Wall Surface Transducer System

Abstract

A transducer assembly for mounting on a wall surface or other surface for converting electrical energy to sound or vice versa. The invention is an improvement on prior art devices of similar character in providing improvement in frequency response and truer sound reproduction. The improvement comprising a housing formed from two cup-shaped members whose edges of peripheral joinment are curved surfaces, the curvature of said surfaces being identical, equal, and complementary to each other. Consult the specification for other features and details of the invention.

Description

The present invention relates to a wall surface mounted transducer device and system and more particularly to an improvement in such devices for producing a truer reproduction and more uniform frequency response.

There is presently available sound transducers which do not have the normal paper diaphragm for translating voice coil movements of an acoustical diaphragm or pump. Such devices are mounted upon a wall or other surface by screws and the like devices and couple acoustical energy directly to the wall surface so as to excite or vibrate the wall in accordance with the acoustical energy and thereby produce sound. Fidelity and frequency response of such devices while adequate for some purposes, do not have a true sound reproduction and the frequency responses are not uniform. This lack of fidelity and frequency response is believed to be due, at least in part, to the fact that prior devices utilized housings the coupling walls of which are relatively plain frustums of cones joined base to base, which it is believed introduce distortion in coupling of the translated or transduced energy to the wall surface per se and vice versa. Accordingly, an object of the present invention is to provide a sound transducer which has a truer sound reproduction and more uniform frequency response. A further object of the invention is to provide such a unit for use in connection with a system for remotely exciting wall surfaces utilizing conventional alternating current wiring in a house, for example.

The above and other advantages, features and objects of the present invention will best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1. is a partial cutaway section of a top plan view of a wall surface sound transducer constructed in accordance with the invention;

FIG. 2 is a cross section elevation view taken along the lines 2-2 of FIG. 1;

FIG. 3 is an isometric view of the voice coil of the invention;

FIG. 4 is a partial cross-sectional view showing one mounting arrangement; and

FIG. 5 is a schematic block diagram showing the invention as utilized in conjunction with a system for remotely exciting a plurality of walls using conventional alternating current house wiring.

With reference now to FIGS. 1--3 of the drawings, a sound transducer constructed in accordance with the present invention comprises a molded cup-shaped base member 10, a molded cup-shaped cover member 11, magnet assembly 12 and coil assembly 13, connected by leads 14 to terminals 16 passing through apertures or slots 17 to the exterior of molded base member 10.

Base member 10 and cover member 11 are preferably molded from a polycarbonate resin such as Lexan or nylon, for example. Base cover member 10 has molded integral therewith mounting hub 18 projecting from the axial center of its exterior surface 19. A threaded metal insert 20 is molded in or otherwise secured in a central bore 21 in mounting hub 18. A wall, which it is desired to excite, is prepared by driving a threaded screw (not shown) or otherwise adhering a like threaded member to the wall in projecting relation therefrom and then threading same into threaded insert 20 so that hub end 22 is in snug and flush abutment with the wall surface (see FIG. 4).

On the opposite side of housing 10 from mounting hub 18 is a cylindrical voice coil form or cylinder mounting hub 23 to which the end of voice coil form 24 telescopes over and is secured thereto by an adhesive, such as an epoxy adhesive.

Spaced radially from mounting hub 18 is a thickened portion 19 of base cover member 10 which is annularly shaped and concentrically disposed about hub 18. An outer annular groove 16 and an inner annular groove 27 in effect renders the thickened portion 19 a corrugated structure to afford sufficient flexibility that audio energy being coupled therethrough is substantially undistorted.

Cover member 11 is molded to have an enlarged magnet assembly receiving recess 30 defined by an annular rib 31. The magnet assembly comprises a core 32 having a reduced portion 33 integral therewith and onto reduced shoulder portion 33, keeper washer 34 is force fitted or otherwise secured to form uniform magnetic circuit. A relatively large ferrite magnet 36 is secured by an annular rib 37 of adhesive such as epoxy adhesive (for example) to keeper washer 34 and ferrite magnet 36 has an axial opening or hole 38 which is coaxially centered with magnet core 32. A shim 39 is placed between the shoulder 40 and keeper washer 34. Keeper washer 41 is adhesively secured to ferrite magnet 36 by an epoxy bead 42 and has an opening or hole 43 through which the end of magnet core 32 passes whereby the end 44 of magnet core 32 is flush with the outer surface 46 or keeper washer 41. Aperture or hole 43 and keeper washer 41 is slightly larger than the diameter of core part 32 to permit passage of voice coil assembly 13 into position in the magnetic gap between the walls of hole 43 and the outer surfaces of core member 32. In this way, large magnetic fluxes are concentrated into the gap where the voice coil assembly 13 is located.

