Abstract:
A portable timepiece has a pipe extending from a case and a winding stem for transmitting a rotational force to a timepiece movement in the case. A crown is connected to the winding stem for rotational movement therewith and for detachable engagement with an outer periphery of a male threaded section of the pipe to prevent unintentional rotation of the crown. The crown has a crown shaft for rotating the winding stem, a crown head having a female threaded section for threaded engagement with the male threaded section and mounted for undergoing rotation to rotate the crown shaft in a state in which the engagement between the male and female screw sections is released. A clutch couples together the crown shaft and the crown head to prevent rotation of the crown shaft in a state in which the male and female threaded sections are engaged with one another and couples the crown shaft and the crown head to allow the crown shaft to rotate during rotation of the crown head in a state in which the male and female threaded sections are not engaged with one another.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to portable timepieces and, more specifically, to a portable watch in which a crown is held so as not be turned unintentionally or carelessly by utilizing engagement of screws. 
   2. Description of the Prior Art 
   Conventionally, a crown for operating a watch movement incorporated in a case band is a single component and includes a crown shaft section that moves the watch movement in association with the crown shaft section and a crown head that is formed integrally with the crown shaft section. The crown shaft section is inserted in a winding stem pipe, which is attached to the case band, and the crown head is fitted into a pipe end, which is located outside the case band, of the winding stem pipe. 
   There is known a portable watch in which, in order to prevent this crown from being turned carelessly, a male screw section is formed on an outer periphery of the pipe end, which is located outside the case band, of the winding stem pipe, and a female screw section is formed in the crown head to detachably engage the male screw section at the pipe end (see JP-A-57-46181 (page 1, right column, line 8 to page 2, left column, line 7, and  FIGS. 1 and 2 )). 
   In this portable watch, in a normal state in which the watch movement is not operated, the crown is engaged with the male screw section of the pipe to bring the crown head into abutment against an outside surface of the case band, whereby careless turn of the crown can be controlled. An operation for holding the crown so as not to be turned carelessly will be hereinafter referred to as a screw lock operation, and a state in which the crown is held will be hereinafter referred to as a screw lock state. In addition, when the watch movement is operated, the winding stem connected to the watch movement can be turned together with the crown after the engagement of the crown with the male screw section is released to bring the crown into a pulled state. 
   Incidentally, a mechanical portable watch, in which a watch movement operated by a winding stem has a spiral spring as a drive source, is made such that, in a state in which a crown is arranged in a position where the crown is not pulled out, the spiral spring is wound up by a turning operation for this crown. In addition, a portable watch, in which a watch movement operated by a winding stem has plural operation modes, is made such that, in a state in which a crown is arranged in a position where the crown is not pulled out, the operation modes are switched by a turning operation for this crown. 
   A state in which a crown is arranged in a position where the crown is not pulled out is generally referred to as a “zero stage”. On the other hand, a position where the crown is pulled out for calendar adjustment or the like is generally referred to as a “first stage”. There is also known a portable watch in which, depending upon a situation, a crown can be pulled out to a pulled-out position of a “second stage” that is a position for time setting. 
   It is undesirable to apply the technique of the JP-A-57-46181 to a portable watch, which has a function of winding up a spiral spring with a crown arranged in a “zero stage”, or a portable watch, which has a function of changing an operation mode, due to the following reasons. 
   That is, in the portable watch of the JP-A-57-46181, the crown shaft section and the crown head are integrally formed. Thus, in the screw lock operation for engaging the crown in the male screw section of the winding stem pipe, since the crown shaft section is also turned, the winding stem connected to this crown shaft section is also turned together with the crown. 
   Consequently, in the application of the present invention to the portable watch having the function of winding up the spiral spring, the spiral spring is wound up as the crown is engaged with the male screw section of the winding stem pipe. A winding-up operation for the spiral spring is performed by manual winding or automatic winding. However, it is impossible to know in which winding state the spiral spring in the case band is. Therefore, in a state in which the spiral spring is wound up to a considerable degree, the screw lock operation with respect to the crown may be performed. In this case, the screw lock operation becomes particularly heavy, which is inconvenient. Accordingly, an excessive operation force is applied to the male screw section and the female screw section, and abrasion of these screw sections is accelerated. 
