EP2713225B1 - Timepiece provided with a day/night time display and day/night time display device - Google Patents

Description

The present invention relates to a digital day / night time display device comprising a window in a dial showing at least one digit corresponding to an indication of one hour; a disk of hours comprising, distributed uniformly along its periphery the digits of the hours 1 - 12, and shaped so that the light can pass either through the figures or through a part of the disk hours around these figures ; a day / night disk located under the hours disk having two different color or shadow zones; and a drive mechanism for rotating the hour disk and the day / night disk. The invention also relates to a timepiece provided with such a time display device.

The present invention aims to achieve such a day / night time display that allows a good readability of the hour by large numbers and a dynamic indication of time that passes by a constant dragging movement of the hours disk and a differentiation of the hours of the day from those of the night.

The invention also aims to achieve a digital time display to vary the color of the figures located in the window of the dial or the bottom of the counter indicating the time during the transition day / night to indicate even more markedly l flow of time with movement of this transition day / night or night / day. We therefore try to represent dynamically the arrival of dawn and dusk to mark the transition night / day or vice versa.

Document CH-153246 discloses a jumping hour timepiece comprising a disc of the hours in which the hour digits can be cut. This timepiece can also include a disc day / night located under the aperture of the dial showing the hour, this disk with two different color areas. This day / night disc is indexed from half a turn to six o'clock in the evening and six o'clock in the morning to change the appearance of the numeral placed in the aperture of the dial indicating whether it is an hour of the night or an hour of the day.

Such a display or both disks, hour and day / night, are actuated step by step almost instantaneously does not represent the march of time or the day / night transition in a progressive and continuous manner.

The present invention relates to a digital day / night digital display device overcoming the disadvantages of the prior art cited above and to achieve the desired goal; day / night digital time display device comprising a window in a dial showing at least one digit corresponding to an indication of one hour; a disk of hours comprising, evenly distributed along its periphery, the numbers of the hours 1 - 12 shaped so that the light can pass either through the numbers or through a portion of the hours disk around these figures; a day / night disk located under the hours disk having two different color or shadow zones; and a drive mechanism in rotation of the hour disk and the day / night disk, this display device is distinguished by the fact that the two zones of the day / night disk extend under the disk of the hours comprising the numerals 1 -12; and in that the drive mechanism in rotation of the hours disk and the day / night disc comprise means arranged to drive the hours disc continuously at the rate of two turns in 24 hours and continuous drive means but intermittently, ie a trailing rotation which is periodically interrupted or stopped, of the disc day / night at the rate of one turn in 24 hours.

The invention also relates to a timepiece comprising a day / night digital time display device as described above.

• La figure 1 illustre une montre bracelet munie du dispositif d'affichage indiquant midi et dix minutes.
• La figure 2 illustre la montre de la figure 1 affichant minuit et dix minutes.
• La figure 3 illustre partiellement en perspective le mécanisme du dispositif d'affichage.
• La figure 4 est une coupe illustrant le dispositif d'affichage.
• La figure 5 est un détail du mécanisme d'entraînement du dispositif d'affichage.
• La figure 6 est un tableau illustrant différentes positions des éléments principaux du mécanisme d'affichage pour des heures différentes.
• Les figures 1 et 2 illustrent une montre bracelet munie du dispositif d'affichage horaire digital jour/nuit selon l'invention.

The accompanying drawing illustrates schematically and by way of example a timepiece provided with the digital day / night time display device and an embodiment of said display device.

• The figure 1 illustrates a wristwatch with the display device indicating noon and ten minutes.
• The figure 2 illustrates the watch of the figure 1 displaying midnight and ten minutes.
• The figure 3 partially illustrates in perspective the mechanism of the display device.
• The figure 4 is a section illustrating the display device.
• The figure 5 is a detail of the drive mechanism of the display device.
• The figure 6 is a table illustrating different positions of the main elements of the display mechanism for different times.
• The Figures 1 and 2 illustrate a wristwatch provided with the digital day / night digital display device according to the invention.

