EP2585882B1 - Timepiece anti-shock system - Google Patents

Description

The present invention relates to a shock-absorbing bearing for an axis of a mobile part of a timepiece. The axle comprises a tigeron extended by a pivot and the bearing comprises a support, said support being provided with a housing provided to receive a suspended pivot system in which the tigeron is inserted.

The technical field of the invention is the technical field of fine mechanics.

TECHNOLOGICAL BACKGROUND

The present invention relates to bearings for timepieces, and more particularly of the type allowing shock absorption. Manufacturers of mechanical watches have for a long time designed many devices making it possible to absorb the energy resulting from an impact, in particular from a side impact, by the axis by abutting against a wall of the hole in the base unit that it crosses, while allowing a momentary movement of the tigeron before it is returned to its rest position under the action of a spring.

The figures 1 and 2 illustrate a so-called inverted double cone device which is currently used in timepieces on the market.

A support 1, the base of which has a hole 2 for the passage of the balance axis 3 terminated by a tigeron 3a, makes it possible to position a kitten 20 in which are immobilized a pierced stone 4 crossed by the tigeron 3a and a stone against -pivot 5. The kitten 20 is held in a housing 6 of the support 1 by a spring 10 which comprises in this example of radial extensions 9 compressing the counter-pivot stone 5. The housing 6 comprises two spans 7, 7a in the form of inverted cones on which are supported complementary spans 8, 8a of the kitten 20, said spans to be performed with a very large precision. In the event of an axial impact, the pierced stone 4, the counter-pivot stone 5 and the axis of the balance move and the spring 10 acts alone to return the balance axis 3 to its initial position. The spring 10 is dimensioned to have a limit of movement so that beyond this limit, the axis of the balance comes into contact with stops allowing said axis to absorb the shock, which the pins of the axis do not can do under penalty of breaking. In the event of a side impact, that is to say when the end of the shank unbalances the kitten 20 out of its rest plane, the spring 10 cooperates with the complementary inclined planes 7, 7a; 8, 8a to recenter the kitten 20. Such bearings have, for example, been sold under the brand Incabloc®. These springs can be made of phynox or brass and are made by traditional cutting means.

It is also known shock-absorbing bearings in which the spring, the drilled stone and the counter-pivot stone form a whole. The advantage of these shock absorbing bearings is that they are less expensive.

Thus, the document US 3'942'848 describes a shock-absorbing bearing comprising an annular body intended to be driven into a bridge or a plate. A spring formed to define a conical housing is secured to the body. This housing forms a slider inside which a conical pivot of the balance engages. In such a construction, the pivoting conditions are unfavorable, the metal-to-metal pivoting causing significant friction. In addition, a crapaudine type bearing according to this document US 3,942,848 , cooperating with a conical pivot is ill-suited for a quality timepiece, the positioning of the balance being imprecise.

Furthermore, the springs used in these shock-absorbing bearings are made of crystalline metal. However, the use of crystalline metals for these springs can cause some problems. Indeed, crystalline metals are characterized by weak mechanical properties such as limited elastic deformation which can lead to plastic deformation if the shocks are too high. This is amplified by the fact that current springs cannot be designed with complex shapes and hence the elastic deformation of current springs is very close to the elastic limit.

Thus, if too great a shock is applied to the timepiece, the movement of the stones and of the balance can be of great amplitude and, consequently, a plastic, that is to say permanent deformation of the spring can occur. The spring becomes less effective in absorbing shocks and re-centering the axis of the balance in its rest position because it no longer returns to its original shape and therefore loses elasticity.

This permanent deformation can also occur during the handling of said springs during their installation, when they are removed to operate the lubrication or during touch-up or after-sales service operations.

It is also known shock-absorbing bearings in which the spring, the drilled stone and the counter-pivot stone form a whole. The advantage of these shock absorbing bearings is that they are less expensive.

