Patent Publication Number: US-2007097795-A1

Title: Timepiece with a calendar function and/or a time setting function, and method of assembling the timepiece

Description:
BACKGROUND OF THE INVENTION  
      1. Technical Field  
      The present invention relates to timepieces and more particularly to timepieces with a calendar function to display a date and/or a time setting function to set the time by receiving a standard time and frequency signal, and methods of assembling the timepiece.  
      2. Background Art  
      In the past, timepieces with a calendar function to display a date comprise a ring-like day indicator, on which a series of dates are printed, disposed rotatably and concentrically on a main plate, and a date indicator drive wheel meshing rotatably with gear teeth provided along the inner periphery of the day indicator such that the day indicator is rotated by rotation of the day indicator drive wheel.  
      With such a timepiece with a calendar function as disclosed especially in Unexamined Japanese Patent Publication 2004-144482, in order to dispose the day indicator rotatably and concentrically on the main plate the ring-like day indicator comprises a guide cylinder provided coaxially therewith on a lower surface of the inner peripheral part thereof, wherein the gear teeth are provided along the inner periphery of the guide cylinder, and a plurality of rolls are provided rotatable on the main plate so as to rotate in contact with the outer periphery of the guide cylinder, thereby guiding the day indicator.  
      However, the structure of the timepiece is complicated, the number of parts of the timepiece is great and the assembling operation is complicated. Especially, the plurality of rolls must be provided on the main plate so as to be in contact with the outer periphery of the guide cylinder of the day indicator. Therefore, high attachment accuracy is required and the assembling operation is troublesome.  
     SUMMARY OF THE INVENTION  
      The present invention provides a timepiece with a calendar function/time setting function, which has a simply structure and is easy to assemble and a method of assembling the timepiece.  
      The objects, features and advantages of the present invention will become apparent in the following detailed description of the present embodiment and modifications thereof when read in conjunction with the accompanying drawings wherein the same reference numerals denote like or similar parts throughout the several views. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION  
       FIG. 1  is a front view of a wristwatch in accordance with an embodiment of the present invention;  
       FIG. 2  is a cross sectional view taken along a line II-II in  FIG. 1 ;  
       FIG. 3  is a bottom view of the  FIG. 1  wristwatch with a case back removed;  
       FIG. 4  is a front view of a timepiece module of the  FIG. 1  wristwatch;  
       FIG. 5  is a bottom view of the  FIG. 4  timepiece module;  
       FIG. 6  is a front view of the  FIG. 4  timepiece module with a solar panel and a dial plate removed;  
       FIG. 7  is a front view of the  FIG. 6  timepiece module with a day indicator maintaining plate removed;  
       FIG. 8  is a bottom view of the  FIG. 5  timepiece module with a circuit board removed;  
       FIG. 9  is a bottom view of the  FIG. 8  timepiece module with a wheel train bridge removed;  
       FIG. 10A  is an enlarged front view of each of # 1 -# 5  pulse motors of the  FIG. 8  and  9  timepiece module;  
       FIG. 10B  is an enlarged side view of that motor of  FIG. 10A ;  
       FIG. 11  is a cross sectional view of a three-hand wheel train taken along a line XI-XI of  FIG. 9 ;  
       FIG. 12  is an upside down cross sectional view of a three-hand wheel train taken along a line XII-XII of  FIG. 7 ;  
       FIG. 13  is a cross sectional view of a two-hand wheel train taken along a line XIII-XIII of  FIG. 9 ;  
       FIG. 14  is an enlarged cross sectional view of a part A of  FIG. 13  involving a fixing screw and its vicinities;  
       FIG. 15  is a cross sectional view of a second-hand-dedicated wheel train taken along a line XV-XV of  FIG. 9 ;  
       FIG. 16  is a cross sectional view of a day indicator wheel train taken along a line XVI-XVI of  FIG. 9 ;  
       FIG. 17  is an enlarged cross sectional view of a second hand wheel of the  FIG. 11  three-hand wheel train positioned on the main plate with a jig;  
       FIG. 18  is a front view of the timepiece module of  FIG. 1 , illustrating positioning of the day indicator;  
       FIG. 19  is a cross sectional view taken in  FIG. 18 ;  
       FIG. 20  is a bottom view of the wristwatch where the  FIG. 3  timepiece module is positioned within the case by a module support;  
       FIG. 21A  is a front view of the module support of  FIG. 20 ;  
       FIG. 21B  is a side view of the module support of  FIG. 20 ;  
       FIG. 21C  is a bottom view of the module support of  FIG. 20 ;  
       FIG. 22A  is a cross sectional view taken along a line XXIIA-XXIIA of  FIG. 20 ;  
       FIG. 22B  is a cross sectional view taken along a line XXIIB-XXIIB of  FIG. 20 ;  
       FIG. 23  is a schematic enlarged cross sectional view of a timepiece module of the first modification of the embodiment; and  
       FIG. 24  is an enlarged cross sectional view of a second modification. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT  
      Referring to  FIGS. 1-22B , a multi-hand timepiece in the form of a wristwatch according to one embodiment of the invention will be described. As shown in  FIGS. 1-3 , the wristwatch comprises a case  1  over which a bezel  1   a  is provided with a crystal  2  provided through packing  2   a  over the bezel  1   a . A timepiece module  3  is received within the case  1 . A case back  4  is attached through a waterproof ring  4   a  to the lower end of the case  1 . # 1 -# 4  push bottom switches  5   a - 5   d  are provided on the side of the case  1  at 3 and 9 o&#39;clock.  
      As shown in  FIG. 2 , the timepiece module  3  comprises a wheel train block  6 , a circuit board  7 , an antenna  8  and a power source which, for example, includes a battery  9 , which are supported by a ring-like plastic module maintaining plate  10  ( FIGS. 21A-21C ) into the case  1 . A solar panel  11  and a dial plate  12  are superposed on the wheel train block  6  in this order and attached by a support ring  13  to the wheel train block  6 .  
