GB1061141A - Improvements in and relating to vehicle telescopic suspension units - Google Patents

Abstract

1,061,141. Hydraulic shock absorbers. ARMSTRONG PATENTS CO. Ltd. Aug. 20, 1963 [July 5, 1962], No. 25833/62. Heading F2S. A telescopic hydraulic suspension unit for vehicles comprises a telescopic hydraulic shockabsorber having an internal low-pressure chamber for the hydraulic medium and a coil suspension spring 88 coaxially surrounding the shockabsorber. One end of the spring 88 is fixed with respect to one of the telescopic parts of the shock-absorber while a cylindrical hydraulic ram means carried by the other telescopic part provides a seating for the other end. The ram means is supplied with pressurized hydraulic fluid from a pressure source, a release valve allowing the ram means to be exhausted to the low pressure chamber whenever the telescopic parts extend beyond a predetermined mean position relative to each other. In the construction shown the shock-absorber includes a piston 20 working in a cylinder 10 and having a central bore communicating with a tubular piston-rod 22. A pump piston 32 which supplies pressurized fluid to the ram means is slidably received within the piston 20 and rod 22 its movement being limited by engagement with a projection in the piston bore. The pump piston 32 comprises a slidably mounted bush formed at the upper end with a valve seat, the sleeve in its lower position allowing fluid to flow across the pump piston but in its upper position engaging with a further valve seat of the pump piston-rod 30 to prevent the flow of fluid (Fig. 9, not shown). The pump piston-rod 30 projects into a dome 18 of an annular cup member 16 to form a pump chamber 96, the member 16 also closing the cylinder 10 and a further cylinder 12 concentric therewith. A reservoir 40 is provided between the cup member 16 and a cap 38. Plate valves 36, 32 having leak paths control the flow of hydraulic fluid through the piston 20 and between the reservoir 40 and the working cylinder 10 and, for large shocks, spring-loaded damping valves 55, 57 each connect one end of the working cylinder to the reservoir through annular chamber 42 between the cylinders 10, 12 and a passage 44. The hydraulic ram means comprises a ram cylinder 72 within which slides a ram 74 having a skirt 76 which is slidably mounted on the cylinder 12, the lower end of the skirt being formed with a flange portion 82 against which the spring 88 abuts. The flange portion engages a circlip 83 to limit its downward movement. The pump chamber 96 connects with the ram chamber 80 through a spring-loaded delivery valve, an annular clearance and a groove 90 and a passage connects the ram chamber 80 through the release valve to the reservoir 40. The release valve consists of a spring-loaded valve ball which is engaged by a push-rod and ball assembly, the ball being slidably located in the pump piston-rod bearing 46 and received in a depression in the pump piston-rod (Fig. 1, not shown). The end cap 16 is further provided with a pump inlet valve and a pump overload relief valve. If the shockabsorber is extended beyond its normal riding position due to hydraulic fluid being pumped continuously into ram chamber 80 through the load delivery valve the pump piston 32 engages with the piston 20 and the piston-rod 30 is withdrawn from the chamber 96 unseating the ball and opening the release valve to partly vent the ram chamber. Similarly if the shock-absorber is shortened due to a heavy load the pressure of the hydraulic fluid in the pump chamber 96 increases due to the continuous pumping action of piston 32 and the pressurized fluid is then pumped through the load delivery valve into ram chamber 80 to extend the shock-absorber to its mean riding position. In a modification, Figs. 5, 6, 7, 8 (not shown), the ram slides on the outer surface of the ram cylinder, the ram chamber being formed between the outer cylinder 12 and the skirt of the ram. Further in place of the cylindrical mounting bush at the upper end of the shock-absorber a part of the vehicle frame is interposed between a pair of resilient buffer members. The pump may be situated independently of the suspension unit such that the pump may actuate several of these units.