Thus, the document US 3,942,848 describes a shock-absorbing bearing comprising an annular body intended to be driven into a bridge or a plate. A spring formed to define a conical housing is secured to the body. This housing forms a slider inside which a conical pivot of the balance engages. In such a construction, the pivoting conditions are unfavorable, the metal-to-metal pivoting causing significant friction. In addition, a crapaudine type bearing according to this document US 3,942,848 , cooperating with a conical pivot is ill-suited for a quality timepiece, the positioning of the balance being imprecise.

We also know from the document EP 2 015 147 a shock-absorbing bearing for a timepiece. It comprises a pivot member comprising at least one elastic arm and a central portion comprising a hole inside which a pivot is intended to be in contact, formed integrally in a pellet of a monocrystalline material.

Furthermore, the fact of using a spring formed to define a conical housing has the drawback of having a radial play which depends on the play or on the axial displacement. Indeed, the conical shape of the spring allows, in normal times to maintain the axis of the wheel. But when the springs deform, the spring moves axially and radially. However, when the spring moves axially, the conical shape of the spring implies that a radial displacement is also present. It is then observed that the greater the axial displacement, the greater the radial play.

It is known from the document EP 1 696 153 to use amorphous metal for watchmaking gear parts.

SUMMARY OF THE INVENTION

The object of the invention is to alleviate the drawbacks of the prior art by proposing to provide an anti-shock system for a timepiece which is more resistant to shocks and which allows better positioning of the axis of the damped wheel.

To this end, the invention relates to a shock-absorbing bearing as defined by claim 1. This shock-absorbing system for a timepiece is characterized in that said pivot system is designed to absorb, at least in part, the shocks suffered. by the timepiece mobile and in that the pivot system is formed in one piece made of a completely amorphous metal alloy, and in that said pivot system is a pellet comprising an annular part, a central part and elastic arms connecting the central part to the annular part, the central part comprising a recess so that the pivot which is engaged therein can rotate freely therein.

A first advantage of the present invention is that it enables the anti-shock systems to withstand shocks better. Indeed, amorphous metals have more interesting elastic characteristics. The elastic limit σ _e is increased, which makes it possible to increase the ratio σ _e / E so that the material sees the stress beyond which it does not resume its initial shape. The pivot system can then be subjected to a greater stress before being plastically deformed and the part can thus undergo greater impacts without the shock absorber system losing its effectiveness.

Another advantage of the present invention is that it allows pivot systems to be produced. Indeed, as the amorphous metal is able to withstand higher stresses before plastically deforming, it is possible to produce springs of smaller dimensions without losing resistance.

Advantageous embodiments of these pivot systems are the subject of the dependent claims.

In a first advantageous embodiment, said pivot system is made of a completely amorphous material.

In a second advantageous embodiment, said metal alloy comprises at least one metal element of the precious type or one of its alloys.

In a third advantageous embodiment, said precious metallic element comprises gold, platinum, palladium, rhenium, ruthenium, rhodium, silver, iridium or osmium.

In another advantageous embodiment, said pivot system is a pellet comprising an annular part, a central part and elastic arms connecting the central part to the annular part, the central part comprising a recess so that the pivot which therein is engaged can turn freely.

In another advantageous embodiment, the recess consists of a cylindrical portion having at its end a rounded convex portion.

One of the advantages of these embodiments is to make it possible to produce pivot systems of more complex shapes. In fact, amorphous metal is very easy to shape and allows the manufacture of parts with complicated shapes with greater precision. This is due to the particular characteristics of the amorphous metal which can soften while remaining amorphous for a certain time in a given temperature range [T _g - T _x ] specific to each alloy. It is thus possible to shape it under a relatively low stress and at a low temperature, allowing the use of a simplified process such as hot forming, while reproducing very precisely fine geometries because the viscosity of the The alloy strongly decreases as a function of the temperature in said temperature interval [T _g - T _x ]. Therefore, it becomes possible to realize complex and precise pivot systems but simply.