   Further, in the application of the present invention to the portable watch having the function of changing an operation mode, an operation mode is changed freely following the screw lock operation with respect to the crown. Consequently, the technique, which utilizes engagement of screws to prevent a crown from being turned carelessly, cannot be applied to the portable watch of this type. 
   A problem that the present invention is to solve is in providing a portable watch in which a crown can be held so as not to be turned carelessly utilizing engagement of screws without being restricted by a function of a watch movement, durability can be improved, and a screw lock operation for the crown is light. 
   SUMMARY OF THE INVENTION 
   In order to solve the problem, the present invention is a portable timepiece, such as a portable watch, in which a crown is held so as not to be turned carelessly utilizing engagement of screws, the crown including: a crown shaft that moves a winding stem in association with the crown shaft; a crown head that has a female screw section to be detachably engaged with a male screw section of a pipe attached to a case band and turns the crown shaft in a state in which this engagement is released; and a clutch that couples the crown shaft and the crown head so as to prevent turn of the crown shaft in a state in which the engagement is completed, and couples the crown shaft and the crown head so as to make it possible to turn this crown shaft following the crown head in a state in which the engagement is released. 
   In the present invention, by releasing the engagement of the female screw section of the crown head with the male screw section of the pipe, restraint of the crown head is released to allow this crown head to turn, and a relative position of the crown head and the crown shaft with respect to the axial direction changes, and the crown head and the crown shaft are coupled by the clutch. Consequently, a turning operation for the crown head under this coupling state is transmitted to the crown shaft via the clutch. Consequently, as the winding stem is turned, the watch movement in the case band can be operated. After this operation, the crown head is moved in the axial direction so as to come closer to an outside surface of the case band, and the female screw section of the crown head is engaged with the male screw section of the pipe, whereby the coupling by the clutch is released, and then the crown head comes into abutment against the outside surface of the case band to come into the screw lock state. In this way, immediately before the engagement of the crown head with respect to the pipe is completed, the crown head and the crown shaft are coupled again by the clutch. Thus, at a point when the engagement is completed immediately after this re-coupling, the turn of the crown shaft is prevented by the crown head held in the screw lock state. In this case, with the screw lock operation for obtaining the screw lock state, the crown head and the crown shaft are not coupled until the engagement is about to be completed. Thus, it is possible to control the crown shaft not to turn to transmit the turn to the watch movement following the screw lock operation. 
   In a preferred form of the present invention, the clutch includes: first and second driven sections, which are formed in a polygon or a gear shape and provided in parallel to each other in an axial direction of the crown shaft apart from an outer periphery of the crown shaft by a dimension of movement in the axial direction of the crown head; and a driving section that has a fitting hole of the same shape as these driven sections, is provided in the crown head, and is detachably engaged with the first and the second driven sections following the movement in the axial direction of the crown head. Thus, the present invention is excellent in that a structure of the clutch is simple. 
   In a preferred form of the present invention, a shaft portion between the first and the second driven sections are formed in a size to be inscribed in the fitting hole. Thus, the present invention is excellent in that, in moving the crown head in the axial direction, the driving section is guided to the shaft portion between the first and the second driven sections, and the crown head can be moved in the axial direction easily while controlling fluctuation in a posture of the crown head such as inclination. 
   In a preferred form of the present invention, the driving section is made of a ring that is fixed to an inner periphery of the crown head. Thus, the present invention is excellent in that a joint trace, which appears on a visually recognizable end face of the crown head, is preferable in appearance because the joining trace can contribute to giving impression that the crown head is machined with a lot of trouble. 
   In a preferred form of the present invention, the driving section is provided integrally with the crown head. Thus, the present invention is preferable in that there is no deficiency in coupling of the crown shaft and the crown head based on attachment deficiency of the driving section to an inner surface of the crown head, and the function of the clutch can be maintained surely for use in a long period. 
