Composite wire for the manufacture of jewelry articles

Abstract: A composite wire for the manufacture of semifinished products to be subjected to an emptying process in the field of goldsmithery. The wire comprises a support core (1) developing essentially along one of its longitudinal axes in a nonprecious metal that is removable by chemical or electrochemical means as well as a plurality of sections (3, 4 and 5) in precious metal having an essentially longitudinal development of which at least a portion of each one is radially engaged in the core.

Description: The present invention relates to a composite wire for the manufacture of jewelry articles and more particularly for producing semifinished products, from which said jewelry articles are obtained, by subjecting them to a emptying process. The invention also relates to a process for the production of said composite wire as well as ornamental articles, in particular of an annular form, or the chains made with said articles which can be manufactured from said composite wire by means of mechanical processing and an emptying process. The techniques for the production of "hollow" articles or, in other words, articles composed of tubular elements conformed in various ways to form chain links, earrings, charms and the like in precious metals are well known in the field of goldsmithery. The most widely used technique in the manufacturing of ornamental articles made of hollow wire, mainly for ornamental chains, is the one in which there is used a composite wire formed from a support core in a nonprecious metal (iron, copper or special alloys, such as tombak), on which a lamina of precious metal is folded. The lamina is firmly secured to the support core by engaging the longitudinal edges of the lamina in respective axial grooves formed on the surface of the support core and subjecting this intermediate semifinished product to the mechanical process of drawing in order to obtain the desired diameter. The composite wire obtained with this technique can be used in manual or mechanical processing just as a common solid wire is used, for example, to produce ornamental chains. The internal support core is subsequently removed (emptying process) by means of chemical or electrochemical treatment to which the products are subjected. This technique is described in Italian patent no. 1154682, and in DE-A-832 734. With the process described above, it is possible to obtain wire material of a conventional form allowing only for the possibility of changing the cross section. Furthermore, with said technique, it is not possible to create a wire comprising more than one type of precious metal. Finally, the possibility of being able to propose new ornamental shapes and new techniques for producing such shapes, having a high level of flexibility of application and offering opportunities for creative activity on the part of the designer is in high demand in the field of gold craftsmanship. The object of the present invention is, therefore, to provide a composite wire of a novel structure that can be used in the field of gold craftsmanship for the manufacturing of semifinished products to be subjected to a process of emptying which would, after said treatment, give rise to articles of jewelry having an original configuration. A further object of the present invention is to provide a composite wire of the above-mentioned type as well as a method to produce such wire which provides the designer with a vast range of possibilities to create articles of jewelry having an original configuration. These and other objectives, which will become apparent in the description which follows, are accomplished with the composite wire according to the present invention whose novel feature consists in the fact that it comprises an elongate support core in a nonprecious metal that can be removed by chemical or electrochemical means as well as a plurality of elongate sections in precious metal of which at least a portion of each is radially engaged in said core. In one currently preferred embodiment of the invention, said sections engage in grooves having a depth equal to the width of the sections or are incorporated in said core inside grooves which have a depth greater than their width and close over them. Said sections can have a substantially flat, curvilinear or C-shaped laminar form. Further characteristics and/or advantages of the composite wire according to the invention will become apparent in the description which follows of some embodiments thereof, given as examples but not limitative, with reference to the attached drawings in which: figure 1 is a perspective view of a length of support core with laminar sections engaged therein for the production of a composite wire according to a first embodiment of the invention; figure 2 is a perspective view of a length of support core with angular sections engaged therein for the production of a composite wire according to a second embodiment of the invention; figure 3 is a perspective view of a length of support core with rounded sections engaged therein for the production of a composite wire according to a third embodiment of the invention; figure 4 is an enlarged partial cross sectional view of a possible variation of a composite wire according to the invention; figures 5 and 6 in a schematic view of an oval untwisted link, respectively in a plan view and a sectional view, made from the composite wire corresponding to figure 1 after it has been subjected to drawing; figure 7 shows an example of a length of ornamental chain including twisted links of the type shown in figures 5 and 6; figures 8, 9 and 10 show three examples of cross sections of composite wires according to the present invention which can be made by combination of different sections engaged with a support core. With reference to figure 1, it has been indicated at 1 a length of a workpiece made of iron, copper or an alloy, having an elongate form and a circular cross section. On the side surface four grooves 2 are formed, each of which engages a flat laminar section 3 having a thickness and width equal, respectively, to the width and depth of the groove. The engagement of sections 3 in core 1 is stabilized and made permanent by means of drawing which, at the same time, reduces the dimensions of the assembly to those desired, transforming it into