EP0943224B1 - Electroacoustic transducer comprising spring contacts formed with at least one bend - Google Patents

Description

The invention relates to an electroacoustic transducer comprising asubstantially hollow cylindrical magnet system which is substantially centro-symmetrical withrespect to a transducer axis, a diaphragm which is capable of vibrating in thedirection of the transducer axis, a voice coil which is connected to thediaphragm, which has been wound from coil wire, and which has two coil leads, andtwo contact terminals which, viewed in the direction of the transducer axis, aredisposed inside the substantially hollow cylindrical magnet system and which are eachconnected to one coil lead.

An electroacoustic transducer of the type defined in the opening paragraphis known from thedocument DE 25 03 828 C3. In this known transducer the two contactterminals are formed by two contact pins which extend through the bottom wall of a pot-shapedsupporting element and which are mechanically fastened to this bottom wall, as aresult of which the contact faces formed by the contact tips of the contact pins areimmovable, i.e. stationary. However, an undesirable consequence of this is that when aknown transducer is mounted in an electroacoustic device the two contact pins should enterinto operative engagement either with resilient mating contacts or with stationary matingcontacts which have been positioned very accurately with respect to the contact tips, in orderto assure proper contact between the contact tips of the contact pins and the mating contacts.In the known transducer the two contact pins have exactly equal radial distances from thetransducer axis, as a result of which the known transducer cannot be mounted or built into anelectroacoustic device in an arbitrary relative position because the contact pins do not enterinto operative engagement with the mating contacts provided in the relevant electroacousticdevice in the case of an incorrect relative position; this makes it more expensive to mount theknown transducer.

It is an object of the invention to preclude the above-mentioned problemsand to provide an improved transducer of the type defined in the opening paragraph. Toachieve this object, according to the invention, an electrodynamic transducer of the type defined in the opening paragraph is characterized in that the contact terminals are formed byspring contacts formed with at least one bend, which spring contacts have at least two limbswhich extend transversely to the transducer axis and which each have a first limbmechanically connected to a part of the transducer, and which each have a second limbhaving contact faces for engagement with mating contacts and whose contact faces aremovable substantially parallel to the transducer axis, and the contact faces of both springcontacts have different radial distances from the transducer axis. The construction of thecontact terminals as spring contacts having at least one bend and having contact faces whichare movable substantially parallel to the transducer axis ensures that contact faces of thespring contacts always engage properly with the mating contacts of an electroacoustic device,while dimensional tolerances can be substantially ignored. It is to be noted that according to the invention it isparticularly advantageous that the spring contacts have at least one bend and the limbs of thespring contacts extend transversely to the transducer axis, because in this way theconstruction of the spring contacts and, as a consequence, of the entire transducer is alsovery compact in radial directions. The construction of the spring contacts with at least onebend further has the advantage that it is possible to accommodate both spring contacts almostwholly inside the hollow cylindrical magnet system. Besides, owing to the measure that in atransducer in accordance with the invention both spring contacts have different radialdistances from the transducer axis, it is achieved in a simple manner that a transducer inaccordance with the invention can be mounted in any desired relative position in anelectroacoustic device in which the contacts adapted to mate with the spring contacts areannular and coaxial with the transducer axis, i.e. the transducer need not be brought into agiven relative position, which has the advantage that mounting of the transducer in such adevice can be as simply as possible.

In a transducer in accordance with the invention it has proved to beadvantageous if the first limbs of the spring contacts formed with at least one bend aremechanically connected to a bottom wall of a substantially pot-shaped contact holder which ismounted in a hollow cylindrical part of the magnet system with its hollow cylindricalcircumferential wall. This is advantageous for a simple mounting of the spring contacts in atransducer in accordance with the invention.

In a transducer in accordance with the invention it has further proved tobe very advantageous if the two spring contacts formed with at least one bend are disposed atleast for the greater part inside the substantially hollow cylindrical magnet system, alsoviewed in a direction transverse to the transducer axis. In this way, the dimension of a transducer in accordance with the invention can also be particularly small in the direction ofthe transducer axis.

