HK1108739B - Annual calendar mechanism for watch movement - Google Patents

Description

Calendar mechanism for clock movement

Technical Field

The invention relates to an annual calendar mechanism for a timepiece movement, equipped with a month indication mechanism. This type of annual calendar mechanism displays exactly one day of the month, with a single correction of one or two days per year to change the date to the first day of march at the end of february.

Background

EP patent No.0987609 discloses a timepiece movement almanac in the name of frid ric Piguet. According to this patent, the mechanism comprises a date disc having 31 internal serrations on a first plane, marked with 31 numbers, each corresponding to a day of a month, the numbers being displayed sequentially through holes in the surface. The driving wheel assembly of the date disc comprises a driving wheel which is connected to the hour wheel of the timepiece movement by means of an intermediate wheel assembly. This driving wheel device completes one rotation in 24 hours in cooperation with a drive pin (driver finger), and can control the display of the date by driving the date dial one by one every day through its internal gear.

The Piguet mechanism further comprises means for correcting the date display at the end of each month of less than 31 days. The date disc therefore comprises a second toothed wheel located on a second plane and fixed with the date disc. This additional gear has two parallel teeth, which are spaced 31 a week apart from each other and which drive monthly wheels that carry a monthly cam (monthcam) through two intermediate wheels. The month cam is driven and adjusted at the end of each month through the additional gear and rotates one circle every year. Which brings about the rotation of the fine gears associated with the months of less than 31 days, these gears being adjusted at the beak (peak) of the lever (lever) at the end of each month of less than 31 days. When the lever is turned along its beak on the moon cam, it drives, through a further step, a correction wheel set (correction wheel set) which, in cooperation with a correction pin, is able to cooperate with the second gear at the end of each month of less than 31 days, to drive the date disc at the end of each month of less than 31 days. The correction wheel assembly is configured to complete one revolution in 24 hours as a date driven wheel assembly.

The mechanism described has several disadvantages. First, as just seen, the month cam, which comprises an indication identifying the month of each year and displayed successively through the holes of the dial, is driven by a gear fixed to the date disc. Thus, it is not possible to correct the month indication if the date mechanism is not simultaneously active. This is inconvenient when, for example, the timepiece is stopped on day 10 of the given month and when one wishes to reset it again to the correct date, i.e. day 15 of the next month. In this case, one has to rotate all the numbers associated with the date indication downwards in succession, from 11 th to 31 th, and then from 1 st to 15 th.

Furthermore, the means for correcting the indication of the date at the end of each month of less than 31 days require the date disc to be equipped with a second toothed wheel having two juxtaposed serrations 31 spaced apart from each other. Each time driven continuously by the two saw teeth moving forward 24 to adjust the month cam. If a quick correction device is used, it is not possible to determine which of the two serrations of the second gear of the date disc drives the month cam, so that the change of state can only be displayed between the date display and the indication of the month. Therefore, this quick correction mechanism cannot be used in the annual calendar mechanism disclosed in the Piguet patent.

Finally, the Piguet mechanism cannot be used with instant calendar devices. Thus, referring to the figures of the Piguet patent, it can be seen that at midnight on day 30 of the month with 30 days, the date ring is indicated as 31 st. As a result, the indication of the date of the timepiece is erroneous during the period 21:00 on day 30 of the month with 30 days to 02:30 on day 1 of the following month with 30 days.

Disclosure of Invention

It is an object of the present invention to overcome the above-mentioned drawbacks, among others, by providing an annual calendar mechanism for a timepiece movement, which is particularly simple and quick to correct.

The invention therefore relates to a timepiece annual calendar mechanism comprising a date disc with 31 digits, each digit corresponding to a day indicating each month, and which is equipped with: a first internal gear having 31 serrations; a date driving wheel device comprising a pin for driving a date disc by one step per day, the date display being controlled via a sawtooth of a first internal gear, said date disc comprising a second gear; additional correction drive wheel means able to cooperate with the second gear to drive the date disc by an additional step at the end of each month of less than 31 days; and a month cam which is driven at the end of each month and performs one revolution per year, characterized in that it comprises month driving wheel means for driving the month cam at the end of each month, said driving wheel means being connected, via a train of wheels, to date driving wheel means and correction driving wheel means, said wheel means assuming a first position in which it has no effect on the month cam, so that the kinematic chain between the date disc and the month cam is broken, said wheel means also assuming a second position which it occupies only when the month changes, and in which it drives the month cam so as to move it forward by one step.