BRIEF DESCRIPTION OF THE FIGURES

• les figures 1 et 2 représentent de manière schématique un système antichoc de pièce d'horlogerie selon l'art antérieur;
• les figures 3 à 5 représentent de manière schématique un système antichoc de pièce d'horlogerie selon l'invention;

The aims, advantages and characteristics of the shock-absorbing system according to the present invention will appear more clearly in the following detailed description of at least one embodiment of the invention given solely by way of non-limiting example and illustrated by the appended drawings in which :

• the figures 1 and 2 schematically show a timepiece shockproof system according to the prior art;
• the figures 3 to 5 schematically represent a timepiece shockproof system according to the invention;

DETAILED DESCRIPTION

The present invention proceeds from the general inventive idea which consists in providing a shock-absorbing system having greater reliability and offering better positioning using a metal alloy at least partially amorphous.

The damper bearing 101, 102 is shown on figure 3 ; the latter illustrates a part 100 of a timepiece provided with bearings according to the invention.

The timepiece represented in the figure 3 comprises a frame comprising a support 103 in which a lower bearing 101 and an upper bearing 102 are mounted. These bearings 101, 102 are mounted in holes made in said support 103. A wheel 105, which may for example be a balance, is pivotally mounted in the bearings. This wheel 105 has an axle 120 provided at its two ends with tigerons 121 carrying pivots 122.

The upper bearing 102 comprises an annular part 127 in the form of a disc 131 having a peripheral wall 128. This annular part also comprises a rim 129 located on the surface of the disc and contiguous to the wall. This annular part 127 is pierced with a central hole 130. The bearing 102 further comprises a pivot means 126 'disposed in the housing formed by the peripheral wall 128 and the rim 129. The pivot means 126' is placed. on the rim 129 at its periphery so as to be suspended. This pivoting means 126 ′ can for example be force-engaged or glued to the annular part 127.

The lower bearing 101 is of identical design to the upper bearing 102, that is to say it comprises an annular part 124 in the form of a disc having a peripheral wall. This annular part also comprises a rim located on the surface of the disc and contiguous to the wall. This annular part 124 is pierced with a central hole 125. The bearing 102 further comprises a pivoting means 126 disposed in the housing formed by the peripheral wall and the rim. This way of pivot 126 can be engaged for example by force or glued to the annular part 124. In the present example, the dimensions of the lower bearing 101 will be smaller than those of the upper bearing 102 in order to show that the size of the bearing is easily adjustable and can be adapted to needs, here by reducing its size for example. Of course, the dimensions of the upper bearing 102 and of the lower bearing 101 may be identical.

However, the lower 101 or upper 102 bearing can be arranged so that the pivot means 126, 126 'is driven directly into the support 103. Said bearing 101, 102 further comprises a part 200 in the form of a ring which serves to maintain the pivoting means 126, 126 'and a part 201 in the form of a disc having a peripheral rim 202 and pierced in its center with a hole 125, 130. This part 201 in the form of pierced disc is used to serve as a stopper and its rim 202 is used to provide a suspended system. The pivoting means 126, 126 'is thus held radially by the walls of the hole made in the support 103 and axially by the annular part 200 and the part in the form of a drilled disc 201.

The pivot means 126, 126 ', visible at the figure 4 are in the form of pellets comprising a solid annular portion 126a, a central portion 126b provided with a blind cylindrical recess 126c and elastic arms 126d. The blind cylindrical recess 126c has a diameter chosen so that the pivot 122 which is engaged therein can rotate freely therein with a minimum of travel. The arms 126d are wound in a spiral so that they connect the central portion 126b to the annular portion 126a. Preferably, the pivoting means 126, 126 ′ comprise three arms. The pivot means 126 'of the upper bearing 102 is mounted in the annular part 127 of said upper bearing 102. The pivot means 126 of the lower bearing 103 is mounted in the annular part 124 of said lower bearing 103. Both annular pieces 127, 124 are then mounted in the hole of the support 103 in sequence so as to allow the insertion of the wheel on its axis.

The wheel is therefore mounted to pivot while being engaged at its pivots 122 in the non-traversing cylindrical recesses 126c of the pivot means 126, 126 'and at the level of its pins 121 in the areas provided for the support 103.

