GB676876A - Improvements in or relating to pilot-valve-controlled relief valves - Google Patents

Abstract

676,876. Fluid-pressure servomotor-control systems; fluid-actuated valves. CURRAN, J. R. April 16, 1949 [April 19, 1948], No. 10256/49. Class 135. A pilot valve controlled relief valve for a tank comprises a pair of opposed diaphragm chambers in one of which a regulated pressure is maintained by a spring control means whilst the other communicates with the tank pressure, so that if the latter exceeds the regulated pressure the diaphragms move and relieve the spring control to cause rapid movement of a member connecting the diaphragms which then operates the pilot valve to operate the relief valve. Pressure in a chamber 90 acts on a diaphragm 13 connected by a shaft 18 to a diaphragm 12 acted on by air pressure supplied through the conduit 80 and pressure regulating valve 53 to maintain a pressure behind the diaphragm 12 equal to the pressure at which the chamber 90 is to be relieved. Excessive pressure in chamber 90 moves the diaphragm 13 and shaft 18 downwards so that a lever 63, pivoted to the shaft at 65 and to the valve casing through a link at 62, relieves the force of adjustable springs 37, 38 acting on a diaphragm 29 of a pressure relief valve 33, 52 seating on the regulating valve. The pressure behind the diaphragm 12 is thus relieved so that the shaft 18 moves more quickly downwards and a spring- loaded abutment 67 carried by the lever 63 moves a pilot valve 70 to close the air supply conduit 86 leading to a diaphragm chamber 85 and open the chamber to atmosphere to allow the spring 88 to open the valve 89 and relieve the pressure in chamber 90.