Patent GB-824078-A (GB)
Title: Aeronautical propeller having safety means for propeller feathering
IPC: B64C11/40
Filed: 1957-11-27
Abstract: 824,078. Variable-pitch propellers. UNITED AIRCRAFT CORPORATION. Nov. 27, 1957 [Nov. 29, 1956], No. 36966/57. Class 114. Variable-pitch propellers are adjusted by an hydraulic motor fed with fluid under the action of a control valve, normally adjusted by a speed governor driven from the engine, and a feathering valve. The housing 14 contains the hydraulic motor which varies the pitch of the blades 12 through suitable cam and gear mechanism. The feathering valve 32 when in its "normal" position (as shown) allows communication between the fluid supply source fed to conduit 28 and conduit 28a, which leads to control valve 34, and also communicates conduits 26a, 26 and 30a, 30, conduit 26 feeding fluid to the hydraulic motor to decrease the pitch and conduit 30 supplying fluid to increase the pitch. The control valve 34 when in its "central" position terminates the flow through conduit 28a from the supply source and this valve is moved by a governor 48, driven from gearing 42, against the action of a spring to connect conduits 28a, 30a to provide fluid to the hydraulic motor to increase the pitch, and when the spring loading is sufficient to overcome the governor action conduit 28a communicates with conduit 26a to decrease the pitch. The supply of hydraulic fluid is provided by a main pump 62 and a standby pump 64 which deliver fluid from a tank 56 supplied by pumps 58 from a tank 54. The main pump 62 delivers fluid through a filter 66 and conduit 22 to the conduit 28 which is provided with a branch conduit 96 leading to a normally closed valve 90. The standby pump 64 delivers through filter 68 to a conduit 70 which communicates, when valve 32 is in its "normal" position, with a conduit 70a leading to a spring loaded valve 72 having a small orifice 88, the main delivery flows through conduit 78 to a drain conduit 80 communicating with the tank 56 while part of the flow passes through the orifice 88 to conduit 82 which communicates through passage 84 of control valve 34, when in its "central" position, with conduit 86 which leads to the drain conduit 80. When control valve 34 is moved to vary the pitch it closes conduit 82 and the pressure in this conduit increases to the value existing in conduit 70a thus allowing valve 72 to close under the influence of its spring, thus the pressure in conduit 70 increases and opens a non-return valve 74 thus permitting the delivery from standby pump 64 to join the delivery from the main pump 62 whenever the pitch is changed. Similarly, when the feathering valve 32 is operated, as described below, conduit 70 is closed and the two deliveries combine as above. The upper ends (as shown) of the valves 32, 34 are connected by a conduit 102 which normally communicate by conduit 100, valve housing 92, conduit 98, valve housing 90 and drain conduit 94 to the tank 54. Feathering is normally performed by actuating cam 114 which moves lever 128 to the right causing an anticlockwise rotation of the lever as it rises on roller 130, this causes a lever 132 to 'turn anticlockwise about a pivot intermediate its length to operate the feathering valve which places conduit 28 in communication with conduit 30. If the'valve 32 should stick so that the lever 132 is unable to operate it, the lever 132 will then rotate in an anticlockwise direction about its connection with the feathering valve, this causes a lever 134 to turn in an anticlockwise direction to open a non-return valve in the housing 92 and close conduit 98 (as shown), fluid from supply conduit 28 now flows through 96, valve housing 92, conduits 100 and 102 to the upper ends of the valves 32, 34. Thus fluid pressure acting on feathering valve 32 may now operate the valve, but if this still remains stuck then the pressure acting on the control valve 34 will move and hold it in a position (as shown) to establish communication between the conduits 28a, 30a to perform the feathering action. As an alternative method of feathering the member 140 in valve housing 90 may be electrically or manually actuated to close the connection between conduits 94 and 98 and open a non-return valve so that fluid from the conduit 28 flows through conduits 96, 98, 100, 102 to the feathering and control valve housings to load the valves as above. Specifications 683,906 and 724,284 are referred to.