Patent Publication Number: US-10775745-B2

Title: Timepiece comprising a day/night display that takes account of seasonal variations

Description:
This application claims priority from European Patent Application No. 16206811.8 filed on Dec. 23, 2016, the entire disclosure of which is hereby incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention concerns a timepiece comprising a timepiece movement, a calendar mechanism and means for indicating the sunrise and sunset that take account of seasonal variations, the timepiece movement comprising a minute wheel set, a motion-work, a member for indicating the hours, and an hour wheel set integral in rotation with the hour indicator member and arranged to be driven by the minute wheel set via the motion-work at a speed of one revolution in 12 hours, or at a speed of one revolution in 24 hours, the calendar mechanism being arranged to be driven via the hour wheel set and comprising means for displaying the date and means for displaying the month, the sunrise and sunset indicating means comprising a sphere that replicates the terrestrial globe, a support, and a ring mounted on the support concentrically to the sphere and arranged to indicate the position of the earth&#39;s terminator, the ring and the sphere being arranged to rotate with respect to each other, at a rate of one revolution in 24 hours, about a first axis corresponding to the polar axis of the terrestrial globe, and the ring being mounted on the support in order also to be able to pivot relative to the sphere about a second axis intersecting the first axis perpendicularly at the centre of the sphere, the sunrise and sunset indicating means further comprising an annual cam having a profile representative of the tilt of the sun with respect to the equatorial plane, and arranged to be driven in rotation at the rate of one revolution per year, a cam follower arranged to cooperate with the cam, and a first kinematic chain arranged to connect the cam follower to the ring, such that the plane subtended by the ring forms with the first axis an angle equal to the angle of tilt of the sun with respect to the equatorial plane. The present invention concerns, in particular, a timepiece of this type, wherein the sunrise and sunset indicating means that take account of seasonal variations also indicate which part of the earth&#39;s surface is in daylight (day) and which part of the earth&#39;s surface is in darkness (night time). 
     PRIOR ART 
     The duration of the day is the time comprised, each day, from the moment when the upper limb of the sun appears above the horizon in the east, at sunrise, until it disappears below the horizon in the west, at sunset. Whatever the time, there is always one half of the earth&#39;s surface that is illuminated by the sun, and another half which is in darkness. The earth&#39;s terminator is the line of demarcation between the portion of the earth which is illuminated and that which is in darkness. Geometrically speaking, the earth&#39;s terminator is a large circle which encircles the earth. This large circle extends in a plane perpendicular to the plane of the earth&#39;s orbit around the sun (called the ecliptic plane). It is also noted that the centre of the earth is on the line of intersection between these two planes. 
     Generally, the length of day varies throughout the year and depends on latitude. This variation is caused by the tilt of the axis of rotation of the earth on itself with respect to the ecliptic plane. This tilt by definition corresponds to the latitude of the tropics which is ±23° 27′. As is well known, the length of day is shortest at the December Solstice in the Northern Hemisphere, and at the June Solstice in the Southern Hemisphere. At the equinoxes, the length of day and night are equal everywhere on earth. 
     There are already known timepieces arranged to indicate the current position of the boundary between day and night and which meet the definition given in the above preamble. Descriptions are found, in particular, in European Patent documents EP2911013, EP2977832 and EP3007012 in the name of the Applicant. However, the use and the design of these timepieces present a certain number of difficulties. 
     In particular, these timepieces comprise an annual cam which has a profile representative of the tilt of the sun with respect to the equatorial plane, and which is arranged to be driven in rotation by the movement at the rate of one revolution per year. One drawback of these timepieces is that it may be problematic to return the annual cam to the correct position after an indeterminate period of stoppage of the timepiece. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to overcome the aforementioned drawbacks of the prior art. The invention achieves this object by providing a timepiece movement. 
     According to the invention, the timepiece comprises a calendar mechanism arranged to be driven via the hour wheel set and which comprises means for displaying the date and means for displaying the month. The timepiece also comprises a third kinematic chain which connects the hour wheel set to the annual cam via the month display means. A first advantage of this feature is that, after an indeterminate period of stoppage of the timepiece, the annual cam can automatically be returned to the correct position without any possible error, simply by resetting the date of the calendar mechanism. 
     According to the invention, the calendar mechanism is driven by the hour wheel set. In these conditions, when the wearer of the timepiece changes the hour indication, for example to correct it, the hour correction automatically results in correction of the calendar mechanism and the annual cam. 
