HK1249197B - Running equation of time mechanism controlled by a differential device - Google Patents

Description

Time-operated equation mechanism controlled by differential device

Technical Field

The present invention relates to a running equation of time mechanism for a timepiece, and more particularly to a running equation of time mechanism that drives a minute hand for true solar time that is concentric with a hand of a movement.

Background Art

It is well known that there is a difference between true solar time (the time elapsed between two consecutive passages of the Sun above the meridian at the same location) and mean solar time, or civil time, which is the average duration of all true solar days in a year. This difference between civil time and true solar time reaches +14 minutes and 22 seconds on February 11 and -16 minutes and 23 seconds on November 4. These values vary very little from year to year.

In order to indicate the difference between civil time and true time, some timepieces include, in addition to a hand indicating the minutes of civil time, a so-called equation of time mechanism comprising a hand that moves on a graduated scale to indicate the difference between the minutes of civil time and the minutes of true solar time on a given day. This true solar time minute hand is actuated by an equation of time cam whose profile is determined by the difference between mean solar time and true solar time for each day of the year.

Another mechanism for indicating the difference between civil time and real time is known as the "equation of time mechanism." The hand mechanism of a timepiece equipped with an equation of time mechanism includes two concentric minute hands, one indicating the minutes of civil time and the other indicating the minutes of real time. At any given moment, the distance between the civil time minute hand and the real solar time minute hand is determined by the difference between mean solar time and real solar time for the day of the year in question. Similar to the equation of time mechanism, the real solar time minute hand of the equation of time mechanism is actuated by an equation of time cam.

This equation of time cam rotates at a rate of one revolution per year, driven by a simple or permanent calendar mechanism. Simple calendar mechanisms are configured to indicate the day of the week, month, month, or moon phase, but do not take into account the varying number of days in each month (months with 28, 29, or 30 days). In other words, the user of a watch with a simple calendar mechanism must make manual corrections at the end of each month with fewer than 31 days. For example, on February 28 or April 30, manual corrections must be made. Similar to a simple calendar mechanism, a permanent calendar mechanism can indicate the day of the week, date, month, and moon phase. However, unlike a simple calendar mechanism, the permanent calendar mechanism automatically takes into account the length of each month (28, 29, and 30 days), eliminating the need for manual intervention. The permanent calendar mechanism therefore automatically takes leap years into account.

An example of a time-equation mechanism is disclosed in European Patent Application Publication No. 1286233A1 in the name of the applicant. Figure 1 of the present patent application is taken from the above European Patent Application Publication No. 1286233A1 and shows a time-equation mechanism driven by a differential device.

The figure also shows an equation of time cam 1, the profile of which is determined by the difference between mean solar time, or civil time, and true solar time for each day of the year. Driven by a simple or perpetual calendar mechanism incorporated into the timepiece, this equation of time cam 1 rotates at a rate of one revolution per year. This equation of time cam 1 carries a month disc 2, which rotates at the same speed as cam 1 and aligns the position of this cam with the date indicated by the calendar mechanism, so that the solar time minute hand 4 indicates the exact difference between the minutes of civil time and the minutes of true solar time.

The simple or permanent calendar mechanism can be of any known type and will not be fully described herein. For a correct understanding, it is sufficient to understand that the calendar mechanism drives the equation of time cam 1 at a rate of one full rotation per year. However, for illustrative purposes only, a date wheel set 6 is shown driving a hand 8 indicating the date (from 1 to 31). This date wheel set 6 rotates at a rate of one full rotation per month. This date wheel set 6 is actuated by the calendar mechanism and drives the equation of time cam 1 via an intermediate date wheel 10, which can reverse its direction of rotation, and a reduction wheel set 12, which can reduce the rotation speed from one full rotation per month to one full rotation per year.

