US1920299A - Dynamic loud speaker - Google Patents

Description

Aug. 1, 1933. J FANGER 1,920,299

DYNAMIC LOUD SPEAKER Filed June 17, 1930 5'4 Invehfor Herman d Fan Patented Aug. 1, 1933 UNITED STATES wit-2 DYNAMIC LOUD sr-EAKER Herman J. Fanger, Oakland, Calif., assignor of. one-half to Edmund B. Week, Jr., 0akland,'

Calif.

Application June; 17, 1930. Serial No. 461,718

7 Claims. (o1. 179- 4155.)

This invention relates to sound reproduction, and especially by the aid of electrodynamic means.

Electrodynamic loud speakers an air actuator, such as a diaphragm or a large cone, which serves to produce sound vibrations in response to the, signaling impulses received in an electric circuit. In order to move this actuator in accordance with the sound impulses, it has been common to provide a magnetic field in a narrow air gap, usually annular in form. In this air gap is introduced a conductor, which is moved electrodynamically in, response to the signaling impulses, as by being in direct electrical connection with the source of impulses. This structure, in the form of a thin annular coil, is disposed around the central pole piece, and either directly or indirectly causes the air actuator tobe moved adjacent the center thereof.

In such devices it has been common to clamp the edges of the air actuator or cone adjacent its periphery, and to position the conductor that responds to the electric impulses in the gap. This coilor conductor is free to movefaxially of the gap, as it is influenced by the signaling impulses, the clamping of the air actuator and use of aspider centering device, serving to maintain thev coil in proper concentric aline'ment in the gap.

This usual form of electrodynamic reproducer fails to reproduce the sound accurately for reasons now to be set'forth. As the moving coil is urged axially in theair gap, the diaphragm or air actuator is bent or distorted, or held so firmly as to dampen out certain vibrations to theair actuator by the annular coil or otherwise; this distortion taking place mainly adjacent the clamped edge. This tends to makethe air actuator respond inaccurately to the sound waves, and especially those of a definite frequency determined by the physical characteristics of the apparatus. Furthermore, the movement is so great, and there is so much inertia in the moving system that the mechanical movement of the.

actuator is not exactly in synchronism with the signaling impulses to be reproduced. 7

It is one of the objects of my invention to improve this condition, and especially by ensuring that the entire actuator will move uniformly without fluttering or other disturbing actions.

It is another object of my invention to operate 'theair actuator adjacent its center with short movements thatfollow' the signaling impulses to be reproduced in substantially exact synchronism, whereby the quality of the reproduction usually include I iron clad structure for the coil 13, including a is very materially improved. I-n this Way I have discovered that'fluttering of'the actuator is entirely eliminated, and it is furthermore, much more sensitive, while yet giving a great deal of volume. I

I produce'these results by arranging the conductor influenced by the impulses to be reproduced in such away that its movement is restricted, and by leaving the outer edge of the air actuator free. Apparently, standing waves may be produced in the-body or the airac'tuator which seems to produce greater power even with a small motion adjacent itscenter. Furthermore, the problem of centering the conductor is easily and inexpensively solved, and the conductor can be joined directly to the center pole piece.

7 Accordingly, it is another object of my invention to provide a dynamic loud speaker unit, in which the conductor responding to the-impulses to be reproduced is permanently joined to one or both of the pole pieces, preierably by the aid of some yielding or resilient material, such as rubber, which permits slight movement of the conductor in the gap, and also tends to counterbalance the momentum of the air actuator and.

attached parts.

My invention possesses many other advantages, and'has other objects which may bemade more easily apparent from a consideration of severalembodiments of my invention. For this purpose I have shown a few forms in the drawing accompanying and forming a part of the present specification. I shall now proceed to describe these forms in detail, which illustrate the general principles of my invention; but it is to be understood that this'detailed description is not to be taken in a limiting sense, since the scope of my invention is best defined by the appended claims. 1 7

Referring to the drawing:

Figure 1 is a diagrammatic sectional view of a dynamic loudspeaker embodying my invention, the air actuator itself being shown relatively smaller in size in order to save'space; and v V Figs. 2, 3, and 4 are similar diagrammatic 1 1 1 views showing-modified forms of the invention.

