Hybrid magnetically suspended and rotated centrifugal pumping apparatus and method

• US 6,595,762 B2
• Filed: 10/01/2001
• Issued: 07/22/2003
• Est. Priority Date: 05/03/1996
• Status: Expired due to Term

• Current Assignee: World Heart Corporation (Medtronic Plc)
• Original Assignee: Medquest Products, Inc. (Maverick Venture Management LLC), University of Virginia Patent Foundation (University of Virginia)
• Inventors: Maslen, Eric H., Long, James W., Allaire, Paul E., Olsen, Don B., Bearnson, Gill B., Khanwilkar, Pratap S.
• Primary Examiner(s): TYLER, CHERYL JACKSON
• Application Number:
  US09/968,690
• Publication Number:
  US 20020094281A1
• Time in Patent Office: 659 Days
• Field of Search: 417/356, 417/423.7, 417/420, 415/900, 416/3, 416/186.R, 416/188
• US Class Current: 417/423.7
• 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 60/422 the force acting on the blood contacting member being electromagnetic, e.g. using canned motor pumps
• CPC Class Codes: A61M 60/523 using blood flow data, e.g. from blood flow transducers
• CPC Class Codes: A61M 60/546 of blood flow, e.g. by adapting rotor speed
• CPC Class Codes: A61M 60/806 Vanes or blades
• CPC Class Codes: A61M 60/82 Magnetic bearings
• CPC Class Codes: F04D 13/0666 the motor being of the plane gap type
• CPC Class Codes: F04D 29/041 Axial thrust balancing
• CPC Class Codes: F04D 29/048 magnetic; electromagnetic
• CPC Class Codes: F05B 2200/23 Logarithm
• CPC Class Codes: F05B 2240/51 magnetic
• CPC Class Codes: F05B 2240/511 with permanent magnets
• CPC Class Codes: F05B 2240/515 electromagnetic
• CPC Class Codes: F16C 2316/18 Pumps for pumping blood
• CPC Class Codes: F16C 32/044 Active magnetic bearings
• CPC Class Codes: Y10S 415/90 Rotary blood pump

Abstract

An apparatus and method for a centrifugal fluid pump for pumping sensitive biological fluids, which includes (i) an integral impeller and rotor which is entirely supported by an integral combination of permanent magnets and electromagnetic bearings and rotated by an integral motor, (ii) a pump housing and arcuate passages for fluid flow and containment, (iii) a brushless driving motor embedded and integral with the pump housing, (iv) a power supply, and (v) specific electronic sensing of impeller position, velocity or acceleration using a self-sensing method and physiological control algorithm for motor speed and pump performance based upon input from the electromagnetic bearing currents and motor back emf—all fitly joined together to provide efficient, durable and low maintenance pump operation. A specially designed impeller and pump housing provide the mechanism for transport and delivery of fluid through the pump to a pump output port with reduced fluid turbulence.

Claims

1. Apparatus for pumping sensitive biological fluids comprising:

a construct having an exterior, a hollow interior having walls therein, at least one housing permanent magnet disposed therein, and an axial center;

an inlet for passage of fluids through the construct and into the hollow interior of the construct;

an outlet for passage of fluids through the hollow interior of the construct;

an impeller disposed within the hollow interior of the construct and out of contact therewith for controlling fluid flow through the hollow interior of the construct;

a plurality of magnetic actuators which provide six axes of control, including one axial translational axis, and one rotational axis;

at least one impeller permanent magnet juxtaposed to the housing permanent magnet for suspending the impeller out of contact with the hollow interior of the construct;

a motor for selectively rotating the impeller to thereby control fluid flowing through the apparatus, and

wherein at least one of the five axes controlled for moment axial translation and radial translation is controlled by a set of permanent magnets and wherein the set of permanent magnets is magnetized in an axis parallel to an axis of rotation of the impeller.

2. The apparatus of claim 1, wherein the inlet is integral with the construct exterior.

3. The apparatus of claim 1, wherein the outlet is integral with the construct exterior.

4. The apparatus of claim 1, wherein the outlet is radially located from the axial center of the construct.

5. The apparatus of claim 1, wherein the impeller comprises arcuate blades.

6. The apparatus of claim 1, wherein the impeller comprises arcuate passageways whereby fluid flow through the construct is gradually redirected from the inlet to the outlet.

7. The apparatus of claim 1, wherein at least one of the magnetic actuators is an electromagnet.

8. The apparatus of claim 7, wherein the magnetic actuators comprise a plurality of electromagnets.

9. The apparatus of claim 1, wherein at least one of the five axes controlled for moment axial translation and radial translation is controlled by a set of permanent magnets attached to the housing.

