Transcutaneous energy transfer device with magnetic field protected components in secondary coil

• US 20020038138A1
• Filed: 09/20/2001
• Published: 03/28/2002
• Est. Priority Date: 07/06/1998
• Status: Abandoned Application

• Current Assignee: Farhad Zarinetchi, Michael G. Verga, Robert M. Hart, Stephen J. Keville
• Original Assignee: Farhad Zarinetchi, Michael G. Verga, Robert M. Hart, Stephen J. Keville
• Inventors: Zarinetchi, Farhad, Keville, Stephen J., Hart, Robert M., Verga, Michael G.
• Application Number:
  US09/957,254
• Publication Number:
  US 20020038138A1
• Time in Patent Office: Days
• US Class Current: 607/61
• CPC Class Codes: A61N 1/3787 from an external energy source

Abstract

The invention provides a transcutaneous energy transfer device having an external primary coil and an implanted secondary coil inductively coupled to the primary coil, electronic components subcutaneously mounted within the secondary coil and a mechanism which reduces inductive heating of such components by the magnetic field of the secondary coil. For one embodiment of the invention, the mechanism for reducing inductive heating includes a cage formed of a high magnetic permeability material in which the electronic components are mounted, which cage guides the flux around the components to prevent heating thereof. For an alternative embodiment of the invention, a secondary coil has an outer winding and either a counter-wound inner winding or an inner winding in the magnetic field of the outer winding. For either arrangement of the inner coil, the inner coil generates a magnetic field substantially canceling the magnetic field of the outer coil in the area in which the electronic components are mounted.

Claims

1. A transcutaneous energy transfer device comprising:

an external primary coil to which energy to be transferred is applied;

an implanted secondary coil inductively coupled to said primary coil, each of said coils producing a magnetic field; and

electronic components subcutaneously mounted within said secondary coil,

characterized by the inclusion of a mechanism which reduces inductive heating of said components by said magnetic field.

2. The transcutaneous energy transfer device of claim 1, wherein said mechanism includes a cage formed of a high magnetic permeability material in which said electronic components are mounted.

3. The transcutaneous energy transfer device of claim 2, wherein said material is a ferromagnetic material.

4. The transcutaneous energy transfer device of claim 2, wherein the material of said cage is sufficiently thick so that magnetic field values in the material are well below saturation.

5. The transcutaneous energy transfer device of claim 2, wherein the material of said cage is sufficiently thick so that significant heat dissipation in the material does not occur.

6. The transcutaneous energy transfer device of claim 2, wherein the material of said cage is as thin as possible while still being sufficiently thick so that magnetic field values in the material are well below saturation and significant heat dissipation in the material does not occur.

7. The transcutaneous energy transfer device of claim 6, wherein said cage is thicker in areas of the cage experiencing high flux density and thinned in other areas.

8. The transcutaneous energy transfer device of claim 6, wherein said cage is formed of a layer of ferromagnetic material laminated with at least one layer of low magnetic conductivity material.

9. The transcutaneous energy transfer device of claim 1, wherein said mechanism includes said secondary coil being wound with a first number N₁ of outer windings and a second number N₂ of counter-wound inner windings, N₁ being larger than N₂, N₁, N₂ and the diameters of both the outer and inner windings being selected such that the magnetic field caused by the coils in the region of said components is reduced sufficiently to prevent significant component heating.

10. The transcutaneous energy transfer device of claim 9, wherein N₁, N₂ and the diameters of the windings are selected so that the magnetic fields caused by the windings substantially cancel in the region of said components.

11. The transcutaneous energy transfer device of claim 9, wherein N₁ is approximately 19, N₂ is approximately seven the diameter of the outer winding is approximately 2.5″

and the diameter of the inner winding is approximately 1.5″

.

12. The transcutaneous energy transfer device of claim 1, wherein said mechanism includes said secondary coil being wound with a first number N₁ of outer windings and including a second number N₂ of inner windings in the magnetic field of the outer windings, N₁ being larger than N₂, N₁, N₂ and the diameters of both the outer and inner windings being selected such that the magnetic field caused by the coils in the region of said components is reduced sufficiently to prevent significant component heating.

14. The transcutaneous energy transfer device of claim 13, wherein said thickness of said cage walls is a minimum thickness that results in magnetic flux density through said cage walls is approximately equal to said saturation density.

16. The transcutaneous energy transfer device of claim 15, wherein said cage has flanges that extend the high permeability shield material within the flux pathway.

17. The transcutaneous energy transfer device of claim 16, wherein said cage comprises:

a cylindrical base;

a lid shaped in the form of a disk; and

said flanges integral with said base, said flanges extending a high magnetic permeable region from base into the magnetic flux pathway.

18. The transcutaneous energy transfer device of claim 17, wherein said flange is in-line with a shortest flux pathway between said primary and secondary coils.

19. The transcutaneous energy transfer device of claim 17, wherein said flange extends from base immediately adjacent to said secondary coil to guide said magnetic flux lines back toward said primary coil.

13. A transcutaneous energy transfer device comprising:

an external primary coil;

an implantable secondary coil coupled to said primary coil;

a cage formed of a high magnetic permeability material located within said secondary coil to reduce inductive heating of electronic components mounted therein caused by a magnetic field of said primary and secondary coils,

wherein said cage has walls of varying thickness such that a lowest total mass is achieved without exceeding the saturation density of said cage material.

15. A transcutaneous energy transfer device comprising:

an external primary coil;

an implantable secondary coil coupled to said primary coil;

a cage formed of a high magnetic permeability material located within said secondary coil to reduce inductive heating of electronic components mounted therein caused by a magnetic field of said primary and secondary coils,

wherein said cage has a geometry configured to maximize permeability in flux pathway between the primary and secondary coils.

20. A transcutaneous energy transfer device comprising:

an external primary coil;

an implantable secondary coil coupled to said primary coil;

a cage formed of a high magnetic permeability material within said secondary coil to house electronic components, wherein said cage is comprised of;

a base; and

a self-aligning lid.

21. The transcutaneous energy transfer device of claim 20, wherein said base is cylindrical and wherein said lid is shaped in the form of a disk.

22. The transcutaneous energy transfer device of claim 20, wherein said base includes vertical walls and wherein said lid includes an annular recessed shelf circumferentially formed around a mating surface of said lid configured to receive said vertical wall of said base.

24. The transcutaneous energy transfer device of claim 23, wherein said heat distribution layer is comprised of multiple alternating layers of high and low heat conductivity materials.

23. A transcutaneous energy transfer device comprising:

an external primary coil;

an implantable housing formed of a substantially low thermal conductivity medium;

a secondary coil, mounted within said implantable housing, coupled to said primary coil;

a cage formed of a high magnetic permeability material within said secondary coil to house electronic components; and

a heat distribution layer thermally coupled to said cage and to an internal surface of said housing.

25. In a transcutaneous energy transfer system including a primary coil and an implantable secondary coil having an outer first winding having a first number of turns and a first diameter and an inner second winding having a second number of turns and a second diameter, a method for determining said second number of turns, comprising:

a) winding said first winding with a predetermined number of turns;

b) inserting a magnetic field monitoring device in a central region of said secondary coil;

c) applying a dc current through said first winding while monitoring a magnetic field in the central region;

d) winding said second winding in a direction a direction of said first winding using a wire extension from said first winding;

e) monitoring, as said second winding is wound in said step d), a strength of a magnetic field in the central region; and

f) stopping said winding of said second winding when the magnetic field strength reaches approximately zero.