EP3333640B1 - Running time equation mechanism controlled by a differential device - Google Patents

Description

Technical field of the invention

The subject of the present invention is a running equation of time mechanism for a timepiece. More specifically, the invention relates to a running equation of time mechanism driving a true time minute hand concentric with an hour hand.

Technological background of the invention

As we know, there is a difference between true solar time, which corresponds to the time that elapses between two consecutive zenith passages of the Sun at the meridian of the same place, and mean solar time or civil time, which is the average, taken over the year, of the duration of all true solar days. This difference between civil time and real time reached +14 min 22 s on February 11, and -16 min 23 s on November 4. These values vary little from year to year.

To indicate the time difference between civil time and true time, some timepieces have, in addition to the hand which indicates the minute of civil time, a so-called equation of time mechanism which includes a hand which moves next to a graduated scale to indicate the difference between the minute of civil time and the minute of solar time for a given day. This true time minute hand is driven by an equation of time cam whose profile is determined by the difference between mean solar time and true solar time for every day of the year.

Another mechanism for indicating the time difference between civil time and true time is known as the walking equation of time. The hands of a timepiece fitted with a running equation of time mechanism comprises two concentric minute hands, one indicating the minute of civil time, and the other indicating the minute of true time. At any instant, the difference between the civil time minute hand and the true time minute hand is determined by the difference between the mean solar time and the true solar time for the day of the year in question. As with the equation of time mechanism, the true time minute hand of a running equation of time mechanism is driven by an equation of time cam.

The equation of time cam is driven in rotation at the rate of one revolution per year from a date mechanism which may be simple or perpetual. The simple calendar is a mechanism arranged to indicate the day of the week, the calendar of the month, the month of the year or even the phases of the Moon, but which does not take into account the variation in the number of days in the month. (months of 28, 29 or 30 days). In other words, the user of a watch with a simple date mechanism will have to carry out a manual correction at the end of every month that has less than 31 days. For example, on February 28 or April 30, a manual intervention will be required. As regards the perpetual calendar mechanism, it allows, like a simple calendar mechanism, to indicate the day, the date, the month and the phases of the Moon. But unlike a simple calendar mechanism, a perpetual calendar mechanism automatically takes into account the length of the months (28, 29 and 30 days), without manual intervention. A perpetual calendar mechanism therefore automatically takes leap years into account.

An example of a walking equation of time mechanism is disclosed by European patent application EP 1 286 233 A1 on behalf of the Applicant. The figure 1 appended to this patent application is taken from the European patent application EP 1 286 233 A1 mentioned above and illustrates a running equation of time mechanism driven by a differential device.

In this figure is notably visible a cam with equation of time 1 whose profile is determined by the difference, for each day of the year, between the mean solar time or civil time and the true solar time. This equation of time cam 1 is driven in rotation at the rate of one revolution per year from a simple or perpetual calendar mechanism that the timepiece includes. Equation of time cam 1 carries a month disc 2 which rotates at the same speed as it and which enables the position of this equation of time cam 1 to coincide with the date indicated by the date mechanism in order that the minute hand of solar time 4 indicates the exact difference between the minute of civil time and the minute of solar time.

The calendar mechanism, simple or perpetual, can be of any known type and will not be described here in its entirety. It suffices, in fact, for a good understanding, to know that this date mechanism drives the equation of time cam 1 at the rate of one complete revolution per year. However, for illustrative purposes only, a date mobile 6 has been shown driving a hand 8 which indicates the date (from 1 to 31). This mobile with date 6 rotates at the rate of one complete revolution per month. It is actuated by the date mechanism and drives the equation of time cam 1 via an intermediate date deflection wheel 10 which makes it possible to reverse the direction of rotation, and a reduction wheel set 12 which makes it possible to reduce the speed of rotation from one full turn per month to one full turn per year.