Keeper washer 34 is secured in recess 30 by an epoxy adhesive. Magnet assembly 12, being secured by the epoxy securement of keeper washer 34 in the recess or chamber 30, is relatively stationary, the coil form 24 is secured to coil form hub 23 which is opposite to mounting hub 18 so that is moves relative to the magnet assembly 12. Keeper washers 34, 41 and core 32 are galvanized or otherwise coated to reduce hysterisis losses.

An important feature of the invention is in the coupling of relative vibratory movement between the large mass of the magnet assembly 12 and coil assembly 13 to mounting hub 18 in as distortion free a manner as possible. In accordance with the invention, this is accomplished by providing smoothly curved and uniform surfaces between annular rib 30 on cover member 11 to annular rib 50 on base cover member 10. To this end, the outer surface 51 of base member 10 and the outer surface 52 of cover member 11 have a common axis of revolution and are curves generated about a common radius and revolved about a common axis coaxial. In other words, surfaces 51 and 52 constitute a toroidal motion-coupling member for relative translatory movements between magnet assembly 12 and coil assembly 13. Inner surfaces 53 on base cover member 10 and inner surface 54 of cover member 11 have smoothly curved surfaces of equal radius but, as shown, are traced or generated from offset centers so that the thickness of the motion-coupling members gradually increases to the line of jointment 56 between the two members. As shown, to accommodate manufacturing tolerances the edges of the members are beveled as at 56 and have complementary mating surfaces as at 57. An epoxy adhesive, for example is utilized to join the peripheral edges at the complementary mating surfaces. By eliminating any abrupt changes in the motion-coupling sections of base member 10 and cover member 11 a flatter (more uniform) and wider frequency response is achieved and a source of distortion is eliminated.

The voice coil 13 assembly (as well as magnet assembly 12) is of conventional construction in that it comprises an insulating cylinder or form 60 wound with or having secured thereto a conventional voice coil 61 having leads 14 which are held adjacent to insulating cylinder 60 by a tape or other insulating material 62. The end 63 of cylinder 60 is telescopically fitted on shallow hub 23 and secured thereon by adhesive such as an epoxy glue.

The transducer can be mounted on a variety of surfaces, the most common and best including wood, glass, plastic, dry wall, plaster, etc., metal, acoustical tile, or almost any flexible not rigid structure. The unit is preferably not mounted directly over studs, joists, etc., but is preferably mounted between such structural members. While the unit is effective for most surfaces, brick, concrete, or stone surfaces are for the most part too rigid.

It will be appreciated that while the transducer has been described above primarily in connection with producing sound energy as for example where electrical currents corresponding to audio energy are supplied to vice coil 13 which then through the relative translatory movements of magnet assembly 12 and the coupling of such movement via the coupling members described earlier herein to hub 18, excite a wall so the wall serves in effect as an acoustical diaphragm to produce audio energy, the transducer unit of the present invention may also be utilized in converse manner, namely, by connecting a sensitive amplifier to leads 14 of the voice coil assembly the unit may be utilized to detect sounds in a room in which the unit is mounted and thus may serve as a sensor for burglar alarm or other listening system where the transducer constitutes a listening device.

It will also be appreciated that various forms of securement to a wall or other flat planar surface may be effected. For example, a small plate 20P having a screw 20S adapted for threaded engagement with insert 20 (FIG. 4) may have the base there adhesively secured to a glass plate or window wall 20W, for example, and such window wall can then be excited to produce an acoustical output.

