GB558104A - Improvements in or relating to liquid damped telescopic shock absorber struts - Google Patents

Abstract

558,104. Shock-absorbers. AUTOMOTIVE PRODUCTS CO., Ltd., and FOSTER, S. June 15, 1942, No. 8193. [Class 108 (iii)] Relates to a telescopic, shock-absorbing strut, particularly for aircraft undercarriages, of the type comprising a liquid-containing cylinder 10 and a hollow plunger 14 containing a resilient element such as compressed air, the liquid, on compression of the strut, being forced from the cylinder into the plunger through a hollow stem 27 which is attached to the cylinder head 25 and passes through the plunger-head 18, means being provided to restrict the flow of liquid. According to the invention, a restricting orifice 48 is provided in the stem 27 and ports 54 leading from the stem into the plunger 14, to by-pass the restriction, are controlled by a spring- loaded annular valve 50 which opens automatically in the event of excessive pressure to limit the resistance of the strut to a predetermined maximum. The restricting orifice 48 is formed by an internal flange on a tubular sleeve 45 which is housed within a tubular member 39 forming an enlarged extension of the stem 27 and the end 44 of which constitutes a non-return valve engaging a seat 43 on the end of the member 39. On compression of the strut, liquid is displaced by the plunger-head 18 from space 59 and passes through ports 60 into the stem and through the restricting orifice 48, the pressure drop causing downward movement of the sleeve 45 to permit the liquid to pass between the valve seat 43 and valve 44 into the space 55 through ports 57 and into the space 63. Flow into the latter space causes downward displacement of a floating piston 62 against the action of compressed air in space 61. At a predetermined pressure of the liquid above the orifice 48, the valve 50 opens and liquid flows past the valve through ports 54 into space 55. As the strut begins to extend, the sleeve 45 is moved upwardly and the valves 44, 50 are closed, the liquid escaping from space 55 through restricting ports 58 in the plunger-head. As shown in Fig. 1, a bracket 11 is mounted on the cylinder 10 and an arm 12, which carries a wheel axle in a pivoted jaw 16, is pivoted at 13 to the bracket 11 and at 15 to the plunger 14 so that the angle of the plunger relatively to the cylinder varies when the strut is in operation. For this reason, the stem 27 is universally connected at its upper end to the cylinder head 25 and radial movement of the stem in the plunger-head 18 is permitted by a radiallyslidable plate 35 which fits closely around the stem and is held by a spring-ring 37 and plate 36 on a cupshaped part 20 of the plunger-head. The external part 19 of the plunger-head is smaller than the interior of the cylinder to permit it to rock slightly and carries sealing rings 23. In a modification, the restricting orifice 48 is replaced by two restricting orifices in series, one of which is formed by the excesspressure valve.