HK1174979B - Calendar mechanism - Google Patents

Description

Calendar mechanism

Technical Field

The present invention relates to calendar mechanisms, and more particularly to perpetual calendar mechanisms.

Background

Almanac and perpetual almanac mechanisms have long been known, which enable the display of the dates of the months to be automatically incremented, taking into account the months of less than 31 days, and not requiring any manual intervention to correct these months; the perpetual calendar mechanism additionally takes into account leap years in order to increase the date on the last day of february.

The perpetual calendar mechanism uses a cam of type 12 or 48, the latter performing one revolution per year or every four years, respectively, and having notches for different depths for months of less than 31 days. In the case of a cam of type 12, the february notch additionally comprises a year indexed/transposed (index) by Maltese crosses, which defines a smaller depth for the leap year. The beak of the lever, which is restored by a spring, acts on the cams for these date display mechanisms to determine the advance of the date indicator at the end of the month according to the depth of engagement. This results in a relatively complex structure with a number of important parts, which is not very reliable in operation, for example in the event of shocks. Moreover, such a cam system only allows the date wheel and the basic movement to be synchronized in a given direction, so that the date value can only be increased and not decreased during the hour adjustment operation.

To overcome these drawbacks, the solution disclosed in patent document CH 680630 proposes, for example, a perpetual calendar mechanism comprising a program wheel (program wheel) driven by a projecting tooth of a 24-hour wheel and provided with a gear train so that it always moves along a number of steps corresponding to the difference between the days of the month and 31. This mechanism has no lever, balance or spring at all, except for the jumper spring for the indexed date wheel. The transmission system is however very complex, with a large number of planets equipped with long teeth for indexed readjustment, which are arranged eccentrically on the program wheel and are each dedicated to a specific correction. This therefore leads not only to great height requirements on the machine plate, but also to very high production costs, since the shaft requires a high-precision positioning to ensure reliable engagement with the 24-hour wheel.

Document EP1351104 proposes an alternative to the above solution, with the aim of reducing the number of components on the program wheel. Thus, the disclosed calendar mechanism provides a program wheel having a moving element with retractable teeth that slide between an operative position and an inoperative position. Such an arrangement enables the overall thickness of the program wheel to be effectively reduced. However, the sliding moving element has a very specific shape and must be positioned precisely between the abutment and the shoulder with a complex geometry. Furthermore, the control device still comprises a large number of planet wheels with teeth of unequal length, which act on cam surfaces on the sliding elements. Therefore, not only is the reliability of the engagement questionable, but also the wear of the different parts of the control device is aggravated, due to the large number of guide surfaces for the sliding elements.

There is therefore a need for a calendar mechanism, in particular a perpetual calendar mechanism, which overcomes the above-mentioned limitations of the prior art.

Disclosure of Invention

It is an object of the present invention to provide an alternative to conventional calendar mechanisms which has a simplified structure and in which the adjustment of hours and dates can be synchronized in both directions.

It is a further object of the present invention to provide such a solution that minimizes energy losses during different indexing operations, in particular during indexing readjustments at the end of months of less than 31 days.

These objects are achieved in particular by a calendar mechanism comprising a date program wheel (13) driven by a timepiece/clock movement and actuating a wheel train (16-24) for the display of the dates in the months, wherein the program wheel (13) comprises a date indexing gear (13') advanced by one step per day by the timepiece movement, and at least one retractable tooth (128, 129, 130) drivable by the timepiece movement, characterized in that said retractable teeth (128, 129, 130) are mounted to pivot between an active position (128A, 129A, 130A) and an inactive position (128I, 129I, 130I), wherein in said active position said retractable teeth (128, 129, 130) are driven by said timepiece movement, and in said inactive position said retractable teeth (128, 129, 130) are not driven by said timepiece movement.

One advantage of the proposed solution is that only a reduced number of elements for the program wheel and parts with simple geometry for the retractable teeth are required.

Another advantage of the proposed solution is that better meshing reliability is ensured thanks to the reliable positioning of the retractable teeth, each of which is deep and defined by a single degree of freedom of rotation.

An additional advantage of the proposed solution is that better durability is obtained due to the limited wear of each retractable tooth during the respective indexing operation.

Another advantage of the proposed solution is that each readjustment wheel train for automatically indexing the dates in the months of less than 31 days can be easily replaced in a modular manner with meshing levels instead of meshing levels.

Drawings

Exemplary embodiments of the invention are described below and illustrated in the accompanying drawings, wherein:

fig. 1A and 1B show a sectional view and a plan view, respectively, of a control mechanism for 24-hour and day-of-week display associated with a calendar mechanism according to a preferred variant of the invention;

FIGS. 2A and 2B show the cross-sectional view of FIG. 1A and a plan view at another level of engagement of the day's control and display mechanism, respectively;

figure 3A shows a partial cross-sectional view of a calendar mechanism according to a preferred variant of the invention;

figure 3B shows a partial plan view of a calendar mechanism according to a preferred variant of the invention shown in figure 3A, in particular with a program wheel and retractable teeth;

fig. 3C shows a plan view of a display device of a calendar mechanism according to a preferred variant of the invention shown in fig. 3A and 3B;

fig. 4A shows another cross-section of a calendar mechanism according to a preferred variant of the invention, particularly showing the control mechanism for the program wheel, month and leap year display;

FIG. 4B shows a partial plan view of a calendar mechanism according to a preferred variation of the invention shown in FIG. 4A;

figure 5 shows a perspective view of a calendar mechanism according to said preferred variant of the invention, which calendar mechanism uses a preferred embodiment of the different modules shown in the previous figures;

fig. 6A and 6B show that on day 28 of february, non-leap years, the pivoting retractable teeth and the date indexing gear operate respectively at different indexing sequences on their respective meshing levels for a perpetual calendar mechanism using a gear arrangement according to the preferred embodiment shown in fig. 5.

Detailed Description

The calendar mechanism according to the invention is preferably a perpetual calendar mechanism with display of the week, 24 hours, month and leap years. However, it will be appreciated by those skilled in the art that for other types of calendar mechanisms, the various modules forming the calendar mechanism described above may also be used independently of one another; and, by adjusting the number of pivoting teeth and the number of meshing levels, the program wheel can also be adapted to simpler mechanisms, such as a calendar mechanism or a calendar mechanism for months of 30 days.

Fig. 1A and 1B show a sectional view and a plan view of a display mechanism for 24 hours and days of the week of a calendar mechanism according to one preferred modification of the present invention, respectively. Fig. 1A and 1B are enclosed by a housing 0 to indicate the position of the train inside the watch. The case 0 contains buttons 10, 26 and 48 for correcting the day of the week, the day value and the month value, respectively. These correction mechanisms will be further explained below based on fig. 2A, 2B, 3A, 3B, 3C and 4A, 4B. In fig. 1A, an hour hand mechanism can be seen, on which an hour wheel 1, preferably comprising 35 teeth, is provided. The hour wheel 1 meshes with a 24-hour wheel 2 comprising twice the number of teeth (and therefore preferably 70 teeth). Said 24-hour wheel 2, which performs one complete revolution per day, is mounted so as to be rotationally fixed with a transmission wheel 3, said transmission wheel 3 being in mesh with a 24-hour display gear 4 comprising the same number of teeth (for example 46 teeth according to the preferred embodiment shown here). The 24-hour display gear wheel 4 is mounted coaxially with a day star wheel 7 having 7 arms, the star wheel 7 being driven at a rate of once a day on the meshing level shown later in fig. 2B by a pawl 6, the pawl 6 being coaxial with the 24-hour wheel 2. The coaxial mounting of the 24-hour display gear 4 with respect to the day star wheel 7 makes these display parameters more legible, for example by means of concentric rings.

