Calendar mechanism for a timepiece movement allowing to display at least the retrograde calendar

Abstract

The present invention relates to a calendar mechanism for a timepiece in which the date is displayed in a retrograde manner and in which the date return rack (7) actuates the month star (13) and moves it forward one step when said date return rack (7) falls from its high position under the action of its return spring (74) when the last day of a month passes to the first day of the following month.

Description

[0001] The present invention relates to a calendar mechanism for a watch movement allowing at least the date to be displayed in a retrograde manner. Preferably, the calendar mechanism is a perpetual calendar mechanism.

[0002] A retrograde perpetual calendar mechanism is described in the book "Les Montres compliqués" by François Lecoultre on pages 231 to 236. In this mechanism, only the date display is retrograde: the date hand moves on an arc traced on the dial so that when this hand reaches the 28, 29, 30 or 31 at the end of the month, it instantly returns to its starting point on the number 1. The other displays of the day of the week, the month of the year, the moon phases and leap years are conventional.

[0003] In this mechanism, the date hand is carried by a date wheel with triangular teeth secured to a pinion meshing with a rack which tends to pivot the date wheel in a first direction. This date wheel is driven in a second direction by one tooth per day by the mechanism of the timepiece. A pawl is provided to prevent the date wheel from rotating in the first direction. The pawl has an arm resting on a month cam fixed to the month star with twelve teeth. The month cam has s whose depth determines the months with 30 or 31 days as well as a notch in which the leap year cam pivots. This leap year cam has four steps, three of which are equal and a fourth, distinct, determining a leap year.Each time the month star completes a full turn, the leap year cam makes a quarter turn using a suitable mechanism (usually a Maltese cross). The end of the pawl arm ends in a four-notch rack. The position of this rack is therefore regulated by the month cam. A finger attached to the date wheel is used to lift the pawl by acting against the notches of the rack at the desired moment to release the date wheel, which then pivots in the first direction, pushed by the rack. This release takes place at the moment of passage from the last day of the month to the first day of the following month, the position of the end of the pawl arm on the month cam determining the moment of release and limiting the length of the month.

[0004] In this mechanism, only the date is displayed retrogradely. The month display is standard: the month hand is fixed to the month star and must advance one twelfth of a turn to mark the next month at the moment the date hand retrogrades. To do this, the rack has an arm arranged to push a tooth of the month star as it falls.

[0005] Generally speaking, retrograde calendar mechanisms are bulky, particularly in thickness if concentric displays are required.

[0006] The aim of the present invention is to provide a calendar mechanism (simple, annual or perpetual) for a watch movement which allows at least the date to be displayed retrogradely. One aim of the present invention is in particular to provide a calendar mechanism which allows in particular the retrograde display of the date and the month. Another aim of the present invention is to provide a calendar mechanism which allows the retrograde display of the date and which is simple and compact, particularly in terms of thickness.

[0007] The present invention relates to a calendar mechanism for a clock movement according to claim 1.

[0008] The attached figures illustrate schematically and by way of example an embodiment of the calendar mechanism according to the invention. In this embodiment, the calendar mechanism makes it possible to display in particular the date and the month in a retrograde manner. THE figures 1 à 14 illustrate the elements of the calendar mechanism allowing the date to be displayed while the figures 15 And 16 illustrate the elements of the calendar mechanism allowing the display of the month. In particular, The figure 1 is a top view of a portion of a calendar mechanism according to one embodiment of the invention as of January 31. The figure 2 is a top view of the mechanism of the figure 1 illustrating the transition from January 31 to February 1 (before the leap). The figures 3 And 4 are views from above and below of the mechanism on February 1 (after the jump). figure 5 is a top view of the mechanism illustrating the transition from February 1 to February 2 (before the jump). The figure 6 is a top view of the mechanism as of February 2 (after the jump). The figure 7 is a top view of the mechanism on February 28. The figure 8 is a top view of the mechanism illustrating the transition from February 28 to March 1 (before the jump). The figure 9 is a top view of the mechanism as of February 29. The figure 10 is a top view of the mechanism illustrating the transition from February 29 to March 1 (before the jump). The figure 11 is a top view of the mechanism on March 1 (after the jump). The figure 12 is a top view of the mechanism as of April 30. The figure 13 is a top view of the mechanism illustrating the transition from April 30 to May 1 (before the jump). The figure 14 is a view of the mechanism on May 1st. The figure 15 illustrates the elements of the calendar mechanism of the previous figures allowing the display of the month, the month displayed being the month of December. The figure 16 illustrates the elements of the calendar mechanism of the previous figures allowing the display of the month, the month displayed being the month of January.

