EP3479175B1 - Mechanical clock movement - Google Patents

Description

The present invention relates to a mechanical clock movement.

A traditional mechanical watch movement comprises a source of energy, such as a barrel, a going train driven by the energy source, an escapement driven by the going train and an oscillator whose oscillations are maintained by the 'exhaust. The oscillator (or regulating organ) is generally of the balance-spring type. The escapement generally comprises an escape wheel (coaxial and integral wheel and pinion) and an anchor. The pinion of the escapement wheel meshes with the last wheel of the going train while the wheel of the escapement wheel cooperates with the lever, which communicates mechanical energy pulses to the oscillator.

Some movements also include, in the going train between the energy source and the escapement, a so-called "constant-force" device, that is to say a device comprising an intermediate spring periodically charged by the same amount by the source of energy and supplying its energy to the exhaust. Such a constant-force device makes it possible to make the oscillations of the oscillator independent of the winding state of the energy source.

We also know from patent applications WO 99/64936 , WO 2009/118310 and CH 705674 an escapement comprising a bistable blade wound by a winding rocker actuated alternately by two escapement mobiles. A detent rocker integral with the zone of the midpoint of the bistable blade communicates pulses of mechanical energy to the oscillator during changes of state of the bistable blade. The bistable blade is a "constant force" device that periodically supplies the same amount of power to the oscillator via the detent flip-flop. In the present invention, the member which communicates the pulses of mechanical energy to the oscillator, whether it is in the form of a detent lever, an anchor or the like, is called a "striker".

The efficiency of a mechanical clock movement is low. Indeed, the escapement transmits to the oscillator only a small part of the energy which it receives. One of the causes of the observed energy losses is friction between the different parts. In particular, at each pulse communicated by the striker to the oscillator, the striker accompanies (remains in contact with) the oscillator over a pulse angle which is generally between 12° and 20°. In practice, one can even observe a succession of small shocks during the pulse, especially when the frequency of the oscillator is high. Such a chaotic transmission of energy between the striker and the oscillator is an additional obstacle to obtaining good efficiency.

The present invention aims to provide a clock movement with improved performance.

To this end, a clock movement according to independent claim 1 is provided.

Thanks to the relation between the speeds, the striker transmits all its kinetic energy to the oscillator in a single shock and its speed becomes zero immediately after the shock, so that the accompanying phenomenon between the striker and the oscillator and the energy losses that it causes do not exist in the present invention.

According to another embodiment, the present invention proposes a clock movement according to independent claim 2.

The present invention also proposes a method of making a clock movement according to independent claim 9.

Finally, according to another embodiment, the present invention proposes a method for producing a clock movement according to independent claim 10.

• la figure 1 est un bloc-diagramme d'un mouvement d'horlogerie,
• les figures 2 à 10 montrent en vue de dessus différentes phases de fonctionnement d'un échappement à force constante et d'un oscillateur utilisés dans la présente invention ;
• la figure 11 montre en vue de dessus un percuteur d'échappement et un double plateau d'oscillateur utilisés dans la présente invention ;
• la figure 12 montre en vue de dessus une variante du percuteur utilisé dans la présente invention ;
• la figure 13 montre en vue de dessus une autre variante du percuteur utilisé dans la présente invention.

Other characteristics and advantages of the present invention will appear on reading the following detailed description given with reference to the appended drawings in which:

• the figure 1 is a block diagram of a clock movement,
• them figures 2 to 10 show in top view different operating phases of a constant-force escapement and of an oscillator used in the present invention;
• the figure 11 shows a top view of an escapement striker and a double oscillator plate used in the present invention;
• the figure 12 shows a top view of a variant of the firing pin used in the present invention;
• the figure 13 shows in top view another variant of the striker used in the present invention.

With reference to figure 1 and 2 , a mechanical timepiece movement according to the invention comprises an energy source 1, typically consisting of one or more barrels, a going train 2, an escapement 3 and an oscillator 4. The energy source 1 and the train finishing 2 are conventional, so they will not be described. Oscillator 4 is also of conventional type. It comprises, mounted on a balance shaft 6 of axis A, a balance-spring (not shown) and a double plateau. The double chainring includes a large chainring 7, which carries a chainring peg 8, and a small chainring 9.

The escapement 3 is of the type described in the patent applications WO 99/64936 , WO 2009/118310 and CH 705674 . It thus comprises two escapement wheels (not shown), a bistable leaf spring 10, a winding rocker 11 and a striker or trigger rocker 12.

The two escapement mobiles each comprise a pinion which meshes with the last wheel of the going train 2 and an escapement wheel provided not with teeth but with winding cams each terminated by a locking abutment. The two escape wheels cooperate respectively and alternately with escape pins 13 carried by the winding rocker 11.

The winding rocker 11 and the striker 12 pivot around the same axis B which corresponds to the midpoint of the leaf spring 10. In practice, the axis B is for example the axis of a rod driven into the rocker winding 11, pivoting in the bearings of the movement frame and around which the striker 12 pivots.

