CH717357A2 - Watch hairspring in glass or ceramic, with complex geometry. - Google Patents

Abstract

The invention relates to a watch hairspring, having a complex three-dimensional geometry, being in a single-piece form, in particular integral, and being in ceramic or glass.

Description

The present invention relates to a watch hairspring made of glass or ceramic with a complex geometry. It also relates to a sprung-balance oscillator incorporating such a watch balance spring, as well as a watch movement and a timepiece incorporating such a watch balance spring.

The manufacture of an oscillator of the sprung balance type requires meeting many constraints, in particular to meet the following objectives if possible: choose a material whose mechanical properties allow it to satisfy the desired horological functionality; choose a material that can be compatible with existing manufacturing processes to achieve a desired shape; advantageously choose a robust material, the properties of which are stable over time, for example a material not subject to corrosion; advantageously choose a non-magnetic material, to avoid variations in behavior in the presence of a magnetic field; advantageously choose a material that is not very sensitive to temperature variations.

[0003] The existing solutions are based on compromises, and never simultaneously meet all the objectives listed above.

[0004] For example, many watch components are made of metal and are obtained by cutting from a strip or by a LIGA process, making it possible to form components with flanks perpendicular to the length of the strip or to a direction of growth of the strip. deposited metal. These watch components have good mechanical properties, but are generally sensitive to magnetism or to temperature variations, and do not allow complex three-dimensional shapes to be achieved without subsequent plastic deformation.

[0005] Alternatively, other existing methods use glass, a material which has the advantage of being insensitive to magnetic fields and to variations in ambient temperature, of being robust over time while resisting corrosion well. The existing methods of manufacturing a watch component made of glass require phases of plastic deformation of certain portions of the watch component, in order to approach the final shape when the latter is not simple. Such a plastic deformation is delicate, requires a precise operating mode due to the fragility of the material, and induces internal stresses in the material, which are liable to weaken the watch component formed. In addition, to achieve this final shape with precision, it is sometimes necessary to retouch the shapes reached after plastic deformation, which can be tedious. In addition, these watch components are obtained by assembling several distinct portions, particularly when a not very simple shape is desired. In such a case, the assembly requires the use of attachment means, which in practice generate internal stresses in the portions concerned, which may change over time. They are thus detrimental to the reliability over time of the watch component. As a note, these internal stresses can be measured, for example by photo-elasticity or acoustic-elasticity techniques.

In summary, the existing manufacturing processes make it possible to obtain high-performance watch components, but which include drawbacks due to the compromises made.

[0007] Thus, the object of the present invention is to provide an improved watch balance spring, which does not include all or part of the drawbacks of the state of the art.

[0008] More precisely, the object of the invention is to provide a watch balance spring representing an improved compromise between being able to present high-performance mechanical properties, being able to have a complex shape, being resistant to corrosion and presenting the particularity of being insensitive to magnetic field variations and temperature variations.

[0009] To this end, the invention is based on a watch balance spring, characterized in that it has a complex three-dimensional geometry, is in a single-piece form, in particular integral, and is in ceramic or glass.

Said ceramic or said glass may be transparent or translucent at at least one predetermined wavelength, suitable for manufacture by laser engraving.

The watch hairspring may include a first part generally arranged on a first plane and may include at least a second part which does not extend either in a plane parallel to said first plane or in a direction substantially perpendicular to said first plane or which s 'extends over at least two other planes distinct from each other and distinct from said first plane, parallel to said first plane or not.

The hairspring may comprise a first part generally arranged on a first plane and of which a section by a plane perpendicular to said first plane has a rectilinear contour not perpendicular to said first plane.

The hairspring comprises at least a part which is elastically deformed. The hairspring may include a shape at rest without internal stress in the material constituting it.

The hairspring may comprise at least one elastic part arranged on a first plane so that it deforms elastically on this first plane, and may include at least a second part extending neither in a plane parallel to said first plane nor in a direction substantially perpendicular to said first plane or may comprise at least a second part extending over at least two planes distinct from each other and distinct from said first plane, parallel to said first plane or not.

The hairspring may comprise turns and all or part of the turns may have at least one section of shape different from a rectangular shape and / or of ovoidal or elliptical shape and / or comprising a section at least partially recessed.

