CH704771B1 - Watch strap strand reinforcement. - Google Patents

Abstract

The invention relates to a reinforcement (2) for a watch strap strand (1) intended to be housed in a flexible material strand casing (3), characterized in that the reinforcement comprises a connecting element made of a superelastic alloy, the connecting element extending from a fastening element (10) of the strand to a watch case to a member (9) for attaching the strand to a closure element.

Description

[0001] The invention relates to a reinforcement of a watch strap strand. The invention also relates to a bracelet strand comprising such a reinforcement. The invention also relates to a bracelet comprising at least one such strand. Finally, the invention relates to a watch comprising at least one such part.

[0002] Numerous flexible watch straps exist on the market, in particular made of leather, elastomer or thermoplastic-elastomer. However, the durability and performance of this type of bracelets are not always satisfactory compared to the performance of a metal link bracelet.

[0003] To resolve these problems, it has been envisaged to produce bracelets of the hybrid type, that is to say flexible bracelets with reinforcements.

[0004] Document FR 1 591 988, for example, discloses a plastic strap reinforced by a metal frame which is folded over at the ends of the strand so as to form passage holes for the bars. This fold of the metal frame has the function of forming a passage hole for the passage of a bar or a strap fixing screw. Ultimately, the tensile strength of the bracelet is provided by the plastic.

[0005] Document AT 400 551 discloses a bracelet in which, in order to increase the tensile strength of the strands without degrading its flexibility, a two-layer reinforcement is implemented, formed of a resistant net bonded to a flexible blade . This two-layer reinforcement does not improve the tensile strength at the attachments.

[0006] Document AT 407 692 discloses a flexible bracelet with reinforcement present only at the fold of the strand and glued, in order to reinforce the bracelet at the level of the attachment. The tensile strength of the strand is not improved by this solution.

[0007] Document JP7-329 110 discloses a resin strap reinforced with a nylon insert. This insert is, in some embodiments, wrapped around the fasteners. As in document FR 1 591 988, the tensile strength of the bracelet is provided by the resin.

[0008] Numerous models and concepts of flexible bracelets have been described and presented. Nevertheless, the known flexible bracelets all perform relatively poorly mechanically, in particular with regard to the resistance of the strands in traction. It is therefore necessary to make a choice between a flexible leather or elastomer strap that is comfortable and a mechanically efficient metal strap. Flexible bracelets are in particular invariably less robust than metal bracelets, for example in terms of tensile strength or folding strength.

[0009] Also, the aim of the invention is to provide a bracelet which overcomes the drawbacks mentioned above and improves the bracelets known from the prior art. In particular, the invention provides a high performance and comfortable bracelet. The invention also provides a watch comprising such a bracelet.

[0010] A reinforcement according to the invention is defined by claim 1.

[0011] Different embodiments of the reinforcement according to the invention are defined by claims 2 to 10.

[0012] A bracelet strand according to the invention is defined by claim 11.

[0013] Different embodiments of the bracelet strand according to the invention are defined by claims 12 and 13.

[0014] A bracelet according to the invention is defined by claim 14.

[0015] A watch according to the invention is defined by claim 15.

[0016] The accompanying drawing shows, by way of examples, two embodiments of a bracelet according to the invention. Fig. 1 is a perspective view of one embodiment of a bracelet strand according to the invention. Fig. 2 is an exploded view of the embodiment of the bracelet strand according to the invention. Fig. 3 is a perspective view of an embodiment of reinforcement used in the embodiment of the bracelet strand according to the invention. Fig. 4 shows a view of an embodiment of a tube used in the embodiment of the bracelet strand according to the invention at the level of the attachment to the watch case. Fig. 5 is a view of an embodiment of a tube used in the embodiment of the bracelet strand according to the invention at the level of the attachment to a closure member. Fig. 6 is a partial sectional view of one end of the reinforcement embodiment according to the invention. Fig. 7 is a perspective view of the embodiment of reinforcement used in the embodiment of the bracelet strand according to the invention. Fig. 8 is a longitudinal sectional view of the embodiment of reinforcement used in the embodiment of the bracelet strand according to the invention. Figs. 9 to 11 are cross-sectional views of the embodiment of the reinforcement used in the embodiment of the bracelet strand according to the invention. Fig. 12 is a partial sectional view of one end of a variant of the embodiment of the reinforcement according to the invention illustrated in FIG. 6. Fig. 13 is a partial sectional view of one end of a second embodiment of the reinforcement according to the invention. Fig. 14 is a graph showing the variations in flexural stiffness of different embodiments of bracelet strands according to the invention.

