Device for adusting the length of a bracelet

Abstract

The invention relates to a bracelet lengthening device, comprising at least one adjusting assembly (1, 2) that is movable relative to a clasp cover (21), the adjusting assembly (1, 2) and the cover (21) being provided with a fisrt and a second fastening element (23, 35'), respectively, for fastening them respectively in several positions that are able to bring about different bracelet lengths, characterized in that the adjusting assembly (1, 2) and the cover (21) are also provided with a first and a second indexing element (15, 35), respectively.

Description

Introduction

[0001] The present invention relates to a device for adjusting the length of a bracelet, comprising a particular guiding and attachment system for a bracelet, particularly suitable for a bracelet for a wristwatch provided with an extension device and / or provided with a clasp with folding blades arranged between two ends of the bracelet. It also relates to a clasp and a bracelet as such, integrating such a device for adjusting the length of a bracelet, as well as to a wristwatch as such comprising such a device. State of the Art

[0002] A state-of-the-art folding blade clasp, intended to attach the two strands of a watch strap around the wearer's wrist, comprises several articulated blades, which can occupy a first closed position, and a second open position, in which the blades are no longer attached and allow the strap to be inserted or removed. Such a clasp is generally provided with a first adjustment of its position relative to the strap, called a conventional adjustment. However, the final length obtained is often not optimal.

[0003] For this purpose, existing clasps are equipped with a solution allowing a second adjustment of the bracelet length, which can also be called a comfort adjustment, complementary to the first conventional adjustment. Document EP0819391 describes such a solution, which is based on an adjustment link which pivots and can occupy two stable positions inducing two different lengths of the bracelet. The short position is maintained by a notch of an end link of the bracelet which hooks and locks elastically against the adjustment link in its short position. Document EP1908366 describes another solution in which an adjustment link of the bracelet is movable opposite a clasp cover of said bracelet, the adjustment link being fixed to the cover by a notch.These existing solutions require careful handling by a user when adjusting the length of the bracelet, which must achieve adequate positioning of moving elements, for example relative to a notch, which forms a fixing device whose position varies according to the desired length of the bracelet.

[0004] A general objective of the invention is to further improve the convenience of adjusting the length of a bracelet.

[0005] More particularly, the invention proposes a solution for adjusting the length of a bracelet, the operation of which is reliable and the handling intuitive and user-friendly.

[0006] In addition, the moving components of a watchmaking device, in particular a device for adjusting the length of a bracelet, are equipped with guide elements which are subject to numerous constraints, including: mechanical stress during their function of guiding the movement of a component; exceptional mechanical stress during a particular event, such as a fall, shock, tearing, twisting, etc.; environmental stresses such as pollution or the user's sweat, which could possibly generate degradation by corrosion or oxidation.

[0007] The second objective of the invention is to offer a solution which best meets the above-mentioned constraints.

[0008] In particular, a second object of the invention is to provide a guidance solution for moving components of a watchmaking device, making it possible to limit the wear of the guidance elements, to reduce their friction, to reduce the risk of seizure and their corrosion, to limit, or even prevent, the deposition and / or amalgamation of dirt in the guidance elements. Brief description of the invention

[0009] To this end, the invention is based on a bracelet extension device, comprising at least one adjustment assembly movable relative to a clasp cover, the adjustment assembly and the cover being respectively provided with a first and a second fixing elements for their respective fixing in several positions capable of inducing different bracelet lengths, characterized in that the adjustment assembly and the cover are further provided respectively with a first and a second indexing elements for pre-positioning the adjustment assembly not sufficient for its fixing, these indexing elements being distinct from the fixing elements, and in that the first indexing element and the second indexing element are respectively in the form of at least one projection and hollow notches or conversely at least one hollow notch and projections.

[0010] The invention is more precisely defined by the claims. Brief description of the figures