The solar time minute hand 4 is driven by a differential gear device 14 which has as respective inputs a cog driving a civil time minute hand 18, and a rake 20 which cooperates with the equation of time cam 1 (on the figure 1 , the rake 20 is represented in its two extreme positions, once in solid line, and the other time in dot-and-dash line). More specifically, as can be seen in the figure 1 , the differential gear device 14 comprises at least one and, preferably, two planet gears 22 driven by the timer of the watch movement. These two satellite pinions 22 are able to turn on themselves and to roll on the internal toothing 24 of an equation of time wheel 26. The latter also has on its outer periphery a first toothed sector 28 by which it cooperates with a second toothed sector 30 with which the rake 20 is provided at one of its ends. This rake 20 is subjected to the return action of a spring (not shown) fixed to the frame of the watch and which tends to apply a feeler 32 forming the other end of the rake 20 against the profile of the cam of equation time 1. The solar time display train comprises a solar time display pinion 34 placed in the center of the differential gear device 14. This solar time display pinion 34 meshes on the one hand with the satellite pinions 22, and on the other hand carries a solar time display wheel 38 which meshes with a roadway 40 on the barrel from which the solar time minute hand 4 is driven. This cog 38, 40 makes it possible to return the display of the solar minute to the center 42 of the watch movement, so that the solar time minute hand 4 is concentric with the civil time minute hand 18.

The running equation of time mechanism which has just been described operates in the following way.

In normal operation of the watch, the equation of time cam 1, the rack 20 and therefore the equation of time wheel 26 are stationary. On the other hand, the satellite pinions 22 are driven by the clockwork movement of the watch. They therefore turn on themselves and roll on the internal toothing 24 of the equation of time wheel 26, driving the solar time display pinion 34 in rotation, which allows the solar time minute hand 4 to turn concomitantly with the minute hand of civil time 18. The difference between the solar time minute hand 4 and the civil time minute hand 18 therefore remain constant over a period of 24 hours.

Once a day, around midnight, the equation of time cam 1 pivots, driven by the date mechanism which moves the calendar from one day to the next. At this precise moment, the feeler 32 which is in contact with the profile of the equation of time cam 1 in turn causes the rake 20 to pivot. This rake 20, by pivoting, drives the equation of time wheel 26 in rotation. The satellite pinions 22 being, during this brief interval of time, substantially immobile (they make a complete turn on themselves in 1 hour), turn on themselves while being driven in rotation by the equation of time wheel 26, and in turn drive the solar time display pinion 34 so as to again exactly adjust the position of the solar time minute hand.

The running equation of time mechanism described above therefore makes it possible, by means of a civil time minute hand and a solar time minute hand, to display at any time the difference in time between the mean solar time and true time.

We have nevertheless realized in use that reading civil time, respectively real time, was not the most convenient. Indeed, if, with a mechanism in which the minute hand of civil time and the minute hand of real time are concentric, one can easily appreciate the time difference between the minute of civil time and the minute of real time, on the other hand it is more inconvenient to read the time on your watch, whether it is civil time or solar time. Indeed, the user is often forced to remember which of the minute hands corresponds to civil time and solar time, even if the true time minute hand bears a symbol to differentiate it from the civil. Then, after having identified the civil time minute hand, the user must still make an effort to mentally reconstruct civil time by locating the respective positions of the civil time hour hand and the civil time. We will understand that this is not very convenient for a user who wishes to read the time on his watch at a quick glance. In addition, at certain times of the year, when the difference between the minute of civil time and the minute of true time is small, it is difficult to visually appreciate this difference due to the concentricity of the two minute hands of time. calendar and minutes of true time.

The document CH698613 B1 describes a walking equation of time device comprising a differential mechanism.

Summary of the invention

The object of the present invention is to overcome the problems described above as well as others by providing a running equation of time mechanism controlled by a differential gear device which is in particular simpler to read.

To this end, the present invention relates to a running equation of time mechanism according to independent claim 1.

