Abstract:
The present invention is to provide a timepiece. The time piece comprises a ring-shaped mounting member formed of an elastic material and positioned between the annular shell and the ring-shaped bezel. The ring-shaped mounting member includes an engaging portion having a second engagement surface configured to engage with a first engagement surface formed in the annular shell to restrict the ring-shaped bezel from moving relative to the annular shell in a first axial direction to prevent the ring-shaped bezel from separating from the annular shell. The ring-shaped mounting member is deformable with a force, so that the second engagement surface can slide along the first engagement surface to release ring-shaped bezel from the annular shell.

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2013-195771 filed on Sep. 20, 2013, the entire content of which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a timepiece such as a portable timepiece including a bezel that can be rotatively operated. 
     2. Description of the Related Art 
     A timepiece to which a bezel rotatively operated by a user is mounted to a shell of a case is known in related arts (for example, refer to JP-A-2003-43162 (Patent Literature 1)). 
     In the timepiece disclosed in Patent Literature 1, the bezel is mounted to the shell so as to be freely rotated by locking a locked flange portion provided continuously around an inner peripheral surface of the bezel to a locking flange portion provided continuously around an outer peripheral surface of a rising portion included in the shell. Here, both the bezel and the shell are made of a metal, and these flange portions are locked by pressing the bezel onto the case with a strong force of a pressing machine and so on to thereby allow the locked flange portion to climb over to a lower part of the locking flange portion. Accordingly, the bezel is prevented from falling off from the case. 
     Additionally, in the timepiece disclosed in Patent Literature 1, a packing material made of an elastic member is interposed between the outer peripheral surface of the rising portion and the inner peripheral surface of the bezel as well as on the upper side of the locking flange portion. The bezel is held in a still state by the packing material so as not to be flipped. As such packing material is used, the rotation of the bezel is allowed in the case where the user gives a rotation torque exceeding a given degree by the operation of rotating the bezel. 
     When sand particles enter, or dirt is heaped between the shell and the bezel, the rotation operation of the bezel may be heavy (not smooth). Moreover, deterioration of the packing material proceeds with a lapse of time, the rotation operation of the bezel may be heavy as the deteriorated packing material may stick to the shell and the bezel if the rotation operation is not performed for a long period of time. 
     In the maintenance for correcting the above situation, after the bezel is removed from the shell once, the shell and the bezel are cleaned, or the packing material is replaced, then, the bezel is mounted to the shell again. To remove the bezel from the shell in the maintenance, a disassembly tool is inserted between the bezel and the shell, and the bezel is pried off by using this tool. The mounting of the cleaned bezel to the shell is performed by pressing the bezel onto the shell with a strong force. 
     The deformation of the locking flange portion of the shell made of a metal and the locked flange portion of the bezel made of a metal is not easy. Accordingly, as the locking flange portion of the shell and the locked flange portion of the bezel compete with each other with the mounting and removal of the bezel as described above, these flange portions are scraped. Therefore, there is a problem that, as the number of times of removing and mounting the bezel is increased, the engagement allowance between the locking flange portion and the locked flange portion is reduced and the bezel is easily removed from the shell. 
     There is another problem in the related art timepiece that a dedicated packing material is necessary not only for engaging between the locking flange portion and the locked flange portion for holding the state where the bezel is mounted to the shell but also for preventing the wobble of the bezel and for regulating the rotation operation torque. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a timepiece capable of maintaining the reliability for holding the state where the bezel is mounted to the shell as well as capable of preventing the wobble of the bezel and for regulating rotation operation torque without using the dedicated packing material even when the bezel is removed for the maintenance. 
     In order to solve the above problems, there is provided a timepiece including a case including a shell having an annular convex portion and an engaging projection formed at an outer periphery of the annular convex portion so as to extend in a circumferential direction, a ring-shaped bezel having an inner peripheral concave portion surrounding the outer periphery of the annular convex portion and arranged so as to be rotatively operated while covering the outer periphery of the annular convex portion and a ring-shaped mounting member including an outer peripheral portion arranged in the inner peripheral concave portion, an inner peripheral portion with an annular groove enabling elastic deformation in directions close to and away from the outer peripheral portion formed between the inner peripheral portion and the outer peripheral portion, which is continued from the outer peripheral portion, and an engaging portion formed in the inner peripheral portion, capable of being engaged with and disengaged from the engaging projection with the elastic deformation of the inner peripheral portion, which maintains an engaged state between the engaging projection and the engaging portion by an elastic force of the inner peripheral portion. 