The wristwatch has a casing 1 provided with a mirror 2 revealing a dial 3 provided with a minute graduation 4 cooperating with a minute hand 5 and a window 6 revealing a portion of a time disc 7. This hour disc has uniformly distributed along its periphery the numbers 1 to 12 indicating the hours of the day and night, this time disc performing two turns per twenty four hours. The numbers representing the hours cooperate with a fixed reference 8 of the dial to indicate the time. These figures 1 to 12 are, in this embodiment, either cut from the time disk or written on a transparent crown of the hours disk in such a way that these numbers 1 to 12 appear on a colored background or themselves colored coloring that includes an area of a disc day / night 9 located below the time disc.

The day / night disc 9 is coaxial with the time disc 7 and has on a visible crown through the window 6 of the dial 3 two different color zones usually white and gray or black.

The window 6 of the dial 3 may show several digits of the time disk, for example three digits in the illustrated embodiment.

The time disk 7 is driven continuously by the movement of the watch at the rate of two revolutions per twenty-four hours.

The day / night disc 9 is itself driven in intermittent rotation at the rate of one turn per twenty-four hours.

Thus the hours of the day, during which the clear area of the day / night disc is visible through the window 6, appear in light or on a bright background, while the hours of the night, during which the dark area of the disc day / night is visible through the window 6, appear in dark or on a dark background. In variants, the day / night colors can be reversed and, more generally, any colors or shadows could be used to differentiate between day and night.

In an exemplary way, the figure 1 illustrates the watch displaying twelve and ten minutes, the number twelve appearing in clear, while the figure 2 The watch shows midnight and ten minutes, the number twelve appearing dark.

In this embodiment the digits 1-12 are cut from the time disk, this time disk rotates clockwise and the digits 1-12 increase counterclockwise.

As will be seen below, the driving mechanism of the hour disk and the day / night disk is particular in that the hour disk is driven continuously, at a constant speed, by the movement of the watch at the rate of two turns per twenty-four hours, while the day / night disc is intermittently driven. Indeed, this disk day / night is either dragging or continuous with the hours disk, or it is stopped. Preferably, on a twenty-four hour cycle the day / night disc rotates for twelve hours and is kept at rest for the remaining twelve hours. More particularly, in the present embodiment, the day / night disc is driven at an average speed of one revolution per twelve hours from three hours to nine hours and fifteen to twenty-one hours. We thus obtain a dynamic display of dusk and dawn, the change of colors in the window being progressive from five to nine o'clock and from seventeen to twenty-one.

In this first embodiment, the window 6 of the dial shows three digits of the successive hours of the hours 7 disc. These figures are cut out in the disk of the hours 7 and thus leave through these openings the disc day / night 9 underlying.

In this embodiment ( Fig. 1 and FIG. 2 ) the hour disc 7 and the day / night disc 9 turn clockwise. The numbers cut in the time disk 7 follow in decreasing order in the clockwise direction.

The Figures 3 to 6 of the appended drawing illustrate an embodiment of the drive mechanism of the hours 7 disc and the day / night disc 9 for a day / night time display in which the time disc 7 and the day / night disc rotate in the anti direction. -Schedule; the numbers carried by the disc of the hours 7 following in increasing in the clockwise direction.

The hours disk 7 comprises a peripheral ring 7.1 whose width is greater than that of the window 6 of the dial and located under this window 6. This peripheral ring 7.1 of the hour disk 7 is pierced with openings 7.2 representing the numbers 1- 12 distributed evenly over 360 °. These openings 7.2 representing the numbers of 1 to 12 clockwise increase have a size such that three successive figures can appear simultaneously in the window 6 of the dial 3 of the timepiece equipped with this display day / night.

As can be seen, the minute hand 5 cooperating with the minute 4 scale of the timepiece is carried by a roadway 10 carrying at its other end a floorboard 11.

The hour disk 7 is carried by a gun of hours 12, pivoted on the roadway 10, and whose lower end carries the hour wheel 13 of the movement of the timepiece equipped with the day / night time display. A Timer wheel, not shown, kinematically connects the hour wheel 13 to the board 11.

In this example, a second time zone wheel 14 is carried by a second time zone gun 15 rotated on the hour gun 12.

