US1484820A - Acoustic diaphragm - Google Patents

Description

Feb. 26., 1924. 1,484,820

H. DUNCAN ACOUSTIC DIAPHRAGM Filed March :1, 1919 a vwewto c Patented Feb. 26, 1924.

ATENT-cranes.

HARRY L.' DUNCAN, F MAHWAH, NEW JERSEY.

ACOUSTIC DIAPHRAGM.

Application filed March 31. 1919. Serial No. 286,351.

To all whom'it may concern: Be it known that I, HARRY L. DUNCAN, a citizen of the United States, and resident of Mahwah, county of Bergen, State of New 6 Jersey, have made a certain new and useful Invention Relating to Acoustic Diaphragms, of which the followin -is a specification, taken in connection with the accompanying drawing.-

This invention relates especially to acous tic dia hragms for phonographs, telephones and 0t er urposes in which the metallic or other diap ragm is formed with a wavy or fluted edge so that-the edge may be given a definite degree of peripheral elongation.

The diaphragm may be clamped or mounted in such a way that this irregular or fluted edge is forced more or less into the flat or straight position so that in this way the edge diameter of the diaphragm tends to enlarge which automatically places the central portions of the dia hragm under radial tension and increases tlie pitch or efliciency of the diaphragm for many -pur oses. In the case of metal diaphragms tiiecentral portion of the diaphragm may in many cases be advantageously stiffened by bein coned u or corrugated at the same time t at the e ge portion of the diaphragm is given a fluted or wavy shape in suitable dies or other forming tools, and if desired, an edge tensioning ring or member of suitable wavy or fluted, form may in some cases be. advantageously more or less enclosed within or united to the edge portion of the diaphragm and sufficiently flattened in the mounting or subsequent use of the diaphragm so' as to place the portions of the diaphragm within under suitable radial tension. Such dia- 40 phragms may be made of any suitable material and steel or other sheet metal such as brass, bronze or aluminum alloys ma be used in some cases or plastic or moul able material may be used for this purpose, such as celluloid or rubber with or without such unitedv or enclosed metal "tensioning mem-' bers, or fibrous materials .may be used in many cases, and also paper, paper pulp or cloth which may in some cases be advantageously impregnated or coated with cementing material of various kinds, such, for example, as phenolic condensation compositions like bakelite varnish which under theheat curing treatment stifien the fabric'or phragm mounted.

Figs. 3 and 4 are similar sectional views showing other forms of diaphragm.

Fig. 5 is a sectional view showing the edge drawing or fluting of a metallic diaphragm; and

v Fig. 6 shows the diaphragm which may be produced in this way.

Many types of acoustic diaphragms may advantageously be provided with fluted or sinusoidal edge tensioning members formed integral with or secured to the diaphragm so as to have a substantially definite degree of extra peripheral elon ationp When the diaphragms are mounte for use or prior thereto, this edge tensioning member may be more or less flattened 0r straightened so as to have sufficient increased diameter to exert a valuable radial tensioning action on the inner portions of the diaphragm which may either be substantially flat or given any other desired or suitable shape as by stiff-- ening corrugations or projections in some cases. The edge tensioning device naturally has such strength and size as is suited to the size of the diaphragm and for special large diaphragms of six inches or more in diameter heavier edge tensioning members are naturally necessary to properly tension the heavier and thicker diaphragms used under such conditions. In lar e ia phragms it is usuall desirable to ave a greater number of e ge flutes or waves to accommodate the added peripheral length of the tensioning member before it has exerted its, tensioning action. For small diahragms, such 318. 336 more generally used or phonograph and similarpurposes and where the diaphragm is only two or thm inches or so in diameter, thinner and lighter material is usually. desirable for the diaphragm body, and where sheet steel is used for this purpose it may advantageously be given a more uniform structure and elasticity in different directions by special rollmg or preliminary treatment, including cross-rolling or" the plates. Thesteel should of course have as uniform thickness as possible and a good light diaphragm of this character may be three to ten thousandths of an inch or so thick and have such composition as is suited to the particular use of the diaphragm, depending, of course, on whether it is to have magnetic properties or not. In some cases it is advantageous to have the diaphragm center stifi'ened so as to get more uniform action in connection with the operating mechanism connected therewith and as indicated in Fig. 1 the diaphragm l of such sheet metal, for instance, may have its center 3 coned or dished up in such form as to give suitable stiflness at the same time that the edge portions of the diaphragm are given a fluted or wavy form in the stamping or shaping devices. For many purposes it is desirable to simultaneously force together the diaphragm and edge tensioning member which may be used therewith in some cases, and an edge tensioning ring which is of considerably thicker sheet metal than the diaphragm is shown in Fig. 1 and may have four to six times as great thickness as the diaphragm and may have a radial width much greater than its thickness. as is indicated. Ample radial strength and stiffness may thus be secured combined with the facility of bending transversely to the plane of the diaphragm in fluting or straightening the ring. It is sometimes desirable to have the tensioning ring or member 6 arranged in the stamping die when the diaphragm is shaped up and its edge fluted with or without coning or stiffening of the center portion and in such case the diaphragm edge may be flanged down around the tensioning ring so as to form a flange 4, a subsequent spinning or shaping operation being resorted to if desired to force the extremeedge 5 of this diaphragm around the other side of the stiff ening ring which is thus more or less enclosed by the diaphragm edge. The part 2 of the diaphragm edge is shown as somewhat separated from the tensioning ring 6 for greater clearness. although it is of course understood that these parts will be forced closely and tightly together at the same time that the diaphragm edge and tensioning ring are fluted or corrugated to the desired extentwhich for small diaphragms may mean a difference of a sixteenth to an eighth of an inch or so between the planes of the high points, such as 2, and the low points, such as 12.- of the diaphragm edge which may have four to six or more flutes therein. With metal diaphragms it is usually desirable to definitely secure the diaphragm edge to any tensioning ring or member that may be used, and for this purpose the diaphragm edge and tensioning ring may be soldered, welded or otherwise united while still in their fluted or wavy form and for this purpose they maybe clamped together in any desired way after the tensioning member and flat or other diaphragm have been edge fluted and in some cases annealed to relieve local stresses and then spot welded at suitable intervals or soldered together by various soldering compositions depending on the materials used.