[0009] The calendar mechanism according to the invention is intended to equip a clockwork movement to enable the display of at least the date of the month. According to the invention, this display is retrograde.

[0010] In the illustrated embodiment, the calendar mechanism is in particular a perpetual calendar mechanism for displaying, among other things, the date, month and leap year.

[0011] A 24-hour wheel (not shown) is pivoted at A and is arranged to be driven one revolution per day by the clockwork movement comprising the calendar mechanism. This 24-hour wheel carries a 24-hour finger 1 arranged to drive once a day a large lever 2 pivoted at B on the clockwork movement. Preferably and as shown in the figures, the 24-hour finger 1 cooperates with a correction pawl 21 of the large lever to allow the time display of the clockwork movement to be set counterclockwise without correcting the date and without breaking the mechanism.

[0012] The large lever 2 is subjected to the action of a return spring 22 which tends to keep it in a first rest position resting against a stop not shown. When the 24-hour finger 1 drives the large lever 2, it pivots it at B against the action of its return spring 22.

[0013] A drive pawl 23 is pivoted on the large lever 2 and is subjected to the action of a return spring 230. The drive pawl 23 is intended to cooperate with a date wheel 3 with triangular teeth to advance the latter by one step in a first direction when the large lever 2 pivots driven by the 24-hour finger 1. The date wheel 3 carries a date indicator (not illustrated) which can take any suitable form.

[0014] A jumper 4 positions the date wheel 3 and prevents it from pivoting in a second direction opposite to the first. To do this, the jumper 4 comprises a first positioning arm 41 arranged to cooperate with the teeth 31 of the date wheel 3 for positioning and locking the latter. A return spring 40 is arranged to force the jumper 4 against the teeth 31 of the date wheel 3.

[0015] A blocker 5 is pivoted at C and comprises a first arm 51 arranged to cooperate with a second blocking arm 42 of the jumper 4. The blocker 5 is subjected to the action of its return spring 53 which tends to push said blocker 5 into a position in which the first arm 51 is in abutment against a stud 54 driven into the clockwork movement. The blocker 5 further comprises a second arm 52 arranged to cooperate with an arm 24 of the large lever 2. As will be seen later, the blocker 5 makes it possible to retain the jumper 4 outside the toothing 31 of the date wheel when passing the end of a month to allow the retrograde return of the date wheel 3.

[0016] A date pinion 6 is integral with the date wheel 3 and is engaged with a date rack 7 pivoted at D. The date rack 7 is subjected to the action of its return spring 74 which tends to pivot it towards a stop 75 fixed on the watch movement. In particular, the date rack 7 tends to pivot the pinion 6 and the date wheel 3 in a second direction opposite to the first direction (direction of actuation of the large lever 2 on the date wheel 3). The date rack 7 carries a month pin 71 arranged to cooperate with an intermediate lever 8 pivoted at E on a month lever 9 itself pivoted at F on the watch movement.

[0017] The intermediate lever 8 has a slot 81 crossed by a pin 43 fixed on the jumper 4 of the date wheel 3. When the date rack 7 reaches its high position at the passage from the last day of the month to the first day of the following month, the month pin 71 pushes the intermediate lever 8 which pivots at E and acts on the second pin 43 to pivot the jumper 4 which then releases the date wheel 3 and the blocker 5. The latter then falls to block the jumper 4 outside the teeth 31 of the date wheel 3.

[0018] The month rocker 9 comprises a feeler 91 which is arranged to bear against a month cam 10. The month cam 10 comprises a first portion 101 whose profile is calculated to determine the months with 30 or 31 days between March and January and a second portion 102 for the month of February. This second portion 102 has in its center a notch 1022 to allow a tooth of a leap year cam 11 pivotally mounted on the month cam 10 to pass.

