EP0646338A1 - Hollow body made of precious metal or alloy of precious metals, used as jewel or jewellery item - Google Patents

Abstract

A thin-walled hollow body made of a precious metal or an alloy of precious metals for use as an item of jewellery. A core (6) made of a plastic or wax is provided in the hollow body as a permanent support for the thin outer wall (1, 2). <IMAGE>

Description

The invention relates to a hollow body made of a noble metal or a noble metal alloy for use as jewelry or jewelry. Such pieces of jewelry are known from EP-A-0 195 132. They are produced by electroplating, in that the precious metal is electrolytically deposited on an electrically conductive or electrically conductive shaped core which has the spatial contour of the piece of jewelry and, after the desired layer thickness has been reached, the Material of the mandrel is released from the hollow body by chemical or thermal means. The term "electroforming" has become common for this process.

This method has the advantage that hollow pieces of jewelry of almost any shape with thin wall thicknesses, ie with economical use of precious metals, can be produced inexpensively. However, this advantage is linked to the disadvantage that the pieces of jewelry have a low mechanical stability, which in particular in the area where attachment eyes, connecting links or connecting links, brochures, lugs, hooks, securing devices or the like are required on the hollow body due to tensile or bending forces Deformation of the wall of the hollow body causes or the wall thickness is gradually removed by abrasive or rubbing stress and is thereby further weakened. In order to counteract this, it is known from EP-A-0 195 132 to increase the wall thickness of the hollow body in the particularly stressed areas by additional application of noble metal, for example by depositing the noble metal in a smaller layer thickness on the mandrel to be coated or is deposited with the formation of predetermined breaking points, so that the wall initially weakened in this way is subsequently opened slightly and a metallic one Reinforcement part can be soldered or inserted in any other way. This procedure is complex and partially nullifies the actual advantage of the galvanoplastic process, the inexpensive production and the precious metal savings.

From DE-PS 39 18 920 it is already known to insert a metallic functional part, e.g. to embed part of a clasp, which consists of the same noble metal material as the outer wall of the hollow body and in places emerges from the mold core material, so that the functional part connects with the resulting outer wall of the hollow body during electrolytic metal deposition. Such a functional part can act like a strut and thereby stabilize the hollow body to a certain extent, but without eliminating the disadvantage that the outer wall of the hollow body remains sensitive to mechanical damage.

The present invention has for its object to show a way how such thin-walled jewelry can be protected against damage in a simpler and cheaper way.

This task is solved amazingly simply by that a core made of a plastic or wax is provided in the hollow body for permanent support of the thin outer wall, and the desired result can be achieved particularly simply and elegantly if the material of the mold core, which is always removed in the well-known galvanoplastic or electroforming process , does not detach, but simply and simply left in the hollow body.

• Gegenüber dem bisherigen Elektroforming-Verfahren wird der letzte Schritt, nämlich das Herauslösen des Formkernmaterials, eingespart.
• Der im Hohlkörper verbleibende Kern stabilisiert die Aussenwand des Hohlkörpers vollflächig. Damit wird z.B. ausgeschlossen, dass ein auf diese Weise hergestelltes Schmuckstück, wenn es zu Boden fällt, eine Beule bekommt, was bisher durchaus vorkam.
• Das Schmuckstück wiegt schwerer in der Hand und macht deshalb einen wertvolleren Eindruck.
• Der den hohlen Schmuckstücken bisher eigene, störende, blecherne Klang ist verschwunden.
• Vor allem aber bietet die Erfindung die Möglichkeit, die Wandstärke der Aussenwand nochmals drastisch zu verringern, und dadurch weit mehr Edelmetall einzusparen, als das bisher in Anwendung des Elektroforming-Verfahrens möglich war.
• Da das Material des Kerns nicht mehr herausgelöst werden muss, gibt es weniger Einschränkungen bei seiner Auswahl, insbesondere muss nicht darauf geachtet werden, dass es sich leicht ausschmelzen oder leicht thermisch zersetzen oder chemisch herauslösen läßt. Zweckmässigerweise verwendet man dafür einen leicht spritzbaren oder gießbaren Kunststoff oder ein Wachs.

