Patent Grant
9516928
The invention relates to a watch strap strip reinforcement. The invention also relates to a strip for a strap including such a reinforcement. The invention further relates to a strap including at least one such strip. The invention relates, finally, to a watch including at least one such strip.
Numerous flexible watch straps are commercially available, especially made from leather, elastomer or thermoplastic-elastomer. However, the durability and the performance of straps of this type are not always satisfactory in comparison with the performance of a metallic link bracelet.
In order to address these problems, consideration has been given to producing straps of the hybrid type, that is to say flexible straps having reinforcements.
A strap made from a plastic material reinforced by a metallic fitting which is folded back at the extremities of the strip in such a way as to form holes permitting the passage of the bars is known, for example, from document FR1591988. The purpose of this folding-back of the metallic fitting is to form a through hole for the passage of a bar or a screw for fixing the strap. The tensile strength of the strap is ultimately assured by the plastic material.
Known from document AT400551 is a strap in which a two-layer reinforcement formed from a resistant thread glued to a flexible blade is implemented in order to increase the tensile strength of the strips without impairing the flexibility of the strap. This two-layer reinforcement does not improve the tensile behavior at the level of the attachments.
Known from document AT407692 is a flexible strap with a reinforcement that is present solely at the fold of the strip and is glued in order to reinforce the strap at the level of the attachment. The tensile strength of the strip is not improved by this solution.
Known from document JP07329110A is a flexible strap made from resin reinforced by a nylon insert. This insert is wound around the attachments in certain configurations. As in document FR1591988, the tensile strength of the strap is assured by the resin.
Numerous models and designs of flexible straps have been described and presented. Nevertheless, the familiar flexible straps are all rather inefficient mechanically, especially at the level of the tensile strength of the strips. It is thus necessary to make a choice between a flexible strap made from leather or elastomer, which is comfortable, and a mechanically efficient metal bracelet. Flexible straps are invariably known to be less robust than metal bracelets, for example at the level of their tensile strength or bending strength.
The object of the invention is also to make available a strap overcoming the disadvantages mentioned previously and improving the straps that are already familiar from the prior art. In particular, the invention proposes an efficient and comfortable strap. The invention also proposes a watch including such a strap.
A reinforcement according to a first aspect of the invention includes a linking element mechanically connecting or mechanically securing:
Various embodiments of the reinforcement according to the invention are as follows:
A reinforcement according to a second aspect of the invention includes a blade made from a superelastic alloy, the blade extending from an element for fixing the strip to a watch case to an element for fixing the strip to a closure element.
A reinforcement according to a third aspect of the invention includes a blade having a cross-section of which the geometry, in particular the width of the cross-section and/or the thickness of the cross-section, changes along the strip, the blade extending from an element for fixing the strip to a watch case to an element for fixing the strip to a closure element, the geometry changing along the strip or the reinforcement in such a way that the flexural rigidity of the strip, along the strip, has a predetermined profile, in particular a profile that is constant over at least a part of the strip, for example over the half of the strip close to the closure element.
Various embodiments of the reinforcement according to the invention are as follows:
A strap strip according to the invention includes a reinforcement as above and a casing especially a casing made from an elastomer material.
Various embodiments of the strap strip according to the invention are as follows:
A strap according to the invention includes at least one strap strip as above.
A watch according to the invention includes at least one strap strip as above.
A method for determining a geometry of a strap strip according to the invention includes the following stages:
The accompanying drawing depicts, by way of example and without limitation, two embodiments of a strap according to the invention.
One embodiment of a strap strip 1 according to the invention is described below with reference to
The strap strip includes a reinforcement 2 inserted into a casing made from a 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, especially an alloy, in particular being a superelastic alloy or a shape-memory alloy. The second material is flexible. An elastomer such as rubber, a polymer or leather are particularly suitable for use as a second material.
The properties of the first and second materials are distinct in order to separate the stresses as effectively as possible. Preferably produced is a strip of which the architecture is based on a central core or reinforcement and a casing applied around the core, that is to say coating the core at least partially. The reinforcement allows high levels of mechanical strength of the strip to be assured, especially in respect of its tensile behavior (high strength) and its deformation behavior under stress (low deformation). In addition or alternatively, the reinforcement allows high levels of mechanical resistance of the strip to bending to be assured. The actual casing (or coating of the strip) surrounding the reinforcement at least partially allows functions of comfort and aesthetics to be assured in principal, especially by allowing a desired flexibility and/or a desired lightness and/or a desired geometry to be achieved. The casing is preferably molded onto the reinforcement, especially when it is made from an elastomer material. The casing may also be assembled by gluing and/or by stitching around the reinforcement when it is made from leather.