Thanks to these features, the invention provides an annual calendar mechanism in which the date disc is not kinematically connected to the month cam, except for the interval period required for the mechanism to change from the end of the month to the beginning of the month of the following month. The correction of months can thus be done independently of the date correction. Therefore, it can be completed more quickly than the case where the date disc is always connected to the month cam, and at the time of always connection, the date has to be rotated by 31 days in order to correct the indication of the month.

By an additional feature of the invention, the date driving wheel unit, the correction driving wheel unit and the month driving wheel unit are driven by an instant release mechanism.

Thanks to this additional feature, the invention provides an annual calendar mechanism in which the date and month indications are corrected quasi-instantaneously. The display correction step is hardly visible to the user. Furthermore, the timepiece fitted with the date mechanism according to the invention permanently provides an accurate indication of the date and month. This is particularly appreciated when switching from a month of less than 31 days to the first day of the next month. In fact, as mentioned above, in the case of the annual clocks of the prior art, the correction of the display is carried out step by step, taking tens of minutes or even hours to complete, on the known sliding modes, for example in the field of timepieces. During this time, the timepiece provides the wrong date and month indication. Instead, according to the invention, these indications can be corrected instantaneously, so that the timepiece always provides the correct indication to the user.

Drawings

Other characteristics and advantages of the invention will appear more clearly on reading the following detailed description of a particular embodiment of the annual calendar mechanism according to the invention, given in full by way of non-limiting illustration with reference to the accompanying drawings, in which:

FIG. 1 is a plan view of a timepiece equipped with an annual calendar mechanism according to the invention;

FIG. 2 is a plan view of the annual calendar mechanism according to the invention, during the change of the aforesaid date disc from "30 days" to "31 days" at the end of the month of less than 31 days;

FIG. 3 is a similar view to FIG. 2, with an annual calendar mechanism according to the present invention, changing from "30 days" to "31 days" at the end of a month of less than 31 days;

FIG. 4 is a similar view to FIG. 3 with a date mechanism according to the present invention, ready to change from "day 31" to the first day of the month having 31 days;

FIG. 5 is a similar view to FIG. 4 with an annual calendar mechanism according to the present invention, on the first day of months having 31 days;

FIG. 6 is a perspective view of a date disc;

FIG. 7 is a bottom plan view of the instantaneous release system;

FIG. 8 is a top plan view of the instantaneous release system drive wheel;

FIG. 9 is a perspective view of a month star wheel;

FIG. 10 is a perspective view of a lever cooperating with the month star wheel of FIG. 9;

FIG. 11 is a plan view of the dial face of the rapid correction system in a neutral position;

FIG. 12 is a plan view of the bottom cover of the rapid correction system of FIG. 11, here in an intermediate position;

FIG. 13 is a similar view to FIG. 12, but with portions omitted to show components located on a lower face;

FIG. 14 is a plan view of the corrector gear of the quick correction system engaging the date disc gear;

FIG. 15 shows a plan view of the correction gear of FIG. 14 in mesh with the gear of the month star wheel;

FIG. 16 is a plan view of the rapid correction system in the watch time set position; and

fig. 17 is a perspective view of a month indicating dial.

Detailed Description

The invention starts from the general inventive idea consisting in providing an annual calendar mechanism in which the kinematic chain between the date disc and the month star wheel is always in an interrupted state except during the period in which the mechanism needs to change from the last day of the month to the first day of the following month, which allows to correct the date indication and the month indication more quickly in an independent manner, for example at the end of the month of february or when the timepiece has stopped for a long period of time. Furthermore, the annual calendar mechanism according to the invention comprises an instantaneous release system, without external forces, which allows the sudden transition of the date and month indications from the end of one month to the beginning of the next month, so that the transition from one month to the next occurs almost imperceptibly to the user and the clock always provides the correct indication.