In a transducer as defined in the preceding paragraph the spring contactscan be situated wholly inside the substantially hollow cylindrical magnet system, viewed in adirection perpendicular to the transducer axis. However, it has proved to be veryadvantageous if the contact faces of the two spring contacts formed with at least one bend aredisposed outside the substantially hollow cylindrical magnet system, viewed in a directiontransverse to the transducer axis. This is advantageous for an as simple as possibleengagement of the spring contacts with mating contacts of an electroacoustic device when atransducer in accordance with the invention is mounted in such an electroacoustic device.

In all the above-mentioned variants of a transducer in accordance with theinvention the spring contacts can be formed with two bends, i.e. essentially S-shaped. Aconstruction with more bends is also possible. However, it has proved to be veryadvantageous if the two spring contacts are formed with only one bend and, as aconsequence, are substantially U-shaped. This is a satisfactory compromise between acompact construction and a gentle spring characteristic.

All the above-mentioned variants of a transducer in accordance with theinvention are characterized in that the value of the outer diameter of the transducer is at themost 20.0 mm. These transducers consequently have a particularly compact construction.

The above-mentioned as well as further aspects of the invention willbecome apparent from the embodiment described hereinafter by way of example and will beelucidated by means of this embodiment.

The invention will now be described in more detail with reference to thedrawing, which shows an embodiment to which the invention is not limited.

Figure 1 is an underneath view taken at the arrow I in Figure 2 andshowing an electrodynamic transducer embodying the invention, which comprises two contactterminals formed by two substantially U-shaped spring contacts.

Figure 2 shows the transducer of Figure 1 in a side view taken at thearrow II in Figure 1 and partly in sectional view.

Figure 3 shows the transducer of Figures 1 and 2 in a plan view taken atthe arrow III in Figure 2.

Figures 1 to 3 show anelectrodynamic transducer 1 having a transduceraxis 2. To accommodate and hold the individual parts of thetransducer 1 the latter comprisesaplastic housing 3. Thehousing 3 essentially comprises a hollow cylindrical circumferentialwall 4, which changes into a narrowannular bounding wall 5 at the top and which has threemounting projections 6, 7 and 8 at the bottom, which are spaced at equal angles from oneanother. Prior to assembly of the transducer I the mounting projections 6, 7 and 8 projectfrom the circumferential wall 4 in axial directions and after all the parts of thetransducer 1have been mounted in thehousing 3 said projections are bent by means of an ultrasonicprocess.

Thetransducer 1 comprises a substantially hollow cylindrical magnetsystem 9, which is substantially centro-symmetrical with respect to the transducer axis 2 andwhose construction is apparent from Figure 2. The magnet system 9 comprises aring magnet10, which is adjoined by anannular cover disc 11 at its upper side and by anannular coredisc 12 of ayoke 13 at its lower side. Theyoke 13 comprises theannular core disc 12 and,in addition, a hollowcylindrical yoke portion 14, whose end which is remote from thecoredisc 12 extends into the area of thecover disc 11, namely in such a manner that an annularair gap 15 is formed between thecover disc 11 and theyoke portion 14.

A voice coil 16 wound from coil wire is arranged in the air gap 15 and isshown only diagrammatically in Figure 2 because such a construction of a coil wound fromcoil wire is generally known. In known manner the voice coil 16 is secured to adiaphragm17 by means of an adhesive joint, which diaphragm can perform excursions in the directionof the transducer axis 2. Thediaphragm 17 comprises a curvedcentral portion 18 and anannularperipheral portion 19 which is connected to thecover disc 11 by an adhesive with itsedge zone, which lies between the narrow annularbounding wall 5 of thehousing 3 andthecover disc 11.

