EP4202565B1 - Frequency setting of a timepiece oscillator by opto-mechanical deformations - Google Patents

Description

Technical field of the invention

The invention relates to a method for finely adjusting the rate of a mechanical clockwork oscillator comprising at least one inertial mass arranged to oscillate around an axis of rotation and returned to a rest position by elastic return means.

The invention also relates to a mechanical clockwork oscillator suitable for implementing this method.

The invention also relates to a timepiece, in particular a watch, comprising such a mechanical timepiece oscillator.

The invention relates to the field of adjusting the rate of a mechanical watch oscillator, and in particular of an oscillator already fitted into a watch head.

Technological background

Changing the frequency of a mechanical oscillator almost always involves changing the stiffness of the elastic part, such as a spring, or changing its inertia/mass. For example, in the balance springs of mechanical watches, devices for adjusting the stiffness of the balance spring are commonly found, such as varying its active length by moving pins. Another commonly used method is changing the inertia of the balance by moving small masses outward or inward of the balance, such as screws, or eccentric rotating weights.

However, these operations require opening the watch and removing the movement, which tends to distort the result once the case is closed, with a drift sometimes of up to 10 seconds per day, which is unfortunate for movements that need to be adjusted from 0 to +2 seconds per day. In addition, these delicate mechanisms are generally subject to mechanical play which is a source of drift, once the adjustment tool - and the force used for adjustment - are removed.

US 2017/017205 A1 discloses a microsystem for adjusting the rate of a watch oscillator comprising a flywheel comprising an eccentric unbalance and a toothing and arranged to pivot relative to a base plate of the microsystem, which comprises an actuator driving a first active pawl arranged to drive the toothing, and comprises a means for stopping the toothing in position, this actuator being a thermomechanical actuator arranged to transform a flow of energy of light origin (LASER) into a movement of a distal end of this thermomechanical actuator which carries a first active pawl or directly controls a movement of a first active pawl, this microsystem being able to be integrated into a watch comprising a crystal transparent to predetermined wavelength ranges and allowing the passage of a light ray for the adjustment of this microsystem,

Summary of the invention

The invention proposes to precisely adjust the frequency of a mechanical watch oscillator, for example a watch balance spring, without having to disassemble the watch, or more generally the timepiece carrying this oscillator.

For this purpose, the invention relates to a method for finely adjusting the rate of a mechanical clockwork oscillator, according to claim 1.

The invention also relates to a mechanical clockwork oscillator according to claim 17, suitable for implementing this method.

The invention further relates to a timepiece according to claim 23, in particular a watch, comprising such a mechanical timepiece oscillator. Preferred embodiments are defined in dependent claims 2 to 16.

Brief description of the figures

• la figure 1 représente, de façon schématisée et en vue en plan, une montre, avec une tête de montre comportant un élément transparent transmissif qui sépare l'extérieur de la montre et l'intérieur de la montre. Cet élément transparent transmissif, ici représenté sous la forme d'un fond, permet un accès optique à l'utilisateur et à une source optique vers tout ou partie de l'oscillateur de la montre, qui est ici un balancier-spiral dont seul est représenté le balancier, le spiral n'étant pas représenté pour ne pas surcharger les figures. Cette figure 1 représente, en trait interrompu, un rayon laser incident et rencontrant ce balancier;
• la figure 2 représente, de façon schématisée et en vue en plan comme la figure 1, le détail du balancier selon l'invention. Ce balancier comporte, depuis sa serge vers l'élément transparent transmissif, une pluralité de supports disposés par paires symétriques par rapport à l'axe de rotation du balancier. Ces supports supportent, du côté de l'élément transparent transmissif, chacune au moins une masselotte qui est mobile radialement par rapport à l'axe de rotation du balancier. La figure montre, pour chaque support, trois positions différentes d'une telle masselotte, l'une médiane en hachures intermédiaire entre deux positions extrêmes en trait interrompu;
• la figure 3 représente le balancier de la figure 2, en coupe perpendiculaire à l'élément transparent transmissif, lequel sépare, d'une part en partie supérieure de la figure le milieu extérieur dans lequel est positionnée au moins une source laser, et d'autre part en partie inférieure de la figure l'intérieur de la tête de montre qui comporte le balancier. La figure montre la serge portant un support supportant, du côté de l'élément transparent transmissif une telle masselotte qui est mobile radialement par rapport à l'axe de rotation du balancier, sous l'action d'un faisceau émis par la source laser. La figure est centrée sur une masselotte représentée en hachures, et montre une autre position radiale de cette masselotte, représentée en trait interrompu;
• la figure 4 est un graphe qui indique en ordonnée l'écart de marche en secondes par jour, et en abscisse la valeur du déplacement radial symétrique de deux masselottes, en micromètres, et superpose les résultats obtenus pour quatre valeurs de masse de masselotte, de 1,20 mg à 2,40 mg;

• la figure 5 représente, de façon schématisée, et en vue en plan, le principe de la mise en oeuvre d'un actionneur opto-mécanique pour faire mouvoir une masselotte: le support porte des fixations, dont l'une porte l'actionneur opto-mécanique proprement dit, qui comporte deux bras parallèles, formant un U car reliés en bout par un segment commun, le premier bras s'étendant entre une fixation au support et le segment commun, et le deuxième bras s'étendant entre le segment commun et un point de sortie, ici constitué par un col d'un mécanisme amplificateur destiné à amplifier la course de sortie de l'actionneur opto-mécanique pour procurer une course suffisante à la masselotte;
• la figure 6 représente, de façon schématisée, et en vue en plan, une autre variante de l'actionneur opto-mécanique de la figure 5, dont la course de sortie selon une direction linéaire est amplifiée par un amplificateur mécanique, ici un mécanisme de type parallélogramme à quatre cols, qui permet de transformer l'allongement global, ou la rétraction globale, mesurable au point de sortie du deuxième bras, en une course de la masselotte qui soit suffisante pour influencer notablement la marche de l'oscillateur;
• la figure 7 illustre schématiquement le cas où les impulsions attaquent la zone d'écriture du deuxième bras, en haut sur la figure, le mouvement global du point de sortie est alors vers la gauche de la figure, dans un mouvement de poussée de la masselotte;
• la figure 8 illustre le cas opposé à celui de la figure 7, où les impulsions attaquent la zone d'écriture du premier bras, en bas sur la figure, le mouvement global du point de sortie est alors vers la droite de la figure, dans un mouvement de rétraction de la masselotte;
• la figure 9 représente, de façon similaire aux figures 5 à 8, une variante où une masselotte et le support correspondant forment un ensemble monobloc constitué par un chip, sur un niveau unique, le support est alors limité à une zone de fixation pour la fixation sur le balancier; cette variante convient en particulier à l'application de l'invention au cas particulier d'un balancier d'un diamètre de 10,6 mm, porteur de chips de 2 × 2 mm intégrant support et masselotte;
• la figure 10 représente, de façon similaire à la figure 3, une vue en plan du balancier équipé de deux chips selon la figure 9;
• la figure 11 est une vue schématisée, en coupe passant par l'axe de rotation du balancier, et montrant la serge de ce balancier, portant un support, la masselotte n'étant pas représentée, et la source laser d'écriture émettrice pour l'écriture sur les zones d'écriture, ainsi que, monté obliquement en partie gauche de la figure, un laser de détection, dont le rayon réfléchi par le balancier et les éléments qu'il comporte est recueilli en partie droite de la figure par un moyen de recueil tel qu'un photo-détecteur;
• la figure 12 représente, de façon schématisée et en plan, un détail de l'agencement selon la figure 11 avec une source d'écriture laser et une source de détection laser, pour le cas où le balancier oscille, et où le tir laser est synchronisé avec sa position angulaire; la figure représente une partie de la serge du balancier, portant un chip selon la figure 9; l'arc représenté en trait interrompu correspond à la position instantanée de la source d'écriture laser, qui tire perpendiculairement au plan de la figure, et qui peut ainsi écrire dans la zone d'écriture du premier bras inférieur dans le cas d'espèce, pour créer une dilatation moléculaire symbolisée par une petite flèche dans cette zone d'écriture, les petites flèches voisines correspondant à des écritures déjà effectuées dans la même zone avec des positionnements différents en x de la source d'écriture, correspondant à des rayons différents par rapport à l'axe de rotation du balancier; en partie inférieure de la figure est visible depuis la gauche vers la droite une source de détection laser, une lentille convergente, le rayonnement incident vers le balancier, le point de réflexion sur le balancier ou sur les organes qu'il porte, le rayonnement réfléchi, une lentille convergente, et le photo-détecteur;
• la figure 13 juxtapose trois graphes temporels, établis avec en abcisses des échelles de temps différentes, mais qui sont agencés l'un par rapport à l'autre pour mettre en évidence des instants particuliers et les phénomènes qui s'y produisent : le graphe supérieur affiche en ordonnée la vitesse angulaire oméga OME du balancier, le graphe médian affiche en ordonnée la valeur du signal VPD du photo-détecteur, et le graphe inférieur affiche en ordonnée l'intensité optique IIE émise par la source laser d'écriture;
• la figure 14 est un schéma-blocs montrant les liens entre des moyens de pilotage, une table à mouvements croisés pour la manoeuvre du laser d'écriture, ce dernier, un laser de détection, le moyen de recueil du rayonnement réfléchi, et des moyens de mise en mouvement ou d'arrêt de l'oscillateur;
• la figure 15 est un schéma-blocs regroupant les cinq étapes principales du procédé d'ajustement de marche selon l'invention.

