NZ238050A

NZ238050A - Piezo-electric transducer telephone tone sounder

Info

Publication number: NZ238050A
Application number: NZ23805091A
Authority: NZ
Inventors: Avolio Antonio D; Luigi Pesenti
Original assignee: Alcatel Australia
Priority date: 1991-05-03
Filing date: 1991-05-03
Publication date: 1993-07-27

Description

<div id="description" class="application article clearfix"> IU. g °K: ( m-- s i"io 2 3 8 0 5 0 3> s I r- 27 JUL 1993 i"2rto ORIGINAL ["changf ( NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION O-ELECTRIC TRANSDUCER ARRANGEMENT" WE.-4-T.ANDARD TELEPHONES AND GABLES PTY. LIMITED,~ A Company of the Stale of New Sou I h Wales, of 252-280 Botany Road, Alexandria, New South Wales, 2015, Australia, hereby dcclarc the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: I 1 his invention relates to an electro-acousiic transducer of the piezo-ceramic type, which is suitable for use as a piezo-ceramic receiver capsule or as a lone caller in telephone instruments. Piezo-ceramic transducers currently used in telephone instruments comprise essentially a transducer diaphragm, maintained peripherally in position in a cavity between a bottom of the ease with one wall perforated in order to allow the transmission of sound and a cover to which terminals lor external electrical connection arc applied. The electric connection between the diaphragm and these terminals is established either by means of thin wires or extensions of the terminals themselves both soldered on the poles of the diaphragm. Soldering on the diaphragm causes drawbacks. In fact, the solder joints on the ceramic layer often detach: moreover, efficiency problems may arise since the soklerings arc not perfectly equal in all the pieces of a production scries and the efficiency is not constant: last, but not least, costs are high. In oiiler to avoid soldering on the diaphragm several methods are known. One of these methods comptises a telephone transducer with a piczo-cIccLric unit in which the electrical connections to the diaphragm arc established through two spring contact terminals of dutch metal bronze which arc arranged in such a way as to apply pressure, one on the annular portion of the diaphragm substrate and one on the ceramic layer covering the central portion of the substrate. With stiuctures like that the soldering of the diaphragm becomes unnecessary; however, they arc not free from drawbacks. First of all the connection members manufactured by punching and bending from a matrix of rolled material, do not allow a constant contact pressure on the diaphragm bccausc of manufacturing tolerances, and this creates problems of efficiency for the diaphragm. Morcoxcr. the bends could change their angulaiity during the assembling of the unit: the springs require adjusting and consequently the connection members which cannot be forced into the terminal fitting holes of the bottom require a succcssivc scaling of such holes in order to avoid the leakage of the unit. Further, the spring contact on the ceramics applies pressure on the inner area of the diaphragm and this worsens the situation. Another known method comprises a piczo-clcctric acoustic transducer in which a piczo-clcctric vibrator is constituted of a unimorphic vibrator where a piczo-clcctric 2-16 0 5 0 ccnwnic element is bonded to a metallic plate and arranged so that the side of the element will point the opening side of a case. A support ring is formed by an insulating part and a conductive part and a spring terminal is fitted to a notch. The terminal consists of a contact part and a fitting part formed with a spring material and temporarily fixed after a folding piece of the fitting part is fitted in an unnotched thin part of the insulating part. A clamping film is applied to copper foil patterns of a cmcr. External terminals arc inserted into terminal fitting holes of the co\cr and connected to the coppcr foils respectively. Also with this solution soldering on the diaphragm becomes unnecessary: nevertheless it is still not free from drawbacks sincc it uses spring terminals. Moreover, the contact between the ceramics and the corresponding terminals is established at the inner zone of the diaphragm which is not allowed to \ibratc freely. It is therefore an object of the present invention to provide a piczo-clcctric transducer which is not subject to the same deficiencies of the aforementioned prior art transducers. Another object of the present invention is to provide a piczo-clcctric transducer of simplified and economical construction. In order that the invention may be readily carried into effcct, embodiments thereof will now be described in relation to the drawings, in which: Figure 1 is a perspective exploded view of a piezo-ceramic transducer adapted as a piezo-ceramic rcceivcr capsule in a telephone instrument receiver arrangement according to the present invention: Figure 2 shows the transducer of Figure I where the case is formed directly on the bottom of the handset housing, and Figure 3 shows a piezo-ceramic transducer adapted as a tone caller in a telephone subset. Referring to Figure 1. a case 1 houses an elastic element 2, a piezo-ceramic transducer diaphragm 3 and a bottom base 4 which carries the contacts 5, 6, 7 accessible from outside. The case I. made of insulating material, is realised by molding. In an embodiment particularly advantageous it can be molded dircctly on the bottom of the handset housing thus further lowering costs of the transducer. Preferably the case has a circular section and the cover wall is provided with openings S for the transmission of acoustic waves generated by the vibrations of 3 8 0 5 diaphragm 3. Inside on the cover wall, is a circular rib delimiting an annular housing 9 for the elastic element 2 and which is provided optionally with a reference tooth 1 3 that engages in a corresponding notch (not shown in the figure) provided on the inner end of the base 4. 