US2662606A

US2662606A - Elliptical conoidal sound reproducing diaphragm

Info

Publication number: US2662606A
Application number: US141465A
Authority: US
Inventors: Robert E Hurley
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1950-01-31
Filing date: 1950-01-31
Publication date: 1953-12-15
Anticipated expiration: 1970-12-15

Description

Dec. 15, 1953 HURLEY 2,662,606

ELLIPTICAL. CONOIDAL SOUND REPRODUCING DIAPHRAGM Filed Jan. 31, 1950 Ru BERT E. EURLEY Gttorneg Patented Dec. 15, I953 ELLIPTICAL CONOIDAL SOUND REPRODUCING DIAPHRAGM Robert E. Hurley, Moorestown, N. J., assignor to Radio Corporation oi America, a corporation of Delaware Application January 31, 1950, Serial No. 141,465

8 Claims.

My present invention relates to sound reproducing diaphragms, and more particularly to an improved base suspension for conoidal, dynamic loudspeaker diaphragms having an elliptical base periphery.

The structure of conventional elliptical conetype diaphragms for dynamic type loudspeakers, generally, consists of a main body portion of conoidal shape, the base periphery of which is elliptical, with the apex end terminating in a collar to which a cylindrical voice coil form is attached. The base end of the body portion terminates in a radially extending flange or rim provided with one or more radial corrugations, with the outer periphery thereof adapted for clamping or otherwise being secured to a support, such as a conventional dishpan support. The main body portion functions as the sound reproducing portion, while the flange, or rim, functions primarily as a flexible support for the body portion permitting it to move freely in directions parallel to its central axis. As far as the production of sound is concerned, the flange, or rim, has little, if any, function. However, unless it is properly constructed, its stiffness and inertia will adversely affect the natural period of vibration of the main body portion with a consequent loss in efficiency and acoustical qualities of the loudspeaker of which it forms a part.

Although conventional, prior art, elliptical cone-type diaphragms have been found to operate with satisfactor results, they are also found to possess certain disadvantages which are attributable to certain structural features of the flexible base suspension for the main body portion of the diaphragm. For example, in the conventional diaphragm, the flange, or rim, is of uniform width around the entire periphery of the base of the main body portion. Since the corrugations are also of uniform width and follow the elliptical pattern of the base periphery they offer greater stiffness at the portions thereof disposed in the direction of the major axis or" the elliptical base periphery than the portions thereof disposed in the direction of the minor axis. This is due to the fact that the radius of curvature of the corrugations is shorter in the vicinity of the major axis than in the vicinity of the minor axis. Inasmuch as the flange, or

rim, is stiffer along the major axis than along the minor axis, it offers more resistance to axial motion of the main body portion of the dia phragm along the major axis. This difference in resistance results in distortion of the cone and disturbance of uniform oscillations thereof. Furthermore, since the curvature of the corrugations along the major axis is greater than the curvature along the minor axis, the corrugations are subjected to greater stress and strain along the portions thereof disposed along the major axis. During normal operation of the diaphragm, the flange, or rim, is, therefore, more readily subject to rupture in the region adjacent the major axis.

The primary object of my present invention, therefore, is to provide an improved flexible base suspension which will overcome the above as well as other disadvantages of prior art base suspensions for elliptical, cone-shaped, diaphragins.

Another object of my present inve tion is to provide a flexible support for the elliptical base periphery of conoidal diaphragms which will have approximately uniform flexibility or stillness at all points about the elliptical base pe riphery.

Still another object of my present inven is to provide a resilient support for the pe edge of an elliptical, conical-shaped diap wherein the resilient support is less subject to destruction arising out of the continued vihrations of the diaphragm.

A still further object of my present invention is to provide an elliptical colloidal-type diaphragm for use in sound reproducing instruments which will have a base support having substantially uniform stiffness at all points about the diaphragm base periphery.

