Sealless rotary blood pump with passive magnetic radial bearings and blood immersed axial bearings

• US 5,695,471 A
• Filed: 02/20/1996
• Issued: 12/09/1997
• Est. Priority Date: 02/20/1996
• Status: Expired due to Term

• Current Assignee: Thoratec LLC
• Original Assignee: Kriton Medical, Inc.
• Inventors: Wampler, Richard K.
• Primary Examiner(s): Rimell, Sam
• Application Number:
  US08/603,536
• Time in Patent Office: 658 Days
• Field of Search: 623/3, 417/321, 417/423.1, 417/423.7, 417/423.12, 417/203, 417/206, 604/131, 604/151
• US Class Current: 604/131
• CPC Class Codes: A61M 60/148 in line with a blood vessel using resection or like techniques, e.g. permanent endovascular heart assist devices
• CPC Class Codes: A61M 60/178 drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
• CPC Class Codes: A61M 60/232 Centrifugal pumps
• CPC Class Codes: A61M 60/237 the blood flow through the rotating member having mainly axial components, e.g. axial flow pumps
• CPC Class Codes: A61M 60/422 the force acting on the blood contacting member being electromagnetic, e.g. using canned motor pumps
• CPC Class Codes: A61M 60/538 Regulation using real-time blood pump operational parameter data, e.g. motor current
• CPC Class Codes: A61M 60/554 of blood pressure
• CPC Class Codes: A61M 60/804 Impellers
• CPC Class Codes: A61M 60/825 Contact bearings, e.g. ball-and-cup or pivot bearings
• CPC Class Codes: A61M 60/88 Percutaneous cables
• CPC Class Codes: F16C 2316/18 Pumps for pumping blood
• CPC Class Codes: F16C 39/063 Permanent magnets
• CPC Class Codes: H02K 41/03 Synchronous motors; Motors moving step by step; Reluctance motors H02K41/035 takes precedence
• CPC Class Codes: H02K 5/1285 of the submersible type
• CPC Class Codes: H02K 7/09 with magnetic bearings
• CPC Class Codes: H02K 7/14 Structural association with mechanical loads, e.g. with hand-held machine tools or fans with fan or impeller for cooling the machine H02K9/06

Abstract

An implantable rotary blood pump without a shaft seal. The pump includes a rotary element, having a pump impeller on one end. The impeller is specially designed with large, thick blades and tall, narrow blood channels, to minimize hemolysis. The rotary element and the impeller are maintained in radial alignment by respective, passive magnetic bearings. Axial restraint of the rotary element is provided by blood immersed thrust bearings, spaced a slight distance from either end of the rotor. Drive for the rotary element is provided by a structurally integrated, brushless electric motor. A plurality of permanent magnets is arranged in circular fashion within the impeller, constituting a rotor for the motor. The motor'"'"'s stator includes circular windings of conductive wire, located within the pump housing and concentric with the rotor. With the stator energized, electromagnetic forces between the stator and the motor rotor cause the rotary element and the impeller to rotate. During operation, the rotary element shuttles back and forth along its axis between the thrust surfaces in response to heart pulsations. This bi-stable operation of the pump, allows fresh blood to flush through the thrust bearings in continuous fashion, minimizing the likelihood of thrombosis developing from operation of the pumps.

Claims

1. A sealless blood pump, comprising:

a. a pump housing, having an elongated inlet tube on one end and an impeller casing on the other end, said casing including a discharge tube;

b. a rotor mounted for rotation within said housing, said rotor having an elongated shaft portion and an impeller attached to said shaft portion, said impeller being located within said impeller casing;

c. radial magnetic bearings carried by said shaft potion, and radial magnetic bearings carried by said housing for maintaining said shaft portion of said rotor coaxially within said inlet tube of said housing, a primary flow channel for blood being provided by an annular volume between said shaft and said radial magnetic bearings carried by said housing;

d. a thrust bearing for restraining said rotor from translating past a predetermined position along its axis;

e. a motor rotor carried by said impeller; and

f. a motor stator within said housing adjacent said impeller, for producing an electromagnetic field.