     In the present invention, the shell is preferably made of a metal, and the bezel may be made of a metal or a synthetic resin. The mounting member is preferably an integral molded part of an elastic material, for example, a synthetic resin having elasticity in the present invention. The mounting member may be fixed to the inner peripheral concave portion of the bezel by using an adhesive at the outer peripheral portion thereof. Moreover, the mounting member may be held by the bezel so as to relatively move in a rotation direction of the bezel or may be positioned in the bezel so as to be integrally rotated with the bezel in a state where the outer peripheral portion and so on contact the inner peripheral concave portion of the bezel as described in the embodiment in the present invention. 
     In order to mount the bezel to the shell in the timepiece according to the present invention, the bezel is assembled to the case so that the mounting member surrounds the outer periphery of the annular convex portion included in the shell in the state where the mounting member is held in the inner peripheral concave portion of the bezel in advance. Accordingly, the engaging portion of the mounting member climbs over the engaging projection of the annular convex portion and immediately after that, the engaging portion is engaged with the engaging projection in a state of being caught from a root side of the annular convex portion, thereby mounting the bezel to the shell. In order to remove the bezel from the shell in maintenance, it is preferable to add an external force for removing the bezel artificially to the bezel. Accordingly, the engaging portion caught by the engaging projection of the annular convex portion can climb over the engaging projection to thereby remove the bezel from the shell. 
     When the engaging portion climbs over the engaging projection by the mounting/removal of the bezel, the inner peripheral portion of the mounting member is elastically deformed so as to come close to the outer peripheral portion. The deformation can be realized as the annular groove is formed between the inner peripheral portion and the outer peripheral portion. As the inner peripheral portion having the engaging portion is elastically deformed as described above, the engaging portion climbs over the engaging projection while escaping therefrom. Accordingly, it is possible to suppress the engaging portion and the engaging projection to be scraped by competition between them whether the strength between the engaging portion and the engaging projection is the same or different from each other. 
     Furthermore, the inner peripheral portion of the mounting member sandwiched by the shell and the bezel holds the elastically-deformed state while the bezel is mounted to the bezel by the procedures described above. Accordingly, the engaging portion is elastically pressed to the annular convex portion by the elastic force of the inner peripheral portion as well as a reaction force thereof is added to the bezel, thereby holding the bezel in a still state. 
     In the timepiece according to the embodiment of the present invention, the mounting member may include plural grooves communicated to the annular groove, and the inner peripheral portion may be divided into plural portions in a circumferential direction of the mounting member by the grooves. 
     In the embodiment, the inner peripheral members divided into plural portions are not affected by the inner peripheral members adjacent to each other with the grooves interposed therebetween, therefore, elastic deformation can be performed more easily when the bezel is mounted to and removed from the shell. Accordingly, the mounting/removal of the bezel with respect to the shell can be performed more easily. 
     Also in the timepiece according to the embodiment of the present invention, the bezel and the outer peripheral portion may be fitted in a convexo-concave manner so that the mounting member does not move in a thickness direction of the bezel. 
     In the embodiment, the convexo-concave fitting means that the concave portion provided in any one of the bezel and the outer peripheral portion is fitted to the convex portion provided in the other of them. Additionally, plural convex portions and concave portions may be provided. 
     Since the mounting member is held so as not to move in the thickness direction of the bezel by the convexo-concave fitting in the embodiment, it is not necessary to fix the mounting member to the bezel by using an adhesive or a fixing member for holding the mounting member. As the mounting member is not fixed to the bezel, the mounting member can be rotated at a different angle from the rotation angle of the bezel when the mounting member is rotated in accordance with the rotation operation of the bezel. Additionally, since the mounting member can be removed from the bezel, the mounting member can be replaced in the maintenance. 
     Also in the timepiece according to the embodiment of the present invention, the bezel may include at least one hole opening to the inner peripheral concave portion, the mounting member may include a projection of the same number as the hole, and the projection and the hole may be fitted to each other. 
     Since the hole of the bezel is fitted to the projection of the mounting member in the embodiment, the mounting member can be rotated at the same rotation angle as the bezel when the mounting member is rotatively operated. 
