Robust watch parts

Abstract

A method for manufacturing the surface of watch components, particularly external watch components, the method is: Steps to obtain a watch part blank to form the core of a watch part, A manufacturing method comprising the step of depositing a surface coating on a core, wherein the coating is made of a ceramic-metal composite material to form a hard surface for a watch component having a hardness of 500 HV or more, more specifically 600 HV or more, more specifically 750 HV or more, and more specifically 900 HV or more.

Description

Technical Field

[0001] The present invention relates to watch parts, particularly external watch parts. The present invention also relates to watches, particularly wristwatches, containing such watch parts. The present invention also relates to a method for manufacturing such watch parts.

Background Art

[0002] Watch external parts need to obtain a number of mechanical properties, especially on the visible external surface, and these requirements may conflict with each other. Desirable properties include - A very attractive appearance that is compatible with the aesthetic requirements of high-quality watches without defects, - Robustness to withstand external stresses to which the watch is exposed, for example, to prevent deterioration of its outer surface through the appearance of scratches over time, and more generally to maintain all of its mechanical properties for a long time so that the watch parts maintain the same appearance for a long time. including.

[0003] In practice, existing solutions reflect a compromise between these properties. However, these existing solutions have limitations, and there is a need to identify new solutions to optimize the properties and / or appearance of watch external parts, more generally of watch parts.

Summary of the Invention

Problems to be Solved by the Invention

[0004] For this reason, one objective of the present invention is to provide a solution for obtaining watch parts improved with respect to the prior art.

[0005] More specifically, the first objective of the present invention is to provide a solution for forming a watch part in which one of its surfaces has sufficient hardness to withstand external attacks.

[0006] The second objective of the present invention is to provide a solution for forming a watch part in which one of its surfaces has an attractive and robust appearance. [Means for solving the problem]

[0007] Therefore, the present invention relates to watch components, particularly external watch components, the components comprising a core covered with a surface coating made of a ceramic metal composite material, particularly based on tungsten carbide and cobalt-chromium or tungsten carbide and iron-chromium, the coating comprising a hard surface with a hardness of 500 HV or more, more specifically 600 HV or more, more specifically 750 HV or more, and more specifically 900 HV or more.

[0008] The present invention also relates to a method for manufacturing the surface of a watch component, in particular an external watch component, the method being: Steps to obtain a watch part blank to form the core of a watch part, A step of depositing a surface coating on the core, wherein the coating is made of a ceramic-metal composite material in order to form a hard surface of the watch component with a hardness of 500 HV or more, more specifically 600 HV or more, more specifically 750 HV or more, and more specifically 900 HV or more. The present invention relates to a manufacturing method that includes the following steps.

[0009] The present invention is defined more specifically by the claims.

[0010] The object, features, and advantages of the present invention are disclosed in detail in the following description of certain non-limiting embodiments. [Modes for carrying out the invention]

[0011] The concept behind the present invention is to propose a watch component having a very hard surface, which may optionally be finished through a step of laser structuring its surface in order to form relief and / or color scheme. The very hard surface is formed by adding a very hard and thick surface coating to the blank of the watch component.

[0012] In this specification, the expression “material-based” is used to indicate that the material is the primary or dominant element. In particular, the expression “material-based” is used to indicate that an element contains at least 50% by weight of the material. In addition, sometimes the simplified expression “part” is used to refer to a watch part, or even, though inappropriately, a nearly finished watch part blank. The invention is described in particular in the context of watch exterior parts, but may be implemented in any other watch part, as described below.

[0013] A method for manufacturing an external watch component according to one embodiment of the present invention is described in detail below.

[0014] The manufacturing method includes a first step of creating a blank for the external watch component that forms the core of the external watch component. The blank may have various mechanical properties. In the first approach, it may be a relatively porous blank having a low relative density, which is advantageous for reducing weight. In the second approach, it may be a core made of a hard and / or high-density first material. The first material may be the same as or different from the second material of the coating described below. In yet another approach, which may be combined with the approaches described above, the core of the external watch component may be made of a single material or of several different materials.

[0015] The method then includes a second step of depositing a surface coating to form a very hard surface on the watch's external parts. Note that this very hard surface may extend over all or part of the watch's external parts.

