GB841561A - Improvements in or relating to aircraft undercarriages - Google Patents

Abstract

841,561. Hydro-pneumatic shock-absorbers. BRITISH MESSIER Ltd. Nov. 9, 1956 [Nov. 9, 1955], No. 32097/55. Class 108(3). A hydro-pneumatic shock absorber for an aircraft undercarriage leg comprises a tube 27 projecting through the lower end of a casing 17 pivotally connected (at 12, 13,) to the aircraft (not shown), glands 30, 31, defining an annular chamber 77 in which is slidable a piston 40 rigid with the tube 27 and with which shock absorbing means are associated, the tube 27 having mounted at its lower end at least one landing wheel 28. The arrangement is such that when the undercarriage is loaded the tube 27 moves upwardly and projects through and beyond the upper end of the casing 17. As shown, the casing 17 is mounted for steering movement of the aircraft wheels 28 relative to a housing 11 carrying the pivot trunnions 12, 13, under the action of a steering mechanism 20. The chamber 77 is liquid filled, and communicates with a chamber formed by a bore 76 within the tube 27 and above a floating piston 64. The space beneath the piston 64 is charged with pneumatic pressure through a valve 62. Liquid passing from the chamber 77 to the chamber 76 or vice versa, has to pass through ports in a ring-like orifice head 44 disposed between a flanged ring member 43 and the upper face of the piston 40. The upper face of the head 44 is recessed in such way as to connect certain of the holes in each of which is disposed a compression orifice 48. A plate valve 52 is mounted so as to be able to slide axially into a position in which it closes the lower ends of the holes containing the orifices 48. The remaining holes in the head 44 contain rebound orifices 50 which are adapted to be closed by a plate valve 51 similar to the valve 52. Passages 70 lead from an annular space 69 below the head 44 to the chamber 76. Passages 72 lead from the chamber 76 to an annular recess 42 in the periphery of the piston and thus to the annular chamber defined by the lower endface of the piston 40. The recess 42 is connected with the space 69 by a restricted passage 73. A lug (Fig. 2, not shown) rigid with the housing 11, serves for a connection for a retraction jack. Rotation between the tube 27 and the casing 17 is prevented by means of torque links (Fig. 2, not shown). The piston 40 has sufficient clearance in the chamber 77 to permit expansion under high temperatures. A piston ring 54 prevents leakage.