US1951531A - Sound-translating device - Google Patents

Description

March 20, 1934. A. S. RINGEL SOUND TRANSLATI NG DEVI CE Filed Feb. 12, 1951 A TTORNEY.

Patented Mar. 2i), 1934 SOUND-TRANSLTING DEVICE Abraham Somer Ringel, lVlerchantville,- N. J., as'- slgnor, by mesne assignments, to Radio Corporation of America, New York, N, Y., a corporation of Delaware Application February v12, 1931, Serial No. 515,190

17 Claims.

My invention relates to sound-translating devices, such as loudspeakers and microphones, and it has particular relation to translating devices of the electrodynamic type.

In all sound-translating devices of the electrodynamic or moving coil type, with which I am familiar, the magnetic system extends away from the cone and coil, thereby occupying considerable space. Such devices, particularly loudspeakers 1c intended for use in midget radio receivers, take up space that can be used to advantage for other radio apparatus. Furthermore, in centralized radio installations of the type wherein each loudspeaker is disposed in a small niche in the Wall iii of a room, it is highly important that the frontto-back dimension of the apparatus be as small as possible, and that the moving parts thereof be protected against damage.

It is, accordingly, an object of my invention to zo provide a sound-translating device that shall occupy minimum space compatible with efficiency.

Another object of my invention is to provide a sound-translating device wherein all moving parts are adequately protected against damage.

Another object of my invention is to provide a sound-translating device that may be mounted as a unit in a shallow depression in the wall of a room.

Another object of my invention is to provide a loudspeaker that shall be substantially non-directive.

An additional object of my invention is to provide improved means for supplying a loudspeaker with currents at audio frequencies.

A still further and more specic object of my invention is to provide, in a device of the type described, centering means for the moving coil that shall be easily accessible for adjustment.

The foregoing objects and others related thereto I accomplish, in part, by disposing certain of the magnetic system elements of a sound-translating device exteriorly of a substantially conical diaphragm, or a diaphragm having any other desired shape, and by disposing the remainder of the magnetic system elements substantially entirely within the space bounded by the diaphragm. I, furthermore, utilize one of the said magnetic system elements as a support for the large end of the diaphragm and provide the said element with a plurality of openings whereby it serves as an ornamental and protective grille and as an acoustic lter.

In a preferred embodiment of my invention hereinafter described, the remainder of the magnetic system elements, which are entirely within the space bounded by the diaphragm, includes' an element of the magnetic system such as a central pole piece arranged Vto extend entirely through such space.

It` should be understood that the space bounded by the inner surface of said diaphragm includes such space as may be considered to be included within the diaphragmvwhen the latter is regarded as a containeri or enclosing element per se. Regarding a conical diaphragm in the manner in which it is usually employed, with the base or periphery portion extending frontally,v such space is that located within the confines of the conical diaphragm on the front face thereof. More briey and more generally stated, the space bounded by the inner surface of the diaphragm may be regarded as the space within the conical diaphragm on the concave side thereof as distinguished from the convex side.

The novel features that I consider characteristie of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of certain specific embodiments, when read in connection with the accompanying drawing, in which:

Fig. 1 is a front view, in elevation, of a soundtranslating device constructed according to my invention. l

Fig. 2 is a cross-sectional view of the same device taken along a line corresponding to the line II-II in Fig. 1,

Fig. 3 is a front view, in elevation, of a sound'- translating device, of alternative type, also constructed according to my invention,-

Fig. 4 is a cross-sectional view of the device shown in Fig. 3 taken along a line corresponding to the line IV-IV in that ligure,

Fig. 5 is a fragmentary View, partly in section, of a base plate of alternative type,

Fig. 6 is a View, partly sectional and partly diagrammatic, of an alternativeV form of coilsupport and centering device, and

Fig. '7 is an end view of the centering device shown in Fig. 6.

lThe apparatus illustrated in Figs. l and 2 of the drawing includes a U-shape permanent magnet 1 having an opening 3 in the flat portion, connecting the legs 5 thereof, of sufcient size to accommodate a voice-coil '7 and a central pole piece 9. The central pole piece extends rearwardly from a base platei 11, of magneticl mateirial, to. which the legs of the U-shape magnet Vbetween a plurality of diaphragm mounting rings -19 and 21.

The mounting rings provide a supporting frame for the periphery of the diaphragm, which frame is held firmly against or anchored to the inner surface of the base plate 11 by a plu-v rality of bolts 23 or equivalent devices, whereby the diaphragm lies entirely within the legs of the U-shape magnetic elementI and is protected thereby.

The voice coil 7 is carried by a cup-shape coil form axed to the smaller end of the diaphragm, the said form being centered with respect to the annular air-gap defined by the central pole piece and the opening in the U-shape magnet by a centering device 27, such as a screw or the like,which projects through the bottom of the coil-form into the end of the central pole piece.

