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.

1 - 27 . (canceled)  
   
   
       28 . 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.    
   
   
       29 . The blood pump of  claim 28 , wherein said second groove progressively increases in size towards said outlet.  
   
   
       30 . The blood pump of  claim 29 , wherein said leakage flow is between said rotor and a spindle of said housing assembly.  
   
   
       31 . The blood pump of  claim 28 , wherein said second groove cooperates with said body to form an outlet passage in communication with said outlet.  
   
   
       32 . A blood pump comprising: 
 a pump housing defining a pump chamber having an inlet port and an outlet port;    a rotor disposed within said pump housing; and    a torus-shaped volute defined by said pump housing; said volute circumferentially disposed around said pump chamber and forming an outlet passage in communication with said outlet port and increasing in diameter towards said outlet port;    said torus-shaped volute having a size that throttles fluid flow upstream of said outlet port and thereby cause a leakage flow between said rotor and said pump housing.    
   
   
       33 . The blood pump of  claim 32 , wherein said volute is disposed around the entire circumference of said pump chamber.  
   
   
       34 . The blood pump of  claim 32 , wherein said volute is comprised of matching grooves of mating portions of said pump housing.  
   
   
       35 . The blood pump of  claim 32 , wherein said outlet passage has a generally circular cross section.  
   
   
       36 . A method of pumping blood comprising: 
 providing a pump housing defining a pump chamber moving blood from an inlet in said pump housing through an impeller of said pump chamber to an outlet in said pump housing; and    increasing the pressure of said blood in said pump chamber upstream of said outlet so as to force a leakage flow of blood between mating surfaces of said impeller and said pump housing.    
   
   
       37 . The method of  claim 36 , wherein said increasing of the pressure of said blood in said pump chamber comprises passing blood through a throttling volute in said pump chamber.  
   
   
       38 . The method of  claim 37 , wherein passing blood through a throttling volute in said pump chamber comprises passing blood through said volute having a diameter between about 2-5 mm.  
   
   
       39 . The method of  claim 37 , wherein passing blood through a throttling volute in said pump chamber comprises increasing a pressure inside the pump relative to the outlet between about 50% and about 100%.  
   
   
       40 - 42 . (canceled)