GB690038A - Improvements relating to pneumatically operated valve mechanisms - Google Patents

Abstract

690,038. Valves controlled by auxiliary valves. HUGHES, Ltd., G. H. Jan. 15, 1951 [Jan. 14, 1950], No. 974/50. Class 135, A valve mechanism for controlling the supply and release of pressure fluid to pneumatically-operated apparatus is operated by a double-acting differential piston. As shown, a valve casing 5, Fig. 1, housing a spring-urged inlet valve 3 controlling the passage of air from a supply main to the operated apparatus through ports 10, 11, houses in axial alignment with the valve 3 a two-part piston 14 formed with a depending stem 14b having on its undersurface an exhaust valve 28 engageable with a seat 8a and a further reduced diameter stem 14c engagable with the stem 3a of the inlet valve 3. Chambers 16, 13 in which the piston parts 14a, 14e slide are connected by ports 18, 19 respectively, through branch lines to the supply main, a cock being interposed in the branch to the chamber 13. In operation, on the opening of a hand or pedal-actuated valve, air is supplied to ports 10, 18, whence the piston 14 moves downwardly to close the exhaust valve 28 and open the inlet valve 3 to supply air to the apparatus. On completion of the operation, the cock in the branch to the chamber 13 is opened to admit air beneath the larger face of the piston 14 which then moves upwardly to open the exhaust valve and permit the closure of the inlet valve by its spring 9. In a modification, the exhaust valve 28 is resiliently connected to the piston 14 by a spring 29, Fig. 2, to provide a time lag between the closing of the exhaust valve and the opening of the inlet valve. A further two-part piston 22 is provided formed on its lower surface with a valve controlling a port 24 to the chamber 16. Ports 27, 31 connect the upper and lower surfaces of this piston 22 through branch lines to the lines connecting the port 11 to the operated apparatus and the port 10 to the supply main respectively. A further branch having a cock interposed therein connects the port 19 to the operated apparatus. The purpose of the second piston is to trap air in the chamber 16 and hold the valve 3 off its seat even though the supply of air to the port 31 may be stopped.