Abstract:
A device comprises a basic clock movement MB whose time indicators are driven by a first barrel connected to a first wheelwork and a first regulator organ, and an autonomous chronograph module MCA whose indicators are driven by a second barrel independent from the first, connected to a second wheelwork and a second regulator organ. The chronograph module is exclusively composed of mechanical elements. The frequency of oscillation supplied by its regulator is equal N times the frequency of oscillation supplied by the regulator of the base movement, with the coefficient N being definable according to a specific application of the chronograph, so that any chronograph module thus previously defined can work with-the same base movement. The chronograph regulator remains constantly engaged with the corresponding wheelwork. The chronograph module allows a time interval to be read with a minimum precision of a hundredth of second. The organs of the base movement and of the chronograph module are arranged in such a way that in assembled state, the height and overall diameter do not exceed 7.75 mm and 30 mm respectively, the dimensions of the chronograph itself being not greater than 4 mm (height) and 30 mm (diameter) when its elements are mounted on a bottom plate, so that the device can advantageously be integrated in the case of a wrist-watch and affords an aesthetic exterior.

Description:
REFERENCE DATA  
       [0001]     This application is a continuation of international PCT application PCT/CH03/00063 (WO03/065130) filed on Jan. 27, 2003, claiming priority of European patent application EP02405063.5 filed on Feb. 1, 2002, the contents whereof are hereby incorporated. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention concerns a device comprising a usual clock movement and a chronograph module according to the preamble of the independent claim  1 .  
       DESCRIPTION OF RELATED ART  
       [0003]     The market of chronograph watches equipped with a device of this kind has developed considerably during the past years, in particular in the up-market segment. However, a very large proportion of such watches comprise a chronograph plate (hereafter called indifferently chronograph part, module or movement) having a quartz oscillator, whilst a certain clientele feels increasingly attracted to mechanical chronograph watches. With the latter, however, and for reasons that will be explained below, the one skilled in the art encounters notably a problem as regards the precision (also called resolution) of reading.  
         [0004]     Wrist-watches whose case holds a chronograph module or movement equipped with a quartz oscillator enable the wearer to perform measurements of a precision that depends on the type of display, namely on the order of the tenth or of the hundredth of second, according to whether this display is analog or digital respectively.  
         [0005]     CH-667,771 describes a chronograph watch comprising a common central clock movement driving the hour, minute and seconds hands and an autonomous chronograph movement presenting a timekeeper and at least one indicator driven by an electric motor. The organs of the chronograph movement are arranged at the periphery of the usual movement or of the base movement. Each movement comprises its own regulator oscillating at the same frequency as the other. The chronograph movement is provided with an independent case in the shape of a bell covering the basic clock movement and encircling the latter. The two movements are connected by means of a plate interposed between them.  
         [0006]     This construction aims at making an electric chronograph watch at low cost. On the other hand, the precision remains very questionable, the chronograph hand beating the fifth of second (which corresponds to an oscillator at 18&#39;000 oscillations per hour). Furthermore, this document does not supply any teachings to the one skilled in the art as to the arrangement of the organs of the chronograph module or movement, supposing this module were mechanical, nor as to the cooperation between a module of this type and the usual basic clock movement.  
         [0007]     Yet, this arrangement and cooperation gives rise to complex problems as regards reliability and execution both on the technical and on the aesthetic levels—which are not at all resolved by using a quartz chronograph but merely avoided by being circumvented—to a point where the one skilled in the art has always been dissuaded from contemplating said arrangement and said cooperation and a fortiori from assigning himself the task of realizing them.  
         [0008]     In fact, the measurement precision of mechanical chronographs currently available on the market is, for the most part, on the order of 0.125 seconds, the corresponding balance oscillating at 28&#39;800 oscillations per hour, and, more rarely, for certain other, considerably more expensive mechanical chronographs whose balance oscillates at 36&#39;000 oscillations per hour, on the order of 0.1 seconds. This measurement precision cannot be increased with the mechanical chronographs having a common time base for the clock part and the chronograph part, for several reasons. The use for the clock part of a balance oscillating at a greater frequency would modify the unwinding speed of the barrel spring and would diminish the movement&#39;s power-reserve time. Furthermore, an ensemble comprising an escape wheel, pallets, an impulse-pin and a balance pivot, that would be subjected continuously to such service conditions, would show after a couple of months already considerable wear that would inevitably cause an irreversible alteration of the good running of the movement. It must also be stressed that at a high frequency, the energy transmission from the barrel to the sprung balance through the wheelwork and the escapement poses, in continuous use, problems whose solutions would most probably imply the use of complex means that would nevertheless still remain chancy. Thus, by way of example, a balance oscillating at a high frequency has a lower amplitude than the same balance oscillating at a lower frequency. Therefore, it will be more sensitive to variations of the barrel spring&#39;s driving torque and will offer running stability only during the period where the variation curve of said driving torque of the spring is linear.  
