US1484821A - Diaphragm - Google Patents

Description

Feb. 26, 1924. 1,484,821

H. DUNCAN DIAPHRAGM Filed April 2, 1919 phragms for acoustic instruments, f'such as" Patented Feb.- 26, i 1924.

mast I princely,- or MAnw n 'NEw' JERSEY} DIAPHQAGM.

i Application filed April 2,1919; Serial nb 2a'e,9sa

Tohll whomz't y concern: 1 I

Be it known that IfHAItRY L." DUNOAN,' a citizen of the'UnitedStfltes, and resident of Mahwah,county of Bergen, State "Of: New ,Tcrsejghave made a certain new and useful: Invention Relating to .Dia'phragiris, of; which the following va specificat-ion'itaken in connection with the accompanying draw- 11g 1 I z This invention relates "especially v dia phonographs, telephones,*-et c., in which the diaphragm is preferably formed of.-fibrous material, su'chjas the I desired f'nurnber of thicknesses of o suitable cotton jcloth, strong blotting ap r, c'ottonlfibatting, 'et'c.,' --carry,-,

ing and preferably 'quite thoroughly: im pregnated with 'cured phenolic condensation cementing material, such as 'balrelit-e', coin densite." or: Redmanol varnish compositions;

" Various parts of 'th'e diaphragniflmay" be' 'stiflenedi to the desired-extent by 'ior-I'nin'g corrugation-s or "coned up. or arched prom-,-

a nite degreeof peripheral elongation. Such- =ofsubstantially uni-for nqstrength in each I directionand in whichthe threads are pref- -tio1is, thereinand at'the same time .the' edge portions "of the diaphragm may-"be given a' wavyor fluted form so as to Secure a' defi a diaphragm when clamped or 'I'nounted' 'so that this inorenr "'le'ssirregularor wavy,

edgeis forced to a greater extent into flat purpose, the cot-ton threads under such conf ditions after the materialhas been impregatedso as to containdforty to sixty per.

or straightposition is thereby placed under "radial tension in its innerporti'qns because. this flattening-tends to increase the-- edge diameterof the diaphragnil One or "more layers of "such. fabric or-"fibrous material ,m'aybe unitedby the incorporated curedphen'olic condensation cementing material v 7 portions or corrugatedor ,ot herwarpedflor 7 so as to '.form;anj elastic :rigid and strong diaphragm material whichis especially ad'f vantageou's for such tensioning wavy ,ed'ge construction," "'sin-ce th'e desireddefinite" pei I riphera'l. elongation may; be simply and ef-' fectivel'y secured therein by pressure mold.-

-. :ing operations in; suitable-dies when the in asoinewhat diagrammaticv way. anumber heatjciiringof the material is -efl'ectedi In the" accompanying dr ajwingf showing of illustrative embodiments of this inven-}' tion, U H .7

" this charact'en-partly in section. i'

Fig. 2 is a diagrammatic-sectional' view' showing the'inounting of such a diaphrag n;

Fig 1" is aside viewjof aidia'p hragn sure molding and curing action is 'usually should also-have sufliciently long fibre v t0 about 300 to.320 Fahrenheit for fifteen to thirty minutes or so; although by using 1i a .longertime the curing :heat'may be. con-" j' siderably reduced. gThe fibrous n aterial"7 0 4 give the desired strength and coherence dur-i ing" the pressureficuring or molding o ra- ,ci'on where considerabledistortiono jthe' previously forrned sheet or blanketfibrous- ,1 I longer fibre gives greater strength the material occurs at this time and ofj cou-rse' finished article; although the cementing ac- Y tion' of the .bakelite Or other phenolic 'condensation cementingmat'eriaI naturally cures. the fibres together and gives them greatly increased strength under these conditions. For many purposes closely, woven cotton "fabricof which the threads are preferably as i.

erfably loosely twisted is desirable "forfthis cent more or less of dried'bakelitevarnish "No, 1, for example, yielding suflieiently -un- .der the heat curing'treatn ent to permit con- 0 siderab-lei-dist'ortion-so'that-the wavy edge .1

distorted portions oft'he diaphragm can be --'reliably produced, andfrelativelyjconstant shape'ystrength and other properties-secured i when "the. same number. of thicknesses of: "similarly; impregnated "fabric are *used' in each case. As an illustrative exampleslnall phonograph.diaphragmstwoorthreeiinchesv m diameter'may'jbe conveniently formed of 'three or four layers of light muslin-earry v j .Jingabout fifty per cent. of cured bakelite varnish-andgiinited under'such' high fpres '105z 'sure curing conditions as above described so as to. have a'thicknessof some .six to twelve thousandthsof an inch. Under some I conditions,-however,asmaller number or. p cottonbatting may us d with quite-good results. "For larger 'diaphra'gms of six' layers of thicker woven fabric; paper .or

ice 7 inches or more in diameter heavier fabric or other material may, of course, be used or a greater number of layers of the lighter material may be employed, and in such cases a greater number of edge flutes may usually be employed to advantage for such radial tensioning purposes as compared to the relatively small diaphragms two or three inches in diameter where four to six flutes more or less are more convenient and desirable for most purposes.

