Perpetual calendar mechanism for a timepiece movement

Abstract

The present invention relates to a perpetual calendar mechanism (1) for a timepiece movement. The mechanism comprises a date mobile (3), a month mobile arranged so as to perform one revolution every forty-eight months under the control of the date mobile at a rate of one increment per month, and carrying a month-programming wheel having a perimeter whose profile defines a number of steps, the radius of which is dependent on the number of days in each month of a forty-eight month cycle. The mechanism preferably comprises a control rocker pivotably mounted about an axis of rotation and arranged so as to advance the date mobile at a rate of at least one increment per day.

Description

PERPETUAL CALENDAR MECHANISM FOR WATCH MOVEMENT Technical field

[0001] The present invention relates to the field of watchmaking. It relates, more particularly, to a perpetual calendar mechanism for a watch movement, which is arranged to change the date at the end of each month of less than 31 days, including February 29 of leap years according to the main four-year cycle. Such a mechanism is not, however, arranged to take into account exceptional non-leap years of the Gregorian calendar, the next of which will occur in the year 2400. State of the art

[0002] Document EP0191921 describes a perpetual calendar mechanism in which the actuation of the date wheel set and the day wheel set is carried out by means of a control lever pivotally mounted around an axis which coincides with that of the date wheel set.

[0003] At the end of each day, the pivoting of the control lever causes a drive finger to advance the date wheel by 20 steps of its teeth (i.e. 1 / 31 ème of a turn).

[0004] In order to obtain the additional steps of the date wheel at the end of months with fewer than 31 days, a month wheel is provided. The latter comprises a toothed wheel integral in rotation with a programming wheel, the periphery of which has a stepped profile which is representative of the number 25 of days in each month in the 48-month cycle of leap years. The toothed wheel cooperates with a tooth of the date wheel which is longer than the others to pivot at a rate of a step of 1 / 48 èmeof one turn for each complete rotation of the month wheel, which brings the appropriate level of the periphery of the programming wheel opposite a feeler which is integral with the control lever, so as to limit the angular path of the latter to the level of its starting angular position: a greater angular path corresponds to a higher number of steps of the date wheel at the end of months having less than 31 days.

[0005] A day wheel is also provided, and comprises a seven-pointed day star integral in rotation with a day indicator member. The star is actuated by means of an actuating lever pivotally mounted on the frame and arranged to be pivoted at the rate of one step of the teeth of the star 5 (i.e. 1 / 7 of a revolution) at the end of each day by means of cooperation with the free end of the control lever. The day wheel also drives a moon wheel by means of a corresponding return.

[0006] The date wheel set also includes a snail which has a radius which increases in the opposite direction to its direction of rotation (considered 10 statically and if we follow the surface of the cam in the opposite direction to its direction of rotation, such that, during the rotation of the snail, its radius appears to increase if we consider it at a given fixed point), as well as a discontinuity defining a shoulder which is located opposite the free end of an end-of-month drive finger, which takes the form 15 of a pawl, pivotally mounted on said control lever. At the end of the months, the free end of this pawl cooperates with the shoulder formed by the discontinuity of the snail to pivot the date wheel set by an appropriate number of steps (i.e. 1, 2 or 3 steps), depending on the angular path of the control lever as determined by the programming disc.

[0007] The arrangement of this mechanism is relatively complex and requires several pivot axes mounted on the frame, which makes it relatively difficult to implement and hinders freedom of construction.

[0008] An object of the invention is therefore to provide a perpetual calendar mechanism in which the aforementioned defects are at least partially overcome.

[0009] An aim of the invention is to implement a mechanism making it possible to avoid double advancement of the month wheel set when the control lever actuates the date wheel set and when the date wheel set cooperates with the month wheel set.