Fig. 1 is a plan view of a timepiece equipped with an annual calendar mechanism according to the invention. The timepiece as a whole is indicated by the numeral 1, this timepiece having in particular an hour hand 2, a minute hand 4 and a second hand 6. It also comprises a date indicator in the form of a date 8 displayed through an aperture 10 in the dial 12. The time setting can be done by means of the gear crown 14.

If the dial is removed from this timepiece, leaving only the means for carrying out the invention, the rest, as shown in the plan views of fig. 2 to 5, shows three different moments of the annual calendar mechanism according to the invention, for example from 4 months 30 days to 5 months 1 days, switching from a month with less than 31 days to the next month.

From an analysis of fig. 2 and of the perspective view 6, it is possible to explain the operation of the annual calendar mechanism according to the invention. The mechanism comprises a date disc 16, the date disc 16 being composed of a bottom annular disc 18 having a first internal gear 20 and a top annular disc 22 having a second internal gear 24. The first gear 20 includes 31 saw teeth 20a and the second gear 24 includes a single saw tooth 24 a. The top surface of the annular disc 22 includes 31 numbers, each of which corresponds to a day of the month. These numbers are shown sequentially through the holes 10 shown in figure 1. At its bottom face, the annular disc 22 also comprises a cylindrical control member 26, which can be fixed to said annular disc 22 by suitable means, or can be integral with said disc 22. The function of this post 26 will be explained in more detail later. The serrations 22a and 24a thus extend in two different planes, with the serrations 20a extending below the serrations 24 a. As can be observed from fig. 6, the two bottom 18 and top 20 annular discs are arranged in parallel at a distance from each other.

It can also be seen from figures 2 to 5 that jumper 28, which is sprung back by spring tab 30, is applied to toothed wheel 20 of annular disc 18 to angularly position date disc 16 when the latter is not actuated, thus allowing accurate indication of date disc 16 with respect to hole 10.

A date driving wheel device, generally indicated by the numeral 32, is associated with a pin 34, which, via its internal gear 20, can drive the date disc 16 one step per day. In the particular case of figure 2, in which the date mechanism according to the invention is shown in the condition of momentary jump from "30 days" to "31 days", it can be seen that the pin 34 has not yet engaged the internal gear 20 of the bottom annular disc 18. As can be seen in fig. 2 to 5 and in fig. 7 and 8, the date driving wheel assembly 32 comprises a wheel 36 having a pin 34 and driven in rotation by a first driving wheel 38 for one rotation per day. The driving wheel 38 is itself driven by an hour wheel 39 of a traditional watch movement via a wheel device 41, which may be mechanical or electronic, a wheel 43 of the wheel device 41 being driven by the hour wheel 39, a pinion 45 of the wheel device 41 being in mesh with the driving wheel 38. Date driving wheel assembly 32 thus forms a pivot on post 37, stabilizing in the movement at point a. It may also be pivoted in bearings (jewel bearings).

The foregoing is well known in the art, except for the structure of date disc 16. In fact, when the latter is in a determined position, the conventional date disc drive is able to reset the date by means of a quick correction device engaged with the toothed wheel 20, with the aid of a toothed crown. According to such a general system, it is necessary to reset the date, i.e., 2 months, 4 months, 6 months, 9 months and 11 months, at the end of the months of less than 31 days.

We now describe what is added to this mechanism to convert it into an annual calendar mechanism, where, in addition to the end of the 2 month, the end date of each month less than 31 days automatically jumps from "31 days" to "1 day" of the next month.

As already mentioned above, the date disc 16 according to the invention differs from usual date discs in that: which includes additional serrations 24a on the top annular disc 22. Typically at the end of a month of less than 31 days, which is driven once per month by the correction drive wheel arrangement 42. This drive wheel assembly 42 includes a pin 44, which pin 44 is secured to a second drive wheel 46, which is pivotally connected at point B by a sliding pinion gear 48. The second drive wheel 46 is driven by the first drive wheel 38 via an intermediate wheel 50, which meshes with the wheel 36.

