Magnetically suspended and rotated rotor

• US 4,944,748 A
• Filed: 05/09/1988
• Issued: 07/31/1990
• Est. Priority Date: 10/12/1986
• Status: Expired due to Term

• Current Assignee: Don B. Olsen, Gunter W. Bramm
• Original Assignee: Don B. Olsen, Gunter W. Bramm
• Inventors: Bramm, Gunter W., Olsen, Don B.
• Primary Examiner(s): Green, Randall L.
• Assistant Examiner(s): Iantorno, Stephanie L.
• Application Number:
  US07/193,180
• Time in Patent Office: 813 Days
• Field of Search: 623/3, 416/111, 417/356
• 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 the human body to provide a replacement for, or an assist to, the 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 person into which the pump is implanted, the housing having an impellor chamber 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 rotor in said pump chamber out of contact with the walls of the impellor chamber, comprising;

permanent magnet impellor support means 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 disposed 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; and

impellor drive means mounted on the housing for sensing a preselected physical quantity related to the 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 quantity.

2. The pump of claim 1 wherein said physical quantity is the pressure in the inlet passage of the housing.

3. The pump of claim 2 wherein the impellor chamber, the inlet passage and the outlet passage are characterized as being portions of a bore formed through the housing;

wherein an annular restriction is formed in the inlet passage of the pump; and

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

4. The pump of claim 1 wherein said control position is coincident with said null position.

5. The pump of claim 1 wherein the electromagnet control means is characterized as 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 rotor at such times that the rotor 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 rotor.

6. The apparatus of claim 1 in which blood-contacting surfaces of the housing and rotor are each provided with a non-solvent coating.

7. An artificial heart for implantation in the body of a human subject comprising:

a first pump comprising a housing constructed of or coated with a blood compatible material having an inlet passage fluidly connectable to the subject'"'"'s left atrium and an outlet passage fluidly connectable to the subject'"'"'aorta; and

a second pump comprising a housing constructed of or coated with a blood compatible material having an inlet passage connectable to at least one of the subject'"'"'s superior vena cava and inferior vena cava and an outlet passage fluidly connectable to the subject'"'"'s pulmonary artery;

wherein the housing of each of said pumps has an impellor chamber disposed between the housing inlet passage and the housing outlet passage; and

wherein each of said pumps further comprises;

an impellor disposed in the housing impellor chamber and rotatable therein about an impellor rotation axis for drawing blood from the housing outlet passage;

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

permanent magnet impellor means 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 selcted 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 disposed 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; and

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; and

impellor drive means disposed partially on the impellor and partially on the housing for turning the impellor about said rotation axis, wherein portions of the impellor drive means disposed on the impellor are coupled solely magnetically to portions of the impellor drive means disposed on the housing.

8. The apparatus of claim 7 in which blood-contacting surfaces of the housing and rotor are each provided with a non-solvent coating.

9. A pump for pumping blood implantable in the human body to provide a replacement for, or an assist to, the 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 person into which the pump is implanted, the housing having an impellor chamber 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 rotor in said pump chamber out of contact with the walls of the impellor chamber, comprising;

permanent magnet impellor support means 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 disposed 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;

impellor drive means mounted on the housing for sensing the pressure in the inlet passage of the housing related to the flow of blood in the 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 the pressure in the inlet passage of the housing; and

wherein the combined center of gravity of the impellor and portions of the impellor drive means and permanent magnet impellor support means disposed thereon is positioned at the center of buoyancy of the impellor, and wherein a cavity is formed in the impellor to match the average specific gravity of the impellor and portions of the drive means and the permanent magnet impellor support means thereon to the specific gravity of blood.

10. A pump implantable in the human body to provide a replacement for, or an assist to, the 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 person into which the pump is implanted, the housing having an impellor chamber 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 rotor in said pump chamber out of contact with the walls of the impellor chamber, comprising;

permanent magnet impellor support means 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 disposed 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;

comprising;

means for selecting the control position in a displaced relationship to the null position along said support axis, whereby the permanent magnet impellor 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;

impellor drive means mounted on the housing for sensing a preselected physical quantity related to the 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 quantity; and

wherein the combined center of gravity of the impellor and portions of the impellor drive means and permanent magnet impellor support means disposed thereon is positioned at the center of buoyancy of the impellor, and wherein a cavity is formed in the impellor to match the average specific gravity of the impellor and portions of the drive means and the permanent magnet impellor support means thereon to the specific gravity of blood.