Hydrodynamic chamfer thrust bearing

An implantable blood circulating pump, the pump comprising:

• (a) a casing having an interior bore having an axis, an upstream end, a downstream end, and a stop surface bounding the bore, the stop surface being substantially in the form of at least a portion of a conical surface of revolution about the bore axis having a diameter increasing progressively in a downstream direction along the bore axis;
• (b) a rotor disposed within the bore, the rotor comprising a magnetic, biocompatible body including a plurality of vanes defining a plurality of channels therebetween, the rotor being constructed and arranged to impel blood downstream upon rotation of the rotor within the bore in a forward circumferential direction about the axis, the vanes having hydrodynamic thrust bearing surfaces, each such thrust bearing surface having a normal vector with non-zero components in the upstream and circumferentially forward directions and being constructed and arranged to apply a hydrodynamic force to the rotor with a component of the force in the downstream direction upon rotation of the rotor in the forward circumferential direction, wherein the vanes include chamfer surfaces generally in the form of portions of a conical surface of revolution about the axis having increasing diameter in the downstream direction, each thrust bearing surface is positioned completely on a particular chamfer surface and each thrust bearing surface defines a pocket in the chamfer surface, wherein the chamfered surfaces include a chamfer angle such that the chamfered surfaces are positioned at an angle relative to the axis and a generally cylindrical surface of revolution of the biocompatible body, the chamfer angle is in the range of about 20 degrees to less than about 45 degrees;
• and
• (c) a stator disposed in proximity to the casing outside the bore, the stator including one or more electromagnetic coils for applying a magnetic field to the rotor so as to rotate the rotor about the axis.