[0010] Another aim of the invention is to implement a perpetual calendar mechanism allowing independent adjustment of the day wheel and / or the moon wheel. Disclosure of the invention

[0011] More specifically, the invention relates to a perpetual calendar mechanism for a watch movement, as defined by claim 1. This perpetual calendar mechanism comprises: 5

[0012] - a date wheel, arranged to make one revolution per month and carrying a snail whose profile radius increases in the opposite direction to the direction of rotation of said date wheel (considered statically, such that, during rotation of the wheel, its radius appears to increase if it is considered at a given fixed point) and has a discontinuity defining a shoulder, said date wheel being associated with (for example integral in rotation with, or arranged to drive) a date display member;

[0013] - a month wheel arranged to complete one revolution in forty-eight months under the control of said date wheel at the rate of one step per month (i.e. 1 / 48 of a revolution), said month wheel carrying a month programming wheel having a periphery whose profile defines a number of steps whose radius is a function of the number of days in each month of a forty-eight-month cycle, said month wheel being associated with (for example integral in rotation with, or arranged to drive) a month display member;

[0014] - a control lever pivotally mounted around a rotation axis (which is typically distinct from the pivot axis of the date wheel set, even more typically distinct from each of the pivot axes of the date, month and day wheel sets and is typically concentric with the movement) and arranged to advance said date wheel set at a rate of at least one step (i.e. at least 1 / 31 of a revolution) per day, said control lever being arranged to perform a cycle of back-and-forth pivoting movements at a rate of one cycle per day, typically around midnight.

[0015] Said control rocker comprises: 30

[0016] - a sensor arranged to cooperate with said month programming wheel to determine the angular path of said control rocker as a function of the number of days in each month, in particular by defining the starting angular position of the control rocker which it adopts between said operating cycles;

[0017] - a first drive finger arranged to advance said date wheel at a rate of one step per cycle at least at the end of the non-final days of the month (but it is also possible for the first finger to also intervene at the end of the month); 5

[0018] - an end-of-month drive finger, distinct from each of said first and said second drive fingers, arranged to cooperate with said discontinuity at the end of a month in order to advance said date wheel set at a predetermined number of steps as a function of said angular path of said control lever.

[0019] By arranging all of the above-mentioned drive fingers on the control rocker, additional pivot axes for additional control levers are not required. The mechanism is therefore simpler to implement, and gives the manufacturer greater freedom. 15

[0020] Advantageously, the perpetual calendar mechanism further comprises a moon wheel arranged to make one revolution in substantially two lunar months, said control lever carrying a third drive finger, preferably distinct from the other drive fingers mentioned above, arranged to advance said moon wheel at a rate of 20 steps per day, said moon wheel being associated with (for example integral in rotation with, or arranged to drive) a moon display member. A direct drive of the moon wheel via the control lever is a very simple solution, free of return gears and kinematic connection with the day wheel, and therefore further avoids the need for separate pivot axes 25. The absence of this kinematic connection also makes it possible to adjust the moon wheel independently of the day wheel and vice versa.

[0021] Advantageously, the perpetual calendar mechanism comprises a day wheel arranged to complete one revolution per week, in particular at a rate of 30 steps of 1 / 7 of a revolution per day, and associated with (for example integral in rotation with, or arranged to drive) a day indicator organ.

[0022] Advantageously, said control rocker comprises a second drive finger, distinct from said first drive finger, arranged to make advance said mobile by days at the rate of one step per day (that is to say at the rate of 1 / 7 of a revolution per day).

[0023] Advantageously, said control lever is arranged to cooperate with said month wheel set and / or with an intermediate element 5 kinematically linked to said month wheel set, in order to prevent the month wheel set from advancing by two steps (double jump) or more per month under the control of said date wheel set. Said intermediate element is preferably a return wheel and / or a safety toothing. Advantageously, said control lever comprises a safety member, arranged to cooperate with said month wheel set and / or with said intermediate element kinematically linked to said month wheel set, in order to prevent the month wheel set from advancing by two steps (double jump) or more per month. Said safety member is preferably rigidly linked to said lever, for example in one piece or integral with said control lever.

[0024] Advantageously, said control lever (is arranged to cooperate with said month wheel set and / or with said intermediate element kinematically linked to said month wheel set, when said control lever is in an angular position in which it actuates said date wheel set, preferably in an extreme angular position 20 of said control lever.