   In a preferred form of the present invention, a receiving section, which an end of the female screw section comes into contact with and separates from following the movement in the axial direction of the crown head in a state in which the engagement of the male screw section and the female screw section is released, is provided on an outer periphery of the crown shaft closer to an outside surface of the case band than the clutch. Thus, the crown head is positioned with respect to the axial direction of the crown shaft with the end of the female screw section hooked on to the receiving section. 
   In a preferred form of the present invention, the receiving section and the driving section are arranged so as to be opposed to each other in the axial direction, and an elastic body, which biases the crown head in a direction in which the crown head moves away from the outside surface of the case band, is provided between the receiving section and the driving section. Thus, the present invention is excellent in that, simultaneously with the engagement of the male screw section and the female screw section being released, the crown head is moved in the axial direction by a biasing force of the elastic body so as to hook the end of the female screw section on the receiving section, and the driving section is positioned with respect to the second driven section by the hook, whereby the crown shaft and the crown head can be coupled such that the crown shaft can turn. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred form of the present invention is illustrated in the accompanying drawings in which: 
       FIG. 1  is a front view showing a wristwatch in accordance with a first embodiment of the present invention; 
       FIG. 2  is a sectional view showing a screw lock state of a crown along a line  2 — 2  in  FIG. 1 ; 
       FIG. 3  is a sectional view showing a state in which the screw lock state of the crown shown in  FIG. 2  is released; 
       FIG. 4  is a perspective view showing a clutch of the wristwatch according to the first embodiment with the clutch shown in a disassembled state; 
       FIG. 5  is a perspective view showing the clutch in  FIG. 4  in a first coupling state; 
       FIG. 6  is a sectional view showing a wristwatch in accordance with a second embodiment of the present invention in a screw lock state of a crown; and 
       FIG. 7  is a sectional view showing the wristwatch in accordance with the second embodiment of the present invention in a state in which the screw lock state of the crown is released. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First Embodiment 
   A first embodiment of the present invention will be explained with reference to  FIGS. 1 to 5 . 
   In  FIG. 1 , reference numeral  10  denotes a wristwatch as a portable clutch. As shown in  FIGS. 2 and 3 , this wristwatch  10  houses a dial  12 , a watch movement  13 , and the like in a case or watch exterior assembly  11 . As the watch movement  13 , a mechanical watch movement of a manual winding type with a spring as a drive source, an automatic winding type, or a type using both manual winding and automatic winding is used. Note that instead of these watch movement types, a watch movement of a type which can select and a switch a digital display and an analog display as a time display or the like on the dial  12  may be adopted. 
   As shown in  FIGS. 2 and 3 , the watch exterior assembly  11  is formed by mounting a cover glass  15  liquid-tightly on a front surface, which consists of one surface in a thickness direction, of an annular metal case band  14 , and screwing a case back  16  consisting of metal or the like liquid-tightly onto a rear surface, which consists of the other surface in the thickness direction, of the case band  14 . The dial  12  is visually recognizable through the cover glass  15 . The case back  16  is removable. 
   As shown in  FIGS. 2 and 3 , a pipe attachment hole  17 , which pierces this case band  14  in a radial direction, is opened in a part of the case band  14 . One end of the pipe attachment hole  17  opens into a space  14   a  surrounded by the case band  14 , and the other end of the pipe attachment hole  17  is opened to an outside surface  14   b  of the case band  14 . 
   A tubular member (first tubular member) in the form of a pipe  21  is inserted into the pipe attachment hole  17  from the outside of the case band and is attached to the case band  14  by brazing or the like. In  FIGS. 2 and 3 , reference numeral  22  denotes a brazing material. The pipe  21  is made of a metal, such as for example stainless steel, is formed in a cylindrical shape and opened at both ends in an axial direction thereof, respectively, includes a pipe end  21   a  arranged outside the case band  14 , and has a male screw section  24  for holding a crown  31  in the screw lock state on an outer periphery of the pipe end  21   a.    
