GB2094073A - Electrical connecting arrangement for connecting between a cell and the circuit of a watch - Google Patents

Abstract

A thin, deformable insulating washer 7 is interposed between the end portion 3a of the cell terminal strip 3 and the head 4b of a fixing screw 4. The shank 4a of the screw 4 passes with clearance through a hole 6 in the portion 3a of the terminal strip and, at its root, has a frustoconical bearing surface 8 for deforming the internal annular region of the washer 7, to engage it into the hole 6. The result of this arrangement is that the strip 3 is held in contact with a printed circuit track 12 (e.g. in a watch) but is electrically insulated from the screw 4 and has its hole 6 correctly centered with respect to the axis 9 of the screw. The insulating washer 7 avoids the use of more expensive collared washers. <IMAGE>

Description

SPECIFICATION Electrical connecting arrangement for connecting between a cell and the circuit of a watch The present invention concerns an electrical connecting device for connecting between a cell of an electronic watch and the printed circuit of the watch.

More particularly, the invention concerns fixing a terminal strip to the support structure of the watch, the strip making electrical connection between one of the electrodes of the cell and the printed circuit.

In fixing the terminal strip of an electrical watch cell to its support, which in most cases is formed by the support structure of the watch movement, the strip has to be insulated from the support and the fixing member which in most cases is a screw or a similar member. In that case, insulation must be provided not only with respect to the head of the screw but also with respect to the portion of the screw shank which is engaged in the fixing aperture in the terminal strip. In other words, insulation must be provided between the screw and the terminal strip, not only in the direction of the axis of the screw but also transversely.

Hitherto, this problem has been overcome by using washers of insulating material, which also have a collar portion thereon, such washers are interposed between the terminal strip and the head of a screw fixing the strip, the collar portion of the washer being engaged in the hole in the terminal strip and thus preventing any electrical contact between the strip and the screw.

The disadvantage of this arrangement is that insulating washers with collars are generally fairly expensive. The object of the present invention is to overcome this disadvantage.

According to the present invention there is provided an electrical connecting arrangement for connecting a watch cell and a printed circuit, comprising a support to which the printed circuit is fixed, the support having a threaded hole, a conducting terminal strip having a first end for contacting the cell and a second end with an aperture, a headed fixing member with a threaded shank connected to the head by a substantially frustoconical portion, the diameter of the shank being substantially less than the dimension ofthe aperture in the terminal strip, and a deformable insulating washer, the shank of the fixing member passing into the threaded hole through the washer, the aperture in the terminal strip, and an aperture in the printed circuit, the said frustoconical portion deforming the inner margin of the washer into the aperture in the terminal strip.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a view in axial section of a first embodiment of an arrangement for fixing the conducting bar member for contacting the cell of an electronic watch.

Figure 2 is a similar view in axial section of a second embodiment, and Figure 3 is a similar view in axial section of a third embodiment.

Figure 1 shows the plate 1 of the watch movement, the electrical cell 2 and the resilient terminal strip for making contact with one electrode of the cell. The strip 3 is fixed to the movement by a screw 4 which is engaged in a threaded hole 5 in the plate 1. The screw 4 passes with clearance through a hole 6 in the end portion of the strip 3. A thin, deformable washer 7 of insulating material, for example a polyimide which is known under the Trade Mark KAPTON, is interposed between the end portion 3a of the strip 3 and the head 4b of the screw 4. The washer is initially flat. The central hole in the washer 7 is smaller than the hole 6 in the strip 3 so that the shank portion 4a of the screw engages in the washer without appreciable clearance.At its root the shank portion 4a has a frustoconical bearing surface 8 which acts on the annular region of the washer 7, which is adjacent to the internal edge thereof, to deform that region at 7a and to bend it inwardly of the hole 6 in the strip 3. The result of this is that not only is the strip 3 not in electrical contact with the screw 4 but in addition the hole 6 therein is correctly centered with respect to the axis 9 of the screw, by virtue of the deformed portion 7a of the washer 7, which engages into the hole 6. As the head 4b of the screw 6 projects beyond the surface 8, the peripheral portion of the washer 7 remains flat, being gripped between the projecting portion of the head 4b and the end portion 3a of the strip 3.

The above-mentioned portion 3a of the strip 3 is provided with an annular collar portion 3b, which is produced by punching or stamping. The collar portion 3b projects beyond the hole 6 in the portion 3a and engages partly into a recess 10 in the plate 1, coaxial with the threaded hole 5 therein, which receives the screw 4. Co-operation between the annular collar portion 3a and the recess 10 ensures self-positioning of the strip 3 with respect to the axis of the threaded hole 5, before the screw 4 and the insulating washer 7 are fitted, thereby simplifying the assembly operation.

The collar portion 3b is engaged into the substrate 11 of the printed circuit of the timepiece, which can also be made of the polyimide and which it deforms in the same manner as is the washer 7 under the effect of the surface 8 of the screw 4. A copper conducting track 12, the thickness of which is shown in exaggerated form in the drawing, carried by the substrate 11, forms an electrical connection between the strip 3 and the printed circuit, that is to say, between the negative terminal of the cell and the printed circuit, the positive terminal of the battery being connected to earth.