[0025] Advantageously, the perpetual calendar mechanism comprises a return wheel, arranged to drive said month wheel set, said date wheel set being arranged to cooperate with the return wheel so as to advance said month wheel set at a rate of one step per month.

[0026] Advantageously, said date wheel comprises a tooth arranged to cooperate with said return wheel, preferably once a month.

[0027] Advantageously, the return wheel is arranged to rotate around an axis parallel to and separated from an axis of said month wheel set and / or said month programming wheel.

[0028] Advantageously, the perpetual calendar mechanism comprises a safety toothing, said control lever being arranged to cooperate with said safety toothing in order to prevent said advancement of two steps (double jump) or more per month of the month wheel.

[0029] Advantageously, said safety toothing is coaxial with said month wheel or with an intermediate element kinematically linked to said month wheel, for example said return wheel.

[0030] Advantageously, said end-of-month drive finger is pivotally mounted on said control rocker and is held in contact with the periphery of said snail by the effect of an elastic element.

[0031] Advantageously, said first drive finger is pivotally mounted on said control rocker and is subjected to the effect of an elastic element which tends to maintain it in a rest position, defined for example by a stop which limits the angular position of the first drive finger. Said elastic element may be separate from that which acts on the end-of-month drive finger, or the same.

[0032] Advantageously, said month wheel set is arranged to be driven by a month setting wheel which cooperates with a tooth included in said date wheel set, so as to advance said month wheel set at a rate of one step per month. The use of a setting wheel limits the risk of a double jump of the month wheel set, which can occur when the latter is driven directly by the date wheel set. Furthermore, the month setting wheel allows the month wheel set to be more compact than in conventional cases where the latter is driven directly by the date wheel set.

[0033] Advantageously, said control lever further comprises a safety beak arranged to cooperate with a safety toothing that said month return wheel comprises when said control lever is in an extreme angular position during an operating cycle. The risk of a double jump of the month wheel set can thus be eliminated, since the safety beak penetrates into the safety toothing that the month return wheel comprises and prevents it from pivoting when the control lever is in its extreme angular position during an actuation of said date wheel set, in particular its extreme angular position which is not its rest position.

[0034] Advantageously, said control rocker is arranged to carry out said back-and-forth pivoting movement cycle under the effect of a drive ring, the kinematic link between these two elements being obtained for example by means of a pin, a stud or the like.

[0035] The invention also relates to a perpetual calendar mechanism comprising:

[0036] - a date wheel, arranged to make one revolution per month and associated with (for example, integral in rotation with, or arranged to drive) a date display member 5;

[0037] - a month wheel arranged to complete one revolution in forty-eight months under the control of said date wheel and carrying a month programming wheel having a circumference whose profile is a function of the number of days in each month of a forty-eight-month cycle, said month wheel being associated with (for example integral in rotation with, or arranged to drive) a month display member;

[0038] - a control lever pivotally mounted around a rotation axis and arranged to pivot said date wheel.

[0039] Said perpetual calendar mechanism comprises a month return arranged 15 to drive said month wheel set and to be driven by said date wheel set, said month return further comprising a safety toothing, typically in the form of a saw toothing, which cooperates with a safety beak that said control lever comprises, this cooperation taking place when said control lever is in an extreme position 20 during an actuation of said date wheel set.

[0040] By these means, any risk of a double jump when actuating the perpetual calendar mechanism can be avoided, the safety beak cooperating with the safety toothing when actuating the date wheel. 25

[0041] Other aspects of the invention and preferred embodiments are defined in the claims and description below. Brief Description of the Drawings

[0042] Other details of the invention will appear more clearly on reading the following description, made with reference to the appended drawings in which: - Figure 1 is a dial side view of a perpetual calendar mechanism according to the invention, just before the end of February 28 of a non-leap year; - Figure 2 is a bottom side view of the perpetual calendar mechanism in its state of Figure 1; - Figure 3 is an isometric view, dial side, of the perpetual calendar mechanism in its state of Figure 1; 5 - Figure 4 is a dial side view of the perpetual calendar mechanism of Figures 1 to 3, after a first part of the upward travel of the control lever; - Figure 5 is a similar view of Figure 4, the control lever having adopted its second extreme angular position; 10 - Figure 6 is a similar view of Figure 5, after the completion of a complete actuation cycle. Embodiments of the invention

[0043] The structure of the perpetual calendar mechanism 1 according to the invention will be described firstly with reference to FIGS. 1 to 3, this embodiment being non-limiting.

