U.S. patent application number 16/381850 was filed with the patent office on 2019-11-07 for method for fabricating timepiece components including a decorative coating of aventurine.
This patent application is currently assigned to Omega SA. The applicant listed for this patent is Omega SA. Invention is credited to Gregory KISSLING, Claire MCGILL.
Application Number | 20190338425 16/381850 |
Document ID | / |
Family ID | 62110922 |
Filed Date | 2019-11-07 |
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United States Patent
Application |
20190338425 |
Kind Code |
A1 |
MCGILL; Claire ; et
al. |
November 7, 2019 |
METHOD FOR FABRICATING TIMEPIECE COMPONENTS INCLUDING A DECORATIVE
COATING OF AVENTURINE
Abstract
A method for fabricating a timepiece component partly formed of
aventurine, including providing at least one piece of aventurine
formed of a mass of coloured glass containing copper crystals
scattered throughout the mass; grinding at least one piece of
aventurine to obtain a granular powder; depositing at least part of
the granular powder on a surface of a support intended to receive a
decorative coating; then introducing the support with the granular
powder deposited on the surface into a furnace and melting this
granular powder so as to obtain, after removing the assembly thus
obtained from the furnace and allowing the assembly to cool, an
enamel layer made of aventurine which covers the support surface.
The timepiece component is, for example, a dial, a moon phase disc
or a bezel.
Inventors: |
MCGILL; Claire; (Neuchatel,
CH) ; KISSLING; Gregory; (Macolin, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Omega SA |
Biel/Bienne |
|
CH |
|
|
Assignee: |
Omega SA
Biel/Bienne
CH
|
Family ID: |
62110922 |
Appl. No.: |
16/381850 |
Filed: |
April 11, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23D 13/00 20130101;
G04B 45/0015 20130101; G04B 19/12 20130101; C23D 5/08 20130101 |
International
Class: |
C23D 5/08 20060101
C23D005/08; C23D 13/00 20060101 C23D013/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2018 |
EP |
18170444.6 |
Claims
1. A method for fabricating a timepiece component partly formed of
aventurine, comprising the following steps: A) providing at least
one piece of aventurine formed of a mass of coloured glass
containing copper crystals scattered throughout the mass of
coloured glass; B) after step A), grinding said at least one piece
of aventurine to obtain a granular powder; C) making a support from
a material having a higher melting temperature than that of said
mass of coloured glass, this support having at least one surface
intended to receive a decorative coating; D) after steps B) and C),
depositing at least part of said granular powder on said support
surface; E) after step D), introducing the support with the
granular powder deposited on said surface into a furnace and
melting this granular powder so as to obtain, after removing the
assembly thus obtained from the furnace and allowing the assembly
to cool, an enamel layer made of aventurine which covers said
support surface and forms a decorative coating.
2. The method for fabricating a timepiece component according to
claim 1, wherein, between steps B) and D), said at least one part
of the granular powder is mixed with a liquid, said step D)
consisting in application of said mixture to said support
surface.
3. The method for fabricating a timepiece component according to
claim 2, wherein a step of drying said mixture deposited on said
surface is performed in a drying furnace prior to said step E).
4. The method for fabricating a timepiece component according to
claim 1, the sequence of steps D) and E) is repeated several times,
so that said decorative coating is formed of a plurality of enamel
layers made of aventurine and deposited one on top of the
other.
5. The method for fabricating a timepiece component according to
claim 1, wherein said granular aventurine powder is formed of
grains of aventurine, most of which are of larger dimensions
between 50 microns and 200 microns.
6. The method for fabricating a timepiece component according to
claim 2, wherein said granular aventurine powder is formed of
grains of aventurine, most of which are of larger dimensions
between 50 microns and 200 microns.
7. The method for fabricating a timepiece component according to
claim 4, wherein said granular aventurine powder is formed of
grains of aventurine, most of which are of larger dimensions
between 50 microns and 200 microns.
8. The method for fabricating a timepiece component according to
claim 1, wherein, after deposition of the enamel layer made of
aventurine, a flux is deposited on the enamel layer and is fired to
form a transparent upper layer of said decorative coating.
9. The method for fabricating a timepiece component according to
claim 4, wherein, after deposition of the plurality of enamel
layers made of aventurine, a flux is deposited on the plurality of
enamel layer and is fired to form a transparent upper layer of said
decorative coating.
