Watch transmission device

Transmission device (100), for example for a watch mechanism (110), in particular for a winding train (100, 201) of a watch movement (120),

This application claims priority of European patent application No. EP16160743.7 filed Mar. 16, 2016, which is hereby incorporated by reference herein in its entirety.

The invention relates to a transmission device, that is to say for the transmission of movement or energy. It also relates to a watch mechanism comprising such a device. It further relates to a watch movement comprising such a device or such a mechanism. It likewise relates to a timepiece, for example a wristwatch, comprising such a device, such a mechanism or such a movement. The invention finally relates to a method of operation of such a transmission device, of such a watch mechanism, of such a watch movement or of such a timepiece and a method of modification of a timepiece.

Watch barrels, in particular barrels for timepieces with automatic winding, are generally associated with devices for limiting the torque in order to mitigate the risks of overtightening the barrel spring. The devices for limiting the torque that are familiar from the prior art propose the conventional implementation of friction systems that are configured for the sole purpose of preventing the additional winding of the barrel spring beyond a threshold of maximum winding torque. Such friction systems may thus be placed under load very frequently, for example when the barrel spring is constantly wound by an automatic winding mechanism, and are at risk of being particularly susceptible to wear because of this.

Two families of devices for limiting the torque of a barrel are familiar from the prior art.

According to the first family of embodiments, the torque limiting device consists of a friction system which is implemented on the outside of the barrel drum. Such a system is disclosed, for example, in CH 160492, in which a friction mobile is disposed at the interface between an oscillating mass and a barrel, or in document CH146603, in which overtightening of the barrel spring is prevented by the provision of a friction spring carried directly by the support for the oscillating mass. Such constructions are difficult to integrate within the movement and are particularly susceptible to wear.

According to the second family of embodiments, a torque limiting device consists of a friction system which is implemented within the barrel drum. A solution, which is currently adopted nowadays, consists of connecting the barrel spring under friction to the internal wall of the drum by means of an elastic blade commonly referred to as a “slipping spring”, which is attached at the outer extremity of the barrel spring. According to the prior art, the internal wall of the drum may include sliding surfaces and cut-outs in the form of slots, in which the slipping spring is capable of coming into abutment in such a way as to generate high driving torques for the barrel. Such a solution is satisfactory to the extent that it makes it possible to achieve such torque levels at the barrel while maintaining the integrity of the barrel spring. Like the aforementioned solutions, however, the internal wall of the barrel drum may be subject to wear. Patent application EP2420899 proposes, for example, to endeavor to address this problem by means of a particular configuration of barrel drum slots.

The aim of the invention is to make available a transmission device enabling the aforementioned disadvantages to be addressed and enabling the transmission devices that are familiar from the prior art to be improved. In particular, the invention proposes a transmission device enabling the wear due to sliding in a barrel or in a transmission train upstream of the barrel to be limited.

A transmission device according to the invention is defined by claim1.

Different embodiments of the device are defined by dependent claims2to7.

A mechanism according to the invention is defined by claim8.

A movement according to the invention is defined by claim9.

A timepiece according to the invention is defined by claim10.

A method of operation according to the invention is defined by claim11.

Different embodiments of the method are defined by dependent claims12to14.

A method of modification of a timepiece according to the invention is defined by claim15.

An embodiment of a timepiece130is described below with reference toFIGS. 1 to 11. The timepiece is a watch, for example, in particular a wristwatch, and specifically an automatic wristwatch. The timepiece comprises a watch movement120, itself comprising a mechanism110.

The mechanism comprises an energy source200, for example an oscillating mass or a winding crown, a barrel2and a winding train100,201, connecting the energy source to the barrel2. The winding train comprises a transmission device100and a wheel train201enabling a movement to be transmitted to the device only in a first direction.

The transmission device100comprises:an input element6intended to be driven only in the first direction,an output element7,a first mechanical connection61a,71aarranged such that the displacement of the input element in the first direction causes the displacement of the output element in a second direction, anda second mechanical connection9′,9,90,82′,62arranged such that the displacement of the input element in the first direction causes the displacement of the output element in a third direction, the third direction being opposite the second direction.