In the event of an impact, the wheel 105 is subjected to a force which is proportional to the acceleration experienced. This force is transmitted to the bearings by means of the pivots 122. The effect of this force is to deform the elastic arms 126d of the pivoting means 126, 126 'until the axis of the wheel comes to bear, by means of its shanks 121, against the wall of the holes in the annular pieces 127, 124. The wheel is then stopped and blocked by a part of its axis having dimensions much larger than those of the pivots 122 so as not to damage the tigerons 121. As this part has dimensions much larger than those of the pivots, it is able to to undergo much greater constraints without harmful consequences for the mobile.

Preferably, the elastic arms are dimensioned so that the rods 121 come into contact with the annular parts when the acceleration reaches approximately 500g.

Preferably, the pivoting means 126, 126 'are formed by three curved arms 126d whose attachment points, respectively to the annular part 126a and to the central part 126b, are angularly offset by 120 degrees. It is obvious that the elastic function could be provided with a different number of arms, or with other shapes.

It will also be understood that the pivot means 126, 126 ′ comprise a conical recess so that the end of the tigeron can be inserted therein allowing an amplitude difference between the different positions of the watch to be reduced to a minimum. This conical recess known from the patent EP 2 142 965 consists of a trapezoidal or cylindrical portion having at its end a convex rounded portion.

Advantageously, the pivoting means 126, 126 'are made of an amorphous or at least partially amorphous material. In particular, a material is used comprising at least one metallic element. Preferably, the material will be a metal alloy that is at least partially amorphous or even totally amorphous. By at least partially amorphous material it will be understood that the material is capable of at least partially solidifying in the amorphous phase, that is to say that it is capable of losing at least locally all of its crystalline structure.

Indeed, the advantage of these amorphous metal alloys comes from the fact that, during their manufacture, the atoms composing these amorphous materials do not arrange themselves according to a particular structure as is the case for crystalline materials. Thus, even if the Young's modulus E of a crystalline metal and an amorphous metal is the same, the elastic limit σ _e is different. An amorphous metal is thus differentiated by an elastic limit σ _e higher than that of the crystalline metal by a factor of about two to three. This allows amorphous metals to be able to undergo a higher stress before reaching the elastic limit σ _e .

Such pivot means 126, 126 'have the advantage of having higher strength and durability over their crystalline metal counterparts.

Moreover, as the elastic limit of an amorphous metal is higher than that of a crystalline metal by a factor of about two to three, making it possible to withstand higher stresses, it is possible to consider reducing the dimensions of said means. pivot point 126, 126 '. Indeed, as the pivoting means of shock absorber systems made of amorphous metal can withstand a greater stress without being plastically deformed, it is then possible, at equivalent stress, to reduce the dimensions of the pivot means 126, 126 'relative to a crystalline metal.

To achieve these pivoting means 126, 126 ', several methods can be envisaged. It can be envisaged to produce the pivoting means 126, 126 'by using the properties of amorphous metals. In fact, the amorphous metal is very easy to shape, allowing parts with complicated shapes to be manufactured with greater precision. This is due to the particular characteristics of the amorphous metal which can soften while remaining amorphous for a certain time in a given temperature range [T _g - T _x ] specific to each alloy (for example for an alloy Zr _41.24 Ti _13.77 Cu _12.7 Ni _12.7 Be _22.7 , T _g = 350 ° C and T _x = 460 ° C). It is thus possible to shape them under a relatively low stress and at a low temperature, then allowing the use of a simplified process such as hot forming. The use of such a material also makes it possible to reproduce very precisely fine geometries because the viscosity of the alloy decreases sharply as a function of the temperature in the temperature interval [T _g - T _x ] and the alloy conforms to so all the details of the negative. For example, for a platinum-based material, the shaping takes place around 300 ° C for a viscosity reaching 10 ³ Pa.s for a stress of 1 MPa, instead of a viscosity of 10 ¹² Pa.s at temperature Tg.