     The timepiece according to the embodiment of the present invention may further includes a click stop means for holding the bezel in an arbitrary rotation position, in which the click stop means may include a click engaging portion formed by plural projections and depressions formed side by side in the circumferential direction of the mounting member on an end surface of the outer peripheral portion which faces the shell, and a click member pressed onto the click engaging portion by an elastic force, which is engaged with and disengaged from the click engaging portion. 
     In the embodiment, the click member can be pressed to the click engaging portion by the elastic force of the coil spring prepared in addition to the click member. When the click member is formed by a blade spring instead of the above, it is possible to press the click member to the click engaging portion by the elastic force of the click member itself. 
     The mounting member the rotation thereof is restricted with respect to the bezel doubles as part of the click stop member in the timepiece in which the mounting member is rotated at the same rotation angle as the bezel in the embodiment, therefore, positional relationship between indications added to the surface of the bezel and the click engaging portion is properly held without being shifted regardless of the rotation operation of the bezel. 
     According to the invention, it is possible to prevent the engaging projection of the shell and the engaging portion of the mounting member engaged with the projection to thereby hold the bezel in the shell from being scraped and to suppress the reduction of the engagement allowance thereof even when the bezel is mounted and removed for maintenance, therefore, reliability in holding the state where the bezel is mounted to the shell can be maintained. Additionally, as the mounting member is sandwiched by the shell and the bezel in the state where the inner peripheral portion of the mounting member is elastically deformed, there is an advantage that the wobble of the bezel can be prevented and a rotation operation torque can be regulated without using a dedicated packing material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view showing a watch according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view showing part of the watch of  FIG. 1 . 
         FIG. 3  is a view obtained by cross-sectioning a bezel mounting structure of the watch of  FIG. 1  at a position passing an engaging projection of a mounting member. 
         FIG. 4  is a view obtained by cross sectioning a bezel mounting structure of the watch of  FIG. 1  at a position passing a groove of the mounting member. 
         FIG. 5  is a cross-sectional view showing part of the mounting member included in the watch of  FIG. 1 . 
         FIG. 6  is a perspective view showing the mounting member included in the watch of  FIG. 1  seen from the back side. 
         FIG. 7  is a perspective view showing the mounting member included in the watch of  FIG. 1  seen from the front side. 
         FIG. 8  is a cross-sectional view showing a bezel mounting structure of a watch according to a second embodiment of the present invention. 
         FIG. 9  is a perspective view corresponding to  FIG. 7 , showing a mounting member included in the watch according to the second embodiment. 
         FIG. 10  is a perspective view corresponding to  FIG. 7 , showing a mounting member included in a watch according to a third embodiment of the present invention. 
         FIG. 11  is a cross-sectional view corresponding to  FIG. 3 , showing a watch according to a fourth embodiment of the present invention. 
         FIG. 12  is a cross-sectional view showing part of a mounting member included in the watch of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will be explained with reference to  FIG. 1  to  FIG. 7 . 
     A reference numeral  11  in  FIG. 1  and  FIG. 2  denotes a timepiece, for example, a portable timepiece, specifically, a watch such as a diver&#39;s watch. The watch  11  is provided with a case  12  forming an outer package. 
     As shown in  FIG. 2 , required members such as a display plate, for example, a dial  13 , a device for controlling the display of the hour and so on, for example, a movement  15  for controlling the motion of hands  14  for displaying the hour and so on are accommodated in a case  12 . A reference numeral  16  in  FIG. 2  denotes a middle frame supporting the movement  15 . 
     As shown in  FIG. 2  to  FIG. 4 , the case  12  is formed by fixing a circular see-through cover  22  to be a front surface of the watch  11  in a liquid-tight manner on one face of the shell  21  formed in a ring shape in a thickness direction, and by fixing a back lid  23  to be a back surface of the watch  11  in a liquid-tight manner on the other face of the shell  21  in the thickness direction. The shell  21  is made of a metal such as stainless steel and titanium, and the back lid  23  is made of a metal or a synthetic resin. The see-through cover  22  is made of a translucent member, for example, a transparent glass or the like, through which the dial  13  can be seen. Respective reference numerals  24  and  25  in  FIG. 2  to  FIG. 4  denote packing formed in a ring shape by a sealing material for holding liquid tightness of the case  12 . A reference numeral  26  in  FIG. 1  denotes a crown. 