         [0009]     Further to these difficulties are those raised by the questions of cost and aesthetics. On the one hand, it is known that a horological piece and in particular a wrist-watch housing a device comprising a basic clock movement and a fully mechanical chronograph movement is in principle classified in the top of the range. Its price is thus high whilst the precision of its chronograph movement is low and does not even achieve that of a low-market digital display quartz chronograph movement. On the other hand, the making of a horological piece housing a double movement, clock and chronograph, both mechanical, conceivably confronts the clockmaker with a delicate problem of space requirement or volume of the piece, a problem that in the absence of a solution will result in wanting aesthetics likely to compromise the commercial success of the watch. One solution that springs to mind would consist in miniaturizing the organs composing the mechanical chronograph. But although it would serve the aesthetic aspect, it would go against the aim of cost-effectiveness and would certainly raise major technical difficulties. Choosing and applying this solution would therefore not be without technical and commercial risks. These risks seem sufficiently dissuasive to invite the one skilled in the art to conceive and investigate other paths in order to realize the device with a quality to price ratio that is as advantageous as possible.  
         [0010]     It is one aim of the invention to propose a device that palliates the inconvenience of lack of precision while ensuring furthermore a truly reliable reading whatever the characteristic of the chosen regulator, and thus of the expected precision, and excluding all aforementioned disturbances on the clock part of the device&#39;s movements.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     This aim is achieved with the means described in the independent claim  1 , the dependent claims relating to means permitting preferred embodiments of the invention, furthermore at low cost, in keeping with the aforementioned quality-price ratio.  
         [0012]     Tests performed on inventive prototypes equipped with a chronograph whose balance oscillated at 360&#39;000 oscillations per hour made it possible to ascertain that a precision on the order of the hundredth of second was ensured even in continuous use during at least thirty minutes. In other words, the device according to the invention renders possible the making of a top-of-the-range horological piece that is truly fully mechanical and whose chronograph precision bears comparison with a high-quality quartz chronograph. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     An embodiment of the device will be described in detail hereafter, by way of a non-limiting example, supporting the attached drawings, in which:  
         [0014]      FIG. 1  shows a top view of a horological piece in the form of a wrist-watch incorporating a device according to the invention,  
         [0015]      FIG. 2  shows a perspective view of the device in non-assembled state,  
         [0016]      FIG. 3  shows a perspective view of only the chronograph module,  
         [0017]      FIG. 4  shows a perspective representation of the regulator organ, of the wheelwork and of the barrel of the chronograph module,  
         [0018]      FIG. 5  shows a perspective view of a motion-work and small seconds hand gear system of the chronograph module,  
         [0019]      FIG. 6  shows a perspective view of a winding system of the chronograph module,  
         [0020]      FIG. 7  shows a perspective view of a power reserve of the chronograph module,  
         [0021]      FIG. 8  shows a variant embodiment of the example of embodiment represented in FIGS.  1  to  7 ,  
         [0022]      FIG. 9  is a cross-section view of the reset and rewind device in several parts,  
         [0023]      FIG. 10  is a cross-section view of the date correction transmission device from the base movement towards the auxiliary module, and  
         [0024]      FIG. 11  is a diagram indicating the torque of the barrel spring necessary to guarantee a given power-reserve. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     The device according to the invention will be applied advantageously in a chronograph wrist-watch (not specifically referenced), as represented in  FIG. 1 . This watch shows: at two o&#39;clock, a push-piece winding-button (crown)  1  for winding a barrel of the device&#39;s chronograph module—hereafter called autonomous chronograph module MCA—and for commanding the starting and stopping functions of the autonomous chronograph module MCA, at three o&#39;clock, a winding-button (crown)  2  of the device&#39;s clock movement—hereafter called base movement MB—and at 4 o&#39;clock, a push-piece  3  actuated for the resetting to zero and for the flight returning of the autonomous chronograph module MCA. In a preferred embodiment illustrated further below in relation to  FIG. 9 , the watch comprises a single winding-crown allowing to simultaneously reset and rewind, in different axial positions, the base movement MB and the auxiliary chronograph module MCA.  