In both cases, an opening 30 may be made in the casing in order to reveal the reinforcement 2. The visible part of the reinforcement may then be treated in order to avoid any deterioration of it. The opening may perform an aesthetic function and/or the function of revealing the technical nature of the strap strip.
The reinforcement includes an element 6 for fixing the strip to the watch case and an element 5 for fixing the strip to a closure element. The reinforcement includes a linking element 4 mechanically connecting the element 6 for fixing the strip to the watch case to the element 5 for fixing the strip to a closure element. Preferably, the element 6 for fixing the strip to the watch case includes a tube 10 and/or the element 5 for fixing the strip to the closure element includes a tube 9. Alternatively, the element 6 for fixing the strip to the watch case is realized by a first extremity of the linking element, and/or the element 5 for fixing the strip to a closure element is realized by a second extremity of the linking element. The reinforcement 2 principally includes a blade 4, especially a metallic blade, and in particular a blade made from a superelastic metallic alloy.
The element 6 for fixing the strip to the watch case is intended to interact with a second fixing element provided for securing the strip to the watch case, especially to the horns. The first and second elements constitute an attachment. In a similar manner, the element 5 for fixing the strip to a closure element is intended to interact with a second fixing element provided for securing the strip to the closure element, which in particular may be a buckle or a clasp, for example a deployant clasp. The first and second elements constitute an attachment.
As depicted especially in
A bar, a screw or a pin, constituting the second fixing element, is then engaged in each tube 9 and/or 10 in order to fix the strip to the watch case or to the closure element.
The presence of the tubes 9 and 10 principally permits the two extremities of the reinforcement to be secured to the second fixing elements, thereby absorbing the tensile forces in an optimal manner. These tubes provide three additional advantages:
The tubes are selected preferably in the same material as the material of the metallic blade constituting the reinforcement. In particular, when the material of the blade is a superelastic metallic alloy, especially an NiTi alloy, the material of the tubes is preferably a superelastic metallic alloy, and more preferably the same superelastic alloy as that utilized for the blade, especially an NiTi alloy. This advantageous combination permits a robust assembly of the tubes to the extremities of the blade. The assembly of the tubes to the extremities of the blade is preferably achieved by soldering, the soldering being more preferably of the laser type. The recommended assembly by laser soldering permits the localized fusion of the material thereby securing the extremity of the blade and the tube, without the addition of material from outside, while ensuring excellent mechanical performance and good resistance to corrosion. The dimensions of the tubes typically exhibit an external diameter comprised between 1 and 2.5 mm. The tube 10 for the watch case/strip attachment is preferably provided with notches 101 for avoiding degradation of the casing during the use of bar pliers to assemble the strip on the case middle.
Alternatively, tubes made from Phynox, Nivaflex or an equivalent material could also be utilized, with the associated risk that the assembly of the tubes to the extremities of the blade is more difficult to achieve.
The passage of the bar pliers can also be reduced to a strict minimum, and the elasticity of the casing can also be used to compress the bar. In this case, the tube 10 for attachment to the watch case must be much shorter in order to permit this compression.
In a second embodiment of the reinforcement 2′ depicted in
In order to ensure the performance of the strip, the reinforcement must be connected to the attachments while preserving its performance as far as possible. The riveted fold at each extremity permits the provision of a passage for a bar, a screw or a pin intended for the securing of the strip.
Advantageously, as depicted in
The selected tubes are preferably made from Phynox, Nivaflex, superelastic alloy or an equivalent material, which permits good mechanical performance to be assured on the one hand and good resistance to corrosion on the other hand. The dimensions of the tubes typically exhibit an external diameter lying between 1 and 2.5 mm. The tube 10′ for the watch case/strip attachment is preferably provided with notches 101 for avoiding degradation of the casing during the use of bar pliers to assemble the strip on the case middle.
Tests have shown that a rivet made from brass or stainless steel is ideally suited to the desired application. Alternatives other than riveting are conceivable in order to achieve the desired performance. For example, it is possible to staple the fold 20 to the rest of the blade. It is also possible to attach the fold 20 to the rest of the blade by soldering performed, for example, at the extremity of the fold 20. In this case, the soldering may preferably be of the laser type. It is also possible to secure the fold 20 to the rest of the blade by screwing. In this case, bolts are utilized in place of the rivets.
