HK1128776B - Drive mechanism for a timepiece calendar date display - Google Patents

Description

Driving mechanism for a timepiece calendar display

Technical Field

The invention concerns a driving mechanism for a day of the month display of a timepiece comprising a first indicator and a second indicator to which are respectively affixed digits representing the ones and tens of said day of the month, these indicators being driven by a programmed wheel set. The program wheel set carries a day of the month wheel comprising thirty-one teeth, which wheel is in turn driven by a lever beak to move forward by one step, a calendar number being changed.

Background

The mechanisms briefly described in the preceding paragraphs are well known in the art. This mechanism is mounted on a timepiece called a large calendar timepiece in which the day of the month is displayed through a large window provided on the timepiece dial. The display size of the date is larger than the size printed on a separate ring that makes one less revolution and moves by about 11.5 degrees per day.

The first and second indicators, respectively representing the units and tens of the day of the month, are driven by a programmed wheel set as described in document WO 01/77756. The wheel set is arranged to drive the first indicator one step at the end of each day, except at the end of the thirty-first day when it is not driven, and to drive the second indicator one step at the end of the ninth, nineteenth, twenty-ninth and thirty-first days of the month.

The program wheel set has a day of the month wheel with thirty-one teeth, which is driven in a known manner by a beak of a lever, which is in turn controlled by the drive mechanism of the timepiece, or by a manually actuated push-button when it is felt that the date needs to be corrected. In both cases, the change of date occurs when the beak of a lever controlled manually or by a drive mechanism is inserted between two teeth of the day of the month wheel and causes the day of the month wheel to advance one step.

Once the function is completed, the beak is withdrawn from the toothing of the wheel, thanks to the action of a return spring acting on the lever.

One of the main drawbacks of this constructive arrangement is the risk of overspeed (hunting) of one of the indicators. In fact, when the date correction is made by means of the push-button, the force manually exerted on the push-button is not constant, but depends on the force with which the push-button is pushed. The day of the month wheel, together with the programme wheel set associated with it, can drive either a tens indicator or a units indicator, which may advance by two units or only one unit, due to the inertia of the indicator itself exceeding the required rotation angle of a single step. This risk exists for the tens indicator if the correction is made on the ninth, nineteenth, twenty-ninth, and thirty-first days of the month, and for the units indicator if the correction is made on the thirty-first day of the month. This can lose synchronism between the two indicators, which can only be restored by opening the watch to restore the sequence.

In order to avoid the drawbacks described in the preceding paragraph at least when transitioning from twenty-nine days to thirty days and then from thirty days to the first day of the following month, the document WO 01/77756 cited above employs a ratchet and two pins that prevent one or the other indicator from overspeeding. Such a system is relatively complex and requires additional components, thus increasing the price of the timepiece.

Disclosure of Invention

The invention prevents one or the other indicator from overspeeding regardless of the change of day of the month and without adding any additional component to the timepiece. To this end, the drive mechanism of the day of the month display, in addition to complying with the description of the first paragraph of the present description, is also characterized in that, between each change of day of the month, the beak of the lever engages between the first and second teeth of the day of the month wheel; and, at a change of day of the month, the beak is initially disengaged from the first and second teeth and then falls between the second and third teeth of the wheel and thus drives the wheel one step forward.

Drawings

The invention will be described in detail on the basis of the following description, which is illustrated by way of example in the accompanying drawings and given by way of one embodiment, in which:

figure 1 shows the configuration of the mechanism according to the invention between each change of day of the month,

FIG. 2 shows the configuration of the mechanism according to the invention at the beginning of the change of day of the month, said change being due to the action exerted on the correction button,

figure 3 shows the configuration of the mechanism according to the invention at the beginning of a change of day of the month, said change being due to the action exerted by the timepiece movement, an

Fig. 4 shows the configuration of the mechanism according to the invention at the end of each change of day of the month.

Detailed Description

The day of the month display drive mechanism is shown in the previously listed figures. Such a day of the month display comprises two indicators. The first indicator 1 displays the units 3 of the day of the month and the second indicator 2 displays the tens 4 of said day of the month. Indicators 1 and 2 are mounted coaxially with each other and the tens indicator is mounted inside the units indicator. The date is displayed through a large aperture provided on the watch dial, the indicators 1 and 2 being driven by the program wheel set P.