1. a) Chauffage des matrices du moule ayant la forme négative des moyens de pivotement 126, 126' jusqu'à une température choisie,
2. b) Introduction de la préforme en métal amorphe entre les matrices chaudes,
3. c) Application d'une force de fermeture sur les matrices afin de répliquer la géométrie de ces dernières sur la préforme en métal amorphe,
4. d) Attente durant un temps maximal choisi,
5. e) Refroidissement rapide du ressort en dessous de T_g de sorte que le matériau garde sa phase au moins partiellement amorphe,
6. f) Ouverture des matrices,
7. g) Sortie des moyens de pivotement 126, 126' des matrices.

One method used is the hot forming of an amorphous preform. This preform is obtained by melting in a furnace the metallic elements constituting the amorphous alloy. This melting is carried out in a controlled atmosphere with the aim of obtaining as low a contamination of the oxygen alloy as possible. Once these elements are melted, they are cast in the form of semi-finished products, then cooled rapidly in order to retain the at least partially amorphous state or phase. Once the preform has been obtained, the hot forming is carried out in order to obtain a final part. This hot forming is carried out by pressing in a temperature range between the transition temperature vitreous T _g of the amorphous material and the crystallization temperature T _{x of} said amorphous material for a determined time to maintain a totally or partially amorphous structure. The aim is then to retain the elastic properties characteristic of amorphous metals. The various stages of final shaping of the pivoting means are then:

1. a) Heating of the dies of the mold having the negative shape of the pivoting means 126, 126 'to a selected temperature,
2. b) Introduction of the amorphous metal preform between the hot dies,
3. c) Application of a closing force on the dies in order to replicate the geometry of the latter on the amorphous metal preform,
4. d) Waiting for a selected maximum time,
5. e) Rapid cooling of the spring below T _g so that the material keeps its at least partially amorphous phase,
6. f) Opening of the dies,
7. g) Output of the pivot means 126, 126 'of the dies.

The hot forming of the metal or amorphous alloy therefore makes it possible to produce complex and precise parts but also good reproducibility of the part, which is a significant advantage for mass production such as that of the pivoting means 126, 126 'of systems. damper.

According to a variant of this process, casting is used. This process consists in casting the alloy obtained by melting the metal elements in a mold having the shape of the final part. Once the mold when filled, the latter is cooled rapidly to a temperature below T _{g in} order to avoid crystallization of the alloy and thus to obtain pivoting means made of amorphous or partially amorphous metal. The advantage of casting an amorphous metal over casting a crystalline metal is that it is more precise. The solidification shrinkage is very low for an amorphous metal, less than 1% compared to that of crystalline metals which is 5 to 7%.

The processes used for the amorphous metal therefore allow the production of precise parts, which is advantageous for the production of the pivot means with smaller dimensions. This precision is combined with a very high reproducibility of the process, making it easy to produce parts in series.

It will be understood that various modifications and / or improvements and / or combinations obvious to a person skilled in the art can be made to the various embodiments of the invention set out above without departing from the scope of the invention defined by the appended claims.

Claims (4)

1. Shock-absorbing bearing for an arbor (120) of a wheel of a timepiece, said arbor comprising a pivot-shank (121) extended by a pivot (122), said bearing including a support (102, 103) provided with a bed for receiving a suspended pivot system (126, 126') wherein the pivot shank is inserted, said pivot system (126, 126') being arranged to absorb, at least partly, the shocks to which the wheel of the timepiece is subjected, and the pivot system (126, 126') being formed by a single piece made of a completely amorphous metallic alloy, and said pivot system being a chip comprising an annular part (126a), a central part (126b) and elastic arms (126d) connecting the central part to the annular part, the central part comprising a hollow (126c) so that the pivot that is engaged therein can turn freely therein.
2. Shock-absorbing bearing according to claim 1, characterised in that said metallic alloy comprises at least one metallic element of the precious type or one of the alloys thereof.
3. Shock-absorbing bearing according to claim 2, characterised in that said precious metallic element includes gold, platinum, palladium, rhenium, ruthenium, rhodium, silver, iridium or osmium.
4. Shock-absorbing bearing according to claim 1, characterised in that the hollow (126c) consists of a cylindrical portion having at the end thereof a convex rounded portion.

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