      The wheel train block  6  comprises a plurality of wheel trains arranged in a planar manner, and has a chronograph function, which will be described in more detail later. The circuit board  7  is disposed under the wheel train block  6  to drive and control the same. The antenna  8  receives a standard time and frequency signal to set the time and is disposed within the timepiece module  3  at 12 o&#39;clock so as to have a thickness smaller than the total thickness of the wheel train block  6  and the circuit board  7 . The battery  9  supplies electric energy to the respective electric components of the wristwatch that required such energy. The battery  9  is disposed within the timepiece module  3  at 9 o&#39;clock and has a thickness in the range of the total thickness of the wheel train block  6  and the circuit board  7 .  
      As shown in  FIGS. 4-16 , the wheel train block  6  comprises a three-hand wheel train  15 , a two-hand wheel train  16 , a second-hand-dedicated wheel train  17 , and a day indicator wheel train  18  integrated in substantially a planar manner between a ring-like plastic main plate  19  and a plastic wheel-train board  20 . The second-, minute- and hour-hands  16   a ,  15   b  and  15   c  of the three-hand wheel train  15  are attached to the corresponding coaxial cylindrical axles at substantially the center of the timepiece module  3  so as to be turned by the # 1  and # 2  pulse motors  21  and  22 . A 24-hour hand  15   d  is positioned within the timepiece module  3  at 9 o&#39;clock so as to be turned by a wheel train  41 .  
      As shown in  FIGS. 4-9  and  13 , in the two-hand wheel train  16  the minute hand  16   a  and the 24-hour hand  16   b  are attached to the corresponding coaxial tubular axles provided on the timepiece module  3  at 3 o&#39;clock so as to be driven by the # 3  pulse motor  23 . As shown in  FIGS. 4-9  and  15 , in the second-hand-dedicated wheel train  17  a second hand  17   a  is provided on the timepiece module  3  at 6 o&#39;clock so as to be driven by the # 4  pulse motor  24 . As shown in  FIGS. 4-9  and  16 , in the day indicator wheel train  18  the ring-like day indicator  26  is disposed concentrically on the main plate  19  so as to be rotated by the # 5  pulse motor  25 .  
      As shown in  FIGS. 10A and 10B , each of the # 1 -# 5  pulse motors  21 - 25  for the respective wheel trains  15 - 18  includes an energizing coil  27 , a stator  28  and a rotor  29  such that NS magnetic fields produced by a required current flowing through the coil  27  rotate the rotor  29  through the stator  28 . In this case, the rotor  29  is supported rotatably within a cavity in the stator  28  between the main plate  19  and the wheel train bridge  20 .  
      Next, the respective wheel trains  15 - 18  will be described in order. As shown in  FIGS. 7-12 , the three-hand wheel train  15  comprises first and second wheel train systems driven by the # 1  and # 2  pulse motors  21  and  22 , respectively. As shown in  FIGS. 11 and 12 , the first wheel train system comprises a fifth wheel and pinion set  30  driven by the # 1  pulse motor  21  and a second wheel and pinion set  31 , which is a second-hand wheel, driven by the fifth wheel and pinion set  30 .  
      As shown in  FIGS. 7-12 , the second wheel train system comprises a intermediate wheel  32  rotated by the # 2  pulse motor  22 , a third wheel and pinion set  33  rotated by the intermediate wheel  32 , a center wheel and pinion set  34 , which is a second hand wheel, rotated by the third wheel and pinion set  33 , a minute wheel  35  rotated by the center wheel and pinion set  34 , a hour wheel  36 , which is an hour-hand wheel rotated by the minute wheel  35 , and a 24-hour hand wheel  37  that is caused to make a complete revolution in 24 hours due to rotation of the minute wheel  35  through a wheel train  41 .  
      As shown in  FIG. 11 , the fifth wheel and pinion set  30  of the # 1  wheel train system is supported rotatably between the main plate  19  and the wheel train bridge  20  such that the wheel of the set  30  is rotated by a pinion of the rotor  29  of the # 1  pulse motor  21  in a meshed state. As shown in  FIGS. 11 and 12 , the second wheel and pinion set  31 , which is the second hand wheel, has a second hand axle  31   a  supported rotatably at substantially the center of the timepiece module  3  between the wheel train bridge  20  and an intermediate bridge  38  attached to the main plate  19 . A second hand  15   a  is attached to a lower end (see  FIG. 11 ) of the second hand shaft  31   a.    
      The intermediate bridge  38  includes a thin metal plate, for example of stainless steel, attached to the main plate  19  between the same and the wheel train bridge  20 . As shown in  FIGS. 11 and 12 , the intermediate bridge  38  supports a hollow cylindrical holder  39 , within which the second hand shaft  31   a  of the second wheel and pinion set  31  is received rotatably, at substantially the center of the time module  3 . The cylindrical holder  39  is in turn received rotatably within a hollow cylindrical minute-hand shaft  34   a  of a center wheel and pinion set  34 , which is a minute-hand wheel, so as to rotatably support the minute-hand shaft  34   a  with a minute hand  15   b  attached to a lower end of the shaft  34   a . The wheel of the set  34  meshes rotatably with a pinion of the third wheel and pinion wheel  33 .  
      As shown in  FIG. 11 , the intermediate wheel  32  of the # 2  wheel train system is supported between the main plate  19  and the wheel train bridge  20  so as to be rotated by a pinion of the rotor  29  of the # 2  pulse motor  22  in a meshed state. The wheel and pinion set  33  is supported rotatably between the main plate  19  and the intermediate bridge  38  such that the wheel thereof is rotated by a pinion of the intermediate wheel  32  in a meshed state.  
      The center wheel and pinion set  34  is disposed at the center of the main plate  19  such that there is a predetermined gap between a restricting part  19   a  ( FIG. 12 ) of the main plate  19  and the wheel of the center wheel and pinion set  34  and that there is another ring-like gap between an inner periphery  19   b  of the opening in the main plate  19  and a pinion of the center wheel and pinion set  34 , from the standpoint of position restriction. As shown in  FIG. 17 , the second-hand shaft  34   a  of the center wheel and pinion set  34  is accurately positioned by an assembly jig  1 . The hollow cylindrical holder  39  attached to the intermediate bridge  38  can then be inserted rotatably into within the second-hand shaft  34   a , thereby supporting the same rotatably.  