The hairspring can include turns and all or part of the turns can have a variable section along their length.

The hairspring may comprise turns of at least partially recessed section in the shape of an I with a wheelbase, or in the shape of an eight, or in the shape of C.

The hairspring may comprise attachment elements such as a connecting structure and / or a ferrule and / or a stud and / or an axis or a portion of the balance axis and / or a plate and a plate pin. and / or part of a balance.

[0019] The invention also relates to a sprung balance oscillator for a timepiece, characterized in that it comprises a timepiece hairspring as described above.

[0020] The invention also relates to a timepiece, in particular a watch, characterized in that it comprises a horological balance spring as described above.

These objects, characteristics and advantages of the present invention will be explained in detail in the following description of particular embodiments made without limitation in relation to the appended figures among which: Figures 1a to 1e illustrate the geometries of sections of turns of a spiral spring according to different variants of an embodiment of the invention. FIG. 2 represents a glass or ceramic block used in a first step of the method of manufacturing a watch balance spring according to one embodiment of the invention. FIG. 3 diagrammatically represents a second step of the method of manufacturing a watch balance spring according to the embodiment of the invention. FIG. 4a shows in perspective a hairspring for a watch oscillator according to a first variant embodiment of the invention. FIG. 4b represents the hairspring of FIG. 4a according to the section plane A-A. FIG. 5 represents the section of a turn of the hairspring for a watch oscillator according to a second variant embodiment of the invention. FIG. 6 represents in perspective a horological oscillator according to a third variant embodiment of the invention.

The invention achieves the desired object in a simple and surprising manner, by means of a clockwork spiral spring which has a complex three-dimensional geometry, produced in one piece. The hairspring is in one piece, and is made of ceramic, transparent or translucent at at least one predetermined wavelength, or of glass, likewise transparent or translucent at at least one predetermined wavelength. The spiral part is advantageously made integral with the ferrule and the eyebolt, or even with the balance axis.

By this solution, the watch balance spring has the advantages of its material, is insensitive to magnetic fields and to variations in ambient temperature, and is robust over time, particularly by resisting corrosion well.

[0024] In addition, as the watch balance spring is in one piece, it does not present the risks associated with the assembly of several parts, in particular by the addition of internal stresses at the level of the assembly areas. In addition, obtaining the one-piece watch balance spring according to the invention advantageously makes it possible to form it without requiring plastic deformations, and therefore without creating internal stresses liable to modify its behavior over time. As a note, for the watch hairspring which deforms elastically, the aforementioned internal stresses are considered in the rest configuration of the watch hairspring.

On the other hand, the invention also makes it possible to provide a watch hairspring of complex three-dimensional shape, which is naturally advantageous because it makes it possible to freely optimize the shape of the watch hairspring to allow it to fulfill a desired functionality. , without requiring a simplification of the form likely to degrade the function to be fulfilled. By complex three-dimensional shape is meant in particular a shape comprising a first part generally arranged on a first plane and at least a second part which does not extend either in a plane parallel to said first plane or in a direction substantially perpendicular to said first plane, or which extends over at least two other planes distinct from each other and distinct from said first plane, parallel to said first plane or not. In particular, such a shape may comprise a first part generally arranged on a first plane and of which a section taken along a plane perpendicular to said first plane has an outline or a portion of a contour which is not perpendicular to said first plane. As a note, such a shape would not be achievable with the methods currently used based on the growth of layers of material in a single imposed direction. Thus, the invention allows the use of a watch hairspring of complex three-dimensional shape, which is not limited to a two-dimensional shape in a plane which would be extended by a growth in a direction of growth, generally perpendicular to the plane of the two-dimensional shape (such a shape being sometimes called 2D1 / 2 shape, strictly not three-dimensional). Such extended two-dimensional shapes (2D1 / 2) would for example be obtained from a strip or plate of material by cutting or by stamping or by DRIE engraving or by unidirectional growth from a mold (LIGA).

