US1986856A

US1986856A - Sound translating device

Info

Publication number: US1986856A
Application number: US653953A
Authority: US
Inventors: Abraham S Ringel
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1933-01-28
Filing date: 1933-01-28
Publication date: 1935-01-08
Anticipated expiration: 1952-01-08

Description

Jan. 8, 1935. A. s. RINGEL SOUND TRANSLATING DEVICE Filed'Jan. 2s, 193s 2 Sheets-Sheet 2'" Jbmzham flngel,

Patented Jan. 8, 1935 PATEN T" yOFFICE souNn raNsLATiNo; DEVICE Abraham S. Ringel, Merchantvlle, N. J., assigner- America, a. corpora-y The presentjinvention relates to sound translating devices Vandmore particularly, tolloud4 speakers of the movable coil type having a permanent magnet-eld-and a large direct-acting5diaphragm.

In known sound translating devices ,of

moving coil type, for example, the magnetic sysf tern` extends rearwardly of the cone or diaphragm,

to such an extent that considerable space is required for theproper installation thereof in connection with varioustypes of radioreceivers.

vIn vcertain formsof` loudspeakery installations,

such as,=for example, centralized radio for hotels and the like, automobile `and.:midget` radio re-V ceivers, excessive bulk is objectionable. This |is especially true in automobile*L and centralized radio receiver installations where it is4 highly desirable that the distance which the loudspeaker i projects from a supportingfsurface thereforlbe as short as possible, or `the depthwof arecess` therefor, asin a wallA or the like,fbe aslshallow as possible. In suchcases, it is necessary, therefore, that loudspeakersof the character speciiied shall have a minimum front to `back dimension without exposing anyfof the moving partsthereof to injury.

; It is, accordingly, PrQVd-e cupy a minimum amount of space.y A g Another object of my invention` is to provide an object of myinvention to afloudspeaker of the movable coil typehaving af minimum iront lto back dimension. A

A further object of my invention iste/provide4 a loudspeaker vofV the movable coil type1 which is adapted to be 'mounted as. a unit in a shallow de-` l 1 e constructed in 'accordance with my invention,

Y `pression or recelssforined in a `wall or thelike.

lAnother object `of my invention is` to yprovide a loudspeaker of the character specified having `a diaphragm of appreciableactivefarea and depth, which is compact-in formfand particularly adapted for use in connection with automobile e l e e e l which bars are disposed in parallel and serve as radio receiver installations. M i

` -A further object of my inventionis to provide,`

` in a device'of thecharacter descrihed,a`conical Vdiaphragm having avoice-coil form.` attached thereto which shall have a front tcback dimen-`- sion which does not exceed the normal depth of the diaphragm. f i 5 Anotherobject` of, myinyentionds toprovide a sound translating device of nthe character, speci-` ed wherein the magnet systemiconstitutes a support for the diaphragm. r g. Y A further object ctmyinvention is to `provide a loudspeaker of the-movable coil typewhiCh,

, when mounted in a suitable" enclosurecasmg a sound translating device that `shall oc-` form of my invention; and

therefor, .shall have al minimum front to back dimension, f,- U l 1 V,r'lnotherobject ofmyin'vention is to provide a A soundtranslating device ofthe character speciedlswhein "a magnet system` and diaphragm` driving means are mounted as a unit forwardly of and substantially `Withizrthe concave side of thediaphragm. l ,e

A still .further objectief invention is to provideafdevice ofthe type described, wherein ,theobj ectionable effects of resonance `pl'lenomena from the following description of specic em-` bodiments thereof when taken in connection with the accompanying drawings, in which Y Fig. 1 isa front elevational view of my` inven` tion; e e

Fig. a sectional view taken on the line 24,-,2 of Fig. 1;

` Fig.,3 `is"a front` elevationalview of ya modified A Fig. 4 is a sectional` View taken onthe line 4 4 of Fig. 3.

Referring" more particularly tothe drawings,`.

wherein-similar reference ,characters indicate corresponding parts throughout, `a permanent magnetloudspeakenofthe movable coil type,

preferably comprises a ring shape permanent `magnet 10 which is constituted bya plurailty of magnetized laminations 11 of Vsuitable sheet metal. Each of the laminations 11 is formed with ank integral .diametrically ,disposed `cross bar,

an anchorage or `support`124 for a central pol piece 13. The pole piece issecured to one side of the cross-bar assembly 12 by means .of a screw or bolt v14 which extends through the support 12 andinto a ,central threaded bore l5 formedin Fig.'2. f

An outwardly bentyoke plate of ferro-magnetic material, having a relatively large circular opening 17 formed therein intermediate its ends 18, constitutes a second pole piece 19. The second pole piece is also secured to the magnet 10, on the same sideasthe pole piece 13, transverseof,

