Abstract:
A watch case with an interchangeable bracelet system includes a back with a neck to which a portion of a bracelet is removably coupled. A closure element closes the neck and pinches the bracelet against the back of the case. Preferably, the closure element is a ring that is attached to the back of the case by means of a bayonet device consisting of a lug that is inserted in a mating hollow. To prevent accidental separation of the closure element from the case, a compression joint may be placed in a seat provided in either the back of the case or in the closure element. The closure element compresses the joint and frictionally prevents accidental opening. The device enables the bracelet to be changed easily without tools.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an interchangeable bracelet or strap system for a wristwatch. 
     BACKGROUND OF THE INVENTION 
     There are several known examples of wristwatches in which the bracelet or strap thereof is secured by being pinched between two parts of the case. The bracelet may be composed of two separate parts or of two parts connected to each other by a median portion comprising an opening corresponding to the shape of the case or the shape of a portion of the case. 
     For example, French Patent No. 504,267 (Rubattel et Weyermann SA) describes a watch whose bracelet, consisting of a one-piece, rectangular gold band, comprises a round opening that exposes the dial, the inner edge of the opening in the bracelet being gripped between the middle of the case and an apposed bezel. Thus, the bracelet covers the entire case except for the glass and the dial. Another device of the same kind is presented in French Patent No. 1,598,983 (Ervin Piquerez). Here the bracelet does not cover the case. The edge of the central opening of the bracelet conforms to the outer shape of the case and is pinched between the middle of the case and a ring that is screwed either onto the upper portion of the middle or onto the back of the case. 
     Other examples, such as Swiss Patent No. 340786 (Vallon) or No. 355095 (Sorna Watch Co.), disclose bracelets formed of two separate parts with dovetail-shaped ends inserted into slots of corresponding shape provided in the middle of the case to attach the bracelet to the case. The ends of the bracelet parts are held in the slots by the case back, which is screwed on or fastened by means of detents. 
     The essential purpose of the above-described devices is, chiefly for esthetic reasons, to eliminate the need for prongs to fasten the bracelet. 
     The mounting and removal of the bracelet on or from the case—whether by screwing action or even by means of detents—requires a key or tool and virtually must, in practice, be performed by a professional. This is all the more true since, in most of the examples cited above, removal exposes the inner workings of the watch. The known devices therefore cannot be applied to watches sold with a plurality of interchangeable bracelets, which allow the consumer to change the bracelet by himself. 
     There are, of course, various systems quite different from the foregoing examples that enable the user to change the bracelet easily. These include, for example, Swiss Patent No. 685464 (Le Marquand) and European Patent No. 0797132 (Bourquin and Wiser). Although these devices function satisfactorily, they nevertheless require the presence of prongs or excrescences of the same type. 
     SUMMARY OF THE INVENTION 
     The present invention provides a watch case with an interchangeable bracelet that enables the user to change the bracelet easily, without any special tools, and without it being necessary to provide the case with prongs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The detailed description will be better understood in conjunction with the accompanying drawings, showing an embodiment of the invention as an example and wherein like reference characters represent like elements, as follows: 
     FIG. 1 is a partial vertical cross-sectional view of a case with bracelet in accordance with the principles of the present invention; 
     FIG. 2 is a bottom view of a closure element in accordance with the principles of the present invention; 
     FIG. 3 is a bottom view of the back of the case of FIG. 1; 
     FIG. 4 is a side view of the back of the case of FIG. 3; 
     FIG. 5 is an isometric view of the closure element of FIG. 2; and 
     FIG. 6 is an isometric view of the case assembled with the bracelet, the bracelet being only partially mounted thereon. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with the principles of the present invention, a watch case has a back  1  which is readily coupled to and decoupled from a bracelet  3  without the need for special tools. In the embodiment shown in the drawings, bracelet  3  is composed of one piece, the two wrist-engaging parts being connected to each other by an annular portion  12 . Annular portion  12  has an opening able to receive a portion of back  1  of the watch case bound laterally by an annular neck  2 . Neck  2  may extend completely around back  1  or only around a portion thereof. It will be appreciated that bracelet  3  may be formed as two separate parts instead, if desired. In such embodiment an attachment end is provided on each part of the bracelet configured to facilitate attachment to back  1 , such as in neck  2 . 
     Provided below annular neck  2  is a hollow  6  configured for engagement with bracelet  3 . In the embodiment shown in the figures, hollow  6  passes all the way around the portion of back  1  bound by neck  2 . However, a shorter circumferential extent of hollow  6  is within the scope of the present invention as well, as will be appreciated. A flange  14  is formed below hollow  6  with at least one cutout  15  therein to permit access to hollow  6 . In the embodiment of FIG. 3, three cutouts  15  are provided substantially equidistant from one another. However, other configurations are within the scope of the present invention. 
     In order to couple bracelet  3  to the watch case of the embodiment shown in the figures, annular portion  12  of bracelet  3  is placed in annular neck  2  of back  1 . An annularly shaped closure element  4  closes annular neck  2  such as by insertion of at least one lug  5  on closure element  4  through a cutout  15  and into a retaining portion in hollow  6 . In the embodiment of FIG. 2, closure element  4  is provided radially with three inwardly oriented lugs  5  corresponding to the three cutouts  15  in flange  14  of FIG.  3 . However, other configurations are within the scope of the present invention. Annular portion  12  of bracelet  3  is thereby trapped between upper face  9  of closure element  4  and edge  8  of neck  2 . To hold lugs  5  in hollow  6 , closure element  4  is rotated so that lugs  5  move laterally and are completely gripped between flange  14  and the other wall  16  of hollow  6 . 