Fig. 2A is identical to fig. 1A, except for the additional components, which are indicated with 8, which show the elastic indexing element of the day star wheel 7. Fig. 2B shows a plan view of the index wheel train of the day star 7 at a meshing level lower than that of the transmission wheel 3 at the 24-hour display wheel 4. The pin 5 integral with the 24-hour wheel drives a pawl 6, said pawl 6 engaging with the day star wheel 7 to rotate the day star wheel 7 and perform 1/7 revolutions per day. Meshing occurs over a segment between about 10 o 'clock and 11 o' clock on the 24 hour wheel 2 in fig. 2B, which means that in this configuration the daily indexing of the day occurs between about 2 o 'clock and 4 o' clock in the morning. The indexing of the day star 7 by 1/7 revolutions is ensured precisely by the elastic indexing element 8 which positions itself between two teeth of the day star 7, so that each indexing step corresponds exactly to 1/7 revolutions.

The pawl 6 of the 24-hour wheel is preferably provided as a coaxial element with the 24-hour wheel 2, but is not completely fixed in rotation with respect to said 24-hour wheel 2, so that the adjustment of the day of the week can be made independently of the calendar mechanism and of the hour of the day. In fact, the arrangement of said pawl 6 on the meshing gear provides a degree of freedom in rotation between the first abutment 6 'and the second abutment 6 ", in which the pin 5 of the 24-hour wheel will rest against said first abutment 6' when the 24-hour wheel 2 is turned in the anticlockwise direction (i.e. when the hour wheel 1 is turned in the clockwise direction during normal functioning operation of the watch); whereas if the 24-hour wheel were turned in the opposite direction, the pin 5 of the 24-hour wheel would rest against said second abutment 6 ". The amplitude of this degree of freedom preferably corresponds to an angular sector of 20-30 degrees and is determined so that, for the embodiment shown in fig. 2B, it is possible to make the day star wheel 7 turn, for example, in the clockwise direction, without interfering with the normal operation of the hour wheel 1, even if the pawls 6 of the 24-hour wheel are in the engaged position with the teeth of the day star wheel 7, i.e. for the preferred embodiment described, in the sector of between about 10 o 'clock and 11 o' clock of the 24-hour wheel in fig. 2B, as described above. In the case where the pawl 6 of the 24-hour wheel is located between two consecutive teeth of the day star 7 at the moment of adjustment, it will simply be turned in the anticlockwise direction, without causing any resistance to the day star 7 before reaching the second abutment 6 ", and without affecting the operation of the 24-hour wheel 2. Thus, the normal operation of hour wheel 1 is fully protected during the adjustment operation, regardless of the hour at which this adjustment operation is performed. If this operation is carried out with the pawl 6 of the 24-hour wheel between two teeth of the day star wheel 7, the usual daily meshing will no longer occur, since the pawl 6 of the 24-hour wheel will then be located outside the usual meshing section between 10 o ' clock and 11 o ' clock, outside which said first abutment 6 ' will later be readjusted only by the pin 5.

The adjustment of the day of the week is performed by means of a manual actuator 10 provided on the housing 0. According to the preferred embodiment depicted in fig. 2A and 2B, the manual actuator 10 for adjusting the day of the week is a button that is pressed at most 6 times in succession to reach the desired date. For the sake of clarity, the adjustment mechanism 9 enabling the transmission of the pulses from the push-button to the day star-wheel 7 is not shown in fig. 2B; however, such mechanisms are known to those skilled in the art. According to the preferred embodiment shown, the day of the week can therefore only be adjusted in a single direction. Instead of a push button, a shaft can be used as manual actuator 10, in which case the rotation of the shaft can drive the day star wheel 7 in rotation in both directions together with a suitable mechanism 9 for adjusting the day. However, this alternative has the disadvantage that it is not possible to ensure adjustment in the opposite direction when the pawl 6 of the 24-hour wheel meshes with the teeth of the day star wheel 7, since then said pawl 6 will abut against the first abutment 6', so that it is not possible to achieve any correction without damaging the shaft and/or the movement. The preferred solution described on the basis of fig. 2A and 2B avoids this drawback.

The fact that the adjustment of the day of the week never affects the movement of the 24-hour wheel 2 ensures independence not only of such adjustment with respect to the display of hours and minutes, but also with respect to the value of the month and the date in the month determined by the calendar mechanism according to the invention. In fact, the calendar mechanism is driven by the movement of the integral meshing section of the 24-hour wheel 2-as explained further below with reference to the drawings-which is never affected by the adjustment of the day of the week. The correction of the days of the week is therefore independent of the values of the date and month displayed according to the preferred embodiment of the calendar mechanism described in the present invention.

Fig. 3A and 3B show a sectional view and a plan view, respectively, of a drive wheel train for the display of the date in the month, starting from the movement. Fig. 3B shows in particular the position of said wheel train with respect to the casing 0, and the manual correction actuators 10, 26 and 48 for the days of the week, the day of the month and the month, respectively, as described above with reference to fig. 2A and 2B. Fig. 3B will be used to specifically explain the operation of the adjustment mechanism of the date value in the month.

In the following, reference will be made alternately to fig. 3A and 3B, which may be referred to in combination for a better understanding of the drive train of the calendar mechanism according to the preferred embodiment shown. Hour wheel 1 of the movement meshes with 24 hour wheel 2 containing twice the number of teeth. In this case, the 24-hour wheel 2 is provided with a date meshing segment 11, which date meshing segment 11 is composed of 7 teeth spaced apart by 15 degrees, so that the change from one tooth to the other takes place every hour. The date meshing sector 11 of said 24-hour wheel meshes, on a first level a (which is indicated in fig. 3A and is more clear in fig. 3B), with a date indexing wheel 12, which date indexing wheel 12 is composed of 8 teeth on this meshing level. Thus, each day, the 24-hour wheel causes the day indexing wheel 12 to perform one full revolution when engaged with 7 teeth of the engagement section 11, i.e. within an interval of 8 hours. When the day indexing wheel 12 is not engaged with the toothed engagement section 11, it still rests on the non-toothed section of the 24-hour wheel (which is indicated by reference numeral 11' in fig. 3B), and is thus held in place. The meshing sector 11 of the 24-hour wheel and the date and time indexing wheel 12 are therefore preferably arranged so that said date and time indexing wheel 12 performs one complete revolution each day between 18.00 hours and 2.00 hours of the morning and the indexing effected by the date program wheel 13 takes place between 20.00 hours and the midnight.

As can be seen in fig. 3A, the day indexing wheel 12 has a plurality of teeth 28, 29, 30, 31 which are distributed over different meshing levels B, C, D, E. Moreover, these teeth are continuous and therefore can engage with the day program wheel 13 every hour. Fig. 3B shows the meshing level D of the tooth 31 with the date indexing gear 13' of the date program wheel 13, i.e., the third meshing level from the top in fig. 3A. The teeth 31 are preferably arranged to mesh with corresponding teeth 131 of the date indexing gear 13' between 23.00 hours and midnight. Unlike the teeth 31 of the day indexing wheel 12, said teeth 131 are different each day and each time correspond to another tooth of the tooth system of the day indexing gear 13 ', since said teeth 131 are defined only with respect to the teeth 31 of the day indexing wheel 12, wherein said day indexing gear 13' has a uniform external tooth system comprising 31 teeth (i.e. wherein the height of each tooth and the interval between each tooth is the same). Due to the elastic indexing element 14 of the program wheel coming between two consecutive teeth after each jump, the date indexing gear 13' advances by one tooth by pitch.

