EP3598243B1 - Timepiece mechanism with jumping member - Google Patents

Description

The present invention relates to a jumping organ watch mechanism, in particular for the instantaneous display of a temporal quantity such as the date.

Instantaneous display mechanisms comprising a snail cam against which a rocker rests under the action of a return spring applied against the rocker are known in watchmaking. The return spring is a V-shaped, U-shaped or spiral leaf. At each revolution of the cam, the lever slides from the lower part to the upper part of the cam, which gradually arms the return spring, then the lever drops from said upper part to said lower part, this sudden movement, considered instantaneous, being used to actuate an indicator such as a needle associated with a scale or a disk bearing indications and cooperating with a window. Patent applications CH 702137 and EP 2241944 , for example, describe such mechanisms for a minute counter.

Other mechanisms are also known, for example those described in the documents CH 524847 and EP 2799938 , in which a spiral spring has one of its ends which is kinematically connected to a drive member for continuous winding of the spiral spring by the drive member and its other end which is released periodically by a blocking device for periodic winding of the spring hairspring, each disarming having the effect of actuating a jumping indicator member.

All these mechanisms have the drawback that the torque to be produced to wind the spring varies as a function of time. It is indeed necessary to overcome the force of the spring which increases linearly with its degree of winding. This variation in torque affects the regularity of the oscillations of the regulator member of the watch and therefore the precision of the measurement.

The present invention aims to remedy this drawback or at least to attenuate it and to this end proposes a watch mechanism comprising a motor member, a regulating member for regulating the motor member, a jumping member, an actuating spring, a or several gears between the driving member and the actuating spring and a winding and blocking device allowing continuous winding of the actuating spring by the driving member via the gear(s) and periodic disarming of the spring actuation, the actuation spring causing the jumping member to make a jump each time it is unwinded, characterized in that the actuation spring is a spring with non-linear behavior which produces, between a winding angle θ _a and a winding angle θ _b separated by at least 10°, an elastic return moment which does not vary by more than 10%, and in that the actuating spring is pre-wound with a value θ _arm included in the range [θ _a , θ _b ], the clockwork mechanism was nt arranged so that, during its operation, the winding angle of the actuating spring remains in the range [θ _a , θ _b ].

The present invention also proposes a timepiece, such as a clock, a wristwatch or a pocket watch, comprising this timepiece mechanism.

• la figure 1 est un schéma-bloc d'un mécanisme horloger à organe sautant selon l'invention ;
• la figure 2 une vue de dessus d'un dispositif d'armage et de blocage et d'une roue flexible du mécanisme horloger à organe sautant selon l'invention ;
• la figure 3 est une vue de dessus de la roue flexible seule, comprenant un moyeu et une serge reliés par un ressort d'actionnement ;
• la figure 4 est une représentation graphique schématique illustrant l'allure de la courbe d'évolution du moment de rappel élastique exercé par le ressort d'actionnement dans la roue flexible ;
• la figure 5 représente les coordonnées de points définissant une forme particulière de bras élastique pour le ressort d'actionnement ;
• la figure 6 est une représentation graphique du moment de rappel élastique exercé par le ressort d'actionnement dans la roue flexible comprenant des bras élastiques de forme telle que représentée à la figure 5 ;
• la figure 7 est une représentation graphique d'un moment de rappel élastique normalisé exercé par le ressort d'actionnement dans la roue flexible illustrée à la figure 3 selon différentes variantes des bras élastiques du ressort d'actionnement, à savoir de tels bras à section constante (courbe A1) et de tels bras à section variable (courbes A2 à A4), la section variant selon un premier mode de variation ;
• la figure 8 est une représentation graphique d'un moment de rappel élastique normalisé exercé par le ressort d'actionnement dans la roue flexible illustrée à la figure 3 selon deux variantes des bras élastiques du ressort d'actionnement, à savoir de tels bras à section constante (courbe B1) et de tels bras à section variable (courbe B2), la section variant selon un deuxième mode de variation ;