The sliding lever 40 also has a month drive wheel arrangement 52 for driving a month star wheel 54 at the end of each month. For this purpose, the month drive wheel assembly 52 comprises a third drive wheel 56 which has a pin 58 and is driven by the first drive wheel 38 via the wheel 36. As described below, the associated lever 59 is pivoted at point F, which controls the pivoting of the sliding lever 40. This lever 59 is sprung back by the spring 61 and cooperates with the sliding lever 40 via the operating arm 63, the head 65 of the operating arm 63 being sunk in a shaped hole 67 provided in said sliding lever 40.

As shown particularly clearly in fig. 9, the month star wheel 54 comprises a ground wheel with 12 serrations 60, which is positioned by a jumper 62 sprung back by a spring 62, in order to position said month star wheel 54 at an angle when it is not driven. The month star wheel 54 also includes a bottom cam 66 and a top cam 68. The top cam 68 includes 5 tabs 68a-68e distributed therearound, with the 5 tabs 68a-68e corresponding to five months of the year less than 31 days each. The bottom cam 66 avoids the use of a recoil spring by the lever 70 along the outside of the bottom cam 66 via its beak 74, but it may use a recoil spring along the outside of the top cam 68 via its nose (nose) 72. The lever 70 is pivoted at point C and is mounted for free rotation on the sliding lever 48.

As the various components of the invention have been described previously, there is also a need for explanation of the operation of the annual calendar mechanism. Two situations arise depending on whether it is a month less than 31 days or a month equal to 31 days. The case of switching from "30 days" to the first day of the next month of less than 31 days is illustrated by fig. 2 to 5.

In fig. 2, the annual calendar mechanism according to the present invention is shown in a position immediately before the transition from "30 days" to "31 days". In this position, the pins 34 and 44 are released from the first and second floor gears 20 and 24 of the bottom and top annular disks 18 and 22. Likewise, the pin 58 is released from the wheel gear, which has the twelve serrations 60 of the month star wheel 54. Since the instantaneous release system 76 is used and the drag (drawing) correction system, which is characterized by the fact that the correction pin steps through the teeth of the date ring and of the month star wheel, is not used, it is then possible to quickly correct the date disc 16 or the month star wheel 54 at any time.

Shown in fig. 7 and 8 is an instantaneous release system 76. In particular, it comprises a first drive wheel 38 and a wheel 36 with a pin 34. It also comprises a release lever 78 which is sprung back by a spring 80 and contacts a cam 84 via its beak 82. Wheel 36 is secured to cam 84 via pins 86 or by rivets. The pin 86 is free to move within a shaped hole 88 in the drive wheel 38.

The operation of the instant release system 76 is as follows. By rotating, the drive wheel 38 drives the wheel 36 and the cam 84 via the pin 86. The release lever 78 moves, via its beak 82, along the outside of the cam 84 until reaching the point defined by the leaf spring 80, in which it starts to slide abruptly along said cam 84, driving the latter and the wheel 36 to rotate by an angle determined by the shape of the cam 84. The cam 84 and wheel 36 then remain stationary until the drive wheel 38 begins to drive them again via the pin 86 at the bottom of the hole 88.

After release of the instantaneous release system 76 is complete, the date mechanism proceeds sequentially through the position transitions shown in fig. 3, 4 and 5. It will be appreciated that the sequence of movements of the various components forming the date mechanism according to the invention has been interrupted for ease of understanding, but in practice the mechanism changes from the position shown in figure 2 to the position shown in figure 5 in a fraction of a second.

In fig. 3, pin 44 is carried by a second driving wheel 46, which has pushed saw tooth 24a through a step and has driven date disc 16 to complete the display transition from "30 days" to "31 days", this second driving wheel 46 being itself driven by cam 84 and wheel 36 via intermediate wheel 50. The wheel 36 driven by the instantaneous drive system 76 to which this first drive wheel 38 belongs continues to rotate, so that the pin 34 carried by said wheel 36 comes behind the saw tooth 20a of the bottom annular disc 18 and the second operating condition of the mechanism can start as described in figure 4.

