EP1921518A1 - Assembly component comprising overlaid blade-shaped elastic structures and timepiece equipped with this component - Google Patents

Abstract

The assembling element has an inner wall (33) with elastic structures, where each structure is constituted of a radial pile of parallel elastic blades (Ln). Each blade is spaced radially from the adjacent elastic blade (Ln) by a rectilinear insert opening (ln) in two parts, where the parts of the opening are separated by a material bridge (Pn). Final elastic blade of the pile is situated in a side opposite to an initial elastic blade and is spaced radially from rest of the plate by a displacement opening (42), which defines a radial space for an elastic structure (34).

Description

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

The invention more particularly relates to an assembly element made in a plate of brittle material such as silicon, in particular for a timepiece, having an opening provided for the axial insertion of a shaft, the inner wall of the opening comprising elastic structures which are etched in the plate and which each comprise at least one bearing surface for radially clamping the shaft in order to secure the fastening element with respect to the shaft, wherein each elastic structure comprises a first straight elastic blade which extends in a direction tangential to the shaft, the bearing surface being arranged on the inner face of the first elastic blade.

Generally, in timepieces, the assembly elements such as the watch hands and the gears are fixed on their rotary shaft by driving, that is to say that a hollow cylinder is forced on an axis. having a diameter slightly greater than the inside diameter of the cylinder. The elastic and plastic properties of the material used, generally a metal, are used for this hunting. For components made of brittle material such as silicon, which material does not have a usable plastic field, it is not possible to drive a hollow cylinder on a conventional rotating shaft such as those used in mechanical watchmaking , with a diameter tolerance of the order of +/- 5 microns.

In addition, the fixing solution of the connecting element such as a needle must provide sufficient force to hold the element in place during shocks. The force required for a conventional watchmaking needle is for example of the order of a Newton.

To solve these problems, it has already been proposed to produce, in an assembly element such as a silicon spiral spring ferrule, elastic structures in the form of flexible blades arranged around the periphery of the opening, in such a way that to allow the attachment of the ferrule on a shaft in the manner of a hunting, using the elastic deformation of the blades to tighten the shaft and retain the ferrule on the shaft. Such an example of attachment is described in particular in the document EP 1 655 642 .

The invention aims to provide improvements to this solution, in particular to allow the use of this assembly element as a rotary element in a clockwork mechanism, in particular as a watchmaking needle.

For this purpose, the invention proposes an assembly element of the type described above, characterized in that each elastic structure is constituted by a radial stack of several parallel elastic blades, each elastic blade being spaced radially from the adjacent elastic blade by a a two-part rectilinear intermediate light, the two parts of the intermediate light being separated by a bridge of material which connects the two adjacent elastic strips and which is substantially radially aligned with the bearing surface, and in that the last elastic blade of the stack, which is located on the opposite side to the first blade, is radially spaced from the remainder of the plate by a single-piece light, called the deflection lumen, which defines a radial clearance space for the elastic structure.

The assembly element according to the invention makes it possible to improve the clamping force against the shaft, to allow a better distribution of the forces related to the elastic deformation in the material constituting the connecting element, and to allow a better control of the clamping force obtained on the shaft. In particular, the restoring forces of each elastic blade of a stack add up while maintaining a stiffness of each elastic blade as low as possible. A significant bending of the elastic structure is obtained, in particular at the level of the bearing surface, without leaving the elastic domain of the material. Thus, the elastic structures according to the invention offer a radial displacement, following their elastic deformation, which is large enough to compensate for manufacturing tolerances applied to the diameter of a shaft such as those used in timepieces for the training of the needles.

In addition, the elastic structures according to the invention make it possible to optimize the volume available on the assembly element to perform the clamping and fixing function.

