SYSTEM FOR DISPLAYING A PERMANENT DATE WITH SECURITY YEAR CORRECTION

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a perpetual calendar display system with secular correction and in particular such a system mounted in a timepiece. TECHNICAL BACKGROUND OF THE INVENTION

[0002] In the field of timepieces, there are several types of mechanical date displays, depending on the desired level of refinement of the timepiece to which they belong. These include the simple calendar (adjusting by one unit daily), the annual calendar (adjusting by two units when months do not have 31 days), and the perpetual calendar (adjusting the date to account for February and leap years), which corresponds to corrections to the Julian calendar, in which a year represents 365.25 days. In this calendar, all years that are multiples of four are leap years. A perpetual calendar can be displayed, for example, by a mechanism known as a "48-month cam," meaning a 48-month cam that takes into account all the months of a four-year cycle, one of which, February, has 29 days.

[0003] In the Gregorian calendar, a year represents 365.2425 days. This calendar is therefore more precise than the Julian calendar and was adopted much later thanks to improvements in astronomical techniques and timekeeping throughout history. Also, in the Gregorian calendar, century years divisible by one hundred (for example, nineteen hundred, two thousand one hundred, etc.) are not leap years, unless they are divisible by four hundred (two thousand, two thousand four hundred, etc.), in which case they remain leap years. For a timepiece with a mechanical calendar, displaying the date of the month (day number) while keeping pace with the variations in the length of months according to the Gregorian calendar, without requiring correction by the user, is therefore particularly complex. This type of mechanism is sometimes called a secular calendar or calendar. Application EP3040786A1, for example, discloses a Gregorian calendar mechanism.

[0004] However, these calendars remain approximations of a tropical year, partly due to the persistence of time divisions chosen throughout history. Thus, although there are currently no plans to officially correct the Gregorian calendar, it has already been calculated that its approximation adds a full day to astronomical reality every four thousand years. SUMMARY OF THE INVENTION

[0005] The invention aims to provide a perpetual calendar display system that provides secular corrections provided by the Gregorian calendar, and even millennial corrections not provided by the Gregorian calendar, in a simple (little increase in parts and possible adaptation of current mechanisms) and compact (little increase in thickness compared to current mechanisms and integration into the parts of current mechanisms) manner.

[0006] To this end, the invention relates to a perpetual calendar display system for a Gregorian calendar comprising at least one date display coupled to a date display drive device for incrementing the date display by one unit every twenty-four hours, and a counting device for controlling the drive device to selectively increment the date display by a predetermined number of additional units at the end of the month, depending on the number of days in the month, characterized in that the display system comprises a 12- or 48-month cam mechanism and in that the counting device is arranged to form a stop used for counting leap years, the distance of which from an axis of rotation of the 12- or 48-month cam is selectively adjustable in the thickness of the 12- or 48-month cam in order to make the secular corrections of the Gregorian calendar.

[0007] Advantageously, according to the invention, the distance of the stop is selectively adjusted relative to the axis of rotation, typically in 12 or 48 steps distributed over 360 degrees, depending on leap years. This adjustment is made by integrating the stop into a 12- or 48-month cam mechanism to maintain similar operation while ensuring that the latter accurately follows the Gregorian calendar. More specifically, the display system takes into account that century years divisible by 100 (e.g., 1900, 2100, etc.) are not leap years, unless they are divisible by 400 (e.g., 2000, 2400, etc.), in which case they remain leap years.

[0008] It is therefore clear that adapting the 12- or 48-month cam mechanism results in a minimal increase in parts, thus allowing the use of a mechanism whose operation is already proven reliable. It is also immediately apparent that the adaptation is advantageously integrated within the thickness of the 12- or 48-month cam mechanism, thereby avoiding the increased thickness required for secular corrections.

[0009] The invention may also include one or more of the following optional features, taken alone or in combination.