• le mobile satellite réducteur permet de réduire la vitesse de rotation d'un tour complet par heure à un tour complet par douze heures, et le mobile satellite multiplicateur permet d'augmenter la vitesse de rotation d'un tour complet en douze heures à un tour complet par heure ;
• le mobile satellite réducteur et le mobile satellite multiplicateur tournent sur eux-mêmes en décrivant une trajectoire circulaire centrée sur le canon des minutes du temps vrai ;
• le mobile satellite réducteur et le mobile satellite multiplicateur se trouvent à égale distance du canon des minutes du temps vrai ;
• le mobile satellite réducteur et le mobile satellite multiplicateur sont portés libres en rotation par un bâti de différentiel dont le canon des heures du temps civil est solidaire ;
• le mobile satellite réducteur et le mobile satellite multiplicateur sont montés pivotants autour d'une première goupille, respectivement d'une seconde goupille, fixées dans le bâti de différentiel ;
• le mobile satellite réducteur comprend une première roue de satellite solidaire d'un premier pignon de satellite ;
• le pignon de chaussée engrène avec la première roue de satellite, et le premier pignon de satellite roule sur une première denture intérieure d'une couronne de différentiel fixe, ce qui a pour effet de faire tourner le bâti de différentiel ;
• le mobile satellite multiplicateur comprend une seconde roue de satellite solidaire d'un second pignon de satellite ;
• la seconde roue de satellite engrène avec le canon des minutes du temps vrai, et le second pignon de satellite roule sur une seconde denture intérieure d'une couronne de différentiel mobile qui est reliée cinématiquement à la came d'équation du temps ;
• la couronne de différentiel mobile est commandée en pivotement par un levier d'équation du temps muni d'un bec palpeur par l'intermédiaire duquel le levier d'équation du temps suit le profil de la came d'équation du temps ;
• le levier d'équation du temps est maintenu en appui élastique contre le profil de la came d'équation du temps par un ressort ;
  le levier d'équation du temps est pourvu d'une première dent en prise avec une seconde dent correspondante prévue sur la couronne de différentiel mobile pour commander le déplacement de cette dernière ;
• le bâti de différentiel comprend un bâti supérieur fixé sur un bâti inférieur au moyen d'au moins une vis.

According to other features of the invention which are the subject of the dependent claims:

• the reduction satellite mobile allows the speed of rotation to be reduced from one complete revolution per hour to one complete revolution per twelve hours, and the multiplier satellite mobile enables the rotation speed to be increased from one complete revolution in twelve hours to one revolution full per hour;
• the reduction satellite mobile and the multiplier satellite mobile turn on themselves while describing a circular trajectory centered on the true time minute barrel;
• the reduction satellite mobile and the multiplier satellite mobile are at an equal distance from the true time minute barrel;
• the reducing satellite wheel set and the multiplier satellite wheel set are carried free in rotation by a differential frame with which the civil time hours barrel is attached;
• the reducing satellite wheel set and the multiplier satellite wheel set are pivotally mounted around a first pin, respectively a second pin, fixed in the differential frame;
• the reducing satellite mobile comprises a first satellite wheel integral with a first satellite pinion;
• the road pinion meshes with the first satellite wheel, and the first satellite pinion rolls on a first internal toothing of a fixed differential crown, which has the effect of rotating the differential frame;
• the multiplier satellite mobile comprises a second satellite wheel secured to a second satellite pinion;
• the second satellite wheel meshes with the real time minute barrel, and the second satellite pinion rolls on a second internal toothing of a movable differential ring gear which is kinematically connected to the equation of time cam;
• the movable differential crown is controlled in pivoting by an equation of time lever provided with a feeler beak by means of which the equation of time lever follows the profile of the equation of time cam;
• the equation of time lever is maintained in elastic bearing against the profile of the equation of time cam by a spring;
  the equation of time lever is provided with a first tooth meshing with a corresponding second tooth provided on the mobile differential ring gear to control the movement of the latter;
• the differential frame comprises an upper frame fixed to a lower frame by means of at least one screw.

Thanks to these characteristics, the present invention provides a running equation of time mechanism, the switching of which is only formed of a true time minute hand concentric with a civil time hour hand. In the absence of a civil time minute hand, the reading of solar time is therefore immediate. In particular, the problem of reading solar time on days when the difference between the minute of civil time and the minute of solar time is small does not arise. Furthermore, there may be provided, apart from the solar time switch, an additional civil time switch conventionally formed of a supplementary hour hand civil time and a concentric civil time minute hand. In this case too, the reading of civil time is immediate and the user does not have to perform any mental operation to distinguish the minute hand of civil time from the minute hand of solar time, then reconstruct the civil time by assessing the difference between the civil time hour hand and the civil time minute hand.