The other teeth 28, 29, 30 of the day index wheel 12 are used to perform additional readjustments for months of less than 31 days in conjunction with corresponding pivoting retractable teeth 128, 129, 130 provided on the program wheel. The first indexing tooth 29 of the day indexing wheel 12 thus meshes with the first pivoting retractable tooth 129 on a first meshing level B, located just below meshing level a in fig. 3A, for indexing from day 29 to day 30 every february, with the axis of rotation of said first pivoting retractable tooth 129 integral with the day indexing gear 13'. The meshing only occurs when the pivoting tooth is in the so-called "active" position, i.e. when the pivoting tooth can be driven by the corresponding indexing tooth of the day indexing wheel 12. The "active" position 128A, 129A, 130A of each pivoting retractable tooth 128, 129, 130 is illustrated by the different sequential operations in fig. 6 described below. In this case, each pivoting retractable tooth 128, 129, 130 is preferably superimposed on the external tooth system of the day indexing gear 13' on its respective meshing level B, C, E. These pivoting teeth 128, 129, 130 are shown in fig. 3B in the rest positions 128I, 129I, 130I, respectively, during month 3, month 3 not requiring any readjustment due to the inclusion of 31 days.

Similarly, the second indexing tooth 30 of the day indexing wheel 12 can be engaged with the second pivoting retractable tooth 130 when it is in the working position 130A for indexing from day 30 to day 31 in months of less than 31 days, wherein the axis of rotation of said second pivoting retractable tooth 130 is also integral with the day indexing gear 13'. According to the preferred embodiment shown, the meshing occurs on a second meshing level C in fig. 3A, located just below the previous meshing level B.

Finally, the third indexing tooth 28 of the day indexing wheel 12 is engaged with the third pivoting retractable tooth 128 when it is in the working position 128A for indexing from day 28 to day 29 in the month of february in leap years, wherein the axis of rotation of said third pivoting retractable tooth 128 is also integral with the day indexing gear 13'. According to the preferred embodiment shown, the meshing takes place at a third meshing level E, located just below the previously described meshing level D.

As is clear from fig. 3A, the first, second, third and fourth meshing levels are arranged in order from the meshing level a of the day indexing wheel 12 having the day meshing section 11 (B, C, D, E). This arrangement is advantageous because the cam surfaces of the month program wheel 43 are superposed on levels B and C, which facilitates accurate mounting of each component.

As can be seen from fig. 3B, neither the day indexing wheel 12 nor the day indexing gear 13' have long teeth, which facilitates their machining. Moreover, the projections of the indexing teeth 29, 30, 31, 28 on the respective meshing level B, C, D, E are superimposed on the tooth system of the day indexing wheel 12 with meshing sectors 11 on meshing level a: the indexing teeth thus form uniform and continuous toothed sectors in a plane perpendicular to the axis of rotation of the day indexing wheel 12, with a depth such as to enable good meshing reliability, wherein the angular spacing between each tooth itself ensures a unit increment of the day program wheel 13.

Fig. 3B shows the month cam 44, the control surface of which determines the active or inactive position of the pivoting retractable tooth 130 on the meshing level C. Said month cam 44 thus defines a cam surface 441 for months less than 31 days, on which indexing from the 30 th to 31 th of the month can take place, which according to the preferred embodiment shown preferably takes place between 22.00 and 23.00. Said month cam 44 preferably also comprises a cam surface 442 for the month of february on which indexing can take place from the 29 th to the 30 th of the month, which according to the preferred embodiment shown preferably takes place between 21.00 and 22.00. The cam surface for the month of february itself controls the active or inactive position of the pivoting retractable tooth 129 on the meshing level B. The cam surfaces 441,442 of the month cam 44 are distributed over 12 sectors, which can be seen in fig. 3B, but detailed reference is given only in fig. 6A and 6B described below. Each segment of the cam surface corresponds to one month of the calendar year, and the month cam 44 is provided integrally with the month program gear 43, the month program gear 43 being indexed, i.e. changing the value of the month, by 1/12 revolutions at the end of each month. The control train for such indexing operation will be further described below based on fig. 4A and 4B.

At the bottom of fig. 3A, an engagement level F can be seen, which corresponds to the engagement of the intermediate month control wheel 42 with the month program gear 43, and there is also a fixed leap year indexing finger 47, which is normally provided on a fixed wheel 47' as can be seen, for example, in fig. 6A and 6B. The leap year indexing finger 47 allows the maltese cross 46 '(which is more clearly shown in fig. 6) to perform 1/4 revolutions per year, during which the month program gear 43, which is integral with the maltese cross 46', performs one full revolution. The maltese cross 46', which engages with the leap year indexing finger 47 at an additional engagement level, not given a reference numeral in the drawings, is integral with the leap year cam 46, and the cam surface 461 (visible only in fig. 6) of the leap year cam 46 at engagement level E is similar to the cam surface 442 for the month of february. The cam is thus able to advance the date value from 28 to 29 during the night on the 28 th day of the month of february of non-leap years, which according to the preferred embodiment shown preferably occurs between 20.00 and 21.00.

In fig. 3A and 3B it can be seen that, at the meshing level D, via an intermediate date wheel 15 coaxially arranged but freely rotatable with respect to the intermediate month control wheel 42, a date indexing gear 13 'meshes with a date wheel 16, said date wheel 16 also having 31 teeth, like the date indexing gear 13'. Said intermediate date wheel 15 constitutes only one circuit for all the indexing movements on the date program wheel 13 in their entirety in response to the date wheel 16 and, conversely, all the rotational movements of the date wheel 16 in their entirety in a date indexing gear 13 'forming the body of the date program wheel 13, on which date indexing gear 13' there are also mounted pivoting retractable teeth 128, 129, 130, each of which comprises a respective lug 1281, 1291, 1301 the function of which will be further explained below on the basis of fig. 6A and 6B. Thus, there is no need for an elastic indexing element to index the date wheel 16. In case the height in the housing 0 is sufficient, the program wheel 13 and the date wheel 16 may be arranged coaxially, or even meeting/merging. According to the preferred embodiment described, the separation of the program wheel 13 and the date wheel 16 allows the functional separation of the unit formed by the date program wheel 13 dedicated to meshing with the movement in order to automatically correct the dates in the months of less than 31 days, from the unit formed by the date wheel 16, the units wheel 17 and the tens wheel 18, said date wheel 16, units wheel 17 and tens wheel 18 being coaxial with each other, rotationally fixed to each other and dedicated to meshing with a display gear, such as the one shown in fig. 1C.

The unit wheel 17 is divided into 31 equal angular sectors, i.e. a sector with 30 teeth thereon and a sector without teeth. The unit wheel 17 drives a gear for actuating the unit display disc 19 on each day of the month other than No. 1. The ones display disc 20, integral with said gear for actuating the ones display disc 19, is thus indexed by one unit per day, except for the transition from the 31 st day of the month to the 1 st day of the following month, during which only the tens display disc 23 is added. Said gear for actuating the unit display disc 19 comprises 10 teeth and is indexed by pitch by 1/10 revolutions, by means of the elastic indexing element 24 coming to the unit disc between two consecutive teeth.

Similarly, the tens display dial 23 is integrated with an actuating gear, i.e., a gear for actuating the tens display dial 22, the tens display dial 22 having a cross shape with 4 arms and being indexed by 1/4 revolutions during the transition from day 9 to day 10, from day 19 to day 20, from day 29 to day 30, and from day 31 to day 1. The jump of 1/4 revolutions is ensured by the elastic indexing element 24 coming to the tens display disc between two adjacent arms of the cross; and indexing on these date values is ensured by the long teeth provided on the tens wheel 18, said tens wheel 18 also being divided into 31 sectors, but comprising only 4 long teeth, of which 3 are provided at 9 sector intervals, the 4 th long tooth being after the 3 rd long tooth for the transition from day 31 to day 1 of the next month.

