GB2061366A - Clasp structure for wrist watch band - Google Patents

Abstract

A clasp structure for a wrist watch band having a pair of links (20a, 20b) comprises a fastening member (24) secured to strap (20a) and an engaging member (26) secured to strap-end (20b) and having first and second engaging claws (40a, 46a). The fastening member comprises a clamping lever (36) rotatably supported by a transverse pin (32) also serving as a snap-fastening for the claw (40a) which locks the fastening, this clamping lever having first and second cutout holes (36d, 36e, 36f). This first engaging claw (40a) passes through first cutout means (36d, 36e) and engages with the pin (32), and the second engaging claw (46a), which is actually hooked into position first, engages with a marginal portion (36g) of the second cutout means, so that the engaging member (26) is fixedly coupled to the fastening member 24 thereby to interconnect the links together. <IMAGE>

Description

SPECIFICATION Clasp structure for wrist watch band This invention relates to wrist watch bands and, more particulariy, to a clasp structure for such wrist watch bands.

Various clasp structures have heretofore been proposed in the prior art. A typical one of these structures is shown in Fig. 1. In Fig. 1, a wrist watch band has a clasp 2 joining two chains of links 1 a and 1 b, with the clasp 2 being composed of a fastening frame 3 which are fixedly fastened to a desired position of the link 1 a to suitably adjust the length of the band, and an engaging member 4 fixed to an end of the other link 1 b. The fastening frame 3 has a pair of upward flanges 3a and 3b, between which engaging pins 5 and 6 extend. The fastening frame 3 also has an intermediate pin 7 which carries a clamping member 8 having a pressing tongue 8a. The fastening frame 3 is fastened to the link 1 a by engaging the pressing tongue 8a to the surface of the link 1 a.The engaging member 4 comprises an engaging tongue 9 rotatably secured to the end of the link 1 b, and a clasping plate 10 having an engaging claw 1 0a.

With the structure stated above, the engaging tongue 9 is caused to engage the pin 6 and then the clasping plate 10 is pressed relative to the fastening frame 3 such that the engaging claw 1 Oa engages the pin 5, thereby interconnecting the links 1 a and 1 b together.

In actual use, the links 1 a and 1 b are frequently connected or disconnected by engaging or disengaging the engaging member 4 relative to the fastening frame 3. The frequent connection and disconnection of the clasping plate 10 relative to the fastening frame 3 causes the bending of the pin 5 by the action of the engaging claw 1 Oa and finally the clasping force of the fastening frame 3 relative to the link 1 a is reduced. The correction of bending of the pin 5 is difficult to achieve and replacement of the pin 5 is actually impossible due to the pin 5 being supported by the upward flanges 3a and 3b of the fastening frame 3 by which the pin 6 is also carried. It is accordingly required that the fastening frame 3 be replaced with another new one.If the fastening frame 3 is not replaced with the new one, then it happens that the engaging member 4 disengages from the fastening member 3 and so the wrist watch would fall down to the ground, causing damage to the wrist watch.

According to the present invention, there is provided a clasp structure for a wrist watch band having a pair of links, comprising a fastening member adjustably secured to one of the links, and an engaging member fixed to an end of the other one of the links and engageable with said fastening member to interconnect the links to one another, said engaging member having first and second engaging claws, and said fastening member comprising wall means having a pair of upward flanges and facing one side of said one of the links, a single supporting pin carried by the upward flanges of said wall means and serving as an engaging pin, a pressure plate facing another side of said one of the links at a position between said upward flanges, and clamping lever means rotatably supported by said supporting pin, said clamping lever means including cam means engageable with said pressure plate to fixedly retain said fastening member to said one of the links, and first and second cutout means, said first cutout means being formed near said engaging pin, said first engaging claw passing through said first cutout means and engaging with said supporting pin while said second engaging claw engaging with a marginal portion of said second cutout means to lock said engaging member to said fastening member, whereby said pair of links are connected together.

In the accompanying drawings, in which: Fig. 1 is a perspective schematic view of a conventional wrist watch band having a prior art clasp structure; Fig. 2 is a partial cross-sectional view showing an essential part of a clasp according to the present invention; Fig. 3 is an enlarged plan view of a fastening member forming part of the clasp shown in Fig. 2; Fig. 4 is an enlarged perspective view of the fastening member shown in Fig. 3; and Fig. 5 is an enlarged bottom view of the engaging member forming another part of the clasp shown in Fig. 2.