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 jumping organ clock mechanism according to the invention;
• the figure 2 a top view of a winding and locking device and of a flexible wheel of the watch mechanism with a jumping member according to the invention;
• the picture 3 is a top view of the flexible wheel alone, comprising a hub and a rim connected by an actuating spring;
• the figure 4 is a schematic graphic representation illustrating the shape of the evolution curve of the elastic return moment exerted by the actuating spring in the flexible wheel;
• the figure 5 represents the coordinates of points defining a particular form of elastic arm for the actuating spring;
• the figure 6 is a graphic representation of the elastic return moment exerted by the actuating spring in the flexible wheel comprising elastic arms of a shape as shown in figure 5 ;
• the figure 7 is a graphical representation of a normalized elastic restoring moment exerted by the actuating spring in the flexible wheel shown in picture 3 according to different variants of the elastic arms of the actuating spring, namely such arms with constant section (curve A1) and such arms with variable section (curves A2 to A4), the section varying according to a first mode of variation;
• the figure 8 is a graphical representation of a normalized elastic restoring moment exerted by the actuating spring in the flexible wheel shown in picture 3 according to two variants of the elastic arms of the actuating spring, namely such arms with constant section (curve B1) and such arms with variable section (curve B2), the section varying according to a second mode of variation;

The figure 1 is a block diagram of a timepiece mechanism 1 according to the invention, with a jumping member, for a timepiece such as a clock, a wristwatch or a pocket watch. The watch mechanism 1 forms or is part of a watch movement. It comprises a drive member 2, a gear train 3 driven by the drive member 2, a winding and locking device 4 actuated by the gear train 3 and a flexible wheel 5 actuated by the winding and locking device 4.

The driving member 2 is typically in the form of one or more barrel springs housed in one or more respective barrels. The rotation of the gear train 3 and of the barrel or barrels is regulated in a conventional manner by a regulating member 6, for example with escapement and balance-spring. Motor member 2, gear train 3 and regulator member 6 are conventional and will therefore not be described in more detail.

The winding and blocking device 4 is shown in picture 2 . It comprises a winding wheel set 7, a blocking wheel set 8 and a moving frame 9. A wheel 10 of the winding wheel set 7 meshes with the gear train 3 and is continuously driven by the latter. A star wheel 11 of the winding mobile 7, coaxial with and integral in rotation with the wheel 10, is located in a first closed contour opening 12 of the mobile frame 9 and constitutes a rotary drive member cooperating with two drive elements 13 diametrically opposed formed in the wall of the opening 12. A star 14 of the blocking mobile 8 is located in a second opening with a closed outline 15 of the mobile frame 9 and constitutes a rotary blocking member cooperating with two stop elements 16 diametrically opposite formed in the wall of the opening 15. This star 14 is coaxial with and integral in rotation with a pinion 17 forming part of the mobile blocking device 8. The mobile frame 9 is guided in translation along the double arrow F by a device flexible guide 18 with which it preferably forms a single piece. The mobile frame 9 could however be guided in rotation. The assembly 9, 11, 14 forms a blocking device of the type described in patent applications PCT/IB2018/052645 and PCT/IB2018/052646 of the applicant which are incorporated in the present application by reference.

The flexible wheel 5 is shown in figures 2 and 3 . It comprises a hub 19 which is coaxial and integral in rotation with the winding mobile 7, a rim 20 and elastic arms or blades 21 uniformly distributed around the hub 19 and connecting the hub 19 to the rim 20. The rim 20 is thus suspended from the hub 19, and guided in rotation with respect to the hub 19, by the elastic arms 21. The latter together form an actuating spring 22 capable of storing mechanical energy by stretching (by a rotation of the hub 19 with respect to to the serge 20 in one direction, namely the clockwise direction of the picture 2 or 3 ) and restore it by relaxing (by rotating the rim 20 relative to the hub 19 in the Same direction). The respective ends of the elastic arms 21 joined to the hub 19 together constitute a winding end of the actuating spring 22. The respective ends of the elastic arms 21 joined to the rim 20 together constitute a torque delivery end of the actuating spring 22. The flexible wheel 5 further comprises an external toothing 23 secured to the rim 20. This toothing 23 meshes with the pinion 17 of the blocking mobile 8.

The flexible wheel 5 is preferably in one piece. It is for example made of metal, alloy, silicon (typically coated with silicon oxide), plastic, mineral glass or metallic glass. It can be produced by machining or by the LIGA technique, in particular in the case where it is made of a metal or alloy, by deep reactive ion etching called DRIE, in particular in the case where it is made of silicon, by molding, in particular in the case where it is made of plastic or metallic glass, or by laser cutting, in particular in the case where it is made of mineral glass.