The aims, advantages and characteristics of the invention will appear better on reading the detailed description which follows, and with reference to the appended drawings, where:

• there figure 1 represents, schematically and in plan view, a watch, with a watch head comprising a transparent transmissive element which separates the exterior of the watch and the inside of the watch. This transparent transmissive element, here represented in the form of a background, allows optical access to the user and to an optical source to all or part of the oscillator of the watch, which is here a sprung balance of which only the balance is represented, the sprung balance not being represented for do not overload the figures. This figure 1 represents, in a broken line, an incident laser beam meeting this pendulum;
• there figure 2 represents, schematically and in plan view, as the figure 1 , the detail of the balance according to the invention. This balance comprises, from its rim towards the transparent transmissive element, a plurality of supports arranged in symmetrical pairs relative to the axis of rotation of the balance. These supports support, on the side of the transparent transmissive element, each at least one weight which is radially movable relative to the axis of rotation of the balance. The figure shows, for each support, three different positions of such a weight, one median in hatching intermediate between two extreme positions in broken line;
• there figure 3 represents the pendulum of the figure 2 , in section perpendicular to the transparent transmissive element, which separates, on the one hand in the upper part of the figure the external environment in which at least one laser source is positioned, and on the other hand in the lower part of the figure the interior of the watch head which includes the balance. The figure shows the rim carrying a support supporting, on the side of the transparent transmissive element such a weight which is radially movable relative to the axis of rotation of the balance, under the action of a beam emitted by the laser source. The figure is centered on a weight shown in hatching, and shows another radial position of this weight, shown in a broken line;
• there figure 4 is a graph which indicates on the ordinate the deviation in steps in seconds per day, and on the abscissa the value of the symmetrical radial displacement of two weights, in micrometers, and superimposes the results obtained for four values of mass of massotte, from 1.20 mg to 2.40 mg;

• there figure 5 represents, schematically, and in plan view, the principle of the implementation of an optomechanical actuator to move a weight: the support carries fixings, one of which carries the optomechanical actuator itself, which comprises two parallel arms, forming a U because they are connected at the end by a common segment, the first arm extending between a fixing to the support and the common segment, and the second arm extending between the common segment and an output point, here constituted by a neck of an amplifier mechanism intended to amplify the output stroke of the optomechanical actuator to provide sufficient stroke for the weight;
• there figure 6 represents, schematically and in plan view, another variant of the opto-mechanical actuator of the figure 5 , the output stroke of which in a linear direction is amplified by a mechanical amplifier, here a four-neck parallelogram type mechanism, which makes it possible to transform the overall elongation, or the overall retraction, measurable at the output point of the second arm, into a stroke of the weight which is sufficient to significantly influence the operation of the oscillator;
• there figure 7 schematically illustrates the case where the impulses attack the writing zone of the second arm, at the top of the figure, the overall movement of the output point is then towards the left of the figure, in a pushing movement of the weight;
• there figure 8 illustrates the opposite case to that of the figure 7 , where the pulses attack the writing area of the first arm, at the bottom in the figure, the overall movement of the exit point is then towards the right of the figure, in a retraction movement of the weight;
• there figure 9 represents, in a similar way to Figures 5 to 8 , a variant where a weight and the corresponding support form a single-piece assembly consisting of a chip, on a single level, the support is then limited to a fixing zone for fixing on the balance; this variant is particularly suitable for the application of the invention to the particular case of a balance with a diameter of 10.6 mm, carrying 2 × 2 mm chips integrating support and weight;
• there figure 10 represents, in a similar way to the figure 3 , a plan view of the balance wheel equipped with two chips according to the figure 9 ;
• there figure 11 is a schematic view, in section passing through the axis of rotation of the balance, and showing the rim of this balance, carrying a support, the weight not being shown, and the emitting writing laser source for writing on the writing areas, as well as, mounted obliquely in the left part of the figure, a detection laser, the ray of which reflected by the balance and the elements it comprises is collected in the right part of the figure by a collection means such as a photo-detector;
• there figure 12 represents, schematically and in plan, a detail of the arrangement according to the figure 11 with a laser writing source and a laser detection source, for the case where the balance wheel oscillates, and where the laser shot is synchronized with its angular position; the figure represents a part of the balance wheel rim, carrying a chip according to the figure 9 ; the arc shown in a broken line corresponds to the instantaneous position of the laser writing source, which draws perpendicular to the plane of the figure, and which can thus write in the writing area of the first lower arm in this case, to create a molecular expansion symbolized by a small arrow in this writing area, the neighboring small arrows corresponding to writings already carried out in the same area with different positions in x of the writing source, corresponding to different radii relative to the axis of rotation of the balance; in the lower part of the figure is visible from left to right a laser detection source, a converging lens, the incident radiation towards the balance, the reflection point on the balance or on the organs it carries, the reflected radiation, a converging lens, and the photo-detector;
• there figure 13 juxtaposes three time graphs, established with different time scales on the abscissa, but which are arranged in relation to each other to highlight particular moments and the phenomena which occur there: the upper graph displays on the ordinate the angular speed omega OME of the balance, the middle graph displays on the ordinate the value of the signal VPD of the photo-detector, and the lower graph displays on the ordinate the optical intensity IIE emitted by the writing laser source;
• there figure 14 is a block diagram showing the links between control means, a cross-motion table for operating the writing laser, the latter, a detection laser, the means for collecting the reflected radiation, and means for starting or stopping the oscillator;
• there figure 15 is a block diagram grouping the five main steps of the gait adjustment method according to the invention.