[0017] An embodiment of a bracelet strand 1 according to the invention is described below with reference to FIGS. 1 to 12. The bracelet strand is of the flexible type, in particular of the hybrid type, that is to say made of a flexible material but comprising a reinforcement.

The bracelet strand comprises a reinforcement 2 placed in an envelope of flexible material. The reinforcement is preferably made from a first material and the casing 3 is made from a second material. For example, the first material is metallic, in particular an alloy, in particular a superelastic alloy. The second material is flexible. An elastomer, such as rubber, a polymer or leather, can in particular be used as the second material.

[0019] The properties of the first and second materials are distinct in order to separate the constraints as well as possible. Preferably a strand is produced whose architecture is based on a central core or reinforcement and an envelope implemented around the core, that is to say at least partially enveloping the core. The reinforcement ensures high performance in terms of mechanical strength of the strand, in particular in tensile strength (high strength) and in deformation thereof under stress (low deformation). Complementarily or alternatively, the reinforcement ensures high mechanical resistance performance of the strand when bending. The envelope (or coating of the strand) at least partially surrounding the reinforcement makes it possible for its part to ensure mainly comfort and aesthetic functions, in particular by making it possible to obtain a desired flexibility and / or a desired lightness and / or a desired geometry. The envelope can be overmolded on the reinforcement, in particular when it is made of an elastomeric material. The envelope can be assembled by gluing and / or by sewing around the reinforcement when it is made of leather.

[0020] In both cases, an opening 30 can be made in the envelope in order to reveal the reinforcement. The visible part of the reinforcement can then be treated to avoid any deterioration thereof. The opening can have an aesthetic function and / or the function of revealing the technicality of the bracelet strand.

The reinforcement comprises an element 6 for fixing the strand to the watch case and an element 5 for fixing the strand to a closure element. The reinforcement comprises a connecting element 4 mechanically connecting the element 6 for fixing the strand to the watch case to the element 5 for fixing the strand to a closure element. Preferably, the element 6 for fixing the strand to the watch case is produced by a first end of the connecting element. Preferably, the element 5 for fixing the strand to a closure element is produced by a second end of the connecting element. The reinforcement mainly comprises a blade, in particular a metal blade, in particular a blade of superelastic metal alloy.

[0022] The element 6 for fixing the strand to the watch case is intended to cooperate with a second fastening element provided to secure the strand to the watch case, in particular to the horns. The first and second elements constitute a tie. Similarly, the element 5 for fixing the strand to a closure element is intended to cooperate with a second fixing element provided to secure the strand to the closure element, which may in particular be a buckle or a clasp, by example a folding clasp. The first and second elements constitute a tie.

As shown in FIGS. 2 to 6, the element 6 for fixing the strand to the watch case and / or the element 5 for fixing the strand to a closing element is produced by folding the end of the blade 4. Indeed, the first end is folded to form a passage 8 or a loop and part 20 of the end is folded over the blade 4. This folded part 20 or fold is fixed to the blade, in particular by riveting. To do this, the blade and the fold have holes 11 intended to come face to face and receive rivets 12. The second end of the blade is preferably shaped in the same way to make a passage 7 or a buckle, the blade and the fold have holes 13 intended to come into vis-à-vis and to receive rivets 14.

[0024] In order to ensure the performance of the strand, the reinforcement must be connected to the fasteners while maintaining its performance as much as possible. The riveted fold at each end makes it possible to provide a passage for a bar, a screw or a pin intended for fixing the strand.

[0025] Advantageously, as shown in FIGS. 3 to 6, a tube 10 can be placed in the passage 8 and / or a tube 9 can be placed in the passage 7 made at the other end of the reinforcement.

[0026] The reinforcement can thus be folded around the tube or tubes. A bar, screw or pin, constituting the second fastening element, is then engaged in each tube to secure the strand to the watch case or to the closure element.

