies by placing it under tension in a range above its elastic limit unidirnensionally and, while it is so tensioned, forming it by drawing it in forming dies while leaving the lateral margins which extend along the diniension being tensioned free to be pulled into the dies transversely of their length during the die drawing operation.

A number of the advantages described in the above identified patent can be obtained by mounting the present fixture on the die bed of a conventional drawing die press.

Another advantage obtainable by the method and apparatus of the prior patent and obtainable by the present fixture, is the elimination of expensive and bulky holddown devices for the two margins of the stock which are not gripped by the tensioning means, with a consequent large saving in the amount of stock required to form an article.

Additional advantages reside in the fact that less expensive drawing dies can be used when the die drawing is combined with the present fixture, inasmuch as the unit pressure required for drawing of the stock while it is tensioned in a range above its elastic limit and in the absence of the usual marginal hold-down devices is much less than that required in conventional press drawing.

Various specific objects of the invention will become apparent from the following description wherein reference is made to the drawings, in which:

FIG. 1 is an isometric view of a conventional press with drawing dies and the fixture of the present invention installed therein;

FIG. 2 is an enlarged top plan view of the fixture, part thereof being shown in section for clearness in illustration;

FIG. 3 is a vertical cross sectional view taken on the lines 33 in FIG. 2;

PEG. 4 is a fragmentary front elevation, partly in vertical longitudinal section, showing the relation of the parts of the structure when the dies are in closed posiion, and taken as indicated by the line 4-4 in FIG. 2; and

FIG. 5 is a fragmentary front elevation similar to H6. 4-, showing the structure when the dies are in open position.

Referring to the drawings, the press comprises a conventional frame 1 having a bed 2 and a power driven ram 3 which is guided by the upright frame members 4 for cooperation with the bed. A conventional drawing die 5 is mounted on the ram and a complementary drawing die 6 is mounted on the bed 2. Also, conventional die States Patent 0 3,,ll3,67 Patented Dec. ll), 1963 cushions 7, with plates 7a, are mounted in the press beneath the bed 2 and are yieldably urged upwardly by a suitable resilient pressure means, such as the piston and cylinder assemblages 8 to which air under pressure is supplied from a suitable source, such as a compressed air tank 9. The press described is a conventional type of die drawing press and is readily available on the market.

As mentioned in the objects, it is desirable to provide a fixture by which a stock can be stretched into a range above its elastic limit while disposed between the dies while the dies are in open position. For this purpose, fixtures indicated generally at it), and with which the present invention are particularly concerned, are provided.

For convenience in description, the press is described as one which is upright and in which the ram '3 moves vertically toward and away from a horizontal upwardly facing bed 2. The words vertically and horizontally and the like, as used in describing certain parts, are merely for convenience in showing the positions of the parts relative to each other. Such words are not used in their absolute sense as, obviously, the press with the fixtures thereon could be disposed on its side without changing the functioning essentially.

Referring specifically to the fixtures 10, two such fixtures are provided. These fixtures are secured in fixed position on the bed 2, one at one end of the die 6 and the other at the other end. Since the fixtures are the same in form and function, one only will be described in detail. it is to be noted, however, that with two fixtures, one can be used to grip one end of the stock for applying tension thereto while the other grips the other end of the stock and is locked so as to hold the end it grips in fixed position in the tensioning dimension. On the other hand, if desired, both of the devices may be operated to apply tension to the stock by concurrently operating their tensioning means. Whether both are used concurrently for applying tension, or one is used as a holding means while the other is operated to apply tension, depends upon the particular type of work being done and the shape of the dies 5 and 6.

It is desirable to place the stock under tension preparatory to its engagement by the dies 5 and 6, and for this purpose the tensioning means must be arranged at a particular level, usually above the upper face of the die 6 so that the stock is free from contact with either die, but disposed therebetween, while being tensioned.

For this purpose, each fixture 10 comprises a rigid frame 11 which is adapted to be mounted in fixed position on the bed of the press. Mounted in the frame 11 for ver tical reciprocation is an elevator 12 comprising an upper frame member -13 and a bottom frame member 14 with suitable side members l5 disposed therebetween and permanently secured thereto and binding them together. The elevator 7.2 is adapted to be lifted and lowered relative to the frame 11 and bed 2. For this purpose, it is provided along its sides with suitable wear pads 15 which are connected to the side members 15 and bear against slide surfaces on the inner side faces of the frames 11.