     Moreover, according to the invention, the third kinematic chain has either a transmission ratio of 1:744 (in the case where the hour wheel set is arranged to be driven by the motion work at a speed of one revolution in 12 hours), or a transmission ratio of 1:372 (in the case where the hour wheel set is arranged to be driven by the motion work at a speed of one revolution in 24 hours). 
     It can be confirmed that 372 is the number of days that the year would have if all the months had 31 days (and 744 corresponds to two times 372). A calendar mechanism in which all the months have 31 days is called a simple calendar mechanism. In this type of calendar mechanism, at the end of months of less than 31 days, the hand or date disc must be advanced manually to update the calendar. As regards the change of indication of the name of the month, this can occur automatically every time that the date indication changes from the 31st to the 1st day of the month. Those skilled in the art will tend to consider that if the annual cam is not driven via the date display means, the difference between the real time and the current position of the earth&#39;s terminator on the globe will gradually increase. However, if, for example, the date is advanced at the end of the months of less than 31 days using the set-hands mechanism, there is no risk of this date setting operation desynchronizing the calendar mechanism and annual cam. 
     According to a particular embodiment of the invention, the timepiece movement comprises a manually actuatable summer/winter correction mechanism for changing from summer time to winter time, or vice versa, by pivoting the hour wheel set one step forward or backward independently of the motion work. Those skilled in the art will understand that a first advantage of this feature is that it allows the summer time/winter time correction to be made without affecting the indication of the minutes and the indication of the seconds. 
     According to an advantageous variant of the aforementioned embodiment, the manually actuatable mechanism is also arranged to pivot the hour wheel set without affecting the indication of the position of the earth&#39;s terminator on the sphere. Those skilled in the art will understand that one advantage of this feature is that it prevents the position of the ring changing relative to the terrestrial globe when this does not reflect a real movement of the sun with respect to the earth&#39;s surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the invention will appear upon reading the following description, given purely by way of non-limiting example, with reference to the annexed drawings, in which: 
         FIG. 1  is a block diagram briefly illustrating the kinematic connections between different mechanisms of a timepiece according to a first particular embodiment of the invention; 
         FIG. 2  is a block diagram briefly illustrating the kinematic connections between different mechanisms of a timepiece according to a second particular embodiment of the invention; 
         FIGS. 3A and 3B  are respectively a cross-sectional view and a view of an example mechanism, known as such, which comprises a first and a second hour wheel and a disengageable coupling device arranged to make integral in rotation and index, or alternatively to disengage, the two hour wheels. 
         FIGS. 4 a  and 4 b    are views of structural elements of the timepiece. 
         FIG. 5  is another view of structural elements of the timepiece. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  annexed is a block diagram illustrating the kinematic connections associating different mechanisms of a timepiece according to a first exemplary embodiment of the invention. This extremely basic block diagram represents the means for transmitting the driving force provided by the movement to the various mechanisms with the aid of double-thickness arrows, and the kinematic connections which are arranged to transmit the commands manually inputted by a user with the aid of thinner arrows. 
     In the block diagram of  FIG. 1 , the arrows symbolising kinematic connections connect between them symbols which represent different mechanisms of the timepiece. The mechanisms represented by the symbols comprise a drive mechanism  103  that combines a drive member, a regulating member and an escapement, a minute wheel set (referenced  105 ) which is integral with a minute display member and which is arranged to be driven at the rate of one revolution per hour by the drive mechanism, an hour wheel set  107  integral in rotation with an hour display member, a motion work  106  connecting the minute wheel set to the hour wheel set, such that the latter is driven at the rate of one revolution every 12 hours, and a time zone correction mechanism (referenced  101 ) inserted between motion work  106  and hour wheel set  107 . 
     According to the invention, the illustrated timepiece also comprises sunrise and sunset indicating means that take account of seasonal variations, these means comprising a sphere that replicates the terrestrial globe, a support, and a ring which is mounted on the support concentrically to the sphere and arranged to indicate the position of the earth&#39;s terminator. The ring and the sphere are arranged to be driven in order to rotate with respect to one another, at a rate of one revolution in 24 hours, about a first axis corresponding to the polar axis of the terrestrial globe. Further, the ring is mounted on the support in order also to be able to pivot relative to the sphere about a second axis intersecting the first axis perpendicularly at the centre of the sphere. The sunrise and sunset indicating means further comprise an annual cam having a profile representative of the tilt of the sun with respect to the equatorial plane and which is arranged to be driven in rotation at the rate of one revolution per year, a cam follower arranged to cooperate with the cam, and a first kinematic chain arranged to connect the cam follower to the ring, such that the plane subtended by the ring forms with the first axis an angle equal to the angle of tilt of the sun with respect to the equatorial plane. Referring again to  FIG. 1 , it can be seen that, in the embodiment represented, the timepiece comprises a sunrise and/or sunset indicating mechanism  115  which comprises a sphere  117  representing the terrestrial globe and a half-spherical shell  113 , which is arranged concentrically to sphere  117  so as to darken or conceal the half of the earth&#39;s surface which is in darkness (night). Shell  113  has a substantially circular rim  113   a , which forms the ring of the sunrise and sunset indicating means according to the invention. 