      As shown in  FIG. 12 , the minute wheel  35  is supported rotatably by an upright support shaft  40  attached to the intermediate bridge  38  such that the minute wheel  35  rotates, meshing with a cannon pinion of the center wheel and pinion set  34 . The support shaft  40  of the minute wheel  35  is received within a hole  38   a  in the intermediate bridge  38  with a head  40   a  of the support shaft  40  held by a lower end  20   a  of the wheel train bridge  20 .  
      As shown in  FIGS. 11 and 12 , the hour-hand wheel or hour wheel  36  is provided at substantially the center of the timepiece module  3  with a cylindrical shaft  36   a  supported by the minute-hand shaft  34   a  that is received rotatably within the cylindrical shaft  36   a . The 12-hour hand  15   c  is attached to the lower end of the shaft  36   a  (in  FIG. 11 ). A wheel of the set  36  meshes rotatably with a pinion of the minute wheel  35 . Thus, the second-, minute- and hour-shafts  31   a ,  34   a  and  36   a  are disposed coaxially around the same axis.  
      As shown in  FIGS. 7 and 12 , the wheel train  41  includes a first intermediate wheel  42  and a second intermediate wheel (or 24-hour hand wheel) and pinion set  43  which reduce the rotational speed of the minute wheel  35  and transmit an resulting speed to the 24-hour hand wheel  37 . As shown in  FIG. 12 , the first intermediate wheel  42  is pivoted at a support axle  19   c  to a lower end of the main plate  19  so as to mesh rotatably with a pinion of the minute wheel  35 . As shown in  FIG. 12 , the second intermediate wheel and pinion set  43  is pivoted at a support axle  19   d  to the lower end of the main plate  19  such that a wheel of the set  43  meshes rotatably with the first intermediate wheel  41 .  
      As shown in  FIG. 12 , in the 24-hour hand wheel  37  its shaft  37   a  is supported rotatably on the wheel train bridge  19  on the timepiece module  3  at the 9 o&#39;clock position with the 24-hour hand  15   d  attached to the lower end of the shaft  37   a . The wheel  37  meshes rotatably with a pinion of the second intermediate wheel and pinion set  43  so as to make a complete revolution in 24 hours. The 24-hour hand wheel  37 , the first intermediate wheel  42 , the second intermediate wheel and pinion set  43 , the minute wheel  35 , and the hour-hand wheel  36  are resiliently and rotatably supported by a day indicator maintaining plate  55  through resilient ring-like seats such as spring washers  36   b ,  37   b  and  48   b.    
      As shown in  FIGS. 7-9 , and  13 , the two-hand wheel train  16  is disposed over the timepiece module  3  at the 3 o&#39;clock position such that the minute and 24-hour hands  16   a  and  16   b  are turned by the # 3  pulse motor  23 , as shown in  FIG. 1 . More particularly, as shown in  FIGS. 7-9  and  13 , the two-hand wheel train  16  comprises an intermediate wheel and pinion set  45  rotated by the # 3  pulse motor  23 , a center wheel and pinion set  46 , which is a minute-hand wheel, rotated by the intermediate wheel and pinion set  45 , a minute wheel and pinion set  47  rotated by the center wheel and pinion set  46 , and a 24-hour hand  48  that is caused to make a complete revolution in 24 hours by the minute wheel and pinion set  47 , which is rotated by the center wheel and pinion set  46 .  
      As shown in  FIG. 13 , the intermediate wheel and pinion set  45  of the two-hand wheel train  16  has a shaft which is supported between the main plate  19  and the wheel train bridge  20  such that a wheel of the set  45  meshes rotatably with a pinion of the rotor  29  of the # 3  pulse motor  23 . The center wheel and pinion set  46 , which involves the minute-hand wheel, has a shaft  46   a  supported between the main plate  19  and the wheel train bridge  20  in the timepiece module  3  at the 3 o&#39;clock position. A minute hand  16   a  is attached to the lower end of the shaft  46   a . In this state, a wheel of the center wheel and pinion set  46  is rotated by a pinion of the intermediate wheel and pinion set  45  in a meshed state.  
      The minute wheel and pinion  47  has a shaft supported rotatably between the main plate  19  and the wheel train bridge  20  such that a wheel of the set  47  meshes rotatably with a cylindrical pinion of the center wheel and pinion set  46 . A 24-hour hand wheel  48  involves a 24-hour wheel having a hollow cylindrical shaft  48   a  provided in the timepiece module  3  at 3 o&#39;clock with the minute-hand shaft  46   a  of the center wheel and pinion set  46  received rotatably within the cylindrical shaft  48   a , which is supported by the minute-hand shaft  46   a . The wheel of the set  48  meshes with a pinion of the minute wheel and pinion set  47  so as to make a complete revolution in 24 hours.  
      As shown in  FIG. 1 , the second-hand-dedicated wheel train  17  is disposed in the timepiece module  3  at 6 o&#39;clock such that the second-hand  17   a  is turned by the # 4  pulse motor  24 . More particularly, as shown in  FIGS. 7-9  and  15 , the second-hand-dedicated wheel train  17  comprises a fifth wheel and pinion set  50  rotated by the # 4  pulse motor  24 , and a second wheel and pinion set  51 , which involves a second-hand wheel, rotated by the fifth wheel and pinion set  50 .  
      As shown in  FIG. 15 , the fifth wheel and pinion set  50  has a shaft supported rotatably between the main plate  19  and the wheel train bridge  20  such that a wheel of the set  50  meshes rotatably with a pinion of the rotor  29  of the # 4  pulse motor  24 . The second wheel and pinion set  51 , which involves the second hand wheel, has a shaft  51   a  supported rotatably between the main plate  19  and the wheel train bridge  20  with a second hand  17   a  attached to the lower end of the shaft  51   a  (in  FIG. 15 ) such that a wheel of the second wheel and pinion set  51  is rotated by a pinion of the fifth wheel and pinion set  50  in a meshed state.  
