GB1054403A - - Google Patents

Abstract

1,054,403. Self-levelling hydro-pneumatic suspension units. GIRLING Ltd. Nov. 18, 1963 [Oct. 17, 1962], No. 39246/62. Heading F2S. A self-levelling hydro-pneumatic suspension unit for vehicles comprises a piston 12 which works in a cylinder 11 and which has a hollow rod 13 which extends through a seal 30 in a closure 31 for the lower end of the cylinder 11 the upper end of which is closed by a partition 18 with two-way valves 19, 20 and 19, 21 and carries a pneumatic pressure chamber 10, and a solid pumping rod 17 which is secured to the partition 18, is a sliding fit through an axial bore 22 in the piston 12, and extends within a pumping tube 23 which projects downwardly from the piston into the piston rod 13. The pumping tube 23 communicates, through a one-way valve 24 and an annular chamber 25 in the piston 12 with the hollow interior of the piston rod 13 which acts as a reservoir and accommodates a gas-filled bag 27 and, through a duct 33 and another one-way valve 32, with the high pressure chamber in the cylinder above the piston 12. A port 28 in the wall of the piston rod 13 places the annular space 29 between the piston 12 and the sealing unit 31 in communication with the low pressure space of the reservoir. The rod 17 moves upwardly, on expansion of the unit, to draw fluid from the reservoir through the one-way valve 24 and the annular chamber 25 into the pumping tube 23 and downwardly, on contraction of the unit, to pump liquid from the tube 23 and through the one-way valve 32 into the high pressure chamber above the piston 12 to extend the unit. When the unit reaches its maximum permitted extension the lower end of the rod 17 moves out of the bore 22 and into a counterbore 34 so that liquid can return from the high pressure end of the cylinder to the reservoir 26 by way of the counterbore 34 and a passage 36 in the piston connecting the bore 22 to the annular chamber 25 which is in communication with the reservoir 26. The lower end of the rod 17 is preferably tapered so that as the unit approaches its maximum extension the volume of liquid pumped by the piston is progressively reduced. The orifice 36 may be controlled by a plate or other valve.