. one end of the pole piece 13, as clearly shown in l to the magnet 10', and corllpri'ses'a:

connection between the several abutting laminations, constituting the permanentA magnets, andy the respective pairsv of pole pieces' 'andse'cur'ed thereto (Figs. 1, 2, 3 and 4):a:lowreluctance'iron is preferably applied to the aedgesofthe magnet 10, at the juncture between the pole pieces 13 and 19 and the magnet 10inany approvedmanner, such as by spraying or plating4 'n M A` Means whereby a substantially conical diaphragm 24, or a diaphragm KVof someother desired configuration, having a cup-shapevoic'e coil-form 25 attached to the smaller Yendthereof and'which projects 'inwardly Aof its concave` side,`

ing rings 26 fof:y 'no to the' rim portion -21of-=the"magner 1o, on` the side to which the pole pieces. 13 aridfl9'i`aresecured, concentricjy with' the "axial" center-of the pole piece'j'1l3 by meaiisxofsuitable bolts. 27..

'The poripherarodge portion ortho 'diaphragm' 24 or a mountingv ring 2310i fiexiblelma'terial ai# fixed to theV peripheral edge portion thereof'fis clamped betweenVV the "ringsf2fj,` Y'With the diaphragm 24 so mountedyftlfie openjendjof the coilform 25 pro-jects intothe'airgapj23yg defined' by the pole pieces'l3kandvl'9 i1 order to `iifiaintairi the coil-form 25 properlycente'redjin the airfgap` 23, a centeringv screw 30', ,which extends through a central opening formed y r thpottomsrof the coil-form125, ijsfthreaded'intq tlieA reduced free end portion v3,2forir'1e-d conc n trically `with vthe pole piece 13.` j 5 A suitable housing for'the loudspeaker mech-.-

anism hereinbefore describedvcomprises 4a lshallow rectangular casing 33'p`r'ovidezdvr with a detachable back plate 34.V Itis to bequnderstoodyhowever, that a shallow `casing of any' other suitable' configuration may be lltilizedc Thfront face ofthe shell 36,"havi1f1`g a radial outwardlyextending'circumferential flange AS'Z'formed `on one end thereof and a similar inwardlyl extending. circumferential l flange 38 formedon the oppositekend thereof,

which is secured tol the inner sidel of the front wall 39` of the casingj33jby,meansgof suitable screwsg'rivets, or ,thev` like,"y as indicated at' 1.0; with the innerfdiameter: 'of theshe'll36 in registrationl with the'Opening35.1"

,'Ihelength of fthey shell 36j is` such that the flange 38' is Ispaced rearwardly fromfthe front vwall of the casing 33 a suicient distance so that the front face of the v'magnet structure 10vwilllie substan` tially within the front wall 39 of the casing 33,

when the loudspeaker mechanismis disposedn in the opening A and'secured to the flange138 by` meansof the 'sfcrewslndicated at- 41. 1

,'Ifherear; marginal ,edge portions of the casing' 33 are bentat right'ang'lestoprovide radial in-V wardly extendingflanges 42 whereby *the back plateY 34fm`ay bie secured'to the casing 33 as byv means of the screws indicated at 43. The back plate 34 is provided with a plurality of small openings 44 in which suitable rubber bushings 45 are disposed and which serve as outlet passages for the terminal wires 46 leading from the rear of the voice coil-form 25.

The space within the casing 33, not occupied by the loudspeaker mechanismyis partially'lled with suitable acoustic absorbing material 4'7, such as felt or the like, for the purpose of substan- Itially damping out the low frequency resonance peak -resulting from the compliance of the air chamber formedby the casing and the mass of the, diaphragm when the loudspeaker is in operationb Ther felt 47 also serves to prevent the formation of acoustic standing-waves within the casing and their harmful reaction on the sound output from the diaphragm.

Y f `1In vthe modified form of my invention illustrated in Figs. 3 and 4, the magnet structure comprises a pair of substantially vsemi-circular permanent magnets vwhich may be either solid in cross section or'composed of a plurality' of laminations 48 f suitablyA secured together in stacked relation by d u u n y meansof rivets 49, or the like,as shown in Fig. 4, brass,` for example.Y ione ,f therings'26 securedV to provide two separate permanent magnets 50 andll` o Although I have'shown the magnets 50k owing to the manner in which I `secure the pole clearly shown in Fig. 3, the union between the free ends 52l of said magnetsv and said pole pieces being effected by suitably welding the respective parts"t ogether.