[0044] The mechanism 1 comprises a date wheel 3, rotatably mounted on a frame element and comprising a date wheel 5 with 31 teeth, illustrated here in the form of saw teeth but other shapes are possible (for example conventional, triangular, or similar). The date wheel 3 further comprises a snail 6 integral in rotation with the date wheel 5 and the radius of its profile of which increases in the opposite direction to the direction of rotation of the date wheel 3 (considered statically by following the profile of the snail in the direction mentioned, such that, during the rotation of the wheel, its radius appears to increase if it is considered at a given fixed point). The snail 6 also has a discontinuity defining a shoulder 6a, the operation of which will be described below.The date wheel 3 is integral in rotation with, or arranged to drive, a date indicator member 8, here illustrated in the form 30 of a hand integral in rotation with said date wheel 3, but discs, crowns or the like may also be provided, driven directly or indirectly by the date wheel 3.

[0045] One of the teeth 5a of said date wheel 5 is longer than the others, and is arranged to rotate a month wheel 7 by by means of a month return 9 which comprises a toothed wheel 11 which cooperates on the one hand with said longer tooth 5a, on the other hand with a toothed wheel 13 which the month mobile 7 comprises, the gear ratio being predetermined so that the month mobile 7 makes a complete rotation 5 in 48 months in steps of 1 / 48 of a revolution. The return also carries a safety tooth 12, with saw teeth (but other forms could also be suitable), integral in rotation with the toothed wheel 11, and the operation of which will clearly follow below.

[0046] The month wheel 7 further comprises a programming disc 15 whose profile is a function of the length of the months in the normal 48-month cycle of leap years. This type of programming disc 15 is well known to those skilled in the art, in particular in the aforementioned document EP0191921, and therefore does not need to be described in more detail, except to specify that it comprises a plurality of levels having four different radii 15, the longest radii corresponding to months having 31 days, the next ones (in decreasing order of radius) corresponding to months having 30 days, the only level having the next radius corresponding to February 29 of leap years, and the levels having the smallest radii corresponding to February 28 of non-leap years.

[0047] The month display is provided by a month display member 16a making one revolution per year and driven from the teeth of the month wheel 7 by means of an ad hoc gear, but other solutions are possible. The leap year display is provided by a leap year display member 16b making one revolution in four years, for example by being integral in rotation with the month wheel. Of course, even if the display members 16a, 16b have been illustrated in the form of hands, other possibilities are also possible, in a manner similar to that of the dates 8.

[0048] The perpetual calendar mechanism 1 also includes a 30-day wheel 17 pivotally mounted on a frame element and including a seven-pointed star 18 as well as a day display member 19, here illustrated as a hand rotating integrally with the star 18, but other solutions are also possible in a manner analogous to the date display member

[0049] For the remainder, a moon mobile 21 pivotally mounted on a frame element is also present, and comprises a toothed wheel 23 having 59 teeth, as well as a moon display member 25, here represented in the form of a moon disc bearing two representations of the moon (not illustrated) in a known manner, the moon mobile 21 being arranged to complete one revolution in substantially two lunations (59 days), as will appear subsequently. Of course, the moon mobile 21 can be omitted, if desired, or can take any other suitable form (needle, ring, etc.).