In the form shown in Fig. 1, I show a' mag'netic circuit for providing a narrow air gap 11'. This air gap in the present instance is shown exaggerated in size in order'to provide clarity.- The magnetic circuit in this instance includes a cen tral core 12 around which is disposeda field'coil 13. The magnetic circuit is completed by an bottom plate 14., a 'tubuiar' body member 15, and 1 to the air actuator.

an annular pole piece 16, which defines with the opposed face of the core 12, the annularair gap 11.

It is of course understood that any other means for providing a narrow air gap might be another conductor that is mechanically joined In the present instance I show an air actuator 17 in the form of a cone, at the small end of which there is supported a tubular support 18 upon which is wound a signal responsive coil 19 (shown wound ith wire of exaggerated size). This coil or conductor is axially disposed in the gap 11, and being mechanically connected withthe airactuator or cone 1?, any movement of this coil 19 may serve to operate the air actuator. In order to stiffen the cone 1'? at its end, it may be turned down as shown at 20 to form a flangeor rim, or'crimped in one: of a number of ways. This also prevents sagging or loss of the shape of the cone. The edge of the cone is free. As is customary, a 21 can be utilized adjacent the free edge of the cone.

In practicing my invention the coil 19 is restricted against free movement and is retained permanently on the pole face formed by the cen- I tral core member 12. For this purpose I may utilize any desired mechanism. In the present instance, one or more grooves 22, 23 annularly arranged near the top of member 12 are used. These grooves -may be formed by cutting the member 12 or by the, aid of rings joined on the end of the member 12. Disposed in the grooves are supporting rings 24 and 25 whichare preferably made of some slightly yielding or resilient material, such as rubber or felt. These rings can be engaged tightly in the grooves 22, 23 and may be cemented therein. The outer edges of the rings project slightly beyond the outer suriaceof member 12, and the inner diameter of the supporting ,7 tube 18 is pressed tightly down over the projecting surface. Any appropriate means may be used to hold this tubular member firmly to the rings 24, 25. V 4 V 1 In the present instance the rings are narrower at their outside edges than on the inside edges.

The air actuator 17 as well as the coil support these leads. V

The assembly of the device is. comparatively simple. The bands or rings 2 1, 25 are merely stretched over the end oithecore l2and they contract into the groove 22 and 23 provided for maticallycentered. I .1 The operation of the device asdescribed may now beset forth. Signaling impulses sent-to coil l9-by the aid of leads 26, 2'? produce a force tend- 7 ing to .movethe coil 19 axially with respect to the in the annular air gap 11.

The conductor or coil can be utilized directly to operate an air ac-' tuator, or it may be used to influence inductively The coil or conductor l9 is thus auto- I core member 12. These impulses can set up only a comparatively small movement of coil 19, due to the attachment of this coil structure to the core 12. movement is that there is no bad reaction set up between the currents flowing between the coil 19 and the field, that would tend to distort the-field The degree of movement is of the order of one sixty fourth of an inch more or less, in loud speakers having a cone actuator of a foot or so in diameter. The movement of the central portion of the actuator 17 is of course the same as that of the coil 19; but

probably at the free edge of this actuator a larger movement is present, which makes it possible to transmit or reproduce even the low notes with great fidelity.

In the form shown in Fig. 2, a slightly different type of supporting resilient ring is used. In this case the central core 28 is provided with a ring 290i magnetic material which is fastened to a reduced extension 30 of core 28 as by a screw 31. Thus this ring 29 defines a groove 32 in which i can be disposeda flat flexible or resilient ring 33,

clamped ineplace as bya rim or flange 34. A similar ring is fastened at the upper surface of member 29 by a flange 36. These flat rings 33 One of the advantages of this small and 35 project slightly into the air gap 11 and I are fastened to the inside of the tubular coil support 37.