The invention is well adapted to excite interior and exterior nonmasonry walls and, being substantially waterproof, is well adapted for outdoor use. Carrier frequency wire-broadcasting systems utilizing conventional power lines within a building for distribution of signals such as audio, radio broadcast signals and stereo systems, alarm systems and the like are well known. FIG. 5 illustrates an adaptation of this system incorporating the transducer of the present invention to remotely excite a wall with acoustic energy. Thus, a program source, such as Hi Fi set 70 supplies an audio output to a mixer-amplifier 71 which receives as a second input (as a carrier frequency) an output from a low frequency crystal oscillator 72 which is modulated by the audio signal from Hi Fi set 70. A coupler 73, which may be a transformer, capacitances, or other known coupling devices, applies the thus modulated carrier signal from oscillator 72 to a pair of conductors 74 having a male plug 76 adapted for insertion in female convenience outlet 77 which may be in a wall in the room having the Hi Fi set 70. A rectifier 78 converts alternating current power delivered thereto from leads or conductors 74 to direct current and supplies same to oscillator 72 and mixer amplifier 71. In this way, which is, per se, conventional, an entire house-wiring system is adapted as a means for coupling the audio output of Hi Fi set 70 to any room in the building, such as a home. Wiring 79, 80, and 81 are conventional alternating current wiring to receptacles 82 and 83, respectively, so that there is presented at each of these convenience outlets 82 and 83 a carrier frequency from oscillator 72 modulated with the audio signal from Hi Fi sets 70. A receiver unit 84 is provided with conventional male plug 86 and conventional wiring 87 and a filter-coupler such as coupler 88, which may be a transformer (not shown) having a filter (not shown) for blocking the 60 cycle alternating current supply. Filter-coupler 88 passes the modulated carrier from oscillator 72 to detector 89 which produces an output corresponding to the audio signal from Hi Fi set 70. This audio signal is then applied to an audio amplifier unit 90 the output of which is applied to transducer 91 constructed in accordance with the invention and mounted upon a wall 92 in the manner illustrated diagrammatically in FIG. 4A. This system may be operated in a stereo system in which there would be a second channel, each channel being transmitted on a different frequency, respectively, and coupled to house wiring 79 in the manner diagrammatically illustrated in FIG. 5. The modulated RF output coupled to house wiring 79 to convenience outlets 82 and 83, for example, is extracted by a simple plugging in a male plug 86 at any such convenience outlet and then capacitively coupled through a filter unit 88 to detector 89 (which may be a tuned RF detector), the output of which is applied to an audio amplifier 90 which in turn applies the audio signal to transducer 91 to excite the wall with acoustic energy as described herein. For the stereo system, a second transducer may be mounted on the wall in spaced relation from the first transducer to effect stereo reproduction. In this case, of course, audio source 70 would be a stereo Hi Fi set, a stereo receiver, or a stereo public address system, it being understood that at each output of the stereo audio unit 70 is frequency translated a different frequency for coupling to the house wiring 79.

As diagrammatically illustrated in FIG. 5, since the entire house wiring is a conductor for the modulated carrier signals, units may be excited remotely in any room of the structure building or home simply by providing a second unit such as shown in the lower left-hand corner of FIG. 5.

While a preferred embodiment of the invention has been shown and described, it is to be understood that the invention is susceptible to use in many systems, some of which have been referred to above and with various modifications within the scope of the appended claims.

Claims

I claim:

1. In a surface-mounted transducer device wherein an annular magnet assembly has positioned for axial movement in an annular air gap therein a coil adapted to be connected to electrical terminals, and a housing having a first cup-shaped member to which said annular magnet assembly is secured and the second cup-shaped member to which said coil is secured, said cup-shaped members having substantially flat planar parallel surfaces, said cup-shaped members being joined along the peripheral edges thereof, said second cup-shaped member having a single securement point coaxial with said coil and spaced from the outer surface of said second cup member and secured to an engaging transducer mounting surface, the improvement comprising surfaces of said cup-shaped members leading to said edges of peripheral joinment being curved surfaces, the curvature of said surfaces being identical, equal and complementary to each other.

2. The invention defined in claim 1, wherein the radius curvature of said surfaces is about a fixed axis common to both said surfaces.

3. The invention defined in claim 2, wherein the radius of curvature of both surfaces is about a common fixed surface and surfaces formed thereby having a common axis of revolution.

4. The invention defined in claim 1, wherein the said cup-shaped members have gradually increasing thicknesses along said curved surface portions to said point of joinment.