The day / night disc 9 is carried by a day / night gun 16, pivoted on the gun of second time zone 15, and integral with a day / night wheel 17. The ring of the day / night disc 9 visible through the wicket 6 of the dial has a first clear zone 9.1 extending over half of said crown and a second dark zone 9.2 extending over the remainder of this ring.

A moving wheel 18 has a first gear 18.1 engaged with the hour wheel 13, and a second day / night gear 18.2 engaged with the day / night wheel 17.

The hour wheel 13 is driven by the clockwork movement of the watch at the rate of two turns in twenty-four hours in the counter-clockwise direction, but it can be rotated in the other direction during a setting. on time. The first reference 18.1 of the deflection wheel 18 has the same number of teeth as the hour wheel 13 with which it is engaged and thus also performs two turns in twenty-four hours.

The second day / night return 18.2 comprises a toothed sector 19 extending substantially over a quarter of its periphery, ie from 70 ° to 110 ° approximately separated from a solid sector 20 extending substantially over 180 °. Two notches 21, 22 separate the toothed sector 19 from the solid sector 20. In this example, the outer radius of the solid sector 20 corresponds substantially to the radius of the bottom teeth of the teeth of the toothed sector 19, but these rays may be different.

This second day / night rejection 18.2 cooperates with the day / night wheel 17 which comprises two toothed sectors 23, intended to mesh with the toothed sector 19 of the second day / night gear 18.2, extending over substantially a quarter of the circumference of the wheel. wheel day / night 17 each and diametrically opposed to each other. Between these two toothed sectors 23 of the wheel day / night 17 are arranged two lugs 24 having arcuate end faces 25 in an arc of a diameter corresponding to the diameter of the solid sector 20 of the second day / night return 18.2. These lugs 24 have convex curved flanks connecting the lateral ends of the end surfaces 25 to the adjacent toothed sectors 23.

This gearing system makes it possible to drive the day / night wheel 17, and therefore the day / night disc 9 that it carries, from the hour wheel 13 in a continuous but intermittent manner (that is to say a trailing rotation which is periodically interrupted or stopped), at a rate of one revolution per twenty-four hours, which is two times less than the hours disk 7. When the day / night wheel is rotated, it makes a half turn in six o'clock, just like the hours drive.

• en a, le chiffre 12 du disque des heures 7 apparaît en clair à travers le guichet 6 du cadran 3 en regard de l'index 8. L'affichage indique midi. Le disque jour/nuit 9 est orienté de manière à ce que sa zone claire 9.1 forme la moitié supérieure du disque jour/nuit 9. La roue jour/nuit 17 est orientée de telle façon à ce que ses oreilles 24 soient alignées sur une droite reliant l'axe de rotation de la roue jour/nuit 17 à l'axe de rotation du second renvoi jour/nuit 18.2. Le second renvoi jour/nuit 18.2 est positionné de manière à ce que la portion centrale de son secteur plein 20 soit centrée sur une face latérale 25 d'une oreille 24 de la roue jour/nuit 17, le secteur denté 19 de ce second renvoi jour/nuit 18.2 étant dirigé à l'opposé de la roue jour/nuit 17,
• en b, le chiffre 3 s'affiche en clair en regard de l'index 8, l'affichage indique trois heures et les chiffres 2,3,4 apparaissent en clair dans le guichet 6 du cadran. Le disque des heures 7 a été entraîné d'un quart de tour dans le sens anti-horaire par la roue des heures 13 de façon continue et à vitesse constante. Le second renvoi jour/nuit 18.2 a effectué un quart de tour dans le sens horaire, son secteur plein 20 a glissé sur la surface terminale 25 de l'oreille 24 de la roue jour/nuit et cette roue jour/nuit 17 est donc restée immobile de même que le disque jour/nuit 9. Un des flancs du secteur denté 19 commence à coopérer avec un flanc de l'oreille 24 afin que le second renvoi jour/nuit 18.2 entraîne le disque jour/nuit 9 en rotation

