EP2574994A1 - Resonator with tuning fork for mechanical timepiece movement - Google Patents

Abstract

The resonator has an intersection leg (3) oscillated on a side of an axis and comprising a pin that is combined with a fork tooth of an anchor (10). A support (6), two ankles (7, 8) and two arms (15, 16) convert oscillations of the leg of an oscillator (1) into rotational movements of the anchor and transmit mechanical energy from the anchor to the leg of the oscillator in a form of pulses such that a tooth exhibits an amplitude of movement that is axially produced in a direction of the axis during pivoting the anchor and is greater than amplitude of movement of the pin in the direction.

Description

Technical area

The present invention relates to a tuning fork mechanical resonator for a free escapement mechanical clock movement, comprising a tuning fork type oscillator, of which at least a first oscillating branch is intended to oscillate on either side of a first axis and carries at least a first pin associated with at least one first fork tine of an anchor, for pivoting the latter between first and second angular positions and alternately lock and release an escape wheel.

In a known manner, such a mechanism makes it possible, in relation with a source of mechanical energy, to maintain oscillations of the oscillator which is the tuning fork and thus to define a resonator.

The high quality factor of an oscillator as a tuning fork, about ten to fifty times that of a conventional balance wheel, makes it attractive in the context of a watch application.

Furthermore, the present invention also relates to a watch movement provided with such a resonator and a timepiece, in particular but not exclusively of the wristwatch type, equipped with such a watch movement.

State of the art

Numerous clock devices comprising a tuning fork as oscillator have already been disclosed in the state of the art.

For example, the patent FR 73414 A, issued in the name of Louis-François-Clément Breguet on the basis of a request filed in 1866, describes a pendulum whose mechanical oscillator is a tuning fork. A first branch of this tuning fork carries an anchor having two arms arranged to cooperate with an escape wheel, to alternately lock and release the latter. Thus, the anchor does not rotate on the frame of the watch movement, as is usually the case, but has the same oscillating movement as the end of the branch of the tuning fork that carries it. The escapement designed is not free type, since, on the one hand, the anchor has a permanent contact with the escape wheel and, on the other hand, the anchor ensures the attachment of the anchor on the branch of the tuning fork and therefore never leave the anchor. Such an exhaust therefore has the corresponding disadvantages, namely greater wear and chronometric disruption than a free exhaust.

As regards more particularly the wristwatches, Max Hetzel is at the origin of a large number of patented inventions, relating to the implementation of a tuning fork as oscillator, which led to the production of the wristwatch. Accutron (registered trademark) bracelet, marketed by Bulova Swiss SA.

The Accutron watch however includes an electronic resonator since each branch of the corresponding tuning fork carries a permanent magnet associated with an electromagnet mounted fixed on the frame of the watch. The operation of each electromagnet is controlled by the vibrations of the tuning fork, by means of the magnets which it carries, in such a way that the vibrations of the tuning fork are maintained by the transmission of periodic magnetic pulses from the electromagnets to the permanent magnets. . One of the branches of the tuning fork actuates a pawl for rotating the mobile wheels of the finishing gear of the watch. This construction does not lend itself to the use of the ratchet to ensure the maintenance oscillations of the tuning fork.

The patent US 2,971,323 for example, from a deposit dating back to 1957, describes such a mechanism that can not however be suitable for the realization of a purely mechanical watch, that is to say without electronic circuits. Indeed, a real need exists, in terms of market, for purely mechanical timepieces with increased running accuracy compared to known parts.

It should be noted that the Accutron coin is still marketed by Bulova Swiss SA.

The patent CH 594201 , from a 1972 deposit, describes a dual oscillator resonator system. The frequency stability of the oscillations of a tuning fork is exploited, by magnetic interaction, to stabilize the oscillations of a balance of conventional shape, therefore having a lower quality factor than that of the tuning fork. For this purpose, the branches of the tuning fork, on the one hand, and the balance, on the other hand, carry permanent magnets arranged to cooperate with each other. The corresponding interaction makes it possible both to maintain oscillations of the tuning fork and to stabilize oscillations of the pendulum in frequency.

