Classifications

• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B19/00—Indicating the time by visual means
  • G04B19/06—Dials
  • G04B19/12—Selection of materials for dials or graduations markings
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
  • C23D5/00—Coating with enamels or vitreous layers
  • C23D5/06—Coating with enamels or vitreous layers producing designs or letters

Definitions

• the present invention relates to an enamel dial for a watch, as well as to a method for manufacturing an enamel dial.
• Enamel dials have been known for a very long time in the field of watches and clocks. Such dials have been used more particularly for clocks, clocks and for pocket watches. All these dials are round in shape and the enamel is generally deposited on a copper substrate, flat or curved.
• the enamel dials of non-circular shape pose problems of adhesion and difference in coefficient of expansion between the substrate and the white enamel.
• a finishing flux which is a layer of transparent enamel
• cracks can occur in the finishing flux, especially in curved areas of the dial shape, due to the too low hardness of the white enamel which behaves like a moving element.
• the fondant layer does not adhere to white enamel.
• the painted coating deposited on the white enamel layer also poses a problem of deformation of the painted lines. This distortion problem is particularly apparent when letters or numbers are painted, especially when it comes to Roman numerals, consisting of straight lines.
• the object of the present invention is to solve the above problems in order to be able to remedy the faults found on non-circular enamel dials for watches, more particularly for wristwatches.
• the present invention firstly relates to an enamel dial for watches according to claim 1. It also relates to a method of manufacturing an enamel dial for watches, of non-circular shape according to claim 5.
• the substrate used in these examples is mild steel with a very low carbon content, less than 0.08% and preferably 0.004%. These are cold-rolled sheets for vitrification glazing.
• the steels used are designated DC03ED or DC04ED according to European standard EN 10027-1.
• Degreasing can be done either by burning, by treatment with hydrocarbons, or by alkaline degreasing, followed by several rinses. This operation is followed by pickling with dilute sulfuric acid (60 to 90g of concentrated acid with a density of 1.84 / l of water), for ten minutes at a temperature above 70 ° C, immediately followed by neutralization in a slightly alkaline bath at 0.3-0.5% Na 2 O at 65-80 ° C, then drying with hot air.
• dilute sulfuric acid 60 to 90g of concentrated acid with a density of 1.84 / l of water
• the substrate thus prepared is then ready to receive a layer of mass enamel which on the one hand constitutes an agent of adhesion between the support and the white enamel covering which will be deposited later, on the other hand makes it possible to balance the expansions between the substrate and the white enamel covering.
• This mass enamel layer also makes it possible to absorb the gases which emanate from the sheet during cooking.
• the mass enamel used in the following examples has the following composition, expressed in g: Hard frit 40 20 20 Medium frit 40 40 30 Soft frit 20 40 50 Quartz 10 Clay 6 bentonite 0.25 Sodium nitrite 0.10 Borax 0.50 Magnesium carbonate 0.15 Water 50 to 55
• the enamel slip prepared using this composition is ground until the desired fineness and density are obtained, determined experimentally, it being understood that too great a fineness increases the surface tension of the enamel and may cause withdrawal. Then it is passed through a magnetic separator to remove the ferrous particles.
• the mass enamel layer is deposited on the entire substrate (front, back and edge) using a spray gun, followed by drying intended to remove the water before the enamel is cooked. mass. All the usual drying methods can be used, in the open air, in an oven or by radiation.
• the mass enamel is fired in an electric box oven heated between 760 ° and 860 ° C so as to obtain a uniform coating.
• the preparation of white enamel is made from commercial products available in powder form or in pieces. In either case, this product must be ground to obtain a fine powder with regular grains, the size of which is around 10 to 15 ⁇ m.
• the grinding is preferably carried out in an agate grinder. Distilled water is added to the powder and the grinding is interspersed with several washes to remove the impurities and the silt formed by the finest particles of enamel which remain in suspension in the water.
• the enamel obtained is then acidified using nitric acid diluted to 40% (60% acid in 40% water) to dissolve the non-assimilated metallic elements within the enamel, the various salts derived enamel during grinding (silt) and to dissolve organic matter which may be in suspension in water.