The input element is a ratchet6, for example. The input element is pivoted advantageously about a first axis A6. The wheel train201connects the input element mechanically to the energy source200.

The output element is a first plate7, for example. The output element is pivoted advantageously about the first axis A6and/or is intended to be integral in rotation with an arbor4of the barrel2. For example, the output element is intended to be mounted squarely on the arbor4. A screw is provided to immobilize the output element on the arbor4.

In the represented embodiment, the input elements and output elements are pivoted about the same axis A6, and the first and second directions are coincident.

The transmission device has the distinguishing feature of combining two advantageously complementary effects. On the one hand, this device makes it possible to avoid the overtightening of a barrel spring3when this reaches a level of winding approaching its threshold of maximum winding and, on the other hand, this same device makes it possible to diminish, or to diminish significantly, the level of winding of the spring and, in so doing, to distance, or even to distance significantly, the level of winding of the spring from its threshold of maximum winding. For this purpose, the device includes the first mechanical connection permitting the disengagement of the barrel spring and the second mechanical connection which allows the at least partial unwinding of the barrel spring as soon as the disengagement of the spring is effective.

Such a solution makes it possible advantageously to minimize the friction loadings and, in so doing, to minimize the risks of wear, in particular for an automatic timepiece equipped with a winding mechanism of which the speed of winding is optimized. Furthermore, such a solution makes it possible to minimize any disturbances of the torque supplied by the barrel when the barrel spring reaches its threshold of maximum winding. Even more advantageously, such a solution makes it possible to optimize the number of winding turns of the barrel spring in a given barrel volume, thanks to the fact that the device limiting the torque is disposed not only within the barrel drum, but also on the outside of the barrel.

The transmission device according to the invention is distinguished from the embodiments that are familiar from the prior art by the fact that it includes a system allowing the unwinding of the barrel spring as soon as the barrel spring is disengaged from the energy source200once the spring has reached a predefined threshold of maximum winding. More specifically, this device permits the counter rotation of the barrel arbor4, that is to say the rotation of the barrel arbor in a direction counter to that permitting the winding of the barrel spring, during actuation of the winding train of the barrel, for example during actuation of the input element, thereby permitting the at least partial unwinding of the barrel spring when the latter has reached a predefined threshold of maximum winding.

In particular, the transmission device according to the invention is distinguished from the embodiments that are familiar from the prior art by the fact that, in these embodiments, no corresponding device is provided to reduce the loadings in the event of the barrel spring being fully wound, for example no corresponding device being provided to reduce the friction due to sliding and thus the wear.

In order to achieve these aims, the transmission device comprises the first mechanical connection which permits the disengagement of the input element and the output element and which is connected to the second mechanical connection allowing the at least partial unwinding of the spring3.

Advantageously, the transmission device according to the invention may be disposed in place of a conventional ratchet of a watch barrel.

In a first configuration of the transmission device, the winding train winds the barrel spring3for as long as the spring3has not reached a predefined threshold of maximum winding. In this first configuration, the first mechanical connection does not limit the transmitted torque. The barrel arbor4is thus driven in the second direction of rotation such that the spring3is able to wind around the core of the barrel arbor. This direction of rotation coincides with the first direction of rotation of the input element when the winding train is actuated.

Once the spring3has reached a predefined threshold of maximum winding, or a first predefined torque threshold, the first mechanical connection makes it possible to disconnect the input element6from the output element and, accordingly, to disconnect the energy source200from the barrel arbor4. In this second configuration of the transmission device, the rotation of the input element6caused by the energy source no longer causes the rotation of the barrel arbor4and thus no longer acts on the spring3.

