EP3580618B1 - Timepiece driving organ - Google Patents

Description

The present invention relates to a motor member for watchmaking, in particular a motor member with a substantially constant moment of force.

The clockwork drive unit according to the invention can be either a drive unit for a watch movement arranged to drive a going train, or a drive unit for an additional mechanism such as a striking mechanism or a chronograph.

In watchmaking, a barrel is traditionally used as the driving member of a watch mechanism. A barrel is an assembly of at least three elements: a barrel spring consisting of a leaf spring in the form of a spiral, a barrel drum serving as a housing for said spring, said drum being able to rotate freely on a barrel arbor (axis pivoting between bridge and plate), and a barrel cover for closing the barrel drum, said cover also being able to rotate freely on the barrel arbor. Outside the barrel drum, the leaf spring has the shape of an upturned S. The unwinding of the blade, wound against the diameter of the bung of the barrel arbor and seeking to return to its initial shape, produces the energy necessary for the operation of the watch mechanism.

A disadvantage of such a motor member is that its performance is affected by the friction of the coils of the spiral spring against each other and against the inside of the barrel drum, during the unwinding of the barrel. To reduce this friction, it is customary to lubricate the coils of the spring and to deposit an anti-friction coating in the drum. Despite this, such a motor member undergoes energy losses of approximately 15% due to friction.

Another drawback of such a motor member is that the manufacture and shaping of the leaf spring it contains, from its inverted S shape to its spiral shape, must strongly take into account the elastic limit of the material constituting the leaf spring. In addition, the placement of the spiral spring housed in the barrel drum is based on the watchmaker's long experience and requires numerous handling steps. It is also an assembly of several elements.

Such a motor member is therefore expensive and difficult to manufacture.

Furthermore, the moment of force delivered by such a motor member is not constant, which affects the isochronism of the watch mechanism. To alleviate this problem, some watch movements use an intermediate spring of the spiral type between the driving member and the escapement. A disadvantage of this solution is that it complicates the movement by introducing an additional element.

The object of the present invention is to provide an alternative motor member to the barrel comprising a spiral spring traditionally used, and also alternative to the motor members disclosed by the documents CH699988A2 and EP2455820A2 . The object of the present invention is also that of providing a motor member making it possible to overcome, at least in part, the aforementioned drawbacks.

The invention proposes for this purpose a clockwork motor member according to appended claim 1.

The present invention also proposes a timepiece mechanism comprising such a timepiece motor member.

The motor member according to the invention has the advantage of significantly improving the efficiency (average energy loss of between 0 and 3% only against approximately 15% for a traditional spiral spring barrel). Indeed, the monolithic units that compose it do not undergo or very little friction.

In addition, the motor member according to the invention also has the advantage of delivering a substantially constant moment of force, thus improving the isochronism of the watch movement with which it is associated, without requiring an intermediate spring between the motor member and the 'exhaust.

• la figure 1 est une vue en perspective d'une partie d'un mécanisme horloger intégrant un organe moteur d'horlogerie selon un mode de réalisation particulier de l'invention ;
• la figure 2 est une vue de dessus du mécanisme représenté à la figure 1 ;
• la figure 3 est une coupe transversale de l'organe moteur de la figure 1 ;
• les figures 4a, 4b et 4c représentent respectivement, en vue de dessus, une première unité, une unité intermédiaire et une dernière unité de l'organe moteur de la figure 1 ;
• les figures 5a et 5b sont des vues respectivement de dessous et de dessus d'une unité de l'organe moteur équipée d'un dispositif de centrage ;
• la figure 6 est une représentation graphique schématique du moment de rappel élastique exercé dans une unité de l'organe moteur ;
• la figure 7 représente les coordonnées de points définissant une forme particulière de bras élastique pour chaque unité de l'organe moteur ;
• la figure 8a est une représentation graphique du moment de rappel élastique exercé dans une unité donnée de l'organe moteur comprenant des bras élastiques ayant la forme telle que représentée à la figure 7 ;
• la figure 8b est une représentation graphique du moment de force délivré par un organe moteur comprenant onze unités telles que celle étudiée à la figure 8a, empilées et reliées en série ;
• la figure 9 représente, en vue de dessus, une variante d'une unité de l'organe moteur d'horlogerie selon l'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 perspective view of part of a timepiece mechanism incorporating a timepiece drive member according to a particular embodiment of the invention;
• the picture 2 is a top view of the mechanism shown in figure 1 ;
• the picture 3 is a cross section of the motor organ of the figure 1 ;
• the figures 4a, 4b and 4c represent respectively, in top view, a first unit, an intermediate unit and a last unit of the drive member of the figure 1 ;
• the figures 5a and 5b are views respectively from below and from above of a unit of the drive member equipped with a centering device;
• the figure 6 is a schematic graphical representation of the elastic restoring moment exerted in a motor unit unit;
• the figure 7 represents the coordinates of points defining a particular form of elastic arm for each unit of the drive member;
• the figure 8a is a graphic representation of the elastic restoring moment exerted in a given unit of the driving member comprising elastic arms having the shape as represented in figure 7 ;
• the figure 8b is a graphic representation of the moment of force delivered by a motor organ comprising eleven units such as the one studied in figure 8a , stacked and connected in series;
• the figure 9 shows, in top view, a variant of a unit of the clockwork engine member according to the invention.