The wheel train for the display of the day of the month, made up of the elements with reference numbers 16 to 24 from the date wheel 16 to the units display 20 and the tens display 23, can be seen in part in each of figures 3A, 3B and 3C: fig. 3A shows the entire train, but without the elastic indexing elements 21 and 24 of each actuation gear 19 and 22 associated respectively with the units display disc 20 and the tens display disc 23, and fig. 3B shows the meshing levels beneath these units display disc 20 and tens display disc 23, said units display disc 20 and tens display disc 23 thus being visible only in fig. 3C.

The adjustment of the day of the month is carried out by means of a manual actuator 26 provided on the housing 0. According to the preferred embodiment depicted in fig. 3A and 3B, the manual actuator 26 for date adjustment is a push button which is pressed at most 30 times in succession to reach the desired date. Adjustment mechanism 25 is not shown in fig. 3B for clarity, adjustment mechanism 25 enabling the transmission of pulses from the push button to date wheel 16; however, such mechanisms are known to those skilled in the art. Instead of a push button, a shaft could be used as manual actuator 26, in which case the rotation of the shaft could drive the date wheel 16 in rotation in both directions together with a suitable mechanism 26 for adjusting the day of the week. However, according to the preferred embodiment shown, and with the alternative proposed, it is not possible to make such an adjustment of the date when the teeth 28, 29, 30 or 31 of the date index wheel 12 are engaged with the date program wheel 13, that is to say between 20.00 and 24.00. In fact, the direct engagement of the day indexing wheel 12 and the day meshing sector 11 of the 24-hour wheel tends to transmit these indexing operations to the hour wheel 1, which is unlikely to compromise the normal functioning of the movement.

Fig. 4A and 4B show a section and a plan view, respectively, of a calendar mechanism according to a preferred variant of the invention, in which the control wheel train for positioning the month program gear 43 in order to properly position the pivoting retractable teeth, and the wheel train for displaying the months and leap years are described. As in the previous fig. 2A, 2B and 3A, B, C, manual actuators 10, 26 and 48 are shown disposed on housing 0; it will be further seen hereinafter how the adjustment of the months is carried out by means of the manual actuator 48.

In the central part of fig. 4A, a gear wheel can be seen, on which the monthly indexing teeth 32 visible in fig. 4B are provided. Said monthly indexing tooth 32 meshes with a monthly indexing gear 33 having 8 teeth, said monthly indexing gear 33 being fixed together non-rotatably with a month control wheel 41 having 32 teeth, said month control wheel 41 meshing, on a meshing level F, with an intermediate month control wheel 42, said intermediate month control wheel 42 being coaxial with the intermediate date wheel 15 but not fixed non-rotatably with respect to the intermediate date wheel 15, said intermediate month control wheel 42 in turn meshing with a month program gear 43 having 48 teeth, said month program gear 43 being fixed in rotation with a month cam 44 visible in fig. 4B. The monthly indexing gear 33 performs exactly 1/8 revolutions per month due to the elastic indexing element 34 coming between two consecutive teeth of the monthly indexing gear 33. The transmission ratio between the monthly indexing gear 33 and the number of month program gears 43 allows the month program gears 43 to be indexed by exactly 1/12 revolutions per month.

The monthly indexing gear 33 additionally meshes with an intermediate monthly indexing wheel having 23 teeth, which in turn meshes with a gear 36 for actuating the month display having 12 teeth. The gear ratio 8/12 between the monthly indexing gear 33 and the gear 36 for actuating the month display ensures that the gear for actuating the month display performs exactly 1/12 revolutions at the end of each month. Said gear 36 for actuating the month display is non-rotatably fixed with respect to a year indexing tooth 37, said year indexing tooth 37 being positioned on one wheel performing one complete revolution per year. The year indexing tooth 37 meshes with a leap year actuating gear 38 having 8 teeth, which leap year actuating gear 38 is shifted by two teeth, i.e. 90 degrees, during each meshing with the year indexing tooth 37. The leap year actuation gear 38 is non-rotatably fixed relative to an intermediate leap year wheel 39 with 39 teeth, the intermediate leap year wheel 39 meshes with a leap year display wheel 40 also comprising 39 teeth, the leap year display wheel 40 is mounted coaxially with the actuation gear 36 for the month display, so that the indicators of the months and leap years (usually hands pointing to concentric rings provided on the dial) can be set to rotate around the same hand-motion mechanism in order to improve the legibility for the user. It will be understood by those skilled in the art that, for the elements forming the wheel train described in fig. 4A and 4B, i.e. for the (elements 33-36) of the month display, the (elements 37-40) of the leap year display and the (elements 33, 41, 42, 43) of the positioning control of the month program gear 43, the number of teeth described is given as an example, within the framework of the shown preferred variant with sufficient meshing efficiency to implement the invention, but should in no way be considered limiting.

The month program gear 43 is integral with a month cam 44, said month cam 44 comprising a first cam surface 441 visible in fig. 4B for months of less than 31 days, which corresponds to the meshing level C visible in fig. 4A. The cam surface enables the date value in the month to be indexed from 30 to 31. The month cam 44 also comprises a cam surface 442 on the meshing level B for the correction of the month of february, i.e. capable of rotating the date from 29 to 30. In fact, the leap year cam 46 (which is mounted integrally with the month program gear 43 and visible in fig. 4A) is able to rotate the date from 28 to 29 by acting on a pivoting retractable tooth on the meshing level E, just above the meshing level F, at the time of non-leap years. The month program gear 43 is therefore used to determine the active position 128A, 129A, 130A or the inactive position 128I, 129I, 130I of each retractable tooth 128, 129, 130 when readjustment is required, i.e. in the months and in the months of february with 30 days. To do this, the cam surface on each meshing level B, C, E must be arranged so that each pivoting retractable tooth at this level is in the active position for the readjustment for which they are respectively intended, i.e. from 29 to 30 at level B, from 30 to 31 at level C, from 28 to 29 at level E, or so that each pivoting retractable tooth at this level is in the inactive position. According to the described preferred embodiment, the cam surfaces are distributed over 12 sectors, corresponding respectively to one month of the year. Thus, the month program gear 43 (which is rotationally fixed with the month cam 44 acting on the pivoting retractable teeth 128, 129, 130 on the different meshing levels B, C, E) must be synchronized with the displayed and indexed month value each time the date turns from 31 to 01, and vice versa. This is the reason why the control train, which according to the preferred embodiment shown is formed by the elements 15, 16, 32, 33, 41 and 42, is able to achieve a reverse action (retroaction) from the date index gear 13' to the month program gear. The day indexing gear 13' performs at least 1/31 revolutions per day (i.e. an additional readjustment requiring one or more 1/31 revolutions for the months of 30 days and february for the regular day 1/31 and for the last of the months of less than 31 days) in order to index the month program gear 43 by 1/12 revolutions at the end of each month, which occurs simultaneously with the indexing of the gear 36 for actuating the display of months also by 1/12 revolutions.