Preferably, the leaf spring 10 is integral with the striker 12 and with an outer frame (not shown) which surrounds the leaf spring 10, and consists of two elastic blades 10a, 10b each having one end joined to the striker 12 and another end joined to the external frame, fixed to the frame of the movement. The leaf spring 10 has two convexities of opposite directions on either side of its midpoint and can pass from a first stable state to a second stable state by reversing the direction of each of the two convexities. For this purpose, the leaf spring 10 is either prestressed so as to work in buckling or preformed so as to, in the rest state, already present two convexities as described in the international patent application WO 2017/032528 of the present plaintiff. In the first case, the outer frame is deformable to allow buckling of the leaf spring 10. In the second case, the outer frame is rigid.

The winding rocker 11 comprises two arms 14 carrying at their ends two pins 14a, 14b engaged in eyelets (not shown) of the two elastic blades 10a, 10b respectively. An inverse configuration is of course possible where the pins 14a, 14b would be carried by the elastic blades 10a, 10b, respectively, to engage in eyelets of the winding rocker 11. In addition, other modes of connection between the winding rocker 11 and the elastic blades 10a, 10b can be envisaged, for example two pins at the end of each arm 14 of the winding rocker 11 pinching the corresponding elastic blade.

The firing pin 12 comprises a body 15 surrounding the axis B and extended on one side by a fork 16-17 and on the other side by a shank 18. The fork 16-17 performs the function of an anchor fork traditional, namely cooperating with the plate pin 8 to communicate mechanical energy pulses to the oscillator 4, and comprises for this purpose a first horn 16 and a second horn 17. A stinger 19 secured to the striker 12 is capable of cooperate with the small plate 9 of the oscillator 4 to prevent the overturning of the striker 12 in the event of an impact. The tail 18 is itself arranged to cooperate with first and second limit stops 20, 21 fixed relative to the frame of the movement, for example in one piece with the aforementioned outer frame, to limit the angular displacement of the striker 12.

In operation, the winding rocker 11, actuated by a winding cam of one of the escape wheels and acting symmetrically in the zone of the two convexities of the leaf spring 10, deforms the leaf spring 10 from a first from its stable states to a metastable state close to an unstable state corresponding to fourth mode buckling, to wind the leaf spring 10. This winding phase ends when the winding rocker 11 is blocked by a Escape wheel locking abutment with which it cooperates, which maintains the leaf spring 10 in its metastable state and immobilizes the two escapement wheels, the going train 2 and the winding rocker 11. Then the striker 12 located in the zone of the midpoint of the leaf spring 10 acts on the leaf spring 10 to cause it to exceed its unstable state and thus cause it to switch into its second stable state by releasing its energy. The energy allowing striker 12 to deform leaf spring 10 beyond its unstable state from its metastable state is provided by oscillator 4, when chainring pin 8 strikes horn 16 of the fork. This phase, which requires only a small input of energy, can be compared to the release phase of a lever escapement. The relaxation of the leaf spring 10, that is to say its passage from its unstable state to its second stable state, abruptly changes the inclination of the midpoint zone, which causes the striker 12 to pivot, which then communicates an impulse to the plate pin 8 by its horn 17. The deformation of the leaf spring 10 from its metastable state to its second stable state under the action of the plate pin 8 then its relaxation causes a rotation of the rocker d winding 11 which unlocks the escapement wheels and brings the winding rocker 11 into contact with the other escapement wheel to begin a cycle symmetrical to the previous one, after the impulse given to the plate pin 8.

The figures 2 to 10 represent the different operating phases of the escapement and the oscillator. To the figure 2 , the oscillator 4 is in the acceleration phase and traverses the descending sinister angle, the striker 12 is resting against the limiting abutment 20 and the leaf spring 10 is at the end of winding (metastable state). To the picture 3 , the oscillator 4 is close to its maximum speed and begins to traverse the left angle of lift, the horn 16 of the firing pin 12 is struck by the plate pin 8 (release, by a single shock) and the leaf spring 10 is unlocked (between the metastable state and the unstable state). To the figure 4 , the oscillator 4 is at its maximum speed and traverses the left angle of lift, the striker 12 strikes by its horn 17 the pin of the plate 8 to give it an impulse (by a single shock as will be explained later) then that the leaf spring 10 has just switched from the unstable state to the second stable state. To the figure 5 , oscillator 4 decelerates and traverses the ascending left angle, the striker 12 bears against the limit stop 21 and the leaf spring 10 is at the start of winding (it leaves the second stable state). To the figure 6 , the rotation of the oscillator 4 is reversed (maximum left elongation), the striker 12 is resting against the limiting abutment 21 and the leaf spring 10 is being wound (between the second stable state and the metastable state). To the figure 7 , the oscillator 4 is close to its maximum speed and begins to travel through the dexter lift angle, the horn 17 of the firing pin 12 is struck by the plate pin 8 (release, by a single shock) and the leaf spring 10 is unlocked (between the metastable state and the unstable state). To the figure 8 , the oscillator 4 is at its maximum speed and travels through the dexter lift angle, the striker 12 strikes by its horn 16 the plate pin 8 to give it an impulse (by a single shock as will be explained later) then that the leaf spring 10 has just switched from the unstable state to the first stable state. To the figure 9 , the oscillator 4 decelerates and traverses the dexter ascending angle, the striker 12 bears against the limiting abutment 20 and the leaf spring 10 is at the start of winding (it leaves the first stable state). Finally, at the figure 10 the rotation of the oscillator 4 is reversed (maximum dextral elongation), the striker 12 is bearing against the limiting abutment 20 and the leaf spring 10 is being wound (between the first stable state and the state metastable). Then, escapement 3 finds itself in the phase illustrated in figure 2 and the sequence of figures 2 to 10 repeating itself.