The solar time minute hand 4 is driven by a differential gearing 14 having a gear train and a rack 20 as respective input devices. This gear train drives the civil time minute hand 18, and the rack 20 cooperates with the time equation cam 1 ( FIG. 1 shows the rack 20 in its two end positions, one indicated by a solid line and the other by a dashed-dotted line). More specifically, as shown in FIG. 1 , the differential gearing 14 includes at least one, and preferably two, planetary pinions 22 driven by the movement of the watch movement. These two planetary pinions 22 are able to rotate on their own and roll on an inner toothing 24 of a time equation wheel 26. This time equation wheel 26 also has a first toothed section 28 on its outer circumference, which cooperates via this first toothed section 28 with a second toothed section 30 provided on one end of the rack 20. This rack 20 is subject to the return action of a spring (not shown) fixed to the watch frame and tending to press a feeler spindle 32, forming the other end of rack 20, against the profile of equation of time cam 1. The solar time display gear train includes a solar time display pinion 34 arranged at the center of differential gearing 14. This pinion 34 meshes with the planetary pinions 22 and carries a solar time display wheel 38, which meshes with a cannon 40, onto whose tube the solar time minute hand 4 is press-fitted. This gear train 38, 40 returns the solar time minute display 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 time-running equation mechanism just described operates as follows.

In the normal operating mode of the watch, the equation of time cam 1, rack 20, and therefore the equation of time wheel 26 are stationary. However, the planetary pinions 22 are driven by the watch movement. Therefore, they rotate on their own and roll on the inner toothing 24 of the equation of time wheel 26, thereby driving the rotation of the solar time display pinion 34. This allows the solar time minute hand 4 to rotate in conjunction with the civil time minute hand 18. As a result, the distance between the solar time minute hand 4 and the civil time minute hand 18 remains constant over a 24-hour period.

Driven by the calendar mechanism, the equation of time cam 1 pivots once a day at approximately midnight, thus changing the date from one day to the next. At this exact moment, the feeler 32, which contacts the contour of the equation of time cam 1, in turn pivots the rack 20. This pivoting rack 20 drives the equation of time wheel 26 in rotation. During this brief interval, the essentially stationary planetary pinions 22 (which complete one full rotation per hour) rotate, driven by the equation of time wheel 26 and, in turn, driving the solar time display pinion 34, precisely resets the position of the solar time minute hand.

Therefore, the time running equation mechanism described above can display the time difference between mean solar time and true time at any time by means of the civil time minute hand and the solar time minute hand. However, it should be noted that the differential gear device 14 is not located at the center 42 of the watch movement. Therefore, this design is not symmetrical and is not intuitive. In addition, due to the eccentric position of the differential gear device 14, it is necessary to provide another gear train (sun time display wheel 38 and minute pinion 40) to return the solar time display device to the center 42 of the watch movement and ensure the concentricity between the civil time minute hand 18 and the solar time minute hand 4. This other gear train takes up space and may cause malfunctions.

Summary of the Invention

An object of the present invention is to overcome the above-mentioned and other problems by providing an equation of time mechanism controlled by a differential gear device that is more compact and therefore easier to incorporate in a timepiece movement.

To this end, the present invention relates firstly to an equation of time mechanism comprising a pointer device and a real-time minute hand, the pointer device being intended to indicate civil time by means of concentric hour and minute hands, the real-time minute hand being concentric with the civil-time hand, the equation of time mechanism further comprising an equation of time cam having a profile determined by the difference between mean solar time, or civil time, and apparent solar time, or real time, for each day of the year, the equation of time cam rotating at a rate of one revolution per year driven by a watch movement, the position of the real-time minute hand being determined by the position of the equation of time cam, the equation of time mechanism further comprising a differential gear device, a first input device of the differential gear device being formed by a cannon shaft integral with a civil-time minute hand tube on which the civil-time minute hand is press-fitted, and a second input device of the differential gear device being formed by the equation of time cam, the differential gear device being arranged concentrically with respect to the real-time minute hand.

Secondly, the present invention relates to a time running equation mechanism, which includes a pointer device and a real time minute hand, the pointer device being used to indicate civil time by means of concentric hour and minute hands, the real time minute hand being concentric with the civil time hand, the time running equation mechanism also including a time equation cam having a profile determined by the difference between mean solar time or civil time and apparent solar time or real time for each day of the year, the time equation cam rotating at a rate of one revolution per year under the drive of a watch movement, the position of the real time minute hand being determined by the position of the time equation cam, the time running equation mechanism also including a differential gear device, a first input device of the differential gear device being formed by a pinion shaft integral with a civil time minute hand tube on which the civil time minute hand is press-fitted, and a second input device of the differential gear device being formed by the time equation cam, the differential gear device including a planetary reducer wheel set and a planetary multiplier wheel set. The civil time minute hand tube drives the civil time hour hand press-fitted thereon via the planetary reduction gear set, and the civil time hour hand tube drives the real time minute hand press-fitted thereon via the planetary speed increasing gear set.