   The crown  31  includes a crown shaft  32 , a crown head  33 , a clutch member  34  (hereinafter “clutch”), and an elastic body, for example, a coil spring  35 . 
   The crown shaft  32  is made of, for example, metal, preferably stainless steel. As shown in  FIGS. 2 and 3 , the crown shaft  32  includes: a columnar inserting shaft section  32   a  that is inserted into the pipe  21  from the outside of the case band  14 ; a shaft end  32   b  that continues integrally with this inserting shaft section  32   a  and is arranged in the outside of the pipe  21 ; and a receiving section  32   c  that is provided forming a boundary between the inserting shaft section  32   a  and the shaft end  32   b . The receiving section  32   c  is provided closer to the outside surface  14   b  of the case band  14  than the clutch  34 . 
   A winding stem  36 , which transmits a turning force of the crown  31  to the watch movement  13 , is screwed from the inside of the case band and coupled to a tip of the inserting shaft section  32   a . Consequently, the winding stem  36  and the crown shaft  32 , which are coupled to each other, cannot move in the axial direction. An annular waterproof gasket  37 , which consists of an elastic material such as rubber, is inserted in an annular recess formed on an outer periphery of the tip of the inserting shaft section  32   a . This gasket  37  elastically adheres to the annular recess and an inner periphery of the pipe  21 . Consequently, a part between the inner periphery of the pipe  21  and the crown shaft  32  is waterproofed. 
   The shaft end  32   b  has a diameter larger than the inserting shaft section  32   a . The receiving section  32   c  is provided forming an annular brim. This receiving section  32   c  has a diameter larger than outer diameters of the shaft end  32   b  and the male screw section  24 . 
   The crown head  33  is made of, for example, metal, preferably, stainless steel and is formed in a cylindrical shape as shown in  FIGS. 2 and 3 , and has a groove for-preventing slippage in a turning operation on an outer periphery thereof. Moreover, one end face  33   a  of the crown head  33  is formed as a surface that comes into contact with and separates from the outside surface  14   b  of the case band  14 . A female screw section  38 , which is removably engaged with the male screw section  24  in order to obtain the screw lock state, is formed on an inner periphery closer to this one end face  33   a . A diameter of the female screw section  38  is smaller than the diameter of the receiving section  32   c , and an end  38   a  (see  FIG. 2 ) of this female screw section  38  can come into contact with and separate from the receiving section  32   c.    
   The clutch  34  is adapted to couple the crown shaft  32  and the crown head  33  so as to prevent the turn of the crown shaft  32  in a state in which engagement of the male screw section  24  and the female screw section  38  is completed (this coupling will be hereinafter referred to as a first coupling state), couples the crown shaft  32  and the crown head  33  so as to make it possible to turn the screw shaft  32  following the screw head  33  in a state in which the engagement is released (this coupling will be hereinafter referred to as a second coupling state), and releases the coupling in states other than the two states. For this purpose, the clutch  34  has, for example, a first driven section  41 , a second driven section  42 , and a driving section  43 . 
   More specifically, as shown in  FIGS. 2 to 5 , the first and the second driven sections  41  and  42  are in the form of a polygon and, for example, in the form of a regular pentagon and are projected to an outer periphery of the shaft end  32   b . It is preferable to form the first and the second driven sections  41  and  42  in a regular polygon shape, which has sides exceeding that of the regular pentagon, in order to reduce associated movement of the crown shaft  32  with the turn of the crown head  33  in a state in which the first driven section  41  or the second driven section  42  and the driving section  43  are fitted with each other. The first and the second driven sections  41  and  42  and the crown shaft  32  are provided with a predetermined interval in the axial direction. The first and the second driven sections  41  and  42  are provided to be opposed to each other in an axial direction of the crown shaft  32  with positions thereof not deviating in a peripheral direction of the crown shaft  32 . The predetermined interval is equal to a dimension of movement in the axial direction of the crown head  33 . The sides of the first and the second driven sections  41  and  42  extend forming tangent lines with respect to an outer peripheral surface of the shaft end  32   b  located between the first and the second driven sections  41  and  42 . 