     As shown in  FIG. 2  to  FIG. 4 , the shell  21  has an annular convex portion  31  protruding to the front side of the case  12 . The annular convex portion  31  has a support concave portion  32  formed in an opened state at a tip and an inner periphery thereof. A back surface of the periphery of the see-through cover  22  contacts a bottom surface of the support concave portion  32 , and the see-through cover  22  is fixed to the inner side of the annular convex portion  31  in a liquid-tight manner through the packing  24  interposed between a peripheral surface of the see-through cover  22  and the support concave portion  32 . Accordingly, the annular convex portion  31  is provided so as to surround the see-through cover  22 . 
     An engaging projection  33  is formed in an outer periphery of the annular convex portion  31 . The engaging projection  33  extends in a circumferential direction of the annular convex portion  31  and is formed continuously around, for example, the outer periphery of the annular convex portion  31 . The projecting size of the engaging projection  33  is preferably, for example, (0.6±0.1) mm. 
     As shown in  FIG. 4 , the engaging projection  33  includes a first slope  33   a  and a second slope  33   b . The first slope  33   a  is a surface closer to the tip of the annular convex portion  31  than the second slope  33   b  with respect to a root of the annular convex portion  31 , which is inclined so that the engaging projection  33  comes close to the root side of the annular convex portion  31  as being inclined toward a tip surface side thereof. The second slope  33   b  is a surface closer to the root of the annular convex portion  31  than the first slope  33   a  with respect to the root of the annular convex portion  31 , which is inclined so that the engaging projection  33  gets away from the root side of the annular convex portion  31  as being inclined toward a tip surface side thereof. Therefore, the engaging projection  33  is formed in a tapered shape. The second slope  33   b  is used as an engaging surface. 
     The shell  21  has a convex portion  34  and a concave groove  35  surrounding the root portion of the annular convex portion  31 . The convex portion  34  protrudes to the front side of the case  12  to be formed in a ring shape. The concave groove  35  is sectioned by the convex portion  34  and the annular convex portion  31  to be formed in a ring shape, opening to the front side of the case  12 . The shell  21  has an annular step portion  36  at a corner portion between the concave groove  35  and the root portion of the annular convex portion  31 . Accordingly, an annular engaging concave portion  31   a  (refer to  FIG. 4 ) sectioned by the annular step portion  36  and the engaging projection  33  is formed on a peripheral surface of the annular convex portion  31 . 
     A bezel  41  is disposed on the front surface side of the case  12  so as to be rotatively operated. As shown in  FIG. 1 , the bezel  41  has a ring shape an inner diameter of which is larger than that of the see-through cover  22 . The bezel  41  has given indications  42  on the surface thereof. Additionally, projections and depressions  43  for preventing fingers of the operator from slipping when the bezel is rotatively operated by the user are formed around the bezel  41 . 
     The bezel  41  is made of, for example, the same kind of metal as the shell  21 , including an inner peripheral concave portion  44 , a fitting concave portion  45 , at least one hole  46 , a cover portion  47  and an insertion convex portion  48  as shown in  FIG. 3  and  FIG. 4 . 
     The inner peripheral concave portion  44  is formed continuously around the bezel  41  in a circumferential direction as well as opens to an inner space surrounded by the bezel  41  and a back surface of the bezel  41 . The fitting concave portion  45  is formed continuously around the bezel  41  in the circumferential direction as well as opens to a vertical surface sectioning the inner peripheral concave portion  44  along a thickness direction of the bezel  41 . 
     The hole  46  is provided so as to open to the inner peripheral concave portion  44 . Specifically, the hole  46  is provided so as to open to a horizontal surface bending continuously from the vertical surface and sectioning the inner peripheral concave portion  44 . The horizontal surface may be a slope as well as may be a surface with a step. Although only one hole  46  is shown, two holes are provided 180 degrees apart from each other in the circumferential direction of the bezel  41  in the present embodiment. When plural holes  46  are provided, they are provided apart from each other at equal intervals in the circumferential direction of the bezel  41 . It is also possible to provide the holes  46  so as to open to the vertical surface. 
     The cover portion  47  is a portion which protrudes to the center side of the bezel  41  with respect to the inner peripheral concave portion  44  to define the minimum inner diameter of the bezel  41  as well as to cover the tip of the annular convex portion  31 . The insertion convex portion  48  is a portion having a ring shape and formed on the back surface of the bezel  41  to be inserted into part of the concave groove  35 . 
