GB2386028A

GB2386028A - Audio speaker for telephone handset

Info

Publication number: GB2386028A
Application number: GB0204948A
Authority: GB
Inventors: Tony Schultz
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2002-03-02
Filing date: 2002-03-02
Publication date: 2003-09-03
Also published as: GB0204948D0

Abstract

A loudspeaker for a telephone handset, especially a mobile phone (1), includes a piezoelectric disc resonator 13 (eg PZT) which is fitted to a vibratable membrane 9. The membrane 9 serves both as pad of the loudspeaker and as a rain resistant cover for the region occupied by the loudspeaker. The membrane may be moulded integrally with the phone casing or may be a separate sheet fitted to the casing (3). The thickness of membrane is selected to suit the required frequency range of the loudspeaker. The membrane may include a mesa shaped portion 11, and also resilient protrusions 19 which allow the resonator 13 to be snap fitted into position against the membrane. A plastic grill 27 provides mechanical protection for the membrane.

Description

TITLE: AUDIO SPEAKERS FIELD OF THE INVENTION The present invention relates to audio speakers, particularly for telephone handset units.

BACKGROUND OF THE INVENTION Telephone handset units include a transducer known as a speaker which converts electrical signals representing speech of a distant person into audio signals which are a reproduction of the distant person's speech.

Conventionally, the speaker used comprises an electromagnetic transducer device attached to a metal cone which emits audio signals corresponding to vibrations of the transducer unit.

Where the handset unit is a portable or mobile telephone it may be subjected to various unfriendly environmental conditions when carried by a user. One particular condition which can cause severe operational difficulties is the presence of water, e. g. when the handset unit is being carried in heavy rain. Such water can enter the interior of the handset unit via the speaker and can thereby disable or even destroy the inner working components of the handset unit.

SUMMARY OF THE PRESENT INVENTION According to the present invention in a first aspect there is provided an audio speaker for a telephone handset

unit comprising a n electro-acoustic resonator and a vibratable membrane acoustically coupled to and in operation vibrated by the resonator to provide audio signal emissions, wherein the membrane is in the form of a sheet adapted to provide a cover for a region occupied by the speaker when the speaker is fitted in a telephone handset unit and the resonator comprises a body having a face fitted against a surface of the membrane.

According to the present invention in a second aspect there is provided a telephone handset unit including a casing and incorporating a speaker according to the first aspect, wherein the membrane of the speaker forms part of the casing. The membrane may conveniently be formed integrally as part of the casing, although it may alternatively be formed as a separate sheet which can be fitted to the casing to form a part thereof. In both cases, the membrane desirably forms a waterprooof cover for the region inside the casing occupied by the speaker. The handset according to the second aspect may for example comprise a portable or mobile radio telephone unit.

The membrane and casing of the handset unit according to the second aspect may be made of the same material. Such a material is desirably a strong, resilient and impervious material which can be formed into a membrane of suitable dimensions by an appropriate shaping process. The material may comprise a mouldable, thermoplastics material such as a polycarbonate composition. Thus, the handset unit cover may be a moulded thermoplastics product which includes a region of reduced thickness which forms the said membrane.

The membrane may be substantially flat when the speaker is not in operation. The thickness of the membrane may be selected by experimental design to suit the

frequency range of the audio signals to be produced by the speaker.

In a preferred embodiment of the invention, the membrane may have one or more, e. g. at leat two, formations on its inner surface adapted to receive and grip the resonator. Such formations may include protrusions each having a recess or groove in which an edge of the resonator fits. The resonator may comprise a plate or disc. The formations adapted to receive the resonator may conveniently include resilient bendable members which conveniently allow the resonator to be snap fitted in position against the membrane. The membrane may include a mesa shaped portion providing an inwardly facing surface against which a corresponding face of the resonator may be applied.

The resonator may be a known electro-acoustic transducer, e. g. comprising a piezoelectric material, e. g. a ceramic composition, which may be formed into a suitable disc shape. Any of the materials known for use in piezoelectric devices may be used. For example, the material may be the known materal lead zirconate titanate (PZT) optionally compounded or alloyed with one or more other elements as known in the art. Electrodes to provide an input electical signal which may be applied as a voltage across the resonator may be deposited on the rear face of the resonator, i. e. the face opposite to that applied against the membrane. The electrodes may for example comprise nickel plated on the ceramic material and silver coated on top of the nickel. Such known electrodes facilitate the attachment of external electrical connections, e. g. by soldering. The electrodes may be in

the form of an annulus formed concentrically around a disc or any other suitable shapes.

A lightweight grill, e. g. made of a lightweight moulded plastics material, may be provided on the handset according to the second aspect to fit against the outer surface of the membrane, i. e. that opposite to the surface against which the resonator is fitted. The grill may provide a decorative effect to the handset as well as providing mechanical protection for the membrane.

The speaker according to the first aspect of the present invention solves the problem experienced with telephone handsets incorporating prior art speakers of ingress of water through the speaker. The speaker according to the invention can be fitted to a handset unit, e. g. a portable radio telephone unit, to provide a watertight cover for the handset. The speaker according to the invention may be manufactured in a more compact form than conventional telephone handst speakers. The speaker is also simple to assemble and can be manufacured more cheaply than conventional speakers. Furthermore, the speaker according to the invention has a versatile shape and can be fitted in any suitable part of the handset casing.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 is a front elevation of a mobile radio telephone handset incorporating a speaker embodying the invention.

Figure 2 is a cross-sectional end elevation of the handset shown in Figure 1, the cross section being taken on a plane defined by the line A-A shown in Figure 1.