         [0026]     The chronograph watch enables the displaying of the current time by means of an hour hand  5 , of a minutes hand  5  and of a small seconds hand  6  placed at three o&#39;clock. It also allows the displaying of the measurement of an elapsed time by means of a thirty minute counter  7 , placed at nine o&#39;clock at provided with a hand  8 , a chronograph centre seconds hand  9  and a hundredth of second counter  10  placed at six o&#39;clock and provided with a hand  11 . A power-reserve counter  12  of the autonomous chronograph module MCA provided with a hand  12  and placed at twelve o&#39;clock serves to verify said module&#39;s autonomy until the next winding. The graduations of these different counters are indicated on a dial  14 ; in particular, the hundredths of second correspond to hundred markings materialized on a circular scale, the hand  11  effecting a 360° rotation per second to ensure a comfortable and accurate reading of the time interval.  
         [0027]      FIG. 2  is a perspective view showing the principle of the assembly of the autonomous chronograph module MCA with the base movement MB, centring elements and fastening organs being provided. By way of a non-limitative example, the base movement can for example be constituted by a movement of the type 2892 sold by the company ETA SA. A base plate  76  of the autonomous chronograph module MCA exhibits two holes (not visible and not referenced) in which are driven cylindrical pins  16 ,  17  designed to engage in dial pin holes  18 ,  19  of a bottom plate  15  of the base movement MB, for the purpose of a correct angular positioning of the MCA module relative to the MB movement. Fastening means connect the base movement MB and the autonomous chronograph module MCA at their periphery. According to the example, screws  20 A,  21 A go through holes (not visible and not referenced) provided in the plate  76  and are screwed in corresponding threaded holes  20 ,  21  of the bottom plate  15 . Are further represented in this  FIG. 2 : on the one hand, on the autonomous chronograph module MCA and projecting from its flank, a push-piece stem  1 A designed to receive the push-piece winding-crown  1  ( FIG. 1 ) and, emerging from its upper side, a staff  71  of the minutes train, a staff  67  of the seconds train, a staff  61  of the hundredth of second train and a staff  88  of the small seconds hand; on the other hand, on the basic module MB and projecting from its flank, a push-piece stem  2 B designed to receive the winding-crown  2  ( FIG. 1 ) and, emerging from its upper side, in the centre, a wheel  86  of the seconds train and a wheel  77  of the minutes train. As mentioned further above, a single rewind-button (crown) could, by means of the mechanism illustrated in  FIG. 9 , be used to actuate axially and rotationally the two stems  1 A and  1 B.  
         [0028]      FIG. 3  is a perspective view of the two movements in assembled state, showing essentially the autonomous chronograph module MCA covering the base movement MB (visualized principally by its bottom plate  15  and its winding-crown stem  2 B) and illustrating the remarkable and original arrangement and conformation of the main organs and elements of the autonomous chronograph module MCA on its base plate  76 . This extremely closely packed and compact arrangement results from an optimum exploitation of the available volumes, which avoids a costly miniaturization of said organs and elements without sacrificing the aesthetics, this design and construction enabling the device&#39;s dimensions in assembled state to be reduced to extremely low values. According to the described embodiment, these values are on the order of 7.75 mm (height) and 30 mm (overall diameter), whilst the dimensions of the chronograph module MCA itself do not exceed values on the order of 4 mm (height) and 30 mm (diameter). It will be understood that these dimensions afford a wide and extremely varied choice of exteriors for the device and a remarkable and effective aesthetic.  
         [0029]     In order to reduce even further the height of the chronograph movement, it is conceivable to place the elements—which will be discussed in more detail further below (notably regulator organs, barrels, respective wheels, power-reserve, levers, winding systems)—on bridges arranged appropriately, from a single bottom plate, with the basic and chronograph movements then overlapping each other, without preventing the chronograph module&#39;s good running according to the methods that will be described hereafter, although the manufacturing costs will be increased.  
         [0030]     The autonomous chronograph module MCA is equipped with its own barrel  22  and its own regulator organ comprising notably a balance  23 . This characteristic precludes any power take-off on the base movement MB and enables the balance  23  to be stopped without disturbing the sprung balance of the base movement MB.  
         [0031]     The chronograph MCA is started and released by a pressing briefly on the push-piece stem  1 A, i.e. on the winding-crown  1 . Each of these pushing actions produces a displacement in the direction of the chronograph MCA&#39;s centre of a plate  24  comprising grooves in the shape of oblong openings  25 ,  26 , with this displacement, which is guided by screws  27 ,  28  working with said grooves, simultaneously actuating a beak  29 . When the pressure is released, the plate  24  and the beak  29  take their initial positions under the action respectively of a wire spring  40  and of a drawback spring  41 .  
