Patent GB-1089650-A (GB)
Title: Improvements in or relating to hydro-pneumatic shock absorber legs, particularly forvehicles
IPC: B60G15/12
Filed: 1966-05-17
Abstract: 1,089,650. Self-levelling hydro-pneumatic suspension units. HOESCH A.G. May 17, 1966 [May 21, 1965], No. 21831/66. Heading F2S. In a self-levelling hydro-pneumatic suspension leg when a pump piston 17, connected by a flexible rod 19 to a hollow piston rod 4, reciprocates in a pump cylinder 16 above a level control aperture 23 outward movement of the piston 17 causes liquid to be drawn from a reservoir 10, containing a pressurized gas, through a conduit 21 having a suction valve 22 and into the pump cylinder 18, subsequent inward movement of the piston 17 pumping liquid past a spring-loaded valve 20 in the piston 17 and into the pressure chamber 11 of a control tube 8 in which a piston 24 with a seal 25 on the inner end of the rod 4 slides. The pumped liquid then passes past a damping valve 14 into an upper pressure chamber 12 to increase the mean pressure of a gas spring chamber 9 and produce a corresponding higher outward displacement force on the piston 24. Relieving the load on the suspension leg causes a downward movement of the suspension leg the seal 25 on the piston 33 passing below a level adjustment aperture 26 so that liquid flows from the upper pressure chamber 12 past a damping valve 13 and into the reservoir 10 until the piston rod is telescoped inwardly and the leg is returned to its normal height. The piston rod 4 enters an outer casing 3 through a seal 6 which, due to an aperture 27, is only subjected to the relatively low pressure of the liquid in the reservoir 10, an hydraulic stop being provided when, on extension of the leg, the seal 25 closes the aperture 27. A floating piston which separates the gas 9 from the liquid in the chamber 12 may be replaced by a rolling- bellows, or membrane, and a separating piston, bellows &c. may be used in the reservoir 10. An excess pressure valve 29 is fitted in a dividing plate 7 the valve blowing off excess pressure in the chamber 12 to the reservoir. The pump piston 17 and cylinder 16 may be inverted, the piston 19 being hollow and connected to the dividing plate 7 and the cylinder 16 being connected to the base of the hollow rod 4. The latter passes through a short guide tube 5. In a modification, Fig. 2 (not shown), the piston (33) is sealed at (34) to the cylinder (16<SP>1</SP>), the pumping piston 17 of Fig. 1 being dispensed with and a valve (35), (36), which replaces the piston valve 20, is located at the upper end of the cylinder (161). The suction valve (22) is also situated at the inner end of the conduit (21) in the upper end of the cylinder (16<SP>1</SP>). A rolling membrane (30), with a support piston (31) and loaded by a spring (32) to raise the pressure of the gas (9) above that of the liquid in the chamber (12), is employed instead of the floating piston 12 as shown in Fig. 1. By providing a plurality of level control apertures 23, 26, Fig. 1, of different aperture sizes, it is possible to change the effectiveness of level adjustment in small steps. The seal 25 may be made of synthetic resin or cast-iron. The upper part of the unit including the casing 3, plate 7 and the parts therein may be formed as a single exchangeable unit.