[0050] The angular positioning of the date wheel set 3, of the month wheel set 7, 10 of the day wheel set 17 as well as of the moon wheel set 21 can be ensured by ad hoc means (not illustrated), such as for example jumpers which cooperate with their teeth or, in the case of the month wheel set 7, with one of the teeth of the month setting wheel 9. Furthermore, the correction of the wheels 3, 7, 17 and 21 can be ensured by correctors (not illustrated) of any known type.

[0051] The actuation of the mechanism 1 is ensured by a control rocker 27, which is pivotally mounted on a frame element around an axis of rotation A, here centered and coaxial with respect to the movement, but which could alternatively be located at an ad hoc off-center location. The control rocker 27 is arranged to carry out angular movements of the back-and-forth type, between a first extreme angular position defined by the contact between a feeler 29 carried by the control rocker 27, and a second extreme angular position (i.e. an active extreme position) which is reached during an operating cycle of the control rocker 27.The latter is held in its first extreme angular position by an ad hoc return spring 31, here illustrated in the form of a coil spring acting directly on the control rocker 27, but a leaf spring or similar can also serve the same purpose, and it is also possible that the return of the control rocker can be obtained at the level of its drive system or by other ad hoc means.

[0052] The control rocker 27 is rotated in a reciprocating motion by ad hoc means, which are arranged to provide sufficient flexibility to take into account the fact that the first extreme angular position varies depending on the cooperation between the feeler 29 and the disc of months 15, and this according to the radius of the bearing of the latter which cooperates with the sensor 29.

[0053] In the non-limiting embodiment illustrated, the control rocker 27 has a radial slot 33, in which a pin 35 5 is placed, carried by an actuating ring 37, which has the advantage that the latter can be driven by a drive system (not illustrated) located at a location that can be chosen with relatively great freedom. The drive ring 37 is pivoted concentrically to the axis A, but this is not obligatory. However, other solutions for the actuation of the control rocker 27 are also possible, based on one or more wheels, levers, cams, eccentrics or the like.

[0054] The driving of the date wheel set 3 at the end of each day is ensured by a first driving finger 39 which is pivotally mounted on the control lever 27 and is subjected to a return force provided by an elastic element 41 tending to maintain the first driving finger 39 in its rest position. The latter is defined by a stop 40, here taking the non-limiting form of a pin positioned so as to limit the movement of said first driving finger in the direction of the date wheel set 3.

[0055] The first drive finger 39 is therefore part of (or constitutes) a pawl, and is arranged to cooperate with the teeth of the date wheel 5 in order to advance it at the rate of one step of its teeth by pivoting the control lever 27 in the clockwise direction (according to the orientation of FIG. 1) at least at the end of each day which is not the last of the month, and this 25 independently of its initial angular position as determined by the cooperation between the programming disc 15 and the feeler 29. This pivoting takes place around midnight, typically between 9:00 p.m. and 3:00 a.m., even more typically between 11:00 p.m. and 1:00 a.m., at a predetermined time and for a predetermined duration.

[0056] The driving of the day wheel 17 is carried out at the same time by means of a second driving finger 43 carried by the control lever 27 and which cooperates with the star 18 of the day wheel 17 in order to pivot it at the rate of one step of its teeth per actuation. In the embodiment illustrated, this second finger 43 is in one piece with said control rocker 27, but may alternatively be pivotally mounted thereon in a similar manner to the first drive finger 39.

[0057] Similarly, the driving of the moon disc 21 is also ensured by the cooperation between a third driving finger 45 and the toothed wheel 23 which the moon wheel 21 comprises, in order to drive it at the rate of one step of its teeth per actuation.

[0058] The actuation of the date wheel set 3, the day wheel set 17 and the moon wheel set 21 (if present) is thus ensured by a single control lever 27, which pivots around a single axis A. In the illustrated embodiment, the axis A is centered on the mechanism 1, and is adapted so that the axes of the hour hands (not illustrated) can pass through an opening 27a in the control lever 27 which surrounds said axis A. However, the axis A may be off-center relative to the center of the mechanism 1 15 and / or the hour hands, and is not confused with the rotation axis of the date wheel set, being distinct from the latter axis.

