HK1119789B - Assembly element including superposed strip shaped elastic structures and timepiece fitted with the same - Google Patents

Description

Assembly element comprising two series of elastic structures and timepiece fitted with same

Technical Field

The invention relates to an assembly element and a timepiece comprising the same.

The invention relates more particularly to an assembly element made in a sheet of brittle material, such as silicon, in particular for a timepiece, comprising an orifice provided for the axial insertion of a spindle, the inner wall of the orifice comprising elastic structures etched in the sheet and each including at least one bearing surface for radially clamping or pressing the spindle to fix the assembly element relative to the spindle, wherein each elastic structure comprises a first rectilinear elastic strip extending in a tangential direction relative to the spindle, the bearing surfaces being arranged on the inner face of the first elastic strip.

Background

Generally, in a timepiece, an assembly element such as a timepiece hand and a gear is fixed by being pushed into its rotation spindle, i.e. a hollow cylinder is forced onto a pin, the diameter of which is slightly larger than the internal diameter of the cylinder. The elastic and plastic properties of the material used, generally metal, are used for the propulsion within the element. For parts made of brittle materials, such as silicon, that do not have a usable plastic range, it is not possible to advance a hollow cylinder onto a conventional rotating mandrel with a diameter tolerance on the order of +/-5 microns as used in mechanical tabulation.

Furthermore, the solution for fixing the assembled elements, such as the hands, must provide sufficient force to keep the elements in place also in case of shocks. The force required for a conventional timepiece hand is for example in the order of one newton.

To overcome these problems, it has been proposed to use, in an assembly element such as a silicon balance spring collet, a flexible strip-shaped elastic structure arranged on the periphery of the aperture to fix the collet on the mandrel by a push-on type arrangement, using elastic deformation of the strip to grip the mandrel and retain the collet on the mandrel. Examples of such fixing methods are disclosed in particular in european patent No. 1655642.

Disclosure of Invention

The object of the invention is to provide an improvement to this solution, in particular allowing the use of this assembly element as a rotating element in a timepiece mechanism, in particular as a timepiece hand.

The invention therefore proposes an assembly element of the type described above, characterized in that: the assembly element includes a first series of spring structures etched in an upper layer of the plate and a second series of spring structures etched in a lower layer of the plate.

The assembly element according to the invention improves the clamping force on the mandrel, allowing to better distribute the stresses associated with the elastic deformation of the material forming the assembly element, and to better control the clamping force obtained on the mandrel, while maintaining the breaking range away from the material. Furthermore, making the resilient structures in two layers of the panel maximizes the number of resilient structures relative to the volume size.

According to a further feature of the present invention, the elastic structures of the first series are of a different type than the elastic structures of the second series.

The combination of different types of elastic structures between the top layer and the bottom layer allows to combine the technical advantages of both types of structures, for example to optimally withstand linear accelerations along the rotation axis and angular accelerations with respect to the rotation axis.

According to other features of the invention:

-the two series of resilient structures are angularly offset with respect to each other such that at least one portion of their bearing surfaces are angularly offset with respect to each other;

the plate is of the silicon-on-insulator type with a top layer of silicon and a bottom layer of silicon separated by an intermediate layer of silicon oxide;

the plate is an asymmetric silicon-on-insulator type plate with a thin top layer and a thick bottom layer, and the first series of spring structures is made in the top layer and the second series of spring structures is made in the bottom layer;

the assembly element is formed by rotating a rotary element fixedly mounted to the mandrel, the body of the rotary element extending into the top layer and the elastic structure of the second series being made in the axial extension of the body located in the bottom layer;

-the timepiece hands form an assembly element;

-at least one series of elastic structures is of the type in which each elastic structure is formed by a radial stack of several parallel elastic strips, each elastic strip being radially separated from the adjacent elastic strip by a linear separator hole in two parts, the two parts of the separator hole being separated by a bridge of material connecting the two adjacent elastic strips and being substantially radially aligned with the support surface, the last elastic strip of the stack, located on the side opposite the first elastic strip, being radially separated from the remainder of the plate by a hole in a single part, called a clearance hole, which defines a radial clearance space for the elastic structure;

the at least one series of elastic structures is of the type in which each elastic structure is formed by a fork connected to the inner wall of the orifice by a bridge of material, and in which the fork comprises two branches extending generally towards the spindle on each side of the bridge of material, each branch comprising a bearing surface in the vicinity of its free end.

