US1790679A

US1790679A - of salt lake city

Info

Publication number: US1790679A
Authority: US
Publication date: 1931-02-03
Anticipated expiration: 1948-02-03

Description

Feb. 3, 1931. D. R. SEELY ACOUSTIC DIAPHRAGM AND MOUNTING Filed Aug. 20, 1928 HIZ INVOR 0 l .0. E. 55152 7 BY ATTORNEY non a. SEELY, or sam" 1m 01in, uumassmnon 'ro THE um: mio raonuc'rs' Patented Feb. 3, 1931 UNITED STATES, PATENT OFFICE COMPANY, OF SALT LAKE CITY, UTAH, A CORPORATION OF ACOUSTIC DIAPHRAGM AN D MOUNTING Application filed August 20, 1928. Serial No. 300,748.

" or reproducing sounds having frequencies extending over a wide range.

Second. One which shall give forth rich mellow tones.

Third. A wooden diaphragm which shall -be stron durable, and moisture-resistant,

and thus e suited to varying climatic conditions.

In the quest of an improved material for diaphragms, particularly of the kind used for radio loud speakers, I have found that wood has properties which are particularly suited to give forth rich, mellow sounds. The woodma be of different kinds, such as pine, spruce, irch or the like, cut into thin sheets. 7

The ratio of the thickness of a sheet of the wood, to the area of the finished diaphragm,

' forms an important part ofthe invention. This ratio varies between certain limits, but

its maximum I place at one eighth of an inch per square foot of area of the finished diaphragm. As a rule, however, this ratio may be considerably less.

, The superficial shape of the diaphragm may be round, square, elliptical, oblong or otherwise, so long as the conditions for proper vibratory motion are maintained.

1 ,Thin, sheets of wood when first formed, give quite satisfactory results when used as diaphragms, butvery soon, the contraction, due to the seasoning manifested when freshly cut wood fibers are exposed to the atmosphere, cause objectionable cracks and checks to appear, which of course impair the desirable properties of the wood, and soon render the untreated wood diaphragm unfit for service. I V

The treatment accorded the wood sheets, by means of the present invention, gives a high degree 'of permanence to the desirable acoustic properties originally possessed by the wooden sheets, and preserves their capability to give forththe peculiarly rich and mellow tones which-may originally emanate therefrom. My aim is to interfere as little sheets such structural support, strength and toughness, as shall insure their durability. In many cases, my treatment improves the natural acoustic properties of the wood.

To this end, the sheets of wood are, impregnated with a nitrocellulose solution, for instance, ambroid, whichafter the evaporation of the volatile constituents thereof, leaves the resinous fibers of. the wood cemented together. This cementing is effected by the tough, flexible and waterproof residue permeating the pith of the wood after the said evaporation. The wood, further, may be covered with a textile fabric, for example, cambric, whose threads in the war and woof are preferably placed substantial y diagonal with the grain of the wood. The cloth may be cemented or glued to the wood, and both the wood and the cloth impregnated with the nitrocellulose solution.

If desired, the wood may be first impregnated with the nitrocellulose solution, and the cloth be cemented thereto by laying the cloth on the wood and applying a coat of the said solution. After the application of the nitrocellulose solutionthe sheets may be subjected to suitable pressure, applied by means of presses similar to those used in the ordinary laminating of wood for panelsand the like. If .found advantageous, the cloth ma'g be applied to the wood sheets in strips or ribbons rather than in continuous layers, these strips being applied either to one or both surfaces of the wood', and running in one direction on one side of the sheet, and in the transverse direction on the other side of the sheet, or the strips may be criss-icr'ossed in two series, one series being on each surface.

In use, the diaphragm may be supported by a wooden frame conforming to the superficial shape of the diaphragm, said frame having a depth transverse to the surface ofthe diaphragm sufficient to insure; rigidity, and also to form a cabinet or other structure for concealing the loud speaker actuating unit, which latter maybe of any desired type in ordinary use.

I The features of this invention for which the protection of Letters Patent of the United States is desired, are collectively grouped in the claims concluding this specification.

In the drawing, which illustrates merely one embodiment of this invention,

Fig. 1 represents a rear elevation of a loud speaker whose "equipment includes my improved diaphragm and itsmounting;

Fig. 2, a section on line 2, Fig. 1, V v

Fig. 3, a rear elevation, parts being omitted;

Fig. 4-,aminor detail; i.

Figs. 5 and 6, fragmentary elevations showing variations in the structural constitution ofv the diaphragm proper Fig. 5 being a front elevation and Fig. 6 a rear elevation reflected from a mirror plane; and

Fig. 7, a fragmentary cross-section in diagram, greatly enlarged, to show the theoretical structure of this improved diaphragm.

Referring to the drawing, 10 indicates a frame of substantially square superficial configuration, made up of the individual members 12, which may be mitered together at the corners as indicated at 14.

The diaphragm is indicated at 15, and this may be attached to one face of the frame in any suitable manner, such as by gluing or cementing.

Either one or both of the

superficial surfaces

16 and 17 of the diaphragm may be covered with a thin textilefabric such as cambric, applied diagonally with respect to the direction in which runs the grain of the wood at the faces of the diaphragm, some what after the manner indicatedat 18 and 19 in Figs. 1 and 3, the grain of the wood being assumed to run as indicated by the doublepointed arrow 24. The layers of cloth, 18 and 19,.may be cemented to the wooden sheet 15 before the latter is attached to the frame 10, and both surfaces may be treated with amberoid or other nitrocellulose solution, either before or after the diaphragm is applied to the frame 10. v 1 I t v In order to stiffen the diaphragm and to improve its vibratory qualities,'diagonal ribs 20. of wood or other suitable material, may be attached to one face of the diaphragm, and other ribs 21 of similar material may be ap plied transverse to the grain of the wood of the diaphragm.