This complex three-dimensional shape of the invention can also be characterized by a section having a non-rectangular shape. Particularly, in the case of a watch spring, the invention makes it possible to depart from the solutions of the state of the art which are limited to sections of the turns of rectangular shape. Indeed, the invention allows the use of sections of more complex shapes, and which can vary according to the length of a turn. FIGS. 1a to 1e illustrate, by way of example, possible sections for a turn of a watch spring according to different variant embodiments of the invention.

Figure 1a illustrates for example a section in the form of 1 with wheelbase. FIGS. 1b and 1c represent sections of ellipsoidal contour, respectively non-perforated and perforated, which makes it possible to avoid the drawbacks of the presence of angles in a rectangular section, angles which present risks of initiation of rupture during a flexion. Figure 1d shows a C-shaped section and Figure 1e an 8-shaped section. These complex shapes of sections make it possible to optimize the performance of a watch spring, for example by increasing the ratio between rigidity and weight. , which has the effect of reducing the rate differences between the different vertical positions of an oscillator incorporating such a watch spring. In addition, the invention allows the section to be modified along the length of a turn, thus easily adapting to needs.

The method of manufacturing a watch balance spring, shown in Figures 2 and 3, comprises the following steps: Provide a block 30 made of ceramic or glass, transparent or translucent at at least one predetermined wavelength with a view to the etching of the following step; Laser engraving said block according to a predefined complex three-dimensional shape of the watch balance spring; Dissolve the engraved part of the block to free the engraved hairspring.

[0029] FIG. 2 thus represents a block 30 made of ceramic or glass, transparent or translucent with respect to the wavelength of the laser which will be used, from which the watch hairspring will be manufactured in one piece, from so as to obtain a one-piece hairspring, and in a complex three-dimensional shape.

This block 30 therefore has an overall volume greater than the watch hairspring to be manufactured, since the latter will be obtained after a material removal process. In the second etching step, the laser, for example a femtosecond laser, induces a nonlinear absorption of the photons confined in the focal volume of the laser in the material of the block. This absorption forms altered zones 31 corresponding to the external contour of the predefined shape of the watch balance spring to be manufactured. Next, the etching comprises a step of dissolving the material altered by the laser, then a step of rinsing. This process thus corresponds to a selective attack on the block, in order to keep only the desired watch balance spring. This selective attack can be carried out from an acidic fluid, such as hydrofluoric acid, or alternatively from a basic fluid, such as for example a solution of potassium hydroxide.

Depending on the nature of the deterioration, for example after the reduction of Ag ions in a photosensitive glass such as Foturan®, an additional heat treatment step, at a temperature preferably between 500 ° C and 600 ° C, can be carried out before the dissolution step. As a note, this laser engraving step makes it possible to achieve a very high resolution, of the order of a micron.

It emerges from the method described above that the invention makes it possible to obtain a watch balance spring with a complex three-dimensional shape, with great freedom of shape. In addition, this method makes it possible to obtain such a shape without generating internal stresses in the material of the watch balance spring. This absence of internal stresses results in particular from the fact that the method does not require plastic deformation of parts of the hairspring during its manufacture. It is also favored by the fact that the watch hairspring can be obtained entirely from a single block of material, so as to constitute a monobloc hairspring. The ferrule, the eyelet, or even the balance shaft, can thus be integrally formed with the turns of the spiral spring, without requiring an assembly step. As a note, the resulting watch spring can then naturally be assembled with other components, to form a larger assembly, such as a sprung balance, which remains within the scope of the invention.

In addition, the invention also makes it possible to lighten a watch hairspring by minimizing in a targeted manner the distribution of the material directly during the design and manufacture of the watch hairspring, without altering the mechanical properties of the watch hairspring as would be the case by implementing an additional operation of material removal subsequent to the manufacture of the hairspring. Such an approach makes it possible to form hollowed out or perforated parts, compared to the solutions of the state of the art, also including concave shapes.

Finally, when the watch balance spring is shaped, it is naturally possible to modify its surface by known methods in order to adapt its mechanical, tribological or aesthetic properties. For example, it is possible to remove material or to deposit a coating on at least part of the surface of the watch balance spring. Alternatively or additionally, part of the surface can be modified by ion implantation or any other suitable technique. The watch hairspring according to the invention thus remains naturally compatible with carrying out finishing steps known from the state of the art.

