Patent Publication Number: US-2020292994-A1

Title: Timepiece comprising a dial attachment device

Description:
TECHNICAL FIELD 
     The present invention relates to the field of horology and more particularly to a timepiece comprising a device for attaching a dial of the conventional type or of the type comprising a solar cell. 
     TECHNOLOGICAL BACKGROUND 
     Conventionally, a dial of a timepiece comprises, on the lower face side, i.e. on the movement side, metal feet arranged so as to be partly driven into holes machined in the plate of the movement. These metal feet are in particular used to hold the dial in place relative to the movement of the watch during the assembly thereof. The attachment of the dial in the movement plate according to the aforementioned method has the drawback of involving relatively complex machining operations, whereby the dial must be perforated several times with precision before assembling the metal feet. Moreover, in the event of significant impacts, there is still a risk of the feet of the dial breaking. Furthermore, the use of such dials in skeleton-type watches is not very aesthetically pleasing. 
     SUMMARY OF THE INVENTION 
     The purpose of the present invention is thus to overcome the different aforementioned drawbacks. More specifically, one purpose of the invention is to propose a timepiece comprising a dial attachment device which is simple to implement and which ensures that the dial is firmly held in place while guaranteeing mechanical strength, in particular in the event of impacts along the axis of the hands. 
     For this purpose, the invention proposes a timepiece comprising a drive module, a dial comprising a central opening, an hour pipe passing through the central opening of the dial and driven in rotation by the drive module, and a device for attaching the dial. The attachment device comprises:
         a holding tube arranged around the hour pipe and mechanically connected to/integral with the drive module, and   a retaining member arranged between the holding tube and the dial and/or a dial support to which the dial is attached.       

     According to one embodiment, the retaining member is arranged/disposed/situated between the holding tube and the dial and/or a dial support while bearing against a part of the dial that is adjacent to the central opening of the dial and/or against the dial support. Preferably, the retaining member is configured such that it bears against or such that it exerts a distributed axial stress on either an annular area of the dial which is adjacent and concentric to the central opening of the dial, or an annular area of the dial support. 
     According to one embodiment, the part of the dial adjacent to the central opening of the dial defines an annular area that is preferably set back relative to the surface of the dial, such that a surface of the top part of the holding tube is level with the dial. 
     According to one embodiment, the holding tube comprises a first cylindrical part having a first diameter and a second cylindrical part having a second diameter that is less than the first diameter. The retaining member is a washer arranged on the circumference of the second cylindrical part and bearing against the annular area of the dial or against the dial support so as to exert an axial force on the dial or the dial support. 
     According to one embodiment, the retaining member is a resilient ring, preferably of the circlip type, arranged inside a groove made on at least one part of the outer circumference of the holding tube such that the resilient ring bears against the annular area of the dial or against the dial support. 
     According to one embodiment, the holding tube comprises, on the one hand, a first tube mechanically connected to the drive module and comprising a threaded part on the inner circumference thereof, and on the other hand, a second tube in the form of a screw screwed into the threaded part of the first tube. The screw comprises a radial extension in order to form a circular bearing surface. The retaining member is in the form of a gasket, preferably of the O-ring type, arranged against the circular bearing surface of the screw and the annular area of the dial or the dial support so as to exert an axial force on the dial or the dial support. 
     According to one embodiment, the screw is embedded in the central opening of the dial. 
     According to one embodiment, the screw comprises a part which is raised relative to the dial and which extends radially in order to cover the central opening of the dial. 
     According to one embodiment, the timepiece further comprises a movement support and a circuit support arranged between the dial support and the drive module. The stack of each support forms a rigid base preventing the dial from becoming deformed in the event of an axial impact. 
     According to one embodiment, each support comprises a central opening in order to form a recess inside which the holding tube is at least partially adjusted. 