Such a diaphragm may be mounted in a clamping support such as is indicated diagrammatically in Fig. 2 as comprising two clamping members or rings 9, 10 between which the edge portions of the diaphragm may be clamped, suitable 'ashers or cushioning members such as 8 of yielding material being preferably interposed and for this purpose relatively soft fibrous material, such as soft paper or rubber sheeting or the like, may be employed and having sutficient thickness so that the diaphragm edge is firmly engaged throughout its entire periphery-by these clamping or supporting washers. The clamping members are preferably brought together to such an extent as to straighten the wavy or fluted edge portion of the diaphragm sufficiently to secure the radial tensioning desired in the diaphragm body and a considerable increase of pitch can be secured in this way as well as more definite and desirable results for many classes of acoustic work.

Fig. 3 shows a form of diaphragm which may, if desired, be made of substantially uniform thickness throughout the edge portions and adjacent inner portions of the diaphragm, the desired fluted or wavy character of the diaphragm edge being secured by any suitable method depending on the diaphragm material employed. A thin sheet metal diaphragm 1 may be stamped or forced into the desired shape at the same time that the diaphragm center 3 is forced out into more or less conical projecting position which stitfens this part of the diaphragm. The edge portions 14, 15 may be given a fluted or wavy character and may have a half a dozen or more edge flutes such as 14, 15 in which there is a difference of a sixteenth of an inch more or less between the planes of the high and low points in small diaphragms a couple of inches in diameter, this amount of edge fluting depending somewhat on the intended uses of the diaphragm. If desired. however, a diaphragm of this general character with or without corrugated or conically reenforced center portions may in many cases be made 'of celluloid or various rubber compositions,

the degree of edge fluting and the thickness of the diaphragm at various points being of course regulated by the characteristics of the material employed in each case as well as the uses for which it is intended. A desirable material for many forms of diajecting phragm is cloth or other fibrous material coated and preferably more or less thoroughly-impregnated with phenolic condensation cementing com ositions such as bakelite, redmanol or con ensite varnish, several sheets of soft thin and strong paper or fine textured cotton or other cloth being desirable. Several Sheets of thin muslin or other cotton fabric which" has been thoroughly impregnated with bakelite varnish or similar p ienolic condensation cementing material and dried may be cut approximately to size and then assembled in a heated mold which can readily heat the material tov a suflicient extent to render it soft and pliable after which it may be shaped under high pressure and at the proper curing heat for the cementing material employed which for such bakelite compositions is ap roximately 300to 320 Fahrenheit or so or a curin time of ten or twenty minutes. When suc material is united at the high pressure of a number of hundred pounds per square inch the different layers are permanently united b the incorporated cured cementing material so that the'cured diaphragm substantially retains the shape given to it during the molding operation and in this wa a fluted or wavy tensionin edge ma be efinitely formed of such c aracter t at when. partially flattened between rubber or other yielding clamping members a desirable tension may be given to the central part of the diaphragm which may in some cases be simultaneously formed into reenforced proosition during the molding operation. 1g. l-shows another form of diaphragm may be made of such material and may have four to six or more edge flutes or wavy portions, such as 14, 15, connected with a suitably reenforced or stifl'ened dia- A: ghragm center of an desired character. If

