US1656172A - Acoustic-translating device - Google Patents

Description

Jan.

LHEZGAW (II-i. k3. CRUUESE ACOUSTIC TRANSLATING DEVICE Filed Dec. 1922 2 SheetS-ShWt l 5; Sheets-$heet 2 G. B. CZROUSE:

ACOUSTIC TRANSLATING DEVICE iled Dec 6 1922 Jam 17, 1928.

AE l" OFFlClil.

U'ELOUEBIE, 01h STAMFORD, UOI l'NH'U'EIC'UT.

ACOUESTIGJPEANSLATING DlllVICE.

Application died December 6, 1922. Serial No. 605,153.

The SLllJjGCll ll'llllJECl of the present application relates to devices for translating electrical undulations into sound vibrations and the features of invention hereinafter disclosed are directed toward the improvement of such apparatus whereby sound vibrations may be faithfully reproduced.

lllhile certain or all of the features of in vention may be embodied in other forms of devices, within the scope of the appended claims, they may perhaps best he explained as embodied in a telephone receiver. In eniployii the term telephone receiver 1 mean to refer to and include not only reccivers employed in land-line telephony but those employed in radio telephony and telegraphy as Well.

in the receiver now commonly in use in land-line telephony, the motions of the dia' phragm do not exactly correspond to the changes in current in the coils and therefore voices heard over land-line telephones do not sound quite natural. In land line telephony the faithfulness or naturuluess of the voice reproductions is of minor importance so long; as the speech is intelligible. With the advent of radio telegraphy and use of telephone receivers as a part thereof new requirements were introduced but chiefly as to increased sensitivity. In radio telegraphy it is unnecessary that the quality or pitch of the received signals bear any ewctly definite relationship to the undulw ti 15 or transmitted impulses. However, in radio telephony the now common practice of lu'oadcasting or transmitting music and I peeches has introduced new and more severe requirements. It is of great in'iportune" that the music or speech at the transmitting station be faithfully reproduced as to quality as Well as pitch at the receiver or receivers. The metallic diaphragins heretofore commonly employed in receivers for telephone or radio telegraph signals are open to serious objections when employed in the reception of music or speech Where faithful reproduction as to quality and pitch are important. @uch a inetr lic dia phrsgni has a definite natural period of vibration. lt vibrates much more easily at this pitch than at any other. ll hen a receiver embodying such a metallic diaphragm lfl called upon to respond to undulations representing a musical sound consisting of a fundamental and certain definite overtones or harmonies, any harmonic of the same period as the natural period of the dia phragm will be emitted with comparative loudness While the components of other periods will be relatively suppressed. Thus the quality of the reproduced sound is quite different from the transmitted sound. Furtherir re, When the transmitted sound does not comprise a fundamental or har inonic of the same period as the natural period of such a metallic diaphragm, the latter nevertheless sounds a tone of its natural period thereby changing the quality of the transmitted sound and quite often changing a transmitted musical tone or tone-co1nbination into noise.

Among other objects the present invention has for one of its most important purposes to reduce and practically eliminate distortion of the transmitted sound in telephone receivers by providing a diaphragm which does not vibrate freely by itself and has no natural periodtvhich can be delinitely distinguished. To this end, I pro pose to construct the diaphragm. of such material, or combinations of materials, that there is a comparatively high degree of friction between its molecules. In other Words, ll propose to provide a diaphragm which has high internal danuiiing. With this preliminary explanation, ll now refer to the drawings, wherein I have illustrated certain now preferred physical embodiments of the invention and in which:

Fig. l is a plan view, with various parts broken away, illustrating a preferred form of receiver embodying certain features of the invention. lg.

Fig. 1 is a fragmentary sectional eleva tion of an instrument similar to that shown in Figs. 1 to 3 but illustrating a modifica tion.

2 is a sectional elevation taken substantially on the line 2-2 of Fig. 1.

3 is a sectional elevation taken substantially on the line 3-3 of idle. 1.

Fig. 4t is an elevation showing a modified form of the invention Fig. 5 is a plan view (with the dia- (ill tit?

phragm, cap and armature removed) of a modified form of device.

Fig. 6 is a section taken substantially on the line 6-6 of Fig. 5.

Figs. 7 and 8 are respectively a plan view and elevation, on a larger scale, of the diaphragm and armatures shown in Fig. 6.

Fig. 9 is a view similar to Fig. 6 but illustrating a further modification.

Fig. 10 is a fragmentary sectional elevation of a further modification; and,

Fig. 11 is a plan View of certain of the elements shown in Fig. 10.

