US3917914A - Loudspeaker - Google Patents

Abstract

A loudspeaker of the moving magnet type has a vibratable paper cone with an opening at the apex in which a cobalt-rare earth ring magnet is positioned, the entire outside surface of the ring magnet being in contact with the interior surface of the cone. A magnetic circuit path is positioned inside the ring (but not in contact with the ring), the circuit path extending into the cone. An electromagnetic coil is mounted on the circuit path which remains stationary while the ring magnet is free to vibrate. An electrical signal such as a voice signal impressed on the electromagnetic coil will produce movement of the ring magnet corresponding to the signal which will in turn produce vibrations in the cone to produce sound waves corresponding to the signal.

Description

United States Patent [1 1 Parker Nov. 4, 1975 LOUDSPEAKER [75] Inventor: Rollin James Parker, Greenville,

Mich.

[73] Assignee: General Electric Company,

Schenectady, NY.

221 Filed: Mar. 15,1974

21 Appl. No.: 451,482

[52] US. Cl. 179/115 R; 179/120 [51] Int. Cl. H04R 11/02 [58] Field of Search.. 179/115.5 ME, 114 R, 115 R,

Primary Examiner-Kathleen H1 Claffy Assistant Examiner-George G. Stellar [57] ABSTRACT A loudspeaker of the moving magnet type has a vibratable paper cone with an opening at the apex in which a cobalt-rare earth ring magnet is positioned, the entire outside surface of the ring magnet being in contact with the interior surface of the cone. A magnetic circuit path is positioned inside the ring (but not in contact with the ring), the circuit path extending into the cone. An electromagnetic coil is mounted on the circuit path which remains stationary while the ring magnet is free to vibrate. An electrical signal such as a voice signal impressed on the electromagnetic coil will produce movement of the ring magnet corresponding to the signal which will in turn produce vibrations in the cone to produce sound waves corresponding to the signal.

3 Claims, 1 Drawing Figure US. Patent Nov. 4, 1975 3,917,914

LOUDSPEAKER BACKGROUND OF THE INVENTION In conventional loudspeakers a vibratable cone or diaphragm is connected at its apex to a voice coil assembly which is positioned to move with respect to a stationary permanent magnet. Thus, when an electrical signal corresponding to a sound signal is connected through the voice coil the cone or diaphragm is actuated by movement of the voice coil to translate the electrical signal by vibrating the cone or diaphragm to create sound waves corresponding to the electrical signal. Conventionally, the voice coil is positioned exteriorly with respect to the cone or diaphragm, that is, in back of the cone. Conventional structures are represented in Parker US. Pat. Nos. 3,358,089 and 3,440,364.

It has long been recognized that the voice coil could be made stationary and the permanent magnet used to vibrate the speaker cone. However, the permanent magnets formerly available had too much mass per unit of magnetic strength to function satisfactorily as moving magnets in a loudspeaker. Even the alnico magnets were too massive per unit of magnetic strength to serve as moving magnets in a loudspeaker.

The advent of extremely powerful cobalt-rare earth magnets in recent years has made possible greatly improved moving magnet loudspeakers. The preparation of cobalt-rare earth magnets, such as cobalt-Samarium magnets, is described in Benz US. Pat. Nos. 3,655,463, 3,655,464, and 3,695,945 as well as Benz and Martin U.S. Pat. No. 3,684,593, which patents are incorporated herein by reference. The technology for producing extremely powerful cobalt-rare earth magnets is now well known and will not be discussed further herein.

SUMMARY OF THE INVENTION The present invention provides a loudspeaker having a cobaltrare earth type magnet the movement of which imparts mechanical vibrations to the cone or diaphragm of the speaker. In addition, the speaker has the electromagnetic coil assembly positioned in the interior of the cone thereby providing a thin speaker which occupies a minimum of space. The structure is accomplished by having the cobalt-rare earth magnet in the form of a ring the exterior of which is connected to the interior of the cone at the apex thereof. The electromagnet assembly is positioned inside the magnet ring though not in contact therewith with the bulk of its structure extending into the interior of the cone. Other parts of the loudspeaker such as the spider, gasket, and basket or frame are conventional.