         [0032]     From an initial position (chronograph stopped, i.e. set at zero), the extremity of the beak  29 , pivoting around a pin  30 , comes into contact with a flank of a central wing of a cam  31  and makes said cam  31  turn around an arbor  32  by an angle defined by a stop  33 . A catch  34  then drives a lever  35 , a catch  39  makes a launcher  36  pivot around its arbor  37 , and a spring-blade  38  projects tangentially from the outer side of the balance  23 . In so doing, the spring  38  supplies to the balance  23  a starting impulse to put it into motion. A new pressing on the winding-crown  1  leads to the stopping of the chronograph at the end of an identical but inverse process (initial position corresponding to that illustrated in  FIG. 3 , with the balance in motion), with the spring-blade  38  this time coming tangentially into contact with the outer side of the balance  23  and immobilizing the latter.  
         [0033]     A pressure exerted on the push-piece  3  ( FIG. 1 ) causes a resetting to zero of the chronograph module MCA.  
         [0034]     Each resetting to zero is effected by actuating a single hammer  48 . The aforementioned pushing action on the push-piece  3  makes a lever  42  and consequently its beak  44  pivot around a pillar staff  43 , which causes a reverser  45  to be driven with its pin  46 , the latter itself commanding a lever  47  that makes the hammer  48  pivot, which causes the hammer&#39;s three beaks (not referenced) to drop onto cams (heart-pieces)  49 ,  50 ,  51  mounted on the mobiles of the minutes counter, of the seconds counter and of the hundredth of second counter (see also  FIG. 4 ) and thus causes the resetting to zero of the chronograph module MCA.  
         [0035]     When the lever  42  is pushed, the beak  44  remains in contact with the reverser  45  during approximately two thirds of the angular space described by the lever  42  around the pillar staff  43 , then said beak  44  separates tangentially from the extremity of the reverser  45  and the latter returns to its initial position under the action of a drawback spring wound around the pivoting axis of said reverser  45  (in  FIG. 3 , neither this drawback spring nor this pivoting axis are referenced, the pivoting axis being moreover hidden by the reverser  45 ).  
         [0036]     The hammer  48  is fastened to the wheelwork bridge  52  by a screw  53  and an eccentric washer  54 . The eccentric washer  54  enables the regulation of the hammer  48  to be adjusted so that the three beaks of said hammer  48  press simultaneously on the three heart-pieces  49 ,  50  and  51 , the resetting to zero of the chronograph module MCA being thus performed just before the beak  44  leaves the reverser  45 .  
         [0037]     The consequences during the resetting to zero of the chronograph module MCA differ according to whether the balance  23  is stopped or moving.  
         [0038]     If the balance  23  is stopped, the spring-blade  38  is in contact with the balance  23  and the friction exerted by the staffs  61 ,  67 ,  71  ( FIGS. 2 and 4 ) on the wheelwork has no influence on the balance  23 .  
         [0039]     On the other hand, if the balance is moving, the spring-blade  38  is not in contact with the balance  23  and the friction exerted by the staffs  61 ,  67  and  71  on the wheelwork will tend to brake the balance  23 .  
         [0040]     When the pressure on the lever  42  is released, the beak  44 , held by a drawback spring  56 , can pivot around a pin  55  to avoid the reverser  45  and enable the lever  42  to take back its initial resting position under the action of a drawback spring  57 .  
         [0041]     The operating principle described here above thus serves to prevent said balance to stop because of a prolonged friction of the staffs  61 ,  67  and  71  when the autonomous chronograph module MCA is reset at zero with the balance  23  being in motion.  
         [0042]     Thus, a same pressure exerted on the push-piece  3  ( FIG. 1 ) causes a resetting to zero of the chronograph module MCA when the balance  23  is stopped, and a resetting to zero of the chronograph module MCA (operation called flight returning) followed by an automatic restarting of a new measurement (without obligation to push again the push-piece stem  1 A) when the balance  23  is in motion.  
         [0043]     The sprung balance ensemble of the chronograph&#39;s regulator organ is stopped when the latter is not in use.  
         [0044]      FIG. 4  is a perspective view illustrating the arrangement of the regulator organ, of the wheelwork and of the barrel mounted on the base plate  76  of the autonomous chronograph module MCA. According to the example, in this configuration, the sprung balance  23  ensemble is dimensioned to oscillate at a frequency of 360&#39;000 oscillations per hour.  