Calling attention to Figs. 1 to 3, it will be seen that I have there illustrated a watchcase receiver comprising a cup-shaped housing or casing 10 externally screw-threaded to co-operate with the internally-threaded ear cap 11 having the central opening 12. A. diaphragm 13 extends across the housing 10 and is adapted to be vibrated by the preferred form of electromagnetic means which I shall now describe.

The diaphragm 13 has secured the eto, by suitable adhesive material, riveting or other securing means, a disc or button 14 of soft iron or other suitable magnetizable material.

. The receiver is provided with the permanent magnet 15, electromagnets 17 having cores 0r pole-pieces 16, all of which may be secured to the casing 10 in the usual way and which may be substantially of the usual construction except that the pole tips; i. e., the upper ends of the poles 16, are preferably bent toward each other as indicated in Figs. 1 and 3. The receiver may also be provided with the terminal block 18 and cord-attaching eye-member 19 of common and well-known construction.

The diaphragm 13 is preferably constructed of such material, or combination of materials, as to provide a diaphragm having a comparatively high degree of friction between its molecules; i. e., a comparatively high degree of internal damping and having no natural period that can readily be distinguished. For example, a diaphragm built of laminations of paper, cloth, or other fibrous material, impregnated with natural or synthetic gum, or other suitable binder, and baked, if desired, may be employed. At present I prefer to construct the diaphragm 13 of material known in the electrical arts as bakelite-dilecto.

The. efficiency of operation of receivers such as I have described, and in tact other receivers of the same general type, depends on the mean air-gap distance between the poles and armature 1 1. In the practical construction o'l diaphragms such as I have above described it has been found extremely diliicult to produce diaphragms which are absolutely standard as to shape; i. e., some are found to be dished more or less. Therefore, in order to manufacture such receivers at a cost within the means of the average user, it is extremely important, it not essential, that there be some form of means for adjusting the mean distance between the armature and poles and further, it is important that this means be fairly simple. One form or such adjusting means is illustrated in Figs. 1 to anl may be constructed substantially as 'follows.

A ring or annulus 20 oi spring metal, or other resilient material, split at 21 is mounted at the upper end or the casing 10, the upper inner edge of the casing being bev elled and the outer lower edge of the annulus 20 being l cvelled as clearly indicated in Figs. 2 and 3. The diaphragm 1.3 is adapted to upon the upper :l'ace ol the ring 20 and to be eng ged by the annular rib 22 of the cap 11. lly virtue of this construction, when the cap 11. is screwed toward the casing the diaphragm 13 and ring 20 are moved toward the pole-pieces it, such movement being opposed by the inherent resiliency of the ring 20. llhen the cap 11 is screwed in the reverse direction, the ring 20 expands, and moves outwardly forcing the diaphragm 13 against the seat 22.

Means for holding the cap 1.1 and casing 10 in various relative pos tions of adjustment are provided. A preferred form 01' such means will. be found illustrated in Figs. 1 and 2 and may be constructed substantially as follows. A strip 30 0t bridge-like shape is adapted to bear at its lower end against the inner wall oi the housing 10. The upper end of the bridge 30 projects through an opening 31 in the housing and is adapted to engage the inner threaded wall of the cap 11. A screw 32, which passes through an opening in the housing 10, screw-threzuledly engages a suitablytapped opening in the bridge or locking piece 210. Ubviou, y the screw 32 may be turned in either of up posite directions and, when so moved, moves the brid e 30 into looking or release posiion with respect to the cap 1.1, depeinling upon the direction of rotation.

The manipulation and operation ol? the form 01' invention above described as applied to a radio telephone receiving apparatus may be described as follow-2. To adj;

seat

Lilli airgap the locking screw S52 is u... crc\ .cd or loosened. The car cap 11 should then he turned in the proper direction until the armature 14 snaps against the poles 16, due to magneto-motive-force of the perinamcnt magnet 15. This may readily be detected by the click produced by such snapping ol the arn'iature into engagement with the poles. The ear cap 1]. should then be turned in the opposite direction until the diaphragm it and its armatiuhe 1 linore 1 .\\1-. from tho pole pieces as evidenced by a clicking sound. The exact relative position at which the diaphragm moves away from the pole pieces Ill) his

is the leztst oingep that may be employed Wlljl'lOHl] danger of the orinoture i l sticking or freezing on the pole pieces 16 when loud sounds are received. After the siegep odjiiis'tn'ient has been cilectcd the screw is turned to more the bridge 30 into locking; position. end the telephone rogciver n; he connected to the receiving epporstus in the proper manner; i. e, as to polarity of the terminals. By virtue of the composition ind properties of the diophrugni 13, above tllfiCllllGtl, and the occurucy oit' adjustment of the sir-gap, the sounts reproduced will le true lOpl'OtlllehlilllS oi the sounds repred by the electrical unduletions through.

