GB517467A - Improvements in and relating to hydraulic piston valves - Google Patents

Abstract

517,467. Valves. TOWLER, J. M., and TOWLER, F. H. July 20, 1938, No. 21499. [Class 135] A hydraulic control valve comprises a piston valve 2, Fig. 1, sliding in a casing 1, which is provided with a central chamber 4 in connection with a continuously acting pump, and with outer chambers 3, 5 for delivering to hydraulic apparatus. Ports 18 lead from the chamber 4 to the hollow interior of the piston, from which pressure liquid can pass through non-return valves 17 at either end of the piston, and through ports 19 to one or other of the chambers 3, 5 leading to the hydraulic cylinder or cylinders. The valve has reduced parts 11 at its ends, past which the pressure liquid can escape to exhaust. When the valve is in the central position, both of the outer chambers 3, 5 are open to exhaust. When the piston is moved through half its stroke in either direction by means of a hand-lever 20, one chamber is closed to exhaust, and the pressure escapes through one of the non-return valves and through the other chamber, which remains open to exhaust. The full stroke of the piston cuts off from pressure the chamber that is open to exhaust, so that the liquid passes through the other non- return valve to the chamber that has been closed to exhaust, and operates the cylinder connected thereto. In a modification, the valve has two sets 18, 18a, Fig. 3, of central ports, so that pressure passes directly from the pump to the actuated cylinder without passing through the non-return valve. The arrangement may be adapted for supply to single outlet chamber, the piston valve having a single non-return valve and being adapted to open to exhaust at either end.