The invention also proposes a timepiece characterised by comprising at least one assembly element according to any of the previous characteristics.

Drawings

Other characteristics and advantages of the invention will become clearer from the following detailed description, given by way of non-limiting example, with reference to the accompanying drawings, in which:

FIG. 1 is an axial cross-section schematically showing a timepiece fitted with an assembly element formed by the hands of a timepiece made from a sheet of brittle material according to the teachings of the present invention;

fig. 2 to 4 are top views respectively schematically showing the hour, minute and second hands fitted to the timepiece of fig. 1, and they are provided with superimposed elastic strip structures etched in the top and bottom layers of each hand;

FIGS. 5 and 6 are enlarged partial views of the mounting ring of the hour hand of FIG. 2 and the second hand of FIG. 4;

FIG. 7 is a partial perspective view showing a mounting ring of the seconds hand of FIG. 4;

FIG. 8 is a view similar to FIG. 2 showing an alternative embodiment of the resilient structure of the hour hand including raised elements of the bearing surfaces;

FIGS. 9-11 are views similar to FIG. 5 showing a second embodiment of the hour, minute and second hands, respectively, wherein the bottom and top layers include different types of elastic construction;

FIGS. 12-14 are views similar to FIGS. 9-11 showing a third embodiment of the hour, minute and second hands, respectively, wherein the bottom and top layers include different types of elastic construction; and

FIG. 15 is an axial cross-section taken along plane 15-15 showing the mounting ring of the hour hand of FIG. 2.

Detailed Description

In the following description, the same or similar elements will be denoted by the same reference numerals.

Fig. 1 schematically illustrates a timepiece 10 made according to the teachings of the present invention.

Timepiece 10 includes a core 12 mounted within a casing 14 enclosed by a crystal 16. Core 12 rotates about axis a1 to drive an analog display device, here formed by hour hand 18, minute hand 20, and second hand 22, which extend above face plate 24. The hands 18, 20, 22 are fixed in a push-type arrangement by elastic clamping to coaxial cylindrical rotating arbours 26, 28, 30, as will be seen hereinafter.

Preferably, the mandrels 26, 28, 30 are conventional mandrels commonly used in timepiece mandrels, such as metal or plastic mandrels.

In the following description, the axial orientation along the axis of rotation a1 of the hands 18, 20, 22 and the radial orientation with respect to the axis a1 will be used in a non-limiting manner. Furthermore, an element is indicated in terms of inner or outer depending on its radial orientation relative to axis a 1.

The hands 18, 20, 22 form assembly elements, each hand 18, 20, 22 being made in a plate of brittle material, preferably a silicon-based crystalline material.

Fig. 2, 3 and 4 show advantageous embodiments for each of the three hands, respectively for the hour hand 18, the minute hand 20 and the second hand 22. Each pointer 18, 20, 22 here comprises a mounting ring 31, the mounting ring 31 defining an aperture 32, the aperture 32 being provided for fixing the pointer 18, 20, 22 to the associated spindle 26, 28, 30 by axial insertion into the aperture 32. The inner wall 33 of the aperture 32 comprises elastic structures 34, the elastic structures 34 being etched in the plate forming the mounting ring 31, and the elastic structures 34 each comprise at least one bearing surface 36 for radially clamping the associated arbour 26, 28, 30, in order to axially and radially retain the pointer 18, 20, 22 on the arbour 26, 28, 30 and rotationally fix the arbour and the associated pointer to each other.

According to the teachings of the present invention, each pointer 18, 20, 22 comprises a first series of elastic structures 34 of S1 etched in the top layer 39 of the board, and a second series of elastic structures of S2 etched in the bottom layer 41 of the board, as illustrated in cross-section in fig. 15.

Advantageously, each finger 18, 20, 22 is made in an asymmetric plate of silicon of the SOI (silicon on insulator) type, comprising a thin top silicon layer 39 and a thick bottom silicon layer 41 separated by an intermediate silicon oxide layer 43. This type of plate has the particular advantage of facilitating the fabrication of distinct structures by two etching steps, for example by chemically etching the top layer 39 side and by another chemical etch on the bottom layer 41 side, the intermediate layer 43 stopping the etch sufficiently to limit the etching within each of the layers 39 and 41 respectively. After etching the top layer 39 and the bottom layer 41, a further etch is performed to remove the intermediate layer 43 in the determined areas to release the resilient structure 34 to allow for resilient deformation of the resilient structure 34.