In accordance with my present invention, I provide a conical-shaped sound reproducing diaphragm having an elliptical base periphery with a flexible base support comprising a corrugated rim the structure of which has substantially uni form stiffness around the entire periphery of the diaphragm base. In accordance with one modification, the rim and corrugati 11s are made of gradually increasing widths in directions extei ing around the base periphery from the region adjacent the minor axis to the region adjacent the major axis of the base periphery. According to another modification, the Width of the made increasingly larger in the same in the aforementioned modification but the corrugations are of uniform width and increase in number with the increase in width of the The novel features characteristic of my invention, as well as additional objects and advantages thereof, will be better understood from the following detailed description when in connection with the accompanying drawing in which:

Figure 1 is a front view of a conical sound reproducing diaphragm having an elliptical base periphery in accordance with one modification of my present invention,

Figure 2 is a sectional view of the diaphragm shown in Figure 1, taken along the line 2--2 of Figure 1,

Figure 3 is a sectional view similar to Figure 2, taken along the line 33 of Figure 1,

Figure 4 is a view similar to but somewhat smaller than that shown in Figure 1 of a second embodiment of a sound reproducing diaphragm in accordance with my invention,

Figure 5 is an enlarged, sectional view of a portion of the diaphragm and base support shown in Figure 4, taken on the line 5-5 of Figure i,

Fig. 6 is a view similar to Figure 5, taken on the line 58 of Figure 4, and

Figure 7 is a view similar to Figure 5, taken on the line 1-1 of Figure 4.

Referring more particularly to the drawing, wherein similar reference characters desi nate corresponding parts throughout, there is shown in Figures 1 through 3 an elliptical, conoidal, sound reproducing diaphragm l which comprises a main bodyv or sound reproducing portion 3, and a peripheral support therefor comprising a rim or flange 5 which extends from the elliptical base periphery i of the main body portion 5. The apex end of the main body portion 3 terminates in a collar or circular flange 9 for attachment, in suitable manner, to the voice coil of a dynamic loudspeaker.

The rim or flange 5 is radially corrugated, that is, it is provided with one or more circumferential corrugations or undulations ii, the valleys and peaks of which ar arranged successively outwardly from the elliptical base periphery I of the diaphragm body portion 3.

In the process of reproducing sound, the loudspeaker voice coil drives the diaphragm main body portion 3 in axial directions, that is, in directions parallel to the central axis of the dia-, phragm, with the sound output and natural period of vibration of the diaphragm depending upon the flexibility of the supporting rim or flange 5. Due to the elliptical contour of the base periphery i, the rim 5 has greater resistance to movement of the main body portion 3 near its shorter radius of curvature which is disposed in the region of the long or major axis 13 of the elliptical base periphery 5 and less resistance to movement of the body. portion near its longer radius of curvature disposed in the region of the short or minor axis l5. Because of the uneven d stribution of stiffness throughout the length of the rim 5, the natural period of vibration of the body portion 3 is adversely affected with a consequent loss in sound reproducing quality and efficiency. In addition, the portions of the rim 5 in the region of the major axis [3 are more readily subject to fracture because of this uneven distribution of stiflness.

In order to overcome these difiiculties, I; provide a rim or flange 5 of gradually increasing width in directions extending about the base periphery from the region adjacent the minor axis [5 to the region adjacent the major axis l3, as best illustrated in Figures 2 and 3 of the drawing. Accordingly, it will be recognized by those persons skilled in the art, that because of the increase in width of the rim 5, it will be more flexible at the wider portions thereof and con-. sequently have. less stiffness at those portions. With proper design, the rim 5 may be made to have uniform stiffness around the entire length of the base periphery 7 of the elliptical diaphragm i. This may be accomplished by increasing the rim width approximately in direct proportion to the distance the elliptical base periphery 1 is disposed from the diaphragm central axis IT, or, approximately in inverse pro-,

portion to the radius of curvature of the base periphery 1.

The rim corrugations ll either may be ofequal number around the entire length of the rim 5, as shown particularly in the modification illustrated in Figures 1 through 3, or they may vary in number, as shown particularly in the modiflcation illustrated in Figures 4 through 7. If they are of equal number, the widths of the corrugation H are made to increase approximately in direct proportion to the width of the rim 5-. However, if the corrugations vary in number, their widths are uniform throughout their length and they increase in number with the increase in width of the rim 5. For example, as shown in the modification illustrated in Figures 4 through 7, there are two radial corrugations II in the region of the minor axis l5, and three radial corrugations l l in the region of the major axis !3.

Thus, it will be recognized that by varying the width of the flange or rim which supports the sound reproducing elliptical diaphragm at the base periphery, and additionally varying either the width of the corrugations or their number, in the manner described above, the stiffness of the rim may be controlled in such a manner that it will have approximately uniform stiffness at all points around the diaphragm bas periphery. Furthermore, the stresses in the material will be substantially equalized with the result that the material will be less subject to fracture and the efiiciency of the diaphragm greatly enhanced.

It will be recognized by those persons skilled in the art, that I have provided an improved flexible support for the base periphery of elliptical, conoidal sound reproducing diaphragms. While I have described and illustrated but two embodiments of my present invention, it will also be recognized that various changes and modifications are possible within the spirit of my invention. Therefore, I desire that the particular form of my invention described herein shall be considered as illustrative and not as limiting.