         [0045]     In the formula:  
       f   =       1     2   ⁢   Π       ⁢       M   I             
 
         [0046]     It is observed that for a given balance-spring, the frequency is inversely proportional to the square root of the moment of inertia of the balance whose formula can be assimilated to that of a hollow cylinder:  
       I   =       1   2     ⁢     m   ⁡     (       R   2     +     r   2       )             
 
 where:  
             m   =     Π   ⁢           ⁢   h   ⁢           ⁢     ρ   ⁡     (       R   2     -     r   2       )                     I   =       1   2     ⁢   Π   ⁢           ⁢   h   ⁢           ⁢   ρ   ⁢           ⁢     (       R   4     -     r   4       )                 
 
 which leads to:  
       f   =       1     2   ⁢   Π       ⁢       M       1   2     ⁢   Π   ⁢           ⁢   h   ⁢           ⁢   ρ   ⁢           ⁢     (       R   4     -     r   4       )                 
        f Frequency [Hz]    M Elastic torque of the balance-spring [Nm]    I Moment of inertia of the balance [kg·m 2 ]    R Outer radius of the balance [m]    r Inner radius of the balance [m]    h Thickness of the balance [m]    p Specific weight of the balance [kg/m 3 ]       
 
         [0056]     By introducing values for f, R and r in this function, it will be observed that if the frequency is increased for example from 28&#39;800 to 360&#39;000, the diameter of the balance can be divided by approximately five. Experience shows that a balance that is too small does not ensure a good running stability and gives rise to regulating problems. The solution therefore consists in adopting a compromise between a reduction of the balance&#39;s outer diameter, which makes it easier to integrate it in the autonomous chronograph module MCA, and an increase of the balance-spring&#39;s accelerating power as defined by its CGS number.  
         [0057]     In view of these observations, a balance-spring will thus be chosen having technical characteristics allowing a balance to be chosen with dimensions such that the regulator oscillates at the predetermined frequency, that the regulator organ offers good regulating quality and that the balance can be efficiently restarted by the blade-spring  38 .  
         [0058]     A pallet  113  and an escape wheel  58  can be seen in  FIG. 4 ; these elements can be chosen from existing supplies. According to an embodiment of the device described by way of example, a wheel  59 , driven on the staff of the escape wheel  58 , is chosen so that it turns at a speed of 2.5 turns per second, the balance  23  oscillating according to the example at 50 Hz (i.e. 360&#39;000 oscillations per hour). A wheel  60  of the hundredth of second train turns clockwise at a speed of one turn per second. A wheel (not visible in the figure because it is hidden by the heart-piece  51 ), united with the wheel  60 , is mounted on the staff  61  of the hundredth of second train and meshes with a wheel  62  driven on a pinion  63 , the latter meshing with a wheel  64 . A wheel  65  of the seconds train turns clockwise at a speed of one turn per minute thanks to a reverser  66  that connects it to the wheel  64 . A wheel  84  (represented in  FIG. 5 ), hidden by the heart-piece  50  and united with the wheel  65 , is mounted on the staff  67  of the seconds train. This wheel  84  meshes with a wheel  68  driven on a staff united with a wheel  69  that drives a wheel  70  mounted on the staff  71  of the minutes train. The wheel  70  turns clockwise at a speed of one turn in thirty minutes, it meshes with a wheel  72  driven on a staff  73  united with a wheel  74  that meshes with a toothed transmission-wheel  75  of the barrel  22 , with the latter unwinding clockwise under the action of the barrel spring (not represented) at a speed of one turn in 29.7 minutes.  
         [0059]     In a mechanical movement, the barrel spring is generally calculated to perform about 7.5 turns. According to the described embodiment, for reasons of limiting the space requirements, the barrel spring is dimensioned to enable the barrel to perform approximately six turns, which equals a power-reserve of 178.2 minutes. But as explained above, use of a regulator organ whose sprung balance ensemble oscillating at high frequency (360&#39;000 oscillations per hour) reduces use of the motor torque of the barrel spring to the period during which the function Δ motor torque/Δ time is linear, means that the useful power-reserve of the autonomous chronograph module MCA is on the order of hundred and twenty minutes (see  FIG. 12 ).  
         [0060]     During a measurement with a usual mechanical chronograph, the wheelwork of the chronograph part must be uncoupled from the wheelwork of the horological part. In order to prevent the chronograph hands from floating, it is indispensable to immobilize the wheels of the mobiles carrying said hands. With the autonomous mechanical chronograph module MCA according to the invention, this immobilizing operation is not necessary, since—as has emerged from the above description of the wheelwork of the autonomous chronograph module MCA—the gear-train remains permanently constrained by the barrel spring due to the fact that there is no uncoupling system and that on all the mobiles carrying several wheels (for example the wheels  84  and  65  of the seconds train or even the escape wheel  58  and the wheel  59  mounted on the same staff), the latter are united with one another. These characteristics guarantee a permanent rate-resumption of the train-gears.  
