GB978944A - Improvements in hydro-pneumatic self-levelling - Google Patents

Abstract

978,944. Hydropneumatic suspensions; levelling. SOC. D'ETUDES ET D'APPLICATIONS INDUSTRIELLES COMMERCIALES ET IMMOBILIERES INTER-TECHNIQUE. March 19, 1962 [April 4, 1961], No. 10353/62. Heading B7D. A road vehicle suspension system comprises suspension units A and A<SP>1</SP> for the steered wheels and B and B<SP>1</SP> for the non-steered wheels, the latter each comprising a piston 4 operating within a cylinder 6, the pistons 4 being attached to the rigid axle 10 and the cylinders 6 being connected to the sprung part 9 with the interposition of a resilient mount 63. The units A, A<SP>1</SP> each comprise a tube 3 connected to the sprung part 12 with the interposition of a resilient mount 73, the tube being telescopic within a cylinder 5 incorporated within a casing 82, the lower end of which is integral with a stub shaft 11 upon which the wheel is mounted. Each unit comprises a pneumatic spring 1 or 2 having a flexible diaphragm 1a or 2a separating the air from an hydraulic liquid, the liquid space being in communication with the interior of tubes 3 or cylinder 6, respectively, through throttling devices 21 and 23. The hydraulic system comprises a constant volume pump 20 driven from the engine through a cam-shaft 54 and cam 55; a fluid reservoir 21; overload valve 60 and a cushioning device 57 for absorbing percussive effects from the pump. The pressure fluid supply through line 30 is divided in a fixed ratio independent of pressure by a flow divider 30a into lines 35 and 29 leading to the units AA<SP>1</SP> and BB<SP>1</SP> through non-return valves 40, the lines 7 and 8 connecting the units A and A<SP>1</SP>, B and B<SP>1</SP>, respectively, each being provided with throttling orifices 41 and 42. The telescoping tubes 3, 5 and the piston and cylinder 4, 6 are expanded by fluid pressure until orifices 28, 50 are uncovered when the pressure liquid is returned to the reservoir through lines 32, 33 and 25, 26 respectively. Road shocks are transmitted to the air cushions 1 and 2 through the hydraulic fluid. The swinging arm suspension members 68 of the steered wheel assembly are connected by a torsion bar 17 mounted in bearings 18 rigid with the vehicle and the suspension units of the driving wheels are similarly connected by a torsion bar 13 and links 16. When a suspension unit is contracted, e.g. due to loading so that its exhaust orifice, 28 or 50 is covered, flow through the supply line 7 or 8 is checked and, due to the throttling devices 41 and 42, there is a build-up of pressure, tending to restore the suspension device to its former position of equilibrium, augmented by the action of the torsion bar 17 or 13. In the opposite condition, the torsion bar tends to restore the unit to the equilibrium position. The non-return valve 40 and throttling orifices 41 and 42 are incorporated in a single unit, Fig. 2, the valve 40 comprising a rod 44 and flexible annulus which permits flow in one direction and not the other. The throttling orifices are provided in diaphragms 41 and 42. The suspension units BB<SP>1</SP> are described in Specification 917,991, and the units AA<SP>1</SP>, which are subject to torsional strains in operation, comprise the tube 3, slidable within bushes 80 and 81 in an upper sleeve 79 constituting part of the cylinder 5, the sleeve 79 being retained within a tubular member 82 with which the stub shaft 11 is integral and which is mounted in a swivel bearing 86 for steering movement from a steering arm 65. The lower part of the cylinder 5 comprises a sleeve 52 and closed cylinder 78 mounted by a spherical gearing face of a flange 83 upon a bush 84 in the member 82, Fig. 4. A sealing device 49 is provided between the tube 3 and the tubular member 82. The pneumatic springs 1 are mounted on flexible members 76 and a swivel connection 74 is provided in the line 75 communicating with the tube 3. When the pump is inoperative, the hydraulic units tend to contrast due to leakage, and sealing rings 61 and 37 are provided to limit the movement.