' The-'magnetic system, constituted by the bas plate 11, the U-shape element 1, and the central pole piece 9 may, alternatively, be energized by a eld coil 29, as shown in Fig. 4 of the drawing.

It also lies within the scope of my invention to utilize the base plate as a protective grille for the device, as is shown in Figs. 3 and 4 of the drawing, wherein elementsA similar to those illustrated in Figs. 1 and 2 are similarly desig- V nated.

A -The essential difference between the device illustrated in Figs'. 3 and 4 and the modified device shown in Fig. 1, lies in the substitution of a larger cover plate 31, through which extend a plurality of perforations 33, for the small baseplate 11. The' perforations may be circular, as shown, or they may be given any ornamental configuration desirable.

The cover plate, vwhich is also a part of the magnetic circuit, is provided With a plurality of diametrically disposed ears 35 through each of which extends a bolt 37 that cooperates with a suspension lug 39 for the purpose of rmly vclamping the device to the margin of Yan opening in a wall orin an analogous position.

It is also feasible to dispense with the bolts 23 that hold the diaphragm clamping rings 19 and 21 against the rear surface of the baseplate. In such event it is convenient to increase the diameter of the outer ring 19 and to clamp it-betweenashoulder 41 on the U-shape element 11v and the base-plate by means of the screws 13 that hold the base-plate Yand the U-shape element together.

From the foregoing description it will be seen that the magnetic circuit surrounds the diaphragm and that a portion thereof, such as the pole piece 9, extends entirely through the space bounded by the inner surface of the diaphragm, such space, as hereinbefore pointed out, being that space bounded by the surfaces of the concave side of the diaphragm. This space is also adapted to receive and to provide for an acoustic loading means, as will hereinafter be described in connection with Fig. 5.

Furthermore, I have found it desirable, where complete protection of the diaphragm is essential and economy is not an importantfactor, to utilize acup-shaped element entirely enclosing the diaphragm,instead of the U-shape magnet shown. When using the cup-.shape element it is desirable to provide one or more openings 43 therethrough to prevent the entrapped air from del-V soy a beam. The diffusing means may take the form of a separate conical element (not shown) sur-` rounding the central pole piece and the eld coil (if one is used), the contour of the said element approximating the contour of the inner surface' of the cone. The spacing between the sound diffusing element and the inner surface of the cone is difficult to predict accurately inasmuch as the said spacing is, to afgreat extent, dependent upon the diameter of the cone, the maximum amplitudey of movement thereof, the size of the openingsV in the grille and upon other variable factors.

If it were possible to make the entire base plate of relatively thin sheetmaterial the cost of the device would, to some extent Abe lessened. Too thin material, however, gives rise to undesirable magnetic saturation at the point of attachment of the central pole-piece. I, therefore, propose to increase the thickness of an otherwise relatively thin plate, substantially as shown in Fig. 5,- by the addition of .a protuberant portion 45.

In addition to improving the magnetic circuit of the device the protuberant portion may be given such a configuration that it serves as an effective diffuser for high frequency sounds while offering low impedance to sounds at low frequencies.

Direct egress for low frequency sounds is provided for by a plurality of small openings 47, extending through the protuberant portion, While sounds at high frequencies which do not pass readily through the small openings 47, are caused to detour, so to speak, by the inner face of the said portion to emerge, together with sounds at lower frequencies, from a plurality of larger openings 49 provided in the thinner part of the plate. The high frequency sounds are thereby prevented from being directed from the diaphragm in a beam.

The openings 47 have relatively high acoustic Yinertance with respect to sounds at high frequencies but present relatively low impedance to the passage of loW frequnecy sounds and their presence does not adversely influence the diaphragm at such frequencies. In effect, therefore, the diffuser is a low-pass acoustic filter.

Acoustic loading material may be inserted in the openings 47 and 49, if desirable, as shown at 49h in openings 49 for example.

The leads to the voice-coil in either of the alternative forms of my improved device may be brought out from the rear thereof in any desired manner. For example, it is feasible to connect one of the leads directly to the centering device 27 and to connect the other to a metallic soldering lug, or the like, carried upon the bottom of the voice-coil form, from which a single flexible connection may extend to an insulated binding post mounted upon the U-shape magnetic element.

I prefer, however, to dispense entirely with the bottom of 'the coil-form, through whichthe centering device extends, and to utilize, instead,

a plurality of resilient metallic elements 51 and 52 that also serve as intermediate means for connecting the voice coil '7 to the output terminals 53 of an amplifier or the like, as shown in Fig. 6.

The metallic elements, which may be corrugated to give them the requisite amount of compliance, are disposed at right angles to each other and are separated by an insulating spacer 55. The ends of each of the elements are bent over to embrace the coil-form 25 and they may be aflixed thereto by cement or by other appropriate means, such as riveting.

