EP3542226B1 - Clutch system for chronograph - Google Patents

Description

Technical area

The present invention relates to the field of watchmaking. It relates more particularly to a clutch system for a chronograph mechanism.

State of the art

The clutches commonly used in chronographs are typically of two types, namely horizontal clutches and vertical clutches.

In a horizontal clutch, an intermediate mobile is mounted to tilt in the plane of the movement in order to kinematically connect an input mobile, driving, and an output mobile, driven. The input mobile is typically the wheel on the field, integral in rotation with the seconds mobile of the watch movement, and the output mobile is typically the chronograph wheel, integral in rotation with the chronograph seconds hand.

Depending on the angular position of a rocker which carries the intermediate mobile, the input mobile and the output mobile are kinematically connected (engaged state), or this connection is broken because the intermediate mobile is out of range of the mobile. exit (disengaged state). The position of the rocker is typically controlled by means of a column wheel, a shuttle, a cam or similar control means.

This type of clutch is thin and allows the construction of relatively thin chronograph mechanisms. However, since the intermediate mobile and the output mobile each carry a toothing, the tolerances necessary for the proper functioning of the clutch generate a gearing frenzy. This frolic can cause wiggling of the associated display unit, in the absence of other compensatory measures such as the deliberate introduction of friction in the system, for example by means of a friction spring. Furthermore, there is a risk that the top of a tooth of the intermediate mobile comes into contact with a flank of a tooth of the output mobile when the clutch is brought into its engaged state, which results in the The chronograph seconds hand jumps at a certain angle in either direction when the chronograph is started.

In order to minimize the probability of this jump taking place and to reduce its amplitude when it arrives, the intermediate mobile typically comprises a pointed triangular toothing, the output mobile also comprising the same type of toothing, but even finer. Usually, the pitch of the teeth of the output mobile is for example half, or a third, of that of the intermediate mobile.

In order to prevent the chronograph seconds hand from jumping inadvertently as described above, the vertical clutch has been proposed. In this type of clutch, the kinematic connection between the input and output moving parts is effected by means of a pair of friction discs, which are coaxial and which are subjected to a restoring force tending to bring them into contact. mutual by one of their plane faces. In the engaged state, the torque is transmitted between the input mobile and the output mobile by the friction between these friction discs. This kinematic friction linkage eliminates any clutch gearing.

To break the kinematic link and stop the chronograph, a clamp, typically controlled by a column wheel, allows the friction discs to be separated by means of wedge surfaces which are interposed between said discs. By removing these shims, the friction discs fall back on each other, and the kinematic connection is reestablished.

Since there is no penetration of one toothing into another when the vertical clutch is actuated, any untimely jump of the chronograph seconds hand is avoided. However, such a vertical clutch requires a lot of space in the height of the mechanism in order to fit several toothed wheels, the friction discs as well as their return springs, in a coaxial manner. In order to overcome these drawbacks, the document EP1437633 proposed a horizontal clutch which tries to avoid any untimely jump, in which the teeth of the intermediate mobile and of the output mobile are shaped so that no contact between the top of a tooth of the intermediate mobile and the inactive side of the output mobile is is mathematically possible. In fact, in the worst case, that is to say when the tops of two teeth come into direct contact during engagement, the inactive sides of the teeth of the output mobile follow the epicyclic path of the top of a tooth of the intermediate mobile. Consequently, it is in principle impossible for the activation of the clutch to cause an untimely jump behind the output mobile. For reference, the documents EP2251747 and WO2015 / 173372 also reveal the same shape of teeth.

However, this solution requires that the shape of the teeth, as well as the adjustment of the mechanism, are mathematically near-perfect, which is difficult to control during manufacture. Furthermore, any wear of the intermediate mobile and / or of the output mobile will adversely affect this perfect shape, and therefore the risk of an untimely jump will increase over time. This solution, however, does nothing to solve the wiggle problem mentioned above, since in practice a tolerance must still be present to ensure a functional interaction between the teeth of the gear. The introduction of friction into the system, by means of a friction spring for example, therefore remains necessary for this purpose.

The document EP2085832 proposes another variant of a horizontal clutch avoiding any wiggling and any untimely jump, in which the torque is transmitted between the input mobile and the output mobile via three elastic arms extending from a hub towards a cylindrical friction surface. When the ends of these elastic arms bear against this cylindrical surface, which is the internal wall of a hollow cylinder, the transmission of torque between the hub and said surface is ensured by friction, which eliminates any fretting of gearing. In order to disengage the clutch, the ends of the elastic arms are provided with pins which extend perpendicularly to the arms, and which take place in cam tracks formed in a control wheel. In pivoting this control wheel relative to the elastic arms in a first direction, the ends of the latter can be moved away from said cylindrical surface, and brought back into contact with the latter when the control wheel pivots in the direction opposite to the first.

