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

• US 6,324,431 B1
• Filed: 07/02/1999
• Issued: 11/27/2001
• Est. Priority Date: 07/06/1998
• Status: Expired due to Term

• Current Assignee: Abiomed, Inc. (Johnson & Johnson)
• Original Assignee: Abiomed, Inc. (Johnson & Johnson)
• Inventors: Zarinetchi, Farhad, Keville, Stephen J., Hart, Robert M., Verga, Michael G.
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/346,833
• Time in Patent Office: 879 Days
• Field of Search: 607/1, 607/36, 607/32, 607/33, 607/60, 607/61, 128/903
• 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 adapted to receive an alternating drive signal for generating a magnetic field;

an implantable secondary coil having mounted therein electronic components, said secondary coil for inducing a current when said secondary coil is inductively coupled to said primary coil, said induced current in said secondary coil generating a magnetic field; and

a cage formed of a magnetically permeable material enclosing said electronic components to reduce inductive heating of said electronic components caused by the magnetic field of said primary and secondary coils;

wherein said cage has walls of varying thickness.

2. The transcutaneous energy transfer device of claim 1, wherein the thickness of said walls is such that a lowest total mass is achieved while the strength of said magnetic fields in said walls is below a saturation density of said cage material.

3. The transcutaneous energy transfer device of claim 2, wherein said thickness of said cage walls is a minimum thickness such that magnetic flux density of said magnetic fields through said cage walls is approximately equal to said saturation density.

4. The transcutaneous energy transfer device of claim 1, wherein the material has high magnetic permeability in the range of approximately 2000-5000.

5. The transcutaneous energy transfer device of claim 1, wherein the material is a ferrite.

6. The transcutaneous energy transfer device of claim 1, wherein the material is laminated iron.

7. The transcutaneous energy transfer device of claim 1, wherein sidewalls of said cage are thicker than a top wall and bottom wall of said cage.

8. The transcutaneous energy transfer device of claim 7, wherein the strength of said magnetic fields in said cage is greater in said sidewalls than in said top and bottom walls.

9. A transcutaneous energy transfer device comprising:

an external primary coil adapted to receive an alternating drive signal for generating a magnetic field;

an implantable housing;

a secondary coil contained within said implantable housing, said secondary coil having mounted therein electronic components, said secondary coil for inducing a current when said secondary coil is inductively coupled to said primary coil;

a cage formed of a magnetically permeable material enclosing said electronic components, said cage having walls of varying thickness; and

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

10. The transcutaneous energy transfer device of claim 9, wherein said heat distribution layer is comprised of multiple alternating layers of high and low heat conductivity materials.

11. The transcutaneous energy transfer device of claim 9, wherein the material of said cage has high magnetic permeability in the range of approximately 2000-5000.

12. The transcutateous energy transfer device of claim 9, wherein said housing is formed from a material having a thermal conductivity so as to provide a substantially uniform distribution of heat along the housing.