CH718842A2 - Multicolored cermet and/or ceramic article and method of making same. - Google Patents

Abstract

The invention relates to a method for manufacturing a multicolored article in cermet and/or ceramic, produced by injection of at least two materials (2,3) of distinct colors, said article comprising a decoration in relief of a color different from the rest of the article, said decoration being produced by laser ablation after injection of the two materials. The invention also relates to such an article, in particular a horological exterior or movement component, in particular a bezel or a crown.

Description

TECHNICAL AREA

The present invention relates to an article obtained by multiple injection of ceramics and / or cermets. It relates more particularly to a timepiece component such as a bezel, produced by injection of ceramic materials and/or cermets of different colors with a color forming a decoration of the timepiece component.

PRIOR ART

[0002] Ceramic or cermet watch components are generally obtained by a process of injection of a material followed by sintering. These components often feature decoration, such as hour markers and numerals for a bezel, which is a distinct color from the rest of the component. The elements of the decoration are generally added by brazing or gluing on the blank resulting from the sintering. This mechanical assembly between the blank and the elements of the decoration can turn out to be costly and complicated to implement.

[0003] An alternative to this mechanical assembly consists in making a blank by injecting materials of different colors with a color intended to form the decoration after machining. However, making ceramic or cermet components with different colors is complex. Indeed, a significant shrinkage, which can amount to 30%, is observed during sintering. The shrinkage rate will be dependent on several factors which are among others the choice of material and the volume of material injected. This can result in bi-injection or more generally multi-injection processes, differences in shrinkage during sintering which will lead to separation at the junction between the different materials.

To overcome this drawback, it has been proposed in document EP 2 746 243 to inject a single material and to impregnate part of the green body before sintering with a solution comprising a metal acting as a pigment. However, this method has the disadvantage that it is difficult to obtain a uniform color in the mass of the colored part.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the aforementioned disadvantages by proposing a new multi-material injection process limiting the differences in shrinkage between the materials of distinct colors injected, with a subsequent stage of machining the decoration in one of the colors.

[0006] To this end, the present invention relates to a manufacturing process using, during the injection step, an insert having a raised or recessed structure intended to print on the first injected material a surface of grip for the second injected material. This gripping surface makes it possible to maintain the second material injected and thus to reduce shrinkage during the sintering step.

More specifically, the method of manufacturing the article according to the invention comprises the following steps: Provision of at least a first material and a second material, said first material being distinguished from the second material by its chemical composition and more particularly by its color, said first and second materials being either a ceramic or a cermet, Provision of a mold with an imprint comprising a portion provided with a raised or recessed structure intended to form the grip surface on the first material, Injection of said first material into the impression provided with the portion so as to print the structure on a part of the first material and thus form the gripping surface on said part, Injection of the second material on the first material at least at the grip surface to form a green body, Sintering of the green body to form a blank, Machining by laser ablation of at least the second material to produce the decoration in said second material on a background of said first material, Finishing the draft to get the item.

[0008] Advantageously, the method further comprises another machining step before and/or after the sintering step to respectively size the green body and/or the blank.

The present invention also relates to the ceramic article and / or cermet from the manufacturing process. The article according to the invention comprises at least two distinct materials differing by their color, more generally by their aesthetic appearance. According to the invention, the decorated article is made in one piece without discontinuity between the decoration and the rest of the article, unlike an article decorated by attaching the elements of the decoration to the article by soldering or gluing. According to the invention, the decoration as well as the rest of the article are tinted in the mass with a uniform color for each color.

Other characteristics and advantages of the present invention will appear in the following description of a preferred embodiment, presented by way of non-limiting example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF FIGURES

[0011] Figure 1 shows a three-dimensional view of the double cavity of the fixed part of the mold with one of the two cavities comprising an insert with a relief structure according to the invention.

Figure 2 shows a three-dimensional view of the insert with the structure in relief.

Figure 3 shows a sectional view of the mold respectively during the injection of the first material on the right and the second material on the left.

[0014] FIG. 4 represents a three-dimensional view of the green body resulting from the bi-injection of materials.

[0015] Figure 5 shows a partial view of the green body of Figure 4.

[0016] FIG. 6 represents a three-dimensional view of a decorated bezel resulting from the manufacturing process according to the invention.

[0017] Figure 7 shows a plan view of a decorated bezel resulting from the manufacturing process according to the invention.

