Magnetically suspended and rotated rotor

• US 5,326,344 A
• Filed: 11/09/1992
• Issued: 07/05/1994
• Est. Priority Date: 04/04/1985
• Status: Expired due to Term

• Current Assignee: Life Extenders Corporation
• Original Assignee: Life Extenders Corporation
• Inventors: Bramm, Gunter W., Olsen, Don B.
• Primary Examiner(s): Green, Randall L.
• Assistant Examiner(s): BURKE, ELIZABETH
• Application Number:
  US07/953,409
• Time in Patent Office: 603 Days
• Field of Search: 623/3, 600/16-18, 417/356, 416/111
• US Class Current: 623/3.14
• 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 60/232 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 60/515 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: F04D 13/06 the pump being electrically driven
• CPC Class Codes: F04D 15/0066 by changing the speed, e.g. of the driving engine
• CPC Class Codes: F04D 29/048 magnetic; electromagnetic
• CPC Class Codes: F16C 2316/18 Pumps for pumping blood
• CPC Class Codes: F16C 39/063 Permanent magnets
• CPC Class Codes: H02K 7/09 with magnetic bearings

Abstract

The impellor of a blood pump is supported by permanent magnets on the impellor and pump housing and stabilized by an electromagnet on the housing. A control circuit supplies current to the electromagnet to maintain the axial position of the impellor at a control position in which the impellor is in mechanical equilibrium under permanent magnet forces and static axial forces on the impellor to minimize energy consumption in the support of the impellor. The impellor is rotated magnetically and stator coils in the housing are supplied with electric currents having a frequency and amplitude adjusted in relation to blood pressure at the pump inlet to match the flow characteristics of the pump to physiological characteristics of the natural heart. A cavity is formed in the impellor to match the average specific gravity of the impellor and portions of the suspension and drive systems thereon to the specific gravity of blood to further minimize power consumption by the pump. A valve member can be formed on the impellor to mate with a restriction in the pump inlet for pumps used to assist the pumping action of the natural heart.

Claims

1. A pump implantable in a human body having a circulatory system for pumping blood to provide a replacement for, or an assist to, a natural heart, comprising:

a housing constructed of or coated with a blood compatible material having an inlet passage and an outlet passage for connecting the pump into the circulatory system of the human body into which the pump is implanted, the housing having an impellor chamber defining walls fluidly interposed between the inlet passage and the outlet passage;

an impellor constructed of or coated with a blood compatible material disposed in the housing impellor chamber and rotatable therein about an impellor rotation axis for drawing blood into the housing inlet passage and discharging blood from the housing outlet passage;

magnetic suspension means for magnetically suspending the impellor in said pump chamber out of contact with the walls of the impellor chamber, comprising;

permanent magnet impellor support comprising an assembly of permanent magnets mounted on the impellor and on the housing for exerting forces on the impellor tending to align the rotation axis of the impellor with a selected support axis of the housing while tending to drive the impellor axially away from a selected null position on said support axis at such times that the impellor is axially displaced from the null position;

an electromagnet mounted on the housing and positioned thereon to exert a force directed along the support axis on portions of the permanent magnet impellor support means dispose on the impellor at such times that an electric current is passed through the electromagnet, the electromagnet thereby exerting an axial force on the rotor,

electromagnet control means mounted on the housing for detecting a displacement of the impellor from a control position of the impellor on the support axis and passing a current through the electromagnet to drive the impellor toward the control position, the electromagnet control means comprising means for selecting the control position in a displaced relation to the null position along said support axis, whereby the permanent magnet rotor support means will exert a force on the impellor at such times that the impellor is in the control position, thereby enabling the permanent magnets of the permanent magnet impellor support means to balance a static force exerted axially on the impellor; and

impellor drive means mounted on the housing for sensing a preselected physical quantity related to a flow of blood in said circulatory system and magnetically coupled to the impellor for rotating the impellor at a rate varying in accordance with a selected relationship to the value of said physical quantity, said physical quantity being a pressure in the inlet passage of the housing;

wherein the inlet passage of the housing opening into the impellor chamber along the housing support axis and the outlet passage extends tangentially from portions of the impellor chamber displaced radially from the housing support axis and extending circumferentially about the impellor.

2. The pump of claim 1 wherein the inlet passage is characterized as having a first side and a second side, and wherein the housing is characterized as having a first inlet passage and a second inlet passage each of which opens into the impellor chamber along the housing support axis, the first inlet passage disposed to the first side of the outlet passage and the second inlet passage disposed to the second side of the outlet passage.

