GB2130843A - Electro-acoustic transducer and adaptor therefor - Google Patents

Abstract

A telephone transducer 10, 11 has a lip or flange 12 that seats in a clamping ring 14 of an adaptor. A body 20 of the adaptor has a peripheral formation 26 that locates against the front face 11 of the transducer 10, 11 and a flange 22 that engages into the clamping ring 14 to retain the transducer 10, 11 therebetween. The body 20 is formed with through holes defining an acoustic reactance that leads to a cavity 25 between the body 20 and the front face 11. The adaptor enables a 3T telephone transducer to fit into the space of and match the acoustic properties of a 4T telephone transducer. <IMAGE>

Description

SPECIFICATION Electro-acoustic transducer and adaptor therefor The present invention relates to a combined electro-acoustic transducer and adaptor therefor which is particularly intended to convert a 3T telephone transducer so that it can replace a 4T telephone transducer.

Broadly stated the invention provides the combination of an acoustic transducer including a casing having a front face through which sound enters and a circumferential lip of flange bounding the front face with an adaptor comprising a clamping ring formed with an internal seat on which the flange locates and a body that has a peripheral formation that locates against the front face and a formation that engages with a mating formation on the clamping ring to retain the transducer therebetween, the body being formed with through holes defining an acoustic reactance leading to a cavity between the body and the front face that defines an acoustic inertance whereby the transducer will both fit mechanically in a space intended for a transducer of larger size and match the acoustic properties thereof.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a partly sectioned side view of an adaptor for converting a 3T telephone transducer to fit receptacles that take a 4T telephone transducer; and Figure 2 is a view of the adaptor in plan.

In the drawings, a telephone transducer 3T has a body 10 and a cover 11 that fits over the body and defines therewith a circumferential locating lip or flange 1 2. An adaptor clamping ring 14 is internally profiled at 16 to define a seat on which the flange 14 locates so that the lower portion of the flange 12 as viewed in Figure 1 sits in the seat 1 6 as shown. Beyond the seat 16 the clamping ring 14 is out-turned and then up-turned to define an upstanding rim 18 spaced from the flange 12.

An adaptor body 20 has a depending flange 22 that fits between the flange 1 2 and the upstanding rim 18 so that the adaptor body is held in position, and on its inner face, just within the flange 22, is formed with a circumferential land 26 that locates on the periphery of the top face of the cover 11 and limits the travel of the body 20 towards the cover 11 so that the remainder of the cover 11 has a small clearance from the body 20. The cover 11 is formed centrally with six through-holes 24 disposed in a circle concentric with the cover 11 and leading to a cavity 25 defined between the cover 11 and a recessed central region of the inner face of the adaptor body 20.

The adaptor described above not only matches the physical dimensions of the 3T telephone adaptor to those of the 4T transducer but also matches their acoustic properties. The throughholes 24 act as an acoustic reactance and the cavity 26 acts as an inertance, the two together constituting an acoustic converter effective in the frequency range 2.8 to 3.4 kHz with a high frequency cut off at 3.4 kHz.

It will be appreciated that the body 20 and clamping ring 14 can readily be made out of plastics by injection moulding and that the adaptor is rapidly assembled about the transducer since the body is a simple push fit in the clamping ring. Furthermore the force applied to the rim when the transducer and adaptor are installed in a telephone handset aids in keeping the adaptor clamp 14 and body 20 together and tends to prevent them coming apart when subjected to mechanical shock, e.g. if the handset is dropped.

Claims

1. The combination of an acoustic transducer including a casing having a front face 11 through which sound enters and a circumferential lip or flange 12 bounding the front face 11 with an adaptor comprising a clamping ring 14 formed with an internal seat 16 on which the flange 12 locates and a body 20 that has a peripheral formation 26 that locates against the front face 11 and a formation 22 that engages with a mating formation 18 on the clamping ring 14 to retain the transducer therebetween, the body 20 being formed with through holes defining an acoustic reactance leading to a cavity 25 between the body 20 and the front face 11 that defines an acoustic inertance whereby the transducer will both fit mechanically in a space intended for a transducer of larger size and match the acoustic properties thereof.