Detailed description of the invention

The invention proposes to induce permanent mechanical tensions, and therefore a volume expansion, in particular by femtosecond laser excitation, in a flexible micro-mechanism machined in a glass (fused silica) or similar support.

The support is embedded on the inertial mass of the oscillator, in particular the balance wheel, of a mechanical watch. The movement of a part of the mechanism will modify the inertia of this inertial mass, therefore the frequency of the oscillator, in particular the balance wheel-spring. Displacements of the order of several micrometers can be obtained in such glass microstructures by writing parallel internal tension expansion lines, as can be read in particular in the article " Non-contact sub-nanometer optical repositioning using femtosecond lasers”, by Y. Bellouard, in “Optic Express, November 2, 2015, volume 23, No. 22 ".

The microstructures themselves are made using a precise cutting process of +/-1 micrometer, using the same type of laser, followed by chemical attack, as can be read in the aforementioned article, or in the article " Fabrication of high-aspect ratio, micro-fluidic channels and tunnels using femtosecond laser pulses and chemical etching”, by Y. Bellouard et al., in “Optics Express, 2004, 12, pages 2120-2129 ", or on the website of FEMTOprint SA, 6933 Muzzano (CH), on the page

https://www.femtoprint.ch/devices-photos .

The absence of pivots or any other frictional guidance guarantees high positioning accuracy and zero hysteresis. Optical excitation is direct through a glass or any non-absorbing casing separation for the laser wavelength, or defocused at the point of passage.

The invention is illustrated more particularly, and not limitingly, for the case where the oscillator is a watch oscillator, and is a sprung balance.

The invention relates to a method for finely adjusting the rate of a mechanical oscillator 100 for a timepiece, comprising at least one inertial mass 1 arranged to oscillate around an axis of rotation D and returned to a rest position by elastic return means.

According to the invention, and as visible on the figure 15 , in a first step 801, the oscillator 100 is equipped with at least one inertial mass 1 comprising an actuator 35 in a material capable of irreversible local micro-expansion under the action of laser shots. This actuator 35 is arranged to impart to a weight 3 a radial linear stroke relative to the axis of rotation D, directly or via at least one stroke amplifier 36, when a writing zone 39, or more particularly a first writing zone 391 on a first arm 33, or a second writing zone 392 on a second arm 34, which the actuator 35 comprises is subjected to appropriate laser shots. It will be seen later that each writing zone 39, 391, 392, is capable of receiving expansion lines 390 by laser writing.

The name “writing zone 39” concerns the generic case, and the names “first writing zone 391” and “second writing zone 392” concern the preferred, but not limiting, application on respectively a first arm 33, and a second arm 34 of the weight 3.

More particularly, when an inertial mass 1, subjected to a rotational movement, extends on either side of the rotation axis D, this inertial mass 1 is equipped with at least one pair of diametrically opposed actuators 35, in a material capable of irreversible local micro-expansion under the action of laser shots. This is particularly the case when an inertial mass 1 is a balance of a sprung balance type oscillator.

More particularly, when an inertial mass 1, is cantilevered relative to the axis of rotation D, like the inertial masses suspended by flexible blades, which are symmetrical with respect to a plane passing through the axis of rotation D, this inertial mass 1 is equipped with at least one pair of actuators 35 symmetrical with respect to this plane of symmetry.

More particularly, this method is applied to an oscillator 100 with at least two inertial masses 1 each comprising such an actuator 35.

In a second step 802, a first adjustment, in particular a rough one, is made of the initial rate of the oscillator 100 in a first rate range and the rate is measured.

In a third step 803, the direction and value of the deviation in rate to be imparted to the oscillator 100 are calculated to bring it into a second predetermined range of rate, and the direction and value of the stroke to be imparted to each weight 3 included in the oscillator 100 are calculated.

In a fourth step 804, at least one writing zone 39, 391, 392 is subjected to femtosecond laser shots to create at least one expansion line 390 by local molecular expansion of the material to deform the actuator 35 radially relative to the axis of rotation D.

In a fifth step 805, the rate of the oscillator 100 is measured, and if necessary the third step 803 and the fourth step 804 are repeated until the rate of the oscillator 100 is within the second predetermined rate range.

More particularly, during the fourth step 804, a femtosecond laser source 700 is used, mounted on a cross-movement table 710, or with radial travel, so as to increment different series of shots on different radii relative to the axis of rotation D, to create a series of expansion lines 390 in the immediate vicinity of each other.

More particularly, during the fourth step 804, a femtosecond laser source 700 is used to carry out shots in each direction of rotation of the inertial mass 1.

More particularly, during the fourth step 804, control means 790 are used to control the firing of the femtosecond laser source 700, according to the information on the presence or absence of material provided by the combination of a detection laser 750 and a collection means 760 or a photodetector.

More particularly, during the first step 801, an actuator 35 is chosen comprising, on a first arm 33, a first writing zone 391, and on a second arm 34 parallel to the first arm 33 in a radial linear direction L and joining it at a common segment 334, a second writing zone 392. The actuator 35 is thus mounted in an “S” shape between, on the one hand, a fixing zone 30 fixed to a support 2 mounted on the inertial mass 1 or directly fixed to the inertial mass 1, and on the other hand, an output point or a connecting neck 32 for connection with an amplifier mechanism 36. The actuator 35 is arranged to act in two opposite directions in the linear direction L, depending on whether, during the fourth step 804, the writing by femtosecond laser shots takes place in the first writing zone 391 on the first arm 33 for a advance adjustment, or in the second writing area 392 on the second arm 34 for a delay adjustment.

More particularly, during the first step 801, an actuator 35 is chosen with an output point or a connecting neck 32 for connection with an amplifier mechanism 36 which is arranged to amplify the output stroke of the actuator 35, to impart an amplified stroke to the weight 3.

More particularly, this amplifier 36 is of the parallelogram type, and includes a connecting rod system with 310 connecting rods. arranged between flexible necks 31 forming a linear guide in a radial linear direction L.

More particularly, during the first step 801, an actuator 35 is chosen comprising a fixing zone 30 secured to a support 2 mounted on the inertial mass 1. And the support 2 forms a single-block assembly constituting a flexible micro-mechanism, with the actuator 35, an amplifier 36 and the weight 3 mounted in series with each other.

More particularly, during the first step 801, an actuator 35 is chosen comprising a fixing zone 30 fixed to a support 2 mounted on the inertial mass 1 or secured to a support 2, and the actuator 35 and/or the support 2 is made of glass.

More particularly, during the first step 801, the inertial mass 1 is chosen in the form of a balance, which comprises at least one pair of identical and diametrically opposed weights 3 relative to the axis of rotation D.

