CH713456A2 - Clock engine organ. - Google Patents

Abstract

The invention relates to a clock motor unit 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 serge (130, 230 , 330) connected by at least one elastic arm (340). The invention also relates to a clockwork mechanism comprising such a motor member.

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a motor unit for watchmaking, in particular a motor member with a substantially constant moment of force.

The watch motor member according to the invention may be either a motor of a watch movement arranged to drive a finishing train, or a motor member of an additional mechanism such as a striking mechanism or a chronograph mechanism.

[0003] In watchmaking, a barrel has traditionally been used as the driving mechanism of a watchmaking mechanism. A barrel is an assembly of at least three elements: a barrel spring consisting of a spiral spring blade, a barrel drum serving as a housing for said spring, said drum being freely rotatable on a barrel shaft (pivoting shaft between bridge and platen), and a barrel cover for closing the barrel drum, said lid also being freely rotatable on the barrel shaft. Out of the barrel drum, the blade comes out in the shape of an inverted S. The unwinding of the blade, wound against the diameter of the bung of the barrel shaft and seeking to return to its original shape, produces the energy necessary for the operation of the clock mechanism.

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

Another disadvantage of such a motor member is that the manufacture and shaping of the spring blade that it contains, its S shape returned to its spiral shape, must strongly take into account the limit of elasticity of the material constituting the spring blade. In addition, the introduction of the spiral spring housed in the barrel drum is based on a long experience of the watchmaker and requires many handling steps. It is also an assembly of several elements.

Such a motor unit is expensive and difficult to manufacture.

In addition, the moment of force delivered by such a motor member is not constant, which affects the isochronism of the clock mechanism. To alleviate this problem, some watch movements use an intermediate spiral spring between the motor member and the exhaust. 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 alternating drive member to the barrel comprising a spiral spring traditionally used which allows to overcome, at least in part, the aforementioned drawbacks.

The invention proposes for this purpose a clockwork motor unit comprising at least two monolithic units stacked and connected in series, each of these units comprising a hub and a serge connected by at least one elastic arm.

The present invention also provides a watch mechanism comprising such a clock motor unit.

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 15% for a traditional spiral spring barrel). Indeed, the monolithic units that compose it do not undergo or very little friction.

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

Other features and advantages of the present invention will appear on reading the following detailed description with reference to the accompanying drawings, in which: FIG. 1 is a perspective view of a part of a watch mechanism incorporating a clockwork motor member according to a particular embodiment of the invention; fig. 2 is a top view of the mechanism shown in FIG. 1; fig. 3 is a cross section of the driving member of FIG. 1; figs. 4a, 4b and 4c respectively represent, in plan view, a first unit, an intermediate unit and a last unit of the motor unit of FIG. 1; figs. 5a and 5b are views respectively from below and from above of a unit of the motor unit equipped with a centering device; fig. 6 is a schematic graphical representation of the moment of elastic return exerted in a unit of the motor member; fig. 7 shows the coordinates of points defining a particular form of elastic arm for each unit of the drive member; fig. 8a is a graphical representation of the moment of elastic return exercised in a given unit of the motor member comprising resilient arms having the shape as shown in FIG. 7; fig. 8b is a graphical representation of the moment of force delivered by a motor unit comprising eleven units such as that studied in FIG. 8a, stacked and connected in series; fig. 9 shows, in top view, a variant of a unit of the clock motor unit according to the invention.

Figs. 1 and 2 represent a part of a watch mechanism, more precisely a watch movement, comprising a clockwork motor unit 1 according to a particular embodiment of the invention, this motor unit 1 being held in position through an axis 2 of said watch movement. This watch movement furthermore comprises, in particular, a finishing gear train 3, an escapement 4 and a winding mechanism 5a, 5b, as illustrated in FIGS. 1 and 2. In the illustrated example, the winding mechanism comprises a winding stem 5a and a winding gear 5b. In a variant, it could be of automatic type, oscillating weight.