Each element has a central opening 57 slightly larger in diameter than an insulating sleeve 59 which extends therethrough, to permit of lateral movement of the assembly for centering, upon loosening of a clamping bolt 61 threadedly connected to the end of the central pole piece. The head of the clamping bolt is insulated from the rearwardly disposed resilient element 51 adjacent thereto by a Washer 63 of appropriate material such as micanite or the like.

One terminal of the voice-coil is connected to the metallic element 52, which rests against and is in conductive engagement with the pole piece 9, and the other terminal is connected to the metallic element 5l which is provided with a soldering lug 65.

The leads 53, from the ampliiier (not shown) are connected, respectively, to the pole piece 9, or to any part of the magnetic circuit components, and to the soldering lug, thus obviating the necessity for flexible connections to the voicecoil.

It will be apparent from the foregoing description of my improved sound-translating device that it is extremely compact and that it is peculiarly adapted for use in situations where space is at a premium and where protection of the diaphragm against injury is essential. My improved sound-translating device is also advantageous in that it radiates sound substantially non-directively by reason of the inclusion therein oi elements constituting a low-pass acoustic lter and a diffuser for sounds at high frequencies.

Ihe elimination of flexible leads is also an important phase of my invention since such leads are very prone to break during use.

Although I have illustrated and described several specific embodiments of my invention, numerous modifications thereof will be apparent to those skilled in the art to which it pertains. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art or bythe spirit of the appended claims.

I claim as my invention:

l. In a sound-translating device, a diaphragm having a surface of revolution, a voice-coil form affixed to said diaphragm, an element of a magnetic system extending entirely through the space bounded by said diaphragm and supporting means for said voice-coil form carried by said element.

2. In a sound translating device, a substantially conical diaphragm, an element of a magnetic system extending entirely through the space bounded by the inner surface of said diaphragm, and high frequency sound impedance means disposed within the space bounded by the inner surface of said diaphragm and immediately adjacent to the axis thereof, whereby the projection of a narrow beam of high frequency sounds is substantially prevented.

3. In a sound translating device, a substantially conical diaphragm, an element of a magnetic system extending entirely through the space bounded by the inner surface of said diaphragm, and Vhigh frequency sound-diverting means disposed within the space bounded by the inner surface of said diaphragm and immediately adn jacent to the axis thereof, whereby the projection of a narrow beam of high frequency sounds is substantially prevented.

4. In a sound-translating device, a substantially conical diaphragm, a voice-coil form carried by the smaller end of said'diaphragm, an element of a magnetic circuit extending through the space bounded by said diaphragm and into said coil form and means exterior of said diaphragm for centering said coil with respect to said ele ment, said centering means being directly connected with and carried by the end of said magnetic circuit element which extends into said voice coil form.

5. In a sound-translating device, a substantially conical diaphragm, a voice-coil form carried by the smaller end of said diaphragm, an element of a magnetic circuit extending through the space bounded by said diaphragm and into said coil form and means exterior of said diaphragm for centering said coil with respect to said element, said voice-coil form being cup shaped and enclosing the end of said magnetic circuit ele ment extending into it, and said centering means being carried by said end of the magnetic circuit element and extending through the bottom of said cup shaped coil form to cooperate therewith.

6. In a sound translating device, a substantially conical diaphragm, an element of a magnetic system extending entirely through the space 1" bounded by the inner surface of said diaphragm, and acoustic filtering means disposed within the space bounded by the inner surface of said di aphragm and immediately adjacent to the axis thereof, whereby the projection of a narrow beam of high frequency sounds is substantially prevented.

'7. In a sound translating device, a substantially conical diaphragm, an element of a magnetic system extending entirely through the space f bounded by the inner surface of said diaphragm, and low pass acoustic filtering means disposed within the space bounded by the inner surface of said diaphragm and immediately adjacent to the axis thereof, whereby the projection of a narrow beam of high frequency sounds is substantially prevented.

8. In a loudspeaker, a magnet member, a conical diaphragm disposed within the boundaries thereof, and a plurally perforated plate of magnetically permeable material covering the base oi the diaphragm and being in contact with diametrically opposite portions of said magnet member, the perforations adjacent the center of said plate being materially smaller in diameter than the perforations adjacent the periphery thereof, whereby, when the loudspeaker is in operation, the projection of a narrow beam of high frequency sounds is substantially prevented.

9. The invention set forth in claim 8 characterized in that acoustic loading material is disposed in certain of the larger perforations remote from the center of the plate.

10. The invention set forth in claim 8 characterized in that the center of the plate provided with the smaller perforations is materially thicker than the periphery thereof.

