• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a method for producing a component (1) of a watch case made of boron carbide, the method comprising the following steps: providing boron carbide powder; Compacting the boron carbide powder into a preform component under high pressure; Machining the preform component into a chamfered component having a shape approximating the shape of the housing components; Sintering the machined component into a dense sintered component; and grinding and edge grinding the sintered components to obtain the housing components contained in the watch case (1); wherein the shape of the casing components is a three-dimensional shape comprising substantially flat and curved portions with a general dimensional tolerance of ± 0.05 mm and a general angular tolerance of ± 30 arcminutes.
    公开号:CH710903A2
    申请号:CH00402/15
    申请日:2015-03-19
    公开日:2016-09-30
    发明作者:Speicher Ferdinand；Giger David；Graf Andreas
    申请人:Richemont Int Sa；
    IPC主号:
    专利说明:

    area
    The present invention relates to a method for producing a component of a watch case made of boron carbide and a component of a watch case made by this method.
    Description of the Related Art
    A watch case typically comprises four major components: a central portion, a glass or crystal, a crystal surrounding bezel mounted on the central portion, and a bottom which is mounted below the central portion. The bezel or base together with the central portion may, in some instances, be molded from a single piece, and the central portion typically includes two pairs of protruding horns or handles (or occasionally a protruding central handle or 3 or more pairs of protruding handles), normally aligned in a line with the numbers 12 and 6 o'clock and arranged on both sides of the watch case to allow the case to be attached to a watch band. The middle part of the clock encloses the movement. It is typically made of solid metal material.
    The use of a technical ceramic material for watch case has the advantage of being solid and robust, with a rated at the upper end of the Mohs scale hardness and high scratch resistance. Typically, a technical ceramic such as boron carbide has properties similar to diamond in terms of hardness and scratch resistance.
    In addition, technical ceramic materials have a high melting point as well as a low density and a light weight. They also have good resistance to chemical agents (and are thus skin friendly), are nonmagnetic, and generally have properties which allow reproducible finishing, e.g. in terms of polishing. The surface of engineering ceramics also has a metallic luster, which is often an essential feature of watch cases.
    Document FR 2 316 643 discloses a silicon carbide watch case obtained by sintering silicon carbide powder under an inert atmosphere in which a few weight percent (less than 5 weight percent) boron carbide is added.
    The document WO 2012 119 647 describes a composite material with a combination of a noble metal or a precious metal-containing alloy and a boron-based ceramic having a melting point higher than that of the noble metal and a density of at most 4 g / cm 3 , The material can be used for a watch case.
    Components made of hard materials such as engineering ceramics are generally made by molding and sintering, and are subject to dimensional variations - especially through shrinkage during the sintering process - which do not allow to obtain accurate final dimensions from the unprocessed parts.
    As a result, assembling the watchcase components from engineering ceramics such as e.g. Central portion of the watch case, bezel and / or base prove difficult (e.g., in terms of water resistance) due to the imprecise final dimensions of the watch case components. Precise positioning and centering of the various housing components can be difficult to achieve.
    Summary
    Accordingly, it is an object of the present invention to provide a method for producing components of a watch case made of boron carbide having the empirical formula B4C, which avoids the above-mentioned disadvantages. Boron carbide is a high performance ceramic with similar physical properties (e.g., hardness) as diamond.
    This object is achieved according to the invention by a method for producing one or more components of a watch case made substantially entirely of boron carbide, the method comprising the following steps:Providing boron carbide powder;Compacting the boron carbide powder into a preform component under high pressure;Machining the preform component into a chamfered component having a shape approximating the shape of the housing component;Sintering the machined component into a dense component; andGrinding or edge grinding of the dense component;wherein the shape of the housing components is a three-dimensional shape, which essentially comprises combinations of flat and / or curved sections with a general dimension tolerance of ± 0.05 mm and a general angular tolerance of ± 30 arcminutes (± half an arc degree).
    The shape of the housing components may have specific tight tolerances that are well below the general tolerances, which, as mentioned above, assures proper assembly and perfect functioning of the watch case, similar to one made of metal.