[0059] As mentioned above, the month wheel 9 comprises a safety toothing 12, which cooperates with a safety beak 49 carried by the control lever 27 when the latter is in its second extreme angular position20 during an actuation, in order to prevent a double jump of the wheel 9 and therefore of the month wheel set 7. This safety beak can take any suitable form, whether it be a finger, a tooth, a pin, a stud, a rod or the like.

[0060] Along each month, the angular path of the control rocker 27 25 is determined by the radius of the section of the programming disc 15 which is located opposite the feeler 29, this radius determining the angular rest position adopted between the actuations of the control rocker 27.

[0061] In order to ensure the additional steps of the date wheel set 3 at the end of the months, an end-of-month drive finger 47 is pivotally mounted on the control lever 27, and is held in contact with the periphery of the snail 6 under the effect of an elastic element 41. In the illustrated embodiment, the elastic element 41 performs a dual function and acts on the first drive finger 39 as well as on the end-of-month drive finger 47 at the same time, being attached between these two elements 39, 47, but separate elastic elements of any type may alternatively be used.

[0062] For most of the duration of a month, the free end of the end-of-month drive finger 47 slides on the surface of the snail 6 during the 5 movements of the control lever 27 and exerts no influence on the date wheel.

[0063] However, after the actuation cycle to indicate the last day of the month, the free end of the end-of-month drive finger 47 is in contact with the shoulder 6a. Since the initial angular position of the control rocker 27 is determined by the penetration depth of the feeler 29 into the programming disc 15, the initial position of the free end of the end-of-month drive finger 47 also varies according to the radius of the section of the programming disc 15 which cooperates with the feeler 29. The geometry of the control rocker 27, the feeler 29 and that of the end-of-month drive finger 47 are predetermined such that the free end of the end-of-month drive finger 47 comes into contact with the shoulder 6a on the day concerned (whether it is the 28th, 29th, 30th or 31st of the month).

[0064] The arrangement of components illustrated in Figures 1 to 3 corresponds to the end 20 of a 28-day February, before the actuation cycle starts, and the operation of mechanism 1 during this cycle will now be described in connection with Figures 4 to 6.

[0065] Subsequently, and in order to avoid making the figures cumbersome, only the reference signs mentioned in connection with a particular figure will be reproduced. 25

[0066] Figure 4 illustrates the situation after a first part of the upward travel of the control lever 27 under the effect of its drive system, against the effect of the return element 31. The control lever 27 has been driven in the clockwise direction (according to the orientation of Figure 4), the date wheel 30 now being in an angular position corresponding to an indication of 30. To reach this position, the free end of the end-of-month drive finger 47 has pushed the shoulder 6a at a rate of two steps of the toothing of the date wheel 5. The free end of the first drive beak 39 has also come into contact with a tooth of the date wheel 5, but this is not obligatory since it is the end-of-month drive finger 47 which is responsible for driving the date wheel 3 at the end of each month.

[0067] The second training finger 43 and the third training finger 45 remain without effect for the moment.

[0068] Figure 5 illustrates the situation shortly after that of Figure 4, with the control rocker 27 having adopted its second extreme angular position.

[0069] In doing so, the free end of the end-of-month drive finger 47 pushed the shoulder even further, in particular by an additional step of the teeth of the date wheel 5, the first drive finger 39 having followed this movement in contact with a tooth of the latter.

[0070] At the same time, the longer tooth 5a of the date wheel 5a also rotated the month wheel 9 by cooperation with a tooth of its toothed wheel 11, which in turn drove the month wheel. The bearing of the programming disc 15 corresponding to the month of March is now opposite the feeler 29.

[0071] For the remainder, the second drive finger 43 has driven the star 18 of the 20 day wheel 17 at the rate of one step of its teeth, the third drive finger 45 has driven the toothed wheel 23 of the moon wheel 21 in rotation at the rate of one step of its teeth, and the safety beak is penetrated into the teeth of the safety toothing 12 of the month wheel 9 in order to prevent an additional unwanted jump. The indications provided therefore correspond to March 25.

