Patent GB-544340-A (GB)
Title: Improvements in fluid actuated control systems
IPC: B64C25/22
Filed: 1940-07-03
Abstract: 544,340. Valves; hydraulic machines. DOWTY EQUIPMENT, Ltd., (formerly AIRCRAFT COMPONENTS, Ltd.), and MACKENZIE, D. July 3, 1940, No. 11205. [Classes 69 (ii) and 135] [Also in Group XXXIII] In a fluid-actuated control system including two jacks or equivalent devices operable in a pre-determined relationship in at least one direction, the initially operable device, at the appropriate point of its movement, actuates a switch to close an electric circuit to render operable the other jack or equivalent device. As applied to an aircraft undercarriage in which the fairing doors must be held open until the under-carriage is completely retracted, a distributing valve 7 connects one or other end of retracting jacks 12 respectively to pump pressure and exhaust through the pipes 9, 13. A branch 15 from the pipe 9, through which pressure fluid is supplied to retract the jacks 12, leads to a valve casing 16 through which pressure is distributed to jacks 17 for actuating the fairing flaps, the arrangement being such that the jacks 17 cannot move to close the flaps until a solenoid 20 is energized by the closing of a switch 22 actuated by an arm 23 on the plunger of the jack 12. The switches 22 also control an " under-carriage raised" indicator 24. The pipe 15 is connected with a port 15a, Fig. 2, in the valve casing 16, and pressure fluid is normally prevented by a non-return valve 25 from reaching a port 19a and pipe lines 19, 191, 19<SP>11</SP> to retract the jacks 17. A ball valve 28 admits fluid to a passage 27 controlled by another spring-pressed valve 26. When the solenoid 20 is energized the valve 26 is released and fluid flows through a passage 30 and by raising a piston 31 opens the valve 25. Simultaneously a piston 31<SP>1</SP> is raised to open a non-return valve 251 to permit fluid to flow from the upper ends of the jacks through the pipes 181, 18<SP>11</SP>, 18, port 18a, port 32a, pipe 32 and through the valve 7 to exhaust. An exhaust passage 34 from the end of the solenoid casing is closed by a valve 33 when the solenoid is energized but is opened when the circuit is broken to permit fluid to exhaust from beneath the pistons 31, 31<SP>1</SP>. Where it is required that a particular sequence of operations should be preserved in both directions, such as the opening of latches before the opening of bomb release doors and the complete closing of the doors before the closing of the latches, both sets of jacks actuate switches at each end of their strokes to control two solenoids similar to that shown in Fig. 2 but associated with a casing 48 shown in section in Fig. 5. Two non- return valves 51, 53 have their stems slidable in guides 55 on a piston moving in a bore 57, and two non-return valves 52, 54 have stems slidable in guides 58, 61 on two pistons 59, 62 working in separate bores 60, 63. A passage 60a connects the bores 57, 60 and a passage 63a connects the bores 57, 63. The inner and outer ends of the door actuating jacks are connected respectively to the ports 351, 371 and the inner and outer ends of the latch actuating jacks are connected to the ports 391, 40<SP>1</SP>. The ports 49, 50 are connected alternately to pressure and exhaust by the pilot's control valve. When pressure is admitted at the port 49 the valve 52 is raised to admit pressure to the latch actuating jacks through the port 39<SP>1</SP> and simultaneously the piston 56 is depressed to open the valve 53 and put the opposite ends of the same jacks into communication with exhaust through the ports 40<SP>1</SP>, 50. When the stroke is completed one of the solenoids is energized to admit pressure fluid beneath the piston 62 to open the valve 54 and put the outer ends of the door actuating jacks into communication with exhaust through the port 371, passage 63a and port 50 the opposite ends of the jacks being supplied through the valve 51. On admitting pressure fluid through the port 50 it passes through the valve 54 to the outer ends of the door actuating jacks and simultaneously the piston 56 is raised to open the valve 51 to put the opposite ends of the jacks to exhaust. At the completion of the stroke the other solenoid is energized to admit fluid to raise the piston 59 and open the valve 52 to permit the inner ends of the latching-jacks to exhaust through the port 391, passage 60a and port 49, pressure fluid passing to the opposite ends of the jacks through the valve 53 and port 401. At the conclusion of either stroke the corresponding solenoid is de-energized to permit fluid from beneath either piston 59, 62 to escape through the solenoid casing to exhaust. The actuation of landing flaps may be similarly interlocked with the movements of the under-carriage. The source of fluid pressure may be as described in Specification 544,493.