GB185850A - Improvements in means for operating aircraft controls - Google Patents

Abstract

185,850. Norman, J. M., (Representative of Norman, G. H.). 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 variable-stroke hydraulic swash-plate pump and a hydraulic motor, the motor pistons being mounted on a common piston rod and wc,rking in coaxial stationary cylinders the inner ends of which are adapted to communicate with the pump. The pump body 19 is carried by a rotary shaft 12, which is driven by a windmill through bevel gearing 11. The pump body contains a number of parallel cylinders 23, in which can work plungers 28 universally jointed to arms 31 rotating with a swivel pin 32. This pin is carried by a bridge-piece 33, which can be rocked t) tilt the arms 31, as shown in Fig. 3, and so cause the plungers to reciprocate in the cylinders 23 with variable strokes as the pump body 19 rotates with the shaft 12. The control cables leading from the pilot's hand-wheel to the control surfaces pass around pulleys 16 carried by a lever 14, so that, when the control cables are operated, the lever 14 is rocked with its pivot 15, and the arms 31 are tilted in one direction or the other through levers and links 37, 36, 34. Liquid is then pumped, as the pump body 19 rotates, through ports 24, 25 from the motor cylinder 26 to the motor cylinder 27 or vice versa, according to the direction in which the control cables have been operated. Pistons 38, moving in the cylinders 26, 27, are fixed on a single rod 39, which passes through the partition 40 between the cylinders and is connected at its ends to the cables operating the control surfaces. One of the adjustable valves 41 opens if the pressure in one of the motor cylinders, becomes excessive, or when a motor piston reaches the inner end of its stroke. The lever 14 is also connected to the common rod of a pair of resistance pistons 47, working in cylinders 44 which communicate respectively with the motor cylinders 26, 27 through passages 48 and side ducts 49 in a cock 50. If the pilot releases his control wheel, the air pressure on the control surfaces acts through the charged motor cylinder and the connected cylinder 44 to move the lever 14 and the pump arms 31 back into the position ir. which the pump plungers 28 are not reciprocated. To enable the controls to be operated by hand alone, the cock 50 is turned to connect the motor cylinders 26, 27 to one another and to shut them off from the cylinders 44. The pump and motor drain into a tank 54 with a filling cap 64. Liquid is supplied by a gear-wheel pump 56 from the tank to a sump 52 for making good leakage in the motor cylinders and cylinders 44. The tank may also be filled through a filling cap 60 on the cock 50, and air allowed to escape by raising the pump body 19 off its seating 21.