Tubes 9 and / or 10 are optional since the bars, screws or pins could directly engage in passages 7 or 8 without the presence of a tube. However, the presence of tubes is preferred for three reasons: facilitate placement in a mold in the event that the casing is subsequently molded onto the reinforcement; facilitate the introduction of the bar, screw or axis; it is indeed easier to thread a rod in a perfectly circular tube than in a riveted fold; precisely control the length of the strand, i.e. the distance (center distance) between the two axes of the strand / clasp and strand / box fasteners.

[0028] The tubes are preferably chosen from Phynox, Nivaflex or equivalent material, which ensures on the one hand good mechanical performance and on the other hand good resistance to corrosion. The dimensions of the tubes are typically between 1 and 2.5 mm outside diameter. The box / strand attachment tube 10 is preferably provided with notches 101 to avoid damaging the casing when using a bar clamp to mount the strand on the middle part.

[0029] We can also reduce the passage of the bar clamp to the bare minimum and play on the elasticity of the envelope to compress the bar. In this case, the tube 10 attached to the watch case must be much shorter to allow this compression.

A study was carried out to find out the influence on the mechanical strength of the reinforcement of the number of holes 11 or 13 in which the rivets 12 or 14 are housed. In fact, the more holes there are, the greater the distribution. of stresses is homogeneous, but the less material there is to support the stresses. Thus, an optimal number and arrangement with regard to performance have been sought. An arrangement of 6 equidistant holes with a diameter of 0.8 mm ensures excellent performance for a reinforcement width of approximately 10 mm. For reasons of implementation, it may be advantageous to limit the number of holes, for example to two, with a larger diameter, for example approximately 1.2 mm. Simulations and tensile tests confirm that such a configuration allows a level of performance largely sufficient to meet the requirements of the NIHS 92-11 standard, which specifies the threshold values for tensile strength.

[0031] The choice of the rivet is important since it directly participates in the transmission of forces and therefore in the mechanical performance of the strand. The dimensions of the rivet are conditioned by its shear strength (which will determine the minimum body diameter), its interference with the start of the bend (which will determine the maximum flange diameter) and the quality of the riveting (sufficient material bend) .

To guarantee the shear resistance, the following equation is used:

we deduce the minimum diameter of the rivet bodies:

with number_of_rivets, the number of rivets in the assembly.

For our example, the force is 200N per strand / reinforcement (which corresponds to 400 N per bracelet as specified by the NIHS 92-11 standard), the number of rivets is 4 (2 at each end of the strand ) and the tensile strength σr = 410 MPa (for brass, which is a material commonly used for rivets; and which also gives an idea of the behavior with a corrosion resistant stainless steel and showing a higher breaking stress brass). We therefore arrive at a minimum diameter of 0.4 mm; For safety, a diameter of 1.14 mm (i.e. a safety factor greater than 4) was chosen.

[0034] Also in this example, the diameter of the rivet flange was chosen equal to 1.5 mm to avoid interference with the start of the fold. It is possible to increase the flange diameter by moving the rivet away from the fastener and therefore from the passage 7 or 8, which, however, has the consequence of increasing the extent of a rigid zone of the reinforcement located close to the tie.

Riveting the fold 20 with different rivets arranged in different planes transverse to the reinforcement is also possible. The rivets are then preferably arranged in staggered rows. However, such an embodiment has the disadvantage mentioned above, namely to increase the extent of a rigid zone of the reinforcement located near the fastener.

The length of the fold 20, in particular the material remaining between the edge of the rivet hole and one end 21 of the fold 20, is preferably chosen as short as possible without impairing the mechanical performance. Thus, it was verified by simulation that the stress distribution is uniform and that there is no stress concentration due to a hole too close to the end 21 of the fold.

[0037] Tests show that a brass or stainless steel rivet is ideal for the desired application. Other alternatives to riveting are possible to achieve the desired performance. For example, it is possible to staple fold 20 to the rest of the blade. It is also possible to weld the fold 20 to the rest of the blade, as shown in FIG. 12 on which a blade 4 is assembled to a tube 10 by welding or soldering 19, carried out by way of example in the case of FIG. 13 at the end of the fold 20. In this case, the welding may preferably be of the laser type. It is also possible to fix the fold 20 to the rest of the blade by screwing. In this case, bolts are used instead of rivets.

In a second embodiment of the reinforcement 2 'shown in FIG. 13, a blade 4 ́ is assembled to a tube 10 ́ by welding or brazing 19. The tube 10 ́ can also have an extra thickness and a groove intended to receive the end of the blade and to facilitate and / or improve the performance of solder or solder. The first and second embodiments can be combined on the same reinforcement, with the first embodiment at a first end and the second embodiment at a second end.