As a result of these features, the present invention provides a time equation mechanism driven by a differential gear device, the differential gear device being equipped with a planetary reduction wheel set and a planetary speed-increasing wheel set. The civil time minute hand pipe, via the planetary reduction wheel set, drives the civil time hour hand pipe, onto which the civil time hour hand is press-fitted, and the civil time hour hand pipe, via the planetary speed-increasing wheel set, drives the real time minute hand pipe, onto which the real time minute hand is press-fitted. By integrating the functions of generating the civil time hours from the civil time minutes, and generating the real time minutes from the civil time hours and the time equation cam within the differential gear device, a more compact differential gear device is achieved, with the planetary reduction wheel set and speed-increasing wheel set of the differential gear device being returned to the center of the watch movement. The differential gear device according to the present invention is therefore more easily accommodated within the watch movement to which it is mounted, which allows for a reduction in the size of the watch movement and provides more space for accommodating other components of the movement.

According to a preferred embodiment of the present invention, the planetary reduction wheel set and the planetary speed increasing wheel set rotate and form circular tracks centered on the civil time minute hand tube, preferably with the same radius.

The differential gearing according to the invention comprises fewer components and is therefore more reliable. Furthermore, it exhibits an overall radial symmetry centred on the centre of the movement, which facilitates its assembly and arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will emerge more clearly from the following detailed description of an exemplary embodiment of the time-running equation device according to the invention, which example is given purely as a non-limiting example with reference to the accompanying drawings, in which:

- FIG. 1 above is a diagram of a time-equation mechanism driven by a differential device according to the prior art.

- Figure 2 is a top view of the time running equation mechanism according to the invention.

- Figure 3 is a cross-sectional view along line A-A of Figure 2.

- Figure 4 is a cross-sectional view along line B-B of Figure 2.

- Figure 5 is a cross-sectional view along line C-C of Figure 2.

DETAILED DESCRIPTION

The present invention stems from the general inventive concept of equipping an equation of time mechanism with a differential gearing capable of indicating both civil time via a civil time hour hand and a civil time minute hand, and real time minutes via a second minute hand concentric with the civil time hand. The respective drivers (power take-offs) of this differential gearing are, on the one hand, a going train wheel set of a timepiece movement, and, on the other hand, an equation of time cam. According to the present invention, the gear reduction function, which enables the change from civil time minutes to civil time hours, and the speed-up function, which enables the change from civil time hours to real time minutes, are integrated into the differential gearing, making the equation of time mechanism more compact and therefore easier to arrange within a timepiece movement.

One object of the present invention is to integrate an equation of time mechanism into a timepiece, such as a wristwatch, that is, a mechanism whose hand arrangement includes two concentric minute hands, one indicating the minutes of civil time and the other indicating the minutes of real time. To this end, as shown in FIG2 , the equation of time mechanism according to the present invention, generally designated by the reference numeral 44, comprises, on the one hand, a conventional hand arrangement for indicating civil time by means of an hour hand 46 and a minute hand 48, and, on the other hand, a real-time minute hand 50, which is concentric with the civil-time minute hand 48 and indicates the minutes of real solar time. To make it easy for the wearer of the watch to discern the difference between the civil-time minute hand 48 and the real-time minute hand 50, the end of the real-time minute hand 50 may, for example, include a representation of a solar astrological symbol 52. As will be seen in detail in the following description, the exact position of the real time minute hand 50 on a given day is determined once within 24 hours, approximately around midnight, and the civil time minute hand 48 and the real time minute hand 50 then move in unison, with the distance between the two hands 48 and 50 remaining constant on that given day.

FIG2 also shows a portion of the equation of time mechanism 44 according to the invention, and in particular the equation of time cam 54 , the profile of which, it will be remembered, is determined by the difference between mean solar time or civil time and true solar time or solar time for each day of the year.