In fact, in fig. 4, the pin 34 pushes forward the teeth of the saw tooth 20a located at the rear, driving the top annular disc 22. Via its post 26, the latter then pushes the connecting lever 59, which starts to rotate about its pivot centre F. In turn, via its operating arm 63, the connecting lever 59 pushes the sliding lever 40, which carries the third drive wheel 56 and the pin 58 connected to it. By this pushing action, the sliding control lever 40 rotates about its pivot center a and the pin 58 passes through the serrations of the wheel 60 having the 12 serrations of the month star wheel 54. The pin 44 then rotates, but without any action of the removed serrations 24 a. It can be seen from an analysis of fig. 4 that the jumper 28 passes through the space between two consecutive serrations 20a to the space between the next two serrations 20a and soon beyond one of these serrations 20 a. The mechanism, when in this phase of operation, is shown in an intermediate position between "31 days" and "1 day" of the next month.

We begin with reference to fig. 5 to analyze the month change steps. In this position, pin 34 has finished pushing saw tooth 20a one step forward, and then date disc 16 has been driven a further step to convert the display from "31 days" to "1 day" of the next month. This is the first day of a month following a month of less than 31 days. Therefore, the display of the date disc 16 need not be corrected at the end of the month with 31 days of months. As is being described in detail, the pin 44 is thereby released from the second internal gear 24. Driven by wheel 56 driven by wheel 36, pin 58 has pushed month star wheel 54 forward by one step, i.e. one twelfth of a revolution. In the last step, the rotation of the month star wheel 54 is accompanied by the rotation of the bottom cam 66 and of the top cam 68. Beak 74 of lever 70 has followed the outside of bottom cam 66, but nose 72 is located between the two projecting parts of top cam 68. Lever 70 rotates about its pivot center C and simultaneously actuates sliding lever 48, which sliding lever 48 now rotates about its pivot center B, which causes pin 44 to come out of reach of gear 24, so that at the end of the month of less than 31 days, pin 44 is released from said gear 24 and it is not possible to move date disc 16 one step further.

In fig. 5 is the first day of a month having 31 days immediately following a month less than 31 days. The pin 44 is in its final position in which it is released from the second inner gear 24 of the top annular disc 22. It is in this position throughout the month. At the end of the 31-day month, pin 34 converts date disc 16 from "30 days" to "31 days" and then from "31 days" to "1 day" of the next month, as in a conventional calendar. Each time the pin 44 is actuated by the instantaneous release system 76, this does not contribute to the date display, since the pin 44 is released from the second internal gear 24 of the top annular disc 22. The next day, the column 26 pushes the slide lever 40 via the connecting lever 59. Under the effect of this thrust, the lever 40 rotates about a and the pin 58 projects into the teeth of the twelve toothed wheel 60 of the month star wheel 54, pushing said month star wheel 54 one step forward, i.e. one twelfth of a revolution. If a shift is being made from a 31-day month to another 31-day month (7/8 and 12/1), the cams 66 and 68 will maintain the positions of the levers 70 and 48. On the other hand, if shifting to months of less than 31 days, nose 72 of lever 70 will climb above tab 68b and cause rotation of lever 48 so that pin 44 is within range of gear 24 of disc 22, ready to push sawtooth 24a one step forward at the end of the months of less than 31 days. This position is maintained throughout the month. On "30 days" of a month, the serrations 24a will be in the position shown in fig. 3, and the described cyclic process starts again. It will be noted that during the transition from "day 1" to "day 2", the post 26 is completely beyond the connecting lever 59. The latter then returns to its rest position under the pushing action of the elastic tab 61 and is ready to be actuated again by the latter, on passage of said stem 26, when switching from the last day of the current month to the first day of the following month.

From the foregoing, it is clear that during months of less than 31 days, the pins 44 are always located on the path of the serrations 24 of the top annular disc 22. However, since the top annular disc 22 has only one serration 24a, the pin 44 is only active once per month. However, during the 31-day months, the pin 44 is removed from the gear 24, so that it cannot act on the top annular disc 22. Furthermore, the two cams 66 and 68 of the month star wheel 54 materialize the succession between months of less than 31 days and months of 31 days. In the 31-day month, beak 74 of lever 70 is in contact with the projection of bottom cam 68. The lever 70 rotates and, via the sliding lever 48, brings the pin 44 into the rest position. In months of less than 31 days, the nose of the lever 70 contacts the side of the top cam 68 and drives the pin 44 in the active position. Fig. 10 shows a perspective view of the control lever 70.