The figures 1 and 2 represent a part of a timepiece mechanism, more precisely of a timepiece movement, comprising a clockwork motor member 1 according to a particular embodiment of the invention, this motor member 1 being held in position by means of a axis 2 of said watch movement. This watch movement further comprises, in particular, a gear train 3, an escapement 4 and a winding mechanism 5a, 5b, as illustrated in figures 1 and 2 . In the example illustrated, the winding mechanism comprises a winding stem 5a and a winding wheel 5b. In a variant, it could be of the automatic type, with an oscillating mass.

The motor member 1 comprises several monolithic units 110, 210, 310, stacked on top of each other and connected in series, as illustrated in picture 3 . Each of these units 110, 210, 310 comprises a hub 120, 220, 320 and a rim 130, 230, 330 connected by several elastic arms 140, 240, 340 uniformly distributed around its hub 120, 220, 320, as illustrated in figures 4a, 4b and 4c .

The first 110 of said units is associated with a toothing 160 allowing the connection with the winding wheel 5b. This toothing 160 which meshes with the winding wheel 5b is typically carried by a winding wheel 170 coaxial with and integral with the hub 120 of the said first unit 110, as shown in figures 1, 2, 3 and 4a . As a variant, the toothing 160 can be fixed to the rim 130 of the first unit 110. That or that of the hub 120 or of the rim 130 of the first unit 110 which is fixed to the toothing 160, and therefore by which between the energy, constitutes an input element of the stack of units 110, 210, 310.

The last 310 of said units is associated with another toothing 360 which meshes with the going train 3 to deliver a moment of force to it. This other toothing 360 is typically integral with the rim 330 of this last unit 310, as shown in figures 1, 2, 3 and 4c . As a variant, the toothing 360 can be integral with the hub 320 of the last unit 310. That or that of the hub 320 or the rim 330 of the last unit 310 which is integral with said other toothing 360, and therefore through which the energy exits, constitutes an output element of the stack of units 110, 210, 310.

The intermediate units 210 placed between said first 110 and last 310 units are not associated with a toothing, as shown in figures 1, 3 and 4b .

In addition, each of the units 110, 210, 310 according to the invention is unidirectional, that is to say that it has, due to the shape of its elastic arms 140, 240, 340, a privileged direction of rotation. of its rim 130, 230, 330 relative to its hub 120, 220, 320, this direction being defined as that which allows, from the rest state of the unit in question, the greatest relative angular displacement of its serge 130, 230, 330 with respect to its hub 120, 220, 320. The arrows A, B and C, represented respectively on the figures 4a, 4b and 4c , illustrate this preferred direction of rotation of the edges 130, 230, 330 with respect to the hubs 120, 220, 320 for the units 110, 210, 310 of the motor member 1 represented.