According to a preferred embodiment of the calendar mechanism described, the control train of the month program gear, made up of the elements referenced 15, 16, 32, 33, 41, 42, is formed by a first kinematic chain starting from the date indexing gear 13 ' via the intermediate date wheel 15 to the date gear 16, the date gear 16 forming the first element of the date display train (16-24), while a second kinematic chain starting from the date gear 16 and the monthly indexing tooth 32, via the monthly indexing gear 33 and the month control wheel 41 (both rotationally fixed to each other) and the intermediate month control wheel 42, returns to the month program gear 43, the month program gear 43 being arranged coaxially with the date indexing gear 13 ', but rotationally independent of the date indexing gear 13 '. The intermediate gears 15 and 42, i.e. the intermediate date wheel 15 and the intermediate month control wheel 42, are provided as a single intermediate wheel comprising two coaxial and rotationally independent gears, in order to save the maximum amount of space on the board, for example for other movement modules. Said intermediate month control wheel 42 meshes with the month program gear 43 at level F, while the intermediate date wheel 15 meshes with the date index gear 13' at level D. According to the preferred embodiment shown, said intermediate wheels (intermediate date wheel 15 and intermediate month control wheel 42) rotate in opposite directions of rotation to each other, since intermediate date wheel 15 directly meshes with date wheel 16 and therefore rotates in opposite direction to date wheel 16, whereas month intermediate control wheel 42 is driven by a transmission formed by monthly indexing finger 32 integral with date wheel 16 via gears 33 and 41 and therefore rotates in the same direction as date wheel 16.

The adjustment of the months is carried out by means of a manual actuator 48 provided on the housing 0. According to the preferred embodiment depicted in fig. 4A and 4B, the manual actuator 48 for adjusting the day of the week is a push button that is continuously pressed at most 11 times to reach the desired month. For the sake of clarity, the adjustment mechanism 45 is not shown in fig. 4B, said adjustment mechanism 45 allowing the pulses of the push-button to be transmitted to the month program gear 43. However, such mechanisms are known to those skilled in the art. Instead of a push button, a shaft may be used as the manual actuator 48, in which case the rotation of the shaft may drive the month program gear 43 to rotate in both directions together with a suitable mechanism for adjusting the months. However, according to the preferred embodiment shown, and with the proposed alternative, such month adjustments cannot be made while the monthly indexing tooth 32 is in mesh with the monthly indexing gear 33, i.e. during the night from the last day of the current month to the first day of the next month. In fact, the engagement of the indexing tooth 32 will cause the rotation of the date gear 16, which will cause the same movement of the date program wheel 13, the engagement between the teeth 28, 29, 30, 31 of the date program wheel 13 and the indexing gear 12 at 20.00 and 24.00 will cause the rotation of the date meshing section 11 of the 24-hour wheel. This tends to transmit these indexing operations to hour wheel 1, which, as described previously, is not possible without impairing the normal functioning of the movement if the adjustment of the date takes place between 20.00 hours and 24.00 hours.

Figure 5 shows a perspective view of a calendar mechanism according to a preferred embodiment of the invention shown in different previous views. Starting from the hour wheel 1 in the center of the figure, it can be seen a train leading to a date program wheel 13 via a 24 hour wheel 2 and a date meshing sector 11 with 7 teeth meshing with an indexing gear 12. The different teeth 28, 29, 30, 31 of the day indexing wheel mesh with the pivoting retractable teeth 128, 129, 130 of the day program wheel 13 at the respective meshing levels E, B, C, D shown above in fig. 3 and 4, and with the tooth 131 of the day indexing wheel at level D. Also visible in this figure are pivoting retractable teeth 129 and 130, the tooth referenced 128 being hidden. On the left side of the figure, the transmission wheel 3 of the 24-hour wheel (which is rotationally fixed with the 24-hour wheel 2) meshes with a 24-hour display gear 4, said 24-hour display gear 4 rotating around the same motion work as the days of the week star wheel 7 arranged on the lower level. However, the pawl 6 of the 24-hour wheel causing the day star 7 to rotate and the elastic indexing element 8 of the day star are also hidden in this figure.

During each engagement of the day program wheel 13 with one of the teeth of the day indexing wheel 12, the day indexing gear 13' (on which the pivoting retractable teeth 128, 129 and 130 are mounted to pivot) performs 1/31 revolutions. The date gear 16 is made to rotate by the same angle by the intermediate date wheel 15. The unit wheel 17 and the tens wheel 18 are visible above the date wheel 16, and it is clearly visible that the 4 long teeth of the tens wheel 18 are arranged at the position of the 9 th, 19 th, 29 th and 31 th teeth of said tens wheel 18, the 31 th tooth of the unit wheel 17 being hollowed out. The date display mechanism is not shown for clarity. It should be noted, however, that no elastic indexing element is used on the periphery of the date wheel 16, since the movement of said date wheel 16 is still synchronized with the movement of the date indexing gear 13 ', which date indexing gear 13' itself is indexed by the elastic indexing element 14 of the program wheel (hidden in fig. 5).

The whole of the train of wheels for the display of the date in the month is not shown in fig. 5, since the various display disks and indexing elements (the reference numbers 20-24 can be seen in fig. 3C) and the monthly indexing tooth 32, coaxial with the date wheel 16 and rotationally fixed, are hidden under the date wheel 16. However, it is possible to see a monthly indexing gear 33 which enables a month control wheel 41 (said monthly indexing gear 33 being rotationally fixed with said month control wheel 41) to drive in rotation a month program gear 43 through an intermediate month control wheel 42, and also meshing with the wheel train for the month display, the tooth system of said month program gear 43 being hardly visible below the tooth system of the date indexing gear 13'. The month program gear 43 is rotationally fixed with a month cam 44, said month cam 44 comprising cam surfaces distributed on different meshing levels. In particular, the projections of the first cam surface 441 for correction from day 30 to day 31 can be seen on the engagement level C, and the projections of the second cam surface 442 for correction from day 29 to day 30 in the month of february can be seen on the engagement level B. To facilitate the machining of the month cam 44 as a single part or as two concentric parts mounted one on top of the other, it is clear that the preferred embodiment of the invention uses the same cam surfaces on the meshing levels B and C for the months of february: in fact, the first cam surface 441 in the corner region 4402 on engagement level C (details can be seen in fig. 6A and 6B) is completely hidden by the second cam surface 442 on engagement level B.

At the top of fig. 5, an intermediate monthly indexing wheel 35 can be seen, which meshes with a gear 36 for actuating the month display, hidden under the monthly indexing teeth 37, said gear 36 being coaxial with the monthly indexing teeth 37 and rotationally fixed. The monthly indexing teeth 37 perform one full revolution a year and mesh with a gear 38 for actuating the leap year display, said actuating gear 38 being coaxial and rotationally fixed with an intermediate leap annual wheel 39, said intermediate leap annual wheel 39 meshing with a leap year display wheel 40 having the same number of teeth. The leap year display wheel 40 is arranged coaxially with the gear for actuating the month display in order to provide better legibility for the user of the watch.

Fig. 6A shows that on the 28 th month of the non-leap year, for the perpetual calendar mechanism according to the preferred embodiment shown in the drawings, the pivoting retractable teeth 128, 129 and 130 operate with different indexing sequences of the respective teeth 28, 29, 30 of the day indexing wheel 12 on their respective meshing levels. For such dates, the calendar mechanism must be readjusted by 3 date values, which is achieved by the cooperation of each of the 3 pivoting retractable teeth 128, 129 and 130 with the indexing teeth 28, 29, 30 of the date indexing wheel 12 at their respective meshing levels E, B and C.

The upper part of the figure shows the position of the day index sector 11 and the different teeth 28, 29, 30, 31 at 20.00 of the 28 th day of the month of february. At this time, the tooth 28 of the date indexing wheel 12 meshes with a pivoting retractable tooth 128, the pivoting retractable tooth 128 being mounted to pivot about a rotation axis 128 'integral with the date indexing gear 13'. According to the preferred embodiment shown, the axis of rotation 128 ' of the retractable tooth 128 pivoting is located slightly set back from the 25 th tooth, referenced 25 ' of the date indexing gear 13 '. During the passage from day 27 to day 28 of the month, the pivoting retractable tooth 128 is brought into the working position 128A by the leap year cam 46, the leap year cam 46 being integral with the maltese cross 46 ', the maltese cross 46 ' being indexed once a year by the fixed leap year indexing finger 47, the leap year indexing finger 47 itself being integral with the fixed wheel 47 '. According to the preferred embodiment shown, the fixed wheel 47' is coaxial with the month program wheel 43 and with the date program wheel 13.