[0039] It should be noted that the solutions known from the state of the art are not satisfactory. A simple bend as in document FR 1 591 988 only marginally improves the tensile strength. Indeed, unlike the invention, in this document, it is the elastomer overmolding that ensures the strength of the fastener.

[0040] In the invention, the reinforcement is first produced which makes it possible to mechanically connect the element for fixing the strand to the watch case to the element for fixing the strand to the closing element. Thus, at this stage of implementation, a mechanical tensile action of 50 N, or even 100 N, or even 200 N, on the reinforcement does not make it possible to deform the fixing element, in particular to open a fold, as is the case in the prior art. In particular, a mechanical tensile action on a tube or another element located in the passage 7 or 8 does not allow the tube or the other element of the reinforcement to be released, except to break the reinforcement. The strand wrapper is then put in place around the reinforcement. Thus, in the embodiments described, the fasteners of the fasteners (allowing attachment to the box or to the clasp) are secured to the reinforcement.

The main role of the reinforcement 2 is to ensure the mechanical strength of the strand. Given the need to have a flexible strap and the criterion of resistance to different forces, the reinforcement preferably comprises mainly a strip or a metal strip 4. In particular, the use of a superelastic metal alloy also allows to improve the resistance to folding.

[0042] To ensure that strong deformations of the strand do not cause permanent deformation, for example during a 180 ° bend of the strand on itself, a superelastic alloy is advantageously used for the reinforcement. Superelasticity is manifested in some very specific alloys which show a transition between an austenitic phase and a martensitic phase. Superelasticity is characterized by the complete recovery of the shape of the sample when the applied stress ceases. In the temperature range where austenite is stable, martensitic transformation can be induced under stress. The stress is exerted first in the elastic strain domain of the austenite, with a stress proportional to the strain. Above a critical value, austenite turns to martensite. When the stress ceases, there is total reversion of the martensite towards the austenite until zero strain since, at the stress temperature, it is the austenite structure which is stable. The great interest of this property is the great possibility of deformation in an “elastic” domain while the stress varies. The elasticity of these alloys can reach ten times that of steel.

There are several alloys with superelastic properties. For example, an alloy based on Nickel and Titanium NiTi (trade name Nitinol) can be used, mainly because this alloy shows excellent resistance to corrosion and is biocompatible. Other superelastic alloys, such as CuAIBe, CuAINi or CuZnAI, can also be used.

The tests confirmed that the NiTi alloy reinforcement has excellent corrosion resistance, even in unfavorable cases (association of materials promoting the equivalent of galvanic corrosion and of a prestressing of the metal strip), and this after two months of salt spray test.

The blades used can have a zero initial curvature and the curvature of the strand can be obtained during the molding of the casing. It is also conceivable to give the blade an initial curvature (preform) with a suitable manufacturing process.

As the invention makes it possible to decouple or rather to limit the existing coupling between the "mechanical strength" and "aesthetic / comfort" functions, the reinforcement can be dimensioned on its own without taking into account the envelope. It remains obvious that the addition of a casing further improves the tensile strength.

[0047] The NIHS 92-11 standard stipulates that a watch strap must be able, as shown in fig. 7, resist a tensile force F of 200 N per strand without breaking (permanent deformation is tolerated). These requirements can be increased, the breakage of the bracelet then being ensured by the shear breakage of the pins of the bars.

The reinforcement is then dimensioned according to the maximum tensile force F that the strand must be able to withstand without breaking, by estimating the stresses equivalent to the maximum force, which must be less than the elastic limit of the material. For the dimensions used in the context of the tests, with a minimum width of 7.4 mm, a thickness of 0.1 mm of the blade makes it possible to obtain a limiting force before plastic deformation of 440 N, i.e. largely above the desired values and largely in below the elastic limit and breaking stress of the material.

In addition, simulations and tests have shown that the stress concentrations generated around the rivets remain below the limit plasticization stress, even for an applied tensile force greater than 300 N. The lateral deflection resistance and in tension are also in the accepted criteria.