10. The apparatus of claim 9, wherein the impeller comprises an integrated combination of an impeller for fluid flow through the construct and a rotor being controlled by the motor thereby allowing the motor to control rotation of the impeller, the integrated combination of the impeller and the rotor forming interior sides of a first return flow chamber and a second return flow chamber, respectively, for permitting fluid flow around the suspended impeller.

11. The apparatus of claim 10, wherein the interior side of the rotor forming the second return flow chamber includes a second member having a curvature corresponding to a curvature of walls of the hollow interior of the construct, the second member being coupled to a first member by impeller wherein impeller chambers are formed from (i) the arcuate blades, (ii) the first member, and (iii) the second member, thus forming the arcuate passageways for the gradual redirection of fluid from the inlet to the outlet.

12. The apparatus of claim 11, wherein the second member includes a second magnetic material for interaction with a second electromagnetic thrust bearing and a second electric activation coil, wherein the second electromagnetic thrust bearing and the second electric activation coil stabilizes the impeller and controls a combination of two degrees of freedom in radial position, axial position, external radial forces, and external thrust forces which act upon the impeller.

13. The apparatus of claim 11, wherein the second member comprises a rotor integrally formed therein and the rotor having a plurality of permanent magnets disposed thereon for interaction with the motor wherein the rotor may be rotated by the motor and thereby rotate the impeller.

14. The apparatus of claim 1, further comprising a positioning structure for controlling six axes of impeller motion, said positioning structure including a hybrid magnetic bearing system wherein a first impeller permanent magnetic bearing set and a first housing permanent magnetic bearing set each comprise at least one permanent magnet ring situated about the impeller and the housing, with polarities arranged so that positive radial stiffnesses are generated, such that the impeller operates in a centered position relative to the two radial displacements for control of two of the six axes.

15. The apparatus of claim 14, wherein a first impeller magnetic target set and the first housing electromagnetic bearing set comprise electromagnetic bearings which control the remaining axial displacement and two angular displacements of the six axes so that the impeller operates in a centered position with regard to the axial and two angular axes.

16. The apparatus of claim 1, further comprising a positioning structure for controlling six axes of impeller motion, said positioning structure including a hybrid magnetic bearing system wherein a first impeller permanent magnetic bearing set and a first housing permanent magnetic bearing set each comprise at least one permanent magnet ring situated about the impeller and the housing, with polarities arranged so that positive radial stiffnesses are generated and soft magnetic iron is employed on one or more of the ring faces to focus the magnetic flux between the permanent magnet rings, such that the impeller operates in a centered position relative to the two radial displacements for control of two of the six axes.

17. The apparatus of claim 16, wherein a first impeller magnetic target set and the first housing electromagnetic bearing set comprise electromagnetic bearings which control the remaining axial displacement and two angular displacements of the six axes so that the impeller operates in a centered position with regard to these three axes, a third angular axis being controlled by the motor.

18. The apparatus of claim 1, further comprising a positioning structure for controlling six axes of impeller motion, said positioning structure including a hybrid magnetic bearing system wherein a first impeller permanent magnetic bearing set and a first housing permanent magnetic bearing set each comprise a set of multiple permanent magnet rings situated about the impeller and the housing, with polarities arranged so that positive radial stiffnesses are generated and soft magnetic iron is employed on at least one of the ring faces to focus the magnetic flux between the permanent magnet rings, such that the impeller operates in a centered position relative to the two radial displacements for control of two of the six axes.

19. The apparatus of claim 18, wherein a first impeller magnetic target set and the first housing electromagnetic bearing set comprise electromagnetic bearings which control the remaining axial displacement and two angular displacements for control of three of the six axes so that the impeller operates in a centered position with regard to these three axes.

20. The apparatus of claim 1, further comprising a positioning structure for controlling six axes of impeller motion, said positioning structure including a hybrid magnetic bearing system wherein a first impeller permanent magnetic bearing set and a first housing permanent magnetic bearing set each comprise a set of multiple permanent magnet rings situated about the impeller and the housing, with polarities arranged so that positive radial stiffnesses and positive moment stiffness are generated and soft magnetic iron is employed on at least one of the ring faces to focus the magnetic flux between the permanent magnet rings, such that the impeller operates in a centered position relative to the two radial displacements and the two angular displacements for control of four of the six axes.

21. The apparatus of claim 20, wherein a first impeller magnetic target set and the first housing electromagnetic bearing set comprise electromagnetic bearings which control the remaining axial displacement of the six axes so that the impeller operates in a centered position with regard to this axis.

