System for adjusting the length of a bracelet

Abstract

The invention relates to a system for adjusting the length of a bracelet, intended for a clasp (10) having two strands, said system comprising at least one guide (50) attached to the clasp by a fastening system (32-35, 52, 57) and a sliding carriage (40), wherein the carriage is connected to one of the strands and the length of the bracelet can be adjusted by moving the carriage. The system according to the invention is modular because it does not require special machining of the clasp in order to allow integration of the system into the clasp.

Description

BRACELET LENGTH ADJUSTMENT SYSTEM Domain The present invention relates to a system for adjusting the length of a bracelet, in particular a watch bracelet, a clasp comprising the system and a wristwatch comprising the system. The invention also relates to a clasp and a wristwatch comprising such an adjustment system. In other embodiments, the adjustment system according to the invention can be applied to other products such as a belt for example. State of the Watch straps typically include a mechanism for adjusting the strap length while the watch is being worn. For example, in the case of two-strand leather or synthetic straps, the free end of one strand has a series of holes running lengthwise along the strap. The free end of the other strand has a connecting device, such as a pin buckle, that allows the two strands to be joined by inserting the pin into the hole corresponding to the desired length. In the case of metal link bracelets, the length can be adjusted, for example, by removing or adding a link to one or both strands of the strap.However, in both cases, the possible adjustments to the usable length of the bracelet are quite crude, and it is possible that the circumference of the wearer's wrist will fall between two adjacent settings, making it difficult to achieve a comfortable fit. Clasps equipped with a mechanism to finely adjust the length of the 1 P-0723-WO; 15 / 10 / 2025 The mechanisms for wristbands are known from the prior art. These mechanisms include a locking or locking device to prevent unintentional or accidental lengthening and / or shortening of the bracelet. Generally, the aim is to prevent unintentional lengthening, as the risk of unintentional shortening is lower. Furthermore, the ability to quickly shorten the bracelet without activating a release mechanism is also desirable for the wearer, as it allows them to easily tighten (or adjust) the bracelet around their wrist at any time. For example, a user whose hand on the arm wearing the wristwatch is occupied can still tighten the bracelet by applying pressure with their other hand to a section of the bracelet in the direction intended to shorten it. Publication EP2868222 describes a folding clasp for a bracelet comprising a bracelet length adjustment device. This device includes a moving part connected to a first linking member intended to be attached to a free end of a first bracelet strand, and a support rigidly fixed to a blade or the clasp cover. The moving part includes a carriage with a rack, and the support is equipped with a locking piece comprising a jaw for engaging with teeth of the rack. In the locked position, the jaw prevents the rack from moving and thus prevents the length adjustment. Publication WO2019 / 166671 describes another bracelet clasp incorporating means for adjusting the bracelet length. In this publication, the device for adjusting the usable bracelet length is integrated with the cover. A distinctive feature of the clasp, according to this publication, is that it does not require an actuating or manipulating element to release the fine adjustment stop from its engagement with the rack. Publication EP4059374 describes an alternative bracelet clasp construction incorporating means for adjusting the bracelet's length. 2 P-0723-WO; 15 / 10 / 2025 allowing for quick adjustment. More specifically, this publication concerns a bracelet clasp with an adjustment device comprising a pivoting element, said element being actuable by a user to activate the length adjustment. Publication EP2875747 shows a clasp that allows the bracelet length to be adjusted by applying force to the bracelet strand attached to a moving part. To lengthen the bracelet, the user opens the clasp and presses down on a support surface to release the prong and move the moving part in the direction the bracelet is being lengthened. US patent 6,944,916 discloses a clasp equipped with a fine adjustment mechanism comprising two lateral slides, the movement of which unlocks the mechanism by releasing two lateral racks secured to the free end of one of the two bracelet strands. In this clasp, the mechanism is activated laterally. Furthermore, the clasp cover assists in guiding the racks. In the fine adjustment mechanism disclosed in US patent 11,730,240, a pivoting actuating element is arranged in the cover to cooperate with a rack that slides between the side walls of the clasp cover. The clasp must be opened to make a fine adjustment. The actuating element must also be operated to shorten the usable length of the bracelet. Existing systems have certain drawbacks: for example, a large number of parts makes them complex and expensive to manufacture. In other designs, this can be a reliability issue: the bracelet adjustment is not consistently secure and tends, for example, to allow accidental and unwanted extensions of the bracelet, thus risking loss of the watch. In some constructions, when the clasp cover includes a 3 P-0723-WO; 15 / 10 / 2025 Because the lid, with its rack and / or slides, cannot (or is difficult to) produce in certain materials such as ceramics, precious metals, or other high-quality materials, it consequently limits the choice of materials available for manufacturing at least this part of the clasp. Since the lid is a visible part of the system, it is sometimes desirable to make it from such high-quality materials, which is therefore not possible, as explained above. Machining the lid (or cover), particularly its inner surfaces, is expensive, and the present invention aims to minimize such machining. One objective of the invention is to implement a fine adjustment mechanism that can be easily integrated into various types of lids and / or standard lids. Another objective of the invention is to implement an independent assembly, a kind of module, which contains all the elements of a fine adjustment mechanism, and which can be arranged on a clasp in a modular way, requiring minimal adaptation of the clasp to allow integration of the mechanism, for example under a cover. Other constructions are not easy to manipulate to obtain the desired result (shortening or lengthening the bracelet) or are not intuitive for the user, making them impractical. Summary of the invention One aim of the invention is therefore to improve existing systems. Another objective of the present invention is to provide a simple and reliable system for finely adjusting the length of a bracelet. Another objective of the present invention is to provide a system for fine-tuning the length of a bracelet that requires only a few parts and / or uses 4 P-0723-WO; 15 / 10 / 2025 standard parts in the technical field. Another objective of the present invention is to provide a fine adjustment system for the length of a bracelet that can be used on bracelet clasp parts made of different materials, such as metal (precious or not), ceramics, sapphire and other various materials (precious or not). In some embodiments, the invention relates to a clasp for a wristwatch strap in which the means for finely adjusting the length are gathered in an adjustment module. This modular construction makes it possible, on the one hand, to overcome the limitation recognized above in the materials that can be used to manufacture the clasp, in particular its visible parts: the invention allows the use of many more materials for these parts of the clasp, such as the lid. Furthermore, its modular construction allows it to be added to existing clasps with a few simple adaptations. In some execution modes, the adjustment means are invisible when the bracelet is worn, for example with a wristwatch. In some execution modes, the adjustment means are visible in a limited way when the bracelet is worn, for example with a wristwatch. In some execution modes, the adjustment means are accessible when the clasp is in an open configuration. In some execution modes, the adjustment means are accessible when the clasp is in a closed configuration. In some embodiments, the invention relates to a system for adjusting the length of a bracelet, the system being arranged to allow adjustment of 5 P-0723-WO; 15 / 10 / 2025 The bracelet length is adjusted by relative movement between two bracelet strands or two bracelet sections. The system is arranged to be attached to a wristwatch clasp. The system comprises a guide arranged to be attached to the clasp, for example, to a clasp cover, and a carriage arranged to slide relative to the guide. The carriage may be connected to one of the bracelet strands or sections and, by its movement relative to the guide, allows for adjustment of the bracelet length. The system preferably includes a locking mechanism arranged to ensure at least one locked position of the carriage and a second unlocked position. In one execution mode, the system includes a movable actuating member mounted on the guide, arranged to be activated by a user to move from said blocked position to said released position. In one execution mode, the