The tooth 28 of the date indexing wheel 12 meshes with the pivoting retractable tooth 128 on the meshing level E, so that the date program wheel 13 is driven for 1/31 revolutions, for example according to the view of fig. 6A, in a direction of rotation S1 (here clockwise of the hands of the watch) identical to the direction of rotation of the 24-hour wheel 2 and opposite to the direction of rotation of the hour wheel 1. It should be noted that the direction of view of fig. 6A and the subsequent direction of view of fig. 6B is, for example, opposite to the direction of view of fig. 3B, in fig. 3B hour wheel 1 is rotated in the direction of the hands of the watch and 24 hour wheel 2 and meshing section 11 are driven in the opposite direction of the hands of the watch.

The elastic indexing element 14 of the date program wheel enables the date indexing gear 13 'to be indexed by pitch by a precise 1/31 revolutions in the direction S1, said date indexing gear 13' then meshing on the date display train (see reference numerals 15-24 shown in the other figures), while the first elastic return element 1282, which cooperates with the first lug 1281 fixed to the pivoting retractable tooth 128, enables said tooth to be returned and held in the lowered rest position after indexing.

The month cam 44 is divided into 12 equal corner regions respectively corresponding to one month, and respective reference numerals from 4401 for the 1 month to 4412 for the 12 month are given. As is clear from this first part of fig. 6A, the leap year cam surface 461 of the leap year cam 46 on meshing level E is identical to the cam surface 441 for months of less than 31 days on level C, visible at the bottom of this figure, and the cam surface 442 for months of february, visible in the middle of this figure. Therefore, according to the plan view of the month cam 44 starting from level B, all the above cam surfaces 441,442 and 461 are superposed for the months of february corresponding to the corner region denoted by reference numeral 4402. This arrangement facilitates machining and assembly of the parts forming the month program wheel 43, since it is sufficient to verify the centring of these different cam surfaces to ensure the proper functionality of the operation of each pivoting retractable tooth 128, 129 and 130.

A second illustration will be seen from the top of fig. 6A, following downwards arrow S, which indicates the direction in which the indexing sequence operation at the end of the month of february is performed, and which shows a sectional view of the day program wheel 13 and of the month program wheel 43, on another meshing level B, at which the tooth 29 of the day indexing wheel 12 meshes with a pivoting retractable tooth 129 of the day program wheel 13, said pivoting retractable tooth 129 being mounted so as to pivot about a rotation axis 129 'integral with the day indexing gear 13'. According to the preferred embodiment shown, the rotation axis 129 ' is located slightly set back from the 26 th tooth, referenced 26 ', of the date indexing gear 13 '. This sequential operation occurs at 21.00 when 24 hour wheel 2 has advanced date engaging section 11 of the 24 hour wheel one tooth forward and caused date indexing wheel 12 to rotate 1/8 revolutions to engage tooth 29 behind tooth 28. During the passage from the 28 th day to the 29 th day of the month, when the pivoting retractable tooth 128 retreats into the rest position 128I (i.e., the indexing has been performed the previous hour), the pivoting retractable tooth 129 enters the active position 129A due to the cam surface 442 for the month of february of the month cam 44. However, in the case of the month february in leap years, as a conventional meshing on level D (see fig. 6B below), the working position 129A of the pivoting retractable tooth 129 is already active when going from day 28 to day 29 of the month in the middle of the night. Similar to the previous illustration on meshing level E at the top of fig. 6A, it is evident that the cam surface 442 of the month cam 44 for the month of february (i.e. for the indexed readjustment of this month from day 29 to day 30) is identical to the cam surface 441 of the month cam for the same month of february. The elastic indexing element 14 of the day program wheel enables the day indexing gear 13' to be indexed to rotate once again through exactly 1/31 revolutions in the direction S1.

As in the case of the first pivoting retractable tooth 128, the second elastic return element 1292, cooperating with the second lug 1291 fixed to the pivoting retractable tooth 129, enables said tooth to be returned after indexing and to be kept in the lowered rest position.

Further downwards along the arrow S indicating the direction of execution of the indexing sequence operation at the end of the month of february, a third illustration can be seen at the bottom of fig. 6A, which shows a sectional view of the date program wheel 13 and of the month program wheel 43 along a third meshing level C, which is located just below level B according to the preferred variant shown in particular in fig. 3 and 4, on which level C the tooth 30 of the date indexing wheel 12 meshes with a pivoting retractable tooth 130 of the date program wheel 13, said pivoting retractable tooth 130 being mounted so as to pivot about a rotation axis 130 'of said pivoting retractable tooth 130 integral with the date program wheel 13'. According to the preferred embodiment shown, the rotation axis 130 ' is located slightly set back from the second tooth (reference numeral 2 ') of the date indexing gear 13 '. This sequential operation occurs at 22.00 when 24 hour wheel 2 has again advanced the date meshing section 11 of the 24 hour wheel by 1 tooth and rotated the date indexing wheel 12 one 1/8 revolutions to mesh onto tooth 30 after tooth 29 on the date indexing wheel 12. Likewise, when the pivoting retractable teeth 129 return into the inactive position 129I when going from the 29 th to the 30 th day of the month (i.e. the indexing has been performed the previous hour), the pivoting retractable teeth 130 have already entered the active position 130A due to the cam surface 441 of the month cam 44 for the months less than 31 days. However, for the usual 30-day month, the operative position 130A of the pivoting retractable tooth 130 is already active when going from day 29 to day 30 of the month at midnight after the conventional daily meshing on level D (see fig. 6B below). Similar to the previous illustration of fig. 6A on the meshing levels B and E, it can be seen that the cam surfaces 441 and 442 of the month cam 44 are identical for the same month of february (i.e. for the month of february in the angular sector referenced 4402). However, on this meshing level C, in the corner zone 4404 corresponding to the month of april, the corner zone 4406 corresponding to the month of june, the corner zone 4409 corresponding to the month of september and the corner zone 4411 corresponding to the month of 11, four other identical projections can be seen, so as to perform readjustment from the 30 th to the 31 th days for the last day of the month from 22.00 to 23.00. It should also be noted that, for the pivoting retractable teeth 128 and 129, the third elastic return element 1302 (which cooperates with the third lug 1301 fixed to the pivoting retractable tooth 130) enables said teeth to be returned after indexing and to be kept in the lowered rest position.

The elastic indexing element 14 of the day program wheel enables the day indexing gear 13' to be indexed again with pitch for this last indexing readjustment by a precise 1/31 revolutions in the direction of rotation S1.

As can be seen in particular from the different illustrations of fig. 6A, all the pivoting retractable teeth 128, 129, 130 preferably have the same geometry, which on the one hand greatly simplifies the manufacture of the date program wheel 13, while also simplifying the manufacture of the spare part of the retractable teeth, which does not require any machining of the special elements for the adjustment of the date in the month. The simple and uniform geometry of each pivoting retractable tooth 128, 129, 130 together enables the use of an equally uniform cam surface at each level (B, C, E) for indexing readjustment as described above, so that these teeth are superposed on the external tooth system of the day indexing gear 13' in the working position 128A, 129A, 130A. Thus, the complexity of the entire proposed calendar mechanism is greatly reduced compared to conventional mechanisms.

