Patent GB-1139364-A (GB)
Title: High-pressure metal forming apparatus and method
Inventor: FUCHS FRANCIS JOSEPH
IPC: B21D26/033
Filed: 1966-02-24
Abstract: 1,139,364. Stamping. WESTERN ELECTRIC CO. Inc. 24 Feb., 1966 [1 March, 1965], No. 8110/66. Heading B3Q. A high-pressure drawing-press in which a blank in a cylinder is shaped direct or through a plunger by fluid in the cylinder, comprises a piston slidable relatively to the cylinder for pressurizing the fluid, the cylinder being expanded elastioally by the fluid-pressure during the drawing operations and allowing some of the fluid to escape past the piston into an annular chamber surrounding the cylinder where it exerts an inward pressure on the cylinder counteracting the outward pressure. In one form, Fig. 1, the blank 100 is held by a screwthreaded ring 108 against a drawing die 107 in the cylinder 102 in which is slidable pistons 113, 119. Surrounding the cylinder is a segmental cylinder 126 enclosed in a housing 127 between which and a casing 129 is the annular chamber 128. Pressure-fluid escaping past a limited expansion packing 114 on the upper piston 113 passes, through a radial passage 124, into the annular chamber 128 where it applies inward pressure, intensified by the segmental cylinder, to the inner cylinder. Passages 109 in the circumference of the clamping ring 108 supply pressure-fluid to the perimeter of the blank to assist in drawing the blank into the shape of a cup 101. A valve 148 is connected to the annular chamber 128, to a cylinder driving the upper piston 113 and to a reservoir, so that when the cylinder-pressure is reduced, the annular chamber is connected to the reservoir. In another form, Fig. 4, stepped pistons 234, 241 are used which have limitedexpansion packings on the end and on the step, allowing the fluid to enter annular cylinders 237, 247 for preventing " mushrooming " of the piston-ends. Fluid passes the step-packing 239 before entering the radial passage 225 in the segmental cylinder 211. In a further form, Figs. 5 and 11, the die 604 is screwed into a holder 601, clamping the blank 100 against the holder, and a lower, annual piston 609 entering a chamber in the die supplies pressure-fluid, through passages 605, 612, radially inwardly on the blank-perimeter. Pressure-fluid in the top of the cylinder 614 acts on the blank through a plunger 617. As before, fluid escaping, past the top-piston 331, is directed to the annular chamber 317 surrounding the segmental cylinder 306. Any fluid entering the latter escapes through passages 329 in a retaining member 309. Instead of using a segmental cylinder to intensify the external pressure on the working cylinder (401), Fig. 7 (not shown), a number of nesting cylinders (413, 423, 433) may be used, assembled by screw-threading or force-fitting. The upper piston (409) has a step for each cylinder and a wear-sleeve (411, 421, 432, 438) on each step past which the fluid escapes to the next outer annular chamber (414, 424, 434) for applying inward pressure. The wear-sleeves also act as pressure-relieving valves (Fig. 9), moving away from the piston and creating passages (436). In a further multi-cylinder form (Fig. 10), the piston (514) is stationary and the working cylinder (502) is moved on to the piston. A first annular chamber (521) surrounds the cylinder, and fluid escaping downwards enters a second chamber (523) surrounding the second cylinder (512). Fluid may escape upwardly from the second chamber to a third (526) and then to a fourth (528). Fluid from the first chamber (521) is fed behind the blank 100, through passages (506).