More particularly, during the first step 801, the oscillator 100 is integrated into a watch head 500 of a watch 1000, which watch head 500 comprises at least one transparent transmissive element 600, which separates the exterior and the interior of the watch 1000, and allows optical access to at least one laser to at least the inertial mass 1 of the oscillator 100 of the watch.

In a static variant, during the first step 801, the oscillator 100 is equipped with stopping means or a second stop arranged to rest on an inertial mass 1, and the fourth step 804 is carried out in a blocked position of the inertial mass 1.

In a dynamic variant, during the fourth step 804, the femtosecond laser writing shots are carried out during the oscillation of the inertial mass 1, the angular position and the shots of which are synchronized.

More particularly, during the fourth step 804, the shots are carried out with a femtosecond laser, for example and not limited to a wavelength between 900 and 1100 nm, a pulse duration between 200 and 350 fs, a pulse energy approximately between 200 and 300 nJ, a repetition rate of 700 to 900 kHz. It is quite obvious that a different femtosecond laser (wavelength, pulse duration and energy) can be used, provided that it can modify the material in the same way described above.

The invention also relates to a mechanical oscillator 100 for a timepiece comprising at least one inertial mass 1 arranged to oscillate about an axis of rotation D and returned to a rest position by elastic return means, suitable for implementing this method. According to the invention, at least one inertial mass 1 comprises an actuator 35 in a material capable of irreversible local micro-expansion under the action of laser shots. The actuator 35 is arranged to impart to a weight 3 a radial linear stroke relative to the axis of rotation D, directly or via at least one stroke amplifier 36, when a writing zone 39, 391, 392, which the actuator 35 comprises is subjected to appropriate laser shots.

More particularly, the actuator 35 comprises, on a first arm 33, a first writing zone 391, and on a second arm 34 parallel to the first arm 33 in a radial linear direction L and joining it at a common segment 334, a second writing zone 392, the actuator 35 thus being mounted in an “S” shape between, on the one hand, a fixing zone 30 fixed to a support 2 mounted on the inertial mass 1 or directly fixed to the inertial mass 1, and, on the other hand, an output point or a connecting neck 32 for connection with an amplifier mechanism 36, the actuator 35 being arranged to act in two opposite directions in the linear direction L, depending on whether femtosecond laser shots are applied in the first writing zone 391 on the first arm 33 for an advance adjustment, or in the second writing area 392 on second arm 34 for delay adjustment.

More particularly, the actuator 35 comprises an output point or a connecting neck 32 for connection with an amplifier mechanism 36 arranged to amplify the output stroke of the actuator 35, to impart an amplified stroke to the weight 3. And the amplifier 36 is of the parallelogram type, and comprises a connecting rod system with connecting rods 310 arranged between flexible necks 31 forming a linear guide in a radial linear direction L.

More particularly, the actuator 35 comprises a fixing zone 30 secured to a support 2 mounted on the inertial mass 1, and the support 2 forms a single-piece assembly constituting a flexible micro-mechanism, with the actuator 35, an amplifier 36 and the mass 3 mounted in series with each other.

More particularly, the actuator 35 comprises a fixing zone 30 fixed to a support 2 mounted on the inertial mass 1 or secured to a support 2, and the actuator 35 and/or the support 2 is made of glass.

More particularly, the inertial mass 1 is a balance, which comprises at least one pair of identical and diametrically opposed weights 3 relative to the axis of rotation D.

The invention also relates to a timepiece, in particular a watch 1000, comprising at least one such mechanical oscillator 100. According to the invention, the watch 1000 comprises a watch head 500 comprising at least one transparent transmissive element 600, which separates the exterior and the interior of the watch 1000, and allows optical access to at least one laser to at least the inertial mass 1 of the oscillator 100 of the watch.

The figures illustrate non-limiting embodiments of the invention, in the particular case where the inertial mass 1 is a balance wheel.

There figure 1 represents a timepiece 1000, in particular a watch, with a watch head 500, comprising a transparent transmissive element 600, such as a back, a crystal, or the like, which separates the exterior of the watch and the interior of the watch. This transparent transmissive element 600 allows optical access to the user and to an optical source to all or part of the oscillator 100 of the watch, and, in this case, at least the balance wheel 1, the balance spring not being shown so as not to overload the figures. This figure 1 represents, in a broken line, an incident laser beam RL meeting the pendulum 1.

The invention proposes to adjust precisely, and through a casing that is at least locally transparent or of low optical absorption such as this transparent transmissive element 600, the frequency of a sprung balance by means of a focused laser beam. The oscillator 100 is either already roughly adjusted to +/- 15 seconds per day, for example using screws not shown, or precisely matched to an appropriate balance spring in this range. The action of the laser allows fine adjustment to 0-2 seconds per day, by moving small weights towards the outside or towards the inside of the balance 1, thus modifying its inertia, and therefore modifying the frequency of the oscillator, and thus allowing precise adjustment of the rate of the watch.

There figure 2 shows, in plan view like the figure 1 , the detail of the balance 1 according to the invention. This balance 1 comprises, from its rim 19 towards the transparent transmissive element 600, a plurality of supports 2 arranged in symmetrical pairs relative to the axis of rotation D of the balance. These supports 2, in particular chips, each support, on the side of the transparent transmissive element 600, at least one weight 3 which is radially movable relative to the axis of rotation D of the balance 1. figure 2 shows, for each support 2, three different positions of such a weight 3, one median in hatching intermediate between two extreme positions in broken line, at a radial distance X from the position intermediate. This limited number of radial positions of the weights 3 is only a special case to leave the figure readable.

The figures illustrate particular variants where each support 2 is attached to the balance 1, for ease of execution; another variant where the supports 2 and the balance 1 form a single-piece assembly is possible, although more expensive to produce.

There figure 3 is a section perpendicular to the transparent transmissive element 600, which separates, on the one hand in the upper part of the figure the external environment in which at least one laser source 700 is positioned, and on the other hand in the lower part of the figure the interior of the watch head which comprises the balance 1. This balance 1 comprises, from its rim 19 towards the transparent transmissive element 600, a plurality of supports 2 arranged in symmetrical pairs with respect to the axis of rotation D of the balance. These supports 2 support, on the side of the transparent transmissive element 600, each at least one weight 3 which is movable radially with respect to the axis of rotation D of the balance 1, under the action of a beam emitted by the laser source 700. figure 3 is centered on a weight 3 shown in hatching, and shows another radial position of this weight 3, shown in a broken line. The weights 3 are thus secured to a support 2, itself fixed on the rim 19 towards the outside of the balance 1 as illustrated.

The displacement amplitude depends on several parameters of the laser exposure. This amplitude can be controlled very precisely, and the weights 3 remain in place after an exposure, and it is possible to move the weights 3 in both directions over a fixed number of cycles. In order not to disturb the imbalance, the supports 2 must be grouped in pairs, diametrically opposed, and they must be adjusted simultaneously to the same amplitude. The Figures 2 and 3 illustrate the simplest case with a single pair of supports 2. Another variation is to have an even number 2N of supports 2, N being an integer ranging from 1 to typically 10, and depending mainly on the diameter of the balance 1 and on the possibility of geometrically implanting these pairs of supports 2. In this configuration with a plurality of supports 2, not only the frequency but also the unbalance can be adjusted.