The opposite free end portions of the pole pieces54 and 55 extend inwardly of the annulus formed by'the

magnets

50 and 51 and laterally therefrom, as clearly shown in Fig. 4. The free endportion of the pole piece 54 terminates in a cylindrical portion 56 having a reduced end portion-'57 which is provided with a,4 small central bore threaded for the reception of a suitable screw, whilethe'` free end portion of the pole piece 55 terminates in an annular sleeve 58 which encircles the cylindrical portion 56 in spaced relation thereto and concentric therewith whereby an annular air-gap 59 is formed.

Means whereby a conical diaphragm 60, similar tothe diaphragm 24 describedl in connection with Figs. 1 and 2, is secured tothe

pole piece members

54 and 55, comprises a pair of clamping rings 61 of non-magnetic material. One of the rings 61 is secured to one side of the outer end portions of the

pole pieces

54 and 55,` concentric with the axial center of the cylindrical portion 56, as by means of fillet welding, screwsor the like.V The flexible peripheral edge portion of the diaphragm -is clamped between the rings 61, the outer ring being secured to the inner ring by means of suitable screws 62.v V

- With the diaphragm 60 mounted in this manner, the open end of a voice coil-form63, a similar to the previously`7 described coil-form 25, projects into the air-gap 59 defined by theinner free ends of thepole pieces 54 and55,l In order to maintainthe voice coil-form 63 properly centeredl in the air-gap 59, a centering screw 64,A which eX- tends-through a central opening formed in the bottom 65-ofA the coil-form 63',- is threaded into the reduced end portion 57formed concentrically with the cylindrical portion 56 ofthe pole piece 54.

The loudspeaker mechanism described in connection with Figs. 3 and 4 is also adapted to bev housed and secured in a casing, by means of the screws 66, except that its front to back ydimension may be less than the casing shown in Fig.

2. The reason for this is that thefront to back dimension of the loudspeaker mechanism, shown in Fig. 4, is appreciably` less Vdue to the novel construction and assembly of the

laminated magnets

50 and 51 and the polepieces54 and 55;` l

In order that the rigidity of the

pole pieces

54 and 55 may be increased, I may connect a bracing bar 67 of any suitable non-magnetic material in any approvedvmannerto the pole pieces, as

indicated by the broken lines in Fig. 4.

Although I have shown certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, isnot lto be restricted except pieces defining an annular air-gap, means providing a path of lowV magnetic reluctance` between said magnet and pole pieces, a frustroconical diaphragm having `a reentrant coil form attached thereto carried by said magnet oo-axially therewith whereby said coil-form is disposed in said air-gap, means carried by one of said pole pieces for centering said coil-form in said air-gap; a hollow casing includinga shouldered annular recess for the reception of said magnet and diaphragm, and means for securing said magnet within said recess and casing.

2. In a sound-translating device, a laminated permanent ring magnet including a pair of pole pieces deiining an air-gap, means providing a path of low magnetic reluctance between said maget and pole pieces, `a conicaldiaphragm having a reentrantcoil-form attached thereto carf ried by said magnet co-axially therewith whereby of the pole-pieces.

are supported.

said coil-form in said air-gap, l a casing having an annular flanged recess therein for the reception of said magnet and diaphragm, means for securing said magnet to the flanged portion of said casing, and acoustic damping means within said casing whereby resonance peaks are minimized.

3. In a sound translating device, a ring-shape permanent magnet having a transverse portion, an apertured pole-piece supported `from diametrically opposed portions'of the'periphery of the magnet, and a central pole-piece supported from 1 the ,transverse portion and extending into the aperture to provide an air-gap.

'4.` The invention as set forth in claim 3 characterized in that the permanent magnet is constituted by a plurality of relatively thin laminations.

5. The invention set forth in claim 3 characterized in thatvmaterial having low magnetic reluctance is disposed between the opposed portions of the ring-shape magnet and at leastlone 6. The invention set forth in claim 3 characte'rized in that material having low magnetic reluctance is disposed between the opposed portions of the ring-shape magnet and both of the pole -pieces 7. In combination, a ring-shape permanent magnet, `an L-shape element aflixed to and supported from said magnet, the longer portion of said member extending radially inward from the periphery of the magnet and the shorter portion of said member extending axially of said magnet to constitute a pole-piece, a yoke-plate cooperating with said pole-piece to define an annular air- A gap, said yoke-plate being aixed to and supported by said magnet ata point substantially diametrically opposite to the point at which the L-shape member is affixed.

8. The invention set forth in claim 7, characterized in that the ring-shape permanent magnet is constituted by a plurality of semi-circular elements the ends of which are disposed in abutting relation `adjacent the points at which` the L- shape member and the yoke-plate, respectively,

ABRAHAM s. RLNGEL.