However, if this does not appear explicitly in this patent, it is obvious that this mechanism is necessarily coupled to a mechanical escapement to convert the periodic oscillation of the balance into a unidirectional movement to ensure the drive of the mobile of a cog finishing. Thus, it is likely that the balance is coupled to a conventional mechanical escapement arranged to maintain the oscillations. Consequently, the mechanism described in this document makes it possible to improve the frequency stability of the oscillations of a balance wheel, but this is done at the cost of a complexity and a much larger space requirement compared to a conventional one-way mechanism. oscillator. In addition, the high quality factor of the tuning fork is only partially used in the solution presented since, in the end, it is the pendulum which controls the movements of the finishing gear train, in a similar way to what is being done. works in classical systems.

Alternative solutions, more adapted to the spatial constraints specific to the construction of a wristwatch, had also been disclosed. Indeed, the patent US 3,208,287 , from a deposit dating from 1962, describes a resonator comprising a tuning fork coupled to an escape wheel by means of magnetic interactions. More specifically, the tuning fork carries permanent magnets cooperating with the escape wheel, the latter being made of a magnetic conductive material. The escape wheel is kinematically connected to a source of energy that can be mechanical or take the form of a motor, while it includes openings, in its thickness, such as that it forms a magnetic circuit of variable reluctance when it is driven in rotation, in relation with the magnets carried by the tuning fork.

Consequently, a permanent interaction of substantial intensity takes place between the tuning fork and the escape wheel, which can be described as magnetic locking, such a construction therefore consisting of a non-free exhaust. The energy input of the escape wheel to the tuning fork to maintain oscillations, even if it is weak, is continuous and constitutes a significant source of disturbance from the point of view of the isochronism of these oscillations. oscillations. Similarly, the guidance of the escape wheel by the tuning fork is continuous.

Thus, the type of interaction involved in this construction is close to a contact, which is unfavorable from the point of view of the accuracy of operation.

The pendulum of Louis-François-Clément Breguet being set apart, all these mechanisms involve a magnetic interaction and none is suitable for the realization of a purely mechanical timepiece, that is to say not including neither electronic nor magnetic interaction.

Disclosure of the invention

A main object of the present invention is to overcome the disadvantages of tuning fork resonators known from the prior art, by proposing a resonator for a mechanical timepiece, in particular for a wristwatch, having a quality factor and isochronism high as well as an escapement of free type.

When it comes to implementing a tuning fork-type oscillator in a watch in connection with a free escapement, particularly in a wristwatch, a certain number of technical problems arise.

The frequency of the oscillations of a tuning fork is much greater than that of a balance-spring. For example, the aforementioned Accutron has its tuning fork that vibrates at a frequency of 360Hz, compared to the 4Hz balance springs of most current mechanical watches. Thus, the adaptation of a conventional free escapement so that it operates in relation to a tuning fork is not obvious. In addition, the higher vibration frequency of the tuning fork should result in greater energy expenditure and component wear than with a sprung balance.

The amplitude of the vibrations of a clock tuning fork is small. For example, the amplitude of the tuning fork vibrations of the Accutron is 0.036mm, compared to the amplitude of oscillations of the balance peg in a balance spring system, of the order of 2mm.

Such a small amplitude makes the exhaust components more difficult to achieve than in the case of a sprung balance.

In addition, the higher operating frequency and the reduced amplitude imply that the corresponding exhaust should act on a larger portion of the oscillation of the tuning fork and the exhaust perturbation should therefore be greater than in the conventional case.

A further problem is that the oscillatory movement of the blades or branches of the tuning fork is almost linear, compared to the circular movement of the balance. Thus, the axial displacement of the end of the branch of a tuning fork is very small.

This linear movement requires modifications to the components of the exhaust since, in particular, the question of the inputs and outputs of an ankle in an anchor fork becomes problematic.

In addition, it will be noted that the lateral amplitude of the oscillations of a tuning fork branch, that is to say in a direction substantially perpendicular to the direction of the branch, is capable of strongly varying, up to 50% by average value according to Max Hetzel. Because of this variation, the ankle must be able to move out of the fork so as not to be disturbed during an additional arc greater than the average, that is to say to ensure that the vibration of the oscillator is free during the additional arc, a necessary condition for the realization of a free escape. We must therefore solve the difficulty related to the problem of entry and exit of the ankle with reference to the anchor fork.

Finally, we can still note that the implementation of a tuning fork in a wristwatch involves a problem in terms of size. Indeed, the tuning fork used in the Accutron model has a length of 25mm, compared to the current diameter of a pendulum, of the order of 10mm.

