HK1119786B - Timepiece including a mechanism for correcting a device displaying a time related quantity - Google Patents

Description

Timepiece comprising a mechanism for adjusting a display device of a time-related quantity

Technical Field

The invention relates to a timepiece including a mechanism for adjusting/correcting a time-dependent quantity of display means. More specifically, the invention relates to a timepiece of the type comprising a bidirectional adjustment mechanism for a device for displaying a time-related quantity, such as a calendar mechanism.

Background

Devices that display time-related quantities, such as calendar mechanisms, are mostly based on systems with a control arm that follows the contour of a cam and actuates a date indicator member each day. Typically, at one point of its profile, the cam has a steep face or step that marks the transition from the last day of a given month to the first day of the next month. The presence of this steep face at a point on the cam profile causes problems when one wishes to adjust, for example, the date indicator value in a counter-clockwise direction. In fact, there is no difficulty when it is desired to adjust the date indication value in the clockwise direction, in other words, when it is desired to shift from a given date to a date one unit greater than the preceding date. The control arm follows the cam profile and moves the date indicator member forward step by step. When the control arm reaches a position in which the cam profile marks the steep face of the transition from the last day of a given month to the first day of the following month, the control arm drops, moving the date indicator member one step forward. This is not the case when it is desired to move the date indicator member backwards. In fact, in this case, there will be a moment when the control arm hits the steep face of the cam profile and is blocked. And thus the date indication value cannot be adjusted.

Various solutions have been proposed to overcome this problem. By way of example, a multifunction timepiece is known from EP patent application No. 0851321 to Seiko instruments inc, which comprises a lever for adjusting a small hour hand, which pushes the tail of the hammer. Causing the hammer to pivot counterclockwise and into a condition in which the hammer is no longer in contact with the actuation cam. The Seiko document does not disclose a bidirectional adjustment mechanism comprising an adjustment member in the form of a ring cam actuated by a control stem, which is able to move the arm away from the lever of the cam against which the arm normally rests, via a return cam on which it acts.

An actuating mechanism for a time-setting device of a timepiece is also known from EP patent No. 1336907 to Richemont International s.a. More specifically, the actuating mechanism comprises a control ring arranged concentrically with respect to the centre of the watch. Depending on the engagement position of the crown, the control ring can occupy two radial positions via the action of the curved lever. The Richemont document does not mention that the control ring has a cam profile on its inner circumference.

From CH patent No. 660440 to Dubois & D praz s.a. there is also known a perpetual calendar mechanism in which a large lever is lifted by the lever of another lever mechanism. The Dubois & sepraz document does not disclose an adjustment mechanism in which the arm of the control lever is moved away from the cam against which it normally abuts via a return lever cooperating with an adjustment member shaped like a ring cam.

Finally, a mechanical date display device and a timepiece equipped with such a display device are known from the CH patent No. 674290 to Roth. In one embodiment disclosed in this document, it can be seen that when the crown is operated using a push-button, a lever having two arms is moved so that the toothed ring of its rack drives the pinion. This document does disclose an actuating device in the form of a ring cam. However, it does not disclose actuating the control cam via a return cam cooperating with a cam profile provided on the inner periphery of the ring cam.

Disclosure of Invention

In view of the foregoing, it is an object of the present invention to provide a timepiece including a novel adjustment mechanism for a display device, such as a date, for adjusting the display device in a clockwise, i.e., forward, and in a counter-clockwise, i.e., backward, direction.

Accordingly, the invention discloses a timepiece comprising a bidirectional adjustment mechanism for a display of a time-related quantity, such as the date, said display being actuated by a toothed-rack-equipped lever, said lever being controlled by a cam against which said lever abuts via an arm; this lever is brought to rest against the cam and said display device is moved backwards by a second lever, called the return lever, also equipped with a rack, via which an adjustment member actuated by the control stem is used to move the arm of the lever away from the normally resting cam.

Thanks to these features, the invention provides a timepiece comprising an adjustment mechanism capable of adjusting a display device of a time-related quantity, such as a date display device, forwards and backwards, independently of the fact that it is actuated by a lever itself controlled by a cam. This remarkable effect is obtained thanks to the fact that the adjustment mechanism according to the invention comprises a second lever which is controlled by the disconnection transmission means via the control stem and which temporarily moves the control lever out of the path of the cam against which it normally abuts. The user can thus adjust the display mechanism backwards because the lever is not in the path of the cam and therefore does not strike the cam, despite the cam being rotated.

