U.S. patent application number 10/836249 was filed with the patent office on 2004-11-25 for process for the production of a piece of jewellery.
Invention is credited to Altenberger, Rudolf, Huter, Michael, Rauch, Thomas.
Application Number | 20040231158 10/836249 |
Document ID | / |
Family ID | 32686613 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040231158 |
Kind Code |
A1 |
Altenberger, Rudolf ; et
al. |
November 25, 2004 |
Process for the production of a piece of jewellery
Abstract
A process for the production for a piece of jewellery by casting
metal around a precious stone, wherein prior to the casting
operation the precious stone is provided with a colouring
agent-bearing coating and that during or after the application of
the coating, the latter is subjected to an energetic treatment
which causes those transformations of the coating which would occur
without the energetic treatment upon casting the metal around the
precious stone.
Inventors: |
Altenberger, Rudolf;
(Kolsass, AT) ; Huter, Michael; (Innsbruck,
AT) ; Rauch, Thomas; (Innsbruck, AT) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
32686613 |
Appl. No.: |
10/836249 |
Filed: |
May 3, 2004 |
Current U.S.
Class: |
29/896.41 |
Current CPC
Class: |
A44C 17/04 20130101;
Y10T 29/4959 20150115 |
Class at
Publication: |
029/896.41 |
International
Class: |
A44C 027/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 23, 2003 |
AT |
A 800/2003 |
Claims
1. A process for the production of a piece of jewellery by casting
metal around a precious stone, characterised in that prior to the
casting operation the precious stone is provided with a colouring
agent-bearing coating and that during or after the application of
the coating, the latter is subjected to an energetic treatment
which causes those transformations of the coating which would occur
without the energetic treatment upon casting the metal around the
precious stone.
2. A process according to claim 1 characterised in that the
energetic treatment includes heating to a temperature of between
950.degree. C. and 1250.degree. C. for a period of 1 to 20
minutes.
3. A process according to claim 2 characterised in that the
energetic treatment includes a tempering operation at a temperature
of between 700.degree. and 800.degree. C. for a period of at least
one hour.
4. A process according to claim 1, characterised in that the
colouring agent-bearing coating is provided with a protective
covering.
5. A process according to claim 4 characterised in that Li, Mg, Zn,
B, Ce, Ti, Si, Zr or Al is contained in the covering.
6. A process according to claim 1 characterised in that a
transitional layer is arranged between the precious stone and the
coloured coating.
7. A process according to claim 1 characterised in that the rear
side (2) of the precious stone (1) is protected by a ring (3)
formed by the poured-in metal (4).
8. A precious stone which is suitable for the production of an
article of jewellery by pouring metal therearound according to
claim 1 characterised in that the precious stone is provided with a
colouring agent-bearing coating of per se variable colour, which no
longer substantially changes by virtue of an energetic treatment
upon heating to a temperature below 1250.degree. C.
Description
[0001] The invention relates to a process for the production of a
piece of jewellery by casting metal around a precious stone.
[0002] A process of that kind is also suitable in particular for
stones which are relatively good value for money, in which the
separate production of a part of the piece of jewellery from
precious metal and the fact of joining it to the stone by a
goldsmith signify a relatively high level of expenditure.
[0003] The precious stones for use in the process of the general
kind set forth are in particular stones whose natural colour has
been artificially enhanced or altered. There are two methods
available for altering the colour of the stone, and a basic
distinction is to be drawn between them: it is possible to cause
colouring elements to diffuse into the stone or however it is
possible for a coloured layer, for example a pigment-bearing layer,
to be fixedly joined to the stone.
[0004] It is only the second kind of colour alteration that is of
interest here as it is substantially more suitable for industrial
mass production. For example it is known from U.S. Pat. No.
3,837,884 (Balzers) for a blue colour layer to be applied to a main
body by vapour deposition of cobalt oxide, aluminium oxide and
silicon oxide. Although those layers are tempered for a period of
about 30 minutes at about 300.degree. C. in an oxygen-bearing
atmosphere, they are not stable under the conditions of the process
of the general kind set forth.
[0005] It was surprisingly found that precious stones which are
provided with a colour coating thereon can be processed in a
casting process if it is provided that, during or after the
application of the coating, the latter is subjected to an energetic
treatment which causes those transformations of the coating which
would occur without the energetic treatment upon casting the metal
around the precious stone.