The program wheel set 8 drives the first indicator 1 of the unit 3 one step at the end of each day, except at the end of the thirty-first day when it is not driven. Thus, fig. 3 and 4 show that the units indicator 1 has a star 25(star), which star 25 has 10 branches 26 which mesh with a wheel 27 comprising thirty teeth 28, which wheel 27 is fixed on the program wheel set P. Wheel 27 has a space 29 without teeth so that indicator 1 of units 3 is not driven when the date goes from the thirty-first day of the end of the month to the first day of the following month, the number 1 remaining stationary and therefore usable for two days.

The program wheel set 8 is also arranged to drive the second indicator 2 of the tens 4 one step at the end of the ninth, nineteenth, twenty-ninth and thirty-first days of the month. The figure thus shows that indicator 2 of the tens 4 has a pinion 30, which pinion 30 has 4 branches 31, which branches 31 mesh with one of four lugs 32 fixed to the program wheel set 8, which lugs are arranged on wheel set 8 to drive indicator 2 of the tens 4 one step forward at the end of the date mentioned.

The figure also shows that the program wheel set 8 carries a day of the month wheel 9 having thirty-one teeth 10, these teeth 10 being evenly distributed around wheel 9. The day wheel 9 in this month is in turn driven by beak 15 of lever 16. In the embodiment shown in the figures, the return spring 17 acts on the lever 16, the lever 16 pivoting about an axis 18.

Fig. 1 shows the configuration of the drive mechanism between each change of day of the month. According to the inventive idea of the present invention, this is a rest position, in which beak 15 of lever 16 engages between first tooth 11 and second tooth 12 of day of the month wheel 9. This arrangement has the first distinct advantage of locking the mechanism so that it is insensitive to shocks that may be applied to the timepiece, which might inadvertently rotate the day of the month wheel during the period between date changes. This arrangement is therefore a departure from the arrangement normally adopted in the prior art, in which the beak of the toothing of the wheel 9 is released, so that insensitivity to shocks can only be ensured by one jumper spring 34 acting on the toothing. The engagement of beak 15 with the toothing of the day of the month wheel is ensured by the force of a return spring 17 pressing on lever 16. As shown in fig. 1, the date displayed is 24 days.

Fig. 2 shows the configuration of the drive mechanism at the beginning of the change of day of the month due to the action exerted on the correction button. In this figure, the push button itself is not shown, but the stem 21 connected to the push button is shown. The stem is biased by a spring 35. Fig. 2 shows beak 15 of lever 16 manually disengaged from day of the month wheel 9 to correct the date. This release is achieved by the stem 21 of the push button. The stem 21 cooperates with a driving pin 22 mounted on the lever 16 and rotates said lever clockwise when the stem 21 is moved in the direction of the arrow B, the movement of the stem being effected by a manual action exerted on a push-button connected to the stem. Consequently, beak 15 of lever 16 is now disengaged from first tooth 11 and second tooth 12 and is opposite second tooth 12 and third tooth 13 of day of the month wheel 9. As shown in fig. 2, the displayed date is still 24 days.

Fig. 3 shows the configuration of the drive mechanism at the beginning of the change of day of the month due to the action exerted by the timepiece movement. This is a change in day of the month such as occurs at the end of each day. Here beak 15 of lever 16 is disengaged from day of the month wheel 9 by a cam 19 driven by the timepiece movement, this cam 19 making one revolution every twenty-four hours when rotating in the direction of arrow a and cooperating with a finger 20 provided on lever 16. As in the previous case, the beak of the lever is disengaged from the first tooth 11 and the second tooth 12 and is opposite the second tooth 12 and the third tooth 13 of the day of the month wheel 9. As shown in fig. 3, the displayed date is still 24 days.

Fig. 3 also shows that the cam 19 has a first rising section (sector)23 with a smaller inclination. When cam 19 rotates in the direction of arrow a, finger 20 of lever 16 is actuated by climbing over this first sector 23, rotating lever 16 clockwise to release its beak 15 from the toothing of day of the month wheel 9. As shown in fig. 3, the release is maximized when the top of finger 20 reaches the end of first section 23.

Fig. 4 shows the configuration of the drive mechanism at the end of a change of day of the month. Fig. 4 shows that beak 15 has fallen between second tooth 12 and third tooth 13 of day of the month wheel 9, which has made said wheel rotate clockwise and indicator 1 of unit 3 has advanced by one step, when said indicator has been shifted from 4 to 5, the displayed date having been shifted from 24 to 25 days. The change of the day of the month is effected manually by releasing the pressure exerted on the push-button, or mechanically by a timepiece movement at the end of the day.

