Patent GB-1142682-A (GB)
Title: Improvements in and relating to vehicle suspension units
Inventor: BARTRAM MERVYN
IPC: B60G17/027
Filed: 1965-05-01
Abstract: 1,142,682. Self-levelling suspension units. ARMSTRONG PATENTS CO. Ltd. 2 May, 1966 [1 May, 1965], No. 18418/65. Heading F2S. A self-levelling telescopic hydraulic suspension unit comprises a telescopic hydraulic shockabsorber having a piston 20 and piston-rod 22 working within a pressure cylinder 10 surrounded by a coaxial outer cylinder 12 which co-operates with the cylinder 10 to define a low pressure annular hydraulic chamber 14, said pressure cylinder 10 communicating through damper valves 66, (56), Fig. 2 (not shown), with said low-pressure chamber 14, an externally cylindrical end closure member 34, 36 closing and relatively locating the cylinders 10, 12 at their ends remote from that which the piston 20 is introduced into the cylinder 10, the closure member 34, 36 defining a high pressure hydraulic chamber 42 and an hydraulic reservoir chamber 84 which communicates with the low-pressure chamber through a one-way valve (50), Fig. 2 (not shown), a ram cylinder, 78, engaged in fluid-tight sliding relation on the closure member 34, 36 and the outer cylinder 12, fluid control valves 88, 80 in the closure member 34, 36 for controlling fluid flow between the high pressure chamber 42, the ram cylinder 78, and the reservoir 84 and a valve actuating member 92 displaceable axially of the unit. The latter is responsive to departures of the unit from a predetermined mean length and co-operates with the control valves 88, 80 to establish a fluid flow calculated to restore the unit to the predetermined mean length. A suspension spring 76 is constrained between a piston rod abutment 30 and the ram cylinder 78. The high pressure chamber 42 is connected at 86 to a source of high pressure fluid and, if the vehicle weight increases, the member 92, in the form of a cam bar and fully extended from the hollow piston rod 22 by a spring 96, initially moves relative to the plug cap 34, 36 causing a ball 102 of a ram cylinder inlet valve 80 to ride up a shoulder on the cam bar 92 and, through a plunger 104, to open the valve 80. Further compression of the unit causes a stop pad 112 on the cap 34 to engage the upper end of the cam bar 92 which then moves with the cap 34. The initial relative displacement between the cam bar 92 and the cap 36 is not sufficient to move a ball 108 of a ram cylinder outlet valve 88 out of a recess 106 in the cam bar 92. While the valve 80 is held open high pressure fluid flows from the chamber 84 into the ram cylinder 78 to extend the unit to its mean height, whereupon the shoulder 100 disengages from the cam bar 92 and the valve 80 closes. If the weight acting on the vehicle is reduced, the unit extends under the action of the spring 76, the ball 102 remaining on a flat 98 of the cam bar 92 as the latter moves relative to the plug cap 36 so that the inlet valve 80 remains closed. When the extension of the unit is sufficient the ball 108 rides out of the recess 106 to displace the plunger 110 of the outlet valve 88 so that fluid can escape through the open valve 88 from the ram cylinder 78 and pass, through a restrictor 90, into the reservoir 42. The reservoir 42 is connected at (44), Fig. 2, (not shown), to an external reservoir, and, by means of a duct 46, to the low pressure chamber 14. Annular rubber stops 32 are located between a two-part lower end cap 16, 18 and the abutment 30 at the end of the piston rod 22.