GB889529A - Pressure sensitive valve apparatus and hydraulic systems embodying such apparatus - Google Patents

Abstract

889,529. Valves. H.M.L. (ENGINEERING) Ltd. June 18, 1958 [April 10, 1957], No. 11777/57. Class 135. Pressure-sensitive valve apparatus comprises a pilot valve device 1 of the piston-type loaded in one direction by a spring 23 and including a part 18 having a piston face subject to the pressure in a reference pressure chamber 15 opposing the spring, the pilot valve controlling communication between this chamber and pressure supply and relief ports 12, 10 respectively so as to maintain a constant pressure in the chamber, and a main valve device 2 of the piston-type having opposed pistons 28, 31, subject respectively to the pressure in the reference pressure chamber 15 and to a pressure supplied to a loading port 38 from a passage or conduit 47 the pressure in which is controlled by the main valve member 28, so that it is maintained in a predetermined relationship to the reference pressure in chamber 15. The conduit 47 constitutes a common delivery line of a number of hydraulic pumps 39-42 which feed this line through check valves 43-46, over-pressure in the line 47 being controlled by successive by-passing of the flows from the individual pumps, whose deliveries are connected also to successive inlet ports 33-36 of the main valve 2 and are relieved into a common return port 33a.