CH703344A2 - Shock absorbing bearing for balance staff of mobile of mechanical watch, has spring that is arranged to exert axial force on pivot system and is made of partially or totally amorphous material with metal element - Google Patents

Abstract

The bearing has a circular support (101) with a housing (106) to receive a pivot system in which a rod (103a) of a balance staff (103) is inserted. A radial and axial deformation spring (110) is arranged to exert the axial force on the system. The spring is made of partially or totally amorphous material with metal element e.g. precious metal element or alloy with precious metal element such as gold, platinum, palladium, rhenium, ruthenium, rhodium, silver, iridium or osmium. The system includes a bush (120) arranged in the housing and supporting a pierced jewel (104) traversed by the rod.

Description

The present invention relates to an anti-shock system for an axis of a mobile of a timepiece. The shaft comprises a beam, having a support, said support being provided with a housing adapted to receive a pivot system in which the tigeron is inserted. The shockproof system further comprises elastic means arranged to exert on said pivot system at least one axial force.

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

BACKGROUND TECHNOLOGY

The present invention relates to bearings for timepieces, particularly of the type for damping shocks. The mechanical watch manufacturers have long since designed numerous devices allowing an axis to absorb the energy resulting from an impact, in particular a side impact, by abutment against a wall of the hole of the base block that it crosses. while allowing a momentary movement of the tigeron before it is brought back to its rest position under the action of a spring.

Figs. 1 and 2 illustrate an inverted double-cone device that is currently used in timepieces on the market.

A support 1, whose base comprises a hole 2 for the passage of the balance shaft 3 terminated by a tigeron 3a, allows positioning a kitten 20 in which are immobilized a pierced stone 4 crossed by the tigeron 3a and 5. The kitten 20 is held in a housing 6 of the support 1 by a spring 10 which comprises in this example radial extensions 9 compressing the pivoting stone 5. The housing 6 comprises two bearing surfaces 7, 7a in FIG. form of inverted cones on which support complementing 8, 8a litters of the kitten 20, said staves to be executed with very high accuracy. In the event of an axial impact, the pierced stone 4, the counter pivot stone 5 and the axis of the balance arm move and the spring 10 acts alone to bring the balance shaft 3 back to its initial position. The spring 10 is dimensioned to have a limit of displacement so that beyond this limit, the balance shaft 3 comes into contact with abutments 14 allowing said axis 3 to absorb the shock, which the tigers 3a of Axis 3 can not do without breaking. In case of lateral impact, that is to say when the end of the tigeron imbalances the kitten 20 out of its resting plane, the spring 10 cooperates with the complementary inclined planes 7, 7a; 8, 8a to refocus the kitten 20. Such bearings have for example been sold under the trademark Incabloc <®>. These springs can be made of phynox or brass and are manufactured by traditional means of cutting.

However, the use of crystalline metals for these springs can cause some problems. Indeed, the crystalline metals are characterized by a low elasticity that can lead to plastic deformation if the shocks are too high. This problem is amplified by the fact that the current springs can not be designed with complex shapes and, therefore, the elastic deformation of the current springs is very close to the elastic limit.

Thus, if an excessive shock is applied to the timepiece, the movement of the stones and the pendulum may be of large amplitude and, therefore, a plastic deformation that is to say permanent spring can happen. The spring becomes less effective to dampen shocks and refocus the axis of the balance in its rest position because it does not resume its original shape and therefore loses elasticity.

This permanent deformation can also occur during handling of said springs during their introduction, when removed for lubrication operations or during retouching or after-sales operations.

SUMMARY OF THE INVENTION

The invention aims to overcome the disadvantages of the prior art by proposing to provide a shockproof system of timepiece more efficient and better resistant to shocks.

For this purpose, the invention relates to the shockproof timepiece system cited above which is characterized in that the spring is made of at least partially amorphous material.

A first advantage of the present invention is to allow shock systems to better withstand shocks. Indeed, amorphous materials have more interesting elastic characteristics. The elastic limit σe is increased, which makes it possible to increase the ratio σe / E so that the material sees the stress beyond which it does not return to its initial shape to increase. The spring can then undergo a higher stress before plastically deforming and the workpiece can thus suffer greater shocks without the anti-shock system losing efficiency.

Another advantage of the present invention is to allow the production of smaller springs. Indeed, as the amorphous materials are able to withstand higher stresses before deforming plastically, it is possible to make smaller springs without losing resistance.