The annual calendar mechanism according to the invention also comprises quick correction means as shown in figure 11 and in the subsequent figures. Generally indicated by the numeral 90, this quick correction device comprises a correction pinion 92 having three pin friction members driven by an intermediate wheel 94, the quick correction device itself being driven by a rotary rod 96 through a sliding pinion 98 and a second intermediate wheel 100. The sliding control lever 102 is rotated at point D, which is located in the center of the second intermediate wheel 100, and the sliding control lever 102 carries the correction pinion 92.

The quick correction device 90 is normally in a neutral position in order not to interfere with the normal operation of the annual calendar mechanism according to the invention. The lever 104 of the time-setting mechanism of the movement can occupy three different positions as a function of the respective positions of the rotary lever 96 and of the extractor 106. In fig. 12 and 13, the control lever 104 is shown in the neutral position and the turn lever 96 is in the advanced position. It has a time-setting train 108, a pin 110 of which train 108 projects on the side of the watch (not shown) into a slot 112 in a control lever 114. The lever 114 is rotated at point E and the lever 114 has a post 116, the post 116 holding the sliding lever 102 in place by snapping into a V-shaped cut out portion 118 of the sliding lever 102.

When the rotating lever 96 is pulled out into the neutral position, the lever 104 rotates and its pin 110 pushes the lever 114 and its post out of the sliding lever 102. The sliding pinion 98 then drives the intermediate wheels 94 and 100 and the correction pinion 92. Depending on the direction of rotation of the rotary lever 96, the sliding control lever 102 rotates at point D and the correction pinion 92 drives the date disc 16 through its first internal gear 20 or the month star wheel 54 through its twelve-toothed wheel 60. When the rotary lever 96 is in the time-setting position, the lever 104 is rotated in the opposite direction and its pin 100 again retains the lever 114 and the post 116 received in the V-cut portion 118.

The annual calendar mechanism according to the invention finally also comprises a month indicator as shown in figure 17. Designated as a whole by the numeral 120, the month indicator comprises a disc 122 which produces an indication of the twelve months of the year. The indicator disk 122 is fixed on an axle 124, the axle 124 having two holes 126 through which the axle 124 engages with two corresponding studs 128 carried by the month star wheel 54. The month indicator 120 thus formed is limited by a key supported by a tube of a support tray (not shown).

It goes without saying that the invention is not limited to the embodiments described above and that various simple modifications and variants can be made by those skilled in the art without departing from the scope of the invention defined by the appended claims.

Claims (14)

1. An annual calendar mechanism for a timepiece, comprising: a date disc (16) marked with 31 numbers indicating a day corresponding to each month, having a first internal gear (20) comprising 31 serrations (20 a); -a date driving wheel device (32), said date driving wheel device (32) comprising a first pin (34) to drive the date disc (16) through one step per day via a toothing (20a) of the first internal gear (20) to control the display of the date, said date disc (16) comprising a second gear (24); a correction drive wheel device (42) able to cooperate with the second toothed wheel (24) to drive the date disc (16) through a further step at the end of the month of less than 31 days; and a month star wheel (54) configured to be driven at the end of each month and to complete one revolution per year, characterized in that: said annual calendar mechanism comprises a month driving wheel device (52) for driving a month star wheel (54) at the end of each month, said month driving wheel device (52) being connected to the date driving wheel device (32) and to an additional correction driving wheel device (42) via a wheel train (35, 56), said month driving wheel device (52) being in a first position in which it does not act on the month star wheel (54) thereby disconnecting the kinematic link between the date disc (16) and the month star wheel (54), and a second position in which it is only located when a month change occurs in which it drives the month star wheel (54) one step forward, so that the correction device (90) can act on the date disc (16) without any action on the month star wheel (54).