Referring again to Fig. 2, it can be seen that the time equation cam 54 is fixed on the time equation wheel 56, and this time equation wheel 56 is driven with the speed of one full circle per year by the simple or permanent calendar mechanism (not shown) included in the timepiece.Described simple or permanent calendar mechanism can be any known type, and this paper will not be described in detail.In order to ensure correct understanding of the present invention, it is enough to understand that this calendar mechanism drives the time equation wheel 56 that the time equation cam 54 is fixed thereon with the speed of one full circle per year.This calendar mechanism comprises the date wheel 58 that rotates with the speed of one full circle per month and drives the date indicating device 104 simultaneously.In addition, time equation wheel 56 is driven by date wheel 58 via intermediate date wheel 60 and reduction wheel pair 62, and this intermediate date wheel 60 can make the direction of rotation reverse, and this reduction wheel pair 62 can reduce the rotating speed from one full circle per month to one full circle per year.

According to the present invention, the real time minute hand 50 is driven by a differential gearing 64, the corresponding input of which (see FIG3 ) is a wheel set 66 of the going train that drives the civil time minute hand 48, and an equation of time lever 68 that cooperates with the equation of time cam 54. More specifically, as shown in FIG3 , a civil time minute hand pipe 70 is driven by the going train wheel set 66 of the timepiece movement via a cannon pinion 72 integral with the civil time minute hand pipe 70. In turn, the civil time minute hand pipe 70 drives a planetary reduction wheel set 74 formed by a first planet wheel 76 and a first planet pinion 78 integral with the first planet wheel 76.

The planetary reduction wheel set 74 is mounted to pivot about a first pin 80 pressed into an upper differential frame 82, integral with which is a civil time hour hand tube 84, onto which the civil time hour hand 46 is press-fitted. Driven by the civil time minute hand tube 70 via the first planetary wheel 76, the first planetary pinion 78 rolls on a first internal toothing 86 of a first differential crown wheel 88, which is stationary and carried by the watch movement. By rolling on the first internal toothing 86 of the stationary differential crown wheel 88, the first planetary pinion 78 thereby pivots the upper differential frame 82 and, in turn, the civil time hour hand tube 84, which is integral with the upper differential frame 82. Proper selection of the transmission ratios between the civil time minute hand tube 70, the first planetary wheel 76, the first planetary pinion 78, and the stationary differential crown wheel 88 results in a reduction of 1:12 between the minutes and hours of civil time, thereby enabling a civil time display. In other words, the planetary reduction wheel set 74 makes it possible to change from civil time minutes to civil time hours by a reduction of 1:12.

As shown in FIG4 , the planetary speed-increasing wheel set 90 is formed by a second planet wheel 92 and a second planet pinion 94 integral with the second planet wheel 92. The planetary speed-increasing wheel set 90 is freely mounted around a second pin 96, which is pressed into the upper differential cage 82 integral with the civil time hour hand tube 84. When the civil time hour hand tube 84, and thus the upper differential cage 82, rotate, they drive the second pin 96 and, consequently, the planetary speed-increasing wheel set 90, whose second planet pinion 94 rolls on a second internal gear 98 of a movable differential crown wheel 100, which, as will be seen below, meshes with the time equation cam 54. The second planet wheel 92, in turn, drives the solar time minute hand tube 102, onto which the real time minute hand 50 is press-fitted. Correct selection of the transmission ratios between civil time hour hand 84, second planet wheel 92, second planet pinion 94, and movable differential crown wheel 100 results in a 12-fold increase in speed between the hours of civil time and the minutes of true time, and thus enables a true time display. In other words, planetary speed-increasing wheel set 90 makes it possible to change from civil time hours to true solar time minutes by a 12-fold increase in speed.

As can be seen from the above, the planetary reduction gear set 74 and the planetary speed increasing gear set 90 rotate and form a circular trajectory centered on the civil time minute hand tube 70. Preferably, the planetary reduction gear set 74 and the planetary speed increasing gear set 90 move on a circle with the same radius centered on the civil time minute hand tube and are angularly spaced apart from each other.