In a traditional escapement, the angle of impulse, ie the angle traveled by the striker between the start of the impulse and the end of the impulse, is between 12° and 20°. In the present invention, on the other hand, this pulse angle is very small, typically less than 1.5° or even 1°. Indeed, during the design of the movement according to the invention, the various parameters of the movement, in particular the quantity of mechanical energy stored in the leaf spring 10 at each of its windings, the geometry of the striker 12 and the moments of inertia of the striker 12 and of the oscillator 4, are chosen in such a way that the striker 12 transfers all its kinetic energy to the oscillator 4 in a single shock ( figure 4 and 8 ), the firing pin 12 having zero speed just after the impact, the residual energy in the leaf spring 10 then bringing the striker 12 to rest against one of the limiting stops 20, 21 ( figure 5 and 9 ).

• pour la conservation du moment cinétique : $$\frac{I_1\cdot {\omega }_{1i}-I_1\cdot {\omega }_{1f}}{d_1}=\frac{I_2\cdot {\omega }_{2f}-I_2\cdot {\omega }_{2i}}{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">d</figure-callout>}}_2}$$
  
• pour la conservation de l'énergie cinétique : $$\frac{I_1\cdot {\omega }_{1\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="imgf0001.png"\; state="\{\{state\}\}">i</figure-callout>}}^2}{2}-\frac{I_1\cdot {\omega }_{1\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="imgf0001.png"\; state="\{\{state\}\}">f</figure-callout>}}^2}{2}=\frac{I_2\cdot {\omega }_{2\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="imgf0001.png"\; state="\{\{state\}\}">f</figure-callout>}}^2}{2}-\frac{I_2\cdot {\omega }_{2\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="imgf0001.png"\; state="\{\{state\}\}">i</figure-callout>}}^2}{2}$$
  
  où
• I₁ est le moment d'inertie du percuteur 12 (incluant tous les éléments qui tournent avec lui, comme le dard 19) par rapport à son axe de rotation B,
• I₂ est le moment d'inertie de l'oscillateur 4 (incluant tous les éléments qui tournent avec lui, comme l'arbre de balancier 6) par rapport à son axe de rotation A,
• ω_1i est la vitesse angulaire du percuteur 12 juste avant l'impulsion qu'il donne à l'oscillateur 4,
• ω_1f est la vitesse angulaire du percuteur 12 juste après ladite impulsion,
• ω_2i est la vitesse angulaire de l'oscillateur 4 juste avant ladite impulsion,
• ω_2f est la vitesse angulaire de l'oscillateur 4 juste après ladite impulsion,
• d₁ est le bras de levier du percuteur 12 (cf. figure 11), c'est-à-dire la distance entre l'axe de rotation B et la droite d'action des forces d'action-réaction F₂ et F₁ exercées par le percuteur 12 et la cheville de plateau 8 l'un sur l'autre au moment du choc (impulsion), et
• d₂ est le bras de levier de l'oscillateur 4 (cf. figure 11), c'est-à-dire la distance entre l'axe de rotation A et la droite d'action des forces d'action-réaction F₂ et F₁ exercées par le percuteur 12 et la cheville de plateau 8 l'un sur l'autre au moment du choc (impulsion).

According to the theory of elastic shocks, the equation of conservation of angular momentum and the equation of conservation of kinetic energy can be written as follows:

• for conservation of angular momentum: $$\frac{I_1\cdot {\omega }_{1I}-I_1\cdot {\omega }_{1f}}{{}_1}=\frac{I_2\cdot {\omega }_{2f}-I_2\cdot {\omega }_{2\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="imgf0001.png"\; state="\{\{state\}\}">I</figure-callout>}}}{{}_2}$$
  
• for the conservation of kinetic energy: $$\frac{I_1\cdot {\omega }_{1I}^2}{2}-\frac{I_1\cdot {\omega }_{1\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="imgf0001.png"\; state="\{\{state\}\}">f</figure-callout>}}^2}{2}=\frac{I_2\cdot {\omega }_{2\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="imgf0001.png"\; state="\{\{state\}\}">f</figure-callout>}}^2}{2}-\frac{I_2\cdot {\omega }_{2I}^2}{2}$$
  
  where
• I ₁ is the moment of inertia of the striker 12 (including all the elements which rotate with it, such as the dart 19) with respect to its axis of rotation B,
• I ₂ is the moment of inertia of oscillator 4 (including all the elements that rotate with it, such as the balance shaft 6) with respect to its axis of rotation A,
• ω _1i is the angular speed of the striker 12 just before the impulse which it gives to the oscillator 4,
• ω _1f is the angular speed of striker 12 just after said pulse,
• ω _2i is the angular speed of oscillator 4 just before said pulse,
• ω _2f is the angular speed of oscillator 4 just after said pulse,
• d ₁ is the lever arm of striker 12 (cf. figure 11 ), that is to say the distance between the axis of rotation B and the line of action of the action-reaction forces F ₂ and F ₁ exerted by the striker 12 and the plate pin 8 one on the other at the time of the shock (impulse), and
• d ₂ is the lever arm of oscillator 4 (cf. figure 11 ), that is to say the distance between the axis of rotation A and the line of action of the action-reaction forces F ₂ and F ₁ exerted by the striker 12 and the plate pin 8 one on the other at the moment of the shock (impulse).