Brief description of figures

• la figure 1, déjà citée, est une vue d'un mécanisme d'équation du temps marchante selon l'art antérieur mû par un dispositif différentiel ;
• la figure 2 est une vue de dessus du dispositif d'équation marchante selon l'invention ;
• la figure 3 est une vue en coupe d'un mécanisme d'affichage du temps solaire et d'un mécanisme d'affichage du temps civil tous deux situés du même côté d'un cadran d'une pièce d'horlogerie, et
• la figure 4 est une vue en coupe d'un mécanisme d'affichage du temps solaire et d'un mécanisme d'affichage du temps civil situés pour l'un du côté d'un cadran d'une pièce d'horlogerie, et pour l'autre du côté d'un fond de la pièce d'horlogerie.

Other characteristics and advantages of the present invention will emerge more clearly from the detailed description which follows of an embodiment example of a running equation of time device according to the invention, this example being given for purely illustrative purposes and not limiting only in connection with the attached drawing on which:

• the figure 1 , already cited, is a view of a running equation of time mechanism according to the prior art driven by a differential device;
• the figure 2 is a top view of the working equation device according to the invention;
• the picture 3 is a sectional view of a solar time display mechanism and a civil time display mechanism both located on the same side of a dial of a timepiece, and
• the figure 4 is a sectional view of a mechanism for displaying solar time and of a mechanism for displaying civil time, one located on the side of a dial of a timepiece, and the other on the side of a back of the timepiece.

Detailed description of an embodiment of the invention

The present invention proceeds from the general inventive idea which consists in providing a running equation of time mechanism comprising a switch whose role is to indicate the solar time or real time by means of a civil time hour hand and a real time minute hand concentric with the civil time hour hand, the switch not having a civil time minute hand. With such an arrangement, the reading of the true time is immediate since the user does not need to differentiate between the civil time minute hand and the true time minute hand before being able to read the solar time. or real time. In the case of the present invention, one can even speak of a true display of solar time or true time since only the minute of true time differs to some extent from the minute of civil time during the year, whereas real time and civil time are identical. The civil time hour hand therefore merges with the real time hour hand, so that the indication provided to the user by the handpiece formed of a civil time hour hand and a Concentric true time minute hand matches exact true time. In addition, the device for displaying solar time or true time according to the invention can be advantageously supplemented by a civil time switch comprising an hour hand and a concentric minute hand and which are driven by the same roadway as the true time display device. Thus, the user can, with a simple glance, read the true time and the civil time in a clear and precise manner.

The object of the present invention is to integrate into a timepiece such as a wristwatch a new kind of running equation of time mechanism, the hand-fitting of which includes a true time minute hand concentric at a civil time hour hand. For this purpose, and as can be seen in the figure 2 , the running equation of time mechanism according to the invention, designated as a whole by the general reference numeral 44, comprises a switch whose role is to indicate solar time or true time by means of an hour hand of the civil time 46 and a true time minute hand 50, concentric with the civil time hour hand 46, and which indicates the true time minute. To allow the bearer to the watch to easily identify the true time minute hand 50, the latter may, for example, end with a representation of the astrological symbol of the sun 52. As will be seen in more detail in the remainder of this description, the exact position of the true time minute hand 50 for a given day can be determined once in 24 hours, around midnight, or else be continuously adjusted.

You can also see on the figure 2 part of the running equation of time mechanism 44 according to the invention, and in particular an equation of time cam 54 whose profile, it will be recalled, is determined by the difference between the mean solar time or civil time, and the solar time or true time for each day of the year.

Always in contact with the figure 2 , it can be seen that the equation of time cam 54 is fixed to an equation of time wheel 56 which is driven at the rate of one complete revolution per year by a simple or perpetual calendar mechanism (not shown) that comprises the timepiece. This date mechanism can be of any known type and will not be described here in detail. It suffices, in fact, for a good understanding of the invention, to know that this date mechanism drives the equation of time wheel 56 on which the equation of time cam 54 is fixed at the rate of a complete revolution. per year. In the case where the date mechanism is also used to display the date, this date mechanism may comprise a date wheel 58 which rotates at the rate of one complete revolution per month, driving a date indicator 104. On the other hand , the equation of time wheel 56 is driven by the date wheel 58 via an intermediate date return wheel 60 making it possible to reverse the direction of rotation, and a reduction wheel set 62 which makes it possible to reduce the rotation speed d one full turn per month to one full turn per year.