The first and second embodiments may be combined on the same reinforcement, with the first embodiment at a first extremity and the second embodiment at a second extremity.
It should be noted that the solutions that are familiar from the prior art are not satisfactory. A simple fold, as in document FR1591988, improves the tensile behavior only marginally. In fact in this document, unlike the invention, it is the elastomer overmolding that permits the strength of the attachment to be assured in this case.
In the invention, the reinforcement which permits the element for fixing the strip to the watch case to be connected mechanically to the element for fixing the strip to the closure element is realized first. Thus, at this stage of realization, the application of a mechanical tensile loading of 50 N, or 100 N or 200 N to the reinforcement does not permit the deformation of the reinforcement and the fixing element, as is the case in the prior art. In particular, the application of a mechanical tensile loading to a pin or a bar that is present in the tube 9 or 10 does not permit the tube or the other element to be released from the reinforcement, other than by breaking the reinforcement. Thus, in the described embodiments, the elements for fixing the attachments (permitting fixing to the watch case or to the closure) are secured to the reinforcement.
The principal role of the reinforcement 2 is to ensure the mechanical strength of the strip. Having regard for the requirement to have a flexible strap and for the criterion of resistance to the various efforts, the reinforcement principally includes a leaf or a metal blade 4. In particular, the use of a metallic superelastic alloy also permits the flexural rigidity to be improved.
In order to guarantee that strong deformations of the strip do not give rise to permanent deformation, for example when the strip is folded back on itself through 180°, a superelastic alloy is utilized advantageously for the reinforcement. Superelasticity is apparent in certain highly specialized alloys, which demonstrate a transition between an austenitic phase and a martensitic phase. The superelasticity is characterized by the complete recovery of the form of the sample when the applied stress ceases. In the range of temperatures within which the austenicity is stable, the martensitic transformation may be brought about under stress. The stress is first exerted in the range of elastic deformation of the austenite at a level of stress proportional to the deformation. Above a critical value, the austenite is transformed into martensite. When the stress ceases, total reversion of the martensite to austenite takes place to the point of zero deformation, since it is the austenite structure that is stable at the temperature at which the stress is applied. The great relevance of this property is the major possibility of deformation in an “elastic” range when the stress varies. The elasticity of these alloys may reach ten times that of steel.
There are several alloys which possess superelastic properties. It is possible to utilize an alloy based on nickel and titanium, NiTi (commercial name Nitinol), for example, principally because this alloy has excellent resistance to corrosion and is biocompatible. Other superelastic alloys, such as CuAlBe, CuAlNi or CuZnAl alloys, can also be utilized.
Tests have confirmed that the reinforcement made from NiTi alloy and, in particular, that a blade made from NiTi assembled by laser soldering to the tubes made from NiTi alloy, possesses excellent mechanical strength and corrosion resistance, even under unfavorable conditions (combination of materials favoring the equivalent of galvanic corrosion and prestressing of the metallic blade), after two months' testing in a saline mist.
The blades utilized can have an initial zero curvature, and the curvature of the strip may be obtained during molding of the casing. It is also conceivable to impart an initial curvature (preform) to the blade by the use of a suitable manufacturing process.
Since the invention makes it possible to separate, at least up to a point, the contributions to the functions of “mechanical strength” and “aesthetics/comfort”, the reinforcement may be designed without taking account of the casing. It is obvious that the addition of a casing further improves the tensile strength.
Standard NIHS 92-11 states that a watch strap must be capable, as illustrated in
The reinforcement is then dimensioned according to the maximum tensile force F which the strip must be able to withstand without breaking, by estimating the stresses equivalent to the maximum force, which must be lower than the elastic limit of the material. For the dimensions utilized in the context of the tests, with a minimum width of 7.4 mm, a thickness of 0.1 mm for the blade will permit a limit force of 440 N before plastic deformation to be obtained, which is well above the desired values and well below the elastic limit and the ultimate tensile strength of the material.
In addition, simulations and tests have shown that the stress concentrations generated in the vicinity of soldering or rivets remain below the ultimate plastification stress, even for an applied tensile force greater than 300 N. The tests have also shown that such a configuration permits a level of performance that is largely sufficient to meet the requirements of standard NIHS 92-11, which specifies the threshold tensile strength values. The strengths in lateral deviation and in traction are also within the permissible criteria.