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

The first 110 of said units is associated with a toothing 160 for connection with the winding gear 5b. This toothing 160 which meshes with the winding gear 5b is typically carried by a winding wheel 170 coaxial and integral with the hub 120 of said first unit 110, as shown in FIGS. 1, 2, 3 and 4a. As a variant, the toothing 160 may be integral with the serge 130 of the first unit 110. The one or the one of the hub 120 or of the serge 130 of the first unit 110 which is integral with the toothing 160, and hence through which 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 work train 3 to deliver a moment of force. This other toothing 360 is typically integral with the serge 330 of the latter unit 310, as shown in FIGS. 1, 2, 3 and 4c. Alternatively, the toothing 360 may be integral with the hub 320 of the last unit 310. The one or the hub 320 or the serge 330 of the last unit 310 which is integral with said other toothing 360, and therefore by which out energy, 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 FIGS. 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 preferred direction of rotation of its serge 130,230,330 with respect to its hub 120, 220, 320, this direction being defined as that which makes it possible, from the rest state of the considered unit, the greatest relative angular displacement of its serge 130, 230, 330 relative to its hub 120, 220, 320. The arrows A, B and C, respectively shown in FIGS. 4a, 4b and 4c illustrate this preferred direction of rotation of the serrations 130, 230, 330 relative to the hubs 120, 220, 320 for the units 110, 210, 310 of the motor unit 1 shown.

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 directions of opposite privileged rotation. For example, when the motor unit comprises three units 110, 210, 310, it can comprise a first unit 110 whose preferred direction of rotation is the counterclockwise direction (as represented in FIG. 4a), a single intermediate unit 210 of which the preferred direction of rotation is the clockwise direction (corresponding to a unit 210 as represented in FIG 4b returned) and a last unit 310 whose preferred direction of rotation is the counterclockwise direction (as shown in FIG 4c).

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

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

The preferred direction of rotation of the first 110 and the last 310 units and the choice of input and output elements (serge or hub) depends on the position of the motor member 1 in the clock mechanism and depends of the winding mechanism 5a, 5b and the work train 3. The preferred direction of rotation of the intermediate units 210 is given according to their number and in the direction of the first 110 and last 310 units.

As illustrated in FIGS. 1 to 4c, the hubs 120, 220, 320 of the units 110, 210, 310 of the motor unit 1 comprise bores 150, 250, 350, for example circular, these bores 150, 250, 350 being traversed by the axis 2 of the watch movement, said axis 2 being preferably fixedly mounted relative to the movement, for example in the movement stage. 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 about the axis 2 .

In variants, the hubs 120, 220, 320 of the units 110, 210, 310 of the motor unit 1 may not include bores 150, 250, 350. The motor member may, in this case, be maintained 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 with respect to the plate. This motor unit may, in addition, be placed in a drum.

The structure of the motor member 1 involves the centering of the hub 120, 220, 320 of each unit 110, 210, 310 relative to its serge 130, 230, 330.

However, the drive member 1 may comprise one or more hub centering devices for 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 opposite zones of the serge 130, 230, 330 of a unit 110, 210, 310 and secondly, positioned free in rotation on the axis 2. FIGS. 5a and 5b are views respectively from below and from above of a unit 110, 210, 310 of the motor 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 unit 1 is designed, in particular by its shape, to exercise, in this unit 110 , 210, 310, a substantially constant elastic return moment over a range of angular displacement of the serge 130, 230330 of said unit 110, 210, 310 with respect to its hub 120, 220, 320 of at least 10 °, of preferably at least 15 °, for example about 21 °.

By "substantially constant moment" is meant a moment not varying by more than 10%, preferably 5%, more preferably 3%, typically 1.5%, it being understood that this percentage may be further decreased.

More specifically, Mmin and Mmax respectively are the values of the minimum and maximum moments exerted in a unit 110, 210, 310 of the motor member 1 over a given range of angular displacement of its serge 130, 230, 330 relative to at its hub 120, 220, 320, the moment exerted in this unit 110, 210, 310 is substantially constant since the inequation "(Mnax-Mnin) / ((Mnax + Mnin) / 2) <0.1" is verified, more precisely, since the inequation << (Mmax-Mnin) / ((Mnax + Mnin) / 2) <y% >>, with y = 10, preferably 5, more preferably 3, for example 1.5, is checked.

Let θ be the angular displacement of the serge 130, 230, 330 of a unit 110, 210, 310 of the motor member 1 with respect to the hub 120, 220, 320 of the same unit 110, 210, 310, 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, FIG. 6 illustrates the evolution Μ (θ) of the elastic return 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.