2. An apparatus as in claim 1 in which said radial magnet bearings bias said rotor axially against said thrust bearing.

4. An apparatus as in claim 1 in which said radial magnet bearings comprise a plurality of forward radial magnets, said forward radial magnets including a plurality of ring inlet magnets and a corresponding plurality of ring shaft magnets, in which like poles of corresponding inlet magnets and shaft magnets face each other.

5. An apparatus as in claim 4 in which said radial magnet bearings further comprise a plurality of rearward radial magnets, said rearward radial magnets including a plurality of casing magnets and a corresponding plurality of impeller magnets, in which said impeller is generally disc-like in configuration and said impeller magnets extend transversely through said impeller and are arranged in circular fashion around an outer periphery of said impeller, said casing magnets being located in either side of said impeller in proximity to respective impeller magnets, and in which opposite poles of corresponding casing magnets and impeller magnets face each other.

6. An apparatus as in claim 1 in which said motor rotor comprises a plurality of arcuate, planar, magnetic segments arranged in generally circular fashion on said surface of said impeller, said segments having outwardly facing poles of identical polarity.

7. An apparatus as in claim 6 in which said motor stator comprises a circular winding of electrically conductive wire, generally concentric with said shaft.

3. A sealless blood pump comprising:

a pump housing, having an elongated inlet tube on one end and an impeller casing on the other end, said casing including a discharge tube;

a rotor mounted for rotation within said housing, said rotor having an elongated shaft portion and including an impeller attached to said shaft portion, said impeller being located within said impeller casing;

radial magnetic bearings for maintaining said shaft portion of said rotor coaxially within said inlet tube of said housing, a blood flow path being provided by an annular volume between said shaft and said housing;

a thrust bearing for restraining said rotor from translating past a predetermined position along its axis;

a motor rotor on a surface of said impeller; and

a motor stator within said housing adjacent said surface of said impeller, for producing an electromagnetic field;

said thrust bearing restraining said rotor within two predetermined axial positions, between which said rotor may shuttle in response to a varying blood pressure across said inlet tube and said outlet tube.

8. A sealless blood pump, comprising:

a. a pump rotor, said rotor having an elongated shaft with an upstream end and a downstream end, said rotor further including an impeller attached to said downstream end of said shaft;

b. a pump housing, said housing having an elongated inlet tube on one end, said shaft being enclosed by and concentric with said tube, said housing further including a casing on the other end surrounding said impeller, said casing having an outlet tube;

c. radial magnetic bearings carried by said shaft portion and radial magnetic bearings carried by said housing for coaxially maintaining said shaft within said tubular inlet of said housing for rotation about a longitudinal axis, said radial magnetic bearings carried by said shaft and said radial magnetic bearings carried by said housing providing between them an annular volume defining a primary flow channel for blood;

d. a first thrust bearing within said casing, said impeller having a bearing surface in contact with said first thrust bearing;

e. a permanent magnet motor rotor carried by said impeller;

f. an electromagnetic motor stator within said housing adjacent said impeller;

g. a power supply having an electrical output in connection with said motor stator.

9. An apparatus as in claim 8 in which said impeller includes a plurality of blades with arcuate channels therebetween, said channels extending from an upstream portion of the blades to a downstream portion thereof, the downstream portion of each of said channels being oriented in a direction opposing a direction of impeller rotation.

10. An apparatus as in claim 8 in which said radial magnet bearings comprise a plurality of forward radial magnets, said forward radial magnets including a plurality of ring inlet magnets and a corresponding plurality of ring shaft magnets, in which like poles of corresponding inlet magnets and shaft magnets face each other.

11. An apparatus as in claim 10 in which said radial magnet bearing further comprise a plurality of rearward radial magnets, said rearward radial magnets including a plurality of casing magnets and a corresponding plurality of impeller magnets, in which said impeller is generally disc-like in configuration and said impeller magnets extend transversely through said impeller and are arranged in circular fashion around an outer periphery of said impeller, said casing magnets being located on either side of said impeller in proximity to a pole of a respective impeller magnets, and in which opposite poles of corresponding casing magnets and impeller magnets face each other.

