US2737138A - Drop hammer - Google Patents

Description

nited States Patent ice DROP HAB/[MER Charles F. Derbyshire, Chuia Vista, Calif., assignor to Rohr Aircraft Corporation, Chula Vista, Calif., a corporation of California Application January 6, 1955, Serial No. 480,103 Claims.` (Cl. 113-44) This invention relates to the art of drop forging and is particularly directed to'a means for forming sheet metal in a drop hammer in which the force of the descending drop hammer ram is used to compress a mass of resilient material against a workpiece to cause the workpiece to conform to the shape of a forming die. j

In forming sheet metal in a drop hammer the forming means employed is subjected to considerable shock and stress from the speed and force with which it is brought into Contact with the workpiece by the rapidly descending ram of the hammer. Drop hammers incorporating resilient material have heretofore been considered impracticable for use for metal forming because of the difficulties encountered in constructing and mounting the forming means in a manner which would enable it to withstand the severe stresses and shock to which it is subjected.

It is therefore an object of this invention to provide a forming means for use in a drop hammer in which a mass of resilient material is compressed to a forming pressure by the force of the descending drop hammer ram which is capable of withstanding the shock and stresses set up during the forming. Another object is to provide a drop. hammer having a massive boxenclosing resilient forming material and means for supporting such box on the hammer ram in a manner which permits vthe box to continue moving down for a short time after the ram has been brought to rest at the bottom of its stroke. Y

A further object is to provide forming means as before mentioned which is adaptable for use in any conventional type drop hammer. A further object is to provide forming means as above mentioned which is of relatively simple and economical construction.

These and other objects and advantages'will become apparent as the description of the invention proceeds. For a better understanding of the invention reference is made to the accompanying drawing illustrating a preferred embodiment thereof in which: j

Fig.` l is a bottom view of the lower face of the forming means attached to the drop hammer ram;

Fig. 2 is a cross sectional view of the entire forming apparatus vmounted in a drop hammer including va Section on a reduced scale of Figfl taken on line 2-2, and

Fig. 3 is an enlarged view of a portion of Fig. 2 illustrating the manner in which the forming means is secured to the drop hammer ram.

With reference to Fig. 2 of the drawing, the forming apparatus is shown mounted in a drop hammer having a vertically movable ram positioned over a stationary anvil 11. Ram 10 comprises a horizontal face plate 12 of substantial size and weight and a centrally disposed upwardly extending vertical section 13. The ram is elevated to a position above anvil 11 from which it is permitted to drop freely to provide the force necessary to form a workpiece, by means of ropes 14 attached to vertical section 13 and extending upwardly to a winch (not shown). The ram is guided for vertical movement by two or more vertical cylindrical columns 9 along which are slidable lugs 8 attached to the ends of the ram. 'Ille 2,737,138 Patented Mar. 6, 1.956

forming means attached to the lower surface 15 of plate 12 comprises a hollow box wall 16 composed of rigid steel plates 17, 18 and 19 welded together, as indicated at 20. A rigid steel plate 21 is placed over the upper end 22 of box wall 16 forming a cavity 23. A pad 24 of rubber is disposed on the upper surface 25 of plate 21, pad 24 being of such size as to cover substantially all of surface 25. A body 26 of rubber is disposed within cavity 23 with its upper surface 27 in contact with the lower surface 28 of plate 21 and the sides 29 thereof in contact with the inner surface 30 of box wall 16. The lower surface 31 of body 26 is exposed and is positioned at a level above the lower surface 32 of plate 17 which forms the lower end of box wall 16. Pad 24 is preferably composed of rubber with a Shore durometer hardness within the range of 30 to 40 and the rubber of body 26 has a hardness within the range of 60 to 80. The outer edge of plate 17 which forms a portion of outer Wall 33 of box wall 16 is provided with outwardly extending portions 34 each of which is provided with a slot 35 for a purpose to be explained. The above described assembly is secured to ram 10 against lower surface 15 of plate 12 by means of bolts 36 which are slidably contained in vertically aligned openings 37 extending through box wall 16, plate 21, pad 24 and plate 12. VThe lower ends 38 of openings 3'7 are counterbored to receiveheads 39 of bolts 36 so that they do not project beyond the surface 32 of plate 17. The upper ends 40 of bolts 36 extend above the upper surface 41 of plate 12 a substantial distance and are screw threaded for engagement by nuts 42. n Surroundingy the shank 43 of each of bolts 36 between nuts 42 and upper surface 41 of plate 12 is a resilient member 44 which is preferably made of a rubber-like resilient material, for a purpose to be explained. Secured to .anvil 11 is a base plate 45 having an upwardly projecting pedestal 46 the upper surface 47 of which is adapted to support a forming die 48 on which the sheet metal workpiece 49 to be formed is placed. Pedestal 46, is of such size and shape to permit it to enter the lower end of cavity 23 in telescoping engagement with box wall 16. Base plate 45 is provided with vertical columns 50 adapted to enter slots 35 in sliding engagement with projecting portions 34 as ram 10 descends to accurately guide box wall 16 into telescoping engagement with pedestal 46 on base plate 45.