[0019] The role of the leap year cam 11 is to determine whether the current year is a leap year or not, i.e. whether the month of February has 28 or 29 days. In the illustrated embodiment, the leap year cam 11 is a satellite pivoted on the month cam 10 and formed of 8 teeth, of which six teeth 111 are whole for non-leap years and the months of February with 28 days and 2 teeth 112 are truncated for leap years and the months of February with 29 days (the reverse is of course possible, i.e. six truncated teeth and two whole teeth). The leap year cam 11 is driven by a fixed wheel 12 with nine teeth which is coaxial with the month cam 10.

[0020] Thus, the month rocker 9 and by extension the intermediate rocker 8 can take four different positions depending on the current month.

[0021] Finally, according to the invention, the date rack 7 also carries a month finger 72 pivotally mounted on said rack 7 and subjected to the action of a return spring 73. The month finger 72 is arranged to drive a month star 13 secured to the month cam 10 when the date rack 7 falls. The month star 13 is subjected to the action of its positioning jumper 14 and for its part drives the display of the months.

[0022] This month display may be of any suitable shape. Preferably, it is also a retrograde display as illustrated in the figures 15 And 16The calendar mechanism according to the present embodiment thus further comprises a truncated toothed pinion 15 secured to the month star 13. The truncated toothed pinion 15 comprises a toothed sector 151 and a toothless sector 152 and is arranged to drive a month rack 17 pivoted at G on the clockwork movement. The month rack 17 is subjected to the action of its return spring 171 which tends to pivot it in the direction opposite to the driving direction of the truncated toothed pinion 15. Finally, the month rack 17 meshes with a month display pinion 18 which carries the month indicator (not shown). Preferably, a play-compensating device is provided between the month rack 17 and the month display pinion 18. Such a device may take the form of a special toothing for the month display pinion 18.

[0023] The operation of the calendar mechanism according to the embodiment of the invention illustrated in the figures will now be described.

[0024] THE figures 1 , 7 , 9 , 12 illustrate the calendar mechanism as described above at the end of the month, respectively January 31, February 28 (non-leap year), February 29 (leap year) and April 30. The large lever 2 is held in its rest position resting on its stop by its return spring 22. The feeler 91 of the month lever 9 rests on the area of ​​the profile of the month cam 10 corresponding to the current month.

[0025] In this end-of-month position, jumper 4 is pushed by its return spring into a position in which its first arm 41 is held in the teeth 31 of date wheel 3. Date wheel 3, date pinion 6 and consequently date rack 7 are thus blocked by jumper 4. Arm 51 of blocker 5 bears against second arm 42 of jumper 4 pushed by its return spring 53. Date rack 7 is engaged with date pinion 6 blocked by jumper 4 but does not cooperate with intermediate lever 8 or month star 13.

[0026] In the figure 1 , the feeler 91 is supported on an area of ​​the first portion 101 of the month cam 10 corresponding to at least January with 31 days.

[0027] In the figure 12 , the feeler 91 rests on an area of ​​the first portion 101 of the month cam 10 whose depth corresponds to the month of April at 30 days.

[0028] There figure 7 illustrates the case of a non-leap year, the month of February ending on the 28th. In this case, the feeler 91 is supported against an entire tooth 111 of the leap year cam 11 which is located in the notch 1022 of the second portion 102 of the month cam 10.

[0029] There figure 9 illustrates the case of a leap year, the month of February ending on the 29th. In this case, the feeler 91 rests against a truncated tooth 112 of the leap year cam 11 which is located in the notch 1022 of the second portion 102 of the month cam 10.

[0030] THE figures 2 , 8 , 10 And 13 illustrate the passage from the last day of the month to the 1st day of the following month just before the retrograde jump, i.e. respectively the passage from January 31 to February 1, from February 28 to March 1, from February 29 to March 1 and from April 30 to May 1.

[0031] At the end of a month, the 24-hour finger 1 driven by the 24-hour wheel comes into contact with the correction pawl 21 and pivots the large lever 2. The drive pawl 23 comes into contact with the toothing 31 of the date wheel 3 to advance the latter by one step in a first direction. Simultaneously, the arm 24 of the large lever 2 comes into contact with the second arm 52 of the blocker 5 and pivots it against the action of its return spring 53.