According to a complementary feature of the invention, the adjustment mechanism is formed by a ring cam actuated by a control stem, against the profile of which the return lever bears via an arm.

Thus, there is an annular part advantageously centred on the centre of the timepiece movement. Due to the geometry and flatness of the annular part, the part is easier to manufacture and also enables control of a plurality of time-dependent quantities of display devices arranged at different positions on its circumference.

Drawings

Further characteristics and advantages of the invention will emerge more clearly from the detailed description that follows of an exemplary embodiment of the adjustment mechanism according to the invention, given purely by way of non-limiting example with reference to the accompanying drawings, in which:

fig. 1 is a top view of the dial of a watch comprising an adjustment mechanism according to the invention;

FIG. 2 is a top view of the adjustment mechanism according to the present invention in a normal operating position;

FIG. 3A is a perspective view of the adjustment mechanism of FIG. 2, showing an adjustment member actuated by the control stem;

FIG. 3B is an enlarged detail view of the area enclosed by the circle in FIG. 3A;

FIG. 3C shows the adjustment mechanism when it has been actuated by the control stem; and

figure 4 shows the adjustment mechanism of figure 2 in an off position, in which the arm of the lever is out of the path of the cam.

Detailed Description

The invention proceeds from the following general inventive idea: a timepiece is provided comprising an adjustment mechanism for a time-dependent quantity display device, such as a date device, which is capable of adjusting the device in both directions, i.e. forwards and backwards. To achieve this object, the invention teaches: in the backward adjustment phase, the control lever of the display device has to be moved out of the path of the cam. A disconnecting or disconnecting mechanism is therefore provided, which is actuated by the control stem, moving the arm of the control lever away from the cam against which it normally abuts, via another lever, called the return lever.

The invention will be described in connection with a date display device. However, it is clear from reading this description that the invention is not limited to date display devices, but is equally applicable to day of the week display devices, 24 hour display devices, and more generally to any type of device that displays a time-related quantity.

One exemplary embodiment of a timepiece comprising an adjustment mechanism according to the invention is shown in fig. 1. The timepiece, designated as a whole by the general reference numeral 3, comprises, in its centre, a set of time zone hands formed by an hour hand 5a, a minute hand 5b and a second hand 5c, which move over a circular dial 7. This time zone mechanism is disclosed in EP patent application No.1544691 of the present applicant and will therefore not be further described here.

The watch 3 further includes:

a backward or reverse date display formed by a pointer 9a, the pointer 9a moving in front of an arc dial 9b extending between "1" and "31";

a backward day display formed by a pointer 11a, the pointer 11a moving along a dial 11b marked from "MON" to "SUN";

a backward 24-hour display formed by a pointer 13a, the pointer 13a moving along a dial 13b in the shape of a circular arc extending between "1" and "24".

The watch display also includes a small second indicator 15.

The timepiece whose adjustment mechanism is shown in the top view of fig. 2 is a time zone watch comprising a reversible 24-hour display corresponding to the local time of the place where the wearer of the watch normally lives, and a 12-hour display corresponding to the time of the time zone of the place where the wearer of the watch temporarily stays. As will be seen hereinafter, if the wearer of the watch wishes to adjust the time in time zone, the date indicator and the day of the week indicator must also be adjusted; if the wearer of the watch wishes to reset the time of the watch, the reversible 24-hour display must also be adjusted.

As can be seen from fig. 2, the adjusting mechanism of the watch comprises, in particular in the centre of the watch, an intermediate wheel 1 fixed to an hour wheel 1 a. In other words, the intermediate wheel 1 rotates in the clockwise direction and completes one revolution within 12 hours. The intermediate wheel 1 is engaged with the calendar driving wheel 2, and the calendar driving wheel 2 is rotated counterclockwise at a rate of 1 turn per 24 hours. The calendar driving wheel 2 is equipped with a finger 4 via which the calendar driving wheel 2 drives the calendar wheel 6 one step per day, the calendar wheel 6 being indicated by a positioning lever spring 8 in position (index) and equipped with a cam 10. The cam 10 has a steep face or step 12 at one location on its profile which marks the transition from the date of the last day of a given month to the date of the first day of the next month, i.e. from "31 days" to "1 day". As will be seen in detail hereinafter, it is normally not possible to adjust the date backwards, due to the presence of the steep face 12 on the profile of the cam 10.

