Patent ID: 6871845

Claim:
A self-pumping, hydropneumatic suspension strut unit with an internal level control for a vehicle, the strut unit comprising: a low pressure chamber ( 6 ) and a high pressure chamber ( 7 ) for storing a damping medium under pressure, the high pressure chamber ( 7 ) comprising a gas cushion ( 19 ) for displacing the stored damping medium from the high pressure chamber ( 7 ) when the damping medium is less than a predetermined pressure; a working cylinder ( 16 ) associated with the low and high pressure chambers ( 6 , 7 ); a piston ( 11 ) sealed in the working cylinder ( 16 ) so as to define a first volume ( 18 ) of the working cylinder ( 16 ) in fluid communication with the high pressure chamber ( 7 ); a piston rod ( 2 ) connected to the piston ( 11 ) and axially displaceable in an inward direction and an outward direction relative to the working cylinder ( 16 ); a pumping rod ( 3 ) axially mounted at one end of the working cylinder ( 16 ); a regulating bore ( 10 ) disposed on the pumping rod ( 3 ) at a first location of the pumping rod ( 3 ) so that the regulating bore ( 10 ) is closed when the first location is received in the piston rod ( 2 ) and so that; the regulating bore ( 10 ) places the low pressure chamber ( 6 ) in two-way fluid communication with the first volume ( 18 ) when the regulating bore ( 10 ) is open; a cavity ( 12 ) defined axially in the piston rod ( 2 ) for receiving the pumping rod ( 3 ) and providing a one-way fluid communication path from the low pressure chamber ( 6 ) to the first volume ( 18 ), a bypass ( 9 ) associated with the cavity ( 12 ) and defined at a second location on the pumping rod ( 3 ) so as to be closed when the second location is received in the piston rod ( 2 ), the second location being disposed more proximate to an end of the piston rod ( 2 ) mounted in the working cylinder ( 16 ) than the first location and the bypass ( 9 ) being disposed for placing the cavity ( 12 ) in additional fluid communication with the first volume ( 18 ) when the bypass ( 9 ) is open; and means for producing an elastic force for urging the piston rod ( 2 ) in the inward direction; wherein when pressures in the low pressure chamber ( 6 ) and in the high pressure chamber ( 7 ) are equal, the means for producing an elastic force displaces the piston rod ( 2 ) in the inward direction so that the piston rod ( 2 ) and the pump rod ( 3 ) cooperate to increase the pressure in the high pressure chamber ( 7 ) to the predetermined pressure whereupon the damping medium displaces the piston rod ( 2 ) in the outward direction until the regulating bore hole ( 10 ) is open so that the pressure between the low pressure chamber ( 6 ) and the high pressure chamber ( 7 ) is equalized.