After verifying the feasibility of a resonator of the type mentioned above, in terms of operating frequency and energy consumed, the Applicant sought to solve the problem of resonator construction to take into account the small amplitude of the oscillations of the branches of a tuning fork.

Indeed, the calculations made by the Applicant have led to the conclusion that, for example, a vibrating tuning fork at a frequency of 50 Hz with a vibration amplitude of 0.07 mm has a level of energy expenditure similar to that a conventional balance spring. In addition, for such a tuning fork, an escapement which acts only on 50% of the amplitude of the vibrations of the tuning fork blade causes only an increase in the chronometric error by a factor of 33%, which confirms the feasibility of such a system.

In order to answer the general technical problem mentioned above, it has emerged that the present invention relates more particularly to a resonator of the type described above, characterized in that it comprises integral conversion member of the first pin and arranged for ,
on the one hand, to transform the oscillations of the first branch of the oscillator into rotational movements of the anchor by the transmission of first pulses to the latter, and,
on the other hand, transmitting mechanical energy from the anchor to the first branch of the oscillator in the form of pulses,
such that the first tooth has an axial displacement amplitude, substantially in the direction of the first axis, during the pivoting of the anchor, greater than the displacement amplitude of the first pin substantially in the direction of the first axis.

Indeed, it follows from the foregoing geometric considerations that, in the conventional oscillator-anchor-escapement system, the plateau pin, integral with the oscillator and actuating the anchor to disengage the escape wheel, has a displacement amplitude axial, considering here the axis of the anchor when it is oriented towards the axis of the balance, greater than that of the anchor. However, when the oscillator is a tuning fork, it has been noted that the amplitude of the axial displacements of the ends of its blades is insufficient to ensure the entry of the anchor into the anchor fork, as well as its exit out of the fork.

Also, the present invention provides that the amplitude of the axial displacements of the teeth of the anchor fork is greater than that of the anchor, a conversion member being provided to ensure the good cooperation between these elements and, finally, to allow the correct operation of a free exhaust.

The conversion member can be made in various forms without departing from the scope of the present invention.

According to a first embodiment, it can be provided that it comprises a rocker, intended to be pivotally mounted on a frame member of the watch movement and secured to the first pin so as to be pivotable relative to the first leg of the oscillator, the rocker carrying a second pin intended to cooperate with the first tooth and with a second tooth of the fork to rotate the anchor.

According to a preferred alternative embodiment, it comprises a support arranged on the first branch of the oscillator and carrying the first pin and a second pin, the latter being intended to cooperate alternately and respectively with the first tooth and with a second tooth. fork and being located at a relative distance slightly less than the relative distance between the first and second fork teeth.

Thanks to these features, the present invention makes it possible to implement a mechanical resonator for a timepiece comprising a tuning fork associated with a free escapement.

Advantageously, the anchor comprises a frame having first and second arms respectively carrying the first and second fork teeth.

According to a preferred embodiment, the anchor is integral with an anchor rod intended to ensure its mounting on the watch movement, the first and second arms extend substantially from the anchor rod.

Several alternative embodiments may be envisaged, depending on the constraints to be met in terms of space in particular. Thus, the anchor comprises first and second additional arms intended to cooperate alternately with the escape wheel, these first and second arms, on the one hand, and the first and second additional arms, on the other hand, being able to all be arranged in the same plane, or in two separate planes.

Furthermore, it can also be provided that the resonator comprises a second escape wheel, arranged to cooperate with either the same anchor, or with an additional anchor arranged to cooperate with the second branch of the oscillator.

Brief description of the drawings

Other features and advantages of the present invention will appear more clearly on reading the detailed description of preferred embodiments which follows, made with reference to the accompanying drawings given as non-limiting examples and in which:

- the Figures 1a and 1b represent illustrative diagrams of constraints to be taken into account for the implementation of the present invention;

- the figure 2 represents a schematic front view of a mechanical resonator for watch movement according to a first embodiment of the present invention;

- the figure 3 represents a schematic front view of a mechanical resonator for a watch movement according to a first embodiment of the resonator of the figure 2 ;

- the figure 4 represents a schematic front view of a mechanical resonator for a watch movement according to a second embodiment of the resonator of the figure 2 ;

- the figure 5 represents a schematic front view of a mechanical resonator for a watch movement according to a third embodiment of the resonator of the figure 2 ;

- the Figures 6a, 6b, 6c, 6d and 6th represent views of a functional detail of the resonator of the figure 2 , in successive configurations, and

- the figure 7 represents a schematic front view of a mechanical resonator for a watch movement according to a second embodiment of the present invention.