The adjusting mechanism according to the invention has a control rod 14, which control rod 14 is provided with an arm 16 at one end thereof, via which arm 16 the control rod 14 abuts against the cam 10 during normal operation; furthermore, the lever 14 comprises a rack 18 at its other end, the lever 14 being engaged via the rack 18 with a date display wheel 20, the date display wheel 20 carrying a date indicator 9a (not visible in fig. 2). The control lever 14 is pivoted at 22 and a second lever, referred to as a return lever 24, is pivoted at 26. The return lever 24 is similar in structure to the control lever 14 and includes, inter alia, a rack 28, the return lever 24 being engaged with the date display wheel 20 via the rack 28. As can be seen by studying fig. 2, the return lever 24 is biased by the spring element 30 so as to tend to rotate in a clockwise direction. Consequently, the return lever 24 in turn tends to rotate the date display wheel 20 anticlockwise, the date display wheel 20 tending to rotate the control lever 14 clockwise and keeping the arm 16 of the return lever 24 against the profile of the cam 10.

As can be seen by studying the figures, in the example shown, the spring element 30 is integral with the return rod 14 and abuts against the stop 32 so as to be rewound. To achieve this result, the rod may be made, for example, by LIGA photo-etching techniques. It goes without saying, however, that the spring element 30 can be made in the form of a separate component from the return lever 24.

At the opposite end with one end of the rack 28, the return rod 24 has a sensing portion (sensory) 34, the sensing portion 34 cooperating with a disconnect generally indicated by reference numeral 36. In the example shown in the figures, the disconnecting or separating member 36 takes the form of a ring cam 38 centred at the centre of the movement, and the sensing portion 34 of the return lever 24 abuts against the internal profile of the ring cam 38. As can be seen by a closer examination of fig. 2, in the case of the adjustment mechanism according to the invention shown in this figure, the sensing portion 34 of the return rod 24 is positioned on its inner contour by a recess 40 in the ring cam 38. The reason for the presence of the recess 40 will be understood by reading the following description. It will be observed that the ring cam 38 has two other similar recesses for controlling two other means for displaying a time-related quantity, as will be explained in detail hereinafter.

As can be seen in fig. 2, the arm 16 of the lever 14 is located at the bottom of the steep face 12 on the profile of the cam 10. This means that the date indicating mechanism to which the calendar wheel 6 and associated cam 10 belong has just shifted from the last day of a given month, day "31", to the first day of the following month, day "1". Now, assume that it is necessary to adjust the date from this state. No particular problem will be observed if the calendar wheel 6 is rotated clockwise during the adjustment: the arm 16 of the lever 14 will follow the contour of the cam 10 and drive, via its rack 18, the date indicator wheel 20, which will as a result progressively accumulate the date indication value. However, this is not the case when adjustment of the date indicator value causes the calendar wheel 6 and hence the cam 10 to rotate in the opposite direction. In fact, in this case, the arm 16 of the control lever 14 will strike and be blocked by the steep face 12 of the profile of the cam 10 and the mechanism will be blocked. This is why the arm 16 of the control lever 14 must be moved out of the path of the cam 10 when the date indication value is adjusted backwards. A ring cam 38 associated with the control stem 42 is provided for overcoming this problem.

In fact, as can be seen in fig. 3A and better in fig. 3B, the control stem 42 is kinematically connected to the ring cam 38 via an element 44, which element 44 converts the linear movement of said control stem 42 into a pivoting movement of said ring cam 38. Thus, the motion transfer element 44 includes three staking pins 46, 48 and 50. A first 46 of these three pegs forms a pivot axis for the transition element 44. The switching element 44 is connected to the control stem 42 via a second pin 48. Thus, the pin 48 projects into an annular groove 52 provided at a point along the length of the control stem 42. Finally, the movement transformation element 44 is kinematically coupled with the ring cam 38 via a third pin 50, which third pin 50 is freely movable in an elongated hole 54 provided in said ring cam 38.

