CH715614B1 - Process for decorating a watch element. - Google Patents

Abstract

The method according to the invention comprising the following steps: a) forming an enamel coating on a timepiece such as a dial (1) or a bracelet, b) engraving at least one groove in the enamel coating , c) carrying out at least one firing step to reduce the depth of the at least one groove, and d) painting a pattern (3) on the enamel coating, this step being carried out between steps a) and b) , between steps b) and c) or after step c). This process makes it possible to produce on the timepiece element a decoration in structured relief, for example of the azulejos type, and/or a decoration of great precision.

Description

The present invention relates to a method of decorating a timepiece element, in particular an element of a wristwatch, pocket watch or clock. The timepiece element is for example a dial or a bracelet.

The present invention relates more particularly to a method of decoration using the technique of painting on enamel. According to such a method, an enamel coating is formed on the element to be decorated and then a pattern is painted on the surface of the enamel.

[0003] The enamel painting technique requires great dexterity from the enameller given the generally small dimensions of the item to be decorated. For example, to create a decoration imitating "Azulejos", enamelled earthenware tiles decorated with designs and used for covering walls and floors, the enameller must give the impression of relief at the level of the joints of the tiles and a certain harmonious asymmetry. between them by painting a trompe l'oeil motif, by hand, in a miniaturized way. It is furthermore difficult for the enameller to precisely delimit a design in order, for example, to leave room for a functional part of the timepiece element, such as a scale in the case of a dial, or for another part decorative.

[0004] In general, it is understood that the decorations on enamel are difficult to reproduce, have a long production time and require know-how known to few enamellers.

Also, the present invention aims to provide a method to overcome these problems of the prior art or at least to mitigate them. To this end, there is provided a method of decorating a timepiece element comprising the steps of: a) forming an enamel coating on the timepiece element, b) engraving at least one furrow or groove in the enamel coating, c) carrying out at least one firing step to reduce the depth of the at least one groove, d) painting a pattern on the enamel coating, this step being carried out between steps a) and b) , between steps b) and c) or after step c).

Particular embodiments are defined in the dependent claims.

[0007] The present invention further provides a timepiece element according to claim 12 as well as a timepiece according to claim 16.

Other characteristics and advantages of the present invention will appear on reading the following detailed description given with reference to the appended drawings in which: FIG. 1 represents a watch comprising a dial decorated by the process according to the invention; FIG. 2 is a diagram showing the different steps of the method according to the invention.

[0009] By "groove" or "groove" is meant a recess of material of a determined depth, along a line which may be straight or curved, over a length determined by the shape of the pattern that the we want to show.

[0010] There may be a single groove, for example when this defines a circle, or several grooves. The furrows can be parallel to each other, concentric or can intersect or join in a determined pattern.

[0011] The pattern may be of geometric shape or of any figurative shape.

[0012] As examples of patterns, it can be described in a non-limiting manner that the grooves can form a square, a rectangle, a diamond, a grid, the outline of a flower, a bird or any other design.

Figure 1 shows a timepiece comprising a dial 1 decorated by the method according to the invention. In the example illustrated, the timepiece is a wristwatch. It could, as a variant, be a pocket watch or a clock. Dial 1 has, on the side visible to the user, an enamelled surface decorated with a grid 2, a pattern 3 painted on the squares of the grid 2 and a ring 4.

[0014] The grid 2 imitates the joints between the earthenware tiles of an "Azulejos" type coating. The painted pattern 3 can be plain, geometric or figurative. Advantageously, the style of the painted pattern 3 is reminiscent of the designs which decorate Azulejos. The tiles of an Azulejos coating generally measure about fifteen centimeters on a side and have asymmetrical edges, joined to each other by a binder. The process according to the invention which will be described makes it possible to obtain an Azulejos rendering in miniature and in a reproducible manner.

[0015] The ring 4 is an annular zone of the surface of the enamel in which the grid 2 and the painted pattern 3 are absent. The ring 4 bears a scale which identifies the seconds on the dial 1. In the example illustrated in figure 1, the enamel, therefore in particular the ring 4, is white in color and the painted pattern 3 is colored blue. The colors of the enamel and the painted pattern 3 may change depending on the desired pattern and final rendering. Pattern 3 is painted on the outside and inside ring 4.

The process for obtaining dial 1 is shown in Figure 2.

[0017] At a first step E1, a support is provided, here a metal dial, for example in gold, silver or copper.

[0018] In a second step E2, an enamel coating is formed on the surface of the dial intended to be exposed to the view of the user. The enamel may be of the same type as the enamels traditionally used in watchmaking. It initially comes in the form of a powder which, when mixed with water, becomes a paste which can be spread over the surface of the dial. Baking, at a temperature typically between 700° C. and 1000° C., preferably between 800° C. and 900° C., preferably between 800° C. and 835° C., makes it possible to solidify the enamel. The operations of deposition of the paste and solidification by baking can be repeated a certain number of times until obtaining a multilayer coating having the desired termination. Typically, multiple firings are performed.

The enamel obtained has a thickness of between 0.3 mm and 0.4 mm, for example 0.35 mm.

[0020] In a third optional step E3, the enamelled surface of the dial is polished.

In a fourth step E4, grooves are etched in the enamel, for example mechanically using a cutter, such as a diamond cutter, or physically using a laser, such as a nano laser . These furrows form the grid 2 illustrated in figure 1 and two concentric circles delimiting the ring 4.