system includes an indexing device placed on the carriage. In one embodiment, the cooperation of the locking member and the indexing member prevents the carriage from sliding relative to the guide in the blocked position of the carriage in at least one direction of sliding. In some embodiments, the invention relates to a clasp for a bracelet (for example, for a watch) comprising two strands, the clasp comprising a system for adjusting the length of said bracelet by relative movement of said strands, said system comprising at least one cover, a support and / or guide fixed to the cover by fastening means, and a carriage sliding on the cover, the carriage being linked to one of said strands and allowing, by its movement, the adjustment of the bracelet length, the clasp comprising locking means for blocking the movement of said carriage, the locking means comprising at least one actuating member movably mounted on the guide to ensure at least a first locked position of the carriage and a second unlocked position of the carriage, an indexing member placed on the 6 P-0723-WO; 15 / 10 / 2025 carriage, the cooperation of the actuating member and the indexing member preventing the carriage from sliding relative to the guide in the carriage's locked position. In some embodiments, the carriage and guide are arranged such that the movement of the carriage relative to the guide is guided entirely and / or solely by the system and / or the guide and / or independently of a cover and / or the side walls of a cover of the clasp. The relative movement of the carriage with respect to the guide is preferably a sliding motion. In some execution modes, the locking means contribute to guiding the carriage. In some embodiments, the guide, the carriage and optionally at least part of the fastening system form an assembly which constitutes said length adjustment system. In embodiments, the locking means include a locking element arranged pivotally in and / or on said guide or arranged on said guide so as to be able to perform a translational movement, preferably in a substantially radial direction. In embodiments, the carriage comprises two lateral longitudinal elements, an indexing member or at least a partial indexing member positioned on at least one of said lateral longitudinal elements, preferably on each of the two lateral longitudinal elements. In some embodiments, an upper wall of the cover includes an opening, the actuation means being located in said opening and / or being actuationable through said opening. In some embodiments, a first fastening means includes one or 7 P-0723-WO; 15 / 10 / 2025 several elements chosen from a spring bar, a pin and / or a screw, preferably arranged in an orthogonal direction. In some embodiments, a second fastening means comprises one or more elements selected from a spring bar, a pin and / or a screw, preferably arranged orthogonally to the component In embodiments, the carriage and the guide are arranged so that the movement of said carriage relative to the guide is guided entirely and / or solely by said system and / or by said guide and preferably independently of a cover and / or the side walls of a cover of the clasp. In embodiments, the actuating member and / or the locking member is arranged in said at least one opening so as to limit a relative displacement of the carriage with respect to the guide in a transverse direction and / or so as to guide the displacement of the carriage in a longitudinal direction. In embodiments, the guide and preferably the locking member and / or the actuating member includes surfaces for guiding the movement of the carriage in the longitudinal direction. In some embodiments, the indexing element is a rack with teeth. In some embodiments, the actuation means is an internal push-lever accessible from an inside side of the cover for its actuation. In some embodiments, the actuation means is an external push-lever accessible from an outside side of the cover for its actuation. 8 P-0723-WO; 15 / 10 / 2025 In some execution modes, the actuation means is an external button accessible from an outside side of the cover (30') for its actuation. In some embodiments, the means of fixing the guide are at least a spring bar and / or a screw. In some embodiments, the push-lever is mounted on a first guide fixing means or on a second adjustment guide fixing means. In some embodiments, the actuation means is held in a stable position by at least one spring. In some execution modes, the internal and external push-levers or the button are fixed to each other. In some embodiments, the internal and external push-levers are fixed by at least one screw. In some embodiments, at least the lid is made of metal, precious metal, ceramic, or a mixture of materials. In some embodiments, the invention relates to a watch strap, said strap being combined with a clasp as described in the present application. In one aspect, the invention relates to a bracelet link, preferably for a wristwatch, comprising the system of the invention. In embodiments, the invention relates to a wristwatch combined with a strap as described in this application or with a clasp as described in this application. 9 P-0723-WO; 15 / 10 / 2025 The system of the invention is advantageous because it is modular in that it does not require any special machining of the clasp to allow the integration of the system into the clasp. Other aspects and preferred embodiments of the invention are defined in the independent and dependent claims and in the description below. The invention and its various embodiments will be better understood from the detailed description that follows and the figures in this application. Brief description of the drawings Figure 1 illustrates a perspective view of a clasp according to an embodiment of the invention in the open position and viewed from inside a watch strap. Figure 2 illustrates a perspective view of the clasp of figure 1 in the closed position and seen from the outside. Figures 3 to 5 illustrate respectively a perspective view from below, a perspective view from above and a cross-sectional view of the system of the invention according to an embodiment of the system of the invention, used in the clasp shown in figures 1 and 2. Figures 6 to 10 illustrate transparent top and cross-sectional views of the system of the execution mode of Figures 3 to 5 arranged in a clasp cover. Figures 11 and 12 illustrate a perspective view of a system of another embodiment of the invention arranged in a clasp cover and seen from outside the cover. 10 P-0723-WO; 15 / 10 / 2025 Figures 13 to 15 illustrate side and perspective views of the system according to the execution method of Figures 11 and 12. Figures 16 to 20 illustrate transparency and cross-sectional views of the embodiment shown in figures 11 and 12 arranged in a lid. Figures 21 and 22 illustrate a perspective view of the system of another embodiment of the invention seen from the outside and arranged in a cover. Figures 23 to 25 illustrate side and perspective views of the system of the invention according to the embodiment of Figures 21 and 22. Figures 26 to 30 illustrate transparent and cross-sectional views of the execution of figures 21 to 25 with the lid. Figures 31 and 32 illustrate a perspective view of a system of another embodiment of the invention arranged in a cover and seen from outside the cover. Figures 33 to 35 illustrate side and perspective views of the system according to the execution method of Figures 31 and 32. Figures 36 to 40 illustrate transparent and cross-sectional views of the execution of figures 31 to 35 with the lid. Figure 41 illustrates a perspective view of the system of another embodiment of the invention arranged in a cover and seen from outside the cover. Figures 42 to 44 illustrate transparency and cross-sectional views of a system of the invention according to the embodiment of Figure 41. 11 P-0723-WO; 15 / 10 / 2025 Figures 45 to 47 illustrate transparent top and cross-sectional views of the execution of figures 41 to 44 with the lid. Detailed description In the different embodiments of the invention described below, there are elements and parts having the same numerical references and they are identical or equivalent and their role / function applies in an identical or equivalent way to each embodiment. Figure 1 shows a general perspective view of a watch strap clasp 10 comprising the system of the invention 25. The clasp is intended to be connected to two free ends of a strap. Schematically, the strap is illustrated by its two terminal links 21, 22, each being fixed to one end of the clasp 10. The clasp 10 conventionally comprises a folding buckle with a base 11 including two spaced side rails 12 attached to a spacer 13, intended to be connected to the terminal link 21 of the bracelet, and a folding arm 14 including two prongs 15, 16 for holding the buckle in a closed position, as described in the publications mentioned above. This clasp is given as an illustrative example and other clasps may be used. The clasp 10 also includes a cover 30 with pushers 31 for pressing on the arms 15, 16 and opening the buckle, as described, for example, in publications EP2868222 and EP2875747 mentioned above, and openings 32, 33, 34, 35. The openings 32-35 are formed as through holes in the two lateral flaps 27 of the cover. A movable carriage (or moving part) 40, which will be detailed in the following figures, is also visible in the cover 30. The invention is not limited to the type of closure mechanism described in these publications and can be implemented in a