22. The apparatus of claim 1, further comprising a positioning structure for controlling six axes of impeller motion, said positioning structure including a hybrid magnetic bearing system wherein the first impeller permanent magnetic bearing set and the first housing permanent magnetic set each comprise a set of multiple permanent magnet rings situated about the impeller and the housing, with polarities arranged so that positive axial stiffness and positive moment stiffnesses are generated and soft magnetic iron is employed on at least one of the ring faces to focus the magnetic flux between the permanent magnet rings, such that the impeller operates in a centered position relative to the axial displacement and the two angular displacements for control of three of the six axes.

23. The apparatus of claim 22, wherein the first impeller magnetic target set and the electromagnetic bearings control two radial displacements so that the impeller operates in a centered position with regard to these two axes.

24. The apparatus of claim 1, wherein the plurality of magnetic actuators form a magnetic system comprising:

a first construct permanent magnet disposed on a first wall of the hollow interior of the construct,

a second construct permanent magnet disposed on a second wall, opposite the first wall, of the hollow interior of the construct,

a first impeller permanent magnet disposed on the impeller distal to the axial center of the construct and juxtaposed with the first construct permanent magnet,

a second impeller permanent magnet disposed on the impeller distal to the axial center of the construct and juxtaposed with the second construct permanent magnet,

a first construct permanent magnet set disposed on the first wall of the hollow interior of the construct,

a second construct permanent magnet set disposed on the second wall of the hollow interior of the construct,

a first impeller permanent magnet set disposed on the impeller proximate to the axial center of the construct and juxtaposed with the first construct permanent magnet set, and

a second impeller permanent magnet set disposed on the impeller proximate to the axial center of the construct and juxtaposed with the second construct permanent magnet set,

wherein the arrangement provides radial stabilization and, due to angular positioning, provides a degree of translational stabilization of the impeller and the impeller is prevented from contacting the hollow interior of the construct by magnetic fields.

25. The apparatus of claim 24, wherein the magnetic system further comprises self correcting positioner for dynamically positioning the impeller during operation such that the impeller is constantly out of contact with the construct.

26. Apparatus of claim 24, wherein the magnetic system further comprises,

at least one coil disposed in the first wall of the construct housing and at least another one coil disposed in the second wall of the construct housing, the at least one coil being juxtaposed between (i) the first construct permanent magnet and (ii) the first construct permanent magnet set, and at least another one coil being juxtaposed between (i) the second construct permanent magnet and (ii) the second construct permanent magnet set;

at least one electromagnetic thrust bearing disposed in the construct housing about the at least one coil and the at least another one coil; and

an electronic controller for controlling electric current in at least one coil and at least another one coil thereby causing changes in forces exerted by at least one electromagnetic thrust bearing.

27. Apparatus of claim 26, further comprising a physiological controller for controlling a rate of rotation of the impeller so that the rate of rotation corresponds to the physiological state of a person using the apparatus of the present invention, said physiological controller being coupled to the electronic controller, said electronic controller further including a monitor for monitoring change of electronic parameters selected from the group consisting of (i) bearing currents in the at least one electromagnetic thrust bearing, (ii) bearing voltages in the at least one electromagnetic thrust bearing, (iii) motor currents, and (iv) motor voltages.

28. The apparatus of claim 1, further comprising of physiological controller for controlling the rate of rotation of the impeller so that the rate of rotation corresponds to the physiological state of a person using the apparatus of the present invention.

29. The apparatus of claim 28, wherein the electronic controller comprises a monitor for monitoring change of electronic parameter selected from the group consisting of

(i) bearing currents in at least one electromagnetic thrust bearing;

(ii) bearing voltages in at least one electromagnetic thrust bearing;

(iii) motor currents; and

(iv) motor voltages.

30. The apparatus of claim 1, wherein the motor comprises a stator integrally formed within a wall of the hollow interior of the construct, the stator having windings fixed therein for receiving current from a motor controller.

31. The apparatus of claim 1 wherein the motor comprises a rotor having a circumference integrally formed as part of the impeller, the rotor having a plurality of permanent magnets disposed therein such that (i) poles of the plurality of permanent magnets alternate between north and south and (ii) the plurality of permanent magnets are arranged to form a circular pattern concentric with the circumference of the rotor.

32. The apparatus as defined in claim 1, further comprising a plurality of electromagnetic segments which are individually controlled to provide the six axes of control.

33. The apparatus as defined in claim 1, wherein the magnetic actuators provide six axes of control, including (i) one axial translational axis, (ii) two radial translational axes, and (iii) three rotational axes comprising two axes controlled for moment and one axis controlled by motor rotation.

