Patent GB-1035043-A (GB)
Title: Improvements relating to vehicle suspension systems
Inventor: WILKINS DOUGLAS BRIAN
IPC: B60G17/04
Filed: 1963-07-31
Abstract: 1,035,043. Self-levelling suspension struts. GIRLING Ltd. July 17, 1964 [July 31, 1963], Nos. 25354/63 and 8867/64. Heading F2S. [Also in Division B7] In a vehicle suspension system a pump 10, Fig. 1 (not shown), feeds hydraulic fluid from a reservoir 11 through a control valve 12 and pipes 13, 14 to pairs of self-levelling suspension struts 15, 15, and 16, 16 associated respectively with the front and rear wheels of the vehicle hydraulic fluid being returned from the struts through pipes 17, 19 and relief valves 18, 20 to the reservoir 11. As shown in Fig. 2 a pump 29 which draws fluid from a reservoir 24 and which is driven by the vehicle engine, not shown, supplies fluid under pressure, through a non- return valve 33 and a pipe 32 to a hydraulic accumulator 22 which delivers fluid through pipes 27, 23 leading to front suspension struts 21, 21 and through a pipe 28 to rear suspension struts, not shown. Exhaust pipes such as 25 with relief valves 26, 26 connect the suspension struts such as 21, 21, to the reservoir 24, the pipe 32 having a branch pipe 34 leading to a pressure relief valve 35, 36. In an alternative arrangement, Fig. 3 (not shown), a reciprocatable pump 42, driven e.g. by the vehicle engine through a clutch 43 and supplying pressure fluid from a reservoir 45 to an accumulator 41 through pipes 46, 48, has a pressure connection 50 to a piston and cylinder unit 51, 53 in the clutch for disengaging the latter when the pump pressure exceeds a predetermined value. In the systems shown in Figs. 2, 3 the pumps may be of the rotary type and may be driven by an electric motor or by vacuum, and the delivery pipes leading from the accumulators 22 or 41 may include valves which close when the pressure from the pumps cease or fall below a predetermined value. Such a valve, Fig. 7 (not shown), includes a coned valve which is urged off its seat in the pressure delivery line by a piston-and-cylinder unit which is under the influence of the pump pressure. Each suspension strut, Fig. 4 (not shown), comprises a piston 63 which is mounted on a hollow piston rod 64 which works in a cylinder 62 open to atmosphere at its lower end, the pressure chamber above the piston 63 communicating, through a two-way valve arrangement, 68, 69, in a closure member 21 for the upper end of the cylinder 62, with the hydraulic compartment 66 of the suspension unit 60 mounted upon the closure member 21. A diaphragm 67 separates the hydraulic compartment 66 of the suspension unit 60 from a gas spring compartment 65. A valve spool 70 in a blind axial passage 71 in the closure 21 controls inlet and outlet passages 72, 73 connected respectively to the pipe line from the pump or accumulator and the exhaust pipe to the reservoir, the inlet passage 72 being connected below the outlet passage 73 and the spool 70 being urged by a spring 74 against a circlip abutment 75 in the open end of the bore 71 in which position it covers the inlet passage 72. An orifice 76 in the base of the valve spool 70 is normally closed by a seal 81 on the upper end of an axially-movable control rod 77 which is slidable in a bore 78 in the piston 63 and which is urged upwardly by a spring 80. During compression of the strut the valve spool 70 is urged upwardly by the rod 77 to uncover the inlet passage 72 so that fluid under pressure can enter the cylinder 62 above the piston 63. Upon extension of the strut the rod moves away from the valve spool 70 which closes the inlet passage 72, fluid being forced through the orifice 76 in the valve spool and returned to the reservoir when the strut is again compressed. If the loading of the vehicle is increased more fluid under pressure enters the cylinder to maintain the effective length of the strut at its predetermined value as indicated in Fig. 4. In a modification, Fig. 5 (not shown), the suspension unit is separate from the strut which is generally similar to the one shown in Fig. 4 the valve spool being made of sufficient axial length to provide a range of positions in which both inlet and outlet passages are closed during normal short-term oscillations when the vehicle is in motion. The pair of suspension struts for the rear of the vehicle are connected to the same suspension unit. To avoid hydraulic lock by fluid trapped above the valve spool a duct is made through the upper end of the control rod in alignment with the passage through the base of the valve spool.