[0011] These objects, characteristics and advantages of the invention will be explained in detail in the following description of particular embodiments made without limitation in relation to the attached figures among which: There figure 1 represents a perspective view of a clasp cover incorporating a device for adjusting the length of a bracelet according to one embodiment of the invention. The figure 2 represents a sectional view along a longitudinal plane of a clasp cover incorporating the device for adjusting the length of a bracelet according to the embodiment of the invention. The figure 3 represents a sectional view along a transverse plane of the clasp cover at the level of the bracelet length adjustment device according to the embodiment of the invention. The figure 4represents a perspective view of a clasp cover integrating the device for adjusting the length of a bracelet according to the embodiment of the invention in a phase of manipulation of a link of the adjustment device. The Figure 5 represents a perspective view of a guide element of the device for adjusting the length of a bracelet according to the embodiment of the invention. The figure 6 represents a sectional view of a first variant embodiment of the guide element of the device for adjusting the length of a bracelet according to the embodiment of the invention. The figure 7 represents a sectional view of a second variant embodiment of the guide element of the device for adjusting the length of a bracelet according to the embodiment of the invention. The figure 8represents an alternative embodiment of a sub-part of the device for adjusting the length of a bracelet according to the embodiment of the invention. The figure 9 represents another variant embodiment of a sub-part of the device for adjusting the length of a bracelet according to the embodiment of the invention.

[0012] A device for adjusting the length of a bracelet within a clasp according to one embodiment of the invention will now be described.

[0013] Such a device for adjusting the length of a bracelet comprises two lateral extension links 2 arranged around a bar 3, and a link 1 mounted to rotate about this bar 3. The two lateral extension links 2 are movable relative to a cover 21 of the clasp. This assembly comprising the link 1 and the two lateral links 2 arranged on a bar 3 forms an adjustment assembly of the device for adjusting the length of a bracelet. Alternatively, the adjustment assembly may take a form other than that of this embodiment. It may be a single-piece, single-component, or advantageously comprise an assembly of several components.

[0014] The cover 21 comprises two side walls 22 each comprising a slide. Each slide forms a second guide element 30, which cooperates with a first guide element 10 positioned at the ends of the bar 3. Thus, the adjustment assembly also comprises a first guide element 10.

[0015] In this embodiment, the first guide element 10 is advantageously in the form of a pad or a roller or a ball and the second guide element 30 is in the form of a slide or a slide, or a bore, or a cutout, or a groove, shaped to receive such a pad or such a roller or such a ball. The pads or rollers or balls arranged at each end of the bar 3 thus slide parallel, in their respective opposite slides, according to a movement corresponding substantially to a translation.

[0016] In this embodiment, the first guide element 10 is in the form of an element separate from the links 1, 2. In this particular construction, two pads with slightly arched profiles are arranged respectively on either side of the two lateral links 2, and are assembled to these lateral links 2 by means of the bar 3. To do this, the pads have a central bore 11 provided for their positioning around a cylindrical receiving element 4 at the end of the bar 3, as is particularly visible on the figure 3 .

[0017] The bar 3 comprises an annular central part 33 in which a spring 34 is arranged, which exerts an elastic thrust force on the cylindrical receiving elements 4 positioned at the end of the bar 3, and indirectly on the first guide elements 10, in the direction of the cover 21, and more precisely in the direction of the side walls 22 of the cover 21.

[0018] In this embodiment, the first guide elements 10, i.e. the pads or rollers or balls, are made of a single piece. In addition, they are entirely made of a high-performance polymer, belonging to the family of polyaryletherketones (PAEK), in particular polyetheretherketone (PEEK).

[0019] The applicant's studies have shown that such a polymer has the advantage of optimizing the reliability and durability of components with better resistance to wear and abrasion. In particular, the performance in terms of sliding and durability is superior, among other things, to that of polymers from the polyacetal family.

[0020] Alternatively, the first guide elements 10 could only comprise a portion made of a high-performance polymer, belonging to the family of polyaryletherketones (PAEK), in particular PEEK. In particular, this portion could be at a guide surface, intended to come into contact with the second guide element 30, i.e. the slide or the slide. This portion can thus take the form of a surface coating at the contact zones or the friction zones. In particular, a PEEK conformation can be formed around a pad, in particular overmolded onto a pad. By way of example, the first guide element 10 can comprise a core covered with a coating comprising the polymer material belonging to the PEAK family, forming all or part of the guide surface.

[0021] Alternatively, these guide elements 10 could be made of another material, for example metal.

[0022] There figure 8 represents an alternative embodiment in which the first guide element 10 is directly fixed to a lateral mesh 2. In this alternative, fixing studs 12 are provided on a lateral face of the first guide element 10 to be driven into bores of a lateral extension mesh 2. This fixing can, for example, be implemented by driving, riveting, gluing, welding or brazing. The guide element 10 comprises a guide surface 13, on its second lateral face.