In the above description, the adjusting mechanism according to the invention is for a timepiece of the time zone watch type, but this example is given by way of illustration only, and the invention is applicable to any type of device displaying a time-related quantity. In the case of this time zone watch, therefore, the control stem 42 has three stable positions, namely: a middle position in which the movement can be wound up, a first extracted position in which the 12 hour time zone indicator can be adjusted (the indicator is a jump indicator that moves forward or backward by one hour without affecting the minute display), and a second extracted position in which the time of the watch can be set. These three positions of control stem 42 are generally indexed by the extractor 56 of the basic movement, extractor 56 forming the link between extractor positioning rod spring 60 and said control stem 42.

It is assumed below that control stem 42 is pulled out to move it from the intermediate winding position to the first pulled-out position. In this case, the control stem 42 drives the pin 48, which causes the motion-converting element 44 to pivot about a pivot axis embodied as the pin 46. In turn, the pin 50 fixed to the transition member 44 slides in the elongated hole 54 and causes the ring cam 38 to pivot counterclockwise. Thereby being in the position shown in fig. 3C, in which the ring cam 38 has rotated counterclockwise.

The counterclockwise pivoting of the ring cam 38 moves the arm 16 of the control lever 14 out of the path of the cam 10 as shown in fig. 4. In fact, due to the action of the pivoting of said annular cam 38, the sensing portion 34 of the return rod 24 creeps backwards along the face 58 of the recess 40 and slides on the inner periphery of the annular cam 38. During this time, the return lever 24 pivots anticlockwise and causes the control lever 14 to also pivot anticlockwise via the date display wheel 20, with the result that the arm 16 of the control lever 14 moves out of the path of the cam 10. It will be clear that during this movement the date indicator 9a (not visible in fig. 2) driven by the date display wheel 20 will move and reach the bottom of the date dial, i.e. slightly beyond the date "31 days".

Consider the reason why it is necessary to move the arm 16 of the lever 14 out of the path of the cam 10. It is assumed that the control stem 42 is brought into its first extracted position, which means that it is desired to adjust the time zone time indication value. Thus, control stem 42 will be rotated forward or backward by one time step (hour step) depending on whether it is desired to accumulate or reduce the time zone time indication value. When the control stem 42 rotates, the hour wheel (not shown) rotates, thereby rotating the intermediate wheel 1 as well. If the intermediate wheel 1 is rotated clockwise, i.e. in the direction in which it is in the normal operating mode, the cam 10 rotates clockwise and the arm 16 of the lever 14 will slide along the profile of said cam 10 without causing any problems. However, if the intermediate wheel 1 is rotated anticlockwise in the clockwise time zone indication value adjustment phase, the cam 10 will rotate anticlockwise and the arm 16 of the control lever 14 will strike the steep face 12 of said cam 10 and be blocked. This is why in this case it is necessary to move the arm 16 of the control lever 14 out of the path of the cam 10.

As mentioned hereinbefore, the present invention is not limited to the adjusting mechanism for the date display device. In fact, the invention is very widely applicable to any type of time-related quantity display device, such as in particular a device displaying the day of the week or a 24-hour display device, as shown in fig. 2 and 4 of the present patent application. It will be observed by studying these figures that, in addition to the date display device, the applicant is equipped with a device for displaying the day of the week for the movement, which has substantially the same structure as the date display device. More specifically, the day display device includes a day drive wheel 2a that rotates counterclockwise when driven by the intermediate wheel 1. The day drive wheel 2a is equipped with a pawl 4a, and the day drive wheel 2a drives a day wheel 6a via the pawl 4a at a one-step-per-day rate, the day wheel 6a including 14 teeth and thus completing one revolution within 14 days. The day wheel 6a is therefore equipped with a cam 10a having a double cam profile, the cam 10a having two steep faces 12a1 and 12a2 symmetrical about the geometric centre of said cam 10 a. It goes without saying that this cam profile is only a matter of choice for the designer, and that it is also possible to complete one revolution in seven days using a cam of the same simple profile as the cam 10 carried by the calendar wheel 6. Each of the two steep faces 12a1 and 12a2 of the cam 10a marks the transition of the day of the week indicator from the last day of the week to the first day of the next week (i.e., from sunday to monday). It should be noted that the day wheel 6a is indexed by the jumper spring 8 a.

The adjustment mechanism for the day display device comprises a lever 14a, which lever 14a abuts via its arm 16a against the profile of the cam 10a and meshes via its rack 18a with the day display wheel 20 a. There is also provided a return lever 24a biased by a spring element 30a, the return lever 24a including a rack 28a at one end thereof and engaging with the day display wheel 20a via the rack 28a, and at the other end thereof, the return lever 24a including a sensing portion 34a in a recess 40a on the inner contour of the ring cam 38.

