Transition valving by means of non-return valves

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

• fluid pressure-operated displacement means associated with said housing, 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 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 cooperating to define a nominal valve overlap;
• wherein the improvement comprises:
• 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,
• fluid non-return valves in each of the second oil passageways to permit the flow of oil therethrough only in a direction to the first oil passageway from the oil chambers;
• and
• a fluid valve means associated with the device and connected to the chambers by third fluid passageways, and pilot operated check valves are imposed in the third fluid passageways to permit fluid flow thereby only in a direction to the chambers from the fluid valve means.