CLOCKWORK MECHANISM COMPLETING A DRIVING SPRING ACCOMPANIMENTING WITH A DRIVED SPRING

Description

[0001] The present invention relates to a clockwork mechanism comprising a driving wheel and a driven wheel, said driving wheel being intended to transmit, during at least one shock, at least one impulse to said driven wheel capable of causing the movement of said driven wheel.

[0002] We know of clockwork mechanisms of this kind in which the impulse given by a driving element to a driven element is undesirable, but nevertheless occurs as a result of the mechanism's normal operation, due to a shock that can negatively impact said normal operation. Such a mechanism is, for example, a correction mechanism for an hour hand, preferably arranged to be operated by a winding stem, and comprising a first hour wheel driven by a minute train linked to the wheel carrying the minute hand, and a second hour wheel carrying the hour hand and connected to the first hour wheel by an elastic coupling mechanism. Such a mechanism allows the hour hand to advance by one hour incrementally without moving the minute hand. This allows for very easy time setting, for example, when changing time zones.

[0003] The elastic coupling mechanism comprises a star attached to the first hour wheel, as well as a jumper and its return spring against the star, carried by the second hour wheel. This elastic coupling mechanism allows the first hour wheel to drive the second hour wheel to display the time, while also providing a clutch / disengagement function and selective indexing of the hour hand in one of its twelve angular positions when correcting the hour hand. More specifically, when correcting the hour hand alone, the second hour wheel is actuated by the winding stem so that, as it rotates, the jumper carried by the second hour wheel is lifted by a tooth of the star on the first hour wheel, which remains stationary, and then falls back between two teeth of the star.

[0004] This elastic coupling mechanism is well-known and usually works reliably. However, when the second hour wheel carrying the jumper is configured to drive a high-energy complication, this second hour wheel must exhibit significant torque. Consequently, when correcting the hour hand alone, if the jumper carried by the second hour wheel, which is part of the driving mechanism, falls abruptly onto the star wheel, the impact can unexpectedly deliver an impulse to the star wheel and the first hour wheel attached to it, which together form the driven mechanism. This impulse can accidentally cause a micro-displacement of both the star wheel and the first hour wheel. Repeated impacts of the jumper on the star wheel can therefore lead to accidental micro-displacements of the first hour wheel, which can then be transmitted to the dial via the minute train.This can result in the minute hand moving unexpectedly, especially when the movement is of the friction wheel type. Consequently, the minute hand gradually shifts from its normal position due to the uncontrolled movement of the first hour wheel.

[0005] Document FR 2307301 A1, for example, discloses a time correction mechanism for switching from one time zone to another.

[0006] The present invention aims to remedy these drawbacks by proposing a clockwork mechanism allowing control of the movement of a driven mobile working with a leading mobile, this control meaning preventing any movement of the driven mobile or allowing a predetermined movement of said driven mobile, depending on the destination of said clockwork mechanism.

[0007] For this purpose, the present invention relates to a clockwork mechanism according to claim 1.

[0008] The clockwork mechanism according to the invention comprises a driving wheel and a driven wheel, said driving wheel being intended to transmit, during at least one shock, at least one impulse to said driven wheel capable of causing the movement of said driven wheel.

[0009] According to the invention, the leading mobile and the led mobile are configured to have moments of inertia such that the ratio of the moment of inertia of the led mobile to the moment of inertia of the leading mobile is greater than 0.9, so as to control the movement of said led mobile by the leading mobile.

[0010] Such control of the movement of the driven mobile by the leading mobile makes it possible to stop a planned but undesired impulse of the leading mobile on the driven mobile and thus prevent its propagation to said driven mobile as well as to other components of the mechanism linked to said driven mobile.

[0011] The present invention also relates to a timepiece according to claim 5.

[0012] In the context of the present invention, the term "driving component" refers to the component that, at the moment of impact, is intended to deliver an impulse, as well as, if any, all parts that are rotationally attached to it. The term "driven component" refers to the component that, at the moment of impact, is intended to receive said impulse, as well as, if any, all parts that are rotationally attached to it.

[0013] In the context of the present invention, the impulse, whether intentional or not, is anticipated and occurs during the normal operation of the mechanism. This typically excludes the case of an impulse associated with an accidental shock.

[0014] Other features and advantages of the present invention will become apparent from the following detailed description of an embodiment of the invention, given by way of non-limiting example, and made with reference to the accompanying drawings in which: there figure 1 is a perspective view from below of a clockwork mechanism according to the invention, in the case of a mechanism for correcting an hour hand; and the figure 2 is a top view of the mechanism of the figure 1 the first hour wheel not being shown.

[0015] The present invention relates to a clockwork mechanism comprising a driving wheel working with a driven wheel. More specifically, the driving wheel is capable of cooperating directly with the driven wheel, without an intermediate component, or indirectly, via an intermediate wheel acting as a link.