$${\omega }_{2i}=\frac{2\cdot I_2\cdot d_1\cdot d_2}{I_1\cdot d_2^2+I_2\cdot d_1^2}\cdot {\omega }_{1f}+\frac{I_2\cdot d_1^2-I_1\cdot d_2^2}{I_1\cdot d_2^2+I_2\cdot d_1^2}\cdot {\omega }_{2f}$$

The system of equations (1)-(2) can be rewritten as follows: $${\omega }_{1I}=\frac{I_1\cdot {}_2^2-I_2\cdot {}_1^2}{I_1\cdot {}_2^2+I_2\cdot {}_1^2}\cdot {\omega }_{1f}+\frac{2\cdot I_2\cdot {}_1\cdot {}_2}{I_1\cdot {}_2^2+I_2\cdot {}_1^2}\cdot {\omega }_{2f}$$

$${\omega }_{2I}=\frac{2\cdot I_2\cdot {}_1\cdot {}_2}{I_1\cdot {}_2^2+I_2\cdot {}_1^2}\cdot {\omega }_{1f}+\frac{I_2\cdot {}_1^2-I_1\cdot {}_2^2}{I_1\cdot {}_2^2+I_2\cdot {}_1^2}\cdot {\omega }_{2f}$$

By imposing a zero kinetic energy, therefore a zero angular velocity, of the striker 12 after the impulse (ω _1f = 0), the solution of this system of equations is as follows: $${\omega }_{1I}=\frac{2\cdot I_2\cdot {}_1\cdot {}_2}{I_2\cdot {}_1^2-I_1\cdot {}_2^2}\cdot {\omega }_{2I}$$

In practice, the moment of inertia I ₁ of the striker 12 will most often be much lower than the moment of inertia I ₂ of the oscillator 4, the ratio I ₂ /I ₁ being typically greater than 10, even 50, even to 100, even to 500, or even to 1000. The solution of the system of equations (1)-(2) can therefore be expressed as follows: $${\omega }_{1I}\cong \frac{2\cdot {}_2}{{}_1}\cdot {\omega }_{2I}$$

Thus, by ensuring that at the moment of the impact the angular speed of the striker 12 is approximately equal to 2 d ₂ /d ₁ times the angular speed of the oscillator 4, the speed of the striker 12 will be zero just after the impact. , which implies that all of its kinetic energy will have been communicated to oscillator 4 and that striker 12 will not accompany oscillator 4. This results in a significant improvement in the efficiency of the escapement and in the chronometry of the movement.

• en augmentant la quantité d'énergie mécanique emmagasinée par le ressort-lame 10 à chaque armage (par exemple en augmentant le flambage ou l'épaisseur du ressort-lame 10),
• et/ou en augmentant l'écartement des cornes 16, 17 du percuteur 12,
• et/ou en diminuant le moment d'inertie I₁ du percuteur 12.

To obtain relation (5) or (6) above, it is possible to act on the ratio of the lever arms d ₂ /d ₁ and/or on the speeds ω _1i and ω _2i . At a constant d ₂ /d ₁ ratio, the striker 12 must be accelerated relative to the strikers of the state of the art in order to reach the speed of 2·(d ₂ /d ₁ )·ω _2i at the moment of the impulse. Such an acceleration can be obtained for example:

• by increasing the quantity of mechanical energy stored by the leaf spring 10 on each winding (for example by increasing the buckling or the thickness of the leaf spring 10),
• and/or by increasing the spacing of the lugs 16, 17 of the striker 12,
• and/or by reducing the moment of inertia I ₁ of the striker 12.

All of these parameters can be adjusted during motion design using simulation software.

Thus, for example, the spacing E of the horns 16, 17 (measured between the respective points of the horns 16, 17 which strike the plate pin 8 during the impulses, cf. figure 11 ) is greater than 1.5 times, preferably 1.6 times, preferably 1.7 times, preferably 1.8 times, preferably 1.9 times, more preferably 2 times, the diameter D of the plate pin 8. Such a spacing is thus greater than the spacing of 1.06 (=0.35/0.33) times the diameter of the pin that is conventionally observed in escapements.

By "diameter of the chainring peg", we mean its diameter strictly speaking, in particular when the chainring peg is of semi-circular shape. as shown, or more generally its largest dimension perpendicular to the plane which contains the axis of rotation A of the oscillator 4 and which constitutes a plane of symmetry for the platter pin 8. The platter pin 8 may have other shapes than that shown, for example the shape of a finger or part of a finger extending radially from an annular part mounted on the balance shaft 6.

In addition to the acceleration of the striker 12 that it allows, the wide spacing E of the lugs 16, 17 according to the invention promotes the exit of the pin 8 from the fork 16-17 after the impulse by allowing it, given the zero speed of the striker 12, to leave said fork without touching the other horn than that having communicated the impulse to it. Thanks to this feature too, the efficiency of the escapement and the chronometry of the movement are improved.