• Another effect of the acidification of the enamel is to harden it. This hardening is directly linked to the proportion of acid introduced into the enamel slip, which makes it possible to adjust the hardness of the enamel layer, as will be explained below.
• the good hardness of the white enamel is the condition so that the finishing fondant layer does not crack, in particular at the level of the curve.
• the tests carried out have shown that the hardness of the white enamel must be between 5 and 6, preferably around 5.5, on the Mohs scale, used to measure the hardness of mineral materials.
• the good hardness of the white enamel is the condition so that the lines painted on its surface do not deform.
• the hardness measurement on the Mohs scale is a rough measurement, lacking in sensitivity in the case of the present invention.
• this hardness is adjusted based on the deformation of the paint lines on its surface, as well as on the absence of cracking of the finishing fondant layer, that is to say - say according to the result obtained.
• the adjustment of this hardness varies from one enamel to another and can only be determined empirically. However, for the same enamel, this adjustment is perfectly reproducible.
• the enamel Once the enamel has been ground to the desired particle size and acidified, it is stored in airtight containers. Part of the enamel is wetted with distilled water, the other part is dried. The wet enamel is applied with a brush and then dried before being baked between 700 ° and 790 ° in an oven box. It is then slowly cooled and then degreased with industrial alcohol.
• a second layer of dried enamel is then applied, using a very fine sieve, and a second firing is carried out. Finally, apply a new layer of dried enamel followed by firing. When the enamel is cold, it is degreased and ironed in the oven to even out the three layers.
• the enamel is then stoned with 15 ⁇ - 9 ⁇ sandpaper and water to avoid overheating, until a regular desired thickness is obtained over the entire surface of the dial.
• the final equalization is carried out after a further degreasing with alcohol, by ironing the dial in the oven between 700 ° and 790 ° C.
• the frosted enamel during stoning becomes vitrified and tightened. This can be repeated if necessary.
• the thickness of the dial is at most 1.1 mm, including the thickness of the substrate, that of the mass enamel covering the two faces of the substrate and that of the white enamel.
• the next step is to deposit the paint.
• This painting includes the numbers and the characters intended to indicate the hours, the minutes and various indications relating in particular to the mark.
• This paint can also be decorative and include several colors, using the usual vitrifiable paints sold for enamel and which generally consist of metallic oxide pigments which are mixed with a fatty essence or another suitable dispersion medium. , in a proportion depending on the desired consistency.
• vitrifiable colors are ground very finely and are applied with a brush to the white enamel, then they are fired between 750 ° C and 830 ° C, which has the effect of vitrifying the colors and embedding them in the white enamel.
• the last step is to apply the finishing fondant.
• This fondant is prepared by alternating grinding and washing as for white enamel without the addition of nitric acid, for approximately 35 minutes. The purpose of this operation is to improve the transparency of the fondant finish. When sufficiently ground and washed, the finishing fondant is dried.
• the total thickness of the finishing fondant layer is of the order of 0.1 mm.
• the paint adapts perfectly to the texture of the white background and the finishing flux does not crack during stoning.

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• Chemical & Material Sciences (AREA)
• Metallurgy (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Organic Chemistry (AREA)
• Glass Compositions (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Magnetic Heads (AREA)
• Physical Vapour Deposition (AREA)

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• 2002
  • 2002-10-22 EP EP02405902A patent/EP1413649A1/de not_active Withdrawn
• 2003
  • 2003-10-17 DE DE60323117T patent/DE60323117D1/de not_active Expired - Lifetime
  • 2003-10-17 AU AU2003269661A patent/AU2003269661A1/en not_active Abandoned
  • 2003-10-17 WO PCT/CH2003/000678 patent/WO2004038066A2/fr active IP Right Grant
  • 2003-10-17 EP EP03750226A patent/EP1554415B1/de not_active Expired - Lifetime
  • 2003-10-17 AT AT03750226T patent/ATE405691T1/de not_active IP Right Cessation
• 2005
  • 2005-07-26 HK HK05106355.1A patent/HK1074062A1/xx not_active IP Right Cessation

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