According to the invention, the true time minute hand 50 is driven by a differential gear device 64 which has respective inputs (see picture 3 ) a mobile 66 of a going train and an equation of time lever 68. The mobile 66 of the going train drives the civil time hour hand 46, while the equation of time lever 68 cooperates with the equation of time cam 54.

More precisely, as seen in the picture 3 , a civil time hours cannon 70 is driven by the mobile 66 of the going train of the timepiece movement of the timepiece via a roadway 72 fixed for example by driving on a roadway pinion 74. In turn, the carriage pinion 74 drives a reduction satellite wheel set 76 formed of a first satellite wheel 78 and a first satellite pinion 80 secured to the first satellite wheel 78.

The geared satellite wheel set 76 is pivotally mounted around a first pin 82 fixed for example by driving in a differential frame 84 to which the civil time hour barrel 70 is attached on which the civil time hour hand 46 is driven. Driven by the carriage pinion 74 via the first satellite wheel 78, the first satellite pinion 80 rolls on a first internal toothing 86 of a first differential crown 88 which is carried by the clock movement and which is fixed . By rolling on the first internal toothing 86 of the fixed differential ring gear 88, the first satellite pinion 80 pivots the differential frame 84 and therefore the civil time hours barrel 70 which is integral with the differential frame 84. By a judicious choice of the gear ratios between the road pinion 74, the first satellite wheel 78, the first satellite pinion 80 and the fixed differential crown 88, a reduction of one twelfth is achieved between the minute of civil time and the civil time and the display of civil time is thus obtained. In other words, the reducing mobile satellite 76 makes it possible, by a reduction of one twelfth, to pass from the minute of civil time to the hour of civil time.

As also visible on the picture 3 , a multiplier satellite wheel set 90 is formed of a second satellite wheel 92 and a second satellite pinion 94 secured to the second satellite wheel 92. The multiplier satellite wheel set 90 is mounted free around a second pin 96 fixed for example by driving in the differential frame 84 to which the civil time hours barrel 70 is attached. When the civil time hours barrel 70 and therefore the differential frame 84 rotate, they drive the second pin 96 and, consequently, the multiplier satellite mobile 90 whose second satellite pinion 94 rolls on a second internal toothing 98 of a mobile differential ring gear 100 which, as will be seen below, is in engagement with the equation of time cam 54. The second satellite wheel 92 in turn drives a true time minute barrel 102 on which the true time minute hand 50 is driven. By a judicious choice of gear ratios between the true time hour barrel civil 70, the second satellite wheel 92, the second satellite pinion 94 and the mobile differential crown 100, a multiplication by twelve is carried out between the hour of civil time and the minute of true time and we thus obtain the 'at display of the minute of true time. In other words, the multiplier mobile satellite 90 makes it possible, by a multiplication by twelve, to pass from the hour of civil time to the minute of true time.

It follows from the above that the reducing satellite mobile 76 and the multiplier satellite mobile 90 turn on themselves while describing a circular trajectory centered on the barrel of the hours of civil time 70. Preferably, the reducing satellite mobile 76 and the mobile multiplier satellite 90 move on the same circle, centered on the barrel of civil time hours 70, being angularly spaced.

The mobile differential crown 100 is controlled in pivoting by the equation of time lever 68 provided with a feeler tip 106 through which the equation of time lever 68 is in contact with the profile of the cam of equation of time 54. This equation of time lever 68 is held in elastic support against the profile of the equation of time cam 54 by a spring 108. This equation of time lever 68 is also provided with a first tooth 110 in engagement with a corresponding second tooth 112 provided on the differential crown mobile 100 to control the movement of the latter. It is in fact understood that at an instant close to midnight when the date mechanism changes the date, it controls the advance of one step of the date wheel 58. During this brief instant when the date change occurs, the differential frame 84 and therefore the civil time hours cannon 70 can be considered immobile. By pivoting, the mobile differential crown 100 drives the second satellite pinion 94 and therefore the second satellite wheel 92 which, in turn, meshes with the true time minute barrel 102 on which the minute hand of the true time 50. The position of the true time 50 minute hand is thus adjusted for the day to come. In the case of a dragging date mechanism, the position of the true time minute hand 50 is continuously adjusted.