As can be seen on the curve Μ (θ) of FIG. 6, this elastic return moment follows an evolution in three phases: for an angle θ between 0 and a first value θΊ, the moment of elastic return increases rapidly with the angular displacement θ, this phase corresponds to the winding phase ; beyond this first value θΊ, the unit 110, 210, 310 is in a stable phase. Indeed, between this first value θ! and a second value θ2, the elastic return moment is substantially constant with respect to the angular displacement θ; beyond this second value 92, the moment of elastic return increases again until reaching a limit value Miimite, for an angular displacement θ = θ3. This value M | imite depends on the properties of the material in which the unit 110, 210, 310 is made and corresponds to the maximum stress that can undergo a unit 110, 210, 310.

For a given monolithic unit, it is possible to define limit values of angles Omin_y% and 0max y% between which the elastic return moment is substantially constant, with a constancy of y%. For example, if one wants to obtain a constancy of the elastic return moment of 5%, one defines with the aid of the curve Μ (θ), the values of the angles θπίη_5% and 0max 5% so that the inequality: "(Mnax-Mnin) / ((Mnax + Mnin) / 2) <0.05" be checked; with Mnax the maximum elastic return moment on the range of angles [θπίη_5%, 0max_5%] and Mnin the minimum elastic return moment on this same interval.

The monolithic units 110, 210, 310 having a curve Μ (θ) of the type shown in FIG. 6 differ from conventional elastic structures.

Their properties are based on a sinuous shape of their elastic arms which deform so as to generate a substantially constant elastic return moment (the curve Μ (θ) has a plateau). 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 referred to in the above article uses parametric polynomial curves such as Bezier curves to determine the geometric shape of the elastic arms.

The Bézier curves are defined, together with a series of m = (n + 1) control points (Qo, Q ,, ... Qn), 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 140, 240, 340 of the motor unit 1 is a Bezier curve whose control points have been optimized to take into account, in particular, the dimensions of the unit 110, 210, 310 to be designed and the constraint "(Mmax-Mmin) / ((Mmax + Mmin) / 2) <0.05" sought. The inequation "(Mmax-Mmin) / ((Mmax + Mmin) / 2) <0.05" corresponds to a constancy of the elastic return moment of 5% over an angular range [0min_5%, 0max_5%] · [0039 More specifically, the geometrical shape of each of the elastic arms 140, 240, 340 of the motor unit 1 is defined by the set of points Σ = ((Ο,,,,,,,,,,,,, where the s "are the Bernstein polynomials given by the function = avect e ίθ '1] · and where Q, are the control points Qo to Qn. It corresponds to the graphical representation in an orthonormal frame of the set of points defined by the pairs of coordinates (x; y) defined respectively by the functions x (t) and y (t), t ε [0, 1], below: Στη- 1

Qix Bi (t) t = 0 Στη-1

Qiy Bifa i = 0 where Qix and Qiy are respectively the x and y coordinates of the Q, control points.

The formulas indicated above give the coordinates of a Bézier curve of order m, that is to say a Bézier curve based on m control points. For practical reasons, such a Bézier curve can be decomposed 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 Bezier curves.

Using this principle, the Applicant has designed a particular unit of a motor member, said particular unit comprising twenty-three elastic arms evenly distributed around the hub. The dimensions of this particular unit are as follows:

Outside diameter of the serge: 12 mm

Outer diameter of the hub: 2 mm

Internal diameter of the serge: 10 mm

Height: 0.15 mm

Thickness of the Elastic Arms: 60 μm [0042] As part of this design, seven control points Qo, Qi, Q2, Q3, Q4, Qs, Qe were used. The coordinates of these control points are shown in Table 1 below.

Table 1: Coordinates of control points Qo to Qe.

Variables Coordinates x [mm] Coordinates y [mm]

Q 0.756625 ~ 0.653875

Q1,87325__1,619_ Q2__2,8125 __- 0,59125 Q3__3,4375__0,4535 Q4__3,75__1,032875

Qs__4,375__0_

With these seven control points it would have been possible to achieve a seven-order Bezier curve. However, according to the principle indicated above, the Bezier curve has been decomposed into two segments, one first segment corresponding to a fourth order Bezier curve based on checkpoints Qo to Q3 and a second segment corresponding to a fourth order Bézier curve based on checkpoints Q3 to Q6.