     According to one embodiment, the dial comprises or is formed by at least one solar cell. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Other features and advantages of the present invention will appear after reading the plurality of embodiments, which are provided for purposes of illustration only and not intended to limit the scope of the invention, given with reference to the accompanying drawings, wherein: 
         FIG. 1  shows a partial sectional view of the timepiece showing the dial attachment device according to a first embodiment of the invention; 
         FIG. 2  shows a partial sectional view of the timepiece showing the dial attachment device according to a second embodiment of the invention; 
         FIG. 3  shows a partial sectional view of the timepiece showing the dial attachment device according to a third embodiment of the invention; and 
         FIG. 4  shows a partial sectional view of the timepiece showing the dial attachment device according to a fourth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As a whole, the device for attaching a dial according to the invention described hereinbelow, according to different embodiments, can be implemented in mechanical or quartz watches comprising a dial of the conventional/classic type, i.e. a dial comprising, for example, indexes distributed at regular intervals around the periphery of the dial, numbers representing the hours, for example in the form of appliques attached to the dial and, depending on the calibre, one or more apertures indicating, for example, the date or other information. The dial attachment device according to the invention can also be implemented in watches comprising a dial of the non-conventional type. The attachment device according to the invention is, for example, particularly well suited for attaching a dial comprising or formed by a solar cell for powering, for example, a battery and/or an electronic module of a so-called smart watch. 
     In the different embodiments shown in  FIGS. 1 to 4 , the device for attaching the dial  12  comprises a holding tube  15  arranged about the hour pipe  14   b  and is mechanically connected to the drive module  10 , for example by hooking, by way of a radial extension  18 . Moreover, this attachment device further comprises a retaining member  20   a  to  20   c . This retaining member  20   a  to  20   c  is preferably a part fixed thereto. Such a retaining member  20   a  to  20   c  is a part that is preferably flexible and/or deformable, intended to be arranged between a second cylindrical part  15   b  of a holding tube  15  and the dial  12  or the dial support  17  of the watch. More specifically, under the effect of this second cylindrical part  15   b , this retaining member  20   a  to  20   c  is capable of bearing against a part of the dial that is adjacent to a central opening  13  of this dial  12  and/or against the dial support  17 . 
     With reference to  FIG. 1 , which shows a first embodiment of the invention, the timepiece comprises in particular a drive module  10 , the dial  12  provided with a central opening  13 , a cannon-pinion  14   a  and an hour pipe  14   b  passing through the central opening  13  of the dial  12  and driven in rotation by the drive module  10 . The dial  12  is attached to a dial support  17 , for example by means of a double-sided adhesive  30   a . The shape of the dial support  17  is substantially identical to the shape of the dial  12 . The dial support  17  is mounted on a movement support  26 , which is attached to a circuit support, preferably a printed circuit support  28 , for example by means of a double-sided adhesive  30   b . The stack of the different supports  17 ,  26 ,  28  forms a rigid base on which the dial  12  rests, which has the benefit of preventing the dial  12  from becoming deformed in the event of an axial impact. 
     This rigid base is particularly well suited to a dial  12  in particular formed by a solar cell so as to prevent the glass substrate of the cell from potentially breaking in the event of a significant axial impact. 
     The timepiece comprises the device for attaching the dial  12  comprising the retaining member  20   a , the holding tube  15  arranged about the hour pipe  14   b  and mechanically connected to the drive module  10 . The holding tube  15  comprises a first cylindrical part  15   a  having a first diameter D 1  and a second cylindrical part  15   b  having a second diameter D 2  that is less than the first diameter D 1 . The first cylindrical part  15   a  is housed inside a tubular portion formed by the stack of the central openings of the dial support  17 , of the movement support  26  and of the printed circuit support  28 . This retaining member  20   a  comprises a retaining washer  20   a  and is arranged on the circumference of the second cylindrical part  15   b . This retaining washer  20   a  extends radially such that the periphery thereof bears against the dial support  17  in order to exert an axial force on the dial support  17 . One end of the first cylindrical part  15   a  comprises the radial extension  18 , which is, for example, annular in shape, and which is mechanically connected or attached to a bridge  10   a  of the drive module  10 . 