Preferably, all the units 110, 210, 310 (not including teeth) are identical (in particular the arms 140, 240, 340 have the same shape) and are stacked coaxially and head to tail, two successive units having different directions of rotation. privileged opposites. For example, when the motor member comprises three units 110, 210, 310, it can comprise a first unit 110 whose preferred direction of rotation is clockwise (as shown in figure 4a ), a single intermediate unit 210 whose preferred direction of rotation is counterclockwise (corresponding to a unit 210 as shown in figure 4b turned over) and a last unit 310 whose preferred direction of rotation is clockwise (as shown in figure 4c ).

As already indicated, the units 110, 210, 310 are also connected in series, these units 110, 210, 310 being two by two connected alternately by their edges 130, 230, 330 and by their hubs 120, 220, 320.

In the example of the picture 3 , rim 130 of first unit 110 is integral with rim 231 of first intermediate unit 211, hub 221 of this first intermediate unit 211 is integral with hub 222 of second intermediate unit 212 and so on, hub of the last intermediate unit being integral with the hub 320 of the last unit 310.

The privileged direction of rotation of the first 110 and of the last 310 unit and the choice of the input and output elements (serge or hub) depends on the position of the driving member 1 in the watch mechanism and depends on the mechanism of crown 5a, 5b and of the going train 3. The preferred direction of rotation of the intermediate units 210 is granted according to their number and according to the direction of the first 110 and last 310 units.

As shown in figures 1 to 4c , the hubs 120, 220, 320 of the units 110, 210, 310 of the motor member 1 comprise holes 150, 250, 350, for example circular, these holes 150, 250, 350 being traversed by the axis 2 of the movement watchmaker, said axis 2 preferably being mounted fixed relative to the movement, for example in the plate of the movement. This axis 2 positions the motor member 1 and helps to keep the hubs 120, 220, 320 of all the units 110, 210, 310 aligned, the hubs 120, 220, 320 being free to rotate around the axis 2 .

In variants, the hubs 120, 220, 320 of the units 110, 210, 310 of the drive member 1 may not include holes 150, 250, 350. The drive member may, in this case, be held in position , for example, by means of two axes mounted on the hubs 120, 320 respectively of the first 110 and last 310 units, these axes being, respectively, integral in rotation with said hubs 120, 320 and free in rotation with respect to a fixed part of the movement, typically in relation to the plate. This driving member can also be placed in a drum.

The very structure of the drive member 1 involves the centering of the hub 120, 220, 320 of each unit 110, 210, 310 with respect to its rim 130, 230, 330. However, the motor member 1 can comprise one or more hub centering devices aimed at reinforcing the centering of the hubs 120, 220, 320. Such devices typically comprise a rigid junction element 6, on the one hand, fixed integrally to two diametrically opposed zones of the rim 130, 230, 330 of a unit 110, 210, 310 and on the other hand, positioned free in rotation on the axis 2. The figures 5a and 5b are respectively bottom and top views of a unit 110, 210, 310 of the drive member 1 equipped with such a centering device.

In general, the set of elastic arms 140, 240, 340 of each unit 110, 210, 310 of the motor member 1 is designed, in particular by its shape, to exert, in this unit 110, 210, 310, a substantially constant elastic return moment over a range of angular displacement of the rim 130, 230 330 of said unit 110, 210, 310 relative to its hub 120, 220, 320 of at least 10°, preferably d at least 15°, for example approximately 21°.

“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 Mmin and Mmax respectively be the values of the minimum and maximum moments exerted in a unit 110, 210, 310 of the engine member 1 over a given range of angular displacement of its rim 130, 230, 330 with respect to its hub 120, 220, 320, the moment exerted in this unit 110, 210, 310 is substantially constant as soon as the inequality "(Mmax-Mmin)/((Mmax+Mmin)/2) ≤ 0.1" is verified, more specifically, when the inequality “(Mmax-Mmin)/((Mmax+Mmin)/2) ≤ y%”, with y=10, preferably 5, more preferably 3, for example 1.5, is verified.

Let θ be the angular displacement of the rim 130, 230, 330 of a unit 110, 210, 310 of the motor member 1 relative to the hub 120, 220, 320 of this same unit 110, 210, 310 in its direction of rotation privileged, θ being equal to zero when said unit 110, 210, 310 is at rest, that is to say when all its elastic arms 140, 240, 340 are at rest, the figure 6 illustrates the evolution M(θ) of the elastic restoring moment exerted by the set of elastic arms 140, 240, 340 of a unit 110, 210, 310 in this unit as a function of the angular displacement θ.

