Patent GB-943294-A (GB)
Title: Improvements in or relating to hydro-pneumatic suspension device for vehicles
IPC: B60G15/12
Filed: 1961-07-24
Abstract: 943,294. Vehicle suspensions. USTAV PRO VYZKUM MOTOROVYCH VOZIDEL PRAHA. July 24, 1961 [July 27, 1960], No. 26716/61. Heading B7D. A vehicle suspension system comprises a plurality of hydro-pneumatic suspension levelling units, the units being initially fed with oil to bring them to the operating height by a pump 27 which is associated with a power braking, steering or hoisting mechanism and may be connected to its normal circuit, or to the suspension system, by a three-way valve 30. Each unit comprises a main cylinder 1 in which operates a piston 4, 5 and a small cylinder 3, integral with the head of cylinder 1, in which operates a piston 6 connected to the main piston 4, 5, which is connected to the vehicle axle, the cylinder 1 being connected to the vehicle body. The unit is initially retracted and pressure fluid flows from the pump 27 through non-return valve 32 and line 33 until the latter is blocked by the piston 6. On the head of cylinder 1 is provided a cap 8 enclosing a diaphragm 7 separating an air chamber above from an oil compartment below, a spring 12 acting upon the diaphragm and the air chamber being in communication through a passage 14 with a second chamber 11. The cylinder 3 communicates with the oil chamber 10 in the cap 8 through a non-return valve 17 and a passage 34 is provided for the free flow of liquid between the chamber 10 and cylinder 1. At the base of cylinder 1 a reservoir 2 communicating with the pump reservoir 29 is provided and a pipe 15 connects the reservoir 2 with the cylinder 3 through a non-return valve 16. Connections between the cylinder 1 and pipe 15 are made by pipes 24 and 25 which include a valve 21 with a wide head 22. An aperture 18 connects the cylinder 3 with the cylinder 1 and the interior of piston 4, 5 has an aperture 19, and apertures controlled by valves 20. In the riding position, oscillations of the piston 4, 5 are subjected to a springing effect from the air in the cap 8. Upon excessive movement, the spring 12 and diaphragm 7 would seal the opening 14 to the second air chamber 11. The oscillations of piston 4, 5 cause a pumping action in cylinder 3, the oil normally returning through aperture 18. When the piston 6 covers aperture 18, oil is pumped from pipe 15 past non-return valve 16 and is forced into the chamber 10 and returns to the cylinder 1 through passage 34, thereby forcing the piston 4, 5 downwardly and so effecting height adjustment. On downstroke of the piston 4, 5, oil is forced into the reservoir conduit 15 past the valve 23 which is subject to the oil pressure prevailing in the cylinder 1 upon its head 22. Upward movement of the piston 4, 5 is damped by passage of fluid through the valves 20. At a lower position of the piston 4, 5 oil returns to reservoir through the passage 19 when this is within the reservoir 2. In a modification, Fig. 2, the cylinder 3<SP>1</SP>, located outside the cylinder 1, acts in a corresponding manner, the piston 6<SP>1</SP> being actuated by an abutment 36 on the axle above a certain mean position. In a further modification, Fig. 3, height adjustment is effected only when the vehicle is laden. Until the aperture 18 is closed, the pump 27 cannot fill the apparatus, and can only do so when the vehicle is laden and the aperture 18 is closed, liquid otherwise returning through the passages 43, 44 and 45 to the reservoir.