12. An apparatus as in claim 8 further including a second thrust bearing within said inlet tube, said shaft having a bearing surface at said upstream end in contact with said second thrust bearing.

14. An apparatus as in claim 8, in which said radial magnet bearings bias said rotor axially against said first thrust bearing.

15. An apparatus as in claim 8 in which said motor rotor includes a plurality of arcuate, planar, magnetic segments arranged in generally circular fashion on said surface of said impeller, said segments having outwardly facing poles of identical polarity.

16. An apparatus as in claim 8 in which said motor stator includes a circular winding of electrically conductive wire, generally concentric with said shaft.

13. A sealless blood pump, comprising:

a pump rotor, said rotor having an elongated shaft with an upstream end and a downstream end, said rotor further including an impeller attached to said downstream end of said shaft;

a pump housing, said housing having an elongated inlet tube on one end, said shaft being enclosed by and concentric with said tube, said housing further including a casing on the other end surrounding said impeller, said casing having an outer tube;

radial magnetic bearings for coaxially maintaining said shaft within said tubular inlet of said housing for rotation about a longitudinal axis, an annular volume between said shaft and said housing defining a blood flow path;

a first thrust bearing within said casing, said impeller having a bearing surface in contact with said first thrust bearing;

a permanent magnet motor rotor on a surface of said impeller;

an electromagnetic motor stator within said housing adjacent said surface of said impeller;

a power supply having an electrical output in connection with said motor stator;

further including a second thrust bearing within said inlet tube, said shaft having a bearing surface at said upstream end in contact with said second thrust bearing;

said first and second thrust bearings being spaced apart a distance slightly greater than the length of said rotor, wherein blood pressures between said inlet tube and said outlet tube vary to shuttle said rotor between said first and second thrust bearings.

17. A centrifugaI blood pump having a rotor, an inlet tube and an impeller casing, said inlet tube including a bearing supporting the rotor for rotation about a longitudinal axis, comprising:

a. said rotor being rotatable within the inlet tube, said rotor having an upstream end and a downstream end;

b. a disc-shaped impeller having a central, upper face portion attached to said downstream end of said rotor and located within the casing, said impeller having a plurality of blade sectors, each of said sectors being separated from an adjacent sector by a channel extending continuously from said upper face portion to a lower face portion, each of said channels beginning with a leading edge, adjacent said shaft and ending with a trailing edge at an outer periphery of said impeller, said channel serving as a continuous fluid path through the impeller from said upper face portion to said lower face portion and functioning to increase the effective working area of the impeller; and

c. a blood flow path on the outside of said rotor for bringing the blood to said upper face portion for passage through said channels.

18. A device as in claim 17 further including a rotor motor for rotating said shaft and said impeller in said direction of rotation.

19. A device as in claim 17 further including a rotor motor, said motor including:

a plurality of permanent magnets on said upper face portion of said impeller;

a motor stator adjacent said upper face portion of said impeller, said stator including an electrically conductive coil; and

, a power supply providing electrical power to said stator, thereby imparting torque to said rotor in said direction of rotation.

20. A device as in claim 19 in which said permanent magnets include arcuate magnetic segments located on each of said sectors.

21. A sealless blood pump, comprising:

a pump housing, having an inlet tube on one end and an impeller casing on the other end, said casing including an outlet;

a rotor mounted for rotation within said housing, said rotor having an elongated shaft portion and including an impeller attached to said shaft portion, said impeller being located within said impeller casing;

radial magnetic bearings carried by said shaft portion, and radial magnetic bearings carried by said housing for maintaining said shaft portion of said rotor within said inlet tube of said housing, a primary flow channel for blood being provided by an annular volume between said shaft and said radial magnetic bearings carried by said housing; and

thrust bearings for restraining said rotor from translating past a predetermined position along its axis, said thrust bearings restraining said rotor within two predetermined axial positions, between which said rotor may shuttle in response to a varying blood pressure across said inlet tube and said outlet.

