EP0615415A1

EP0615415A1 - Process for producing cast and set pieces of jewellery.

Info

Publication number: EP0615415A1
Application number: EP92924652A
Authority: EP
Inventors: Manfred Mueller
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-12-05
Filing date: 1992-12-03
Publication date: 1994-09-21
Anticipated expiration: 2012-12-03
Also published as: AU3084592A; HUT67814A; ATE134488T1; EP0615415B1; DE4140121C2; DE59205524D1; HU9401683D0; CN1078182A; WO1993010686A1; JPH07505061A; CA2125152A1; SK67694A3; DE4140121A1; FI942629A0; AU674836B2; FI942629A; CZ136794A3

Abstract

In order to produce pieces of jewellery with one or several set stones, a master pattern with settings for the stones is produced, a master mould is produced by moulding from the master pattern, a model is produced in the master mould with a castable or injection mouldable modelling mass that can be ejected by heating from the master mould, the stones are inserted into the model and set by deformation of the setting, a casting mould is produced by embedding the model in a fire-resistant moulding mass and by ejecting the modelling mass from the casting mould, metal is cast into the casting mould by a spin casting or vacuum moulding process and the piece of jewellery is removed from the mould once the metal has cooled down.

Description

Process for the production of set, cast jewelry

The invention is based on a method with the features specified in the preamble of claim 1.

DE-38 24 574 AI describes a lost wax casting process for the manufacture of jewelry. After this

First, a master model of the piece of jewelry is produced. Then a master mold is produced by molding the master model. The molding can be done by pouring a molding compound, for example a two-component silicone rubber mixture, into a container in which the master model is arranged, allowing the molding compound to harden, then cutting the body thus formed into two halves and takes the original model. It is also possible to place the master model between two blocks of thermoplastic material and to heat them under pressure until they plastically deform

shape and nestle the original model, creating a lifelike impression of the original model in the two blocks (DE-35 46 188 AI). The two-part archetypes formed in this way are also called rubber molds because they usually consist of more elastomeric material. A modeling compound, in particular a wax, is then poured into such a master mold by casting or injection molding. After the modeling compound has cooled, the master mold is opened and the model is removed. Several models are usually put together to form a model tree and this is then embedded in a fireproof molding compound. The molding composition is understood here as "fire-resistant" if it withstands the action of a molten metal from which the piece of jewelry is made without changing its shape. After the model tree has been embedded in the refractory molding compound, the modeling compound of which the model tree consists is expelled by heating; if the modeling clay is a wax or a low-melting metal, it is melted out (lost wax process); if the modeling clay is plastic, it is burned out. The molten metal from which the pieces of jewelry are to be made is then poured into the casting mold thus produced. So that the metal penetrates into the last corners and ramifications of the casting mold, it is rotated during casting (centrifugal casting) or the casting is supported by the use of negative pressure (vacuum casting). After solidification and cooling, the tree consisting of the pieces of jewelry is removed from the mold and the pieces of jewelry are separated from one another. It is also known to cast jewelry with one or more set stones for the manufacture of jewelry. For this purpose, a master model of the piece of jewelry is produced, in which the stones are set, and this master model is molded to form the master form. Such a master form, which is a negative form of the piece of jewelry, accordingly contains recesses for the stones. The stones for the piece of jewelry are inserted into these recesses of the original shape, then the shape is poured or injected with the modeling compound and the model of the piece of jewelry formed in this way is further processed in the manner described above. However, it is difficult to insert the stones in the correct position in the master mold and to fix them in such a way that after pouring or injecting the modeling clay, they have exactly the position that they should also have in the later piece of jewelry. Rather, it happens again and again that the position of the stones is changed by the casting or overmolding, and that the extent of the molding varies from model to model, partly due to deviations in the shape of the stones from one another.