A display disc 24 is fixed, for example glued, to the rim 20. In the example shown, the display disc 24 is a date display disc bearing two series of indications “1” to “31 » and the rim 20 and the display disc 24 perform together in a jumping manner, with one jump per day, one turn in two months. The indications carried by the display disk 24 are successively visible through an aperture of a dial of the timepiece. The display disc 24 could be one piece with the flexible wheel 5.

The operation of the clockwork mechanism 1 is as follows.

The winding mobile 7 and with it the hub 19 rotate continuously, according to a rhythm determined by the oscillations of the regulating member 6, in the clockwise direction of the picture 2 under the action of the motor member 2 exerted via the gear train 3. In doing so, they continuously arm the actuating spring 22. Most of the time, the blocking mobile 8, which is under tension due to the torque the actuating spring 22, is blocked by one of the stop elements 16 against which rests on one of the branches of star 14, which keeps rim 20 stationary and therefore the torque delivery end of actuating spring 22.

The rim 20 is released periodically at times which are determined by the meeting between the star 11 of the winding mobile 7 and each of the drive elements 13. As soon as a branch of the star 11 comes into contact with the one of the drive elements 13, it cooperates with the latter to move the mobile frame 9 in order to disengage the star wheel 14 of the locking mobile 8 from the stop element 16 against which it was resting. Under the action of the actuating spring 22, the rim 20 and the blocking mobile 8 begin to rotate abruptly until another branch of the star 14 comes to rest on the other element of stop 16. During this sudden movement, considered instantaneous with respect to the movement of the gear train 3 and the winding mobile 7, the indication visible through the aperture is replaced by the following one and the actuating spring 22 is partially disarmed.

The different gear ratios in the watch mechanism 1 and the number of branches of each of the stars 11 and 14 are chosen so that the actuating spring 22 accumulates between two successive unwindings (two successive jumps of the serge 20) the same quantity of energy than that released at each disarming.

The watch mechanism 1 as described above and illustrated in figure 1 and 2 is an example of implementation. Many variations are possible.

For example, the clockwork mechanism 1 could be adapted to cause the display disk 24 to display a quantity other than the date, such as the month, the day of the week, the hour, the minute or the second.

The winding mobile 7 could be kinematically connected to the hub 19 in a way other than by being integral in rotation with the latter, for example by means of one or more gears. The blocking mobile 8 could be kinematically connected to the rim 20 by more than one gear. Another one modification could consist in making the driving member 2 mesh directly with the wheel 10.

The winding and blocking device 4 is advantageous in particular for protecting the watch mechanism 1 against shocks and for reducing friction, as explained in the patent applications PCT/IB2018/052645 and PCT/IB2018/052646 . However, it is possible to use other winding and blocking devices, such as the one described in the application for patent EP 2799938 or even winding and blocking devices allowing only semi-instantaneous movement (partly dragging, partly jumping) of the display disc.

Instead of being constituted by rim 20 and display disc 24, the jumping member of watch mechanism 1 could be constituted by hub 19. Hub 19 would then be coaxial and integral in rotation with blocking wheel set 8 while that pinion 17 which meshes with toothing 23 carried by rim 20 would be coaxial and integral in rotation with winding mobile 7. The number of branches of each of stars 11 and 14 would be adapted accordingly. Such a variant, where the actuating spring 22 is armed by the rim 20 and disarmed by the hub 19, can be used in particular to display a magnitude by means of a needle integral in rotation with the hub 19. The needle can, for example, being a dead seconds hand.

In all cases, according to the present invention, the elastic arms 21 which constitute the actuating spring 22 are specially shaped to improve the constancy of the torque or elastic return moment exerted by this actuating spring 22, and therefore the constancy of the torque necessary to continuously arm this actuating spring 22, and thus improve the regularity of the oscillations of the regulating member 6.

For the understanding of the invention, the behavior of the flexible wheel 5, considered in isolation, that is to say free of any interaction with the winding mobile 7 and with the locking mobile 8, is described below. . The picture 3 represents this isolated flexible wheel 5.

The insulated flexible wheel 5 shown in picture 3 has, due to the shape of its elastic arms 21, a privileged direction of rotation of its rim 20 with respect to its hub 19, this direction being defined as that which allows, from its state of rest, the greatest displacement relative angle of its rim 20 with respect to its hub 19. This preferred direction of rotation is clockwise at the picture 3 .

