EP1991916B1 - Micromechanical piece with form opening for assembly on a spindle - Google Patents

Abstract

The part has an opening (2) alternatively forming zones (8) for rigidification and positioning elastic deformation zones (10). The zones (10) are formed by a tab (12) of the part. The tab is formed of recesses (13, 15) opening into the opening and delimiting the tab whose end (14) extends above a theoretical contour of a cylindrical shaft (5) and provides a locking function when the shaft is placed. The part is made of a frangible material that is chosen among glass, silicon and quartz.

Description

Technical area

The present invention relates to a micro-mechanical part comprising a shaped opening intended to facilitate assembly on an axis for a moving part, or on a stud for a fixed part, and to limit or eliminate the risk of breaking the part during the driving on the axis or the stud, especially when said part is made of a brittle material.

Technological background

In the field of micro-mechanics, which will subsequently be more particularly illustrated by the watchmaking field, the driving technique is very widely used, for example for securing a wheel on a shaft. When material constituting the part has a plastic domain, which is the case of metals and alloys, it is known to calculate the tolerances necessary for the shaft and the bore so as to have a tight fit without risk of breaking the part, or of to deform it. When the material does not have, or very little, plastic field, which is the case of glass, quartz or silicon, there is a great risk of breaking the workpiece during assembly.

However, these materials are increasingly used in watchmaking due in particular to their insensitivity to magnetic fields, their very low coefficient of thermal expansion, and their density much lower than that of metals or alloys. In addition, modern machining technologies enable complex shapes to be produced with great precision.

If a greasy adjustment is made to avoid stresses in the brittle material, then there is a risk of disengagement or non-driving of a movable member by the shaft. To overcome this drawback, it is possible to use the bonding technique long used to fix a hairspring on a ferrule, as described, for example, in the patent. FR 1 447 142 . The patent US 3,906,714 describes an embodiment in which the point of glue makes it possible both to fix the hairspring to a ferrule ring and said ring to the balance shaft.

The use of an adhesive, however, has the disadvantage of requiring additional machining steps to provide housing for the glue, and additional tasks at the time of assembly. In addition aging phenomena can cause a certain game over time.

In the document EP 1 331 528 , which relates to an escapement mechanism anchor for a watch movement, to avoid the risk of breakage when mounting the male part of a stinger in the shaped opening in a fork, it is envisaged to provide the opening of elastic tongues. Moreover, in certain embodiments such as that shown in FIG. 30 of the document, the rigid zones of the opening have bearing surfaces that make it possible to position the stinger relative to the fork in a predefined orientation.

The documents US 3,672,150 and CH 338146 disclose a micromechanical part with stiffening zones and alternating positioning zones around an opening.

The solutions envisaged in this document are not completely satisfactory because they do not allow precise centering of the male part in the opening.

Summary of the invention

The present invention therefore aims to overcome the disadvantages of the aforementioned prior art by providing a micromechanical part, in particular watchmaker, made of a brittle material which can be assembled by driving on an axis or a stud without risk of rupture.

For this purpose the invention relates to a micro-mechanical part made from a plate of a brittle material having an opening for driving an axis or a stud. By "brittle" material is meant a material having no plastic deformation domain, such as glass, quartz or silicon.

The invention is defined by claim 1.

These plate portions are in the form of a tongue that presses tangentially on the axis during the driving. The stiffening and positioning zones and the tongues are arranged alternately about the axis, each tongue being separated from the adjacent stiffening zones by a recess, and the stiffening and positioning zones are distributed in a substantially regular manner around the opening.

• chaque zone de rigidification et de positionnement comportant au moins une portée prévue pour être en contact avec l'axe, les portées sont réparties de manière sensiblement régulière autour de l'ouverture pour assurer le centrage de l'axe dans l'ouverture;
• chaque zone de rigidification et de positionnement constitue une portée qui est délimitée par les deux évidements encadrant ladite zone de rigidification et de positionnement;
• chaque languette décrit globalement une courbe de profil déterminé, et les deux évidements adjacents sont constitués par deux fentes allongées globalement de même profil que la courbe de ladite languette;
• le matériau cassant est choisi parmi le verre, le quartz et le silicium.

According to other aspects of the invention:

• each stiffening and positioning zone comprising at least one bearing surface intended to be in contact with the axis, the bearing surfaces are distributed substantially uniformly around the opening to ensure the centering of the axis in the opening;
• each stiffening and positioning zone constitutes a range which is delimited by the two recesses flanking said stiffening and positioning zone;
• each tab generally describes a determined profile curve, and the two adjacent recesses are constituted by two generally elongated slots of the same profile as the curve of said tongue;
• the brittle material is selected from glass, quartz and silicon.

The invention also proposes an arrangement for immobilizing a micro-mechanical part comprising an opening by driving on a support block comprising a positioning stud. The micro-mechanical part is made with any of the preceding features.

The invention also proposes an arrangement for fixing by driving a moving micro-mechanical part in rotation, continuous or alternative, on a shaft. The micro-mechanical part is made with any one of the preceding claims.