[0032] By pivoting, the date wheel 3 drives the date pinion 6 which in turn drives the date rack 7 which pivots against the action of its return spring 74 to reach its high position. The month pin 71 then comes into contact with the intermediate lever 8, the position of which is determined by the month lever 9 resting on the month cam 10, and pivots it. The intermediate lever 8 acts on the pin 43 of the jumper 4 and then lifts said jumper 4 into a raised position in which the first arm 41 of said jumper 4 is no longer in the teeth 31 of the date wheel 3 ( figures 2 , 8 , 10 And 13 ).

[0033] The date wheel 3 is released and can then pivot in the second direction under the action of the date rack 7 to bring the date indicator back to the 1st of the month. This retrograde return is detailed below.

[0034] The 24-hour finger 1 continues its rotation until it releases the correction pawl 21. The large lever 2 then returns to its rest position pushed by its return spring 22: the drive pawl 23 comes out of the teeth 31 of the date wheel 3 and the arm 24 of the large lever 2 releases the blocker 5 ( figures 3 And 4 , 11 And 14). In doing so, the blocker 5 pivots until it comes to rest on its stud 54 pushed by its return spring 53. In this position, it prevents the jumper 4 from falling back into the teeth 31 of the date wheel 3 and keeps said jumper 4 in its raised position. Thus, since nothing holds the date wheel 3, the date rack 7 pivots under the action of its return spring 74 and falls until it comes to rest against the stop 75. In doing so, the date rack 7 drives the date pinion 6 which pivots so that the date indicator it carries returns back to indicate the number 1 again.

[0035] According to the invention, when falling, the date rack 7 drives the month star 13 by one step thanks to the month finger 72 which in the high position of the rack, when passing the end of a month, comes into the teeth of the month star 13. The month star 13 drives the month cam 10 which is integral with it and the feeler 91 of the month lever 9 is now opposite the area of ​​the month cam 10 indicating the following month. It should be noted that in the illustrated embodiment, the month lever is not subject to the action of a spring. Thus, this month lever is not always forced against the month cam 10. At the end of the month, the month pin 71 comes into contact and pushes the intermediate lever 8 and the month lever 9 until the feeler 91 of the latter comes to bear against the month cam 10.

[0036] THE figures 3 And 4illustrate the case of the transition to February 1 of a non-leap year, the feeler 91 therefore coming to bear on an entire tooth 111 of the leap year cam 11 which is located in the notch 1022 of the second portion 102 of the month cam 10 intended for the month of February.

[0037] THE figures 11 And 14 illustrate the case of the transition to March 1, respectively to May 1, the feeler 91 therefore coming opposite a zone of the first portion 101 of the month cam 10 corresponding to the month of March, respectively May.

[0038] Just after the jump, the 1st of a month, the blocker 5 is still resting on its stud 54 in a position in which it prevents the jumper 4 from falling back into the teeth 31 of the date wheel 3. Said date wheel 3 is positioned by the rack 7 resting on its stop 75. This is preferably adjustable to avoid any display shift between the 1st and the other days of the month.

[0039] THE figures 5 And 6 illustrate the passage from the 1st to the 2nd day of the month, more precisely, the passage from February 1st to February 2nd.

[0040] Starting from the situation of the figure 3 illustrating the 1st of February of a non-leap year, at the end of a day, the 24-hour finger 1 driven by the 24-hour wheel comes into contact with the correction pawl 21 and pivots the large lever 2. The drive pawl 23 comes into contact with the teeth 31 of the date wheel 3 to advance it by one step in a first direction. Simultaneously, the arm 24 of the large lever 2 comes into contact with the second arm 52 of the blocker 5 and pivots it away from the stud 54 against the action of its return spring 53. In doing so, the blocker 5 releases the jumper 4 which falls back into the teeth 31 of the date wheel 3 and resumes its role for positioning and blocking this wheel.

[0041] The date pinion 6 secured to the date wheel 3 in turn drives the date rack 7 which pivots against the action of its return spring 74 and moves away from the stop 75. The indicator carried by the date pinion 6 displays the 2. The date wheel 3 pivots until the arm 41 of the jumper 4 falls back into the teeth 31 ( figure 5 ).