After each finger 18, 20, 22 has been etched, the top layer 39 and the bottom layer 41 remain connected by portions of the middle layer 43 that are not etched. These connections are here located on the periphery of the orifice 32 within the ring 31.

According to the embodiment shown, the bottom silicon layer 41 remains exclusively below the mounting ring 31 of each cursor 18, 20, 22 and it forms a bottom axial extension with respect to the remainder of the body of the cursor 18, 20, 22, which is formed inside the thin top layer 39, as can be seen in fig. 15.

A first advantageous embodiment of the elastic structure 34 according to the invention is now described by checking the hour hand 18, as shown in fig. 2, and in an enlarged manner in fig. 5, and in a sectional manner in fig. 15. It will be noted that the elastic structure 34 is shown here at rest, i.e. before being deformed by insertion of the relevant mandrel 26, 28, 30.

According to a first embodiment, the elastic structures 34 of the first series S1 and of the second series S2 are of a similar type, here of a type comprising rectilinear and parallel strips L of substantially constant radial thickness_nIs stacked radially. Elastic strip L_nEach extending in a tangential direction relative to the associated spindle 26. Each elasticityThe support surface 36 of the structure 34 is arranged on the first elastic strip L of the stack on the mandrel 26 side₁On the inner face 38. In each elastic structure 34, each elastic strip L_nWith adjacent elastic strip L_n+1、L_n-1By forming two parts I_na、I_nbIn-line separator orifice I_nRadially split, separator bore I_nTwo parts of (I)_na、I_nbBy connecting two adjacent elastic strips L_nAnd a bridge P of material substantially radially aligned with the bearing surface 36_nAnd (4) separating. In the elastic strip L_nA continuous series of bridges P of material therebetween_nThus forming the radial connecting beams 40.

Advantageously, each separator orifice I_nHas a rounded profile, for example a semi-circular profile, to prevent the accumulation of mechanical stresses at the ends, which might result when the elastic strip L is used_nThe initiation of cracks upon bending.

In the illustrated example, the stack-forming elastic structure 34 includes three elastic strips L₁、L₂、L₃And two separator holes I₁、I₂. Separator orifice I_1nIs substantially constant and the same here.

According to another characteristic of the invention, the last elastic strip L of the stack₃Is positioned at the first elastic strip L₁Opposite side, the elastic strip L₃The remainder of the plate from which the pointer 18 is formed is radially separated by a hole 42 in a single part, this hole 42 being called a clearance hole 42. The minimum radial thickness of the clearance hole 42 determines the maximum radial clearance of the spring structure 34. Preferably, the radial thickness of the clearance hole 42 is substantially constant and greater than the separator hole I_nIs measured in the radial direction.

Preferably, the elastic strips L of each elastic structure 34 forming the thick bottom layer 41_nLess than the number of elastic strands L of each elastic structure 34 forming the thin top layer 39_nThe number of (2).

When the mandrel 26 is inserted into the aperture 32,the force exerted on the support surface 36 results in all the elastic strips L of each elastic structure 34_nSo that the strips L are elastically deformed_nIs moved radially outward, thereby reducing the radial thickness of the clearance hole 42 to the right side of the beam 40. The elastic deformation generates a radial clamping force on the mandrel 26, similar to the pushing arrangement.

It will be noted that the connecting beam 40 connects all the elastic strips L_nInterconnected such that they can both deform simultaneously when radial forces are applied to the bearing surface 36 and such that the mechanical stress is distributed at several locations to minimize the risk of breakage.

Preferably, within each elastic structure 34, an elastic strip L_nFrom the first stacked elastic strip L₁To the last elastomer L₃Gradually decreasing, which generally follows the curvature of the outer cylindrical wall 44 of the mounting ring 31.

According to the embodiment shown in fig. 5, each separator bore I_nIs substantially constant over its entire length, and all of these separator holes I_nAre substantially equal in radial thickness. To obtain maximum clamping force on the mandrel 26, each separator hole I in a given material volume of the mounting ring 31_nIs minimized.