• dans chaque structure élastique, la longueur des lames élastiques diminue progressivement depuis la première lame élastique jusqu'à la dernière lame élastique de l'empilement;
• l'épaisseur radiale de chaque lame élastique est sensiblement constante sur toute sa longueur, et, dans chaque structure élastique, l'épaisseur radiale des lames élastiques diminue progressivement depuis la première lame élastique jusqu'à la dernière lame élastique de l'empilement;
• l'épaisseur radiale des lumières intercalaires est sensiblement constante pour chaque lumière intercalaire et sensiblement constante d'une lumière intercalaire à l'autre;
• l'épaisseur radiale minimale de la lumière de débattement est supérieure ou égale à l'épaisseur radiale des lumières intercalaires;
• le profil de chacune des extrémités de chaque lumière intercalaire est arrondi;
• la surface d'appui de la première lame élastique comporte des éléments discrets en relief qui augmentent la friction entre l'arbre et la surface d'appui;
• la paroi intérieure de l'ouverture comporte au moins trois structures élastiques qui sont réparties régulièrement autour de l'arbre;
• la paroi intérieure de l'ouverture est constituée par deux structures élastiques et par une surface d'appui fixe, les premières lames élastiques des deux structures élastiques définissent entre elles un angle déterminé, et la première lame élastique des deux structures élastiques se rejoignent à l'une de leurs extrémités fixes;
• le contour de la paroi intérieure de l'ouverture a globalement la forme d'un triangle isocèle, et la surface d'appui fixe constitue la base du triangle isocèle;
• la surface d'appui fixe est agencée à l'extrémité libre d'une découpe en saillie à l'intérieur de l'ouverture;
• l'élément d'assemblage est constitué par un élément rotatif prévu pour être monté solidaire à rotation sur l'arbre;
• l'élément d'assemblage est constitué par une aiguille horlogère.

According to other features of the invention:

• in each elastic structure, the length of the elastic blades gradually decreases from the first elastic blade to the last elastic blade of the stack;
• the radial thickness of each elastic blade is substantially constant over its entire length, and in each elastic structure, the radial thickness of the elastic blades gradually decreases from the first elastic blade to the last elastic blade of the stack;
• the radial thickness of the intermediate lights is substantially constant for each intermediate light and substantially constant from one intermediate light to the other;
• the minimum radial thickness of the deflection light is greater than or equal to the radial thickness of the intermediate lights;
• the profile of each of the ends of each intermediate light is rounded;
• the bearing surface of the first elastic blade comprises discrete elements in relief which increase the friction between the shaft and the bearing surface;
• the inner wall of the opening comprises at least three elastic structures which are evenly distributed around the shaft;
• the inner wall of the opening is constituted by two elastic structures and a fixed support surface, the first elastic blades of the two elastic structures define between them a determined angle, and the first elastic blade of the two elastic structures meet at the same time. one of their fixed ends;
• the outline of the inner wall of the opening has generally the shape of an isosceles triangle, and the fixed bearing surface is the base of the isosceles triangle;
• the fixed bearing surface is arranged at the free end of a protruding cutout inside the opening;
• the connecting element is constituted by a rotary member adapted to be mounted to rotate with the shaft;
• the assembly element is constituted by a watchmaker's needle.

The invention also proposes a timepiece characterized in that it comprises at least one connecting element according to one of the preceding characteristics.

• la figure 1 est une vue en coupe axiale qui représente schématiquement une pièce d'horlogerie équipée d'éléments d'assemblage constitués par des aiguilles horlogères réalisées conformément aux enseignements de l'invention;
• les figures 2 à 4 sont des vues de dessus qui représentent schématiquement respectivement l'aiguille des heures, l'aiguille des minutes, et l'aiguille des secondes équipant la pièce d'horlogerie de la figure 1 et qui sont pourvues de structures élastiques à lames superposées;
• la figure 5 est une vue agrandie d'une partie de la figure 2 qui représente la bague de fixation de l'aiguille des heures;
• la figure 6 est une vue agrandie d'une partie de la figure 4 qui représente la bague de fixation de l'aiguille des secondes;
• la figure 7 est une vue similaire à celle de la figure 6 qui représente une variante de réalisation des structures élastiques comportant des éléments discrets en relief sur la surface d'appui.

Other features and advantages of the present invention will appear more clearly on reading the detailed description which follows, made with reference to the accompanying drawings given by way of non-limiting example and in which:

• the figure 1 is an axial sectional view which schematically shows a timepiece equipped with assembly elements constituted by watch hands made in accordance with the teachings of the invention;
• the Figures 2 to 4 are views from above which schematically represent respectively the hour hand, the minute hand, and the second hand equipping the timepiece of the figure 1 and which are provided with elastic structures with superposed blades;
• the figure 5 is an enlarged view of some of the figure 2 which represents the fixing ring of the hour hand;
• the figure 6 is an enlarged view of some of the figure 4 which represents the fixing ring of the seconds hand;
• the figure 7 is a view similar to that of the figure 6 which represents an alternative embodiment of the elastic structures comprising discrete elements in relief on the bearing surface.

In the remainder of the description, identical or similar elements will be designated by the same references.

On the figure 1 schematically shows a timepiece 10 which is made in accordance with the teachings of the invention.