     Such connection of closure element  4  into hollow  6  by means of lugs and cutouts may be described as a bayonet connection and provides a simple manner of coupling and decoupling closure element  4  to the watch case to secure and to release, respectively, bracelet  3 . It will be appreciated that such connection is simple to achieve as well as to release, and thus permits a user to secure and to release a bracelet  3  to the watch case as desired without the need for any tools. Because lugs  5  are held in a retaining portion formed in hollow  6  away from cutouts  15 , once lugs  5  are inserted in hollow  6  no further tightening is required, as would be the case with a screw-on closure element as in the prior art. Thus, tools are also obviated because of the lack of a need to tighten closure element  4  onto the watch case in the closed position. 
     In order to facilitate manual manipulation of closure element  4  without a special tool, a grasping surface preferably is formed on the lower face of closure element  4 . For example, radial grooves  16  may be made in the lower face of closure element  4  to provide an adequate grip for the fingers of the user wishing to change bracelet  3  as shown in FIG.  2 . It will be appreciated that other configurations facilitating manual manipulation of closure element  4  are within the scope of the present invention. 
     To halt the rotational travel of closure element  4  so that the at least one lug  5  does not reach and fall out the next cutout  15 , a stop  11  is fastened in hollow  6 . In the embodiment shown in FIGS. 1,  3 , and  4 , stop  11  is in the form of a cylindrical key driven into a radial hole made in the back of the hollow  6 . Other configurations of stop  11  which block further, unwanted movement of a lug  5  within hollow  6  are within the scope of the present invention. 
     Although stop  11  does halt the rotation of closure element  4  in the closing direction, it has no effect in the opening direction opposite the closing direction, returning lugs  5  to cutouts  15  through which lugs  5  entered hollow  6 . To prevent accidental rotation of closure element  4  in the opening direction causing untimely opening of closure element  4  and release of bracelet  3 , it is necessary to inhibit slippage of closure element  4  in the opening direction. To this end, it is possible, for example, to increase the thickness of bracelet  3  slightly so that closure element  4  compresses bracelet  3  when in a closed position. As a result, the pressure so exerted on upper face  9  of closure element  4  frictionally prevents closure element  4  from slipping in reverse and in the opening direction. However, such compression, which must be exactly proportioned, requires, on the one hand, that bracelet  3  be made of a compressible and/or deformable material, and on the other hand, that the thickness of bracelet  3  be very precisely machined. The first requirement is not met in the case of a metal bracelet, and the second is very difficult to achieve in practice. 
     To obtain the desired effect of pressure and hence friction between closure element  4  and bracelet  3  and/or the watch case to prevent accidental dislodgment of closure element  4  and consequent opening, a rotation-inhibiting element is provided between closure element  4  and the watch case. Such rotation inhibiting-element may inhibit relative rotation in any manner known to one of ordinary skill in the art. For instance, the rotation-inhibiting element may increase friction between closure element  4  and a portion of base  1 . Alternatively, or in addition, the rotation-inhibiting element may exert a restraining force against closure element  4  to restrain closure element  4  against further rotation. Such force exerts pressure on upper face  9  of closure element  4  to prevent accidental or undesired slippage of closure element  4  in the opening direction. If desired, the rotation-inhibiting element may be held within a portion of back  1  or closure element  4 . In the embodiment of FIG. 1, a seat  7  is provided in edge  8  of neck  2  shaped to hold a rotation-inhibiting element in the form of a compression joint  10 , such as an O-ring. Although seat  7  and compression joint  10  are annular in FIG. 1, other configurations are within the scope of the invention. Closure element  4  compresses joint  10  via annular portion  12  of bracelet  3 . Annular portion  12  thereby exerts friction on upper face  9  of closure element  4 , preventing closure element  4  from rotating in the opening direction. Of course, the dimensions of joint  10  are to be calculated so that the friction allows the user to open closure element  4  without undue effort so that the user may easily exchange bracelets  3  as desired. Thus, the rotation-inhibiting element acts as a braking element which provides just enough resistance to prevent accidental opening of closure element  4  yet not so much as to make intentional opening of closure element  4  unduly difficult. It will be appreciated that the provision of a rotation-inhibiting element is separate and independent from the particular manner of coupling closure element  4  to the watch case to secure bracelet  3  in place with respect to the watch case, such as the bayonet connection described above. 
     Another feature which may be provided in the watch case and bracelet system of the present invention is a connection between bracelet  3  and the watch case which inhibits accidental separation of bracelet  3  from the watch case. In the embodiment of FIG. 1, circular cut-outs  13  and  17  are provided respectively in back  1  of the watch case and on upper face  9  of closure element  4  and confront each other. Bulges of corresponding shape on bracelet  3 , such as at annular portion  12 , preferably are inserted into cut-outs  13  and  17  to secure the attachment of bracelet  3  to the watch case. As such, the bulges are locked between closure element  4  and back  1  when closure element  4  is in a closed position. 
     The embodiment described herein constitutes an illustrative embodiment. Other forms are possible, however. For example, the case can have plural backs, for instance disposed one on top of the other; the attaching device can have plural annular necks; the bracelet can be formed of two separate parts, in which case there can be two necks; the device can comprise plural closure elements, or only one lug instead of three, in which case the lug must have a sufficient angular dimension; finally, the hollow receiving the lugs can be divided into a plurality of segments instead of being continuous, or a plurality of hollows may be provided, such as spaced at different distances from back  1 . The compression joint  10  could also be placed in a seat  7  provided in upper face  9  of closure element  4 , instead of in edge  8  of neck  2 . It is also conceivable for a plurality of stops  11 , instead of just one, to be placed in hollow  6 . 
     Thus, it will be clear to those skilled in the art that the present invention may be embodied in other specific forms, structures, arrangements, proportions, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. One skilled in the art will appreciate that the invention may be used with many modifications of structure, arrangement, proportions, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description.