GB1409875A - Hydropneumatic suspension unit for'ehicles - Google Patents

Abstract

1409875 Self-pumping self-levelling systems GIRLING Ltd 10 Oct 1972 [15 Oct 1971] 47983/71 Heading F2S A hydropneumatic self-pumping self-levelling suspension unit or system for a vehicle, in which the load is supported by gas in a pressure chamber, the volume of gas being variable in accordance with the load by liquid drawn from a reservoir 7, has a pressure relief valve 41-44 which is normally closed but opens to place the pressure chamber in communication with the reservoir 7 when the pressure within the pressure chamber exceeds a predetermined value because of a sudden shock loading. The pressure relief valve is required to be a plurality of valve members 42 held on to their seats 43 by an annular washer 44. The load-bearing pressure chamber (not shown) may be inside the unit, or outside the unit and connected to it by a union 36. During the normal levelling operation with the unit contracted under increased load to less than its mean length and the piston 17 covering a levelling port 40, liquid is pumped from the reservoir 7 via a valve 29 into a hollow piston-rod chamber 16 (on downward movements of the piston) and from the chamber 16 via a valve 33 (on upward movements of the piston) into the chamber above the piston and into a chamber 34 which is in communication with the load-bearing pressure chamber. As the piston oscillates pumping continues until sufficient liquid has been pumped from the reservoir 7 to the pressure chamber to force the piston down until the unit is extended to its mean length, and the piston uncovers the levelling part 40 to allow flow back from the pressure chamber to the reservoir 7 and prevent further extension of the unit. However in the event of a sudden shock loading the pressure in the pressure chamber opens the pressure relief valve 41-44 and allows liquid to flood back into the reservoir 7.