The timepiece 10 comprises a movement 12 mounted inside a casing 14 closed by a lens 16. The movement 12 drives in rotation, about an axis A1, analog display means constituted here by a hour hand 18, a minute hand 20, and a second hand 22, these hands extending above a dial 24. The needles 18, 20, 22 are fixed on shafts 26, 28, 30 of cylindrical rotation coaxial elastic clamping, like a hunting, as will be seen later.

Preferably, the shafts 26, 28, 30 are conventional shafts commonly used in watch movements, for example shafts made of metal or plastic material.

In the remainder of the description, non-limiting use will be made of an axial orientation along the axis of rotation A1 of the needles 18, 20, 22 and a radial orientation relative to this axis A1. In addition, elements will be qualified interior or exterior, in the radial orientation, with respect to the axis A1.

The needles 18, 20, 22 constitute connecting elements, each needle 18, 20, 22 being made in a plate of brittle material, preferably of crystalline material based on silicon.

The Figures 2, 3 and 4 represent an advantageous embodiment for each of the three needles, respectively for the hour hand 18, the minute hand 20, and the second hand 22. Each needle 18, 20, 22 here comprises a fixing ring 31 which delimits an opening 32 provided to allow the fixing of the needle 18, 20, 22 on the shaft 26, 28, 30 associated by axial insertion in the opening 32. The inner wall 33 of the opening 32 comprises structures elastic members 34 which are etched in the plate forming the fixing ring 31 and which each comprise at least one bearing surface 36 for radially clamping the associated shaft 26, 28, 30 in order to retain the needle 18 radially and axially, 20, 22 on the shaft 26, 28, 30, and in order to make the shaft and the associated needle integral with rotation.

We now describe a first advantageous embodiment of the elastic structures 34 according to the invention by considering the hour hand 18 such that represented on the figure 2 and as shown enlarged on the figure 5 . Note that the elastic structures 34 are here represented at rest, that is to say before being deformed by the insertion of the shaft 26, 28, 30 associated.

Each elastic structure 34 is constituted by a radial stack of several linear lamellae L _n rectilinear and parallel, of substantially constant radial thickness, which each extend in a tangential direction relative to the associated shaft 26. The bearing surface 36 of each elastic structure 34 is arranged on the inner face 38 of the first elastic blade L ₁ of the stack, on the side of the shaft 26. In each elastic structure 34, each elastic blade L _n is radially of the elastic blade spaced L _{n + 1,} L _n-1 adjacent a separator hole I _n rectilinear in two parts I _na, I _nb, both parts I _na, I _nb of the separator hole I _n being separated by a material bridge P _n which connects the two adjacent elastic strips L _n and which is substantially radially aligned with the bearing surface 36. The continuous sequence of material bridges P _n between the elastic strips L _n thus forms a radial connecting beam 40.

Advantageously, the end of each intermediate light I _n has a rounded profile, for example in a semicircle, so as to avoid an accumulation of mechanical stresses at the ends which could lead to breakouts during the bending of the elastic blades L _n .

In the example shown, the stack forming the elastic structure 34 comprises three resilient blades L ₁ , L ₂ , L ₃ and two intermediate lights I ₁ , I ₂ . The radial thicknesses of the intermediate lights I _n are here substantially constant and identical.

According to another characteristic of the invention, the last elastic blade L ₃ of the stack, which is located on the opposite side to the first blade L ₁ , is spaced radially from the rest of the plate forming the needle 18 by a light 42 in a single part, called deflection light 42, which defines a radial clearance space for the associated elastic structure 34. It should be noted that the minimum radial thickness of the deflection lumen 42 is determined, firstly, by the minimum radial slot thickness allowed by the process used to etch the plate of brittle material and, secondly, by the maximum radial displacement of the elastic structure 34. The largest of these two parameters will be chosen for the minimum radial thickness of the deflection lumen 42. Preferably, the radial thickness of the deflection lumen 42 is substantially constant and superior. to the radial thickness of the intermediate lights I _n .

When the shaft 26 is inserted into the opening 32, the force exerted on the bearing surface 36 causes elastic deformation of all the elastic blades L _n of the elastic structure 34 so that the central portion of these blades L _n moves radially outward, reducing the radial thickness of the deflection lumen 42 to the right of the beam 40. This elastic deformation produces a radial clamping on the shaft 26 in the manner of a hunting.

It is noted that the connecting beam 40 makes it possible to bind all the elastic strips L _n between them, so that they can all be deformed simultaneously when a radial force is applied to the bearing surface 36, and in such a way as to distribute mechanical stresses in several places to minimize the risk of breakage.