[0016] Therefore, the coating preferably includes a very hard second material that is different from the first material that forms the core of the watch's external parts. According to one embodiment, the surface coating has a density higher than that of the core, and / or the second material has a density higher than that of the first material that forms the core.

[0017] In other words, the first material may have a lower density than the second material. More generally, the second step may include depositing at least one layer of a surface coating having a higher density than the density of at least one core of the part. The second step may also, in particular, form a surface having a degree of porosity lower than the degree of porosity of at least one core of the part, ideally a non-porous surface. The second step makes it possible to obtain a watch part having a particularly high level of hardness on the surface, which is formed by the coating. The hardness is 500 HV or higher, more preferably 600 HV or higher, more preferably 750 HV or higher, and more preferably 900 HV or higher.

[0018] Advantageously, in this embodiment, the deposition of the surface coating may be carried out by thermal spraying at particularly high temperatures, especially above 800°C. Such modifications utilize, for example, high-temperature spraying at 900°C, of ​​ceramic and / or metallic particles, such as tungsten carbide (WC) and cobalt-chromium (CoCr) particles (where cobalt-chromium acts as a binder between WC particles in the coating), and the WC particles may have an average diameter of 40 μm, or even smaller. As an alternative, other binders such as iron-chromium (Fe-Cr) are also conceivable. Note that in the above example, the surface coating layer includes particles of a first material, such as tungsten carbide (WC), and particles of a second material, such as cobalt-chromium (CoCr), which acts as a binder. The second material remains optional, as the binder is not essential. Thermal spraying may be of the plasma type (VPS, an acronym for "vacuum plasma spraying"), which has numerous advantages, such as enabling the spraying of many different materials, such as ceramics, oxides, and metals, which allows for the modification of the chemical properties of the material.

[0019] To minimize the porosity of the coating layer, the particle size of the powder is important and, as is well known to those skilled in the art, must be adjusted for each layer composition and each application. The use of particles with bimodal or multimodal dimensional distributions is particularly preferred.

[0020] This approach offers the advantage of enabling the acquisition of thick layers, particularly those with thicknesses of 80 μm or more, even 100 μm or more, even 150 μm or more, even 200 μm or more, even 250 μm or more, even 300 μm or more, and even 350 μm or more. Advantageously, the second step, which involves depositing a surface coating, deposits material thicknesses between 20 μm and 400 μm, even between 80 μm and 400 μm, and even between 150 μm and 350 μm, either as a single layer of the same material or as multiple layers of different materials.

[0021] Alternatively, other spraying or deposition techniques are also possible. Anodizing, in particular plasma electrolytic oxidation, can be used. Cold spraying is also possible. In the latter case, the cold spraying technique is carried out at a temperature lower than the melting point of the powder and / or lower than the phase transition temperature (e.g., lower than 900°C) to form the high-hardness layer. The cold spraying technique makes it possible to coat temperature-sensitive part blanks and / or deposit powder while maintaining its structure. The spraying technique is adapted, in particular, to the material used. In any case, the selected coating technique offers the advantage of allowing the coating to be deposited as a thick layer, especially at the thickness values ​​mentioned above.

[0022] Therefore, spraying makes it possible to obtain a thick layer of coating. Advantageously, the particles are sprayed in combination with a binder, in the form of simultaneous spraying of powders of different materials, which makes it possible to obtain a particularly high-quality surface coating layer. Alternatively, it is also possible to spray the particles without a binder. As a further alternative, black cermets, for example, of the Al2O3-Ti or Al2O3-Cr type, can be used to obtain a polishable, black sample with a hardness of about 500 HV. Alternatively, other materials can be used, for example, carbides, nitrides, and / or oxides of metallic elements such as Ti, Al, Cr, and Zr. Therefore, spraying makes it possible to obtain a thick layer formed from, for example, TiN, TiC, or TiCN, from Cr2O3, from Al2O3, or from ZrO2. Advantageously, oxide, carbide, or nitride particles are sprayed in combination with a binder, and more generally, the coating is in the form of a ceramic-metal composite material. By adjusting the relative content of ceramic and metal, it is possible to change the properties of the coating material, such as toughness and hardness. One advantage of this approach stems from the fact that spraying technology is compatible with a wide range of materials.