Referring now to Fig. 2, there is shown a wrist watch band 20 equipped with a clasp 22 according to the present invention, with the band 20 comprising a pair of links 20a and 20b. The clasp 22 comprises a fastening member 24 secured to an end portion of the link 20a, and an engaging member 26 secured to an end of the link 20b. The fastening member 24 comprises a flat wall 28 engaging a lower surface of the link 20a, a pressure plate 30 engaging an upper surface of the link 20a. The flat wall 24 has a pair of upward flanges 28a by which a single supporting pin serving as an engaging pin 32 is fixedly carried. A clamping lever 34 is rotatably supported by the engaging pin 32.

As best shown in Fig. 4, the clamping lever 34 comprises an upper wall 36, an engaging portion 36a integral with the upper wall 36 and arranged to engage the engaging pin 32 at three points, with the engaging portion 36a having a tip 36b serving as a cam whose engaging tip is displaced from the Y axis crossing center of the pin 32 by a suitable distance I (about 0.3 mm), and a stop portion 36c extending from the engaging portion 36a and serving as means to prevent rotation of the cam 36b when the stop portion 36c abuts against the pressure -plate 30.

In accordance with the present invention, the upper wall 36 and the engaging portion 36a are formed with rectangular cutouts 36d and 36e, respectively, adjacent to the engaging pin 32. The wall 36 also has another cutout 36f formed at the end of the wall 36, with a marginal portion 369 near the cutout 36f serving as an engaging portion which will be described later.

As shown in Figs. 2 and 5, the engaging member 26 comprises an upper plate 40 having its one end formed with an engaging claw 40a and its another end rotatably supported by a pivot pin 42 carried by upward flanges 44 of a fixed member 46 secured to the link 20b. The fixed member 46 has its free end formed with an engaging claw 46a.

With the arrangement mentioned above, the engaging claw 46a of the engaging member 46 is engaged with the marginal portion 36g of the cutout 36f and, thereafter, the upper plate 40 is pushed by a finger such that the engaging claw 40a passes through the cutouts 36d and 36e and finally engages with the supporting pin 32. In this manner, the engaging claws 40a and 40b of th'e engaging member 40 are retained by the engaging pin 32 and the marginal portion 369 of the cutout 36f and accordingly the engaging member 40 is fixedly retained by the fastening member 34. Thus, the links 20a and 20b are interconnected to one another.In Fig. 2, the arrow A shows a direction of force acting on the marginal portion 369 when the engaging claw 46a is caused to engage the marginal portion 369 of the cutout 36f, and the arrow B indicates a direction of force acting on the supporting pin 32 when the engaging claw 40a is caused to engage with the supporting pin 32. The flat wall portion 36 of the clamping lever 34 is relatively long and, therefore, it is easy to manipulate the clamping lever 34 when it is required to release the clamping lever 34 by engaging the finger's claw to the end of the clamping lever 34.

It will now be appreciated from the foregoing description that the present invention makes it possible to employ a simple mechanism composed of a single supporting pin serving as an engaging pin with which an engaging claw of an engaging member engages, and a clamping lever formed with a cutout having a marginal portion with which another engaging claw of the engaging member engages, thereby overcoming the shortcomings encountered in the prior art. During forming of the clamping lever, the cutouts 36d, 36e and 36f are formed simultaneously when the clamping lever is formed by stamping and, therefore, the clamping lever can be formed in the simplest way without increasing the operating or machining steps. Another advantage is that the clasp structure of the present invention is highly reliable for a long period, to reliably prevent the uncoupling of the clasp structure in the use of a wrist watch. In addition, the clasp structure of the present invention employs a minimum number of parts, achieving a lower manufacturing cost as well as easy manipulation of the clasp structure.

Claims (3)

1. A clasp structure for a wrist watch band having a pair of links, comprising a fastening member adjustably secured to one of the links, and an engaging member fixed to an end of the other one of the links and engageable with said fastening member to interconnect the links to one another, said engaging member having first and second engaging claws, and said fastening member comprising wall means having a pair of upward flanges and facing one side of said one of the links, a single supporting pin carried by the upward flanges of said wall means and serving as an engaging pin, a pressure plate facing another side of said one of the links at a position between said upward flanges, and clamping lever means rotatably supported by said supporting pin, said clamping lever means including cam means engageable with said pressure plate to fixedly retain said fastening member to said one of the links, and first and second cutout means, said first cutout means being formed near said engaging pin, said first engaging claw passing through said first cutout means and engaging with said supporting pin while said second engaging claw engaging with a marginal portion of said second cutout means to lock said engaging member to said fastening member, whereby said pair of links are connected together.

2. A clasp structure according to claim 1, in which said fastening means comprises wall means facing one side of said one of the links, and a pair of said clamping lever means comprises cam means engageable with said pressure plate to fixedly retain said fastening member to said one of the links.

3. A clasp structure according to claim 2, in which said clamping lever means further comprises stop means integral with said cam means to prevent rotation of said clamping lever means.