Improvements in or relating to fluid control apparatus more particularly for pressurized fuel tanks

摘要

715,200. Fluid-pressure servomotor-control systems. VICKERS-ARMSTRONGS, Ltd., and DAWSON, R. A. May 29, 1952 [June 15, 1951], No. 14229/51. Class 135 A valve unit for maintaining in an aircraft fuel tank a predetermined pressure above that of the ambient atmosphere consists of a pilot valve 13 actuated through a system of levers and links by a piston 4 subject on its upper face to atmospheric pressure and on its lower face to tank pressure, and a main valve plunger 23 coacting with a seat 24 and controlled by the pilot valve. The arrangement is such that for small deviations from the required pressure differential the pilot valve is opened to a small extent to allow inert gas or air to pass from an inlet chamber 29 to an axial passage in the main valve plunger throttled by a needle 30, and thence through a passage 25 and past the pilot valve to an outlet 26 to the tank. Larger openings of the pilot valve cause pressure above the main valve plunger 23 to be relieved sufficiently for the latter to open and permit flow direct to the outlet. The plunger 23 has a rubber cone 31 to form a seal when the valve is closed and is fitted with a copper washer 32. The connection between the piston 4 and the pilot valve consists of a lever 7 on a fixed pivot 8 and connected by an H-link 10 to a lever 11 on a fixed pivot 12. A spring 17 having a fixed abutment 18 loads the piston 4 through a drum 15 connected by a bridge 14 to the piston. The unit has two inlets, one (not shown) for inert gas, and the other 28A for air. Each inlet has a non-return valve and that in the air inlet is normally closed by higher pressure in the gas inlet but opens in the event of failure of that pressure. A relief valve may be fitted to the unit to relieve excessive pressure in the tank.