clasp comprising another 12 P-0723-WO; 15 / 10 / 2025 The clasp mechanism, preferably a mechanism comprising one or more actuating elements intended to be operated by a user to open the clasp, as described in the publications mentioned in the introduction above. The invention can also be implemented in a clasp comprising a mechanism lacking an activating element for opening. Document EP4238447 discloses such a mechanism and mentions some different clasp systems that can be used in clasps on wristwatches. In the embodiment shown, the system 25 of the invention is rigidly connected within the cover of a clasp. The invention also provides for a connection to another part of a clasp, for example, to the base 11 or to the flap 14. The modular system of the invention can also be attached to another type of clasp, such as a buckle or a combined clasp (flap and buckle). The cover can only partially cover the clasp blades, and can be a cap or a hood. Figure 2 illustrates the cover 30 seen from another side relative to Figure 1. The cover comprises a top wall 26 and two side walls or side flaps 27. The openings 34, 35, the corresponding openings 32, 33 seen in Figure 1, as well as the openings 36 of the pushers 31 are arranged on either side in the side flaps 27. On the right side of the cover 30, we can see the fixing end 41 of the carriage 40 to the terminal link 22 of the bracelet (see figure 1). Figures 3 to 5 illustrate in more detail the system 25 comprising the adjustment carriage 40 and the guide 50 according to one embodiment of the invention. The carriage 40 includes an attachment end 41 for a link (22) of the bracelet. This link is not part of the clasp, and the invention also covers the use of a bracelet made of leather or soft plastic, or other materials, by 13 P-0723-WO; 15 / 10 / 2025 example. As will be understood from the rest of this description, the carriage 40 is mobile relative to the guide 50 and thus mobile in the cover 30, which allows fine adjustment of the bracelet length. The carriage 40 includes a rack with two teeth 42, 43, which, in the embodiment shown, are located on the side of the cover 30 and are situated on each side of the guide 50, the latter allowing the carriage 40 to be held in a fixed position or alternatively allowing it to slide for length adjustment, the movement being between the carriage 40 and the guide 50. The latter is fixedly mounted in the cover 30, the axes 52 and 57 (for example bars, pins and / or screws) being inserted into the openings 32-35 of the cover (see figure 1). According to this description, the parallel teeth 42, 43 can be considered as a single set of teeth or as partial teeth of an indexing member and / or of a set of teeth comprising both sets. It should be noted that the invention can be implemented with a single set of teeth 42, 43 instead of two. The guide 50 serves, on the one hand, to guide the longitudinal movement of the carriage 40 and, on the other hand, it constitutes the fixed element of the adjustment system of the invention. The system can be rigidly attached to a clasp, for example in the cover as shown, by means of the guide 50. The guide can also be considered as a "support" for the carriage 40, the latter being carried by and / or connected to the guide. The guide also functions as a support for the actuating member and / or for a locking member 65 comprising the locking elements 53, 54. The definitions of longitudinal, transverse (or orthogonal) and radial directions and other orientations or situations in space are known in the field of watch clasps and are detailed, for example, in document WO2019166671 A1, pages 9 and 10. 14 P-0723-WO; 15 / 10 / 2025 A person skilled in the art will notice that the carriage 40 is larger than the support 50. More specifically, the extension, the dimension of the carriage in the longitudinal direction (the length) is greater than the extension of the guide in the same direction. In the execution mode shown, the extension (or dimension) of the carriage in the radial direction (in particular the thickness) is greater than the extension of the guide in that same direction. In the execution mode shown, the extension in the transverse / orthogonal direction of the carriage 40 and the guide 50 is substantially identical. This is unusual because, in the prior art, the moving part is generally integrated into or framed by the support that enables and guides its movement. In the embodiments shown, it is the carriage 40 that frames the guide 50. In the mechanism of the embodiment shown, the guide 50 is smaller than the element guided by the guide, here the carriage 40, as described above. The carriage 40 comprises, forms and / or is substantially made up of a frame including lateral openings or slots 48.1, 48.2, 49 in which the guide 50 is located. It is through the openings that the guide is fixed to the clasp, preferably to the lateral walls 27 of a cover. In the embodiment shown, the carriage 40 forms a frame comprising, on each of its two lateral sides, a pair of longitudinal elements 44, 45, separated by the slot 49 on each side. Each of the two pairs comprises an upper lateral longitudinal element 44 and a lower lateral longitudinal element 45, the lower element 45 being the one radially closer to the wrist of a wearer of a wristwatch including the clasp in the closed position. 15 P-0723-WO; 15 / 10 / 2025 The opening 49 is arranged on each side between the pair of elements 44, 45. At each of their two ends in the longitudinal direction, the longitudinal elements 44, 45 are connected by a transverse 46, 47, respectively. Thus, the cross member 46 connects both the two upper elements 44 and the two lower elements 45 at a first end, and the cross member 47 connects the two upper elements 44 and the two lower elements 45 at a second end. The fastening member 41 is connected, preferably rigidly, to said second end and / or to the cross member 47. The longitudinal lateral elements 44 are preferably substantially parallel. Similarly, the lateral elements 45 are preferably substantially parallel. Finally, the lower and upper lateral elements 44 and 45 on each side are substantially parallel. Note, for example, in Figure 5, that the lateral elements 44 and 45 are slightly curved. This curvature follows and / or corresponds to the overall curvature of the clasp, the purpose of which is to better adapt the clasp to the wrist of the wearer of a wristwatch that includes the clasp. As can be seen in figures 3 and 4, the frame formed by the longitudinal elements and the transversals delimits a lower central opening or window 48.2 between the elements 45 (fig. 3), and the two transversals and an upper central opening or window 48.1 between the elements 44 and the two transversals (fig. 4). The racks 42, 43 are arranged on and / or along the longitudinal elements 44, here on their respective upper faces. A pivoting locking member 65 is arranged to pivot on the guide 50 and passes through the upper window 48.1. The element 65 comprises two lateral teeth 53, 54, arranged to cooperate with the interdental spaces of one of the racks 42, 43, respectively. The teeth 53, 54 are more generally "locking elements," but for the sake of space economy, the term "teeth" is also used in this description. 16 P-0723-WO; 15 / 10 / 2025 When the teeth are engaged with their respective rack, as shown in Fig. 4, the movement of the carriage relative to the guide 50 is blocked in the direction of the bracelet extension. The teeth of the dentures 42, 43 are oriented radially, here upwards. Consequently, the movement of the locking elements 53, 54 to switch between the locked and unlocked positions takes place in (or is parallel to) a radial and longitudinal plane. The system 25 of the embodiment shown is symmetrical, and the movement of the locking elements takes place in at least one plane (e.g., AA) that is parallel to the plane of symmetry of the clasp, as shown by the cross-section in Fig. 7. According to a preferred embodiment, the system 25 of the invention is functional independently of a dedicated or specific guiding structure arranged in the clasp, for example in the lid. A specific and / or dedicated structure and / or arrangement used to guide the movement of the trolley would be, for example, a rail, edges, and / or longitudinal grooves specifically arranged in the cover to guide the trolley. Such rails are often provided in the prior art, for example in EP2868222 and US11730240B2. According to one embodiment, two side walls, for example of a cover or another element of the clasp or bracelet, are used to help guide the carriage, preferably without a dedicated guide structure being arranged in the walls and / or the cover. The side walls are preferably devoid of one or more guide rails. As a result, the system of the invention can be integrated into a standard clasp cover. The system of the invention can also be integrated into a bracelet link, for example, a metal-link bracelet. In this case, the bracelet preferably includes a special and / or machined link arranged to accommodate the system of the invention. 