[0023] Alternatively, a lateral mesh 2 may comprise a projection, in particular a circular or oblong projection, which acts as a pad. This projection is formed on a flank of said mesh 2 and forms the guide element 10 of the adjustment assembly. In this particular case, the mesh 2 is in one piece. It may be made of a high-performance polymer, in particular a polymer material belonging to the family of polyaryletherketones (PAEK), in particular PEEK. Alternatively, the projection may be overmolded onto a flank of the lateral mesh 2. Alternatively again, the projection may be coated with PEAK, for example PEEK, over all or part of its surface.

[0024] Naturally, a guide element 30 of the cover 21 could also comprise a material belonging to the family of polyaryletherketones (PAEK). In other words, any of the two guide elements 10, 30 may comprise in whole or in part a material belonging to the family of polyaryletherketones (PAEK) on all or in part of its guide surface. Alternatively, the two guide elements may comprise such a material or any other material.

[0025] The second guide element 30 may be made of steel or a precious material, such as gold or platinum. Alternatively, the second guide element 30 may be made of ceramic. More particularly, it may be integral with a cover made of ceramic or steel or a precious material, such as gold or platinum. As mentioned above, the second guide element 30 may alternatively be made of a high-performance polymer, in particular a polymer material belonging to the family of polyaryletherketones (PAEK), in particular PEEK. More particularly, it may be integral with the cover of the clasp made entirely of PEEK. Alternatively, the second guide element 30 may be attached to the cover, preferably made of steel or a precious material, such as gold or platinum. Alternatively, the second guide element 30 may be attached to a cover made of ceramic.

[0026] For example, the clasp cover is provided with slides arranged in side walls formed on either side of said cover. In this particular case, the cover is a single piece. It may be entirely composed of a high-performance polymer, in particular PEEK. Alternatively, only the slides may be coated with a polymer material belonging to the polyaryletherketone (PAEK) family, in particular PEEK, over all or part of their surface. Alternatively, the entire cover may be made of another material, for example a metal.

[0027] In the polyaryletherketone (PAEK) family, the chosen material can be unfilled or filled. A filler makes it possible to optimize, among other things, the tribological and mechanical characteristics of the component. For example, the filler can comprise at least reinforcing fibers and / or a lubricating agent and / or graphite. Alternatively, the filler can also comprise at least one pigment, in particular for the purpose of coloring the component.

[0028] According to exemplary embodiments, the material chosen will be PEAK, in particular PEEK, polyetheretherketone (PEEEK), polyetherketone (PEK), polyetherketoneketone (PEKK) or a copolymer thereof and / or a mixture of polymers. Furthermore, this polymer material may advantageously comprise at least one filler of polytetrafluoroethylene (PTFE), molybdenum sulfide, tungsten disulfide, hexagonal boron nitride, carbon fibers, aramid fibers, glass fibers, graphite, graphene, carbon nanotubes, polyimides, polyphenylene sulfide, diamond nanoparticles, polysilsesquioxanes, boron fibers or a combination of two or more of these. The preceding list is naturally non-limiting.

[0029] In a particular embodiment, the material is PEEK that contains 20% PTFE, for example Victrex ®< 450FE20. In another embodiment, the material is PEEK that contains 30% additive, including carbon fibers and / or graphite and / or PTFE. In another embodiment, the material is PEEK that contains 30% carbon fibers and additional additives, including graphite and / or PTFE. As an alternative or in addition to the carbon fibers, the fibers contained within the PEEK may be aramid fibers or boron fibers. Examples of PEAK or PEEK that can be used include, but are not limited to: Victrex ®< PEEK 450FC30, Ketron ®< HPV, Tekapeek ®< PVX, KetaSpire ®< KT-820 SL30, AKROTEK ®< PEAK CF30, AvaSpire ®< AV-651 CF30, AvaSpire ®< AV-722 SL30, AvaSpire ®< AV-755 SL45.Note, in all cases, and in particular in all the embodiments described, the PEEK polymer can be replaced by any other polymer from the PEAK family.

[0030] According to a particular embodiment, the component comprises 65% PEEK, 15% carbon fibers, 10% PTFE, 8% carbon nanotubes, and 2% nanodiamond.

[0031] The element or part of the element made of material belonging to the family of polyaryletherketones (PAEK) is manufactured by any method or combination of methods known to those skilled in the art. According to an alternative embodiment, the surface of the component or part of the component made of material belonging to the family of polyaryletherketones (PAEK) may be structured, in particular micro-structured, in particular for the purpose of shaping a first element in order to further optimize the tribological and / or wear behavior of the PEAK surface or to allow better distribution of a lubricant. This structuring may be obtained directly during the molding of the part or subsequently by machining or micro-machining, for example by laser texturing (in English laser surface texturing or LST) or by chemical etching. Any other technique or combination of techniques may also be implemented to obtain structuring or micro-structuring.