Advantageously, for each cursor 18, 20, 22, the number of elastic structures 34 arranged around the aperture 32 in the elastic structure 34 of each series S1, S2 is chosen as a function of the diameter of the relative arbour 26, 28, 30 and as a function of the radial space available between the inner wall 33 of the aperture 32 and the outer wall 44 of the mounting ring 31 of the cursor 18, 20, 22. Therefore, the larger the diameter of the mandrels 26, 28, 30 and the smaller the radial space described above, the larger the number of elastic structures 34.

Thus, in this embodiment, because the diameter of arbour 26 associated with hour hand 18 is much greater than the diameter of arbour 30 associated with second hand 22, and because the outer diameter of mounting ring 31 does not vary proportionally, the number of elastic structures 34 is chosen equal to four in each of series S1, S2 for hour hand 18, and equal to two in each of series S1, S2 for second hand 22. In an intermediate manner, the number of elastic structures 34 in each series S1, S2 for minute hand 20 is here equal to three.

It will be noted that, for hour hand 18 and minute hand 20, elastic structures 34 are regularly distributed about axis a1, so that the shape of the internal profile of aperture 32 is generally square and triangular, respectively.

It will be noted that making the fixing system with at least three elastic structures 34 facilitates centering the mounting ring 31 with respect to the relative arbour 26, 28, 30.

Advantageously, the number of elastic structures 34 is the same in the two series S1, S2, but the elastic structures 34 of the first series S1 are angularly offset with respect to the elastic structures 34 of the second series S2. Thus, if the hour hand 18 in fig. 5 is considered, the elastic structure 34 of the two series S1, S2 is offset by pi/4. The angular offset allows the elastic clamping force to be suitably distributed over the periphery of the mandrel 26 while the support surface 36 of the elastic structure 34 of the first series S1 is angularly offset relative to the support surface 36 of the elastic structure 34 of the second series S2. This angular offset also has advantages with respect to fabrication during the etching step, as it minimizes the surface of the intermediate face 43 whose two lateral faces are released after RIE plasma etching on both sides of the plate (SOI).

According to the embodiment shown, the elastic structure 34 of each series S1, S2 is angularly offset by pi/3 in the minute hand 20 and by pi/2 in the second hand 22.

According to another advantageous feature, the elastic strip L is interposed between the elastic structures 34 of the first series S1 and the elastic structures 34 of the second series S2_nThis allows the value of the resilient clamping force on the mandrel 26 to be more finely adjusted. This also allows the clamping force value to be used as the elastic strip L_nIs adjusted as a function of the axial thickness of the two layers 39, 40, because the elastic strip L of the bottom layer 41 is due to the difference in axial thickness between the two layers 39, 40_nElastic strip L axially closer to top layer 39_nIs thick.

The specific structure of the seconds hand 22 will now be described with particular reference to fig. 6 and 7, each series S1, S2 of which has only two elastic structures 34 and one fixed support surface 46. According to this embodiment, the first elastic strip L of the two elastic structures 34 of each series S1, S2₁An acute angle beta is defined between them and they are substantially joined at one of their fixed ends. The angle β has a value of thirty degrees, for example.

For simplicity of illustration and ease of description, the two layers 39, 41 of the pointer 22 and the series S1, S2 of the associated elastic structure 34 are shown side by side in fig. 6.

The structure of top layer 39 and the associated elastic structure will now be described in view of the fact that the structure of bottom layer 41 is similar but offset by a half turn (S1).

The fixed bearing surface 46 extends tangentially with respect to the relative spindle 30 and it forms the base of an isosceles triangle, the two other sides of which are defined by the first elastic strips L of the two elastic structures 34₁Is formed by the inner face 38. The fixed bearing surface 46 is here arranged at the free end of a generally trapezoidal cutout 48, projecting inside the aperture 32. The cut-out 48 is etched in the plate forming the finger 22 and here the cut-out 48 comprises two side walls 50, 52, the side walls 50, 52 each being parallel to the first line L of the opposite elastic structure 34₁And (4) extending.

The arbour 30 associated with the second hand 22 is intended to abut against the fixed support surface 46 and against the support surface 36 of the elastic structure 34.

It will be noted that the profile of the inner wall 33 of the orifice 32 has a generally isosceles triangular shape.

