US1844108A - Method of manufacturing acoustic impedance elements - Google Patents

Description

Feb. 9, 1932. I E 1,844,108

METHOD OF MANUFACTURING ACOUSTIC IMPEDANGEE-MILEMENTS Filed June 19, 1930 S-Sheets-Sheet 1 INVENTOP E. H SMVTHE 7 BY ATTORNEY E. H. SMYTHE Feb. 9, 1932.

METHOD MANUFACTURING ACOUSTIC IMPEDANCE ELEMENTS Fil ed June 19. 1930 '3 Sheets Sheet 2 FIG. I0

lNVE/VTOR 5. H. SMVTHE ATTORNEY Feb. 9, 1932. SMYTHE 4 1,844,108

METHOD OF MANUFACTURING ACOUSTIC IMPEDANCE ELEMENTS Filed June 19, 1939 3 Sheets-Sheet 3.

FIG. /4

FIG. /5

YINVENTOR E. H. SM) THE alwam A TTORNEV 10 way. The results desired to circular in on," i s of I a composite layer. onaflatcoremaybe iledinstacksofdesireddimenterialnottobeattackedby Patented Feb. 9, 1932' UNITED STATES PATENT OFFICE- nnwm a. marina, or aversion, minors, sssienon mo m1. mnrnon nanomroams, moonrom'rnn, or new roan; n. Y, a cbarona'rron or new you:

mnon or immacrnnme scenario nmmncn Application fled June 19, mo. sum Io. mus.

This invention relates to acoustic impedance elements of resistive or energy dissipa- An object of this invention is to manufacturecacoustic impedance elements of predetermined characteristics in a variety of configurations and sizes ina sim 1e and accurate s obtained with an acoustic impedance element being known, the dimensions-breadth, width and length of the acoustic passage-ways therein-may be determined in accordance with the disclosure 15 in the pending application of P. B. Flanders,

Serial No. 273,523, filed April 28, 1928.

In accordance with this invention and in its preferable form, layers of two materials, one ,of which is later to be dissolved out or otherso wise removed, are alternately plated upon a conducting core until a compos te layer of the desired thickness is obtained, having a de-' sired number of layers of material, each layer of a desired thickness and that of the mamin a be dissolved out, being such that when removed in a solvent, apertures of redetermined dimension are obtained.- en

. the composite layer is built up to the desired is or the daired thicknessmay be cut therefrom, each slice provided withstrength meansupononeor each surface and then 'p in a solvent whereby the soluble is dissolved out,

degree, and-if the core 168V? a grid-work, the apertures in which provi e sound ways of predetermined acoustic pro In another Olin .t

after having been built up cut imam}? dfirml together-by latlng' "sionan p a thinlayer ofmateriil th thesolventtobe usedtoremove one of the alternatelyplated or by slim facso erespecti' ve pstogether. maythenbe'cnt fromfisbarandsubjectetl totheactionofanhppropriatesolventtodissolveoutoneofthematerialsusedinformingl t of invention,

said mathe adjacent 's'urthe composite layer. When the thin plating is employed to secure the strips into a single bar, no other su port is necessary to maintain the non'dissolved material properlyspaced. When, however, the strips are' sweated together, a supporting frame-work on oneqreach In still another embodiment of tion, individual acoustic im maybe manufactured by usmg ductive material and mounting alternately invennee elements thereon washer-like members of conductivematerial and of non-conductive material, the latter being, preferably, of larger diameter than the former. The asembly is then immersed alternately in lating baths of chosen materials thereby b ding up on each individual condudive washer, annuli'of the two 'material sh Upon completion ofthe' plating operations, subunit is removed from the core, provided with a supporting frame-work or the immersed in an appropriate solution w y one of the plat materials. ma be dis olved out;

the embodiments of a core of 'conthe, invention :dehereinbefore, it has been said-that" when a unit or slice of the desimdthickness is obtained it should be provided with, strengthening meansor asuppo work-before one of the alternately-plated materials is out or otherwise m.- moved. Instead of providing this onthe of said slioeor unit, radial bands of material of groater-width than the of the'slicc or unit may be painted thereon? Then, whm, the slice or- A i-a as section toutedunitissubjectedto the action-ofana v priate solutio theportions theinsula g -ds will not' as attacked as. freeportions and-a umt havingthedesimdacoustic-p ysandintegralsup isobtamed. U

