Rotary hydraulic machine

A rotary hydraulic machine comprising a casing, a shaft mounted for rotation in said casing, said shaft having an eccentric bearing surface intermediate its ends, a plurality of cylinder-piston assembly units disposed radially of and spaced around and exerting radial thrust toward said bearing surface, means individually oscillatingly mounting each of said assembly units on said casing about an axis substantially parallel to said shaft so that the cylinders and pistons of the cylinder-piston assembly units reciprocate relative to each other in a predetermined order upon rotation of said shaft, inlet and outlet passageways disposed in said shaft parallel to the axis thereof for circulating hydraulic fluid through said machine, angularly spaced inlet and outlet cavities in said shaft in communication with said inlet and outlet passageways respectively and opening onto said bearing surface, protruding change-over zones formed on said bearing surface effectively separating said inlet and outlet cavities from each other, and a distribution ring received on said bearing surface cooperating with said change-over zones and disposed between said bearing surface and said cylinder-piston assembly units, said distribution ring having a plurality of generally radial passages each facing and communicating with one of said cylinder-piston assembly units and also communicating alternately with said inlet and outlet cavities, and means permitting eccentric circular movement of said distribution ring while preventing its rotation with said bearing surface on said shaft comprising at least one annular plate arranged around said shaft and adjacent to said distribution ring member, there being a plurality of arcuate guiding openings in said annular plate and a corresponding plurality of guiding pin means in contact therewith, said pin means being fixed relative to one of said casing and distribution ring.