22. A sealless blood pump, comprising:

a pump housing, having an inlet tube on one end and an impeller casing on the other end, said casing including an outlet;

a rotor mounted for rotation within said housing, said rotor having an elongated shaft portion and an impeller attached to said shaft portion, said impeller being located within said impeller casing;

radial magnetic bearings for maintaining said shaft portion of said rotor within said inlet tube of said housing, a blood flow path being provided by an annular volume between said shaft and said housing;

thrust bearings for restraining said rotor from translating past a predetermined position along its axis, said thrust bearings restraining said rotor within two predetermined axial positions, between which said rotor may shuttle in response to a varying blood pressure across said inlet tube and said outlet;

said thrust bearings being located at opposed ends of said rotor with the distance between said thrust bearings being greater than the overall length of said rotor.

23. A sealless blood pump as defined by claim 22, in which at least one of said thrust bearings is adjustable thereby enabling the distance between thrust bearings to be adjusted so that the distance between the thrust bearings is slightly greater than the overall length of the rotor.

24. A sealless centrifugal blood pump having an inlet tube and an impeller casing, said inlet tube including a bearing for supporting a rotor for rotation about a longitudinal axis, comprising:

a rotor, said rotor comprising a rotatable, elongated support shaft within the inlet tube, said shaft having an upstream end and a downstream end;

a disc-shaped impeller having a central, upper face portion attached to said downstream end of said shaft and located within the casing, said impeller having a plurality of blade sectors, each of said sectors being separated from an adjacent sector by a channel extending from said upper face portion to a lower face portion;

said channels serving as a fluid path through the impeller and functioning to increase the effective working area of the impeller; and

a plurality of permanent magnets unitary with and located within said blade sectors.

25. A sealless centrifugal blood pump as defined by claim 24, in which said impeller is thick in the axial direction and said permanent magnets comprise magnets which extend substantially through said impeller in the axial direction.

26. A sealless centrifugal blood pap having an inlet tube and an impeller casing, said inlet tube including a bearing for supporting a rotor for rotation about a longitudinal axis, comprising:

a rotor, said rotor comprising a rotatable, elongated support shaft within the inlet tube, said shaft having an upstream end and a downstream end;

a disc-shaped impeller having a central, upper face portion attached to said downstream end of said shaft and located within the casing, said impeller being thick in the axial direction and having a plurality of blade sectors, each of said sectors being separated from an adjacent sector by a channel extending from said upper face portion to a lower face portion;

said channels serving as a fluid path through the impeller and functioning to increase the effective working area of the impeller; and

said impeller blade sectors defining sealed, individual hollow chambers to reduce the density of the impeller.

27. A sealless centrifugal blood pump as defined by claim 26, including a plurality of permanent magnets carried by said impeller, and in which said impeller is thick in the axial direction and said permanent magnets comprise magnets which extend substantially through said impeller in the axial direction.

28. A sealless blood pump, comprising:

a pump housing, having an inlet tube on one end and an impeller casing on the other end, said casing including an outlet;

a rotor mounted for rotation within said housing, said rotor having an elongated shaft portion and an impeller attached to said shaft portion, said impeller being located within said impeller casing;

radial magnetic bearings carried by said shaft portion, and radial magnetic bearings carried by said housing for maintaining said shaft portion of said rotor within said inlet tube of said housing, a primary flow channel for blood being provided by an annular volume between said shaft and said radial magnetic bearings carried by said housing; and

a rotor motor, said motor including a plurality of permanent magnets carried by said impeller, a motor stator including an electrically conductive coil, said motor stator having a ring-shaped configuration and surrounding said rotor.

29. A sealless blood pump as defined by claim 28, in which said ring-shaped motor stator is in axial alignment with said permanent magnets.

30. A sealless blood pump as defined by claim 28, in which said ring-shaped stator comprises a circular pole piece surrounded by windings.

31. A sealless blood pump as defined by claim 28, in which said magnets carried by the impeller comprise arcuate magnetic segments.