This construction is nevertheless very complex, and is not compatible with standard movements, thus requiring a dedicated construction.

The aim of the invention is therefore to provide a clutch system for a chronograph in which the aforementioned drawbacks are at least partially overcome.

Disclosure of the invention

More specifically, the invention relates to a clutch system for a chronograph mechanism, as defined by the independent claim. This system comprises an input mobile intended to be driven by a driving member, such as a barrel, a motor or the like, an output mobile intended to drive at least one display member such as a second hand of chronograph, as well as an intermediate mobile.

This intermediate mobile is in permanent kinematic connection with a first mobile chosen from among said input mobile and said output mobile, typically the input mobile, but the reverse arrangement is also possible. The intermediate mobile is mounted so that it can move between an engaged state in which said input mobile is in kinematic connection with said output mobile and the chronograph is operating, and a disengaged state in which said kinematic connection is broken and the chronograph is stopped.

According to the invention, the clutch further comprises a first friction wheel integral in rotation with said intermediate mobile, and a second friction wheel integral in rotation with a second mobile chosen from said input mobile and said output mobile, this second mobile being the mobile opposite said first mobile, therefore typically the output mobile. These friction wheels are at least partially coplanar, that is to say they are located at least partially in the same plane, and are arranged to transmit a rotation between said intermediate mobile and said second mobile, or vice versa depending on the arrangement chosen, when said intermediate mobile, and therefore said clutch system, is in the engaged state.

The clutch further comprises a first safety wheel integral in rotation with the intermediate mobile, which comprises a first safety toothing, and a second safety wheel integral in rotation with said second mobile, which comprises a second safety toothing. These safety teeth are shaped so as to interpenetrate each other when said intermediate mobile is in the engaged state.

Since the rotation between the intermediate mobile and the second mobile is effected by friction between the friction wheels instead of meshing between teeth, no wiggling of the output wheel (and therefore of an associated indicating member) occurs when the chronograph is started. Furthermore, since the overall construction resumes that of a conventional horizontal clutch, the clutch system of the invention can be easily integrated into a standard movement, without (or with little) modification.

Advantageously, the intermediate mobile is pivotally mounted on a rocker controlled by an elastic element. The use of an elastic element to control the rocker makes it possible to predetermine the contact force between the friction wheels, and thus to optimize it.

Advantageously, the elastic element is carried by a control lever, which can, for example, be controlled by a control member such as a column wheel, a shuttle or a cam, and which comprises stops arranged so as to prevent the intermediate moving body (and thus the clutch system) from changing state during an impact. The control lever therefore defines a limit for the displacement of the intermediate mobile in each of its states, which prevents unwanted angular displacements of the output mobile in the disengaged state, and avoids breaking the kinematic link when the intermediate mobile is in the engaged state.

Advantageously, the elastic element comprises a free end which interacts with said rocker in order to control it, said stops being located on either side of the free end. Therefore, in the event of a shock, the free end of the elastic element, which may for example take the form of a fork, comes into contact with one of these stops. A simple and compact arrangement is thus proposed.

Advantageously, one of said stops is arranged to prevent said intermediate mobile and said second mobile from interacting during an impact when said intermediate mobile is in its disengaged state, the other of said stops being arranged to prevent said safety teeth can go out of range of each other during an impact when said system is in its engaged state.

The system may further comprise a return meshing on the one hand with said first mobile and on the other hand with said intermediate mobile. This reference can, where appropriate, include a backlash adjustment toothing.

Advantageously, the safety teeth include each of the teeth having a width of at most a quarter, preferably at most a fifth, of the pitch of said toothing, measured at the maximum depth of interpenetration of said safety teeth. The probability that the teeth will abut against each other when starting the chronograph is thus reduced, and the size of the jump, if there is any, is minimized since the safety teeth are relatively thin. .

Said first mobile can be said input mobile and said second mobile can be said output mobile. In this case, advantageously, the upstream sides of the first safety wheel as well as the downstream sides of the second safety wheel are curved. Therefore, in the case where a tooth of the first safety wheel abuts against a tooth of the second safety wheel, a slight additional acceleration of the second mobile can occur before the kinematic friction connection is established. This acceleration is less visible to a user than a jump. In the opposite case, that is to say if the first mobile is the output mobile and the second mobile is the input mobile, the upstream sides of the second safety wheel, as well as the downstream sides of the first safety wheel, can be curved with the same effect.

