Blood pump having a magnetically suspended rotor

• US 6,244,835 B1
• Filed: 07/19/1999
• Issued: 06/12/2001
• 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: University Of Pittsburgh (University of Pittsburgh of The Commonwealth System of Higher Education)
• Inventors: Antaki, James F., Paden, Bradley, Burgreen, Gregory, Groom, Nelson J.
• Primary Examiner(s): Hoang, Tu Ba
• Assistant Examiner(s): PWU, JEFFREY C
• Application Number:
  US09/356,662
• Time in Patent Office: 694 Days
• Field of Search: 417/356, 417/423.12, 417/423.3, 417/203, 417/45, 417/423.1, 417/423.7, 600/131, 600/16, 604/131, 604/151, 415/900, 623/3
• US Class Current: 417/356
• 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 60/268 the displacement member being flexible, e.g. membranes, diaphragms or bladders
• 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 60/515 Regulation using real-time patient data
• CPC Class Codes: A61M 60/538 Regulation using real-time blood pump operational parameter data, e.g. motor current
• CPC Class Codes: A61M 60/82 Magnetic bearings
• CPC Class Codes: A61M 60/831 using filtered blood as purge fluid
• CPC Class Codes: A61M 60/871 Energy supply devices; Converters therefor
• 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 3/005 with a conventional single stage rotor
• 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 32/0474 for rotary movement
• CPC Class Codes: H02K 1/276 Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
• 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 blood pump preferably has a magnetically suspended rotor that rotates within a housing. The rotor may rotate about a stator disposed within the housing. Radial magnetic bearings may be defined within the stator and the rotor in order to suspend the rotor. The radial magnetic bearings may be passive magnetic bearings that include permanent magnets disposed within the stator and the rotor or active magnetic bearings. The pump may further include an axial magnetic bearing that may be either a passive or an active magnetic bearing. A motor that drives the rotor may be disposed within the housing in order to more easily dissipate heat generated by the motor. A primary flow path is defined between the rotor and the stator, and a secondary flow path is defined between the stator and the rotor. Preferably, a substantial majority of blood passes through the primary flow path. The secondary flow path is large enough so that it provides adequate flushing of the secondary flow path while being small enough to permit efficient operation of the radial magnet bearings across the secondary flow path.

Claims

1. A pump for pumping blood, comprising:

a housing;

a stator, disposed within the housing and being coupled to the housing, and comprising;

(i) a first end, disposed at the inlet, about which a plurality of stator blades are disposed and that has a first diameter;

(ii) a second end, disposed at the outlet, that is substantially conically shaped and about which a plurality of stator blades are disposed, the second end having a second diameter that is larger than the first diameter;

(iii) a stationary hub that connects the first end to the second end and having a third diameter that is smaller than the second diameter;

a rotor, disposed within the housing and suspended around the stationary hub;

a radial magnetic bearing, defined by a stator magnet disposed within the stator and a rotor magnet disposed within the rotor, that magnetically suspends the rotor between the stator and the housing;

a primary blood flow path being defined between the rotor and the housing;

a secondary blood flow path being defined between the rotor and the stator, the primary flow path being larger than the secondary flow path and the secondary flow path being sized so that the stator magnet can interact with the rotor magnet and so that shear stresses on the blood flowing through the pump are minimized; and

a motor, disposed within the housing, the motor communicating with the rotor across the primary flow path to rotate the rotor and thereby pump blood through the pump.

2. The pump of claim 1, wherein the flow through the secondary flow path opposes the flow through the primary flow path.

3. The pump of claim 1, wherein the secondary flow path comprises an entrance disposed between the second end of the stator and the rotor, a substantially inward radial flow path defined between the second end of the stator and the rotor, a substantially axial flow path defined between the stator stationary hub and the rotor and an exit, defined between the stator stationary hub and the rotor.

4. The pump of claim 1, further comprising a magnetic thrust bearing for axially aligning the rotor within the housing.

5. The pump of claim 4, wherein the magnetic thrust bearing comprises an active magnetic bearing.

6. The pump of claim 5, wherein the active magnetic thrust bearing comprises a pair of thrust coils, disposed within the housing, that each interact with one of a pair of poles, disposed within the rotor, to place an axial force on the rotor.

7. The pump of claim 6, wherein the active thrust bearing further comprises a sensor, disposed within the stator, for sensing the axial position of the rotor, and an electro-magnetic controller, disposed within the pump, that controls the electrical current flowing through the thrust coils to position the rotor axially within the housing.