17 P-0723-WO; 15 / 10 / 2025 In other words, the guide 50 and the carriage include the structural elements that guide the carriage 40, which is necessary for length adjustment. These structural elements are arranged to allow longitudinal movement during the length adjustment and also to prevent further relative movement between the guide 50 and the carriage. The way in which the carriage 40 and the guide 50 restrict and direct the carriage's movement will be described below. The guide 50 comprises a body or support 50.3 whose external dimensions follow the general shape of an oblong bar oriented transversely within the carriage 40. The body 50.3 comprises an upper surface 68 (Fig. 15) and a lower surface 69 (Fig. 3), defining the thickness of the body. This thickness in the radial direction corresponds to (or is slightly less than) the distance between the lower and upper longitudinal elements 45, 44 of the carriage 40. The ends of the bar 50.3 are thus each located in one of the lateral slots 49 delimited by the elements 44-47. In this way, the longitudinal elements 45, 44 frame the guide 50 and allow the latter to limit the radial movement of the carriage. As can be seen, for example, in the cross-sections shown in Figures 5 and 10, the assembly formed by the locking member 65 and the push-lever 51 has a V-shaped (or L-shaped) profile, in which one wing of the V comprises the push-lever 51 and the other wing comprises the locking member 65. The pivot axis is located at the junction of the wings of the V. In several embodiments of the invention, the locking member is integral with the actuating member or with at least one actuating member, if the system 25 comprises several. In one embodiment, an actuating member is rigidly connected to, or integral with, the locking member. In another embodiment, described later, the actuating member is arranged to cooperate with and / or act upon the locking member 65, without being connected to or integral with it. 18 P-0723-WO; 15 / 10 / 2025 The locking member 65 comprises a central part arranged to pass through the upper window 48.1 formed between the two upper longitudinal elements 44 (Fig. 4). The extension of the window 48.1 in the transverse direction is delimited by the inner surfaces 67 of the longitudinal elements 44. Furthermore, the central part comprises two lateral faces 68 (Figures 4, 13 and 66), each of which faces an inner face 67 of the respective lateral longitudinal element 44. The transverse extension of the central part of the locking member 65 is small enough to pass through the window 48.1, but large enough to prevent relative transverse movement between the guide 50 and the carriage 40. The faces 67 and 68 of the frame 40 and of the locking member 65, respectively, can be in contact with each other and constitute sliding surfaces which prevent relative movement in the transverse direction while allowing and / or guiding the movement of the carriage 40 in the longitudinal direction. Thanks to the dimensions of the body 50.3, the locking member 65 and the carriage 40, in particular the openings or windows 47.1, 48.2 and 49 provided in the frame 44-47, the invention achieves relative guidance between the carriage and the guide, this guidance functioning in the absence of a dedicated guide structure machined in the cover 30 or another structural element of the clasp 10. The side walls 27 can contribute to the guidance in the longitudinal direction without a dedicated structure being machined inside the cover. As can be seen in Figure 4, the locking elements 53, 54 are made in the form of two lateral extensions or appendages relative to the central part of the locking member, which is defined by the lateral surfaces 68. In other words, the locking member 65 includes said central part to pass through the window 48.1 and then rest upon, 19 P-0723-WO; 15 / 10 / 2025 by means of the locking elements 53, 54, on either side on the teeth arranged on the lateral longitudinal elements 44. The body 50.3 of the guide 50 further includes two parallel through holes 50.1 and 50.2 in the transverse direction. Each of these holes creates an opening on each of the two lateral sides of the body 50.3. Considering the oblong bar shape of the body oriented in the transverse direction and having two ends, the openings of the holes 50.1 and 50.2 are located at the two opposite ends of the oblong bar. These holes are intended to house spring bars 52, 57 used to connect the guide 50 rigidly to the cover by placing the free ends of each of the bars in a pair of opposite holes 32, 34 and 33, 35 respectively, arranged in the side flaps of the cover as described above. The body 50.3 also includes a central recess or housing, the locking member 65, and return elements arranged within said recess. The return elements, here two torsion springs 55, 56, serve to force the locking member into a locked position. In the illustrated embodiment, an internal push-lever 51 is mounted to rotate freely on an axis (Fig. 3). The push-lever 51 is integral, for example rigidly connected or as a single unit, with the locking member 65. The axis of rotation of the assembly 51, 65 is here the bar 52 which passes through the opening 50.1 of the body 50.3, so that the pressure on the internal push-lever 51 has the effect of a rotation of the locking member 65 around the axis 52 which disengages teeth 53, 54 from teeth 42, 43 and allows relative movement between the carriage 40 and the system 50. Based on what has been described, it will be understood that the bar 52 fulfills the dual function of being both a fixing element for the guide 50 to the clasp and the axis of 20 P-0723-WO; 15 / 10 / 2025 pivoting of the locking member 65. It would also be possible to provide a tube that forms the locking axis, with the bar 52 being threaded through the tube. In this case, the bar 52 can stabilize the tube and / or is coaxial with the tube. Furthermore, it will be understood that the bars 52 and 57, used to connect the guide 50, and thus the system 25, to the clasp, pass through the lateral slots 49 provided by the frame 44-47 of the carriage. The slots 49 are therefore openings or passages in the carriage that allow the guide, which is located in the carriage, to be connected to the cover without hindering the relative movement of the carriage with respect to the guide during length adjustment.The invention envisages other elements for fixing the guide 50 to the clasp, such as screws, pins, nails, embedded parts, etc., as well as combinations including fixing elements of different types, such as a bar and one or more screws, for example. The invention provides for one or more fixing elements which pass through one of the openings 48.1 or 48.2 (the openings in the radial direction) to fix the guide to the clasp, for example to the lid. In the embodiment shown, the fixing bars 52, 57 are spaced longitudinally. In this way, a fixing system is obtained that allows the system to be secured to the clasp. In one embodiment, the fastening system is part of the system 25 of the invention. In another embodiment, the fastening system is not part of the system and is not included within it. For example, where the system is attached to the clasp by means of screws, the screws are not necessarily included in the system. In the embodiment shown, the bar 52 forms the pivot axis of the push-lever and is preferably included in the system of the invention. As can be seen in Figure 3, the push-lever 51 passes through and / or is actuated through the lower window 48.2 of the carriage 40, on the opposite side, in the radial direction, from the teeth 42, 43. In one embodiment, the member 21 P-0723-WO; 15 / 10 / 2025 The actuation mechanism is arranged to be activated through an opening in the carriage 40 and / or arranged by the frame 44-47 of the latter. The springs 55, 56 act on the locking member and allow the push-lever to be kept in a stable position in which the locking elements 53, 54 are engaged in the teeth 42, 43 which blocks the relative movement of the parts 40, 50. Figures 6 to 8 illustrate a position in which it is possible to lengthen the bracelet, Figure 7 illustrating the section along axis AA of Figure 6 and Figure 8 illustrating the section along axis BB of Figure 6. Section AA extends in the transverse and longitudinal plane which, in the embodiment shown, constitutes the plane of symmetry of the system. In the position shown in these figures, referred to for example as "unlocked", the internal push-lever 51 has been pressed, which has the effect of rotating it around the axis 52 of the locking member 65 and disengaging the locking elements 53, 54 from the rack teeth 42, 43 as seen in figures 7 and 8. The position illustrated is that in which the bracelet has the largest diameter since the carriage 40 is against the guide 50 which is fixed in the cover 30. The carriage travel stop is formed by the cross member 46 (figure 3). It should also be noted that the cover 30 includes a concavity 38 machined in the inner face of the upper wall 26. This concavity creates additional space to allow the locking member 65 and / or the locking elements 53, 54 to pivot when the push-lever 51 is actuated. The concavity 38 can be omitted, for example by moving the fixing of the system 25 downwards in the flaps of the cover. As can be seen from Figures 7 and 8 and the shape of the teeth 42, 43 and the locking elements 53, 54, it is necessary to press on the internal push-lever 51 to lengthen the bracelet. Conversely, to shorten the bracelet, this is not necessary, and the slope of the teeth 42, 43 22 P-0723-WO; 15 / 10 / 2025 allows shortening by simply acting on the bracelet in the direction of shortening in the longitudinal direction. Figures 9 and 10 illustrate a position in which the bracelet is shortened, Figure 9 illustrating the cut along axis AA of Figure 6 and Figure 10 illustrating the cut along axis BB of Figure 6. Here, the cross member 47 is against the guide 50, and it is not possible to lengthen the bracelet further using the length adjustment