According to an advantageous embodiment, shown in fig. 6, in each elastic structure 34, each elastic strip L_nIs substantially constant over its entire length, and the elastic strip L_nFrom the stacked first elastic strips L₁To the last elastic strip L₉Progressively lower, each elastic structure 34 of the first series S1 here comprisingTwenty-one elastic strip L_nThese elastic strips L_nDecreases in length from the inside outwards, and each elastic structure 34 of the second series S2 here comprises nine elastic strips L_nThese elastic strips L_nDecreases in length from the inside outwards. Thus, the elastic strip L₁Is adapted to its length, which allows for all elastic strips L_nA substantially uniform flexibility is obtained despite the different lengths thereof. The invention thus homogenizes the mechanical stress over the entire material volume for fixing, i.e. here over the entire mounting ring 31.

Of course, in the elastic strip L_nThis difference in thickness therebetween may be applied to other embodiments of the pointers 18, 20, 22.

It will be noted that each stacked elastic strip L is formed_nThe number of which can be modified according to various parameters, in particular as a function of the available radial space, as a function of the desired clamping force on the relative arbour, as a function of the type of material used for manufacturing the relative hands 18, 20, 22. Preferably, the elastic strip L_nLess in the thick bottom layer 41 than in the thin top layer 39.

Fig. 8 shows an alternative embodiment of the hour hand 18, which differs from the previous one in that: each bearing surface 36 is provided with discrete raised elements 54, the raised elements 54 increasing the friction between the spindle 26 and the bearing surface 36 to improve the rotational fixation between the spindle 26 and the pointer 18. In the first line L₁The teeth of the internally etched triangular profile form here the discrete raised elements 54.

Of course, this variation may be applied to the bearing surfaces 36, 46 arranged in the apertures 32 in the minute hand 20 and the second hand 22 described with reference to fig. 3 and 4.

According to the second embodiment shown in fig. 9 to 11, the elastic structures 34 of the two series S1, S2 arranged on each hand 18, 20, 22 are of different types. More specifically, the elastic structure 34 of the first series S1 is a structure having stacked elastic strips L_nIs of a type such that,as described and illustrated with reference to the first embodiment, and the elastic structures 34 of the second series S2 are of the type having fork-shaped elastic structures 34.

Each elastic structure 34 of the second series S2 is formed by a fork which is connected to the inner wall 33 of the orifice 32 by a bridge 56 of material and which comprises two branches 58, 60 extending generally towards the mandrels 26, 28, 30 on each side of the bridge 56 of material. In addition, each limb 58, 60 includes a bearing surface 62, 64 adjacent a free end 66, 68 thereof.

According to a second embodiment, the two branches 58, 60 of each elastic structure 34 are bent towards each other, so as to form an almost closed "C" shape.

The second embodiment is described in consideration of the hour hand 18 as shown in fig. 9. It will be noted that the elastic structure 34 is represented here at rest, i.e. before being deformed by insertion of the relative mandrels 26, 28, 30.

Each branch 58, 60 of each elastic structure 34 has a substantially parabolic shape, with a first fixed end 70, 72 thereof arranged on the bridge 56 of the relative material and a second free end 66, 68 thereof facing the free ends 66, 68 of the other branches 56, 58 of the elastic structure 34.

Preferably, the free ends 66, 68 of the branches 58, 60 of each elastic structure 34 are sufficiently close that the inner face of each branch 58, 60 is substantially tangential to the axial surface of the mandrel 26 in the vicinity of the free ends 66, 68, so that the bearing surface 62, 64 of each branch 58, 60 is located on the inner face of its free end portion opposite the mandrel 26.

When the mandrel 26 is inserted into the aperture 32, the radial force acting on the bearing surfaces 62, 64 causes an elastic deformation of the two branches 58, 60 of the elastic structure 34, so that the free ends 66, 68 of the branches 58, 60 move radially outwards. This elastic deformation generates a radial clamping force on the mandrel 26, similar to the pushing arrangement.

Preferably, the elastic structures 34 are regularly distributed around the axis a 1.

The inventionIs shown in fig. 12 to 14. This third embodiment is similar to the second embodiment in that the elastic structures 34 of the first series S1 are formed by stacking elastic strips L_nThe elastic structure 34 of the second series S2 is formed by a fork with two branches 58, 60. The third embodiment differs from the second embodiment mainly in that each elastic structure 34 comprises a main portion 74 extending on each side of the bridge 56 of material. Each branch 58, 60 extends in a linear direction from the end of the main portion 74 opposite the bridge 56 of material. Each branch 58, 60 is inclined with respect to the radial direction towards the associated branch 58, 60. The bearing surface 62, 64 of each limb 58, 60 is arranged at a free end 66, 68 of the limb 58, 60.

