GB682508A - Improvements in or relating to gravity-operated valve mechanisms - Google Patents

Abstract

682,508. Fluid-pressure servomotor-control systems ; valves. ROLLS-ROYCE, Ltd. Jan. 18, 1950 [May 5, 1949], No. 12089/49. Class 135. A gravity-operated valve mechanism for use in an aircraft fuel system to ensure that fuel is withdrawn from the lowermost end of the fuel tank irrespective of the altitude of the aircraft, comprises a casing having a pair of oppositely disposed inlet ports arranged for alternative connection to a common outlet port in accordance with the direction of tilting by gravity means, which means control a fluid-operated motor to actuate valve members controlling the inlet ports. As shown, a casing 35, Figs. 1, 2, having inlet ports 36, 37 and an outlet port 38 has a double-coned valve member 42 engageable with seats 41, and divided by a flexible diaphragm 44 into chambers 34a, 34b, and slidably and rotatably mounted on a spindle 40 carried by spiders 39 in the casing. The chambers 34a, 34b are each provided with an inlet duct 53 communicating with its associated inlet port and an outlet duct 52 controlled by a valve element 51 carried on an arm 50 secured to a spindle 47 journaled in a bracket 46 secured to the valve member 42. The spindle 47 is located at right-angles to the spindle 40 and carries at its ends curved arms 48 mounting pendulum weight 49. A second bracket 55 secured to the valve member 42 carries an evacuated cylinder 57 closed at its ends and housing a steel ball 56. The mechanism is mounted in the aircraft with the spindle 40 directed fore and aft, the inlet 36 being forward and connected to the bottom after end of the tank and the inlet 37 connected to the bottom forward end of the tank. In level flight, fuel is drawn through both inlets and passes through the valve to the outlet. Should the aircraft be put into a climb the valve mechanism will rock about the spindle 47 so that the outlet duct 52 from the chamber 34b is closed by the associated valve element 51. Chamber 34b will then be subjected to the full pressure head of fuel so that the diaphragm 44 will be distorted. The valve member 42 will then slide on the spindle 40 to close the port 37 under the action of its own weight, the pressure of the fuel and the impact of the ball 56 on the end of its cylinder 57. Fuel then is withdrawn from the after (lower) end of the tank through the inlet 36. Conversely if the aircraft is put into a dive, fuel is drawn through the inlet 37 from the forward (lower) end of the tank. The cylinder 57 and ball 56 also ensure that the mechanism assumes a vertical position during, e.g. banking of the aircraft. In another embodiment, the casing 35, Fig. 4, having inlet ports 36, 37 and an outlet port 38 houses a cylindrical drum 60 closed at its ends by inwardly coned plates 61, mounted on bushes 76 slidable on a rod 75. Flexible diaphragms 63 secured around their peripheries to the drum are engageable with seats surrounding the inlet ports, and together with the coned plates 61 form chambers 70, 71 connected to a source of pressure fluid, e.g. compressed air, through passages 73, 74 and to exhaust through passages 77, 79 controlled by valve elements 78 slidably mounted on the rod 75. Movement of the valve elements 78 is controlled by a pendulum device having a swinging frame 81 pivoted on pins 82 to a fixed frame 83 supported and secured respectively to the left and right coned plates 61. The frame 81 carries at its lower end a pair of parallel evacuated cylinders 84 closed at their ends and housing steel balls 85. On the aircraft diving, the balls 85 run forwards causing the forward valve 78 to close the outlet from the chamber 70, pressure builds up therein whence the inlet port 36 is closed and, as before, fuel is taken from the lower forward end of the tank.