US1745937A - Acoustic device - Google Patents

Description

C. KYLE ACOUSTIC DEVICE Feb. 4, 1930.

Filed Maron 12. 192e IIIIIIIII'II- liPatented Feb. 4, 1,930

conm KYLE, or su JOSE, cALmonmA,

UNITED nEPnonUcEns PATENTS coarom'rron,

:common E NEVADA 'ASSIGNOIEt, BY MESNE ASSIGNMENTS, TO

F S'I.` CHARLES, ILLINOIS, A COR- Aeous'rrc DEVICE Application led March 12,1928. Serial No. 260,832.'

This invention relates to an electrostatic acoustic device for transmitting and receiving purposes, as in radio broadcasting and receiving, etc. It is known that true sound reproduction,

free from disturbing resonant notes and" distortions, is best obtained by means of apparatus working on an electrostatic or con.

- denser principle. An electrostatic transmitter or reproducer -usually consists of a rigld plate and a flexible plate, the latter serving las a diaphragm.4 The diaphragm andthe plate are placed as closely'together as'possible, as the etliciency is in direct' ratio to 15 the square of the distance or spacing'maintained between the same. While an electrostatic or condenser ,type of acoustic device is fairly satisfactory, there are objections, as a considerable spacing must be maintained, usually'a sixty-fourth of an inch or more, i. e., flexing or bending of the diaphragm when struck by sound waves or when electrically actuated, will otherwise 4permit the plates to contact. Also due to the flexing of the diaphragm, devices of this character are fairly limited in size. For instance, the averagecondenser or electrostatic microphone as used is seldom `over three inches inA diameter and as such is not ideal for low frequency sound-wave transmission or reproduction, nor are devices of this character altogether suitable as receivers or loud speakers, as the area presented is too smallor proper air coupling.

thin; to provide a structure which permits` close spacing between the diaphragm and the plate; to provide a structure which permits division of a large 'area diaphragm into a number of cooperating diaphragms of comparatively small-area; and further, toA pro'- vide a-structure which permits rigid clampof the diaphragm tomaintain uniform .3, but they are considerably larger in diameter than the holes 2. C indicates the dia-V The object of 'the present invention is to" generally improve and simplify the construcspacing and to prevent mechanical vibrations, etc. l

The invention is shown, by way of illustration, inthe accompanying drawings, in which:

Figure 1 is a planview of a portion of the acoustic device, said view being broken away to show the rigid and the exible plates,lthe

insulating medium and the clamping plate,

Figure 2- is an enlarged transverse cross- 60 section of a portion of the acoustic device,

Figure 3 is a partial section showing a ximodified. form of the structure.

Referring to the drawings in detail, A in-l dicates a rigid plate which is providedwith v a plurality of holes or perforations, such as indicated at 2. B indicates a plate constructed of a, dielectricmaterial. This plate is also provided with holes or perforations phragm plate which is thin and iexible. Itl

ris disposed on top of the dielectric plate B and is rigidly clamped or secured thereto by means of a clamping plate D. This plate is also provided with holes or perforations such as indicated at 4, the perforations being of a size substantially the same as the holes 3 formed in the dielectric plate.

The plate A may 'be constructed of any metal desired. For instance, steel, brass, copper, aluminum, etc., and it should be fairly thick or heavy so-as -to prevent vibra-tion;l thereof when the acousticdevice is in opera- The plate C is also constructed of metal, such as steel, brass, aluminum, etc., but it should be asthin as possible as it must be able to iiex or bend when struck by vsound waves, as when used as a transmitter or when' electrostatically attracted b the plate A, when it is used as a repro ucer or a loud speaker Thin shim metal or leaf metal, such as gold leaf, aluminum leaf, etc. may be employed. The flexible plate C is unperforated and as 'such covers the perforations 2 and 3 formed-inthe respective plates A and B, and as the perforations 3 are comparatively large a diaphragm is formed over yeach set of The spacing maintained between lthe flexible plate C andthe rigidplate A should be the spacing between them must accordingly be sufficient to prevent contact when the device is in operation. The spacing will, -accordingly, be in proportion to the diameter of the holes 3, and in few instances will eX- ceed 3/1000 of an inch.

. The plate'D merely serves as a clamping late to secure the diaphragm C and the dielectric plate B in rigid contact with the plate A. Bolts such as indicated at 5 may be employed, these bolts extending through the plates A, B, C and D, and insulating t sleeves and washers may be employed as indicated at 6 to prevent short-circuiting of the plates. .The plate D may be constructed of any material desired, the material employed be1ng of no importance as long as the'plates A and C are insulated with relation to eachother. The bolts may be placed at staggered intervals as shown in Figure 1, and any suitablenumber may be employed. The holes 4 formed in the clampingplate are preferably of the same diameter as the holes 3 in the dielectric plate B. This to insure a rigid support for the diaphragm'and also to provide as large a coupling area as possible between the movable portions of the diaphragm and the air.

The device so constructed is ready for use and may be connected with any transmitting or receiving radio set or in any electric circuit where sound is to. be transmitted or received. When usedas a loud speaker in a radio receiving set, it is preferable to employ po'wei` amplification in the audio frequency side of the circuit 5 the two terminals leading from the audio frequency amplifying power circuit being connected, one with the plate A and one with the diaphragm C. A modulated or varying current potential is in this manner applied to the two plates, and electrostatic attraction, varying according to the degree of applied potential, will cause movement of the flexible belt or diaphragm with relation to the rigid plate, and

as the diaphragm makes a -direct coupling with the surrounding atmosphere, sound or acoustic vibrations will result.I The manner of connecting an electrostaticl device of this character in a transmitting circuit is well known, and a detailed description thereof should be unnecessary.