The insulated flexible wheel 5 can be reinforced by rotation of its rim 20 relative to its hub 19 through an angle θ in its preferred direction of rotation, the angle θ=0° corresponding to the rest position of the flexible wheel 5 isolated, that is to say in the position in which the actuating spring 22 is at rest (exerts no elastic return moment). During such winding, the actuating spring 22 deforms to exert a restoring moment M(θ) depending on the position θ of the rim 20 relative to the hub 19, tending to cause the rim 20 to pivot relative to the hub 19 in the opposite direction to the winding direction, that is to say in the opposite direction to the privileged direction of rotation, thus tending to make it return to its resting state.

When the rim 20 is in the angular position in which the angle θ is equal to x°, it is said that the flexible wheel 5 or the actuating spring 22 is armed with x°.

The actuating spring 22 is designed, in particular by its shape, to exert, in the flexible wheel 5, an elastic return moment M(θ) that is substantially constant over a range of angular positions [θ _a , θ _b ] of the serge 20 with respect to hub 19 by at least 10°, preferably by at least 15°, preferably by at least 20°, preferably by at least 25°.

“Substantially constant” moment is understood to mean a moment not varying by more than 10%, preferably 5%, more preferably 3%, typically 1.5%, it being understood that this percentage can be further reduced.

More specifically, let M _min and M _max respectively be the values of the minimum and maximum moments exerted by the actuating spring 22 in the flexible wheel 5 isolated over a given range of angular positions of the rim 20 relative to the hub 19, the moment exerted by the actuating spring 22 is substantially constant when the inequality “(M _max - M _min )/((M _max + M _min )/2) ≤ 0.1” is verified, more precisely, when the inequality "(M _max - M _min )/((M _max + M _min )/2) ≤ y%", with y=10, preferably 5, more preferably 3 , for example 1.5, holds.

• pour un angle θ compris entre 0° et une première valeur θ_a, le moment de rappel élastique augmente rapidement avec le déplacement angulaire θ ;
• au-delà de cette première valeur θ_a, le ressort d'actionnement 22 est dans une phase stable. En effet, entre cette première valeur θ_a et une seconde valeur θ_b, le moment de rappel élastique est sensiblement constant par rapport au déplacement angulaire θ, la courbe M(θ) prenant la forme d'un plateau ;
• au-delà de cette deuxième valeur θ_b le moment de rappel élastique augmente à nouveau jusqu'à atteindre une valeur limite M_limite, pour un déplacement angulaire θ=θ_limite. Cette valeur M_limite dépend des propriétés du matériau dans lequel le ressort d'actionnement 22 est réalisé et est atteinte lorsque le ressort d'actionnement 22 subit la contrainte maximale qu'il peut supporter.

The figure 4 schematically illustrates the shape of the evolution curve of the elastic return moment M(θ) as a function of the relative angular position θ of the rim 20 with respect to the hub 19. As can be seen, this curve is non-linear and the elastic restoring moment M(θ) globally follows an evolution in three phases:

• for an angle θ between 0° and a first value θ _a , the elastic restoring moment increases rapidly with the angular displacement θ;
• beyond this first value θ _a , the actuating spring 22 is in a stable phase. Indeed, between this first value θ _a and a second value θ _b , the elastic restoring moment is substantially constant with respect to the angular displacement θ, the curve M(θ) taking the form of a plateau;
• beyond this second value θ _b the elastic restoring moment increases again until it reaches a limit value M _limit , for an angular displacement θ=θ _limit . This _limit value M depends on the properties of the material in which the actuating spring 22 is made and is reached when the actuating spring 22 undergoes the maximum stress that it can withstand.

It is possible to define limit values of angles θ _{a_y%} and θ _{b_y%} between which the elastic restoring moment is substantially constant, with a constancy of y%. For example, if one wants to obtain a constancy of the elastic restoring moment of 5%, one defines using the curve M(θ) the values of the angles θ _{a_5%} and θ _{b_5%} so that the inequality: "(Mmax-Mmin) / ((M _max +M _min )/2) <0.05" is verified; with M _max the maximum elastic restoring moment over the range of angles [θ _{a_5%} , θ _{b_5%} ] and M _min the minimum elastic restoring moment over this same interval.

In the watch mechanism 1, the actuating spring 22 is pre-armed with a value θ _arm included in the range [θ _a , θ _b ] and the gear ratios and the numbers of branches of the stars 11 and 14 are chosen so that the winding angle θ remains in this range during operation of said mechanism, so that the elastic return moment remains substantially constant. The closer the pre-winding value θ _arm chosen is to the value θ _a, the greater the operating range of the actuating spring 22 may be. Each unwinding of the actuating spring 22 brings the winding angle θ back to the value θ _arm .