• pour un angle θ compris entre 0 et une première valeur θ₁, le moment de rappel élastique augmente rapidement avec le déplacement angulaire θ, cette phase correspond à la phase d'armage ;
• au-delà de cette première valeur θ₁, l'unité 110, 210, 310 est dans une phase stable. En effet, entre cette première valeur θ₁ et une seconde valeur θ₂, le moment de rappel élastique est sensiblement constant par rapport au déplacement angulaire θ ;
• au-delà de cette deuxième valeur θ_2, le moment de rappel élastique augmente à nouveau jusqu'à atteindre une valeur limite M_limite, pour un déplacement angulaire θ=θ₃. Cette valeur M_limite dépend des propriétés du matériau dans lequel l'unité 110, 210, 310 est réalisée et correspond à la contrainte maximale que peut subir une unité 110, 210, 310.

As it is visible on the curve M(θ) of the figure 6 , this elastic restoring moment follows an evolution in three phases:

• for an angle θ between 0 and a first value θ ₁ , the elastic restoring moment increases rapidly with the angular displacement θ, this phase corresponds to the winding phase;
• beyond this first value θ ₁ , unit 110, 210, 310 is in a stable phase. Indeed, between this first value θ ₁ and a second value θ ₂ , the elastic restoring moment is substantially constant with respect to the angular displacement θ;
• beyond this second value θ _{2 ,} the elastic restoring moment increases again until it reaches a limit value M _limit, for an angular displacement θ=θ ₃ . _{This limit} value M depends on the properties of the material in which the unit 110, 210, 310 is made and corresponds to the maximum stress that a unit 110, 210, 310 can undergo.

For a given monolithic unit, it is possible to define limit values of angles θ _{min_y%} and θ _{max_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 _{min_5%} and θ _{max_5%} so that the inequality : “(Mmax-Mmin) / ((Mmax+Mmin)/2) < 0.05” is verified; with Mmax the maximum elastic restoring moment over the interval of angles [θ _{min_5%} , θ _{max_5%} ] and Mmin the minimum elastic restoring moment over this same interval.

The monolithic units 110, 210, 310 exhibiting a curve M(θ) of the type of that shown in figure 6 differ from conventional elastic structures. Their properties are based on a sinuous shape of their elastic arms which deform in such a way as to generate a substantially constant elastic restoring moment (the curve M(θ) has a plateau). In addition, due to their sinuous shape, the elastic arms 140, 240, 340 of a given unit 110, 210, 310 have the advantage of being able to be relatively long without the risk of rubbing against each other during rotation. of the rim 130, 230, 330 of said unit 110, 210, 310 with respect to its hub 120, 220, 320.

Obtaining such elastic arms requires a specific and parameterized design. They can for example be obtained 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, 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 , ... Qn), by a set of points whose coordinates are given by sums of polynomials of Bernstein weighted by the coordinates of said control points.

The geometric shape of each of the elastic arms 140, 240, 340 of the motor member 1 is a Bézier curve whose control points have been optimized to take into account, in particular, the dimensions of the unit 110, 210, 310 to be designed as well as the constraint "(M _max -M _min )/((M _max +M _min )/2) ≤ 0.05" sought. The inequality “(Mmax-Mmin)/((Mmax+Mmin)/2) ≤ 0.05” corresponds to a constancy of the elastic restoring moment of 5% over an angular range [θ _{min_5%} , θ _{max_5%} ].

où les $B_i^n$

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

et où les Q_i sont les points de contrôle Q₀ à Qn. 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 Qix et Qiy sont respectivement les coordonnées x et y des points de contrôle Q_i.More specifically, the geometric shape of each of the elastic arms 140, 240, 340 of the motor member 1 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 Qn. 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 Qix and Qiy 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 unit of a motor member, said particular unit comprising twenty-three elastic arms distributed uniformly around the hub. The dimensions of this particular unit are as follows: External diameter of the serge: 12mm Outside diameter of the hub: 2mm Inner diameter of the serge: 10mm Height: 0.15mm Thickness of the elastic arms: 60µm