[0023] The sprayed particles are, more advantageously, in the case of thermal spraying, in a semi-paste state so that they disperse upon impact and form a uniform and high-density layer. In contrast to the solid particles (or "cold particles") that produce an irregular structure in the case of the aforementioned "cold" spraying, which is particularly well suited to blanks made of material based on high-temperature sensitive first materials, the term "semi-paste state" means a semi-solid or semi-liquid state. The resulting coating layer may therefore have low porosity and be slightly coarsely condensed.

[0024] Thus, the core of the external parts of the clock forms a substrate that receives a surface coating. The first material of the core (or the substrate formed by it) may be a metal alloy such as steel (e.g., 904L steel or other stainless steel), or a magnesium alloy (e.g., ZK60), or a titanium alloy (e.g., Grade 5 Ti), or an aluminum alloy. The first material may be a metal, or a metal alloy, or a metal superalloy, and / or an amorphous or partially amorphous alloy, including elements such as Fe, Mg, Al, Ti, Au, Pd, Pt, Ni, Si, and / or Co, among others. Alternatively, it may be a ceramic, particularly a ceramic based on alumina or zirconia.

[0025] The difference in the coefficient of thermal expansion of specific materials such as metals and ceramics induces stress when the temperature changes. The selection of the first material of the core, the shape of the core, and the surface finish advantageously takes this aspect into account. Optionally, it is also possible to heat the core to a specific temperature (which varies depending on the composition of the core, the atmosphere, and the pressure in the deposition chamber) to minimize the generation of stress when the surface coating is sprayed.

[0026] According to other embodiments, the second step of depositing at least one surface coating layer may be carried out using additive manufacturing. For this reason, the second step of depositing at least one layer of the surface coating enables the formation of at least one high-hardness layer.

[0027] According to one embodiment, the second step of depositing at least one layer of the surface coating may include a plurality of substeps for depositing the coating, i.e., the creation of superimposed layers resulting in a surface coating consisting of a plurality of distinct layers. In such a case, these layers may be produced by a single modified embodiment of the above-described modification or by different modified embodiments. In addition, these layers may be made of the same material or different materials. For example, it is possible to combine a thick first layer within the same coating that provides hardness and protection of the substrate (e.g., WC+Co-Cr, 250 μm thick, giving a hardness of 900 to 1200 HV) with a subsequent second layer made of another material that provides appearance or color (e.g., Grade 5Ti, up to 20 μm thick, or more generally, a metal or metal alloy of e.g., Au, Ag, Pt, Pd type, with a thickness between 500 nm and 20 μm).

[0028] In all cases, the second step allows for the formation of at least one layer of high-hardness coating, which itself may represent a surface coating.

[0029] Of course, it is also possible to combine the various modified embodiments described above to enable obtaining a part in which at least the first surface achieves high hardness. For example, the first surface may be coated according to one of the modifications described above, and a separate second surface may be coated according to another of the modifications described above, thereby enabling the two separate surfaces to have different hardness and / or different materials. In any case, the resulting watch exterior part component is provided with a high-hardness surface, which extends over all or part of the component. The high-hardness surface is formed by a coating made of a ceramic-metal composite material.

[0030] On the other hand, as described above, it is possible to treat only a portion of the surface of a component according to the present invention. For example, certain surfaces of a component with a very complex shape may be left untreated. According to other embodiments, certain surfaces of a component intended to perform a specific function, such as surfaces that are combined with other components or surfaces that are held by the user, may also not be subjected to the treatment according to the present invention. For example, these untreated surfaces may be, for example, screw threads or bar / bullet holes, surfaces that assemble the case body or bezel or case back or the crown or push piece or bracelet strap elements, or surfaces that assemble the oscillating weight or pockets on the movement ébauche. These may also be surfaces that serve as an interface with the user, such as the surface of a push piece or the crown.