[0006] In the production of a piece of jewellery, as defined in the
opening part of this specification, the stone is firstly exposed
for a relatively long period of time to that temperature at which
the wax pattern which finally is to be replaced by the cast-in
precious metal is burnt out. That temperature is of the order of
magnitude of 750.degree. C. Then, when the precious metal is being
poured in, the surface of the stone is heated to a temperature
which is between 950.degree. and 1050.degree. in the case of
silver, between 950.degree. and 1250.degree. in the case of gold
and between 1800.degree. and 1900.degree. C. for platinum. As is to
be discussed hereinafter with reference to the embodiments, it is
sufficient if the stones provided with a colour layer are briefly
heated to the temperature at which the metal is poured in and/or
are heated to the temperature for burning out the wax pattern over
a relatively long period of time, in order to reduce to a minimum
the colour changes which still occur in the pouring-in operation
itself.
[0007] Further features of the invention will now be described in
greater detail with reference to the drawing and the embodiments by
way of example.
[0008] FIGS. 1-3 are diagrammatic view of three conventional phases
in the process according to the invention, and
[0009] FIG. 4 is a view in section through a detail of a piece of
jewellery produced in accordance with the invention.
[0010] The production of a piece of jewellery by casting metal
around a precious stone is known per se. As shown in FIG. 1 the
stone 1 is embedded in mould material 5, whereas firstly wax 6
serve as a place-holder for the metal of the stone setting. Then
the wax 6 is expelled by heating to about 750.degree. C., thus
resulting in the hollow space 7 shown in FIG. 2. That hollow space
7 is finally filled with metal 4 which surrounds the stone 1, as
shown in FIG. 3.
[0011] As an example of a piece of jewellery, FIGS. 1-3 show a ring
but the invention can be used wherever the surface of a stone, in
particular the rear side 2 thereof (see FIG. 4), is provided with a
coloured coating which could be adversely affected by pouring in
metal 4.
[0012] A prerequisite for application of the process according to
the invention is firstly that the stone retains its optical
properties even when metal is cast therearound. Glass and quartz
for example can be readily provided with a heat-resistant colour
layer, but normal glass would melt at the specified temperatures.
Glass would already become cloudy at the temperatures which are
usual for burning out the wax.
[0013] A basically suitable stone, for example zirconium oxide, is
now provided with a colour layer. The most common methods for that
purpose are vapour deposition, sputtering, chemical vapour
deposition and so forth. Specifically by reactive sputtering onto a
slightly heated substrate, it is possible directly to apply most
organic colours even at low temperatures.
[0014] In particular dyestuffs whose basic compositions are known
as inorganic coloured pigments, in particular inorganic materials
which have a "streak", are considered for colouring the stone. Such
dyes are known in connection with ceramic glazes and with surface
colouring of glass. Colours layers based on oxidic pigments with a
rutile, cassiterite, zircon, baddeleyite, corundum, haematite,
olivine, spinel, gamet and perovskite structure are particularly
suitable. Colour layers based on nitridic and more especially
oxinitridic pigments also appear to be highly suitable for the
process as well as colour layers based on carbides and carboxides.
Colour layers based on sulphides, sulphates, phosphates, cyanogen
components as well as metal colloids need special embedding but
they are suitable even when they have a melting point in the
proximity of or just below the pouring-in temperature.
[0015] If a stone prepared in that way were to be further processed
in the procedure shown in FIGS. 1-3, that would result in unwanted
and substantially uncontrolled colouration of the stone. Such
colouration effects are quantified in accordance with the "Colored
Stone Grading System" of the Gemological Institute of America. In
that respect colour impression (hue), tone (light/dark) and colour
saturation are assessed. The effect achieved by the invention
provides that stones which, without particular post-treatment of
the coloured coating, in accordance with at least one of the
specified criteria, would experience a change by more than two
points in the pouring-in operation, now exhibit a deviation of at
most two points, normally at most one point. That is achieved by an
energetic treatment which anticipates the loading which occurs when
burning out the wax and when pouring in the metal.