      The day indicator  26  is driven through the day indicator wheel train  18  by the # 5  pulse motor  25 . As shown in  FIGS. 7-9  and  16 , the day indicator wheel train  18  comprises a fifth wheel and pinion set  52  rotated by the # 5  pulse motor  25 , and an intermediate wheel and pinion set  53  rotated by the fifth wheel and pinion set  52 , a date indicator driving wheel and pinion set  54  rotated by the intermediate wheel and pinion set  53 , and a day indicator  26  rotated by the day indicator driving wheel and pinion set  54 . As shown in  FIG. 16 , the fifth wheel and pinion set  52  of the day indicator wheel train  18  has a shaft supported rotatably between the main plate  19  and the wheel train bridge  20  such that a wheel of the set  52  is rotated by a pinion of the rotor  29  of the # 5  pulse motor  25  in a meshed state.  
      As shown in  FIG. 16 , the intermediate wheel and pinion set  53  of the day indicator wheel train  18  has a shaft supported rotatably between the main plate  19  and the wheel train bridge  20  such that a wheel of the set  53  is rotated by a pinion of the fifth wheel and pinion set  52  in a meshed state. The day indicator driving wheel and pinion set  54  is pivoted at a downward support axle  19   e  integral with the lower end of the main plate  19  such that a wheel of the set  54  meshes rotatably with a pinion of the intermediate wheel and pinion set  53 .  
      As shown in  FIGS. 6, 7  and  18 , the ring-like day indicator  26  is disposed concentrically within a raised ring-like guide  19   f  provided concentrically on, and substantially equal in outer diameter to, the main plate  19  such that there is a substantially constant-width ring-like gap between the day indicator  26  and the outside guide  19   f . Dates are indicated on the day ring  26  at predetermined intervals. The ring-like day indicator  26  has gear teeth  26   a  arranged along an inner periphery thereof and meshing with a pinion of the day indicator driving wheel  54  (see  FIG. 16 ) so as to make a complete revolution in a month. As shown in  FIGS. 13 and 15 , the day indicator  26  has a thinned inner periphery portion including the gear teeth  26   a  at which the day indicator  26  is supported rotatably by a maintaining plate  55 .  
      As shown in  FIGS. 18 and 19 , the main plate  19  has therein a plurality of (for example, three) guide holes  76  arranged at the 12, 4 and 10 o&#39;clock positions along the ring-like gap between the main plate  19  and the inside day indicator  26  and overlapping the day indicator  26  into which holes a like number of guide pins  77  will be inserted for positioning purposes.  
      As shown in FIGS.  6 ,  11 - 16  and more particularly  FIG. 13 , a ring-like day indicator maintaining plate  55  has a diameter somewhat larger than the inner diameter of the day indicator  26  and is disposed concentric with the day indicator  26  so as to support the day indicator  26  rotatably at its thinned peripheral part. The plate  55  is fixed to the main plate  19  by two screws  56  in a state in which the day indicator maintaining plate  55  supports the 24-hour hand wheel  48  of the second-hand wheel train  16  at a protrusion (not shown) provided on the outer periphery thereof. The 24-hour hand wheel  48  has gear teeth of a reduced thickness provided along the outer periphery thereof so as not to interfere with the inner wheel teeth  26   a  of the day indicator  26 .  
      As shown in  FIGS. 13 and 14 , each screw  56  is composed of a head  57  and a screw part  58 . The head  57  is composed of a truncated conical part  57   a  disposed in a complementary hole  55   b  provided in the day indicator maintaining plate  55  and a disk part  57   b  integral with the head part  57   a  received in a complementary recess  59  in the main plate  19 .  
      In order to assemble the day indicator  26  in place on the main plate  19 , the main plate  19  is first disposed on an assembly jig G 2  such that the plurality of guide holes  76  provided in the main plate  19  align with the like number of pin holes  78  provided in the jig G 2  (step  1 ). Each pin hole  78  in the jig G 2  is somewhat larger than a respective guide hole  76  in the main plate  19 .  
      Then, as shown in  FIG. 19 , the ring-like day indicator  26  is disposed substantially concentrically within the circular guide  19   f  provided on the main plate  19  such that a ring-like gap is formed between the guide  19   f  and the day indicator  26  (step  1 ). A plurality of guide pins  77  each having an upper tapering part and a lower thicker part are then inserted from below into the like number of aligned holes  78  and  76  provided in the jig G 2  and the main plate  19  so as to come gradually into contact with the outer periphery  26   b  of the day indicator  26  at the tapering parts thereof, thereby positioning the day indicator  26  in place relative to the main plate  19  (step  3 ).  
      The positioned day indicator  26  is then supported ratatably by the day indicator maintaining plate  55  against the main plate  19  (step  4 ) such that the day indicator  26  overlap rotatably in its thinned inner periphery part with the day indicator maintaining plate  55 . The day indicator maintaining plate  55  is then fixed to the main plate  19  with the screws  56 . Then, the guide pins  77  are removed from the main plate  19 , which is then removed from the jig G 2 .  
      As shown in FIGS.  8 ,  11 - 13 , attached to the wheel train bridge  20  for the wheel train block  6  are a leaf spring  61  that has # 1 , # 2  and # 3  spring parts  61   a ,  61   b  and  61   c  to elastically press the ends of the second-, minute- and second-hand shafts  31   a ,  46   a , and  51   a  of the three-hand, two-hand, and second-hand-dedicated wheel trains  15 ,  16  and  17 , and a plurality of support springs  61   d  and  61   e  abutting elastically on the circuit board  7 .  
      As shown in  FIGS. 2 and 20 - 22 B, the timepiece module  3  to which the wheel train block  6 , circuit board  7 , antenna  8  and battery  9  are attached is incorporated into the case  1  by the module maintaining plate  10 . In this timepiece module  3 , the circuit board  7  is disposed below the wheel train block  6 . The antenna  8  is disposed in the timepiece module  3  at  120 &#39;clock in a range of the total thickness of the wheel train block  6  and the circuit board  7  with a part of the antenna  8  underlying the day indicator  26  of the day indicator wheel train  18 . The battery  9  is disposed in the timepiece module  3  at the 9 o&#39;clock position with a part thereof disposed below the day indicator  26  of the day indicator wheel train  18 , the three-hand wheel train  15  and the 24-hour hand wheel  43 . The module maintaining plate  10  supports these components into the case  1 .  