The pivoting of the movable differential crown wheel 100 is controlled by an equation of time lever 68, equipped with a feeler beak 106, via which the equation of time lever 68 contacts the profile of the equation of time cam 54. The equation of time lever 68 is resiliently held against the profile of the equation of time cam 54 by a spring 108. The equation of time lever 68 is also provided with a first tooth 110, which meshes with a corresponding second tooth 112 provided on the movable differential crown wheel 100 to control the movement of the movable differential crown wheel 100. It will be appreciated that, near midnight, when the calendar mechanism changes the date, it causes the date wheel 58 to advance one step. During this brief moment when the date change occurs, the upper differential frame 82, and therefore the civil time hour hand 84, can be considered stationary. By pivoting, the movable differential crown wheel 100 drives the second planetary pinion 94 and thus the second planetary wheel 92, which in turn meshes with the solar time minute hand tube 102 on which the real time minute hand 50 is press-fitted. The position of the real time minute hand 50 is thus set for the next day.

5, it can be seen that at least one, and preferably two, screws 114 allow the upper differential frame 82 to close onto the lower differential frame 116. Thus, when the differential gear arrangement 64 according to the present invention operates, the upper and lower differential frames 82 and 116 rotate together.

Of course, the invention is not limited to the embodiments that have just been described, and those skilled in the art may envisage various simple modifications and variations without departing from the scope of the invention as defined by the appended claims.

Glossary

1. Time equation cam

2. Month disk

4. Solar time minute hand

6. Date wheel set

8. Pointers

10. Middle date wheel

12. Reduction wheel set

14. Differential gear unit

18.Civil time minute hand

20. Rack

22.Planetary pinion

24. Internal gear ring

26. Time Equation Wheel

28.First toothed section

30. Second toothed section

32. Touch rod

34. Solar time display pinion

38. Solar time display wheel

40. Toothed shaft

42. Center

44. Time running equation mechanism

46.Civil time hour hand

48.Civil time minute hand

50. Real time minute hand

52. Sun Astrology Symbol

54.Time Equation Cam

56. Time Equation Wheel

58. Date Wheel

60. Middle date wheel

62.Reduction gear set

64. Differential gear device

66. Wheel sets

68. Time Equation Lever

70.Civil Time Minutes

72.Split gear shaft

74.Planetary reduction gear set

76.First planetary gear

78.First planetary pinion

80. First Pin

82.Upper differential frame

84.Civil time hour hand

86.First internal gear ring

88. Fixed differential crown wheel

90. Planetary speed increaser gear set

92. Second planetary gear

94. Second planetary pinion

96. Second Pin

98. Second internal gear ring

100. Movable differential crown wheel

102. Real time minute hand tube

104.Date indication device

106. Beak

108. Spring

110.First tooth

112. Second tooth

114. Screws

Claims (19)

