GB876274A - Improvements in and relating to hydraulically or pneumatically operated rams - Google Patents

Abstract

876,274. Hydraulic apparatus. STOTHERT & PITT Ltd. June 21, 1960 [June 30, 1959], No. 22486/59. Class 69 (2). [Also in Group XXVIII] A fluid-operated double-acting ram 1 has means for automatically controlling the acceleration and deceleration of its piston 3 comprising two pressure-relief valves 19, 20, each in communication with both sides of the piston, the valves being set so that, in whichever direction the piston may be travelling, at a predetermined pressure differential they operate to pass fluid from one side of the piston to the other. The piston is secured to a rod 8 which carries a valve housing 14 connected by passages 9, 10 in the rod 8 to opposite sides of the piston. The passages 9, 10 are interconnected by bores 17, 18 each associated with one of the relief valves 19, 20. Upon a predetermined pressure differential occurring in the chambers on opposite sides of the piston during its movement, valve 19 or 20 opens to relieve the pressure by passing fluid from the side of the piston at higher pressure to the other side of the piston. The valves are accessible externally of the apparatus for adjustment purposes. In an alternative embodiment, the valves are housed in a collar on the rod which has transverse bores interconnecting the passages 9, 10 for passing the fluid relieved by the valves 19, 20.