     As shown in  FIG. 2  to  FIG. 4 , a mounting member  51  is held in the bezel  41  so as not to fall off therefrom, and the bezel  41  is mounted to the shell  21  through the mounting member  51  so as to be rotatively operated. 
     The mounting member  51  is an integral molded part made of a material which can be elastically deformed, for example, a synthetic resin such as plastic having elasticity, which is formed in a ring shape as shown in  FIG. 6  and  FIG. 7 . As shown in  FIG. 3  to  FIG. 7 , the mounting member  51  includes an outer peripheral portion  52 , a base portion  53 , an inner peripheral portion  54 , grooves  55 , an engaging portion  56 , projections  57  and a fitting convex portion  58 . 
     The outer peripheral portion  52  is a portion disposed in the inner peripheral concave portion  44  so as to contact the vertical surface sectioning the inner peripheral concave portion  44 . The fitting convex portion  58  protrudes from the outer periphery of the outer peripheral portion  52 . The fitting convex portion  58  is formed continuously around the outer peripheral portion  52 . The fitting convex portion  58  is a portion to be fitted to the fitting concave portion  45 . 
     The base portion  53  is formed so as to be continued from the outer peripheral portion  52 . The base portion  53  has a flat surface  53   a  contacting the horizontal surface sectioning the inner peripheral concave portion  44 , and the projections  57  project from the flat surface  53   a  with the same number and the same positions as the holes  46 . The projections  57  are portions to be fitted to the holes  46 . 
     The inner peripheral portion  54  is continued from the based portion  53  with an annular groove  59  formed between the inner peripheral portion  54  and the outer peripheral portion  52 . Therefore, the inner peripheral portion  54  and the outer peripheral portion  52  are connected to each other through the base portion  53 . As shown in  FIG. 5 , the width of the annular groove  59  is gradually increased as getting away from the base portion  53 . 
     A length of the inner peripheral portion  54  is shorter than a length of the outer peripheral portion  52 . The inner peripheral portion  54  is divided into plural portions in a circumferential direction of the mounting member  51  by the plural grooves  55  communicated to the annular groove  59  and provided at equal intervals in the circumferential direction of the mounting member  51  as shown in  FIG. 6  and  FIG. 7 . The inner peripheral portion  54  can be elastically deformed in directions to be close to and away from the outer peripheral portion  52 , and the elastic deformation is allowed by the annular groove  59 . Moreover, as the inner peripheral portion  54  is divided into plural portions by respective grooves  55 , elastic deformation can be further facilitated. 
     The engaging portion  56  protrudes at a tip portion of the inner peripheral portion  54  as well as to a side surface not facing the outer peripheral portion  52 . The engaging portion  56  is formed continuously around the inner peripheral portion  54 . The engaging portion  56  is a portion to be fitted to the engaging concave portion  31   a  of the shell  21  as well as to be engaged to the second slope  33   b  of the engaging projection  33  from the root portion of the annular convex portion  31 . 
     As shown in  FIG. 5 , the engaging portion  56  includes a slope-state surface  56   a  and an engaging surface  56   b . The slope-state surface  56   a  is formed in a slope or an arc surface. The engaging surface  56   b  is formed in a slope similar to the second slope  33   b  of the engaging projection  33 . 
     The mounting member  51  is mounted to the bezel  41  by fitting respective projections  57  to the holes  46  of the bezel  41  respectively as well as by convexo-concave fitting the fitting convex portion  58  to the fitting concave portion  45  of the bezel  41 . The mounting state is shown in  FIG. 3  and  FIG. 4 . The mounting member  51  can be held so as not to move in the thickness direction of the bezel  41  by the above convexo-concave fitting. Accordingly, it is not necessary to use an adhesive or a fixing member to maintain the fixing state of the mounting member  51  with respect to the bezel  41 . 
     In the above mounting state, the outer peripheral portion  52  of the mounting member  51  is disposed in the inner peripheral concave portion  44  of the bezel  41 . The outer periphery of the outer peripheral portion  52  contacts the vertical surface sectioning the inner peripheral concave portion  44  in a vertically standing state without being adhered to the vertical surface, and the flat surface  53   a  of the base portion  53  contacts the horizontal surface sectioning the inner peripheral concave portion  44  without being adhered to the horizontal surface. 
