GB783927A - Improvements relating to pilot valves - Google Patents

Abstract

783,927. Fluid-pressure servomotor-control systems. BRISTOL CO. Aug. 23, 1955 [Aug. 24, 1954], No. 24222/55. Class 135. A pilot valve for controlling pressure fluid flow to a controlled element, e.g. a pneumatic control device 14 in response to flow variations of a relatively small fluid flow initiated by independent control means comprises a body 18 having an inlet coupled to a pressure fluid source at 16, an outlet coupled at 17 to the controlled element and two spaced valve seats, one in the inlet and the other 24 on the side of the outlet away from the inlet, an elongated restriction tube 30 extending between the seats and through the inlet to carry an inlet valve plug 32, an element, e.g. a piston 31, connected to the tube for forming a variable-volume chamber 19 having an orifice 27 and open to the tube 30, and seating as a valve at 24 to allow pressure fluid to flow past valve 32 to outlet 17 or, when valve 32 is seated and the piston unseated, to exhaust fluid from 17 via an opening 25. The movement of the piston and plug is effected by either a flapper 27 or a lever operating the stem of an internal valve controlling the orifice. A manifold air-supply block is described into which several pilot valves are screwed and which allow spring-loaded valves to seat and prevent loss of fluid-pressure when the pilot valves are removed.