DETAILED DESCRIPTION

The present invention relates to a manufacturing process by injection of an article made with at least two distinct materials which are either a cermet or a ceramic. The term “distinct materials” means materials that differ in their aesthetic appearance, and in particular their color. This results in differences in chemical compositions. It can be the same base material with different pigments to change the color or different base materials. By way of example, it may be the same base material of zirconium oxide with, on the one hand, a black pigment to obtain a black material and, on the other hand, alumina to obtain the color white. More generally, the ceramics can be nitrides, carbides and/or oxides. Similarly, cermets may comprise a ceramic phase comprising carbides, nitrides and/or oxides and a phase of a metallic binder chosen, for example, from precious elements such as ruthenium, rhodium, palladium, osmium, iridium, platinum, gold and silver.

[0019] The article according to the invention can be a decorative article such as a constituent element of watches, jewellery, bracelets, etc. In the watchmaking field, this article can be a trim component such as a middle part, a back, a bezel, a bezel insert, a pusher, a crown, a bracelet link, a buckle, a dial, a hand , a dial index, etc. It can also be a component of the movement such as an oscillating weight, a plate, etc. By way of illustration, the article is a bezel 1 made with two ceramics of different colors, for example black and white, with one color which forms the background and another color which forms the decoration 11 as represented in FIGS. 6 and 7. Still by way of example, it could be an acronym on a watch crown.

The article is made by injecting different materials to form a green body and by sintering said green body. The manufacturing process is illustrated below for an article comprising two distinct materials, but it could be an article comprising 3, 4, etc. different materials with production of a gripping surface for each of the successive injected materials. Similarly, it is illustrated for an article with a decoration of the same color whereas there could be decorations of different colors.

The manufacturing process comprises the following steps with reference to Figures 1 to 7: Provision of at least a first material 2 and a second material 3, said first material being distinguished from the second material by its color and therefore by its chemical composition, said first and second materials being either a ceramic or a cermet. Thus, the first and second materials can both be a ceramic or both a cermet or even one material can be a ceramic and the other a cermet, Provision of a mold 5 with a cavity 6 comprising a portion 7, also called an insert, comprising a raised or recessed structure intended to form a gripping surface on the first material injected (fig.1). Preferably, said structure is in relief. This structure is preferentially discontinuous. It can thus be formed of a multitude of studs 7a (fig.2) or hollows. This discontinuous structure is preferred over a continuous structure such as a groove or a tongue for better retention of the material. Preferably, the hollows or studs respectively have a depth or a height of at least 0.2 mm. Preferably, there are 1 to 10 studs or recesses, more preferably 1 to 3 per 10 mm<2> of surface. Injection of said first material 2 into the cavity 6 provided with the insert 7 so as to print the structure on part of the first material 2 and thus form the attachment structure for the second material 3, Injection of the second material 3 on the first material 2 at least at the grip surface to form a green body 8 (fig.3 and fig.4), Sintering of the green body 8 to form a blank, Machining by laser ablation of at least the second material 3 of the green body 8 or of the blank to produce a decoration 11 standing on the first material 2 of the blank, the second material 3 being hollowed out down to the first material 2 to reveal the latter and leaving in said second material 3 only a decoration 11, Finishing the blank to form the item.

[0022] During the machining step, the first material can also be slightly hollowed out to remove the material at the level of the attachment zone which would have remained visible next to the decoration. In other words, it involves removing the structure printed on part of the first material that would be visible next to the decor. In the presence of more than two materials of different colors, the different materials can be hollowed out to draw decorations of different colors. Thus, in the presence of a third material injected on the second material, the third material can be dug up to the second material or even to the first material to form a decoration standing on the second material or on the first material or partly on the second matter and on the first matter.

[0023] The laser ablation machining step can be performed before sintering, ie. on the green body, or after sintering, i.e. on the draft.

The laser ablation is preferably carried out with a pulsed laser such as a picosecond, nanosecond or femtosecond laser.

[0025] The method may also include another machining step, also called a second machining step, intended to size the green body and/or the blank. Preferably, it is operated on the green body before sintering so that the material is not too hard. The present invention does not exclude this machining step being carried out partly before sintering and partly after sintering.

The method may optionally include a debinding step before the sintering step if the materials have been injected with a system of organic binders (paraffin, polyethylene, etc.).

[0027] After machining by laser ablation, the manufacturing process includes a finishing step such as polishing, satin-finishing, matting, etc.

