Magnetically suspended and rotated rotor

• US 5,385,581 A
• Filed: 03/02/1992
• Issued: 01/31/1995
• Est. Priority Date: 04/04/1982
• Status: Expired due to Fees

• Current Assignee: Life Extenders Corporation
• Original Assignee: Life Extenders Corporation
• Inventors: Bramm, Gunter L., Olsen, Don B.
• Primary Examiner(s): Green, Randall L.
• Assistant Examiner(s): BURKE, ELIZABETH
• Application Number:
  US07/810,006
• Time in Patent Office: 1,065 Days
• Field of Search: 623/3, 600/16, 417/356, 415/111
• 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 60/178 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 60/196 replacing the entire heart, e.g. total artificial hearts [TAH]
• CPC Class Codes: A61M 60/221 the blood flow through the rotating member having both radial and axial components, e.g. mixed flow pumps
• 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 60/531 using blood pressure data, e.g. from blood pressure sensors
• CPC Class Codes: A61M 60/546 of blood flow, e.g. by adapting rotor speed
• CPC Class Codes: A61M 60/569 synchronous with the native heart beat
• CPC Class Codes: A61M 60/804 Impellers
• CPC Class Codes: A61M 60/806 Vanes or blades
• CPC Class Codes: A61M 60/812 Vanes or blades, e.g. static flow guides
• CPC Class Codes: A61M 60/814 Volutes
• CPC Class Codes: A61M 60/816 Sensors arranged on or in the housing, e.g. ultrasound flow sensors
• 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 32/0444 Details of devices to control the actuation of the electromagnets
• 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. An apparatus comprising:

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 in the human body, the pump comprising;

a housing 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, and the blood being passed through portions of the housing during the pumping of the blood and the housing having surfaces which are contacted by blood during pumping of the blood through the housing;

an impellor disposed in the impellor chamber in the housing and rotatable therein about an impellor rotation axis for drawing blood into the housing inlet passage and discharging blood from the housing outlet passage, the impellor having surfaces which are contacted by the blood during the pumping of the blood through the housing, the surfaces of the housing and the impellor which are contacted by blood being provided with a non-solvent coating;

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

permanent magnet impellor support means comprising an assembly of permanent magnets mounted on the impellor and on the housing for existing 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 electromagnetic 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 impellor; and

electromagnetic 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 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 said quantity, said physical quantity being a pressure in the inlet passage of the housing.

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

3. 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 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.

4. The pump of claim 1 configured for pumping a liquid having a specific gravity;

wherein a 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 a center of buoyancy of the impellor; and

wherein a cavity is formed in the impellor to match an average specific gravity of the impellor and portions of the drive means and permanent magnet impellor support means thereon to the specific gravity of the liquid to which the pump is configured for pumping.

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

a housing having an inlet passage and an outlet passage for connecting the pump into a circulatory system of the human body into which the pump is implanted, the housing having an impellor chamber fluidly interposed between the inlet passage and the outlet passage;

an impellor 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, the surfaces of the housing and the impellor which are contacted by blood being provided with a non-solvent coating;

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

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

6. The pump of claim 5 further comprising electromagnet control means comprising means for selecting a control position of the impellor on the support axis in a displaced relation to a null position along said support axis, whereby the impellor drive means will exert a force on the impellor at such times that the impellor is in the control position, thereby enabling the impellor drive means to balance a static force exerted axially on the impellor.

7. The pump of claim 6 wherein said control position is coincident with said null position.

8. The pump of claim 6 configured for pumping a liquid having a specific gravity;

wherein a 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 a center of buoyancy of the impellor; and

wherein a cavity is formed in the impellor to match an average specific gravity of the impellor and portions of the impellor drive means and permanent magnet impellor support means thereon to the specific gravity of the liquid to which the pump is configured for pumping.

9. The pump of claim 5 configured for pumping a liquid having a specific gravity;

wherein a combined center of gravity of the impellor and portions of the impellor drive means and the magnetic suspension means is positioned at a center of buoyancy of the impellor; and

wherein a cavity is formed in the impellor to match an average specific gravity of the impellor and portions of the impellor drive means and the magnetic suspension means to the specific gravity of the liquid to which the pump is configured for pumping.

10. The pump of claim 9 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 nose portion of the valve member into said restriction.