         [0061]     Furthermore, on a usual chronograph, the operation of uncoupling the wheelwork of the chronograph part from the wheelwork of the horological part (base movement MB or intermediate wheels of the base movement situated in the chronograph module), and/or of uncoupling these wheelworks from one another, causes jumps, in particular during starting up of the chronograph, which can distort the measurement by several tenths of seconds. This defect is avoided by the present invention. To effect the resetting to zero of the counter hands mounted on the staffs  61 ,  67  and  71  ( FIG. 4 ), the latter are mounted on their respective trains with a known friction system (for example, by an elastic washer, by indenting, etc.).  
         [0062]     As compared with a mechanical chronograph comprising an additional usual chronograph module in which the wheelwork and the arrangement of the counters can be modified, the present invention further gives the possibility of modifying the frequency of oscillation of the balance-spring, the measurement resolution and the power-reserve of the autonomous chronograph module MCA. Generally, the frequency of oscillation supplied by the regulator of the autonomous chronograph module MCA is equal to N times the frequency of oscillation supplied by the regulator organ of the base movement MB; for example, for a base movement of a frequency of 28&#39;800 oscillations per hour, N can be chosen at 12.50, so that the autonomous chronograph module MCA beats the hundredth of second. These characteristics allow the realization of a practically unlimited range of products in all the sectors and commercial niches, from the chronograph watches for the general public to those of top-of-the-range watch-making, up to products reserved for professional use.  
         [0063]      FIG. 5  illustrates one of the many ways of transferring the time indications supplied by the base movement MB through the autonomous chronograph module MCA to the time hands  4 ,  5  and  6  placed on the dial  14  ( FIG. 1 ).  
         [0064]     The wheel  77  mounted on the cannon-pinion of the base movement MB meshes with an intermediate wheel  78  driven on a staff  79  united with the intermediate wheels  80 ,  81 . The intermediate wheel  80  drives a cannon-pinion  82  carrying the minutes hand  5  and mounted freely on a tube  85 , with the intermediate wheel  81  driving an hour-wheel  83  carrying the hours hand  4 .  
         [0065]     A wheel  86  mounted on the seconds staff of the base movement MB meshes with an intermediate wheel  87  that drives a wheel  89  driven on a staff of the small seconds hand  88  placed at three o&#39;clock. To avoid floating of the small seconds hand  6 , a wire spring (not represented) can press inside a groove  90  of the staff  88  of the small seconds hand.  
         [0066]     This design makes it possible to arrange—according to a current practice—the staff  67  of the trotteuse (direct-drive seconds-hand)  9  of the chronograph in the centre of the MCA module (see also  FIG. 4 ) and offers the user a display of the time interval measured by the autonomous chronograph module MCA.  
         [0067]     It is obvious that other designs can easily be conceived. Thus,  FIG. 8  (comparable to  FIG. 2 ) represents a variant embodiment according to which a seconds staff  67 B, a cannon-pinion  82 B and an hour-wheel  83 B of the base movement MB have been extended so as to go through a central opening  115  of the autonomous chronograph module MCA and to display the hour, minute and second in the centre of the dial  14 . According to this embodiment, the seconds hand of the autonomous chronograph movement MCA is borne by a staff  88 A placed at three o&#39;clock on a counter.  
         [0068]      FIG. 6  is a perspective representation of the winding system of the autonomous chronograph module MCA mounted on the base plate  76 . The manual winding of the barrel  22  is performed by rotating the push-piece stem  1 A, in resting position, in the same clockwise direction than that required for manually winding the basic mechanical movement MB, necessary for restarting the latter when it has not been worn during a sufficiently long period and the barrel spring is totally unwound (automatic movement). The push-piece stem  1 A is guided by a block  91  and held in place by a spring-blade  92 . A pressure exerted from below on the extremity of a catch  93  frees the push-piece stem  1 A and makes it possible to remove the movement from its case represented in  FIG. 1  and not referenced, provided that the same operation is effected on the winding-crown stem  2 B (not represented in this Figure).  
         [0069]     A bevel-wheel  94  actuated by a driving square  95  of the push-piece stem  1 A drives an intermediate wheel  96  meshing with a coupling wheel  97 . This wheel  97  is engaged with an intermediate wheel  98  if it turns anti-clockwise around its staff  114 , or uncoupled from this intermediate wheel  98  if it turns clockwise, the staff  114  being truncated in amygdaline shape. The intermediate wheel  98  driven by the coupling wheel  97 , when it turns anti-clockwise, meshes with an intermediate wheel  99  actuating a ratchet  100  mounted on a core  101  of the barrel  22 . The winding of the barrel spring is thus effected by rotating the ratchet  100  clockwise (the clicking system required for conserving the energy stored by the barrel spring during winding, known by the one skilled in the art, is not represented).  