• la pièce de micro-mécanique constitue une pièce d'un mouvement horloger choisie parmi une roue d'échappement, une étoile, une roue dentée, une virole, un levier et une ancre;
• l'axe et l'ouverture ont en outre des contours procurant un effet anti-rotation;
• le contour de l'axe et de l'ouverture est de forme oblongue ou triangulaire;
• les zones en contact de l'axe et de l'ouverture sont pourvues de rugosité ou de cannelures;
• la pièce de micro-mécanique comporte au moins un point de soudure ou un point de colle fixant la pièce de micro-mécanique sur l'axe.

According to variants of this arrangement:

• the micro-mechanical part constitutes a part of a watch movement chosen from an escape wheel, a star, a gearwheel, a ferrule, a lever and an anchor;
• the axis and the opening also have outlines providing an anti-rotation effect;
• the outline of the axis and the opening is oblong or triangular;
• the areas in contact with the axis and the opening are provided with roughness or grooves;
• the micro-mechanical part comprises at least one welding point or an adhesive point fixing the micro-mechanical part on the axis.

Brief description of the drawings

• la figure 1 est une représentation en perspective d'un premier mode de réalisation d'un assemblage selon l'invention;
• la figure 2 est une vue de dessus du premier mode de réalisation appliqué à une roue d'échappement;
• la figure 3 est une vue de dessus, d'un deuxième mode de réalisation appliqué à une étoile, et
• la figure 4 est une vue de dessus d'un troisième mode de réalisation appliqué à une roue dentée;
• la figure 5 est une vue similaire à celle de la figure 2 qui représente un mode de réalisation préféré de l'invention.

Other features and advantages of the present invention will appear in the following description of various embodiments, given by way of illustration and without limitation with reference to the accompanying drawings in which:

• the figure 1 is a perspective representation of a first embodiment of an assembly according to the invention;
• the figure 2 is a top view of the first embodiment applied to an escape wheel;
• the figure 3 is a view from above, of a second embodiment applied to a star, and
• the figure 4 is a top view of a third embodiment applied to a gear wheel;
• the figure 5 is a view similar to that of the figure 2 which represents a preferred embodiment of the invention.

Detailed description of the invention

We refer to Figures 1 and 2 to describe a first embodiment. The figure 1 represents in perspective a portion of plate 1 to be secured to a support block 11 by means of a cylindrical stud 3 passing through an opening 2 formed in said plate 1.

The plate 1 consists of a brittle material, ie a material that does not have a plastic domain in normal temperatures of use, such as glass, quartz or silicon. The plate 1 may simply be a construction element, for example a plate, a bridge or a dial of a timepiece. It can also have a functional role by supporting a printed circuit or a MEMs to be secured to the block 11. To avoid breaking the workpiece during assembly by driving, the opening 2 is a shaped opening shown in plan view on a larger scale at the figure 2 .

The figure 2 As an example, there is shown a silicon escapement wheel mounted on a cylindrical shaft intended to be pivoted between two bearings. As can be seen, the contour of the opening 2 does not follow the circular contour of the shaft 5 by alternately presenting stiffening and positioning zones 8 and zones 10 with elastic deformation. It is noted that the zones 8 of stiffening and the zones 10 with elastic deformation extend in the plane of the plate 1, as represented on the Figures 1 and 2 , since they define the shape of the opening 2. The zones 10 with elastic deformation are provided to deform in the plane of the plate 1.

To show that the stiffening zones 8 exert no clamping function on the shaft 5, the space 9 between said zones 8 and the shaft 5 has been greatly exaggerated. The stiffening zones 8 serve to center the escape wheel with respect to the shaft 5. As can be seen in FIG. figure 2 the zones 8 of stiffening are distributed angularly in a regular manner around the opening 2. There are here three zones 8 of stiffening.

The areas with elastic deformation 10 are obtained by producing in the wafer 1 recesses 13, 15 opening into the central opening and delimiting in this example a tongue 12 whose end 14 extends beyond the theoretical contour of the shaft 5 and thus ensures a clamping function when the shaft 5 in place by driving. On the figure 2 it is found that each tongue 12 is separated from the adjacent stiffening zones 8 by a recess 13, 15, so that each tongue 12 is connected to the wafer 1 in a zone distinct from the zones 8 of stiffening. As shown on the figure 2 , the tongues 12 are distributed angularly in a regular manner around the shaft 5, between the zones 8 of stiffening. The opening 2 thus has alternately, on its periphery, a zone 8 of stiffening and a tongue 12. As can be seen on the figure 2 each tab 12 generally describes a profile curve determined, here a curved arc curve. In addition, the two adjacent recesses 13, 15 are constituted by two generally elongated slots of the same profile as the curve of said tongue 12.

The figure 5 represents a preferred embodiment of the invention similar to that of the figure 2 , in which the zones 8 of stiffening are represented such that they are in reality, that is to say without exaggerating the space 9 between said zones 8 and the shaft 5. It is noted that each zone 8 of stiffening comprises at least one bearing surface 16 intended to be in contact with the cylindrical wall of the shaft 5. These bearing surfaces 16 are evenly distributed around the opening 2 to ensure the centering of the shaft 5 in the opening 2. More particularly, each zone 8 of stiffening constitutes a bearing surface 16 which is delimited by the two recesses 13, 15 surrounding said zone 8. Each stiffening zone 8 therefore has here an arcuate profile which generally follows the radius of curvature of the cylindrical wall of the shaft 5. The spans 16 allow precise positioning of the wheel relative to the shaft 5. The tongues 12 provide the radial clamping function, the catch-up function of the manufacturing sets at the opening , and el guarantee the centering of the shaft 5 in the opening 2.

