EXPANDABLE COMFORT FLAP

Description

Technical field of the invention

[0001] The present invention relates to the field of watchmaking and jewelry, and in particular to bracelet links. State of the art

[0002] In the field of watchmaking in particular, devices for adjusting the useful length of a bracelet in various positions corresponding to the size of the user's wrist have long been known. For leather or plastic bracelets, this is usually done by joining two bracelet strands using cooperation means consisting of a buckle and a pin arranged on a first strand, the pin being inserted into holes arranged on a second strand which is passed through the pin.

[0003] In the case of metal bracelets, made up of a plurality of articulated links, the devices for adjusting the useful length are most often integrated directly into a clasp, for example a folding clasp. The adjustment is then generally carried out in the open position of the clasp.

[0004] However, most of these adjustment devices pose recurring problems of fine adjustment of the bracelet length due to the discrete nature of the adjustment positions, the granularity of which is defined by the notching or any other device defining minimum gaps between two consecutive adjustment positions.

[0005] Thus, more particularly for metal bracelets, it has been sought to obtain additional settings allowing automatic adjustment of the length, for example using elastic elements allowing adaptation of the length of the bracelet according to the conditions of use of the watch, such as for example according to the external temperature and humidity conditions having a significant influence on the circumference of the user's wrist.

[0006] Patent application EP3744209A discloses, for example, a bracelet with elastic links of a particular structure using pre-stressed springs arranged between two articulation rods between central links and lateral links, and whose trigger threshold is defined by the weight of the bracelet itself. The travel of each link is however limited to less than one millimeter, which requires, on the one hand, the arrangement of a large number of links to obtain a sufficient automatic adjustment range for elongation of the bracelet. Furthermore, this solution requires a very particular arrangement of elastic elements capable of extending along the curvature of each central link, which significantly increases manufacturing costs.

[0007] In the context of diving watches, arrangements of elastic elements in clasps are also known for adjusting the length of the watch strap on the one hand to the extra thickness generated by the suit, and on the other hand to the pressure variations depending on the depth at which the dive is carried out. Document EP2606762B1 describes an example of a clasp provided that a continuous length adjustment device corresponding to a specific diving mode where a continuous length variation is possible via elastic return elements. This type of diving-specific adjustment is alternatively added to a fine and indexed adjustment device for the length of the strap via a notch in the clasp cover in the case of normal use of the watch, i.e. outside of diving.A disadvantage of this type of device is that it is relatively bulky and complex to assemble; furthermore, the elastic elements are not completely hidden under the blades of the folding clasp, which exposes them to pinching during the extension and retraction phases of the spring, the maximum travel of which is relatively long. Then, the fact that the springs are not hermetically covered from below the clasp to the outside of the blades easily allows dust or other debris from skin or rubber to penetrate under the clasp and thus impair the proper functioning of the elastic adjustment mechanism. Finally, the torsional stresses exerted on the spring to follow the curvature of the clasp cover are also disadvantageous for ensuring long-lasting performance in terms of reliable holding forces around the user's wrist.

[0008] US patent US2848864 describes an expandable articulated bracelet solution with a device according to the preamble of claim 1, this bracelet using an elastic inserted in a parallelepiped case sliding inside a shell open in its upper part.

[0009] American patent US25518507 similarly describes an expandable articulated bracelet solution using an elastic inserted within an internal link formed by a base ending in a curved tongue and covered with a cover, the assembly thus formed sliding inside an external link.

[0010] US patent US2744379 describes a solution similar to that of US2848864 above, with parallelepiped shape correspondence between a sliding part inside an external link, with simply a doubling of the elastic elements.

[0011] There is therefore a need for an adjustment solution free from these known limitations. Summary of the invention

[0012] An object of the present invention is to provide an alternative fine adjustment solution for a bracelet, which increases wearing comfort without requiring any operation by the wearer of the bracelet.

[0013] Yet another aim of the present invention is to provide a solution for fine adjustment of the length of a bracelet whose reliability is guaranteed over time.

[0014] According to the invention, these aims are achieved by means of a clasp for a timepiece in accordance with the characteristics of the main claim; Yet another aim of the present invention is to provide a solution for fine adjustment of the length of a bracelet whose reliability is guaranteed over time.