• en c, le disque des heures 7 a continué sa rotation et l'affichage indique quatre heures et demie dans le guichet 6 du cadran. Les chiffres apparaissent toujours en clair indiquant que c'est le jour soit seize heures trente. Le disque jour/nuit 9 est maintenant entraîné en rotation dans le sens horaire par la denture du secteur denté 19 du second renvoi jour/nuit 18.2 coopérant avec l'un des secteurs dentés 23 de la roue jour/nuit 17,
• en d, le disque des heures 7 a continué sa rotation et le chiffre cinq est en face de l'index 8. Le disque jour/nuit 9 a également continué sa rotation le secteur denté 19 du second renvoi jour/nuit engrenant avec le secteur denté 23 de la roue jour/nuit 17. Les chiffres 4, 5 et 6 sont affichés dans le guichet 6 du cadran 3 et on remarque que le chiffre six est à moitié clair et à moitié sombre du fait de la position relative du disque jour/nuit 9 par rapport au disque des heures 7. C'est le début du crépuscule qui est indiqué non seulement par l'affichage de l'heure mais également par la présence d'un chiffre partiellement foncé, le six, les autres chiffres 4,5 visibles dans le guichet 6 étant toujours clairs,
• en e, le disque des heures 7 a continué de tourner et le chiffre 6, moitié clair moitié sombre, est en face de l'index 8. L'affichage indique dix-huit heures. Le chiffre cinq est clair, le chiffre sept est sombre de sorte que l'indication dynamique du crépuscule apparaît. Le disque jour/nuit 9 continue à être entraîné en rotation à la même vitesse que le disque des heures 7 par la roue des heures 13, le mobile de renvoi 18 et la roue jour/nuit 17,

• en f, le disque des heures 7 a continué à être entraîné et le chiffre sept est en face de l'index 8. L'affichage indique donc dix-neuf heures. La moitié du chiffre six apparaît en sombre et les chiffres sept et huit apparaissent également en sombre dans le guichet 6. Le disque jour/nuit 9 a continué à être entraîné en rotation synchrone avec le disque des heures 7 par le mobile de renvoi 18 et la roue jour/nuit 17. La moitié du chiffre six et les deux chiffres sept et huit apparaissent en sombre indiquant dynamiquement la progression du crépuscule dans le guichet 6,
• en g, le disque horaire a continué à tourner et l'affichage indique dix-neuf heures trente, l'index 8 étant situé entre les chiffres sept et huit. Tous les chiffres ou portions de chiffres apparaissant dans le guichet 6 du cadran apparaissent en sombre, le disque jour/nuit 9 ayant également été entraîné en rotation par le mobile de renvoi 18 et la roue jour/nuit 17. La totalité des chiffres visibles dans le guichet 6 sont sombre ce qui indique que l'heure affichée est une heure de la nuit. Dans cette position le secteur denté 19 du second renvoi jour/nuit 18.2 est prêt à quitter le secteur denté 23 de la roue jour/nuit 17, mais un flanc du secteur plein 20 commence à coopérer avec un flanc de l'oreille 24 de la roue jour/nuit pour continuer à entraîner celle-ci en rotation et donc le disque jour/nuit 9 en même temps que le disque des heures 7,
• en h, le disque des heures 7 a continué à être entraîné et le chiffre neuf se présente sous l'index 8. Le disque jour/nuit 9 a également continué sa rotation entraîné par le mobile de renvoi 18 coopérant avec la roue jour/nuit 17. Ce disque jour/nuit a maintenant effectué un demi tour et sa zone foncée se trouve centrée sur le guichet 6. Les chiffres 8, 9,10 apparaissant dans le guichet 6 sont donc d'apparence foncée. L'affichage indique vingt et une heures, le chiffre 9 étant en face de l'index 8, et indique que c'est la nuit par sa couleur. La roue jour/nuit 17 est maintenant bloquée par la coopération de la périphérie du secteur plein 20 du second renvoi jour/nuit avec la face latérale 25 d'une oreille 24 de la roue jour/nuit,
• en i, le disque des heures a continué sa rotation et le chiffre 12 est en face de l'index 8. Le disque jour/nuit 9 est resté immobile pendant cette dernière rotation du disque des heures 7 le secteur plein 20 du second renvoi jour/nuit 18.2 glissant le long de la face latérale 25 de l'oreille 24 de la roue jour/nuit 17. L'affichage indique minuit les chiffres 11, 12, 1 apparaissant dans le guichet 6 étant foncés.