device. In the position shown, called for example "blocked", the internal push-lever 51 is not pressed but is in its stable position thanks to the springs 55,56. The teeth 53 and 54 are meshed in their respective teeth 42, 43, as can be seen in figure 9, for example tooth 43 are in an interdental space of the tooth 42. As can be understood by considering the position of the end 41 of the carriage relative to the cover 30, in figures 9 and 10, the bracelet is in a state of maximum shortening (the crossbar 47 against the guide 50) and its lengthening is not possible without support on the internal push-lever 51. Figure 11 illustrates another embodiment of the invention in which the elements identical to those in the previous embodiment have the same numerical references. In this embodiment, as can be understood by comparing Figures 11 and 2, the guide 50 includes an external push-lever 58 accessible from the top of the cover 30'. Said cover 30' is therefore similar to cover 30 with openings 34, 35, and 36, but additionally includes a window 37 which allows the external push-lever 58 to be actuated to unlock the bracelet length adjustment system. Figure 12 shows the same view as Figure 11, but the push-lever 58 is in a different position, the rest position. More precisely, Figure 11 illustrates a position, referred to as "activated" or "unlocked," allowing the bracelet length to be increased, while the position in Figure 12 is a position 23 P-0723-WO; 15 / 10 / 2025 blocked, which only allows the bracelet to be shortened. Figures 13 to 15 illustrate in detail the external push-lever 58 mounted on a guide 50 similar to that described in the preceding figures. As illustrated in Figures 13 to 15, the system 25 of this embodiment includes in particular a guide 50 as described previously, with a body 50.3, an internal push-lever 51, openings 50.1 and 50.2, a shaft 52 (the shaft present in the opening 50.2 in the assembly is not shown but is for example similar to the shaft 52, for example a bar), and a locking member 65 comprising locking elements 53, 54, the internal push-lever 51 being mounted on the shaft 52, the springs 55 and 56 maintaining the internal push-lever 51 in a stable position. This embodiment further includes an external push-lever 58 which allows activation of the system from outside the cover 30'. The push-lever 58 is for example mounted on a cross member 59 which is located between the locking elements 53, 54.To allow the system to be mounted, and since the push-lever 58 may be larger than the opening formed by the window 37 in the cover 30', the push-lever is preferably fixed in a removable manner to the cross member 59, for example by means of the screws 60, 61 so that the system 25 can first be mounted in the cover 30' without the push-lever 58, then the latter is mounted by screwing it onto the cross member 59. Other equivalent means of fixing are of course possible. As the push-lever 58 is made integral with the pivoting element 65 comprising the locking elements 53, 54, the push-lever 58 is itself arranged to pivot. Furthermore, in the embodiment shown, the internal push-levers 51 and external push-levers 58 are rigidly linked and arranged to pivot synchronously. The first and second modes of execution described above show two possibilities concerning the actuation member: a first mode of execution comprising only an internal actuation member 51. In this case, it is 24 P-0723-WO; 15 / 10 / 2025 It is necessary to open the clasp to actuate the actuation member in order to adjust the length, particularly to lengthen the bracelet. In the second embodiment, the user has a choice between two separate actuation members: an internal member 51 and an external member 58. By choosing the external actuation member 58, it is not necessary to open the clasp, as the latter can be actuated from outside the clasp and is accessible to the user wearing a wristwatch equipped with the clasp incorporating the system of the invention. The invention also covers the possibility that an internal actuation member 51 is absent, an external actuation member being, in principle, sufficient for a functional system. According to this embodiment, the system comprises only an external actuation member 58.In cases where an external button or push button is present, a push-lever 51 may be absent, and the locking member 65 may replace the push-lever and is preferably made in the form of a simple lever. Figures 16 to 20 illustrate the operation of this embodiment of the invention in a manner similar to Figures 6 to 10, and reference is made to the description of those figures. Figures 17, 19, 18, and 20 illustrate cross-sections along axes AA and BB of Figure 16, respectively. The difference in the embodiment shown in Figures 16 to 20 is that the guide 50 includes an external push-lever 58 that allows actuation from the outside. As seen in Figures 17 and 18, the push-lever 58 is tilted to the right (corresponding to the position illustrated in Figure 11), and in this position, the tooth 53 is moved away from the teeth 42, which allows relative movement between the carriage 40 and the guide 50, and thus the lengthening of the bracelet. In figures 17 and 18, as in figures 7 and 8, we are at the stop (see the position of the carriage 40 relative to the guide 50) which corresponds to the maximum elongation of the bracelet. Similarly, in figures 19 and 20, as in figures 9 and 10, we are at the opposite end stop, which corresponds to the maximum shortening of the bracelet (see the position of the carriage 40 relative to the guide 50). As can be seen 25 P-0723-WO; 15 / 10 / 2025 In Figure 19, tooth 53 is meshed with teeth 42, which blocks the movement of the carriage 40 relative to the guide 50, and this position corresponds to that illustrated in Figure 12. To allow the bracelet to be lengthened, the external push-lever 58 must be pressed as illustrated in Figures 11, 17 and 18. As can be deduced from Figure 19, given the shape of tooth 53 and teeth 42, it is possible to move from the position of Figure 17 to that of Figure 19 without acting on the external push-lever 58 (or internal 51): the length of the bracelet can therefore be easily shortened. However, its lengthening requires acting on the external push-lever 58 (or internal 51 as in the embodiment described previously) to disengage the locking elements 53, 54 from the teeth 42, 43 (as illustrated in figures 17 and 18, or 7 and 8). As can be understood from the description above, in the embodiment shown in Figures 11 to 20, a user can operate the external push-lever 58 from outside the cover 30' or the internal push-lever 51 from inside. Since the internal push-lever 51 is located inside the clasp when the latter is closed, it is necessary to open the clasp in order to actuate the internal push-lever 51. In contrast, the external push-lever can be operated from the outside, even when the clasp is in the closed position, for example, when a user is wearing a wristwatch with the clasp on their wrist. Figures 21 to 30 illustrate another embodiment of the invention. This embodiment is based on that illustrated in Figures 11 to 20, but in the system 25' of this other embodiment, the push-lever 58' is mounted on the axis 57 and not on the axis 52, so that its movement is reversed compared to the embodiment of Figures 11 to 20: this reversal is visible in Figures 21 and 22 by comparison with Figures 11 and 12. As can be seen in Figures 21 and 22, the movement of the push-lever 58' is to the left and not to the right as in Figures 11 and 12. Figures 23 to 25 illustrate in more detail the construction of system 25' and the 26 P-0723-WO; 15 / 10 / 2025 Guide 50', the elements identical to those in previous embodiments having the same numerical references. In this embodiment, and as seen particularly in Figures 23-25, the push-lever 58' is mounted on the axis 57 and can rotate around this axis when the system is activated. More precisely, the springs 55 and 56 and the internal push-levers 51 and external push-levers 58' are mounted on the axis 57 and no longer on the axis 52 as in the embodiments described previously. The general operation is the same, while the direction of actuation of the push-levers is reversed. Figures 26 to 30 show a more detailed explanation of how this embodiment works. Figures 27 and 28 illustrate cross-sections along axes AA and BB of Figure 26, respectively. As shown in Figures 27 and 28, the tooth 53' is lifted by the rotation of the external push-lever 58', which allows the carriage to slide on the guide 50'. In Figures 27 and 28, the system 25' is at its stop, and the position corresponds to the maximum shortening of the bracelet (see the position of the carriage 40 relative to the guide 50'; see also Figures 19 and 20). In figures 23, 28 and 30, we see the screw 60 which, as illustrated in figure 15, allows the push-lever 58' to be mounted on the cross member 59' in the same way as described with reference to the execution method of figures 11 to 20, of which screws 60, 61 are found in the execution method of figures 21 to 30 as illustrated in these figures.Equivalent means are of course possible in place of screws 60, 61. In Figures 29 and 30, which are cross-sections along axes AA and BB of Figure 26 respectively, the system is locked because tooth 53' is meshed with teeth 42, preventing relative sliding between carriage 40 and guide 50'. In Figures 29 and 30, the carriage 40 is positioned approximately halfway along its travel relative to guide 50'. This execution method has the advantage of being more