According to another advantageous characteristic of the invention, visible on the figure 4 , 8 and 11 , the impulse communicated by the striker 12 to the oscillator 4 occurs while the plate pin 8 is on the center line, that is to say while the plate pin 8 is crossed symmetrically by the plane containing the axis of rotation A of the oscillator 4 and the axis of rotation B of the striker 12. This position of the plate pin 8 corresponds to the equilibrium position of the oscillator 4. Communicate the impulse on the line of centers makes it possible not to affect the isochronism of the oscillator.

One can nevertheless, as a variant, choose to carry out the impulse while the plate pin 8 is located after the center line, this in order to promote the exit of the pin 8 from the fork 16-17 after the impulse in allowing it to exit from said fork without touching the other horn than that having communicated the impulse to it. A pulse after the line of the centers gives a delay to the movement but, thanks to the unique shock that the pulse produces in the present invention, this delay will remain constant so that it can be corrected by a simple adjustment of the inertia. of the balance wheel and/or the active length of the hairspring.

The couples of materials commonly used in the escapements for the striker and the pin of the plate, such as steel-ruby, silicon-ruby and silicon-silicon, have coefficients of restitution ε of approximately 1. These materials therefore allow the obtaining elastic shocks, that is to say shocks corresponding to equations (1) and (2) above. It is nevertheless noted in the present invention that the relation (5) constitutes an optimum in terms of efficiency of the escapement for a given coefficient of restitution ε, even if the latter is less than 1.

The striker 12 (or at least the fork 16-17) and the pin 8 are each made of one of the following materials: steel, preferably tempered; aluminum oxide, preferably ruby, more preferably ruby obtained by the Verneuil process; silicon, preferably monocrystalline, preferably also coated with silicon oxide; metallic glass. All combinations of these materials are possible to form the couple of materials of the striker 12 and the pin 8.

The firing pin 12 illustrated in figures 2 to 11 is balanced, in other words its geometry is chosen so that its center of gravity is located on its axis of rotation B. Such a striker shape makes the latter insensitive to the linear shocks received by the clockwork movement. The figure 12 shows a variant of the firing pin used in the present invention. According to this variant, the striker, designated by 12 ', is not balanced but on the contrary has an unbalance which confers on it in particular two arms 22, 23 which extend the lugs 16, 17. These two arms 22, 23, located on the 'other side of the axis of rotation B relative to the tail 18, replace said tail. They thus cooperate respectively with limiting stops 20', 21' to limit the angular movement of the striker 12'.

The unbalance of the striker 12' is chosen so that during the shocks (impulses) communicated by the striker 12' to the plate pin 8 the reaction forces at the level of the axis of rotation B are minimal, thus making it possible to optimize the transmission of energy between striker 12' and oscillator 4 and therefore the efficiency of the escapement.

où

• m₁ est la masse du percuteur 12',
• d₁ est le bras de levier du percuteur 12' c'est-à-dire la distance entre l'axe de rotation B et la droite d'action des forces d'action-réaction F₂ et F₁ exercées par le percuteur 12' et la cheville de plateau 8 l'un sur l'autre au moment du choc (impulsion),
• I₁ est le moment d'inertie du percuteur 12' par rapport à son axe de rotation B, et
• L_G est la distance entre l'axe de rotation B du percuteur 12' et la droite parallèle à la droite d'action des forces F₂, F₁ et passant par le centre de gravité G du percuteur 12'.

En choisissant le balourd du percuteur 12' pour que la relation (7) ci-dessus soit satisfaite, la composante parallèle aux forces F₂, F₁ de la force de réaction exercée au niveau de l'axe de rotation B lors d'une impulsion est nulle.More precisely, the unbalance of the striker 12' is chosen so that the following relationship is satisfied: $${}_1=\frac{I_1}{m_1\cdot L_G}$$

where

• m ₁ is the mass of striker 12',
• d ₁ is the lever arm of the striker 12 'that is to say the distance between the axis of rotation B and the line of action of the action-reaction forces F ₂ and F ₁ exerted by the striker 12 'and the plateau pin 8 on top of each other at the moment of impact (impulse),
• I ₁ is the moment of inertia of striker 12' with respect to its axis of rotation B, and
• L _G is the distance between the axis of rotation B of the striker 12' and the line parallel to the line of action of the forces F ₂ , F ₁ and passing through the center of gravity G of the striker 12'.

By choosing the unbalance of the striker 12' so that relation (7) above is satisfied, the component parallel to the forces F ₂ , F ₁ of the reaction force exerted at the level of the axis of rotation B during a impulse is zero.

• un autre type de dispositif à force constante qu'un ressort-lame bistable pourrait être utilisé ;
• les cornes 16, 17 pourraient faire partie de l'oscillateur 4 et la cheville de plateau 8 pourrait faire partie du percuteur 12 ;
• au lieu d'être monté sur un axe physique 6, l'oscillateur 4 pourrait être du type à pivot flexible ;
• au lieu d'être monté sur un axe physique, le percuteur 12 pourrait lui aussi être du type à pivot flexible.

The present invention has been described above by way of example only. It goes without saying that many modifications could be made without departing from the scope of the claimed invention. For instance :

• another type of constant force device than a bistable leaf spring could be used;
• the horns 16, 17 could be part of the oscillator 4 and the plate peg 8 could be part of the striker 12;
• instead of being mounted on a physical axis 6, the oscillator 4 could be of the flexible pivot type;
• instead of being mounted on a physical axis, the striker 12 could also be of the flexible pivot type.