In thetransducer 1 shown in Figures 1 to 3 thecover disc 11, theringmagnet 10, thecore disc 12 of theyoke 13 and thediaphragm 17 all have the same outerdiameter, which is adapted accurately to the inner diameter of the circumferential wall 4 ofthehousing 3 in such a manner that thecore disc 12 of theyoke 13, thering magnet 10 aswell as thecover disc 11 and, consequently, also thediaphragm 17 are positioned exactlywith respect to the transducer axis 2 by means of the circumferential wall 4 of thehousing 3.This also results in an exact positioning of the voice coil 16 in the air gap 15, so that alwaysan unimpeded vibration of the voice coil 16 is guaranteed.

The voice coil 16 made of coil wire has two coil leads 20, of which onlyonelead 20 is shown in Figure 2. Thetransducer 1 further has two contact terminals, whichare both shown in Figure 1, but only one of these contact terminals is visible in Figure 2.Each of the two contact terminals is electrically connected to a coil lead, preferably bysoldering but clamping is also possible. Viewed in the direction of the transducer axis, thetwo contact terminals are disposed inside the substantially hollow cylindrical magnet system9.

As is apparent from Figure 2, the contact terminals in the transducershown in Figures 1 to 3 are preferably formed by substantially U-shapedspring contacts 21and 22 havinglimbs 23 and 24, which extend transversely to the transducer axis 2 and ofwhich afirst limb 23 is mechanically connected to a part of thetransducer 1 and of which asecond limb 24 has contact faces 25 for cooperation with mating contacts, which contactfaces 25 are movable substantially parallel to the transducer axis 2. Thecontact faces 25 areeach formed by a spring contact portion bent away from the second limb 24. Suitably, thetwo contact faces 25 of the twospring contacts 21 and 22 are situated at different radialdistances from the transducer axis 2, as is clearly shown in Figure 1.

As stated hereinbefore, thefirst limb 23 of each of the twospring contacts21 and 22 is mechanically connected to a part of thetransducer 1. This part of thetransducer1 for mounting the twospring contacts 21 and 22 is formed by a substantially pot-shapedcontact holder 26. Thefirst limbs 23 of the twoU-shaped spring contacts 21 and 22 aremechanically connected to a bottom wall 27 of the pot-shaped contact holder 26. By meansof its hollow cylindrical circumferential wall 28 the pot-shaped contact holder 26 is mountedin the hollowcylindrical yoke portion 14 of theyoke 13 of the magnet system 9.

At the location of its free end thefirst limb 23 of each of the two U-shapedspring contacts 21 and 22 has aterminal lug 29, which is inclined relative to saidlimb and which extends through the bottom wall 27 of the pot-shaped contact holder 26 andis connected to arespective coil lead 20. In this way the twoterminal lugs 29 provide anelectrical connection between, on the one hand, the coil leads 20 and, consequently, thevoice coil 26 and, on the other hand, the twoU-shaped spring contact 21 and 22.

As also stated hereinbefore, the U-shapedspring contacts 21 and 22 aresituated inside the substantially hollow cylindrical magnet system 9, viewed in the directionof the transducer axis 2. As is apparent from Figure 2, the twoU-shaped spring contacts 21and 22 of thetransducer 1 as shown in Figures 1 to 3 are disposed at least for the greaterpart inside the substantially hollow cylindrical magnet system 9, also viewed in a direction transverse to the transducer axis 2. Viewed in a direction transverse to the transducer axis 2,only the contact faces 25 of the twoU-shaped spring contacts 21 and 22 are situated outsidethe substantially hollow cylindrical magnet system 9.

As regards theelectrodynamic transducer 1 of Figures 1 to 3 it is to benoted that thistransducer 1 is shown to an enlarged scale, i.e. approximately five times fullscale. At full scale of thetransducer 1 the value of the outer diameter D of thetransducer 1indicated in Figure 3 has a nominal value of 13.2 mm. Thetransducer 1 is thereforeparticularly compact and is therefore very suitable for use in telecommunication devices,such as portable telephones and the like.

