Patent ID: 8821138

Claim:
A gerotor apparatus, comprising: a housing; an outer gerotor disposed within the housing; and an inner gerotor disposed within the outer gerotor; wherein: at least one of the inner gerotor and the outer gerotor is configured to rotate with respect to the other, at least one of the inner gerotor and the outer gerotor has first and second layers, the first layer is a ceramic, and the second layer is a non-ceramic; wherein a combination of the housing, the outer gerotor, and the inner gerotor is configured for at least a compression or an expansion of fluid; wherein at least one of the inner gerotor and the outer gerotor further comprises protrusions or knobs coupling the first layer to the second layer; and wherein the protrusions or knobs either extend from the first ceramic layer into the second non-ceramic layer or extend from a common point in one of the layers radially outward into the other of the layers.