[0010] The 12- or 48-month cam mechanism may include a large rocker arm designed to contact the stop of the counting device in order to determine whether the date display should selectively show the twenty-ninth day of February. It is understood that the large rocker arm of the 12- or 48-month cam mechanism does not need to be specially adapted for the display system according to the invention to function.

[0011] According to a first embodiment, the counting device may include a finger-Maltese cross assembly formed within the thickness of the 12- or 48-month cam to create a reduction gear relative to the cam. Depending on whether the cam is 12 or 48 months, the reduction is adjusted so that the Maltese cross completes one revolution in, preferably, 20 years.

[0012] Furthermore, the counting device preferably includes a secular wheel housed within the thickness of a toothed wheel coaxially attached to the 12- or 48-month cam. One portion of the thickness may have teeth designed to cooperate with a finger coaxially attached to the Maltese cross, and a second portion may have a cam track designed to cooperate with a cam track follower that controls the movement of the stop used for counting leap years. The complete gear train is adapted so that the secular wheel completes one revolution in, preferably, four hundred years.

[0013] In the first embodiment, the stop used for counting leap years can therefore be formed by a pin moving relative to one of the February reliefs on the 12- or 48-month cam, thus allowing the selective application of a February with twenty-eight or twenty-nine days. A straight or curved movement relative to the axis of rotation of the 12- or 48-month cam can be envisaged without departing from the scope of the invention. By way of non-limiting example, a radial movement of the stop, that is to say, oriented along a radius originating from the axis of rotation of the 12- or 48-month cam, can be implemented.

[0014] According to a second embodiment, the counting device may include a finger-Maltese cross assembly, formed within the thickness of a toothed wheel coaxially attached to the 12- or 48-month cam, in order to form a reduction gear relative to the 12- or 48-month cam. Depending on whether the cam is 12- or 48-month, the reduction is adjusted so that the Maltese cross completes one revolution in, preferably, 20 years.

[0015] Furthermore, the counting device preferably includes a secular wheel, housed within the thickness of the 12- or 48-month cam. One section of the thickness may have teeth designed to cooperate with a finger coaxially attached to the Maltese cross, and a second section may have a cam track designed to form the stop used for counting leap years. The complete gear train is adapted so that the secular wheel completes one revolution in, preferably, four hundred years.

[0016] In the second embodiment, it is understood that the stop used for counting leap years is preferentially formed by the secular cam itself. The second embodiment therefore comprises fewer parts than the first embodiment. As a non-limiting example, a rotational movement of the stop, that is, around an axis offset from the axis of rotation of the 12- or 48-month cam, can be achieved.

[0017] In the second embodiment, the stop used for counting leap years can therefore be formed by the movable cam track forming part of one of the February reliefs of the 12- or 48-month cam, thus allowing the selective application of a February with twenty-eight or twenty-nine days. A straight or curved movement relative to the axis of rotation of the 12- or 48-month cam, or even a rotation around an axis offset from that of the 12- or 48-month cam, can be envisaged without departing from the scope of the invention. By way of non-limiting example, a rotary movement of the cam track allows the relief (bump, flat, or hollow) of the 12- or 48-month cam to be corrected; that is, depending on its orientation relative to the relief, it blocks, stops, or hollows it in order to selectively control the amplitude of movement of the large rocker arm.

[0018] Regardless of the embodiment, the counting device can, according to a particular variant, be further arranged to form a counter-stop which, mounted vertically above the relief of the 12 or 48 month cam used for counting leap years, via an additional reducing gear, allows a leap year to be removed every four thousand years in relation to the Gregorian calendar.

[0019] Advantageously, according to the invention, the display system uses a 12- or 48-month cam mechanism adapted to correct the Gregorian calendar. More specifically, the display system in the millennium variant removes a leap year from years that are multiples of four thousand (for example, four thousand, eight thousand, etc.) to provide a better approximation of the length of a tropical year by forcing, with the help of a stop, for example, the transition from February 28, 4000 directly to March 1, 4000, whereas normally, according to the Gregorian calendar, the year four thousand is a leap year.

