Perpetual calendar mechanism

The perpetual calendar mechanism includes a date mobile (16, 28-31), a date lever (3) bearing a small click (14), a correction lever (4) driving a great click (40) and a finger (2) driving the levers (3, 4). The date mobile (16, 28-31) is shifted instantaneously by the small click (14) during the transition from one day to the next within a month and during the transition from the last day of a month of 31 days to the first day of the following month, and partly in a dragging manner by the great click (40) during the transition from the last day of a month of less than 31 days to the first day of the following month.

The present invention concerns a perpetual or annual calendar mechanism for a timepiece such as a wristwatch.

The perpetual or annual calendar mechanisms generally comprise a driving lever bearing a small click cooperating with a 31-tooth date wheel of a date mobile for the transition from one day to the next within a month and for the transition from the last day of a month of 31 days to the first day of the following month, and a great click cooperating with a snail correction cam of the date mobile for the correction of the last days of months of less than 31 days.

In some of these mechanisms, the driving of the date mobile by the small and great clicks during each transition from one day to the next is dragging, that is to say that it's effected in a slow manner, generally over several hours. During this time, the date of the current day progressively gives way to the date of the next day in the date display window provided in the dial of the watch. This solution is not really satisfactory, because it is prejudicial to the display accuracy and to the aesthetic of the watch.

In other mechanisms, the driving of the date mobile by the small and great clicks during each transition from one day to the next is instantaneous. The date display on the dial therefore changes instantaneously at midnight, which is appreciable. However, here, a non negligible risk exists that at the end of the transition from the last day of a month of less than 31 days to the first day of the following month, the date mobile pursues its movement due to its inertia, therefore causing an erroneous display of the date. This risk is particularly present during the transition from the 28th of Feb. to the 1st of Mar. when the date mobile has to complete a four pitch jump in an instantaneous manner.

The present invention aims to remedy the aforementioned drawbacks of the known perpetual or annual calendar mechanisms, or at least to alleviate them, and provides for this purpose a calendar mechanism according to the appended claim1, particular embodiments being defined in the dependent claims.

With reference toFIGS. 1 to 5, the perpetual calendar mechanism according to the invention is mounted on a plate1intended to be located in a watch case between the movement and the dial.

This mechanism comprises in particular a date finger2, a date lever3and a correction lever4. The levers3,4are mounted about a same pivot axis5, but are free to rotate one relatively to the other.

The date finger2is continuously driven counter-clockwise at one revolution per day by a pin6solid with a 24-hour wheel7meshing with a 12-hour intermediate wheel8solid with the hours wheel of the watch. The date finger2cooperates each day, from a given time, with a finger9(cf.FIG. 4) of the date lever3and a finger10(cf.FIG. 5) of the correction lever4, to progressively lift these two levers3,4against the action exerted on the date lever3, respectively on a pivoting shuttle11cooperating with the correction lever4, by respective return springs12,13.

The date lever3comprises, in addition to finger9, a first small click14and a second small click15which, during the transition from one day to the next, cooperate respectively with a 31-tooth date star-wheel16and a seven-tooth days star-wheel17to make them rotate instantaneously by one pitch. The days star-wheel17bears a display hand18associated with a weekdays display area19on the dial of the watch (FIG. 6). The angular position of the date star-wheel16and that of the days star-wheel17are indexed by jumpers20,21, respectively.

The correction lever4comprises at one of its ends a rack22engaged with a corresponding rack23of the pivoting shuttle11, and at another end a feeler consisting of a finger24in which a feeler pin25is secured, the feeler pin25being, in rest position of the correction lever4, in contact with a months cam26or a leap year cam27(FIG. 5).

Each lever3,4extends partly on one side of the pivot axis5and partly on the other side of the pivot axis5. It should be particularly noted, concerning the correction lever4, that the feeler24-25is located on the side opposite to the one of the rack22and the finger10. The shape of each lever3,4is chosen advantageously so that the centre of gravity of the lever3,4be substantially on the pivot axis5. In this way, the mechanism becomes less sensitive to impacts. Moreover, one or several ball bearings can be associated with the pivot axis5of levers3,4to reduce the friction coefficients.