Figure 3 is an enlarged version showing more detail of part (labelled B in Figure 2) of the cross-sectional end elevation of the handset shown in Figure 2.

Figure 4 is an enlarged perspective view of the speaker of the handset shown in Figures 1 to 3 as viewed from the inside of the handset.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION As shown in Figures 1 and 2, a portable radio telephone handset unit 1 includes a casing 3 including a speaker 5 and a window 7 for a display. The unit 1 will also include operational circuitry provided on one or more printed circuit boards, a battery, a keypad for entry of telephone numbers and control function signals, a microphone and an antenna all of which may be constructed and operated in a conventional manner. For simplicity, these components are not shown in the drawings.

The casing 3 of the unit 1 is a moulded product formed of a tough, resilient thermoplastics material. In the region of the speaker 5, the casing 3 comprises a thin membrane 9 as shown in Figure 3. The membrane 9 includes a mesa shaped portion 11 providing an inwardly facing surface against which is fitted a piezoelectric resonator disc 13.

The resonator disc 13 is snap-fitted and gripped in position by a ring of formations 15 provided on the inner surface of the membrane 9 around the mesa shaped portion 11. As best seen in Figure 4, the formations 15 which are projections formed integrally with the membrane 9 comprise

four location ridges 17 and four clips 19 alternating in a ring structure. The resonator disc 13 is located in position by the ridges 17 and gripped in position by the clips 19. The clips 19 are resilient, bendable members each providing a recess 20 in which an edge of the resonator disc 13 is located by snap fitting. A disc 21 made of silver on nickel is plated on the ceramic piezoelectric material of the resonator disc 13 on the inner face of the resonator disc 13 and a concentric annulus 22 also of silver on nickel is also plated on the same face around the disc 21 but isolated therefrom. Conducting leads 23 and 25 are attached by soldering to the annulus 22 and sic 21 respectively.

In operation, electrical signals from the receiver circuitry (not shown) of the handset unit 1 are applied via the leads 23 and 25 as varying voltages applied to the resonator disc 13. The resonator disc 13 produces corresponding vibrations by the piezoelectric effect. These vibrations are acoustically coupled to the membrane 9 which vibrates to provide output audible information, e. g. reproduced speech of a person in a remote location operating another telephone unit in radio communication with the unit 1.

The region of the casing 3 in which the speaker is provided is covered by a lightweight grill 27 for decorative effect and to provide some mechanical protection to the membrane.

Claims

CLAIMS 1. An audio speaker for a telephone handset unit comprising an electro-acoustic resonator and a vibratable membrane acoustically coupled to and in operation vibrated by the resonator to provide audio signal emissions, wherein the membrane is in the form of a sheet adapted to provide a cover for a region occupied by the speaker when the speaker is fitted in a telephone handset unit and the resonator comprises a body having a face fitted against a surface of the membrane.
2. An audio speaker according to claim 1 wherein the membrane is substantially flat on its outer surface when the speaker is not in operation.
3. An audio speaker according to claim 1 or claim 2 and wherein the thickness of the membrane is selected by experimental design to suit the frequency range of the audio signals to be produced by the speaker.
4. An audio speaker according to claim 1, claim 2 or claim 3 and wherein the membrane has one or more formations adapted to receive and grip the resonator.
5. An audio speaker according to claim 4 wherein the membrane includes formations which comprise protrusions on its inner surface, one or more of the protrusions having a recess or groove in which an edge of the resonator fits.
6. An audio speaker according to claim 4 or claim 5 wherein the formations adapted to receive the resonator include one or more resilient bendable members which allow the resonator to be snap-fitted in position against the membrane.
7. An audio speaker according to claim 5 or claim 6 and wherein the resonator comprises a plate or disc and the

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formations comprise a ring of formations comprising location ridges alternating with protruding clips providing recesses to receive an edge of the resonator.
8. An audio speaker according to any one of the preceding claims wherein the membrane includes a mesa shaped portion providing an inwardly facing surface against which a corresponding face of the resonator is applied.
9. An audio speaker according to any one of the preceding claims wherein the resonator comprises a piezoeletic transducer disc.
10. An audio speaker according to claim 9 and wherein electrodes are deposited on the transducer disc.
11. An audio speaker according to claim 10 and wherein the electrodes comprise silver on nickel platings.
12. An audio speaker according to claim 9 or claim 10 and wherein the electrodes comprise a disc and an annulus formed around the disc on an inner face of the transducer disc.
13. A telephone handset unit including a casing and incorporating a speaker according to any one of the preceding claims wherein the membrane of the speaker forms part of the casing.
14. A telephone handset unit according to claim 13 and wherein the membrane is formed integrally as part of the casing.
15. A telephone handset unit according to claim 14 and wherein the casing including the membrane is formed of a moulded thermoplastics material.
16. A telephone handset unit according to claim 13 and wherein the membrane is formed as a separate sheet which is fitted to the casing to form a part thereof.

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17. A telephone handset unit according to any one of claims 13 to 16 wherein the membrane forms a waterprooof cover for the region inside the casing occupied by the speaker.
18. A telephone handset unit according to any one of claims claims 13 to 16 and wherein a lightweight grill is provided on the handset to fit against an outer surface of the membrane.
19. A telephone handset unit according to any one of claims 13 to 18 and wherein the unit comprises a portable radio telephone unit.
20. A speaker according to any one of claims 1 to 12 and substantially as described herein with reference to the accompanying drawings.
21. A telephone handset unit according to any one of claims 13 to 19 and substantially as described herein with reference to the accompanying drawings.