[0020] It is therefore clear that adapting the 12- or 48-month cam mechanism results in a minimal increase in parts, thus allowing the use of a mechanism whose operation is already proven reliable. It is also immediately apparent that the adaptation is advantageously integrated within the thickness of the 12- or 48-month cam mechanism, resulting in a minimal increase in thickness compared to the mechanism with simple secular corrections.

[0021] Finally, the invention relates to a timepiece comprising a clock movement, characterized in that it includes the display system as presented above coupled to the clock movement. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features and advantages of the invention will become clear from the description given below, which is by way of example and in no way limiting, with reference to the attached drawings, in which: there figure 1is a schematic view of a timepiece according to the invention; the figures 2 to 4 are partial views of a first variant of a first embodiment of a Gregorian calendar display system according to the invention; the figures 5 and 6 are partial views of a second variant of the first embodiment of a Gregorian calendar display system according to the invention; the figures 7 and 8 are partial views of a thousand-year-old variant of the first embodiment of a Gregorian calendar display system according to the invention; the figures 9 to 12 are partial views of a second embodiment of a Gregorian calendar display system according to the invention. DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

[0023] In the various figures, identical or similar elements bear the same references, possibly with an additional subscript. Therefore, a description of their structure and function is not systematically repeated.

[0024] In all that follows, orientations are the orientations of the figures. In particular, the terms "upper", "lower", "left", "right", "above", "below", "forward" and "backward" are generally understood in relation to the direction in which the figures are represented.

[0025] By "horological component 2", we mean all types of timekeeping or measuring instruments such as clocks, small clocks, watches, etc...

[0026] By "watch movement 3", we mean all types of mechanisms capable of counting time whether they are powered by mechanical energy (e.g. a barrel) or electrical energy (e.g. a battery).

[0027] As illustrated in the figure 1 The invention relates to a timepiece 2 comprising a display system 1 coupled, for example via the hour wheel, to a clock movement 3 and intended to display at least one date display 4 of a Gregorian calendar. The display system 1 may include, in addition to the date display 4, a day of the week display 5 and a month of the year display 6. Other calendar values ​​can of course be considered, such as a moon phase display (not shown) or a leap year display (not shown), that is to say, an indication identifying whether the current year includes a February 29th or not, without departing from the scope of the invention.

[0028] The invention advantageously allows for the display of a perpetual calendar, incorporating at least the secular corrections provided by the Gregorian calendar, in a simple and compact manner. More specifically, the display system 1 takes into account the fact that secular years divisible by one hundred (e.g., nineteen hundred, two thousand one hundred, etc.) are not leap years, unless they are divisible by four hundred (e.g., two thousand, two thousand four hundred, etc.), in which case they remain leap years.

[0029] Advantageously, according to the invention, the perpetual calendar display system 1 for a Gregorian calendar uses a modified 12- or 48-month cam mechanism, rather than such a mechanism to which a bulky external module has been added to provide secular corrections. More specifically, it comprises the date display 4, which is moved by a drive device 7, itself selectively corrected by a counting device 9. The drive device 7 for the date display 4 is designed to increment the date display 4 by one unit every twenty-four hours. The drive device 7 includes, in particular, a large rocker 11 equipped with at least one lever 12. Since the drive device 7 is not modified compared to a 12- or 48-month cam mechanism, it will not be described further.

[0030] As an example, the explanation of a 12- or 48-month cam mechanism is given in Chapter 9.7, entitled "Perpetual Calendar," of the book "Theory of Horology," by Charles-André Reymondin et al., Fédération des Écoles Techniques (FET), July 2015, ISBN 2-940025-47-9, or in Chapter 9.7, entitled "The Perpetual Calendar Watch," of the book "The Theory of Horology," by Charles-André Reymondin et al., Fédération des Écoles Techniques (FET), July 2015, ISBN 2-940025-49-5. The part numbers for the 12- or 48-month cam mechanism described below are taken from Chapter 9.7.