intuitive and may be preferred by users and can be applied to the execution method of Figures 2 to 10: in such a case, the push-lever 51 is mounted on the bar 57 and not the bar 27 P-0723-WO; 15 / 10 / 2025 52 and the above description applies accordingly. In some variants, the system includes only an internal push-lever 51 and in other variants only an external push-lever 58, 58'. In the illustrated embodiments including an external push-lever 58, 58', or button 70, an internal push-lever 51 has also been illustrated so that the adjustment can be made by operating either of said push-buttons / button, but it is obvious that if the system includes an external push-lever 58, 58', or button 70, the internal push-lever 51 can be dispensed with and the construction simplified. Figures 31 to 40 illustrate another embodiment of the present invention. In this embodiment, the external push-lever has the form of a button 70 which moves in translation and not in rotation as in the embodiments described above. Figures 31 and 32 illustrate perspective views of the 30" cover in two positions of the button 70: in figure 31 the button 70 is pressed (or "activated") which allows adjustment of the bracelet length and in figure 32 the system is locked (the rest position) so that an elongation (at least) of the bracelet is not possible according to the principles of the modes of execution shown. It is noted at this stage that the invention covers the possibility that the change in length by means of the system of the invention can be blocked in both directions, lengthening and shortening, and that, consequently, it is necessary to activate an actuating member in order to be able to change the length in any of the two longitudinal directions. The operating principle of the system according to the execution mode shown in Figures 31 and 32 is similar to that illustrated in Figures 11 to 20, and reference is made to the description of these figures above. 28 P-0723-WO; 15 / 10 / 2025 The numerical values ​​are identical for the same parts of the device. The difference lies in the actuation mechanism of the 25" adjustment system, as described below. In this configuration, the 25" system includes a button 70 that is guided in translation and allows a user to push on the button 70 or on the internal push-lever 51 to adjust the length. To guide the translational movement of the button 70, the cover 30" includes a precise opening 37.1, the dimensions of which correspond to those of the button so as to guide the button through the opening 37.1. The cover also includes a concavity 37.2, which is not through but is wider, to facilitate the depressing of the button 70 by a user. Preferably, in the rest position, the button 70 is flush with, or only slightly protrudes from, the outer surface of the upper wall 26 of the cover, as shown in Figure 32. This avoids protruding structures that increase the risk of the clasp snagging, for example, on clothing.To activate button 70, it descends below the upper surface of the cover, as seen in figure 31. The concavity 37.2 facilitates the actuation of the button with a finger, for example the thumb, whose dimensions may be larger than those of button 70. The button 70 is kinematically linked to the crossbar 59" for example by an opening 71 in the button 70 into which the crossbar 59" is inserted to make these two parts of the system joined and / or to arrange them so that the translational movement of the button 70 results in the rotation of the internal push-lever 51. In the 25" system of this embodiment, the actuation means 70 is not rigidly connected to the locking element 65, but arranged to be able to act on the latter (and / or to cooperate with it) in order to cause the pivoting of the locking element 65, generally against the force of at least one return element, here torsion springs 55, 56. 29 P-0723-WO; 15 / 10 / 2025 Figures 36 to 40 illustrate the operation of this embodiment, figures 37, 39 and 38, 40 illustrating cross-sections respectively along axes BB and CC of figure 36. When the user presses the button 70 (figures 37-38), the push-lever 51 rotates around the axis 52 clockwise and the system is disengaged so that the bracelet length can be adjusted in both directions: as seen in figure 38, the tooth 53 is raised relative to the teeth 42 of the rack and the carriage 40 can move freely by sliding on the guide 50. In figures 39 and 40, the button 70 is released and the locking elements 53-54 are engaged with the teeth of the rack 42-43. This mode of execution also includes springs 55, 56 which allow the push-lever 51 to be kept in a stable position as described previously. It should be noted that not only does the button 70 act on the push-lever 51 when pressed by a user, but, conversely, the pivoting push-lever 51 is arranged to act on the button by means of the force of the return element 55, 56 so as to allow the latter to move in translation towards the rest position when the user is no longer pressing the button. As can be understood from the shape of the teeth 42 of the rack, the system allows the bracelet to be shortened without it being necessary to press the button 70 (position of the push-lever 51 as illustrated in figures 39 and 40) whereas lengthening requires pressing said button 70 (position of the push-lever 51 as illustrated in figures 37 and 38). In an unillustrated variant, this embodiment with button 70 can be applied to the embodiment shown in Figures 21 to 30, in which the internal push-lever 51 is mounted on axis 57 and on axis 52. The construction is 30 P-0723-WO; 15 / 10 / 2025 similar to that of figures 31 to 40 but with the mounting on axis 57 as in figures 21 to 30. In another variant, the push-lever 51 can be modified so as to lack an internal push button in all embodiments that include an external actuation element, such as a push button or knob. In these cases, element 51 can be designed as a lever only, and would no longer be a push-lever. Figures 41 to 47 illustrate another embodiment of the present invention. In the 25" system of this embodiment, a button 75 is also used, as in the embodiment described previously. The button 75 is also arranged to move in translation, but in this embodiment, the button 75 has a different construction, as described below. Figure 41 shows a top perspective view of the cover 30" with the button 75 in the window 37. Figures 42 to 47 illustrate in detail the operation of this embodiment. In this embodiment, the carriage 40' differs from the carriages 40 of the previously described embodiments in that the rack teeth 42, 43 are located on the inside of the carriage 40' (as can be seen in Figures 42-47) and not on an outside as illustrated, for example, in Figures 4, 17, 18, 24 and 34. The button 75 itself includes locking elements 76, 77 which mesh with the rack teeth 42, 43 to lock or unlock the system by translational movement of said button 75. The button 75 comprises two radially oriented appendages, each appendage being fitted with a locking element 76, 77. Alternatively, the button 75 could be described as having the shape of an inverted T, with the locking elements 76, 77 arranged on the two arms of the T. The 50" guide includes an opening 82 providing access to a housing 81. The button 75 is mounted in the housing 81 so as to emerge through 31 P-0723-WO; 15 / 10 / 2025 The opening 82 and thus protrude from the guide. The button 75 also includes a housing 74 in which are housed two cylindrical springs, which bear against the bottom in the housing 81, as seen in figure 42. The translational guidance of the button 75 is achieved by the shape of the housing 81 and by the opening 37 in the cover. The operation of this execution mode can be understood for example in figures 45 to 47, figures 46 and 47 illustrating sections respectively along the axes AA and BB of figure 45. In a rest position, the locking elements 76, 77 of the button 75 are engaged with the teeth 42, 43. This position is stabilized by the springs 78 which push the button 75 away from the system 50". When button 75 is pressed, the device is in the position illustrated in figures 46 and 47: button 75 is moved towards system 50", compressing springs 78, and locking elements 76, 77 disengage from the rack teeth 42, 43, as illustrated in figure 47. Since button 75 is mounted in guide 50", which is itself integral with cover 30", the movement of the carriage 40' allows the bracelet length to be adjusted by its relative movement with respect to cover 30". When button 75 is released, it rises due to the action of springs 78, and the locking elements 76, 77 engage with the teeth 42, 43, thus locking the adjustment. As in the other modes of operation, the shape of the teeth 42, 43 of the rack allows the bracelet to be shortened without pressing the button. However, to lengthen it, it is necessary to press button 75. As mentioned above, the length adjustment system of the invention can be implemented such that actuation of the actuating member, for example a pusher and / or a push-lever, is necessary both to lengthen and shorten the clasp. This can be 32 P-0723-WO; 15 / 10 / 2025 adjusted by modifying the shapes of the teeth of the carriage teeth 42, 43 and the locking elements 53, 54. It is also noted that, while shortening is generally possible without activating the actuating mechanism (pusher, lever-pusher), the user must apply a certain force in the longitudinal direction of the shortening in order to force the locking elements out of the interdental space of the teeth. This is described, for example, in paragraph