     Furthermore, the tip of the outer peripheral portion  52  protrudes from the back surface of the bezel  41  in the mounting state. Additionally, the inner peripheral portion  54  of the mounting member  51  is inclined with respect to the outer peripheral portion  52  in the mounting state. 
     The mounting member  51  is held by fitting the fitting convex portion  58  to the fitting concave portion  45  so as not to fall off from the bezel  41 . Moreover, the mounting member  51  is held so as not to move in the thickness direction of the bezel  41  by the contact of the flat surface  53   a  to the horizontal surface and the above convexo-concave fitting. The mounting member  51  is positioned by fitting the projections  57  to the holes  46  so as not to move in the circumferential direction of the bezel  41 . 
     The bezel  41  is mounted to the shell  21  through the mounting member  51  held in the above manner. The operation is performed by covering the annular convex portion  31  with the bezel  41  so that the mounting member  51  surrounds at least the outer periphery of the annular convex portion  31  of the shell  21  and pressing the bezel  41 . 
     In this case, first, the inner peripheral portion  54  is elastically deformed in a direction coming close to the outer peripheral portion  52  as the engaging portion  56  of the mounting member  51  contacts the outer periphery of the annular convex portion  31 . The engaging portion  56  contacts the engaging projection  33  of the annular convex portion  31  as the pressing of the bezel  41  proceeds, therefore, the inner peripheral portion  54  is further elastically deformed. Accordingly, the engaging portion  56  climbs over the engaging projection  33 . 
     At this time, the first slope  33   a  of the engaging projection  33  contacts the slope-state surface  56   a  of the engaging portion  56 . Accordingly, the pressing of the bezel  41  is not stopped by the engaging portion  56  being caught by the engaging projection  33 . Additionally, the inner peripheral portion  54  is divided into plural portions by respective grooves  55  and can be elastically deformed easily. Therefore, the engaging portion  56  can climb over the engaging protrusion  33  easily by a guide operation of the first slope  33   a  and the slope-state surface  56   a.    
     Just after the engaging portion  56  climbs over the engaging protrusion  33 , the tip of the outer peripheral portion  52  of the mounting member  51  contacts a bottom surface of the concave groove  35 . Accordingly, the movement by pressing of the bezel  41  is stopped. 
     In addition to the above, the engaging portion  56  enters the engaging concave portion  31   a  of the annular convex portion  31  as the inner peripheral portion  54  is restored toward an obliquely upper left direction in  FIG. 3  due to the elastic force just after the climbing, and the engaging surface  56   b  of the engaging portion  56  is engaged with the second slope (engaging surface)  33   b  of the engaging protrusion  33  in a state of being caught from the root side of the annular convex portion  31 . Accordingly, the bezel  41  is positioned in the thickness direction of the case  12  to be mounted to the shell  21 . It is preferable that the outer peripheral portion  52  which contacts the bottom surface of the concave groove  35  is elastically deformed in the above mounting state, because the engagement between the engaging portion  56  and the engaging protrusion  33  becomes more stable, and the mounting state of the bezel  41  becomes more stable. 
     According to the above mounting, the insertion convex portion  48  of the bezel  41  enters the concave groove  35  of the shell  21  and is fitted to the inner periphery of the convex portion  34 . Accordingly, the bezel  41  is prevented from moving in a radial direction of the shell  21 . Moreover, the cover portion  47  of the bezel  41  covers the tip surface of the annular convex portion  31  formed in the shell  21  and is arranged so as to be close to a peripheral edge of the see-through cover  22 . It is also preferable to allow the tip surface of the annular convex portion  31  to be exposed between the inner periphery of the cover portion  47  and the peripheral edge of the see-through cover  22  by omitting the cover portion  47  or shortening the protruding width of the bezel  41  to the center direction. 
     In the state where the bezel  41  is mounted to the shell  21  as described above, the mounting member  51  is sandwiched between the annular convex portion  31  of the shell  21  and the bezel  41  and the inner peripheral portion  54  holds the elastic deformation. Accordingly, the engaging portion  56  is elastically pressed to the outer periphery of the annular convex portion  31  due to the elastic force of the inner peripheral portion  54  as well as a reaction force thereof is added to the bezel  41 . 
     Due to the reaction force, the bezel  41  is held so as not to wobble in the radial direction. Additionally, a rotation operation force of the bezel  41  is regulated by a frictional engagement force between the outer periphery of the annular convex portion  31  and the inner peripheral portion  54  elastically contacts thereof. The prevention of wobble of the bezel  41  and the regulation of the rotation operation force of the bezel  41  can be realized by using the mounting member  51  without requiring a dedicating part for realizing them. 