[0031] THE figures 2 to 12examples are presented only with a 48-month cam mechanism. However, the invention can also be applied to a 12-month cam mechanism, i.e., to form a selectively movable stop on the leap year cam in order to provide equivalent secular corrections provided by the Gregorian calendar, or even millennial corrections not provided by the Gregorian calendar.

[0032] The counting device 9 is designed to control the drive device 7 in order to selectively increment the date display 4 by a predetermined number of additional units at the end of the month, based on the number of days in the Gregorian calendar month. In the example of the figure 2The counting device 9 includes a beak 13 formed on the lever 12 and a counting wheel 15 for counting the months in four-year cycles. The counting wheel 15 includes at least one toothed transmission wheel 16 coupled to the clockwork movement 3 and coaxially fixed to a 48-month cam 17, i.e., the toothed wheel 16 and the 48-month cam 17 are fixed in rotation around the same axis A.

[0033] Advantageously, according to the invention, the counting device 9 is arranged to form a stop 19, 39 which, by contact with the free end of the beak 13, is used to count leap years. The stop 19, 39 has a distance relative to the axis A of rotation of the 48-month cam which is selectively adjustable within the thickness E of the 48-month cam 17 in order to provide the secular corrections of the Gregorian calendar.

[0034] Since the distance of the stop 19, 39 is selectively adjusted by being integrated into a 48-month cam mechanism 17, the invention advantageously allows the 48-month cam mechanism 17 to function similarly (for example, the large rocker 12 of the 48-month cam mechanism 17 does not need to be adapted for the display system 1 according to the invention to work) while ensuring that the 48-month cam mechanism 17 accurately follows the Gregorian calendar. More specifically, the display system 1 takes into account that century years divisible by one hundred (e.g., nineteen hundred, two thousand one hundred, etc.) are not leap years, unless they are divisible by four hundred (e.g., two thousand, two thousand four hundred, etc.), in which case they remain leap years.

[0035] It is therefore clear that adapting the 48-month cam mechanism 17 results in a minimal increase in parts and allows the use of a mechanism whose operation is already proven reliable. It is also immediately apparent that the adaptation is advantageously integrated within the thickness of the 48-month cam mechanism 17, thus avoiding the increased thickness required for secular corrections.

[0036] In a first embodiment illustrated in figures 2 to 8 A single stop 19 is preferentially moved into one of the four recesses 21 of the February cam 17 of the 48-month period in order to selectively apply a February of twenty-eight or twenty-nine days. In a second embodiment illustrated in figures 9 to 12, the stop 19 is formed by a movable cam path forming part of one of the four February recesses 21 of the 48-month cam 17 in order to selectively apply a February of twenty-eight or twenty-nine days.

[0037] According to a first variant of the first embodiment illustrated in the examples of figures 2 to 4 The counting device 9 comprises a 48-month cam 17 that completes one revolution every four years in a typical manner. However, advantageously according to the invention, the 48-month cam 17 receives within its thickness E a pin 20 forming the stop 19, a Maltese cross 23, and a finger 24. The pin 20 can slide within the recess 21 to change the depth of the recess 21. The Maltese cross 23 is pivotally mounted on the shaft B (attached to the wheel plate 16) and has five wings 22 designed to cooperate with the finger 24. In the example of the figures 2 to 4, finger 24 is fixed, that is to say it is mounted on a point of the watch movement 3, and it is the rotation of the mobile 15 around the axis A which will allow the contact between the Maltese cross 23 and finger 24.

[0038] The finger assembly 24 - Maltese cross 23 thus forms a reduction gear fully integrated into the 48-month cam. In the example of the figures 2 to 4 , the reduction is adapted so that the Maltese cross 23 makes a turn preferentially in 20 years by the passage of one of the five wings 22 of the Maltese cross 23 by the finger 24 at each complete rotation of the cam 17 of 48 months every four years.