By referring to the figure 2 , it can be seen that at least one and preferably two screws 114 make it possible to close the differential frame 84 on a lower differential frame 116. The differential 84 and lower 116 frames therefore rotate together when the differential gear device 64 according to the invention works.

As also illustrated in picture 3 , roadway 72 drives a second roadway 118 via an intermediate idler wheel 120. This second roadway 118 is fixedly mounted on a civil time minute barrel 122 on which is driven a civil time minute hand 124. The minute barrel civil time 122 drives via a second reduction mobile 126 comprising a reduction wheel 128 fixed on a reduction pinion 130 a second civil time hour cannon 132 on which is driven a second civil time hour hand 134. Thanks to the use of the intermediate return wheel 120, the civil time display by means of the second civil time hour hand 134 and the civil time minute hand 124 rotates in the right direction above a dial of watch 136. The intermediate return wheel 120 also makes it possible to ensure sufficient spacing between the time display solar and the true time display so that these two displays do not interfere with each other.

The reading of civil time is thus also immediate and the user does not have to perform any mental operation to distinguish the civil time minute hand from the solar time minute hand, then reconstruct the civil time by appreciation of the gap between the civil time hour hand and the civil time minute hand. In addition, it will be appreciated that the same power take-off is used to produce the minute of true time on the one hand, and the civil time on the other hand, which considerably simplifies assembly.

In the example shown in picture 3 , the solar time or true time display device and the civil time display device are arranged on the same side of the watch dial 136. In the example illustrated in figure 4 , the solar time or true time display device is arranged on the dial side of the watch 136, while the civil time display device is arranged on the side of a bottom 138 of the watch. It can be seen in this exemplary embodiment that it is possible to dispense with the intermediate return wheel 120 because there is no need to correct the direction of rotation of the second civil time display device when it is the other side of the watch.

It goes without saying that the present invention is not limited to the embodiment which has just been described and that various simple modifications and variants can be envisaged by those skilled in the art without departing from the scope of the invention as defined. by the appended claims.

Nomenclature

1.

Equation of time cam

2.

disc of months

4.

Solar time minute hand

6.

Calendar mobile

8.

Needle

10.

Intermediate date wheel

12.

Discount Mobile

14.

Differential gear device

18.

Civil time minute hand

20.

Rake

22.

Planet gears

24.

Internal teeth

26.

Equation of time wheel

28.

First gear sector

30.

Second gear sector

32.

Feeler

34.

Solar time display gear

38.

Solar time display wheel

40.

roadway

42.

Center

44.

Walking equation of time mechanism

46.

Civil time hour hand

50.

True time minute hand

52.

Sun astrological symbol

54.

Equation of time cam

56.

Equation of time wheel

58.

Date wheel

60.

Intermediate date wheel

62.

Discount Mobile

64.

Differential gear device

66.

Mobile

68.

Equation of time lever

70.

Canon of the hours of civil time

72.

roadway

74.

road sprocket

76.

Mobile satellite reducer

78.

First satellite wheel

80.

First satellite gear

82.

first pin

84.

Differential frame

86.

First internal toothing

88.

Fixed differential crown

90.

Mobile satellite multiplier

92.

Second satellite wheel

94.

Second satellite gear

96.

Second pin

98.

Second internal toothing

100.

Mobile differential crown

102.

True time minute canon

104.

Date indicator

106.

Feeler tip

108.

Competence

110.

first tooth

112.

second tooth

114.

Screw

116.

Lower differential mount

118.

Second carriageway

120.

Intermediate idler wheel

122.

Civil time minute canon

124.

Civil time minute hand

126.

Second gear reducer

128.

Reduction wheel

130.

Reducer pinion

132.

Second civil time hour canon

134.

Second civil time hour hand

136.

Watch dial

138.