     In the present embodiment, the projections  57  of the mounting member  51  are respectively fitted to the two holes  46  of the bezel  41 . Therefore, when the bezel  41  is rotatively operated by the user, the mounting member  51  is rotated around the annular convex portion  31  at the same rotation angle as the bezel  41 . 
     In the case of performing maintenance of the periphery of the bezel  41 , an external force that can remove the bezel  41  may be added to the bezel  41  for removing the bezel  41  from the shell  21 . 
     Accordingly, the inner peripheral portion  54  of the mounting member  51  is elastically deformed in the direction of coming close to the outer peripheral portion  52 . In this case, as the inner peripheral portion  54  is shorter than the outer peripheral portion  52  in accordance with the height of the annular step portion  36  of the shell  21 , the tip does not contact and rub the bottom surface of the concave groove  35  in accordance with the elastic deformation of the inner peripheral portion  54 . Therefore, it is certain that the inner peripheral portion  54  is elastically deformed. 
     When the engaging portion  56  climbs over the engaging projection  33  of the annular convex portion  31  in accordance with the elastic deformation of the inner peripheral portion  54 , the bezel  41  is removed from the shell  21 . At this time, the engaging portion  56  can easily climb over the engaging projection  33  by a guide operation of the second slope  33   b  of the engaging projection  33  and the engaging surface  56   b  of the engaging portion  56 . Furthermore, the inner peripheral portion  54  is divided into plural portions by respective grooves  55  and can be elastically deformed more easily. 
     The bezel  41 , the annular convex portion  31  of the shell  21  and the mounting member  51  are cleaned in a state where the bezel  41  is removed, maintenance of the periphery of the bezel  41  can be performed. Moreover, the mounting member  51  can be replaced in addition to the cleaning if necessary, which enables the maintenance around the bezel  41 . 
     As described above, when the bezel  41  is mounted to and removed from the shell  21 , the engaging portion  56  of the mounting member  51  climbs over the engaging projection  33  of the annular convex portion  31 . At this time, the inner peripheral portion  54  of the mounting member  51  is elastically deformed so as to be close to the outer peripheral portion  52 . In other words, the engaging portion  56  climbs over the engaging projection  33  while escaping therefrom with the elastic deformation of the inner peripheral portion  54  having the engaging portion  56 . Accordingly, it is possible to suppress the engaging portion  56  and the engaging projection  33  to be scraped whether the strength between them is the same or different from each other even though the engaging portion  56  and the engaging projection  33  compete each other at the time of mounting and removing the bezel  41 . 
     Therefore, the reduction of engagement allowance between the engaging portion  56  and the engaging projection  33  in the state where the bezel  41  is mounted to the shell  21  can be suppressed. As a result, the reliability in holding the state where the bezel  41  is mounted to the shell  21  can be maintained even when the mounting/removal of the bezel  41  are repeated. 
       FIG. 8  and  FIG. 9  show a second embodiment of the present invention. Since components of the second embodiment are the same as those of the first embodiment except the following explanation, the same components or components having the same functions as the first embodiment are denoted by the same reference numerals as the first embodiment and the explanation thereof is omitted. 
     In the second embodiment, the holes of the bezel  41  and the projections  57  of the mounting member  51  to be fitted to the holes explained in the first embodiment are omitted. Therefore, the bezel  41  and the mounting member  51  which is not adhered thereto can slide and move relatively in the circumferential direction. Components other than the components explained above are the same as those of the first embodiment including components not shown in  FIG. 8  and  FIG. 9 . 
     Accordingly, the problems of the present invention can be solved also in the second embodiment due to the reason explained in the first embodiment. Additionally, the fitting concave portion  45  of the bezel  41  and the fitting convex portion  58  of the mounting member  51  that is not fixed to the bezel  41  by an adhesive can slide at the convexo-concave fitting portion between them. Accordingly, when the mounting member  51  is rotated following the rotatively-operated bezel  41 , the mounting member  51  is allowed to be rotated at a different angle from the rotation angle of the bezel  41 . 
       FIG. 10  shows a third embodiment of the present invention. Since components of the third embodiment are the same as those of the first embodiment except the following explanation, the same components or components having the same functions as the first embodiment are denoted by the same reference numerals as the first embodiment and the explanation thereof is omitted. 