Amorecomletezund offliis inventiomwill :2, 211,, which follows held in spaced relation afterthe insulating The ma rials whic ers .0

Fig.1 except that the composite layer is 4 built up on a tubular member;

acoustic impedance elements may be obtained;

Fig. 3 illustrates one step in providing a slice cut from the bar of Fig. 2 with a supporting frame-work;

Fig. 3--A illustrates an alternative method to provide a slice cut from the bar of Fig. 2 with a supporting structure,

Fig. 4 shows the slice of Fig. 3 after being provided with a supporting frame-workand dipped in an appropriate solvent to dissolve. out the layers of one material;

5 Bgig. 5 is a section of Fig. 4 along the line -Fig. 6 illustrates the application of an acoustic impedance element in an acoustic channel;

Fig. 7 illustrates a modification of the method comprising this invention;

Fig. 8 is a section of the showing in Fig. 7 along the line 8-8;

Figs. 9, 10 and 11 and 11A illustrate stages in carrying out another application of this invention employing the composite layer shown in Figs. 7 and 8;

Fig. 12 shows another embodiment of the composite layer of Figs. 7 and 8 from which acoustic impedance elements may be formed;

Figs. 13 and 14 illustrate-the application of this invention to the formation of individual acoustic impedance elements;

Fig. 15 illustrates .a use in an acoustic channel of acoustic impedances manufactured in accordance with this invention.

There is shown in Fi s. 1 and 2 a cylindrical core member 1 of e ectrically conductive material, not soluble in the solutions in which it is immersed, upon which has been built up a COIDFOSltB layer 2 comprising alternate laymaterials 3 and 4 which have been plated thereon and upon one another by immersmg the conductive core as anelectrode first a plating bath of one material and then mto that of the other. Before alternate immersions the last layer of plating material 1s rinsed in an appropriate solutlon and may if desired be lished or buffed to smooth out irregularities on its surface and to provide a good platin surface for the succeedmg layer of materia As shown in Fig. 1A, a tubular core member 5 may be employed in preference to the solid core 1.

1 From the composite bar shown in Fig. 2,

I a slice 13 of the desired thickness may be cutandon; one or each surface coated, as

in' Fig. 3, with an insulating paint'6 except on those portions .9 whereon it is desired to plate a supporting and insoluble framework whereby alternate annuli of the slice may be .to, for instance:

. however, a thic coating has been washed off and the slice 13 immersed in an appropriate solution whereby the alternate layers of the material 4. are dissolved out, leaving the structure shown in Figs. 4and 5: an acoustic impedance element provided with a supporting rib structure 10,

and defining a plurality of concentric acoustic channels 11.

Fig. 3-A shows another method of providing the acoustic device with a supporting structure for its unit or slice. Each surface, preferably, of the slice 13 is coated with radial bands 46 of an insulating material, said bands being greater width than the thickness and concentric annuli 3 in spaced relationv of the slice and not being subject to the action of the solvent or other means used to remove one of the materials from the slice. When the unit is immersed in an appropriate soluneed of a supporting frame-work on one or each surface of the unit.

The use of the acoustic unitso fabricated "in a sound channel whose cross sectional area is desired to be kept constant is illustrated-in Figure 6 wherein the core portion of the unit "13 has been reamed and tapped whereby .molded portions 16 and 17 may be mounted on opposite-surfaces thereof. The unit 13 may be secured by bolts 19 between the flanges 15 of the acoustic channel defining members 18.

It will beunderstood that instead of using a cylindrical core and thus forming cylindrical acous'tic members, a core of any desired eometrical configuration may be employed ependent, of course, u on the use to which the unit obtained there rom is to be put and the characteristic desired. Furthermore,

after the slices of desired thickness are cut/ from the bar, a supporting frame-work need not necessarily be plated thereon but a previously formed skeleton may be attached thereby soldering, sweating or the like.

- In carrying out this invention, the material to be dlssolved is plated to a thickness determined ,by the characteristics desired in the acoustic impedance units. This thickness is between one mil and five mils, although it may be less or reater as desired. Usually, es of one'mil is employed whereby, if the transverse breadth and the length of the acoustic channels are of appropriatedimensions, an impedance unit having a substantially resistive characteristic, only, may be obtained. It is to be understood, how ever, that this invention is in no way restricted to the manufacture of acoustic units of that characteristic only. b It lmay e a ernate y tion when the unit was dipped into the appropriate. solvent after being provided with a supporting member.

