MAGNETIC TRANSDUCER

• US 3,671,684 A
• Filed: 11/06/1970
• Issued: 06/20/1972
• Est. Priority Date: 11/06/1970
• Status: Expired due to Term

• Current Assignee: George C. Tibbetts, Joseph A. Sawyer
• Original Assignee: George C. Tibbetts, Joseph A. Sawyer
• Inventors: George, C. Tibbetts, Joseph, A. Sawyer
• Primary Examiner(s): Ralph D. Blakeslee
• Application Number:
  US05/087,629
• Time in Patent Office: 592 Days
• Field of Search: 179/114A,115A,117,119 325/235
• US Class Current: 381/189
• CPC Class Codes: H04R 11/00 Transducers of moving-armature or moving-core type acoustic diaphragm of magnetisable material directly coacting with electromagnet H04R13/00
• CPC Class Codes: H04R 2225/49 Reducing the effects of electromagnetic noise on the functioning of hearing aids, by, e.g. shielding, signal processing adaptation, selective (de)activation of electronic parts in hearing aid

Abstract

A miniaturized electromechanical transducer has magnets providing polarizing flux across a working gap, an electrical signal coil, an armature extending through the coil and into the working gap, and a casing of particular configuration. The casing comprises a sleeve of magnetic material, elongate in the direction of its axis, which substantially surrounds the armature, coil, and magnets, said sleeve providing a substantially uninterrupted high permeability path between the magnets.

Claims

1. A magnetic transducer comprising a pair of magnets having a working gap therebetween, an electrical signal coil, an armature extending in a first direction through said coil into said gap and having a vibratable portion in said gap, and a sleeve comprising one piece of high magnetic permeability material fabricated to encircle an axis and to be elongate along the axis, said axis extending in said first direction, said sleeve interconnecting said pair of magnets and substantially surrounding said coil, said armature and said magnets.

2. A magnetic transducer as in claim 1 wherein said armature has a second portion extending to a joint with said sleeve, said joint having low reluctance to magnetic signal flux.

3. A magnetic transducer as in claim 1 further comprising a closure at an end of said sleeve.

4. A magnetic transducer as in claim 3 wherein said closure comprises high magnetic permeability material.

5. A magnetic transducer as in claim 3 further comprising a bulkhead within said sleeve and substantially partitioning the sleeve.

6. A magnetic transducer as in claim 5 further comprising an element at the end of said sleeve spaced from said bulkhead to define an acoustic compliance chamber.

7. A magnetic transducer as in claim 6 wherein said acoustic compliance chamber has an aperture in one of its walls to the exterior of the transducer, for conduction of sound therethrough.

8. A magnetic transducer as in claim 6 wherein said element is apertured for conduction of sound.

9. A magnetic transducer as in claim 6 further comprising at least one additional wall dividing said acoustic compliance chamber into at least two acoustic compliance chambers.

10. A magnetic transducer as in claim 9 further comprising acoustical impedance means interconnecting at least one pair of acoustic compliance chambers.

11. A magnetic transducer as in claim 6 further comprising an acoustic diaphragm connected to said vibratable portion of the armature, said diaphragm being outside of and spaced from said sleeve, and a cover over and spaced from said diaphragm and attached to said sleeve, the space between the cover and diaphragm being connected by acoustic impedance means through the wall of the sleeve to said acoustic compliance chamber.

12. A magnetic transducer as in claim 2 wherein said second portion is vibratable, and said armature is folded in that said vibratable portion and said second portion face and are spaced from each other.

13. A magnetic transducer as in claim 12 wherein said second portion has an extremity extending into a gap between one magnet and said sleeve, and a shim of magnetic material lies between said magnet and said extremity.

14. A magnetic transducer comprising a pair of magnets having a working gap therebetween, an electrical signal coil, an armature extending through said coil and having a vibratable portion in said gap, and a sleeve elongate along an axis threading the sleeve anD being fabricated in one piece of high magnetic permeability material, said sleeve interconnecting said pair of magnets, said sleeve having a substantial perforation through the wall thereof, said armature comprising a portion attached to the sleeve and extending along said perforation to substantially close the perforation, said sleeve and said second-named portion of the armature constituting mean substantially surrounding said coil, said magnets, and said first-named portion of the armature.

15. A magnetic transducer as in claim 14, wherein said second-named portion is vibratable, and said armature is folded in that said first-named portion and said second-named portion face and are spaced from each other.

16. A magnetic transducer comprising a pair of magnets having a working gap therebetween, each magnet having a pole surface facing away from the working gap, said pole surfaces being of opposite polarity, an electrical signal coil, an armature extending through said coil and having a vibratable portion in said gap, and a longitudinally seamless sleeve, elongate along an axis threading the sleeve, having surface portions facing toward each of said pole surfaces respectively, the sleeve substantially surrounding said coil, armature and magnets, said sleeve comprising a direct unbroken high magnetic permeability path between said surface portions substantially throughout the extent of the sleeve.

17. A magnetic transducer as in claim 16 wherein said armature has a second portion extending to a joint with said sleeve, said joint having low reluctance to magnetic signal flux.

18. A magnetic transducer having, in combination, a tubular longitudinally seamless sleeve of high magnetic permeability material having a closed annular cross section substantially throughout the length of the sleeve and having open ends, a pair of magnets having a working gap therebetween, each magnet being within the sleeve and connected thereto by means having low reluctance to magnetic flux, an electrical signal coil within the sleeve, and an armature within the sleeve, the armature extending through said coil and having a vibratable portion in said gap.

19. A transducer according to claim 18, in which the signal coil is supported by attachment to the inner surface of the sleeve.

20. A transducer according to claim 18, in which the armature is attached to the sleeve by a joint having low reluctance to magnetic signal flux.

21. A transducer according to claim 20, in which the armature has a second portion which partitions for magnetic shielding purposes the interior of said sleeve.

22. A magnetic transducer comprising a pair of magnets having a working gap therebetween, an electrical signal coil, an armature extending through said coil and having a vibratable portion in said gap, and a sleeve comprising one piece of high magnetic permeability material fabricated to encircle an axis and to have an opening extending from one extremity to the other along said axis, said sleeve interconnecting said pair of magnets and substantially surrounding said coil, said armature and said magnets, said armature extending to a joint of low magnetic reluctance with said sleeve, and having a second portion which for magnetic shielding purposes substantially closes said opening.