Inside of the frame 10 may beblocks 25, to which is attached the cross-piece 26, the latter being spaced apart from the diaphragm 15' sufficiently far to clear the

ribs

20 and 21. On the cross-piece 26 is mounted any desired vibratory actuating unit 27, such as one of the well known electromagnetic push-and-v pull type. This unit may be held in place by means of the strap 28,

Strap 28 engages the bolts 29, the latter being fastened in thebase 30, which inturn may be attached to the cross-piece- 26 by means of the screws 31. The armature40 of diagonal to the grain of the wood, Whichis assumed to extend 1n the direction indicated by the arrows 35. It is evident that the

strips

32 or 38 as the case may he, might be omitted, thus; leaving only one series of strips on each side of the diaphragm, these two. remaining series of strips however, being preferably transverse to each other; Taking the small circle 42- as a point of reference, it will be noted that the

strips

32 and 36 alternate with

strips

34 and 38 respec-' tively, in relative positions. 7 I

The wood sheets may be single in ply, or they may be laminated so as to be composed of two or more plies. In a multiple-ply sheet, the directions of the grains of the individual plies would be perpendicular to each other or to one another, as the case might be, but the warp and woof ofthe cloth, if used, would nevertheless be sub stantially diagonal to the grain of the face laminations. c,

It is to be understood that the textile fabric is not used in all cases, as the treatment of the wood with the nitrocellulose solution alone adds strength and durability to the wood. However, in cases where still greater strength and durability are desired, the textile fabric is employed. i

In Fig. 7 is indicated the structure of this improved diaphragm in accordance withits fundamental theory. The pith 49 is saturated with the nitrocellulose solution, which latter upon evaporation of its volatile constituents, leaves the pith permeated with the tough, solidified constituents of the nitrocellulose solution. The solidified constituents serve to flexibly cement the resinous fibers or minute'tubes bO of the wood together, thusproducing a durable material for diaphragms. The optionalcovering of cloth for the superficial faces ofjthe wood sheet, as hereinbefore mentioned, is indicated at 18.and 19 (Fig. 7). I

In the present instance, each side of the square inside the frame 10fmight be one foot long,.in'-which casethe dimension 51 in Fig. 7 would be one-eighth inch or less.

While a specific embodiment of this invention is herein shown and described, it is to be clearly understood that variations within the scope of the accompanying claims,

may be resorted towithout jeopardizing my patent protection.

'Having fully; described my invention, what I claim is:

1. An acoustic diaphragm formed of a sheet of wood which has been impregnated with a nitrocellulose solution.

2. An acoustic diaphragm formed of a sheet of wood in which are retained the solidified constituents of a nitrocellulose solution.

3. An acoustic diaphragm formed of a sheet of wood which has been impregnated with a nitrocellulose solution, and having cloth cemented to the superficial surface of said sheet.

4. An acoustic diaphragm formed of a sheet of wood in which are retained the solidified constituents of a nitrocellulose solution, and having cloth cemented to the superficial surface of said sheet.

5. An acoustic diaphragm formed of a sheet of wood which has been impregnated with a nitrocellulose solution, and having cloth cemented to the superficial surface of 'said sheet, said cloth having its warp and woof in dia onal relation to the grain of the said wood s eet.

6. An acoustic diaphragm formed of a sheet of wood in which are retained the solidified constituents of a nitrocellulosesolution, and having a textile fabric cementedto the superficial surface of said sheet, said textile fabric having its Warp and woof in diagonal relation to the grain of the said wood sheet.

7. An acoustic diaphragm formed of a sheet ofwood, and a layer of textile fabric attached to the superficial surface of said wooden sheet, the warp and the Woof of the said textile fabric being substantially diagonal to the grain of the said wooden sheet.

8. An acoustic diaphragm composed of wood less than one-eighth inch in thickness for each square foot of superficial area of the said diaphragm, said wood having been impregnated with a solution of nitrocellulose.

9. An acoustic diaphragm comprising a sheet of wood having a thickness one-eighth inch or less for each superficial square foot of area of the said diaphragm, and a mass of the solidified constituents of a nitrocellulose solution permeating the sheet.

10. An acoustic diaphragm comprising a sheet of wood one-eighth inch or less in thickness for each superficial square foot area thereof, and a layer of textile fabric attached to the said sheet, the warp and woof of the textile fabric being substantially diagonal to the grain of the said wood.

11. An acoustic diaphragm comprising a sheet of wood, a textile fabric cemented to the face of the said sheet, the Warp and the Woof of the said textile fabric being substantially diagonal to the grain of the said Wood, and a nitrocellulose residue in a cemented relation to the said textile fabric and the said I wooden sheet.

12. An acoustic diaphragm comprising a sheet of wood, a nitrocellulose residue permeating the said wood, and a textile fabric cemented to the surface of the said wood.

13. An acoustic diaphragm com rising a sheet of wood, layers of textile abric cemented to the face of the said sheet, the warp and the woof of the said textile fabric being substantially diagonal to the grain of the said wood, a nitrocellulose residue permeating said diaphragm, a frame having a configuration corresponding to the contour of the said diaphragm, said diaphragm attached to said frame, and means for operably mounting an actuating unit within said frame in a manner such that said unit may be connected to said diaphragm.

14. A wooden diaphragm having a thickness less than one-eighth inch for every square foot of superficial area of said diaphragm, a frame having a configuration corresponding .to the perimeter of said diaphragm and rigidly fastened to said frame along said perimeter, the members of said frame being substantially transverse to the surface of said diaphragm, and having their outer surfaces flush with the edges of said diaphragm, and means for operably mounting an actuating unit for said diaphragm within said frame.

In testimony whereof I sign my name hereto.

DON R. SEELY.