Moreover, the present invention is not limited to a rotary striker. The striker can in fact be mobile in translation rather than in rotation, like the 12" striker illustrated in figure 13 . Such a movable striker in translation can be actuated for example by a movable frame of the type described in the patent application WO 2013/144236 .

$$\frac{m_1\cdot v_{1i}^2}{2}-\frac{m_1\cdot v_{1f}^2}{2}=\frac{I_2\cdot {\omega }_{2f}^2}{2}-\frac{I_2\cdot {\omega }_{2i}^2}{2}$$

où

• m₁ est la masse du percuteur 12" (incluant tous les éléments qui se déplacent avec lui, comme le dard 19),
• I₂ est le moment d'inertie de l'oscillateur 4 (incluant tous les éléments qui tournent avec lui, comme l'arbre de balancier 6) par rapport à son axe de rotation A,
• v_1i est la vitesse linéaire du percuteur 12" juste avant l'impulsion qu'il donne à l'oscillateur 4,
• v_1f est la vitesse linéaire du percuteur 12" juste après ladite impulsion,
• ω_2i est la vitesse angulaire de l'oscillateur 4 juste avant ladite impulsion,
• ω_2f est la vitesse angulaire de l'oscillateur 4 juste après ladite impulsion, et
• d₂ est le bras de levier de l'oscillateur 4, mesuré comme indiqué précédemment.

In the case of a striker moving in translation, the system of equations (1)-(2) is replaced by the following two equations: $$m_1\cdot v_{1I}-m_1\cdot v_{1f}=\frac{I_2\cdot {\omega }_{2f}-I_2\cdot {\omega }_{2I}}{{}_2}$$

$$\frac{m_1\cdot v_{1I}^2}{2}-\frac{m_1\cdot v_{1\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="imgf0001.png"\; state="\{\{state\}\}">f</figure-callout>}}^2}{2}=\frac{I_2\cdot {\omega }_{2\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="imgf0001.png"\; state="\{\{state\}\}">f</figure-callout>}}^2}{2}-\frac{I_2\cdot {\omega }_{2I}^2}{2}$$

where

• m ₁ is the mass of the 12" firing pin (including all the elements that move with it, such as the 19 dart),
• I ₂ is the moment of inertia of oscillator 4 (including all the elements that rotate with it, such as the balance shaft 6) with respect to its axis of rotation A,
• v _1i is the linear speed of the 12" striker just before the impulse it gives to oscillator 4,
• v _1f is the linear speed of the striker 12" just after said pulse,
• ω _2i is the angular speed of oscillator 4 just before said pulse,
• ω _2f is the angular speed of oscillator 4 just after said pulse, and
• d ₂ is the lever arm of oscillator 4, measured as indicated previously.

$${\omega }_{2i}=\frac{2\cdot m_1\cdot d_2}{m_1\cdot d_2^2+I_2}\cdot v_{1f}+\frac{I_2-m_1\cdot d_2^2}{m_1\cdot d_2^2+I_2}\cdot {\omega }_{2f}$$

This system of equations can be rewritten as follows: $$v_{1I}=\frac{m_1\cdot {}_2^2-I_2}{m_1\cdot {}_2^2+I_2}\cdot v_{1f}+\frac{2\cdot I_2\cdot {}_2}{m_1\cdot {}_2^2+I_2}\cdot {\omega }_{2f}$$

$${\omega }_{2I}=\frac{2\cdot m_1\cdot {}_2}{m_1\cdot {}_2^2+I_2}\cdot v_{1f}+\frac{I_2-m_1\cdot {}_2^2}{m_1\cdot {}_2^2+I_2}\cdot {\omega }_{2f}$$

By imposing a zero kinetic energy, therefore a zero linear speed, of the striker 12" after the impulse (fast = 0), the solution of this system of equations is as follows: $$v_{1I}=\frac{2\cdot I_2\cdot {}_2}{I_2-m_1\cdot {}_2^2}\cdot {\omega }_{2I}$$

In practice, the orbital moment of inertia m ₁ .d ₂ ² of striker 12" will most often be much lower than the moment of inertia I ₂ of oscillator 4, the ratio I ₂ /(m ₁ ·d ₂ ² ) being typically greater than 10, even 50, even 100, even 500, or even 1000. The solution of the system of equations (1')-(2') can therefore be expressed as follows: $$v_{1I}\cong 2\cdot {}_2\cdot {\omega }_{2I}$$

Claims (16)

1. Timepiece movement comprising an oscillator (4) which can rotate about a first axis (A), a striker (12) which can rotate about a second axis (B) for communicating mechanical energy impulses to the oscillator (4), a source of energy (1) and a transmission device (1-3) connecting the source of energy (1) to the striker (12), the transmission device (1-3) comprising a constant force device (10) for periodically storing an amount of energy to be provided to the striker (12), the constant force device (10) comprising a bistable resilient member, the striker (12) or the oscillator (4) comprising a fork (16, 17) arranged to cooperate with a pin (8) of the oscillator (4) or of the striker (12) respectively, the fork comprising first and second horns (16, 17), the fork (16-17) and the pin (8) each being made from one of the following materials: steel, aluminium oxide, silicon, metallic glass, characterised in that said amount of energy, the geometry of the striker (12) and the moments of inertia of the striker (12) and of the oscillator (4) are selected such that upon each impulse communicated to the oscillator (4) by the striker (12) the following relationship is substantially met: $${\omega }_{1i}=\frac{2\cdot I_2\cdot d_1\cdot d_2}{I_2\cdot d_1^2-I_1\cdot d_2^2}\cdot {\omega }_{2i}$$