[0015] According to the invention, these aims are achieved by means of a clasp for a timepiece in accordance with the characteristics of the main claim; the characteristics of the dependent claims relate to advantageous embodiments.

[0016] In particular, these aims are achieved by means of an automatic length adjustment device for a bracelet, comprising a frame articulated around a first fixing axis and a connecting element articulated around a second fixing axis, characterized in that the connecting element is connected to said frame by means of at least one elastic element and a slide, the elastic element being arranged longitudinally in a longitudinal insertion orifice passing through the slide of corresponding shape.

[0017] The advantages of the proposed solution are both aesthetic and functional, since the length adjustment mechanism is now completely hidden, making it more robust and with a correspondingly longer lifespan.

[0018] Another advantage of the proposed solution is the reduction of costs, since it is possible to use standard springs.

[0019] Yet another advantage is the ease of integration into a standard link bracelet as an inter-segment element, or into any other type of bracelet, for example, made of elastomer or leather, close to the clasp.

[0020] According to a preferred embodiment, the automatic length adjustment device for a bracelet according to the invention is characterized in that a housing is provided in a central part of the frame to receive the slide which has a shape whose cross section corresponds to that of the housing of the frame, and is mounted to slide relative to the latter.

[0021] In this way, the device is completely invisible when the springs are not stressed in extension, the slide fitting inside the frame replacing a link. Furthermore, the sliding movement of the slide is guided according to a single degree of freedom due to the shape correspondences between the slide and the housing of the frame without having to require additional guiding elements for this, which increases wearing comfort.

[0022] According to another even more preferred embodiment, the automatic length adjustment device for a bracelet is characterized in that the slide is fixed to the connecting element. Thus, the slide is configured as a simple extension of the male type connecting element which is inserted into a female part of the frame constituted by its internal central housing, and the level of prominence of the slide outside the frame easily indicates the level of length adjustment.

[0023] According to an even more preferred embodiment, the automatic length adjustment device according to the invention is characterized in that the slide is inserted into an opening of a central attachment part of the connecting element, and fixed to the central attachment part using a first bar, and that the elastic element is fixed on the one hand to the slide via a second bar, and to the frame via a third bar.

[0024] In this way, the attachment of the slide to the connecting element is dissociated from that of the elastic element connecting the slide to the frame, which makes the assembly more modular and intuitive, as well as minimizing the stresses applied to the elastic element.

[0025] According to another preferred embodiment, the automatic length adjustment device for a bracelet according to the invention is characterized in that the slide moves in a rectilinear path between a rest position and a maximum extension position.

[0026] Thus, any form of torsional stress is limited on the elastic element, which significantly increases the lifetime of the proposed solution.

[0027] According to a particularly preferred embodiment, the stroke of the automatic length adjustment device for a bracelet according to the invention is between 3 mm and 5 mm. Thus, it is possible to achieve the desired length adjustment only by means of a single extensible element providing a sufficient adjustment range to guarantee wearing comfort in all circumstances.

[0028] According to an even more preferred embodiment, the automatic length adjustment device for a bracelet according to the invention is characterized in that the slide is further provided with a vertically oriented elastic ratchet arranged to fit into a central groove, the front end of which forms a stop surface limiting the travel of the slide.

[0029] In this way, the slide is easily retained in the frame by means of a very simple and effective stop mechanism, and is parallel fixed to the frame. Such a configuration thus gives excellent compactness and ergonomics to the proposed automatic length adjustment device.

[0030] According to an even more preferred embodiment, the automatic length adjustment device for a bracelet according to the invention is characterized in that the elastic ratchet is removably inserted into a vertical housing of the slide. Thus, the device proposed for extending the size of the bracelet is of extremely simple and modular construction, which easily allows the replacement of the ratchet only and not of the slide in its entirety, in particular within the framework of an after-sales service of the comfort link proposed.

[0031] According to yet another preferred embodiment, the automatic length adjustment device for a bracelet according to the invention is characterized in that the elastic element(s) are arranged to exert a restoring force of between 5 and 10 Newtons. In this way, wearing comfort is optimal because the holding force of the bracelet around the wrist is always sufficient to prevent any slipping.