Once the arbor4has been disconnected from the energy source, rotation of the input element6caused by the energy source permits the activation of a second mechanical connection allowing the at least partial unwinding of the spring3. In this third configuration of the transmission device, the barrel arbor4is driven in a third direction of rotation such that the spring3is able to unwind around the core of the barrel arbor. This direction of rotation is contrary to that of the direction of rotation of the input element6when the drive train is actuated.

Once the spring3has been unwound, at least partially, the transmission device1reverts to the first configuration, in which the winding train, under the influence of the energy source, winds the barrel spring for as long as the spring3has not reached the predefined torque threshold.

Preferably, the first mechanical connection comprises one or a plurality of arms71, for example one or a plurality of arms formed on the output element, and one or a plurality of protrusions61a, for example one or a plurality of protrusions formed on the input element, the arms and the protrusions interacting, for example, by positive engagement. In the represented embodiment, the first mechanical connection comprises two arms71formed on the output element7and two protrusions61aformed on the input element6, the arms and the protrusions interacting by positive engagement.

The one or more arms71may, for example, be integrally formed with the output element7. The extremities71aof the arms are advantageously provided in order to interact with the protrusions61aformed on an internal wall61of the input element.

Thus, as represented inFIGS. 2 and 3, when it is set in motion, the input element6drives the barrel arbor4by means of its protrusions61a, which guide each of the extremities71aformed on the output element7. Accordingly, the barrel arbor4is driven in a direction of rotation such that the spring3is able to wind around the core of the barrel arbor4.

Advantageously, the first mechanical connection is arranged, furthermore, such that it permits the free displacement of the input element6relative to the output element7when the intensity of the mechanical torque exerted by the input element on the output element exceeds a given threshold.

For this purpose, for example,the one or more arms are flexible, andthe one or more arms and/or the one or more protrusions have one or a plurality of slopes610,710, andthe one or more slopes are arranged such that the one or more flexible arms flex when the intensity of the mechanical torque exerted by the input element on the output element exceeds a given threshold.

In fact, once the spring3has been wound sufficiently for the torque threshold to be reached, that is to say when a predefined winding threshold has been reached, the arms71flex during actuation of the protrusions61asuch that they are able to retract as represented inFIG. 4, and, by so doing, to permit the extremities71ato interrupt their contact with the protrusions61asuch that the internal wall61of the input element6is able to slide against the extremities71aof the arms71, as represented inFIG. 5. In fact, due to the presence of the slopes610and/or710, the action of the input element on the output element comprises forces which may be broken down as follows:orthoradial forces (in relation to the axis A6) generating a torque about the axis A6, andradial forces (in relation to the axis A6) causing flexing of the arms.

A maximum threshold for the transmissible mechanical torque is determined in this way, depending on the orientation of the slopes and the rigidity of the arms.

Once the arms have flexed sufficiently, the output element7and, consequently, the arbor4are thus disconnected from the input element6. In this second configuration of the transmission device represented inFIG. 5, the rotation of the input element caused by the winding train no longer causes the rotation of the output element7or that of the barrel arbor4and thus no longer acts on the spring3.

As soon as the input element6and the output element7have been disconnected, the second mechanical connection permitting the partial unwinding of the spring3may be activated.

As represented inFIGS. 6 to 11, the second mechanical connection advantageously comprises:a frame9′ comprising a first toothing91,a wheel9comprising a second toothing92intended to engage with the first toothing,an Oldham coupling90mechanically connecting the wheel9and the output element7,a cam profile84′, anda finger62.

For example, the wheel9is integral in rotation with the output element7via the Oldham coupling. The wheel has an axis of rotation A9that is capable of displacement in a plane perpendicular to the axis A4of rotation of the barrel arbor4and relative to the axis A4such that, in the third configuration of the transmission device, the wheel9is able to engage with an internal toothing of a crown formed on the frame of the movement9′ or fixed on the frame of the movement.

In the embodiment illustrated in the figures, the axis A4of rotation of the barrel arbor4is coincident with the first axis A6.