The frames ll, at their ends, have inwardly directed rigid portions 17 which are adapted to engage the ends of the elevator 12 near their sides so as to constrain the frame 12- in fixed position endwise of the frame 11 and in a direction toward and away from the dies. Suitable Wear pads 18 are provided on the portions 17 of the stationary frame and corresponding 'wear pads l? are provided on the ends of the elevator 12. By virtue of these frame portions 17, the wear pads 18 and 19, and the lateral inner surfaces of the frame ll engaging the wear pads 16, the elevator is guided for lineal movement in a generally upright path while constrained from movement laterally or endwise.

The elevator is adapted to be supported for vertical movement by the stationary frame 11 on the die bed in a position to be engaged by suitable lift rods which extend through conventional openings in the bed 2. Beneath the bed, the lift rods engage the upper faces of the plates 7a which are supported yieldably by the piston and cylinder assemblages of the die cushions '7, heretofore mentioned.

This arrangement provides a die cushioning means which is a resilient means and acts through the rod 28 for yieldably holding the elevator in predetermined raise position above the bed 2.

Mounted on the ram 3 for movement therewith are pusher posts 21 which are adapted to engage the upper member 13 of the elevator 12 and push the elevator downwardly against the yieldable resistance of the die cushioning means as the ram descends on its forming stroke. The pusher posts 21 preferably are in the form of rigid sleeves Z2 fixedly mounted on plates 23 which, in turn, are xedly secured on the ram or die by suitable bolts 24. Rods 25 are mounted in the sleeves 22 in telescopic relation and for adjustment endwise therein. Preferably, adjustment is provided by complementary threads on the interior of the sleeves and on the exterior of the rods 25, with a suitable lock nut as for locking the rods 2-5 in the adjusted position.

By virtue of this adjustment, the elevator can be moved downwardly in a preselected relation to the closure of the dies.

Mounted on the elevator l2. are tensioning means for applying tension to the stock. The tensioning means include gripping heads arranged in a row and transversely of the elevator and mounted thereon for movement in a direction toward and away from the dies in a generally horizontal path transversely of the path of the ram.

In the form illustrated, the heads are mounted on a slide frame or carriage 3t? havins a top frame portion 31 and a lower frame portion 3 2. The top frame portion comprises a bottom plate 33 and a top plate 34 with suitable upright tie plates 35 disposed thereoetween and permanently fixed thereto. This divides the top portion into a plurality of open end compartments 36 in each of which is mounted a suitable gripping head.

Each gripping head comprises a lower jaw 38 rigid with the bottom plate 33, an upper movable jaw 39 connected to the upper plate 34 so as to swing toward and away from the die. A suitable connection is provided by means of a ball and socket joint, including a ball 4t? engaged in a socket 41 in the upper frame member. The jaws have cooperating gripping =faces 42 and 43 so arranged that when the jaw 39 is moved toward the dies, the metal stock, indicated at S, can be gripped at its margin therebetween. Preferably, the jaws are one set of jaws common to the entire row of heads, but they may be separate sets of jaws for each ead, if desired.

in order to operate the jaws for opening and closing them, the movable jaw 39 is connected to a suitable piston and cylinder assemblage by means of a clevis secured to a rod 45 of a piston 47' which is reciprocable in a cylinder which may be operated by an air or hydraulic pressure in a conventional manner under the control of a suitable reversing valve. if desired, the cylinder may be of the spring returned type. The cylinder 48 is connected to a suitable bracket &9 by means of a horizontal pivot 5t and the bracket '49 is connected to the plate or member 3i? in fixed position thereon. The lower portion 32 of the carriage comprises a plate 53 from which is suspended a solid metal body member 54. The body member is provided with a plurality of cylinder bores 55' arranged in a row parallel to the gripping jaws and with their antes extending generally horizontally toward and away from the dies, or the mid-portion of the bed 2.

Mounted within each cylinder 55 is a piston 56 having a piston rod 5'7 which is connected in fixed position by a suitable bolt or other means 58 to the elevator 12, as best illustrated in FIG. 4. A suitable packing gland S9 with a compression ring llis provided for sealing the cylinder 55 with a slide fit about the rod 57. A suitable packing gland 61 secured by a compression plate 62 is provided for sealing the opposite end of each cylinder 55.