    The invention also relates to components of a watch case manufactured by the method disclosed herein and to a watch case having at least one of the case components.
    The inventive method enables the manufacture of components of a boron carbide watch case with a complex three-dimensional shape and low and low dimensional and angular tolerances that allow for the achievement of accurate final dimensions as well as the accurate assembly of the manufactured watch case components.
    Brief description of the drawings
    The invention will be better understood with reference to the given example of an embodiment and illustrated by the figures; show it:<Tb> FIG. 1 <SEP> is a top view of a watch case, according to an embodiment;<Tb> FIG. 2 <SEP> a bottom view of the watch case;<Tb> FIG. 3 <SEP> is a cross-sectional view of the watch case along a line from 3 o'clock to 9 o'clock in FIG. 1; and<Tb> FIG. 4 <SEP> is a cross-sectional view taken along a second B-B in FIG. 3.
    Detailed description of possible embodiments
    Fig. 1 shows a top view of a watch case 1, comprising components of a watch case with a central part 2 of the watch case, a bezel 3 to the crystal 8, a bottom 5 with a ring 6 to the bottom glass 10, two crown protection parts. 7 and two pairs of handles or horns 4. According to one embodiment, at least one of the components of the watch case is made substantially entirely of the high performance ceramic boron carbide (B4C). In a preferred embodiment, all of the above-mentioned components are made substantially entirely from boron carbide.
    Boron carbide is a covalently bonded solid having a complex rhombohedral crystal structure, having a high melting point (about 2400 ° C and more), an extremely high hardness compared to other ceramics (Vickers hardness: about 2400 kg / mm 2) > and more), a low density (about 2.52 g / cm 3) and a high neutron absorption cross section (eg good shielding properties against neutrons). It is a high-performance ceramic material which contains the dopant carbon as an additive in the range of up to 8.8 to 20.0 mol%. Boron carbide has been used in many engineering applications, such as light ceramic armor (e.g., inboard ballistic vests), wear resistant components (e.g., blasting nozzles and abrasive wheels), and controls in nuclear power plants.
    Table 1 compares the properties of zirconia (ZrO 2) ceramics with the properties of boron carbide. Zirconia is one of the most widely used ceramics for the manufacture of ceramic watch cases.
    As can be seen from Table 1, boron carbide is lighter, brittle, stiffer and more temperature resistant than zirconia.<Tb> density <September> g / cm <3> <September> 6.1 <September> 2.5<Tb> bending strength <September> MPa <September> 1450 <September> 500<tb> Young's modulus <SEP> GPa <SEP> 210 <SEP> 460<tb> Vickers hardness <SEP> GPa <SEP> 1300 <SEP> 3200<tb> Maximum application temperature <SEP> ° C <SEP> 1500 <SEP> 2000<tb> Table 1 <SEP> <SEP> <SEP>
    Fig. 2 shows a view from below of the watch case 1 and Fig. 3 shows a cross-sectional view of the watch case. According to one embodiment, the components may be monolithic or multiple components may be used to form a composite watchcase 1. In other words, one or more components of the watch case, including the central part 2 with horns 4, the bezel 3, two Kronenschutzteiie 7 and a bottom ring 6 can be made of boron carbide. Other watch components such as crowns, drivers, slides, rockers, clamps, etc., may also be made of boron carbide. In one embodiment, the entire watch case, including all components of the watch case, can be made of boron carbide. Fig. 4 shows a cross-sectional view taken along a line B-B in Fig. 3, wherein the middle part 2 and the Kronenschutzteiie 7 are shown from the top view.
    Because of their chemical structure, ceramic materials can not be melted. The raw material is a powder which is converted into an end component by a multi-step process.
    According to one embodiment of a method for producing at least one of the components made entirely of boron carbide of a watch case, the method comprises the following steps:Providing boron carbide powder;Compacting the boron carbide powder into a preform component under high pressure, and preferably substantially under vacuum;Machining the preform component into a chamfered component having a shape approximating the shape of the housing component;Sintering the processed component to obtain a dense component; andGrinding the sintered component to obtain the housing component.