The date star-wheel16is solid with a 31-tooth date wheel28, a units wheel29having 29 teeth plus an empty space29′ taking up the space of two consecutive teeth, a four-tooth tens wheel30and a snail correction cam31. The assembly formed by the date star-wheel16, the date wheel28, the units wheel29, the tens wheel30and the correction cam31will be referred to as “date mobile” in the following of this description.

The units wheel29is engaged with a ten-tooth units pinion32bearing a units disk33on which there is displayed a sequence of digits 0 to 9 of great size representing the units of the date. The tens wheel30cooperates with an eight-tooth tens pinion34bearing a tens disk35on which are displayed two consecutive sequences of digits 0 to 3 of great size representing the tens of the date. The pinions32,34are each subject to the action of a jumper36,37, respectively. The units and tens disks33,35are juxtaposed, and allow the display of the date in two respective large windows38,39provided in the dial of the watch (FIG. 6).

The gear formed by the units wheel29and the units pinion32is shown in detail onFIG. 7. As described, the teeth of the wheel29and of the pinion32have an epicycloidal shape, and each tooth of the wheel29, when aligned along the imaginary line passing through the respective centres of the wheel29and of the pinion32, is centred between teeth of the pinion32, and reciprocally. This toothing arrangement of the units wheel29and of the units pinion32enables both the depth of penetration of these toothings to be increased and the date mobile16,28-31to be locked in its angular position with respect to the units pinion32owing to the fact that at every moment, except when the date mobile16,28-31is in an angular position corresponding to the 31st or to the 1st, a tooth of the units wheel29is located between two teeth of the pinion32. When the date mobile16,28-31is in an angular position corresponding to the 31 st or to the 1 st, the toothing of the units pinion32is facing the empty space29′. In this position, the date mobile16,28-31is blocked in a direction by a tooth of the units pinion32close to a tooth of the units wheel29, and in the other direction by a tooth of the tens pinion34close to a tooth of the tens wheel30.

The shuttle11(FIGS. 2 and 5) is pivotably mounted about the same axis as the tens pinion34and the tens disk35, but is free to rotate with respect to this pinion34and this disk35. A great click40articulated to the shuttle11cooperates with the correction cam31to shift in a dragging manner the date mobile16,28-31by one or several pitches depending on the angular position of the months cam26or of the leap year cam27detected by the feeler24-25of the correction lever4during the transition from the last day of a month of less than 31 days to the first day of the following month.

The date wheel28is engaged with a 31-tooth intermediate date wheel41mounted about the same axis as the units pinion32and the units disk33, but free to rotate with respect to this pinion32and this disk33(FIGS. 1,2,3). The intermediate date wheel41meshes with an intermediate pinion42which itself meshes with a 31-tooth months wheel43. This months wheel43drives a months disk44coaxial with the months wheel43and comprising a finger45on its periphery, through a pin46solid with the wheel43and located in a hole46′ of the months disk44larger than itself (FIGS. 2,3,5).

The finger45of the months disk44cooperates at the end of each month with a 12-tooth months pinion47to drive it by one pitch, so that it makes one revolution per year. This months pinion47, with which the months cam26is solid, bears a month display hand48associated with a month display area49on the dial of the watch (FIGS. 3,6) and is subject to the action of a jumper47′ (visible onFIG. 2).

The months pinion47drives a 48-month wheel50, with 48 teeth, mounted about the same axis as the months wheel43and the months disk44, but free to rotate with respect to the same, to drive it at the rate of one revolution in four years. A first 30-tooth year wheel51is solid with the 48-month wheel50. A second 30-tooth year wheel52mounted about the same axis as the months pinion47, but free to rotate with respect to this pinion47, is driven by the first year wheel51. This second year wheel52, with which the leap year cam27is solid, bears a leap year display hand53associated with a corresponding display area54on the dial of the watch.

