GB668543A - Improvements in or relating to shock absorbers - Google Patents

Abstract

668,543. Hydro-pneumatic s h o c k - a b - sorbers. ELECTRO-HYDRAULICS, Ltd., and JECIES, S. Dec. 15, 1949 [Dec. 30, 1948], No. 33553/48. Class 108(iii) A shock-absorber comprises two telescopic cylinders 1, 4, Fig. 2, in which are formed two main chambers A, B, filled with damping liquid and in mutual communication, and two springs C, D, of different characteristics, each separated from the liquid by at least one floating piston so that on telescoping of the cylinders under load, energy is absorbed by the damping liquid, and stored by compression of at least one of the springs C, over the whole stroke of the shockabsorber, the second spring D being compressed only if the load exceeds a predetermined amount. The spring D is formed by compressed air acting on a floating piston 11, movement of which is limited by an annular stop 16. Liquid communicates through damping orifices 6 with the space B. The spring C is formed by compressed air which acts on a further floating piston 8. An additional port 17 in the head 5 connects the space A with the annular space E between the cylinders 1, 4. In a modification, Fig. 1 (not shown), there is no port 17 and the annular stop 16 is replaced by a diaphram having apertures, which may be valved, to damp rebound movement of the shock-absorber. The ports 6 may also be valved to damp rebound. In operation, on compression, liquid damping occurs through the ports 6, and the piston 8 is driven downwards against the air spring C. When a predetermined pressure is attained in chamber A, the piston 11 is also deflected. In Fig. 3, the piston 11 and spring D are within the lower end of the cylinder 4, and the spring C and piston 8 within a tube 19 rigid with the cylinder head 2. Movement of the piston 11 is limited by a diaphragm 25 having damping apertures 26 which may be valved. The outer end of the tube 19 carries a counter piston 20 slidable within the cylinder 4. In operation, on compression, liquid pressure in chamber A (which builds up, due to damping caused by flow to space B) acts on piston 8, and at a predetermined pressure piston 11 is also' deflected. In a modified arrangement of the spring D, Fig. 4, a further floating piston 32 is provided, movement of both pistons 11 and 32 being limited by respective annular stops 31, 33. Inflation orifices are provided at 24, 30 for the respective compressed air springs D2, D1 formed by the pistons 32, 11. The compressed air springs C, D may be replaced by deformable solids, e.g., coil and rubber springs. and each may comprise a series of springs having stepped loadings. The Specification includes curves, Fig. 5 (not shown), indicating the relative performance of conventional shock-absorbers and those according to the invention. The invention is applicable to the nose wheel of aircraft tricycle undercarriages.