Advantageous embodiments of this shockproof system are the subject of dependent claims 2 to 9.

One of the advantages of these embodiments is to make it possible to produce springs of more complex shapes. Indeed, the amorphous metal is very easy to shape and allows the manufacture of 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 [Tg - Tx] specific to each alloy. It is thus possible to shape it under a relatively low stress and at a low temperature then allowing the use of a simplified process such as hot forming, while reproducing very precisely fine geometries because the viscosity of the the alloy decreases greatly as a function of the temperature in said temperature range [Tg - Tx]. Therefore, it becomes possible to achieve complex and precise springs but simply.

BRIEF DESCRIPTION OF THE FIGURES

The objects, advantages and features of the anti-shock 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 drawings. annexed in which: <tb> - figs. 1 and 2, <sep> already cited, schematically represent a shockproof timepiece system according to a first embodiment of the invention; <tb> - figs. 3 to 5 <sep> schematically represent a shockproof timepiece system according to a second embodiment of the invention.

DETAILED DESCRIPTION

The present invention proceeds from the general inventive idea of providing a shock absorbing system having greater reliability by using an at least partially amorphous material having at least one metal element. The present invention can take different forms.

Figs. 1 and 2 already cited illustrate an anti-shock system according to a first embodiment. This system comprises a support 1, whose base comprises a hole 2 for the passage of the balance shaft 3 terminated by a tigeron 3a, which allows to position a kitten 20 in which are immobilized a pierced stone 4 crossed by the tigeron 3a and a counter pivot stone 5. The support 1 is a part of revolution comprising a circular flange 11. This flange 11 is interrupted in two diametrically opposite locations by an opening 12 so as to create two semi-circular flanges 11a, 11b. The opening 12 is formed partly in the two semicircular edges 11a, 11b so as to materialize two returns 13. The kitten 20 is held in a housing 6 of the support 1 by elastic means such as a spring 10 which comprises in this example of the radial extensions 9 compressing the counter-pivot stone 5. The spring 10 is of the axial type and has a form of lyre arranged to bear under the return semicircular flanges 11a, 11b. The housing 6 comprises two bearing surfaces 7, 7a in the form of inverted cones on which support complementary bearing surfaces 8, 8a of the kitten 20, said bearing surfaces to be executed with very high accuracy. In the event of an axial impact, the spring 10 acts alone to bring the balance shaft 3 back to its initial position. In case of lateral impact, that is to say when the end of the tigeron imbalances the kitten 20 out of its resting plane, the spring 10 cooperates with the complementary inclined planes 7, 7a; 8, 8a to refocus the kitten 20.

Figs. 3 and 4 illustrate an anti-shock system according to a second embodiment. The bearing comprises a support 101 of circular shape delimiting a housing 106 whose center is pierced with a hole 102 to allow the passage of a balance shaft 103 terminated by a rod 103a.

The support 101 may be either an independent part driven or fixed by any other means in the frame of the watch movement, or be part of another part of the movement, such as a bridge or a plate.

As can be seen, the kitten 120 which supports the pierced stone 104 traversed by the tib 103a and the counter-pivot stone 105 is suspended in the housing 106 by a spring 110. The spring 110, shown in perspective at the fig. 5, is of the radial type and is composed of three parts. A first part is constituted by a scalloped peripheral rigid ring 111 which is mounted in force against the wall 106a of the housing 106 by resting on a bead 106b located at the bottom of the housing 106 so as to provide a space allowing a certain axial movement of the spring 110. The second part consists of a central rigid support 113 of generally annular shape. As seen in fig. 5, the pierced stone 104 is driven into the opening of the support 113 whose inner wall 113a has a number of recesses 117 whose main purpose is to provide a certain elasticity for non-destructive driving of the pierced stone 104. The third part of the spring 110 is constituted by elastic means 112 joining the peripheral ring 111 and the central support 113, said elastic means 112 being chosen to have a reaction force both along the axis of the beam and perpendicular thereto . The kitten 120 is made of two parts. A first part integrated in the spring 110, is constituted by the central support 113 supporting the pierced stone 104, as described above. A second part is constituted by a cover 123 which is fitted on the central support 113 to immobilize the counter pivot stone 105 on the upper surface 113b. In the example shown, the casing of the cover 123 is obtained by means of tabs 125 extending along the outer wall 113c of the central support 113, through recesses 115 provided in said wall 113c between the attachment points of the arm 114, 116, 118. The areas where the cover 123 has no tabs 125, rest on the upper bearing surface 113b of the central support 113. To secure the casing of the cover 123 on the central support 113 can for example bonding, welding or riveting.

