US2861531A - Hydraulic forming attachment for presses - Google Patents

Description

Nov. 25, 1958 OL R 2,861,531

HYDRAULIC FORMING ATTACHMENT FOR PRESSES Filed July 10, 1956 2 Sheets-Sheet 1 Nov. 25, 1958 H, MQLLER 2,861,531

' HYDRAULIC FORMING ATTACHMENT FOR PRESSES Filed July 10, 1956 2 Sheets-Sheet 2 d mdw /zw Unite States HYDRAULIC FORMING ATTACHMENT FOR PRESSES F Hugo Miiller, Trollhattan, Sweden, assignor to Svenska iaeroplan Aktiebolaget, Linkoping, Sweden, 21 corporatron of Sweden Application July 10, 1956, Serial No, 596,992 3 Claims. c1. 113-44 This invention relates to the art of forming sheet metal blanks into a wide variety of dished or cupped objects by means of hydraulic pressure applied to the blank through an elastic wall, and it is thus closely related to the invention disclosed in the copending application of Hugo Moller, Serial No. 473,926, filed December 8, 1954, now Patent No. 2,761,405.

Presses especially designed to utilize this method of shaping and forming sheet metal blanks are not new to the art, but a press specifically designed for this purpose is not only expensive, but limited in its use.

As in the aforesaid copending application of Hugo Mtiller, it is a primary object of this invention, therefore, to provide a device which may be readily installed in a conventional press to convert the same to the forming of sheet metal blanks by hydraulic pressure applied to the blank through an elastic or conformable Wall.

In the device of the aforesaid copending application, the elastic wall was positioned across the mouth of a bore opening to the bottom of a body member, overlying the die cavity in which the blank was to be formed. Hydraulic pressure was exerted on a blank placed in the die through said elastic wall by the descent of a plunger in the body bore as a consequence of closure of the press. According to the aforesaid copending application, however, the plunger was forced downwardly by the press into a liquid filled receptacle defined jointly by the bottom of the plunger itself, the wall of the bore inwardly of the mouth thereof, and the elastic wall closing the mouth of the bore.

With this construction, the operativeness of the device depended to a large degree upon the provision of exceptionally good fluid-tight seals between the plunger and the wall of the bore in which it reciprocated, and also between the elastic wall and the wall of the bore in the body member. Obviously, the provision of highly effective sealing means in a device of the character described was not only expensive, but the presence of such seals represented a potential source of trouble.

It is a purpose of the present invention, therefore, to provide a device of the character described wherein hydraulic forming pressure is applied to a blank in a die cavity as a consequence of descent of a plunger during closure of the press, but wherein the plunger acts upon a liquid-filled entirely closed sack, an exposed bottom wall of which bears against the blank to exert formingvpressure thereon. The provision of a closed elastic liquid-filled sack in a device of the character described is highly advantageous since it obviates the need for employing complicated and troublesome seals between the plunger and the wall of the bore in which it operates, and between the wall of the bore in the body member and the conformable or elastic wall across the mouth thereof.

More specifically, it is a purpose of this invention to provide a device of the character described incorporating a closed liquid-filled elastic sack which is adapted to be acted upon by a plunger as a consequence of closure of apron, and wherein the sack is-mountecl in the bore of 2,861,531 Patented Nov. 25, ,9 3

Still another purpose of this invention resides in the provision of a device of the character described which incorporates a liquid-filled elastic sack having a removable closure, and wherein the plunger cooperates with the closure for the sack during the pressure stroke of the plunger to effect sealing of the sack with an effectiveness which increases in proportion to the increase in the pressure of liquid in the sack.

In this respect, it is a more specific purpose of this invention to provide a device of the character described wherein the plunger has a well in its bottom of a size and depth to receive a filler neck on the top wall of the sack when the plunger descends onto the sack, and wherein the closure for the sack has a tubular shank portion fitting in said neck to be expanded by the pressure of liquid in the sack in the power stroke of the plunger to effect sealing of the neck with a fluid tight joint which increases in effectiveness in proportion to the increase in the pressure of liquid in the sack.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel method and construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a perspective view partly in section, illustrating the device of this invention mounted in a conventional doubleacting press, the press being shown open; and

Figure 2 is a view similar to Figure l, but illustrating the position of the parts when the press is closed.