• écart de marche $$\mathrm{\Delta }\mathrm{M}=86400*\mathrm{x}*\left(2\mathrm{R}+\mathrm{x}\right)/\left({\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+\mathrm{Io}/2\mathrm{m}\right),$$
  
• avec R la valeur en mètres du rayon neutre de giration de la masselotte 3, lo l'inertie de base du balancier sans masselottes, en kg*m², et m la masse d'une masselotte en kg.

For the simple special case of two diametrically opposed supports 2, illustrated by the figures, the relationship between the rate deviation (deviation from the ideal frequency) of the oscillator 100, in seconds per day, and the radial displacement X of two weights 3, in meters, is given by the following equation:

• walking gap $$\mathrm{\Delta }\mathrm{M}=86400*\mathrm{x}*\left(2\mathrm{R}+\mathrm{x}\right)/\left({\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+\mathrm{Io}/2\mathrm{m}\right),$$
  
• with R the value in meters of the neutral radius of gyration of the mass 3, lo the basic inertia of the balance without masses, in kg*m ² , and m the mass of a mass in kg.

• rayon extérieur du balancier = 5.3 mm;
• giration à R = 4 mm;
• inertie du balancier sans masselottes: 2^e-9 kg*m^2;
• masse d'une masselotte: 1.2 ≤ m ≤ 2.4 mg;
• plage visée +/- 15 secondes par jour.

There figure 4 illustrates the numerical application of the previous equation to a classic mechanical watch balance, with the following characteristics:

• outer radius of the balance = 5.3 mm;
• gyration at R = 4 mm;
• inertia of the balance without weights: 2 ^e-9 kg*m ^2;
• mass of a mass: 1.2 ≤ m ≤ 2.4 mg;
• target range +/- 15 seconds per day.

• courbe C1 pour m= 1,20 mg;
• courbe C2 pour m= 1,60 mg;
• courbe C3 pour m= 2,00 mg.
• courbe C4 pour m= 2,40 mg.

The graph of the figure 4 indicates on the ordinate the deviation in rate ΔM in seconds per day, and on the abscissa the value of the symmetrical radial displacement of two weights, in micrometers, and superimposes the results obtained for four values of weight mass:

• curve C1 for m= 1.20 mg;
• curve C2 for m= 1.60 mg;
• curve C3 for m= 2.00 mg.
• curve C4 for m= 2.40 mg.

For example, curve C2, relating to weights 3 with a mass of 1.6 mg, corresponds to the displacement of +/- 10 micrometers of a glass parallelepiped of 0.30 × 1.33 × 1.70 mm ³ , on either side of its zero position. The frequency adjustment obtained here is +/- 11 seconds per day. This range can be easily extended, either by increasing the mass of the weights, or by increasing the peak-peak travel. One variant consists in particular in loading, on this glass plate, an additional mass, made of metal or any other ad hoc material.

The choice of the optomechanical actuator is essential for obtaining a reproducible and precise result. The already mentioned publication " Non-contact sub-nanometer optical repositioning using femtosecond lasers", by Y. Bellouard, in "Optic Express, November 2, 2015, volume 23, No. 22 » describes an ultra-precise positioning device, capable of being used for the alignment of optical fiber axes, which requires positioning to within a few nanometers. This is a demonstrator made in a glass wafer, with a thickness of approximately 500 micrometers, commonly used in packaging and in microfluidic applications.

There figure 5 schematically sets out the principle: the support 2 carries fasteners 30, one of which carries the optomechanical actuator 35 itself, which comprises two parallel arms 33 and 34, forming a U because they are connected at the end by a common segment 334, the first arm 33 extending between a fastener 30 and the common segment, and the second arm 34 extending between the common segment 334 and an output point, here non-limitingly constituted by a connecting neck 32 with an amplifier mechanism 36. The other fastener 30 carries the weight 3, connected by the neck 31, acting as a center of rotation.

THE figures 2, 3 , And 5 illustrate particular variants where each weight 3 is attached to a support 2 at the level of its fixings 30, for ease of execution.

Another variant, visible on the figures 6 And 9 has 12 , where the weight 3 and the corresponding support 2 form a single-piece assembly, in particular a chip, which makes it possible to produce the weight 3 and the support 2 on the same level, the support 2 is then limited to a fixing zone 30 for fixing on the balance 1.

Similarly, it is also conceivable that the weights 3, the supports 2, and the balance 1 form a single-piece assembly, although this variant is even more expensive to produce.

According to the invention, this first arm 33 and this second arm 34 are intended to receive laser pulses, and comprise writing zones respectively 391, 392, at the level of which bursts of very brief laser pulses, emitted by the laser source 700, will create, in the thickness of the material, a local modification of its structure by molecular expansion, this expansion being rapidly stopped by the stopping of the pulses, and the deformation therefore remaining a permanent deformation. These core deformations are infinitesimal, and therefore the method consists in locally juxtaposing a large quantity of zones thus expanded, to achieve a cumulative expansion sufficient to sufficiently move the weight 3 in a linear direction L. Advantageously a mechanical amplifier 36, for example a mechanism of the parallelogram type with four necks such as visible on the figure 6 , makes it possible to transform the overall elongation, or the overall retraction, measurable at the exit point of the second arm 34, into a stroke of the weight 3 which is sufficient to significantly influence the operation of the oscillator 100.

We understand that the movement is different, depending on whether the laser pulses attack the first arm 33 or the second arm 34: the figure 7 illustrates the case where the pulses attack the second writing zone 392 of the second arm 34, the overall movement of the exit point is then in the direction of arrow B, in a pushing movement of the weight 3. While the figure 8 illustrates the case where the pulses attack the first writing zone 391 of the first arm 33, the overall movement of the exit point is then in the direction of arrow A, opposite to the direction of arrow B, in a retraction movement of the weight 3. It is thus possible to move a weight 3 radially in one direction or the other.

The laser action does not cause cutting, or even superficial engraving, the goal is a molecular reordering at the heart of the material, in its thickness. The notion of writing expansion lines is a periphrasis to describe the application of series of pulses according to a network whose projection of the trajectories on the plane of the mass appears as a series of very close parallel expansion lines, or very sharp zig-zag expansion lines, or other; the goal is indeed to expand the material at the core, and to accumulate very close expansions along the same linear direction L.

By writing expansion lines in the volume of the material at the writing zones 39, in particular first writing zone 391, second writing zone 392, this material expands following the action of these zones subject to compressive stresses. This state results from very intense, but sufficiently brief, point heating so as not to liquefy the material. There is just a very slight expansion of the volume, the material remaining solid. This point heating is achieved by a burst of very brief pulses from a femtosecond laser, for example what is described, but not limited to, by the article already cited " Non-contact sub-nanometer optical repositioning using femtosecond lasers”, by Y. Bellouard, in “Optic Express, November 2, 2015, volume 23, No. 22 » (Yb-fiber amplified laser, from Amplitude Systèmes SA, wavelength = 1030 nm, pulse duration 270 fs, pulse energy about 250 nJ, repetition rate 800 kHz). The beam is focused through a lens into a spot of a few micrometers, at a working distance of the order of 6 mm. A precise three-dimensional scan of a few micrometers of these pulses thus makes it possible to define one or more volumetric zones under stress. It is obvious that a different femtosecond laser (wavelength, pulse duration, energy and repetition rate) can be used provided that it can modify the material in the same way described above. The working distance of the focusing lens can be varied depending on the shaping optics and the focusing of the laser beam.