[0016] The clockwork mechanism according to the invention is such that the driving element is designed to transmit to the driven element, upon impact, by sudden instantaneous contact, and in a foreseen but unintentional manner, at least one impulse such that it could cause an unintended movement of said driven element. Such a mechanism is, for example, a correction mechanism for an hour hand as described above, said mechanism comprising a first hour wheel driven by a minute train connected to the wheel bearing the minute hand and attached to a star wheel, and a second hour wheel carrying the hour hand and connected to the first by an elastic coupling mechanism, said second wheel carrying a jumper cooperating with said star wheel.In this example, when setting the time, the leading mechanism typically includes the second hour wheel as well as the hour hand and the jumper it carries, and the driven mechanism typically includes the first hour wheel and the star it carries.

[0017] In this description, the definition of the leading / driven roles corresponds to the roles of the two moving parts involved at the moment of impact, regardless of their roles when there is no impact. In particular, the leading part is defined as the part that, at the time of impact, is intended to deliver an impulse to the driven part, even though there is a mode of operation that does not generate an impact in which the leading / driven roles can be reversed.

[0018] According to the present invention, the leading mobile and the driven mobile are arranged or configured to have moments of inertia such that the ratio of the moment of inertia of the driven mobile to the moment of inertia of the leading mobile is greater than 0.9, so as to control the movement of said driven mobile.

[0019] Therefore, the driven object has a moment of inertia which is close to, and preferably greater than, or even much greater than, that of the leading object, the ratio of the moments of inertia being chosen so that, during a collision of the leading object on the driven object, a predicted but unintentional impulse of the leading object on the driven object is stopped by the driven object, preventing any unintended movement, its velocity remaining zero or so that a voluntary impulse of the leading object working with the driven object gives said driven object an angular acceleration of a determined value which is only necessary for its movement as predicted by its function.

[0020] Advantageously, the ratio of the moment of inertia of the driven moving part to the moment of inertia of the leading moving part is greater than or equal to 1, preferably greater than or equal to 1.2, preferably greater than or equal to 1.5, preferably greater than or equal to 2, and more preferably greater than or equal to 3. This can be translated for example into a difference between the moment of inertia of the driven moving part and the moment of inertia of the leading moving part greater than or equal to 0 mg*mm 2< preferably greater than or equal to 20 mg*mm 2< , preferably greater than or equal to 50 mg*mm 2< , preferably greater than or equal to 100 mg*mm 2< , and more preferably greater than or equal to 200 mg*mm 2< .

[0021] The ratio of the moments of inertia of the driven / driving moving part as sought according to the invention is obtained in various ways, used alone or in combination: The driving element may have recesses configured to reduce its moment of inertia in order to obtain the desired ratio of the moments of inertia of the driven element to the driving element. For example, the driving element may be a wheel in which recesses, through or not, are provided to reduce its weight. The recesses may be of any shape and / or size adapted to the configuration of the driving element; the driving element may be made of a first material having a density less than 5000 kg / m³, the driven element being made of a material having a density greater than 7000 kg / m³, or the driving element may be made of a first material having a density at least twice that of the driven element, in order to obtain the desired ratio of the moments of inertia of the driven element to the driving element.For example, the leading element can be made of titanium, aluminum, or silicon, while the driven element is made of steel, brass, or gold. In addition to the component intended to receive the impulse, the driven element may include an additional component made of a second material with a density greater than 8000 kg / m³ or at least twice the density of the leading element, so as to obtain the required ratio of the moments of inertia of the driven element to the leading element. This additional component is fixed to the component intended to receive the impulse. For example, the component of the driven element intended to receive the impulse from the leading element can be attached to an additional component made of gold or platinum, and can take the form of weights, for example. In this example, the leading element would be made of brass, nickel silver, steel, aluminum, ruby, or silicon.

[0022] The clockwork mechanism of the present invention is such that the driving mobile comprises a jumper and the driven mobile comprises a star, said jumper being intended to exert on said star, at the moment of impact, a torque greater than 10 g.mm, preferably greater than 40 g.mm, preferably greater than 60 g.mm, preferably greater than 100 g.mm, and more preferably greater than 200 g.mm.

[0023] According to an example of an embodiment of the invention with reference to figures 1 et 2 , the clockwork mechanism of the invention constitutes a correction mechanism for an hour hand 1, preferably arranged to be operated by a winding stem and not a pusher.

[0024] As described in the preamble, this time-setting mechanism, used particularly when changing time zones, allows the hour hand to advance by one hour without moving the minute hand.

[0025] The mechanism 1 comprises a first hour wheel 2 driven by a minute train linked to the wheel bearing the minute hand. These elements, known to those skilled in the art, are neither shown nor described in detail here. The mechanism also includes a second hour wheel 4 carrying the hour hand (not shown) and arranged so that the first hour wheel 2 and the second hour wheel 4 are superimposed and concentric.

[0026] In another variant intended to produce a timepiece comprising two hour hands, namely a first hand to traditionally display home time, and a second hand to display local time which varies according to time zones, the first hour wheel 2 may carry said first hand to indicate home time, the second hour wheel 4 then carrying the hand to indicate local time.