[0031] According to one advantageous modified embodiment, the core structure is configured to optimize adhesion, particularly on the external surface forming a substrate intended to receive a surface coating. For this reason, the method may include an optional intermediate step of preparing the surface of a watch external part blank by creating roughness on the surface, or by forming a suitable chemical composition, particularly by sandblasting, prior to the step of depositing the surface coating. Sandblasting may be used, for example, to obtain a roughness Ra between 3 and 10 μm, with a target value of 5 μm. Very light sandblasting may be preferred on substrates with lower hardness. Therefore, it is preferable to prepare the substrate surface by appropriate treatment, such as mechanical treatment (e.g., sandblasting) and / or localized heating (using a laser, electron beam), in order to obtain particularly suitable surface roughness and / or chemical composition.

[0032] Therefore, in all cases, the method comprises a first step of obtaining a watch exterior component that forms the core of the watch exterior component, and a second step of depositing a surface coating on the core, the coating being made of a ceramic metal composite material based on tungsten carbide and cobalt-chromium, or tungsten carbide and iron-chromium, to form a hard surface of the watch exterior component with a hardness of 500 HV or more, more preferably 600 HV or more, more preferably 750 HV or more, or more preferably 900 HV or more. More generally, in all cases, the hard surface may be based on or made of a ceramic metal composite material.

[0033] The method then includes an optional intermediate step, which may include grinding and / or polishing and / or textureping and / or microbead blasting of the hard surface of the watch exterior parts. Such an optional step may offer the advantage of removing surface roughness and surface oxidation resulting from the spraying and / or correcting geometric defects caused by deposition and / or reducing surface roughness. The intermediate step may be carried out by any traditional mechanical or chemical means. The intermediate step may also be carried out directly by laser treatment, as described below, following deposition, depending on the desired final appearance.

[0034] Such optional intermediate steps may also contribute to the creation of a simpler and / or more accurate final shape of the part blank. For example, it is possible to machine a part so that it is intentionally smaller than a standard, such as a case body that is approximately 200 μm smaller than the standard. The deposition of the surface coating described above includes a thickness that significantly exceeds the amount smaller than the standard. Finally, a portion of the thickness of the surface coating is removed by mechanical grinding using a special grinding gear. For example, in the case of a case body smaller than the 200 μm standard, a 400 μm thick coating is produced, and then approximately 200 μm of thickness is removed.

[0035] A variation of this approach allows for a simpler way to reach the final shape of a part compared to what was previously required to directly obtain the same shape on a blank without using a coating. This can be achieved by applying the method unevenly to various treated surfaces of the part so that the produced coating alters the shape of the blank, thereby advantageously defining the final shape of the part blank. For example, it is possible to create the simplest possible part blank using press working, then apply a surface coating to obtain a more complex final part surface than that obtained before press working, and subsequently machine the surface coating. The aforementioned reduction of the part blank below a certain size is not necessarily applied proportionally. It is also possible to deposit and / or remove a variable thickness of the surface coating. Optional steps of grinding and / or polishing contribute to creating the final shape of the part in such cases.

[0036] The manufacturing method then includes an optional third step of laser structuring of the hard surface of the part in order to form a relief and / or color scheme on the hard surface. In particular, depending on the laser settings, it is possible to form a relief on the hard surface and / or further produce a color scheme on the hard surface.

[0037] According to one embodiment, the third step of structuring using a laser includes satin finishing, soft sandblasting, or sandblasting of the hard surface.

[0038] The deposits obtained in the above-described surface coatings have the specific characteristic of sometimes forming a surface with a high degree of roughness. The third finishing step of the method of the present invention makes it possible to achieve a surface finish with sufficient, non-porous, and roughness that meets technical and aesthetic objectives, as well as an advantageous aesthetic appearance, through the use of a laser. One particularly challenging technical problem is actually obtaining such an acceptable surface appearance. While producing a thick coating according to the embodiments of the present invention offers the advantage of being robust against potential delamination, among other things, it carries the risk of exhibiting surface defects or microporous structures that are typically encountered after certain mechanical treatments of such surfaces.

[0039] Performing finishing work using laser structuring surprisingly makes it possible to alleviate the technical problem. In particular, in addition to obtaining the desired roughness, and more specifically the desired structuring and / or coloration using laser processing, the laser processing also makes it possible to fill and / or close any remaining porosity, perhaps through localized melting of one or more components of the coating.