The non-limiting mechanism of Figures 5 to 8 presented here because of its great simplicity, comprises an actuator 35 in an "S" shape in a radial linear direction L, and arranged to act in two opposite directions in this same direction, depending on whether the writing takes place in the upper zone of the second arm 34 (advance) or the lower zone of the first arm 33 (retraction). The amplifier 36 comprises, without limitation, a connecting rod system with connecting rods 310 between flexible necks 31 forming a linear guide in the linear direction L, and makes it possible to amplify the stroke of the actuator by a multiplying factor Km, so that the embedded square table, i.e. the weight 3, moves by an amplitude of a few micrometers.

According to the information in the article already mentioned above (Y. Bellouard, 2015), for blocks of 200 parallel planes written in a volume of overall length of approximately 1 mm in the linear direction L, we obtain, with the laser parameters above and according to the figures: a multiplying factor Km of 6, an amplified stroke of the weight 3 of approximately 5 micrometers, for 200 expansion lines written over a length of 1 mm; the specific displacement at the actuator 35, in the linear direction L, is therefore, per written line: 5 / (200 * 6) = 4.167 nm / line (or plane).

The same technique can be used to cut the microstructure itself, according to the articles cited above. A first step consists of writing, using the same core expansion process under the action of a laser, volumetric zones to be removed in a glass plate (fused silica). In a second step, the plate is subjected to a chemical attack, which selectively removes the stressed parts. The machining obtained is also precise to the micrometer, and allows these glass microstructures to be produced.

THE Figures 9 and 10 illustrate the application of the invention to the particular numerical example presented above, with a balance with a diameter of 10.6 mm (outer diameter of the rim 19); the diameter 190, here 8.0 mm, corresponds to the diameter of gyration of the centers of mass of the weights. The actuator 35 and the amplifier 36 are adapted to limit the plane dimensions of the supports 2 to a square with a side of 2.0 mm, in particular a glass chip, with a thickness of 0.3 mm, which carries, on the same single level, the weight 3 and the support 2 limited to at least one fixing zone 30, for fixing to the balance 1 and for suspending the actuator 35, the amplifier 36, and the weight 3.

The mechanism schematized on the Figures 5 to 8 is thus modified for reasons of compactness and adaptation to the typical dimensions of a sprung balance. We assume that the same sigma constraints, applied to an actuator beam of smaller section, give rise to the same linear displacement of 4.167 nm / line, by virtue of Hooke's law: dl/l = E*sigma, with dl = increase in length, l = length of the zone, E = Young's modulus of the material. To obtain the same amplitude as the previous actuator, the writing length of the 200 expansion lines must therefore be identical and equal to 1 mm in the linear direction L.

As illustrated in figure 9 , for a glass support 2 with a thickness of 0.3 mm, the mass of the rectangular pallet which constitutes the weight 3 is worth 1.6 mg, which corresponds to the rate - displacement relationship C2 of the graph of the figure 4 .

The distance between the middle of two bending necks 31 delimiting a connecting rod 310 is, in this example, 1.40 mm, and the distance between the middle of the lower bending neck 31 and the connecting neck 32 is 0.14 mm. These necks bending 31 or connection 32 have here a width of 20 micrometers, which is acceptable from a technological point of view. The multiplying factor Km between the stroke of the actuator and that of the mass is worth, by virtue of the ratio of the lever arms: Km = 1.400 mm / 0.140 mm = 10

The maximum linear amplitude of the structure is: +/- x = Km * 200 expansion lines * 4.167 nm/line = 2000*4.167 nm = +/- 8.33 micrometers, which corresponds, via graph C2, to approximately +/- Δwalk = +/- 9 seconds per day.

The resolution of the adjustment per written line and considering 200 expansion lines for each of the two ranges of 9 seconds per day is therefore d_marche (1 line) = 9/200 = 0.045 seconds per day and per line, which is largely sufficient to adjust a walk in a range of 0 - 2 seconds per day.

It is noted that two zones 1 mm long in the linear direction L allow a single advance correction of +9 seconds per day and a delay correction of -9 seconds per day. To have several writing cycles, it is possible either to increase the number of supports 2 or to increase the mass, which has the effect of having to write fewer expansion lines for the same displacement, and therefore to reserve space on the first arm 33 and on the second arm 34 for subsequent writings.

With regard to the implementation of the rate adjustment, a starting state is considered where, before correction, the rate of the watch is assumed to be known and measured, with the case closed. To perform the correction, a dedicated setting is used to precisely position the watch head. A microscopic objective and a positioning stage with xy crossed movements then allow the centering of the laser source 700, in particular a femtosecond laser, on the balance 1.

From this point, two options arise: either the balance wheel is immobilized by a blocking/braking lever, such as a stop-seconds or the like, or a spatial stopping and holding mechanism of the oscillator, and the laser shot is fired at a stationary target, or the pendulum 1 is still oscillating, and the laser shot must then be synchronized with its angular position.

The case where the balance is immobilized, and the laser shot is carried out on a stationary target, can be resolved with semi-automatic positioning for example and not limited to control means managing a camera with image recognition software which centers on the axis of rotation D of the balance.

In the case where the pendulum 1 oscillates, and where the laser shot is synchronized with its angular position, the method is more complex, but more advantageous because the adjustment is carried out in flight, without the need to stop the pendulum. The shot can be started with the beginning of the passage of the support 2 through a detection laser beam 750, as illustrated in the Figures 11 and 12 .

There figure 11 is a schematic view, in section passing through the axis of rotation D of the balance 1, and showing the rim 19 of this balance, carrying a support 2, the weight 3 not being shown, and the laser writing source 700 for writing on the writing zones 39, 391, 392, as well as, mounted obliquely in the left part of the figure, such a detection laser 750, the ray of which reflected by the balance 1 and the elements which it comprises is collected in the right part of the figure by a collection means 760 such as a photo-detector.

There figure 12 illustrates the detail of the arrangement according to the figure 11 with a laser writing source 700 and a laser detection source 750, for the case where the balance 1 oscillates, and where the laser shot is synchronized with its angular position; the rim 19 of the balance 1 carries a chip according to the figure 9 ; the arc shown in a broken line corresponds to the instantaneous position of the laser writing source 700, which draws perpendicular to the plane of the figure, and which can thus write in the first writing zone 391 of the first arm lower 33 in this case, to create an expansion line 390, that is to say a molecular expansion symbolized by a small arrow in this first writing zone 391, the neighboring small arrows corresponding to other expansion lines 390, that is to say writings already carried out in the same zone with different positions in x of the writing source 700, corresponding to different radii relative to the axis of rotation D of the balance 1. In the lower part of the figure is visible from left to right a laser detection source 750, a converging lens 770, the incident radiation towards the balance 1, the reflection point on the balance 1 or on the organs that it carries, the reflected radiation, a converging lens 780, and the photo-detector 760.