     With reference to  FIG. 2 , which shows a second embodiment of the invention, the retaining member  20   b  comprises a resilient ring  20   b . This resilient ring  20   b  is arranged inside a groove  22  made on the outer circumference of the holding tube  15  such that the resilient ring  20   b  bears against the dial support  17 . The resilient ring can, for example, be of the circlip type in order to ease disassembly of the attachment device. Similarly to the first embodiment, the holding tube  15  is housed inside the tubular portion formed by the stack of the different supports  17 ,  26 ,  28  in order to produce this rigid base suitable for a dial  12  comprising or formed by a solar cell. One end of the holding tube  15  comprises the radial extension  18 , that is, for example, annular in shape, and that is attached to a bridge  10   a  of the drive module  10 . 
     According to  FIG. 3 , which shows a third embodiment of the invention, the holding tube  15  comprises a first tube  16   a  comprising, on the one hand, a radial extension attached to a bridge  10   a  of the drive module  10 , and on the other hand, a threaded part on the inner circumference thereof. The first tube  16   a  is housed inside the tubular portion formed by the stack of the different supports  17 ,  26 ,  28  producing this rigid base. The holding tube  15  further comprises a second tube  16   b  in the form of a screw screwed into the threaded part of the first tube  16   a . The screw  16   b  comprises, at one end, a radial extension  24  in order to form a circular bearing surface  24   a . In the attachment device, the retaining member  20   c  comprises a gasket  20   c , for example of the O-ring type. This gasket  20   c  is arranged against the circular bearing surface  24   a  of the screw  16   b  and the dial support  17  so as to exert an axial force on the dial support  17 . The screw  16   b  is embedded in the central opening  13  of the dial  12 . In order to attach a conventional dial, the diameter of the radial extension  24  is preferably substantially identical to the diameter of the central opening  13  of the dial in order to procure an advantageous aesthetic appearance. 
     Alternatively, the retaining member  20   c  of the attachment device comprises a gasket  20   c  which is arranged against the circular bearing surface  24   a  of the screw  16   b  and the dial support  17 . Under these conditions, the radial extension  24  forming a circular bearing surface  24   a  defined at the end of said screw  16   b  is thus capable of directly exerting an axial force on the dial support  17  by way of the retaining member  20   c.    
     According to  FIG. 4 , which shows a fourth embodiment of the invention, the device for attaching the dial comprises a holding tube of a similar design to that of the third embodiment, with the exception that the screw  16   b  comprises a part  32  that is raised relative to the dial  12  which extends radially in order to cover the central opening  13  of the dial  12 . This embodiment is particularly suited for a dial comprising or formed by a solar cell, since the raised part  32  has the advantage of concealing the solar cell&#39;s cutting defects. 
     The retaining washer  20   a  according to  FIG. 1 , the circlip  20   b  according to  FIG. 2 , and the second tube  16   b  in the form of a screw screwed into the threaded part of the first tube  16   a  according to  FIGS. 3 and 4  all have the advantage of preventing the hands from being driven out during a significant axial impact. 
     It goes without saying that the invention is not limited to the embodiments described with reference to the figures and alternatives could be implemented without leaving the scope of the invention. For example, the holding tube  15  according to any of the embodiments described hereinabove can be adapted so as to bear against or exert an axial stress directly on the dial  12  itself and not on the dial support  17 , or indeed directly on both the dial support  17  and the dial  12 . For this purpose, the dial  12  can, for example, comprise a dial part that is adjacent to the central opening  13  of the dial against which bears the retaining member, such as the retaining washer  20   a , the circlip  20   b  or the gasket  20   c  depending on the embodiment chosen from among those described hereinabove. The part of the dial that is adjacent to the central opening  13  can define an annular area that is set back relative to the largest part of the surface of the dial, such that a surface of the top part of the holding tube is level with the dial. 
     The attachment device according to the invention has the advantage of allowing dials to be produced using different materials which are not compatible with the manufacture of dials having feet. These dials can in particular be obtained using plastic, metal or glass injection methods.