EP3324249A1 - Clutch system for chronograph - Google Patents

Abstract

Clutch system (1) for a chronograph mechanism, said system (1) comprising: - An input mobile (3) intended to be driven by a motor member; - An output mobile (5) for driving at least one display member; - An intermediate mobile (9) in permanent kinematic connection with a first mobile (3; 5) selected from said mobile input (3) and said mobile output (5), said intermediate mobile (9) being mounted so that it can evolve between an engaged state wherein said input mobile (3) is in kinematic connection with said output mobile (5), and a disengaged state in which said kinematic link is broken. According to the invention, said system (1) further comprises: a first friction wheel (17) integral in rotation with said intermediate mobile (9) and a second friction wheel (19) integral in rotation with a second mobile (5; 3) selected from said input mobile (3) and said output mobile (5), said friction wheels (17, 19) being at least partially coplanar and being arranged to transmit rotation between said intermediate mobile (9) and said second mobile (5; 3), or vice versa when said system (1) is in engaged state; a first safety wheel (37) integral in rotation with said intermediate mobile (9) and comprising a first safety toothing, and a second safety wheel (39) integral in rotation with said second mobile (5; 3) and comprising a second safety toothing, said safety toothing being shaped to interpenetrate each other when said intermediate mobile (9) is in engaged state.

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

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

In a horizontal clutch, an intermediate mobile is pivotally mounted in the plane of movement to connect kinematically an incoming mobile, driving, and an output mobile, led. The input mobile is typically the field wheel, 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 seconds hand of the chronograph.

Depending on the angular position of a lever that carries the intermediate mobile, the mobile input 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 of output (disengaged state). The position of the rocker is typically controlled via a column wheel, a shuttle, a cam or similar control means.

This kind of clutch is thin and can build relatively thin chronograph mechanisms. However, since e mobile intermediate and the output mobile each have a toothing, the tolerances necessary for the proper functioning of the clutch generate a gearing. This frolicking can cause wriggling of the associated display member, in the absence of other compensation 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 has the result that the chronograph seconds hand jumps from a certain angle in either direction when the chronograph starts.

In order to minimize the probability that this jump takes place and to reduce its amplitude when it arrives, the intermediate mobile typically has a pointed triangular toothing, the mobile output also having the same type of teeth, but even thinner. Usually the pitch of the toothing 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 inadvertently jumping as described above, the vertical clutch has been proposed. In this type of clutch, the kinematic connection between the input and output mobiles 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 with each other. mutually by one of their plane faces. In the engaged state, the torque is transmitted between the input mobile and the output mobile by friction between these friction discs. This frictional kinematic connection eliminates any clutch gearing.

To break the kinematic link and stop the chronograph, a clamp, typically controlled by a column wheel, separates the friction discs via wedge surfaces that interpose between said discs. By removing these wedges, the friction discs fall back on one another, and the kinematic link is restored.

Since there is no penetration of a toothing in another at the time of the actuation of the vertical clutch, any inadvertent jump of the seconds hand of the chronograph is avoided. However, such a vertical clutch requires a lot of room in the height of the mechanism to accommodate several gears, the friction discs and their return springs, coaxially. In order to overcome these disadvantages, the document EP1437633 proposed a horizontal clutch which attempts to avoid any unwanted jump, in which the teeth of the intermediate mobile and of the mobile output are shaped such that no contact between the top of a tooth of the intermediate mobile and the inactive side of the mobile output n ' is mathematically possible. Indeed, in the worst case, that is to say when the tops of two teeth come into direct contact during the clutch, the inactive flanks of the teeth of the output mobile follow the epicyclic trajectory of the top of a intermediate mobile tooth. Therefore, it is in principle impossible that the activation of the clutch causes an inadvertent jump behind the mobile output.

However, this solution requires that the shape of the teeth and the development of the mechanism are mathematically almost perfect, which is difficult to control during manufacture. Moreover, a possible wear of the intermediate mobile and / or the mobile output will harm this perfect shape, and therefore the risk of an inadvertent jump will increase over time. This solution, however, does nothing to solve the problem wriggling 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 in the system, by means of a friction spring for example, remains necessary for this purpose.

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

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

The object of the invention is therefore to provide a chronograph clutch system 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 motor member, such as a cylinder, 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 selected from said mobile input and said mobile output, typically the mobile input, 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 operates, and a disengaged state in which said kinematic link 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 fixed in rotation with a second mobile selected from said mobile input and said mobile output, this second mobile being the mobile opposite said first mobile, typically the mobile output. These friction wheels are at least partially coplanar, that is to say that 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 conversely according to the arrangement chosen, when said intermediate mobile, and therefore said clutch system, is in engaged state.