DESCRIPTION OF THE DRAWING The drawing is a partial sectional view of a loudspeaker structure formed in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, the loudspeaker consists of a basket or frame composed of a rigid material such as sheet metal having a generally cone shape with the wide portion of the cone serving as the front of the speaker and the narrow or apex portion serving as the 2 back. The back of the frame 10 has an opening which is covered by a cover 11 composed of rigid sheet metal or plastic material which also serves as the terminal board of the speaker.

The front of the speaker has a circular gasket 12 composed of a resilient material positioned within the perimeter of the front portion of the basket or frame 10. A vibratable cone 13 is fastened to the gasket 12, the resiliency of the gasket 12 enabling the cone 13 to have freedom of movement. The cone 13 is usually formed ofa paper product such as a heavy hard-surface paper. The apex of the cone 13 is centered by means of a fabric spider 14 which allows the cone or diaphragm 13 freedom of movement.

The apex of the cone 13 is fastened to a ring-shaped magnet 15 composed of cobalt-rare earth material. A frame member 16 defining a magnetic circuit path is mounted upon the cover or terminal board 11 and extends through the ring magnet 15. The member 16, however, does not make contact with the ring magnet 15 and thus does not impede movement of the magnet 15. Mounted upon the metal frame 16 is an electromagnetic coil 17 having a pair of leads 17a to which a sound signal may be fed. A cap or cover 18 serves to limit the accumulation of dust on the magnetic parts of the speaker.

When the speaker is in operation a sound signal is introduced to the electromagnetic coil 17 through the leads 17a. This signal produces mechanical vibrations corresponding to the sound signal. Positioning the electromagnet 17 on the interior of the cone 13 results in a very thin speaker having minimal space requirements. It also allows for a very stable suspension system. Having the ring magnet at the apex of the cone 13 minimizes lateral motion and allows for wider tolerances. Thus the present speaker is more easily manufactured than conventional speakers. Its assembly and control of tolerances are simplified.

While the present invention has been described with reference to a specific embodiment it is obvious that there may be variations which properly fall within the scope of the invention. Therefore, the invention should be limited in scope only as may be necessitated by the scope of the appended claims.

What I claim as new and desire to secure by letters patent of the United States is as follows:

1. A loudspeaker comprising:

a vibratable cone having an open apex;

a ring magnet of the cobalt-rare earth type positioned with its peripheral circular surface within, and in solid contact with, the apex of said cone;

a magnetic circuit positioned within the ring of said magnet but not in direct contact therewith, said magnetic circuit extending interiorly of said vibratable cone;

an electromagnetic coil mounted on said magnetic circuit;

and means for positioning said vibratable cone, ring magnet, magnetic circuit and electromagnetic coil whereby said ring magnet and cone are vibratable in response to an electrical signal impressed on said coil.

2. A loudspeaker as claimed in claim 1 in which the cobalt-rare earth ring magnet is composed of cobalt and samarium.

3. A loudspeaker as claimed in claim 1 in which the vibratable cone is a paper product.

Claims (3)

1. A loudspeaker comprising: a vibratable cone having an open apex; a ring magnet of the cobalt-rare earth type positioned with its peripheral circular surface within, and in solid contact with, the apex of said cone; a magnetic circuit positioned within the ring of said magnet but not in direct contact therewith, said magnetic circuit extending interiorly of said vibratable cone; an electromagnetic coil mounted on said magnetic circuit; and means for positioning said vibratable cone, ring magnet, magnetic circuit and electromagnetic coil whereby said ring magnet and cone are vibratable in response to an electrical signal impressed on said coil.

2. A loudspeaker as claimed in claim 1 in which the cobalt-rare earth ring magnet is composed of cobalt and samarium.

3. A loudspeaker as claimed in claim 1 in which the vibratable cone is a paper product.

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