If we refer to the figure 6 representing the rotation cycle of the hours 7 disc and the day / night disc 9 (the minute hand 5 being suppressed so as not to overload the drawing) we see:

• in a, the number 12 of the hours disk 7 appears in clear through the window 6 of the dial 3 next to the index 8. The display indicates noon. The day / night disc 9 is oriented so that its clear area 9.1 forms the upper half of the day / night disc 9. The day / night wheel 17 is oriented so that its ears 24 are aligned on a straight line connecting the axis of rotation of the day / night wheel 17 to the axis of rotation of the second day / night return 18.2. The second day / night return 18.2 is positioned so that the central portion of its solid sector 20 is centered on a lateral face 25 of an ear 24 of the day / night wheel 17, the toothed sector 19 of this second return day / night 18.2 being directed opposite the day / night wheel 17,
• at b, the number 3 is displayed in light next to the index 8, the display indicates three hours and the numbers 2,3,4 appear in clear in the window 6 of the dial. The hour 7 record was driven a quarter turn in the counter-clockwise by the hour wheel 13 continuously and at a constant speed. The second day / night rejection 18.2 has made a quarter turn in the clockwise direction, its solid sector 20 has slipped on the terminal surface 25 of the ear 24 of the day / night wheel and this day / night wheel 17 has therefore remained stationary as well as the disc day / night 9. One of the flanks of the toothed sector 19 begins to cooperate with a sidewall of the ear 24 so that the second forward day / night 18.2 causes the disk day / night 9 in rotation

• in C, the hours disk 7 has continued its rotation and the display indicates four and a half hours in the window 6 of the dial. The numbers always appear in clear indicating that it is the day is half past six. The day / night disc 9 is now rotated in the clockwise direction by the toothing of the toothed sector 19 of the second day / night rejector 18.2 cooperating with one of the toothed sectors 23 of the day / night wheel 17,
• in d, the hours disk 7 has continued its rotation and the number five is in front of the index 8. The day / night disc 9 has also continued its rotation the toothed sector 19 of the second day / night rejoining meshing with the sector toothed 23 of the wheel day / night 17. The numbers 4, 5 and 6 are displayed in the window 6 of the dial 3 and we note that the number six is half light and half dark because of the relative position of the disc day / night 9 in relation to the hours disk 7. It is the beginning of the twilight which is indicated not only by the display of the time but also by the presence of a partially dark digit, the six, the other digits 4 , 5 visible in the window 6 being always clear,
• in fact, the hour disk 7 has continued to turn and the digit 6, half light half dark, is in front of the index 8. The display indicates eighteen hours. The number five is clear, the number seven is dark so that the dynamic indication of twilight appears. The day / night disc 9 continues to be rotated at the same speed as the hours disc 7 by the hour wheel 13, the deflection wheel 18 and the day / night wheel 17,

