Patent Publication Number: US-11022943-B2

Title: Device for attaching a bracelet

Description:
This application claims priority from European Patent Application No. 17197367.0 filed on Oct. 19, 2017, the entire disclosure of which is hereby incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to the field of horology or jewelry. More specifically, it concerns a method for attaching a strap or bracelet to an object, particularly a watch case. 
     BACKGROUND OF THE INVENTION 
     Generally, straps or bracelets, made of leather or metal, are attached to the horns of a watch case by means of a bar formed of a tube, inside which are mounted two pistons that move in translation, and an elastic member disposed between said pistons and intended to drive them outwardly of the tube. Said bar is mounted inside a housing provided for this purpose at one end of the bracelet, and the pistons are engaged in blind bores facing them in the horns of the case. 
     To detach a strap or bracelet attached to a case in this manner, it is necessary to have a tool designed to push the pistons back inside the tube, against the stress exerted by the elastic member, and thereby remove them from the bores. The wearer of the watch does not permanently carry such a tool, and moreover, the tool can be inconvenient to use. This is why bracelets provided with such an attachment device are generally permanently secured to the case. 
     There are also attachment devices that allow the bracelet to be removed from the case without using a tool. Such devices usually comprise a bar, of the type described above, on which is mounted, through the tube, a member for actuating the pistons. Said actuation member is, for example, a radial finger integral with one of the pistons, as described in Swiss Patent No CH327838. The finger is slidably mounted through an axial slot made in the tube, and its movement along the slot pushes one of the pistons inside the tube. 
     CH Patent No. 614589 discloses a watch case with a device for attaching a strap to the case, the central horn has a cylindrical passage that is slit longitudinally over the entire length of the horn, to allow insertion of a bar for attaching a strap. The bar takes the form of a cylinder with a flat portion along its entire length to allow the bar to pass when it is inserted into the passage and to hold the bar in place when the latter occupies a determined angular position. 
     The attachment devices thus described are generally employed for interchangeable bracelets or straps which the user can then change as desired. They are not, however, free of drawbacks. It will be noted in particular, that they require major structural modifications to the bar, such as, for example, making an opening in the tube, or transforming the pistons. These changes entail significant extra manufacturing costs. These attachment devices also include a protruding element, namely the actuating member, which may snag or injure the wearer of the watch. 
     SUMMARY OF THE INVENTION 
     The present invention makes it possible to overcome these drawbacks by proposing a device for attaching a bracelet or strap to a watch case, the device comprising, on the one hand, a bar secured to the watch case by means of at least one horn, and on the other hand, an insert integral with the end of the bracelet, wherein the bar and the insert are complementary in order to cooperate by fitting one inside the other to form removable assembly means able to make the bracelet interchangeable. 
     According to the invention, the bar is formed by two cylindrical shafts having at least one flat portion, said flat portion being arranged to cooperate by interlocking or fitting with at least one housing made in said at least one insert, said at least one housing having a substantially rectangular opening for receiving said at least one flat portion, wherein each shaft is telescopic in order to move from a first position A, in which the shaft is deployed and the inset is positionable on the bar shaft, to a second position B, in which the bar is retracted and said insert is locked onto the bar shaft. 
     According to other advantageous variants of the invention:
         the bar includes at least one guide track extending over all or part of its length;   said at least one track includes at least one notch, said notch being configured to define position B, called the retracted position;   the horn includes guide means arranged to slide inside said at least one track;   the guide means include a guide pin arranged to cooperate with said guide track;   said guide track is L-shaped, the base of the L receiving said locking notch that defines the position B or locked position of the shaft;   the shaft includes at least one collar at at least one end, said at least one collar forming an axial retaining element;   said at least one collar cooperates with at least one lateral stop surface of the watch case;   the watch case comprises a median horn including a passage whose diameter corresponds to the diameter of the bar shaft;   the bar includes two shafts each including two parallel and symmetrical flat portions, arranged to cooperate with said housing of said insert;   said housing takes the form of a groove with an opening, the housing having a C-shaped cross-section.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will appear more clearly from the following detailed description of an example embodiment of a device for attaching a strap or bracelet according to the invention, this example being given solely by way of non-limiting illustration with reference to the annexed drawing, in which: 
         FIG. 1  illustrates an exploded perspective view of a watch case equipped with an attachment device according to the invention. 
         FIGS. 2 a  and 2 b    represent a transverse cross-section of the watch case with the device respectively in the deployed and retracted position. 
         FIGS. 3 a  and 3 b    illustrate a bar of an attachment device according to the invention. 
         FIG. 4  illustrates a cross-sectional view of the insert attached to the watch case via the bar. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1 to 4  illustrate a wristwatch and detailed views of the device for attaching bracelet  2  to watch case  1  according to a preferred embodiment of the invention. The device for attaching bracelet  2  to watch case  1  includes, on the one hand, a bar  4  secured to the watch case by means of at least one horn integral with the case, and on the other hand, an insert integral with the end of bracelet  2 , wherein bar  4  and insert  20  are complementary and cooperate by interlocking or fitting with each other to form removable assembly means able to make the bracelet interchangeable. 
     As can be observed in  FIGS. 2 a  and 2 b   , the watch case includes a median horn comprising a passage  30  whose diameter corresponds to the diameter of the shaft of bar  4  such that the latter can turn freely inside the housing. Median horn  3  consists of a single piece and can be arranged to be removable and held on watch case  1  by means of screws for example. Such an arrangement makes it possible to assemble and disassemble the horn quickly and easily. It is also possible to envisage the horn being formed with the watch case. 