Fig. 15 is illustrative of an application of acoustic impedance elements formed in the ways previously outlined. Elements 40 are positioned in an acoustic channel 37 and are supported at their peripheries b a ring mem ber '39 in spaced relation to efine an annular volume 42 and a member 44, defining, an acoustic channel 38, which extends through the central portions of said acoustic elements and is provided with aplurality of vents 41 leading into the annular volume 42. It will be apparent that the structure shown is capable of a' variety of uses, for instance, providing a leakage path or a combined series and leakage path for the acoustic disturb- It is to be understood thatthe above de- I scriptionrelates to what are believed to be erred methods only of carrying out this.

pre invention and that the latters scope is not to be limited other than by the appended claims.

What is claimed is:-

l. The method of manufacturin .an apertured structure which comprises ormin a composite body of alternate layers of di erent materials, securing said layers tolmeans composite body of alternate layers of for holding themin spaced relation, and'afterwards-removing one of said materials.

2. The method of manufacturin an apertured structure which comprises ormin a ferent materials, forming on one or both surfaces a frame-work integral therewith, andafterwards removin one of said materials.

3..The method 0 manufacturing an apertured structure which comprises forming a composite body of alternate layers of different materials by alternate electrodepositions of said materials, securing said layers to a common support, and afterwards removing one of said materials.

4. The method of manufacturing an apertured structure which comprises immersing a member as an electrode alternately in plat-- ing ,baths of different materials, thereby forming a composite layer thereon, providmg a supporting frame-work for said layer,

and afterwards removing one of said materials to form a structure having a plurality of passageways.

5. The method of manufacturing an ap ertured structure which comprises forming a composite body of alternate adherent layers of different materials, securing said layers to means for holding them in spaced relation, and afterwards removing one of saidmate rials.

6. The method of manufacture which comprises forming a finely laminated bi-metallic plate having the laminations parallel to the surface of the plate by alternate electrodepositions of said metals on a central portion of said plate, securing alternate lammations, at least, to a common support, and

- afterwards removing one of the materials to form a finely slotted structure.

7. The method of manufacturing an aooustic impedance element which comprises immersing a conductive member alternatelyin plating baths of different materials, whereby a composite layer of alternate layers thereof is formed thereon, providing a supporting structure for said layer, and after-' wards removing one of said materials to form a slotted structure acoustic channels. v

8. The method of manufacturing an acoustic impedance element which comprises providing a plurality of" building up a composite layer of aplurality of alternate layers of different materials, cutting slices from said layer transverse to the planes of said alternate layers, securing said layers tomeans for holding them in spaced relation, and afterwards removing one of said materials to form a slottecLstruct-ure.

9. The method of manufacturing an acoustic-impedance element which comprises immersing a member as an electrode alternately in plating baths of different materials, whereby a composite layer is formed thereontconsisting of alternate layers of said mas:

. terials, cutting said composite layer transverse: to the planes of its alternate layers,-

whereby a slice of a desired thickness is obtained, securing said layers to a common supmaterials to form a slotted structure.

10. Themethod of manufacturing.

!10 z-port, and afterwards removing one of said acoustic impedance element which comprises forming a iinely laminated bi-metallic coattherefrom a u'nitof desired thickness, associating supportin means for the laminations into said unit, an removing one of the metals 7 to form .a finely slotted structure..

11. The method of -manufacturing an 7 acoustic impedance element which comprises .electrodepositing. u n a conductivecore thin alternate layers 0 a plurality of materials to form a composite layer, cutting therefrom a slice of desired thickness, a sup- W porting frame-work on one or. both 0 .its sur faces, and thereafter removing one of the I 7 materials to leave. a slotted structure.

The method of manufacturing usf ingon a core member, thereafter slicing i acoustic impedahce element which comprises immersing an electrode member alternately in plating baths of diiierentimaterials, thereby fprming a composite layer thereon, re-

movmg said composite layer from said electrode, cutting said layer into strips, piling the said strips in stacks, securing them togl'ether, cutting said stacks into slices and 'pping said slices into an appropriate solution whereby one of saidplated materials is dissolved out leaving a structure with a plurality of apertures therein.

In witness whereof, I hereunto subscribe my name this 14th day of June, 1930.

EDWIN H. SMYTHE.

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