US2549138A - Loud-speaker diaphragm - Google Patents

Description

April 17, 1951 Q E, TEV S 2,549,138

LOUD-SPEAKER DIAPHRAGM Filed Oct. 4, 1946 INVENTOR. (Ii/feral F. Sim/ens Patented Apr. 17, 1951 LOUD-SPEAKER DIAPHRAGM Clilford E. Stevens, Glen Ridge, N. 1., assignor to Stevens Products Inc., East Orange, N; J a cor poration of New Jersey Application October 4, 1946, Serial No. 7 01,372

1 Claim.

This invention relates to radio loud-speaker cone diaphragms and to a method and apparatus for forming same and is an improvement invention of the invention described and claimed in copending application by Leslie Stevens, bearing Serial No. 296,555 filed September 26, 1939, now issued as Patent No. 2,411,066 dated November 12, 1946.

The object of the invention is to provide a loud-speaker cone diaphragm adapted to be rigidly secured by its periphery to an annular support means in a position for its apex to be attached to the vibrating armature of a loudspeaker mechanism with the body of the cone free to vibrate in response to the armature vibrations Without transfer of said vibrations to the said support means.

Another object is to provide a method and means of forming such a loud-speaker diaphragm.

Still another object is to provide a loud-speaker cone diaphragm having a one-piece structure in which the vibrating cone area is edge-secured through an annular flexing section to an annular ring part having sufficient body adapting the same to be fixedly secured to an annular support means for the cone.

Other objects and advantages will be apparent as the invention is more fully hereinafter disclosed.

In accordance with these objects I have discovered that in order to eliminate the transmission of cone vibrations from the cone to the support means, with its attendant introduction of undesired vibrational sound emanations, the I cone periphery must be flexibly sustained by a flexing ring integral therewith, the outer periphery of which also must be rigidly sustained free of the support means by a relatively heavy or thick ring member also integral therewith, having sufficient body to dampen the cone vibrations transmitted thereto through the flexing ring, which ring member must be fixedly secured to the support means in-a vibration-free joint.

The obtaining of such a composite structure in a one-piece cone body presents many problems and difficulties which are substantially completely solved by the present invention;

In said copending application there is described and claimed an apparatus for forming one-piece cone diaphragms which comprises a vertically sustained cylindrical container having a centrally located drainage opening in the bottom thereof and an annular shoulder in the side wall thereof at a horizontal level above the bottom with a fluid permeable conically shaped former member seated by its periphery on said shoulder and an annular partition member seated on the bottom of said container and concentrically disposed about the said drainage opening, the upper edge of the partition member being knife-edged and contacting the under surface of the former member and the said partition member being provided with a plurality of openings therethrough, the number and diameter thereof being selected to provide a determined rate of flow of fluid through the partition member to the drainage opening less than that through the central portion of the former member to the drainage opening.

By this arrangement, when the container is filled with fluid such as Water, to a determined level above the former member and a determined quantity of pulp suspension is dispersed in the ifuid above the former member and the fluid in the container then is permitted to drain, by gravity flow, out through the centrally located drainage opening, the thickness of pulp deposit obtained on the former member in the outer area between the partition knife-edge and the periphery is less than that obtained over the central portion of the former member due to this difference in the rate of flow provided.

The relatively thin peripheral edge section obtained in this manner by the practice of the method and in the apparatus of the above noted copending application is corrugated by pressure molding means into a plurality of annular reverse bends disposed concentrically about the cone apex leaving a narrow peripheral band or flange extension thereon for securing the cone diaphragm upon an annular support disposed concentrically about the vibrating armature element of the loud-speaker device, the reverse bends being relied on to provide flexibility during operational vibration of the cone on the armature.

I have found, however, that the narrow peripheral band or flange extension thus provided on the cone diaphragm i difiicult to secure upon the annular support means and that it has insufiicient body to inhibit, dampen or prevent the transfer therethrough to the support means of cone vibrations incompletely dampened in the flexing corrugated thin section with the result that undesired vibrations are set up in the support means or in the unsecured portions of the band or flange, thus introducing sound emanations interfering with and superposed upon the sound vibrations imparted to the cone by the vibrating armature.

I have discovered that total elimination of 3 these undesired sound emanations may be obtained by providing a peripheral band or flange section on the one-piece cone diaphragm which has a thickness approximating that of the cone area and a width which approximates the width of the thin corrugated section after corrugation.

To obtain such a one-piece cone diaphragm by the casting method and means of said prior application, it is necessary to provide a modified form of partition member therein which divides the area of the container underlying the porous former member into three chambers instead of two, namely, a central chamber underlying the center cone part of the former member within which the drainage opening is centrally located; a first annular chamber underlying the porous member a distance inwardly from the periphery having controlled sized openings therefrom communicating with the centrally located chamber and providing the desired lesser rate of fiow therethrough to obtain the desired thickness differential of pulp fiber deposit between the two areas, and an outer second annular chamber communicating with the central chamber in such manner as to provide therethrough a rate of how approximating that of the central chamber, thereby to obtain on the former member overlying this area a thickness of pulp fiber deposit approximating that of the cone area.

Various alternative means are available to one skilled in the art to attain this desired result. The preferred means of the present invention is that illustrated in the accompanying drawings to which reference should be made before further disclosure of the invention.

In the drawings:

Fig. l is a sectional side elevational view of the cone casting apparatus improved in accordance with the present invention to obtain the improved cone product of the present invention;

Fig. 2 is an enlarged top view of a part of the improved partition member of the device of Fig. l by means of which the improved cone product of the present invention is obtained;

Fig. 3 is a sectional side elevational view of the cast cone product produced in the apparatus of Fig. l; and

Fig. 4 is a sectional side elevational view of the molded cast cone product improved in accordance with the present invention.