These grooves are dug to a depth less than the thickness of the enamel coating so as not to reach the metal support of the dial. The depth of the grooves forming the grid 2 is for example at least 0.01 mm and for example between 0.01 mm and 0.3 mm. The furrows which delimit the ring 4 are shallower than those forming the grid 2. The depth of the furrows delimiting the ring 4 is for example at least 1 μm and for example comprised between 1 μm and 0.03 mm.

[0023] This enamel etching step advantageously makes it possible to reproducibly divide the enamel surface of the dial into miniature tiles, without having to assemble and glue them subsequently. It also makes it possible to precisely define the zone of the dial constituting the ring 4 and therefore to precisely delimit the zones of paint of the pattern 3, outside and inside the ring 4. The enameller will thus be able to produce its pattern in areas well defined by engraved grooves, allowing it a perfect layout.

As regards the grid 2, the engraving is preferably carried out irregularly, with imperfectly straight edges, to give the appearance of tiling. It is advantageous to use mechanical tools in order to obtain this irregular effect. For ring 4, on the other hand, the engraving is carried out regularly. For this purpose, it is advantageous to use a laser.

In a fifth step E5, the pattern 3 is painted on the enamelled surface of the dial. The paint used consists in particular of oxides and binders.

[0026] In a sixth step E6, the dial thus decorated is placed in the oven to be baked there at a temperature typically between 700° C. and 1000° C., preferably between 800° C. and 900° C., preferably between 800° C. C and 835°C. This step sets the paint.

Typically, the succession of steps E5 and E6 is implemented several times, for example for each application of a color or shade of color.

[0028] The E6 firing step(s) advantageously allow the enamel to sag and partly resume its place in the grooves forming the grid 2, thus accentuating the irregular nature of these grooves and the appearance of jointed tiles . Unlike the grooves forming the grid 2, the grooves delimiting the ring 4 engraved in step E4 have a sufficiently small depth so that after step E6 or the last step E6 these grooves are filled in by the enamel and have therefore disappeared, leaving only a trace of a pattern 3 of great precision.

[0029] In a variant of the invention, a cooking step similar to step E6 is carried out between the etching step E4 and the painting step E5 in order to reduce the depth of the grooves forming the grid 2 and to accentuate their irregular nature, step E5 preferably being followed by cooking step E6.

In another variant of the invention, the steps of etching E4 and painting E5 are reversed. In this variant, one or more firing operations can be implemented between the pattern painting step and the etching step in order to fix the paint.

In the present invention, the E3 polishing and E4 etching steps can be reversed.

It is also possible to modify the method according to the invention so that at the etching step E4, only the grooves forming the grid 2 are engraved or, conversely, only the grooves delimiting the ring 4 are engraved.

[0033] Furthermore, it goes without saying that the grooves engraved in step E4 could form a pattern other than a grid and could delimit a zone of the surface of the enamel having a shape other than a ring.

The present invention can be applied to other timepiece elements than a dial, for example to a bracelet.

The method according to the invention makes it possible to give a structured relief and/or a precise outline to a timepiece element independently of the work of the enameller. It also allows time savings for the enameller and reproducibility of the pattern which can be envisaged on a larger volume of parts. High design precision and increased decor fidelity can be obtained, in accordance with the requirements of fine watchmaking. It will be noted that these results are obtained by means in particular of an operation of engraving the enamel going against the criteria of homogeneity and smoothness of the enamel prevailing in fine watchmaking.

Claims (16)

1. Method for decorating a timepiece element comprising the following steps: a) forming an enamel coating on the timepiece element, b) etching at least one groove in the enamel coating, c) carrying out at least one cooking step to reduce the depth of the at least one groove, d) painting a pattern on the enamel coating, this step being carried out between steps a) and b), between steps b) and c) or after step c). 2. Method according to claim 1, characterized in that the at least one groove engraved in step b) comprises at least a first groove whose depth is reduced, but which does not disappear, in step c). 3. Method according to claim 2, characterized in that the at least one first groove forms a grid creating with the painted pattern the appearance of jointed decorated tiles. 4. Method according to claim 2 or 3, characterized in that the at least one first groove has a depth of at least 0.01 millimeter, preferably between 0.01 millimeter and 0.3 millimeter. 5. Method according to one of claims 1 to 4, characterized in that step d) is carried out between steps b) and c), in that the at least one groove engraved in step b) comprises at least one second groove which disappears in step c) and in that this at least one second groove serves to delimit the painting of the pattern in step d). 6. Method according to claim 5, characterized in that the at least one second groove forms at least one circle. 7. Method according to claim 5 or 6, characterized in that the at least one second groove forms two concentric circles. 8. Method according to one of claims 5 to 7, characterized in that the at least one second groove has a depth of at least 1 micrometer and preferably between 1 micrometer and 0.03 millimeter. 9. Method according to one of claims 1 to 8, characterized in that in step b) the etching of the at least one groove is carried out mechanically and/or by means of a laser. 10. Method according to one of claims 1 to 9, characterized in that the timepiece element in step a) is metallic. 11. Method according to one of claims 1 to 10, characterized in that the timepiece element in step a) is a dial or a bracelet. 12. Timepiece element decorated according to the process according to claim 1, comprising: - a support, – an enamel coating on the support, – grooves engraved in the enamel coating and forming a first pattern on at least part of its surface, – a second pattern painted on said at least part of the surface of the enamel coating. 13. Timepiece element according to claim 12, characterized in that the first pattern is a grid. 14. Timepiece element according to claim 12 or 13, characterized in that the support is metallic. 15. Timepiece element according to one of claims 12 to 14, characterized in that it is a dial or a bracelet. 16. Timepiece, such as wristwatch, pocket watch or clock, comprising a timepiece element according to one of claims 12 to 15.