Moving magnet transducer

• US 4,000,381 A
• Filed: 05/23/1975
• Issued: 12/28/1976
• Est. Priority Date: 05/23/1975
• Status: Expired due to Term

• Current Assignee: Shure Brothers Incorporated
• Original Assignee: Shure Brothers Incorporated
• Inventors: Tichy, Thomas H., Plice, Gerald W.
• Primary Examiner(s): Stellar, George G.
• Application Number:
  US05/580,536
• Time in Patent Office: 585 Days
• Field of Search: 179/104, 179/114 R, 179/114 A, 179/114 M, 179/115 R, 179/115 A, 179/115.5 R, 179/115.5 E, 179/115.5 DV, 179/107 E
• US Class Current: 381/418
• 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 11/06 Telephone receivers

Abstract

A miniature acoustical transducer. The transducer includes a diaphragm, spring member and electromagnetic coils secured within a substantially cylindrical housing. The coils are arranged on opposite sides of the spring member. The spring member carries a permanent magnetic member and is connected to the diaphragm. Movement of the magnetic member relative to the electromagnetic coils varies the reluctance of the magnetic circuit defined by the coil and an associated core member.

Claims

1. An acoustical transducer comprising, in combination:

a housing having a first end portion, an intermediate portion and a second end portion, said housing defining a substantially cylindrical interior chamber having a central axis, said housing including an end panel closing said first end portion, said end panel having a sound opening for passage of acoustical waves therethrough;

a diaphragm secured substantially within said first end portion, substantially adjacent said end panel and in direct communication with sound opening, said diaphragm defining a front and rear cavity in said interior chamber;

a spring member secured substantially within said intermediate portion of said housing, said spring member having a central region substantially aligned with said central axis;

a hollow lightweight tube connecting said spring member and said diaphragm, said tube linking said front cavity and said rear cavity to substantially improve the frequency response of said transducer;

a magnet member secured to said spring member substantially within said central region; and

a pair of substantially annular electromagnetic circuits secured within said housing on opposite sides of said spring member, said electromagnetic circuits being substantially coaxial with said chamber, said electromagnetic circuit including a coil and a core member having a predetermined reluctance, movement of said magnetic member toward said core member reducing said predetermined reluctance;

said magnetic member having a relaxed state relative to said pair of electromagnetic coils;

said spring member, connector means and diaphargm cooperatively defining bias means for urging said magnetic member towards said relaxed position.

2. An acoustical transducer as claimed in claim 1 wherein said spring member is a substantially circular plate spring.

3. An acoustical transducer as claimed in claim 2 wherein said substantially circular plate spring member is slotted about said central region to provide flexibility.

4. An acoustical transducer as claimed in claim 1 wherein said core member defines an air gap.

5. An acoustical transducer as claimed in claim 4 wherein said magnetic member moves substantially within said air gap in response to energization of said coil and acoustical wave impinging upon said diaphragm.

6. An acoustical transducer as claimed in claim 5 wherein movement of said magnetic member towards said core member reduces said air gap and thereby reduces said predetermined reluctance of said core member.

7. An acoustical transducer as claimed in claim 1 wherein said magnetic member is a permanent magnet.

8. An acoustical transducer as claimed in claim 7 wherein said magnetic member is samarium cobalt (SmCo).

9. An acoustical transducer as claimed in claim 1 wherein said magnetic member is substantially annular and defines an inner wall.

10. An acoustical transducer as claimed in claim 9 wherein said tube securingly engages said inner wall of said magnetic member.