US Patent 7278841 Gerotor pump

Improved gerotor pumps comprising laterally constrained floating rings, thereby providing an orthogonal degree-of-freedom and allowing gerotor sets positioned therein to establish their own preferred mesh orientation, and additionally wherein the outer rotor of the gerotor set is forcibly positioned against the inner rotor of the gerotor set at the gerotor set's in-mesh position whereat there is little relative motion between the inner and outer rotors, thereby resulting in a substantially friction- and wear-free meshing action of the gerotor set.