Referring now to the accompanyingdrawings in which like reference characters have been applied to like parts in the two views, the numeral 5 designates the table of a conventional double-acting press having a pair'of press heads 6 and 7 which may be moved downwardly toward the table 5 either simultaneously or consecutively. Since the press head operating means forms no part of this invention, it has not been illustrated.

The adaptor device of this invention may be said to comprise three main components, a die holder 8, a body member 9 and a plunger 10. The die holder is adapted to seat fiatwise upon the press table 5 to which it may be adjustably anchored as by a series of dogs 11. As shown, the die holder is in the form of a ring or annulus having a flat top surface 12 parallel to the surface of the table 5, and a cylindrical bore 13 to receive a die 14.

The die, of course, may be held by the die holder 8 in any desired position beneath the press heads, and it has an annular top wall 15 which is preferably fiat and flush with the top wall 12 of the die holder. The cavity 16in the die opens upwardly at the top of the die, inwardly of its annular top wall 15.

The body member 9 of the adaptor device of this invention is readily removably secured to the underside of the outer press head 6, directly over the die holder, by a series of screws 18 spaced from one another around the edge of a hole 19 in the bottom of the head 6. The main portion of the body member 9 comprises a cylindrical block of metal having an upwardly facingannular shoul- 4 der 21 engaging the underside'of the outer'press 'head'6 around the edge of the hole 19 therein, and into which the screws 18 are threaded soas to securely'hold the body member in position upon the outer press head. The body member also has a flat bottom face 22 parallel to the shoulder 21 and of a size to overlie the top surfaces 12 and of the die holder and the die 14therein.

At its upper portion, the body member 9 has a coaxial neck 24 of reduced diameter which projects upwardly through the hole 19 in the bottom of the press head, in spaced concentric relation thereto, and a vertical bore 25 extends axially through the neck and into the larger diameter lower portion of the body 9 to communicate with a counterbore 26 in the lower portion of the body member. The counterbore 26 opens tothe underside of the body member and provides a compartment in the lower end portion of the body member in which the closed liquid-filled elastic sack 27 of this invention is mounted.

The elastic sack 27 is preferably made of substantially heavy rubber although it will be understood that any other material having the flexible and elastic characteristics of rubber may be employed. As seen best in Figure 1, the sack has a substantially flat circular bottom wall 28, a cylindrical side Wall 29 integrally joined to the peripheral portion of the bottom wall and a substantially flat top wall 30 integrally joined at its periphery with the upper end of the side wall. Projecting upwardly from the center of'the top wall and integral therewith is a tubular neck 31 closed by a removable plug 32, and which provides for filling the sack with liquid 33.

As will appear at greater length hereinafter, the plug 32 has a disc-like top portion 34 which overlies the upper end of the neck 31 and a tubular shank portion 35 which is received within the neck 31 with a snug lit and opens to the interior of the sack. The lower end of the shank portion of the plug is preferably provided with an outwardly directed annular flange 36 which engages under the top wall 30 at its junction with the neck. It is important to note that the plug 32 is likewise made of a resilient or elastic material such as rubber.

As seen best in Figure 1, the cylindrical side wall 27 of the sack has a diameter to snugly fit the wall of the counterbore 26, and the length of the sack is such that its top wall 30 seats against the downwardly facing shoulder 38 provided by the bottom of the counterbore 26 in the body member, while the bottom wall 28 of the sack extends across the mouth of the counterbore to normally lie in a plane either flush with the underside of the body member or spaced slightly above its underside.

The sack is removably retained in the counterbore 26 by means of a circumferential bead 40 on its side wall, intermediate the axial ends of the sack, snugly received in and fitting a circumferential groove 41 in the wall of the counterbore.

The plunger 10 preferably, though not necessarily, has a close sliding fit in the bore 25 in the body member. It projects upwardly through the hole 19 in the underside of the press head 6 and is normally supported in an elevated position on the body member by means of a helical spring 43 loosely encircling the neck 24 on the upper end of the body member and confined axially between the upwardly facing shoulder 21 on the body member and an enlarged head 44 on the upper end of the plunger. The spring 43 thus levitates the plunger so that when the press is open the liquid-filled sack 27 is relieved of the weight of the plunger. In this position of theparts, the enlarged head 44 on the top of the plunger is also spaced somewhat from the bottom of the inner press head or ram 7.