10. The method for fabricating a timepiece component according to
claim 1, wherein a final step of polishing said decorative coating
is performed.
11. The method for fabricating a timepiece component according to
claim 1, wherein said support is metal.
12. The method for fabricating a timepiece component according to
claim 1, wherein the timepiece component is a part of a watch case,
notably a bezel.
13. The method for fabricating a timepiece component according to
claim 1, wherein the timepiece component is a part of a watch
movement, notably a bridge or an oscillating weight.
14. The method for fabricating a timepiece component according to
claim 1, wherein the timepiece component is a display element,
notably a dial or a moon phase indicator disc.
15. The method for fabricating a timepiece component according to
claim 14, wherein the inner rim and the outer rim form lateral
stops for said granular powder deposited on said surface during at
least a first sequence of steps D) and E).
16. The method for fabricating a timepiece component according to
claim 15, wherein said support has at least one embossed motif
inside said surface, said motif forming a lateral stop for said
granular powder deposited on said surface during at least said
first sequence of steps D) and E), the motif being eventually flush
with said decorative coating.
17. The method for fabricating a timepiece component according to
claim 14, wherein the timepiece component is a dial which has a
convex upper surface, which is at least partially defined by the
upper surface of said decorative coating.
18. The method for fabricating a timepiece component according to
claim 14, wherein an enamelling process is performed on a surface
of said support on the side opposite to that of said surface
intended to receive said decorative coating, said enamelling
process forming a counter-enamel to conserve the initial shape of
said support.
19. The method for fabricating a timepiece component according to
claim 14, wherein said decorative coating has a thickness of
between 200 and 300 microns.
Description
FIELD OF THE INVENTION
[0001] The present invention concerns a method for fabricating
timepiece components including a decorative coating of aventurine,
in particular a method for fabricating watch dials partially formed
of aventurine.
BACKGROUND OF THE INVENTION
[0002] It has been known for a long time to make watches
incorporating, for decoration, parts made of precious or
semi-precious stones. In particular, it is known to make dials from
precious stones, for example lapis-lazuli, which give watches the
character of jewelry.
[0003] To make dials from precious or semi-precious stones,
firstly, stones are provided which are cut into thin slices, which
are then polished and cut. Current cutting techniques make it
possible to cut various profiles and to make apertures in the thin
slices obtained. It will be noted that, to make the stone dial less
brittle and to ensure its positioning in the watch, those skilled
in the art generally bond fine slices of stone onto metal supports,
preferably made of noble metal.
[0004] Conventional techniques for making dials from precious or
semi-precious stones have also been used to fabricate aventurine
dials. It will be noted that the term `aventurine` was initially
used to describe a particular coloured glass that was formerly made
in Murano glass works in Italy. This coloured glass has a
characteristic sparkle owing to the presence of tiny copper
crystals which are formed when the glass melts at a high
temperature in a furnace and which become larger as the glass
obtained slowly cools. Afterwards, the term `aventurine` was used
to refer to natural stones, in particular coloured quartz stones
which had such a sparkle.
[0005] Aventurine glass can be found in various colours, especially
red, blue and green. Pieces of aventurine glass look like
semi-precious stones, so that those skilled in the art consider
them to be artificial semi-precious stones that are generally
called `aventurine`. Once the available pieces have been cut and
the slices or other shapes have been polished, this aventurine
glass makes the dials or other timepiece components made from these
pieces of aventurine look very much like natural stone. There are
pieces of aventurine that have a deep blue colour, owing to the
presence of cobalt in their composition, which are particularly
valued for horological applications, since the sparkling of the
tiny copper crystals make the dials obtained from these pieces of
aventurine look like a beautiful starry sky.
[0006] To make dials and display discs/rings for timepieces with
aventurine, the person skilled in the art crafts this material as
semi-precious stones or quartz crystals are crafted, by cutting
pieces of aventurine into thin slices which are then bonded to
metal supports. Such dials and display discs/rings adorn the
watches of several watch brands including OMEGA, Jaquet Droz and
Bulgari.TM. watches.
[0007] The fabrication of dials from aventurine as described above
has various drawbacks. Indeed, these aventurine dials are difficult
to prepare and to assemble. Cutting aventurine pieces into thin
slices and cutting the desired profiles into these slices generates
quite a lot of waste. Further, aventurine quite often has small air
bubbles which appear after polishing and which make the thin slices
obtained unusable. Moreover, these thin slices are fragile and
therefore brittle. They are awkward to handle and assembling these
thin slices with their respective supports to make the dials is a
complex operation.
