Transition valving by means of non-return valves

A rotary fluid pressure device of the type including housing means having a fluid inlet port and a fluid outlet port;

• fluid pressure-operated displacement means associated with said housing means, and including an internally-toothed ring member, and an externally-toothed star member eccentrically disposed within said ring member for relative orbital and rotational movement therebetween to define a plurality of expanding and contracting fluid volume chambers in response to said orbital and rotational movements, and minimum and maximum volume transition chambers;
• a valve member cooperating with said housing mean to provide fluid communication between said inlet port and said expanding volume chambers and between said contracting volume chambers and said outlet port;
• said valve member and said housing means cooperating to define a nominal valve overlap;
• said device being characterized by:
• a first oil passage with relatively high pressure fluid therein surrounding the gear set,
• a plurality of second oil passageways connecting the first oil passageway to the expanding and contracting oil chambers, and
• fluid non-return valves in each of the second oil passageways to permit the flow of oil therethrough only in a direction from the first oil passageway to the oil chambers.