[0032] According to a particular embodiment of the invention, it has been seen that the guide element or the part of the guide element, which may be a polymer or metal part, is coated at least partially with a coating comprising a material belonging to the family of polyaryletherketones (PAEK), in particular PEEK. In such an embodiment, the coating may be applied using conventional dispersion spraying techniques, electrostatic spraying techniques or overmolding. A coating may also be applied to an element according to one of the preceding embodiments with or without micro-structuring of the surface of said component: for example a DLC coating or any other suitable coating technique. Micro-structuring of the surface may also be carried out after application of the coating.

[0033] In addition, according to the embodiment, the relative movement of the link 1 and the extension side links 2 relative to the clasp, i.e. of the adjustment assembly relative to the clasp, comprises an indexing device, which makes it possible to predetermine certain stable relative positions of this adjustment assembly relative to the clasp. Such an indexing device is implemented by means of indexing elements respectively of the adjustment assembly on the one hand and of the clasp on the other hand.

[0034] Thus, according to the embodiment, the first guide element 10 comprises a first indexing element 15. By way of example, the Figure 5illustrates a guide element 10 which comprises an indexing element 15 in the form of several projections directly made on the guide element, in particular a single-piece pad. These projections may have a hemispherical conformation. Alternatively, these projections may have any other geometry, such as a rectangular and / or elongated geometry. These projections are intended to cooperate with a second indexing element 35 in the form of a succession of notches arranged within a slide forming the second guide element 30 of a clasp cover, as represented by the Figures 1 and 2. In this embodiment, the projections are made from the material of the first guide element, for example PEAK, in particular PEEK, if the assembly is in one piece. Alternatively, the projections may be made from another material, and may in particular be formed on a pad of which at least one portion is made or is coated with PEAK.

[0035] As an example of implementation, the figure 6 represents a guide element 10 in the form of a pad, comprising a cylindrical opening in which an indexing element 15 is mounted, distinct from the guide element, advantageously by driving. This cylindrical opening 11 may be in the extension of that provided for mounting the guide element at the end of the bar 3, or a separate opening.

[0036] There figure 7illustrates another variant in which a guide element 10, in the form of a pad, is formed, in particular overmolded, around an indexing element 15, distinct from the guide element. This results in a result similar to that of the figure 6 .

[0037] Alternatively, the indexing element 15 can be implemented by a cylindrical receiving element 4 of the bar 3, in particular by one end of a cylindrical receiving element 4 of the bar 3, as represented by the figure 9 To do this, the cylindrical receiving element 4 passes right through the guide element 10, in particular through a central bore 11 provided for the positioning of said guide element, in order to be able to cooperate with the second indexing element 35. Thus, the first indexing element 15 can be distinct from the guide element 10. In particular, the first indexing element 15 can be implemented by the bar 3.

[0038] As a note, the indexing device described above can be combined with a complementary indexing device for a bracelet link relative to a clasp cover, that is to say that it can complement a conventional indexing system, such as a bar indexing system or a ball indexing system notably implementing a 35' toothing such as that shown in the Figures 1 and 2. This conventional indexing device in fact fulfills the function of a fixing device, movable in the longitudinal direction of the clasp, of the adjustment assembly of the bracelet length adjustment device. Thus, this movable fixing device is capable of inducing different bracelet lengths. This fixing device can thus comprise a tooth 23 arranged on the link 1, subjected to a spring 24 exerting a force holding the tooth 23 against the corresponding toothing 35' of the cover. In this embodiment, the toothing 35' is arranged on the inner face of the upper wall of the cover 21, perpendicular to the side walls 22 which comprise the second guide devices 30 of the adjustment assembly, as well as the second indexing element 35. The tooth 23 and the toothing 35' form fixing elements of the fixing device, respectively of the adjustment assembly and of the cover.It appears that in this embodiment, the second fixing element 35' of the clasp cover 21 and the second indexing element 35 of the clasp cover 21 are arranged on two separate faces of the cover 21. Any other arrangement could be envisaged, preferably with the second fixing element 35' and the second indexing element 35 arranged in two different areas of the cover.

