Magnetically suspended miniature fluid pump and method of designing the same

• US 6,447,265 B1
• Filed: 09/20/1999
• Issued: 09/10/2002
• Est. Priority Date: 06/26/1996
• Status: Expired due to Term

• Current Assignee: National Aeronautics and Space Administration (Government of the United States of America), University Of Pittsburgh (University of Pittsburgh of The Commonwealth System of Higher Education)
• Original Assignee: United States Administrator of National Aeronautics and Space Administration, University Of Pittsburgh (University of Pittsburgh of The Commonwealth System of Higher Education)
• Inventors: Antaki, James F., Paden, Bradley, Burgreen, Gregory, Groom, Nelson
• Primary Examiner(s): TYLER, CHERYL JACKSON
• Application Number:
  US09/398,878
• Time in Patent Office: 1,086 Days
• Field of Search: 417/356, 417/352, 417/353, 417/354, 417/423.7, 417/423.12, 417/410.1, 415/900, 415/10, 415/91, 415/200, 415/218.1, 415/219, 415/221, 416/3, 416/241.R
• US Class Current: 417/354
• 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 60/812 Vanes or blades, e.g. static flow guides
• CPC Class Codes: A61M 60/816 Sensors arranged on or in the housing, e.g. ultrasound flow sensors
• CPC Class Codes: A61M 60/818 Bearings
• CPC Class Codes: A61M 60/822 specially adapted for being actively controlled
• CPC Class Codes: F04D 13/0633 Details of the bearings
• CPC Class Codes: F04D 13/064 Details of the magnetic circuit
• CPC Class Codes: F04D 13/0646 the hollow pump or motor shaft being the conduit for the working fluid
• CPC Class Codes: F04D 29/048 magnetic; electromagnetic
• CPC Class Codes: F04D 3/02 of screw type
• CPC Class Codes: F16C 2316/18 Pumps for pumping blood
• CPC Class Codes: F16C 2360/44 Centrifugal pumps in general F04D
• CPC Class Codes: F16C 32/0493 integrated in an electrodynamic machine, e.g. self-bearing motor
• CPC Class Codes: H02K 1/274 the rotor consisting of two or more circumferentially positioned magnets
• CPC Class Codes: H02K 1/276 Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
• CPC Class Codes: H02K 1/2791 : Surface mounted magnets; Inset magnets
• CPC Class Codes: H02K 29/06 : with position sensing devices H02K29/03 takes precedence
• 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
• CPC Class Codes: Y10S 415/90 : Rotary blood pump

Abstract

A rotary pump for pumping fluids through a patient having a housing with an internal region, a stator member and an impeller positioned within the housing and having impeller blades, wherein the impeller is magnetically suspended and rotated, and wherein the geometric configuration of the rotary pump is sized and proportioned to minimize stagnant and traumatic fluid flow within the rotary pump. The plurality of magnetic impeller blades are preferably rare earth, high-energy-density magnets selected from the group consisting of samarium cobalt and neodymium-iron-boron alloy.

Claims

1. A device for pumping fluid, comprising:

(a) a housing having an upstream end a downstream end and an internal region through which said fluid flows when the device is pumping;

(b) an impeller positioned within said housing and having a substantially conically shaped nose, a substantially conically shaped tail and a mid-section extending between the nose and the tail that has a plurality of substantially helically shaped magnetic impeller blades;

(c) a stator

(c₁) downstream stator blades extending from the housing such that the impeller tail is axially aligned with the downstream stator, the downstream stator blades being curved to conform to the substantially conically shaped tail, the downstream stator blades being for recovering velocity energy as pressure energy from said fluid exiting said downstream end of said plurality of magnetic impeller blades;

(c₂) upstream stator blades extending from the housing such that the impeller nose is axially aligned within the upstream stator, the upstream stator blades being curved to conform to the substantially conically shaped nose, the upstream stator blades being for directing fluid to the impeller;

(d) means for levitating said impeller within said housing such that said impeller is substantially centered within said housing and the impeller nose is axially aligned within the upstream stator blades and the impeller tail is axially aligned within the downstream stator blades; and

(e) means for rotating said impeller which exerts a force on said plurality of magnetic impeller blades.

2. A rotary pump for pumping fluid through a patient comprising:

(a) a housing having an internal region through which said fluid flows when the rotary pump is pumping;

(b) an impeller positioned within said housing and having

(b₁) an upstream end and a downstream end;

(b₂) an exterior wall;

(b₃) an interior wall defining a void;

(b₄) a plurality of outboard magnetic impeller blades extending outwardly from the exterior wall which each having an upstream end and a downstream end;

(b₅) a plurality of inboard blades extending inwardly from said interior wall;

(c) a first stator member for recovering velocity energy as pressure energy from said fluid exiting said downstream end of said plurality of impeller blades, said first stator member being attached to said housing;

(d) means for levitating said impeller which substantially centers said impeller within said housing comprising a plurality of electromagnets positioned inside the interior wall of the impeller and outside of the housing and ferromagnetic material disposed within the first stator member; and

(e) means for rotating said impeller which exerts a torque on said plurality of outboard magnetic impeller blades causing said impeller to rotate.