The advantages that can be achieved are convincing:

• Compared to the previous electroforming process, the last step, namely the removal of the mold core material, is saved.
• The core remaining in the hollow body stabilizes the entire surface of the outer wall of the hollow body. This prevents, for example, that a piece of jewelry produced in this way, if it falls to the floor, gets a bump, which has so far been the case.
• The piece of jewelry weighs heavier in the hand and therefore makes a more valuable impression.
• The annoying, tinny sound that is unique to hollow jewelry has disappeared.
• Above all, however, the invention offers the possibility of drastically reducing the wall thickness of the outer wall again, and thereby saving far more precious metal than was previously possible using the electroforming process.
• Since the material of the core no longer has to be removed, there are fewer restrictions in its selection, in particular no care must be taken to ensure that it easily melts out or is easily decomposed thermally or chemically removed. It is expedient to use an easily sprayable or pourable plastic or a wax for this.

The invention is suitable for hollow bodies with or without built-in metallic functional parts. If functional parts are required, they are best embedded in the core during casting or injection molding by inserting it into the negative mold of the hollow body and then filling this mold with the core material, or by inserting it into a plastic or a wax.

It is of course also possible, if less profitable, to subsequently pour or spray a thin-walled hollow body for stabilization with a suitable plastic or wax.

Initial tests have confirmed that one is in use the invention can get by with wall thicknesses that are not more than 60 microns. It is therefore preferred to end the electrolytic metal deposition on the core when the layer thickness has reached 40 to 60 μm.

Figur 1

zeigt eine Schließe in der Draufsicht, und

Figur 2

zeigt die Schließe im Längsschnitt längs der Linie II-II.

An embodiment of the invention is shown in the accompanying drawings.

Figure 1

shows a clasp in plan view, and

Figure 2

shows the clasp in longitudinal section along the line II-II.

Figures 1 and 2 show a clasp for jewelry. The clasp has a shape similar to a longitudinally halved banana with a flat bottom 1 and with a bulging over the bottom 1, approximately semicircular in cross section 2, which in the example shown has a cord-like relief for reasons of appearance alone. At one end of the clasp there is an eyelet 3 to which, for example, a chain or necklace can be attached, and at the opposite end there is an opening 4 through which a catch attached to the other end of the chain or necklace enters Interior of the Clasp inserted and can be locked in a guide member 5 arranged therein.

The guide part 5 and the eyelet 3 are connected by a web 7 and together form a functional part. It consists of the same material as the base 1 and the curved wall 2 of the clasp and can be produced by a casting process. To produce the clasp, the functional part is inserted into a negative form of the clasp and the negative form is then poured out with a pourable or sprayable material, in particular with a low-melting plastic, so that a composite part made of plastic 6 and the functional part is contained. By appropriately designing the negative mold, it is ensured that the eyelet 3, the inner region of the guide part 5 and the underside of the functional part remain uncovered by the plastic 6. The plastic is then made superficially conductive by immersion in a chemical metallization bath, and the composite part is then immersed as a mold core in an electrolytic metallization bath. For this purpose, a wire can be attached to the eyelet 3, through which a cathodic potential can be imparted to the mandrel. In the electrolytic bath, the mold core as a whole, ie both on the plastic surface and on the areas not covered by the plastic of the functional part coated with precious metal. After the desired layer thickness has been reached, preferably not more than 60 μm, the resulting hollow body is removed from the electrolytic bath and rinsed. He's basically done with it. The plastic 6 remains in the hollow body, the entire outer surface of which is supported by the plastic and the functional part embedded therein. The wall thickness of the hollow body is shown exaggeratedly thick in FIG. 2 for the sake of illustration.

Claims (7)

Thin-walled hollow body, produced by the electroforming process from a noble metal or from a noble metal alloy, for use as jewelry or jewelery, characterized in that a core (6) is cast from one in the hollow body for permanent support of the thin outer wall (1, 2) - Or sprayable non-metallic substance, in particular from a plastic or wax is provided. Hollow body according to claim 1, characterized in that the core (6) contains a metallic functional part (3, 5, 7) directly connected to the outer wall (1, 2), which consists of the same material as the outer wall. Hollow body according to claim 1 or 2, characterized in that the plastic is a thermoplastic. A method for producing a hollow body according to claim 1, characterized in that the hollow body is poured or injected with the plastic or wax. A method of manufacturing a hollow body according to claim 1 by using the one of the steps Casting or injection molding the core in a negative form of the hollow body, Metallizing the core, - Strengthening the metallization by electrolytic metal deposition - Removing the core material from the hollow body thus formed existing electroforming process with the proviso that the core material is not removed. A method according to claim 5, characterized in that the reinforcement of the metallization is terminated when a layer thickness of at most 75 µm, preferably at most 40 to 60 µm, is reached. A method according to claim 5 or 6, characterized in that a functional part (3, 5, 7) is embedded in the core material during manufacture of the core (6), which consists of the same material as the outer wall of the hollow body and at least at one point from the Core material emerges.

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