In addition, the thickness of the casing may be selected in such a way as to optimize the flexural rigidity of the strip. For a blade thickness of 0.1 mm, the permissible radius of curvature is 0.7 mm (by comparison, a central stainless steel blade (type 1.4310) tolerates a minimum radius of curvature of 5 mm only). The thickness of the coating of the strap is then selected in such a way as to provide a radius of curvature greater than the permissible limit in the event of the strip being folded through 180°.
The NiTi alloy loses its superelastic properties below 0° C. However, the alloy regains all its properties as soon as the temperature rises above this limit. Thus, a blade that is bent with a radius of 2 mm at −16° C. will retain this curvature for as long as the temperature remains below 0° C., but will once again become perfectly straight as soon as the temperature becomes higher (resumption of form in 8 s at 20° C.). Similarly, the blade made from superelastic alloy retains all its superelastic properties following coating (overmolding conditions: typically T>180° C. for several minutes). This temperature-related behavior may vary depending on the selected superelastic alloy. Thus, certain alloys are suitable for use at a lower temperature, although with an associated decrease in the maximum operating temperature.
The blades depicted in
In order to illustrate this in the case of a complex casing geometry, reference is made to
Thanks to such an architecture, an in particular thanks to the variation in the cross-section of the reinforcement along the strip, it is possible to obtain a desired profile for the flexibility of the strip along the latter. The graphics in
The strips having a variable reinforcement cross-section are optimized to ensure a constant rigidity for the entire length of the strip with a nominal value equal to 1 on the y-axis. It can be appreciated that the variable cross-section of the reinforcement makes it possible to compensate to a very large extent for the effects of the variations in the cross-section of the casing: between points 10 and 28, the variation between the minimum and maximum rigidity values falls from more than 25% for a reinforcement with a constant cross-section to 4% for a reinforcement with a variable cross-section, which is no longer perceptible. In the graphic in
It is thus possible to proceed according to the following stages in order to determine a geometry of a strap strip, in particular in order to determine a geometry for a reinforcement, and especially in order to determine the width and/or the thickness of the reinforcement for a watch strap strip:
In the examples in
In all cases, the profile of the blade along the strip does not change in the same direction as the profile of the casing; that is to say the width of the blade and the width of the casing change in opposite directions along the strip. In other words, the rates of change in the width of the blade and in the width of the casing along the profile have opposite signs. The profile of the blade does not follow the profile of the casing over at least one portion of the strip, for example over at least half of the strip. In more general terms, the rate of variation in the value of the inertia of the cross-section of the blade along the strip is of an opposite sign to the rate of variation in the value of the inertia of the cross-section of the casing over at least one portion of the strip or the reinforcement, for example over at least half of the strip. Thus, the value of the inertia of the cross section of the blade and the value of the inertia of the cross-section of the casing change in opposite directions over at least one portion of the strip or the reinforcement, for example over at least half of the strip.
Similarly, the rate of variation in the thickness value of the blade along the strip may be of a sign opposite to the rate of variation in the thickness value of the casing over at least one portion of the strip or the reinforcement, for example over at least half of the strip. Thus, the thickness value of the blade and the thickness value of the casing may change in opposite directions over at least one portion of the strip or the reinforcement, for example over at least half of the strip.
Similarly, the rate of variation in the width value of the blade along the strip is of an opposite sign to the rate of variation in the thickness value of the casing over at least one portion of the strip or the reinforcement, for example over at least half of the strip. Thus, the width value of the blade and the thickness value of the casing change in opposite directions over at least one portion of the strip or the reinforcement, for example over at least half of the strip.
It should also be noted that the example in
Thanks to such an architecture, and thanks in particular to the variation in the cross-section of the reinforcement along the strip, it is possible to achieve a desired profile for the flexibility of the strip along its length, especially a constant profile over a portion of the length of the strip or over the entire length of the strip.
In conclusion, the use of a reinforcement with a variable width makes it possible to compensate for the effect of the external geometry of the strip. It even permits a substantial reduction in the effect due to the presence of an element extending below the bottom plane of the strip, such as a comfort cushion.
The area of the strip that is wound around the wrist may thus have an almost constant flexibility and may provide significantly enhanced wearing comfort.
The reinforcement thus has a cross-section of which the geometry, in particular the width of the cross-section, changes along the strip in such a way that the flexural rigidity of the strip, along the strip, has a predetermined profile, in particular a constant profile over at least one portion of the strip, for example over at least half of the strip, for example over the half of the strip close to the closure element. The expression “constant profile” is used here to denote that the flexural rigidity of the strip does not vary by more than 20% of a nominal value, or preferably does not vary by more than 10% of the nominal value, and ideally does not vary by more than 5% of the nominal value.