From FR-PS 1,599,866 it is already known to embed gemstones in a wax model, to assemble such wax models into a wax model tree and to further process them into cast jewelry pieces using a lost wax process. In this case, however, the gemstones are not inserted into a special setting on the wax model, but instead are inserted into a wax model produced without a setting. Accordingly, the cast piece of jewelry has no special setting for the stones.

The object of the present invention is to improve the method mentioned at the outset in such a way that stones which are positioned exactly in the piece of jewelry are obtained in the simplest possible manner. This object is achieved by a method with the features specified in claims 1 or 2. Advantageous developments of the invention are the subject of the dependent claims.

In the method according to the invention, as in the known method, a master model is first produced from the piece of jewelry to be produced. This master model has one or more settings corresponding to the number of gemstones provided, but the gemstones are not used in the master model. With a prong setting e.g. the prongs that are supposed to hold the gemstones are not bent inward, but they retain their original orientation that they had before the insertion of gemstones. A negative form is then produced as the original form from the original model, in which no gemstone has yet been inserted, and a model of the piece of jewelry is cast in this original form. Wax is preferably used as the modeling material, but other pourable or injectable modeling materials can also be used, which can be solidified by cooling, e.g. low-melting metals, or which can be solidified by crosslinking, e.g. Polyester resins, epoxy resins, polyurethanes and the like plastics. The modeling clay must, however, be liquefied or decomposed (pyrolyzed) by heating and thus be able to be expelled.

The model produced in this way is now fitted with gemstones by inserting them into the frames provided for this purpose. Since the model is a positive form of the piece of jewelry, the stones can be inserted into the settings from the completely exposed top of the piece of jewelry as in the case of an original piece of jewelry, but do not have to be laboriously difficult as in the known lost wax technique accessible recesses of a negative form (original form) are inserted. The stones can be inserted into the sockets of the model from the modeling compound (in particular wax model), for example by means of a slim suction applicator, with the aid of which the respective stone is sucked in, picked up, inserted into the socket and then left there by switching off the suction air. The stone then only needs to be fixed in the socket. If the model is made of a low-melting metal, it can be fixed like an original piece of jewelry, in the case of a claw setting by bending the claws inwards and thereby holding the respective gem in the setting. If, on the other hand, the modeling clay is - as preferred - a wax or a plastic, then the stones are preferably fixed in their holders by softening and plastically deforming them through the action of heat, and best of all by having the shape of the upper Tool adapted to the end of the holder is heated, placed on the holder and this is deformed in a single step by pressing the tool against the stone. This is not only possible in the case of prong or grain frames, which grip the stones in places like fingers, but also in frame frames, which encompass the stone over its entire circumference. In the case of a frame mount, one would expediently use a tool with a frame-shaped contact surface at its tip as a tool for plastically deforming the mount, which tool is placed on the edge of the frame mount and then pressed against the surrounding stone edge. With a prong or grain Conversely, it is expedient to use a tool which has projections corresponding to the position of the prongs or grains, with which the heated tool is placed on the prongs or projections, as a result of which they soften, flow and encompass the adjacent stone edges, for which purpose a short touch with the tool is enough. It has been shown that all prongs or grains do not have to be deformed in order to fix the gemstones, because a prong deformed by the action of heat has more intimate contact with the stone edge than a metallic pretzel pressed in a conventional manner against the stone edge. It is therefore preferred that only a subset of the prongs or grains is deformed in the case of claw or grained frames, while the rest remain undeformed. In this way, despite the deformation of individual prongs because of the still undeformed prongs, the usual impression of a conventional prong setting is retained. In a claw setting with four claws per stone, preferably only two claws lying opposite one another are deformed, in a setting with six claws preferably three claws are deformed.