• in f, the hours disk 7 has continued to be driven and the number seven is in front of the index 8. The display thus indicates nineteen hours. Half of the number six appears in dark and the numbers seven and eight also appear dark in the window 6. The day / night disc 9 has continued to be rotated synchronously with the hours disk 7 by the mobile 18 and the day / night wheel 17. Half of the number six and the two digits seven and eight appear in dark, dynamically indicating the progress of the twilight in the window 6,
• in g, the time disk continued to rotate and the display indicates nineteen thirty, the index 8 being located between the numbers seven and eight. All the digits or portions of digits appearing in the window 6 of the dial appear in dark, the day / night disc 9 having also been rotated by the moving wheel 18 and the day / night wheel 17. The totality of the figures visible in FIG. Gate 6 is dark which indicates that the time displayed is an hour of the night. In this position, the toothed sector 19 of the second day / night shift 18.2 is ready to leave the toothed sector 23 of the day / night wheel 17, but a flank of the solid sector 20 begins to cooperate with a sidewall 24 of the wheel. day / night wheel to continue to drive it in rotation and thus the disc day / night 9 at the same time as the disc hours 7,
• in h, the hours drive 7 has continued to be driven and the number nine is under the index 8. The disc day / night 9 has also continued its rotation driven by the moving wheel 18 cooperating with the wheel day / night 17. This disc day / night has now performed a half turn and its dark area is centered on the window 6. The numbers 8, 9,10 appearing in the Box 6 are therefore dark in appearance. The display indicates twenty-one hours, the number 9 is in front of the index 8, and indicates that it is night by its color. The day / night wheel 17 is now blocked by the cooperation of the periphery of the full sector 20 of the second day / night rejection with the lateral face 25 of an ear 24 of the day / night wheel.
• i, the hours disk has continued its rotation and the number 12 is in front of the index 8. The day / night disc 9 has remained motionless during this last rotation of the hour disc 7 the full sector 20 of the second day reminder / night 18.2 sliding along the side face 25 of the ear 24 of the wheel day / night 17. The display indicates midnight figures 11, 12, 1 appearing in the window 6 being dark.

During this passage day / night, from noon to midnight, the disc of the hours 7 made a complete turn but the disc day / night did, him, carried out only half a turn of intermittently, driven by the second day / night return of half a turn between fifteen o'clock and twenty-one hours and remaining motionless from twelve o'clock to fifteen o'clock and from twenty-one o'clock to midnight. During the period between fifteen o'clock to four thirty o'clock, the speed of the day / night disc 9 is not constant but changes gradually (but not linearly) in order to reach a speed of one revolution per twelve hours at the end of this period. During the period between 16:30 to 19:30, the speed of the day / night disc 9 is constant and equal to one revolution per twelve hours. During the period between nineteen thirty-nine hours, the speed of the day / night disc 9 is again not constant and changes gradually (but not linearly) so that the disc stop at the end of this period.

The passage from night to day is carried out similarly through steps a to i except that the day / night disc during its half turn progressively places the light area below the window 6 of the dial 3 to make a dynamic representation from dawn to dawn between four thirty and seven thirty.

This day / night time display is particularly interesting in that the hours disk 7 has only twelve digits 1 to 12, which allows to have a large dimension for these figures and therefore good readability. In addition the color of the bottom of the wicket 6 or the numbers 1 to 12 indicates not only whether it is the day or the night but also gives a dynamic indication of the progress of the twilight, respectively the sunrise.

This result is obtained by the fact that the hours disk 7 bearing the numbers from 1 to 12 performs two complete turns in twenty-four hours and that the day / night disc performs a single complete revolution in twenty-four hours and that its training is during certain time intervals stopped. Thus, depending on the time of day, the day / night disc 9 can either be stationary or be driven with the hours disc 7. This intermittent drive of the disc day / night 9 could in different embodiments of the display be realized differently. with other means than the moving wheel and the wheel day / night described for example using a mechanism comprising a Maltese cross or other mechanism.

With the present day / night time display, the representation of the effect day / night is not done instantaneously as is usually done but is done gradually so that during the transition day / night or vice versa a part visible number (s) is darker than the rest.

In the embodiment described, the day / night disc rotates with the disc hours from 3am to 9am and from 15h to 21h, the rest of the time it is immobile.

In this embodiment, the day / night disc rotates at the same speed as the hour disc during the period from 4.30 pm to 1.30 pm and during the period from 4.30 am to 7.30 pm either when a border between the zones 9.1 and 9.2 is visible in the window 6. In variants it is possible to modify the speed of rotation of the day / night disk so that it is different from the speed of rotation of the disk of the hours when a border between the zones 9.1 and 9.2 is visible in the window 6. In this way the visual effect of the transformation day / night or vice versa can be changed, for example so that the color under number 6 gradually changes from light to dark or vice versa as it goes from one side of the counter 6 to the other.

The numbers 1-12 can be either cut into the hours disk as in the embodiments described but they could be formed of a transparent or translucent material. In other variants it is the disk of the hours which can be transparent or translucent and in this case it is no longer the figures that appear in light / dark during the transition day / night but it is the bottom of the wicket 6 which changes color or hue gradually, the day / night disc being visible between the numbers 1-12 through the transparent hour disc. Similarly, the hour disk may have a skeleton shape, so that it has portions cut around the numbers.