   The driving section  43  engages with and disengages from the first and the second driven sections  41  and  42  selectively, has a fitting hole  43   a  of the same shape as the first and the second driven sections  41  and  42 , that is, the regular pentagon as illustrated in  FIG. 4  in the case of this embodiment, and is provided in the crown head  33 . This driving section  43  is formed of a ring of metal, for example, stainless steel having the fitting hole  43   a  and is fixed to an inner periphery at the other end on the opposite side of one end, where the female screw section  38  of the crown head  33  is provided by, for example, caulking. Due to this caulking, a visually recognizable joint trace  43   b  of a ring shape appears on the end face of the crown head  33 . Such fixing of the driving section  43  is preferable in appearance because the fixing can contribute to giving impression that the crown head  33  is machined with a lot of trouble. 
   A shaft portion  32   bc  between the first and the second driven sections  41  and  42  of the shaft end  32   b  is made in a thickness inscribing each side of the fitting hole  43   a  included in the driving section  43 . Consequently, since the driving section  43  is guided to the shaft portion  32   bc  when the crown head  33  is moved in the axial direction, the crown head  33  can be moved in the axial direction easily and smoothly while controlling fluctuation in a posture of the crown head  33  such as inclination. Therefore, engagement and disengagement operations of the fitting hole  43   a  of the driving section  43  with respect to the first and the second driven sections  41  and  42  are easy. 
   The coil spring  35  is nipped between the receiving section  32   c  and the driving section  43 , which are opposed to each other in the axial direction of the crown shaft  32 , and is provided while always biasing the crown head  33  in a direction in which the crown head  33  moves away from the outside surface  14   b  of the case band  14 . 
   In the wristwatch  10  including the above-mentioned structure, a state in which the crown  31  is arranged in a position where the crown  31  is not pulled out (generally referred to as a “zero stage”) is shown in  FIG. 2 . In this “zero stage”, the female screw section  38  of the crown head  33  is engaged with the male screw section  24  of the pipe  21 , and the one end face  33   a  of the crown head  33  is positioned in contact with the outside surface  14   b  of the case band  14 , and moreover, the fitting hole  43   a  of the driving section  43  of the clutch  34  is fitted in an outer periphery of the first driven section  41  (this fitting state is shown in  FIG. 5 ). 
   Consequently, in a state in which the coil spring  35  is compressed strongly between the driving section  43  and the receiving section  32   c  of the crown shaft  32 , regardless of the fact that the crown head  33  is biased in the direction in which the crown head  33  moves away from the case band  14 , the crown head  33  is not moved in the axial direction because of the engagement. At the same time, since the clutch  34  is in the first coupling state, and the fitting hole  43   a  of the driving section  43  and the first driven section  41  are engaged with each other, the crown shaft  32  is prevented from turning with respect to the crown head  33 . In this way, in the “zero stage”, the crown  31  is in the screw lock state. In this screw lock state, as shown in  FIGS. 1 and 2 , a part of the shaft end  32   b  of the crown shaft  32  projects from the crown head  33 . Consequently, a user is capable of visually recognizing that the crown  31  is in the screw lock state, in which the crown  31  is held so as not to be turned carelessly, according to a positional relation of the shaft end  32   b  of the crown shaft  32  with respect to the end face of the crown head  33 . 
   When time setting for the watch movement  13  is performed, the crown  31  in the screw lock state is pulled out to the position, which generally referred to as the “first stage”, and turned. That is, first, the crown head  33  is turned in a loosening direction to bring the crown head  33  into a state in which the female screw section  38  thereof is disengaged from the male screw section  24  of the pipe  21 . In this case, in an initial stage of the turn of the crown head  33  in the loosening direction, since the driving section  43  and the first driven section  41  are fitted with each other, the crown shaft  32  is turned in association with the crown head  33 . However, the crown head  33  moves axially in a direction in which the crown head  33  moves away from the outside surface  14   b  of the case band  14  in accordance with the turn in the loosening direction thereof, the fitting of the driving section  43  and the first driven section  41  is released promptly in the initial stage. Consequently, the transmission of a turning force to the watch movement  13  according to the association of the crown shaft  32  with the crown head  33  turned in the loosening direction is substantially negligible. 