8. A pump for pumping blood, comprising:

a housing defining an inlet and an outlet;

a stator, disposed within the housing and being coupled to the housing, and comprising a first end, disposed at the inlet, a second end, disposed at the outlet, and about which a plurality of stator blades are disposed and a stationary hub that connects the first end to the second end;

a rotor, disposed within the housing and suspended around the stationary hub of the stator, a primary blood flow path being defined between the rotor and the housing and a secondary blood flow path being defined between the rotor and the stator, the rotor having a substantially conically shaped end disposed proximate to the first end of the stator and a cylindrical portion disposed upstream of the substantially conically shaped end;

a plurality of impeller blades being disposed about a periphery of the rotor, each of the impeller blades having a first portion that is substantially helical in shape about the substantially conically shaped end and a second portion extending from the substantially conically shaped end onto the cylindrical portion of the rotor and being curved so as to approach a line that is parallel to a longitudinal axis of the pump, the first portion imparting pressure energy, rotational velocity and axial velocity to blood flowing through the pump when the rotor is rotated and the second portion imparting rotational kinetic energy to the blood and directing the blood to the stator blades;

a magnetic bearing, defined by a stator magnet disposed within the stator and a rotor magnet disposed within the rotor, that magnetically suspends the rotor between the stator and the housing, the stator magnet and the rotor magnet communicating across the secondary flow path; and

a motor, disposed within the housing, the motor communicating with the rotor across the primary flow path to rotate the rotor and thereby pump blood through the pump.

9. The blood pump of claim 8, wherein each rotor blade comprises a rounded tip that reduces shear stresses imparted on the blood flowing through the pump.

10. The blood pump of claim 8, wherein each rotor blade comprises a fillet that connects the first portion and the second portion of each respective rotor blade to the rotor, such that localized regions of flow stagnation are reduced.

11. A blood pump for pumping blood, comprising:

(a) a stator comprising,

(a₁) a first end around which a plurality of stator blades are disposed;

(a₂) a second end around which a plurality of stator blades are disposed and that is substantially conically shaped;

(a₃) a stationary hub, that connects the first end to the second end;

(b) a rotor that is magnetically suspended about the stator, comprising,

(b₁) a substantially conically shaped end that is disposed proximate to the first end of the stator;

(b₂) a substantially cylindrical portion that is connected to the substantially conically shaped end;

(b₃) a plurality of impeller blades extending from the substantially conically shaped end to the substantially cylindrical portion;

(c) a magnetic bearing defined by a magnet disposed within the stationary hub of the stator and a magnet disposed within the substantially cylindrical portion of the rotor that suspends the rotor in a radial direction from the stator; and

(d) a housing in which the stator is disposed and in which the rotor is disposed as the rotor is suspended, the housing having an inner surface that extends from the first end of the stator to the second end of the stator and that conforms to the shape of the substantially conically shaped end of the rotor and the substantially cylindrical portion of the rotor to define a smooth passage for blood to flow between the rotor and the housing, and thereby reduce shear stresses on the blood flowing through the pump and that conforms to the second end of the stator to provide a relatively smooth passage for blood to flow between the second end of the stator and the housing to prevent flow stagnation and flow reversal.

12. A pump for pumping blood, comprising:

a housing defining an inlet and an outlet;

a stator, disposed within the housing and being coupled to the housing, and comprising;

(i) a first end, disposed at the inlet, about which a plurality of stator blades are disposed and that has a first diameter;

(ii) a second end, disposed at the outlet, and being substantially conically shaped and having a plurality of stator blades disposed thereabout, the second end being substantially conically shaped and having a second diameter that is larger than the first diameter of the first end of the stator;

(iii) a stationary hub that connects the first end to the second end and that has a third diameter that is smaller than the second diameter;

a rotor, suspended around the stationary hub of the stator and disposed between the housing and the stator, the rotor comprising;

(i) a substantially conically shaped end disposed proximate to the first end of the stator, to provide a smooth passage of blood flow from the first end of the stator to the rotor;

(ii) a cylindrical portion disposed upstream of the substantially conically shaped end and suspended about the stationary hub of the stator, an outer diameter of the cylindrical portion being approximately equal to the second diameter of the second end to provide a smooth passage of blood flow from the cylindrical portion of the rotor to the second end of the stator;

a magnetic bearing, defined by a stator magnet disposed within the stator and a rotor magnet disposed within the rotor, the magnetic bearing magnetically suspending the rotor between the stator stationary hub and the housing; and

a motor, disposed within the housing, that communicates with the rotor to rotate the rotor and thereby pump blood through the pump.