   

   where I₁ is the moment of inertia of the striker (12) with respect to the second axis (B), I₂ is the moment of inertia of the oscillator (4) with respect to the first axis (A), ω_1i is the angular speed of the striker (12) just before the impulse which it provides to the oscillator (4), ω_2i is the angular speed of the oscillator (4) just before said impulse, d₁ is the lever arm of the striker (12) and d₂ is the lever arm of the oscillator (4), and in that the spacing (E) between the first and second horns (16, 17), measured between the respective points of the first and second horns (16, 17) which strike or are struck by the pin (8) during said impulses, is greater than 1.5 times, preferably greater than 1.6 times, preferably greater than 1.7 times, preferably greater than 1.8 times, preferably greater than 1.9 times, more preferably greater than 2 times, the diameter (D) of the pin (8).
2. Timepiece movement comprising an oscillator (4) which can rotate about an axis (A), a striker (12"), which is displaced in a linear manner, for communicating mechanical energy impulses to the oscillator (4), a source of energy (1) and a transmission device (1-3) connecting the source of energy (1) to the striker (12"), the transmission device (1-3) comprising a constant force device for periodically storing an amount of energy to be provided to the striker (12"), the constant force device (10) comprising a bistable resilient member, the striker (12") or the oscillator (4) comprising a fork (16, 17) arranged to cooperate with a pin (8) of the oscillator (4) or of the striker (12") respectively, the fork comprising first and second horns (16, 17), the fork (16-17) and the pin (8) each being made from one of the following materials: steel, aluminium oxide, silicon, metallic glass, characterised in that said amount of energy, the geometry and mass of the striker (12") and the moment of inertia of the oscillator (4) are selected such that upon each impulse communicated to the oscillator (4) by the striker (12") the following relationship is substantially met: $$v_{1i}=\frac{2\cdot I_2\cdot d_2}{I_2-m_1\cdot d_2^2}\cdot {\omega }_{2i}$$

   

   where m₁ is the mass of the striker (12"), I₂ is the moment of inertia of the oscillator (4) with respect to said axis (A), v_1i is the linear speed of the striker (12") just before the impulse which it provides to the oscillator (4), ω_2i is the angular speed of the oscillator (4) just before said impulse and d₂ is the lever arm of the oscillator (4), and in that the spacing (E) between the first and second horns (16, 17), measured between the respective points of the first and second horns (16, 17) which strike or are struck by the pin (8) during said impulses, is greater than 1.5 times, preferably greater than 1.6 times, preferably greater than 1.7 times, preferably greater than 1.8 times, preferably greater than 1.9 times, more preferably greater than 2 times, the diameter (D) of the pin (8).
3. Timepiece movement as claimed in claim 1, characterised in that the ratio I₂/I₁ is greater than 10, preferably greater than 50, preferably greater than 100, preferably greater than 500, more preferably greater than 1000.
4. Timepiece movement as claimed in claim 2, characterised in that the ratio I₂/(m₁·d₂ ²) is greater than 10, preferably greater than 50, preferably greater than 100, preferably greater than 500, more preferably greater than 1000.
5. Timepiece movement as claimed in claim 1 or 3, characterised in that the striker (12') has an unbalance selected such that the following relationship is substantially met: $$d_1=\frac{I_1}{m_1\cdot L_G}$$

   

   where d₁, I₁ and m₁ are respectively the lever arm, the moment of inertia with respect to the second axis (B) and the mass of the striker (12') and L_G is the distance between the second axis (B) and the straight line passing through the centre of gravity (G) of the striker (12') and in parallel with the force (F2) exerted by the striker (12') on the oscillator (4) at the time of the impulse.
6. Timepiece movement as claimed in claim 1, 3 or 5, characterised in that said amount of energy, the geometry of the striker (12) and the moments of inertia of the striker (12) and of the oscillator (4) are selected such that the impulse angle travelled by the striker (12) upon each impulse communicated to the oscillator (4) is less than 1.5°, preferably less than 1°.
7. Timepiece movement as claimed in any one of claims 1 to 6, characterised in that the striker (12) and the oscillator (4) are arranged so that each of said impulses is communicated to the oscillator (4) whilst it is substantially in its angular position of equilibrium.
8. Timepiece movement as claimed in any one of claims 1 to 6, characterised in that the striker (12) and the oscillator (4) are arranged such that each of said impulses is communicated to the oscillator (4) whilst it is in a position past its angular position of equilibrium.
9. Method for producing a timepiece movement comprising an oscillator (4) which can rotate about a first axis (A), a striker (12) which can rotate about a second axis (B) for communicating mechanical energy impulses to the oscillator (4), a source of energy (1) and a transmission device (1-3) connecting the source of energy (1) to the striker (12), the transmission device (1-3) comprising a constant force device (10) for periodically storing an amount of energy to be provided to the striker (12), the constant force device (10) comprising a bistable resilient member, the striker (12) or the oscillator (4) comprising a fork (16, 17) arranged to cooperate with a pin (8) of the oscillator (4) or of the striker (12) respectively, the fork comprising first and second horns (16, 17), the fork (16-17) and the pin (8) each being made from one of the following materials: steel, aluminium oxide, silicon, metallic glass, the method comprising a step of designing the movement followed by a step of manufacturing the movement, the method being characterised in that during the step of designing the movement, said amount of energy, the geometry of the striker (12) and the moments of inertia of the striker (12) and of the oscillator (4) are selected such that upon each impulse communicated to the oscillator (4) by the striker (12) the following relationship is substantially met: $${\omega }_{1i}=\frac{2\cdot I_2\cdot d_1\cdot d_2}{I_2\cdot d_1^2-I_1\cdot d_2^2}\cdot {\omega }_{2i}$$