     In the third embodiment, the inner peripheral portion  54  of the mounting member  51  is not divided into plural portions and is continuously formed around the circumference in the circumferential direction. Other components are the same as those of the first embodiment including components not shown in  FIG. 10 . 
     Accordingly, the problems of the present invention can be solved also in the third embodiment due to the reason explained in the first embodiment. 
       FIG. 11  and  FIG. 12  show a fourth embodiment of the present invention. Since components of the fourth embodiment are the same as those of the first embodiment except the following explanation, the same components or components having the same functions as the first embodiment are denoted by the same reference numerals as the first embodiment and the explanation thereof is omitted. 
     The watch  11  according to the fourth embodiment further includes a click stop means  61  for holding the bezel  41  at an arbitrary rotation position, in which the insertion convex portion of the bezel  41  and the convex portion of the shell  21  explained in the first embodiment are omitted. 
     As shown in  FIG. 11 , the click stop means  61  includes, for example, a click engaging portion  62 , a click member  63  and a coil spring  64 . 
     The click engaging portion  62  is formed at an end surface of the outer peripheral portion  52  that contacts the bottom surface of the concave groove  35  provided in the shell  21  as shown in  FIG. 12 . The click engaging portion  62  is formed by plural projections and depressions alternately arranged in the circumferential direction of the mounting member  51 . Each convex portion  62   a  (refer to  FIG. 12 ) of the click engaging portion  62  has a triangle shape which protrudes toward the bottom surface of the concave groove  35  in a tapered manner. Additionally, each concave portion  62   b  (refer to  FIG. 12 ) of the click engagement portion  62  formed between adjacent triangle convex portions  62   a  is widened toward the bottom surface of the concave groove  35 . 
     As shown in  FIG. 11 , an accommodating groove  38  opening to the bottom surface of the concave groove  35  is formed in the shell  21 . The accommodating groove  38  is formed, for example, by a circular vertical hole. The click member  63  and the coil spring  64  are accommodated inside the accommodating groove  38 . 
     The click member  63  is made of, for example, a steel ball. The click member  63  can move in the axial direction of the accommodating groove  38  and is prevented from falling off from the accommodating groove  38  by an opening edge portion  38   a  narrowing the opening of the accommodating groove  38 . The coil spring  64  biases the click member  63  with the elastic force thereof. The biasing makes part of the click member  63  protrude from the accommodating groove  38 , and a protrusion is pressed onto the click engaging portion  62 . 
     The protrusion of the click member  63  can be engaged with and disengaged from the click engaging portion  62  freely, and the bezel  41  is held so as not to rotate improperly by the engagement. As the bezel  41  is rotatively operated, the click member  63  is pressed by the convex portions  62   a  of the click engaging portion  62  as well as pushed into the accommodating groove  38  against the biasing force of the coil spring  64 . Accordingly, the click member  63  is disengaged from the click engaging portion  62 , therefore, the rotation operation of the bezel  41  is maintained. Just after that, the click member  63  is pressed to the concave portions  62   b  of the click engaging portion  62  by the biasing force of the coil spring  64 , thereby engaging the click engaging portion  62  with the click member  63 . 
     Therefore, when the user stops rotation operation in a state where the bezel  41  is rotated at an arbitrary angle, the bezel  41  can be held at a position (arbitrary position) where the rotation operation of the bezel  41  is stopped by the click stop means  61 . As the engagement/disengagement between the click member  63  and the click engaging portion  62  are repeated with the rotation operation of the bezel  41 , the sense of moderation can be given with percussive noise caused by the engagement/disengagement. 
     In the fourth embodiment, the mounting member  51  is rotated at the same rotation angle as the bezel  41  by the fitting between the projections  57  and the holes  46 . In the watch  11  according to the fourth embodiment, the mounting member  51  doubles as part of the click stop member  61  as described above. Accordingly, the positional relationship between indications added to the surface of the bezel  41  and the click engaging portion  62  is not misaligned regardless of the rotation operation of the bezel  41 . 
     Components other than the components explained above in the fourth embodiment are the same as those of the first embodiment including components not shown in  FIG. 11  and  FIG. 12 . 
     Therefore, the problems of the present invention can be solved also in the fourth embodiment due to the reason explained in the first embodiment.