      As shown in  FIGS. 8 and 9 , the upper portions of the antenna  8  and the battery  9  are received in cavities  62   a  and  62   b , respectively, provided in the main plate  19 . In the wheel train block  6 , a pulse motor having the highest drive frequency, for example the # 4  pulse motor  24  for the second-hand-dedicated wheel train  17 , is disposed at a remotest position from the antenna  8  so as not to deteriorate the reception sensitivity of the antenna  8 .  
      A solar panel  11  and a transparent dial plate  12  are disposed on the wheel train block  6  and attached by a holder ring  13  to the wheel train block  6 . The solar panel  11  receives external light through the transparent dial plate  12 , thereby generating an electromotive force, which is fed to the battery  9  and used as a part of the energy fed from the battery  9 . As shown in  FIG. 1 , hour numerals  12   a  are printed on the dial plate  12  with a window  12   b  through which a date displayed on the day indicator  26  is visible. A 24-hour dial around which the 24-hour hand  15   d  of the three-hand wheel train  15  sweeps is printed on the dial plate  12  at 9 o&#39;clock. A concentric-circlular 60-minute- and 24-hour-graduated subdial  12   d  around which the minute hand  16   a  and the 24-hour hand  16   b  of the two-hand wheel train  15  sweeps are printed on the dial plate  12  at 3 o&#39;clock. A 60-second-scaled subdial  12   e  around which the second hand  17   a  of the second-hand-dedicated wheel train  17  sweeps is printed on the dial plate  12  at 9 o&#39;clock.  
      As shown in  FIG. 20 , the timepiece module  3  is positioned in the case  1  by the module maintaining plate  10  disposed therebelow. As shown in  FIGS. 21A and 21   b , the plastic module maintaining plate  10  has a gourd-shaped opening  10   a  therein through which the battery (not shown) received in the battery reception cavity  62   b  can be exchanged and through which leads (not shown) are connected between the circuit board and another electronic component (not shown) provided on an inner surface of the case back around the center thereof. A plurality of position restrictors  10   b  are disposed along the outer periphery of the module maintaining plate  1  for position restiction.  
      As shown in  FIGS. 22A and 22B , the timepiece module  3  is disposed within the case  1  through the ring-like panel cover  63  disposed concentrically under the crystal  2 . The plurality of protrusions  10   b  of  FIGS. 21A and 21B  provided along the outer periphery of the module maintaining plate  10  are fitted into the like number of pairs of cavities  64  and  65  provided on the inner and outer peripheries of the case  1  and the whole of the main plate  19  and wheel train bridge  20  provided at the same positions as the protrusions  10   b  so as to position the timepiece module  3 .  
      In use, the operative mode of this wristwatch is changed to any desired one of a basic timepiece mode, a chronograph mode, a world time mode, an alarm mode, and a time set mode by operating a corresponding one of the # 1 -# 4  push button switches  5   a - 5   d . In the basic timepiece mode, the present time is displayed; in the chronograph mode, time is measured; in the world time mode, the respective times of the cities in the world are displayed; in the alarm mode, an alarm time is displayed; and in the time set mode, the time is set. These modes will be described sequentially next.  
      In  FIG. 1 , in the basic timepiece mode the # 2  pulse motor  22  of the three-hand wheel train  15  operates to cause the minute and 12-hour hands  15   b  and  15   c  and the 24-hour hands  15   d  to sweeps around the dial  12  and the subdial  12   c , respectively, thereby indicating the time in minutes and hours in the 12- and 24-hour systems. Simultaneously, the # 4  pulse motor  24  of the second-hand-dedicated wheel train  17  operates to turn the second hand  17   a , thereby indicating a “second” time. In addition, the # 5  pulse motor  25  of the day indicator wheel train  18  operates to turn the day indicator  26 , thereby indicating the present date in the window  12   b  of the dial plate  12 . Since at this time the # 1  pulse motor  21  of the three-hand wheel train  15  does not operate, the second hand  15   a  is at a stop at a reference (or 12 o&#39;clock) position. Since the # 3  pulse motor  23  of the two-hand wheel train  16  does not operate either, the minute and 24-hour hands  16   a  and  16   b  are at a stop at the reference position.  
      When the # 4  push button switch  5   d  is operated in the basic timepiece mode, the operative mode changes to the chronograph mode. At this time, the second hand  17   a  of the second-hand-dedicated wheel train  17  is reset to the reference position while the second, 12-hour and 24-hour hands  15   b ,  15   c  and  15   d  of the three-hand wheel train  15  and the day indicator  26  of the day indicator wheel train  18  continue their operations performed so far, thereby indicating the reference time. When in this state the # 4  push button switch  5   d  is again operated, the chronograph mode starts, the # 1  pulse motor  21  of the three-hand wheel train  15  operates, thereby turning the second hand  15   d . Simultaneously, the # 4  pulse motor  24  of the second-hand-dedicated wheel train  17  operates to turn the second hand  17   a , which causes the # 3  pulse motor  23  of the second hand wheel train  16  to operate to turn the minute and 24-hour hands  16   a  and  16   b.    
      At this time, the # 1  pulse motor  21  of the three-hand wheel train  15  causes the second hand  15   a  to turn at a speed of one revolution per minute. The # 4  pulse motor  24  of the second-hand-dedicated wheel train  17  causes the second hand  17   a  to turn at a high speed of one revolution per second. The # 3  pulse motor  23  of the two-hand wheel train  16  turns the minute hand  16   a  at a speed of one revolution in 60 minutes and the 24-hour hand  16   b  at a speed of one revolution per 24 hours. Thus, the second hand  17   a  of the second-hand-dedicated wheel train  17 , the second hand  15   a  of the three-hand wheel train  15  and the minute hand  16   a  and 24-hour hand  16   b  of the two-hand wheel train  16  are turned to measure time.  