   The fitting of the driving section  43  and the first driven section  41  is released as described above, whereby the first coupling state of the crown shaft  32  and the crown head  33  by the clutch  34  is released. Simultaneously with this, the crown head  33  is moved easily without a manual operation along the axial direction of the crown shaft  32  by a spring force (biasing force) of the coil spring  35 . The crown shaft  32  is never turned following this movement in the axial direction. 
   In accordance with this movement in the axial direction of the crown head  33 , the clutch  34  comes into the second coupling state to couple the crown shaft  32  and the crown head  33 . That is, the fitting hole  43   a  of the driving section  43  is fitted to an outer periphery of the second driven section  42 . Simultaneously with this second coupling state being created, the end  38   a  of the female screw section  38  comes into abutment against the receiving section  32   c  of the crown shaft  32 , and the movement in the axial direction of the crown head  33  is regulated. The crown head  31  released from the screw lock state is held in the pulled-out position, which is generally referred to as the “first stage”, by positioning according to this regulation as shown in  FIG. 3 . This is preferable in that the second coupling state is maintained by the spring force of the coil spring  35  even if a hand is lifted during a time-setting operation to be explained next. 
   The crown  31  can be turned manually in this pulled-out position. That is, in the second coupling state in which the fitting hole  43   a  of the driving section  43  is fitted to the outer periphery of the second driven section  42 , turn of the crown head  33  is transmitted to the crown shaft  32  via the clutch  34 . Since a turning force is given to the watch movement  13  via the winding stem  36  following the transmission of the turn, adjustment of time-setting or the like for this watch movement  13  can be performed. 
   After this adjustment, the crown  31  is brought into the lock state (see  FIG. 2 ) again. An operation for obtaining this screw lock state is carried out by pushing back the crown head. 33  in the direction of the case band  14  against the coil sprig  35 , and then the female screw section  38  of this crown head  33  is turned in a tightening direction to screw the female screw section  38  into the male screw section  24  of the pipe  21 . Consequently, the one end face  33   a  of the crown head  33  comes into abutment against the outside surface  14   b  of the case band  14 , and the clutch  34  comes into the first coupling state immediately before this abutment. Thus, the crown  31  can be brought into the screw lock state so as not to be turned carelessly at the time when the wristwatch  10  is carried or the like. 
   In this operation for obtaining the screw lock state, the clutch  34  is released from the second coupling state of the crown head  33  and the crown shaft  32  in the early stage of the turn of the crown head  33 . In addition, immediately before completion of engagement of the male screw section  24  and the female screw section  38 , the clutch  34  comes into the first coupling state for coupling the crown head  33  and the crown shaft  32 . Then, the transmission of the crown head  33  is never transmitted to the crown shaft  32  in most of the period in which the crown head  33  is turned in the tightening direction, that is, from a point when the clutch  34  is released form the second coupling state until the clutch  34  comes into the first coupling state. 
   Incidentally, in a stage immediately before the engagement of the female screw section  38  with the male screw section  24  is completed, since the clutch  34  comes into the first coupling state, the crown shaft  32  turns following the crown head  33  that is turned in the tightening direction. However, an amount of turn of the crown head  33 , which is required from a start point of this following turn until the one end face  33   a  of the screw head  33  comes into abutment against the outside surface  14   b  of the case band  14  and the engagement is completed, is a little. Consequently, the association of the crown shaft  32  with the crown head  33 , which is turned in the tightening direction, is substantially negligible. 