[0039] As illustrated in the examples of figures 2 to 4The counting device 9 further comprises a toothed wheel 16 coaxially fixed to the cam 17, which typically completes one revolution every four years. However, advantageously according to the invention, the wheel 16 receives within its thickness a secular moving part 25, a control follower 28, and a tenon 29 (concealed at the figure 4 but comparable to that of the figure 6 ).

[0040] The secular mobile 25, pivotally mounted against the outer diameter of the circle 30 centered on axis C, comprises, on a first lower part of its thickness, teeth 26 intended to cooperate with the tenon 29 coaxially fixed to the Maltese cross 23, and, on a second upper part of its thickness, a cam track 27 intended to cooperate with the follower 28 of the cam track controlling the movement of the stop 19, the distance of which relative to axis A is selectively adjustable. As visible in the figure 4, the cam track 27 has three notches 31 distributed successively every ninety degrees in order to take into account century years divisible by one hundred (for example one thousand nine hundred, two thousand one hundred, etc.) which are not leap years, unless they are divisible by four hundred (for example two thousand, two thousand four hundred, etc.) where they remain leap years.

[0041] It is for this last case that there is no fourth notch 31 distributed at ninety degrees with the three notches 31. The absence of notch will allow the follower assembly 28 - pawn 20 and therefore incidentally the stop 19 to be moved less deeply in the recess 21 so that the counting device 9 maintains a twenty-ninth day of February in years divisible by four hundred, such as, for example, in the year two thousand or two thousand four hundred as well as all other years not divisible by one hundred. It is understood that the notches 31 conversely allow the stop 19 to be moved deeper into the recess 21 (equivalent to the fixed depths of the other recesses 21 for the month of February) so that the counting device 9 imposes, at most, a twenty-eighth day of February in years divisible by one hundred but not by four hundred, such as, for example, the years two thousand one hundred, two thousand two hundred, and two thousand three hundred. In the example of the figures 2 to 4 , the complete gear is adapted so that the secular mobile 25 makes a turn preferentially in four hundred years by the passage of one of the twenty teeth of the toothing 26 through the tenon 29 at each complete rotation of the Maltese cross 23 every twenty years.

[0042] A second variant of the first embodiment is illustrated in the examples of figures 5 and 6The counting device 9 differs essentially from the first variant in the arrangement of the pin 20', resulting in a reversal of the direction of the secular mobile 25' and the tenon 29. Thus, advantageously according to the invention, the 48-month cam 17 receives within its thickness E a pin 20' forming the stop 19, a Maltese cross 23, and a finger 24. The pin 20' is elastically mounted in cantilever of an elastic arm 32 and can move within a recess 21' that is enlarged compared to the first variant of the first embodiment. The Maltese cross 23 and the finger 24 are identical to those of the first variant.

[0043] As seen at the figure 6The secular moving part 25', pivotally mounted against the outer diameter of a circular portion 30' of the wheel 16, comprises, on a first upper part of its thickness, teeth 26 intended to cooperate with the tenon 29 coaxially fixed to the Maltese cross 23, and, on a second lower part of its thickness, a cam track 27' intended to cooperate with the follower 28' of the cam track controlling the movement of the stop 19, the distance of which from the axis A is selectively adjustable. As visible in the figure 5 , the cam track 27' has three notches 31' distributed successively every ninety degrees as in the first variant in order to take into account century years divisible by one hundred (for example one thousand nine hundred, two thousand one hundred, etc.) which are not leap years, unless they are divisible by four hundred (two thousand, two thousand four hundred, etc.) where they remain leap years.

