GB666511A - Improvements in or relating to piston and cylinder centring and damping apparatus - Google Patents

Abstract

666,511. Aircraft undercarriages. BRITISH MESSIER, Ltd. March 30, 1950 [April 25, 1949], No. 10949/49. Class 4. [Also in Group XXXII] A centring and damping apparatus comprises, in combination, a damping device comprising two relatively slidable parts, one a damping cylinder and the other a fluid damped piston working therein so designed that movement of the piston from an intermediate position in the cylinder is damped in both directions, and a fluid pressure actuated centring device also comprising two relatively slidable parts, one a cylinder and the other a piston or plunger-means to work therein, one part of the centring device being mechanically coupled to one part of the damping device to move therewith and the other part of the centring device being likewise coupled to the other part of the damping device, so that the centring device opposes movement of the piston in the damping cylinder and urges it towards this position as soon as it moves therefrom in either direction. In the arrangement shown, as applied to a damper which is connected between a bogie truck and a shock absorber leg of an aircraft undercarriage, a piston 22, carried by a hollow piston rod 23 is movable in a liquid filled cylinder 19 which communicates at one end through an orificed valve 29 with a reservoir cylinder 27. The piston 22 is provided with a valve 25 having an orifice 26. A plunger 31 within the reservoir cylinder 27 and which may be loaded by a spring 32 or by compressed air, carries a rod 33 which serves as an index to the amount of liquid within the cylinder. In the position shown, in which the piston 22 is centred relative to the cylinder 19, a free piston 38 which carries a. hollow extension 39 abuts a shoulder 37 within the piston rod 23 and seals a vent 41 to atmosphere, which when the piston 38 moves away from the shoulder, communicates with an annular space between the extension 39 and a reduced diameter portion of the piston rod 23. A rod 42, extending with clearance through the piston 38 from the opposite end of the cylinder 19 'terminates in a head 43 which bears on the inner face of the piston 38. The piston rod 23 is charged with compressed air through a valve 44 and the arrangement is such that, in operation of the damper, the force resisting compression and extension movements is the same. In a modification, a fluid pressure connection may be provided to enable, the damper to be centred only when the undercarriage is to be retracted. In a further modification, Fig. 3 (not shown), the piston 38 may have a passage therethrough additional to that afforded by the clearance between the rod 42 and the piston 38.