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>Table 1: Coordinates of control points Q₀ to Q₆.</i> Variables x-coordinates [mm] y-coordinates [mm] Q ₀ 0.756625 0.653875 Q ₁ 1.87325 1,619 Q ₂ 2.8125 -0.59125 Q ₃ 3.4375 0.4535 Q ₄ 3.75 1.032875 Q ₅ 4,375 0 Q ₆ 5 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 of the particular unit. A certain number of these pairs of coordinates are given in table 2 below. <i>Table 2: Coordinates of passage points of the optimized elastic arm</i> x [mm] y [mm] 0.756625 0.653875 1.086132 0.854582 1.404044 0.903348 1.709407 0.838756 2.001267 0.699389 2.278672 0.523828 2.540668 0.350656 2.786302 0.218455 3.014621 0.165807 3.224671 0.231295 3.4155 0.4535 3.524275 0.58159 3.648736 0.628816 3.787142 0.611048 3.937748 0.544158 4.098813 0.444016 4.268592 0.326492 4.445344 0.207458 4.627324 0.102784 4.812791 0.028341 5 0

The graph of the figure 7 shows the geometry of the external diameter of the hub, of the internal diameter of the serge and of one of the elastic arms of the particular unit that the applicant has designed, the geometry of said arm being defined by a curve passing through the set of coordinates of points defined in Table 2 above. This graph is produced in an orthonormal frame.

The figure 8a represents the results of a simulation of the evolution of the elastic return moment of the particular unit thus produced as a function of the angular displacement of its rim relative to its hub.

The simulation carried out considers a particular unit made in an alloy based on cobalt, nickel and chromium, more precisely in Nivaflex ^® 45/18 (Young's modulus E= 220 GPa) but any suitable material can be used. For example, materials such as silicon (E=130 GPa), typically coated with silicon oxide, metallic glass, plastic or CK101 (unalloyed construction steel) are also suitable and allow obtaining units monoliths whose elastic restoring moment is substantially constant over the same angular ranges [θ _min , θ _max ].

The angular range of operation allowing the delivery of a substantially constant moment being a constant linked to the shape of the elastic arms, it is important to take into account the ratio between the elastic limit and the Young's modulus of the material to choose the material.

It emerges from the analysis of the results presented to the figure 8a that a constancy of 3% of the elastic restoring moment is obtained for an angular displacement of the rim of the particular unit studied with respect to its hub between θ _{min_3%} , i.e. 13°, and θ _{max_3%} , i.e. 34° , i.e. over an operating range of 21°.

By increasing the number of control points when designing the elastic arms 140, 240, 340, it should be possible to increase the precision of the shape of these elastic arms and thus improve the constancy of the moment of force.

A motor member 1 comprising eleven units identical to the particular unit studied in figure 8a , stacked and connected in series, was also designed. A simulation made it possible to graphically represent the moment of force delivered by the rim 330 (output element) of the last unit 310 of this motor member 1 as a function of the angular displacement of the rim 330 of the last unit 310 with respect to the hub 120 (input element) of the first unit 110. The results of this simulation are presented in figure 8b (curve C2).

The figure 8b also represents the elastic restoring moment of a single particular unit identical to that studied in figure 8a as a function of the angular displacement of its rim relative to its hub (curve C1).

As you can see on this figure 8b , the value of the moment of force exerted by the drive member 1 comprising eleven units, when it is in its stable phase, (approximately 5 N.mm) is unchanged with respect to the value of the elastic return moment exerted by the set of elastic arms of an isolated monolithic unit, in this unit, in its stable phase. Each angle θ _{min_3%} and θ _{max_3%} for motor component 1 is equal to eleven (i.e. the number of units placed in series) times the corresponding angle θ _{min_3%} and θ _{max_3%} for a unity. Indeed, θ _{min_3%} and θ _{max_3%} for eleven units are respectively 143° and 374°.

The series arrangement of such units therefore makes it possible to increase the amplitude of the angular displacement associated with the delivery of a substantially constant moment while maintaining the intensity of this moment.