As seen best in Figure 1, the lower end of the plunger 10 has a downwardly opening well 46 formed therein of a diameter to freely slidingly receive the neck 31 and the plug therein upon descent of the plunger. The depth of the well 46 is also substantially equal to the height of the neck 31 plus the head of the plug therein so that when the plunger is forced downwardly by the inner press head 7, the plugged neck of the liquid-filled sack will engage the bottom of the well 46 in the plunger substantially at the same time that the portions of the plunger surrounding the well engage the top wall 30 of the liquidfilled sack.

Although Figure I shows the plunger fully disengaged from the neck 31 and spaced a substantial distance above the topwall 30 of the liquid filled sack, these parts have been so illustrated merely for the sake of clarity. In actual practice the plunger does not leave the top wall of the sack when the press opens, so that there is no problem of air pockets between the plunger and the sack, and no need for venting such pockets, which would be the case if the spring 43 lifted the plunger entirely off of the liquid filled sack.

With the construction described, it will be seen that whenever downward pressure is exerted upon the top wall 30 of the liquid-filled sack by the plunger during closure of the press in the manner illustrated in Figure 2, the increasing pressure of liquid in the sack is manifested in the hollow shank portion 35 of the plug 32 so as to tend to radially expand the shank portion of the plug and thus tightly engage its outer surface with the inner surface of the neck 31 on the sack. At the same time, the neck 31 is tightly clamped between the shank portion of the plug and the wall of the well in the underside of the plunger. In this way, the elastic sack is closed by a seal, the effectiveness of which increases in proportion to the build-up of pressure of liquid in the sack as the plunger descends during closure of the press.

It will also be observed that rubbing friction between the sack and the walls of the chamber in the lower portion of the body member is substantially eliminated with the result that there is practically no wear upon the sack itself at its areas which lie contiguous to the body member. Only the lower end portion or face of the plunger contacts that portion of the top wall 30 of the sack which lies between the centrally disposed neck 31 and the bore 25 in which the plunger operates, and during the descent of the plunger, while it is possible that the top wall of the sack may be deformed around the exterior of the lower end of the plunger, such deformation takes place with a folding in action practically entirely without rubbing friction.

' If the bottom wall 28 of the elastic sack is spaced a slight distance above the bottom 22 of the body member, as shown, the slight space which results may be employed to accommodate a wear disc 48 of rubber or other similar elastic material, it being understood that the wear disc is of a size to overlie the entire underside of the bottom wall 28 of the sack. The wear disc may be removably secured in position flatwise engaging the underside of the bottom wall 28 on the sack as by having its peripheral edge portions snapped into a circumferential groove 49 in the bottom portion of the body member directly adjacent to the mouth of the counterbore 26 therein.

Except for the fact that the bottom of the plunger 10 bears directly upon a closed liquid-filled sack in the compartment provided by the counterbore 26 in the bottom portion of the body member, the operation of the adaptor device of this invention is substantially the same as that in the aforesaid copending application of Hugo Mtiller, Serial No. 473,926, filed December 8, 1954, now Patent No. 2,761,405. Assuming that the parts have been set up in the manner described and that the press is open, the body member 9 will occupy a raised position a substantial distance above the top of the die holder and the die 14 therein. With the press open, the metal blank to be formed in the die is placed on top of the die with its upper portions resting upon the flat upper face 12 of the die holder. Thereafter, an annular pres sure plate or washer S1 is laid on top of those portions of the blank which overlie the upper faces 12 and 15 of the die holder 8 and die 14, respectively. This plate or washer may be formed of a suitable hard Wood or other similar material, and its central aperture is preferably slightly larger than the mouth of the cavity 16 in the die. If desired, a second wear disc 48' similar to the wear disc 48 but of a size to be received in the central hole of the pressure plate 51, may be placed upon the blank inside the plate 51. Such a second disk 48' is especially useful where the depth of the cavity to be formed is deeper than it is practicable to form in one operation, in which event the disk 48 is of a size to fill the cavity in the blank resulting from the first pressing operation. This avoids unnecessary strain upon the wear disk 48 and the sack 27 and, of course, eliminates possible entrapment of air during the second pressing operation.

