This invention relates to a releasable fastener. It relates particularly to the kind of fastener that might be used on a watch bracelet but it also applies to fasteners suited to a jewellery bracelet, a belt or necklace, for example.

Whilst conventional watch bracelets are normally adjustable, the adjustment usually has to be effected in a stepwise manner and it can be rather a troublesome operation to make the adjustment. The user therefore may be disinclined to reposition the setting once an acceptable working position has been reached. It is known, for example that on a hot day the watch bracelet can feel uncomfortably tight and then some users would prefer to take off the bracelet rather than try to make a temporary adjustment of the bracelet length.

The present invention was devised to provide a bracelet adjustment which may be loosened or tightened as may be necessary during the day and without the user having to remove the watch from the wrist.

According to the invention, there is provided a releasable fastener having a first fastener part carrying a tongue with a toothed edge, and a second fastener part having a socket for the said tongue, the socket at an edge thereof having a rotatable worm drive screw positioned so that threads on the screw may engage teeth on the tongue when the tongue has been

inserted in the socket.

The fastener may include spring means whereby the toothed edge of the tongue and the threads of the screw are urged towards one another, thereby permitting a resilient operation allowing rapid engegement or disengagement of the fastener parts.

In one embodiment, the spring means comprises one or more springs which bear against an axle supporting the worm drive screw such that the screw will be pushed towards the side of the socket intended to accommodate the toothed edge of the tongue. Conveniently, an axle supporting the worm drive screw is provided by a straight portion of a spring which is resiliently mounted within the second fastener part.

In a different embodiment, the spring means comprises a resiliently mounted stop which is provided at a side of the socket opposite to that having the worm drive screw. The stop then serving to push the tongue edge towards the screw so the teeth may be engaged thereby.

The invention also comprises a watch or jewellery bracelet including the releasable fastener.

By way of example, some particular embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a plan view of the releasable fastener,

Figure 2 is a side view of a complete fastener, bracelet

and watch,

Figure 3 is a plan view of the first fastener part carrying the tongue,

Figure 4 is a similar view of the second fastener part,

Figure 5 is an end view of Figure 4,

Figures 6 and 7 show different internal arrangements of the second fastener part,

Figures 8 and 9 are views of the two parts of a different embodiment.

As depicted in Figures 1 and 2, the fastener comprises a first fastener part 1 carrying a tongue 2 with a toothed edge 3. A second fastener part 4 has a socket 6 for the tongue 3 and a rotatable worm drive screw 7 having threads capable of engaging teeth of the toothed edge 3. Each fastener part is mounted on a bracelet portion 8 and the bracelet portions support a watch 9.

It will be noted that the bracelet portions 8 have to be curved in order to fit round a user\'s wrist. Similarly, the first and second fastener parts 1,2 have been given curved shapes so that they will be compatible.

In operation of the watch bracelet, to fasten the watch, the user will hold the bracelet round the wrist and push the tongue 2 into the socket 6 of the fastener part 4. The user then manually rotates the screw 7 to tighten the bracelet and the watch is secured to the wrist. Minor adjustments to the

screw 7 may be made during the day to ensure maximum comfort to the user. The screw 7 allows the smallest adjustment to be effected in a very simple manner.

Figure 3 shows the first fastener part 1 with the tongue 2 when separated from the remainder of the fastener. It will be observed that the toothed edge 3 carries teeth which appear to recede below the plane of the Figure as the end of the tongue 2 is approached. This effect is to be expected because the part 1 and tongue 2 must be curved in order to conform to the required shape of the bracelet.

Figure 4 shows the second fastener part 4 and this also is curved longitudinally in order to enclose the tongue 2 and to fit the required bracelet shape. The fastener part 4 includes the socket 6 for receiving the tongue 2 and the worm drive screw 7 for gripping the toothed edge 3.

Figure 5 is an end view taken from the lower end of Figure 4. The socket 6 is seen to have a wall with a concave profile and this serves to receive a convex guide portion 10 (Figure 3) located around the periphery of the tongue 2. The guide portion 10 assists correct location of the tongue in the socket 6 and smooth operation of the fastener.

Whilst the embodiment described so far has a rigid connection between the toothed edge 3 and the screw 7, there can be an advantage if these two components are resiliently mounted with respect to one another. This can enable a quick insertion

of the toothed edge 3 past the screw 7 so that the bracelet may be rapidly fastened and the facility for making minor adjustments by turning the screw is still available.

Figures 6 and 7 show two possible arrangements for mounting the screw 7 in the fastener part 4. In Figure 6, the screw (not shown) is carried on an axle 11 which is urged by two springs 12 in the direction of the socket 6. The screw 7 can thus be resiliently mounted on the axle 11 with respect to the toothed edge 3.

In Figure 7, the fastener part 4 is provided with an internal passage 13 into which a spring having a long resilient arm 14 is locked. The spring arm 14 is then able to serve as an axle upon which a worm drive screw (not shown) can be mounted.

The releasable fastener of the invention, when incorporated in a watch bracelet has been found to provide a secure and comfortable fixing and a bracelet which may be quickly fixed to and removed from the wrist. Minor adjustments in the bracelet tightness may be made whenever required and this may be done without removal of the bracelet or even without looking at the bracelet.

The foregoing description of embodiments of the invention has been given by way of example only and a number of modifications may be made without departing from the scope of the invention as defined in the appended claims. For

instance, Figures 8 and 9 show a different embodiment where the socket 6 is concealed within the fastener part 4. In this instance, the tongue 2 will be fully supported when it is within the socket and no guide portion 10 may be needed.