To obtain the nonlinear shape of the curve M(θ) shown in figure 4 , the elastic arms 21 can be shaped by topological optimization by applying the teaching of the publication "Design of adjustable constant-force forceps for robot-assisted surgical manipulation", Chao-Chieh Lan et al., 2011 IEEE International Conference on Robotics and Automation, Shanghai International Conference Center, May 9-13, 2011, China.

The topological optimization discussed in the aforementioned article uses parametric polynomial curves such as Bézier curves to determine the geometric shape of the elastic arms.

Bézier curves are defined, together with a series of m=(n+1) control points (Q ₀ , Q ₁ , ... Q _n ), by a set of points whose coordinates are given by sums of Bernstein polynomials weighted by the coordinates of said control points.

The geometric shape of each of the elastic arms 21 of the actuating spring 22 is a Bézier curve whose control points have been optimized to take into account, in particular, the dimensions of the flexible wheel 5 to be designed as well as the constraint “( M _max -M _min )/((M _max +M _min )/2) ≤ 0.05” sought. The inequality “(M _max -M _min )/((M _max +M _min )/2) ≤ 0.05” corresponds to a constancy of the elastic restoring moment of 5% over an angular range [θ _{a_5%} , θ _{b_5%} ].

où les $B_i^n$

sont les polynômes de Bernstein donnés par la fonction $$B_i\left(t\right)=\frac{\left(m-1\right)!}{i!\left(m-1-i\right)!}{t}^i{\left(1-t\right)}^{m-i-1}\mathrm{avec}\mathrm{t}\in \left[0,1\right],$$

et où les Q_i sont les points de contrôle Q₀ à Q_n. Elle correspond à la représentation graphique dans un repère orthonormé de l'ensemble des points définis par les couples de coordonnées (x ; y) définis respectivement par les fonctions x(t) et y(t), t ∈ [0, 1], ci-dessous : $$x\left(t\right)={\displaystyle {\sum }_{i=0}^{m-1}{Q}_{\mathit{ix}}{B}_i\left(t\right)}$$

$$y\left(t\right)={\displaystyle {\sum }_{i=0}^{m-1}{Q}_{\mathit{iy}}{B}_i\left(t\right)}$$

dans lesquelles Q_ix et Q_iy sont respectivement les coordonnées x et y des points de contrôle Q_i.More specifically, the geometric shape of each of the elastic arms 21 is defined by the set of points $${\displaystyle {\sum }_{I=0}^{\mathrm{not}}{B}_I^{\mathrm{not}}\left(\mathrm{you}\right).Q_I,\mathrm{with}\mathrm{you}\in \left[0,1\right],}$$

where the $B_I^{\mathrm{not}}$

are the Bernstein polynomials given by the function $$B_I\left(\mathrm{you}\right)=\frac{\left(m-1\right)!}{I!\left(m-1-I\right)!}{\mathrm{you}}^I{\left(1-\mathrm{you}\right)}^{m-I-1}\mathrm{with}\mathrm{you}\in \left[0,1\right],$$

and where the Q _i are the control points Q ₀ to Q _n . It corresponds to the graphic representation in an orthonormal frame of reference of the set of points defined by the pairs of coordinates (x; y) defined respectively by the functions x(t) and y(t), t ∈ [0, 1], below : $$x\left(\mathrm{you}\right)={\displaystyle {\sum }_{I=0}^{m-1}{Q}_{\mathit{ix}}{B}_I\left(\mathrm{you}\right)}$$

$$\mathrm{there}\left(\mathrm{you}\right)={\displaystyle {\sum }_{I=0}^{m-1}{Q}_{\mathit{there}}{B}_I\left(\mathrm{you}\right)}$$

in which Q _ix and Q _iy are respectively the x and y coordinates of the control points Q _i .

The formulas given above give the coordinates of a Bézier curve of order m, that is, a Bézier curve based on m control points. For practical reasons, such a Bézier curve can be broken down into a succession of Bézier curves of order less than m, in which case the geometric shape of each of the elastic arms is a succession of Bézier curves.