The invention also relates to a timepiece movement comprising a chronograph mechanism provided with a clutch system as described above, as well as a timepiece comprising such a movement.

Brief description of the drawings

• Figure 1 est une vue isométrique d'un système d'embrayage selon l'invention en état débrayé ;
• Figure 2 est une vue isométrique du système d'embrayage de la figure 1 en état embrayé ; et
• Figure 3 est une vue en plan du mobile intermédiaire et du mobile de sortie du système de la figure 1, vus de dessous par rapport à l'orientation de la figure 1.

Other details of the invention will emerge more clearly on reading the following description, given with reference to the appended drawings in which:

• Figure 1 is an isometric view of a clutch system according to the invention in disengaged state;
• Figure 2 is an isometric view of the clutch system of the figure 1 in engaged condition; and
• Figure 3 is a plan view of the intermediate mobile and the output mobile of the system of the figure 1 , seen from below in relation to the orientation of the figure 1 .

Embodiment of the invention

The figures 1 and 2 illustrate a clutch system 1 for a chronograph according to the invention, in the disengaged respectively engaged state.

As generally known, the system 1, of the horizontal type, comprises an input mobile 3, arranged to be driven by a basic movement (not illustrated) that comprises the timepiece in which the system 1 is integrated. The input mobile 3 can, for example, be integral in rotation with the mobile of the seconds of said movement, or driven by the latter. Alternatively, another suitable mobile can be used for the same purpose.

The input mobile 3 is in selective kinematic connection with an output mobile 5, which is a chronograph seconds mobile in this case, and which also carries a reset cam 7.

This selective kinematic connection is effected by the intervention of a first intermediate mobile 9, mounted freely in rotation on a rocker 11 and in permanent kinematic connection with the input mobile 3. This rocker 11 also carries a reference 13 which meshes in permanence on the one hand with the input mobile 3, and on the other hand with a toothing 15 that includes the intermediate mobile 9. A pivoting of the rocker can establish or break a kinematic connection between the first intermediate mobile 9 and the output mobile 5. The engaged state respectively disengaged from the intermediate mobile 9 therefore determines the corresponding state of the system of clutch 1.

Alternatively, in a reverse construction, the first intermediate mobile 9 may be in permanent kinematic connection with the output mobile 5, by means of the return 13 similarly to the first variant, a pivoting of the lever thus bringing the first mobile intermediate 9 in kinematic connection with the input mobile. The following description deals with the first of these variants, as illustrated in the figures; the modifications to implement the second variant are within the abilities of those skilled in the art and should not be described in detail.

In the embodiment shown, the gear 13 comprises a slotted-tooth backlash take-up toothing, but a conventional wheel is also possible. It is also conceivable to provide only one intermediate mobile 9, therefore meshing directly with the input mobile 3.

The rocker 11 is mounted to pivot around the same axis of rotation as the input mobile, but a slight offset between the axes of rotation of these elements is admissible.

In order to drive the output mobile 5 when the system 1 is in the engaged state, the intermediate mobile 9 comprises a first friction wheel 17, which is arranged to come into contact with a second friction wheel 19 which the mobile comprises. 5. The materials of the friction wheels as well as their finish (presence of layers, roughness, etc.) can be chosen according to the needs of the watchmaker to ensure torque transmission with an appropriate contact force.

This contact force is provided by an elastic element 21, which also controls the rocker 11, as will appear more clearly below.

The elastic element 21 is a leaf spring carried by a control lever 25, mounted to pivot about an axis of rotation 29 and subjected to a return force by means of an elastic return element 31 which tends to rotate counterclockwise (according to the orientation of the figures), and so in maintaining its tail 33 in contact with the column wheel 27. The latter controls the control lever 25 in a conventional manner. Alternatively, the control lever 25 can be controlled by a shuttle system, a cam, or the like.

The free end of the elastic element 21 has a fork 35, which interacts with a tenon 23 located at an end remote from the pivot axis 29 of the control lever 25. When the control lever 25 is rotated clockwise under the control of the column wheel 27, the resilient member applies a force which rotates the rocker 11 counterclockwise. The friction wheels 17, 19 therefore come into contact with one another, and the input mobile 3 is thus in kinematic connection with the output mobile 5 (see figure 2 ). The elastic element 21 provides the force necessary to keep the friction wheels 17, 19 in contact with one another, and to generate the radial force necessary to ensure the good transmission of torque without slipping.