In thetransducer 1 as shown in Figures 1 to 3 a proper contactengagement with mating contacts of an electroacoustic device such as a portable telephone orthe like is always guaranteed owing to the construction of the contact terminals as U-shapedspring contacts 21 and 22, whosecontact faces 25 are movable substantially parallel to thetransducer axis 2. As a result of the U-shaped construction of thespring contacts 21 and 22,since the twolimbs 23 and 24 extend adjacent one another in the direction of the transduceraxis 2, thespring contacts 21 and 22 and, consequently, theentire transducer 1 are verycompact in radial directions. The U-shaped construction of the twospring contacts 21 and 22further has the advantage that both spring contacts are accommodated substantially whollyinside the magnet system 9 of thetransducer 1. Since the twospring contacts 21 and 22 havedifferent radial distances from the transducer axis 2 it is further achieved in a simple mannerthat thetransducer 1 can be mounted in an electroacoustic device in an arbitrary relativeposition if this device comprises a circular and an annular contact, which are both coaxialwith the transducer axis 2, or two annular mating contacts, which are coaxial with thetransducer axis 2, for cooperation with thespring contacts 21 and 22.

The invention is not limited to the embodiment described above by way ofexample. In the embodiment described above thefirst limb 23 of the twoU-shaped springcontacts 21 and 22 is fully straight, i.e. rectilinear. However, if desired, this first limb canalso be bent if this is required in view of the available space or for reasons of design. In theembodiment described above the outer second limb 24 covers the innerfirst limb 23 of eachof the twoU-shaped spring contacts 21 and 22 for the greater part, viewed in the direction ofthe transducer axis 2, since the twolimbs 23 and 24 of eachspring contact 21 or 22 extendparallel to one another. However, it is possible to arrange the outer limb 24 in an inclinedposition with respect to theinner limb 23. It is also possible to use S-shaped spring contactsinstead of U-shaped spring contacts.

Claims (6)

1. An electroacoustic transducercomprising

   a substantially hollow cylindrical magnet system (9) which is substantially centro-symmetricalwith respect to a transducer axis (2),

   a diaphragm (17) which is capable of vibrating in the direction of the transduceraxis (2),

   a voice coil (16) which is connected to the diaphragm (17), which has been woundfrom coil wire, and which has two coil leads (20), and two contact terminalswhich, viewed in the direction of the transducer axis (2), are disposed inside the substantiallyhollow cylindrical magnet system (9) and which are each connected to one coil lead (20),

   characterized in that the contact terminals are formed by spring contacts (21, 22) formed with at leastone bend, which spring contacts (21, 22) have at least two limbs (23, 24) which extend transversely to thetransducer axis (2) and which each have a first limb (23) mechanically connected to a part of thetransducer (1), and which each have a second limb (24) having contact faces (25) for engagement withmating contacts and whose contact faces (25) are movable substantially parallel to the transduceraxis (2), and the contact faces of both spring contacts (21, 22) have different radial distances from thetransducer axis (2).
2. A transducer (1) as claimed in Claim 1,characterized in that the first limbs (23) ofthe spring contacts (21, 22) formed with at least one bend are mechanically connected to a bottomwall (27) of a substantially pot-shaped contact holder (26) which is mounted in a hollow cylindricalpart of the magnet system (9) with its hollow cylindrical circumferential wall (28).
3. A transducer (1) as claimed in Claim 1 or 2,characterized in that the twospring contacts (21, 22) formed with at least one bend are disposed at least for the greater part insidethe substantially hollow cylindrical magnet system (9), also viewed in a direction transverse tothe transducer axis (2).
4. A transducer (1) as claimed in Claim 3,characterized in that the contact faces (25)of the two spring contacts formed with at least one bend are disposed outside thesubstantially hollow cylindrical magnet system (9), viewed in a direction transverse to thetransducer axis (2).
5. A transducer as claimed in any one of the preceding Claims,characterizedin that the two spring contacts (21, 22) are formed with only one bend and, as a consequence, aresubstantially U-shaped.
6. A transducer (1) as claimed in any one of the preceding Claims,characterizedin that the value of the outer diameter of the transducer (1) is at the most 20.0 mm.

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