Of the 31 teeth of the date indexing gear 13 'in fig. 6A and 6B, only the first and second teeth of the date indexing gear 13' and the 25 th to 30 th teeth (whose reference numbers are 1 ', 2', 25 ', 26', 27 ', 28', 29 ', 30', respectively) have been indicated, as has the tooth 131, this tooth 131 cooperating with the tooth 31 of the date indexing wheel 12 in order to be used in the described example for indexing from the 31 th day to the first day of the next month when going from 2 month 28 to 3 month 1 of the non-leap year. When the pivoting retractable teeth 128, 129 and 130 are in the working position respectively (i.e. 128A in the first illustration at the top of fig. 6A, 129A in the second illustration in the middle of fig. 6A, and 130A in the third illustration at the bottom of fig. 6A), they hide the teeth 28 ', 29 ' and 30 ' of the day indexing gear respectively according to the described preferred embodiment. However, these teeth can be seen in the bottom illustration of fig. 6B described below.

Fig. 6B shows the last month index sequence operation, which follows the previous three index readjustments of fig. 6A for day 28 of 2 months in a non-leap year, but which also occurs from 23.00 to midnight on all other dates in the year. It can be seen that the same arrow S for the last indexing of the month as in the preceding fig. 6A points downwards to indicate the direction in which the indexing sequence operation is performed. Lugs 1281, 1291 and 1301 and elastic elements 1282, 1292 and 1302 are also shown in this figure, which differs from the previous figures 5 and 3B, which are not shown in figure 5 for the sake of clarity, while figure 3B only shows said lugs.

The first illustration at the top of fig. 6B is a sectional view of the date program wheel 13 and of the month program wheel 43 on a fourth meshing level D, which, in the preferred embodiment, as shown in particular in fig. 3 and 4, is located just above level C, on which the toothing 31 of the date indexing wheel 12 meshes with the toothing 131 of the date indexing gear 13'. This sequential operating operation occurs at 23.00 when the 24-hour wheel 2 has advanced the date engaging section 11 of the 24-hour wheel by one tooth again relative to the previous illustration at the bottom of fig. 6A and has caused the date indexing wheel 12 to rotate 1/8 revolutions to engage on tooth 31 behind tooth 30 on the date indexing wheel 12.

The bottom illustration of fig. 6B shows a plan view of the program wheel 13 and the month cam 44, in which the elements between the fixed wheel 47' and the leap year indexing finger 47 from the first meshing level a (which is between the date meshing sector 11 and the date indexing wheel 12) up to the meshing level E can be seen. It is also clear that once the day of the month has been indexed to day 3/1 at midnight, the different retractable teeth 128, 129 and 130 pivoted on their respective meshing levels E, B and C about their axes 128 ', 129', 130 'are in the inactive positions 128I, 129I, 130I, at which time the day indexing wheel 12 has performed a further 1/8 revolutions so that the tooth 31 is no longer meshed with the day indexing gear 13'. The elastic elements 1282, 1292 and 1302, which cooperate with the lugs 1281, 1291 and 1301 of the pivoting retractable teeth 128, 129 and 130, respectively, keep these teeth in the rest position. Even if the date indexing wheel 12 comprises 8 teeth at the level a meshing with the date meshing section 11, it comprises only four teeth at each meshing level B, C, D, E meshing with the date program wheel 13, more precisely only one tooth at each level B, C, D, E, so that the driving of the date indexing wheel 12 by the last tooth of the meshing section 11 at the next time does not have any effect on the movement of the date program wheel 13. The date indexing gear 13' will therefore not be driven in rotation after this moment. However, the control train described above, and in particular based on fig. 4B (reference numerals 15, 16, 32, 33, 41, 42), will still index the month gear 43 integral with the month cam 44 by 1/12 revolutions in the direction S2 opposite to the direction S1 each time the 1 st day passes from the 31 st day to the next month. To prevent too much energy being used by the movement during each month change, in an alternative embodiment, the type of monthly indexing teeth associated with the month display and with the reverse action on the month program gear 43 may be separated. According to the proposed embodiment, these monthly indexing teeth are convergent, since the monthly indexing tooth, referenced 32, simultaneously causes the indexing of the gear 36 for actuating the month display and of the month program gear. In an alternative embodiment, it is possible to envisage that the second indexing tooth meshes in level F with the month control wheel 41 (which is not rotationally fixed with the monthly indexing gear 33) so that said tooth can be angularly moved forward by a value of a few days between the 10 th and 20 th days of the month, for example, so that the indexing of the month program wheel does not take place simultaneously with the indexing of the display of the current month, so that no very large moment for the simultaneous indexing operation is required at the end of the month, while ensuring the proper positioning of the date program wheel 43 when the retractable tooth must be brought into the operative position, i.e. for a sufficiently long time before the last few days of the month. Moreover, the day indexing wheel 12, which has performed a complete revolution after meshing with the 7 teeth of the toothed meshing sector 11, will be held in position by the surface of the sector 11' without teeth (which prevents the day indexing wheel 12 from rotating) visible in all the illustrations of fig. 6A and 6B, until the next meshing with said same toothed sector.

The reliability of the meshing proposed by the calendar mechanism according to the invention is improved compared to mechanisms that make use of complex cam surfaces and/or movements that have several translation members for the retractable teeth, since the position of pivoting the retractable teeth 128, 129 and 130 is determined only by the single degree of freedom of rotation that each tooth has about its axis of rotation 128 ', 129 ' and 130 '. Thus, the cam surfaces for the different indexing readjustments to be performed do not need to be at all very complex to show the pivoting retractable teeth 128, 129, 130 in their working positions 128A, 129A and 130A, since the height distance between the different angular zones 4401-4412 of the month cam 44 determines only their angular course during their change of state (i.e. from the non-working position to the working position, or vice versa). This height is chosen so that each of the pivoting retractable teeth, when in the working position 128A, 129A and 130A, overlaps the tooth system of the day indexing gear 13' at its respective meshing level. Although in fig. 6B the rotation axes 128 ', 129 ', 130 ' of the pivoting retractable teeth do not all lie on the same circle, i.e. at equal distances from the rotation center of the date indexing gear 13 ', this arrangement may be advantageous if the cam surface 441 for months less than 31 days, the cam surface 442 for february and the cam surface 461 for leap years are identical for february on different meshing levels E, B, C to achieve an overlapping arrangement of the pivoting retractable teeth 128, 129, 130 with respect to the 28 th, 29 th and 30 th teeth (respectively referenced 28 ', 29 ' and 30 ') of the date indexing wheel.

As can be seen from the views of fig. 6A and 6B, readjustment of the days missing at the end of the months of less than 31 days is carried out by the calendar mechanism according to the invention in turn hourly over a period of at most 4 hours (i.e. from 20.00 hours to 24.00 hours), first at each of the 3 readjustment meshing levels E, B, C and then at the regular day indexing level D, while the day indexing wheel 12 is driven by the meshing sectors 11 of the 24-hour wheel. All the pivoting retractable teeth are driven by the same clockwork train, more precisely by the same component (i.e. the day index wheel 12), so that no dedicated train for each correction is required, which simplifies the construction of the proposed calendar mechanism compared to conventional mechanisms. The number of teeth of the day indexing wheel 12, which is fixed to 8 according to the preferred embodiment chosen, has been chosen to perform a rotation around a sufficient angle to index the day program wheel 13 comprising the day indexing wheel 13' and the pivotally retractable teeth 128, 129, 130 mounted thereon by 1/31 revolutions, with a suitable depth of engagement. Moreover, the fact that the day indexing wheel 12 performs exactly one complete revolution per day enables a similar movement to be repeated by a day cycle starting from the same position. The fact that the meshing level B, C, E is separate from the meshing level D of the day indexing operation for all readjustment operations at the end of the month enables modular substitution, preferably by meshing levels, for each component of the day program wheel 13 and the day indexing wheel 12. This possibility provided by the calendar mechanism according to the invention is very advantageous because meshing level D will be used, for example, daily, while level B will be used once a year, level C5 times a year, and level E once a year in three of the four years, which are not leap years.