[0008] It will also be noted that even transferring motifs and/or
hour symbols onto slices of aventurine is likely to crack them. If
it is wished to have motifs and/or hour symbols embossed on a dial,
it is possible to make them from metal by an electroforming process
on an aventurine slice; but such a method is generally performed on
the aventurine slice before it is bonded to its support. This
method requires various handling operations, so there is a
significant risk of breaking the slice. It is also possible to
obtain metal motifs and/or hour symbols, particularly made of noble
metal, by structuring the metal support of the dial so that these
motifs and/or hour symbols are in relief relative to the receiving
surface to which the aventurine slice will be bonded. In this
latter case, it is necessary to cut into the aventurine slice
numerous small apertures corresponding to these motifs and/or hour
symbols. However, the process of assembling a thin aventurine slice
thus perforated to its support carries a significant risk of
breaking it. Indeed, the slightest mechanical stress exerted on
such a slice can break it, for example: light pressure exerted on
the slice when the edge of one of its apertures is partially
abutting on a corresponding relief, or simply friction between the
slice and a motif or hour symbol as the slice is set in place. It
is understood, therefore, that it is necessary to have
manufacturing tolerances so that small gaps appear between the
embossed motifs and/or hour symbols and the perforated aventurine
slice, which is detrimental to the aesthetics of the dial and
therefore to its quality.
[0009] Next, it was noted that, even once bonded to their
respective supports, these thin aventurine slices remain fragile
and can crack or break in case of shocks to which watches must
generally be resistant. In case of shocks, it was also observed
that small fragments of aventurine sometimes break away from the
surface of dials coated with aventurine slices. This creates small
crevasses visible to the naked eye, which thus impairs the
aesthetic appearance of these dials. Moreover, these small
fragments can easily get into the watch movements of watches
provided with aventurine dials thus damaged by shocks and impair or
block their functioning.
[0010] Finally, another drawback lies in the fact that possible
embodiments are limited by the fact that flat aventurine slices are
generally used for making dials, so that the dials are flat. It is,
of course, possible to machine pieces of aventurine to make
aventurine glass that is convex, at least on top, but the
manufacturing cost will be very high.
[0011] The aforementioned drawbacks, and possibly also others,
arise as regards decorating other external parts of a watch with
aventurine, for example bezels, or parts of watch movements, for
example bridges or oscillating weights, using techniques similar to
those described above for the fabrication of dials and display
discs/rings, namely cutting portions into a piece of aventurine to
obtain solid aventurine parts which are then polished and bonded to
supports arranged to receive these solid aventurine parts.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide
timepiece components, in particular dials, having at least one
surface coated with aventurine to form a decorative coating, while
overcoming the various problems mentioned in the description of the
prior art.
[0013] To this end, the invention relates to a method for
fabricating a timepiece component partly formed of aventurine,
characterized by the following steps:
[0014] A) Providing at least one piece of aventurine formed of a
mass of coloured glass containing copper crystals scattered
throughout the mass of coloured glass;
[0015] B) After step A), grinding said at least one piece of
aventurine to obtain a granular powder;
[0016] C) Making a support from a material having a higher melting
temperature than that of said mass of coloured glass, this support
having at least one surface intended to receive a decorative
coating;
[0017] D) After steps B) and C), depositing at least part of the
granular powder on said support surface;
[0018] E) After step D), introducing the support with the granular
powder deposited on said surface into a furnace and melting this
granular powder so as to obtain, after removing the assembly thus
obtained from the furnace and allowing the assembly to cool, an
enamel layer made of aventurine which covers said support
surface.
[0019] The fabrication method according to the invention is
remarkable in that a decorative coating is thus obtained which
perfectly provides the aesthetic features of aventurine, namely the
look of a semi-precious stone with the sparkle specific to
aventurine. It is surprising that the time spent in a furnace does
not substantially reduce the sparkling of the tiny copper crystals,
since copper oxidises easily and then has a dull, green or black
colour. Tests performed with enamel powders to which was added a
granular powder of oxidation metal, notably copper, gave negative
results, with no sparkling. In the case of copper filings, the
grains of copper blackened in the furnace. Next, even with
non-oxidation metals, in particular with a gold powder, the
remarkable sparkle of aventurine is not obtained. Further, it is
difficult to obtain a homogeneous distribution of the gold powder
in the enamel.