3. The rotary pump of claim 2 wherein said first stator member further comprises:

a downstream set of stationary blades which converge around said downstream end of said impeller to define a plurality of fluid flow regions and a downstream passageway and wherein the rotary pump further comprises a second stator member, that is attached to an upstream end of the rotary pump, and comprises an upstream set of stationary blades which converge around said upstream end of said impeller to define a plurality of fluid flow regions and an upstream passageway.

4. The rotary pump of claim 3 wherein said upstream set of stationary blades and said downstream set of stationary blades comprise permanent magnetic material.

5. The rotary pump of claim 3 wherein said impeller is substantially axially symmetric and the impeller upstream end comprises a substantially conical-shaped nose and the impeller downstream end comprises a substantially conical-shaped tail, and

wherein the shapes of said upstream passageway and said downstream passageway correspond to the shapes of said conical-shaped nose and said conical-shaped tail, respectively, such that when said impeller nose is positioned within said upstream passageway, a gap is formed between the upstream set of stationary blades and said impeller nose and likewise, when the impeller tail is positioned within said downstream passageway, a gap is formed between said downstream set of stationary blades and said impeller tail.

6. The rotary pump of claim 5 wherein said rotary pump further comprises means for sensing the position of said impeller within said housing and changing the net flux across said gaps in order to move said impeller to the centered position.

7. The rotary pump of claim 3 further comprising an inducer blade which extends around and is attached to said substantially conical-shaped impeller nose.

8. The rotary pump of claim 3, wherein said levitating means comprises a conical electromagnet bearing which includes a plurality of coils, magnetic bearing targets positioned on said impeller, a plurality of backiron segments, and the downstream and upstream sets of stationary blades being magnetic.

9. The rotary pump of claim 8 wherein the levitating means further comprises a plurality of permanent magnets positioned between said plurality of coils and said backiron such that a permanent magnetic bias is provided.

10. The rotary pump of claim 2 wherein said rotating means comprise a brushless DC motor, wherein an electromagnetic field coil extends around the exterior of said housing and adjacent to said plurality of outwardly extending magnetic impeller blades.

11. The rotary pump of claim 2 wherein the rotating means comprises a variable reluctance motor.

12. The rotary pump of claim 2, wherein said outwardly extending plurality of magnetic impeller blades are high-energy-density, rare earth magnet selected from the group consisting of samarium cobalt and neodymium-iron-boron alloy.

13. The rotary pump of claim 2 further comprising an inflow cannula having a first end and a second end, wherein said first end is connected to said housing and said second end substantially has an hourglass configuration and is connectable to a heart.

14. The rotary pump of claim 2, wherein said outwardly extending plurality of magnetic impeller blades are helical in shape.

15. The rotary pump of claim 2, wherein said first stator member has a first portion, a second portion, and a plurality of stationary blades attached to said stator member at said first portion thereof, and wherein said stator member second portion extends axially within said interior wall of said impeller.

16. The rotary pump of claim 15 wherein said first stator member is generally an ellipsoid having a substantially conical-shaped tail and a substantially conical-shaped nose, and said inboard impeller blades are concave such that the curvature thereof corresponds with the curvature of said first stator member.

17. The rotary pump of claim 15 further comprising means for preventing axial movement of said impeller within said housing.

18. The rotary pump of claim 17 wherein the means for preventing axial movement comprises both the impeller and the first stator member having permanent magnets.

19. The rotary pump of claim 18 wherein said outboard impeller blades are helical in shape and the impeller exterior wall generally is tapered in order to pump fluid.

20. The rotary pump of claim 19 wherein the number of said plurality of outboard impeller blades is three.

21. The rotary pump of claim 17 wherein the means for preventing axial movement comprises electromagnets positioned in the first stator member and said impellers, comprising at least a portion which is made from ferromagnetic material.

22. The rotary pump of claim 2, wherein said first stator member has a hub with a first portion and a second portion, a set of upstream stationary blades attached to and extending from said first stator member first portion, and a set of downstream stationary blades attached to and extending from said stator member second portion, wherein said downstream stationary blades and said upstream stationary blades are attached to said housing.

23. The rotary pump of claim 2 further comprising position sensors located on said impeller for detecting axial movement of said impeller.

24. The rotary pump of claim 2 further comprising means for modulating said rotary pump impeller speed in order to create a pulse.