US2234833A - Acoustical apparatus - Google Patents

Description

J. PRESTON 3 ACOUSTIGAL APPARATUS March 11, 1941.

Filed May 29, 1937 Erwentor Patented Mar. 11, 1941 UNITED STATES PATENT OFFICE ACOUSTICAL APPARATUS ware Application May 29, 1937, Serial No. 145,467

4 Claims.

This invention relates to acoustical apparatus, and more particularly to acoustical diaphragms and mountings therefor.

The advantages of a direct acting diaphragm have been long recognized, as has also the desirability of having such diaphragms act as nearly like a true piston as possible. Because of its lightness and almost ideal piston-like action, aluminLun has been rather extensively used for direct acting cones. In such cones or diaphragms, the peripheral portions have been bent back to provide a suitable mounting ring for the diaphragm. The chief objection to the use of aluminum cones of this type, where the displacement of the cone exceeds that of a few mils, is the breakdown of the peripheral suspension because of the relatively low elastic limit of aluminum.

The primary object of my present invention is to provide an improved mounting for aluminum and other similar diaphragrns which will be free from the defect heretofore noted.

More specifically, it is an object of my invention to provide an improved mounting for aluminum cones so that the cones may be displaced a distance greater than the elastic limit thereof would permit under the conditions of use of prior art aluminum cones.

Anotherobject of my invention is to provide an improved diaphragm suspension as aforesaid which is inexpensive of manufacture and highly efiicient in use.

A further object of my invention is to provide, in electro-acoustical apparatus which includes a diaphragm, an improved suspension member for said diaphragm which will avoid the necessity of additional centering means for the diaphragm with respect to the magnetic structure associated therewith.

In accordance with my present invention, I make the mounting ring of a material which is stiff in its own plane but which is flexible in a plane at right angles to its own plane, the material preferably having an elastic limit greater than that of aluminum. When such a mounting is used, the danger of breaking down is eliminated and the life of the cone is greatly increased.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment thereof when read in connection with the accompanying drawing, in which the single figure is a cross-sectional view of a so-called conical diaphragm and mounting therefor.

Referring more specifically to the drawing, I have shown a cone or diaphragm I provided with a voice coil form 3 on which a voice coil 5 is wound, the cone I being so mounted with respect to the pole pieces I and 9 of a suitable magnetic structure that the voice coil 5 is disposed within the air gap II.

For mounting the cone or diaphragm l on a suitable supporting member (not shown) I employ a mounting ring [3 of a material which is stiff in its own plane but which is flexible enough to permit movement of the cone l in a plane at right angles to its own plane. The ring 13 may be cemented It!) the peripheral flange 2 of the diaphragm I, or secured thereto in any other suitable manner. Among the materials which I have found suitable for this purpose are phosphor bronze, steel, and fiber. These materials are all tough and capable of withstanding repeated stresses at high frequencies without breaking down, as would aluminum. Moreover, the use of i any of these materials insures proper centering of the voice coil 5 in the air gap ll without the necessity of providing any additional centering means such as the spiders conventionally found in most loud speakers and made necessary when using mounting rings of leather, felt, rubber, rubberized fiber or the like known in the prior art, and all of which fail to have the necessary stiffness in the plane of the suspension ring.

From the foregoing description, it will be obvious that I have provided an improved suspension for diaphragms which is free from the disadvantages present in prior art mountings. Although I have shown and described but one specific embodiment of my invention, I am fully aware that many other modifications thereof are possible, and I therefore desire that my invention shall not be limited except insofar as is made necessary by the prior art and by the spirit of the appended claims.

I claim:

1. In electroacoustical apparatus, the combination of means providing a magnetic field and including an air gap, a diaphragm having a voice coil form located in said air gap, and an annular mounting member for said diaphragm secured to the peripheral portion thereof, said mounting member being stiff in its own plane and relatively flexible in a plane normal to its own plane and being of a material which has an elastic limit greater than that of the material of said diaphragm, and said mounting member constitutin the sole means for supporting said diaphragm and for retaining said voice coil form in said air gap in predetermined relation thereto.

2. The invention set forth in claim 1 characterized in that said mounting member is made of fiber.

3. The invention set forth in claim 1 characterized in that said mounting member is made 10 of phosphor bronze.

4. In acoustical apparatus, the combination of a vibratable diaphragm made of aluminum and a substantially plane mounting member therefor attached to the peripheral portion of said diaphragm, said mounting member being stiff in its own plane but flexible in a plane normal to its own plane, and being of a material which has an elastic limit greater than that of aluminum.

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