Patent GB-775294-A (GB)
Title: Improvements in or relating to shock absorbers for vehicles
IPC: B62K25/06
Filed: 1953-04-15
Abstract: 775,294. Hydraulic shock absorbers. CREFFIELD, J. K. [July 15, 1954], No. 10305/53. Class 108(3). A shock absorber comprises a hydraulic transmission embodying an actuator member 7, Fig. 2, interposed between the resilient suspension medium 5 and either the sprung or unsprung mass, a pump for displacing hydraulic fluid to or from the actuator 7 and means to control the movement of the actuator by varying the liquid displaced by the pump, so as to vary the ratio of the relative vertical movement of approach of the sprung and unsprung masses to consequent deflection of the resilient medium. In Fig. 2, a floating cylinder 7 carrying the actuator piston 6, is slidable in relation to a reservoir cylinder 15 carrying a piston 8 and the connection 1 to the sprung mass, and a cylinder 12 carrying the connection 2 to the unsprung mass. A metering rod 19 rigid with the cylinder 12 coacts with a damping orifice 18 in the piston 8. Expansion of the ports is limited by a stop 22 and a seal ring 24 is provided. In operation, on compression, pressure developed by the piston 8 in the cylinder 7 acts on the lower face of bushes 9, 10, rigid with the upper and lower ends of cylinder 7. This deflects the cylinder upwardly and carries with it the piston 6 to impose additional loading on the suspension spring 5. Liquid damping action occurs due to flow through ports 26 (which may be valve controlled) a port 13 leading to the lower face of bush 10 and the metering orifice 18. In a modified construction, Fig. 3 (not shown) the piston 8 is slidable in a cylinder rigid with the unsprung mass connection 2. The cylinder 7 is mounted in coaxial sliding relation with the outside of the latter cylinder. The ports 26 are controlled by a flap valve which closes against the return of liquid from the reservoir on rebound. Liquid flows back through apertures in the valve which are masked by a washer plate held by a shim at a predetermined spacing from the valve. In Fig. 4, a leaf spring 108a and an hydraulic actuator piston and cylinders 107, 105, are disposed in series between the sprung mass (S.M.) and the unsprung mass (U.S.M.). The cylinder 105 is fed with liquid from a reservoir 110 by the action of a rotary pump 100. A reducing valve 102 is provided to bleed liquid from the output of the pump 100. The loading of the valve 102 is variable according to the setting of a linkage 104 which depends on the distance between the sprung and unsprung masses. Non- return valves 106, 112, further control liquid flow to and from the cylinder 105. In a modification, Fig. 1 (not shown), the spring 108a is a coil spring and the valve 102 is a rotary form of slide valve, but controlled by a linkage similar to 104. It may, however, be controlled manually. The pump 100 is replaced by a reciprocating pump having its piston and cylinder connected respectively to S.M. and U.S.M. The action of the valve 102 may be supplemented by the action of suitable respective flow control orifices in the conduit leading to the cylinder 105 and the return conduit to the reservoir. The former, Fig. 6b (not shown) is such as to promote laminar flow. The latter, Fig. 6a (not shown) is such as to promote turbulent flow. This has the effect of stiffening the cylinder 105 in proportion to the velocity of the shocks imparted to U.S.M. In a further modification of Fig. 4, Fig. 5 (not shown), the spring 108a is provided by a pneumatic cylinder forming an extension of the cylinder 105. The pump is a reciprocating one, and is combined with the valve 102 which is in the form of a stem rigid with the pump piston. The stem is arranged to progressively cut off ports which provide an escape path to the reservoir, as U.S.M. and S.M. relatively approach. The suspension spring may be a torsion bar or rubber spring.