Mode (s) of realization of the invention

The Figures 1a and 1b represent illustrative diagrams of constraints to be taken into account for the implementation of the present invention, more precisely in terms of geometry to be respected, to ensure good cooperation between a tuning fork branch and an exhaust anchor fork.

The figure 1a schematically illustrates the displacement of an anchor, of radius R, to evaluate which relation exists between the angle of rotation that it travels, between first and second rays, and the displacement of its end in the direction of the second radius, c that is to say substantially in the axis of the tuning fork branch.

The bold lines 201 and 202 illustrate the first and second positions that the anchor can take when it pivots in response to a pulse transmitted by a tuning fork branch, shown schematically by the thin lines 203 and 204.

More precisely, when the anchor is in the position of the line 201, the tuning fork branch (line 203) must be able to pass in front of a first of its fork teeth without touching it, whereas when found in the position of the line 202, it must be able to transmit an impulse to the branch of the tuning fork (line 204), by the other tooth of its fork, to maintain oscillations of the tuning fork.

The axial displacement of the end of the anchor, in the direction of the branch of the tuning fork is given by: $$R\cos \mathrm{at}-R=R\left(1-\frac{{\mathrm{at}}^2}{2}+\cdots -1\right)\approx -\frac{R{\mathrm{at}}^2}{2}\mathrm{.}$$

It follows that the axial displacement of the anchor is of a smaller order than its angle of rotation.

For the usual order of magnitude of an anchor having a conventional shape, that is to say parallel teeth and a length of the order of 2.1 mm, the anchor having a pivot of 5 degrees, the formula above gives an axial displacement of its end of about 0.008mm, less than one hundredth of a millimeter.

In general, the clearance phase corresponds to about 2 degrees of pivoting of the anchor. Thus, when the branch of the tuning fork leaves a first tooth of the fork after pushing it, there remain 3 degrees of pivoting at the anchor during which the other tooth must present an axial displacement sufficient to be able to transmit a pulse to the branch of the tuning fork. This angle of 3 degrees corresponds to an axial displacement of 0.005mm.

Considering the case of a conventional plateau pin, having a lifting phase representing an angle of 30 degrees, the lift begins at an angle of the order of 15 degrees and ends at an angle of the order of 9 degrees. In this case, the axial displacement of the peg is generally of the order of 0.046 mm (for a 0.7 mm diameter of the peg trajectory), which gives a relative axial displacement of the order of 0.05 mm between the ankle and the corresponding fork tooth of the anchor.

If it is assumed that the overlap between the tooth and the ankle is approximately 0.025mm at the end of the clearance, there is 0.025mm remaining between the tooth and ankle to let it enter the fork. Such dimensions are very small, at the limit of a practical realization.

It is for this reason that the fork has a well defined width, to facilitate the entry of the ankle.

The figure 1b schematically illustrates the displacement of a fork of width 2S.

The width 2S of the fork facilitates the entry of the peg into the fork by contributing to the axial displacement mentioned above, since it is of the same order as the angle a: a rotation of an angle a of a horizontal arm of length S gives a vertical displacement of -S.sin (a) is about -Sa So, if the fork has a height R, in the axial direction, and the wall of each of its teeth is at a distance S of the axis then, for a small rotation of angle a, the axial displacement due to R is about Ra ² and the displacement due to S is about Sa

For example, by positioning a fork wall 0.25 mm from the anchor axis (usual order of magnitude for a conventional pendulum escapement), the axial displacement of the wall is increased by 0.25. °) -sin (3 °)) is about 0.009, which allows to increase the passage size from 0.025mm to 0.03mm.

