Centrifugal Pump

Abstract

The pump, which is for implantation into a human heart, has a flow path through a housing ( 1 ), a rotatable pump member ( 21 ) within the housing for causing fluid to flow along the flow path, the pump member being rotatably coupled to the housing about an upstream bearing ( 32 ) and a downstream bearing ( 33 ). The downstream bearing comprises a bearing member ( 34 ) on the pump member and a complementary bearing formation ( 35 ) on the housing, The pump has a mechanical adjuster ( 42 ) for fine adjustment of the position of the bearing formation ( 35 ) along an axis (A) of the pump member; the mecahnical adjuster being preferably one or more screws ( 42 ) for adjustable movement of a boss ( 40 ) along the axis (A), the adjustable movement being permitted by flexure of a plate member ( 41 ) integral with the boss.

1 - 14 . (canceled) 
     
     
         15 . A centrifugal pump comprising:
 a) a housing comprising a fluid inlet, a fluid outlet, a flow path which extends between the fluid inlet and the fluid outlet, and a plate member forming part of the housing;   b) a rotatable pump member including an impeller configured to rotate about an axis of the pump member, the impeller being within the housing and configured to cause fluid to flow along said flow path from said fluid inlet to said fluid outlet;   c) an upstream bearing for coupling the pump member to the housing;   d) a downstream bearing comprising a bearing member on the pump member and a bearing formation on the housing, said bearing formation being complementary to said bearing member; and   e) a mechanical adjuster for fine adjustment of the position of said bearing formation along the axis of the pump member, said mechanical adjuster being configured to flex the plate member and move the bearing member along the axis of the pump member.   
     
     
         16 . A pump according to  claim 15 , wherein the bearing formation is provided in a boss integral with the plate member. 
     
     
         17 . A pump according to  claim 16 , wherein the boss has an outer circumferential surface and the bearing member has an inner circumferential portion, and wherein the outer circumferential surface is complementary in shape and size to the inner circumferential portion. 
     
     
         18 . A pump according to  claim 17 , wherein the complementary shape and size provide a clearance spacing between the bearing formation and the bearing member. 
     
     
         19 . A pump according to  claim 15 , wherein the plate member comprises a flexible diaphragm surrounding the bearing formation. 
     
     
         20 . A pump according to  claim 19 , wherein the mechanical adjuster comprises a helically threaded screw that is coaxial with the pump member. 
     
     
         21 . A pump according to  claim 20 , wherein the helically threaded screw has a first end with a head arranged to act on the bearing formation and a second end having a drive arrangement configured to permit the screw to be driven to act on the bearing formation. 
     
     
         22 . A pump according to  claim 21 , wherein the second end is substantially flat, apart from said drive arrangement. 
     
     
         23 . A pump according to  claim 21 , wherein the first end is substantially flat and is connected to the body of the screw by a frustoconical portion which tapers inwardly to said first end. 
     
     
         24 . A pump according to  claim 15 , which is a cardiac pump in which the flow path is a primary blood flow path, wherein said impeller has an impeller shroud defining a secondary blood flow path between said pump member and said housing, said secondary blood flow path comprising an entrance and an exit; said entrance and exit being in fluid communication with said primary blood flow path, with said exit being upstream in said primary flow path relative to said entrance, such that blood flow along said primary flow path results in reduction of pressure at said exit relative to that at said entrance and consequent flow of blood along said secondary flow path. 
     
     
         25 . A cardiac pump according to  claim 24 , wherein said housing comprises a cannula section and a pump section including a pumping chamber, said inlet being disposed on said cannula section and said outlet being disposed on said pumping chamber. 
     
     
         26 . A cardiac pump according to  claim 25 , in which said cannula section is configured to extend from an internal part of the ventricle to straddle the wall of the ventricle.