Of course, the pierced stone 104 and the counter-pivot stone 105 can both be crimped or driven inside the wall 113a of the rigid central support 113, provided of course to give said wall a sufficient height which will generally be greater than the height of the rest of the spring 110.

In an example of FIG. 5, the resilient means are formed by three curved arms 114, 116, 118 whose attachment points, respectively to the peripheral ring 111 and the central support 113, are angularly offset by 120 degrees. It is obvious that the elastic function could be ensured with a different number of arms, or with other forms.

Advantageously, the spring 10, 110 is made of an amorphous material or at least partially amorphous. In particular, a material comprising at least one metal element is used. Preferably, the material will be an amorphous metal alloy. It will be understood by at least partially amorphous material that the material is capable of solidifying at least partially in amorphous phase, that is to say that it is able to locally avoid that its atoms do not arrange in crystalline form by means of a sufficient cooling rate.

Indeed, the advantage of these amorphous metal alloys comes from the fact that, during their manufacture, the atoms of these amorphous materials do not arrange 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 substantially identical, the elastic limit σe is different. An amorphous metal is thus differentiated by an elastic limit σe higher than that of the crystalline metal by a factor of about two to three. This allows the amorphous metals to be able to undergo a greater stress before reaching the elastic limit σe. Amorphous metals plastically deform more difficultly and break brittle when the applied stress exceeds the elastic limit. Surprisingly, precious amorphous metals have good mechanical properties. The metal element of said material may then comprise gold, platinum, palladium, rhenium, ruthenium, rhodium, silver, iridium or osmium.

Such springs 10, 110 have the advantage of having a higher strength and longevity compared to their crystalline metal equivalents.

Indeed, as the amorphous metal has a higher elastic limit, it is necessary to apply a higher stress to deform plastically. As a result, a spring 10, 110 of amorphous metal has a better resistance to the stresses applied to it during an impact because it will deform elastically over a wider stress interval and return to its initial position once the shock completed. As this stress interval, in which the spring 10, 110 is elastically deformed, is wider for a spring 10, 110 of amorphous metal than for its crystalline metal equivalent, it allows said spring 10, 110 of amorphous metal to withstand constraints that would plastically deform a similar spring of crystalline metal. As soon as the deformation is elastic, these springs 10, 110 are no longer unfolded to return them to their original position and therefore they get tired less which improves their longevity.

Furthermore, since the elastic limit of an amorphous metal is higher than that of a crystalline metal by a factor of about two to three to withstand higher stresses, it is possible to reduce the dimensions of said spring 10, 110. Indeed, as a spring 10, 110 shockproof system of amorphous metal can withstand a higher stress without deforming plastically, it is then possible, with equivalent stress, to reduce the dimensions of the spring 10, 110 with respect to a similar spring made of a crystalline metal.

To achieve these springs 10, 110, several methods are possible.

First, it is possible to achieve them as in the prior art, that is to say by cutting by wire or water jet or by machining or stamping.

However, it can be envisaged to make the spring 10, 110 using the properties of amorphous metals. Indeed, the amorphous metal has a great ease in shaping allowing 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 [Tg - Tx] specific to each alloy (for example for a Zr41.24Ti13.77Cu12.7Ni10Be22 alloy. 7, Tg = 350 ° C and Tx = 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 fine geometries very precisely because the viscosity of the alloy decreases sharply as a function of the temperature in the temperature range [Tg-Tx] and the alloy thus allies the details of the mold. For example, for a platinum-based material, the shaping is done around 300 ° C for a viscosity up to 10 <3> Pa.s for a stress of 1 MPa, instead of a viscosity of 10 < 12> Pa.s at the temperature Tg.

