GB486955A - Improvements in or relating to fluid pressure operated jacks - Google Patents

Abstract

486,955. Retractable alighting gear for aircraft. AUTOMOTIVE PRODUCTS CO., Ltd., and PARKER, S. M. Nov. 11, 1936, No. 30801. [Class 4] [Also in Group XXIX] The undercarriage of an aircraft is retracted and extended by a plurality of fluid-pressure jacks operating in unison, each jack having end position locking means released by the fluid-pressure and means for preventing operation until all the other jacks are freed by their locking means so that all the jacks commence operation together. In the Figure, the plungers 12, 13 of a pair of jacks 10, 11 are locked in retracted position by pairs of locking levers 20 engaging under flanges 18 on the plungers. Pressure fluid is supplied by a pipe 40 to valve cylinders 29, 29a on each jack, each cylinder having a piston 26, 26a for operating the locking levers 20 and for controlling a pair of mushroom valves 31, 34. Pipe connections 46, 46a supplying pressure fluid to the upper ends of the jacks are connected in each case to the valve cylinder of the other jack, the admission openings to these pipes being initially closed by the valves 34. Considering first the action of the valve mechanism on jack 10, admission of pressure fluid by the supply pipe 40 lowers piston 26 to open the locking levers 20. At the moment when the jack plunger is released, valve 31 seats in an aperture 20 and cuts off the pressure supply to piston 26, and valve 34 admits fluid to connection 46 to apply pressure to the head of jack 11. Similarly, pressure is not applied to jack 10 until the levers 20 have released jack 11. Consequently, neither jack can operate until both are released, and both commence operation together. To contract the jacks, fluid is applied to their lower ends by a pipe 41, the flanges 18 snapping past the locking levers 20 when fullycontracted. If the jacks are locked in both end positions, the interlocking valve systems are duplicated. In an arrangement of four jacks, the jacks are connected together in pairs as in Fig. 1, and the pairs are similarly interconnected by supplementary valve devices associated with each pair. The application of the invention to jacks having locking means as described in Specification 434,493 is also described.