From the component orientation shown on the figure 2 , when the column wheel 27 rotates by one step, the elastic return element 31 rotates the control lever 25 counterclockwise, and the elastic element 21 rotates the rocker 11 so that the first wheel friction wheel 17 moves away from the second friction wheel 19. The components thus return to their position shown in the figure. figure 1 , and the kinematic link between the input mobile 3 and the output mobile 5 is broken.

In comparison with the force required to maintain the gear between the teeth of the intermediate mobile and the output mobile in a conventional horizontal clutch, that provided by the elastic element 21 of the present invention is relatively low.

In order to make the system 1 insensitive to shocks despite the relatively weak force exerted between the friction wheels 17, 19, several arrangements are provided.

First, at the level of the intermediate mobile 9 and the output mobile 5, respective safety wheels 37, 39 are provided. These safety wheels 37, 39 are visible on an enlarged scale on the figure 3 , in which their orientation is reversed with respect to that of figures 1 and 2 .

A first safety wheel 37 comprising a first safety toothing is integral in rotation with the intermediate mobile 9, and a second safety wheel 39 comprising a second safety toothing is integral in rotation with the output mobile 5. These teeth are shaped as such. so that during normal operation of the clutch they do not come into contact with each other. There is therefore no meshing between these wheels 37, 39, and they do not contribute to the transmission of torque between the intermediate mobile 9 and the output mobile 5 during normal operation of the clutch system 1.

As such, when the clutch is in disengaged condition (see figure 1 ), these teeth are out of reach of each other. When the clutch is in the engaged state (see figures 2 and 3 ), the teeth of these teeth interpenetrate, and are therefore within reach of each other.

During an impact which moves the output mobile 5 angularly relative to the intermediate mobile 9, the safety teeth interact in order to limit this angular displacement. This movement is thus limited to the angle traversed until a tooth of the first safety toothing comes into contact with a tooth of the second safety toothing. The pitch of these teeth being low, the user will not notice this slight displacement of the chronograph seconds hand.

The shape of the teeth of the safety teeth is also particular, since the teeth do not participate in the transmission of torque, and only serve as stops in the event of an impact. In fact, during normal operation of the system 1, they do not mesh according to the usual use of the term, since they interpenetrate freely and without contact or transmission of torque. The teeth are therefore relatively thin compared to their length. In the variant shown in the figures, the width of the teeth is substantially a quarter of the pitch of said toothing, measured at the maximum depth of interpenetration.

The tops of the teeth are pointed and asymmetrical; considering the first safety wheel 37, the downstream faces of its teeth are substantially oriented radially, while the upstream faces of said teeth have a curvature. The teeth of the second wheel safety 39 have the opposite shape, so that, if the toothings abut in the direction of rotation of operation, the most curved respective flanks interact, the less curved respective flanks interacting in the case of an impact causing a rotation of the mobile of exit in the opposite direction.

The small width of the teeth minimizes the likelihood of the teeth interacting during a system 1 engagement, and minimizes the jump when it occurs. In addition, the asymmetric shape chosen for the safety teeth promotes a "jump" forward. In the case of such an interaction, the upstream curved face of one tooth slides on the curved face of the other until the friction wheels 17, 19 act again to drive the output mobile 5 This interaction of the safety gears generates a slight momentary, imperceptible acceleration of the chronograph seconds hand and not a visible jump when the chronograph is started. A noticeable untimely jump is thus eliminated. It should be noted here that the "inactive" sides of the teeth in the sense of the patent EP1437633 , that is to say the downstream sides of the teeth of the first safety wheel 37 and the upstream sides of the teeth of the second safety wheel, are very steep, and extend in an essentially radial direction. However, other forms of toothing are also possible.

The elastic element 21 is relatively weak in order to be able to absorb all the manufacturing imperfections such as bad rounds, inaccurate positioning of the pivots etc. and to minimize the stresses exerted on them. The first friction wheel 17 is therefore pressed less strongly against the second friction wheel 19 than with conventional toothings, and there is therefore also a risk that an impact could angularly displace the lever 11 from its normal position. Without the provision of the safety means described below, this movement could for example momentarily interrupt the kinematic connection in the engaged state, or could create a transient kinematic connection between the intermediate mobile 9 and the output mobile 5 in the disengaged state. the clutch.