[0042] The 24-hour finger 1 continues its rotation until it releases the correction pawl 21. The large lever 2 returns to its rest position pushed by its return spring 22: the drive pawl 23 comes out of the teeth 31 of the date wheel 3 and the arm 24 of the large lever 2 releases the blocker 5. In doing so, the blocker 5 falls back to rest on the second arm 42 of the jumper 4 ( figure 6 ) which has returned to its position in toothing 31 of date wheel 3. The date indicator now displays 2.

[0043] When the normal date changes during the month, the sequence is substantially the same: The 24-hour finger 1 driven by the 24-hour wheel comes into contact with the correction pawl 21 and pivots the large lever 2. The drive pawl 23 comes into contact with the toothing 31 of the date wheel 3 to advance it by one step in the first direction. Simultaneously, the arm 24 of the large lever 2 comes into contact with the second arm 52 of the blocker 5 and pivots it. The jumper 4 lifts when the date wheel 3 rotates, actuated by the drive pawl 23. As it lifts, the pin 43 of the jumper 4 slides in the slot 81 of the intermediate lever 8 without affecting the position of the latter or of the month lever 9.

[0044] The date pinion 6, secured to the date wheel 3, in turn drives the date rack 7, which pivots a little more against the action of its return spring 74. The date indicator takes one step.

[0045] The 24-hour finger 1 continues its rotation until it releases the correction pawl 21. The large lever 2 returns to its rest position pushed by its return spring 22: the drive pawl 23 comes out of the teeth 31 of the date wheel 3 and the arm 24 of the large lever 2 releases the blocker 5. In doing so, the blocker 5 falls back to rest on the second arm 42 of the jumper 4.

[0046] Thus, according to the invention, the calendar mechanism as illustrated allows the date to be displayed retrogradely in a simple manner. In addition, by moving back the date rack 7 also drives the month star 13 for the month display. The release of the jumper at the end of the month by the pin carried by the rack also makes it possible to produce a calendar mechanism whose thickness at the date wheel is reduced. In addition, by driving the month display by the date rack which brings the date indicator back to 1 in a retrograde manner, the months are changed in a simple manner without increasing the consumption for the movement compared to a known mechanism.

[0047] As previously indicated, preferably, the calendar mechanism according to the invention is also arranged to display the month in a retrograde manner.

[0048] THE figures 15 And 16illustrate the return to the display of months when moving from December 31 to January 1.

[0049] In the figure 15 , we can see the components of the month display of the calendar mechanism in a configuration corresponding to the month of December. This figure shows the month star 13 held by its jumper 14. The month rack 17 is engaged with the toothed sector 151 of the truncated toothed pinion 15 secured to the month star 13 and with the month display pinion 18 which carries the month indicator (not shown). At the end of the day on December 31, the 24-hour finger 1 driven by the clockwork movement actuates the large lever 2 which pivots against the action of its spring 230 and drives the date wheel 3 by one step.

[0050] By pivoting, the date wheel 3 drives the date pinion 6 which in turn drives the date rack 7 which pivots again against the action of its return spring 74 to reach its high position. The month pin 71 then comes into contact with the intermediate lever 8, the position of which is determined by the month lever 9 resting on the month cam 10, and pivots it. The intermediate lever 8 acts on the pin 43 of the jumper 4 and then lifts said jumper 4 into a raised position in which the first arm 41 of said jumper 4 is no longer in the teeth 31 of the date wheel 3 ( figures 2 , 8 , 10 And 13 ). The date wheel 3 moves back so that the indicator displays the 1st again.

[0051] As it falls, the date rack 7 drives the month star 13 by one step thanks to the month finger 72 which, in the high position of the date rack 7, comes into the teeth of the month star 13. The month star 13 drives the month cam 10 which is integral with it and the feeler 91 of the month lever 9 is now opposite the area of ​​the first portion 101 of the month cam 10 indicating the month of January.