      When the # 4  push button switch  5   d  is operated again in this state, the chronograph mode stops, and the second hand  17   a  of the second-hand-dedicated wheel train  17 , the second hand  15   a  of the three-hand wheel train  15 , and the minute hand  16   a  and 24-hour hand  16   b  of the two-hand wheel train  16  stop, thereby displaying the measured time. Then, when the # 4  push button switch  5   d  is again operated, the chronograph mode again starts, thereby starting time measurement as in the above case. When the # 4  push button switch  5   d  is once again operated, the chronograph mode stops and the measured time is displayed. When the second push button switch  5   b  is then operated, the basic timepiece mode is restored.  
      When a user operates the # 1  push button switch  5   a  in the basic timepiece mode, the operative mode is changed to the world time mode. At this time, the second hand  15   a  of the three-hand wheel train  15  indicates a particular one of the local city names, excluding the name of the city where the user is now, displayed on the ring-like panel cover  63 , the minute hand  16   a  and the 24-hour hand  16   b  of the two-hand wheel train  16  indicate the time of the time zone of the local city whose name is indicated by the second hand  15   a , and the second hand  17   a  of the second-hand-dedicated wheel train  17  indicates both the “second” times of the time zones of that city and the city where the user are t now. Both the “second” times are the same. The minute, 12-hour and 24-hour hands  15   b ,  15   c  and  15   d  of the three-hand wheel train  15  and the day indicator  26  of the day indicator wheel train  18  continue their operations performed so far, thereby indicating the time of the time zone of the city where the you are now.  
      The respective city names are printed on the panel cover  63  at intervals of two minutes with a reference city name printed at a 12 o&#39;clock position of GMT. When the # 1  push button switch  5   a  is pushed and then once more pushed in one second, the second hand  15   a  of the three-hand wheel train  15  moves, thereby indicating an adjacent city name. This causes the minute hand  16   a  and 24-hour hand  16   b  of the two-hand wheel train  16  to indicate a local time of the adjacent city. When the # 1  push button switch  5   a  is operated while operating the # 2  push button switch  5   b , the home time and the local time change places. When only the # 2  push button switch  5   b  is operated, the basic timepiece mode is restored.  
      When the # 3  push button switch  5   c  is operated in the basic timepiece mode, the operative mode changes to the alarm mode. At this time, the second hand  15   a  of the three-hand wheel train  15  indicates “ON” displayed in the vicinity of the 11 o&#39;clock position, and the second hand  16   a  and 24-hour hand  16   b  of the two-hand wheel train  16  indicate an alarm time. The second hand  17   a  of the second-hand-dedicated wheel train  17 , the minute, 12-hour and 24-hour hands  15   b ,  15   c  and  15   d  of the three-hand wheel train  15 , and the day indicator  26  of the day indicator wheel train  18  continue their operations performed so far, thereby indicating the reference time. When the # 4  push button switch  5   d  is operated, the basic timepiece mode is restored.  
      When the # 2  push button switch  5   b  is operated in the basic timepiece mode, the operative mode changes to the time set mode. At this time, the second hand  15   a  of the three-hand wheel train  15  indicates “Y” (Yes) displayed in the vicinity of the 3 o&#39;clock position, and the minute hand  16   a  and 24-hour hand  16   b  of the two-hand wheel train  16  indicate a result of the last reception by the antenna  8 . The second hand  17   a  of the second-hand-dedicated wheel train  17  and the minute, 12-hour and 24-hour hands  15   b ,  15   c  and  15   d  of the three-hand wheel train  15  and the day indicator  26  of the day indicator wheel train  18  continue their operations performed so far, thereby indicating the reference time.  
      When in this state the # 2  push button switch  5   b  is again operated for two seconds, the second hand  15   a  of the three-hand wheel train  15  indicates “READY” displayed in the vicinity of the 7 o&#39;clock position, the second hand  17   a  of the second-hand-dedicated wheel train  17  is returned to the reference position and the antenna  8  is caused to receive a standard time and frequency signal.  
      As described above, according to this wristwatch, the wheel train block  6  having the chronograph function comprises the in-plane arrangement of the plurality of wheel trains; that is, the three-hand wheel train  15 , the two-hand wheel train  16 , the second-hand-dedicated wheel train  17 , and the day indicator wheel train  18 . Thus, the whole thickness of the wheel train block  6  is restricted. Thus, the assembling operation is efficiently achieved. Since the circuit board  7  is disposed below the wheel train block  6  having the in-plane arrangement of the plurality of wheel trains without being divided into parts, the assembly efficiency is improved. Since each of the antenna  8  and the battery  9  is disposed compactly beside the totality of the wheel train block  6  and the circuit board  7  so as to be thinner than their total thickness. Thus, the whole timepiece does not increase in thickness.  
      The wheel train block  6  comprises the three-hand wheel train  15  in which the # 1  and # 2  pulse motors  21  and  22  turn the second, minute and 12-hour hands  15   a ,  15   b  and  15   c  attached to the corresponding coaxial shafts  31   a ,  34   b  and  36   a , respectively; the two-hand wheel train  16  in which the # 3  pulse motor  23  turns the minute and hour hands  16   a  and  16   b  attached to the corresponding coaxial shafts,  46   a  and  48   a ; the second-hand-dedicated wheel train  17  in which the # 4  pulse motor  24  turns the second hand  17   a  alone; and the day indicator wheel train  18  in which the # 5  pulse motor  25  turns the day indicator  26 . Thus, these wheel trains  15 - 18  each can be driven independently and hence changed to either a time system or a chronograph system as required, thereby providing various combinations of multi-function displays based on these systems.  
      For example, as in the above embodiment, the # 2  pulse motor  22  that turns the minute and 12-hour hands  15   b  and  15   c  of the three-hand wheel train  15 , the # 4  pulse motor  24  that turns the second hand  17   a  of the second-hand-dedicated wheel train  17 , and the # 5  pulse motor  25  that turns the day indicator  26  of the day indicator wheel train  18  can be driven for the time system. The # 1  pulse motor  21  that turns the second hand  15   a  of the three-hand wheel train  15 , the # 3  pulse motor  23  that turns the minute and hour hands  16   a  and  16   b  of the second-hand wheel train  16 , and the # 4  pulse motor  24  that turns the second hand  17   a  of the second-hand-dedicated wheel train  17  can be driven for the chronograph system.  