Preferably, in each elastic structure 34, the length of the elastic blades L _n decreases progressively from the first elastic blade L ₁ to the last elastic blade L ₃ of the stack, which makes it possible to follow globally the curvature of the wall outer cylindrical 44 of the fixing ring 31.

According to the embodiment shown on the figure 5 , the radial thickness of each intermediate light I _n is substantially constant over its entire length and the radial thickness of all the intermediate lights I _n is substantially equal.

To obtain a maximum clamping force on the shaft 26, in a given volume of material of the fixing ring 31, the radial thickness of each intermediate light I _n is minimized.

Advantageously, for each needle 18, 20, 22, the number of elastic structures 34 arranged around the opening 32 is chosen as a function of the diameter of the associated shaft 26, 28, 30 and as a function of the available radial space between the inner wall 33 of the opening 32 and the outer wall 44 of the fixing ring 31 of the needle 18, 20, 22. Thus, the larger the diameter of the shaft 26, 28, 30 and the greater the radial space mentioned above is low, the greater the number of elastic structures 34 is important.

Thus, in the present embodiment, as the diameter of the shaft 26 associated with the hour hand 18 is much larger than the diameter of the shaft 30 associated with the second hand 22, and as the diameter outside the fixing ring 31 does not evolve proportionally, it was selected a number of elastic structures 34 equal to four for the hour hand 18 while the number of elastic structures 34 is equal to two for the needle Secondly, the number of elastic structures 34 in the minute hand 20 is here equal to three.

It is noted that, for the hour hand 18 and the minute hand 20, the elastic structures 34 are evenly distributed around the axis A1, so that the inner contour of the aperture 32 generally has a square shape and a triangular shape respectively.

We now describe, considering in particular the figure 6 , the specific structure of the second hand 22 whose opening 32 comprises only two elastic structures 34 and a fixed bearing surface 46. According to this embodiment, the first elastic blades L ₁ of the two elastic structures 34 define between they have an acute angle β and they are substantially joined to one of their fixed ends. The angle β for example has a value of about thirty degrees.

The fixed bearing surface 46 extends in a tangential direction, relative to the associated shaft 30, and forms the base of an isosceles triangle whose two other sides are formed by the inner face 38 of the first elastic blades. L ₁ of the two elastic structures 34. The fixed bearing surface 46 is here arranged at the free end of a cutout 48, generally trapezium-shaped, projecting inside the opening 32. The cut 48 is engraved in the plate forming the needle 22 and here it comprises two side walls 50, 52 which each extend parallel to the first blade L ₁ of the elastic structure 34 vis-à-vis.

The shaft 30 associated with the seconds hand 22 is designed to bear against the fixed bearing surface 46 and against the bearing surfaces 36 of the elastic structures 34.

Note that the contour of the inner wall 33 of the opening 32 has the overall shape of an isosceles triangle.

According to an advantageous embodiment represented on the figure 6 in each elastic structure 34, the radial thickness of each elastic blade L _n is substantially constant over its entire length, and the radial thickness of the elastic blades L _n decreases progressively from the first elastic blade L ₁ to the last blade elastic L9 of the stack, each elastic structure 34 having here nine elastic blades L _n of decreasing lengths, from the inside to the outside. Thus, the radial thickness of the elastic blades L ₁ is adapted to their length, which allows a substantially homogeneous flexibility of all the elastic blades L _n , despite their differences in length. The invention thus makes it possible to homogenize the mechanical stresses throughout the volume of material used for fixing, that is to say here in the entire fixing ring 31.

Of course, this variation in thickness between the elastic strips L _n may be applied to other embodiments of needles 18, 20, 22.

Note that the number of elastic blades L _n forming each stack can be adapted according to various parameters, in particular according to the available radial space, depending on the desired clamping force on the shaft associated, depending on the type of material used to manufacture the needle 18, 20, 22 associated.

On the figure 7 there is shown an alternative embodiment of the second hand 22 which differs from the previous embodiment in that each bearing surface 36, 46 is provided with discrete elements in relief 54 which increase the friction between the shaft 30 and the bearing surfaces 36, 46 so as to improve the rotational connection between the shaft 30 and the needle 22. These discrete elements in relief 54 are constituted here by teeth of triangular profile.

Of course, this variant embodiment is applicable to the bearing surfaces 36 arranged in the openings 32 of the hours 18 and minute hands 20 described in connection with the Figures 2 and 3 .

Although the present invention has been described in connection with assembly elements constituted by needles 18, 20, 22, it is not limited to these embodiments. Thus, the connecting element may be constituted by another type of rotary element, for example by a toothed wheel used in a clockwork movement. The connecting element may also be constituted by a non-rotating element, for example a plate of brittle material intended to be assembled on another element comprising a fixing shaft, or tenon, of metal.