Using the coordinates of the control points Qo to Q6 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 number of these pairs of coordinates are given in Table 2 below.

Table 2: Cross-point coordinates of the optimized elastic arm x [mm] y [mm] 0.756625 0.653875 1.086132 0.854582 1.404044 0.903348 1.709407 0.838756 2.001267 0.699389 2,278,652 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 l 0 [0045] The graph of the fig. 7 shows the geometry of the outer diameter of the hub, the internal diameter of the serge and one of the elastic arms of the particular unit that the applicant conceived, the geometry of said arm being defined by a curve passing through all the point coordinates defined in Table 2 above. This graph is made in an orthonormal frame.

FIG. 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 serge with respect to its hub.

The simulation carried out considers a particular unit made of an alloy based on cobalt, nickel and chromium, more specifically 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 (non-alloy structural steel) are also suitable for obtaining units. monolithic whose moment of elastic return is substantially constant over the same angular ranges [0min, 0max].

The angular operating range for the delivery of a substantially constant moment being a constant related 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 appears from the analysis of the results presented in FIG. 8a that a constancy of 3% of the elastic return moment is obtained for an angular displacement of the serge of the particular unit studied with respect to its hub between 0min_3%, ie 13 °, and 0max 3%, ie 34 ° , or over an operating range of 21 °.

By increasing the number of control points during the design of 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 unit 1 comprising eleven units identical to the particular unit studied in FIG. 8a, stacked and connected in series, has also been designed. A simulation made it possible to graphically represent the moment of force delivered by the serge 330 (output element) of the last unit 310 of this motor unit 1 as a function of the angular displacement of the serge 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 FIG. 8b (curve C2).

FIG. 8b also represents the moment of elastic return of a single particular unit identical to that studied in FIG. 8a according to the angular displacement of its serge relative to its hub (curve C1).

As can be seen in this fig. 8b, the value of the moment of force exerted by the motor unit 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 θπίη_3% and 0max 3% for the motor unit 1 is equal to eleven (that is to say the number of units placed in series) times the corresponding angle θπίη_3% and 0max 3% for one unit. Indeed, 0min 3% and 0max 3% for eleven units are respectively 143 ° and 374 °.

The series arrangement of such units thus increases 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 found that a motor unit 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 substantially constant on an angular displacement range of the output element, serge 330 or hub 320, of its last unit 310 relative to the input element, serge 130 or hub 120, of its first unit 110 of at least (px 10) °, preferably at least (px 15) °, for example about (px 21) °.

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

Advantageously, the clock mechanism incorporating the drive member 1 may comprise stops for maintaining said drive member 1 in the angular displacement range of the output element of its last unit 310 relative to the element. input of its first unit 110 for delivering a moment of substantially constant force.

As indicated above, the drive member 1 can be made of any suitable material, particularly with regard to its elastic limit and its Young's modulus.

The units 110, 210, 310 can be manufactured separately and then assembled. They may for example be manufactured by machining, especially 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 by molding, especially in the case where they are made of plastic or metal glass. The units 110, 210, 310 obtained can then be assembled together, typically by gluing, welding or brazing.

Alternatively, the motor member 1 can be made in one piece monolithic, for example 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 units whose preferred direction of rotation is the same are aligned, which allows obtaining a advantageous aesthetic effect, as illustrated in FIGS. 1 and 2.

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

Claims (15)