11. In a sound translating device, the combination with a conical diaphragm, of a protective casing enclosing said diaphragm and comprising a base plate adapted to form closure means for a wall opening and a cup shape member secured tothe base plate and enclosing the diaphragm between it and the base plate, said cup shape member having a central opening, a coil form connected with the diaphragm located in said opening, a central pole piece secured to the base plate and extending through said opening and within the coil form, and means secured to the end of the pole piece adjacent the coil form for adjusting the position of the coil form within the opening, said means extending exteriorly of the casing, whereby the coil form maybe adjusted without dismantling the device. f

l2. In a sound translating device, the combination with a conical diaphragm, of a protective casing enclosing said diaphragm and comprising a base plate adapted to form closure means for a wall opening and a cup shape member secured to the base plate and enclosing the diaphragm between it and the base plate, said cup shape member having a central opening, a coil form connected with the diaphragm located in said opening, a central pole piece secured to the base plate and extending through said opening and within the coil form, and means secured to the end of the pole piece adjacent the coil form for adjusting the position of the coil form within the opening, said means extending exteriorly of the casing whereby the coil `form may be adjusted Without dismantling the device, said last named means being arranged to provide electrical circuit terminals and including two insulated, resilient, metallic members secured to the coil form at spaced points, and said base plate having a plurality of openings of different size, the smaller openings being more adjacent to the center of the plate, whereby an acoustic filter is provided.

13. In a sound translating device, the combination of a base plate adapted to be mounted in a wall opening and having openings providing a grille, a magnet having its legs secured to the base plate in a position to lie within said wall opening, said magnet having a central opening spaced from the base plate, a coil form in said opening, a central pole piece extending from andsecured to the base plate, said pole piece having one end located Within the coil form and said central opening, a frustro-conical diaphragm flexibly secured along its case end to the base plate and at its opposite end to one end of the coil form, and means extending from said end of the pole piece exteriorly of the central opening, whereby the coil form may be adjusted. Y

14. In a sound translating device, the combination of a base plate adapted to be mounted in a wall opening and having openings providing a grille, a cup shape magnet having an edge secured to the base plate in a position to lie Within said wall opening and adapted to form a closed pro tective cover at the rear of the plate, said magnet having a central opening spaced from the base plate, a con form in said opening, a central pole piece extending from and secured to the base plate, said pole piece having one end located within the coil form and said central opening, a frustro-conical diaphragm flexibly secured along its base end to the base plate and at its opposite end to one end of the coil form, means extending from said end of the pole piece exteriorly of the central opening, wherebylthe coil form may be adjusted, and an electro-magnetic field coil surrounding the central pole piece and located between the inner conical face of the diaphragm and the base plate, whereby it is adapted to pass a magnetic ilux through the base plate, the vcup shape magnet and the central pole piece.

15. In a sound translating device, the combination of a base plate adapted to be mounted in a wall opening and having openings providing a grille, a cup shape magnet having an edge secured to the base plate in a position to lie Within said wall opening and adapted to form a closed protective cover at the rear of the plate, said magnet having a central opening spaced from the base plate, a coil form in said opening, a central pole piece extending from and secured to the base plate, said pole piece having one end located Within the coil form and said central opening, a frustro-conical diaphragm flexibly secured along its base end to the base plate and at its opposite end to one end of the coil form, and means extend-v ing from said end of the pole pieceY exteriorly of the central opening, whereby thecoil form may be adjusted, certain of rsaid openings adjacent the center of said base plate being of relatively small size for the passage of low frequency sounds, and certain others of said openings being of a larger size for the passage of low and high frequency sounds, thereby to provide a sound filter, and a Ventilating opening in said cup shape magnet.

16. ln a sound translating device, the combination of a base plate adapted to be mounted in a Wall opening and having openings providing a grille, a magnet having its legs secured to the base plate in a position to lie within said wall opening, said magnet having a central opening spaced from the base plate, a coil form in said opening, a centrai pole piece extending from and `secured to the oase plate, said pole piece having one end located within the coil form and said central opening, a frustro-conical diaphragm flexibly secured along its base end to the base plate and at its opposite end to one end of the coil form, means extendingfrom said end of the pole piece exteriorly of the central opening, whereby the coil form may be adjusted, said means being adapted toresiliently connect the opposite end of the coil form with the pole piece and including two resilient metallic elements adjustably secured to the adjacent end of the central pole piece and being further secured to the coil form at spaced points, and means for insulating said elements whereby they are adapted to provide electrical circuit terminals. i

l'l. An electrical sound translating device including in combination, a base plate of magnetic material, a conical diaphragm mounted on and supported by said base plate, the base of said diaphragm being adjacent vto said base plate, a magnetic core member mounted on the base plate and extending therefrom through the apex of the conical diaphragm, and a frame of magnetic material surrounding the apex of said conical diaphragm and detachably secured to the base plate independently of the diaphragm, whereby said frame may be removed from the base plate Without interfering with the diaphragm.

ABRAHAM SOMER RINGEL.

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