GB1229880A - - Google Patents

Abstract

1,229,880. Hydraulic shock absorbers. OLEO INTERNATIONAL HOLDINGS Ltd. 8 Jan., 1969 [23 Jan., 1968; 30 May, 1968], Nos. 59636/68 and 25687/68. Heading F2S. A valve for providing, in an hydraulic shock absorber, a damping-force (R) to fluid-velocity (V) characteristic of the form shown as A + B in Fig. 8, consists of a composite valve member 42-43, Fig. 2, which is spring biased toward a liquid outlet 37. The valve provides a flow path passing in series through an orifice 45 in the inner valve element 43 and an annular gap 46 between the elements 42 and 43. In parallel with these is a flow path which is closed until sufficient fluid pressure has built up to move the complete valve member against its spring 44 and so displace the valve surface 41 from the outlet 37. At low flow velocities only the series path is open and the orifice 45 (whose characteristic is A in Fig. 8) is less restricted than the gap 46. At higher flow velocities, relative axial separation of the two valve elements progressively lessens the resistance of the gap 46 (whose characteristic is B). The combined effect is the substantially linear characteristic A+B of Fig. 8. At higher velocities, the parallel flow path opens and the resistance to flow will not increase further-hence the horizontal (" cutoff ") portion of the overall characteristic as shown in Fig. 8. Varying the spring bias, by rotating screw 48, can make the overall characteristic correspond to the A+C curve in Fig. 8. In the shock absorber of Fig. 1 (not shown), a piston is contained in the inner one of three concentric tubes so interconnected by ports that both directions of piston movement result in flow of fluid in the same direction between the innermost and outermost tubes. The valve of Fig. 2 is interposed in this flow path, the valve's longitudinal axis (left to right in Fig. 2) being disposed perpendicular to the shock absorber axis and tangential to an imaginary cylinder situated in the annular gap between the outermost tube and the intermediate tube of the shock absorber. Figs. 3 to 6 (not shown) depict modifications of the Fig. 2 valve, in which (a) the elements corresponding to 41 and 43 of Fig. 2 have conical interengagement; (b) the screw 48 of Fig. 2 is replaced by a rolling diaphragm fluid displacer. The latter is designed to be operated by a compressed air supply in a vehicle in whose suspension system the valved shock absorber is incorporated.