[0072] Figure 6 illustrates the situation after the complete actuation cycle is completed.

[0073] The control rocker 27 is lowered under the effect of its return element 31, the feeler 29 now being in contact with the bearing corresponding to the month of March of the programming disc 15. The starting angular position of the control rocker 27 has thus been defined for the month of March, which has 31 days, and consequently the free end of the end-of-month drive finger 47 will cooperate with the shoulder 6a only at the end of the 31st of the month, the advancement of the date wheel 3 being ensured between the 1st and the end of the 30th of the month being therefore ensured by the first drive beak 39 as described previously. At the end of the month, the starting position of the end-of-month drive finger 47 ensures that the free end of the latter only cooperates with the shoulder 6a at the end of the 31st of the month and pivots the date wheel 3 at the rate of a single step of the teeth of the date wheel 5.

[0074] The operation of the mechanism 1 at the end of a month having 29 or 30 days 10 can easily be deduced from the above, the corresponding bearings of the programming disc 15 ensuring that the starting angular position of the control lever 27, and consequently of the free end of the end-of-month drive finger, cooperates with the shoulder 6a at the end of the appropriate day in order to rotate the date wheel set at a rate of two 15 or three steps, as appropriate.

[0075] Although the invention has been described in connection with particular embodiments, variations are, of course, possible, without departing from the scope of protection defined by the claims.

Claims

Claims 1. Perpetual calendar mechanism (1) for a watch movement, comprising: - a date wheel set (3), arranged to complete one revolution per month and carrying a snail (6) whose radius of its profile increases in the opposite direction to the direction of rotation of said date wheel set (3) and has a discontinuity defining a shoulder (6a), said date wheel set (3) being associated with a date display member (8); - a month wheel set (7) arranged to complete one revolution in forty-eight months under the control of said date wheel set (3) at a rate of one step per month and carrying a month programming wheel (15) having a periphery whose profile defines a number of steps whose radius is a function of the number of days in each month of a forty-eight-month cycle, said month wheel set (7) being associated with a month display member (16a);- a control lever (27) pivotally mounted about a rotation axis (A) and arranged to advance said date wheel set (3) at a rate of at least one step per day, said control lever (27) being arranged to perform a cycle of back-and-forth pivoting movement at a rate of one cycle per day, in which said control lever (27) comprises: - a feeler (29) arranged to cooperate with said month programming wheel (15) to determine the angular path of said control lever (27) as a function of the number of days in each month, - a first drive finger (39) arranged to advance said date wheel set (3) at a rate of one step per cycle at least at the end of the non-final days of the month;- an end-of-month drive finger (47) arranged to cooperate with said discontinuity (6a) at the end of a month in order to advance said date wheel set (3) at a predetermined number of steps as a function of said angular path of said control lever (27).

2. Perpetual calendar mechanism (1) according to claim 1, characterized in that said control lever (27) is arranged to cooperate with said month wheel set (7) and / or with a kinematically linked intermediate element; said month wheel (7), in order to prevent an advancement of two steps ("double jump") or more per month of the month wheel under the control of said date wheel (3). 5 3. Perpetual calendar mechanism (1) according to claim 2, characterized in that said control lever (27) comprises a safety member (49), arranged to cooperate with said month wheel and / or with said intermediate element kinematically linked to said month wheel (7), in order to prevent an advancement of two steps ("double jump") or more per month of the month wheel. 4.Perpetual calendar mechanism (1) according to claim 2 or 3, characterized in that said control lever (27) is arranged to cooperate with said month wheel set (7) and / or with an intermediate element kinematically linked to said month wheel set (7), when said control lever (27) is in an angular position in which it actuates said date wheel set, preferably in an extreme angular position of said control lever.

5. Perpetual calendar mechanism (1) according to any one of claims 2-4, comprising an intermediate wheel (9), arranged to drive said month wheel set (7), said date wheel set (3) being arranged to cooperate with the intermediate wheel (11) so as to advance said month wheel set (7) at a rate of one step per month.