The calendar mechanism achieves that the date display is always synchronised with respect to the movement, and in both directions, so that the adjustment of the hour (which is normally achieved by rotating the crown provided on the case 0) will be transmitted to the hour wheel 1 and subsequently to the calendar mechanism. This is advantageous during travel to a destination whose time zone lags the original location (e.g., the west coast of the united states lags europe by 9 hours). A user of a watch equipped with a calendar mechanism according to the invention only needs to adjust the hours of his/her watch to less than 9 hours, so that the date will be automatically adjusted backwards, for example from 3 months 1 to 28 or 29 days of february, without any special operation for the adjustment of the date in the month. The use of such a watch is simpler than a watch with a conventional date mechanism, for which no synchronism with the movement is provided during adjustment in the opposite operating direction.

Claims (15)

1. A calendar mechanism comprising a date program wheel (13), said date program wheel (13) being driven by a timepiece movement and actuating a train of wheels (16-24) for the display of the dates in the month, wherein said date program wheel (13) comprises a date indexing gear (13 ') and a plurality of retractable teeth (128, 129, 130), said date indexing gear (13') being advanced one step per day by said timepiece movement, said plurality of retractable teeth (128, 129, 130) being drivable by said timepiece movement, characterized in that said retractable teeth (128, 129, 130) are each mounted so as to pivot between an active position (128A, 129A, 130A) in which said retractable teeth (128, 129, 130) are driven by said timepiece movement and an inactive position (128I, 129I, 130I), in the rest position (128I, 129I, 130I) the retractable teeth (128, 129, 130) are not driven by the timepiece movement, wherein the active position (128A, 129A, 130A) and the rest position (128I, 129I, 130I) of the retractable teeth (128, 129, 130) are determined by a cam surface (441,442, 461).

2. The calendar mechanism according to claim 1, wherein the date indexing gear (13') has a uniform external tooth system comprising 31 teeth and the drive train (1, 2, 11, 12) actuated by the timepiece movement is indexed in one step; the retractable teeth (128, 129, 130) are integral with the date indexing gear (13') and are driven to an operating position (128A, 129A, 130A) by the same drive train (1, 2, 11, 12) actuated by the timepiece movement.

3. The calendar mechanism according to claim 2, characterized in that the active position (128A, 129A, 130A) or the inactive position (128I, 129I, 130I) of the retractable tooth (128, 129, 130) is controlled by the position of a month program gear (43), the month program gear (43) being indexed by a control train (15, 16, 32, 33, 41, 42) driven by the date indexing gear (13') in 1/12 revolutions per month.

4. The calendar mechanism according to claim 3, characterized in that the control train (15, 16, 32, 33, 41, 42) comprises an intermediate wheel comprising two coaxial gears (15, 40) capable of independent rotation, of which the first gear is an intermediate date wheel (15) driven by the date indexing gear (13') and meshing with the date wheel (16) of the train of wheels (16-24) for the display of the dates in the months and the second gear is an intermediate month control wheel (42) driven by the date wheel (16) and meshing with the month program gear (43).

5. Calendar mechanism according to claim 4, wherein the month program wheel (43) comprises separate cam surfaces (441,442) distributed over at least a first meshing level (B) and a second meshing level (C) of the date program wheel (13), wherein the cam surfaces (441,442) are distributed over 12 zones (4401, 4402, 4403, 4404, 4405, 4406, 4407, 4408, 4409, 4410, 4411, 4412), each of which zones corresponds to a month of the year and determines the position of at least two retractable teeth (129, 130).

6. The calendar mechanism according to claim 5, wherein the cam surfaces (441,442) on the first and the second meshing levels (B, C) are identical for the month of February.

7. A calendar mechanism according to claim 1, further comprising a day display mechanism (5-8) driven by the timepiece movement, the day display mechanism (5-8) being adjustable independently of the calendar mechanism at any time of day.

8. The calendar mechanism according to claim 1, wherein the calendar mechanism is a perpetual calendar mechanism, the date program wheel (13) comprising a first pivoting retractable tooth (129) meshing in a first meshing level (B) for indexing from 29 to 30 in february, a second pivoting retractable tooth (130) meshing in a second meshing level (C) for indexing from 30 to 31 in less than 31 days of months, and a third pivoting retractable tooth (128) meshing in a third meshing level (E) for indexing from 28 to 29 in leap years of february, wherein the date indexing gear (13') meshes in a fourth meshing level (D).

9. The calendar mechanism according to claim 8, characterized in that it comprises leap year cams (46) integral with a maltese cross (46') mounted to pivot on the month program wheel (43), wherein the leap year cams (46) act on the third meshing level (E) of the calendar program wheel (13), the profile of the cam surfaces (461) of the leap year cams (46) on the third meshing level (E) being identical to the cam surfaces (441,442) on the first and the second meshing level (B, C) for the month of february.

10. The calendar mechanism according to claim 9, wherein the month program wheel (43) is coaxial with the date program wheel (13) and meshes, per month, at a fifth meshing level (F) with an intermediate month control wheel (42), this intermediate month control wheel (42) forming part of a control train (15, 16, 32, 33, 41, 42) driven by the date indexing gear (13').

11. A calendar mechanism according to claim 10, wherein the timepiece movement comprises a 24-hour wheel (2) having a date meshing segment (11) with a plurality of teeth which mesh with a date indexing wheel (12) of the calendar mechanism at a sixth meshing level (a), wherein the date indexing wheel (12) rotates at most one full revolution in 24 hours, the date indexing wheel (12) of the calendar mechanism additionally comprising a first meshing segment (29), the date indexing wheel (12) of the calendar mechanism additionally comprising indexing teeth (29, 30, 31, 28), at least one of which is located at the first meshing level (B), the second meshing level (C), the third meshing level (E) and the fourth meshing level (D), respectively.

12. The calendar mechanism according to claim 11, wherein the first indexing tooth (29) of the day indexing wheel (12) meshes, at a first meshing level (B), with the first pivoting retractable tooth (129) in the working position (129A) for indexing from 29 to 30 in february; a second indexing tooth (30) of said day indexing wheel (12) meshes, at a second meshing level (C), with a second pivoting retractable tooth (130) in an operating position (130A) for indexing from 30 to 31 in months of less than 31 days; -a third indexing tooth (28) of the day indexing wheel (12) meshes with a third pivoting retractable tooth (128) in an operating position (128A) in a third meshing level (E) for indexing from 28 to 29 in the months of february in leap years, and-a fourth indexing tooth (31) meshes with a tooth (131) of a day indexing gear (13') in a fourth meshing level (D), wherein the first, second, third and fourth meshing levels are arranged in order (B, C, D, E) starting from the day indexing wheel (12) and the sixth meshing level (a) of the day meshing section (11).

13. The calendar mechanism according to claim 12, wherein the projection of the indexing teeth (29, 30, 31, 28) in a plane perpendicular to the axis of rotation of the day indexing wheel (12) forms a continuous and uniform toothed segment.

14. The calendar mechanism according to claim 8, further comprising a month display mechanism (33-36) driven by a date wheel (16) of the wheel train (16-24) for the display of the date in the month, and a leap year display mechanism (37-40) driven by the month display mechanism (33-36) and comprising a leap year indicator gear (40) coaxial with the month indicator gear.

15. The calendar mechanism according to any one of claims 11 to 14, wherein the indexing teeth (29, 30, 31, 28) of the day indexing wheel (12) are arranged to engage with the date program wheel (13) at hourly intervals in sequence at the first, second, third and fourth engagement levels (B, C, D, E) while the date engaging section (11) of the 24-hour wheel (2) engages with the day indexing wheel (12).