[0020] In a preferred variant, the sequence of steps D) and E) of
the fabrication method is repeated several times, so that the
decorative coating is formed of a plurality of enamel layers made
of aventurine and deposited one on top of the other. It will be
noted that the plurality of deposited enamel layers eventually
forms only one enamel layer of greater thickness. This decorative
coating thus has a thickness that gives the decorative coating a
certain depth and conceals the support well. However, preferably,
the decorative coating has a thickness of between 200 and 300
microns (200-300 .mu.m). Such a thickness remains relatively small
compared to the aventurine slice made in the prior art which
generally have a thickness of between 400 and 500 microns. The
present invention thus makes it possible to make dials having a
smaller thickness.
[0021] In another preferred variant, after making one or more
enamel layer(s) formed of aventurine, a flux is deposited on the
aventurine enamel obtained and it is fired to form a transparent
upper layer which is homogeneous and has a regular upper
surface.
[0022] In another preferred variant, a final step of polishing the
decorative coating is performed, this polishing can have a
preliminary phase consisting of stone cutting to better level out
the upper surface of the decorative coating. Polishing is made
easier to carry out and the result is generally better when a flux
layer is deposited on the aventurine enamel. Indeed, the cooled
flux layer can be polished to give a perfectly smooth upper
surface, whereas the aventurine enamel is problematic for polishing
due to the presence of copper crystals in the aventurine enamel
which may be at or close to its surface.
[0023] In a particular implementation of the method of the
invention, enamelling is performed on a back surface of the
support, i.e. on the opposite side to that of the surface intended
to receive the decorative coating, this enamelling forming a
counter-enamel to better preserve the initial shape of the support
when one or more enamel layers are formed to make the decorative
coating and to prevent cracks appearing in this decorative coating
as it is made.
[0024] Other particular features of the present invention will be
described below in addition to other advantages of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The invention will be described in more detail below with
reference to the annexed drawings, given by way of non-limiting
example, and in which:
[0026] FIG. 1 is a top view of a dial obtained by a first
implementation of the method for fabricating a timepiece component
according to the invention.
[0027] FIG. 2 is a sectional view of a support forming the body of
the dial of FIG. 1 and intended to receive a decorative coating
according to the invention.
[0028] FIG. 3 is a cross-section of the dial of FIG. 1.
[0029] FIG. 4 represents pieces of aventurine used to make a
decorative coating according to the invention.
[0030] FIG. 5 is microscope magnified image of a granular powder
obtained by grinding, in the context of the present invention,
pieces of aventurine like those represented in FIG. 4.
[0031] FIG. 6 is a top view of a dial obtained by a second
implementation of the method for fabricating a timepiece component
according to the invention, this dial being represented without the
hour symbols which are subsequently arranged on the upper surface
of the dial so as to stand above the decorative coating.
[0032] FIG. 7 is a bottom view of the dial support of FIG. 6.
[0033] FIGS. 8 and 9 are cross-sectional views respectively along
the lines VIII-VIII and IX-IX of FIGS. 7 and 6.
[0034] FIG. 10 is a sectional view, similar to that of FIG. 2, of a
support machined according to the invention to form a convex
dial.
[0035] FIG. 11 is a cross-section, similar to that of FIG. 3, of a
convex dial obtained by the fabrication method of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0036] Referring to FIGS. 1 to 5, there will be described an
implementation of the method for fabricating a display element, in
particular a watch dial, according to the invention.
[0037] To fabricate dial 2, firstly, there is made a support 4 with
a stiff base having the general shape of a disc. This support 4 is
formed of a material having a melting temperature higher than
1000.degree. C. A surface 6, intended to receive a decorative
coating, is machined in the support on its upper side, i.e. on the
side of the dial that is visible once incorporated inside a watch
case. In the variant represented in the Figures, the support is
metal, particularly made of gold or silver, and has motifs 8
intended to be visible in the finished product, these motifs being
integral with the base of the support. In this variant, motifs 8
are the Roman numerals from I to XII. Thus, the number of motifs is
relatively high and some of these motifs, namely the V and the X,
have a contour with a complex shape with sharp inside angles.