The clutch further comprises a first safety wheel secured to rotate 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 to interpenetrate each other when said intermediate mobile is in 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 wriggling of the output wheel (and therefore of an associated indicating member) occurs when turning on the chronograph. Moreover, 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 member. 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 may, for example, be controlled by a control member such as a column wheel, a shuttle or a cam, and which has stops arranged so as to prevent the intermediate wheel (and thus the clutch system) from changing state during an impact. The control lever thus defines a limit of displacement of the intermediate wheel in each of its states, which prevents unwanted angular displacements of the mobile output in disengaged state, and avoids breaking the kinematic link when the intermediate mobile is in engaged state.

Advantageously, the elastic element comprises a free end which interacts with said rocker to control it, said stops being located on either side of the free end. Therefore, in case of shock, the free end of the elastic element, which can for example take the form a fork, comes in 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 interact during an impact when said intermediate mobile is in its disengaged state, the other of said stops being arranged to prevent said safety toothing. can get out of range of each other during an impact when said system is in its engaged state.

The system may further comprise a reference meshing on the one hand with said first mobile and on the other hand with said intermediate mobile. This referral may, if necessary, include teeth to catch play.

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

Said first mobile may be said mobile input and said second mobile may be said mobile output. In this case, advantageously, the upstream sides of the first safety wheel and the downstream flanks 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 further acceleration of the second wheel can occur before the kinematic friction connection is established. This acceleration is less visible for a user than a jump. In the opposite case, that is to say if the first mobile is the mobile output and the second mobile is the mobile input, the upstream sides of the second safety wheel, and the downstream flanks of the first safety wheel, can be curved with the same effect.

The invention also relates to a watch 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 appear more clearly on reading the description which follows, 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 mobile output 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 chronograph according to the invention, in the disengaged state respectively engaged.

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

The input mobile 3 is in selective kinematic connection with an output mobile 5, which is a chronograph second 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 free to rotate on a rocker 11 and in permanent kinematic connection with the mobile input 3. This rocker 11 also carries a reference 13 which meshes with permanence on the one hand with the mobile input 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 mobile intermediate 9 and the mobile 5. The engaged state respectively disengaged from the intermediate mobile 9 determines the corresponding state of the clutch system 1.

Alternatively, in a reverse construction, the first intermediate mobile 9 can be in permanent kinematic connection with the mobile output 5, through the reference 13 in a similar manner to the first variant, a pivoting of the rocker thus bringing the first mobile intermediate 9 kinematic connection with the mobile input. The description which follows deals with the first of these variants, as illustrated in the figures; the modifications for implementing 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 reference 13 comprises a set of teeth to catch slack teeth, but a conventional wheel is also possible. It is also conceivable to provide only one intermediate mobile 9, thus meshing directly with the mobile input 3.

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

In order to drive the mobile output 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 that includes the mobile The materials of the friction wheels as well as their finish (presence of layers, roughness, etc.) may be chosen according to the needs of the watchmaker to ensure the transmission of torque with an appropriate contact force.

This contact force is provided by an elastic element 21, which also controls the rocker 11, as will become clearer later.

The elastic element 21 is a leaf spring carried by a control lever 25, pivotally mounted about an axis of rotation 29 and subjected to a restoring force via an elastic return element 31 which tends to the rotate counterclockwise (according to the orientation of the figures), and thus maintain 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 may be controlled by a shuttle system, a cam, or a similar system.

The free end of the elastic element 21 includes a fork 35, which interacts with a pin 23 located at an end remote from the pivot axis 29 of the control lever 25. When the control lever 25 pivots clockwise under the control of the column wheel 27, the elastic member applies a force that pivots the latch 11 counterclockwise. The friction wheels 17, 19 therefore come into contact with each other, and the input mobile 3 is thus kinematically connected to the output mobile 5 (see FIG. figure 2 ). The elastic member 21 provides the force necessary to keep the friction wheels 17, 19 in contact with each other, and to generate the radial force necessary to ensure good slip-free torque transmission.

From the orientation of the components shown on the figure 2 when the column wheel 27 is pivoted one step, the elastic return member 31 pivots the control lever 25 counterclockwise, and the elastic member 21 pivots the lever 11 so that the first wheel friction 17 deviates from the second friction wheel 19. The components thus return to their position illustrated in the figure 1 , and the kinematic connection between the input mobile 3 and the output mobile 5 is broken.

In comparison with the force required to maintain the gearing between the toothing of the intermediate wheel and the output wheel in a conventional horizontal clutch, that provided by the elastic element 21 of the present invention is relatively small.

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

Firstly, at 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 in relation 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 device 9, and a second safety wheel 39 comprising a second safety toothing is rotationally integral with the output device 5. These toothings are formed of such 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 mobile output 5 during normal operation of the clutch system 1.

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

During a shock that moves the output mobile 5 angularly relative to the intermediate mobile 9, the safety teeth interact to limit this angular displacement. This displacement is thus limited to the angle traveled 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 seconds hand of the chronograph.