The monolithic unit 10 shown in FIG. 9 comprises resilient arms 40 exerting a substantially constant elastic return moment over a range of angular displacement of the serge 30 of said unit relative to its hub 20 by at least 10 °, preferably at least 15 °, by example of 21 ° approximately. One way 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 be clear to those skilled in the art that the present invention is in no way limited to the embodiments presented above and illustrated in the figures. For example, it is very conceivable to make a motor unit 1 comprising a number of monolithic units different from that shown in the figures and / or comprising units with resilient arms of shapes different from those shown in the figures and or whose number of elastic arms is different from that shown in the figures, a monolithic unit may in particular have only one elastic arm. The value of the moment of force reached in the stable phase of the motor member can in particular be adjusted by varying the number of elastic arms that comprise the units that constitute it, the thickness of the elastic arms and / or 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 [0min, θΠ3χ] on which the moment of force delivered is substantially constant can, in turn, be adjusted by adjusting the number of stacked units and connected in series. In addition, as already indicated, the toothing 360 associated with the last unit 310 of the motor unit 1 according to the invention may, as desired, be integral with the hub 320 or the serge 330 of this unit 310. In particular, it can be carried directly by said serge 330 or by said hub 320. In the same way, the toothing 160 associated with the first unit 110 of the motor unit 1 according to the invention can, as desired, be integral with the hub 120 or the serge 130 of this unit 110. In particular, it can be carried directly by said serge 130 or by said hub 120. [0071] The skilled person can further easily adjust, depending on his requirements (that is to say for example according to the number of units that comprises the drive member 1, as the toothing 360 is secured to the hub 320 or the serge 330 of the last unit 310, depending on the teeth 160 is integral with the hub 120 or the serge 130 of the first unit 110, lon the preferred direction of rotation chosen for any one of the units ...), the arrangement of the serge-serge and hub-hub connections of a motor unit 1 according to the invention. In addition, the moment of force delivered by the motor member 1 may allow the setting in motion of another type of gear only a work train 3 or an additional mechanism such as a striking mechanism or chronograph. claims 1. Clockwork motor unit (1) 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 serge (130, 230 , 330) connected by at least one elastic arm (140, 240, 340). 2. Engine member (1) according to claim 1, characterized in that it comprises a first toothing (160) for the connection between said monolithic units (110, 210, 310) and a winding mechanism (5a, 5b) and a second toothing (360) for delivering a moment of force by said monolithic units (110, 210, 310). 3. Engine member (1) according to claim 2, characterized in that the first toothing (160) is integral with the hub (120) or the serge (130) of a first (110) of said monolithic units (110, 210 , 310). 4. Engine (1) according to one of claims 2 or 3, characterized in that the second toothing (360) is integral with the hub (320) or the serge (330) of a last (310) of said units monolithic (110, 210, 310). Motor element (1) according to one of the preceding claims, characterized 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 two to two head-to-tail. 6. Engine member (1) according to one of the preceding claims, characterized in that each of said monolithic units (110, 210, 310) comprises a plurality of resilient arms (140, 240, 340) uniformly distributed around its hub (120, 220, 320). 7. Engine member (1) according to one of the preceding claims, characterized in that it comprises at least one device (6) for centering the hubs (120, 220, 320). 8. Motor member (1) according to one of the preceding claims, characterized in that the at least one elastic arm (140, 240, 340) of each monolithic unit (110, 210, 310) is designed to exercise a moment of substantially constant elastic return over a range of angular displacement of the serge (130, 230, 330) of said monolithic unit (110, 210, 310) with respect to its hub (120, 220, 320) of at least 10 °, preferably at least 15 °, for example about 21 °. 9. Engine member (1) according to one of the preceding claims, characterized 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 driving member (1) delivers a substantially constant moment of force over a range of angular displacement of an output member, serge (330) or hub (320), of the stack monolithic units (110, 210, 310) relative to an input member, serge (130) or hub (120), said stack of at least (px 10) °, preferably at least (px 15). ) °, for example about (px 21) °. 10. Engine member (1) according to one of the preceding claims, characterized in that the or each elastic arm (140, 240, 340) of any one of said units (110, 210, 310) is sinuous . Motor unit (1) according to one of the preceding claims, characterized in that the geometrical shape of the or each elastic arm (140, 240, 340) of any one of said monolithic units (110, 210, 310). is a Bézier curve or a succession of Bezier curves. 12. Clock mechanism characterized in that it comprises a motor member (1) according to any one of claims 1 to 11. 13. Watchmaker mechanism according to claim 12, characterized in that it comprises an axis (2) passing through the hubs (120, 220, 320) of the monolithic units (110, 210, 310). 14. Watchmaking mechanism according to claim 12 or 13, characterized in that it comprises stops for holding the motor member (1) in a range of angular displacement of an output member, serge (330) or hub ( 320), the stack of monolithic units (110, 210, 310) with respect to an input element, serge (130) or hub (120), said stack for the delivery of a moment of substantially constant force. 15. Watchmaking mechanism according to one of claims 12 to 14, characterized in that it comprises a winding mechanism (5a, 5b) arranged to arm the drive member (1) and a train (3) arranged to be driven by the drive member (1).