An electrostatic speaker constructed as here illustrated is highly efficient, as an exceedingly small spacing may be maintained between the rigid and the flexible plates. A thin diaphragm or plate may be employed, which may be constructed of leaf metal, shim metal, or the like, and faithful `tone reproduction is accordingly the result, as such diaphragms have comparatively little weight or inertia of their own, and furthermore are sensitive both to high and low soundwave frequencies. The device may be constructed so large as to present an air coupling equal to several square feet. In fact, limits, as far as area is concerned, is unrestricted. Mechanical rattles, buzzing, and' other tone distortions are avoided, as the structure is exceedingly rigid and substantial and free of vibratin T periods of its own.

If a flexible unperforated diaphragm is employed, such as shown in my Patent No.l 1,644,387, issued October 4, 1 927 land entitled Acoustic device, a clamping plate such as indicated at' F in Figure 3 may be employed to advantage. I n this modification indicates the rigid perforated plate, H the VfieX- ible diaphragm, and J the flexible conductor.

The perforated plate G is in this instance upreferably punched in such a manner that raised surfaces 17 are formed around each hole or perforation. The diaphragm H rests on the raised surfaces and is slightly elevated or raised with relation to the sloping surfaces indicated -at 18. formed in the clamping plate as indicated at 19, are larger in diameter than the perforations in the plate G. The solid portions of The perforations the clamping plate, indicated at 20,'willthus only engage the high spots 17 of the Aplate G and the diaphragm and the flexible conductor will be rigidly clamped tothese points with relation to the rigid plate, while the remaining portions of the diaphragm and the flexible conductor will'be free to vibrate. This clamping of portions of the diaphragm and the flexible conductor is important when certain diaphragm materials are employed, for instance, paper, mica, celluloid and similar materials present a hard surface to the rigid plate G and as such have a tendency to buzz or rattle, but where materials of this character are rigidly clamped where the high spotsareencountered, rattling or buzzing is v substantially eliminated.

- While certainfeatures of the presentinvention have been more or less specifically illustrated and described, I wish it understoodV that various changes may be resorted to within the scope of the appended claims; similarly, that the materials and finishes of the several parts. employed may be such as the manufacturer may decide or varying conditions or uses may demand. v

Having thus described my invention, what I claim and desire to secure by Lettersv Pat-` ent is:

1. Anacoustic' device comprising a perforated plate, dielectric perforated plate diS- posed in contact therewith, the perforations in the dielectric plate being larger than the perforations'in the first-named plate and concentric therewith, and a flexible' conductor covering the dielectric plate and forming a diaphragm.v

2. An acoustic' device comprising a' perforated plate, a dielectric perforated plate disposed in contact therewith, the perforations in the dielectric plate being larger than the perforations inthe first-named plate and concentric therewith, a flexibleconductor coveringlthe.dielectricplate and forming a diaphragm, anda clamping plate engaging the diaphragm and maintaining it in contact with the dielectric'plate. f

3'. An acoustic Adevice comprising a perforated plate, agilielectric perforated plate disposed in contact therewith, the perforationsfin-the dielectric plate being larger .than the perforationspin the first-named plate and concentric therewith, a flexible conductor covering the dielectric plate and formingadiaphragm, and a clamping plate engaging the diaphragm and maintaining it in contact with the dielectric plate, said clamping plate having perforations formed therein lsubstantially ofy the same size as the perforations in the dielectric plate and aligning therewith.

' .4. An acoustic devicecomprising a dielectric perforated plate, a perforated conductor plate disposed on one side, a flexible conductor plate disposed on the opposite side and forming a1` diaphragm, Aand means clamping all ofthe plates together and maintaining the plates inrigid contact with relation lto each other.v Y

V"5. An acoustic device comprising a`rigid erforated conductor plate, a flexible conductorjplate'forming a diaphragm, a, dielectric plate interposed between the rigid plate and the diaphragm plate, said dielectric plate being perforated and the perforations being larger than the perforations in the rigid plate and being concentric therewith so as to leave `an exposed surfacearound each perforation in the rigid plate.

device comprising a rigid perforated conductor plate, a flexible conductor plate forming a diapliragni,l a dielectric plate interposed between the rigid plate and Vthe diaphragm plate, said dielectric plate being perforated and the perforationsl being larger than the perforations in the rigid plate "and being concentric therewith so as to leave an exposed surface around each perforation diaphragm, and a, clamping plate engaging the 'flexible conductor, said clamping plate having perforations formed therein which are larger in diameter than the perforations-in the rigid plate.

- 8. An acoustic device comprising a rigid plate, meansfor providing a plurality of high points on the plate, said plate having perforations formed thereinintermediate the lhigh points, a flexible diaphragm placed in contact with the high points of the rigid plate,-

.perforated plate, a flexible diaphragm covering the plate, a flexible conductor covering the diaphragm,l and a clamping .plateengaging the flexible conductor. and exerting pressure on theconductor and the diaphragm so as to maintain them in rigid Contact with the.

rigid plate.

10. An acoustic device comprising a rigid perforated plate, a flexible diaphragm covering the plate, a flexible conductor covering the diaphragm, and a foraminated clamping plate engaging the flexible conductor and exerting pressure on the conductor and the diaphragm so as to maintain them in rigid contact with the rigid plate. v

'COLIN KYLE in the rigid plate, said dielectrcplate maintaining a fixed s acing between portions of the diaphragm p ate and the rigid plateand means clamping the plates together.

7. An acoustic device comprising a rigid perforated plate, a'flexible diaphragm covering the plate, a flexible conductor covering the

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