As indicated in Fig. 1 the diaphragm 1 may be formed of a number of layers of cotton or other suitable fabric carrying and preferably thoroughly incorporated with such phenolic condensation cementing material as dried bakelite varnish compositions. Several layers of two ounce cotton fabric of this character carrying about fifty per cent by weight ofrsuch cementing material may be assembled in a suitable mold and forced together under pressure of a number of hundred pounds per square inch, preferably in accurately shaped or equalizing molds preventing excessive local pressures so that the fibrous material is not destroyed or distorted locally to an undesirable extent; During this heat curing and molding of the diaphragm 1 the edge portions 4 are preferably given a wavy or fluted form, three to six high spots such as 4 being formed therein with a corresponding number of intermediate low spots. A sinusoidal wavy form is desirable for this fluted or wavy edge which may of course merge into the relatively flat portion of the diaphragm within at any suitable point, although it is not necessary in all cases for the wavy or transversely distorted portions to extend more than about a third of the way to the center of the diaphragm. In some cases it is desirable to reenforce and strengthen this wavy edge portion by incorporating therewith additional impregnated fibrous material during the heat curing and molding of the diaphragm and as shown in Fig. 1 an edge tensioning ring 5 may be used composed of additional thicknesses of impregnated cloth, paper or other fibrous material which may be arranged on one or both sides of the other layers or interposed between them so that under the heat curing treatment they become securely cemented and united to the edge portions of the diaphragm sheets or layers so as to proportionately strengthen this wavy tensioning edge portion.

When used such a diaphragm may advantageously be yieldingly clamped or mounted between any suitable form of elastic or yielding clampin supporting surfaces, such as circular or flat sectioned rings or gaskets of vulcanized rubber, soft paper or the like, and Fig. 2 shows diagrammatically a suitable arrangement for this purpose in which the clamping supporting means may comprisea rigid clamping ring or member 6 provided with a recess having an internal shoulder or flange 8 against which the rubber ring or yielding clamping member 9 may abut on its inner side, while at the same time sufficient free space is provided in the clamping means outside of this rubber ring, so that its free outward expansion can take lace during the clamping of the diaphragm.

he clamping members 6, 7 of brass or other suitable material may thus support the soft and yielding elastic vulcanized rubber clamping rings or members 9 which prefer ably have somewhat rounded contact surfaces for engagement with the diaphragm edge, such contact surfaces being advanta-' geously located toward the outer edge of these yielding clamping rings or members so that the initial contact occurs at this point and a considerable radial tensioning may thus be secured on any diaphragm through the outward radial expansion of the clamping rings caused by their transverse compression, even aside from the radial tensioning secured by the flattening of the wavy edge portions of such a specially shaped diaphragm as described. In the mounting the elastic clamping rings or members may be forced together as by screws 10 so as to engage the diaphragm on each side throughout its entire periphery which is of course desirable and subsequent pressure yieldingly forces the wavy diaphragm edge into relatively flat position, thus tending to increase the diameter of this edge portion of the diaphragm and simultaneously exert radial tension on the inner portions which is desirable for many purposes because securing increased pitch and more reliable vibration in response to various impulses.

Fig. 3 shows another form of diaphragm in which not only the active vibrating portion is of substantially uniform thickness throughout, but in which the edge portion may also be of substantially the same thickness and such a diaphragm may be formed of the desired number of layers of such coated or impregnated cloth or other fabric or fibrous material. The different parts of the diaphragm may under such conditions be stiffened or strengthened by appropriately shaping them, the center 3 of this diaphragm 1 being coned up or projecting from the plane of the diaphragm body to a progressively increasing extent which gives greatly increased stiffness thereto and promotes the vibration of this part of the diaphragm as a unit by minimizing local bending distortion thereof. A uniform thickness edge portion of a wavy character may be advantageously formed on such a diaphragm. As indicated the high spots 12 may be sufiioiently distorted as compared to the low spots 13 to secure a considerable definite increased peripheral length so as to exert a desirable radial tensionin action when these wavy edge portions are attened. For some purposes it is desirable to form any suitable transversely extending stiffened portion such as the integral stiffening rib or corrugation 11 between such a wavy edge portion and the inner portions of diaphragms of these types. Such a stiffener or rib may have sufficient stiffness transverse to the plane of the diaphragm to minimize or prevent undesirable buckling displacement of the partswithin, which may be radially tensioned by the edge portions through the curved connections shown in connection with the rib. Such a diaphragm may be molded in suitable shaped molds under high pressure so as to compact the fibrous material and quite thoroughly shape it to the contour of the mold at the same time that the phenolic condensation cementing material is cured or solidified into its strong solid condition in which it gives such a high degree of resilient strength to the incorporated cotton or other suitable fibrous material.

