Patent GB-1009526-A (GB)
Title: Hydraulic system for aircraft landing gear and hydraulic actuator therefor
IPC: B64C25/22
Filed: 1962-07-31
Abstract: 1,009,526. Fluid pressure apparatus. KAMAN AIRCRAFT CORPORATION. July 31, 1962 [Nov. 9, 1961], No. 29376/62. Heading F1P. [Also in Division B7] A fluid pressure actuator 10, Fig. 1, for a retractable aircraft landing gear, comprises a piston 18 dividing a cylinder 12 into first and second working chambers 24, 26, first and second ports 66, 70 communicating respectively with the chambers, and valve means for controlling the flow path of working fluid between the first port and a third port 64 in accordance with the position of the piston, the flow path being closed at one limit of the stroke of the piston and open at the other limit. The piston and its rod 20 have a bore 38 in which is slidably received a tube 46 at one end secured to a base 16 of the actuator and at the other end having radial bores 60 and a seal 62, the latter end of the tube being closed. In the position shown, the bores 60 are closed to prevent flow of fluid from the chamber 24 to the inside of the tube 46 and the third port 64. When fluid pressure supplied through port 66 to chamber 24 has moved the piston 18 to its extreme right hand position, the bores 60 are uncovered so that fluid from port 66 can flow to port 64. The piston can be retracted by fluid supplied to port 70. The actuator may have more than one set of openings 60, each set leading to separate mechanisms so that the mechanisms are sequentially operated. In a system for an aircraft landing gear using the actuator 10 to operate a movable fairing or door 72, Fig. 2, and a further actuator 76 to operate the landing wheel 74, each actuator is controlled by a valve 78, 98, valve 78 being connected to a supply 80 of fluid pressure and valve 98 being connected to third port 64 of the actuator 10 so that it is only operative to raise or lower the wheel when the actuator 10 is in its extended position and the door 72 open. The actuator 10 can be operated by the valve 78 to close the door with the wheel in its lower position, raising of the wheel only being possible when the actuator 10 has been operated to open the door. The operation of the valve 78 may be effected by a solenoid 110 controlled by contacts 120, 122 engaged by a contact 119 on the operating handle 108 of the valve 98, and contacts 112, 114 engaged by the contacts 116, 118 on the wheel 74 when in its raised or lowered position, the arrangement being such that the valve 78 is moved to its door opening position whenever the wheel is not in its fully raised or lowered position. When the handle 108 is moved from its wheel-retracted position, shown in Fig. 2, contacts 119, 120 are opened to de-energise solenoid 110 so that the valve 78 is moved to extend the actuator 10 and open the door, the full extension of the actuator permitting fluid from the third port 64 to flow to valve 98 and actuator 76 to extend the wheel 74. When the wheel is fully extended, the engagement of contacts 118, 114, together with the already closed contacts 119, 122 of the handle, energizes solenoid 110 to move the valve 78 to the door-closing position. Similar action occurs when the handle 108 is moved to the wheel-retract position.