In the example described, the day / night disc is rotated while the hour disc displays from 3 to 9 o'clock and from 3 to 9 pm. In variants, the day / night disc could be driven for two equal or different periods of length, for example four to eight hours each during twenty four hours. These periods can also be centered respectively on a time other than 6h or 18h.

The hours display of the present invention could be used for home time with a traditional hour hand for local time or vice versa.

The hour disc and the day / night disc could also turn clockwise in variants. For example, this direction of rotation can be particularly advantageous in the case where the display of the hours and the fixed mark 8 are at the 6h position of the dial.

Preferably, the light and dark areas of the day / night disc each extend over half of its periphery, ie 180 °.

Claims (11)

1. Digital day/night display device, particularly for a time piece comprising an hours disc (7) comprising, distributed along its periphery, ciphers from 1 to 12 representing the hours, and realized such that light can pass either through the ciphers or through a portion of the hours disc surrounding the ciphers; a rotative day/night disc (9), located under the hours disc (7) comprising a first zone (9.1) and a second zone (9.2) of different colors or shades; and a mechanism driving in rotation the hours disc (7) and the day/night disc (9); characterized by the fact that the first zone (9.1) and the second zone (9.2) of the day/night disc (9) extend under the ciphers 1 - 12 of the hours disc (7), and by the fact that the mechanism driving in rotation the hours disc (7) and the day/night disc (9) comprises means adapted for driving the hours disc in a continuous way and at constant speed at the rate of two revolutions in twenty-four hours and continuous driving means but intermittently, that is to say a dragging rotation which is periodically interrupted, for the day/night disc (9) at a rate of one revolution in twenty-four hours.
2. Display device according to claim 1, characterized by the fact that the device comprises an aperture (6) in a dial (3) through which at least one cipher corresponding to one hour indication can be seen, the hour disc (7) being pivoted under the dial (3) so that during its rotation the ciphers which it carries appear through the aperture (6).
3. Display device according to claim 1 or 2, characterized by the fact that the day/night disc (9) is adapted to be driven in rotation through its driving means during two periods of 4 to 8 hours of duration during twenty-four hours and that the day/night disc is stand still the rest of the time.
4. Display device according to claim 3, characterized by the fact that the day/night disc (9) is adapted to be driven in rotation during the intervals of time for which the hours disc displays 3h to 9 h and 15h to 21 h.
5. Display device according to one of claims 2 to 4, characterized by the fact that the aperture (6) has a dimension permitting to see three consecutive ciphers of the hours disc (7).
6. Display device according to one of claims 1 to 5, characterized by the fact that the first and second zones of the day/night disc are each of the same dimension and extend on one angular extension of 180°.
7. Display device according to one of the preceding claims, characterized by the fact that the driving mechanism of the hours disc (7) and of the day/night disc (9) comprises a hours wheel (13) fast with the hours disc (7), a day/night wheel (17) fast with the day/night disc (9) and an intermediate mobile (18) connecting cinematically the hours wheel (13) to the day/night wheel (17).
8. Display device according to claim 7, characterized by the fact that the intermediate mobile (18) comprises a first intermediated wheel (18.1) meshing with the hours wheel (13), the toothing of this first intermediate wheel having the same number of teeth as the toothing of the hour wheel.
9. Display device according to claim 8, characterized by the fact that the day/night wheel (13) comprises two opposed toothed sectors (23) and two opposed lobes (24) comprising each a concave lateral face and two convex sides.
10. Display device according to claim 9, characterized by the fact that the intermediated mobile (18) comprises a second intermediate day/night wheel (18.2) comprising a toothed sector (19) and a plain sector (20) cooperating with the day/night wheel (17).
11. Time piece comprising a movement, characterized by the fact that it comprises a digital day/night hour display according to one of the preceding claims; the watch movement being adapted for driving the hours disc (7) of the display in a continuous manner and at a constant speed at the rate of two revolutions in twenty-four hours.

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