The Oldham coupling comprises the output element7, a second plate8and a third plate8′, on which the wheel9is fixed. The first and second plates are capable of displacement in the plane perpendicular to the axis A4relative to the output element7. For this purpose, the second plate8is movably mounted in translation, according to a first direction slide D1, on the output element7. The first slide is realized, for example, by means of oblong cutouts82on the second plate8interacting with drive pins72provided on the output element, the drive pins being provided, for example, so as to engage in cutouts, as represented inFIG. 7. The third plate8′ is likewise movably mounted in translation, according to a second direction slide D2, on the second plate. The second slide is realized, for example, by means of oblong cutouts83′ on the third plate8′ interacting with drive pins83provided on the second plate8, the drive pins being provided, for example, so as to engage in cutouts, as represented inFIG. 7. The directions D1and D2are preferably orthogonal. The plate8′, and thus the wheel9, are therefore capable of displacement in the plane perpendicular to the axis A4relative to the output element7and to the arbor4, in such a way that the wheel9is able to move into engagement with the frame9′.

In the first and second configurations, the axis of rotation A9of the wheel9coincides with the axis A4of rotation of the barrel arbor4, the axis A4likewise coinciding with the axis A6of rotation of the input element6, as represented inFIG. 6. The wheel9thus pivots concentrically with the barrel arbor4, and the second toothing92of the wheel9is beyond the reach of the first toothing91of the frame9′.

The transmission device also comprises a mechanism121for the activation/deactivation of the second mechanical connection. This activation/deactivation mechanism makes it possible to control the eccentricity of the wheel9relative to the axis A4. The displacements in the plane of the plate8′ are brought about by the actuating finger62that is part of the activation/deactivation mechanism121. This finger is integrally formed, for example, with the input element6.

FIG. 8illustrates the transmission device in a transitory phase. This transitory phase may coincide with the second configuration described previously. It should be noted that the finger62is provided so as to interact with at least one cam surface84′ of the plate8′ in such a way as to cause the axis of rotation A9of the wheel9to be displaced relative to the axes of rotation A4, A6of the arbor4and of the input element6, and thereby to permit the engagement of the wheel9with the frame9′. For this purpose, the cam surface84′ is eccentric relative to the axes A4, A6. Preferably, the cam surface84′ is realized by an external edge of the third plate8′.

The respective teeth92,91of the wheel9and of the frame9′ in this case are configured in order to permit the adequate engagement of the wheel9and of the frame9′, independently of the angular position of the toothing92of the wheel9relative to the toothing91of the frame9′ during the disengagement of the action of the mechanism121, that is to say during the displacement of the plates8,8′ and of the wheel9relative to the frame9′.

Once the respective toothings of the wheel9and of the frame9′ have become engaged, they are maintained in engagement as a result of the interaction of the finger of the input element6and the cam surface84′ defining an external circumference of the plate8′. The finger62and the cam surface84′ are configured and arranged in order to define the position of the axis A9of the wheel9on one and the same circle C9of the radius R9centered on the coinciding axes A4and A6, as represented inFIG. 9. The wheel9is thus able to describe a hypocycloidal trajectory relative to the frame9′ as a result of the rotation of the input element6.

In this third configuration, the barrel arbor4is maintained in an angular position determined by the blocking of the toothing92of the wheel9within the toothing91of the frame9′. These toothings may be substituted for a ratchet of the kind that is necessarily used in a conventional barrel system. Rotation of the input element6and the finger62, under the influence of the winding train, for its part causes the displacement of the wheel9as a result of the eccentric displacement of the plate8′ relative to the axes A4, A6, for example the displacement of the axis A9of the wheel9along the circumference of the circle C9. During the displacement of the wheel9, the interaction by engagement of the first and second toothings91and92of the wheel9and of the frame9′ causes a counter rotation of the arbor4, that is to say a rotation of the barrel arbor4in a direction counter to that of the input element6. This results in the unwinding of the spring3, as represented inFIG. 10.