For the tuning fork, the situation is more complex because the movement of its branch or blade is almost linear, while with the pendulum the plateau pin has a rotary motion.

ce qui revient au même calcul en notant que l'angle de rotation de la branche est a=arctan(A/R) soit environ A/R.For example, for a vertical branch of length R vibrating at an amplitude A, the vertical displacement is $$\sqrt{R^2-{\mathrm{AT}}^2}-R=R\left(1-\frac{{\mathrm{<figure-callout\; id="2"\; label="AT"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">AT</figure-callout>}}^2}{2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}+\cdots -1\right)\approx -\frac{{\mathrm{<figure-callout\; id="2"\; label="AT"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">AT</figure-callout>}}^2}{2R},$$

which amounts to the same calculation by noting that the angle of rotation of the branch is a = arctan (A / R) is about A / R.

For example, for the Accutron with branches 20mm in length, but only 2/3 is in apparent circular motion, and an amplitude of 0.036mm, the vertical displacement is - 0.00005mm, so imperceptible for the application that interests us.

Similarly, for a tuning fork of length equal to 20mm, with an amplitude of 0.07mm and an anchor of 2.1mm having a clearance of 1 degree at 0 degrees, the above calculations lead to the calculation of a vertical displacement of the branch of the tuning fork of 0.0001mm and a vertical displacement of the anchor of 0.0003mm, a difference of 0.0004mm, which is not acceptable.

It is therefore advisable to consider a fork of greater width allowing the ankle to enter.

Consider, for example, a fork whose walls are at a distance S from the axis of the anchor. The displacement in a direction parallel to the axis between 1 degree and 0 degrees is thus S.sin (1 °) is about 0.017.S. By setting S = 2.5mm, this gives an axial displacement of 0.44mm. In addition, the ankle on the tuning fork also turns from a certain angle. It can be calculated that the entry into the range is at an amplitude of 0.035mm, for a blade of 20mm in length of which 2/3 are in rotation, this representing an angle of 0.002625 = 0.15 degree, the axial displacement being 0.0066mm. This gives a relative displacement of 0.045mm, an input of 0.022mm.

So for this basic example, the fork should have walls at least 2.5mm apart in reference to the anchor axis, for a total length of 5mm.

These calculations are based on the assumption that the vibrations of the tuning fork are approximately circular. In reality, the movement is more complex and one should refer to the exact behavior of a bar bent for more precision. The calculations presented here are indicative therefore, in practice, the exact geometry of the range will have to be adapted to the exact trajectory of the vibrations of the tuning fork.

The above considerations have led the Applicant to review the geometry of the fork and, therefore, that of the conventional plateau peg.

The figure 2 represents a schematic front view of a mechanical resonator for watch movement according to a first embodiment of the present invention.

This resonator comprises an oscillator 1 of tuning fork type, here substantially U-shaped in a non-limiting manner, whose base 2 is intended to be secured to a frame member of a watch movement (not shown for clarity) to allow the branches 3 and 4 to vibrate with reference to the base, in known manner.

Alternatively, the tuning fork may have a different shape, for example and preferably a shape similar to that described and illustrated in the patent US 3,447,311 .

As mentioned above, the amplitude of the vibrations of the tuning fork is very small and would not be suitable for producing a conventional resonator, simply by replacing the balance spring system with a tuning fork.

Also, the Applicant has carried out research to develop a tuning fork mechanical resonator for a watch movement comprising a conversion member arranged for,
on the one hand, to transform the movements of a fork branch into rotational movements of an anchor by the transmission of first pulses to the latter, and,
on the other hand, to transmit mechanical energy from the anchor to the branch of the tuning fork in the form of pulses,
such that the teeth of the anchor fork have an axial displacement amplitude, that is substantially in the direction of the axis of the tuning fork leg, during the pivoting of the anchor, greater than the amplitude of displacement of the anchor fork. the end of the tuning fork leg substantially in its axial direction.

The figure 2 illustrates an exemplary embodiment of a resonator according to an illustrative mode of the invention.

The free end 5 of a first branch 3 of the tuning fork is provided with a support 6 carrying first and second pins 7 and 8 filling the function of the plateau pin in a conventional system, as will be apparent from the detailed description of the Figures 6a to 6e .

The support 6 has an elongate shape, in a direction substantially perpendicular to the direction of the first leg 3, being fixed thereto by its middle, the pins 7, 8 being disposed at its respective ends.

The pins 7, 8 cooperate with an anchor 10, more precisely with first and second teeth 11 and 12 of the anchor defining an anchor fork.