In general, the applicant has been able to observe that a drive member 1 comprising p units 110, 210, 310, p being an integer greater than or equal to two, allows the delivery of a moment of force that is substantially constant over a range of angular displacement of the output element, rim 330 or hub 320, of its last unit 310 relative to the input element, rim 130 or hub 120, of its first unit 110 of at least (p × 10) °, preferably at least (p×15)°, for example approximately (p×21)°.

When p=2, the motor member 1 does not include an intermediate unit 210 but only includes a first unit 110 and a last unit 310 stacked and connected by their respective edges or by their respective hubs.

Advantageously, the timepiece mechanism incorporating the motor member 1 can comprise stops making it possible to maintain said motor member 1 in the range of angular displacement of the output element of its last unit 310 with respect to the input element of its first unit 110 allowing the delivery of a substantially constant moment of force.

As indicated above, the motor member 1 can be made of any suitable material, in particular as regards its elastic limit and its Young's modulus.

Units 110, 210, 310 can be manufactured separately and then assembled. They can for example be manufactured by machining, in particular in the case where they are made of metal or an alloy such as Nivaflex ^® , by DRIE etching in the case of silicon for example, or even by molding, in particular in the case where they are made of plastic or metallic glass. The units 110, 210, 310 obtained can then be assembled together, typically by gluing, welding or brazing.

As a variant, the motor member 1 can be produced in a single monolithic part, for example by using 3-dimensional printing techniques or laser cutting techniques, typically in mineral glass.

Advantageously, the units 110, 210, 310 stacked coaxially are arranged so that the elastic arms 140, 240, 340 of the units whose preferred direction of rotation is the same align, which makes it possible to obtain an advantageous aesthetic effect. , as illustrated in figures 1 and 2 .

In variants, the motor member 1 can comprise monolithic units of different shape from that illustrated in figures 1, 2 and 4 . They may in particular take a form as shown in figure 9 .

The monolithic unit 10 shown in figure 9 comprises elastic arms 40 exerting a substantially constant elastic restoring moment over a range of angular displacement of the rim 30 of said unit relative to its hub 20 of at least 10°, preferably at least 15°, for example around 21°.

A means of obtaining such elastic arms 40 is in particular described in the article “Functional joint mechanisms with constant torque outputs”, Mechanism and machine theory 62 (2013) 166-181, Chia-Wen Hou et al.

It will clearly appear to those skilled in the art that the present invention is limited only by appended claim 1 and is thus not limited to the embodiments presented above and illustrated in the figures.

It is for example very well conceivable to produce a motor member 1 comprising a number of monolithic units different from that represented in the figures and/or comprising units with elastic arms of different shapes from those represented in the figures and/or whose the number of elastic arms is different from that shown in the figures, it being possible in particular for a monolithic unit to have only one elastic arm.

The value of the moment of force reached in the stable phase of the driving member can in particular be adjusted by acting on the number of elastic arms that comprise the units which constitute it, on the thickness of the elastic arms and/or on the material used. . In particular, in a monolithic unit comprising q elastic arms, q being an integer greater than or equal to 2, the moment of force exerted by all of these q elastic arms in the monolithic unit in its stable phase is typically equal to q times the moment of force exerted, in a similar monolithic unit comprising only one of these elastic arms, by said single elastic arm in this unit, in its stable phase.

The angular range [θ _min, θ _max ] over which the moment of force delivered is substantially constant can, for its part, be adjusted by adjusting the number of units stacked and connected in series.

It is also possible for at least one or each of the elastic arms of the units according to the invention to have a variable section, for example a variable thickness. The section could typically be larger on the hub side than on the rim side.

In addition, as already indicated, the toothing 360 associated with the last unit 310 of the motor member 1 according to the invention can, as desired, be integral with the hub 320 or rim 330 of this unit 310. In particular, it can be carried directly by said rim 330 or by said hub 320.

In the same way, the toothing 160 associated with the first unit 110 of the motor member 1 according to the invention can, as desired, be secured to the hub 120 or to the rim 130 of this unit 110. In particular, it can be carried directly by said rim 130 or by said hub 120.