     Referring again to  FIG. 1 , it can be seen that the illustrated timepiece also comprises a calendar mechanism arranged to be driven via the hour wheel set  107 . The calendar mechanism represented comprises means for displaying the date  123  and means for displaying the month  125 . According to the invention, the calendar mechanism is of the ‘simple calendar’ type. As is well known to those skilled in the art, in a simple calendar mechanism, at the end of months of less than 31 days, the date display must be advanced manually to correct the date. As regards the change of indication of the name of the month, this occurs automatically every time that the date indication changes from the 31st to the 1st day of the month. 
     In the illustrated example, the hour wheel set is arranged to drive month display means  125  via a reduction gear train  118 , which does not go through date display means  123 . Reduction gear train  118  is composed as follows: hour wheel set  107  is integral in rotation with a reduction wheel set (not represented) which comprises an 18-tooth pinion. As shown in  FIGS. 4 a  and 4 b   , the pinion of the reduction wheel set meshes with a 36-tooth wheel of a first intermediate wheel set (referenced  119 ) which is therefore arranged to complete one revolution in 24 hours. First intermediate wheel set  119  also comprises two fingers  130  which are arranged, once every 24 hours, to cooperate respectively with one of the teeth of a date star-wheel comprising 31 teeth, and with one of the teeth of a 40-tooth star-wheel, which forms part of a second intermediate wheel set (not represented), in order to advance each of the two star-wheels one step. The second intermediate wheel set also comprises a 10-tooth pinion arranged coaxially with the 40-tooth star-wheel. The 10-tooth pinion is arranged to mesh with a toothing of 93 teeth of an annual wheel set of month display means  125 . 
     Still referring to  FIG. 1 , it is seen that the timepiece represented also comprises a tilt control mechanism (referenced  109 ) which comprises an annual cam  111  and a cam follower (not represented). According to the invention, hour wheel set  107  drives the annual cam via a third kinematic chain  118  which passes through month display means  125 . In the illustrated example, annual cam  111  is borne by the annual wheel set of the month display means. The annual wheel set thus forms part of both tilt control mechanism  109  and month display means  125 . It will thus be understood that, in the illustrated example, the third kinematic chain which, according to the invention, connects hour wheel set  107  and annual cam  111 , is formed by reduction gear train  118  which was described above in relation to date display means  125 . The ratio of reduction gear train  118  is 1:744. However, it is worth bearing in mind that, in the illustrated example, hour wheel set  107  is arranged to make one complete revolution every 12 hours (see  FIG. 4 b   ). Those skilled in the art will understand that, according to the invention, the hour wheel set could alternatively be arranged to rotate at the rate of one revolution every 24 hours (see  FIG. 4 a   ) instead of every 12 hours, and that, in such case, the ratio of the reduction gear train would be 1:372; the train would then be shortened. 
     According to the embodiment of the invention illustrated in  FIG. 1 , the movement of shell  113  relative to sphere  117  is the result of the combination of distinct rotations about two perpendicular axes that intersect at the centre of the sphere. The first of these two rotations is made by Earth, which is arranged to rotate at the rate of one revolution in 24 hours about the first of these two axes, and the other rotation corresponds to the pivoting of the dark half-spherical shell representing the dark  113  (dark half-sphere) about the second axis and manifests as a variation in the angle of tilt of the half-sphere with respect to the first axis. Since the movements of dark half-sphere  113  and of sphere  117  with respect to one another are two functionally independent movements, sunrise and/or sunset indicating mechanism  115  is represented twice in  FIG. 1 . Referring to the Figure, it will be understood that mechanism  115  is represented once to depict the rotation of sphere  117  at the rate of one revolution in 24 hours about the first axis, and a second time to depict the pivoting of dark half-sphere  113  about the second axis. 
