Vehicle suspension systems

Claim 1

A vehicle suspension system for a vehicle having a structure supported on at least two pairs of wheels by means of a liquid-filled strut for each wheel of first and second pairs of wheels, first and second valves controlled by sensors responsive to up-and-down movement of respective wheels of a first wheel pair to admit liquid under pressure or release liquid to or from a chamber of the respective struts to resist vehicle roll, a third valve controlled by a sensor responsive to up-and-down movement of the structure relative to the second pair of wheels to admit or release liquid under pressure to or from both struts of the second pair, the struts of the second pair each having a second liquid chamber the volume of which varies with up-and-down movement, each such second chamber being in open communication with the chamber of a strut of the first pair so that the pressure in said second chamber of each strut of the second pair varies with the pressure in the first chamber of one of the struts of the first pair, the arrangement being such that the changes of pressure in said second chambers produce roll resistance at the second pair of wheels in the same sense as the roll resistance produced at the first pair of wheels, wherein each strut has a sensor associated therewith for indicating the amount and sense of departure from a datum position and the system includes means for controlling the flow rate through each valve to or from the associated strut(s) in such a manner that each said flow rate is proportional to the sensed departure (or the algebraic sum of the sensed departures) from the datum position or positions, the direction of flow being such as to restore the associated strut or struts to the datum position(s).