GB258790A - Improvements in and relating to presses for drawing sheet metal - Google Patents

Abstract

258,790. Fitzpatrick, H. D., (Marquette Tool & Manufacturing Co. March 9, 1926. Cupping.-A press for drawing sheet metal is provided with means for applying a constant pressure to the draw-ring during the drawing operation, and for preventing backlash on the release of this pressure at the end of the stroke. The draw-ring 15 is supported by pins 16 resting on a pressure-pad 17 carried by a spring 27 mounted on a ring 26 which is adjustably supported on a plate 23 by a nut 25. The plate 23 is supported by a spring 2 carried by a plate 21 which is supported by fixed hangers 43. A fixed piston 30 works within a cylinder 29 carried by a rod 18 passing loosely through the plate 21. The upper end of the cylinder 29 is constantly open to the atmosphere by way of a port 18<a>, the lower end of the cylinder communicating with a valvebox 34 by connections 35, 38, Fig. 3, fiuid-pressure being admitted to the valve-box through a pipe 32, Fig. 1. On the drawing stroke of the press the spring 27 is first compressed to a given extent after which drawing proceeds with a constant pressure on the blank-holder, due to the thrust pins 28. A charge of fluid under pressure is thereby admitted to the cylinder 29, this charge being slowly expelled on the return of the upper die, thus preventing a violent return of the blankholder. A number of such cushioning devices may be fitted.