a wire which can be used as if it were a conventional solid wire to produce links, link chains, annular pieces of jewelry and the like. Afterwards, the opposite ends of each annular element are soldered to each other in a known way and the support core is finally removed by means of a conventional chemical or electrochemical treatment (emptying process). In the embodiment of the invention shown in figure 2, laminar sections 4 of precious metal extending along corresponding surface portions of core 1 are secured to support core 1. The anchoring of laminar sections 4 is carried out by bending their edges 4a into angles that engage in adjacent pairs of grooves 2 formed axially on the side surface of core 1. The engagement of edges 4a in support core 1 is stabilized and made permanent by drawing, as in the previous case. In the embodiment of the invention shown in figure 3, the sections in precious metal engaged in grooves 2 of support core 1 are bars 5 with a curved cross section, in particular circular or elliptical, and a height lower than the depth of grooves 2. In this case, subjecting the assembly formed by support core 1 and bars 5 engaged in grooves 2 to drawing, the bars remain incorporated in core 1 as the pressure acting on the core closes grooves 2 over bars 5. Obviously the cross section of the support core can be different from the circular one illustrated above, just as the shape, the cross section and the number of sections in precious metal engaged or incorporated in said core can be different. Furthermore, combinations of sections of different shapes and natures can be used. Non-limitative examples of such possible variations are illustrated in figures 8, 9 and 10. In particular, the composite wire shown in figure 10 has more than one bar in precious metal inserted in each groove, for example white gold 21 and yellow gold 22 with the interposition of a bar in removable metal 23 such as copper so that, in the final product, the remaining elements in precious metal are spaced apart. To increase the stability of the connection between the laminar sections in precious metal and the support core, the cross section of said sections can advantageously have a trapezoidal shape, substantially as illustrated in figure 4, with the larger base of the cross section placed at the bottom of the respective groove. In this way, as a result of the drawing, the side faces of the groove close against the corresponding side faces of the section thus creating a sort of dovetail connection which makes radial sliding impossible. Another possible solution for obtaining the same result consists in carrying out the grooves at an inclination with respect to the radial direction. Also in this case, the deformation induced by the forces of compression acting during drawing on the shape of the groove and the cross section of the section eliminate the risk of radial sliding of the section. One practical example of the use of a composite wire according to the embodiment of figure 1 is illustrated in figures 5 and 6 in which a flat oval link for ornamental chains obtained from the composite wire, following soldering and subsequent chemical emptying, is schematically shown. The link is composed of four annular flat laminar elements 10, 11, 12 and 13 extending radially from a common symmetrical circumferential axis in angularly spaced positions of 90°. The four laminar elements are fixed with their ends to the opposite faces of a transverse disc member 14 formed during soldering between the opposite ends of each link. Obviously, in the majority of cases, the link is subjected to torsion both when it is made and when it is connected to other links and therefore the radial laminar elements will assume a twisted appearance both with respect to the circumferential axis of symmetry as well as with respect to the median plane of the link. The analogous configurations of links that can be obtained with composite wires according to the embodiments of figures 2 and 3 are not illustrated since they are obvious to a person skilled in the field. In figure 7 a length of chain realized with links such as the one illustrated in figure 5, but subjected to torsion, combined with conventional links having a continuous surface is shown as an example. There are many advantages to the use of the composite wire according to the invention in the field of craftsmanship of articles in precious metal. The most significant of these are the following: the possibility of creating links for chains, or in any case annular pieces of jewelry, in two or more different types of precious metal or in different chromatic gradations of a single precious metal, such as yellow gold, white gold and pink gold; the possibility of obtaining a wide variety of links for chains, or in any case annular pieces of jewelry, by varying the number, form, arrangement and combination of sections in precious metal engaged both with a mainly radial development and a circumferential development; the possibility of inserting more than one disc member 14 to create more discontinuities along the annular development of the piece of jewelry; the possibility of creating links, or in any case annular pieces of jewelry, having a mixed shape or, in other words, formed by half a link of continuous surface and half a link of radial or circumferential sections obtained by diametrically cutting one link having a conventional continuous surface and another link, such as the one in figure 5, of equal dimensions and subsequently soldering of the two halves together; the possibility of creating links, or in any case annular pieces of jewelry, having a spiral or multiple helical appearance by correspondingly twisting the composite wire before its processing, for example, in a chain making machine. Although the most frequent foreseeable application for the composite wire according to the invention is in the field of the manufacture of ornamental chains, it is clear that it can be used also for the production of bracelets, earrings and pendants in general as well as central and intermediate elements of necklaces, chokers, bracelets and the like. Variations and/or modifications can be brought to the composite wire for the field of gold craftsmanship according to the present invention without departing from the scope of the invention as set forth in the appended claims.