Further, the spaces provided between some motifs for receiving the
decorative coating have a small width. Surface 6 is flat and
machined into support 4. The dial has at least one aperture 14
delimited by an inner rim 12 which projects from surface 6; this
support also has an outer rim 10 projecting from surface 6 and
delimiting the external edge of this surface. Dial feet 18 are
secured to the underside of support 4.
[0038] Further, to fabricate dial 2, there is provided at least one
piece of aventurine 20A-20C, which is formed of a mass of coloured
glass containing copper crystals scattered throughout the mass.
Stocks of such pieces of aventurine formerly fabricated in the
Venice area, in particular in Murano, are available and offered for
sale by various specialised companies. These pieces of aventurine
can have various dimensions, notably of several centimetres, and
various shapes. They come from slabs of aventurine formed in the
crucible of glass work furnaces. To form the decorative coating, at
least one piece of aventurine is ground to obtain a granular powder
22. The grain size can be variable. Preferably, in order to damage
as few copper crystals as possible, it is intended not to grind the
pieces of aventurine into too fine a powder, but to obtain a
granular powder formed of grains of aventurine, most of which
having their respective larger dimensions, between 50 microns and
200 microns.
[0039] To make the decorative coating, at least part of granular
powder 22 is deposited on surface 6 of support 4. Next, support 4
and the granular powder deposited on surface 6 are introduced into
a furnace in which this granular powder is at least partially
melted (i.e. is in a viscous state) so as to obtain, after removing
the assembly thereby obtained from the furnace and allowing the
assembly to cool, an enamel layer made of aventurine which covers
surface 6 of the support and forms a decorative coating 16 which
adheres strongly to the support. Generally, the temperature during
firing of the granular powder is between around 700.degree. and
900.degree.. The firing time in the furnace is, for example, around
two minutes. Preferably, the assembly removed from the furnace is
cooled slowly so as to avoid thermal shock which could cause
deformations of the assembly and cracks to appear in the enamel
layer.
[0040] In a first prepared variant, after preparing the granular
powder of aventurine and prior to depositing the latter on surface
6, at least part of this granular powder, intended for the
decorative coating of dial 2, is mixed with a liquid, notably
distilled water. Thus, the deposition of granular aventurine powder
on surface 6 consists of application of this mixture to surface 6
of support 4. Such application can be performed using a brush. If
the granular aventurine powder is deposited in liquid paste form,
there is preferably provided a step of drying the liquid paste,
i.e. the mixture formed of the granular powder and the liquid, once
deposited on surface 6, this drying step being performed in a
drying furnace prior to the introduction of the support and the
granular powder spread over surface 6 into the furnace. By way of
example, the temperature in the drying furnace is between
50.degree. and 200.degree.. The drying time depends on the
thickness of liquid paste deposited, its viscosity and the intended
drying temperature.
[0041] Depending on the desired thickness of the enamelled
decorative coating, the sequence of steps, from the deposition of
granular aventurine powder to its slow cooling after melting in the
furnace, is repeated several times, so that the decorative coating
is eventually formed of a plurality of enamel layers made of
aventurine which are deposited one on top of the other. Preferably,
the decorative coating has a thickness of between 200 and 300
microns (200-300 .mu.m), but this range of values is non-limiting.
It will be noted that inner rim 12 bordering aperture 14 and outer
rim 10 form lateral stops for the granular powder deposited on
surface 6 during at least a first sequence of steps from the
deposition of granular aventurine powder to its cooling after
melting in the furnace. Likewise, motifs 8, embossed inside surface
6, form lateral stops for the granular powder deposited on this
surface during at least the aforementioned first sequence of
steps.
[0042] The fabrication method according to the invention has the
advantage that the decorative coating formed of aventurine
precisely follows the contours of the motifs arranged inside the
decorative coating and also the contours of the rims bordering the
apertures, so that there is no gap between the aventurine enamel
and these motifs and rims. As a further advantage, it will be noted
that the motifs can be relatively complex and have small spaces
between them, because a granular aventurine powder is deposited in
the manner of an enamelling process.