The person skilled in the art can also easily adjust, according to his needs (that is to say for example according to the number of units that the motor member 1 comprises, according to whether the toothing 360 is integral with the hub 320 or the rim 330 of the last unit 310, depending on whether the toothing 160 is integral with the hub 120 or the rim 130 of the first unit 110, depending on the preferred direction of rotation chosen for any of the units, etc.) , the arrangement of the serge-serge and hub-hub connections of a motor member 1 according to the invention.

In addition, the moment of force delivered by the driving member 1 can allow the setting in motion of another type of gear train than a finishing gear train 3 or of an additional mechanism such as a striking or chronograph mechanism. .

Claims (14)

1. Drive member (1) for a timepiece comprising at least two monolithic units (110, 210, 310) stacked and connected in series, each of these units comprising a hub (120, 220, 320) and a rim (130, 230, 330) which are connected by at least one elastic arm (140, 240, 340), the or each of the elastic arms (140, 240, 340) of any of said units (110, 210, 310) is of sinuous shape.
2. Drive member (1) as claimed in claim 1, characterised in that it comprises a first toothing (160) permitting connection between said monolithic units (110, 210, 310) and a winding mechanism (5a, 5b) and a second toothing (360) permitting the outputting of a moment of force by said monolithic units (110, 210, 310).
3. Drive member (1) as claimed in claim 2, characterised in that the first toothing (160) is fixed relative to the hub (120) or to the rim (130) of a first one (110) of said monolithic units (110, 210, 310).
4. Drive member (1) as claimed in any one of claims 2 or 3, characterised in that the second toothing (360) is fixed relative to the hub (320) or to the rim (330) of a last one (310) of said monolithic units (110, 210, 310).
5. Drive member (1) as claimed in any one of the preceding claims, characterised in that the shape of the at least one elastic arm (140, 240, 340) is the same for all the monolithic units (110, 210, 310) and in that the monolithic units (110, 210, 310) are unidirectional and are placed in twos in opposing directions.
6. Drive member (1) as claimed in any one of the preceding claims, characterised in that each of said monolithic units (110, 210, 310) comprises a plurality of elastic arms (140, 240, 340) uniformly distributed around its hub (120, 220, 320).
7. Drive member (1) as claimed in any one of the preceding claims, characterised in that it comprises at least one device (6) for centring the hubs (120, 220, 320).
8. Drive member (1) as claimed in any one of the preceding claims, characterised in that the at least one elastic arm (140, 240, 340) of each monolithic unit (110, 210, 310) is designed to exert an elastic return moment varying by no more than 10%, preferably 5%, over a range of angular displacement of the rim (130, 230, 330) of said monolithic unit (110, 210, 310) with respect to its hub (120, 220, 320) of at least 10°, preferably of at least 15°.
9. Drive member (1) as claimed in any one of the preceding claims, characterised in that it comprises p monolithic units (110, 210, 310), p being an integer greater than or equal to two, and in that the elastic arms (140, 240, 340) are designed so that the drive member (1) outputs a substantially constant moment of force over a range of angular displacement of an output element, rim (330) or hub (320), of the stack of the monolithic units (110, 210, 310) with respect to an input element, rim (130) or hub (120), of said stack of at least (p × 10)°, preferably of at least (p × 15)°.
10. Drive member (1) as claimed in any one of the preceding claims, characterised in that the geometric shape of the or each elastic arm (140, 240, 340) of any one of said monolithic units (110, 210, 310) is a Bezier curve or a succession of Bezier curves.
11. Timepiece mechanism characterised in that it comprises a drive member (1) as claimed in any one of claims 1 to 10.
12. Timepiece mechanism as claimed in claim 11, characterised in that it comprises an axle (2) passing through the hubs (120, 220, 320) of the monolithic units (110, 210, 310).
13. Timepiece mechanism as claimed in claim 11 or 12, characterised in that it comprises stop elements making it possible to keep the drive member (1) within a range of angular displacement of an output element, rim (330) or hub (320), of the stack of monolithic units (110, 210, 310) with respect to an input element, rim (130) or hub (120), of said stack permitting the outputting of a substantially constant moment of force.
14. Timepiece mechanism as claimed in any one of claims 11 to 13, characterised in that it comprises a winding mechanism (5a, 5b) arranged to wind the drive member (1) and a gear train (3) arranged to be driven by the drive member (1).

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