[0027] The second hour wheel 4 is connected to the first hour wheel 2 by an elastic coupling mechanism. In a known manner, the elastic coupling mechanism comprises a twelve-toothed star 6, here fixed to the first hour wheel 2, and a jumper 8 returned against the star 6 by its return spring 10, carried here by the second hour wheel 4. The jumper 8 and its return spring 10 are positioned on the plate of the second hour wheel 4.

[0028] The driving wheel according to the invention comprises the second hour wheel 4 and the driven wheel comprises the first hour wheel 2, driven by the timer gear linked to the wheel housing, the driving / driven roles being the roles of the wheels during the correction of the time, when the second hour wheel 4 is operated by the winding stem for correction and is then likely to generate an impulse on the first hour wheel 2, at the moment of the shock when the jumper 8 falls back on the star 6. Outside of the correction mode and in normal operating mode the second hour wheel 4 is driven by the first hour wheel 2 by the elastic coupling mechanism, which does not generate any shock between the jumper and the star, the driving wheel in the sense of the invention then becoming a driven wheel again.

[0029] In the example shown, the jumper 8 and its spring are carried by the second hour wheel 4 and belong to the driving wheel and the star 6 is attached to the first hour wheel 2 and belongs to the driven wheel.

[0030] According to the invention, the driving and driven parts are configured such that the ratio of the moment of inertia of the driven part to the moment of inertia of the driving part is greater than 0.9, so as to control the movement of said driven part. To this end, in the example shown, the plate of the second hour wheel 4 has various recesses 12 in the form here of three circular sectors and an oblong opening concentric to the axis of the second hour wheel 4 and distributed around the cannon pinion of said second hour wheel 4. It is clear that the recesses can have any other suitable shape and arrangement.

[0031] In this configuration, the second hour wheel 4 is therefore lightened compared to a standard solid board, so that the moment of inertia of the driving wheel is reduced to 288 mg*mm 2< while the driven wheel has a moment of inertia of 273 mg*mm 2< (for example by choosing for the first hour wheel 2 a suitable material or an appropriate embodiment to increase its moment of inertia compared to a standard wheel) so that the ratio of the moment of inertia of the driven wheel to the moment of inertia of the driving wheel is about 0.95.

[0032] Thanks to the mechanism of the invention, any impulse from the jumper 8, carried by the second hour wheel 4 (the driving wheel), to the star 6, which is fixed to the first hour wheel 2 (the driven wheel), has a dampened effect due to the difference in inertia between the two moving parts, the driven and driving parts. This reduces the risk of unwanted movement of the star 6 under dynamic stress during a collision between said star 6 and the jumper 8. Thus, the effect of the jumper 8, carried by the second hour wheel 4, has no influence on the first hour wheel 2, which is fixed to the star 6 and meshes with the minute train. The impulse delivered by the jumper 8 of the driving wheel to the star 6 of the driven wheel is therefore not propagated to the rest of the time-setting mechanism, so that the minute hand does not experience any shift.

Claims

1. Timepiece mechanism comprising a driving mobile (4) and a driven mobile (2), the driving mobile (4) being intended to transmit, in the event of at least one shock, at least one pulse to said driven mobile able to cause said driven mobile (2) to move, the driven mobile (2) comprising a starwheel (6) and the driving mobile (4) comprising a jumper (8) able to exert, on said starwheel (6), in the event of said shock, a torque greater than 10 g.mm, preferably greater than 40 g.mm, preferably greater than 60 g.mm and more preferably greater than 100 g.mm, wherein: - the driving mobile (4) has recesses (12); and / or - the driving mobile (4) is made from a material having a density at least twice lower than the density of the driven mobile (2); and / or - the driven mobile comprises an additional component made from a material having a density at least twice higher than the density of the driving mobile; such that the driving mobile (4) and the driven mobile (2) respectively have moments of inertia such that the ratio of the moment of inertia of the driven mobile (2) to the moment of inertia of the driving mobile (4) is greater than 0.9 so as to control initiation of movement of said driven mobile (2).

2. Timepiece mechanism as claimed in claim 1, characterised in that the ratio of the moment of inertia of the driven mobile (2) to the moment of inertia of the driving mobile (4) is greater than or equal to 1, preferably greater than or equal to 1.2, preferably greater than or equal to 1.5, even more preferably greater than or equal to 3.

3. Timepiece mechanism as claimed in claim 1 or 2, characterised in that it constitutes a mechanism (1) for correcting an hour hand, the driven mobile comprising a first hour wheel (2) driven by a minute going train and the driving mobile comprising a second hour wheel (4) bearing said hour hand and connected to the first hour wheel (2) by a resilient coupling mechanism.

4. Timepiece mechanism as claimed in claim 3, characterised in that the first hour wheel (2) and the second hour wheel (4) are arranged so as to be superimposed concentrically.

5. Timepiece comprising a timepiece mechanism as claimed in any one of claims 1 to 4.