6. Perpetual calendar mechanism (1) according to claim 5, wherein said date wheel (3) comprises a tooth (5a) arranged to cooperate with said return wheel (11).

7. Perpetual calendar mechanism (1) according to claim 5 or 6, wherein said return wheel (11) is arranged to rotate around an axis parallel to and separated from an axis of said month wheel set (7) and / or said month programming wheel (15).

8. Perpetual calendar mechanism (1) according to any one of the preceding claims, comprising a safety toothing (12), said control lever (27) being arranged to cooperate with said safety toothing in order to prevent an advancement of two steps ("double jump") or more per month of the month wheel set.

9. Perpetual calendar mechanism (1) according to claim 8, wherein said safety toothing (12) is coaxial with an intermediate element kinematically linked to said month wheel set (7), for example said idler wheel (11), or with said month wheel set (7).

10. Perpetual calendar mechanism (1) according to any one of the preceding claims, comprising a day wheel (17) arranged to make one revolution per week and associated with a day indicator member (19), said control lever (27) comprising a second drive finger (43) arranged to advance said day wheel (17) at a rate of one step per day. 11.

12. Perpetual calendar mechanism (1) according to any one of the preceding claims, further comprising a moon wheel (21) arranged to make one revolution in substantially two lunar months, said control lever (27) carrying a third drive finger (45) arranged to advance said moon wheel (21) at a rate of one step per day, said moon wheel being associated with a moon display member (25).

12. Perpetual calendar mechanism (1) according to any one of the preceding claims, wherein said end-of-month drive finger (47) is pivotally mounted on said control lever (27) and is held in contact with the periphery of said snail (6) by the effect of an elastic element (41).

13. Perpetual calendar mechanism (1) according to any one of the preceding claims, wherein said first drive finger (39) is pivotally mounted on said control lever (27) and is subjected to. the effect of an elastic element (41) which tends to maintain it in a rest position.

14. Perpetual calendar mechanism (1) according to claims 12 and 13, in which said elastic element (41) acting on said first drive finger (39) and the same elastic element (41) which acts on the end-of-month drive finger (47).

15. Perpetual calendar mechanism (1) according to any one of the preceding claims, in which said month wheel set (7) is arranged to be driven by a month setting wheel (9) which cooperates with a tooth (5a) included in said date wheel set (3), so as to advance said month wheel set (7) at a rate of one step per month. 16.Perpetual calendar mechanism (1) according to the preceding claim, wherein said control lever (27) further comprises a safety beak (49) arranged to cooperate with a safety toothing (12) that said month return (9) comprises when said control lever (27) is in an extreme angular position during an actuation of said date wheel set.

17. Perpetual calendar mechanism (1) according to any one of the preceding claims, wherein said control lever (27) is arranged to carry out said cycle of back-and-forth pivoting movement under the effect of a drive ring (37).

18. Perpetual calendar mechanism (1) according to any one of the preceding claims, wherein the pivot axis (A) of said control lever (27) is distinct from the rotation axis of said date wheel set (3). 19.Perpetual calendar mechanism (1) comprising: - a date wheel (3), arranged to make one revolution per month and associated with a date display member (8); - a month wheel (7) arranged to complete one revolution in forty-eight months under the control of said date wheel (3) and carrying a month programming wheel (15) having a periphery whose profile is a function of the number of days in each month of a forty-eight-month cycle, said month wheel (7) being associated with a month display member (16a); - a control lever (27) pivotally mounted and arranged to pivot said date wheel set (3), in which said perpetual calendar mechanism (1) comprises a month setting wheel (9) arranged to drive said month wheel set (7) and to be driven by said date wheel set (3), said month setting wheel (9) further comprising a safety toothing (12) which cooperates with a safety beak (49) that said control lever (27) comprises, this cooperation taking place when said control lever is in an extreme position during an actuation of said date wheel set (3). 20.Perpetual calendar mechanism (1) according to the preceding claim, wherein said safety toothing (12) takes the form of saw teeth.

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