[0054] of EP2875747A1. Since the resting position is stabilized by a return element (e.g., springs), the force exerted by these elements must be overcome by the user. The length adjustment system of the invention also allows the bracelet length to be shortened following actuation of the actuation means. In this case, the shortening can occur without the user needing to overcome the force exerted by the return element 55, 56, 78. The assembly of the elements described above in its different modes of execution is carried out in a simple manner. For example: the "module" comprising the carriage 40 and the guide 50, 50', 50" is first assembled with the bars 52, 57, the springs 55, 56, and the internal push-lever 51, as illustrated in Figure 3 (in which the bar 57 is still missing from the opening 50.2), or as illustrated in Figures 15 or 25, but in these figures without the external push-lever 58, 58' if the window 37 of the cover 30' is smaller than said push-lever 58, 58'. The "module" is then inserted into a cover 30 or 30' (depending on the embodiment) to arrive at the assembly shown in Figure 1. The bars 52, 57 enter the openings 32, 33, 34, 35 of the cover 30, 30' respectively, by their ends. and in this way the guide 50, 50' is fixedly mounted in the cover. Of course, the bar 52 and 57 can be replaced by an equivalent system, for example screws and / or pins to fix the 33 P-0723-WO; 15 / 10 / 2025 Guide 50, 50' to cover 30, 30'. As cover 30, 30' is fixed to the end link 21 of the bracelet, via arm 14 and base 11, guide 50, 50' is fixed relative to link 21. The bracelet length is therefore adjusted by sliding the carriage 40 along guide 50, 50' as illustrated in Figures 7 to 10, 17 to 20 and 27 to 30. This mounting principle can be applied to all embodiments. It should be noted at this stage that the fine adjustment system of several of the shown execution modes can be operated without screwing and / or without the need to screw components in order to secure them. In other words, the installation of the adjustment system in a clasp, preferably under the cover or hood, can be carried out very quickly and / or without the use of any tools. Those skilled in the art will observe that the system of the invention comprises only three dedicated and / or specifically machined parts, namely the carriage, the guide, and the push-lever or pusher. The other parts, such as the spring bars 52, 72, or the torsion springs 55, 56, are standard, commercially available parts. Any suitable material may be used to form the parts of the various embodiments described in this application: for example, metal, or metal alloys, precious or non-precious, synthetic materials, ceramics, any other suitable material, etc. In some embodiments, precious materials are used for the visible parts. Embodiments have been described to provide a comprehensive understanding of the principles of the structure, function, manufacture, and use of the systems and processes of the invention. The systems and processes specifically described in this application and illustrated in the accompanying drawings are non-limiting embodiments of the scope of the present invention. The features illustrated or described in relation to one embodiment may be combined with the features of other embodiments. 34 P-0723-WO; 15 / 10 / 2025 of execution. Such modifications and variants are intended to be included within the scope of the present invention. While this invention has been described in conjunction with a number of embodiments, alternatives, modifications, equivalents, and variants that are within the spirit and scope of the present invention are also covered by this application. 35 P-0723-WO; 15 / 10 / 2025