[0044] Therefore, similarly to the first variant, the cam track 27' allows the follower assembly 28' - pawl 20', and thus incidentally the stop 19, to be displaced most of the time in the recess 21' so that the counting device 9 maintains a twenty-ninth day of February, as for example in the year 2000 or 2004 and all other years not divisible by one hundred. It is understood that the notches 31' conversely allow the stop 19 to be moved deeper in the recess 21' (equivalent to the fixed depths of the other February recesses 21) so that the counting device 9 imposes, at most, a twenty-eighth day of February in years divisible by one hundred but not by four hundred, as, for example, in the years 2000, 2002, and 2003. In the example of the figures 5 to 6, the complete gear is adapted so that the secular mobile 25' makes a turn preferentially in four hundred years by the passage of one of the twenty teeth of the toothing 26 through the tenon 29 at each complete rotation of the Maltese cross 23 every twenty years.

[0045] In the second embodiment, the stop used for counting leap years is preferably formed by the secular cam itself. The second embodiment therefore comprises fewer parts than the first embodiment. By way of non-limiting example, a rotational movement of the stop, that is, around an axis offset from the axis of rotation of the 12- or 48-month cam, can be achieved.

[0046] In the figures 9 to 12An example of a second embodiment is presented. It can be seen that the counting device 9 includes a cam 17 of 48 months making one revolution every four years in the usual way. However, advantageously according to the invention, the 48-month cam 17 receives, in its thickness E, the secular mobile 45 forming the stop 39 and a tenon 49. The secular mobile 45, mounted pivotally (along an axis offset from that of the 48-month cam 17) against the internal diameter of a circular part of the 48-month cam 17, has, on a first upper part of its thickness, teeth 46 intended to cooperate with the tenon 49 coaxially fixed to a Maltese cross 43 (located in the thickness of the toothed wheel 16), and, on a second lower part of its thickness, a cam track 47 intended to cooperate with the beak 13 thus forming several stops 39 to change the depth of the recess 21" according to the rotation of the secular mobile 45.It will be understood that the 21" opening leads to the cam track 47.

[0047] As seen at the Figure 10 The cam track 47 has three notches 51 spaced successively every ninety degrees to accommodate century years divisible by one hundred (e.g., nineteen hundred, two thousand one hundred, etc.) which are not leap years, unless they are divisible by four hundred (two thousand, two thousand four hundred, etc.) in which case they remain leap years. The movable cam track 47 thus complements the February recess 21" of the 48-month cam 17 in order to selectively apply a February with twenty-eight or twenty-nine days. In the example of the figures 9 to 12 , the movement is rotary in order to close or extend the 21" recess of the cam 17 of 48 months allowing to selectively control the amplitude of movement of the large rocker 11.

[0048] As illustrated in the examples of figures 2 to 4 The counting device 9 further comprises a toothed wheel 16 coaxially fixed to the 48-month cam 17, which makes one revolution every four years in a typical manner. However, advantageously according to the invention, the wheel 16 receives within its thickness a finger 44 and the Maltese cross 43. The Maltese cross 43 is pivotally mounted on the shaft B (fixed to the cam 17 of the 48-month cam) and has five wings 42 designed to cooperate with the finger 44. In the example of the figures 9 to 11 , finger 44 is fixed, that is to say it is mounted on a point of the watch movement 3, and it is the rotation of the mobile 15 around the axis A which will allow the contact between the Maltese cross 43 and the finger 44.

[0049] The assembly thus forms a reduction gear fully integrated into the toothed wheel 16. In the example of the figures 9 to 12, the reduction is adapted so that the Maltese cross 43 makes a turn preferentially in 20 years by the passage of one of the five wings 42 of the Maltese cross 43 by the finger 44 at each complete rotation of the cam 17 of 48 months every four years.

[0050] Therefore, similarly to the first embodiment but with fewer parts, the cam track 47, and thus incidentally the stop 39, closes the recess 21" most of the time so that the counting device 9 maintains a twenty-ninth day of February, as for example in the year 2000 or 2004 and all other years not divisible by one hundred. It is understood that the notches 51 conversely allow the recess 21" to be lengthened or extended to place a stop 39 closer to the axis A (equivalent to the fixed depths of the other February recesses 21) so that the counting device 9 imposes, at most, a twenty-eighth day of February in years divisible by one hundred but not by four hundred, as for example in the years 2001, 2002 and 2003. In the example of the figures 9 to 12, the complete gear is adapted so that the secular mobile 45 makes a turn preferentially in four hundred years by the passage of one of the twenty teeth of the toothing 46 through the tenon 49 at each complete rotation of the Maltese cross 43 every twenty years.