[0043] Comparative tests concerning the shock resistance of dials
made according to the invention and prior art dials, which are made
with aventurine slices cut into pieces of aventurine and bonded to
respective supports, demonstrated that dials with the enamelled
aventurine coating according to the invention have better shock
resistance. Various reasons may explain this result. Firstly, it
will be noted that the enamelling process ensures that the first
aventurine enamel layer adheres securely to the support. To
increase this adherence, the surface of the support intended to
receive the decorative coating can be treated, for example this
surface can be oxidised to obtain the formation of chemical bonds
between the support and the decorative coating. Next, it was
observed that the most frequently detected damage to dials having
an aventurine slice is detachment of material (in the form of tiny
pieces of glass) which causes small crevasses to appear in the
upper surface of the dial. This detachment of material could be
caused by inhomogeneities in the pieces of aventurine, which are
reduced or removed when the granular aventurine powder is melted in
the furnace. Further, it is likely that cutting the slices of
aventurine produces micro-cracks in the surface of the slices, due,
in particular, to the copper crystals present in the aventurine,
these micro-cracks forming incipient cracks for the small pieces of
glass.
[0044] In a second preferred variant, after deposition of one or
more enamel layers made of aventurine, it is arranged to deposit a
flux on the upper layer of aventurine enamel. This flux is fired to
form a transparent upper layer of decorative coating 16. This flux
is formed of a glass that melts generally at a lower temperature
than the melting temperature of the granular aventurine powder.
This flux layer improves the levelling of the upper surface of the
decorative coating and makes it more regular and smoother, in
particular by filling small crevasses or slight depressions in the
surface of the aventurine enamel and/or covering copper crystals
which may appear at the surface of the aventurine enamel. Thus, the
flux prevents any oxidation of aventurine crystals at the surface
of the aventurine enamel. Another important advantage of the
surface layer of transparent glass lies in the fact that the
surface of this surface layer is easier to polish and that it is
therefore possible to obtain perfectly smooth and brilliant
surfaces relatively easily. On the contrary, polishing the
aventurine enamel is difficult to perform satisfactorily, since any
copper crystals found at the surface of the enamel or in direct
proximity thereto are detached during polishing, which results in
surface porosity. Moreover, the copper crystals that are removed
from the surface during polishing scratch the surface of the
enamel. The flux, which does not contain metal crystals, does not
suffer from this problem.
[0045] As already mentioned above, a final step of polishing the
decorative coating is generally carried out. This final polishing
step may have several phases, namely a preliminary phase consisting
in lapping to remove a significant amount of material and level the
upper level of decorative coating 16, which is followed by one or
more polishing phases with removal of less material and carried out
to obtain a perfectly smooth and shiny surface. It will be noted
that this polishing step is also used to remove any enamel that may
cover all or part of motifs 8, these motifs being eventually flush
with decorative coating 16 and having shiny upper surfaces.
[0046] With reference to FIGS. 6 to 8, there will be described
below a second implementation of a method for fabricating a dial
according to the invention. The various steps and variants of the
first implementation are involved, respectively may be involved, in
the context of the second implementation and will not be described
in detail again here. The second implementation differs from the
first implementation in that an enamelling process is performed on
a surface 38 of support 4A of dial 24, on the opposite side to that
of the surface 6A intended to receive decorative coating 26; this
enamelling process forms a counter-enamel 48. This counter-enamel
balances stress inside the support, to limit as far as possible any
deformations of the support when the assembly formed by this
support and the enamel deposited on both sides of the support is
fired in the furnace, and more particularly during the cooling
operations that follow. It is understood that a counter-enamel
becomes increasingly necessary the smaller the thickness of the
dial. Thus, for a support whose base has a thickness substantially
equal to 1.0 millimetre or more, it is possible not to have a
counter-enamelling process. However, for dials having a final
thickness of less than 1.0 millimetre, it is preferable to provide
a counter-enamelling process. By way of example, the base of the
support has a thickness of 0.55 millimetres, while decorative
coating 26 and counter-enamel 48 each have a thickness of 0.15
millimetres, so that the dial has a total thickness of 0.85
millimetres.
[0047] In the context of the second implementation of the
fabrication method according to the invention, an enamelling step
is thus performed on a surface of support 4A on the opposite side
to that of surface 6A intended to receive the decorative coating,
this enamelling step being used to form a counter-enamel 48 to
conserve the initial shape of the support when the assembly formed
by this support and the enamel deposited on both sides of the
support is fired in the furnace, and more particularly during the
cooling operations that follow.
[0048] Support 4A of dial 24 has several apertures, namely one
aperture 28 for the moon phase display and three circular apertures
14, 14A and 14B for passage of the hand pipes provided for the
display of various data, notably the current time, a time interval
(chronograph), or calendar data. It will be noted that one or more
rectangular openings for calendar data can be provided in the dial,
each defining an aperture revealing calendar data (in a
non-represented variant).
