Patent GB-633078-A (GB)
Title: Improvements in control systems for hydraulic jacks applicable to the operation of aircraft landing flaps
IPC: B64C13/00
Filed: 1946-10-28
Abstract: 633,078. Hydraulic machines; fluid-pressure servomotor-control systems. HOBSON, Ltd., H. M., and WESTBURY, R. Oct. 28, 1946, No. 31896. [Classes 69 (ii) and 135] In a remote-control system, e.g. for operating the landing flaps of an aircraft, of the kind comprising a double-acting hydraulic jack, the supply of pressure-liquid to which is controlled by a valve in a signal line, the pressure in which is controlled by a sender-unit responsive to an operating member, non-return valves are disposed in the conduits between the jack cylinder and the control valve, said non-return valves including means controlled by the operating- member, but independent of the pressure in the signal line, for supplying pressure-liquid to the non-return valves to move them to open position. As shown in Fig. 2, a button 31, on the pilot's control lever 26, when depressed permits the rapid movement of the lever to the desired flap setting, which movement operates the sender unit to vary the fluid-pressure in a signal line 28 to operate a valve 23 which controls a hydraulic jack 20, 21 and an output member 22 to slowly move the flaps to their desired setting and which at the same time closes a switch 32 to open a solenoid-actuated valve 35. A pressure line 24, which through the valve 23, one or other of conduits 18 and non-return valves 100, supplies the jack cylinder 20 with pressure liquid, is, on the valve 35 being opened, connected with lines 14 to supply the smaller ends 13, Fig. 1, of piston valves 16. The piston valve 16 associated with that end of the cylinder not being supplied with pressure liquid is thereby moved leftwards to open an associated non-return ball-valve 10 and thus exhaust that end of the cylinder through a line 116, a chamber 15, the associated conduit 18, the valve 23 and an exhaust line 25. Although the valve 35 immediately closes on the release of the button 31 and liquid from the lines 14 exhausts between the valve and its solenoid to the line 25, the. valve 10 will remain open due to the pressure difference on the two sides of the piston all the time liquid is exhausting from the cylinder, i.e. until the jack 21, and hence the flaps, reach their desired position and the valve 23 is returned by follow-up linkage to its neutral closed position, whence a spring 11 will close the valve 10 and hydraulically lock the jack 21 until the button 31 is again depressed and the lever 26 moved. In a modification, the solenoidactuated valve 35 is replaced by a pilot valve 52, Fig. 3, which is operated by a lever 49 on the depression of the button 31 to connect the pressure line 24 with the lines 14 via lines 53, 54 and on release of the button connects the lines 14 with the exhaust line 25. The smaller side of the jack piston 21 is in constant communication with the supply line 24 through a conduit 118, whilst the larger side is alternatively opened to supply and exhaust lines through a conduit 218 and a control valve 123. A followup linkage 45, 47, 48 connecting the output member 22 with the control valve 123 returns the latter to its neutral closed position after the flap has reached its desired setting. Specifications 483,049, 597,286 and 621,396 are referred to.