2. The combination as claimed in claim 1, wherein the body 20 is formed with a depending circumferential flange 22 that is a push fit with an upstanding rim 18 on the clamping ring 14.

3. The combination of claim 1 or 2, wherein the clamping ring 14 and the body 20 are injection mouldings in a plastics material.

4. The combination of an electro-acoustic transducer with a mechanical and acoustic adaptor substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electro-acoustic transducer and adaptor therefor The present invention relates to a combined electro-acoustic transducer and adaptor therefor which is particularly intended to convert a 3T telephone transducer so that it can replace a 4T telephone transducer. Broadly stated the invention provides the combination of an acoustic transducer including a casing having a front face through which sound enters and a circumferential lip of flange bounding the front face with an adaptor comprising a clamping ring formed with an internal seat on which the flange locates and a body that has a peripheral formation that locates against the front face and a formation that engages with a mating formation on the clamping ring to retain the transducer therebetween, the body being formed with through holes defining an acoustic reactance leading to a cavity between the body and the front face that defines an acoustic inertance whereby the transducer will both fit mechanically in a space intended for a transducer of larger size and match the acoustic properties thereof. An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a partly sectioned side view of an adaptor for converting a 3T telephone transducer to fit receptacles that take a 4T telephone transducer; and Figure 2 is a view of the adaptor in plan. In the drawings, a telephone transducer 3T has a body 10 and a cover 11 that fits over the body and defines therewith a circumferential locating lip or flange 1 2. An adaptor clamping ring 14 is internally profiled at 16 to define a seat on which the flange 14 locates so that the lower portion of the flange 12 as viewed in Figure 1 sits in the seat 1 6 as shown. Beyond the seat 16 the clamping ring 14 is out-turned and then up-turned to define an upstanding rim 18 spaced from the flange 12. An adaptor body 20 has a depending flange 22 that fits between the flange 1 2 and the upstanding rim 18 so that the adaptor body is held in position, and on its inner face, just within the flange 22, is formed with a circumferential land 26 that locates on the periphery of the top face of the cover 11 and limits the travel of the body 20 towards the cover 11 so that the remainder of the cover 11 has a small clearance from the body 20. The cover 11 is formed centrally with six through-holes 24 disposed in a circle concentric with the cover 11 and leading to a cavity 25 defined between the cover 11 and a recessed central region of the inner face of the adaptor body 20. The adaptor described above not only matches the physical dimensions of the 3T telephone adaptor to those of the 4T transducer but also matches their acoustic properties. The throughholes 24 act as an acoustic reactance and the cavity 26 acts as an inertance, the two together constituting an acoustic converter effective in the frequency range 2.8 to 3.4 kHz with a high frequency cut off at 3.4 kHz. It will be appreciated that the body 20 and clamping ring 14 can readily be made out of plastics by injection moulding and that the adaptor is rapidly assembled about the transducer since the body is a simple push fit in the clamping ring. Furthermore the force applied to the rim when the transducer and adaptor are installed in a telephone handset aids in keeping the adaptor clamp 14 and body 20 together and tends to prevent them coming apart when subjected to mechanical shock, e.g. if the handset is dropped. Claims

1. The combination of an acoustic transducer including a casing having a front face 11 through which sound enters and a circumferential lip or flange 12 bounding the front face 11 with an adaptor comprising a clamping ring 14 formed with an internal seat 16 on which the flange 12 locates and a body 20 that has a peripheral formation 26 that locates against the front face 11 and a formation 22 that engages with a mating formation 18 on the clamping ring 14 to retain the transducer therebetween, the body 20 being formed with through holes defining an acoustic reactance leading to a cavity 25 between the body 20 and the front face 11 that defines an acoustic inertance whereby the transducer will both fit mechanically in a space intended for a transducer of larger size and match the acoustic properties thereof.

2. The combination as claimed in claim 1, wherein the body 20 is formed with a depending circumferential flange 22 that is a push fit with an upstanding rim 18 on the clamping ring 14.

3. The combination of claim 1 or 2, wherein the clamping ring 14 and the body 20 are injection mouldings in a plastics material.

4. The combination of an electro-acoustic transducer with a mechanical and acoustic adaptor substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.