[0032] According to yet another preferred embodiment, the automatic length adjustment device for a bracelet according to the invention is characterized in that the slide comprises a first cylindrical longitudinal through-orifice intended to receive a first elastic element and a second cylindrical longitudinal through-orifice intended to receive a second elastic element arranged symmetrically with respect to the longitudinal axis of the slide.

[0033] The proposed doubling of the elastic elements makes it possible to minimize the stresses on each of them during each adjustment of the bracelet length and thus further increase the lifespan of the proposed automatic adjustment mechanism.

[0034] Another object of the present invention is to provide a bracelet solution emulating the comfort of elastomer or leather, for example, in terms of elasticity, but while retaining the appearance of a rigid metal bracelet.

[0035] This aim is achieved in particular by means of a bracelet comprising a series of central links and lateral links articulated with respect to each other, and which further comprises an automatic length adjustment device according to one of the preceding claims, characterized in that the connecting element comprises a central attachment piece connected to a first lateral link and a second lateral link using a first bar.

[0036] An advantage of such a solution is that it makes it very easy to integrate the automatic length adjustment device proposed within the framework of the present invention into a traditional metal link bracelet.

[0037] According to a preferred embodiment of such a bracelet, the central attachment part has a shape corresponding to a central half-link. Thus, the integration of the adjustment mechanism is carried out as transparently as possible with respect to the other links of the bracelet. According to an even more preferred embodiment for such a bracelet according to the invention, the frame of the automatic length adjustment device has a first length substantially equal to a second length corresponding to that of the lateral links.

[0038] This variant further conceals the automatic length adjustment device, the frame then fictitiously replacing a central link, and making the location of the automatic length adjustment device almost imperceptible to the naked eye.

[0039] According to an even more preferred embodiment for such a bracelet according to the invention, in which the slide has a shape corresponding to that of a housing arranged in a central part of the frame, extending over a first width corresponding substantially to that of the central links of the bracelet, and over a third length less than or equal to the first length of the frame, so as to be able to be housed entirely in the housing of the frame and not visually generate an intermediate segment, when extending the length, which is not particularly visible or unattractive compared to the rest of the bracelet.

[0040] According to a further preferred embodiment for the bracelet according to the invention, the travel between a rest position and a maximum extension position of the slide is defined as being substantially equal to half of a fourth length of a central link.

[0041] In this way, it is possible to best conceal the length adjustment device regardless of the adjustment required to achieve automatic extension of the bracelet length, as it will not only be virtually undetectable at rest, but also at maximum extension where the level of extension will tend to recreate a full central link completing the central half-link at the central attachment piece. Brief description of the drawings

[0042] Other advantageous characteristics will emerge more clearly from the following description of a particular embodiment of the invention given by way of non-limiting example and represented by the appended drawings, in which: there figure 1 is a three-dimensional top view of a portion of a bracelet provided with an automatic length adjustment device according to a preferred embodiment of the invention, which is shown at rest; figure 2 is a three-dimensional top view of a portion of a bracelet provided with the automatic adjustment device according to the preferred embodiment illustrated in the figure 1 , now shown in the fully extended position; the figure 3 is a three-dimensional exploded top view of an automatic adjustment device according to a preferred embodiment of the invention; figure 4 is a three-dimensional exploded view from below of an automatic adjustment device according to the preferred embodiment for the invention illustrated by the figure 3 ; THE Figures 5A and 5B are sagittal sectional views of the automatic length adjustment device according to the preferred embodiment illustrated in the figures 3 And 4 previous ones along the BB axis, respectively at rest and in extended position. Detailed description

[0043] In the following, a preferred embodiment of the invention will be described in which the bracelet is composed of metal links and the automatic length adjustment device is fully hidden in the bracelet, and the dimensions of the bracelet constituent elements correspond to those of the articulated links of the bracelet. In this way, the integration of the device is optimal from both an aesthetic and functional point of view, since the best possible performance in terms of automatic adjustment capacity is guaranteed using a modular device that can easily be integrated into a bracelet, and more particularly between the end of a strand and a clasp.

