Patent ID: 6883473

Claim:
A rotary fluid pressure machine comprising a stator, a first surface formed on an interior surface of the stator as a surface of revolution about a first axis, a rotor, a second surface formed on part of the rotor as a surface of revolution about the first axis, the first and second surfaces being mounted for relative sliding rotation, a cylinder formed in the rotor and extending substantially radial to the first axis, a piston slidable axially in the cylinder and being in a sliding fit therein, a crank shaft, coupling means interconnecting the piston and the crank shaft, the coupling means causing reciprocation of the piston in the cylinder to rotate the crank shaft or rotation of the crank shaft to cause reciprocation of the piston in the cylinder, a port formed in the stator extending through said first surface at a predetermined circumferential location in the stator, fluid passing to or from the cylinder through said port, drive means interconnecting the rotor and the crank shaft, the drive means being arranged to rotate the rotor and the crank shaft relative to the stator at predetermined speeds and directions of rotation, and a plurality of said cylinders and said pistons being disposed along a length of the crank shaft such that, in use, an area of said first surface swept by each one of said plurality of cylinders is different from an area of said first surface swept by any other of said plurality of cylinders.