Preferably, the main portion 74 of each elastic structure 34 extends parallel to the inner cylindrical wall 33 of the orifice 32 in a substantially circumferential direction, which maximizes the length of the main portion 74 and the rectilinear branches 58, 60 to distribute the stresses associated with the elastic deformation of the branches 58, 60 over a greater volume.

An advantage of the third embodiment is that a self-locking effect is created when the mandrels 26, 28, 30 and associated fingers 18, 20, 22 are assembled to each other. In fact, the inclination of the branches 58, 60 allows a dynamic reaction to the acceleration in rotation, which makes this embodiment particularly suitable for fixing assembly elements subjected to high angular accelerations, or for the case in which the rotating elements have a significant imbalance in weight distribution, as is the case for the hands of a timepiece.

In the third embodiment, the two branches 58, 60 of each elastic structure 34 exert thrust in opposite directions, so that each branch 58, 60 opposes the relative rotation of the pointer 18, 20, 22 with respect to the relative arbour 26, 28, 30 in the preferred direction of rotation. In the example shown in fig. 12, the first branch 58 of each resilient structure 34 resists relative rotation of the pointer 18 in a counterclockwise direction, and the second branch 60 of each resilient structure 34 resists relative rotation of the pointer 18 in a clockwise direction. The resilient structure 34 of the third embodiment thus provides a particularly effective rotationally fixed arrangement between the hands 18, 20, 22 and the associated arbours 26, 28, 30.

Having the elastic structure 34 in the form of a fork comprising one tangentially or circumferentially oriented portion (portion 56) and a rectilinear portion (branches 58, 60) oriented towards the relative arbour 26, 28, 30 reduces the stiffness of the elastic structure 34, which allows a radial clearance of sufficient value to allow fixing of said structure to the arbour 26, 28, 30, in particular to allow compensating for the diametral tolerances of the arbour. Each elastic structure 34 must have sufficient flexibility to be fixed to a mandrel having a diameter smaller than the nominal value and to a mandrel having a diameter greater than the nominal value.

The advantages mentioned herein with reference to the third embodiment apply in part to the first embodiment, since having the resilient structure comprising two branches 58, 60 provides the advantage of dynamic reaction to angular acceleration. Furthermore, the curved branches 58, 60 of the second embodiment also allow to obtain a reduction of the stiffness of the elastic structure 34 and a sufficient radial clearance for fixing to the mandrel.

It should be noted that in the first and second embodiments, each elastic structure 34 has an axial symmetry plane P extending along a radius through the middle of the bridge 40 of material.

When provided with elastic strips L_nThe combination of different types of spring structures used in the second and third embodiments is particularly advantageous when the stacked spring structures 34 are arranged in a thin top layer 39 and the fork-shaped spring structures 34 are arranged in a thick bottom portion 41. In practice, the smallest possible aperture in the silicon layer is dependent on the thickness of the layer due to the manufacturing and etching processes. The elastic clamping force of each elastic structure 34 is proportional to the third power of the axial thickness of the elastic structure 34, which means that a layer comprising a relatively reduced number of elastic strips, as is the case with fork-shaped structures, will present difficulties in establishing a sufficient clamping force. Thus, the elastic structure 34 most suitable for the thin topsheet 39 is provided with stacked elastic strips L_nBecause they employ a large number of elastic strips. Furthermore, such elastic strips with a stack in this top layer 39L_nThe arrangement of the elastic structure 34 minimizes the elastic strip L_nThe radial space in between, and thus the elastic strip L is increased_nThereby compensating for the elastic strips L_nLow axial thickness of (a) results in a low elastic restoring force.

Of course, the above-described embodiments may be combined with each other or with other embodiments. In particular, the elastic structure 34 may be of different types, for example formed according to the teachings of european patent No 1655642. The type of elastic structure 34 chosen for each layer 39, 41 may also be reversed with respect to the described embodiment, in particular with stacked elastic strips L_nElastic structures 34 of the type in question may be arranged in the bottom layer 41 and fork-shaped elastic structures 34 may be arranged in the top layer 39.

According to a variant (not shown), the fingers 18, 20, 22 can be made in a symmetrical SOI-like plate, i.e. a plate in which the top layer 39 and the bottom layer 41 have the same thickness.