2. The annual calendar mechanism according to claim 1, characterized in that the date driving wheel means (32) and the month driving wheel means (52) are carried by a first sliding lever (40), the rotation of which is carried by a connecting lever (59), and in that the correction driving wheel means (42) are carried by a second sliding lever (48), the rotation of which is controlled by a lever (70) cooperating with the month star wheel (54).

3. The annual calendar mechanism according to claim 2, characterized in that the rotation of the connecting control lever (59) is itself controlled by a post (26) carried by the date disc (16), the result of said rotation causing the month driving wheel means (52) to mesh with the month star wheel (54) and to move the latter one step forward at the end of each month, the control lever (70) rotating and placing the correction driving wheel means (42) on the path of the second toothed wheel (24) if the upcoming month is less than 31 days.

4. The annual calendar mechanism according to any of claims 1 to 3, characterized in that the month drive wheel means (52) comprise a second pin (58) which drives the month star wheel (54) one step forward per month, and in that the correction drive wheel means (42) comprise a third pin (44) which drives the date disc (16) one step further at the end of each month of less than 31 days.

5. The annual calendar mechanism according to claim 2 or 3, characterized in that the month star wheel (54) comprises a wheel (60), the wheel (60) having 12 serrations and a graduated month cam (68), the month cam (68) comprising 5 projections (68a-68e), corresponding respectively to 5 months of less than 31 days of a year, the lever (70) being moved along the profile of the month cam (68) by means of a beak (72).

6. The annual calendar mechanism according to claim 5, characterized in that the month star wheel further comprises a cam (66), the lever (70) being moved along the profile of said cam (66) via a nose (74).

7. The annual calendar mechanism according to any of claims 1 to 3, characterized in that the second gear wheel (24) comprises a single saw tooth (24 a).

8. The annual calendar mechanism according to claim 2 or 3, characterized in that the annual calendar drive wheel means (32) comprise a wheel (36) carrying a first pin (34), and which is kinematically coupled to a first driving wheel (38), the first driving wheel (38) itself being driven in rotation by a hour wheel (39), wherein the correction drive wheel arrangement (42) comprises a third pin (44) via which it drives the date disc (16) by means of the second gear wheel (24), the third pin (44) is fixed to a second drive wheel (46) driven by the first drive wheel (38) through an intermediate wheel (50) which meshes with the wheel (36), and, wherein the month drive wheel arrangement (52) comprises a third drive wheel (56) carrying a second pin (58), via a second pin (58), the month drive wheel means (52) drive the month star wheel (54).

9. The annual calendar mechanism according to claim 8, characterized in that the date drive wheel means (32), the correction drive wheel means (42) and the month drive wheel means (52) are all driven by an instantaneous release device (76).

10. The annual calendar mechanism according to claim 9, characterized in that the instantaneous release mechanism (76) comprises a release lever (78) sprung back by a spring plate (80) which abuts via a beak (82) against a cam (84), the wheel (36) being fixed by a pin (86) on the cam (84) contacted by the beak (82), the pin (86) being free to move within a hole (88) of the wheel (36).

11. The annual calendar mechanism according to any one of claims 1 to 3, characterized in that the date disc (16) comprises a graduated bottom annular disc (18) and a top annular disc (22), the bottom annular disc (18) carrying the first internal gear wheel (20) and the top annular disc (22) carrying the second gear wheel (24).

12. The annual calendar mechanism according to any of claims 1 to 3, characterized in that the correction means (90) comprise a correction pinion (92) carried by the sliding control lever (102) and driven by an intermediate wheel (94), the intermediate wheel (94) itself being driven by a rotating lever (96).

13. The annual calendar mechanism according to claim 12, characterized in that when the rotary lever (96) is in the rotary or time-setting position by the action of the second lever (114) and the post (116), the sliding lever (102) is in the intermediate position, the post (116) being stuck in a cut-out portion (118) of said sliding lever (102), when the latter is in the correcting position, the first active date indicating correcting position and the second active month indicating correcting position depending on the direction of rotation of the lever.

14. The annual calendar mechanism according to any of claims 1 to 3, including a month indicator (120) comprising a disc (122), the disc (122) being intended to produce an indication of the months of the year and being fixed to a hub (124) via which hub (124) it is fitted on the month star wheel (54).