Claims

DEMANDS 1. A bracelet length adjustment system (25, 25', 25", 25"), the system being arranged to allow bracelet length adjustment by relative movement between two bracelet strands or two bracelet sections, the system being arranged to be able to be attached to a wristwatch clasp, said system comprising: a guide (50, 50') arranged to be attached to the clasp, for example to a clasp cover (30, 30'), and a carriage (40, 40') arranged to slide relative to the guide, the carriage (40, 40') being linked to one of said strands or bracelet sections and allowing, by its movement relative to the guide, bracelet length adjustment; a locking member (65) arranged to ensure at least a first locked position of the carriage and a second unlocked position of the carriage; an actuating member (51, 58, 58', 70, 75) mounted movably on the guide (50,50'),arranged to be activated by a user to move from said locked position to said unlocked position, an indexing member (42, 43, 42', 43') placed on the carriage (40, 40'), the cooperation of the locking member (51, 58, 58', 70, 75) and the indexing member preventing the sliding of the carriage (40, 40') relative to the guide (50, 50') in the locked position of the carriage in at least one direction of sliding.

2. System according to claim 1, wherein structural elements (44-47, 66-69) enabling said movement of the carriage to be guided are arranged on said guide (50,50') and / or on the carriage (40).

3. System according to any one of the preceding claims, wherein the clasp, and in particular the cover, is devoid of a specific and / or dedicated structure and / or arrangement for guiding the movement of the carriage. 36 P-0723-WO; 15 / 10 / 2025 4. System according to any one of the preceding claims, wherein the dimensions of the carriage (40) in the longitudinal direction, in particular the length, and preferably in the radial direction, in particular the thickness, are greater than the corresponding dimensions of the guide (50).

5. System according to any one of the preceding claims, wherein the carriage (40) comprises a frame (44-47), the guide being placed inside and / or within said frame.

6. System according to any one of the preceding claims, wherein the carriage (40) comprises a frame (44-47) including at least one opening (48.1, 48.2, 49) arranged to allow the guide (50) to be fixed to a structural element of the clasp, for example to the lid, without hindering the movement of the carriage (40) relative to the guide when adjusting the length.

7. System according to any one of the preceding claims, wherein the carriage (40) comprises at least one opening (48.1, 48.2), the actuating member and / or the locking member being arranged on the guide so as to pass through said opening.

8. System according to any one of the preceding claims, wherein a pivot axis of a locking member (65) serves to connect the guide (50) to the clasp and / or wherein the system (40, 50) comprises a fastening system (32-35, 52, 57) for connecting the system to the clasp, the fastening system comprising an arrangement (52, 57) which is coaxial with respect to the pivot axis of a pivoting locking member (65).

9. System according to any one of the preceding claims, wherein a frame of the trolley (40) includes an open portion (49) on each lateral side of the trolley, so as to allow the guide (50) to be fixed laterally to the clasp through said open portions. 37 P-0723-WO; 15 / 10 / 2025 10. System according to any one of the preceding claims, wherein the carriage (40) comprises a frame (44-47) including a lateral slot (49) in the longitudinal direction, the guide (50) being arranged to be fixed to the clasp through said lateral slot (49).

11. System according to any one of the preceding claims, wherein the carriage (40) comprises two lateral sides and substantially parallel lateral longitudinal elements (44, 45) arranged at least one of said two lateral sides, a guide opening (49) being provided between said longitudinal elements (44, 45).

12. System according to claim 11, wherein said lateral longitudinal elements comprise a lower longitudinal element (45) and an upper longitudinal element (44), the guiding opening (49) being provided between said lower and upper longitudinal elements (45, 44).

13. System according to any one of the preceding claims, wherein the indexing member comprises a rack with teeth (42, 43, 42', 43') whose teeth are oriented in a radial direction, preferably upwards and / or towards the cover of the clasp.

14. System according to any one of the preceding claims, wherein the actuating member is arranged so as to be able to be actuated from outside a clasp comprising the system and / or without it being necessary to open the clasp comprising the system.

15. System according to any one of the preceding claims, wherein the actuating member is arranged to be actuated by exerting a force in a radial direction and / or in a direction having a radial direction component.

16. A system according to any one of the preceding claims, wherein the actuating member is arranged so as to be depressable, preferably 38 P-0723-WO; 15 / 10 / 2025 against the force of a restoring element.

17. System according to any one of the preceding claims, wherein the actuation member (51, 58, 58', 70, 75) comprises a pusher and / or a push-lever.

18. System according to any one of the preceding claims, comprising a fastening system for enabling rigid connection of the guide to the clasp, preferably to the clasp cover, the fastening system comprising at least first and second fastening elements separated in the longitudinal direction.

19. Bracelet clasp (10) comprising the system according to any one of the preceding claims.

20. Wristwatch comprising the system according to any one of claims 1 to 18 or a clasp according to claim 18. 39 P-0723-WO; 15 / 10 / 2025

Images