32. A sealless blood pump, comprising:

a pump housing, having an inlet tube on one end and an impeller casing on the other end, said casing including an outlet;

a rotor mounted for rotation within said housing, said rotor having an elongated shaft portion with a transverse dimension smaller than an inner dimension of said inlet tube, said rotor further including an impeller attached to said shaft portion, said impeller being located within said impeller casing;

radial magnetic bearings for maintaining said shaft portion of said rotor within said inlet tube of said housing, a blood flow path being provided by an annular volume between said shaft and said inner diameter; and

a thrust bearing for restraining said rotor from translating past a predetermined position along its axis, said thrust bearing being located outside of the axis of rotation of said rotor.

33. A sealless blood pump as defined in claim 32, in which said thrust bearing outside of said axis of rotation of said rotor comprises an annular thrust bearing surface on said casing, adjacent a face of said impeller.

34. A sealless blood pump as defined by claim 33, in which said casing has an inner wall and an outer wall, said impeller has an upper face and a lower face, and said annular thrust bearing surface is positioned on said inner wall of said casing, adjacent said upper face of said impeller.

35. A sealless blood pump as defined by claim 32, including a second thrust bearing operating with said first mentioned thrust bearing for restraining said rotor to predetermined axial positions, between which said rotor may shuttle in response to a varying blood pressure across said inlet tube and said outlet.

36. A sealless blood pump as defined in claim 35, in which at least one of said thrust bearings is adjustable thereby enabling the distance between thrust bearings to be adjusted.

38. A sealless blood pump as defined by claim 35, in which said thrust bearings are located at opposed ends of said rotor with a distance between said thrust bearings being greater than the overall length of said rotor, at least one of said thrust bearings being adjustable thereby enabling the distance between thrust bearings to be adjusted.

37. A sealless blood pump, comprising:

a pump housing;

a rotor mounted for rotation within said housing;

radial magnetic bearings for maintaining said rotor within said housing; and

thrust bearings for restraining said rotor from translating past a predetermined position along its axis, said thrust bearings restraining said rotor within two axial positions between which said rotor may shuttle in response to a varying blood pressure.

39. A sealless blood pump, comprising:

a pump housing, having an inlet tube on one end and an impeller casing on the other end, said casing including an outlet;

a rotor mounted for rotation within said housing, said rotor having an elongated shaft portion and including an impeller attached to said shaft portion, said impeller being located within said impeller casing;

radial magnetic bearings carried by said shaft portion, and radial magnetic bearings carried by said housing for maintaining said shaft portion of said rotor within said inlet tube of said housing, a primary flow channel for blood being provided by an annular volume between said shaft and said radial magnetic bearings carried by said housing; and

a thrust bearing for restraining said rotor from translating past a predetermined position along its axis, said thrust bearing being located outside of the axis of rotation of said rotor.

40. A sealless blood pomp as defined in claim 39, in which said thrust bearing outside of said axis of rotation of said rotor comprises an annular thrust bearing surface on said casing, adjacent a face of said impeller.

41. A sealless blood pump as defined by claim 40, in which said casing has an inner wall and an outer wall, said impeller has an upper face and a lower face, and said annular thrust bearing surface is positioned on said inner wall of said casing, adjacent said upper face of said impeller.

42. A sealless blood pump as defined by claim 39, including a second thrust bearing operating with said first mentioned thrust bearing for restraining said rotor to predetermined axial positions, between which said rotor may shuffle in response to a varying blood pressure across said inlet tube and said outlet.

43. A sealless blood pump as defined in claim 42, in which at least one of said thrust bearings is adjustable thereby enabling the distance between thrust bearings to be adjusted.

44. A sealless blood pump, comprising:

a pump housing, having an inlet tube on one end and an impeller casing on the other end, said casing including an outlet;

a rotor mounted for rotation within said housing, said rotor having an elongated shaft portion and an impeller attached to said shaft portion, said impeller being located within said impeller casing;

radial magnetic bearings carried by said shaft portion, and radial magnetic bearings carried by said housing for maintaining said shaft portion of said rotor within said inlet tube of said housing, a primary flow channel for blood being provided by an annular volume between said shaft and said radial magnetic bearings carried by said housing; and

a rotor motor, said motor including a plurality of permanent magnets located within said impeller and extending axially;

a motor stator including an electrically conductive coil, said motor stator having a ring-shaped configuration and located within said housing.