GB1082947A - Flow control valves - Google Patents

Abstract

1, 082, 947. Fluid-pressure servomotor systems. BRISTOL SIDDELEY ENGINES Ltd. Aug. 18, 1965 [May 21, 1964], No.21081/64. Heading G3P. [Also in Divisions F1 and F2] The supply to a turbine 10 driving a pump 11 is controlled by a flap 20 pivoted at 18 and having an extension 21 defining a chamber 25 the pressure in which is controlled by a pilot valve 26. When the pilot valve is closed, pressure is equalized across the extension via a clearance 23 around the periphery thereof, and the flap is moved to the open position by flow in the duct 12. When the pump output pressure reaches a predetermined value, it lifts ball 29 and acts on a bellows 28 to open the pilot valve, thereby reducing the pressure in chamber 25 and causing the extension to move the flap to restrict flow. The flap and extension are mass balanced but the latter is larger in area to provide aerodynamic unbalance. In Fig. 2 (not shown), the flap is upstream of its pivot point and the extension is downstream thereof. When the pilot valve is closed, the build up of pressure in chamber (25), via leakage path (35), opens the valve. To prevent shocks, an eccentric (18a) on the flap hinge progressively throttles path (35) as the valve opens. In Fig. 3 (not shown), both the flap and its extension are downstream of the pivot point, counterbalance being provided by a weighted lever (41). When the pilot valve is open, pressure in chamber (25) closes the valve. A space (42) serves to damp movement of the flap. In Fig. 3A (not shown), space (70) communicates via bore (74) with the downstream side of the flap and a space (76) is controlled by a pilot valve (82) communicating with a region of low-pressure. When the pilot valve is open, the pressure difference across extension (86) closes the valve. In Figs. 4 and 5, a pair of flaps 54a, 54b are pivoted at 53 and may be balanced by respective weighted levers. These flaps are connected at 55, 55a to further flaps 56a, 56b the free ends of which are guided in slots 58. Pilot valves 61, 64 within the chamber 60 defined by the flaps serve to vary the pressure in that chamber and are operable by any desired control device. When the pilot valves are closed, the pressure in the chamber exceeds that the fluid-flow around the flaps and the latter are thus moved to restrict flow. The pivot may lie on the wall of the duct, in which case one pair of flaps are omitted. Direct feedback may be provided by arranging for closure members carried by the flaps to co-operate with variable pilot valve holes 63, 64. Such an arrangement could be used as a variable geometry air intake or jet propulsion nozzle, the pilot valves being controlled in response to Mach number or the pressure ratio between selected points in the controlled flow. The leading flap 56 would constitute a compression ramp or multiple shock wave generating system, and the trailing flap may be convexly curved to act as a subsonic diffuser.