GB711113A - Improvements in and relating to liquid level control devices applicable, e.g. to aircraft fuel tanks - Google Patents

Abstract

711,113. Fluid-pressure servomotor-control system. PARKER APPLIANCE CO. Aug. 8, 1952, No. 19987/52. Class, 135. [Also in Group XVII] A liquid level control device, e.g. for an aircraft fuel tank, comprises two inlet valves in series and closable individually by separate pilot valves each operable by a float, the floats being operable at the same or different levels. The inlet valves are housed in a body 10, Fig. 1, the first valve comprising a closure member 53 carried by a diaphragm 57 and being spring-urged to a seat 28. The second valve similarly comprises a closure member 54 carried by a diaphragm 57a and spring-urged to a seat 33. The two members are guided by a fixed pin 63 providing clearances 77, 78 through the diaphragms whereby the liquid flowing from inlet 20 to open both valves and flow through outlet 22 into the tank, also bleeds to the spring chambers 75, 76 at the rear of the diaphragms. Bores 79, 82 lead from the chambers 75, 76 respectively, to pipes 100, 114 extending to pilot valves 97, 111, Fig. 2, open to the tank interior and fixed at the top thereof. The pilot valves comprise closure members 90, 91, respectively, operable by floats 104, 118, set for different liquid levels. Thus, as the tank fills, float 104 will be raised to seat member 90 thus permitting pressure to build up in chamber 75 and ultimately balance the inlet pressure on the diaphragm, whereupon spring 59 seats member 53. Should this fail to happen and the liquid level continue to rise, float 118 will be raised to cause seating of member 54. If both floats are set for the same liquid level, the inlet valves will close substantially simultaneously.