      For example, the # 1  and # 2  pulse motors  21  and  22  that turn the second, minute, 12-hour, and 24-hour hands  15   a ,  15   b , and  15   c  and  15   d  of the three-hand wheel train  15 , and the # 5  pulse motor  25  that turns the day indicator  26  of the day indicator wheel train can be driven for the time system. The # 3  pulse motor  23  that turns the minute and hour hands  16   a  and  16   b  of the two-hand wheel train  16  and the # 4  pulse motor  24  that turns the second hand  17   a  of the second-hand-dedicated wheel train  17  can be driven for the chronograph system. Alternatively, the respective pulse motors  21 - 25  can be driven in other different combinations of the time and chronograph systems as required and can also provide various functions including indicating the world time.  
      In this wristwatch, the three-hand wheel train  15 , the two-hand wheel train  16 , the second-hand-dedicated wheel train  17  and the day indicator wheel train  18  are assembled with the main plate  19  and the train wheel bridge  20  in a planar manner. In addition, in assembly, these wheel trains  15 - 18  operate independently and can be incorporated separately into the case, thereby further increasing the assembly efficiency.  
      In this case, the day indicator  26  of the day indicator wheel train  18  disposed concentrically on the main plate  19  overlaps with each of the antenna  8  and the battery  9  disposed at different positions in the same plane. The day indicator  26  is very thin, and the antenna  8  and the battery  9  are incorporated compactly. Thus, the whole thickness of the timepiece module  3  and hence the whole wristwatch do not increase, which brings about a wristwatch reduced in size.  
      In this wristwatch, the main plate  19 , where the wheel trains  15 - 17  are arranged, has thereon the ring-like raised guide  19   f  formed concentric therewith and having substantially the same outer diameter as the main plate for position restricting purposes. The day indicator  26  of the day indicator wheel train  18  is disposed substantially concentrically within the ring-like guide  19   f  with a ring-like gap between the day indicator  26  and the outside guide  19   f . The wheel trains  15 - 17  are arranged within the day indicator  26 . The main plate  19  therein has the plurality of guide holes  76  arranged along the ring-like gap between the main plate  19  and the day indicator  26 .  
      When the plurality of pins  77  are inserted into the like number of guide holes  76 , the day indicator  26  is easily positioned accurately in place within the ring-like guide  19   f  on the main plate  19  due to contact with the pins  77 . In this case, since only the ring-like guide  19   f  provided concentrically on the main plate and the plurality of guide holes  76  in the ring-like gap on the main plate  19  within the guide  19   f  are required. Thus, this positioning structure is simple, which allows the assembling operation to be achieved easily.  
      The day indicator  26  is supported rotatably and concentrically on the main plate  19  by the day indicator maintaining plate  55  so as to overlap in inner periphery with the same. Thus, the area of the day indicator maintaining plate  55  that is in contact with the day indicator  26  is not large. In assembly, the day indicator  26  is accurately positioned relative to the main plate  19 . Thus, the plate  55  can be easily and accurately attached to the main plate  19 .  
      When the day indicator maintaining plate  55  is fixed to the main plate  19  by the two screws  56 , a truncated conical head part  57   a  of a head  57  of each screw  56  is received in a complementary-shaped hole  55   b  formed in the day indicator maintaining plate  55 , a disk part  57   b  of the head  57  is received in a complementary-shaped recess  59  provided in the main plate  19 , and an outer threaded stem  58  of the screw  56  is screwed into an inner screwed hole  60   a  in the cylindrical female screw  60  imbedded in the main plate  19 . Thus, the tightening force of the screws  56  to the day indicator maintaining plate  55  is constant and the day indicator maintaining plate  55  is fixed to the main plate  19  without being deformed such that the day indicator  26  is supported rotatable.  
      Thus, the solar panel  11  and the dial plate  12  are assembled in a flat state over the day indicator maintaining plate  55 . In addition, the spacing between the dial plate  12  and each of the hands  15   a - 15   d ,  16   a ,  16   b  and  17   a  of the respective wheel trains  15 - 17  is sufficient to ensure that these hands are prevented from coming into contact with the dial plate  12  and can sweep well around the dial plate  12 .  
      While in the timepiece module  3  of the embodiment it is illustrated that each of the antenna  8  and the battery  9  is disposed below the day indicator  26  so as to overlap the same and that the battery  9  is disposed below each of the wheel train of the three-hand wheel train  15  and the 24-hour hand wheel  43  so as to overlap with the same, the antenna  8  and the battery  9  may be disposed on the opposite sides of the whole of the wheel train block  6  and the circuit board  7  so as not to overlap with the wheel train block  6 , as in the first modification of  FIG. 23 . Also in this case, the height of each of the antenna  8  and the battery  9  is required to be in a range of the total thickness of the wheel train block  6  and the circuit board  7 . The timepiece module  3  is supported within the case  1  by the module maintaining plate  10 . Thus, the wristwatch of the first modification is thinner than that of the embodiment.  
      While in the embodiment and the first modification the timepiece module, which comprises the wheel train block  6 , circuit board  7 , antenna  8  and battery  9  is illustrated as incorporated into the case  1  with the module maintaining plate  10 , the wheel train block  6 , circuit board  7 , antenna  8  and battery  9  may be assembled with the housing  70 , thereby forming the timepiece module  71 , which is then assembled into the case  1  with the module maintaining plate  10 , as shown in a second modification of  FIG. 24 . In this case, the whole thickness of the wristwatch increases solely by the thickness of the housing  70 , but the timepiece module  71  is easy to assemble, thereby improving productivity.  
      While in the present embodiment and the first and second modifications the multi-hand wristwatches according to the present invention have been described, the present invention is also applicable to other pocket watches, traveling watches, alarm clocks, table clocks and wall clocks.  