1. A time-running equation mechanism comprising a pointer device and a real time minute hand (50), the pointer device being used to indicate civil time by means of concentric hour hands (46) and minute hands (48), the real time minute hand (50) being concentric with the civil time hour hands (46) and minute hands (48), the time-running equation mechanism (44) further comprising a time equation cam (54), the time equation cam (54) having a profile determined by the difference between mean solar time and actual solar time for each day of the year, the time equation cam (54) being driven by a clock movement at each Rotating at a rate of one revolution per year, the position of the real time minute hand (50) is determined by the position of the time equation cam (54). The time running equation mechanism (44) also includes a differential gear device (64). The first input device of the differential gear device (64) is formed by a toothed shaft (72) integral with the civil time minute hand tube (70) pressed onto the civil time minute hand (48). The second input device of the differential gear device (64) is formed by the time equation cam (54). The differential gear device (64) is concentrically arranged about the real time minute hand (50). 2. A time-running equation mechanism, comprising a pointer device and a real time minute hand (50), the pointer device being used to indicate civil time by means of an hour hand (46) and a minute hand (48), the time-running equation mechanism (44) further comprising a time-running cam (54) having a profile determined by the difference between mean solar time and actual solar time for each day of the year, the time-running cam (54) rotating at a rate of one revolution per year driven by a clock movement, the position of the real time minute hand (50) being determined by the position of the time-running cam (54), the time-running equation mechanism (44) further comprising a differential gear device (64), the differential gear device (64) being... 4) The first input device is formed by a geared shaft (72) integral with the civil time minute hand tube (70) on which the civil time minute hand (48) is press-fitted, and the second input device of the differential gear device (64) is formed by the time equation cam (54). The differential gear device (64) includes a planetary reduction gear pair (74) and a planetary speed-increasing gear pair (90). The civil time minute hand tube (70) drives the civil time hour hand tube (84) on which the civil time hour hand (46) is press-fitted via the planetary reduction gear pair (74). The civil time hour hand tube (84) drives the real time minute hand tube (102) on which the real time minute hand (50) is press-fitted via the planetary speed-increasing gear pair (90). 3. The time-running equation mechanism according to claim 2, characterized in that the planetary reduction gear pair (74) enables the rotational speed to be reduced from one full revolution per hour to one full revolution per twelve hours, and the planetary speed-increasing gear pair (90) enables the rotational speed to be increased from one full revolution per twelve hours to one full revolution per hour. 4. The time-running equation mechanism according to claim 2, characterized in that the planetary deceleration wheel pair (74) and the planetary speed-increasing wheel pair (90) rotate and form a circular trajectory centered on the civilian time minute hand tube (70). 5. The time-running equation mechanism according to claim 3, characterized in that the planetary deceleration wheel pair (74) and the planetary speed-increasing wheel pair (90) rotate and form a centered circular trajectory on the civilian time minute hand tube (70). 6. The time-running equation mechanism according to claim 4, characterized in that the planetary deceleration wheel pair (74) and the planetary speed-increasing wheel pair (90) are equidistant from the civilian time minute hand tube (70). 7. The time-running equation mechanism according to claim 5, characterized in that the planetary deceleration wheel pair (74) and the planetary speed-increasing wheel pair (90) are equidistant from the civilian time minute hand tube (70). 8. The time-running equation mechanism according to any one of claims 2 to 7, characterized in that the planetary deceleration wheel pair (74) and the planetary speed-increasing wheel pair (90) are mounted to rotate freely on an upper differential frame integral with the civil time minute hand tube (46). 9. The time-running equation mechanism according to claim 8, wherein the planetary reduction gear pair (74) is mounted to pivot about a first pin (80) press-fitted in the upper differential frame (82). 10. The time-running equation mechanism according to claim 9, wherein the planetary reduction gear pair (74) includes a first planetary gear (76) integrally formed with the first planetary pinion (78). 11. The time-running equation mechanism according to claim 10, characterized in that the civilian time minute tube (70) meshes with the first planetary gear (76), and the first planetary pinion (78) rolls on the first internal gear ring (86) of the fixed differential crown gear (88), which has the effect of rotating the upper differential frame (82). 12. The time-running equation mechanism according to claim 8, wherein the planetary speed-increasing wheel pair (90) is mounted to pivot about a second pin (96) press-fitted in the upper differential frame (82). 13. The time-running equation mechanism according to claim 12, wherein the planetary speed-increasing gear pair (90) includes a second planetary gear (92) integrally formed with the second planetary pinion (94). 14. The time-running equation mechanism according to claim 13, characterized in that the second planetary gear (92) meshes with the real time minute hand tube (102), and the second planetary pinion (94) rolls on the second internal gear ring (98) of the movable differential crown wheel (100), the movable differential crown wheel (100) being kinematically connected to the time-running cam (54). 15. The time-running equation mechanism according to claim 14, characterized in that the pivoting of the movable differential crown wheel (100) is controlled by a time equation lever (68) provided with a beak (106), the time equation lever (68) following the contour of the time equation cam (54) via the beak (106). 16. The time-running equation mechanism according to claim 15, wherein the time equation lever (68) is elastically held against the contour of the time equation cam (54) by a spring (108). 17. The time-running equation mechanism according to claim 15, characterized in that the time-running equation lever (68) is provided with a first tooth (110), the first tooth (110) meshing with a corresponding second tooth (112) provided on the movable differential crown wheel (100) to control the movement of the movable differential crown wheel (100). 18. The time-running equation mechanism according to claim 16, characterized in that the time equation lever (68) is provided with a first tooth (110), the first tooth (110) meshing with a corresponding second tooth (112) provided on the movable differential crown wheel (100) to control the movement of the movable differential crown wheel (100). 19. The time-running equation mechanism according to claim 8, wherein the upper differential frame (82) is fixed to the lower differential frame (118) by means of screws (130).