[0044] There figure 1is illustrated a three-dimensional top view of a part of a bracelet 100, in particular for a wristwatch, which is articulated around central links 10, having a first width W 1 and a length L 0 , as well as lateral links 12, having a second width W 2 and a second length L 2 . The total width W of the bracelet 100 is thus equal to W = W 1 + 2*W 2 .

[0045] The automatic length adjustment device 17 of the bracelet is shown, on the figure 1, in a retracted position P 0 corresponding to a position where the elastic elements it comprises are not stressed in extension, and therefore at rest. In this position, this device is completely hidden in the bracelet and moreover, the ratio between the length L 0 of the central links and the first length L 1 of a frame 7 replacing a central link 10, is calculated in such a way that it goes as unnoticed as possible visually; in this figure, this ratio between L 1 and L 0 is approximately 1.5.

[0046] The frame 7 preferably has a total width W equal to that of the bracelet 100, and has a central part 70 whose width corresponds to the first width W 1 of the central links 10, and lateral parts 72 whose width corresponds to the second width W 2 of the lateral links. The frame 7 is articulated around a first axis 9, which can connect it either to a clasp or to other links of the bracelet 100, and its central part 70 is of parallelepiped shape while its two lateral parts are of rounded shape like the lateral links 12 in order to visually integrate as best as possible the automatic length adjustment device 17 as an inter-segment element between consecutive links of the bracelet.

[0047] This frame 7 is connected to a central attachment piece 11, the shape of which is rounded on one side and straight on the other, corresponding to a half-link of length L 0 / 2 so that in the extended position P 1 illustrated on the figure 2 next, when the length of the extension stroke C corresponding to the maximum extension level of the length of the bracelet is chosen to preferably also correspond to a substantially equivalent length L 0 / 2, the length L 0 of a complete central link 10 is then emulated. This attachment piece 11 is connected on either side to a first lateral link 12A and a second lateral link 12B via a first bar 2, the width of which corresponds to the total width W of the bracelet 100, to form a connecting element 1, illustrated further on the figure 3which constitutes an intermediate sub-assembly with respect to the rest of the bracelet 100, to which it is articulated by means of a second axis 13, which also has a length equal to the total width W of the bracelet. As can be seen on the figures 1 And 2 , the second articulation axis 13 passes through the other ends of the first lateral link 12A and the second lateral link 12B relative to those passed through by the first bar 2, as well as one end of a central link 10, itself connected, via its other end, to two lateral links 12 of the bracelet 100. Preferably, still with a view to optimal visual integration with the bracelet, each of the first and second lateral links 12A and respectively 12B of the connecting element of the automatic length adjustment device 1 of the bracelet 100 correspond, in size and shape, to each of the lateral links 12 of the bracelet 100.

[0048] At one end of the frame 7, arranged close to the first axis 9 for fixing and articulating the latter with respect to a clasp or other elements of the bracelet, there is a third bar 8 extending over the entire width of the frame 7 intended to retain one end of one or more elastic elements 6 (hidden in this figure and visible only from the figure 3 next, also placing the second attachment bar 4 from their end opposite the slide 3, on the figure 2next, showing the automatic length adjustment device 17 in the extended position P 1 ). At the other end of the frame is materialized the demarcation line AA with respect to the attachment piece 11, which is only virtual here in the sense that no gap is available between it and the frame 7 in the retracted position P 0 . Thus, in such a configuration, the attachment piece 11 constitutes a sort of extension of the frame 7 in the retracted or retracted position P 0 where the entire mechanism used for the extension is thus almost invisible outside the demarcation line AA.