The plate8′, in particular the cam surface84′ forming the periphery of the plate8′, is returned against the finger62by a spring63, as represented inFIG. 11. This spring is realized, for example, by two flexible blades63acting through contact on a cylindrical revolution seat85′ and coaxial with the wheel9, as represented inFIG. 11. The spring63thus returns the wheel9into the position of rest, the position of rest being a position in which the first and second toothings are not engaged.

The speed of unwinding of the spring3is controlled in this case by the number of toothings of the first and second toothings91and92of the wheel9and of the frame9′.

Advantageously, the second mechanical connection is arranged in such a way that it permits a free displacement of the output element relative to the input element when the input element has performed a displacement of determined amplitude relative to the frame9′. In the represented embodiment, the second mechanical connection is arranged in such a way that it permits a free displacement of the output element relative to the input element when the input element has performed a displacement of approximately half a turn relative to the frame9′.

The unwinding of the spring3may likewise be stopped by means of the mechanism121. The counter rotation of the arbor4may be stopped, for example, as soon as the finger62of the input element is positioned facing towards a hollow82′ provided on the cam surface84′ of the plate8′. The angular amplitude of the counter rotation of the arbor4is thus given by the extent of an angular portion of the cam surface84′ defining an external circumference of the plate8′. In the represented embodiment, this angular extent is in the order of 150°, and as such permits a counter rotation of the barrel arbor4in the order of 150°. It is, of course, possible to increase this value to approximately 200°, or 300°, or 350°, for example when the plate8′ is provided with a single and unique hollow on the cam surface, and when the input element6and the output element7are provided respectively with a single and unique protrusion61aand a single and unique extremity71aof the arm. The latter displacement could also be approximately one third of a turn. In this latter instance, the first connection would comprise preferably three arms71interacting with three protrusions61a.

The mechanism121comprises, apart from the finger62, the cam surface84′, the spring63, a centering surface provided on the input element and a centering surface85′ for the plate8′. The whole is arranged in such a way that the surface85′ may be maintained against the centering surface64in such a way as to reposition the wheel9coaxially with the input element6when the spring is sufficiently unwound. Once the surface85′ has been recentered against the surface64, the first and second toothings are out of reach. As soon as the extremities71aof the output element7are in abutment against the protrusions61of the input element6, the transmission device is thus once more in the first configuration, as illustrated byFIG. 2. Advantageously, the extremities71aof the output element7may be in abutment against protrusions61of the inlet element6as soon as the finger62of the input element is positioned facing towards a hollow82′ in the cam surface84′ of the plate8′.

In the represented embodiment, the second connection may be activated as soon as the first connection is no longer active. More specifically, the second connection may be activated when the first connection is no longer active. The second and third configurations of the transmission device may thus coincide. The first connection is preferably reactivated after the second connection has been deactivated.

In the whole of this document, a mechanical connection between two elements is said to be active when it connects these two elements in such a way as to drive them, for example in rotation.

A mode of implementation of a method of operation of a transmission device or of a watch mechanism or of a watch movement or of a timepiece according to the invention is described below with reference toFIG. 13. The method comprises at least one iteration of the following steps:a first step210, which consists of causing the interaction, for example by connecting together, of the input and output elements6,7via a first mechanical connection61a,71a, such that the displacement of the input element in a first direction causes the displacement of the output element in a second direction,a second step220, which consists of disengaging the input and output elements,a third step230, which consists of causing the interaction, for example by connecting together, of the input and output elements via a second mechanical connection9′,9,90,82′,62, such that the displacement of the input element in the first direction causes the displacement of the output element in a third direction, the third direction being opposite the second direction,a fourth step240, which consists of disengaging the input and output elements.

Advantageously, steps210to240are implemented in the order indicated below.

Advantageously, step210(and the following steps220to240) are repeated after step240.

The first disengagement is realized when the intensity of a mechanical torque exerted by the input element on the output element exceeds a given threshold. This first disengagement is a deactivation of the first mechanical connection. Advantageously, the interaction of the input and output elements6,7according to the first mechanical connection consists of joining the elements together, or of connecting the elements in such a way that any displacement of one involves the same displacement of the other.