Of course, the number of zones 8 of stiffening and the number of tongues 12 could be greater than that which is shown.

The figure 3 corresponds to a second embodiment representing a timer star having in its center an opening of form 4 providing an anti-rotation effect. Indeed, the end 7 of the shaft 5 is machined with a non-circular contour in the shape of a triangle with rounded corners. The shape opening 4 follows this contour, but having, as in the first embodiment, a succession zones 8 for stiffening and positioning and areas 10 for elastic deformation.

The figure 4 corresponds to a third embodiment in which the piece, for example of silicon, is a toothed wheel having in its center a shaped opening 6 having as previously an "anti-rotation" function. In this example, the shape opening 7 is oblong.

It is of course possible to imagine any other non-circular contour to provide an anti-rotation effect, without departing from the scope of the present invention.

It is furthermore possible, in any of the embodiments which has just been described, to provide the ends 14 of the zones of elastic deformation 10 and the shaft 5 with roughnesses, for example grooves, to further reduce the risk. due to rotation of the workpiece on the tree.

The examples given in the foregoing description concern parts in continuous rotation, but it is quite obvious that the person skilled in the art can adapt the same principle to parts having reciprocating movement, such as a lever, a rocker, a ferrule , an anchor or an escape wheel.

Depending on the application for which the micro-mechanical part is intended, it is possible to finalize the assembly of the part on its axis with a gluing or welding step which makes it possible to ensure a more rigid fixation if this is necessary. Glue or solder completes fastening by elastic tongues. In this case, the fastening by the tongues constitutes an intermediate fixing step guaranteeing a precise centering of the axis in the opening, with a catch of the games, and the step of bonding or welding constitutes a final fixing step.

Claims (13)

1. Micro-machining part made from a plate (1) made of a material that does not have any plastic deformation region including at least one aperture for driving in a shaft (3, 5), wherein the aperture is a shaped aperture (2, 4, 6) including rigidifying and positioning zones (8) and resilient deformation zones (10) for gripping the shaft (3, 5), wherein each resilient deformation zone (10) is formed by a portion (12) of plate (1) having a recess (13, 15) on either side joining the aperture and having the shape of a tongue whose end (14) opens tangentially into the aperture (14), the rigidifying and positioning zones (8) and the tongues lying in the thickness of the plate (1) and being arranged to be located alternately around the shaft, each tongue being separated from the adjacent rigidifying zones (8) by a recess (13, 15), and the rigidifying and positioning zones (8) being distributed in a substantially regular manner around the aperture (2, 4, 6).
2. Micro-mechanical part according to claim 1, wherein each rigidifying and positioning zone (8) includes at least one shoulder (16) that will be in contact with the shaft (3, 5), characterized in that the shoulders (16) are distributed in a substantially regular manner around the aperture (2, 4, 6) in order to centre the shaft (3, 5) in the aperture (2, 4, 6).
3. Micro-mechanical part according to claim 2, characterized in that each rigidifying and positioning zone (8) constitutes a shoulder (16) which is delimited by the two recesses (13, 15) framing said rigidifying and positioning zone (8).
4. Micro-mechanical part according to any of the preceding claims, characterized in that each tongue (12) describes overall a curve of determined profile, and in that the two adjacent recesses (13, 15) are formed by two elongated slots with the same overall profile as the curve of said tongue (12).
5. Micro-mechanical part according to any of the preceding claims, characterized in that the brittle material is selected from among glass, quartz and silicon.
6. Immobilising device of a micro-mechanical part including an aperture by driving said part onto a support block (11) including a positioning stud (3) characterized in that the micro-mechanical part is made in accordance with any of the preceding claims.
7. Device according to claim 6, characterised in that the micro-mechanical part comprises at least one weld point or one dot of adhesive securing the micro-mechanical part to the shaft.
8. Securing device of a micro-mechanical part that is continuously or alternately mobile in rotation onto a shaft (5) by driving in, characterized in that the micro-mechanical part is made in accordance with any of claims 1 to 5.
9. Device according to claim 8, characterized in that the micro-mechanical part constitutes a part in a timepiece movement selected from among an escape wheel, a star wheel, a toothed wheel, a collet, a lever and a pallet.
10. Device according to claim 8, characterized in that the shaft and the aperture further have contours providing an anti-rotational effect.
11. Device according to claim 10, characterized in that the shape of the contour of the shaft and the aperture is oblong or triangular.
12. Device according to claim 10, characterized in that the contact zones of the shaft and the aperture are provided with surface roughness or flutes.
13. Device according to any of claims 8 to 12, characterized in that the micro-mechanical part includes at least one weld point or dot of adhesive fixing the micro-mechanical part onto the shaft.

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