The invention is therefore particularly suitable for the manufacture of a watch spring, in particular for a watch oscillator, such as a spring comprising a part in the form of a spiral, more simply called a "spiral spring" or "spiral", of a watch oscillator called a sprung balance, as has been described above. Indeed, such a hairspring, and more generally a sprung balance, can advantageously benefit from a complex three-dimensional shape for its optimization. Advantageously, such a hairspring comprises a first part formed of turns, arranged generally in a first plane, and deforming elastically in this first plane. Among the possible geometries of a hairspring manufactured within the scope of the invention, it is possible to underline the following advantageous characteristics, in a nonlimiting manner: Optimization of the inter-turn distance, to prevent the turns from touching each other during impacts, by playing either on the stiffness of the section or on the staggering of different levels in different planes; Positioning of the plane of the hairspring in the plane of the balance; The formation of a short, or partially cylindrical, cylindrical hairspring; The combination of a variable pitch and a variable section of the turns; for example, the section may have a variable dimension, in terms of height and / or width. This variation may or may not be homothetic; The formation of an oscillator comprising several balance springs; Optimization of the end curve of the hairspring; Modulating the stiffness of the spiral spring as a function of the angle, for example with a specific geometry to activate a zone of greater rigidity beyond a certain amplitude of rotation of the spiral.

In addition, the invention advantageously makes it possible to integrate into a hairspring of a watch oscillator complementary portions of the oscillator, not belonging directly to the hairspring. For example, a hairspring can incorporate some or all of the following elements, usually present in a separate form: A ferrule; A fixing eyebolt; A balance axis or part of such an axis; A tray and a tray peg; All or part of a pendulum.

Advantageously, these elements can take complex three-dimensional shapes. The hairspring of the invention can thus be arranged on three distinct planes, mutually parallel or not, or according to more than three planes, for example four or five planes. The invention is therefore very advantageous for any watch component provided with at least one elastic part which is elastically deformed, such as a watch balance spring.

The invention will now be described in the context of several exemplary embodiments, without limitation.

Figures 4a and 4b thus illustrate a spiral 1 made of glass according to a first variant embodiment. This monobloc hairspring incorporates a ferrule and its eyebolt, integrally formed with the turns. The hairspring firstly comprises a first part arranged in a first plane P1. This first part comprises a ferrule 2 at the level of the central part of the hairspring 1, intended for fixing the hairspring on a balance shaft, formed integrally and integrally formed with the turns 3 of the hairspring. The turns 3 are wound in the first plane P1 around the ferrule 2. The hairspring 1 is of the Breguet type, and comprises an outer coil which rises in a second plane P2 parallel to the first, where it follows a known curve 4 of the curved type. by Phillips. Finally, at the end of this terminal curve, the hairspring 1 comprises a piton 5, which extends in a third plane P3 distinct and perpendicular to the two preceding planes. This eyebolt 5 is also integral with the hairspring 1. The hairspring according to this first variant embodiment is therefore made of glass, in one piece, and extends overall in three distinct planes P1, P2 and P3. The turns of the spiral 1 have a rectangular section.

A second variant embodiment differs from the first variant described above in that the section of the turns, shown in Figure 5, has a shape of 1 with wheelbase. Thus, this section comprises a rectangular core 13, delimited on its two ends by rectangular footings 14, extending perpendicularly to the core 13, centered on this core 13. The height h of the turns is greater than its thickness e (measured on web 13). Advantageously, the various edges (concave as well as convex) are slightly rounded. The hairspring can be in amorphous silica or in Borofloat® 33 from Schott.