         [0070]      FIG. 7  represents in perspective an embodiment of a power reserve device of the autonomous chronograph module MCA, the information relating to the power reserve being displayed at noon on the dial  14  by the hand  12  ( FIG. 1 ). According to the embodiment, it is necessary that one turn of the ratchet  100  ( FIG. 6 ) during winding causes an angular displacement of a staff  102  of power reserve around its axis, equal to and in opposite direction to that generated by one turn of the transmission-wheel  75  of the barrel  22  on the same staff  102  during operation of the autonomous chronograph module MCA. During winding, the ratchet  100  and the wheel  98  driven on the staff  106  turn at the same speed and in the same direction (clockwise), one wheel  103  united with a staff  106  meshes with an outer teething of a sun crown  104 , the inner teething of the sun crown  104  drives a planetary wheel  105 , the wheel  105  being united with a planetary wheel  107  pressing on an inner teething of a sun crown  108  for making the staff  102  of the power reserve turn anti-clockwise by an angle of 30.375 degrees per turn of the ratchet  100 .  
         [0071]     When the autonomous chronograph MCA is running, the transmission-wheel  75  of the barrel  22  drives a wheel  109 , this wheel  109  being united with a pinion  110  and held by a set-bridge  111 . The pinion  110  meshes with an outer teething of the sun crown  108 , the inner teething of the sun crown  108  drives the planetary wheel  107  united with the planetary wheel  105  pressing on the inner teething of the sun crown  104  for making the staff  102  of the power reserve turn clockwise by an angle of 30,375 degrees per turn of the transmission-wheel  75  of the barrel  22 .  
         [0072]     According to this embodiment, the power reserve of the autonomous chronograph module MCA is approximately hundred and twenty minutes, the barrel  22  completes one turn in 29.7 minutes, with one turn of the barrel  22  corresponding to a rotation by 30.375 degrees of the staff  102  of the power reserve. The approximate power reserve of the autonomous chronograph module MCA thus corresponds to an angle of rotation of 127.72 degrees of the power reserve&#39;s staff  102 .  
         [0073]     In order to guarantee that the winding or running of the autonomous chronograph module MCA does not give rise to an unwinding of the barrel spring beyond the limits defined above, a safety device limiting the rotation of the power reserve staff  102  can be provided; this device (not represented) can consist for example of driving a banking-pin in a hole provided on a planetary disc  112 , this pin working with an oblong opening concentric with the axis of the staff  102  and provided on a mechanism-cover.  
         [0074]      FIG. 9  illustrates a preferred embodiment of the invention in which a single winding-crown  1 ′, preferably positioned at 3 o&#39;clock, allows to act both on the base movement MB than on the additional module MCA. For this purpose, the stem  2 B′ of the base module MB is modified by the adjunction of a knob having a teething  201  and a groove  202 . The threading on the stem, which usually allows the external winding-crown  2  to be fastened, is however eliminated.  
         [0075]     The stem  1 A′ of the additional module is provided with a threaded blind hole into which the stem  220  of the winding-crown  1 ′ is screwed. A square  213  on the stem  220  allows the winding-crown  1 ′ to be fastened to esp. disunited from the stem  1 A′ by means of an appropriate tool. In a variant embodiment, the winding-crown  1 ′ could be fastened directly on the stem  1 A′. A winding-crown pinion  211  is unitedly mounted on the stem of the auxiliary module MCA. In position (A), i.e. when the winding-crown  1 ′ is completely pushed axially against the watch case, this pinion  211  engages both with an intermediate wheel  96 ′ of the gear-train for rewinding the barrel  22  and with the teething  201  of the assembly  200  on the stem  2 B′.  
         [0076]     In the illustrated example, the radius of the pinion  211  is dictated by the distance between the axis of the stem  1 A′ and the plane of the intermediate wheel  96 ′. The engaging ratio between the pinion  211  and the teething  201  is thus imposed by the thickness of the base movement and of the additional module. It can be useful to choose a number of turns and the torque to be applied on the winding-crown to rewind or reset the base module. In practice, it is for example comfortable to use an engaging ratio equal to one, making it possible to rewind and reset the base movement with the optimal number of turns and torque initially devised for this movement. In a variant embodiment not illustrated, the pinion  211  can thus be replaced by two side-by-side pinions of different diameters engaging one with the intermediate wheel  96 ′, the other with the teething  201 .  