[0040] The present invention also allows for the formation of several different structures through specific use of lasers, depending on the desired final appearance. Several different laser treatments may be combined on the same hard surface of the part.

[0041] For example, tests were conducted in-house on blanks made of steel and magnesium alloy, known as reference number ZK60, which were surface-ground and polished and coated with a layer of WC+CoCr produced by thermal spraying as described above. Other tests were conducted using blanks coated with a layer of WC+CoCr material, which were then textured with a relatively strong satin finish and subsequently subjected to various laser finishing treatments. These finishing treatments allowed for the formation of laser soft sandblasting, laser sandblasting, and laser satin finishes. Other tests were carried out with additional laser treatments to form color schemes, exhibiting a wide variety of appearances obtainable by this approach according to various embodiments of the present invention. Multiple different plates, each with its own initial texture, either macrobead-blasted or satin-finished, were produced with color schemes ranging from gray through gold to brown. As a variation, other colors such as navy blue (dark purple), blue, or green can also be obtained while maintaining the structure.

[0042] These structuring and coloration tests were performed on the hard surfaces of these blanks using two consecutive laser treatments: a first laser treatment to obtain surface structure and finish, and a second laser treatment to obtain coloration. Surprisingly, the second laser treatment did not affect, or significantly impair, the structuring obtained by the first laser treatment; that is, no changes to the structuring were visible to the naked eye. According to modified embodiments, it is possible to combine several laser finishing substeps to form several surface structures, the effects of which, in particular, structuring and coloration are combined. Those skilled in the art will know how to optimize the laser parameters to obtain the desired results.

[0043] Other technical problems arise in the case of watch external parts with complex shapes, such as the case body. In particular, an additional objective of the present invention in such cases is to obtain a uniform appearance on all surfaces of the part, especially at contact points where different surfaces meet (for example, at the contact point between the side wall of the case body and the top surface of the case body). For this purpose, the processing equipment used in the context of the present invention is capable of controlling the tracking of complex surfaces and contact points between two surfaces. In one embodiment, the method, particularly in the third step of the method, performs tracking of the point where the laser is focused, based on the three-dimensional shape of the part defined by a CAD file or based on measurements of the three-dimensional surface.

[0044] The present invention also relates to, but is not limited to, the parts obtained by the manufacturing method according to the present invention, particularly to external watch parts.

[0045] Therefore, the present invention makes it possible to form any watch component, which comprises a core coated with a surface coating made of a ceramic metal composite material based on tungsten carbide and cobalt-chromium, or tungsten carbide and iron-chromium, the coating comprising a hard surface with a hardness of 500 HV or more, more preferably 600 HV or more, more preferably 750 HV or more, and more preferably 900 HV or more.

[0046] Such external watch components may include a core made of the first material, which is covered with a coating that includes a hard surface made of a second material different from the first material. In such cases, the coating may have a thickness between 20 μm and 400 μm, more specifically between 80 μm and 400 μm, more specifically between 150 μm and 350 μm, more specifically between 20 and 200 μm, and more specifically between 60 μm and 100 μm. The coating may have a degree of porosity of 0.5% or less, more specifically 0.1% or less, more specifically 0.05% or less, and more specifically 0.01% or less, and / or the core may have a degree of porosity higher than that of the coating, and / or the degree of porosity of the core may be 0.5% or less.

[0047] The present invention is particularly suitable for the manufacture of watch components, such as case bodies, bezels, case backs, crowns, push pieces, clasp parts, or bracelet strap elements, especially links or link assemblies or fasteners, or oscillating weights, or plates or bridges.

[0048] Furthermore, according to certain versions of the present invention, at least a portion or one area of ​​a component, in particular a watch component, may include a constructed hard surface, and the remainder of the component may have other, in particular conventional, structures. For this reason, the present invention also relates to a watch component that includes a constructed hard surface only in a specific portion. In a modified example, the watch component may include several different portions, each containing a differently constructed hard surface.

[0049] The present invention also relates to a clock, particularly a wristwatch, including the clock component.

[0050] Ultimately, the present invention makes it possible to combine two primary objectives of watch components that have not been achieved before. The present invention makes it possible to successfully form components that are hard, resistant, and have a thick surface layer that is particularly resistant to scratches, while also having an aesthetically pleasing, long-lasting, and durable appearance that can exhibit a variety of looks.