     According to the invention, the pivoting motion about the second axis is controlled using annual cam  111 , whose profile is representative of the relative tilt of the sun above or below the equatorial plane of the earth. The cam follower (not represented) is arranged to transmit the variations in the cam profile to half-spherical shell  113  through a first kinematic connection  112 . According to the first embodiment of the invention, dark half-sphere  113  is mounted to pivot on a fixed support and the arrangement of indicator mechanism  115 , like that of first kinematic connection  112 , may conform, for example, to the description given in European Patent document EP 2911013. This document is incorporated by reference in the present description. 
     Referring again to  FIG. 1 , it can be seen that the timepiece whose operation is represented also comprises a certain number of corrector mechanisms which are arranged to be manually actuated by the wearer of the timepiece. First of all, as already mentioned, a time zone correction mechanism (referenced  101 ) is inserted between motion work  106  and hour wheel set  107 . As will now be explained, mechanism  101  can be controlled in two different ways depending upon whether the change of hour relates to an actual change of longitude, following a journey for example, or relates to the change from winter time to summer time, or vice versa. In the illustrated example, when the wearer of the timepiece changes time zone during a trip, he can correct the time indication by means of control stem  131  of the timepiece. In order to do this, he must move stem  131  into position T 2  before rotating the crown to move the hour hand forwards or backwards in a series of one-hour jumps. As was seen above, hour wheel set  107  drives month display mechanism  125  and annual cam  111  via third kinematic chain  118 . Further, hour wheel set  107  also drives date mechanism  123  and Earth  117  in its rotation about the first axis. It will thus be understood that annual cam  111 , calendar mechanism  123 ,  125  and sunrise and/or sunset indicating mechanism  115 , are arranged to advance synchronously, not only when they are driven by drive mechanism  103 , but also when they are manually driven forwards or backwards by means of control stem  131  in position T 2 . 
     In the illustrated example, at the change from winter time to summer time or from summer time to winter time, the wearer of the timepiece can move the time indication exactly one hour forward or back by actuating pusher P 2 . When it is actuated, pusher P 2  acts not only on time zone correction mechanism  101 , but also on a disengagement mechanism  133 , so as to disengage second kinematic chain  120  (see also  FIG. 5 ), which is arranged to drive Earth in rotation at the rate of one revolution in 24 hours. It will be understood that disengaging the second kinematic chain prevents the relative angular position of dark half-sphere  113  with respect to sphere  117  being affected by transitions between summer time and winter time. 
     In addition to the aforementioned time zone correction mechanism  101 , the timepiece of the present example comprises a conventional type of time-setting mechanism. This time-setting mechanism allows the wearer of the timepiece to set the time with the aid of control stem  131  of the timepiece. In order to do this, he must move stem  131  into position T 3  before rotating the crown. As in most current timepieces, the time-setting mechanism is arranged to drive motion work  106 , which in turn drives minute wheel set  105  and hour wheel set  107 . As was the case previously with correction of the time zone, hour wheel set  107  drives month display mechanism  125  and annual cam  111  via third kinematic chain  118 . Further, hour wheel set  107  also drives date mechanism  123  and Earth in its rotation about the first axis. It will thus be understood that annual cam  111 , calendar mechanism  123 ,  125  and sunrise and/or sunset indicating mechanism  115 , are arranged to advance synchronously, also when they are driven manually forwards or backwards by means of control stem  131  in position T 3 . 
     Finally, the calendar mechanism of the timepiece of the present embodiment also comprises a month corrector mechanism. When the wearer of the timepiece wishes to correct the month indication, for example following an indeterminate period of stoppage of the timepiece, he can move the month indication step-by-step forwards or backwards by actuating pusher P 1 . As in the present example, the annual wheel set of month display means  125  also carries annual cam  111 , this latter advances synchronously with the date indication, event when the date indication is changed with the aid of the date corrector. 
       FIG. 2  annexed is a very similar block diagram to that of  FIG. 1 , but illustrating the kinematic connections associating different mechanism of a timepiece according to a second exemplary embodiment of the invention. As will be seen, the second embodiment is very similar to the first and, in particular, the correction mechanisms arranged to be actuated by the wearer of the timepiece are identical to those which were described in relation to the first embodiment.  FIG. 2  represents a drive mechanism  203  that combines a drive member, a regulating member and an escapement, a minute wheel set (referenced  205 ) which is integral with a minute display member and which is arranged to be driven at the rate of one revolution per hour by the drive mechanism, an hour wheel set  207  integral in rotation with an hour display member, a motion work  206  connecting the minute wheel set to the hour wheel set such that the latter is driven at a rate of one revolution every 12 hours, a time zone correction mechanism (referenced  201 ) inserted between motion work  206  and hour wheel set  207 , a tilt control mechanism (referenced  209 ) which comprises an annual cam  211 , and a cam follower (not represented), and finally a sunrise and/or sunset indicating mechanism (referenced  215 ) comprising a sphere  217  that replicates the terrestrial globe and a half-spherical shell  213 , which is arranged concentrically to the sphere. 