The shape of the teeth of the safety teeth is also special, since the teeth do not participate in the transmission of torque, and serve only as stops in case of shock. Indeed, 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 torque transmission. The teeth are therefore relatively thin in relation 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 sharp and asymmetrical; considering the first safety wheel 37, the downstream faces of its teeth are substantially radially oriented, while the upstream faces of said teeth have a curvature. The teeth of the second safety wheel 39 have the opposite shape, so that, if the toothing stops in the direction of rotation of operation, the respective curved sidewalls interact, the respective sides less curved interacting in the case of a shock causing a rotation of the output mobile in the opposite direction.

The small width of the teeth minimizes the likelihood of the teeth interacting during a clutch of the system 1, and minimizes the jump when it arrives. In addition, the asymmetrical 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 teeth generates a slight imperceptible momentary acceleration of the chronograph seconds hand and not a visible jump when the chronograph is started. A perceptible inadvertent jump is thus eliminated. It should be noted here that the "inactive" flanks of the teeth in the direction of the EP1437633 , that is to say the down flanks of the teeth of the first safety wheel 37 and the upstream flanks of the teeth of the second safety wheel, are very steep, and extend in a substantially radial direction. However, other forms of teeth are also possible.

The elastic element 21 is relatively small to absorb all manufacturing imperfections such as mals-round, inaccurate positioning 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 with conventional teeth, and there is also a risk that a shock can angularly move the rocker 11 from its normal position. Without the provision of the security means described below, this displacement could for example temporarily interrupt the kinematic link in the engaged state, or could create a transient kinematic link between the intermediate mobile 9 and the output mobile 5 in the disengaged state of the clutch.

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 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 case of impact.

The first safety arm 41 is positioned and shaped so that, in the disengaged state ( figure 1 ), it is impossible for the teeth of the first safety wheel 37 to be within range 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. .

In the same manner, the second safety arm 43 is positioned and shaped so that, in the engaged state ( figure 2 ), it is impossible that the teeth of the two safety wheels 37, 39 go out of range of each other. In this case, the delay of the second hand generated by a shock that breaks the kinematic link is limited to the arc traveled 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 restore their kinematic connection under the effect of the elastic element 21, and the drive of the mobile output 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 one direction or the other, it is unlikely that the user will perceive it following 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)

Clutch system (1) for a chronograph mechanism, said system (1) comprising: - An input mobile (3) intended to be driven by a motor member; - An output mobile (5) for driving at least one display member; - An intermediate mobile (9) in permanent kinematic connection with a first mobile (3; 5) selected from said mobile input (3) and said mobile output (5), said intermediate mobile (9) being mounted so that it can evolve between an engaged state in which said input mobile (3) is in kinematic connection with said output mobile (5), and a disengaged state in which said kinematic link is broken; characterized in that said system (1) further comprises: a first friction wheel (17) integral in rotation with said intermediate mobile (9) and a second friction wheel (19) integral in rotation with a second mobile (5; 3) selected from said input mobile (3) and said output mobile (5), said friction wheels (17, 19) being at least partially coplanar and being arranged to transmit rotation between said intermediate mobile (9) and said second mobile (5; 3), or vice versa when said system (1) is in engaged state; a first safety wheel (37) integral in rotation with said intermediate mobile (9) and comprising a first safety toothing, and a second safety wheel (39) integral in rotation with said second mobile (5; 3) and comprising a second safety toothing, said safety toothing being shaped to interpenetrate each other when said intermediate mobile (9) is in engaged state. System (1) according to the preceding claim, wherein said intermediate mobile (9) is pivotally mounted on a rocker (11) controlled by an elastic member (21). System (1) according to claim 2, wherein said elastic element (21) is carried by a control lever (25) having stops (41, 43) arranged in order to prevent said intermediate mobile (9) from changing state during an impact. System (1) according to claim 3, wherein said elastic element (21) comprises a free end (35) which is arranged to interact with said rocker (11), said stops (41, 43) lying on the side and side another of said free end (35). System (1) according to one of claims 3 and 4, wherein one of said stops (41) is arranged to prevent said intermediate mobile (9) and said second mobile (5; 3) can interact during a shock when said intermediate mobile (9) is in its disengaged state, the other of said stops (43) being arranged to prevent said safety teeth can go out of range of each other during an impact when said intermediate mobile (9) is in its engaged state. System (1) according to one of the preceding claims, further comprising a return (13) meshing on the one hand with said first mobile (3; 5) and on the other hand with said intermediate mobile (9). System (1) according to claim 6, wherein said return (13) comprises a clearance toothing clearance. System (1) according to one of the preceding claims, wherein said safety teeth each comprise teeth having a width of at most one quarter, preferably at most one fifth, of the pitch of said toothing, measured at the maximum depth of interpenetration of said safety teeth. System (1) according to one of the preceding claims, wherein said first mobile (3; 5) is said mobile input (3) and said second mobile (5; 3) is said mobile output (5). System (1) according to the preceding claim, wherein the upstream flanks of the first safety wheel and the downstream flanks of the second safety wheel are curved. Clockwork movement comprising a chronograph mechanism provided with a clutch system (1) according to one of the preceding claims. Timepiece comprising a movement according to claim 11.

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