Vehicle seats

Claim 1

A vehicle seat comprising a base part, a seat part guided by a mechanical linkage for upward and downward movement relative to the base part, a gas spring connected between the seat and base parts and carrying the load of the seat part, the gas spring comprising a piston and cylinder device defining a liquidcontaining chamber and a gas containing chamber and in which a drive piston is movable within the liquid-containing chamber of the cylinder, the drive piston being carried on a hollow piston rod which extends through an end wall of the chamber, and in which a restricted flow passage extends from one side of the drive piston to the other to permit a flow of liquid therethrough to damp the movement of the piston within the cylinder, a control valve within said hollow piston rod, a piston-rod reservoir communicating via the control valve with the liquid-containing space on the side of the drive piston remote from the piston rod, the control valve being operable from outside the cylinder to permit liquid to flow into or out of the piston-rod reservoir thereby to vary the static-load position of the drive piston within the cylinder and hence the position of the seat part relative to the base part, the opposite end wall of the liquidcontaining chamber being formed by a floating piston which fits slidingly within said cylinder opposite said drive piston, and separates said liquid-containing chamber from said gas-filled chamber, said floating piston forming an inner end wall of the gas-filled chamber of the gas spring.