In using the above described forming apparatus ram 10 and the forming means attached thereto are elevated above anvil 11 to a distance sutlicient so that when ram 10 is permitted to drop its momentum will be great enough to provide the force necessary to form the workpiece. Base 45 is positioned on anvil 11 so that pedestal 46 is in alignment with cavity 23. Ram 10 is permitted to drop freely toward anvil 11 causing the lower surface 31 of resilient body 26 to forcibly contact workpiece 49 pressing it against die 48. An instant before this, columns 50 enter Vslots 35 to guide the lower end of box wall 16 into telescoping engagement with projecting pedestal 46 of base plate 45. The continued downward movement of ram 10 presses body 26 against workpiece 49 and die 4S with such force that the rubber is compressed within cavity 23 to such an extent that it iiows around workpiece 49 and die 48 and down against upper surface 47 of pedestal 46. The force with which the highly compressed rubber presses workpiece 49 against die 48 is suicient to cause the workpiece to conform to the shape of the die. The above described forming operation takes place very quickly and the rapid descent of rarn 10 is abruptly stopped by the upward pressure of the rubber 26 against the lower surface 28 of plate 21 while the lower face 32 of plate 17 is still a substantial distance above base plate 45. Due to the very large pressures set up by rubber 26 against box wall 16, the box wall must be made thick and heavy to withstand the high pressures and therefore hasgalglargegmomentum at the instant the rainllfisbrouglit to rest. To gradually decelerate the box wall and pre vent excessively large tensions from beingset upin" bolts' 36 such as would be developed if the downward movement of the box wall weremarrested instantaneously, box

wall`16 is permitted to continue its downward 'movement after ram 10 has been stopped. The box wall4 .pulls bolts bers 44 may be made in various shapes, andjsi'zes'andof various materials,lin the illustrated 'configurationVV each member consists of a pair of rubber pads 44A and 44B which surround the shank 43 of eachbolt'36 andareposi-v tioned between at metallic washers 51.' The continued downward movement of box'wall 16' after ram 10 has stopped permits its upper end 22 to` move away from lower surface 28 of plate 21 for a short distance. Topprevent the entry of any of the rubber 26 into theresultant gap, a retaining member 52, preferably shaped in cross section asfshown in the drawing and having one side 53 attached to lower surface 28 ofplate 21and its other'side 54 extending downwardly in sliding engagement with inner surface 30 of box wall 16, extends around the upper end of cavity 23. When the downward movement of'box wall 16 has stopped, the resiliency of members 44 causesfthem to return to their original shape thereby moving bolts 36 upwardly and drawing end 22 of box wall 16'back`into contact with lower surface 2i3-of plate21. Members 44 are constructed of resilient material which; offersa strong resistance to compression so as toeffectively de-- celerate and stop the downward movement of box wall 16 within a short distance, hence their returnV tof their original shape exerts a strong upwardkthrust against nuts 42 Amoving bolts 36 and box wall 16 upwardly with "con' siderable force and bringing end 22 into'forcible contact with surface 28 of plate 21. The force with which boxv wall 16 contacts plate 21 is prevented from damaging any part of the forming apparatus or drop hammer by resilient pad 24 which provides a resilient 'cushioncapable of absorbing most of the shock ofthe forciblecontact.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The presentembodiment of the invention is therefore tobe considered' as in all respects illustrative and restrictive, the scopejof'jthe invention being indicated by theapp'end'ed claims, and'all changes which come within the meaning and' range of equivalency of the claims are intended tobe embraced' therein.

Having thus described my invention, what I.claim as new and useful and desire to secure by Letters Patent is; l., In a drop hammer for forming a ductile sheet 'tojth'ev shape of a forming die disposed under the sheet; a sta-` tionary pedestal engaging the bottomof thedie; a'V ram over the die and supported for freeivertical/movement towards the die under the action of gravity; a heavy rigid boxe'wallhavi'ng alargeivertical cavity extending therethrough; a rigid plate disposed on the upper end of said box'wall 'andextending across the top ofsaid cavity, said ram, box wall and plate being provided with a plurality of spaced apart vertically aligned openings therethrough; means for suspending said box wall and plate from said ram comprising a plurality of fasteners having shanks passing upwardly through said openings, the Shanks of said fasteners slidably engaging the marginal walls of the openings in said ram; rigid members attached to the upper ends ofsaid fasteners and projecting therefrom at a sub stantial distance abovek the upper surface of said ram; resilient members of substantial thickness surrounding said fastener shanks between said rigid members and the upper surface of said ram; resilient cushioning means disposed between said rigid plate and said ram; a body of resilient flowable material disposed within said cavity, the upper surface of said body being in contact with said rigid plate and the bottom surface thereof disposed at a level above the lower end of Said box wall, the marginal wall of said pedestal being constructed to telescopically engage the lower portion of the marginal wall of said cavity when the ram is permitted to drop whereby said body of resilient ow'able material is compressed within said cavity and around said die thereby deforming the ductile sheet to the contour ofthe die.

2. A drop hammer as claimed in claiml, in which said resilient cushioning means is a pad of rubber-like material coveringrsubstantially the entire upper surface of said rigid plate.

3.' A .drop hammer as claimed in claim 1, in whichv a horizontal base'plate'in contact with the bottom of said pedestal has a plurality of spaced apart upstanding columns andsaid box wall is provided with outwardly projecting guides arranged and constructed to slidably engage said columns to guide the marginal wall of said cavity into telescopic engagement with the marginal wall of said pedestal as the ram descends.

4. A dropY hammer as claimedv in claim l, in Whch said fasteners arebolts having screw' threaded upper ends and saidrigid members projecting from the fasteners comprise knuts screwed onto said threaded upper ends and thin metal washers disposed against said nuts and the resilient members surrounding said fastener Shanks.

5. A drop hammer as claimed in claim 1, in which a rigid retaining member is secured to said rigid plate and has a vertical portion in sliding engagement with the top portion of the marginal wall of said cavity to confine said bodyY of` resilient owable material within said cavity.

References Cited in the le of this patent UNITED STATES PATENTS 682,866 Asche Sept. 17, 1901 933,010 Wilzin Aug. 31, 1909 2,263,680 Fitzgerald Nov. 25, 1941 2,415,788 Champer Feb. 1l, 1947 2,606,516 Raynes Aug. 12, 1952 FOREIGN PATENTS 502,864" Belgium May 15, 1951

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