[0051] Thanks to the deposition of the coating, particularly by spraying, a hard and thick surface coating can be obtained, which is completely resistant to delamination, has a long-lasting aesthetic appearance, and has considerable flexibility in terms of the chemical properties of the coating, making it particularly compatible with a wide range of powders and chemical properties. For example, it is also possible to functionalize the coating by laser structuring and / or to obtain soft sandblasted, sandblasted, or satin-finish type surface conditions and finishes.

Claims

1. A method for manufacturing the surface of watch components, particularly external watch components, wherein the method is: A step of obtaining a watch part blank to form the core of the aforementioned watch part, A step of depositing a surface coating on the core, wherein the coating is made of a ceramic-metal composite material in order to form a hard surface of the watch component with a hardness of 500 HV or more, more specifically 600 HV or more, more specifically 750 HV or more, and more specifically 900 HV or more. The steps include, Manufacturing method.

2. The ceramic metal composite material is based on tungsten carbide and cobalt-chromium, or on tungsten carbide and iron-chromium. The manufacturing method according to claim 1.

3. The step of depositing the surface coating is carried out by thermal spraying or cold spraying, particularly at a high temperature of 800°C or higher. The manufacturing method according to claim 1 or 2.

4. The step of depositing a surface coating involves depositing a material thickness between 20 μm and 400 μm, more specifically between 80 μm and 400 μm, or more specifically between 150 μm and 350 μm, or depositing a material thickness of 80 μm or more, more specifically 100 μm or more, more specifically 150 μm or more, more specifically 200 μm or more, more specifically 250 μm or more, more specifically 300 μm or more, or more specifically 350 μm or more, as a single layer of the same material or as multiple layers of different materials. The manufacturing method according to any one of claims 1 to 3.

5. The method includes a preliminary step of preparing the surface of the watch component blank by creating roughness on the surface, particularly by sandblasting, or by forming a suitable chemical composition, prior to the step of depositing a surface coating. The manufacturing method according to any one of claims 1 to 4.

6. The method includes the steps of grinding and / or polishing and / or texture and / or microbead blasting the hard surface. The manufacturing method according to any one of claims 1 to 5.

7. The method includes a step of laser structuring the hard surface in order to form a relief and optionally a color scheme on the hard surface. The manufacturing method according to any one of claims 1 to 6.

8. The step of depositing the surface coating is not performed over the entire surface of the blank, and surfaces having complex shapes and / or screw threads or bar / bullet holes, which are intended to be assembled with other parts or gripped by a user, are not covered by the step of depositing the coating. The manufacturing method according to any one of claims 1 to 7.

9. Watch components, particularly external watch components, the components include a core covered with a surface coating made of a ceramic metal composite material, particularly based on tungsten carbide and cobalt-chromium or tungsten carbide and iron-chromium, the coating including a hard surface with a hardness of 500 HV or more, more specifically 600 HV or more, more specifically 750 HV or more, and more specifically 900 HV or more. Watch parts.

10. The core is made of a first material that is solid or has a degree of porosity of 0.5% or less, and even 0.1% or less. The watch component according to claim 9.

11. The coating has a thickness between 20 μm and 400 μm, more specifically between 80 μm and 400 μm, more specifically between 150 μm and 350 μm, more specifically between 20 and 200 μm, and more specifically between 60 μm and 100 μm. The watch component according to claim 8 or 9.

12. The coating has a degree of porosity of 0.5% or less, more preferably 0.1% or less, more preferably 0.05% or less, and / or the core has a degree of porosity higher than that of the coating. A watch component according to any one of claims 9 to 11.

13. The hard surface includes a structure obtained using a laser that forms a relief and optionally a color scheme on the surface. A watch component according to any one of claims 9 to 12.

14. The aforementioned component is an external watch part, selected from the case body, bezel, case back, crown, push piece, part of the clasp or bracelet strap element, particularly a link or link assembly or fastener, or the aforementioned component is a watch movement part, such as a oscillating weight or a movement ébauche such as a plate or bridge. A watch component according to any one of claims 9 to 13.

15. A clock comprising at least one component as described in any one of claims 9 to 14.

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