3. The pump of claim 2 wherein the impellor comprises an impellor body having a generally conical first end portion having a base and a generally conical second end portion having a base, the second end portion disposed coaxially with the first end portion such that the first and second end portions are joined at their respective bases and provide apices for the first and second end portions which are disposed on the impellor rotation axis at opposite ends of the impellor body.

4. The pump of claim 3 wherein the impellor further comprises a plurality of curved vanes disposed on the first and second end portions of the impellor body.

5. The pump of claim 3 wherein the impellor further comprises two hollow, frusto-conical duct-forming shells mounted on the impellor body, each duct-forming shell extending coaxially about one of the first and second end portions of the impellor body to form an annular duct thereabout.

6. The pump of claim 5 wherein each duct forming shell is characterized as having a radially outermost surface and wherein the impellor further comprises a plurality of curved vanes formed on the radially outermost surface of each of the duct-forming shells.

7. The pump of claim 5 wherein the impellor further comprises a plurality of hollow, frusto-conical intermediate shells mounted on the impellor body in each of the annular ducts extending about the first and second end portions of the impellor body.

8. The pump of claim 3 configured for pumping a liquid having a selected specific gravity, wherein a combined center of gravity of the impellor and portions of the drive means and permanent magnet impellor support means disposed thereon is positioned at a center of buoyancy of the impellor;

and wherein a cavity is formed in the impellor body to match an average specific gravity of the impellor, portions of the drive means disposed on the impellor, and portions of the permanent magnet impellor support means disposed on the impellor to the selected specific gravity of the liquid to which the pump is configured to pump.

9. The pump of claim 8 wherein the impellor further comprises a plurality of curved vanes disposed on the first and second end portions of the impellor body.

10. The pump of claim 8 wherein the impellor further comprises two hollow, frusto-conical duct-forming shells mounted on the impellor body, each duct-forming shell extending coaxially about one of the first and second end portions of the impellor body to form an annular duct thereabout.

11. The pump of claim 10 wherein each duct forming shell is characterized as having a radially outermost surface and wherein the impellor further comprises a plurality of curved vanes formed on the radially outermost surface of each of the duct-forming shells.

12. The pump of claim 10 wherein the impellor further comprises a plurality of hollow, frusto-conical intermediate shells mounted on the impellor body in each of the annular ducts extending about the first and second end portions of the impellor body.

13. The pump of claim 1 wherein the impellor chamber, the inlet passage and the outlet passage are characterized as being portions of a bore formed through the housing;

and wherein the impellor is characterized as having a plurality of vanes formed thereon to drive fluid axially of the impellor in response to rotation of the impellor in the housing.

14. The pump of claim 13 wherein the impellor is characterized as having a form of a rod having an outer peripheral surface and tapered ends extending axially along the rotation axis of the impellor;

and wherein said vanes are formed on the outer peripheral surface of the impellor.

15. The pump of claim 13 wherein the impellor is characterized as comprising a ring-shaped portion having coaxial inner and outer peripheral surfaces centered on the impellor rotation axis;

and wherein said vanes are formed on the inner peripheral surface of the ring-shaped portion of the impellor.

16. The pump of claim 15 wherein an annular restriction is formed in the inlet passage of the housing;

and wherein the pump further comprises a valve member mounted on the impellor adjacent said annular restriction, the valve member having a nose portion shaped to mate with said annular restriction whereby the inlet passage of the housing can be closed by movement of the valve member nose portion into said annular restriction.

17. The pump of claim 13 wherein the outlet passage of the housing is formed about an outlet flow axis intersecting the housing support axis at an obtuse angle.

18. The pump of claim 17 wherein the inlet passage of the housing is formed about an inlet flow axis intersecting the housing support axis at an obtuse angle.

19. The pump of claim 18 wherein the housing comprises:

an integrally formed outlet flow control vane in the housing outlet passage, the outlet flow control vane extending along the outlet passage in a parallel relation to the outlet flow axis; and

an integrally formed inlet flow control vane in the housing inlet passage, the inlet flow control vane extending along the inlet passage in a parallel relation to the inlet flow axis.

20. The pump of claim 17 wherein the housing comprises an integrally formed outlet flow control vane in the housing outlet passage, the outlet flow control vane extending along the outlet passage in a parallel relation to the outlet flow axis.