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Publication numberUS1372862 A
Publication typeGrant
Publication dateMar 29, 1921
Filing dateJun 30, 1917
Priority dateJun 30, 1917
Publication numberUS 1372862 A, US 1372862A, US-A-1372862, US1372862 A, US1372862A
InventorsCarmody Harold J
Original AssigneeHarry Ufland, Joseph M Levine
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
US 1372862 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)




Imam/ed Mm. 299 w21.

narran srarss Parana canina.


Specification of Letters Patent.


Patentes Mai. as, raar.,

.,glpplication tiled-.Tune 30, 1917, Serial No. 178,030. Renewed August 6, 1920. Serial No. 401,821.

To all whom t may concern:

Be it known that I, HAROLD' J. CARMODY, a citizen of the United States, residing in VVoodhaven, in the county of Queens and State of New York, have invented certain new and useful Improvements in Transmitters, of which the following is a full, clear, and exact description.

My invention relates to transmitters of a type suitable for use in telephony and dictaphone wo-rk, as well as in all relations requiring a' transmitter of great sensitiveness coupled with adaptability for use under different conditions.

More particularly stated, my invention is a sensitive microphone, in which l seek to attain a number of advantages, among which are the following:

l. To employ a plurality of separate diaphragms, one located back of another and each adapted to control a current, the aggregate control of the diaphragms being cumulative.

Il. To virtually equalize the lengths of the respective paths whereby sound waves reach the several diaphragms in order to enable the diaphragms to vibrate in exact umson.

Ill. To so arrange the loose carbon particles as to prevent undue freedom of movement thereof, and by so doing toprevent the production of certain undesirable noises during the transmission of sounds.

1V. To render the transmitter compact and to give it such form as to enable it to work in any position in which it may be placed.

Figure 1 is a view partly in elevation and p artl 1n sectlon, showing one re resentat1ve orm of my improved transmitter.

Fig. 2 is a section on the line 2-2 ofv Fig. 1,' looking in the direction indicated bythe arrows.

Fig. 3 is a section corresponding to the proximate middle lportion of Fig. 2, but showing a different arrangement of the carbon particles and parts immediately associated therewith.

Fig. 4 is a section showing another arrangement of the carbon particles and parts immediately associated therewith, this tlgure being otherwise similar to Fig. 3.

A casing is shown at 5 and in this instance is made of metal though if desired it can be composed of rubber, wood or any preferred material. The casing is fitted with a front plate 6 and a rear plate 7.

The front plate 6 is provided with a number of acoustical openings 8, 9, conveniently designated as sound holes. They are each of arcuate form, and they are collectively arranged in two concentric circles, as may be understood from Fig. 1, the circle made up of the holes 9 being of greater diameter than the one composed of the holes 8. The front plate 6 is provided with a cone 10 and the. rear plate 7 has a somewhat similar cone 11. These cones are for the purpose of deflecting and guiding the sound waves, as hereinafter described.

Located within the casing 5 and abutting the front plate 6 thereof is an annulus 12, which is provided with a frusto-conica-l portion 13, preferably integral with it, and secured to the rear plate 7 in any appropriate manner. for instance by solder 14.

Another annulus 15 is located within the casing, and held in position by any suitable means. ln this particular instance the annulus 15 is provided with a flange 16, integral with it and of annular form, and this flange is by screws 17 secured directly to the adjacent portion of the front plate 6.

The annulus 15 supports a. plate 18, mounted rigidly in position. lThe plate 18 is preferably but notnecessarily made of conducting material. It has a compara' jected to the action of sound waves.,

The thick portion 19 of the plate 18 is provided with pockets 22, 23, each having in this instance the proximate form of an oblate spheroid. There are two groups of the pockets 22, 23, each arranged substantially into the form of a circle. The pockets 22 are nearly but not quite closed by the presence of the diaphragm 20, the pockets 23 being likewise nearly but not quite closed by the presence of the diaphragm 21. The opening of each pocket 22, 23 is restricted; that is to say, each pocket is of undercut form, so that its opening, in close proximity to the adjacent diaphragm, has a cross diameter short as compared with the maximum cross diameter of the pocket.

Each pocket is filled with a number of loose particles 24 of carbon or other semiconducting material, preferably spherical in form and polished. These carbon particles, which, if spherical, are known as carbon balls, are of sufficient number and volume to nearly but not quite fill each pocket. With the device in normal position, as indicated in Figs. 1 and 2, the upper mean level of the mass of carbony particles in any one of the pocketsis a little higher than the uppermost part of the opening of the pocket in question. Such being the case, every carbon grain in direct engagement with a diaphragm is in engagement with other carbon particles resting upon it. In other words, no carbon particle in direct engagement with a diaphragm can he altogether free, as other carbon particles above it have more or less tendency to confine it and restrict its vibratory movements.

I have made the discovery that certain undesirable noises, often heard in the telephonic receiver, are traceable to undesirable vibratory movements of carbon particles in the transmitter. For instance some noises suggestive of' squealing lor wailing are due to the undue freedom of loose carbon particles, resting upon the top ofthe general mass of carbon particles in the transmitter, and usually in actual contact with the diaphragm or very close to it. The vibration of the diaphragm causes such relatively free carbon particles to dance. roll and quiver, and by so doing-to disturb the proper electrical action of the transmitter.

