Patent GB-754470-A (GB)
Title: Improvements in or relating to valve mechanism
IPC: G05D9/00
Filed: 1954-03-25
Abstract: 754,470. Fluid-pressure servomotor-control systems. KOEHLER AIRCRAFT PRODUCTS CO. March 25, 1954 [March 27, 1953], No. 8730/54. Class 135. A valve mechanism for controlling the supply of fluid under pressure to a tank or reservoir so as to maintain a predetermined level therein comprises a housing with a valve seat therein, a single valve member co-operable with the seat and a pair of flexible diaphragms each of greater area than the valve seat operatively connected to the valve member and defining two separate fluid pressure chambers within the housing each in communication with the fluid pressure supply, the fluid pressure chambers being connected with separate bleed ports, each individually controlled by means sensitive to the level of fluid in the tank or reservoir so that the valve member is operated upon closure of either bleed port. In Fig. 1, the two diaphragms 21, 31 are clamped peripherally between housing parts 10, 20, 30 and centrally to fittings 24, 34 of which 24 supports the valve member 14 and 34 carries an elongate member 40a with a passage 40 connecting the highpressure inlet 11 through a strainer 28 with the upper pressure chamber 52. The inlet 11 communicates with the lower pressure chamber 50 through a throttling aperture 41 which is progressively throttled by the elongate member 40a as the valve member approaches its seat 12. Similarly the upper end of the elongate member 40a co-operates with a further throttling aperture 44 to restrict the entrance of fluid to the chamber 52 as the valve member 14 approaches its seat. The chambers 50, 52 communicate via passages 55, 80 and recesses 56 with bleed ports 60 controlled by tilting valves 58. The valves 58 are pivoted to threaded stems 72 adjustably mounted on carrier plates 67 thereby forming toggle arrangements for controlling the operation of the valves. The valves 58 are each operated independently by floats 65 of cork or the like secured to the plates 67. The floats 65 and the plates 67 are mounted side by side within a ported shell 85 carried by the housing member 30 and their upward movement is limited by a single stop 77 adjustable on a threaded pin 78. The plates 67 are pivotally mounted on pins 68, 69 supported in brackets 70. The closing of either or both of the valves 58 causes the main valve 14 to close. The complete valve may be mounted in an 'inverted position in which case the stop 77 is arranged at the opposite side of the plate 67 relative to the float. In a modification suitable for low pressures the elongated member 40a is modified so that there is no progressive throttling of the inlets to the two pressure chambers as the main valve closes. The assembly comprising the main valve, the two diaphragms and the pressure chambers may be located outside the tank or reservoir and connected to the bleed control valves 58 by two pipes. In this case the valves 58 and their associated floats are mounted as a unit within the tank or reservoir. This arrangement is particularly applicable to aircraft fuel tanks which are subsequently jettisoned since the main valve and its associated diaphragms are not lost. The Specification describes three arrangements of fuel tanks for aircraft.