Low frequency sound transducer

• US 4,907,209 A
• Filed: 04/10/1989
• Issued: 03/06/1990
• Est. Priority Date: 10/31/1983
• Status: Expired due to Fees

• Current Assignee: Martin Marietta Corporation
• Original Assignee: Martin Marietta Corporation
• Inventors: Sewell, John M., Werner, William F.
• Primary Examiner(s): STEINBERGER, BRIAN
• Application Number:
  US07/334,767
• Time in Patent Office: 330 Days
• Field of Search: 310/26, 310/DIG. 1, 367/156, 367/158, 367/168, 367/189
• US Class Current: 367/168
• CPC Class Codes: B06B 1/085 using multiple elements, e.g. arrays

Abstract

A low frequency sound producer including a plurality of magnetostrictive vibrators arranged seriatim end to end to define a ring. Each vibrator unit includes a plurality of laterally related magnetostrictive rods which, in the illustrated embodiment, are formed of rare earth magnetostrictive material. Structure is provided for compressively prestressing the rods. The prestressing structure includes permanent magnets for providing a permanent magnetic bias in the rods. Coils are magnetically coupled to the rods for causing the desired magnetostriction thereof corresponding to an input AC signal applied to the coils. Opposite ends of the individual vibrator units define facial abutments in defining the continuous ring configuration. In the illustrated embodiment, the ring configuration is polygonal and the facial abutment surfaces at the ends of the units define a 60° included angle. The entire sound producer is provided with an outward enclosure of synthetic resin whereby each vibrator unit defines an enclosed water-sealed assembly.

Claims

1. A magnetostrictive vibrator for producing low frequency sound, said vibrator comprising:

a plurality of laterally related rods each formed of rare-earth magnetostrictive material and each having a cross section;

permanent magnets for providing a permanent magnet bias in said rods; and

coil means magnetically coupled to said rods for causing magnetostriction of the rods corresponding to an input AC signal applied to said coil means; and

wherein said permanent magnets comprise means compressively urged against at least one end of the rods for transmitting to the rods compressive pre-stressing forces.

2. The magnetostrictive vibrator of claim 1 wherein said rods are substantially rectilinear.

3. The magnetostrictive vibrator of claim 1 wherein said rods are formed of a compound comprising Tb.sub..28 Dy.sub..72 Fe₂.

4. The magnetostrictive vibrator of claim 1 wherein said prestressing means comprises resilient prestressing means.

5. The magnetostrictive vibrator of claim 1 wherein said vibrator is enclosed in a synthetic resin.

6. A magnetostrictive vibrator for producing low frequency sound, said vibrator comprising:

a plurality of laterally related rods each formed of rare earth magnetostrictive material;

permanent magnets for providing a permanent magnet bias in said rods;

coil means magnetically coupled to said rods for causing magnetostriction of the rods corresponding to an input AC signal applied to said coil means; and

means for compressively prestressing said rods, said prestressing means including magnetic keepers for conducting flux between said coil means.

7. A magnetostrictive vibrator for producing low frequency sound, said vibrator comprising:

a plurality of laterally related rods each formed of rare earth magnetostrictive material;

permanent magnets for providing a permanent magnet bias in said rods;

coil means magnetically coupled to said rods for causing magnetostriction of the rods corresponding to an input AC signal applied to said coil means; and

means for compressively prestressing said rods, prestressing means including magnetic keepers for conducting flux between said coil means through said permanent magnets.

8. A low frequency sound producer, comprising:

at least three magnetostrictive vibrators arranged seriatim end-to-end to define a ring, each vibrator comprising;

a plurality of laterally related rods each formed of rare-earth magnetostrictive material and each having a cross section;

permanent magnets for providing a permanent magnetic bias in said rods;

coil means magnetically coupled to said rods for causing magnetostriction of the rods corresponding to an input AC signal applied to said coil means; and

means defining facial abutments at opposite ends of successive vibrators; and

wherein said permanent magnets comprise means compressively urged against at least one end of the rods for transmitting to the rods compressive pre-stressing forces.

9. The low frequency sound producer of claim 8 wherein said ring is polygonal.

10. The low frequency sound producer of claim 8 wherein said ring is polygonal and said facial abutment means also define a 60°

included angle.

11. The low frequency sound producer of claim 8 wherein said sound producer is provided with an enclosure coating of synthetic resin.

12. The low frequency sound producer of claim 8 wherein each said vibrator comprises a water-sealed assembly.

13. The low frequency sound producer of claim 8 wherein said rods are formed of a compound comprising Tb.sub..28 Dy.sub..72 Fe₂.

14. A low frequency sound producer, comprising:

at least three magnetostrictive vibrators arranged seriatim end-to-end to define a polyhedral ring, each vibrator comprising;

a pair of spaced apart rods in parallel with one another formed of rare-earth magnetostrictive material and each rod having a cross section;

rare-earth permanent magnets for providing a permanent magnetic bias in said rods; and

coil means magnetically coupled to said rods for causing magnetostriction of the rods corresponding to an input AC signal applied to said coil means; and

wherein said permanent magnets comprise means compressively urged against at least one end of the rods for transmitting to the rods compressive pre-stressing forces.

15. The low frequency sound producer of claim 14 wherein each vibrator further includes means for coupling the coil means in series.

16. The low frequency sound producer of claim 14 wherein said rods are spaced in the axial direction of the ring.

17. A low frequency sound producer comprising a plurality of magnetostrictive vibrators arranged seriatim end-to-end to define a polyhedral ring, each vibrator comprising:

a pair of parallel spaced rods formed of rare earth magnetostrictive material;

means for compressively prestressing said rods;

rare earth permanent magnet means for providing a permanent magnetic bias in said rods;

coil means magnetically coupled to said rods for causing magnetostriction of the rods corresponding to an input AC signal applied to said coil means; and

keeper means for coupling the coil means in series.

18. A low frequency sound producer comprising a plurality of magnetostrictive vibrators arranged seriatim end-to-end to define a polyhedral ring, each vibrator comprising:

a pair of parallel spaced rods formed of rare earth magnetostrictive material;

means for compressively prestressing said rods;

rare earth permanent magnet means for providing a permanent magnetic bias in said rods;

coil means magnetically coupled to said rods for causing magnetostriction of the rods corresponding to an input AC signal applied to said coil means; and

keeper means for coupling the coil means in series, said keeper means being arranged to direct compressive forces against the opposite ends of the rods.

19. A magnetostrictive vibrator, comprising:

a rare earth rod having a first cross section;

a permanent magnet urged against at least one end of said rod, providing a permanent magnetic bias in said rod; and

a coil coupled to said rod causing magnetostriction of said rod corresponding to an input signal; and

wherein said permanent magnet comprise means compressively urged against at least one end of the rod for transmitting to the rod compressive pre-stressing forces.