[0050] In addition, the thickness of the envelope can be chosen so as to optimize the resistance of the strand to bending. For a blade thickness of 0.1 mm, the admissible bending radius is 0.7 mm (by comparison, a central stainless steel blade (type 1.4310) only tolerates a minimum bending radius of only 5 mm). The thickness of the coating of the bracelet is then chosen so as to ensure a radius of curvature greater than the limit allowed during a 180 ° bend of the strand.

[0051] The NiTi alloy loses its superelastic properties below 0 ° C. However, the alloy regains all of its properties as soon as the temperature rises above this limit. Thus, a blade bent with a radius of 2 mm at –16 ° C retains this curvature as long as the temperature is below 0 ° C, but becomes perfectly straight again as soon as the temperature is higher (resumption of the shape in 8 s at 20 ° C). Likewise, the superelastic alloy blade retains all of its superelastic properties following coating (overmolding conditions: typically T> 180 ° C for several minutes). This temperature behavior can vary depending on the superelastic alloy chosen. Thus, some alloys allow use at lower temperatures, but with a decrease in the maximum temperature of use.

The blade shown in FIGS. 3 and 7 to 11 has a complex shape, with a side section that varies along the strand. This allows the rigidity and flexibility of the bracelet to be finely adjusted along the strand. In fact, the flexibility of the strand varies significantly if the thickness of the strand and / or its width vary, and / or if an opening 30 is cut in the strand for aesthetic or comfort reasons. For a complex bracelet strand as shown in fig. 1, these variations in flexibility can make it difficult to wear the watch and can interfere with its tactile appreciation. The approach is to compensate for the variation in the flexural modulus (Young's modulus times inertia around the neutral fiber of the metal core) of the casing by playing on the inertia of the blade, in particular on its width. The objective is to ensure a predefined flexibility of the strand throughout the latter, in particular constant, over the entire length of the strand or, failing this, over part of the strand, in particular near the closure element since it is in this zone that the radius of curvature of the wrist varies the most. Preferably, the thickness of the blade does not vary along the blade.

To illustrate this, reference is made to FIGS. 8 and 9 to 11. Fig. 9 is a section at the level of the plane A – A of FIG. 8, fig. 10 is a section at the plane B – B of FIG. 8 and fig. 11 is a section at the level of the plane C – C of FIG. 8. It is noted that the geometries of the section of the strand are different at the level of these three planes. In fact, the geometry of the section of the casing 3 and / or the geometry of the section of the reinforcement 4 changes along the strand. In particular, the section of the casing changes to provide aesthetic functions and the section of the reinforcement changes to provide a mechanical function, in particular a mechanical function related to comfort. Fig. 9 also shows an opening 30, and FIG. 11 shows the fold 20 of the reinforcement. This architecture makes it possible to have a constant flexibility of the strand, in particular on the part of the strand close to the closure element, and to compensate for the variations in rigidity due to the presence of an opening or, more generally due to the variations in envelope section.

Thanks to such an architecture, in particular thanks to the variation of the section of the reinforcement along the strand, it is possible to obtain a desired profile of flexibility of the strand along the latter. The graphs in fig. 14 illustrate these profiles. The points shown indicate the flexural stiffness or flexibility of the bracelet in different positions of the strand for four types of strands, namely: a 57.5 mm long strand with a constant section reinforcement (l = 57.5, cst), a 57.5 mm long strand with a variable section reinforcement (l = 57.5, var), a 71.5 mm long strand with a constant section reinforcement (l = 71.5, cst), a 71.5 mm long strand with a variable section reinforcement (l = 71.5, var).

The strands with variable reinforcement section are optimized to ensure constant rigidity throughout the strand, with a nominal value equal to 1 on the ordinate. It can be seen that the variable section of the reinforcement makes it possible to compensate to a very large extent the effects of variations in the section of the envelope: between points 10 and 28, the variation between the minimum and maximum stiffness values falls by more than 25% for a constant section reinforcement at 4% for a variable section reinforcement, which is no longer perceptible. On the graph of fig. 14, the abscissa points 14, 21 and 28 correspond approximately to the locations of profiles A – A, B – B and C – C in figs. 8 to 11.

In conclusion, the use of a variable width reinforcement compensates for the effect of the outer geometry of the strand. It even significantly reduces the effect due to the presence of a reinforcement extending under the lower plane of the strand, such as a comfort cushion.

[0057] The winding zone of the strand around the wrist can then exhibit almost constant flexibility and provide significantly increased wearing comfort.