esired, such a sti ened center may comprise a series of corrugations 17, 18, 19, the center 16 being flat if desired and stiffened in other ways under some conditions. The Fig. 4 diaphragm may, however, be formed of steel or other metal in many cases and the flat diaphragm center 16 may under these conditions be advantageous for cooperation with magnetic actuating or other members which do not need to be given special shape in order to cooperate pro erly therewith.

In some cases the edge utes or peripheral elongation of a diaphragm may be formed in other ways, as for instance, by edge drawing rolls such as are diagrammatically indicated in Fig. 5. The two sets of rolls of this character, such as 22, 23, may be arranged on shafts 24 and one or both sets positively rotated so that a sheetmetal diaphragm 20 arranged between these three or four pairs of conical fluting rolls may be subjected to a compressing and drawing operation at each pass between the rolls so that its peripheral portion may be drawn out or elongated to the desired extent as determined b the length of this rolling treatment and t e ressure and conditions thereof. The diap ragm 20 after such an edge rolling or flutin treatment is preferably stamped in suita le dies to give more definite shape to the edge flutes 21', 25, which may thereafter be employed for tensioning the inner portions of the diaphragm by clamping them between relativel flat clamping or supporting surfaces. his flattens the fluted or wavy edge portions sufiiciently so that they can exert a desirable tension: ing action on the central portions of the diaphra m which is of greater efiiciency because 0 the hardening and strengthening] ofthe metal during the ed e fluting'rolling operation to which it has een subjected.

This invention has been disclosed in connection with a number of illustrative embodiments, forms, proportions, elements,

parts, shapes, materials, compositions, conditions, and methods of preparation, production and use, to the details of which disclosure the invention is not of course to be limited, since what is claimed as new and what is desired to be secured by Letters Patent is set forth in the appended claims:

1. The acoustic diaphragm havin a stiffened center and edge portions, an a metallic fluted edge tensionlng ring having four to six flutes to secure increased peripheral elongation and enclosed by and secured to the edge portion of said diaphragm, so that said tensioning ring may be flattened in the diaphragm supporting devices to radially tension the inner central portions of the diaphragm.

2. The acoustic diaphragm having a metal lic fluted edge tensioning ring enclosed by and secured to the edge portion of said diaphragm, so that said tensioning ring may be flattened to radially tension the inner central portions of the diaphragm.

3. The acoustic diaphragm having a metallic fluted edge tensioning ring secured to the edge portion of said diaphragm and adapted to have its fluted portions flattened to radially tension the inner central portions of the diaphragm.

4. The acoustic diaphragm having a flat sectioned metallic edge tensioning member having three or more flutes and enclosed within and secured to the edge portion of said diaphragm and adapted to'be flattened in the diaphragm supporting devices to radially tension the inner central portions of the diaphragm.

5. The acoustic diaphragm having a wavy tensioning member secured to the outer portion of saiddiaphragm and adapted to be flattened in the diaphragm supporting devices to radially tension the inner portions of the diaphragm.

6. The acoustic diaphragm comprising a stifiened center and edge portions having a fluted form to secure substantially definite increased peripheral elongation and adapted to be flattened in the diaphragm supporting devices to radially tension the inner portions of the diaphragm.

7. The acoustic diaphragm comprising outer portions having a Wavy form to secure substantially definite increased elongation and adapted to be flattened to radially tension inner portions of the diaphragm.

8. The acoustic diaphragm comprising outer portions which have been flattened from a fluted form comprising three or more flutes to impart substantially definite radical tension to inner portions of the diaphragm.

9. The acoustic diaphragm comprising outer portions which have been distorted from a'substantially definite wavy form to impart radial tension to inner portions of the diaphragm.

10. The acoustic diaphragm having a flattened Wavy tensioning member secured to the outer portion of said diaphragm and imparting radial tension to inner portions of the diaphragm.

HARRY L. DUNCAN.

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