The present invention is applicable to a needle 18, 20, 22 made in a silicon wafer comprising a single layer of silicon, as well as in a Silicon On Insulator (SOI) type wafer which comprises an upper layer and a lower layer of silicon separated by an intermediate layer of silicon oxide.

Claims (14)

Connecting element (18, 20, 22) made in a plate of a brittle material such as silicon, in particular for a timepiece (10), comprising an opening (32) provided for the axial insertion of a shaft (26, 28, 30), the inner wall (33) of the opening (32) having elastic structures (34) which are etched into the plate and which each have at least one bearing surface (36) for clamping radially to the shaft (26, 28, 30) to secure the fastener (18, 20, 22) relative to the shaft (26, 28, 30), wherein each elastic member (34) comprises a first straight elastic blade (L ₁ ) which extends in a tangential direction relative to the shaft (26, 28, 30), the bearing surface (36) being arranged on the internal face (38) of the first elastic blade (L ₁ ), characterized in that each elastic structure (34) is constituted by a radial stack of several elastic blades (L _n ) by alleles, each elastic blade (L _n ) being radially spaced from the adjacent elastic blade (L _n ) by a two-part rectilinear intervening light (I _n ), the two parts of the intermediate light (I _n ) being separated by a bridge of material (P _n ) which connects the two adjacent elastic strips (L _n ) and which is substantially radially aligned with the bearing surface (36), and in that the last elastic blade (L _n ) of the stack, which is located on the side opposite to the first blade (L ₁ ), is spaced radially from the remainder of the plate by a single-piece light, called the deflection lumen (42), which defines a radial clearance space for the elastic structure (34). Connecting element (18, 20, 22) according to the preceding claim, characterized in that , in each elastic structure (34), the length of the elastic blades (L _n ) decreases progressively from the first elastic blade (L ₁ ) until to the last elastic blade (L _n ) of the stack. Connecting element (18, 20, 22) according to the preceding claim, characterized in that the radial thickness of each elastic blade (L _n ) is substantially constant over its entire length, and in that in each elastic structure ( 34), the radial thickness of the elastic blades (L _n ) decreases progressively from the first elastic blade (L ₁ ) to the last elastic blade (L _n ) of the stack. Connecting element (18, 20, 22) according to the preceding claim, characterized in that the radial thickness of the spacers (I _n ) is substantially constant for each intermediate light (I _n ) and substantially constant a light interlayer (I _n ) to the other. Connecting element (18, 20, 22) according to the preceding claim, characterized in that the minimum radial thickness of the deflection lumen (42) is greater than or equal to the radial thickness of the intermediate lumens (I _n ). Connecting element (18, 20, 22) according to any one of the preceding claims, characterized in that the profile of each of the ends of each intermediate light (I _n ) is rounded. Connecting element (18, 20, 22) according to any one of the preceding claims, characterized in that the bearing surface (36) of the first elastic blade (L ₁ ) comprises discrete elements in relief (54). which increase the friction between the shaft (26, 28, 30) and the bearing surface (36). Connecting element (18, 20, 22) according to any one of the preceding claims, characterized in that the inner wall (33) of the opening (32) comprises at least three elastic structures (34) which are uniformly distributed around the tree (26, 28). Joining element (18, 20, 22) according to one of Claims 1 to 7, characterized in that the inner wall (33) of the opening (32) consists of two resilient structures (34) and a fixed bearing surface (46), in that the first elastic blades (L ₁ ) of the two elastic structures (34) define between them a determined angle (P), and in that the first elastic blade (L ₁ ) two elastic structures (34) meet at one of their fixed ends. Connecting element (18, 20, 22) according to the preceding claim, characterized in that the contour of the inner wall (33) of the opening (32) is generally in the shape of an isosceles triangle, and in that the fixed bearing surface (46) forms the base of the isosceles triangle. Connecting element (18, 20, 22) according to the preceding claim, characterized in that the fixed bearing surface (46) is arranged at the free end of a cutout (48) projecting inside the the opening. Connecting element (18, 20, 22) according to any one of the preceding claims, characterized in that it consists of a rotary element (18, 20, 22) designed to be mounted fast to rotate on the shaft (26, 28, 30). Connecting element (18, 20, 22) according to the preceding claim, characterized in that it consists of a watchmaker's needle (18, 20, 22). Timepiece (10) characterized in that it comprises an assembly element (18, 20, 22) according to any one of the preceding claims.

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