     In the illustrated example, hour wheel set  207  drives the annual cam via a third kinematic chain  218 , which could be identical to kinematic chain  118  described above in relation to the first exemplary embodiment. 
     In the second embodiment, as in the first, the relative movement of half-sphere  213  and sphere  217  is the result of the combination of distinct rotations about two perpendicular axes that intersect at the centre of the sphere. However, according to the second embodiment, it is dark half-sphere  213  which simultaneously makes the two rotations, since sphere  217  is not driven. This operating mode is made possible by the fact that the support (not represented), on which dark half-sphere  213  is mounted, is a rotating support. Still referring to  FIG. 2 , it is clear that in the illustrated embodiment, hour wheel set  207  is connected to the rotating support (not represented) by a kinematic chain  220  (hereinafter the “second kinematic chain  220 ”) which is provided with a disengagement mechanism  233  which could be quite similar to disengagement mechanism  133  described above in relation to the change from summer time to winter time. With the exception of disengagement mechanism  233 , the arrangement of indicator mechanism  215  and that of second kinematic connection  220  could, for example, conform to the description in one or other of European Patent documents EP2977832 and EP3007012. These two documents are incorporated by reference in the present description. 
     Referring again to  FIG. 2 , it can be seen that a reference mechanism  216  is inserted between tilt control mechanism  209  and indicator mechanism  215 . It can be seen that mechanism  216  comprises an output connected to indicator mechanism  215 , and two inputs. A kinematic connection  221  (called the ‘fourth kinematic connection’  221 ) connects hour wheel set  207  to the first of the two inputs. Mechanism  216  is thus driven by the hour wheel set through its first input, called the ‘driving input’. It can also be seen that the cam follower (not represented) is connected to the second input by a kinematic connection  212  (called the ‘first kinematic connection’  212 ) arranged to transmit the variations in the cam profile. Mechanism  216  is thus controlled by the profile of cam  211  through its second input, called the ‘control input’. Just like second kinematic connection  220 , the output of mechanism  216  is arranged to drive indicator mechanism  215  at a speed of one revolution in 24 hours. However, mechanism  216  drives the indicator mechanism with a certain offset with respect to second kinematic connection  220 . Mechanism  216  can be realized in many ways without departing from the scope of the present invention. It may, for example, be a differential mechanism, especially a differential mechanism as described in European Patent No EP 2977832. It may also be a disengagement mechanism, especially a disengagement mechanism as described in European Patent No EP3007012. 
     Still referring to  FIG. 2 , it can be seen that the illustrated timepiece also comprises a calendar mechanism formed by the combination of a display mechanism for displaying the date  223  and a display mechanism for displaying the month  225 . This calendar mechanism is of the ‘simple calendar’ type. 
     Referring now to  FIGS. 3A and 3B , the summer/winter correction mechanism, which is generally designated by the reference  101 , will now be described in more detail. It will be recalled that mechanism  101  was already represented in  FIG. 1 , inserted between motion work  106  and hour wheel set  107 . Moreover, mechanism  201  represented in  FIG. 2  could be identical to mechanism  101 . Mechanism  101  comprises a first pipe?  2 , called the inner pipe, intended to be mounted in rotation in a conventional manner, about an axis of rotation X, on a cannon-pinion C driven by drive mechanism  103  (shown in  FIG. 1 ). Inner pipe  2  bears an indicator hand  4  forming the hour hand, which is externally pressed onto a free end of pipe  2  projecting from mechanism  101 . 