For supplying pressure fluid to, and venting the cylinder at the head end of the piston, a pipe is threadedly connected to the compression plate 6.2 and, in turn, is connected to a suitable flexible hose leading through a reversing control valve to a source of fluid under pressure. The pipe 63 extends through a suitable passage 65 in the elevator for movement axially relative to the elevator.

For supplying pressure to and venting the rod end of the cylinder, a suitable pipe 66 is provided and is connected at one end to a flexible hose 67 by which it is connected, in turn, to the reversing control valve. The pipe 66 is connected to the cylinder at a position such that it is just to the left of the piston in FIG. 4, when the carriage is moved to its closest position to the die.

The piston rod 57 is made of large diameter so that only a small amount of ilui-d need be supplied to the rod end of the cylinder for clfectirn a rapid return of the carriage to starting position adjacent the die.

Pressure fluid is supplied from a suitable pump 69 driven by a motor 7% through the reversing valve '71. The reversing valve 71 may be a remote control valve, if desired. It is arranged not only to reverse the pressure but, in an intermediate position, to seal both ends of the cylinders 55 so as to lock the carriage in a fixed position in event it is desired to apply stretch forming tension to one end of the stock by one of the carriages only While using the other as a mere anchor for the other end of the stock.

With the arrangement desired, the fixtures can be mounted between the upright end frame members of the press at the ends of the dies without in any Way changing the operating mechanisms of the press and without making complicated connections between the fixture and the press operating parts. By virtue of the lift rods Ztl on the elevators, the stretch forming heads can be lifted to a position where they can grip the opposite margins of the stock at the ends of the dies while the stock is between and in spaced relation to both dies, and can apply the stretch forming tension thereto by operating the pistons so for moving either 'or both the carriages relative to the associated elevators.

In order to insure that the frames 11 retain their positions in spaced relation to each other endwise of the die, suitable connections are made therebetween. In the form illustrated, the connections include sleeves 74 rigidly secured to the stationary frames '11 and turnbuckle bolts 75 threadedly engaged with the sleeves 74, respectively, so that the frames Ii can be drawn toward or pushed away from each other and held rigidly in the position to which they have been moved.

By virtue of this connection, the stationary frames can be adjusted for a suitable distance endwise of the bed and locked in position, if desired. When so moved, the lift rods 29 are passed through different sets of holes conventionally provided in the bed 2,.

Suitable downstops 77 are mounted on the stationary frames in position to engage the underside of the elevator and limit its downward movement in a position in which the pipe 66 is clear of the bottom of the stationary frame it is apparent that with these fixtures fastened onto the bed or the press, the stock can be tensioned to the degree desired preparatory to the closure of the die. While held under the tension, the elevators can be moved downwardly in the desired relation to the downwar movement of the ram so that the die closure and position of the stretched stock can be related as desired. Thus the stock can be laid over the lower male die 6 before or during die closure. Usually, the margins gripped by the jaws or gripping heads are at a level at least as low as, and preferably somewhat below, the level of the corresponding margins of the male die when the dies begin closing. The exact position depends upon the shape of the part and is regulated by adjustment of the push rods 25.

Having thus described my invention, I claim:

A drawing press including a horizontal die bed, upright guide frame members at the ends of the bed, respectively, a power driven ram mounted on, and guided by, the guide members for reciprocation in an upright path toward and away from said bed, complementary male and female drawing dies defining, when closed, a concavo-convex pattern, one :die being mounted on the ram for movement in opposite directions thereby parallel to the closed position of the one die, and the other die being mounted in fixed position on the bed, stretch units arranged at opposite ends of the dies and said units including gripping heads, respectively, operable to engage and grip opposite margins of a length of sheet metal stock, respectively, for applying tension thereto endwise of the ram preparatory to, and during, drawing of the stock by cooperation of the dies, at least one unit comprising an elevator movable upwardly and downwardly relative to the bed, power means to move the elevator upwardly and downwardly in pre-selected relation to closure of the dies, a carriage supported on the elevator for movement relative thereto along a generally horizontal path endwise of the ram toward and away from the dies, co-actin'g means on the carriage and elevator guiding the carriage for movement relative to the elevator along said generally horizontal path, the gripping head of said one unit being mounted on the carriage for movement therewith, and a piston and cylinder assemblage means drivingly interconnecting the carriage and elevator for moving the carriage along said horizontal path relative to the elevator for applying yieldable tension to the stock for stretching the stock.

References Cited in the file of this patent UNITED STATES PATENTS