Patent GB-527716-A (GB)
Title: Improvements in servo-assisted control systems
IPC: B64C13/24
Filed: 1939-04-12
Abstract: 527,716. Fluid-pressure servomotor-control systems. SPLADIS SOC. POUR L'APPLICATION D'INVENTIONS SCIENTIFIQUES, and PELTERIE, R. ESNAULT-. April 12, 1939, No. 11136. Addition to 510,300. [Class 135] The servomotor control mechanism of the parent Specification is so modified that only one pump is required, additional valves being provided to restrict or shut-off the discharge from the pump into the conduit in which the pressure is not to be increased also, on failure of the power supply, manual operation under an increased gear ratio is automatically available. In the arrangement shown in Fig. 2 a vehicle steering wheel is connected to the central pinion 3 of an epicyclic gear box 4 on the casing of which is a projection 14 situated between the stems 46, 47 of valves 44, 45 controlling the discharge from chambers 35, 38 from which conduits 28, 29 lead to hydraulic cylinders for turning the road wheels. Inlet valves 52, 53 controlling the supply of fluid from a pump to the chambers have stems 58, 59 engaging the valves 44, 45. Movement of the casing caused by turning the wheel tends to close one of the valves 44, 45 and increases the pressure in the corresponding chamber and conduit; simultaneously the valve 52 or 53 of the other chamber moves towards the closed position. The relative diameters of the heads of the valves 52, 53 and stems 54, 55 determine the degree to which the valves are balanced by the fluid pressure. In a modification the valves 52, 53 open in the direction of flow and each is actuated from the valve 44 or 45 of the other conduit. To allow a greater range for manual operation, the projection may be made withdrawable consequent on failure of the power supply, or the valves may be opened by resilient means sufficiently stiff to transmit the forces during power assisted operation but adapted to yield during manual operation. A greater range is also allowed by the parts 141, 142 as described below with reference to Fig. 7. Figs 5. and 7 show mechanism for operating an aircraft elevator 107 fixed to a shaft 106. A hand lever 100 pivoted at 101 is connected by a rod 102 to the casing 104 of an epicyclic gear comprising four sets of planetary pinions fixed to the shaft 106 and a sleeve thereon respectively. The sleeve carries an arm 110 connected by rods 111, 112 to the pistons of hydraulic cylinders 115, 116 and the shaft 106 carries arms 117 connected bv rods 118-121 to the pistons of hydraulic cylinders 126-129. Part only of the servo power is transmitted through the gear i.e. by the cylinders 115, 116, the remainder being transmitted by the cylinders 126-129 acting directly on the elevator. In the event of failure of the power supply, the supply of fluid to chamber 133 stops whereupon bellows 135 expand and release a spring- pressed plunger 132 which then engages a notch in a collar on one of the central pinions. The elevator may then be operated manually, the gear acting as a reduction gear. Fig. 7 shows the valve arrangements forming the equivalent of the valves of Fig. 2. Fluid from the pump normally flows by pipes 138, ports 116, 167 in a sleeve 141 and chambers 154, 158 to return pipes 162. On movement of the casing 104 clockwise, a rod 142 connected thereto is moved to the left closing the port 166 and partially closing the port 167. The whole of the liquid then flows into a chamber 159 and via a pipe 164 to the cylinders 115, 127 and 129 to assist the movement of the elevator in a clockwise direction. The sleeve 141 being connected to the elevator moves to the left and reopens the ports 167 a little whereupon a state of equilibrium of the forces is reached. If the lever 100 is allowed to return to its mean position, the rod 142 moves to the right, the port 167 opens still more, the pressure in the cylinders 115, 127, 129 falls and the elevator returns towards its mean position owing to air pressures. Specification 510,304 also is referred to.