[0051] Whatever the embodiment, the counting device 9 can, according to a particular variant, called millennial, be further arranged to form a counter-stop 59 which, mounted vertically above the relief of the 12 or 48 month cam used for counting leap years, via an additional reducing gear, allows a leap year to be removed every four thousand years in relation to the Gregorian calendar.

[0052] In the example of figures 7 and 8 , the counting device 9 is adapted from the first variant of the first embodiment of the figures 2 to 4to apply the millennium variant. However, of course, it is possible to apply the millennium variant to the other variants and / or embodiments described without departing from the scope of the invention.

[0053] As illustrated in figures 7 and 8The 48-month cam 17 is adapted by adding a notch 31 to the secular moving part 25 in order to distribute the notches 31 symmetrically, that is, so that they are distributed at equal consecutive angles with respect to the center C, along the cam track 27, here every ninety degrees of the circular cam track 27. The second adaptation concerns the follower 28 controlling the pin 20, which has a greater thickness compared to the first variant of the first embodiment in order to continue to make contact with the cam track 27 but also with a cam track 67 forming the counter-stop 59 in a higher plane. It is therefore understood that the adaptation of the 48-month cam mechanism results in a slight increase in thickness in the millennium variant and thus allows the use of a mechanism whose operation is already reliable.

[0054] Furthermore, the counting device 9, in the millennial variant, includes an additional reducing gear formed by a millennial finger 64 - mobile 65 assembly in order to utilize the complete rotation of the secular mobile 25 relative to the toothed wheel 16 so that the counting device 9 removes a twenty-ninth day of February every four thousand years. In the example of the figures 7 and 8 The finger 64 is fixed to the toothed wheel 16, that is to say, it is mounted integrally with it or formed as a single unit, and centered on the axis C of rotation of the secular moving part 45. It is therefore the rotation of the millennial moving part 65 around the axis C that will allow contact between the teeth 66 of the millennial moving part 65 and the finger 64.

[0055] The 65th millennium moving part, pivotally mounted against the external diameter of the shaft D (offset relative to the axis C of rotation of the 45th secular moving part), has, on a first upper part of its thickness, teeth 66 intended to cooperate with the finger 64 (located within the thickness of the toothed wheel 16), and, on a second lower part of its thickness, a cam track 67 intended to cooperate with the follower 28, thus forming several counter-stops 59 to change the depth of the recess 21 according to the rotation of the 45th secular moving part and the 65th millennium moving part. In the example of the figures 7 and 8 , the complete gear is adapted so that the secular mobile 65 makes a turn preferentially in four thousand years by the passage of one of the ten teeth of the toothing 66 by the finger 64 at each complete rotation of the secular mobile 45 every four hundred years.

[0056] As seen in figures 7 and 8The cam track 67 has a notch 71 to accommodate millennial years divisible by four thousand (four thousand, eight thousand, etc.) which are not leap years. The movable cam track 67 therefore allows the pin 20, which includes the stop 19, to be pushed further into the recess 21 of the cam 17 by 48 months every four thousand years in order to selectively remove a February of twenty-nine days compared to the Gregorian calendar, in favor of a February of 28 days.

[0057] Advantageously, according to the invention, the display system 1 uses a 48-month cam mechanism adapted to correct the Gregorian calendar. More precisely, the display system 1 in the millennial variant removes a leap year (four thousand, eight thousand, etc.) to provide a better approximation of the length of a tropical year by forcing, with the help of the counter-stop 59, for example, the transition from February 28, 4000 directly to March 1, 4000, whereas normally, according to the Gregorian calendar, the year 4000 is a leap year.