The second disengagement is realized when the input element has executed a displacement of determined amplitude relative to a frame once the input and output elements have been connected via the second mechanical connection, for example by half a turn of the input element. This second disengagement is a deactivation of the second mechanical connection. Advantageously, the interaction of the input and output elements6,7according to the second mechanical connection consists of connecting the elements in such a way that any first displacement of one involves a second displacement of the other, the first and second displacements being different.

Preferably, as seen previously, the first and the second mechanical connections are activated in a mutually exclusive fashion. In other words, when the first mechanical connection is effective, the second mechanical connection is ineffective, and vice versa.

A mode of implementation of a method of modification of a timepiece or a method of repair of a timepiece is described below.

The method comprises a step involving the removal of a barrel ratchet and a step involving the fitting of a transmission device as described previously in place of the barrel ratchet. Advantageously, the method comprises a step of integrating a device9′ comprising the first toothing91with a frame of the movement of the timepiece.

Such a transmission device makes it possible to achieve a limitation of the torque applied to the barrel. The limitation of the torque makes it possible to reduce the loadings on the elements of the first mechanical connection by means of the second mechanical connection, the partial unwinding of the spring3enabling a level of torque remote from or substantially remote from the threshold of maximum winding of the barrel to be re-established, while fully meeting the good chronometric performance of the timepiece. Such a device consequently makes it possible to reduce considerably the variations in torque supplied by the barrel when the barrel spring has reached a threshold of maximum winding, and thus to minimize the variations in torque to the oscillator with respect to the known solutions from the prior art.

FIG. 12illustrates two winding curves for two distinct transmission devices. The number z9′, z9of the first and second respective toothings of the frame9′ and of the wheel9makes it possible to adjust the angular range travelled by the counter rotation of the arbor4depending on the angular range travelled by the input element6once the device1is in its third configuration. The curves represent the torque C depending on the displacement T of the input element.

In a first specific case illustrated by the curve shown as a solid line, the ratio z9/z9′ is lower than two. Once the spring has reached the threshold of maximum winding, it will be noted that the angular range travelled by the counter rotation of the arbor4is lower than the angular range travelled by the input element6. This is exemplified by the fact that, in the phase401of unwinding the spring, the absolute value of the slope of an affine function similar to the “unwinding” curve is lower than that of an affine function similar to the “winding” curve when the device is once more in its first configuration in a phase of winding402.

In a second specific case illustrated by the curve shown as a dashed line, the ratio z9/z9′ is equal to two. Once the spring has reached the threshold of maximum winding, it will be noted that the angular range travelled by the counter rotation of the arbor4is equal to the angular range travelled by the input element6. This is exemplified by the fact that, in the phase301of unwinding the spring, the absolute value of the slope of an affine function similar to the “unwinding” curve is equal to that of the affine function corresponding to the “winding” curve when the device is once more in its first configuration in a phase of winding302. In other words, in the second specific case, the unwinding and winding curves are symmetrical.

In a third specific case, not represented here, the ratio z9/z9′ may also be greater than two. In this specific case, the angular range travelled by the counter rotation of the arbor4is greater than the angular range travelled by the input element6. Advantageously, such a configuration makes it possible in particular to reduce the number of loadings of the elements of the first mechanical connection.

Another advantage of the device according to the invention derives from the fact that the elements permitting the limitation of the torque are not integrated within the barrel, and it is thus possible to optimize the geometry of the barrel drum in such a way as to permit the additional winding of the barrel spring and thereby to permit a gain in the autonomy of the timepiece equipped with such a barrel.

In the represented embodiment, the transmission device is disposed in place of a conventional ratchet of a barrel. It is, of course, possible to dispose this device differently within the winding train, whether manual or automatic, of the barrel and/or to cause it to interact with a conventional ratchet.

Such a transmission device is provided in order to interact both with a barrel of a going train of a watch movement and with a barrel integrated within a watch movement, for example a striking mechanism, in particular an alarm mechanism.