Dual piston strut

A strut for suspending a wheel assembly from a vehicle frame comprising, in combination:

• a main cylinder housing adapted for attachment to a wheel assembly, said main cylinder housing having a bore defining a pressure chamber and having an inlet port for admitting a compressible liquid into said housing pressure chamber;
• a tubular piston adapted for attachment to a vehicle frame, said tubular piston having a bore defining a pressure modulation chamber and having an inlet port for admitting compressible liquid into the pressure modulation chamber, said tubular piston having an annular head disposed in slidable, sealing engagement against the main cylinder housing bore thereby dividing the main cylinder housing chamber into a bounce chamber and a rebound chamber;
• a piston rod mounted on the main cylinder housing and projecting through the main cylinder housing chamber into slidable, sealing engagement against the bore of the tubular piston;
• said piston rod and tubular piston being intersected by flow passages for connecting the bounce chamber into flow communication with the rebound chamber;
• valve apparatus coupled in fluid communication with the bounce chamber, rebound chamber and modulation chamber for controlling the flow of compressible liquid from one chamber to another, said valve apparatus including
• a variable flow restrictor interposed between the bounce chamber and the rebound chamber for adjusting the rate of flow of compressible liquid from the bounce chamber to the rebound chamber and from the rebound chamber to the bounce chamber, respectively;
• and,
• a check valve interposed between the pressure modulation chamber and the bounce chamber for permitting one way flow of compressible liquid from the pressure modulation chamber into the bounce chamber, and for blocking reverse flow thereof.

A suspension system for use on a vehicle having a frame, a wheel structure, and means for generating a vehicle operating parameter signal, said suspension system comprising:

• a liquid spring adapted to be operably interposed between the vehicle frame and wheel structure for utilizing a compressible liquid to exert spring and damping forces to reactively control relative vertical displacement between the vehicle frame and wheel structure, said liquid spring including a main cylinder having a bore defining a main pressure chamber and a duel piston assembly disposed within said main pressure chamber, said dual piston assembly including a piston rod attached to the main cylinder and a tubular piston movably mounted on the piston rod, said tubular piston having a head portion dividing the main pressure chamber into a bounce chamber and a rebound chamber, a tubular strut portion projecting out of the main pressure chamber, and a bore formed in the tubular strut portion defining a pressure modulation chamber, said pressure modulation chamber having an inlet port for admitting compressible liquid into said pressure modulation chamber;
• valve apparatus coupled in fluid communication with the bounce chamber, rebound chamber and pressure modulation chamber for controlling the interchamber flow of compressible liquid from one chamber to another;
• and
• control apparatus coupled to said liquid spring for controlling the bounce chamber pressure, pressure modulation chamber pressure and interchamber flow rate in response to a sensed variation in a vehicle operating parameter signal.

A liquid spring suspension system for use on a vehicle having a frame and a wheel structure, said suspension system comprising:

• a liquid spring including a tubular housing having a main chamber disposed therein for containing a compressible liquid, a tubular piston reciprocally disposed in said chamber and having a head portion dividing the main chamber into bounce and rebound chambers and having a bore, a piston rod mounted on said housing and slidably and sealingly engaged against the bore of the tubular piston, said tubular piston having an external end portion disposed outwardly of said housing and internally defining a pressure modulation chamber having a flow port through which a compressible liquid may be flowed into and out of said pressure modulation chamber, and a damping flow annulus defined between the bounce and rebound chambers;
• means for operatively associating said liquid spring with said frame and said wheel structure in a manner such that relative vertical movement between said frame and said wheel structure causes relative axial translation between said tubular piston and said housing;
• and,
• means for adjustably restricting interchamber flow between the bounce and rebound chambers in response to variation in at least one vehicle operating parameter, to thereby selectively vary the damping force of said liquid spring.