FIG. 6 illustrates a one-piece watch oscillator 20 made of glass according to a third variant embodiment. This one-piece horological oscillator 20 integrates an axis and a balance, integrally formed with the balance spring. The axis extends between two ends 21a, 21b, and comprises three curved cylindrical portions 26, 26 ', 26 "connected to the ends 21a, 21b and extending equally around the axis (A) of rotation of the clock oscillator (defined by a straight line connecting the two ends 21a, 21b). Advantageously, the three portions 26, 26 ', 26 "thus define a recess at the level of the axis. The horological oscillator 20 further comprises a hairspring 23 extending in a plane P1, arranged around the axis of the hairspring. It is connected to the axis by its inner end acting as a connecting structure 22 replacing the traditional ferrule. Advantageously, this connecting structure passes or passes substantially through the axis (A) of rotation of the axis. This arrangement is made possible by the hollowed-out conformation of the axis. It is thus possible to optimize the geometry of the spring, in particular the inner and / or outer curve of the spring. This connecting structure is also integral with the other parts of the clock oscillator 20. Three arms 24, 24 ', 24 "extend respectively from each portion 26, 26' 26" of the axis of the balance to a circular rim 25, arranged around the axis of the balance, in the plane of the hairspring 23.

Naturally, the invention is not limited to this third variant described: the hairspring could be different, not plane, for example of the Breguet hairspring type and / or distributed over two or more planes. As a further variant, it could be a cylindrical or helical hairspring or a spherical hairspring. In another variant, the rim 25 and / or the arms 24, 24 ', 24 "could comprise internal threads or threaded tenons. The latter would be obtained directly during the manufacturing process of the clock oscillator 20, in particular during the manufacturing process. The etching step explained above, without any subsequent step. Such threads could make it possible to screw in nuts. In another variant, the end of the hairspring would be directly attached to an arm of the balance.

The invention has been described on the basis of a watch balance-spring made of glass. As a variant, it could be implemented with a material having similar properties, such as a ceramic, transparent or translucent at the wavelength of the laser.

Naturally, the invention is not limited to a watch spring, such as a balance spring, or to a watch oscillator. It relates to any watch component of complex three-dimensional shape. Advantageously, such a horological component comprises at least one part which is elastically deformed.

The invention also relates to a balance-spring oscillator, to a watch movement and to a timepiece as such comprising a balance-spring according to the invention.

Claims (12)

1. Watch hairspring, characterized in that it has a complex three-dimensional geometry, is in a single-piece form, in particular integral, and is in ceramic or glass. 2. Watch hairspring according to the preceding claim, characterized in that said ceramic or said glass is transparent or translucent at at least one predetermined wavelength, suitable for manufacture by laser engraving. 3. Watch hairspring according to claim 1 or 2, characterized in that it comprises a first part generally arranged on a first plane and in that it comprises at least a second part which does not extend either in a plane parallel to said plane. first plane or in a direction substantially perpendicular to said first plane or which extends over at least two other planes distinct from each other and distinct from said first plane, parallel to said first plane or not. 4. Watch hairspring according to one of the preceding claims, characterized in that it comprises a first part generally arranged on a first plane and of which a section by a plane perpendicular to said first plane has a rectilinear contour not perpendicular to said first plane. 5. Watch hairspring according to one of the preceding claims, characterized in that it comprises a shape at rest without internal stress in the material constituting it. 6. Watch hairspring according to one of the preceding claims, characterized in that it comprises at least one elastic part arranged on a first plane so that it deforms elastically on this first plane, and in that it comprises on the other hand. at least a second part extending neither in a plane parallel to said first plane nor in a direction substantially perpendicular to said first plane or in that it comprises at least a second part extending over at least two planes distinct from each other and distinct from said foreground, parallel to said foreground or not. 7. Watch hairspring according to one of the preceding claims, characterized in that it comprises turns and in that all or part of the turns has at least one section of shape different from a rectangular shape and / or of ovoid shape or elliptical and / or comprising an at least partially recessed section. 8. Watch hairspring according to one of the preceding claims, characterized in that it comprises turns and in that all or part of the turns has a variable section along their length. 9. Watch hairspring according to one of the preceding claims, characterized in that it comprises turns of section at least partially recessed in the shape of 1 with a wheelbase, or in the shape of an eight, or in the shape of C. 10. Watch hairspring according to one of the preceding claims, characterized in that it comprises fastening elements such as a connecting structure and / or a ferrule and / or a stud and / or an axis or an axis portion. balance and / or a plate and a plate pin and / or part of a balance. 11. Spiral balance oscillator for a timepiece, characterized in that it comprises a timepiece hairspring according to one of claims 1 to 10. 12. Timepiece, in particular a watch, characterized in that it comprises a watch balance spring according to one of claims 1 to 10.