   Therefore, it is possible to control the crown shaft  32  not to turn following the screw lock operation, which has already been described, for obtaining the screw lock state to transmit the turn to the mechanical watch movement  13 . Consequently, in the screw lock operation, the spiral spring included in the watch movement  13  is controlled not to be a load. Therefore, for example, even in a state in which the spiral spring is wound up considerably, the screw lock operation for the crown  31  can be performed lightly, and operability is high. Note that, in the case in which the watch movement  13  is not mechanical but has the function of changing an operation mode with the crown  31  arranged in the “zero stage” position, a turning force following the screw lock operation for the crown  31  is controlled not to spread to the watch movement as described above. Thus, an operation mode is never changed carelessly. 
   In addition, since the screw lock operation in the mechanical clock movement  13  having the spiral spring can be performed lightly as described already, an excessive turning operation force is never applied to the male screw section  24  and the female screw section  38 . Thus, durability of these screw sections  24  and  38  can be improved. 
   Second Embodiment 
   A second embodiment of the present invention will be explained with reference to  FIG. 6  showing the screw lock state of the crown  31  and  FIG. 7  showing a state in which the screw lock state of the crown  31  is released. Since this second embodiment is basically the same as the first embodiment, components same as those in the first embodiment are denoted by reference numerals and signs identical with those in the first embodiment, and an explanation about the components will be omitted. Components different from those in the first embodiment will be explained. 
   In the second embodiment, the female screw section  38 , which is formed in an inner surface of a tubular member (second tubular member) and is provided separately from the crown head  33 , is fixed to the inner periphery at one end in the axial direction of the crown head  33  by caulking. Moreover, the driving section  43  of the clutch  34  is formed integrally with the inner periphery at the other end in the axial direction of the crown head  33 . Other than the points explained here, the second embodiment including the structures not shown in  FIGS. 6 and 7  is the same as the first embodiment. 
   Therefore, even with the wristwatch  10  of this second embodiment, the same action as the first embodiment can be obtained to solve the problems that the present invention is to solve. Moreover, since the driving section  43  is provided integrally with the crown head  33 , there is no deficiency in attachment of the driving section  43  to the crown head  33 . Consequently, there is not deficiency in coupling of the crown shaft  32  and the crown head  33  due to the deficiency in attachment, the function of the clutch  34  can be maintained surely over a long-term use, and a caulking trace can be made invisible. 
   The present invention is not limited to both the embodiments described above. For example, the crown head  33  can be formed in a length that substantially covers the entire outer periphery of the shaft end  32   b  when the crown head  33  is in the screw lock state. In this structure, while maintaining a function of allowing a user to know whether a state of the crown  31  is the screw lock state or the state in which screw lock is released according to a mutual positional relation between the end face of the crown head  33  and the shaft end  32   b  of the crown shaft  32 , the second driven section  42  can be made less likely to be operated in the screw lock state to turn the crown shaft  32  carelessly. 
   In the present invention, the coil spring  35  of the crown  31  may not be provided. In this case, in bringing the crown head  33  into the screw lock state, the crown head  33  is not subjected to resistance of the coil spring.  35 . Consequently, the crown head  33  can be moved in the axial direction toward the outside surface  14   b  of the case band  14  with a light operation. 
   In both the embodiments described above, the first and the second driven sections  41  and  42  of the clutch  34  are formed with regular polygonal projections, and the driving section  43  is constituted to have the regular polygonal fitting hole. Alternatively, in the present invention, the first and the second driven sections  41  and  42  can be formed of external gears, and the driving section  43  can be formed of an internal gear. 
   According to the present invention, it is possible to control the crown shaft not to turn following the screw lock operation to transmit the turn to the watch movement. Consequently, a portable watch can be provided in which the screw lock operation for the crown can be performed lightly so that durability of the male screw section of the pipe and the female screw section of the crown head can be improved, and moreover, it is possible to hold the crown so not to be turned carelessly or unintentionally by utilizing engagement of screws without being restricted by functions of the watch movement, for example, a function of winding up a spiral spring and a function of changing an operation mode.