5 At the upper end of the inner wall of the case is an annular stop tooth 14 designed to snap on the upper edge of the bottom base 4. The piezo-ceramic diaphragm 3 is of composite type and consists of a metallic discoid plate 1 1 having a central portion of one of its sides covered, in a known and conventional manner, with a piezo-ceramic element 12 plated on its free surface with a 10 layer of conductive material. The piezo-ceramic element is provided with a terminal area 10 which extends through the circular annulus and forms a pole of the vibrator while the other pole is formed by the remaining annulus portion 11a not covered by the ceramic layer. The elastic element 2 consists preferably of an O-ring of elastomeric material 15 which assures a uniform elastic coupling contact between terminals 5, 6 and the diaphragm poles 10, 11 a respectively. The capsule bottom base 4 consists of a circular spool of insulating material provided with two through holes extending axially and located at diametrically opposite positions and at a distance which is comprised between the diameter of the ceramic 20 element 1 2 and the diameter of the metallic plate 11. Two feedthrough terminals (5, 6) are forced into said through holes and constitute the contacts accessible from outside. Advantageously such terminals have a nail-shaped configuration and are made of plated (eg. silverplated) metal. The nail heads abut from one side on the end face of the 25 spool and from the other on the diaphragm 3 when the transducer is assembled. A through-hole 16 axially extending is designed to realise damping microleaks of diaphragm 3. Figure 3 illustrates an embodiment in which the transducer is used as a ringer in a telephone subset. In it a case 1' houses the elastic element 2, the piezo-ceramic 30 transducer diaphragm 3 and a bottom base 4' which carries the contacts 5, 6 accessible from outside. The case 1' is of plastic material and consists of two cylindrical, coaxial and adjacent portions of different diameters. The lower diameter portion is closed at one end by an end-wall having an opening 8' for transmission of acoustic waves generated 4 n JUN1993.; 238 050 by ilie \ibrations of the diaphragm 3. Inside the free end of lhe greater diameter portion is an annular tooth 14' designed to snap on the bottom base 4'. Both the portions define, at the inner interface zone, an annular housing 9' for fthc clastic element 2, which besides assuring the uniform clastic coupling contact between terminals 5. 6 antl diaphragm poles 10, I I, pro\idcs for scaling in order to a\oitl leakage of the transducer. On the annular step outside the case are two bosses 19 provided with holes 20 for fixing the transducer to the frame of the telephone subset. The assembly of the transducer is carried out in a \cry simple manner. After the 10 positioning of the elastic element 2 inside the annular housing 9. 9', the diaphragm 3 is laid down thereon with the ceramic clement 12 pointing the opening side of the case 1.1' (the correct orientation of pole 10 is determined automatically by the machine which performs the positioning of the diaphragm). Thereafter the bottom base assembly 4. 4' is positioned with the terminal heads 15 pointing the diaphragm and pushed in. ill lis compressing the elastic clement 2 until the annular tooth 14. 14' snaps on the base 4. 4'. In such a way the heads of terminals 5 and 6 make an ohmic contact respectively with the poles 10 and 11 of diaphragm 3. whilst the clastic reaction of the clement 2 assures a uniform clastic coupling for maintaining such ohmic contact. 20 The operation of the piezo-ceramic transducer is well known to those skilled in the art and therefore will not be described here. Thus the imcntion acliie\cs the above mentioned objects. The piezo-ceramic transducer according to the present invention besides eliminating all the drawbacks of the prior art transducers is very easy to manufacture and 25 assemble with rcduccd costs as compared with those of conventional piezo-ceramic transducers. This is due to the fact thai spring shaped terminals have been eliminated. While the imcntion has been described with reference to specific embodiments thereof, it should be noted that it is capable of several modifications and variations 30 all falling within the sphere of the invcnti\c concept. For instance, the bottom base 4 of the transducer when used as a piezo-ceramic receive capsule may be provided with a circumferential groove along the lateral surface for housing a coil 1.5 electrically connected to the terminal 6 contacting the metallic plate 11 and to a third terminal 7 provided on the end of the spool 4 and also 5 2 i ft o acccssiblc from outside, said coil 15 being designed to generate an auxiliary magnetic field which may influence the deaf prothesis. Notchcs 17, 18 arc suitably provided on the base 4 for the passage of the coil leads to terminals 6, 7. </div>

