Rotary valve for fluid motor or pump

A rotary valve construction coupled to a drive shaft of a fluid motor or pump for selectively controlling fluid flow to a plurality of cavities defined by a stator having internal teeth and a rotor coupled to the drive shaft and having one less external tooth than the number of the teeth of said stator and in mesh with said stator eccentrically for orbital travel about an axis of rotation, said rotary valve construction comprising:

• a pin coaxially coupled to the drive shaft;
• an eccentric circular cam including a driving eccentric shaft and a driven eccentric shaft having a phase difference of 90.degree. with said driving eccentric shaft, said driven shaft having an axis aligned with the axis of said stator, said driving shaft having an elongated hole receiving said pin in a position offset from the axis of said driven eccentric cam by an amount corresponding to the radius of the path of orbital travel of the rotor with respect to said stator so that the orbital rotation of the rotor is transmitted to said eccentric cam;
• a commutator movably fitted on the driven eccentric shaft of said eccentric circular cam for orbital rotation therewith, said commutator having opposite sides and a pair of annular grooves formed in said sides and in communication with each other;
• a spacer rotatably accommodating said commutator and determining a clearance on each side of said commutator, said commutator being rotatable within said spacer and defining a peripheral cavity therewith;
• a port member having a plurality of passages selectively connecting (a) said cavities defined by the teeth of said stator and said rotor and selectively expanded and contracted in response to orbital rotation of said commutator and (b) the annular grooves of said commutator or (c) said peripheral cavity, said port member further having a pair of fluid passages respectively providing permanent communication between said annular grooves of said commutator and said peripheral cavity with the ambient atmosphere through said spacer;
• an end cover axially secured to said stator;
• said port member and said spacer being axially secured, in this axial order, between said stator and said end cover, said end cover rotatably supporting said eccentric circular cam;
• and
• seal means between said end cover and said commutator at locations between the annular groove on the commutator and said peripheral cavity and between the annular groove on the commutator and the eccentric cam.