Using this principle, the applicant has designed a particular flexible wheel 5 comprising three elastic arms 21 distributed uniformly around the hub 19. This flexible wheel 5 corresponds to that shown in the figures. The dimensions of this flexible wheel 5 are as follows: Gear head diameter: 26.12mm Outside diameter of the hub: 4mm Inner diameter of the serge: 20mm Height : 0.2mm Thickness of the elastic arms: 90µm Curvilinear length of each arm: 9.82mm

As part of this design, seven control points Q ₀ , Q ₁ , Q ₂ , Q ₃ , Q ₄ , Q ₅ , Q ₆ were used. The coordinates of these control points are shown in Table 1 below. <i><u>Table 1: Coordinates of control points Q₀ to Q₆.</u></i> Variables x-coordinates [mm] y-coordinates [mm] Q ₀ 1.51325 1.30775 _Q1 3.7465 3,238 _Q2 5,625 -1.1825 _Q3 6.875 0.907 _Q4 7.5 2.06575 _Q5 8.75 0 _Q6 10 0

With these seven control points it would have been possible to produce a Bézier curve of order seven. However, according to the principle indicated above, the Bézier curve was broken down into two segments, a first segment corresponding to a curve of Bézier of order 4 based on control points Q ₀ to Q ₃ and a second segment corresponding to a Bézier curve of order 4 based on control points Q ₃ to Q ₆ .

By using the coordinates of the control points Q ₀ to Q ₆ above in the aforementioned functions x(t) and y(t), the applicant obtained the coordinates of the points defining the geometric shape of an elastic arm. A certain number of these pairs of coordinates are given in table 2 below. <i><u>Table 2: Coordinates of passage points of the optimized elastic arm</u></i> x [mm] y [mm] 1.51325 1.30775 1.68007363 1.44081204 1.84553716 1.55126447 2.00961079 1.64031297 2.17226475 1.70916325 2.33346924 1.759021 2.49319447 1.79109191 2.65141065 1.80658168 2.808088 1.806696 2.96319672 1.79264057 3.11670703 1.76562109 3.26858914 1.72684325 3.41881325 1.67751275 3.56734958 1.61883528 3.71416834 1.55201653 3.85923975 1.47826221 4.002534 1.398778 4.14402132 1.31476961 4.28367191 1.22744272 4.42145598 1.13800304 4.55734375 1.04765625 4.69130543 0.95760806 4.82331122 0.86906416 4.95333134 0.78323024 5.081336 0.701312 5.20729541 0.62451514 5.33117978 0.55404534 5.45295932 0.49110832 5.57260425 0.43690975 5.69008477 0.39265534 5.80537109 0.35955078 5.91843343 0.33880177 6.029242 0.331614 6.137767 0.33919317 6.24397866 0.36274497 6.34784717 0.4034751 6.44934275 0.46258925 6.54843561 0.54129312 6.64509597 0.64079241 6.73929403 0.7622928 6,831 0.907 6.93563488 1.05729003 7.048549 1.16318025 7.16930663 1.22863834 7.297472 1.257632 7.43260938 1.25412891 7.574283 1.22209675 7.72205713 1.16550322 7.875496 1.088316 8.03416388 0.99450278 8.197625 0.88803125 8.36544363 0.77286909 8.537184 0.652984 8.71241038 0.53234366 8.890687 0.41491575 9.07157813 0.30466797 9.254648 0.205568 9.43946088 0.12158353 9.625581 0.05668225 9.81257263 0.01483184 10 0

The graph of the figure 5 shows the geometry of the external diameter of the hub 19, of the internal diameter of the rim 20 and of one of the elastic arms 21 of the flexible wheel 5 that the applicant has designed, the geometry of said arm being defined by a curve passing through the set of point coordinates defined in Table 2 above. This graph is produced in an orthonormal frame.

The figure 6 represents the results of a simulation of the evolution of the elastic return moment of the flexible wheel 5 isolated thus produced as a function of the angular position θ of its rim 20 with respect to its hub 19.

The simulation carried out considers the insulated flexible wheel 5 made of silicon coated with a layer of silicon oxide 3 μm thick, but any suitable material can be used. For example materials such as Nivaflex ^® 45/18 (alloy based on cobalt, nickel and chromium), CK101 (unalloyed structural steel) or other alloys, plastic, mineral glasses or metallic glasses, for example Vitreloy 1b, are also suitable and make it possible to obtain flexible wheels whose elastic return moment is substantially constant over the same angular ranges [θ _a , θ _b ].

The angular operating range allowing the delivery of a substantially constant moment being a constant linked to the shape of the elastic arms 21, the operating angle θ _b must be less than the angle θ _lim corresponding to the limit before yielding or rupture of the actuating spring 22. This makes it possible to define the maximum thickness that it is possible to achieve on the arms.

