Rotary hydraulic machines

Claim 1

A rotary hydraulic machine comprising a housing having an inlet and an outlet, a rotor mounted within the housing, a plurality of pistons slidable in radial bores in the rotor, the said bores successively communicating, in use, with the inlet and the outlet, a port plate fixed in the housing and engaged by the rotor to act as a valve to control communication between said bores in the rotor and the inlet and outlet, said rotor including ports communicating respectively with the bores and opening onto a face of the rotor which is engaged by said port plate, said port plate having a kidney-shaped port spaced from the edge of the port plate in the path of movement of the rotor ports thereover, by a distance greater than the width of each of said rotor ports, and a cam ring surrounding the rotor and having an internal cam surface engageable by the pistons, the cam ring also having an external surface of revolution which engages a corresponding surface within the housing, and the cam ring being rotatable within the housing about the axis of said outer surface, said outer surface being eccentric with respect both to the axis of the cam surface and the axis of the rotor, and means for rotating the cam ring within the housing, the cam ring being positioned so as to provide movement of said piston while said ports are shut, whereby, in use, there is a period in each revolution of the rotor when each port is shut off by the port plate so that liquid in the associated bore is subjected to a change of volume and pressure, said machine further including two cam rings arranged with the areas of their external surfaces equally spaced from the axis of the rotor, said axes lying in a common plane and which the rotor has two rows of radial bores slidably containing pistons engaged with the internal cam surfaces of the cam rings respectively.