In assembling this form of the device the held in place by the clamping flanges 40 and 41.

In the modificationshown in Fig. 4, I utilize a coil structure of double form which operates in a manner similar to that disclosed in my prior application, Serial No. 308,152, filed September 25, 1928, and entitled Dynamicloudspeaker unit.

' In this instance, the magnetic circuit is formed with two annular air gaps 42 and 43 in each of which there is a coil section 44 and 45. The central core member 46 has two grooves 47 and 48 porting rings 49 and 50 of the same general characteras the rings 24 and 25 of Fig. 1.: The magnetic circuit inthis instance is completed by a pair of conical magnetic members or annular structure 52. The elements 50, 51 define a space in which the field coil 53 can be accommodated.

foraccommodatingthe elastic or resilient sup- A non-magnetic strap member 54 extendsacross the bottom conical member 50 .for supporting the central core member 46.

In all of the four forms disclosed the same advantages ar present. substantially exact synchronism with the signal- 1 ing impulses, are produced adjacent the center.

of the air actuator, which has a free outer edge that thus insures against improper movements the core end and may be used in connection with a disk (perforated or solid) such as thin cloth The coil movements in 130 pole pieces 50, 51 joined externally by the tubular incorporated in a mass of phenolic condensation product such as bakelite. This ring may be, inserted in and/or fastened to the small end of the cone and centered over a spacer by any suitable means, such as a screw.

I claim: 1. in a dynamic sound reproducer, means providing a magnetic field in an air gap, said means comprising a pair of magnetic members closely spaced to define the gap, a conductor insaid gap, influenced by signal current impulses, and means for supporting said conductor on one of said roe; iii-SIS whereby relative sliding movement between said supporting means and the conductor is prevented, supporting means being located a groove in the pole face.

2. In a dynamic sound reproducer, means providing a magnetic field in an air gap, said means comprising a pair of magnetic members closely spaced to d fine the gap, a conductor in said gap, influenced by signal current impulses, and means for supporting conductor directly on one of said m mbers and on a surface defining the whereby relative sliding movement between said supporting means and the conductor is prevented, said supporting means being located in a groove in the pole face, and being of 'ielding nature.

In a dynamic sound reproducer, means providing a magnetic field in an air gap, said means comp ing a pair of magnetic members closely spaced to define the gap, a conductor in said gap, influenced by 'gnal current impulses, and means i r suppo ting said conductor directly on one of said members and on a surface defining the gap, whereby relative sliding movement between said supporting means and the conductor is preventsupporting means being located in an groove in the pole face.

in dynamic sound reproducer, means providing a magnetic field in an air gap, said means comprising a pair of magnetic members closely spaced to define the gap, a conductor in said gap, influenced by signal current impulses, and means for supporting said conductor directly on one of said members and on a surface defining the gap, whereby relative sliding movement between said supporting means and the conductor is prevented, said supporting means being located in a groove in the pole face, and being ,of yielding nature, and a free edged actuator mechanically connected to the conductor.

5. In a dynamic sound device, means providing an annular magnetized air gap, a conductor structure insaid gap, for carrying signal current impulses, and means for supporting said structure in said gap so as to restrain motion of the conductor in a direction transverse to the magnetic field, comprising a member of resilient material in said gap permanently joined to the structure. i

6.. In a dynamic sound device, means providing a magnetic field, a conductor in said field for carrying signal current impulses, said means includinga pair of pole pieces defining a gap, and a yielding means for so supporting said conductor on one of said pole pieces thatrelative air actuator operably connected with said structure, said supporting means restraining motion of the structure and actuator to less than one sixty=fourth of an inch.

HERMAN J. FANGER.

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