Rotary fluid displacement device having improved porting

Claim 1

In a rotary fluid displacement device comprising, a housing defining a cylindrical chamber having a cylindrical wall and axially opposite end wall means, a drive shaft journaled in the housing on an axis in spaced parallel relation to the axis of the cylindrical wall, an externally toothed star member fixed on the drive shaft, an internally toothed ring member encompassing the star member and journaled in the chamber concentric therewith, said ring member having internal teeth greater in number than the teeth of said star member and moving into and out of engagement therewith during rotation of said members on their respective axes to provide successively expanding and contracting compartments respectively, said star member and ring member each having axially opposite ends in rotary sliding engagement with said chamber end wall means; characterized by inlet and outlet ports defined by said housing in said end wall means in register with said expanding and contracting chambers respectively, and passage means leading from said ports to the exterior of the housing, said inlet port having one end defining a pair of curved portions angularly displaced from each other, the curvature of each of said portions corresponding to the curvature of a tooth portion of a different respective one of said members and coincident respectively with corresponding tooth portions of both of said members in given relative positions of rotation between said members.