n oot coils.

i l. he understood that two properly connected receivers ouch oi. the term illrstinted in Figs. 1 to ll would preferably be employed tor a head set. For it loud speaker only one instrument would he required. Thus in Fig. 4: l have illustrated on instrum nt in all respects similar to thetillusd in l g 2 one 0 except tluit cup fill, of inetztl or other suitable insteriul, harvinp; o sound simplifying horn 112, connected d for the 121p ll oi: Figs.

1, con'ipuroti've large sent thron -h the receiver, is the when usi to receiver er it loud speaker (Fig, 4: rattling Will take piece unless the diaphragm set tor it comjr srstivoly large oh gop. li o ovoid 3 tlingg the c ill may he turned in the chi ction more ewe from the casing 10 until n disoppezu's. tin eighth of e .1

- e tor this purpose. invention is susceptible to modificain serious 1 spects, in addition to those tion chore noted, Witl'iout departing troin the scope defined in the appended claims. Thus, in lliggs. ii to inclusi o, l. have lllustrotcd a receiver with o diilerent term of urn .ture mid pole tips and l have omitted, in these "e, the oinggop edjust nieuns shown in it?" to .-l. The elements 'll'i", and Elle, end respcc- 1 M. w l 1 is, id, ii, to, 5. The orinzu ll. l iu e to the e c i i soitt iror bent t. trot d in Figs. 6 and 8; i. e., to the .7111 of e hollow trio 'lur p" 'in with o. t at 51. The ornuiture 5O the diaphragm by means. lit wi l ilitt the reluctance of the magnetic appreciably increased, due the l since there practically no t across this joint. The pole tips I bevelled (see liig. 6) to conform pe oi tire armoturc. Due to the :t the orniuture 530 end the JC les E216, the it riner must he in rotating with respect to, 1 nd HIT l he operation of the instruoirent shown in Figs. 5 to 8 is genera ollllllttl to the instrument illustrated in 1 to d, in that tlv e permanent inc net passes :1 continuous llui; through one or one poles 216, 50, and the other pole 216, thus on continuous pull on the diuphrz ll hen an undulating Clll'i t is p through the serially, or otherwise, connected ('OllS 2217, 217, the lid); across the grep is corrcspondingly Varied to inn rilnzttions to the armature end diaphragm in sccorduncc with the electricsl uhdulotion it should he noted that the form of pole and erinoture construction. shown 3' i i .3 to E; possesses the following; zid'vuni among others. For at given eilective len"1 oi 5 path across the cup, at e r motion dieplirzi in, hinore tl .rc con-- tscts N h the pole pieces, is :miiv lnc. "o, :t'or o, iiren relimtuin-o o the iron 0 'e, relntivel c light urniotuie nut is it eed since the this path through the suture is short. ll'urtherinore, since the armature eic tends hetwe n the pole pieces, ti rtelittle nuipgnetic leoltuge troin pole t to pole tip outside oi? the gop.

In Fig. 9 l have illustrated l'jurtl'ier modification, in which two orine'iures Will he noted that the pole pieces ere ure not ent over toward each other but are off as shown, eoch. to cooperate w responding one of the ltllfilt ;lll'QE-S 'lhe ll 1; path between the two mini. is formed by u member 61, oi iron, s1 bevelled at its opposite nds with the orniutures 'lho member *1 suported in any suitable inf-diner, as means of u pedestal (5G or": nonunztgnetio n e.- teriul secured to the and to Wl'iich pedestzil the member 61 is also secured.

