Patent ID: 8409276

Claim:
A heart assist device, comprising: a rotary pump housing having a cylindrical bore, a pumping chamber at one end of the cylindrical bore and a motor stator including an electrically conductive coil located within said housing and surrounding a portion of said cylindrical bore, and also comprising a rotor, said rotor having a cylindrical shaft with an outer surface and at least one impeller appended to one end of said shaft; wherein said rotor comprises a plurality of magnets located within said shaft and opposite said motor stator; wherein said bore has an inner surface that is closely fitted to the outer surface of said shaft forming a journal bearing comprising a journal bearing clearance; wherein when said rotor is positioned and rotates within said bore, said at least one impeller is positioned and rotates within the pumping chamber; and wherein said pumping chamber and said journal bearing are connected by a leak path to allow blood to pass between the pumping chamber and the journal bearing wherein said rotor is solely suspended in the radial direction within said housing by hydrodynamic thrust forces generated by relative movement of said rotor with respect to and within said pump housing.