     Summary of the Embodiment and Modifications  
      As shown in  FIGS. 1-24 , a timepiece with a calendar function comprises: a main plate ( 19 ); and a ring-like day indicator ( 26 ) of a day indicator wheel train ( 18 ) provided rotatable concentrically with and on the main plate, the main plate having a plurality of holes ( 76 ) arranged circumferentially along the outer periphery of the day wheel disposed concentrically with and on the main plate for receiving the plurality of holes in the main plate receiving a like number of guide pins ( 77 ) so as to come into contact with the outer periphery of the day indicator disposed concentrically with and on the main plate to position the day indicator concentrically with and on the main plate.  
      According to this arrangement, when the plurality of pins are inserted into the plurality of holes in the main plate arranged circumferentially along the outer periphery of the day wheel disposed concentrically with and on the main plate, the pins cooperate to come into contact with the day indicator to adjust the position of the day indicator in radial directions and finally position the day indicator exactly concentrically with and on the main plate. This positioning structure is simple and renders the assembling operation easy because it is only required that the main plate has the plurality of holes arranged along the outer periphery of the day indicator when the same is disposed concentrically with and on the main plate and that the like number of guide pins are inserted into the plurality of holes for positioning purposes.  
      As shown in  FIGS. 1-16 , the timepiece may further comprise a day indicator maintaining plate ( 55 ) provided concentrically overlapping in inner periphery with the day indicator ( 26 ) so as to support the day indicator rotatable.  
      Thus, according to this arrangement, the area of the day indicator maintaining plate that is contact with the day indicator is small and it is ensured that the day indicator maintaining plate supports the day indicator rotatable. In assembly, since the day indicator is accurately positioned relative to the main plate, the day indicator maintaining plate can be attached easily and accurately to the main plate.  
      In the timepiece of  FIGS. 13 and 14 , the day indicator maintaining plate ( 55 ) is fixed to the main plate ( 19 ) by screws ( 56 ) that each comprise a head ( 57 ) that includes a truncated conical part ( 57   a ) received in a complementary-shaped hole ( 55   b ) provided in the day indicator maintaining plate and a disk-like part ( 57   b ) integral with the conical head part received in a complementary recess ( 59 ) provided in the main plate and an outer threaded stem ( 58 ) integral with the head screwed into an inner threaded hole ( 60   a ) in the main plate.  
      Thus, according to this arrangement, the tightening force of the screws to the day indicator maintaining plate is maintained substantially constant. Consequently, the day indicator maintaining plate is prevented from being deformed, which is liable to occur if conventional screws are used. The day indicator maintaining plate is well fixed to the main plate in a flat state and the day indicator is well supported rotatable.  
      As shown in  FIGS. 1-22B , a method of assembling a timepiece with a calendar function is provided which comprises the steps of: disposing a day indicator ( 29 ) on a main plate ( 19 ); and inserting a plurality of pins ( 77 ) provided on an assembly jig (G 2 ) into a plurality of holes ( 78 ) provided in the main plate so as to come into contact with the outer periphery of the day indicator, thereby adjusting the position of the day indicator in radial directions to position the day indicator exactly concentrically with and on the main plate.  
      According to this arrangement, when the ring-like day indicator is desired to be disposed exactly concentrically with and on the main plate, the day indicator is first disposed on the main plate. When the plurality of pins provided on the assembly jig are then inserted into the plurality of holes in the main plate, they cooperate to come into contact with the outer periphery of the day indicator, thereby adjusting the position of the day indicator in radial directions to position the day indicator exactly concentrically with and on the main plate. This positioning method is simple and the number of parts required for this positioning operation is low.  
      As shown in  FIGS. 1-24 , the plurality of hand wheel trains (three-hand wheel train ( 15 ), two-hand wheel train ( 16 ), second-hand-dedicated wheel train ( 17 )) may be arranged in a planar manner on the main plate so as to form a wheel train block having a chronograph function. The timepiece may further comprise a circuit board ( 7 ) disposed on the wheel train block for driving the same; an antenna ( 8 ) disposed at a position beside the totality of the wheel train block and the circuit board within their total thickness for receiving a standard time and frequency signal; and a power source ( 9 ), provided beside the totality of the wheel train block and the circuit board at a different position from that at which the antenna is disposed, for feeding electric power to the circuit board and other required elements.  
      Thus, according to this arrangement, the timepiece has a simple structure. In assembly, the day indicator can be easily and accurately positioned relative to the main plate.  
      More particularly, as described above, according to this timepiece, the wheel train block having the chronograph function comprises the in-plane arrangement of the plurality of wheel trains. Thus, the whole wheel train block is thin and the assembling operation is efficiently achieved. Since in assembly the circuit board can be easily in an aligning manner disposed below the wheel train block having the in-plane arrangement of the plurality of wheel trains without being divided into parts, the assembly efficiency is improved. Each of the antenna and the power source is disposed compactly beside the totality of the wheel train block and the circuit board in the range of their total thickness. Thus, the whole timepiece does not increase in thickness.  
      As shown in  FIGS. 1-24 , in the timepiece the day indicator ( 26 ) of the day indicator wheel train ( 26 ) overlaps with the antenna ( 8 ) and the power source ( 9 ) at different positions in substantially the same plane.  
      Thus, according to this arrangement, the day indicator of the day indicator wheel train overlaps with each of the antenna and the power source disposed at different positions in substantially the same plane. The day indicator  26  is very thin. Thus, the whole thickness of the timepiece module  3  and hence the whole wristwatch do not substantially increase. The antenna and the power source are incorporated compactly into the timepiece, thereby reducing the whole size of the timepiece.  
      Various modifications and changes may be made thereunto without departing from the broad spirit and scope of this invention. The above-described embodiments are intended to illustrate the present invention, not to limit the scope of the present invention. The scope of the present invention is shown by the attached claims rather than the embodiments. Various modifications made within the meaning of an equivalent of the claims of the invention and within the claims are to be regarded to be in the scope of the present invention.  
      This application is based on Japanese Patent Application No. 2005-312667 filed on October 27 and including specification, claims, drawings and summary. The disclosure of the above Japanese patent application is incorporated herein by reference in its entirety.