34. The apparatus of claim 1, wherein the impeller comprises straight blades.

35. A continuous flow pump for pumping sensitive biological fluids comprising:

a construct having a first pump housing half and a second pump housing half hermetically sealed to the first pump housing half to form the construct, the construct having a hollow interior and an axial center;

a pump inlet vessel formed from the first pump housing half and having an inlet throughbore for passage of fluids therethrough and into the hollow interior of the construct;

a pump outlet vessel radially located from the axial center of the construct and formed from the first and second pump housing halves and having an outlet throughbore for passage of fluids therethrough from the hollow interior of the construct;

an impeller disposed within the hollow interior of the construct and out of contact therewith and having an impeller intake opening, impeller chambers, and impeller vanes having a spiral curvature for forming the impeller chambers;

a magnetic system comprising a plurality of electromagnetic actuators to provide six axes of control, including (i) one axial translational axis, (ii) two radial translational axes, and (iii) three rotational axes comprising two axes controlled for moment and one axis controlled by motor rotation, wherein at least one of the five axes controlled for moment, axial translation, and radial translation is controlled by a set of permanent magnets in the housing magnetized in an axis parallel to the axis of rotation of the impeller, said electromagnetic actuators being positioned for suspending the impeller out of contact with the hollow interior of the construct and for selectively rotating the impeller to thereby control fluid flowing through the continuous flow pump; and

a motor for controlling rotational speed of the impeller.

36. A method for pumping sensitive biological fluids using a pump comprising the steps of:

selecting a pump device having a magnetically suspended impeller within a housing of the pump having at least one permanent magnet disposed therein, the impeller having arcuately shaped vanes for reducing impact on the sensitive fluids traveling through the pump;

positioning the impeller within the housing according to signals received from a magnetic system that are used to magnetically suspend the impeller;

controlling a plurality of electromagnetic actuators to provide six axes of control, including one axial translational axis and one rotational axes;

positioning the electromagnetic actuators such that at least one of the axes control is controlled by a set of permanent magnets in the housing magnetized in an axis parallel to the axis of rotation of the impeller; and

adjusting the impeller rotational speed and thus the rate of fluid flow according to signals received frog an input and an output of the pump.

37. The method of claim 36, wherein controlling a plurality of electromagnetic actuators further comprises controlling (i) one axial translational axis, (ii) two radial translational axes, and (iii) three rotational axes comprising two axes controlled for moment and one axis controlled by motor rotation.

38. Apparatus for pumping sensitive biological fluids comprising:

a construct having an exterior, a hollow interior having walls therein, at least one housing permanent magnet disposed therein, and an axial center;

an inlet formed from the construct exterior for passage of fluids therethrough and into the hollow interior of the construct;

an outlet formed from the construct exterior for passage of fluids therethrough from the hollow interior of the construct, the outlet radially located from the axial center of the construct;

an impeller disposed within the hollow interior of the construct and out of contact therewith for controlling fluid flow into the inlet, through the hollow interior of the construct, and out of the outlet, the impeller having arcuate blades and arcuate passageways whereby fluid flow through the construct is gradually redirected from the inlet to the outlet;

a magnetic system including at least one impeller permanent magnet juxtaposed to the housing permanent magnet for suspending the impeller out of contact with the hollow interior of the construct; and

a motor which selectively rotates the impeller to thereby control fluid flowing through the apparatus, said motor including stator windings formed within the housing of the construct and arcuately shaped permanent magnets with a soft iron core formed as part of the impeller, said permanent magnets and soft iron core arranged such that magnetic flux is present on only one side of the rotor, interacting with stator windings on the same side.

39. Apparatus for pumping sensitive biological fluids comprising:

a construct having an exterior, a hollow interior having walls therein, at least one housing permanent magnet disposed therein, and an axial center;

an inlet formed from the construct exterior for passage of fluids therethrough and into the hollow interior of the construct;

an outlet formed from the construct exterior for passage of fluids therethrough from the hollow interior of the construct, the outlet radially located from the axial center of the construct;

an impeller disposed within the hollow interior of the construct and out of contact therewith thereby permitting fluid flow into the inlet, through the hollow interior of the construct, and out of the outlet, the impeller having arcuate blades and arcuate passageways whereby fluid flow through the construct is gradually redirected from the inlet to the outlet;

a magnetic system including at least one impeller permanent magnet juxtaposed to the housing permanent magnet for suspending the impeller out of contact with the hollow interior of the construct; and

a motor for selectively rotating the impeller to thereby control fluid flowing through the apparatus;

wherein the impeller is integrated with a rotor being controlled by the motor thereby allowing the motor to control rotation of the impeller, the integrated combination of the impeller and the rotor forming interior sides of a first return flow chamber and a second return flow chamber, respectively, for permitting fluid flow around the suspended impeller;