It emerges from the analysis of the results presented to the figure 6 that a constancy of 2.5% of the elastic restoring moment is obtained for an angular displacement of the rim 20 of the flexible wheel 5 studied with respect to its hub 19 comprised between θ _{a_2.5%} , i.e. 13°, and θ _{b_2.5%} , i.e. 31°, i.e. over an operating range of 18°. The flexible wheel 5 thus produced therefore has an operating range at constant moment (for a constant of 2.5%) of 18°. If we accept a constant of 9.5% of the elastic return moment then the flexible wheel 5 thus produced has an operating range at constant moment of approximately 23°, with θ _{a_9.5%} ≈ 10.5° and _{θb_9.5%} ≈ 33.5°.

Table 3 below gives, by way of indication, the values θ _{a_y%} , θ _{b_y%} and Δθ (range of angular positions at substantially constant moment) associated with the flexible wheel 5 produced by the applicant as a function of the percentage of constancy y considered as well as the associated torque values M _min and M _max . <i><u>Table 3:</u></i> θ _{a_y%} θ _{b_y%} Angle range Δθ (°) _{Mmin Mmax} Percent constancy y (%) 13.5 30.5 17 1,510 1,534 1.6 13 31 18 1,502 1,539 2.5 12.5 31.5 19 1,492 1,543 3.5 12 32 20 1,480 1,548 4.6 10.5 33.5 23 1,432 1,568 9.5

By increasing the number of control points during the design of the elastic arms 21, it should be possible to increase the precision of the shape of these elastic arms 21 and thus improve the constancy of the restoring moment.

It is also possible to improve the constancy of the restoring moment by designing the elastic arms 21 with a variable section. The figure 7 shows different curves representative of a normalized moment of force M(θ) exerted by the flexible wheel 5 isolated as a function of the angular position θ of its rim 20 with respect to its hub 19 (winding angle) for different section variations elastic arms 21. The highest curve, denoted by A1, corresponds to elastic arms 21 of constant section and thickness of 30 μm. The curves located below the curve A1 correspond to elastic arms 21 whose thickness decreases linearly from the hub 19 to the serge 20, the thickness at the point of junction with the hub 19 being 30 μm for each curve, the the thickness at the point of junction with the serge 20 being 29 μm for the curve A2, 28 μm for the curve A3 and 27 μm for the curve A4. An improvement in consistency is observed for curves A2, A3 and A4 compared to curve A1 over a range of angles of reinforcement of length greater than 15°.

Other modes of variation of the section of the elastic arms 21 can be envisaged. The figure 8 shows two curves B1 and B2 representative of a normalized moment of force M(θ) exerted by the flexible wheel 5 isolated as a function of the angular position θ of its rim 20 with respect to its hub 19 (winding angle) for different shapes of section of the elastic arms 21. The highest curve, B1, corresponds to elastic arms 21 of constant section and thickness of 30 μm. Curve B2 corresponds to elastic arms 21 whose thickness decreases linearly from the hub 19 to the middle of the arm then increases linearly from the middle of the arm to the serge 20, the thickness at the junction points with the hub 19 and with the serge 20 being 30 µm, the thickness in the middle of the arm being 29 µm. We notes an improvement in consistency for curve B2 compared to curve B1 over a range of angles of reinforcement longer than 15°.

In general, in cases where the elastic arms 21 have a variable section, this typically varies in a strictly monotonous manner (it increases or decreases without interruption but not necessarily linearly) over at least one continuous portion of the elastic arm representing 10% , preferably 20%, preferably 30%, preferably 40%, of the (curvilinear) length of the elastic arm. The variation of the section is also chosen to improve the constancy of the elastic restoring moment over the range [θ _a , θ _b ] compared to elastic arms of the same shape as the arms 21 but of constant section.

It will clearly appear to those skilled in the art that the present invention is in no way limited to the embodiment presented in the figures.

It is for example very well conceivable to produce a flexible wheel 5 with elastic arms 21 of different shapes from those shown in the figures and/or whose number of elastic arms 21 is different from that shown in the figures. The elastic arms 21 can in particular take a form as described in the article “Functional joint mechanisms with constant torque outputs”, Mechanism and machine theory 62 (2013) 166-181, Chia-Wen Hou et al. The height, length, thickness and/or material of the elastic arms 21, or even the inclination of the elastic arms 21 relative to the hub 19 (in the plane of the flexible wheel 5), can also be modified to adjust the value of the substantially constant elastic restoring moment.