It should be noted that the washer 7 costs virtually nothing as, being produced by punching or stamping, it can be cut out from the waste at the same time as the substrate 11 of the printed circuit is cut out from the sheet of polyimide. Therefore, the stamp for cutting out the substrate only has to be provided with a punch for cutting out the washer, in order for the washer to cost only the trouble for collecting it in a receptacle on the machine.

In the embodiment shown in Figure 2, the terminal strip 13 for connecting to the cell has a hole 14 through which the shank portion 1 5a of a screw 15 passes with clearance. The screw 15 is engaged in a column or pillar portion 16 which forms part of the support structure of the movement and to which the strip 13 is fixed. Athin, deformable, insulating washer 17 is interposed between the strip 13 and the head 1 5b of the screw 15. A frustoconical portion 18 disposed at the root of the shank 15a bears against the washer 17 to deform it and ta give it the form of a frustoconical cup which engages partly, by way of its internal edge, into the hole 14 in the strip 13, bearing against the edge of the hole 14. In this way the strip 13 is insulated from the screw 15, while being centered with respect thereto.

The substrate 19 of the printed circuit which carries a copper conducting track 20, is interposed between the strip 13 and an element 21 of the support structure of the movement. The conducting track 20 forms an electrical connection between the strips 13, and consequently the cell, and the printed circuit of the timepiece.

As in the first embodiment, the insulating washer 17 is flat before being used, so that it can be produced at derisory if not zero cost, as explained.

In the third embodiment illustrated in Figure 3, the terminal strip 30 terminates with a contact end portion 30a for making contact with the cell 32 and with a fixing end portion 30b which is flat and which has a hole 30c. The printed. circuit 34 is fixed on a part of the support structure 36 of the watch. A threaded bore 36a is provided at the location at which the battery bar member 30 is fixed. The printed circuit 34 also has a hole 34a aligned with the threaded bore 36a. The strip 30 is fixed by means of a fixing member, namely a screw 40. The screw 40 comprises a threaded shank 40a, and a flat head 40b which is connected to the threaded shank 40a by a frustoconical fillet portion 40c.

For the purposes of fixing the strip 30, the strip is set in postion in such a way that the hole 30c is disposed above the hole 34a. An insulating washer 42 is fitted onto the body of the screw 40. The insulating washer 42 is initially flat and is of the same nature as the washers 7 and 17 in Figures 1 and 2. The diameter of the central aperture in the washer is substantially equal to that of the threaded shank 40a, and substantially less than that of the hole 30c in the strip 30. The screw 40 is then engaged into the threaded hole 36a. The diameter of the hole 30e is much largerthan that of the screw shank 40a.

Towards the end of the operation of tightening the screw 40, the internal portion 42a of the washer 42 is deformed under the effect of the frustoconical portion 40c. In contrast, the external portion 42b remains flat. This ensures at the same time that the aperture 30c is centered with respect to the axis of the screw thread 36a. At the end of the screw tightening operation, the internal portion 42a of the washer 42 is of a frustoconical shape, thus providing electrical insulation between the strip 30 and the screw 40 transversely. The undeformed external portion 42b of the washer 42, which is gripped between the screw head 40b and the upper surface of the end portion 30b of the bar member provides insulation in the direction of the axis of the screw thread. In addition, a good grip is achieved, because the screw head 40b is flat. The gripping action also ensures electrical contact between the strip 30 and the conducting track 34b of the printed circuit.

It will be seen from the foregoing description that, in all its embodiments, the invention makes it possible to achieve the aims sought to be attained.

The arrangement provides both for good fixing and good electrical insulation. The insulation effect is essentially achieved by means of an insulating washer which is initially flat and which is not critical in its dimensions. The washer is therefore easy and inexpensive to produce.

Claims (5)

1. An electrical connecting arrangement for connecting a watch cell and a printed circuit, comprising a support to which the printed circuit is fixed, the support having a threaded hole, a conducting terminal strip having a first end for contacting the cell and a second end with an aperture, a headed fixing member with a threaded shank connected to the head by a substantially frustoconical portion, the diameter of the shank being substantially less than the dimension of the aperture in the terminal strip, and a deformable insulating washer, the shank of the fixing member passing into the threaded hole through the washer, the aperture in the terminal strip, and an aperture in the printed circuit, the said frustoconical portion deforming the inner margin of the washer into the aperture in the terminal strip.

2. An arrangement according to claim 1, wherein the head of the fixing member is flat and projects beyond the substantially frustoconical portion of the fixing member, and the outer margin of the washer is clamped under the outwardly projecting portion of the head.

3. An arrangement according to claim 2, wherein the support further comprises a recess which is coaxial with the threaded hole, and the second end of the terminal strip has a collar portion extending the aperture in the strip and engaging into the recess.

4. An arrangement according to claim 1, wherein the head of the fixing member is a frustoconical shape and the outer margin of the washer is also clamped under the frustonical surface of the head.

5. An arrangement according to any of claims 1 to 4, with a printed circuit comprising an insulating substrate and a plurality of conducting tracks, wherein the second end of the terminal strip bears on a conducting track.