   

   where I₁ is the moment of inertia of the striker (12) with respect to the second axis (B), I₂ is the moment of inertia of the oscillator (4) with respect to the first axis (A), ω_1i is the angular speed of the striker (12) just before the impulse which it provides to the oscillator (4), ω_2i is the angular speed of the oscillator (4) just before said impulse, d₁ is the lever arm of the striker (12) and d₂ is the lever arm of the oscillator (4), and in that the spacing (E) between the first and second horns (16, 17), measured between the respective points of the first and second horns (16, 17) which strike or are struck by the pin (8) during said impulses, is selected to be greater than 1.5 times, preferably greater than 1.6 times, preferably greater than 1.7 times, preferably greater than 1.8 times, preferably greater than 1.9 times, more preferably greater than 2 times, the diameter (D) of the pin (8).
10. Method for producing a timepiece movement comprising an oscillator (4) which can rotate about an axis (A), a striker (12"), which is displaced in a linear manner, for communicating mechanical energy impulses to the oscillator (4), a source of energy (1) and a transmission device (1-3) connecting the source of energy (1) to the striker (12"), the transmission device (1-3) comprising a constant force device for periodically storing an amount of energy to be provided to the striker (12"), the constant force device (10) comprising a bistable resilient member, the striker (12") or the oscillator (4) comprising a fork (16, 17) arranged to cooperate with a pin (8) of the oscillator (4) or of the striker (12") respectively, the fork comprising first and second horns (16, 17), the fork (16-17) and the pin (8) each being made from one of the following materials: steel, aluminium oxide, silicon, metallic glass, the method comprising a step of designing the movement followed by a step of manufacturing the movement, the method being characterised in that during the step of designing the movement, said amount of energy, the geometry and mass of the striker (12") and the moment of inertia of the oscillator (4) are selected such that upon each impulse communicated to the oscillator (4) by the striker (12") the following relationship is substantially met: $$v_{1i}=\frac{2\cdot I_2\cdot d_2}{I_2-m_1\cdot d_2^2}\cdot {\omega }_{2i}$$

    

    where m₁ is the mass of the striker (12"), I₂ is the moment of inertia of the oscillator (4) with respect to said axis (A), v_1i is the linear speed of the striker (12") just before the impulse which it provides to the oscillator (4), ω_2i is the angular speed of the oscillator (4) just before said impulse and d₂ is the lever arm of the oscillator (4), and in that the spacing (E) between the first and second horns (16, 17), measured between the respective points of the first and second horns (16, 17) which strike or are struck by the pin (8) during said impulses, is selected to be greater than 1.5 times, preferably greater than 1.6 times, preferably greater than 1.7 times, preferably greater than 1.8 times, preferably greater than 1.9 times, more preferably greater than 2 times, the diameter (D) of the pin (8).
11. Method as claimed in claim 9, characterised in that the ratio I₂/I₁ is greater than 10, preferably greater than 50, preferably greater than 100, preferably greater than 500, more preferably greater than 1000.
12. Method as claimed in claim 10, characterised in that the ratio I₂/(m_1\d₂ ²) is greater than 10, preferably greater than 50, preferably greater than 100, preferably greater than 500, more preferably greater than 1000.
13. Method as claimed in claim 9 or 11, characterised in that during the step of designing the movement, an unbalance is selected for the striker (12') such that the following relationship is substantially met: $$d_1=\frac{I_1}{m_1\cdot L_G}$$

    

    where d₁, I₁ and m₁ are respectively the lever arm, the moment of inertia with respect to the second axis (B) and the mass of the striker (12') and L_G is the distance between the second axis (B) and the straight line passing through the centre of gravity (G) of the striker (12') and in parallel with the force (F2) exerted by the striker (12') on the oscillator (4) at the time of the impulse.
14. Method as claimed in claim 9, 11 or 13, characterised in that during the step of designing the movement, said amount of energy, the geometry of the striker (12) and the moments of inertia of the striker (12) and of the oscillator (4) are selected such that the impulse angle travelled by the striker (12) upon each impulse communicated to the oscillator (4) is less than 1.5°, preferably less than 1°.
15. Method as claimed in any one of claims 9 to 14, characterised in that the striker (12) and the oscillator (4) are arranged so that each of said impulses is communicated to the oscillator (4) whilst it is substantially in its angular position of equilibrium.
16. Method as claimed in any one of claims 9 to 14, characterised in that the striker (12) and the oscillator (4) are arranged such that each of said impulses is communicated to the oscillator (4) whilst it is in a position past its angular position of equilibrium.

Images