The casing 3 is made from a polymer material, for example. Polymer materials include the following different families:
The most suitable family for an application in a flexible strap is the elastomer family, and possibly the thermoplastic/elastomer family (mixture of elastomers and thermoplastics generally referred to as “TPE”). In order to facilitate the realization of the strap strip, it is generally advantageous to apply a chemical compound to the surface of the metallic reinforcement which promotes the adhesion of the elastomer to the reinforcement. The compound is selected depending on the elastomer and the reinforcement material utilized, for example by consulting the “Product Selector Guide” for Chemlok/Chemosil adhesives published by the LORD company.
Alternatively, the casing may be made from leather stitched around the reinforcement.
The strip has been described previously applied to a strap consisting of two strips and a clasp. In this preferred case, the strip includes a reinforcement extending from the attachment for the watch case to the attachment for the clasp.
It can also be applied to a strap consisting of two strips and another closure element, such as a tongue-buckle system interacting with tongue holes. The strip in this case may include a reinforcement extending from the attachment for the watch case to the attachment for the buckle or a reinforcement extending from the attachment for the watch case to the tongue holes.
In this document, the expression “the linking element 4 mechanically connects or mechanically secures a first fixing element 6 to a second fixing element 5” is used to denote that the linking element prevents the first element from being separated from the second fixing element, other than by breaking the linking element, under a tensile load of 50 N, or 100 N or 200 N. This remains true even before the casing is positioned around the reinforcement.
| Number | Date | Country | Kind |
|---|---|---|---|
| 620/11 | Apr 2011 | CH | national |
| 11405241 | Apr 2011 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CH2012/000080 | 4/5/2012 | WO | 00 | 11/4/2013 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2012/135967 | 10/11/2012 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2573055 | Pedersen | Oct 1951 | A |
| 3543975 | Bauer | Dec 1970 | A |
| 3610488 | Tracy | Oct 1971 | A |
| 3844136 | Rieth | Oct 1974 | A |
| 3889323 | Reith | Jun 1975 | A |
| 3924418 | Burkle, Jr. | Dec 1975 | A |
| 4573221 | Hirsch | Mar 1986 | A |
| 4821532 | Jaques | Apr 1989 | A |
| D333446 | Butler | Feb 1993 | S |
| 5365753 | Carrola | Nov 1994 | A |
| 5812500 | Webb, Jr. | Sep 1998 | A |
| 6406177 | Fukushima et al. | Jun 2002 | B1 |
| 6968671 | Dal Monte | Nov 2005 | B2 |
| 7013631 | Carrola | Mar 2006 | B2 |
| 7107790 | Frank | Sep 2006 | B2 |
| 8870448 | Bianco | Oct 2014 | B2 |
| 20070067967 | Sima | Mar 2007 | A1 |
| Number | Date | Country |
|---|---|---|
| 400551 | Jan 1996 | AT |
| 407692 | May 2001 | AT |
| 1217062 | Jan 1987 | CA |
| 502787 | Feb 1971 | CH |
| 650891 | Aug 1985 | CH |
| 655220 | Apr 1986 | CH |
| 1806449 | Jun 1969 | DE |
| 2061849 | Jul 1972 | DE |
| 0116384 | Aug 1984 | EP |
| 0133181 | Feb 1985 | EP |
| 1023851 | Aug 2000 | EP |
| 1591988 | May 1970 | FR |
| 51-41476 | Mar 1976 | JP |
| 52-143066 | Nov 1977 | JP |
| 59-144405 | Aug 1984 | JP |
| 59-141809 | Sep 1984 | JP |
| 60-91013 | Jun 1985 | JP |
| 61-123723 | Aug 1986 | JP |
| 63-161515 | Oct 1988 | JP |
| 01-236004 | Sep 1989 | JP |
| 07-329110 | Dec 1995 | JP |
| H-11239506 | Sep 1999 | JP |
| 2000-300313 | Oct 2000 | JP |
| 2006-0090648 | Aug 2006 | KR |
| Entry |
|---|
| International Search Report for PCT/CH2012/000080, Mailing Date of Jul. 10, 2013. |
| Swiss Search Report dated Jul. 12, 2011, issued in Swiss Application No. CH00620/1; w/ English Translation (4 pages). |
| Notification of Reasons for Refusal dated Nov. 17, 2015 issued in counterpart Japanese application No. 2014-502967 (w/ English translation, 14 pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20140053602 A1 | Feb 2014 | US |