wherein the interior side of the impeller forming the first return flow chamber includes a first member having a curvature corresponding to a curvature of walls of the hollow interior of the construct; and

wherein the first member includes a first impeller permanent magnet for interaction with a first housing permanent magnet and a first impeller permanent magnet set for interaction with a first housing permanent magnet set, wherein (i) the first impeller permanent magnet is juxtaposed with the first housing permanent magnet such that a pole of the first impeller permanent magnet repels a pole of the first housing permanent magnet and (ii) the first impeller permanent magnet set is juxtaposed with the first housing permanent magnet set such that poles of the first impeller permanent magnet set repel poles of the first housing permanent magnet set thereby preventing contact between the first member and the housing; and

wherein the first impeller magnetic set and the first housing magnetic set each comprise a multiple ring configuration about the impeller and the housing, respectively, the multiple ring configuration of each magnetic set comprising at least one first magnetic ring and at least one second magnetic ring disposed in an attractive orientation with the at least one first magnetic ring and the first impeller magnetic set disposed in reverse polarity with the first housing magnetic set.

40. Apparatus for pumping sensitive biological fluids comprising:

a construct having an exterior, a hollow interior having walls therein, at least one housing permanent magnet disposed therein, and an axial center;

an inlet formed from the construct exterior for passage of fluids therethrough and into the hollow interior of the construct;

an outlet formed from the construct exterior for passage of fluids therethrough from the hollow interior of the construct, the outlet radially located from the axial center of the construct;

an impeller disposed within the hollow interior of the construct and out of contact therewith to control fluid flow into the inlet, through the hollow interior of the construct, and out of the outlet, the impeller having arcuate blades and arcuate passageways whereby fluid flow through the construct is gradually redirected from the inlet to the outlet;

a magnetic system including at least one impeller permanent magnet juxtaposed to the housing permanent magnet for suspending the impeller out of contact with the hollow interior of the construct; and

a motor permitting selective rotation of the impeller to thereby control fluid flowing through the apparatus;

wherein the impeller comprises an integrated combination of an impeller for fluid flow through the construct and a rotor being controlled by the motor thereby allowing the motor to control rotation of the impeller, the integrated combination of the impeller and the rotor forming interior sides of a first return flow chamber and a second return flow chamber, respectively, for permitting fluid flow around the suspended impeller;

wherein the interior side of the rotor forming the second return flow chamber includes a second member having a curvature corresponding to a curvature of walls of the hollow interior of the construct, the second member being coupled to a first member by the arcuate blades of the impeller wherein impeller chambers are formed from (i) the arcuate blades, (ii) the first member, and (iii) the second member, thus forming the arcuate passageways for the gradual redirection of fluid from the inlet to the outlet;

wherein the second member includes a second impeller permanent magnet for interaction with a second housing permanent magnet and a second impeller permanent magnet set for interaction with a second housing permanent magnet set, wherein (i) the second impeller permanent magnet is juxtaposed with the second housing permanent magnet such that a pole of the second impeller permanent magnet repels a pole of the second housing permanent magnet and (ii) the second impeller permanent magnet set is juxtaposed with the second housing permanent magnet set such that poles of the second impeller permanent magnet set repel poles of the second housing permanent magnet set thereby preventing contact between the second member and the housing; and

wherein the second impeller permanent magnetic set and the second housing permanent magnetic set each comprise a double ring configuration about the impeller and the housing, respectively, the double ring configuration of each magnetic set comprising a first magnetic ring and a second magnetic ring disposed in an attractive orientation with the first magnetic ring and the second impeller magnetic set disposed in reverse polarity with the second housing magnetic set.

41. Apparatus for pumping sensitive biological fluids comprising:

a construct having an exterior, a hollow interior having walls therein, at least one housing permanent magnet disposed therein, and an axial center;

an inlet permitting passage of fluids through the construct and into the hollow interior of the construct;

an outlet permitting passage of fluids through the construct from the hollow interior of the construct, the outlet radially located from the axial center of the construct;

an impeller disposed within the hollow interior of the construct and out of contact therewith the impeller;

a magnetic system including at least one impeller permanent magnet juxtaposed to the housing permanent magnet, which is magnetized in an axis parallel to the axis of rotation of the impeller for suspending the impeller out of contact with the hollow interior of the construct; and

a motor in rotational engagement with the impeller to thereby control fluid flowing through the apparatus.

42. The apparatus of claim 41, wherein the impeller includes arcuate blades and arcuate passageways whereby fluid flow through the construct as gradually redirected from the inlet to the outlet.