         [0077]     The intermediate wheel  96 ′ on which the pinion  211  engages is chosen so as to enable to wind the base movement MB by actuating the winding-crown  1 ′ in a first rotational direction, and to rewind the auxiliary module MCA by actuating this winding-crown in the other rotational direction, which allows these two elements to be rewound independently. In a variant embodiment, it could be considered more convenient to engage the rewinding pinion  211  with an intermediate wheel  96 ′ chosen so that the movement MB and the module MCA are both rewound by actuating the winding-crown in the same direction. In such an embodiment, an engaging ratio between the pinion  211  and the teething  201  different from one could be chosen in order to reduce the torque necessary for rewinding the two modules simultaneously.  
         [0078]     In a variant embodiment not illustrated, in order to avoid inverting the rotational direction of the winding-crown  1 ′ during rewinding of the base movement MB, a middle intermediate wheel could be provided between the pinion  211  and the teething  201 .  
         [0079]     By pulling the winding-crown  1 ′ outwards, the collar  212  drives the stem  2 B′ of the base movement MB outwards through the intermediary of the shoulder  204 . The one skilled in the art will understand that the collar  212  and the assembly  200  can be inverted on the two axes  1 A′ and  2 B′.  
         [0080]     In the example illustrated, the reset mechanism of the base movement MB forces the stem  2 B′ to adopt predetermined axial positions, and thus the collar  212  to adopt one of the three indexed axial positions (A), (B) or (C).  
         [0081]     In the positions (B) and (C), the pinion  211  does not engage any longer with the intermediate wheel  96 ′ but only with the teething  201  of the assembly  200  which is displaced outwards. In position (B), the winding-crown  1 ′ enables to rapidly correct the indicator  250  ( FIG. 10 ) of the base movement. In position  3 , the winding-crown  1 ′ allows the resetting of the base movement.  
         [0082]     An optional pivot, not represented, could be mounted in the prolongation of the stem  2 B′ to reduce the risk of flexion or rupture of this stem. This pivot could pivot in a bearing (not illustrated) worked in the inner face of the watch-case.  
         [0083]      FIG. 10  is a cross-sectional view of the date correction transmission device from the indicator disc  250  of the base movement towards the date disc  254  of the auxiliary module. The date disc  254  of the auxiliary module MCA carries the date indications seen by the watch&#39;s wearer.  
         [0084]     As indicated here above, the winding-crown  1 ′ pulled in position B enables to correct, e.g. to manually advance, the angular position of the disc  250  of the base movement MB through the intermediary of the pinion  211 , of the teething  201  and of the stem  2 B′. According to the invention, the disc  250 , as opposed to the usual date discs, is disengaged from the gear-train of the base movement, for example by removing the day disc; the disc  250  is thus not driven by the base movement, which allows the power necessary to drive it to be saved and thus the power-reserve of the watch to be increased.  
         [0085]     The disc  250  is held by a ring  252  connected or screwed to the auxiliary chronograph module MCA. A pinion  2520  mounted on a shaft  253  works with a teething  251  on the outside of the disc  250 , so that the date corrections on the disc  250  are transmitted to the ring  252  and then to the shaft  253  traversing the auxiliary chronograph module MCA. The shaft  253  is held free to pivot in the movement by a jewel or a bearing  255 , a shoulder  2530  preventing the shaft from coming out through the top of the figure.  
         [0086]     A pinion  2531  mounted at the upper extremity of the shaft  253  engages with a teething  2540  connected with a second date disc  254  on the upper side of the auxiliary module MCA. This date disc is driven by the auxiliary module MCA, through the intermediary of a day disc not represented The upper side of the date disk  254  carries date indications visible for the watch bearer through an opening in the face, these known elements having not been represented. Thus, the date disc  254  is driven and regulated by the high-resolution auxiliary module MCA but can be corrected through the base movement MB by acting on the winding-crown  1 ′.  
         [0087]     In the variant embodiment illustrated in  FIG. 10 , the shaft  253  and the disc  250  of the base module (not visible from outside the watch) are driven in rotation by the date disc  254 . This thus causes an unnecessary movement of parts and an energy loss. In a variant embodiment not represented, the gear constituted by the teething  2540  and the pinion  2532  is replaced by a free coupling, of a type known by the one skilled in the art, permitting only to transmit the correction movements transmitted from the shaft  253  towards the upper date disc  254 , but not the rotations in opposite direction.  
         [0088]     It will be understood that it is also possible, within the framework of the invention, to correct the indication of the upper date disc directly by means of the reset stem  1 A′ of the auxiliary module, without using the correction mechanism of the base movement MB. The solution illustrated in  FIG. 11  has however the advantage of using the date correction mechanism frequently available on the base movement and thus to avoid duplicating this mechanism in the auxiliary module.  
         [0089]     It is obvious that the autonomous chronograph module MCA can be used as such, i.e. not necessarily associated to the base movement MB.