While two orinstures ore employed in the form of the invention illus rated in i9. 9, these ormotures are each spsceo from the center of the dieohrugin so that their Weight is less eiiective in lowering tie period of the diaphragm. li y piecing the orinuturcs un's'y ohrogni conte from the dit i r, the oi, up length 1118, be decreased tor u wen motion of the diaphragm, on d this i ctor o it'- cts ot the r loyinen t 'lli ti l

lee

ture 71, 72, 73, 75, 76 that may be substituted for the diaphragm 213 and armature shown in Fig. 6. In the forms of invention illustrated in Figs. 1 to 9 inclusive I now prefer to employ diaphragms of bakelitedilecto. However, diaphragms of other material such as aluminum, or other metal, may be employed in at least some 01": the con vstructions illustrated in Figs. 1 to 9 with improved results over the prior art devices. In the form shown in Figs. 10 and 11 the diaphragm 71 may be constructed of aluminum, or other suitable material, in the form of a cup whose flange extends between the inner split ring and an outer ring 72. The inner ring 75 may be expanded by means of a tapered screw 76, adapted to screw into the slit of the inner ring, and since the outer ring 72 is comparatively thin, the entire structure 71, 72, 7 5, may be expanded and the diaphragm thereby stretched. By stretching the diaphragm 71 its natural period may be raised without increasing is weight. Itwill be noted that the outer ring 72 is provided with an outwardly projectingledge or flange adapted to rest upon the upper edge of the housing 210 when the elements 71, 72 (armature), 73, 75 and 76 are substituted for the armature 50 and diaphragm 213 of the device shown in Fig. 6.

Instead of employing the structure illustrated in Figs. 1 to 8 to provide for the adjustment of the mean air gap, I may employ that illustrated in Fig. 1". In the last mentioned figure, the diaphragm 13 is carried by the cap 11. A nut 400, externally threaded, screws into the cap 11, the diaphragm 13 being clamped between said gap and nut. The nut is provided with diametrically opposed notches 101 (one of which is illustrated in Fig. 1) into which a spanner wrench or other suitable tool may be insorted to screw the nut into or out of the cap 11. By virtue of this construction, the diaphragm 13 may be readily mounted in or removed from the cap 11. Obviously, by turning the cap 11 in one direction or the other with respect to the casing 10 the mean position of the armature 14- with respect to the poles of the magnets may be adjusted at will. Any desired adjustment may be held by devices 30, 31, 32, not shown in Fig.1 but illustrated in Figs. 1 to 3.

In addition to the advantages above set forth I wish to point out further that by virtue of the improved magnetic circuits disclosed comparatively large wire may be employed in the windings of the in. uments which reduces likelihood of burnouts, a feature which assumes particular importance when the instruments are usel in connection with vacuum tube amplifiers.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of my invention, together with the apparatus which I l-OW con sider to represent the best embodiments thereof, but I desire to have it understood that the apparatus disclosed is only illustrative and that the invention can he carried out by other means. Also, while it is designed to use the various features and elements in the combinations and relations described, some of these may be altered and others omitted and some of the features of each modification may be embodied in the others without interfering with the more general results outlined, and the invention extends to such use.

Bakelite-dilccto is a material made of laminations of paper impregnated with bakelite and heated and pressed. Bakelite is a product made by a chemical union of phenol and formaldehyde.

lVhat I claim is:

1. A telephone receiver coin n'ising in combination, a cup-shaped housing, a split annulus oi resilient material mounted on the inner edge of said housing, said annulus and inner edge being provided with co-acting inclined surfaces, a diaphragm mounted on said annulus, an ear cap screw-ll]rcadcdl connected to said housing and adapted to move said diaphragm toward said housing upon rotation of said cap with respect to said housing, and clcctro-imignetic m nus mounted within said housing for vibrating said diaphragm.

2. A telephone receiver as set forh in claim 1 in which means are provided .l'or locking the cap and housing in various relative positions of adjustment.

A device for translating electrical undulations into sound vibrations and comprising in combination, a casing having :1 body portion and detachable cup portion, an electromagnet secured within said casing, a diaphragm extending across said casing, means for adjusting the position of said diaphragm by relative rotational movement of said cap portion and body portion, and means for releasably locking said cap portion and body portion in various relative positions of adjustment, said last mentioned means comprising a lwking member connected to one of said portions and adapted to engage the other of said portions, and a screw for moving said locking member into engagement with said last mentioned portion.

4. A device for translating electrical undulations into sound vibrations and cmnprising in combination, a casing having a body portion and detachable cap portion. on electromagnet secured within said. casing, a diaphragm extending across said casing, means for adjusting the position of said diaphragm by relative rotational movement oil? said cap portion and body portion, and

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means for releasably looking said cap poi-- iiion and body portion in various IGiEL'fiVG positions of adjustment, said last mentioned means comprising :i bridge-shaped look ng inoinbor adapted to bear at one and against said body portion and at its other end against said cap portion, and a manually adjustable screw cooperating; with said body portion. and bricigeohagod looking member for moving the lower into gripping ong; 5oinont with said cap portion.

in testimony whereof I hoio'to fl ifiil my signature.

GEORGE B CRUUEBE.

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