The months cam26has a periphery the radius of which is variable and depends upon the number of days of the months of the year, the angular position of this cam26defining the current month. The periphery of the cam26comprises, more precisely, (cf.FIG. 5) great radius portions55, corresponding to months of 31 days, intermediate radius portions56, corresponding to months of 30 days, and a small radius portion57(visible onFIG. 2), corresponding to the month of February of a non leap year (28 days). The leap year cam27has on its periphery a unique bump58(FIG. 5) associated with the month of February of leap years. The bump58of the leap year cam27has, during the month of February of each leap year, an angular position in which the angular sector defined by the bump58includes the one defined by the lower part57of the periphery of the months cam26and, during the month of February of each non leap year, an angular position in which the aforementioned angular sectors are separated.

With additional reference toFIGS. 1 and 2, the 24-hour wheel7bearing the pin6for driving the date finger2meshes with a second 24-hour wheel59mounted about the same axis as the days star-wheel17, but free to rotate with respect to this days star-wheel17. This second 24-hour wheel59bears a day/night display hand60associated with a corresponding day/night display area61on the dial of the watch, concentric with the weekdays display area19(FIG. 6).

The perpetual calendar mechanism according to the invention also comprises a moon phase display device. This device comprises (cf.FIGS. 1,2,9A) a moon pinion62driven by the date finger2at one pitch per day and subject to the action of a jumper63. The moon pinion62bears an intermediate pinion64which meshes with a second intermediate pinion65itself meshing with a window wheel66. A third intermediate pinion67is solid with the second intermediate pinion65, and meshes with a moon wheel68. The meshing ratios between the first and second intermediate pinions64,65, between the second intermediate pinion65and the window wheel66and between the third intermediate pinion67and the moon wheel68are such that the window wheel66is driven step by step at one pitch per day and one revolution per moon revolution (29 days, 12 hours and 45 minutes), and that the moon wheel68is driven step by step at an angular speed half as high than that of the window wheel66. The moon wheel68defines a disk69comprising two pellets70diametrically opposed having the colour blue of the sky, the rest of the disk69having the colour yellow of the moon (FIG. 9B). The window wheel66, located above the moon wheel68, defines a disk71with the colour blue of the sky and comprising a circular window72of same diameter as the pellets70(FIG. 9C). In this device, the full moon appears through the window72when the latter is in the six o'clock position and is between the two pellets70. The new moon appears when the window72and one of the two pellets70are at noon. From this noon position, the user will see the moon increase day after day in the right portion of the wheels66,68until full moon, and then decrease in the left portion of the wheels66,68. This moon phase display device is known in itself. It was described by Mr Philip Barat in his Diploma thesis at the Ecole d'Ingénieurs de Genéve (School of Engineering of Geneva) in June 1983.

The perpetual calendar mechanism according to the invention further comprises correctors73,74,75,76allowing manual correction of the angular position, respectively, of the date mobile16,28-31, of the days star-wheel17, of the moon pinion62and of the months pinion47. These correctors73-76are operated by push-buttons (not represented) projecting from the edge of the watch. Each corrector73-75is a mere pivoting member arranged to push a tooth of the date wheel28, of the days star-wheel17and of the moon pinion62, respectively. The corrector76associated with the months pinion47comprises (cf.FIG. 5) two pivoting parts78,79having different pivot axes. The part78bears a pin80cooperating with a slot81of the part79and further comprises a finger82capable of lifting the correction lever4when the latter is in contact with the months cam26or the leap year cam27and a beak83capable of pushing a tooth of the months pinion47after the finger82has lifted the correction lever4to shift the months pinion47clockwise by one pitch.

The perpetual calendar mechanism according to the invention operates in the following manner.

