GB185849A - Improvements in means for operating aircraft controls - Google Patents

Abstract

185,849. Salmon, P. June 14, 1921. Hydraulic transmission of power; machines and apparatus.-A servo-motor for assisting an aircraft pilot to operate the control surfaces, comprises a hydraulic pump of the cog-wheel type and a hydraulic motor of the oscillating vane type, the ports leading to the motor being controlled through a shaft about which the vane oscillates. The pump has three pump wheels 6, 7, 8 driven by a windmill 4. The wheels are mounted in a barrel 10, which can be rotated in its casing 11 to connect the port 17 to one or other of the ports 18 through one or other of the passages 15, and so to cause fluid to be pumped from the passage 19 to the passage 20, or vice versa. The passages 19, 20 communicate respectively through ports 54, 55, Fig. 6, with the spaces between the fixed abutment 24 and the oscillating vane 25 of the motor. The cables 1, Fig. 1, leading to the control surfaces are connected to levers 2, the ends of which are connected to wires 5 and 28. The wires 5 pass around a drum 36, Fig. 3, and lead to the pilot's control wheel. The wires 28 pass around a drum 27, Fig. 3, fixed on a hollow shaft 26 that is secured to the oscillating vane 25 of the motor. When the pilot operates the wires 5, he turns the levers 2, and so takes part of the load. The pull on the wires 5 also turns the drum 36 and, through a sun-wheel 35 and planet wheels 33 on a spider 32, a shaft 31, whereby the pump barrel is rotated and liquid pumped to one side or other of the oscillating vane 25 to turn the drum 27 and exert a further pull on the levers 2 and the control surfaces through the wires 28. The movement of the drum acts through a crown wheel 34 and the planet wheels 33 to return the spider 32 and shaft 31 to the central position. In a modification, the pump barrel is fixed and its casing 11 rotatable. To put the hydraulic apparatus out of action and permit of the control surfaces being actuated entirely by hand-power applied through the wires 5, a cock 37 is turned to open communication between the passages 19, 20 and lock the shaft 31 carrying the spider 32. Spring-loaded relief valves between the passages 19, 20 limit the pressure in the motor. The angular movement of the motor abutment 25 is arrested when ports 44, 45 at its respective sides are connected together through a cavity 46 or 47 in the cylinder casing. Leakage is compensated for by liquid passing from a reservoir 49 through valves 50. The reservoir also supplies liquid to spaces 52, 53 at the end of the pump casing to prevent air from being sucked in.