Patent ID: 7779627

Claim:
A variable-displacement piston-cylinder device comprising: a cylinder, said cylinder defining at least two generally cylindrical chambers in substantially coaxial arrangement and having different diameters; an inlet at each of said at least two chambers, each of said inlets being adapted to selectively conduct a fluid into a respective one of said at least two chambers; an outlet at each of said at least two chambers, each of said outlets being adapted to conduct a fluid out of the respective one of said at least two chambers; a piston, said piston comprising at least two piston members joined to one another in substantially coaxial arrangement and having different diameters corresponding to the different diameters of said cylindrical chambers, wherein each of said at least two piston members is movably and reciprocally received in a respective one of said at least two chambers to define a displacement volume for each of said cylindrical chambers; a controller, said controller being operable to select whether the fluid is conducted into either of said at least two chambers via said inlets; and wherein each of said at least two chambers is independently activatable and deactivatable by said controller selecting whether the fluid is conducted into either of said at least two chambers via said inlets.