The anchor 10 comprises a frame intended to be pivotally mounted on a frame member of the watch movement by means of an anchor rod 14. The frame has first and second arms 15, 16 extending from the anchor rod and each of which carries one of the teeth 11, 12 at its free end.

The frame further has first and second additional arms 18, 19 also extending from the anchor rod 14 and respectively carrying first and second vanes 21, 22 arranged to cooperate with the toothing of a wheel. exhaust 24, substantially conventional. Thus, the anchor 10 is intended to pivot between a first position in which one of its vanes 21, 22 locks the escape wheel 24 in rotation and a second position in which the other pallet locks the escape wheel . When the anchor pivots between one and the other position, the escape wheel is released to turn.

The distance between the pins 7 and 8 is slightly less than the distance between the teeth 11 and 12 to ensure the proper operation of the resonator.

It appears from figure 2 that the resonator according to the present invention allows operation similar to that of conventional resonators, in particular thanks to the fact that the oscillator carries two pins 7 and 8 instead of a single pin, as well as by the particular geometry of the range of anchor. The solution illustrated by way of non-limiting indication not only makes it possible to ensure the anchor an amplitude of sufficient rotation for its good cooperation with the escape wheel, but also to ensure that the pins 7 and 8 can take turns in the fork and drive the anchor appropriately, and they can also get out , symmetrically.

Of course, those skilled in the art can adapt the number of teeth of the escape wheel or the lever arms between the different arms of the anchor according to its own needs and without departing from the scope of the present invention.

In particular, it will be noted that the lever arm of the anchor can be modified by changing the distances between the anchor rod and the fork teeth, on the one hand, and between the anchor rod and the pallets, on the other hand, to adapt the geometry of the anchor as needed. Indeed, a reduction of the lever arm of the fork makes it possible to increase the angle of rotation of the anchor and therefore the range of displacement of the pallets.

In addition, it will also be noted that a reduction of the lever arm of the fork facilitates the construction of the exhaust, since it causes a widening of the rest surface of the pallet and the width of the latter. The increase in the angle of rotation of the anchor increases the displacement of the fork in the axial direction of the anchor, which facilitates the entry and exit of the peg (s). The width of the range can thus be reduced. On the other hand, a priori the energy expenditure is increased in this case, but the person skilled in the art will not encounter any particular difficulty in adapting the sizing of the anchor and its fork according to its own needs.

Note that in the embodiment illustrated on the figure 2 , the first and second arms 15, 16 of the anchor and its first and second additional arms 18, 19 are all located in the same plane. However, other configurations are possible without departing from the scope of the present invention and in particular the constraints to be observed in terms of congestion of the resonator.

The figure 3 represents a schematic front view of a mechanical resonator for a watch movement according to a first embodiment of the resonator of the figure 2 .

The same numerical references as on the figure 2 will be used to simplify the understanding of the figure 3 .

The resonator is basically the same as on the figure 2 with the difference that the first and second additional arms 18, 19 of the anchor 10 extend in a second plane different from that containing the first and second arms 15, 16. In addition, in the embodiment of the figure 3 the mediators, on the one hand, first and second arms and, secondly, additional first and second arms have between them an angle of the order of 80 degrees.

Thanks to these characteristics, the escape wheel can be arranged in a plane different from that of the tuning fork and at a distance from it lower than in the case of the realization of the figure 2 .

Such a configuration makes it possible to reduce the bulk of the tuning-exhaust assembly and lends itself better to its integration into a wristwatch.

The skilled person will not encounter any particular difficulty to change the shape of the anchor according to its own constraints in terms of size.

The figure 4 represents a schematic front view of a mechanical resonator for a watch movement according to a second embodiment of the resonator of the figure 2 . According to this variant, the mediators of the first and second arms 15, 16, on the one hand and the first and second additional arms 18, 19, on the other hand, have between them an angle of the order of 120 degrees.

The figure 5 represents a schematic front view of a mechanical resonator for a watch movement according to a third embodiment of the resonator of the figure 2 . According to this variant, the mediators of the first and second arms 15, 16, on the one hand and the first and second additional arms 18, 19, on the other hand, have between them an angle of the order of 180 degrees.

It emerges figures 4 and 5 that the escape wheel and the tuning fork may possibly be at least partially superimposed, in particular to reduce the bulk of the tuning fork-exhaust assembly as mentioned above.