Fig. 4 shows that stem 21 has returned to its rest position in the direction of arrow C by releasing the manual pressure exerted on the push-button, said return being effected by return spring 35. At this point, lever 16, biased by spring 17, rotates in the anticlockwise direction and its beak 15 comes to rest between second tooth 12 and third tooth 13 of wheel 9, thus rotating said wheel one step as described above.

Thus, the change of day of the month by the correction button does not occur when the button is pressed, but occurs when the button is released. This is the core of the invention, i.e. the actuating force exerted on the day of the month wheel to drive it one step forward comes only from the return spring 17 and no longer from the manual force exerted on the push-button. This manual force is not controllable and therefore not constant, whereas the force of the spring is completely constant and adjustable. As explained in the opening part of the present description, the manual force exerted on the push-button may cause one or the other indicator to overspeed during the date correction and cause one indicator to lose synchronism with respect to the other, which means that the timepiece must be opened to restore this synchronism. According to the invention, an indicator overspeed is not possible, since the force exerted by the return spring on the lever to effect the change of the day of the month is fully controllable and adjustable to prevent any possible overspeed.

Fig. 3 also shows that the cam 19 has a second descending section 24 arranged substantially radially with respect to the axis of rotation 25 of the cam. Second sector 24 has an empty zone in which finger 20 will fall as soon as the cam continues to rotate in the direction of arrow a, i.e. at the moment of the day of the month change. The dropping of finger 20 into said empty region of the cam causes instantaneous rotation of lever 16 in the anticlockwise direction and the interposition of beak 15 between second tooth 12 and third tooth 13, thus causing instantaneous forward movement of the day of the month wheel. Thus causing a momentary change in one or the other indicator. To the best of the applicant's knowledge, no one has proposed instantaneous transition of the day of the month at midnight in a large calendar display timepiece comprising a trailing or semi-instantaneous mechanism that requires tens of minutes in order to pass from one date to another.

Claims (5)

1. A drive mechanism for an intra-month date display for a timepiece, comprising a first indicator (1) and a second indicator (2) to which are affixed the digits representing the units (3) and tens (4) of the intra-month date, respectively, these indicators being driven by a program wheel set (8) which itself carries an intra-month date wheel (9) having thirty-one teeth (10), which in turn is driven by a beak (15) of a lever (16) to move it one step forward during an intra-month date change, wherein the beak (15) of the lever (16) engages between a first tooth (11) and a second tooth (12) of the intra-month date wheel (9); -said beak (15) is initially disengaged from said first tooth (11) and second tooth (12) and then falls between the second tooth (12) and third tooth (13) of said wheel (9) at the time of a day of the month change, so as to move said day of the month wheel one step forward, characterized in that said beak (15) of said lever (16) can be manually disengaged from the day of the month wheel (9) by means of a push-button (21) to correct the date displayed by the timepiece, said push-button (21) cooperating with a pin (22) provided on the lever (16) to move the day of the month wheel (9) one step forward.

2. Mechanism according to claim 1, characterized in that the program wheel set (8) is arranged to drive the first indicator (1) one step at the end of each day, except at the end of the thirty-first day when the first indicator is not driven; and, the second indicator (2) is driven one step at the end of the ninth, nineteenth, twenty-ninth and thirty-first days of the month.

3. Mechanism according to claim 1, characterized in that said lever (16) is pivoted about an axis (18); between each change of day of the month, beak (15) of said lever (16) is engaged and held between first tooth (11) and second tooth (12) of day of the month wheel (9) by the force of a return spring (17) pressing on said lever (16).

4. Mechanism according to claim 3, characterized in that at the end of each day beak (15) of said lever (16) is disengaged from the day of the month wheel (9) by means of a cam (19) driven by the timepiece movement, which cooperates with a finger (20) provided on the lever (16) to move the day of the month wheel (9) one step forward.

5. Mechanism according to claim 4, characterized in that said cam (19) has a first rising sector (23) with a small inclination, said first rising sector being climbed by a finger (20) of said lever (16) before the day of the month changes; the cam (19) also has a second descending sector (24) arranged substantially radially with respect to the axis of rotation (25) of the cam, the second descending sector (24) having an empty zone into which the finger falls upon a change of day of the month to rotate the lever, so that the lever instantaneously moves the day of the month wheel one step forward.