[0049] To delimit the deposited layers of aventurine enamel, as
explained above, apertures 28, 14, 14A and 14B have, on the side of
upper face 25 of the dial, respectively rims 30, 12, 12A and 12B
which project from surface 6A machined into support 4A. Likewise,
to delimit the layer or layers of counter-enamel 48 deposited on
the back of dial 24, apertures 28, 14, 14A and 14B have, on the
underside 36 of support 4A, respectively rims 42, 40, 40A and 40B
which project from surface 38 machined into support 4A. The outer
edge of the decorative coating is delimited by an outer rim 10 and,
likewise, the outer edge of the counter-enamel is delimited by an
outer rim 10A projecting from surface 38.
[0050] Then, on upper face 25 of the dial there are provided, in
surface 6A intended to receive decorative coating 26, embossed
motifs 32, which form a plurality of bases arranged to eventually
receive a plurality of hour symbols 50 which stand above upper face
25 of the dial defined partly by the upper surface of decorative
coating 26. These bases are flush with decorative coating 26. Solid
hour symbols 50 have feet 51 which are inserted into holes arranged
in the bases, the hour symbols being secured by means of a
brazing-solder or adhesive 52 placed in cavities 34 located under
the bases on underside 36 of support 4A.
[0051] It will be noted that the inner profile 44 of rim 10A does
not correspond to that of rim 10, but defines a winding path so as
to encompass cavities 34 in rim 10A. It will also be noted that, to
limit the final thickness of the dial while having a decorative
coating that is thick enough to conceal the support and to give the
decorative coating a certain depth, the thickness of counter-enamel
48 is arranged to be smaller than that of decorative coating 26, as
represented in FIGS. 8 and 9. Thus, the decorative coating can have
a thickness of 0.20 to 0.25 millimetres while the counter-enamel
layer has a thickness of 0.15 millimetres. It will also be noted
that counter-enamel 48 does not have to be made of aventurine but
can be formed of another more common enamel or by a transparent
flux preferably having a substantially identical melting
temperature to that of the coloured aventurine glass. Finally,
support 4A has two holes 46 in underside 36 for two feet intended
to position and secure dial 24 to a watch movement.
[0052] A variant embodiment of a dial 56 according to the invention
will be described with reference to FIGS. 10 and 11. This dial 56
differs essentially from dial 2 of FIGS. 1 to 3 with regard to two
features. Firstly, dial 56 has a counter-enamel layer 66, on its
back face side, which is deposited and formed in a recess machined
into support 4B to define a hollow surface 60 intended to receive
the counter-enamel. The surface is delimited, as in the second
implementation of the invention, by an outer rim 62 and an inner
rim 64 surrounding central hole 14. Secondly, dial 56 has an upper
surface 58 (the main surface seen in the watch), defined by the
embossed motifs 8B and the upper surface of decorative coating 16B
formed of aventurine, which is convex. Thus, decorative coating 16B
is not formed by a flat layer, since the surface 6B intended to
receive it has parts that have a certain incline relative to the
general plane of dial 56.
[0053] Generally, the dial according to the variant described here
has a convex upper surface, which is at least partially defined by
the upper surface of said decorative coating. This embodiment can
be obtained relatively easily by the timepiece component
fabrication method according to the invention. Indeed, the
aventurine is ground and deposited in the manner of an enamelling
process, the granular aventurine powder mixed with a liquid can
then be deposited on non-flat surfaces in the same way as a
deposition on flat surfaces, and firing this granular powder makes
it possible to obtain enamel layers made of aventurine and each
having a relatively constant thickness but a non-flat shape. Next,
the final polishing step, notably diamond polishing, makes it
possible to obtain an upper surface 58 with a curved profile which
is regular and shiny. Making decorative coatings with a curved
outer surface is a great advantage of the fabrication method of the
invention.
[0054] Finally, it will be noted that the timepiece component
fabrication method according to the invention does not apply only
to a display element, particularly a dial or a moon phase indicator
disc, but also to other components. Thus, in other embodiments, the
timepiece component is a part of a watch case, notably a bezel, or
the timepiece component is a part of a timepiece movement, notably
a bridge or an oscillating weight.
* * * * *