In rest position, the date lever3is maintained by its return spring12against an abutment84(visible onFIG. 2) and the correction lever4is maintained by the return spring13acting on the shuttle11in a position where the feeler pin25is resting against the periphery of the months cam26or the leap year cam27. More precisely, in this rest position, the feeler pin25is in contact with an upper part55or an intermediate part56of the periphery of the months cam26when the current month has 31 days or 30 days, respectively, with the portion of the periphery of the leap year cam27other than the bump58in the recess corresponding to the lower part57of the months cam26when the current month has 28 days, or with the bump58of the leap year cam27when the current month has 29 days. Thus, the angular position of the correction lever4in this rest position is different depending on the periphery portion of the months cam26or the leap year cam27that the feeler pin25touches, in other words depending on the current month. Each day, from a given time, between about 6 p.m. and 9 p.m., the date finger2comes into contact with the finger10of the correction lever4and begins to progressively lift this lever4against the action exerted by the return spring13, thus moving the feeler pin25away from the months cam26and the leap year cam27. The time at which the date finger2comes into contact with the finger10depends on the aforementioned angular position of the correction lever4in its rest position, and therefore on the number of days of the current month. The longer the current month is, the more this time will be late and therefore the less the amplitude of displacement of the correction lever4under the action of the date finger2will be great.

During the lifting of the correction lever4, the rack22drives the shuttle11in rotation, which causes the free end of the great click40to slide on the peripheral surface of the correction cam31. During the days other than the last day of a month of less than 31 days, this sliding of the free end of the great click40has no effect on the angular position of the date mobile16,28-31. On the other hand, on the last day of a month of 30 days, 29 days or 28 days, the free end of the great click40comes into contact with the setback, designated onFIG. 5by reference85, of the correction cam31, and begins to push this cam31to shift the date mobile16,28-31clockwise respectively by one pitch, two pitches or three pitches so that the date mobile16,28-31reaches an angular position corresponding to the date31. Next, the correction lever4is released from the action of the date finger2, and the return spring13makes it drop so that it retrieves its rest position. Because the great click40cooperates with the correction cam31during the progressive lifting of the correction lever4, the shift of the date mobile16,28-31by the great click40is dragging. More precisely, each shift by one pitch of the date mobile16,28-31by the great click40comprises a first, slow movement, during which the great click40pushes the correction cam31against the action exerted by the jumper20until the apex of a tooth of the date star-wheel16in contact with the jumper20reaches the tip of the latter, designated by86, and a second, fast movement, initiated by the drop of the jumper20on the other side of said tooth and from which the great click40loses momentarily contact with the setback85.

During the lifting of the correction lever4, the date finger2comes into contact with the finger9of the date lever3, thus causing a progressive lifting of this lever3against the action exerted by the return spring12. The end of the lifting of the date lever3occurs after the end of the lifting of the correction lever4, but before the drop of the correction lever4. As soon as the date finger2releases the date lever3, this lever3drops under the action of the return spring12to retrieve its rest position. During this drop, the first small click14catches a tooth of the date star-wheel16to shift angularly and instantaneously this star-wheel16and therefore the date mobile16,28-31by one pitch. During this same drop of the date lever3, the second small click15catches a tooth of the days star-wheel17to shift angularly and instantaneously this star-wheel17and therefore the weekday display hand18by one pitch to display the following day.

This instantaneous shift by one pitch of the date mobile16,28-31and of the days star-wheel17by the small clicks14,15occurs each day, let it be or not the end of a month of less than 31 days. If the current day is the last day of a month of less than 31 days, this instantaneous shift by one pitch of the date mobile16,28-31will follow the dragging shift of this mobile by the great click40to end the transition from the last day of the current month to the first day of the following month. In all the other circumstances, i.e for the transition of one day to the next within a month or the transition from the last day of a month of 31 days to the first day of the following month, the great click40has no function, and the instantaneous shift by one pitch of the date mobile16,28-31by the small click14is the sole shift undergone by the date mobile16,28-31.

When the date mobile16,28-31is rotated by one pitch, let it be by the small click14in an instantaneous manner or by the great click40in a dragging manner, the units wheel29of the date mobile16,28-31shifts by one pitch the units pinion32so as to change the date unit displayed in the window38to the next unit, except once a month, when the date mobile16,28-31is in an angular position corresponding to the date31. In this position, indeed, the toothing of the units pinion32is facing the empty space29′ of the toothing of the units wheel29and, therefore, is not driven. When the date mobile16,28-31changes from the angular position corresponding to the 31st to the one corresponding to the 1st, the units disk33therefore remains still and the digit 1 of the units remains displayed through the window38.

