Abstract:
A running reserve indicator is provided for a mechanical clockwork provided with a main barrel for driving a gear-train and at least a second barrel for driving a gear-train allocated to an auxiliary function which is performed during a determined period. With the indicator, the running reserve displayed with the aid of a hand and a dial is always equal to the running reserve of the barrel having the smallest reserve.

Description:
This application is a national stage filing under 35 U.S.C. § 371 of International Application No. PCT/CH2004/000434, filed on Jul. 8, 2004. 
     TECHNICAL FIELD 
     The present invention relates to the movements of mechanical watches whose energy is provided by a spring contained in a barrel. It relates more particularly to a running reserve indicator mechanism of a mechanical timepiece movement provided with a main barrel for driving the finishing gear-train and at least one second barrel for driving a gear-train assigned to an auxiliary function that must be performed during a minimum determined period. 
     BACKGROUND 
     Such a mechanism applies particularly well to a chronograph mechanical watch movement displaying the hour and the minute of the measured time with the aid of disks. In this case, the minimum determined period is equal to the maximum measurable time. 
     It is known that this type of display, better than a display by hands, makes it possible to provide indications of large dimensions, hence quicker and easier to read, as may be desired, for example, by aircraft pilots. 
     The problem that then arises is that of the mechanical energy necessary to drive the disks. Specifically, the single barrel risks being under stress, which disrupts the amplitude of the oscillations of the balance and, consequently, the correct operation of the chronograph gear-train. 
     EP application No 03 405532.7 provides a solution to this problem by proposing a movement in which the disks of the hours, the tens of minutes and the units of minutes of measured time are each driven by their own barrel. 
     In such a product, it is very useful, to perform the chronograph function over a minimum period, for the wearer to have an indication of the running reserve the movement has, both for the basic function and for the chronograph function. 
     The object of the present invention is to respond to this need. 
     SUMMARY OF THE INVENTION 
     To achieve this objective, the running reserve indicator mechanism according to the invention, of the aforementioned type, comprises:
         running reserve indicator means comprising a hand and a dial used for reading the position of the hand,   first and second gear-trains connecting respectively the main barrel and the second barrel to said indicator means,   these means and these gear-trains being arranged so that the indicated running reserve corresponds to the time remaining to perform the auxiliary function.       

     Advantageously, the indicated running reserve is that of the barrel having the shortest reserve. 
     According to a preferred embodiment, the indicator means and the gear-trains are such that:
         so long as the timepiece operates without the chronograph function, the hand starts moving only after a running time corresponding to the difference between the running time of the main barrel and that of the second barrel,   as soon as the chronograph function is engaged, the hand starts moving and indicates the running reserve of the barrel having the shortest reserve.       

     Furthermore, the indicator means and the gear-trains are such that:
         so long as the rewinding of the timepiece has not reached a state corresponding to a running time equal to that of the second barrel, the dial rotates but the hand remains immobile,   as soon as the rewinding has reached said state, the dial and the hand rotate at the same time.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features of the invention will emerge from the following description given with reference to the appended drawing in which: 
         FIG. 1  represents a chronograph watch furnished with a movement displaying the measured time with the aid of disks; and 
         FIG. 2  is a view of the members of this movement which provide an indication of its running reserve. 
     
    
    