[0016] Set out hereinafter are some examples of carrying the
process according to the invention into effect. In this respect
designation of the pigments used is implemented by specifying the
CAS registration number of the American Chemical Society. Pigments
suitable for high temperatures are specified in Ullmann's
Encyclopedia of Industrial Chemistry 1986, Vol. A5, in particular
pages 546/547. Those dyes can all be produced in accordance with
the invention either directly or by the selection of a suitable
intermediate, embedding or cover layer, in such a way that they no
longer change their colour in the pouring-in operation.
EXAMPLE 1 (COMPARATIVE TEST)
[0017] A layer which consisted for about 35% by weight of cobalt
oxide, 10% of aluminium oxide and the balance silicon oxide, was
applied by vapour deposition to cubic zirconia, in accordance with
the process described in U.S. Pat. No. 3,837,884. A subsequent heat
treatment produced blue colouration of the layer. Casting in the
stone provided with the coloured layer, without post-treatment,
resulted in discolouration of the stone at the pouring temperature
of 14 ct yellow gold (about 1050.degree. C.).
[0018] In accordance with the invention the coated stone was heated
for 10 minutes at 1200.degree. C. and then tempered for an hour at
750.degree. C. (this corresponds to the wax burning-out
temperature). By virtue of the described heat treatment, no
subsequent changes occurred, not even at the pouring-in temperature
of 14 ct Pd-white gold (1250.degree. C.).
EXAMPLE 2 (COMPARATIVE TEST)
[0019] A pigment of the composition CAS 68186-85-6 (green spinel,
Co.sub.2TiO.sub.4) with some TiO.sub.2 in excess was applied to
zirconia by reactive sputtering at low temperature. When pouring in
14 ct palladium-white gold, a markedly visible change in the green
colour occurred.
[0020] If in contrast the described layer was tempered for a minute
at 1200.degree. C., the coated stone exhibited no noticeable colour
change when the metal was poured in.
[0021] If in contrast the stone tempered at 1200.degree. C. was
cast into a 14 ct yellow gold melt, nonetheless a brownish change
in colour occurred. The change in colour was at the greatest at the
edge where the colour layer was in direct contact with the
alloy.
[0022] If, in addition to the colour layer, a protective layer of
magnesium aluminate was also applied and the stone tempered at
1200.degree. C., the colour shade did not change, even at the
locations at which there was direct contact with the hot yellow
gold alloy.
EXAMPLE 3
[0023] A colour layer based on the pigment CAS 68187-35-9 (brown
haematite, Fe.sub.2O.sub.3) was produced in temperature-stable form
and chemically and mechanically resistant, by a procedure whereby
the iron oxide pigment was applied, jointly with an embedding
matrix of aluminium oxide, to a thin SiO.sub.2 layer. The treatment
for 10 minutes at 1200.degree. C. was followed by a post-treatment
for two hours at 750.degree. C. The colour shade of the pigment
embedded and heat-treated in that way admittedly no longer
precisely corresponds to the colour of the pure pigment, but on the
other hand the colour did not change in the pouring-in
operation.
EXAMPLE 4
[0024] Zirconia was coated by means of the pigment CAS 68187-05-3,
a blue-green spinel with the basic formula Co.sub.2SnO.sub.4. The
pigment layer which was about 125 mm was coated with a dense
protective layer of aluminium oxide and heated for a minute at
1200.degree. C. Subsequently the stone was tempered for 30 minutes
at 750.degree. C. in air. The resulting blue colouration was
maintained when pouring in sterling silver.
[0025] In individual ones of the specified examples, account was
taken of the fact that the coloured coating on a precious stone can
be damaged not only by the temperature which occurs when pouring in
metal. Rather, unwanted changes can also occur at the interface
between the stone and the colour layer and in particular at the
outside of the colour layer, and those unwanted changes can be
avoided by separation layers. In particular that takes account of
the fact that the shine can suffer even in the case of a
colour-fast stone when pouring in metal.
[0026] If there is a wish to also safeguard the colour-coated rear
side of a stone against mechanical attack, in particular against
the impacting action of grinding members or other pieces of
jewellery, as well as the abrasive effect of diamond grinding
grains, then, as shown in FIG. 4, it can be provided that the rear
side of the precious stone is surrounded by a ring formed by the
poured-in metal.
* * * * *