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 fusion is done under a controlled atmosphere with the aim of obtaining contamination of the alloy with impurities as low as possible. Once these elements are melted, they are cast as a semi-finished product, then cooled rapidly to maintain the at least partially amorphous state. Once the preform obtained, the hot forming is performed in order to obtain a final piece. This hot forming is carried out by pressing in a temperature range between the glass transition temperature Tg of the amorphous material and the crystallization temperature Tx of said amorphous material for a predetermined time to maintain a totally or partially amorphous structure. The goal is then to retain the characteristic elastic properties of amorphous metals. The different stages of definitive shaping of the spring 10, 110 are then: <tb> a) <sep> Heating the pliers or dies forming the mold having the negative form of the spring 10, 110 to a chosen temperature, <tb> b) <sep> Introduction of the amorphous metal preform between the hot matrices, <tb> c) <sep> Application of a closing force on the matrices in order to replicate the geometry of the latter on the amorphous metal preform, <tb> d) <sep> Waiting for a chosen maximum time, <tb> e) <sep> Opening the matrices, <tb> f) <sep> Fast cooling of the spring below Tg so that the material keeps its phase at least partially amorphous, and <tb> g) <sep> Spring output 10, 110 of the matrices.

The hot forming of the metal or amorphous alloy thus makes it possible to produce complex and precise parts but also a good reproducibility of the part which is a consequent advantage for mass production such as that of damping system springs.

According to a variant of this method, the casting is used. This process involves casting the alloy obtained by melting the metal elements in a mold having the shape of the final piece. Once the mold is filled, it is cooled rapidly to a temperature below Tgafin to avoid crystallization of the alloy and thus obtain a spring amorphous or partially amorphous metal. The advantage of casting an amorphous metal with respect to the casting of a crystalline metal is to be more precise. The solidification shrinkage, for an amorphous metal, is very low, less than 1% relative to that of the crystalline metals which is 5 to 7%.

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

It can also be understood that the stone against pivot 5, 105 comprises a conical recess so that the end of the taper 3a, 103a can be inserted to allow a difference in amplitude between the different positions of the watch reduced to a minimum.

Claims (9)

1. Shock absorbing bearing for an axis (3, 103) of a mobile of a timepiece, said axis comprising a tigeron (3a, 103a), said bearing comprising a support (1, 101) provided with a housing (6, 106) for receiving a pivot system in which the beam (3a, 103a) is inserted, said bearing further comprising resilient means (10, 110) arranged to exert on said pivot system at least one axial force , characterized in that the elastic means are made of at least partially amorphous material. 2. shock absorbing bearing according to claim 1, characterized in that said elastic means (10, 110) are made of totally amorphous material. 3. shock absorbing bearing according to claims 1 or 2, characterized in that the amorphous material comprises at least one metal element. 4. shock absorbing bearing according to claim 3, characterized in that said at least one metal element is of the precious type or an alloy comprising such a precious metal element. 5. shock absorbing bearing according to claim 4, characterized in that said precious metal element comprises gold, platinum, palladium, rhenium, ruthenium, rhodium, silver, iridium or osmium. 6. shock absorbing bearing according to one of the preceding claims, characterized in that the pivot system comprises a kitten (20) arranged in the housing (6) and supporting a pierced stone (4) traversed by the tigeron (3a) and a counter-pivoting stone (5) and in that the support (1) is a part of revolution comprising a circular flange interrupted in two diametrically opposite locations by an opening (12) so as to create two semi-circular flanges (11a, 11b), said opening being formed in part in the two semi-circular flanges so as to materialize two returns (13) under which the elastic means (10) support to maintain the kitten in the housing (6) of the support (1). 7. shock absorbing bearing according to claim 6, characterized in that the elastic means (10) are a spring (1) having a lyre shape. 8. shock absorbing bearing according to one of claims 1 to 5, characterized in that the housing (106) is arranged to receive a spring (110) with axial and radial deformation and a kitten (120) supporting a pierced stone (104). ) traversed by the tigeron (103a) and a counter-pivoting stone (105), said elastic means (110) being formed by a rigid peripheral ring (111) driven into the housing (6) and connected by elastic means (112) a rigid central support (113) substantially annular and in that the kitten (120) holding the two stones (104, 105) is suspended in the center of the spring (110). 9. Shock absorber bearing according to claim 8, characterized in that the kitten (120) is formed of two parts (113, 123), one being constituted by the central rigid support (113) whose inner wall (113a ) holds the pierced stone (104), the other being formed by a cover (123) secured to the rigid central support (13) to block the counter-pivot stone (15) on the upper support surface (113b) of the central support (113).