What is claimed is:

1. A cone-type sound reproducing diaphragm having an elliptical base periphery and a flexible collar having a radially corrugated portion extending from said base periphery, the width of the radially corrugated portion of said collar increasing in dimension from the portion thereof in the region adjacent the minor axis of said base periphery to the portion of said collar in the region adjacent the major axis of said base periphery.

2. A sound reproducing diaphragm according to claim 1 wherein the width of the radially cor-. rugated portion of said collar varies approximately in direct proportion to the distance said base periphery is disposed from the diaphragm central axis.

3. A cone-type sound reproducing diaphragm having an elliptical base periphery and a flexible collar having a radially corrugated portion extending from said base periphery, the width of the radially corrugated portion of said collar increasing in dimension from the portion thereof in the region adjacent the minor axis of said base periphery to the portion of said collar in the region adjacent the major axis of said base periphery, the width of the radially corrugated portion of said collar varying approximately in direct proportion to the distance said base periphery is disposed from the diaphragm central axis, and the Width of each corrugation varying directly with the width of said collar.

4. A cone-type sound reproducing diaphragm, having anelliptical base periphery, andaflexie. is. adial q ms ted fla ge. exten in from,

said base periphery, the width of said flange from said diaphragm base periphery to the outer periphery of said flange varying approximately in inverse proportion to the radius of curvature of said base periphery, and the width of each corrugation varying directly with the width of said flange.

5. In a conoidal type dynamic loudspeaker diaphragm having a base periphery of elliptical shape, a flexible rim for said diaphragm extending from said base periphery for supporting said diaphragm for relatively free axial movement, said rim having a plurality of corrugations the valleys and peaks of which are arranged successively outwardly from said base periphery and of equal number throughout the length of said rim, the width of the portion of said rim having said corrugations increasing in dimension between the portions disposed respectively in the region thereof opposite to the minor and major axes of said base periphery, the Width of each of said corrugations varying directly with the width of said rim, said width dimension varying approximately as a function of the distance said base periphery is disposed from the diaphragm central axis whereby said rim and said corrugations will offer approximately the same resistance to axial movements of said diaphragm at all points about said base periphery.

6. In a conoidal type dynamic loudspeaker diaphragm having a base periphery of elliptical shape, a flexible rim for said diaphragm extending from said base periphery for supporting said diaphragm for relatively free axial movement, said rim having a plurality of corrugations the valleys and peaks of which are arranged successively outwardly from said base periphery, said corrugations being of uniform width, the width of the portion of said rim having said corrugations increasing in dimension between the portions disposed respectively in the region thereof opposite to the minor and major axes of said base periphery, said corrugations increasing in number with the increase in width of said rim,

said width dimension varying approximately as a function of the distance said base periphery is disposed from the diaphragm central axis whereby said rim and said corrugations will offer approximately the same resistance to axial movements of said diaphragm at all points about said base periphery.

7. An acoustic diaphragm of the direct acting type comprising a body portion of conoidal shape having the base periphery thereof defining an ellipse, and a peripheral flange for supporting said body portion extending from said base periphery, said flange being provided with at least one circumferential corrugation thereby to flexibly support said body portion for freedom of movement in directions axially thereof, said corrugation and said flange increasing in width from the portions thereof disposed in the plane including the central axis of said body portion and the minor axis of said base periphery to the portions thereof disposed in the plane including the central axis of said body portion and the major axis of said base periphery.

8. In a conoidal type dynamic loudspeaker diaphragm having a base periphery of elliptical shape, a flexible rim for said diaphragm extending from said base periphery for supporting said diaphragm for relatively free axial movement, said rim having a plurality of corrugations the valleys and peaks of which are arranged successively outwardly from said base periphery, the width of the portion of said rim having said corrugations increasing in dimension between the portions disposed respectively in the region thereof opposite to the minor and major axes of said base periphery, said width dimension varying approximately as a function of the distance said base periphery is disposed from the diaphragm central axis whereby said rim and said corrugations will offer approximately the same resistance to axial movements of said diaphragm at all points about said base periphery.

ROBERT E. HURLEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,722,805 Lane July 30, 1929 1,825,833 Tennessee at al Oct. 6, 1931 1,913,451 Lane June 13, 1933 1,930,328 Tichenor et al Oct. 10, 1933 2,358,823 OConnor Sept. 26, 1944