Referring to the drawings, the cone casting apparatus of Fig. 1 consists of a vertically sustained cylindrical container I having a gravity flow drainage opening 2 centrally located in the bottom 3 ol the container and an annular seat 4 in the side wall of the container at a horizontal level above the bottom 3 on which is seated fluid permeable comically-shaped former member 5.

The space below the former member 5 is divided. by partition member 6 into three compartments, namely, a central compartment A underlying the central portion of the former member 5 within which the drainage opening 2 is centrally located; an annular compartment B spaced inwardly from the peripheral edge of the former member 5, and an annular compartment C underlying the peripheral edge of the former member 5.

As may be noted from the drawings, compartment C drains by means of the plurality of openings 'i in the base of partition member 6 into compartment A, the diameter and total number of said openings 1 being selected to provide a rate of flow of fluid through former member 5 into the compartment C which approximates that 4 rate of flow through the former member 5 into the central compartment A.

The rate of flow of fluid through former member 5 into compartment B, however, is limited by means of a plurality of openings 8 in the bottom thereof communicating with compartment C to a rate materially less than the rate of fiow into compartments A and C, by selecting the size and number of said openings 8, thereby to obtain on the area of former member 5 over lying compartment B a pulp deposit which is thinner than that over compartments A and C.

In the operation of the device of Fig. l, former member 5 which is constructed in the conical shape indicated of wire mesh screen of appropriate mesh is placed in position upon seat 4 with beaded periphery 5a resting upon annular rubber insert 4a. Partition member 6 contacts the under-surface of former member 5, the contact being made by knife edge 6a and 6b, the distance between the knife edges Ga and 6b defining the width of the former member area overlying compartment B and the Width of the annular thin section obtained in the cast cone product obtained.

Container I is then filled with water by opening valve V1 in water intake line l0, while keeping valve V2 in water discharge line i I closed, to a determined level above former member 5, such level being determined by means of level gauge l2, and a measured quantity of a pulp suspension of desired composition is added to the water above the former member 5 and uniformly dispersed therein. With valve V1 closed, valve V2 is opened and the water in container l is drained out by gravity flow through drainage opening 2 into discharge line H. The rate of such gravity discharge being regulated by vertical adjustment of the line ll about swivel joint [3 as indicated by the two positions a and b.

After the water has drained out of container l at least to a level below former member 5 at seat 4, the former member 5 with its deposit of fibrous material is removed and placed in a drying oven to prepare the fibrous cone blank deposited thereon for removal therefrom.

The cone blank product obtained has the appearance indicated in Fig. 3 wherein the several sections thereof overlying compartments A, B and C, are indicated by A, B and C. As indicated, sections A and C are of approximate identical thicknesses whereas section B is materially thinner approximating one-half that of sections A and C. Section B preferably has a width-approximately double that of section C.

The cone blank is then pressure molded between complementary forms to compact the deposited fibers in the different sections thereof and to annularly corrugate section B into a plurality of identical reverse bends concentrically disposed about the axis of the center cone section A, as well as to shape the same and section C to extend outwardly from the peripheral edge of section A as flange extensions thereon lying in a plane substantially normal to the axis of the cone section A. As indicated, the preferred widths of sections B and C after corrugating section B are approximately equal. This provides an adequate body of material in flange section C to provide for the firm securing of the section to an annular support means, as by cementing the undersurface thereto and to dampen any vibrations carried thereto through flexing section B from the vibrating cone section A.

The particular thicknesses of sections A, B

and C may be varied widely without essential departure from the present invention depending upon the overall cone diameter and composition of fibrous materials comprising the same. However, in most instances I have found that the thickness of flexing section B should approximate 50% of the thickness of sections A and C' and that the width of section B, as formed, should approximate twice that of section C, for consistently good results with most fibrous compositions employed in the art. The width of section C may vary widely depending upon the thickness but, in general, I have found that a width approximating 20 times the thickness is a width consistently producing good results.

Various different fiber compositions may be employed in the forming of the cone product of the present invention. A composition which I have found to produce consistently excellent results consists of a pulp mixture containing 80% kraft and 20% sulphite sized and treated according to weight and resonance requirements.

This mixture of fibers on being pressure molded forms a relatively dense structure having excellent vibrating characteristics with high fidelity in sound reproduction over the entire range of frequencies encountered in the best types of loudspeaker mechanisms to which it is adapted to be attached.

From the above disclosure of the present invention it is believed apparent that the same may be widely varied without essential departure therefrom and all such modifications and adaptations are contemplated thereof as may fall within the scope of the following claim.

What I claim is:

A loud-speaker, diaphragm consisting of a one piece fibrous structure having a center cone section, an annularly corrugated ring section, the corrugations of said ring section being disposed concentrically about the axis of the cone section, and an outer rim section, the thickness of the rim and cone sections being approximately the same with the thickness of the ring section approximately one-half the thickness of the rim and cone sections, the width of the rim section being approximately twenty times its thickness, and *the width of the corrugated ring section being approximately that of said rim section, said ring and rim sections extending from the peripheral edge of the cone section in a plane lying at substantially right angles to the axis of the cone section.

CLIFFORD E. STEVENS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 804,432 Rivers Nov. 14, 1905 1,872,583 Hawley Aug. 16, 1932 1,927,902 Rose Sept. 26, 1933 1,989,015 McKellip Jan. 22, 1935 2,006,830 Hawley July 2, 1935 2,030,501 Cunningham Feb. 11, 1936 2,302,178 Brennan Nov. 17, 1942 2,411,066 Stevens Nov. 12, 1946

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