[0049] There figure 2 , almost all of whose elements are identical to the figure 1and the description of which will therefore not be repeated in detail, highlights precisely the slide 3 in which the elastic element(s) 6 according to the invention are integrated to allow the desired automatic adjustment of the length of the bracelet 100 around the wearer's wrist, according to a predefined value range corresponding to the maximum extension stroke C defining the extended position P 1 . Such a position is obtained when an extension biasing force F', greater than the restoring force F exerted by the elastic elements, is exerted between the central attachment part 10 and the frame. The elastic element(s) are preferably configured in such a way that this restoring force F, illustrated in the figure 3following, which is applied in the opposite direction to that of the extension stress force F', i.e. between 5 and 10 Newton, so that the bracelet can be adjusted easily without at the same time applying excessive stresses on the wrist of the wearer of the bracelet 100, resulting in excessive tightening then generating visible marks when it is removed.Furthermore, the maximum extension stroke C is chosen to be preferably between 3mm and 5mm, which corresponds to an extension less than the size of a link of the bracelet (central or lateral, which have a length rather of the order of 6 to 9 mm), but nevertheless sufficient to be able to adapt to significant relative variations in the size of the wrist, in the event of significant changes in particular in temperature and humidity, while corresponding to a variation in length greater than the standard indexing steps available in a clasp (generally less than 2mm). Furthermore, the proposed automatic length adjustment device guarantees continuous and instantaneous adjustment of the length according to needs, for example in the event of a sudden variation in temperature, between a heated room and a particularly cold outdoor environment in winter for example.Wearing comfort is thus optimized using a device that is compact and easy to integrate into a bracelet, whose aesthetic appearance blends perfectly into the latter, and whose adjustment properties are simultaneously improved.

[0050] THE figures 3 And 4 , which respectively consist of exploded views of the automatic length adjustment device 17 according to the preferred embodiment of the preceding figures seen from above and from below, highlight the manner in which the connecting piece 1 is connected to the frame 7 via the slide 3. In the description which follows, reference will be made indifferently to these two figures to describe the different constituent elements of the proposed automatic length adjustment device 17.

[0051] On the left of the figures 3 And 4, we can see the connecting piece 1 of the automatic length adjustment device 17 formed by the central attachment piece 11, the outer terminal surface 110 of which is rounded so as to correspond to the shape of a central link 10 of the bracelet, and of a first lateral link 12A as well as of a second lateral link 12B of equally rounded shapes. In these figures, a second through hole 112 intended to receive the first bar 2 has been materialized, as opposed to the first through hole 74 of the frame 7 intended to receive the first articulation axis 9. This first bar 2 is also inserted into a first transverse fixing orifice 31 of the slide 3, such that the latter, arranged elsewhere in an insertion opening 111 of the attachment part 11, is thus secured to the connecting element 1, and fixed to the latter without leaving any degree of mutual freedom.

[0052] The slide 3 is furthermore connected to the frame 7 by means of two elastic elements 6, i.e. a first elastic element 6A and a second elastic element 6B, a first end of which is fixed to the frame and the other end of which is fixed to the slide 3 via a second bar 4, the length of which is substantially equal to the first width W 1 of the central links 10, and inserted into a second transverse fixing orifice 32. More precisely, the first elastic element 6A has a first end 61A attached to the frame 7 via the third bar 8 and the second elastic element 6B also has a first end 61B attached to the frame 7 via the third bar 8, while the second end 62A of the first elastic element 6A as well as the second end 62B of the second elastic element 6B are attached to the slide 3 via the second bar 4 inserted into the second transverse fixing orifice 32.Furthermore, each of the first and second elastic elements 6A and 6B respectively are each inserted into a first longitudinal through insertion hole 36A and a second longitudinal through insertion hole 36B; more generally the elastic element 6 is arranged in a longitudinal through insertion hole 36 of the slide 3, of corresponding shape, here cylindrical for a standard spiral spring, and this in such a way as to minimize friction, operating clearances, and thus maximize operating efficiency while at the same time reducing wear. Furthermore, such a configuration makes it possible to operate the slide like a drawer whose return mechanism is completely hidden. In this way, the elastic elements as well as more generally the interior of the proposed length adjustment device are completely protected from the outside.

[0053] On the figure 3The arrow F is illustrated, representing the restoring force exerted by the springs, the shape of which can be chosen as being completely standard, as can the material, typically stainless steel. This reduces manufacturing constraints to a minimum, as well as costs. Doubling the elastic elements allows for better distribution of the constraints and easier adjustment of the desired restoring force intensity.

[0054] The slide 3 also has a “stack” shape, that is to say with a front surface 34 as well as a flat rear surface 33, and a parallelepipedal lateral surface 35 rounded on the edges, with a semi-cylindrical envelope. The frame 7 has a housing 71 of corresponding shape intended to receive the slide and which confines the latter to a rectilinear translational movement according to a single degree of freedom. The slide has a third length L 3 preferably substantially equal to the first length L 1 of the frame.