Claims (15)

1. Timepiece mechanism (1) comprising a drive member (2), a regulator member (6) for regulating the drive member (2), a jumper member (20, 24), an actuating spring (22), one or more gears (3, 10) between the drive member (2) and the actuating spring (22) and a winding and blocking device (4) arranged to permit continuous winding of the actuating spring (22) by the drive member (2) via the gear or gears (3, 10) and periodic letting down of the actuating spring (22), the actuating spring (22) being arranged to cause the jumper member (20, 24) to jump each time it is let down, the actuating spring (22) comprising at least one elastic arm (21), characterised in that the or each elastic arm (21) is sinuous in shape, in that the actuating spring (22) is a spring acting in a non-linear manner, which produces, between a winding angle θ_a and a winding angle θ_b which are separated by at least 10°, an elastic return moment which does not vary by more than 10%, and in that the actuating spring (22) is pre-wound by a value θ_arm included in the range [θ_a, θ_b], the timepiece mechanism (1) being arranged so that, during operation thereof, the winding angle of the actuating spring (22) remains within the range [θ_a, θ_b].
2. Timepiece mechanism (1) as claimed in claim 1, characterised in that the elastic return moment produced by the actuating spring (22) does not vary by more than 5%, preferably not more than 3%, preferably not more than 1.5 %, over the range [θ_a, θ_b].
3. Timepiece mechanism (1) as claimed in claim 1 or 2, characterised in that the winding angles θ_a and θ_b are separated by at least 15°, preferably by at least 20°, preferably by at least 25°.
4. Timepiece mechanism (1) as claimed in any one of claims 1 to 3, characterised in that the actuating spring (22) comprises a plurality of said elastic arms (21) angularly spaced in a regular manner.
5. Timepiece mechanism (1) as claimed in any one of claims 1 to 4, characterised in that the geometric shape of the or of each elastic arm (21) is a Bezier curve or a succession of Bezier curves.
6. Timepiece mechanism (1) as claimed in any one of claims 1 to 5, characterised in that the or each elastic arm (21) has a variable cross-section, the variation in which is selected to improve the constancy of said elastic return moment over the range [θ_a, θ_b] as compared with an elastic arm of the same shape but a constant cross-section.
7. Timepiece mechanism (1) as claimed in any one of claims 1 to 6, characterised in that it comprises a flexible wheel (5) comprising a hub (19), a felloe (20) and the actuating spring (22) connecting the hub (19) to the felloe (20), and in that the jumper member comprises the felloe (20) or the hub (19).
8. Timepiece mechanism (1) as claimed in claim 7, characterised in that the flexible wheel (5) is formed of one piece.
9. Timepiece mechanism (1) as claimed in any one of claims 1 to 8, characterised in that the winding and blocking device (4) comprises a movable member (9), a rotary drive member (11) kinematically connected to the drive member (2) and to a winding end of the actuating spring (22) and arranged to displace the movable member (9), a rotary blocking member (14) kinematically connected to a torque-delivering end of the actuating spring (22) and to the jumper member (20, 24), the rotary blocking member (14) being blocked by the movable member (9) and released periodically by the displacements of the movable member (9) which are caused by the rotary drive member (11).
10. Timepiece mechanism (1) as claimed in claim 9, characterised in that the movable member (9) can move in translation.
11. Timepiece mechanism (1) as claimed in claim 9 or 10, characterised in that the movable member (9) comprises first and second openings with a closed contour (12, 15), the rotary drive member (11) and the rotary blocking member (14) cooperating respectively with the wall of said first and second openings.
12. Timepiece mechanism (1) as claimed in any one of claims 9 to 11 when it depends on claim 7 or 8, characterised in that the jumper member (20, 24) comprises the felloe (20) and the hub (19) is fixed for conjoint rotation with the rotary drive member (11).
13. Timepiece mechanism (1) as claimed in any one of claims 9 to 11 when it depends on claim 7 or 8, characterised in that the jumper member comprises the hub (19) which is fixed for conjoint rotation with the rotary blocking member (14).
14. Timepiece mechanism (1) as claimed in any one of claims 1 to 13, characterised in that the jumper member (20, 24) comprises a display member (24).
15. Timepiece comprising a timepiece mechanism (1) as claimed in any one of claims 1 a 14.

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