On the figure 12 , the left edge of the rim 19 of the balance 1 oscillates up and down in its circular trajectory. The chip 2 is fixed to the balance 1 by its base. The optics is composed of a writing laser source 700 for performing the optical axis writing in the z direction perpendicular to the plane of the balance 1, and a detection laser 750, for example inclined at an angle of 45° relative to the plane of the balance, the axes of the incident and reflected beams of which are included in the xz plane. Their respective spots may be slightly offset in x, but must remain on the same dimension in z.

There figure 13 juxtaposes three time graphs, established with different time scales on the abscissa, but which are arranged relative to each other to highlight particular moments and the phenomena which occur there: the upper graph displays on the ordinate the angular speed omega OME of the balance 1, the middle graph displays on the ordinate the value of the signal VPD of the photo-detector 760, and the lower graph displays on the ordinate the optical intensity IIE emitted by the writing laser source 700.

When pendulum 1 oscillates, its angular speed OME is maximum near the neutral point, i.e. between times t1 and t4 of the graph superior of the figure 13 , which corresponds to a sprung balance oscillating at a few Hz. This area is interesting because the speed does not vary much so it can be considered quasi-constant. The detection laser 750 is thus used to turn on and off a burst of writing pulses, coming from the writing laser source 700.

The VPD signal of the photodetector 760 associated with the detection laser 750 is at the value 1 when its spot is on a full area of the chip 2, that is to say successively fixing area 30/first lower arm 33/second upper arm 34/weight 3, as visible both on the median graph of the figure 13 and on the figure 12 , and the VPD signal is at the value 0 in a slot. Thus, this signal can be used to trigger and trigger the writing of the burst by the writing laser source 700, either between times t2 and t3, and more precisely in a first writing zone 391 for the advance adjustment on the first arm 33, or in a second writing zone 392 for the delay adjustment on the second arm 34. In the example illustrated by the figure 12 , four expansion lines 390 are written in the first advance zone on the first arm 33, which will pull the weight 3 towards the axis of rotation D of the balance 1, and cause a rate advance by increasing the frequency. The start of the optical intensity bursts IIE is triggered by the positive edge of the VPD signal at the instant TON, and their stop is triggered by the negative edge of the VPD signal at the instant TOFF. For example, one alternation, i.e. a half-period, can be used to write an expansion line 390, then shift by an increment x with the writing laser source 700, to write the next adjacent expansion line at the next alternation, and so on. The detection of the direction of rotation is done using the VPD signal, the pattern of which is different depending on the direction. This makes it possible to always turn on the writing laser source 700 in the correct zone.

• Te = Le / (R*A*2π*F), avec R = rayon de giration, A= amplitude angulaire du balancier et F= fréquence de l'oscillateur.

The writing (passage) duration Te in the first advance zone on the first arm 33, or in the second delay zone on the second arm 34, which is a zone of length Le, is given by:

• Te = Le / (R*A*2π*F), with R = radius of gyration, A = angular amplitude of the balance and F = frequency of the oscillator.

In this example, Le = 190 um, R = 4 mm, A = 270°, F = 4 Hz, hence Te = 0.40 ms.

The repetition frequency of the write pulses being 800 kHz in this example, the number of pulses per pass is therefore 800 * 0.40 = 320, and therefore the maximum (cumulative) error of the operation is therefore: 1/320 * (+/-9 seconds per day) = +/- 0.03 seconds per day, which is perfectly satisfactory for the application.

The technique of machining glass using femtosecond lasers and chemical etching, which allows the production of three-dimensional structures precise to the nearest micrometer, is a proven technique.

This technique makes it possible to produce 2 millimeter chips with flexible elements that can move over micrometric amplitudes, with nanometric precision. The actuation of the nano-displacement of the actuator part 35 is carried out by laser writing of internal constraints. A system of flexible necks 31 and connecting rods 310 makes it possible to increase the amplitudes in the linear direction L.

The realization of such a chip 2 is suitable for the precise and reliable adjustment of the rate of a sprung balance, with a precision of 0.03 seconds per day, and a resolution of 0.09 seconds per day, in a range of typically +/-10 seconds per day. Of course, the range amplitude and the resolution can be easily varied by adapting the design.

It may be noted that the invention offers the possibility of carrying out an infinitesimal and irreversible expansion, which, in theory, could allow, by a series of shots on the elastic return element of the oscillator, such that spiral spring, flexible blade or similar, to modify its stiffness; however, the creation of these deformed zones harms the homogeneity of the component, and the risk is an alteration of the elastic properties of this elastic return element. This is why the invention is presented here preferentially for an action on the inertial element, regardless of whether it is suspended by a spiral spring or by elastic blades.

The adjustment system is compact and does not require any additional complications in the 1000 watch, other than the mounting of two or more glass chips 2 on the balance wheel 1.

This adjustment can be carried out directly on a complete watch 1000, provided that the watch head 500 comprises a transparent transmissive element 600, such as a back, a crystal, or other, which is transparent or non-absorbent for the writing laser in optical access on the oscillator. The invention naturally relates to a watch 1000 thus equipped.

There figure 14 illustrates the peripherals and their links: the control means 790, a cross-motion table 710 for operating the writing laser 700, a detection laser 750, the means for collecting the reflected radiation 760, and means 720 for stopping and releasing the oscillator 100.

The external part of the adjustment (positioning, microscope, optics and lasers) typically occupies the volume of an office, which allows for rapid and user-friendly adjustment, both in production and in the store for customer service.

The implementation of the invention is all the better as one achieves an optimization of the absorption of the radiation by the physical protection separation (box, casing), that one realizes a reliable positioning system of the laser spot. Naturally, it is appropriate to adopt a dimensioning adapted for the zones under tension, above certain dimensions determined experimentally, to avoid a increased fragility of these stress areas, which could cause premature rupture during impacts.

Claims (23)