[0052] The truncated toothed pinion 15 has pivoted at the same time as the month star 13 and it is now the toothless sector 152 which faces the month rack 17. The latter is therefore no longer held and pivots pushed by its return spring 171 until it comes to bear on a stop 172, which is preferably adjustable. By falling, the month rack 17 drives the month display pinion 18 which carries the month indicator. This therefore returns backwards until it indicates the month of January again ( figure 16). The mechanism is arranged so that at the next step of the month star 13 (i.e. at the next change of month), the toothed sector 151 of the truncated toothed pinion 15 again comes into engagement with the month rack 17 to pivot the latter against the action of its return spring 171 and thus pivot the month display pinion 18.

[0053] We have also created a simple and secure retrograde display of the months, limiting the size and energy consumption of the movement.

[0054] In the illustrated embodiment, the calendar mechanism is a perpetual calendar mechanism. Alternatively, it could be a simple or annual calendar mechanism.

[0055] Generally speaking, the calendar mechanism according to the invention comprises a date wheel bearing a date indicator arranged to allow the retrograde display of the date; an actuating wheel arranged to be driven by a movement of the timepiece to advance the date wheel by one step per day in a first direction at the end of the day; a date return rack subjected to the action of a return spring and engaged with the date wheel such that the date return rack tends to pivot the date wheel in a second direction opposite to the first; a date jumper cooperating with the date wheel to prevent it from pivoting in the second direction; a blocking wheel controlled by the actuating wheel; a month star arranged to drive a month wheel by one step at the end of each month.

[0056] The mechanism is arranged so that: when the last day of a month passes to the first day of the following month, the actuating wheel set advances the date wheel set by one step in the first direction. The date return rack pivots against the action of its return spring to reach its upper position. In this upper position, the date return rack is arranged to move the date jumper into a raised position in which it no longer blocks the date wheel set. Also when the last day of a month passes to the first day of the following month, the actuating wheel set controls the blocking wheel set to move it into a position in which it holds the date jumper out of reach of the date wheel set, which can thus pivot in the second direction.On the other hand, the date return rack is further arranged to actuate the month star and advance it by one step when it pivots from its high position under the action of its return spring.

[0057] Preferably, the calendar mechanism comprises a a month cam attached to the month star and whose profile determines the length of the months (28, 29, 30 or 31 days); a month feeler arranged to rest on the month cam; an intermediate wheel pivoted on the month feeler and arranged to cooperate with the date return rack and the date jumper.

[0058] In this variant, when the date return rack pivots to its high position at the transition from the last day of a month to the first day of the following month, it pivots the intermediate wheel set which then moves the date jumper to its raised position in which the latter no longer blocks the date wheel set which can thus pivot in the second direction. Preferably, the month cam comprises a first portion for the months of 30 and 31 days and a second portion for the month of February comprising a slot through which a leap year cam passes.

[0059] Preferably, the month display is also a retrograde display. To achieve this, the month display mechanism comprises a truncated toothed pinion secured to the month star and comprising a toothed sector and a toothless sector and arranged to drive a return rack. Said month return rack is subjected to the action of a return spring which tends to pivot it in the direction opposite to the driving direction of the truncated toothed pinion. The month return rack meshes with a month wheel which carries the month indicator. At the end of the last day of December, the month star advances by one step driven by the date return rack and pivots the truncated toothed pinion into a position in which the toothless sector cooperates with the month return rack. This being no longer held, it pivots under the action of its return spring and drives the month wheel which returns backwards in a retrograde manner.

[0060] Preferably, the date and month mobiles are concentric.

[0061] The calendar mechanism according to the invention, whether simple, annual or perpetual, therefore makes it possible to display the date and preferably also the month in a retrograde manner. By driving the months via the date return rack, the consumption on the movement is not increased compared to a conventional solution. The small size of the mechanism, particularly in thickness, offers great freedom in arranging the date and month displays. In particular, they could be concentric and / or placed in the center of the movement. In addition, it is possible to offer large retrograde displays, extending over a large angle or segment.