It should be recalled here that we consider a time zone watch. Therefore, at the first pulled-out position of the control stem 42, if it is desired to adjust the time zone time without changing the local time, it is necessary to adjust the date and day indication value at the same time. Date indication value adjustment is described in detail above. Adjustment of the day indication value is performed in the same manner. In fact, when the control stem 42 is rotated and causes the ring cam 38 to pivot counterclockwise, the sensing portion 34a of the return lever 24a crawls along the side face 58a of the recess 40a and slides on the inner periphery of the ring cam 38 a. The return lever 24a pivots counterclockwise due to the action of the movement of its sensing portion 34a, and causes the control lever 14a to also pivot counterclockwise via the day display wheel 20 a. As a result, the arm 16a of the lever 14a moves out of the path of the cam 10 a. It will be appreciated that during this movement, the day indicator 11a (not visible in figure 2) driven by the day display wheel 20a will move and reach the bottom of the day dial, slightly beyond the indication of "day of the week".

It should therefore be noted that by providing only two recesses 40, 40a on the inner profile of the ring cam 38 opposite the sensing portions 34, 34a of the return levers 24, 24a, it is possible to adjust both the date indication value and the days of the week indication value of the time zone time clockwise and anticlockwise by a single action on the control stem. The adjusting device according to the invention is therefore characterized by simple implementation and is particularly easy to use.

When the control stem 42 is transferred from its first extracted position to its second extracted position in order to set the time of the watch, an additional pivoting of the ring cam 38 will result. However, this additional pivoting has no effect on the return levers 24, 24a because their respective sensing portions 34, 34a have crawled along the sides 58, 58a of the recesses 40, 40a and slid over the inner periphery of the ring cam 38. The arms 16, 16a of the levers 14, 14a are thus still out of the path of the cams 10, 10 a.

As already indicated above, the watch also comprises a 24-hour local time display. Therefore, when adjusting the positions of the hour and minute hands, the 24 hour indication value must also be adjustable. The 24-hour display device therefore comprises an intermediate wheel 60 driven by the watch movement, this intermediate wheel 60 being in mesh with a 24-hour wheel 6b fitted with a cam 10 b. At one point on its profile, the cam 10b has a steep face 12b, indicating the transition from the 24 th hour of the day to the 1 st hour of the following day. The control lever 14b abuts, via its arm 16b, against the profile of the cam 10b and meshes, via its rack 18b, with the 24-hour display wheel 20 b. Similarly, the return lever 24b, which is biased by the spring element 30b, engages the 24-hour display wheel 20b via its rack 28 b. The return lever 24b also comprises a sensing portion 34b, which sensing portion 34b is located in the recess 40b in the normal operating position of the watch (see figure 2). When the control stem 42 is brought to the first extracted position in which the time zone time can be adjusted, the ring cam 38 pivots, and the sensing portion 34b crawls along the side face 58b of the recess 40b and slides over the inner periphery of the ring cam 38. The return lever 24b pivots anticlockwise due to the action of the movement of its sensing portion 34b and causes the control lever 14b to also pivot anticlockwise via the 24 hour display wheel 20. The result is that the arm 16b of the lever 14b is moved out of the path of the cam 10 b.

However, in the first pulled-out position of the control stem 42, rotating the stem 42 in one direction or the other to adjust the time zone time does not affect the 24-hour display. In fact, in its first extracted position, control stem 42 interacts with a relative further gear train, which is not connected to the 24-hour display device. Conversely, in a second extracted position of the control stem, corresponding to the time setting of the watch, the control stem interacts with another gear train associated with the 24-hour display. In the second extracted position of the control stem 42, the 24-hour display device can thus be adjusted without any problem, since the arm 16b of the control lever 14b has been moved out of the path of the cam 10b when said control stem 42 is in its first extracted position.

It goes without saying that the invention is not limited to the embodiments described above and that various simple modifications and variants can be envisaged by the person skilled in the art without departing from the scope of the invention as defined by the appended claims. In particular, it should be clear that when the control stem returns to its intermediate winding position, the ring cams return to their original position, the sensing portions falling back into their respective recesses. The return lever pivots the display wheel due to the action of the movement of the sensing portion, and the control lever returns to abut against the cam thereof. In the adjustment phase, the cam has been rotated and the lever will abut the cam at a different location than the one it abutted before the adjustment, so that the adjustment made will be taken into account by the display device.