1. Method for the fine adjustment of the rate of a mechanical horological oscillator (100) including at least one inertial mass (1), for example but not restricted to: a balance, arranged to oscillate about an axis of rotation (D) and returned to a rest position by elastic return means, characterised in that, in a first step (801), said oscillator (100) is equipped with at least one inertial mass (1) including an actuator (35) in a material suitable for irreversible local micro-expansion under the effect of laser fires, said actuator (35) being arranged to impart to an inertia-block (3) a radial linear travel with respect to the axis of rotation (D), directly or by means of at least one travel amplifier (36), when a writing zone (39; 391; 392), included in the actuator (35) is subjected to suitable laser fires, in a second step (802), a first rough setting of the initial rate of said oscillator (100) is performed in a first rate range and said rate is measured, in a third step (803), the direction and the value of the rate deviation to be imparted to said oscillator (100) are calculated to bring it into a predetermined second rate range, and the direction and the value of the travel to be imparted to each said inertia-block (3) included in said oscillator (100) are calculated, in a fourth step (804), at least one said writing zone (39; 391; 392) is subjected to femtosecond laser fires to create at least one expansion line (390) by local molecular expansion of said material to deform said actuator (35) radially with respect to said axis of rotation (D), in a fifth step (805), the rate of said oscillator (100) is measured, and if required said third step (803) and said fourth step (804) are repeated until the rate of said oscillator (100) is within said second rate range.
2. Method according to claim 1, characterised in that said method is applied to a said oscillator (100) with at least two said inertial masses (1) each including a said actuator (35).
3. Method according to claim 1 or 2, characterised in that, during said fourth step (804), a femtosecond laser source (700) is used, mounted on a table with crossing movements (710) or with radial travel, so as to juxtapose different series of fires on different beams with respect to said axis of rotation (D) to create a series of said expansion lines (390) in the immediate vicinity of one another.
4. Method according to one of claims 1 to 3, characterised in that, during said fourth step (804), a femtosecond laser source (700) is used to perform laser fires in each direction of rotation of said inertial mass (1).
5. Method according to one of claims 1 to 4, characterised in that, during said fourth step (804), control means (790) are used to control the fires of said femtosecond laser source (700), according to the information in respect of the presence or absence of material provided by the combination of a detection laser (750) and a collection means (760) or a photodetector.
6. Method according to one of claims 1 to 5, characterised in that, during said first step (801), a said actuator (35) is chosen including, on a first arm (33) a first writing zone (391), and on a second arm (34) parallel with the first arm (33) along a radial linear direction (L) and joining it at a common segment (334) a second writing zone (392), said actuator (35) thus being mounted in an "S" between, on one hand, a fastening zone (30) fastened to a support (2) mounted on said inertial mass (1) or directly fastened to said inertial mass (1), and, on the other, an exit point or a linking neck (32) for linking with an amplifying mechanism (36), said actuator (35) being arranged to act in two opposite directions along said linear direction (L), whereby, during said fourth step (804), femtosecond laser fire writing takes place in said first writing zone (391) on said first arm (33) for a gain setting, or in said second writing zone (392) on said second arm (34) for a loss setting.
7. Method according to one of claims 1 to 6, characterised in that, during said first step (801), a said actuator (35) is chosen with an exit point or a linking neck (32) for linking with an amplifying mechanism (36) arranged to amplify the exit travel of said actuator (35), to impart an amplified travel to said inertia-block (3).
8. Method according to claim 7, characterised in that said amplifier (36) is parallelogram type, and includes a connecting rod system with connecting rods (310) arranged between flexible necks (31) forming a linear guidance along a radial linear direction (L).
9. Method according to one of claims 1 to 8, characterised in that, during said first step (801), a said actuator (35) is chosen including a fastening zone (30) rigidly connected to a support (2) mounted on said inertial mass (1), and in that said support (2) forms a one-piece assembly forming a flexible micro-mechanism, with said actuator (35), an amplifier (36) and said inertia-block (3) mounted in series with each other.
10. Method according to one of claims 1 to 9, characterised in that, during said first step (801), a said actuator (35) is chosen including a fastening zone (30) fastened to a support (2) mounted on said inertial mass (1) or rigidly connected to a said support (2), and in that said actuator (35) and/or said support (2) is made of glass.
11. Method according to one of claims 1 to 10, characterised in that, during said first step (801), said inertial mass (1) is chosen in the form of a balance, which includes at least one pair of identical said inertia-blocks (3) diametrically opposed with respect to said axis of rotation (D).
12. Method according to one of claims 1 to 10, characterised in that, during said first step (801), said oscillator (100) is incorporated into a watch head (500) of a watch (1000), said watch head (500) including at least one transmissive transparent element (600), which separates the outside and inside of said watch (1000) and enables optical access for at least one laser to at least said inertial mass (1) of said oscillator (100) of the watch.
13. Method according to one of claims 1 to 12, characterised in that, during said first step (801), said oscillator (100) is equipped with stopping means or a stop-seconds means arranged to bear on a said inertial mass (1), and in that said fourth step (804) is performed in a locked position of said inertial mass (1).
14. Method according to one of claims 1 to 12, characterised in that, during said fourth step (804), said femtosecond laser writing fires are performed during the oscillation of said inertial mass (1), wherein the angular position and said fires are synchronised.
15. Method according to one of claims 1 to 14, characterised in that, during said fourth step (804), said fires are performed with a femtosecond laser.
16. Method according to claim 15, characterised in that, during said fourth step (804), said fires are performed with a femtosecond laser, of wavelength between 900 and 1100 nm, pulse time between 200 and 350 fs, pulse energy approximately between 200 and 300 nJ, repetition frequency of 700 to 900 kHz.
17. Mechanical horological oscillator (100) including at least one inertial mass (1) arranged to oscillate about an axis of rotation (D) and returned to a rest position by elastic return means, characterised in that at least one said inertial mass (1) includes an actuator (35) in a material suitable for irreversible local micro-expansion under the action of laser fires, said actuator (35) being arranged to impart to an inertia-block (3) a radial linear travel with respect to said axis of rotation (D), directly or by means of at least one travel amplifier (36), when a writing zone (39; 391; 392) included in said actuator (35) is subjected to suitable laser fires.
18. Mechanical oscillator (100) according to claim 17, characterised in that said actuator (35) includes, on a first arm (33) a first writing zone (391), and on a second arm (34) parallel with the first arm (33) along a radial linear direction (L) and joining it at a common segment (334) a second writing zone (392), said actuator (35) thus being mounted in an "S" between, on one hand, a fastening zone (30) fastened to a support (2) mounted on said inertial mass (1) or directly fastened to said inertial mass (1), and, on the other, an exit point or a linking neck (32) for linking with an amplifying mechanism (36), said actuator (35) being arranged to act in two opposite directions along said linear direction (L), whereby said femtosecond laser fires are applied in said first writing zone (391) on said first arm (33) for a gain setting, or in said second writing zone (392) on said second arm (34) for a loss setting.
19. Mechanical oscillator (100) according to claim 17 or 18, characterised in that said actuator (35) includes an exit point of a linking neck (32) for linking with an amplifying mechanism (36) arranged to amplify the travel of said actuator (35), to impart an amplified travel to said inertia-block (3), and in that said amplifier (36) is parallelogram type, and includes a connecting rod system with connecting rods (310) arranged between flexible necks (31) forming a linear guidance along a radial linear direction (L).
20. Mechanical oscillator (100) according to one of claims 17 to 19, characterised in that said actuator (35) includes a fastening zone (30) rigidly connected to a support (2) mounted on said inertial mass (1), and in that said support (2) forms a one-piece assembly forming a flexible micro-mechanism, with said actuator (35), an amplifier (36) and said inertia-block (3) mounted in series with each other.
21. Mechanical oscillator (100) according to one of claims 17 to 20, characterised in that said actuator (35) includes a fastening zone (30) fastened to a support (2) mounted on said inertial mass (1) or rigidly connected to a said support (2), and in that said actuator (35) and/or said support (2) is made of glass.
22. Mechanical oscillator (100) according to one of claims 17 to 21, characterised in that said inertial mass (1) is a balance, which includes at least one pair of identical said inertia-blocks (3) diametrically opposed with respect to said axis of rotation (D).
23. Watch (1000) including at least one mechanical oscillator (100) according to one of claims 17 to 22, characterised in that said watch (1000) includes a watch head (500) including at least one transmissive transparent element (600), which separates the outside and inside of the watch (1000) and enables optical access for at least one laser to at least said inertial mass (1) of said oscillator (100) of the watch.

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