    The boron carbide powder is pressed or cast into a compact green tea density component.
    During the densification step, the powder particles are brought into close contact under high pressure to produce a "preform" component, also known as a green body. The green part has a low inherent rigidity, which is comparable to blackboard chalk. The shape of the green body in general is similar but not identical to the shape of the finished housing component.
    The low inherent rigidity of the green part allows a relatively simple processing. During the first manufacturing step, the shape of the "preform" component can be fluted using methods known from mechanical processes such as drilling, turning, milling and grinding to form a prefabricated component having a net shape as close as possible to the component of the finished housing component to obtain. Because of the extreme hardness of boron carbide, the processing step is significantly more demanding, more tool-abrasive, and more complex than other engineering ceramics (e.g., alumina, zirconia). In addition, slicing the green part is more important for boron carbide than for other ceramics because the ultimate very high hardness of the material results in reduced opportunities to grind the sintered complex shaped component to high tolerances. Preferably, the cutting step is carried out by means of extremely technical machine tools with diamond coatings.
    The sintering of pure boron carbide to high densities has proved difficult. In one embodiment, specific additives including sintering aids such as carbon, Al 2 O 3 and TiB 2 are added to the boron carbide powder to achieve near full density. Other possible additives that can be added to the boron carbide powder include a "debinding agent". The mixing of these additives with the ceramic powder having a defined grain size is crucial for the final properties of the ceramic component.
    The sintering step can be carried out by hot pressing the boron carbide powder at a sintering temperature above 2000 ° C, for example at about 2100 ° C and under 30-40 MPa uniaxial pressure to obtain dense components. During the sintering step, the green part is sintered into a dense sintered component. During the sintering step, the powder particles are brought into close contact with each other and baked by the high sintering temperatures, whereby the interparticle pores are substantially eliminated. At the same time, the processing aids are dissolved and removed from the sintered component resulting in a shrinkage of the sintered component of between about 20-30%. The sintering step should be controlled to prevent the formation of pores, even very small pores, which could result in breakage of the sintered component during a subsequent cooling step or during later assembly and waterproofing control processes.
    Alternatively, the boron carbide powder may be processed by using a pressureless sintering system such as that described in Lee and R.F. Speyer, "Pressureless Sintering of Boron Carbide," J. Am. Ceram. Soc., 86 [9] 1468 73 (2003). Here, the preform component is placed (placed) in a furnace system of the pressureless sintering system and the furnace is heated to a temperature of the order of about 1100 to 1400 ° C in a H2 / He gas mixture for about 30 to 120 minutes. Thereafter, the furnace plant is emptied for about 120 to 140 minutes to remove substantially residual H2 in a vacuum or in a He atmosphere. Subsequently, the boron carbide powder is sintered by pressureless sintering without sintering additive at about 2300 to 2400 ° C at a heating rate of 100 ° C / minute. The heating rate is set to avoid co-particle coarsening in the temperature range of about 2000 to 2150 ° C, which would otherwise reduce the driving force for sintering. The sintered component has at least 93% relative green density (RD) and a Vickers hardness of more than 2000 kg / mm 2.
    The sintered component may be further processed using hot isostatic pressing (eg, at 2150 ° C for about 125 minutes at 310 MPa argon) to provide hot isostatic pressed structures having relative densities greater than 93% and a Vickersian pressure. Hardness greater than 2000 kg / mm <2>, and typically provide structures with an RD greater than 99% and a Vickers hardness greater than 2500 kg / mm <2>. Hot isostatic pressing is effective for increasing the relative density of closed porosity components (e.g., sintered components having at least about 93% RD).