     According to the invention, bar  4  is formed by at least one cylindrical shaft  40  having at least one flat portion  41 , flat portion  41  being arranged to cooperate by interlocking or fitting with at least one housing  200  made in insert  20  of bracelet portion  2  or of a link. As represented in the Figures, bar  4  is formed by two shafts  40 , each including two parallel and symmetrical flat portions  41 , and the two shafts  40  are separated by a spring  5  that pushes them away from each other, shafts  40  tending to be returned to the deployed position by spring  5  disposed inside housing  30  of horn  3  when the shafts are not locked. 
     Those skilled in the art could devise a single shaft forming bar  4  and would have no particular difficulty in adapting this device to a watch case comprising a conventional pair of horns. 
     Advantageously, shaft  40  is arranged to be telescopic to move from a first position A, in which the shaft is deployed and insert  20  is positionable on shaft  40 , to a second position B, in which the shaft is retracted and the insert is locked on bar shaft  40 . 
     As illustrated in  FIGS. 3 a  and 3 b   , shaft  40  includes at least one L-shaped or bayonet-shaped guide track  42  extending over one portion of its length, track  42  including at least one notch  43 , on the base of the L, to define the retracted position of shaft  40 . 
     Further, shaft  40  includes at least one operating member at its free end for pivoting the bar from a first position A, in which flat portion  41  of the shaft is able to receive the insert, to a second position B in which insert  20  is locked onto bar  4 . 
     As illustrated, the operating member includes a collar  44  integral with each of the ends of shaft  40 , with shaft  40  and collar  44  thus forming a single element. It is also possible to envisage assembling collar  44  to the end of shaft  40  by means of an insertion tip mounted in a hollow portion of shaft  40 . An internal bump is in that case arranged at the end of shaft  40  for cooperating with the insertion tip, so as to snap collar  44  into shaft  40 . Other means of fixing collars  44  can be envisaged, such as, for example adhesive bonding, welding or press fitting. These collars act as axial retaining elements for bar  4  and insert  20 . 
     According to the invention, horn  3  includes guiding and locking means arranged to slide inside track  42  and guide shaft  40  during a change of position. These guide means, seen, in particular, in  FIGS. 2 a  and 2 b   , include at least one guide pin  31  stressed by a spring  32  to limit play and to ensure proper contact of the guide pin in track  42  of shaft  40 . Guide pin  31  also allows the shaft to be locked in the retracted position, as the guide pin cooperates with notch  43 , on the base of the L, to keep shaft  40  in the retracted position. 
     Yet another advantage of such a device is that guide pin  31  can hold shaft  40  on horn  3 , since the shaft cannot be dislodged while guide pin  31  is in place. Thus, there is no risk of losing shaft  40  or spring  5  when the bracelet is changed. Naturally, those skilled in the art could envisage any other type of guide means, such as a projecting lug or post for example. 
     As can be seen in  FIGS. 2 a , 2 b    and  4 , insert  20  includes a housing  200  with a substantially rectangular opening  210  for receiving flat portion  41  of shaft  40 , with the height and length of opening  210  corresponding to the height and length of flat portions  41  of bar  4 . Housing  200  is made in insert  20  of the bracelet portion. Housing  200  takes the form of an open housing formed by a cylindrical groove  210  machined in insert  20  of the bracelet portion. This cylindrical groove includes a rectangular opening  210  for the insertion and holding of cylindrical bar  40  which has two flat portions  41  to match the shape of the housing. It can thus be observed in the cross-sectional view of  FIG. 4  that groove  211  has a C-shaped cross-section. 
     According to the preferred embodiment illustrated in  FIG. 1 , horn  3  has first vertical lateral walls  10 , in which is arranged a cylindrical recess  11  for partially housing collars  44  therein. Collars  44  preferably have a cylindrical shape here to fit inside recesses  11 . 
     To attach bracelet  2  to case  1  as illustrated in  FIGS. 2 a  and 2 b   , pressure is applied to shaft(s)  40  until guide pin  31  abuts against the wall of guide track  42 , then the shaft(s) are pivoted at an angle defined by the guide track, defined here by the length of the base of the L formed by the track, and the pressure applied on the shaft(s) is released so that spring  5  pushes back shaft(s)  40 , which will then move into the deployed position. This kinematic arrangement is seen in  FIG. 3   a.    
     Then insert  20 , which is for example the end of a bracelet portion, is placed on bar  4  by placing opening  210  of housing  200  opposite flat portions  41  of shaft(s)  40  in order to fit bar  4  inside housing  200 . 
     Once insert  20  is in place on bar  4 , the user performs the reverse operations, i.e. applies pressure on the shaft(s) until guide pin  31  abuts on the wall of guide wall  42 , then pivots the shaft about axis A-A by means of the collars into position B, and releases the pressure applied so that the guide pin is placed inside locking notch  43  under the effect of spring  5 . Thus, the bracelet portion can no longer be dislodged as can be observed in  FIG. 2   b.    
     Advantageously, at least one of collars  44  includes a slot arranged on its external face, namely the face visible to the wearer of the watch, to cooperate with a tool or the user&#39;s finger to facilitate manipulation of collar  44  and the locking and/or unlocking of insert  20  on bar  4 . 
     Advantageously, insert  20  matches the shape of median horn  3  to limit play during assembly and to provide a high-quality assembly. 
     In the embodiment described above, the insert is disposed on a bracelet or strap made of leather, synthetic fabric, plastic, metal, ceramic or composite material. Likewise, bar  4  is preferably made of metal but could also be made of plastic, ceramic or composite material. 
     As a result of these different aspects of the invention, there is provided a secure bracelet attachment device allowing the bracelet to be quickly and easily changed. 
     Of course, the present invention is not limited to the illustrated example and is capable of various variants and modifications that will appear to those skilled in the art.