Although the invention has been described with reference to the assembly elements formed by the hands 18, 20, 22, it is not limited to these embodiments. Thus, the assembly element can be formed by another type of rotating element, for example by using a gear wheel inside the timepiece core. The assembly element may also be formed by a non-rotating element, for example provided as a sheet of brittle material assembled on another element comprising a stationary mandrel or a strut made of metal.

Claims (12)

1. An assembly element (18, 20, 22) for a timepiece made in a sheet of brittle material, comprising an aperture (32) provided for the axial insertion of a arbour (26, 28, 30), the inner wall (33) of the aperture (32) comprising elastic structures (34) etched into the sheet and the elastic structures (34) each comprising at least one bearing surface (36, 62, 64) for radially clamping the arbour (26, 28, 30) to fix the assembly element (18, 20, 22) with respect to the arbour (26, 28, 30), characterized in that: the assembly element (18, 20, 22) comprises a first series (S1) of elastic structures (34) etched in the top layer (39) of the plate and a second series (S2) etched in the bottom layer (41) of the plate.

2. The assembly element (18, 20, 22) according to claim 1, characterized in that: the elastic structures (34) of the two series (S1, S2) are of the same type.

3. The assembly element (18, 20, 22) according to claim 1, characterized in that: the elastic structures (34) of the first series (S1) are of a different type than the elastic structures (34) of the second series (S2).

4. The assembly element (18, 20, 22) according to claim 1, characterized in that: the elastic structures (34) of the two series (S1, S2) are angularly offset with respect to each other, so that at least one portion of their bearing surfaces (36) are angularly offset with respect to each other.

5. The assembly element (18, 20, 22) according to claim 1, characterized in that: the brittle material is silicon.

6. The assembly element (18, 20, 22) according to claim 1, characterized in that: the panel is an asymmetric silicon-on-insulator type panel with a top layer of silicon (39) and a bottom layer of silicon (41) separated by an intermediate layer of silicon oxide (43).

7. The assembly element (18, 20, 22) according to claim 6, characterized in that: the sheet is an asymmetric silicon-on-insulator type sheet with a thin top layer (39) and a thick bottom layer (41), and a first series (S1) of resilient structures (34) is made in the top layer (39) and a second series (S2) of resilient structures (34) is made in the bottom layer (41).

8. The assembly element (18, 20, 22) according to claim 7, characterized in that: the assembly element (18, 20, 22) is formed by a rotary element (18, 20, 22) mounted rotationally fixed to the spindle (26, 28, 30), the body of the rotary element (18, 20, 22) extending into the top layer (39), the elastic structure (34) of the second series (S2) being made in the axial extension of the body located in the bottom layer (41).

9. The assembly element (18, 20, 22) according to claim 1, characterized in that: the assembly elements (18, 20, 22) are formed by timepiece hands.

10. The assembly element (18, 20, 22) according to claim 1, characterized in that: the at least one series (S1, S2) of elastic structures (34) is of the type in which each elastic structure (34) is formed by a plurality of parallel elastic strips (L)_n) Each elastic strip (L)_n) With adjacent elastic strip (L)_n) Is composed of two parts (I)_na，I_nb) In-line separator orifice (I)_n) Radially split, separator orifice (I)_n) Is made of a bridge (P) of material_n) Separate, bridges of material (P)_n) Two adjacent elastic strips (L) are connected_n) And substantially radially aligned with the bearing surface (36) and stacked on the first elastic strip (L)₁) Last elastic strip (L) on opposite side_n) Is radially separated from the remainder of the plate by a bore in a single portion, referred to as a clearance bore (42), the clearance bore (42) defining a radial clearance space for the resilient structure (34).

11. The assembly element (18, 20, 22) according to claim 1, characterized in that: the elastic structures (34) of at least one series (S1, S2) are of the type in which each elastic structure (34) is formed by a fork connected to an inner wall (33) of the orifice by a bridge (56) of material, and the fork comprises two branches (58, 60) extending generally towards the mandrels (26, 28, 30) on each side of the bridge (56) of material, each branch (58, 60) comprising a bearing surface (62, 64) in the vicinity of its free end (66, 68).

12. A timepiece (10) characterized by: comprising an assembly element (18, 20, 22) according to any of the preceding claims.