The Figures 6a, 6b, 6c, 6d and 6th represent views of a functional detail of the resonator of the figure 2 , in successive configurations intervening on a half-wave of oscillations of the first branch 3.

From there figure 6a , the first branch 3 of the tuning fork ends its course in the direction of the arrow, to the left of the figure, just before starting in the opposite direction.

In this situation, the first pallet 21 of the anchor 10 cooperates with the toothing of the escape wheel 24 to lock the latter in rotation. The exhaust is here at rest.

When branch 3 returns to the right of the illustration, which is represented on the figure 6b , the second tooth 12 of the anchor is on the path of the second pin 8. When a contact is established between them, a release phase begins by rotating the anchor clockwise on the figure 6b under the effect of the impulse transmitted by the second ankle. The first pallet 21 is lifted from the escape wheel 24 and releases it.

During the disengagement phase, the first tooth 11 rises towards the first peg 7, this situation being illustrated on the Figure 6c .

An impulse phase of the anchor to the first pin 7 then intervenes, as illustrated on the figure 6d , to ensure the maintenance of the oscillations of the first branch 3 of the tuning fork.

At the same time, the second pallet 22 is folded towards the escape wheel 24 until it locks again, as shown in FIG. figure 6e .

The second half-alternation then begins and the same phases intervene again in the same chronological order, in a conventional way.

Thus, it can be seen that for the anchor 10 to cooperate effectively with the escape wheel 24, the greatest distance between the different positions of its teeth 11, 12 must be large, in any case greater than twice the amplitude of the vibrations of the branch 3 of the tuning fork, which is weak as noted above and insufficient alone to move the anchor satisfactorily. This largest distance is that between the respective positions that take the first and second teeth after they underwent the impulse of the corresponding peg, during the phases of disengagement.

In the preceding figures, the resonator according to the invention comprises a conversion member comprising two pins 7.8 associated with two teeth 11, 12 spaced apart to ensure sufficient rotation of the anchor.

However, it is conceivable to make the conversion member in different forms without departing from the scope of the present invention.

The figure 7 represents a schematic front view of a mechanical resonator for watch movement according to a second embodiment of the present invention, to achieve a similar result.

The anchor 100 here has a more conventional shape, with a range 101 of reduced width with reference to that illustrated in the previous figures.

Thus, the conversion member implemented in the present embodiment uses the principle of the lever arm.

This comprises a rocker 110 intended to be pivotally mounted on a frame member of the watch movement, by means of a pivot 111.

The rocker comprises, at a first end, a first pin 112 pivotally mounted on the free end 5 of the first leg 3 of the tuning fork and, at a second end, a second pin 113 engaged between the teeth of the fork 101 to cooperate with it and rotate the anchor 100 when the first branch 3 vibrates.

Here again, the maximum distance between the different positions that can occupy the teeth of the range 101 is greater than twice the amplitude of the vibrations of the branch 3 of the tuning fork. However, the structure of the conversion member ensures both a good transmission of pulses from the anchor to the tuning fork to maintain the oscillations of the latter and a good transmission of pulses from the tuning fork to the tuning fork. anchor to rotate the latter with an amplitude that ensures proper operation of the associated exhaust. Indeed, the lever makes it possible to amplify the amplitude of vibration of the blade of the tuning fork. More specifically, on the figure 6 , the lever arm used is equal to the ratio of the distance between the second pin 113 and the pivot 111 on the distance between the first pin 112 and the pin 111. With this device, a conventional anchor can be used, condition to provide a suitable lever ratio.

If this solution has a more complex construction and a faster wear of the components in play than in the case of the first embodiment, it still allows to achieve a mechanical resonator that meets the characteristics of the invention.

The foregoing description attempts to describe particular embodiments by way of non-limiting illustration and the invention is not limited to the implementation of certain particular features which have just been described, for example the form specifically illustrated and described for the tuning fork, escape wheel or anchor.

It will be noted, for example, that because of their smaller size than in conventional systems, of an order of magnitude, the shape of the pallets should be modified to strengthen the latter. In particular, the rectangular section of conventional pallets is fragile when their width decreases, so a trapezoidal section may be preferred. The thickness of the pallets can also be increased to reinforce them in a complementary manner. The excess width must of course take into account the cooperation of the pallet with the toothing of the escape wheel.

