Blood pump bearing system

• US 6,135,729 A
• Filed: 07/09/1999
• Issued: 10/24/2000
• Est. Priority Date: 11/10/1993
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Aber, Gregory S.
• Primary Examiner(s): Walberg, Teresa
• Assistant Examiner(s): FASTOVSKY, LEONID M
• Application Number:
  US09/354,916
• Time in Patent Office: 473 Days
• Field of Search: 417/420, 417/310, 417/356, 417/423.1, 417/423.12, 417/45, 600/16, 310/254, 604/131
• US Class Current: 417/420
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• 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 60/221 the blood flow through the rotating member having both radial and axial components, e.g. mixed flow pumps
• 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 60/416 transmitted directly by the motor rotor drive shaft
• 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 60/508 Electronic control means, e.g. for feedback regulation
• CPC Class Codes: A61M 60/824 Hydrodynamic or fluid film bearings
• CPC Class Codes: A61M 60/825 Contact bearings, e.g. ball-and-cup or pivot bearings
• CPC Class Codes: A61M 60/827 Sealings between moving parts
• CPC Class Codes: A61M 60/829 having a purge fluid supply
• CPC Class Codes: F04B 17/00 Pumps characterised by combination with, or adaptation to, specific driving engines or motors
• CPC Class Codes: F04B 35/04 the means being electric
• CPC Class Codes: F16C 17/08 for supporting the end face of a shaft or other member, e.g. footstep bearings
• CPC Class Codes: F16C 2316/18 Pumps for pumping blood

Abstract

An apparatus is are provided for a blood pump bearing system within a pump housing to support long-term high-speed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the shaft to support high speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

Claims

1. A fluid pump, comprising:

a pump housing defining therein a fluid path for fluid flow through said pump;

a rotor mounted within said pump housing for rotation therein;

at least one impeller blade on said rotor;

at least one flat ceramic endstone for supporting axial loads acting on said rotor;

a plurality of magnets secured to said rotor; and

a stator in surrounding relationship to said pump housing, said stator and said plurality of magnets being positioned to define a gap therebetween.

2. The pump of claim 1, further comprising:

a shaft with a shaft end for supporting said rotor;

a jewel bearing having an aperture therethrough with a curved inner surface for receiving said shaft end and supporting said shaft end with near line contact around a circumference of said shaft end.

3. The pump of claim 1, wherein:

said plurality of magnets are arranged in helical fashion about said rotor.

4. The pump of claim 1, wherein:

said stator is axially adjustable with respect to said pump housing and said rotor.

5. The pump of claim 1, further comprising:

a radially peripheral edge of said at least one impeller blade, said plurality of magnets being mounted along said radially peripheral edge.

6. A rotary motor, comprising:

a motor housing;

a rotor mounted within said motor housing for rotation about a rotor shaft, said rotor having a circumference;

a stator disposed mounted to said pump housing to produce a magnetic field for rotatably driving said rotor;

a bearing with a substantially torroidial inner surface for supporting said rotor shaft; and

a plurality of individual permanent magnets positioned along said circumference of said rotor with a variable axial position.

7. The rotary motor of claim 6, further comprising:

a radiused shaft end for said rotor shaft; and

an endstone with a flat planar surface for engaging said radiused shaft end.

8. The rotary motor of claim 6, wherein:

said plurality of individual permanent magnets are mounted with a radial spacing to said stator of less than 0.025 inches.

9. The rotary motor of claim 6, further comprising:

at least one impeller blade mounted to said rotor, said plurality of individual magnets being affixed along a peripheral edge of said at least one impeller blade.

10. The rotary motor of claim 6, wherein said stator further comprises:

a plurality of laminations, said laminations being stacked together such that a passageway is formed therein, said passageway being skewed with respect to said rotor shaft.

11. The rotary motor of claim 6, wherein:

said at least one impeller blade has a variable pitch.

12. A rotary motor, comprising:

a motor housing;

a rotor mounted within said motor housing for rotation about a rotor shaft, said rotor having a circumference;

a stator mounted to said pump housing to produce a magnetic field for rotatably driving said rotor;

ceramic contact bearings positioned axially and radially, with respect to said rotor shaft, to support axial and radial loads;

a plurality of individual permanent magnets positioned along said circumference of said rotor; and

a stator mounted to said motor housing comprised of a plurality of laminations.

13. The rotary motor of claim 12, further comprising:

a shaft end formed of a first material, said axially positioned ceramic bearing being formed of a second ceramic material harder than said first material, such that substantially all wear occurs on said shaft end.

14. The rotary motor of claim 12, wherein:

said stator is axially adjustable with respect to said pump housing.

15. The rotary motor of claim 12, further comprising:

a shaft end having a radiused end, said axially positioned ceramic bearing being an endstone with a flat planar surface for engaging said shaft end, said radially positioned bearing being an olive hole ring jewel for receiving said shaft end.

16. The rotary motor of claim 12, wherein:

said plurality of individual permanent magnets are mounted at different axial positions with respect to said rotor shaft such that said plurality of individual permanent magnets define at least a portion of a helical pattern.