Fig. 4 shows another form of diaphragm which may be advantageously produced from such fibrous material, the projecting stiffened center portion 3 being coned up gradually as indicated so as to project beyond the diaphragm body 1 and the edge portions may be given a tensioning action by forming three to six flutes or waves therein having high spots 15 and interposed low spots 14, the planes of which may be a sixteentli .to an eighth of an inch or so apart in the case of relative] small dia hragms two or three inches in iameter. ig. 5 shows another form of diaphragm which may be made of such material and have four to six or more edge flutes or wavy portions, such as 14, 15, connected with a suitably reenforced or stiffened diaphragm center of any desired character. If desired such a stiffened center may comprise a series of corrugations 17, 18, 19, the center 16 being flat,

, if desired, and stiffened in other ways under tion cementing material.

some conditions.

Fig. 6 shows still another form of diaphragm which may be advantageously formed of such fibrous material'carrying or impregnated with cured phenolic condensa- The diaphragm may have fluted or wavy edge portions, if

desired, and may comprise a series of high spots or portions 24 and correspondingly displaced intermediate low portions 26, and if desired also this wavy edge portion may be reenforced by an additional amount of similar impregnated fibrous material, such as the incorporated or united edge tensioning ring 25 which may have several times as great thickness as the inner portions ofthe diaphragm which may be of substantially uniform thickness, of say, five to ten thousandths of an inch in small diaphragms, for example. This diaphragm may have a stiffened central portion comprising a series of corrugations which may be of such form or less conically inclined portions between corrugations or projections, such as 31, 32, 43 and 44 may be progressively flatter so as to more or less gradually approach the plane of the diaphragm outside which gives a desirable arrangement having a stiffening action which may approximate such a coned up shape as shown in Fig. 4, if desired.

Fig. 7 shows another form of diaphragm in which, if desired, the diaphragm center 33 may be coned up or stiffened and may have substantially the same thickness as the diaphragm body 34. In some cases it is desirable to unite or mold a metallic edge tensioning ring into such a diaphragm and for this purpose a fiat or wavy tensioning ring 36 which preferably has a much greater radial width than its thickness may be united to the edge portions of the impregnated fibrous diaphragm material in any suitable way. These edge portions 35 of cloth or paper may in some cases be more or less brought around the metallic tensioning ring 36 so that the enclosing portions 37 are formed thereon which may be securely united to the diaphragm body 34 and to the tensioning ring during the pressure heat molding operation. If desired, however, the metallic edge tensioning ring may be interposed between the different layers of impregnated or coated fabric which may be forced around the ring during the heat moldin so as to secure effective union between 51888 parts. This molding operation may also in some cases serve to give the diaphragm edge portions a wavy or fluted contour similar to that of the tensioning rin although the tensioning ring if not uncfuly stiff may be fluted at the same time that it is enclosed within or united to the fibrous diaphragm material. Such a metallic tensioning ring is desirable for relatively large diaphragms in some cases, although of course temperature expansion is much better equalized when the edge tensioning ring or portion is formed of practically or identically the same material as the inner portions or body of the diaphragm.

This invention has been disclosed in con: nection with a number of illustrative embodiments, forms, proportions, elements.

. ditions, and methods of preparation, pro

parts, shapes, materials, compositions, conmember formed in said diaphragm adjacent its edge portion and joined to its central portion bya curved connection portion.

2. The integral acoustic diaphragm, the central portion of Saiddiaphragm'being stiffened, the'edge portions of said diaphragm being given a Wavy form to secure increased' peripheral elongation and a transversely extending intermediate stiffening member having a portion extending sub stantially perpendicularly to the plane of the diaphragm and formed in said diaphragm adjacent its edge portion and joined to its central portion by a curved connection portion.

3. The acoustic diaphragm, the edge portions of said diaphragm being givena Wavy form to secure increased peripheral elongadiate stiffening member havinga-portion extion and a transversely extending intermetending substantially perpendicularlyto the plane of the-diaphragm and formed'in said diaphragm inside of andclosely adjacent its edge portion.

4:. The acoustic diaphragm-,theedgep'ortions of said diaphragm being given awavy form to secure increased peripheral elongation and a transversely extending'interme diate stiffening member formed in" saiddiaphragm. inside of and closely adjacent its edge portion.

5. The one piece acoustic diaphragm, the edge portions of 'said diaphragm being adapted to exert a radial tensioning action on the central portions and a transversely extending intermediate stiffening, member formed in said diaphragm inside of and adjacent its edge portion, said stiffening member having a portion-extending in adirec tion substantially perpendicular to the plane of the diaphragm.

6. The acoustic diaphragm, the edge portions ofsaid diaphragm being adapted to exert a radial tensioning action on'the'central portions and -a transversely extending intermediate stiffening member formed in' said diaphragm inside of and adjacent its edge portion: HARRY L. DUNCAN;

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