It is also possible to increase the draft of the pallets by making them integral with the arms of the anchor with a certain angle, different from the usual right angle. Such a draw provides security by reducing the possibility for the escape wheel to accidentally release during the rest phase against the pallet.

Those skilled in the art will not encounter any particular difficulty in adapting the content of the present disclosure to their own needs and implementing a mechanical resonator different from that according to the embodiments described herein, but comprising a conversion element enabling the realization of a free escaping resonator as described above, without departing from the scope of the present invention.

It will be noted in particular, as mentioned above, that the invention is not limited to a resonator comprising a single escape wheel or a single anchor. Indeed, a second escape wheel could be associated with the anchor or an additional anchor cooperating with the second branch of the tuning fork.

Note finally that the silicon compound manufacturing technology is particularly suitable for the production of the elements that have been described, in particular because it guarantees good manufacturing accuracy and the silicon elements in contact with each other present reduced friction with reference to materials commonly used in the watchmaking field. These specific characteristics of silicon are magnified here because of the high vibration frequency of the tuning fork.

Claims (12)

Mechanical tuning fork resonator for a free-escaping mechanical watch movement comprising an oscillator (1) of tuning fork type, of which at least one first branch (3) is intended to oscillate on either side of a first axis and carries at least a first peg associated with at least one first fork tine of an anchor (10, 100), for pivoting said anchor between first and second angular positions and alternately locking and releasing an escape wheel (24), characterized in that it comprises a conversion device (6, 7, 8, 15, 16) integral with said first pin and arranged to,
on the one hand, transforming the oscillations of said first branch (3) of said oscillator (1) into rotational movements of said anchor (10, 100) by the transmission of first pulses to said anchor (10, 100);
on the other hand, transmitting mechanical energy from said anchor (10, 100) to said first branch (3) of said oscillator (1) in the form of pulses,
such that said first tooth has an axial displacement amplitude, substantially in the direction of said first axis, during the pivoting of said anchor, greater than the displacement amplitude of said first pin substantially in the direction of said first axis. Mechanical resonator according to claim 1, characterized in that said conversion member comprises a rocker (110), intended to be pivotally mounted on a frame member of the watch movement and, a first end of which is integral with said first pin (112). so as to be pivotable with reference to said first leg (3) of said oscillator (1), said rocker carrying a second pin (113) for cooperating with said first tooth and with a second tooth of said fork (101) for pivoting said anchor (100). Mechanical resonator according to claim 1, characterized in that said conversion member comprises a support (6) arranged on said first branch (3) of said oscillator (1) and carrying said first pin (7) and a second pin (8), these being intended to cooperate alternately and respectively with said first tooth and with a second tooth (11, 12) fork and being located at a relative distance slightly less than the relative distance between said first and second fork teeth. Mechanical resonator according to claim 3, characterized in that said anchor (10) comprises a frame having first and second arms (15, 16) respectively carrying said first and second fork teeth (11, 12). Mechanical resonator according to claim 4, said anchor (10) being integral with an anchor rod (14) intended to ensure its mounting on the watch movement, characterized in that said first and second arms (15, 16) are extend substantially from said anchor rod (14). Mechanical resonator according to claim 5, said anchor (10) comprising additional first and second arms (18, 19) for alternately cooperating with said escape wheel (24), characterized in that said first and second arms (15) , 16) as well as said first and second additional arms (18, 19) are all arranged in the same plane. Mechanical resonator according to claim 5, said anchor comprising first and second additional arms (18, 19) intended to cooperate alternately with said escape wheel (24), characterized in that said first and second arms (15, 16) on the one hand, and said first and second additional arms (18, 19), on the other hand, are arranged in respective first and second respective planes. Mechanical resonator according to any one of the preceding claims, characterized in that it comprises a second escape wheel associated with said anchor (10). Mechanical resonator according to any one of the preceding claims, characterized in that it comprises a second escape wheel associated with an additional anchor arranged to cooperate with the second branch of said oscillator. Resonator according to any one of the preceding claims, characterized in that said oscillator and / or said anchor and / or said escape wheel are made of silicon. Clock movement comprising a mechanical resonator according to any one of the preceding claims. Timepiece comprising a watch movement according to claim 11.

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