GB762722A - Improvements in or relating to locking devices, more particularly for the hydraulic actuators of aircraft landing gear - Google Patents

Abstract

762,722. Hydraulic actuators. BENDIX AVIATION CORPORATION. Oct. 15, 1954 [Nov. 18, 1953], No. 29777/54. Class 69 (2). A hydraulic actuator for raising and lowering the undercarriage of aircraft comprises a piston and cylinder and means for locking the piston at one end of the cylinder. A valve unit is also carried within the cylinder and is actuated to allow pressure liquid to effect movement of the piston only after the locking means is released. The piston in a tube piston 38 slidable within a cylinder 30'and is provided at one end with fingers 102 adapted to spring over an inwardly projecting sleeve 55, when the piston is moved to contract by pressure exerting a force on surface 56, to engage the end 104 of the fingers beyond the end of the sleeve. In this position the fingers are locked by the end of a locking sleeve 68 slidably mounted on inner sections 62, 64 projecting within the cylinder and held in the locking position by a spring 70. Upon pressure fluid entering port 86, it is fed into a chamber 76 by passing over the square edges of a valve 90, Figs. 2 and 3. The pressure exerted bears on the edge 69 of the sleeve 68 and forces it to move against the spring and to release its end from locking engagement with the fingers 102. A projection 103 on the inside of the sleeve 68 engages the valve 90 when the end of the sleeve disengages the fingers and lifts the valve from its seating permitting pressure fluid to pass through holes 94 in section 64 and to flow through a central tube 96. The tube 96 carries a wall 100 at its end which serves as the stationary end wall of an expansion chamber 98 of which the inside of the piston forms the remaining walls. The piston therefore extends to raise the undercarriage. A micro-switch 118 is provided to give an indication whether the locking elements are in their locked or unlocked position, and is operated by a feeler 124 which engages both the fingers and end of tube 68 to ensure their correct positioning. The feeler is pivoted on an arm 120 which holds the contacts of the switch open when the piston is correctly locked in its retracted position.