[0058] The invention is not limited to the embodiments and variations shown, and other embodiments and variations will be obvious to those skilled in the art. Thus, the embodiments and variations can be combined with each other without departing from the scope of the invention. Furthermore, it may be envisaged that technical equivalents of the elements shown above could be found without departing from the scope of the invention. By way of no limitation, other types of reduction gears than those shown above may also be provided.

Claims

1. Perpetual date display system (1) of a Gregorian calendar comprising at least one date display (4) coupled with a date display (4) drive device (7) intended to increment by one unit the date display (4) every twenty-four hours, and a counting device (9) intended to control the drive device (7) in order to selectively increment the date display (4) according to a predetermined number of additional units, at end of month, depending on the number of days in the month, characterised in that the display system (1) comprises a cam mechanism (17) of 12 or 48 months and in that the counting device (9) is arranged to form a stop (19, 39) used to count the leap years whose distance from an axis (A) of rotation of the cam (17) of 12 or 48 months is selectively adjustable in the thickness (E) of the cam (17) of 12 or 48 months in order to make the secular year corrections of the Gregorian calendar.

2. Display system (1) according to the preceding claim, wherein the cam mechanism (17) of 12 or 48 months comprises a large yoke (11) intended to come into contact with the stop (19, 39) of the counting device (9) in order to determine whether the date display (4) must selectively display the twenty-ninth day of the month of February of the year.

3. Display system (1) according to claim 1 or 2, wherein the counting device (9) comprises a pin (24) - Maltese cross (23) assembly formed in the thickness (E) of the cam (17) of 12 or 48 months to form a reduction gear relative to the cam (17) of 12 or 48 months.

4. Display system (1) according to the preceding claim, wherein the counting device (9) further comprises a secular cam (25, 25'), formed in the thickness of a gear (16) attached coaxially to the cam (17) of 12 or 48 months, of which a first part of the thickness comprises teeth (26) intended to cooperate with a pin (29) attached coaxially to the Maltese cross (23), and a second part of the thickness comprises a cam track (27, 27') intended to cooperate with a cam track follower (28, 28') controlling the displacement of the stop (19) used to count the leap years.

5. Display system (1) according to claim 3 or 4, wherein the stop (19) used to count the leap years consists of a pin (20) moving relative to one of the February reliefs (21) of the cam (17) of 12 or 48 months in order to be able to selectively apply a month of February with twenty-eight or twenty-nine days.

6. Display system (1) according to claim 1 or 2, wherein the counting device (9) comprises a pin (44) - Maltese cross (43) assembly formed in the thickness of a gear (16) attached coaxially to the cam (17) of 12 or 48 months, to form a reduction gear relative to the cam (17) of 12 or 48 months.

7. Display system (1) according to the preceding claim, wherein the counting device (9) further comprises a secular cam (45), formed in the thickness (E) of the cam (17) of 12 or 48 months, of which a first part of the thickness comprises teeth (46) intended to cooperate with a pin (49) attached coaxially to the Maltese cross (43), and a second part of the thickness comprises a cam track (47) intended to form the stop (39) used to count the leap years.

8. Display system (1) according to claim 6 or 7, wherein the stop (39) consists of a movable cam track (47) forming a part of one of the February reliefs (21") of the cam (17) of 12 or 48 months in order to be able to selectively apply a month of February with twenty-eight or twenty-nine days.

9. Display system (1) according to any one of the preceding claims, wherein the counting device (9) is further arranged to form a counter-stop (59) which, mounted vertically above the relief (21, 21', 21") of the cam (17) of 12 or 48 months used to count the leap years, via an additional reduction gear, allows a leap year to be removed every four thousand years relative to the Gregorian calendar.

10. Timepiece (2) comprising a watch movement (3), characterised in that it comprises the display system (1) according to one of the preceding claims coupled to the watch movement (3).