Patent ID: 7530801

Claim:
A rotary fluid pressure device of the type having a housing means defining a fluid inlet and a fluid outlet, a fluid energy-translating displacement means defining expanding and contracting fluid volume chambers, a stationary valve member defining fluid passages in communication with said expanding and contracting fluid volume chambers and having a valve surface, a rotary valve member defining valve passages providing commutating fluid communication between said fluid inlet and said fluid outlet and said fluid passages and having a valve surface in sliding, sealing engagement with said valve surface of said stationary valve member, said rotary valve member further having an opposite surface; characterized by: (a) an outer balance ring member having a valve-confronting surface in engagement with said opposite surface; (b) an inner balance ring member having a valve-confronting surface in engagement with said opposite surface, wherein the inner balance ring member includes a retainer member preventing rotation of said inner balance ring member relative to said rotary valve member; and (c) said outer balance ring member and said inner balance ring member cooperating to define a fluid passage for providing fluid communication between one of said fluid inlet and said fluid outlet and said valve passages.