GB540596A - Improvements in or relating to fluid-pressure relief valves - Google Patents

Abstract

540,596. Relief valves. COSTA, H. DA., and PLESSEY CO., Ltd. Sept. 11, 1940, No. 25596/39. [Class 135] A relief valve particularly adapted for use with cartridge-operated starters for internal combustion engines has a piston-actuated main valve controlled by a pilot valve which is spring-loaded to the maximum required pressure and when opened is maintained open by a lower pressure. The main valve 14 which is housed in a strainer 16 formed by a slotted extension on a removable cover 15 is rigidly secured to a hollow piston 19 housing a spring 21 bearing against a washer 22 supported by a shoulder on the casing. The pilot valve 29 co-operates with a removable seat 26 having a slotted extension 27 to form a strainer and is loaded by a spring 34 arranged between an adjustable abutment 35 and a washer 33 resting on a shoulder in the pilot valve spindle. An actuating piston 30 has an inturned flange 37 movable with slight lost-motion between the valve head and the washer so that after a slight initial opening of the pilot valve the pressure transmitted through a passage 24 to the main actuating chamber acts on the piston to move the pilot valve rapidly to its full open position and maintain it open until the pressure has dropped to a predetermined minimum. When the pilot valve closes pressure in the main actuating chamber escapes through a vent 40. The washer 30 is provided with a spring ring 38 to hold the piston in contact with the washer during the return movement of the pilot valve.