The reinforcement therefore has a cross section whose geometry, in particular the width of the cross section, evolves along the strand so that the flexural rigidity of the strand, along the strand, has a determined profile, in in particular, a constant profile over at least part of the strand, for example over half of the strand close to the closure element. By "constant profile" is meant that the flexural stiffness of the strand does not vary by more than 20% of a nominal value, or even preferably does not vary by more than 10% of the nominal value, or even ideally does not vary. of more than 5% of the nominal value.

The casing 3 is for example made of a polymer material. Polymeric materials include the following different families: thermosets, elastomers, thermoplastics. The most suitable family for a flexible strap application is the elastomer family, and possibly that of thermoplastics-elastomers (a mixture of elastomer and thermoplastic generally called "TPE").

[0060] Alternatively, the envelope can be made of leather sewn around the reinforcement.

The strand has been described previously applied to a bracelet comprising two strands and a clasp. It can be applied to a bracelet comprising two strands and another closure element, such as a buckle and pin system cooperating with pin holes. The strand may therefore include a backing extending from the box clip to the buckle clip or a backing extending from the box clip to the barb holes.

In this document, is meant by "the connecting element 4 mechanically connects or mechanically integrates a first fixing element 6 to a second fixing element 5" that the connecting element prevents, except to break the element connection, that the first element can be moved away from the second fixing element, under a tensile force of 50 N, or even 100 N, or even 200 N. This remains true even before the casing is placed around the reinforcement.

Claims (15)

1. reinforcement (2; 2) strand (1) watch strap to be housed in a shell (3) strand non-metallic flexible material, characterized in that the reinforcement comprises a connecting element made of alloy superelastic, the connecting element extending from a member (10; 6; 10) securing the strand to a watch case to a member (9; 5) securing the strand to a closure member. 2. Reinforcement according to claim 1, characterized in that the connecting element has a cross section whose geometry, in particular the width of the cross section and / or the thickness of the cross section, evolves along the strand, the geometry evolving along the strand so that the flexural rigidity of the strand, along the strand, has a constant profile on at least a portion of the strand, for example on half of the strand close to the closure element. 3. Reinforcement according to claim 1 or 2, characterized in that the connecting element (4; 4) mechanically connects or mechanically joins: The element (10; 6; 10) for attaching the strand to the watch case; The element (9; 5) for fastening the strand to the closure element. 4. Reinforcement according to one of the preceding claims, characterized in that the connecting element has a cross section whose geometry, in particular the width of the cross section and / or the thickness of the cross section, evolves along of the strand. 5. Reinforcement according to one of the preceding claims, characterized in that the reinforcement is made of superelastic alloy. 6. Reinforcement according to one of the preceding claims, characterized in that the connecting element forms at least a portion of the element (6) fixing the strand to the watch case, including a loop (8), and or the connecting element forms at least a part of the element (5) for attaching the strand to the closure element, in particular a loop (7). 7. Reinforcement according to the preceding claim, characterized in that the connecting element comprises an end (20) folded and fixed on the connecting element at the element (6) fixing the strand to the watch case and / or the connecting element comprises a folded end and fixed on the connecting element at the element (5) fixing the strand to a closure element. 8. Reinforcement according to the preceding claim, characterized in that the folded end of the connecting element at the element (6) fixing the strand to the watch case is fixed on the connecting element by riveting and / or welding and / or screwing and / or the folded end of the connecting element at the fastening element (5) of the strand to the closure element is fixed on the connecting element by riveting and / or welding and / or screwing. 9. Reinforcement according to one of the preceding claims, characterized in that the connecting element (4) is attached directly to the fastening element (10) of the strand to the watch case and / or the element link (4) is attached directly to the fastening element of the strand to the closure element. 10. Reinforcement according to one of the preceding claims, characterized in that the connecting element comprises a superelastic alloy blade. 11. Strand (1) of a watch strap comprising a reinforcement according to one of the preceding claims. 12. Bracelet strand according to the preceding claim, characterized in that the envelope comprises at least one opening (30) revealing the reinforcement. 13. Strand of bracelet according to claim 11 or 12, characterized in that the envelope is overmolded on the reinforcement. 14. Watchband comprising at least one strand of bracelet according to one of claims 11 to 13. 15. Watch comprising at least one strap strand according to one of claims 11 to 13.