[0039] Thus, the invention also relates to a bracelet extension device, comprising a link comprising a first guide element 10 and a clasp cover 21 comprising a second guide element 30, the link and the cover being linked together in a movably manner by cooperation of their respective guide elements 10, 30, and characterized in that the link comprises a first indexing element 15 which cooperates with a second indexing element 35 of the cover 21.

[0040] As a note, the notching forming a second indexing element complements the notching known from the state of the art, for example the 35' notching particularly visible on the figure 2 , forming a fixing device. The indexing device can thus form a pre-positioning element, which assists the user during an adjustment by allowing adequate positioning of the adjustment assembly, in particular to act adequately on the fixing device. This indexing device is not sufficient for fixing the adjustment assembly, which can easily escape from the various notches to allow adjustment. It does not fulfill a fixing function. It comes in addition to a separate fixing device, as described previously.

[0041] An indexing element may form a single-piece assembly with a guide element, or a separate element, arranged near or through a guide element. The indexing element may also be in the form of an assembly, such as a ball ratchet comprising a ball elastically returned by a spring, the latter being able in particular to complement or be able to replace the spring 34 of the bar 3 more particularly visible on the figure 3 .

[0042] As a note, according to the embodiment, the spring 34 cooperates with the first indexing element 15 so as to exert an elastic thrust force on the first indexing element 15 in the direction of a second indexing element 35 and to allow the release of the first and second indexing elements 15, 35 in the phase of adjusting the length of said bracelet.

[0043] It appears that these indexing elements are subject to stresses very similar to those experienced by the guide elements. Thus, they can also advantageously comprise a polymer material belonging to the family of polyaryletherketones (PAEK). Complementarily or alternatively, they can comprise other materials.

[0044] Alternatively, the first indexing element 15 can be implemented independently of the first guide element 10.

[0045] Thus, the invention also relates to a bracelet extension device, comprising at least one link linked to a clasp cover, the link comprising a first indexing element 15 and the cover 21 of the clasp comprising a second indexing element 35, the two components being linked together in a movably manner, and characterized in that the first indexing element 15 and / or the second indexing element 35 comprises a contact surface, comprising a polymer material belonging to the family of polyaryletherketones (PAEK).

[0046] When adjusting the length of the bracelet, a user rotates the link 1 of the adjustment assembly, in order to release the tooth 23 by one notch from the notch 35' of the clasp, thus opening the fastening device of the adjustment assembly. This action can be carried out by pulling on a strand of the bracelet in a suitable direction. The adjustment assembly thus reaches an open position allowing it to move longitudinally relative to the clasp, by means of the guide elements 10, 30 explained previously. During this movement, the adjustment assembly is automatically positioned successively in the different stable positions predefined by the indexing elements. These indexing elements are advantageously distributed according to a pitch equal to the pitch of the fastening device, and in correspondence, so that each indexing element corresponds to a fastening position.By this means, the adjustment assembly is automatically positioned in the positions predefined by the indexing elements during its longitudinal movement, under the effect of an elastic element of the adjustment assembly, which thus facilitates the positioning of the adjustment assembly at the different possible longitudinal locations, corresponding to different authorized length adjustments. The adjustment of the length of a bracelet thus becomes assisted and very user-friendly. If the user wishes to continue the adjustment, he continues the movement of the adjustment assembly, and his effort allows the release of the intermediate indexing elements encountered, against the effort of the elastic element of the adjustment assembly.

[0047] The invention also relates to a bracelet and / or a clasp and / or a wristwatch, which incorporate(s) a bracelet extension device as described previously.

Claims

1. A bracelet lengthening device, comprising at least one adjustment assembly (1, 2) that is mobile relative to a clasp cover (21), the adjustment assembly (1, 2) and the cover (21) being respectively provided with a first and a second fastening elements (23, 35') for their respective fastening according to several positions capable of inducing different bracelet lengths, characterized in that the adjustment assembly (1, 2) and the cover (21) are also provided respectively with a first and a second indexing elements (15, 35) of pre-positioning of the adjustment assembly being not sufficient for its fastening, these indexing elements being distinct from the fastening elements, and in that the first indexing element (15) and the second indexing element (35) respectively take the form of at least one protuberance and of hollowed out notching or, conversely, of at least one hollowed out notch and of protuberances.