     Inner pipe  2  thus forms an hour pipe, and it carries a first externally toothed wheel  6 , called the lower wheel, comprising a plate  7 . It will be specified here that, advantageously, this lower wheel  6  forms an hour wheel, and more specifically a ‘motion-work hour wheel’, and it meshes with a wheel  8  (partially represented) of motion work  106 . In normal operation, this hour wheel  6  receives time information delivered by wheel  8  of the motion work, which information it transmits, as will be seen below, indirectly to inner hour pipe  2  and to indicator hand  4 . Indeed, lower hour wheel  6  is mounted for free rotation on hour pipe  2 . For this purpose, the end of hour pipe  2 , opposite to the free end thereof carrying hand  4 , comprises a collar  10  forming a shoulder freely supporting a star-wheel  12  on which wheel  6  is fixedly held. Star-wheel  12  comprises a plate  13 , an external toothing  14  and a circular flange  16  arranged edgewise adjacent to toothing  14 , behind and coaxially with the latter, underneath plate  13 . 
     Hour wheel  6  is fixedly held on the side of star-wheel  12  against its toothing  14 . Indeed, hour wheel  6  is force fitted externally onto flange  16 , pressed and/or riveted thereon, via the central part of its plate  7  which has a bore opening. Star-wheel  12  and hour wheel  6  are thus directly integral in rotation and, in this example, as a result of their assembly, form a single piece placed on hour pipe  2 . Star-wheel  12  and hour wheel  6  can thus be moved together concomitantly via wheel  8  of the motion work. 
     The summer/winter correction mechanism also comprises two drive rollers  20  which are stepped and which each have a cylindrical base  22  from which a stud  24  extends in a perpendicular manner. The rollers are both engaged at rest, via their base  22 , in toothing  14  of star-wheel  12  and they rest freely and sideways via this base against the side (unreferenced) of plate  7  of hour wheel  6 . This rest position is also represented in a top view in  FIG. 3B . Rollers  20  are also resiliently held in this rest position in toothing  14 , by elastic return means  26 , which are formed here by a closed annular spring, mounted coaxially to star-wheel  12  and acting radially on the outer periphery of bases  22  of rollers  20 . It will be noted here that spring  26  is freely mounted against drive rollers  20 , without any fixed attachment to mechanism  101 . Spring  26  also rests freely against, and more particularly on, plate  7  of hour wheel  6 . Spring  26  is thus self-supported and self-centering. 
     The summer/winter correction mechanism further comprises a second pipe  30 , called the outer pipe, which comprises a guide bore  31  and which is fixed externally via this bore  31  onto first pipe  2 . This second pipe  30  carries a second externally toothed wheel  32  arranged above lower hour wheel  6  and called the ‘upper wheel’, and more specifically the ‘hour-wheel’. It will be specified here that the upper and lower positions of wheels  6  and  32  refer to the drawing of  FIG. 3A , which represents the correction mechanism with the hour hands oriented upwards. Upper wheel  32  comprises a plate  33  and it meshes via its outer toothing with a wheel  34 , driven in turn by a corrector member, which is manually actuatable from outside the timepiece. 
     Upper wheel  34  thus forms a summer/winter correction wheel which, as will become clear, can directly correct the position of hour pipe  2  and of indicator hand  4 , without acting on the motion work, and therefore without disrupting the other time information, such as the minutes and seconds, which are normally kinematically connected to hour pipe  2  via said motion work. Advantageously, outer pipe  30  is force fitted externally onto inner hour pipe  2  and it is thus secured thereto. These two pipes are therefore integral in rotation and they can be moved together. It will be understood that hour pipe  2 , outer pipe  30  and upper wheel  34  together form hour wheel set  107 . Upper correction wheel  34  can thus act on inner hour pipe  2  via outer pipe  30 . 
     It will be specified that hour pipe  2  is also driven in normal operation by motion work  106 , and in particular by wheel  8  of the motion work. This is why there are radial grooves  36  arranged in plate  33  of correction wheel  32 , in which are freely engaged studs  24 , which can translate radially in said grooves. Rollers  20  can thus drive in rotation correction wheel  32 , and the two pipes  2  and  30 , when star-wheel  12  is itself driven by hour wheel  6 . 
     In order to change to another time zone, the user of the timepiece must rotate correction wheel  34 ; rollers  20  are then angularly displaced and jump (while star-wheel  12  and hour wheel  6  remain stationary) in toothing  14  of star-wheel  12 , making spring  26  oval. Rollers  20  then return to the rest position in toothing  14  of star-wheel  12 , but are offset with respect to the position of  FIG. 2 . Hand  4  then indicates another time zone. It will be specified that, although the toothing of star-wheel  12  has 12 teeth in the Figures (to indicate the 12 hours), this toothing could have 24 teeth for application to a 24-hour timepiece. 
     It will also be clear that various alterations and/or improvements evident to those skilled in the art may be made to the embodiment forming the subject of the present description without departing from the scope of the present invention defined by the annexed claims.