Instead of plastically deforming the socket after inserting the stone, you can also expand it elastically when inserting the stone in order to hold the stone resiliently. Surprisingly, it has been shown that this is even possible if a commercially available wax is used as the modeling compound for the models to be produced in the original mold. With a prong setting you can go through stones alone

Fix the elastic expansion of the socket in the wax model when the prongs are at least 2.5 to 3 mm long. At this minimum length, despite the low elasticity of the wax, it can be bent elastically far enough to be able to insert a stone into the socket. Because of the required minimum length of the prongs, this particularly advantageous variant of the invention is suitable for gripping larger stones. The insertion of a stone into a wax model setting with an elastic widening of the setting is possible not only with prong settings, but also with frame settings, in particular with round settings, which completely enclose a gem along a circumferential edge of the gem.

To a gemstone by spring force in one

To be able to fix the wax model frame, you should have a support for the edge of the stone to be gripped in the frame. Such a support is expediently molded into the wax model after it has been poured, in particular by milling notches in the prongs of a prong setting or by milling a circumferential groove in the case of a frame setting, the milling being simple in view of the soft modeling clay and goes very quickly.

The stones are so easy to insert and fix in the model that even unskilled workers can master them after a short briefing. The method according to the invention is therefore particularly suitable for the industrial mass production of jewelry. Already in the testing phase of the method according to the invention, shows that the cost of setting gemstones can be drastically reduced: compared to the conventional technique of inserting the stones into the cast ring band, the cost of setting can be reduced to 1/10; compared to the conventional wax casting process, in which the stones are already poured into the wax model, the costs can still be reduced to 1/4.

The further processing of the manufactured according to the invention

Model is done as it is known per se in centrifugal casting or vacuum casting of jewelry. The examples given below serve to illustrate this.

1st example:

A master model is made of metal from a piece of jewelry, for example a ring, which is said to have several gemstones. The original model has prong settings for the stones, but the stones are not used. The master model is placed between two blocks of thermoplastic silicone elastomer which are subsequently heated and pressed against one another. As a result, the silicone elastomer is plastically deformed and conforms to the original model, whereby a true-to-nature impression of the original model is produced in the two blocks. The two blocks formed in this way form the two parts of a master mold, into which a wax is then injected. After the wax has cooled, the master mold is opened and the wax model of the piece of jewelry is removed. In the wax-up frames made of, for example, four prongs, the intended ones are then used by means of a suction applicator

Stones are inserted and fixed by placing a fork-shaped tool, the two tines of which are electrically heated and at a distance from two opposing prongs, on two opposing prongs of the respective setting and briefly pressing on them, which softens and compresses the prongs and encompass the stone edge that is adjacent to them. A wax model tree is then formed from a number of wax models produced in this way in a manner known per se, inserted into a cuvette and this is coated with a fine plaster, e.g. with alabaster, poured out. After the plaster has set, the cuvette is heated and the wax is melted out; The plaster cast of the wax model tree remains in the cuvette. The cuvette is heated to a temperature of approximately 750 ° C., inserted into a centrifugal casting machine and a molten 14-carat gold alloy is poured in, which is allowed to solidify in the rotating cuvette. After the cuvette has cooled to about 40 ° C, the plaster is broken up, exposing the cast tree. The pieces of jewelry are now cut from the tree, cleaned and polished if necessary.

The method described in the first example is particularly suitable for pieces of jewelry with small gemstones, for the setting of which one gets by with short prongs that are no more than 2.5 or 3 mm long. In an advantageous further development of the invention, there are particularly simple methods for setting larger gemstones: are explained with reference to the accompanying drawings, in which

FIG. 1 as a second example, a cross section through a wax model of a ring rail with a holder consisting of four prongs or stumps,

Figure 2 is a plan view of the wax model of Figure 1 with a set gem and

FIG. 3 shows, as a third example, a cross section through a wax model of a ring rail with a frame mount.