The tens pinion34is driven by the tens wheel30of the date mobile16,28-31only four times a month, corresponding to the changes of the ten of the date, when the toothing of the tens pinion34is in the path of one of the four teeth of the tens wheel30. Each time the tens pinion34is shifted by one pitch, the tens disk35, solid with the pinion34, also shifts so as to display the next ten of the date in the window39.

Moreover, each rotation by one pitch of the date mobile16,28-31entails, via the intermediate date wheel41and the intermediate pinion42, a rotation by one pitch of the months wheel43and of the months disk44. This rotation by one pitch of the wheel43and the disk44however causes the finger45of the months disk44to rotate the months pinion47only when the date mobile16,28-31changes from an angular position corresponding to the 31st to an angular position corresponding to the 1st, the rest of the time the finger45being outside the toothing of the months pinion47. Each rotation by one pitch of the months pinion47causes the months cam26and the month display hand48located above the months display area49on the dial of the watch to be rotated by one pitch for the transition to the following month. Each rotation by one pitch of the months pinion47also causes a rotation by one pitch of the 48-month wheel50which itself causes, through year wheels51,52, a rotation by one pitch of the leap year cam27and of the leap year display hand53associated with the display area54on the dial of the watch.

The fingers9,10of the levers3,4are designed so that the drop of the date lever3always occurs before the drop of the correction lever4. Thus, the instantaneous shift by one pitch that the date mobile16,28-31makes every day during the drop of the date lever3, which shift, as explained above, causes a shift of the months pinion47and of the months cam27at each end of a month, occurs while the feeler24-25of the correction lever4is apart from the peripheral surface of the cams26,27. In this way, a blocking of the mechanism is prevented.

At any time during the operation of the mechanism, the angular position of the date mobile16,28-31, of the days star-wheel17, of the moon pinion62and of the months pinion47can be corrected manually through the correctors73-76, respectively, and this without a blocking risk. Regarding more particularly the months pinion47, it is to be noted that rotation of this pinion47by the corrector76has never any effect on the angular position of the date mobile16,28-31. Indeed, when this rotation occurs while the finger45is outside the toothing of the months pinion47, the months disk44cannot be driven by the months pinion47. When the rotation of the months pinion47occurs while the finger45is within the toothing of said pinion47, the months disk44is driven by one pitch counter-clockwise, but as the hole46′ is greater than the pin46it receives, the months wheel43remains still, therefore also leaving the date mobile16,28-31still.

The present invention as described above presents several advantages in addition to those already mentioned. One of them is that the change-of-date display is effected instantaneously most of the time, i.e. during the transition from one day to the next within a month and during the transition from the last day of a month of 31 days to the first day of the following month, but with a reduced risk of the date mobile16,28-31being driven by its inertia into a non desired shift, this due to the fact that the shift of the date mobile16,28-31during the transition from the last day of a month of less than 31 days to the first day of the following month is partly effected in a dragging manner. More particularly, it will be noted that, in the illustrated example, the instantaneous shifts of the date mobile16,28-31are always restricted to a single pitch.

Another advantage of the invention is that it allows, by the presence of the two levers3,4bearing respectively the small click14and the great click40, the creation of a sufficient shifting angle for the clicks14,40while freeing some space for another display device, i.e., in the illustrated example, the moon phase display device62-68, and while allowing a great-size display of the date by two juxtaposed disks33,35. In a general manner, it will be noted that the mechanism according to the invention allows for a user-friendly layout of different display areas well readable on the dial of the watch.

The present invention has been described above only by way of example. It goes without saying that modifications can be made without deviating from the scope of the invention. For example, the mechanism could be made merely annual by removing the leap year cam27and the gears associated with it. Another modification could consist in removing the moon phase display device62-68or in replacing it by a tourbillon, for example.