Rotary Blood Pump

Abstract

The present invention provides a rotary blood pump with both an attractive magnetic axial bearing and a hydrodynamic bearing. In one embodiment according to the present invention, a rotary pump includes an impeller assembly supported within a pump housing assembly by a magnetic axial bearing and a hydrodynamic bearing. The magnetic axial bearing includes at least two magnets oriented to attract each other. One magnet is positioned in the spindle of the pump housing while the other is disposed within the rotor assembly, proximate to the spindle. In this respect, the two magnets create an attractive axial force that at least partially maintains the relative axial position of the rotor assembly. The hydrodynamic bearing is formed between sloping surfaces that form tight clearances below the rotor assembly.

What is claimed is: 
     
         1 . A blood pump comprising:
 a housing assembly,   an impeller disposed in said housing assembly   a pump chamber formed from said housing assembly, said pump chamber having an inlet and an outlet; and   an outlet flow path including a first groove positioned around a circumference of the pump chamber forming a torus shape and a second groove connecting to said first groove and said outlet; said second groove having a size larger than a size of said first groove;   said first groove sized so as to throttle flow upstream of said outlet and thereby cause a leakage flow between said impeller and said housing assembly.   
     
     
         2 . A fluid pump comprising:
 a pump housing;   a rotor rotatably disposed in said pump housing;   a plurality of ramps located between said pump housing and said rotor;   a flat surface associated with each of said plurality of ramps;   each of said flat surfaces extending horizontally relative to said angle of its associated ramp;   a passive axial magnetic bearing supporting said rotor and creating a biasing force on the rotor in an axial direction;   said plurality of ramps and said passive axial magnetic bearing sized to cooperate with each other so as to suspend said impeller during operation of said pump.   
     
     
         3 . A method of pumping blood comprising:
 providing a pump housing defining a pump chamber having an inlet and an outlet and a rotor rotatably disposed in said pump chamber;   spinning said rotor   generating a hydrodynamic bearing between said pump housing and said rotor using a plurality of a plurality of lifts positioned between said pump housing and said rotor;   supporting said rotor with a passive axial magnetic bearing   said hydrodynamic bearing and said passive axial magnetic bearing cooperating with each other so as to enhance axial stability to said rotor during rotation of said rotor.