Claims

<div id="claims" class="application article clearfix printTableText"> 23 8 0 ' 0 What we claim is:

1. A piezo-electric transducer comprising a piezo-ceramic transducing diaphragm comprising a metallic support plate, a piezo-ceramic element and two contact areas forming two poles of said diaphragm and being located on the same side of the support 5 plate, said diaphragm being supported about its periphery between an elastic element in a perforated case and a bottom base, said bottom base carrying a pair of feedthrough terminals each having a contact on one end in abutment with a respective contact area of said diaphragm, and the other end connectable from the exterior of the transducer, and wherein the electric connections between the diaphragm and the contacts are 10 maintained by the contact pressure produced by the action of said elastic element.

2. A transducer as claimed in claim 1, wherein said feed-through terminals comprise nail-shaped metallic pins forced into respective through-holes axially extending in said bottom base, so that the nail-head is in abutment on the inner end surface of the bottom base from one side and a contact area in a peripheral position of the diaphragm 15 from the other side.

3. A transducer as claimed in any one of the preceding claims, wherein said perforated case at its open end is provided with an annular tooth configured to snap on the upper end of the bottom base when the latter is placed into said case and pushed in. 20

4. A transducer as claimed in any one of the preceding claims, wherein said elastic element is an O-ring made of elastomeric material and located inside an annular housing formed inside the perforated case.

5. A transducer as claimed in claim 1 or 2, wherein said bottom base comprises a circular spool provided with a further contact electrically connectable from the exterior 25 of the transducer and with a circumferential groove housing a metallic wire winding t 1 JUN ]993~ >. ■> ' 0 r, V. 23 8 0 whose leads are connected to said further contact and to that one of said feed-through terminals which is in contact with the metallic support plate.

6. A transducer as claimed in claim 5, wherein said spool and said perforated case are provided with reference elements which engage each other for the correct positioning of the spool into the perforated case.

7. A transducer as claimed in any one of the preceding claims, wherein said case is integrally formed with a telephone handset housing.

8. A piezo-electric transducer substantially as herein described with reference to Figures 1 - 3 of the accompanying drawings. ALCATEL (S I ICTDAI IA I l«/l!TCn P.M. Conrick Authorized Agent P5/1/1703 O 8 </div>