Claims

1. Calendar mechanism for a timepiece comprising • a date wheel set (3, 6) carrying a date indicator arranged to allow the retrograde display of the date; • an actuating wheel set (2) arranged to be driven by a movement of the timepiece to advance the date wheel set (3, 6) by one step per day in a first direction at the end of the day; • a date return rack (7) subjected to the action of a return spring (74) and engaged with the date wheel set (3, 6) so that the date return rack (7) tends to pivot the date wheel set (3, 6) in a second direction opposite to the first, the date return rack (7) being arranged to pivot against the action of its return spring (74) to reach a high position when the actuating wheel set (2) advances the date wheel set (3, 6) by one step in the first direction when passing from the last day of a month to the first day of the following month;• a date jumper (4) cooperating with the date wheel set (3, 6) to prevent it from pivoting in the second direction; • a blocking wheel set (5) controlled by the actuating wheel set (2); • a month star (13) arranged to drive a month wheel set (18) by one step at the end of each month, the month wheel set (18) carrying a month indicator; ; characterized by the fact thatthe calendar mechanism is arranged so that when the date return rack (7) pivots into its upper position, it cooperates with the date jumper (4) to move said jumper (4) into a position in which it no longer prevents the date wheel set (3, 6) from pivoting in the second direction and so that, when the last day of a month passes to the first day of the following month, the actuating wheel set (2) controls the blocking wheel set (5) to move it into a position in which it retains the date jumper (4) in its position in which it no longer prevents the date wheel set (3, 6) from pivoting in the second direction, said date wheel set (3, 6) then being able to pivot freely in the second direction to return to its start-of-month position; and by the fact thatthe calendar mechanism is arranged so that the date return rack (7) actuates the month star (13) and moves it forward one step when said date return rack (7) falls from its high position under the action of its return spring (74) when passing from the last day of a month to the first day of the following month.

2. Calendar mechanism according to claim 1, characterized by the fact thatit comprises an addition: • a month cam (10) secured to the month star (13) and whose profile (101, 102) determines the length of the months (28, 29, 30 or 31 days); • a month feeler (9) mobile in rotation and arranged to cooperate with the month cam (10); • an intermediate mobile (8) pivoted on the month feeler (9) and arranged to cooperate with the date return rack (7) and the date jumper (4); the mechanism being arranged so that when the date return rack (7) pivots against the action of its return spring (74) to return to its high position at the transition from the last day of a month to the first day of the following month, it cooperates with the intermediate wheel set (8) which then moves the date jumper (4) into its position in which the latter no longer prevents the date wheel set (3, 6) from pivoting in the second direction.

3. Calendar mechanism according to the preceding claim, characterized by the fact thatthe intermediate wheel (8) is a lever (8) pivoted on the month feeler (9) and comprising a slot (81) crossed by a pin (43) of the date jumper (4) so ​​that, apart from the end of a month, the date jumper (4) can pivot when it is lifted by the date wheel (3, 6) which pivots in the first direction driven by the drive wheel (2).

4. Calendar mechanism according to claim 2 or 3, characterized by the fact that the profile of the month cam (13) comprises a first portion (101) characterizing the months of 30 and 31 days from March to January and a second portion (102) for the month of February, said second portion comprising a slot (1022) through which passes a leap year cam (11) arranged to determine the length of the month of February.

5. Calendar mechanism according to one of the preceding claims, characterized by the fact thatit is arranged to allow the retrograde display of the months and comprises a truncated toothed pinion (15) secured to the month star (13) and comprising a toothed sector (151) and a toothless sector (152) and arranged to drive a month return rack (17) in a first direction, said month return rack (17) being subjected to the action of a return spring (171) which tends to pivot it in a second direction opposite to the first, the month return rack (17) meshing with the month wheel (18) so that, when the last day of December passes to the first day of January, the month star (13) advances by one step driven by the date return rack (7) and pivots the truncated toothed pinion (15) into a position in which the toothless sector (152) cooperates with the rake of the months (17), so that, this one no longer being retained,it pivots in the second direction under the action of its return spring (171) and drives the month wheel (18) which returns backwards.

6. Calendar mechanism according to one of the preceding claims, characterized by the fact that the date return rack (7) carries a month finger (72) pivotally mounted on said rack (7) and is subjected to the action of a return spring (73), said month finger (72) being arranged to drive the month star (13) when the date return rack (7) falls from its high position under the action of its return spring (74).

7. Calendar mechanism according to one of the preceding claims, characterized by the fact that the date (3, 6) and month (18) mobiles are concentric.

8. A clockwork movement comprising a calendar mechanism according to one of the preceding claims.

9. Timepiece comprises a movement according to the preceding claim.

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