The wax model of a ring rail 1 shown in FIG. 1 has a socket made of four prongs or stubs 2 to 5, which are 3 mm long. As a support for a larger stone to be gripped, e.g. a rose quartz in Emerald cut, the prongs 2 to 5 have a notch 6 near their upper ends, which can be milled into the prongs 2 to 5 of the wax model or can already be created in the original model, surprisingly the prongs have 2 to 5 sufficient elasticity, the gemstone 7 resiliently snap into the notches 6. For this purpose, the gemstone 7 with its edge to be grasped can first be divided into two adjacent notches e.g. insert prongs 2 and 5 and then press its opposite edge into the notches of the other two prongs 3 and 4. A snapped in this way in prongs 2 to 5

Gemstone 7 does not have to be additionally fixed by thermally deforming the prongs, rather the wax part 1 can be used with the gemstone 7 which is only locked in place

Wax model tree can be processed further. Otherwise, the procedure is the same as in the first example.

The wax model of a ring rail 11 shown in FIG. 3 has a frame socket 12 provided as a recess in the ring rail, in particular a round socket for a round-ground stone 13. To accommodate the edge 14 provided on the circumference of the stone, the socket 12 has an annular groove 15. This socket 12 can largely be pre-formed in the original model and then finished in the wax model, in particular by milling the groove 15 into the wax model. Surprisingly, the stone 13 can be snapped into place by pressing it into the socket and is then fixed by the spring action of the socket modeled in the wax; it is neither necessary to separate the round frame 12 into segments, nor is it necessary to thermally deform the round frame after inserting the stone 13 in order to fix the stone. Otherwise, the procedure in this third example can be the same as in the first example.

The second and third examples are particularly simple and inexpensive to manufacture and have the further advantage that the frames in the finished piece of jewelry look exactly the same as frames in which stones are only inserted after centrifugal casting or vacuum casting.

Claims

Claims:

1. Method of making jewelry with one or more set stones by

- making a master model with frames for the stones,

- production of an original form by molding the original model,

- producing a model from a casting or injection-moldable modeling material which can be expelled by heating in the original mold,

Producing a casting mold by embedding the model in a refractory molding compound and expelling the modeling compound from the casting mold,

- pouring metal into the mold,

- ^" De-molding the piece of jewelry after the metal has solidified,

characterized,

that the master form is formed by molding the master model that does not yet contain any stones, that the stones are rather only inserted into the model produced with the master mold and are grasped by deforming the frames.

2. Process for producing models from a castable or injection-moldable, expellable by heating

Modeling clay,

for the purpose of use in a method for producing jewelry with one or more set stones, in which a mold is formed by embedding the model in a refractory molding compound and then expelling the modeling compound, metal is poured into the casting mold and the respective item of jewelery after the metal has solidified is demolded,

by producing a master model with frames for the stones and producing a master form by molding the master model,

characterized in that the master form is formed by molding the master model that does not yet contain any stones, that the stones are rather only inserted into the model produced with the master form and are grasped by deforming the frames.

3. The method according to claim 1 or 2, characterized gekennzeich¬ net that the existing from the modeling clay

Sockets are plastically deformed after inserting the stones.

4. The method according to claim 3, characterized in that the sockets are thermally deformed.

5. The method according to claim 4, characterized in that one of the shape of the upper end of each

Tool adapted to the socket is heated, placed on the socket and this is deformed in a single step by pressing the tool.

6. The method according to any one of the preceding claims, characterized in that the sockets are only deformed in places.

7. The method according to claim 6, characterized in that only a partial amount of the prongs or grains is deformed in claw or grain settings.

8. The method according to claim 1 or 2, characterized gekenn¬ characterized in that the socket (2-9, 11) is elastically expanded when inserting the stone (7, 13).

9. The method according to claim 8, characterized in that a commercially available wax is used as modeling clay.

10. The method according to claim 8 or 9, characterized gekennzeich¬ net that a support (6, 15) for the stone (7, 13) is molded into the model only after it has been cast.

11. The method according to claim 10, characterized in that the support (6, 15) is milled into the model.

12. The method according to any one of claims 8 to 11, characterized in that it is applied to prong settings with at least 2.5 mm long prongs (2 to 5).

13. The method according to any one of claims 8 to 11, characterized in that it is applied to round versions (11).