Claims (15)

1. Timepiece comprising a bidirectional adjustment mechanism for a display of a time-related quantity, the display being actuated by a control lever (14) which is itself controlled by a cam (10), the control lever (14) abutting against the cam (10), characterized in that it comprises an adjustment member (36) actuated by a control stem (42), the adjustment member (36) moving the control lever (14) out of the path of the cam (10) via a return lever (24) during an adjustment phase of the display, said control lever (14) normally abutting against the cam (10) during a normal operating phase of the timepiece (3).

2. Timepiece according to claim 1, wherein the return lever (24) causes the control lever (14) to abut against the cam (10) in addition to the adjustment period of the display device.

3. Timepiece according to claim 1 or 2, characterised in that the control lever (14) comprises an arm (16) and a first rack (18), the control lever bearing against the cam (10) via the arm (16) and the control lever engaging with a display part (20) of the display device via the first rack (18); the return lever (24) includes a second rack (28) and a sensing portion (34), the return lever engages with the display member (20) via the second rack (28), and the return lever abuts against the adjustment member (36) via the sensing portion (34).

4. Timepiece according to claim 3, wherein the adjustment member (36) is pivotable.

5. Timepiece according to claim 4, wherein the adjusting member (36) is a ring cam (38) actuated by a control stem (42), the sensing portion (34) abutting against the profile of the ring cam (38).

6. Timepiece according to claim 5, characterised in that the annular cam (38) has, in at least one portion of its profile, a recess (40), in which recess (40) the sensing part (34) is located outside during adjustment of the display device; the recess (40) has a side face (58) along which the sensing portion (34) crawls and then slides over the inner periphery of the ring cam (38) during an adjustment phase of the display device.

7. Timepiece according to claim 4, wherein the control stem (42) is kinematically connected to the ring cam (38) via a motion conversion element (44), the motion conversion element (44) converting the linear motion of the control stem (42) into a pivoting motion of the ring cam (38).

8. Timepiece according to claim 7, wherein the movement conversion element (44) pivots about an axis (46) and comprises a first pin (48) and a second pin (50), the movement conversion element being connected to the control stem (42) via the first pin (48) and the movement conversion element being connected to the ring cam (38) via the second pin (50).

9. Timepiece according to claim 8, wherein the first pin (48) projects into a groove (52) provided on the control stem (42); the second pin projects into an elongated hole (54) provided in the ring cam (38).

10. Timepiece according to claim 4, including a calendar driving wheel (2) fitted with a finger (4) which drives a calendar wheel (6) fitted with a calendar cam (10) via the finger (4) at a rate of one step per day, the calendar driving wheel (2) itself being driven by an intermediate wheel (1), the intermediate wheel (1) being driven by a movement, the forward movement of the calendar wheel (6) being transmitted to a date display wheel (20) via a lever (14) abutting against the calendar cam (10).

11. Timepiece according to claim 10, wherein the calendar cam (10) has a steep face or step (12) which marks the transition from "31 days" to "1 day".

12. Timepiece according to claim 4, further comprising a day drive wheel (2a) fitted with a finger (4a) for the day, said day drive wheel (2a) driving a day wheel (6a) fitted with a day cam (10a) via the finger (4a) at a rate of one step per day, said day drive wheel (2a) itself being driven by an intermediate wheel (1), the intermediate wheel (1) being driven by a movement, the forward movement of the day wheel (6a) being transmitted to the day display wheel (20a) via a lever (14) abutting against the day cam (10 a).

13. Timepiece according to claim 12, wherein the day cam (10a) has a steep face or step (12a) which marks the transition from sunday to monday.

14. Timepiece according to claim 4, characterised in that the 24-hour cam (10b) is carried by a 24-hour wheel (6b), the 24-hour wheel (6b) being driven by an intermediate wheel (60), the intermediate wheel (60) itself being driven by the watch movement, the forward movement of the 24-hour wheel (6b) being transmitted to the 24-hour display wheel (20b) via a lever (14) abutting against the 24-hour cam (10 b).

15. Timepiece according to claim 14, wherein the 24-hour cam (10b) has a steep face (12b) which marks the transition between 24:00 and 01: 00.