Claims: A composite wire for the manufacture of semifinished products to be subjected to a process of emptying to produce jewelry articles comprising an elongate support core (1) made of a nonprecious metal that is removable by chemical or electrochemical means; characterised by a plurality of elongate sections (3) in precious metal of which at least one portion of each is radially engaged in said core. A composite wire according to claim 1, wherein said sections (3) are engaged in corresponding grooves (2) having a depth equal to the width of said sections. A composite wire according to claim 1, wherein said sections (3) are incorporated in said core inside grooves (2) which have a depth greater than the width of said sections and close over them. A composite wire according to the previous claims, wherein said sections have a substantially flat laminar form. A composite wire according to any of claims 1, 2 or 3, wherein said sections (3) have a substantially curvilinear cross section. A composite wire according to claim 1, wherein said sections (4) have a substantially flat form with longitudinal edges (4a) folded to an angle on the same side in order to engage in two adjacent longitudinal grooves (2) formed in said core. A process for the production of a composite wire in the field of goldsmithery characterized in that it comprises the following steps: forming a plurality of longitudinal radial grooves (2) on an elongate support core (1) in a nonprecious metal that is removable by chemical or electrochemical means; providing a plurality of sections (3, 4) made of precious metal each having at least one portion suited to engage in one of said grooves; subjecting said core (1) in which said sections (3, 4) are engaged to mechanical processing consisting in radial compression and stretching to reduce the cross section and make secure said at least one portion of each of said sections within said core. A process according to claim 7, wherein said mechanical processing is an operation of drawing. A process according to any of claims 7 or 8, wherein said sections (3, 4) are of a flat laminar form, possibly having longitudinal edges (4a) folded at an angle on the same side or having a curvilinear cross section. A process according to claim 9, wherein the cross section of said sections (3, 4) having a flat laminar form is substantially trapezoidal. A process according to any of claims 7 to 10, wherein said sections (3, 4) having a flat laminar form with edges (4a) bent at an angle on the same side are engaged in adjacent grooves of said core. A process according to claim 7, wherein said grooves form an angle other than zero with respect to the radial direction. An ornamental piece of jewelry having a substantially annular form made from the composite wire according to any of the previous claims, characterized in that it comprises a plurality of substantially laminar or wire-like elements (5) extending along an axis of circumferential symmetry and at least one disc member (14), to opposite faces of which the ends of said plurality of laminar or wire-like elements are connected. An ornamental piece of jewelry according to claim 13, wherein said laminar or wire-like elements (5) have a substantially curvilinear cross section. An ornamental piece of jewelry according to claim 13, wherein said laminar or wire-like elements (5) have a substantially flat cross section. An ornamental piece of jewelry according to any of claims 13 to 15, wherein said laminar or wire-like elements (5) form a helix around a common circumferential axis. An ornamental piece of jewelry according to any of claims 13 to 16, wherein said circumferential axis is twisted with respect to a median plane. An ornamental piece of jewelry according to any of claims 13 to 17 substantially in the form of links of ornamental chains, rings, bracelets, necklaces, earrings, pendants, intermediate or central decorative elements and the like.

Inventors: TERZIANI URBANO, TERZIANI, URBANO
Applicants: CENTO GROUP SPA, CENTO GROUP S.P.A.
Application year: 1998
Main classification: A44C27
IPC codes: B21C37, A44C27, A44C11