2. The bracelet lengthening device as claimed in the preceding claim, characterized in that the adjustment assembly (1, 2) comprises a first guiding element (10), in that the clasp cover (21) comprises a second guiding element (30), the adjustment assembly (1, 2) and the cover (21) being linked to one another movably by a cooperation of their respective guiding elements (10, 30), and in that the first indexing element (15) is arranged on the first guiding element (10).

3. The bracelet lengthening device as claimed in the preceding claim, characterized in that the first guiding element (10) and the first indexing element (15) form a single-piece assembly.

4. The bracelet lengthening device as claimed in claims 2, characterized in that the first indexing element (15) is distinct from the first guiding element (10), notably added onto said first guiding element (10), notably by driving or overmolding, or notably formed at an end of a cylindrical receiving element (4) positioned at the end of a bar 3 of the adjustment assembly (1, 2).

5. The bracelet lengthening device as claimed in the preceding claim, characterized in that the first indexing element (15) comes in a material other than the material of the first guiding element (10), or in that it has a coating in a material other than the material of a coating of the first guiding element (10).

6. The bracelet lengthening device as claimed in one of the claims 2 to 5, characterized in that the adjustment assembly (1, 2) and the first guiding element (10) are two distinct elements or in that the adjustment assembly (1, 2) comprises at least one link (2), the first guiding element (10) forming a single-piece assembly with said link (2).

7. The bracelet lengthening device as claimed in one of the preceding claims, characterized in that the adjustment assembly (1, 2) comprises a spring (34) cooperating with the first indexing element (15) so as to exert an elastic thrust force on the first indexing element (15) toward a second indexing element (35) and to allow the releasing of the first and second indexing elements (15, 35) in a phase of adjustment of the length of said bracelet.

8. The bracelet lengthening device as claimed in the preceding claim, characterized in that the adjustment assembly (1, 2) comprises a first guiding element (10) and / or a first indexing element (15) arranged at the end of a bar (3) of the adjustment assembly, and in that the spring (34) is arranged in the bar (3) so as to exert an elastic thrust force on the first guiding element (10) and / or the first indexing element (15) toward the cover (21).

9. The bracelet lengthening device as claimed in one of the preceding claims, characterized in that the first and second fastening elements (23, 35') on one side take the form of a tooth arranged on a link (1) of the adjustment assembly and on the other side take the form of teeth arranged on an inner surface of the cover (21) of the clasp.

10. The bracelet lengthening device as claimed in one of the preceding claims, characterized in that the second fastening element (35') of the clasp cover (21) and the second indexing element (35) of the clasp cover (21) are arranged on two different zones of the cover (21), notably two distinct or non-aligned faces of the cover (21).

11. The bracelet lengthening device as claimed in one of the preceding claims, characterized in that the adjustment assembly (1, 2) comprises a first guiding element (10) and in that the clasp cover (21) comprises a second guiding element (30), the adjustment assembly (1, 2) and the cover (21) being linked to one another movably by a cooperation of their respective guiding elements (10, 30), in that the first guiding element (10) comprises a guiding surface at least partially in contact with the second guiding element (30), this guiding surface comprising a polymer material belonging to the family of polyaryletherketones (PAEK), and / or in that the first indexing element (15) and / or the second indexing element (35) and / or the second guiding element (30) comprise a polymer material belonging to the family of polyaryletherketones (PAEK).

12. The bracelet lengthening device as claimed in the preceding claim, characterized in that the two respective guiding elements (10, 30) of the adjustment assembly (1, 2) and of the cover (21) can allow a relative sliding of the two guiding elements notably by a translational or substantially translational movement.

13. The bracelet lengthening device as claimed in the preceding claim, characterized in that the first guiding element takes the form of a roller or a runner or a ball, cooperating with the second guiding element taking the form of a slide, a guideway, a cutout, a bore or a groove.

14. The bracelet lengthening device as claimed in one of the preceding claims, characterized in that the indexing elements (15, 35) are distributed according to a pitch equal to the pitch of the fastening device (23, 35'), and correspondingly, such that each position defined by the indexing elements (15, 35) has a corresponding fastening position of the fastening device (23, 35').

15. A deployant clasp for a bracelet, characterized in that it comprises a bracelet lengthening device as claimed in one of the preceding claims.

16. A bracelet, characterized in that it comprises a deployant clasp as claimed in the preceding claim.

17. A timepiece, notably a wristwatch, characterized in that it comprises a bracelet lengthening device as claimed in one of claims 1 to 14 or a deployant clasp as claimed in claim 15 or a bracelet as claimed in claim 16.

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