[0055] On the figure 3 , we can distinguish an elastic ratchet 5 intended to be integrated into the slide 3, and parallel to it in a central longitudinal groove 73 of the frame, at the bottom of the housing 71 provided for the slide 3. This central groove 73 has a front stop 73B, visible on the figure 3 , as well as a 73A rear stop, visible on the figure 4, the space between the front stop 73B and the rear stop 73A defining the extension stroke C of the slide 3 and thus the maximum possible extension level. The elastic pawl 5 has a cylindrical body 50 inserted in a vertical pawl housing 37 arranged at the bottom of the slide 3, and an elastic stud 51 intended to be inserted into the central groove 73 of the housing 70 of the frame 7. Such an arrangement makes it possible to easily manage the stroke of the slide 3, while giving a modular construction to the proposed length adjustment device 17, the entire slide 3 not having to be replaced in the event of fatigue of the elastic element formed here by the stud 51. This stud 51 also allows both the fixing of the slide 3 to the frame 7, to define end-of-travel stops for it and additional guidance in translation throughout its movement.

[0056] THE Figures 5A and 5Bcorrespond to sagittal section views along the BB axis visible on the figure 3 previous and which constitutes an axis of symmetry for the proposed automatic length adjustment device 17. The Figure 5A illustrates this device in the retracted position P 0 corresponding to the figure 1 , while the Figure 5B corresponds to the extended position P 1 corresponding to the figure 2 These two figures will be described jointly because they have the same references and only the automatic adjustment device in a different state.

[0057] On the Figure 5Ain the automatic length adjustment device 17, the frame 7 can be seen on the right and a lateral link 12 of the bracelet, articulated around the connecting axis 113 of the connecting element 1, of which only the central attachment piece 11 is visible, on the left. Between the central attachment piece 11 and the frame 7 is arranged the slide 3, which is inserted into the insertion opening 111 of the central attachment piece 11, on the one hand, and the housing 71 of the frame 7, on the other hand. The slide 3 is fixed in the insertion opening 111 via the first bar 2 which is inserted into the first transverse fixing orifice 31, and is connected on the other hand to the elastic element 6; although here it is a question of the first and second elastic elements 6A-6B, only the second elastic element 6B located behind the sagittal section plane BB is visible on the Figures 5A and 5BThe elastic element 6 formed by the first and second elastic elements 6A and 6B respectively is fixed to the slide using the second bar 4 inserted into the second transverse fixing orifice 32. On the Figures 5A and 5B , the orifices and the fixing bars are jointly referenced for the sake of simplification and readability, hence the joint references “31 / 2” and “32 / 4” corresponding respectively to the first transverse fixing orifice 31 and the first bar 2, and the second transverse fixing orifice 32 and the second bar 4.

[0058] Then the end of the second elastic element 6B which is held by the second bar 4 is hidden, we can distinguish, on the right of the Figures 5A and 5B , at the bottom of the housing 71 of the frame 7, the first end 61B of the second elastic element 6B which is fixed there using the third bar 8.

[0059] Between the retracted position P 0 visible in the figure and the extended position P 1 visible in the Figure 5B, we can see the extension of the spiral spring forming the second elastic element 6B, while the rectangular slide 3 moves in a completely rectilinear manner in the housing 71 of the frame 7, having a corresponding shape. During this movement of the slide 3 and throughout its extension stroke C defining the maximum extension level of the length of the bracelet, the stud 51 of the elastic pawl 5, inserted in the vertical housing 37 of the slide 3, is arranged in the central groove 73 arranged on the lower surface of the frame 7, and is held there under the impulse of an elastic restoring force acting downwards (not shown).This ratchet 5 simply associated with the slide 3 is fixed there in a removable manner in order to constitute a wear part which can be easily replaced, separately from the other constituent elements of the proposed automatic length adjustment device; it also dispenses with any other part to be mounted on the frame to define a stop limiting the level of extension of the springs and consequently the maximum possible elongation of the length of the bracelet and thus contributes to making the proposed solution as compact and as small as possible.