In the example shown, the injection device comprises a mold 5 with a fixed part 5a formed by two cavities 6 with a first cavity 6a intended for the injection of the first material 2 and a second cavity 6b intended to the injection of the second material 3 (fig.1). The first imprint 6a comprises the insert 7 with the structure in relief. In the example, the insert is attached to the cavity but it could also be integral with the rest of the cavity. During injection, the first material 2 is injected into the mold 5 formed of the fixed part 5a and the movable part 5b as shown in FIG. 3 on the right. Then, the mobile part 5a with the first injected material 2 is moved above the fixed part 5b of the other cavity 6b to carry out the injection of the second material 3 (fig.3 on the left). The insert 7 with a structure in relief is intended to print hollows 2a in the first material 2 which will serve as a grip during the injection of the second material 3. FIG. 4 represents the green body 8 resulting from the bi -injection with the second material 3 superimposed on the first material 2. The green body as well as the blank at the end of the sintering comprises a part 4 where the two materials 2 and 3 are superimposed and more specifically overlap (fig. 5). Interlocking is understood to mean that one of the two materials has on its surface a structure filled by the other material. In FIG. 5, the two materials 2 and 3 can be seen which are superimposed with the nesting of one in the recesses 2a formed on the surface of the other.

[0029] To form a bezel, the sprue 10 is cut and the inside diameter of the bezel is hollowed out during the second machining step. Before or after, the second material is hollowed out by laser ablation down to at least the first material to form the decoration 11 in a color distinct from the substrate formed by the bezel.

[0030] Typically, a bezel 1 according to Figures 6 and 7 is obtained by injection of a white zirconia and a black zirconia and by sintering at a temperature of 1400° C. for a time of 48 hours in an oxidizing atmosphere.

Legend

[0031] (1) Article, watch component or bezel (2) First material, also called ceramic a. Hollow (3) Second material, also called ceramic (4) Part of the article (5) Mold a. Fixed part b. Mobile part (6) Impression a. First impression b. Second cavity (7) Insert, also called portion of cavity a. Plot (8) Green body (9) Carrot of the green body (10) Decoration

Claims (13)

1. Method for manufacturing by injection a cermet and/or multicolored ceramic article with a decoration (11) in relief, said method comprising the following steps: – Provision of at least a first material (2) and a second material (3), said first material (2) being distinguished from the second material (3) by its color, said first (2) and second (3 ) materials being either a ceramic or a cermet, – Provision of a mold (5) with a cavity (6) comprising a portion (7) comprising a raised or recessed structure intended to form a gripping surface on the first material (2) after injection, – Injection of said first material (2) into the cavity (6) provided with the portion (7) so as to print the structure on a part of the first material (2) and thus form the gripping surface on said part , – Injection of the second material (3) on the first material (2) at least at the grip surface to form a green body (8), – Sintering of the green body (8) to form a blank, – Machining by laser ablation of the second material (3) on the green body (8) or on the blank to produce the decoration (11) in relief, said second material (3) being dug by laser ablation at least up to the first material (2) to reveal said first material (2) and obtain the decoration (11) in relief in said second material (3) standing on the first material (2), – Finishing the draft to get the article. 2. Manufacturing process according to claim 1, characterized in that the structure of the portion (7) is discontinuous. 3. Manufacturing process according to claim 1 or 2, characterized in that the structure of the portion (7) is in relief. 4. Manufacturing process according to the preceding claim, characterized in that the structure of the portion (7) is formed of a multitude of studs (7a). 5. Manufacturing process according to claim 1 or 2, characterized in that the structure of the portion (7) is hollow and formed of a multitude of hollows. 6. Manufacturing process according to one of the preceding claims, characterized in that the second material (3) is injected onto the first material (2) to form the green body (8) comprising two superimposed layers with a layer of the first material (2) and a layer of the second material (3), said layers being nested one inside the other at the grip surface. 7. Manufacturing process according to one of the preceding claims, characterized in that the first material (2) is partially hollowed out to remove the gripping surface. 8. Multicolored ceramic and/or cermet article with a decoration (11) in relief of a color distinct from the rest of the article, said article being obtained with the manufacturing method according to one of the preceding claims, characterized in that the decoration (11) in relief is in one piece with the rest of the article, said decoration (11) as well as the rest of the article being dyed in the mass with a uniform color for each color. 9. Article according to the preceding claim, characterized in that the article is a watch component for covering or movement. 10. Article according to claim 8 or 9, characterized in that the horological covering or movement component is chosen from the list comprising a middle part, a back, a bezel, a bezel insert, a pusher, a crown, a bracelet link, a buckle, a dial, a hand, a dial index, an oscillating weight and a plate. 11. Article according to the preceding claim, characterized in that the article is the bezel (1) with the decoration (11) in relief formed at least by indexes and numbers. 12. Article according to claim 10, characterized in that the article is the crown with the decoration (11) in relief formed by an acronym. 13. Article according to one of claims 8 to 12, characterized in that the decoration (11) is made of a white zirconia and the rest of the article in a black zirconia.