In order to avoid this risk, the control lever 25 also comprises a first safety arm 41 and a second safety arm 43 located on either side. on the other side of the fork 35 at the end of the elastic element. These safety arms 41, 43 are integral in rotation with the control lever 25, and each serve as a stop for the fork 35 in the event of an impact.

The first safety arm 41 is positioned and formed such that, in the disengaged state ( figure 1 ), it is impossible for the teeth of the first safety wheel 37 to be within reach of those of the second safety wheel 39. In other words, the fork 3 abuts against the first safety arm before these teeth can interact. .

Likewise, the second safety arm 43 is positioned and shaped such that, in the engaged state ( figure 2 ), it is impossible for the teeth of the two safety wheels 37, 39 to go out of reach of each other. In this case, the delay of the seconds hand generated by a shock which would break the kinematic connection is limited to the arc traversed until a tooth of the first safety wheel abuts against a tooth of the second wheel of security. Then, a fraction of a second later, the friction wheels 17, 19 will reestablish their kinematic connection under the effect of the elastic element 21, and the drive of the output mobile 5 by continuous friction as described above.

In such a case, although the indication of the timed seconds has been shifted by a fraction of a second in either direction, it is unlikely that the user will perceive it as a result of the shock.

Although the invention has been described in connection with a particular embodiment, variations are possible without departing from the scope of the invention as defined by the appended claims.

Claims (12)

1. Coupling system (1) for a chronograph mechanism, said system (1) comprising:

   - an input wheel (3) intended to be driven by a drive member;

   - an output wheel (5) intended to drive at least one display member;

   - an intermediate wheel (9) continuously kinematically connected to a first wheel (3; 5) chosen from said input wheel (3) and said output wheel (5), said intermediate wheel (9) being mounted so that it can change between a coupled state in which said input wheel (3) is kinematically connected to said output wheel (5) and an uncoupled state in which said kinematic connection is broken;

   characterized in that said system (1) further includes:

   - a first friction wheel (17) constrained to rotate with said intermediate wheel (9) and a second friction wheel (19) constrained to rotate with a second wheel (5; 3) chosen from said input wheel (3) and said output wheel (5), said friction wheels (17, 19) being at least partially coplanar and being adapted to transmit rotation between said intermediate wheel (9) and said second wheel (5; 3), or vice versa, when said system (1) is in the coupled state;

   - a first safety wheel (37) constrained to rotate with said intermediate wheel (9) and comprising a first set of safety teeth and a second safety wheel (39) constrained to rotate with said second wheel (5; 3) and comprising a second set of safety teeth, said sets of safety teeth being conformed in order to interpenetrate mutually when said intermediate wheel (9) is in the coupled state.
2. System (1) according to the preceding claim, in which said intermediate wheel (9) is mounted to pivot on a lever (11) controlled by an elastic element (21).
3. System (1) according to Claim 2, in which said elastic element (21) is carried by a control lever (25) including abutments (41, 43) adapted to prevent said intermediate wheel (9) from changing state in the event of an impact.
4. System (1) according to Claim 3, in which said elastic element (21) comprises a free end (35) that is adapted to interact with said lever (11), said abutments (41, 43) being situated on respective opposite sides of said free end (35).
5. System (1) according to either one of Claims 3 and 4, in which one of said abutments (41) is adapted to prevent said intermediate wheel (9) and said second wheel (5; 3) being able to interact in the event of an impact when said intermediate wheel (9) is in its uncoupled state, the other of said abutments (43) being adapted to prevent said sets of safety teeth being able to move out of reach of one another in the event of an impact when said intermediate wheel (9) is in its coupled state.
6. System (1) according to any one of the preceding claims, further comprising an intermediate gear wheel (13) meshing on the one hand with said first wheel (3; 5) and on the other hand with said intermediate wheel (9).
7. System (1) according to Claim 6, in which said intermediate gear wheel (13) comprises a set of play compensation teeth.
8. System (1) according to any one of the preceding claims, in which said sets of safety teeth each comprise teeth having a width of at most one quarter, preferably at most one fifth, of the pitch of said set of teeth as measured at the maximum depth of interpenetration of said safety teeth.
9. System (1) according to any one of the preceding claims, in which said first wheel (3; 5) is said input wheel (3) and said second wheel (5; 3) is said output wheel (5).
10. System (1) according to the preceding claim, in which the leading flanks of the first safety wheel and the trailing flanks of the second safety wheel are curved.
11. Timepiece movement comprising a chronograph mechanism provided with a coupling system (1) according to any one of the preceding claims.
12. Timepiece comprising a movement according to Claim 11.

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