    The sintered component may then be subjected to the methods known from mechanical processes, such as grinding, milling and finishing, to obtain the final shape of the finished casing component. The sintered component shows for the first time the extremely high hardness which is characteristic of boron carbide. As mentioned above, boron carbide is one of the hardest known materials and must therefore be ground by diamond-based tools. The grinding step makes it possible to achieve low dimensional tolerances and low angular tolerances. Such tolerances are required for the proper assembly of the various components of the watch case. Because of the extreme hardness of boron carbide, the grinding and finishing step is significantly more demanding than for other ceramics. In particular, the design of the diamond grinding tools and the grinding strategy, including the optimum grinding parameters, must be evaluated and properly selected.
    The grinding and finishing step may include any method that is mechanically applied with various tools and used to obtain surface structures, e.g. polished, satin or blasted finish, is suitable.
    In a preferred embodiment, the grinding and finishing step of the sintered component is performed so that a general mass tolerance of ± 0.05mm and an angular tolerance of ± 30 arc minutes are achieved. It is clear that certain parts of the component may also have tighter tolerances, such as ± 0.015mm.
    The method disclosed herein makes it possible to manufacture components of a watch case having shapes (eg polygons, circles and asymmetrical shapes) with different constant or variable masses (eg length, width and thickness) as well as components with complex shapes and / or two parts. and three-dimensional structures with constant or variable masses, including a variety of curves, dimensions, contours, structural features (eg, lips, reflective areas, security mechanisms, etc.) and the like. The housing components may also be tuned to the shape of areas of the human body such as the wrist.
    reference numbers
    [0033]<Tb> 1 <September> watch case<Tb> 2 <September> midsection<Tb> 3 <September> bezel<Tb> 4 <September> Henkel<Tb> 5 <September> Floor<Tb> 6 <September> bottom ring<Tb> 7 <September> crown protection<Tb> 8 <September> Crystal<Tb> 9 <September> Krone<Tb> 10 <September> ground glass
    权利要求:
    Claims (11)
    [1]
    A method of making at least one substantially completely boron carbide component of a watch case, the method comprising the steps of:Providing boron carbide powder;Compacting the boron carbide powder into a preform component under high pressure;Machining the preform component into a chamfered component having a shape approximating the shape of the housing component;Sintering the machined component into a dense sintered component; andGrinding or edge grinding the dense sintered component to obtain the housing component;the housing component having a three-dimensional shape comprising flat and curved sections with a general dimensional tolerance of ± 0.05 mm and a general angular tolerance of ± 30 arcminutes.
    [2]
    2. The method according to claim 1, wherein certain parts of the housing component also have tighter general tolerances of + 0.015 mm.
    [3]
    3. The process according to claim 1 or 2, wherein the sintering step is carried out at a sintering temperature of over 2000 ° C.
    [4]
    4. The process according to claim 3, wherein the sintering temperature is about 2100 ° C.
    [5]
    The process according to any one of claims 1 to 4, wherein at least one additive is mixed with the boron carbide powder.
    [6]
    6. The process according to claim 5, wherein said at least one additive comprises a sintering aid and / or a debinding agent.
    [7]
    The method according to any one of claims 1 to 6, wherein the housing component is a central part of a watch case (2).
    [8]
    The method according to any one of claims 1 to 7, wherein the component of a watch case comprises at least one of the following: bezel (3), bottom (5) or bottom ring (6) or crown protector (7).
    [9]
    The method according to any one of claims 1 to 6, wherein the component of a watch case comprises an entire watch case (1).
    [10]
    A watch case component obtained by the method according to any one of claims 1 to 8.
    [11]
    11. Watch case (1) with at least one housing component according to claim 9.
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    同族专利:
    公开号 | 公开日
    CH710903B1|2018-09-28|
    CH710903A8|2016-11-30|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2016-10-14| PK| Correction|Free format text: RECTIFICATION INVENTEUR |
    2016-11-30| PK| Correction|Free format text: ERFINDER BERICHTIGT. |
    优先权:
    申请号 | 申请日 | 专利标题
    CH00402/15A|CH710903B1|2015-03-19|2015-03-19|A method of making a component of a watch case made of boron carbide.|CH00402/15A| CH710903B1|2015-03-19|2015-03-19|A method of making a component of a watch case made of boron carbide.|
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