     DETAILED DESCRIPTION 
     The chronograph watch represented schematically in  FIG. 1  is intended to display, on a dial  10 , in conventional manner, the hour, the minute and the second of the current time with the aid of two central hands  11 ,  12  and a small hand  13  at 9 o&#39;clock. 
     The watch also displays the seconds of measured time with the aid of a central hand  14 , while the indications of the hours, tens of minutes and units of minutes of the measured time are provided respectively by three disks  15 ,  16  and  17  appearing behind windows made in the dial  10 . 
     Finally, a small hand  18  and a small rotating dial  19  are placed at 6 o&#39;clock to display the running reserve of the timepiece, as will be described with reference to  FIG. 2 . 
     The movement of this watch has, as a basis, a mechanical caliber of the chronograph type, such as that marketed by the company ETA SA (Switzerland) under the reference 7750. It is coupled to a complementary mechanism described in detail in the abovementioned EP document and driving the disks  15 ,  16  and  17 . 
     In conventional manner, a crown  20  is used for rewinding and setting the time, while two pushbuttons  21  and  22  control respectively the starting and stopping and zeroing of the chronograph mechanism. 
     Reference will now be made to  FIG. 2 , split into two parts  2   a  and  2   b , in which only the members participating in the function for displaying the running reserve are represented. 
       FIG. 2   a  represents at reference number  23  the barrel of the basic movement which forms the main motive force of the watch. This barrel, which typically has a running time of approximately 40 hours, comprises, inside its drum, a spring (not shown) furnished with a sliding strap that is used, when it is fully primed, to limit its being overstressed. Its shaft  24  supports a ratchet  25  that may be driven, from the crown  20 , by the rewind gearwheel and the crownwheel (not shown). The external tooth gear  26  of the drum engages with the finishing gear-train (not shown) which drives the hour hand  11 , minute hand  12  and second hand  13 . 
     Opposite the ratchet  25 , the shaft  24  supports a wheel  27  engaging with an angle transmission  28  which itself engages with a wheel  29  attached to the shaft  30  of a second barrel  31  whose drum also contains a spring with sliding strap and whose running time is that during which the chronograph function must be performed. Typically, this running time is 10 hours. The external tooth gear  32  of the drum of this barrel engages with a gear-train (not shown) driving the disk  17  for displaying the units of minutes of the measured time. The shaft  30  also supports, on the same side, a ratchet  33  which engages with a gear-train terminating at the ratchet of a third barrel (not shown) used to drive the disk  16  for displaying the tens of minutes of the measured time. 
     As described in the EP document already cited, the third barrel actuates a fourth barrel used to drive the disk  15  for displaying the hours of the measured time. 
     Opposite the ratchet  33 , the shaft  30  supports a gearwheel  34  which engages with a wheel  35  whose gearwheel  36  engages with a wheel  37  furnished with a lug  38  and supporting the running reserve indicator dial  19 . 
     The wheel  37  is mounted pivotingly on a shaft  39  on which are mounted the hand  18  indicating the running reserve and, opposite, a wheel  40  (visible in  FIG. 2   b ) furnished with a circular opening  41  whose length corresponds to the time during which the chronograph function must be performed, that is approximately 10 hours. 
     Opposite the hand  18 , the shaft  39  supports, friction-mounted, a wheel  42  which engages with the gearwheel  43  of a wheel  44  whose shaft is used as a pivot to the wheel  35  and which engages with a second gearwheel  45  supported by the shaft  30  of the second barrel  31 . 
     As shown in  FIG. 2   b  in which the hand  18 , the dial  19  and the associated members described with reference to  FIG. 2   a  can be seen, the shaft  39  supports, between the open wheel  40  and the friction wheel  42 , a gearwheel  46  which engages with an angle transmission  47  engaging with a wheel  48  furnished with a circular opening  49  whose length corresponds to a rotation period of approximately 30 hours. A wheel  50 , mounted free in rotation on the shaft  51  of the wheel  48 , is furnished with a lug  52  situated in the opening  49 . 
     The wheel  50  engages with a gearwheel  53  whose shaft  54  supports, friction-mounted, a wheel  55  engaging, by means of an angle transmission  56 , with a gearwheel  57  whose shaft  58  supports a gearwheel  59  engaging, by means of a wolf-tooth gear, with a mobile  60  which engages with the external tooth gear  26  of the drum of the main barrel  23 . 
     The operation of the mechanism according to the invention will now be described in the following four situations:
         rewinding the first 10 hours,   rewinding beyond 10 hours,   running without the chronograph function,   running with the chronograph function.
 