I have made the Jfurther discovery that the undue freedom of the carbon particles can be effectively prevented by a -suitable arrangement of the carbon particles relatively to the diaphragm. Following this idea, I employ such a volume of the carbon particlesas to fill the pockets to a level slightly higher than the uppermost portion of the opening of the pocket, the apparatus being in its normal position. That is to say, I prevent all such particles as have undue freedom from resting against the diaphragm. l f

A ring 25, threaded externally, is fitted into the annulus 15, which is threaded internally to receive this ring. A sound plate 26 is carried by the ring 25, and is provided centrally with an opening 2T. Thisl opening is so located that sound waves, converging upon the cone 11,`are deflected and caused to impinge upon the center of the diaphragm 21. These sound waves, before reaching the cone 11, pass in through the openings 9, and thence between the annulus 12 and the annulus 15, and are deflected by the frusto eonical member 13.

A ring 28, threaded externally, is fitted into the annulus 15. The ring 28 is beveled internally, and carries a sound plate 29, which is provided centrally with an opening 30. This opening coacts with the cone 10 for the purpose of directing sound waves against the center of the diaphragm 20.

A number of partitions 31, each having the general form of a spiral, are spaced equidistant and located between the front plate 6 and the sound plate 28. The spaces between the partitions are essentially sound passages, each of which communicates with onev of the sound holes 8. The inner ends of'these sound passages communicate with the sound hole 30. The spiral passages, because of their form, have a tendency to increase the distance over which sound waves, entering the sound holes 8, must travel in order to impinge upon the center of the diaphragm 20. l

Thus the sound waves which enter through thesound holes 8 have, by virtue ofthe circuitous paths through which they are guided,substantially the same distance to travel, in order to impinge upon the center of the diaphragm 20, that the sound waves, entering through the holes 9, have to travel 'in order to impinge upon the center of the dia hrag'm 21.

Cibnnected to the tw`o diaphragms 20, 21 are two conductors 32, 33, preferably insulated wires, which are connected to a single conductor 34. Another conductor 35, provided with a portion 36 of enlarged diameter, extends through a tube 37 of insulating l' material. This tube extends radially inward through the plate 18, the conductor 35 loeing connected to the massive carbon portion The two conductors lead outwardly through eyes 38,l 39 to a plug 40. By aid of this plug the connections from the transmitter to a circuit can be quickly made orI Levante v manner.

lin Figs. 3 and 4, l show other forms of carbon contacts made in accordance with my l invention.

that 'appearing in plained. rlhe only di'erence is in the shapev ln Fig. 3 the two ,diaphrs appear at 41, 42, and themassive carbon member at v43. rlhe latter is provided with pockets 44,

resting against either diaphragm Qr in immediate proximity thereto, are not unduly free, for .the reason that they have other y carbon particles resting' upon them. j In the form shown in Flg. 4 the d iaphragms appear at 46, 47, and the masslve carbon member-at 48. This member 48'is vprovided with pockets 49 extending entirely throulgh'it and containing carbonparti'cles 50. nism here shown is he structure and actlon for the mecharactically the same as ig. 3 and above exof the pockets 49, which are rounded and have each the proximate form of a prolate spheroid. 1

While l have shown only two diaphras used together, l do not Wishto belimlte thereb as any greater number maybe employe if desired.

My invention is well ada ted for dictaphone vvork, in which it has een tried with considerable success. One advantage 1t has for such Work is that it will operate in any position. lf it be placed in such position I v that one diaphragm lis rendered wholly or partially useless for the time being, the other diaphragm can still be depended upon.l

The movements of the diaphra m 20 are always in unison with those o the diaphra 21. That is rst the two diaphragms swing toward each other and' then they swin further apart.V There is no interference o sound waves, and the edect of the diaphragms' upon the control of the electric current is -cumulatiye The transmitter 1s exceedingly sensitive,

and may be used under great ditculties.

lit is very compact, and may be carried in the pocket, or suspended from the neck of the operator Without any diculty. lFor detective work it is unobtrusive in appear-- ance, and because of itsoutvvard form is not likely to excite suspicion. a

l do not limit myself to the precise form shown, as variations ma be made therein without departing from t e spirit of my invention, the scope of which is commensurate with my claims.

l claim:

l. lin a transmitter the combination of a plurality of diaphragme located one behind the other relatively tothe proximate direction of propagation of sound Waves, and guiding means for enabling aportion of said sound Waves to reach 'one of said diaphras by a comparatively direct path, yet causing another portion of said sound Waves to reach another of said diaphragmev by a comparatively circuitous path of substantialllxy the same length 'as said rst mentioned at Y p' 2. ln a transmitter, the combination of a plurality of microphonic` contacts, a plurality of' sound-,controlled diaphragms tor said contacts, one of said diaphragme being located back of another in the general direction of propagation of the sound Waves, and a casing inclosing said diaphragms and provided With sound passages leading 'to said diaphragms respectively, said sound passages being of dierent lengths in :order to p ragms from the source of the lsound Waves.

enlualize the virtual distances of the dia-f' 3. lln a transmitter the combination orn 'a Vholes in said iront plate to said diahra disposed adjacent said rear plate, and mechanism connected with said front plate and associated with the sound holes thereof for iding sound Waves from said soundhcles s..

spiral paths'to the diaphra disposed adjacent said front plate.




Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4449236 *Apr 8, 1982May 15, 1984Walker Equipment CorporationAnti-side tone transmitter
US4584702 *Dec 19, 1983Apr 22, 1986Walker Equipment CorporationNoise cancelling telephone transmitter insertable in telephone handset receptacle
U.S. Classification381/346, 381/181, 381/352, 381/186
International ClassificationH04R1/32, H04R1/38
Cooperative ClassificationH04R1/38
European ClassificationH04R1/38