Watch bottom

Claims (14)

1. Running equation of time mechanism comprising a hand arrangement, whose purpose is to indicate the apparent or true solar time by means of a civil hour hand (46) and a true solar minute hand (50) concentric with the civil hour hand (46), the hand arrangement being devoid of a civil minute hand, the civil hour hand (46) being pressed on a civil hour pipe (70) driven in rotation by a timepiece movement and driving in turn a true solar minute pipe (102) on which is pressed the true solar minute hand (50), the running equation of time mechanism (44) also comprising an equation of time cam (54) having a profile that is determined by the difference, on every day of the year, between the mean solar time or civil time, and the apparent solar time or true solar time, said equation of time cam (54) being driven in rotation at the rate of one revolution per year by the timepiece movement, the position of the true solar minute hand (50) being determined by the position of the equation of time cam (54), the running equation of time mechanism also including a differential gear device (64), a first input of which is formed by a cannon-pinion wheel (72), which is driven by the timepiece movement and which makes one revolution per hour, and a second input of which is formed by the equation of time cam (54), the differential gear device (64) being arranged concentrically with respect to the true solar minute hand (50), the differential gear device (64) including a planetary gear reduction wheel set (76), via which a cannon-pinion (74), on which the cannon-pinion wheel (72) is fixed, drives the civil hour pipe (70) on which is pressed the civil hour hand (46), and a planetary gear multiplier wheel set (90) via which the civil hour pipe (70) drives the true solar minute pipe (102) on which is pressed the true solar minute hand (50).
2. Running equation of time mechanism according to claim 1, characterized in that the planetary gear reduction wheel set (76) can reduce the speed of rotation from one complete revolution per hour to one complete revolution in twelve hours, and in that the planetary gear multiplier wheel set (90) can increase the speed of rotation from one complete revolution in twelve hours to one complete revolution per hour.
3. Running equation of time mechanism according to any of claims 1 or 2, characterized in that the planetary gear reduction wheel set (76) and the planetary gear multiplier wheel set (90) rotate on themselves describing a circular trajectory centred on the true solar minute pipe (102).
4. Running equation of time mechanism according to claim 3, characterized in that the planetary gear reduction wheel set (76) and the planetary gear multiplier wheel set (90) are equidistant from the true solar minute pipe (102).
5. Running equation of time mechanism according to any of claims 3 or 4, characterized in that the planetary gear reduction wheel set (76) and the planetary gear multiplier wheel set (90) are mounted to rotate freely on a differential frame (84) which is integral with the civil minute pipe (70).
6. Running equation of time mechanism according to claim 5, characterized in that the planetary gear reduction wheel set (76) is mounted to pivot about a first pin (82), and the planetary gear multiplier wheel set (90) is mounted to pivot about a second pin (96), the first and second pins (82, 96) being fixed in the differential frame (84).
7. Running equation of time mechanism according to claim 6, characterized in that the planetary gear reduction wheel set (76) includes a first planetary wheel (78) integral with a first planetary pinion (80).
8. Running equation of time mechanism according to claim 7, characterized in that cannon-pinion (74) meshes with the first planetary wheel (78), and in that the first planetary pinion (80) rolls over a first inner toothing (86) of an immobile differential crown wheel (88), which has the effect of rotating the differential frame (84).
9. Running equation of time mechanism according to any of claims 6 to 8, characterized in that the planetary gear multiplier wheel set (90) includes a second planetary wheel (92) integral with a second planetary pinion (94).
10. Running equation of time mechanism according to claim 9, characterized in that the second planetary wheel (92) meshes with the true solar minute pipe (102), and in that the second planetary pinion (94) rolls over a second inner toothing (98) of a mobile differential crown wheel (100), which is kinematically connected to the equation of time cam (54).
11. Running equation of time mechanism according to claim 10, characterized in that the pivoting of the mobile differential crown wheel (100) is controlled by an equation of time lever (68), provided with a feeler beak (106) via which the equation of time lever (68) follows the profile of the equation of time cam (54).
12. Running equation of time mechanism according to claim 11, characterized in that the equation of time lever (68) is held resiliently abutting against the profile of the equation of time cam (54) by a spring (108).
13. Running equation of time mechanism according to claim 12, characterized in that the equation of time lever (68) is provided with a first tooth (110) meshed with a second corresponding tooth (112) provided on the mobile differential crown wheel (100) to control the movement of the latter.
14. Running equation of time mechanism according to any of claim 5 to 13, characterized in that the differential frame (84) includes an upper frame secured to a lower frame (116) by mean of at least one screw (114).

Images