1. Rewinding the First 10 Hours
       

     When the ratchet  25  is driven, from the crown  20 , by the rewind gearwheel and the crown wheel, the shaft  24  rewinds the spring of the main barrel  23  and, at the same time, the spring of the second barrel  31  by means of the mobiles  27 ,  28  and  29  and the shaft  30 . 
     The gearwheel  34 , also supported by the shaft  30 , drives, by means of the wheel  35  and its gearwheel  36 , the wheel  37  and the running reserve indicator dial  19  which, rotating in the anticlockwise direction, causes the hand  18 , practically immobile, to indicate an increase in the running reserve. At the same time, the lug  38  of the wheel  37  moves freely in the opening  41  of the wheel  40  which, therefore, does not rotate. 
     When the rewinding reaches a state corresponding to a running time of at least 10 hours for the two barrels, the hand  18  indicates, on the dial  19 , a running reserve of 10 hours. The lug  38  also reaches abutment against the end of the opening  41  of the wheel  40 . 
     2. Rewinding Beyond 10 Hours 
     When the rewinding continues, the wheel  40  starts rotating under the action of the lug  38 , thus driving the hand  18  at the same time as its dial  19 , so that the running reserve display remains on 10 hours. Since the wheel  42  is friction-mounted on the gearwheel  46 , it remains in a position corresponding to that of the barrel  31  with which it is connected via the gearwheel  43 , the wheel  44  and the gearwheel  45 . 
     The wheel  40  also drives, via the gearwheel  46  and the angle transmission  47 , the wheel  48  whose opening  49  receives the lug  52  of the wheel  50 . When the rewinding reaches a state corresponding to a running period of approximately 30 hours, this lug reaches abutment against the end of the opening  48 . The wheel  50  therefore begins to rotate and, by means of the mobiles  53 ,  55 ,  56 ,  57  and  58 , drives the gearwheel  59 . The latter, however, due to the presence of the wolf-tooth gear mobile  60 , has no effect on the main barrel  23 . 
     It will be noted that, due to the use of springs with sliding strap, the rewinding by the actuation of the rewinding crown  20  may continue without damage. 
     3. Running without the Chronograph Function 
     In normal operation of the watch, the drum of the main barrel  23  is the only element in action and therefore drives the gear-train for displaying the current time via its outer tooth gear  26 , which also drives the wolf-tooth gear mobile  60  which, in this direction of rotation, communicates its movement to the lugged wheel  50 . 
     Accepting that the timepiece has been fully rewound, the wheel  50  will thus rotate for approximately 30 hours without influencing the display of the running reserve, still on 10 hours, because its lug  52  circulates freely in the opening  49  of the wheel  48 . At the end of these 30 hours of running, the lug reaches abutment on the end of the opening  49  and the wheel  48  starts rotating. By means of the angle transmission  47 , the gearwheel  46  and the shaft  39 , it begins to cause the running reserve indicator hand  18  to rotate in the anticlockwise direction from the 10-hour position. Although the second barrel  31  is inactive and wheel  42  is therefore immobile, the movement of the hand  18  is allowed since this wheel is friction-mounted on the shaft  39 . 
     When the hand  18  has thus traveled along a path corresponding to the movement of the lug  38  in the opening  41  of the wheel  40 , that is 10 hours, it will indicate a 0 reserve on the dial  19  and the main barrel  23  will therefore be discharged by approximately 40 hours. 
     It will be noted that, thanks to the presence of the friction wheel  55  inserted in the gear-train linking the shaft  39  to the barrel  23 , the latter is not prevented from discharging completely when the hand  18  reaches the 0 position. 
     4. Running with the Chronograph Function 
     As soon as the chronograph function is engaged, the second barrel  31  is put into action every minute and influences the indication of the running reserve. Its gearwheel  45  therefore begins to drive, by means of the wheel  44 , the gearwheel  43 , the wheel  42  and the shaft  39 , the running reserve indicator hand  18  which begins to move in the anticlockwise direction. The shaft  39  drives the gearwheel  46  and the wheel  40 . The latter engages via its gearwheel  46  with the angle transmission  47  which drives the open wheel  48 . 
     Evidently, the main barrel is still in action and drives the wheel  50  whose lug  52  will reach abutment against the end of the opening  49  of the wheel  48  after 30 hours, to which is added the time during which the chronograph mechanism has operated, because of the synchronous movement of the wheels  50  and  48 . In other words, if the chronograph mechanism has been engaged for 3 hours, the lug  52  will reach abutment only after 33 hours. As the hand  18  indicates a running reserve equal to 10 hours minus 3 hours, it will reach zero after 40 hours of operation of the main barrel. 
     If the measurement of a measured time begins while the running reserve of the main barrel is less than 10 hours, the lug  52  also causes the wheel  48  to rotate. It is then essential to prevent the two barrels adding their actions together on the control of the hand  18 . 
     It will be noted that, for this purpose, the wheel  48  is also acted upon by the rotation of the wheel  42  driven by the second barrel  31 . Thus, because the wheels  48  and  50  are driven at the same speed and, due to a gear shake equal to at least one minute (made necessary by the fact that the barrel  31  advances in steps of one minute), the lug  52  of the wheel will remain in the same position relative to the end of the opening  49  of the wheel  48 . Thanks to these arrangements, the hand  18  is thus driven without conflict between the two barrels, the same displayed running reserve corresponding to that of the main barrel. 
     The mechanism described is incorporated into a watch furnished with a manual rewind of the barrel springs. It is evident that it may be directly applied to a watch with automatic rewind. 
     In this way, a mechanism for displaying the running reserve is proposed indicating only the running time necessary to perform the chronograph function, set at 10 hours, while the timepiece has, for the current time display function, a reserve of 40 hours. 
     In other words, the indicator hand  18  is driven degressively, from 10 hours to 0:
         either after 30 hours of operation of the timepiece, so long as the chronograph is not engaged,   or as soon as the chronograph is engaged, which requires a reserve of 10 hours.