[0060] Although the invention has been described in the foregoing using an example intended for a wristwatch formed of articulated metal links, it will nevertheless be understood from the following that the person skilled in the art could envisage various variants without departing from the scope of the invention. In particular, the invention could also be used in the context of a piece of jewelry, provided with a clasp or not, and the dimensions of the proposed device as well as its location in the bracelet could be adapted according to requirements.

Claims

1. Device for automatic length adjustment (17) for a bracelet, comprising a rack (7) pivotable about a first fastening axis (9) and a connecting element (1) pivotable about a second fastening axis (13), said connecting element (1) being connected to said rack (7) via at least one elastic element (6) and a slider (3), characterized in that said elastic element (6) is disposed longitudinally in a longitudinal through-hole (36) of said slider (3) of corresponding shape to said elastic element (6).

2. Device for automatic length adjustment (17) for a bracelet according to claim 1, characterized in that a housing (71) is provided in a central portion (70) of the rack for receiving the slider (3), said slider (3) having a shape whose cross-section corresponds to that of said housing (71) of said rack (7) and being slidably mounted relative to said rack (7).

3. Device for automatic length adjustment (17) for a bracelet according to claim 2, characterized in that the slider (3) is attached to said connecting element (1).

4. Device for automatic length adjustment (17) according to claim 3, characterized in that said slider (3) is inserted into an opening (111) of a central attachment part (11) of said connecting element and fixed to said central attachment part (11) by means of a first spring bar (2), and that said elastic element (6) is fixed on the one hand to said slider (3) via a second spring bar (4), and to said rack (7) via a third spring bar (8).

5. Device for automatic length adjustment (17) for a bracelet according to one of the preceding claims, characterized in that said slider (3) moves along a straight path (C) between a rest position (P0) and a position of maximum extension (P1).

6. Device for automatic length adjustment (17) for a bracelet according to the preceding claim, said the length of said path (C) being comprised between 3mm and 5mm.

7. Device for automatic length adjustment (17) for a bracelet according to claim 5 or 6, characterized in that said slider (3) is further provided with a vertically oriented elastic pawl (5) arranged to engage in a central groove (73) whose front end (73A) forms an abutment surface limiting said path (C) of said slider (3).

8. Device for automatic length adjustment (17) for a bracelet according to claim 7, characterized in that said elastic pawl (5) is removably inserted in a vertical housing (37) of said slider (3).

9. Device for automatic length adjustment (17) for a bracelet according to one of the preceding claims, characterized in that said at least one elastic element (6) is arranged to exert a restoring force (F) of between 5 and 10 Newton.

10. Device for automatic length adjustment (17) for a bracelet according to one of the preceding claims, characterized in that said slider (3) comprises a first cylindrical longitudinal through-hole (36A) designed to receive a first elastic element (6A) and a second cylindrical longitudinal through-hole (36B) designed to receive a second elastic element (6B) arranged symmetrically with respect to the longitudinal axis of said slider (3).

11. Bracelet (100) comprising a series of central links (10) and side links (12) articulated to one another, and further comprising a device for automatic length adjustment (17) according to one of the preceding claims, characterized in that said connecting element (1) comprises a central attachment piece (11) connected to a first side link (12A) and to a second side link (12B) by means of a first spring bar (2).

12. Bracelet according to claim 11, said central attachment piece (11) having a shape corresponding to a central half-link.

13. Bracelet (100) according to claim 11, wherein the rack (7) of said device for automatic length adjustment (17) has a first length (L1) substantially equal to a second length (L2) corresponding to that of said side links (12).

14. Bracelet (100) according to claim 12, wherein said slider (3) has a shape corresponding to that of a housing (71) provided in a central portion (70) of the rack (7), extending over a first width (W1) substantially corresponding to that of the central links (10) of said bracelet (100), and over a third length (L3), which is less than or equal to said first length (L1) of said rack (7).

15. A bracelet (100) according to any of claims 11 to 13, wherein the path (C) between a rest position (P0) and a position of maximum extension (P1) of said slider (3) is defined as being substantially equal to the half of a fourth length (L0) of a central link (10).