With the parts thus positioned, the outer press head 6 may then be lowered to bring the underside 22 of the body member down onto the pressure plate 51 to effect clamping of the blank between it and the top of the die and die holder, with a force sufficient to prevent wrinkling of the blank as it is drawn inward during the forming operation. While the outer press head 6 is maintained in its lowered position thus exerting clamping pressure upon the work, the inner press head or ram 7 is lowered to force the plunger 10 down onto the top wall 30 of the liquid-filled flexible sack 27. As will be readily apparent, the closure of the inner press head 7 and resulting descent of the plunger 10 upon the liquid-filled sack acts hydraulically on and through the elastic bottom wall 28 of the sack and the wear discs 48 and 48' underlying the same to cause them to exert downward pressure on the blank, to thus force it into the die cavity and deform the blank to the shape of the cavity.

After the forming operation, the press is opened and the formed part may be quickly dislodged from the die by air pressure acting against the underside of the deformed part. For this purpose, both the die and the die holder are provided with radial passages 53 and 54, respectively, which register with one another. The inner passage 53 in the die communicates with a small diameter bore 55 opening upwardly into the die cavity 16, while the outer passage 54 in the die holder is connectible with an air supply line 56 by which air under pressure may be introduced into the die cavity beneath the deformed part therein after the pressing operation.

From the foregoing description, taken together with the accompanying drawings, it will be readily apparent to those skilled in the art that this invention provides an improved, but simple and highly effective device for quickly and easily adapting any ordinary press to the formation of sheet metal blanks by means of hydraulic pressure acting through an elastic or conformable wall, which elastic wall is formed as part of a closed liquidfilled sack and thus requires no complicated or costly sealing means for the plunger as was previously required in devices of this type.

What is claimed as my invention is:

1. In a device of the type wherein pressure is exerted upon a blank to form the same in a die upon which the blank is supported as a consequence of pressure produced downward motion of a plunger toward the blank: a body member having a vertical bore therethrough, the upper portion of which is smaller in diameter than its lower portion to provide a cylinder, the plunger being reciprocably mounted in said cylinder to enter the larger diameter lower portion of the bore as it descends; an elastic, liquid-filled sack mounted in the larger diameter lower portion of the bore so as to be interposed between the bottom of the plunger and the blank to be formed, said sack having a top wall larger in diameter than the cylinder and having a bottom wall extending across the mouth of the bore and through which the pressure resulting from descent of the plunger upon the sack is hydraulically applied to a blank in place beneath the sack, said sack being imperforate except for a tubular neck which extends from its top Wall toward the plunger, in spaced concentric relation to the wall of the cylinder, said neck providing an inlet for the sack; a plug closing said sack inlet, said plug having a tubular shank portion of elastic material fitting in said neck with its exterior surface in intimate engagement with the inner wall surfaces of the neck, the interior of said tubular neck being in open communication with the interior of the sack so that said shank portion tends to expand in the neck as a consequence of the rise in pressure in the sack which results from the exertion of blank forming pressure on the blank by the sack; and said plunger having a well in its underside of a size and shape to accommodate the neck and its plug when the plunger descends upon the sack so as to prevent expansion of the neck under the expansive force exerted thereon by the shank portion of the plug and to assure seal ing of the neck by the plug with a force which increases in proportion to the build up in liquid pressure in the sack.

2. The device set forth in claim 1, wherein said plug has a disc at its upper end engaging over the upper end of the neck on the sack, and has an outwardly directed annular flange on the inner end of its shank portion which engages under the lower end of the neck at the junction of the latter with the sack to prevent accidental displacement of the plug from the neck.

3. In a device for shaping a sheet metal block to the configuration of a die by forcing the blank into the die by means of hydraulic pressure applied to the blank through an elastic wall: a body member having a vertical bore in its upper portion to provide a cylinder and having a counterbore in its lower portion connecting with the cylinder and opening to the bottom of the body, the junction between the bore and the counterbore forming an abrupt downwardly facing surface; a plunger reciprocable in the cylinder and adapted upon descent thereof to enter the counterbore; an elastic liquid filled closed sack in and substantially filling the counterbore, said sack having a cylindrical side wall snugly engaging the side of the counterbore, a bottom wall which extends across the mouth of the counterbore to bear against the blank to be shaped, and a top wall which in the free condition of the sack has its peripheral portion bearing against said downwardly facing surface which forms the junction between the cylinder and the counter bore while its medial portion extends across the bottom of the cylinder to have the underside of the plunger engage the same and apply pressure thereon as the plunger descends into the counterbore; and interengaging means on the side wall of the sack and the side of the counterbore to constrain the sack against sliding axially in the counterbore.

References Cited in the file of this patent UNITED STATES PATENTS 731,367 Huber June 16, 1903

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