MRI-safe Electro-magnetic Tranducer

• US 20090134721A1
• Filed: 01/05/2009
• Published: 05/28/2009
• Est. Priority Date: 04/01/2002
• Status: Active Grant

• Current Assignee: Med El Elektromedizinische Geraete GmbH
• Original Assignee: MED-EL Elektromedizinische Gerate GmbH (MED-EL Corporation)
• Inventors: Zimmerling, Martin
• Granted Patent: US 8,013,699 B2
• Time in Patent Office: Days
• US Class Current: 310/15
• CPC Class Codes: B06B 1/045 using vibrating magnet, armature or coil system
• CPC Class Codes: H01H 36/0073 actuated by relative movement between two magnets
• CPC Class Codes: H02K 33/16 with polarised armatures moving in alternate directions by reversal or energisation of a single coil system
• CPC Class Codes: H02K 35/02 with moving magnets and stationary coil systems
• CPC Class Codes: H04R 25/606 acting directly on the eardrum, the ossicles or the skull, e.g. mastoid, tooth, maxillary or mandibular bone, or mechanically stimulating the cochlea, e.g. at the oval window

Abstract

An electromagnetic transducer includes a housing. At least one coil is associated with the housing. A spherical magnet within the housing is capable of turning in any direction and of moving along an axis. A first keeper and a second keeper are positioned on opposite sides of the magnet, both the first keeper and the second keeper including magnetically soft material and free to move along the axis. A first biasing member holds the first keeper along the axis, and a second biasing element that holds the second keeper along the axis. The first keeper and the second keeper are attracted by magnetic poles of the magnet in the absence of an external magnetic field, such that opposing magnetic poles of the magnet are aligned parallel to the axis. Alternating current flowing through the at least one coil causes a vibration of the magnet, the vibration transferred to the housing.

Claims

1. An electromagnetic transducer comprising:

a housing;

at least one coil associated with the housing;

a spherical magnet within the housing, the magnet substantially restricted to rotation in any direction and movement along an axis; and

a first keeper and a second keeper positioned on opposite sides of the magnet, both the first keeper and the second keeper including magnetically soft material.

2. The electromagnetic transducer according to claim 1, further comprising:

a first biasing element positioned between the first keeper and the housing, and a second biasing element positioned between the second keeper and the housing, the biasing elements for biasing movement of the spherical magnet.

3. The electromagnetic transducer according to claim 2, wherein the first biasing element holds the first keeper substantially centered on the axis, and wherein the second biasing element holds the second keeper substantially centered on the axis.

4. The electromagnetic transducer according to claim 2, wherein the first biasing member and/or the second biasing member is at least one of elastic, flexible and resilient.

5. The electromagnetic transducer according to claim 2, wherein the first biasing member and the second biasing member prevent the magnet from directly contacting the housing.

6. The electromagnetic transducer according to claim 1, wherein the transducer is substantially free of torque in the presence of an external magnetic field.

7. The electromagnetic transducer according to claim 1, wherein at least one of the spherical magnet and an inner wall of the housing are coated with a material having a low coefficient of friction.

8. The electromagnetic transducer according to claim 7, wherein the material is Teflon.

9. The electromagnetic transducer according to claim 1, wherein the at least one coil includes a plurality of coils, and wherein the induced voltage of the plurality of coils arising from an external RF field is zero.

10. The electromagnetic transducer according to claim 9, wherein the at least one coil includes a first and second outer coil, and a middle coil positioned between the first and second outer coils, wherein the middle coil is winded in a direction opposite the two outer coils, and wherein the number of loops of the middle coil equals the sum of loops of the first and second outer coils.

11. The electromagnetic transducer according to claim 1, wherein a vibration in the housing causes vibration in the magnets so as to cause a current in the at least one coil.

12. The electromagnetic transducer according to claim 1, wherein alternating current flowing through the at least one coil causes a vibration of the magnet, the vibration transferred to the housing.

13. The electromagnetic transducer according to claim 1, wherein the first keeper and the second keeper are attracted by magnetic poles of the magnet in the absence of an external magnetic field, such that opposing magnetic poles of the magnet are aligned parallel to the axis.

14. A method of controlling a transducer, the transducer including a spherical magnet positioned within a housing, the spherical magnet substantially restricted to rotation in any direction and movement along an axis, the method comprising:

positioning a first keeper and a second keeper on opposite sides of the spherical magnet, both the first keeper and the second keeper including magnetically soft material, the first keeper and the second keeper attracted by magnetic poles of the magnet in the absence of an external magnetic field, such that opposing magnetic poles of the magnet are aligned parallel to the axis.

15. The method of claim 14, further comprising:

applying a magnetic field to the transducer, wherein the magnetization of the keepers align in the direction of the external magnetic field, and the spherical magnet turns to align with the external magnetic field.

16. The method according to claim 14, further comprising:

coupling the transducer to a vibratory component of an ear; and

applying an alternating current flowing through at least one coil associated with the housing, so as to cause a vibration of the magnet, the vibration transferred to the housing.

17. The method of claim 14, wherein a vibration in the housing causes a vibration in the spherical magnet, the method further comprising sensing a current in at least one coil associated with the housing.

18. The method according to claim 17, further comprising sensing the stapedius reflex.

19. The method of claim 14, further comprising biasing movement of the spherical magnet.

20. The method of claim 19, wherein biasing includes:

positioning a first biasing element between the first keeper and the housing, and

positioning a second biasing element between the second keeper and the housing.

21. The method according to claim 20, wherein the first biasing element maintains the position of the first keeper, and wherein the second biasing element maintains the position of the second keeper.