The present invention relates to a jewelry stone, made from a natural or synthetic material, in particular a faceted diamond, including a visible frontal part called a crown and a dorsal part that is at least partially hidden when the stone is mounted on a mount, said dorsal part being called pavilion and being separated from the crown by an intermediate part between said crown and said pavilion, called girdle, said jewelry stone including fastening means allowing it to be fastened on said mount, said fastening means including a metal connecting zone located on said pavilion.
It also relates to a method for mounting a jewelry stone as defined above on a mount, said jewelry stone including fastening means arranged to allow it to be fastened on said mount, said fastening means including a metal connecting zone located on said pavilion.
Jewelry stones, in particular diamonds, are intended to be fastened on a mount or frame, for example to form pieces of jewelry or timepieces. According to one known embodiment, stone fastening on a mount is done by depositing, on part of the peripheral surface of the stone, a metal coating allowing it to be closely secured to the mount by a welding, riveting or a similar method.
As an example, publication FR 2,042,156 A describes a jewelry stone having a pavilion on which a layer of metal is deposited. This metal layer makes it possible to weld the stone on a mount. However, such an arrangement has the drawback of not being aesthetically pleasing, since this metallized layer is visible due to the fact that certain incident rays, reflected by an exit interface of the stone situated in the metallized zone, are returned by the stone by total reflection and return the image of the metallized layer.
Publication JP 09173115 A describes a technique for fastening a jewelry stone, such as a diamond, on a mount, in which a first layer, for example an alloy containing titanium (Ti), copper (Cu), silver (Ag) and/or zirconium (Zr), is deposited on the diamond, and a second layer of metal is deposited on the mount, for example a gold (Au) alloy. The two layers of metal are next welded together to securely fasten the diamond on the mount. The metal layer is deposited on the pavilion of the diamond, more particularly, at the middle of the pavilion of the diamond and on a surface which is smaller than the total surface of the pavilion. For the same reasons as above, this technique has an aesthetic drawback, the layer of metal being visible when incident rays reflected in the stone at the metallized zone exit through the crown of the stone.
Publication WO 00/57743 A2 relates to a system making it possible to crimp a precious stone in a hollow jewelry item. The system includes a device used to create a metal fastening zone subjected to the surface of the precious stone and a connecting device serving to fasten the metal fastening zone on a shell of the hollow jewelry piece. To create the metal fastening zone, a circumferential part of the surface of the precious stone is metallized and a layer of metal is deposited by electrolysis on the metallized circumferential part of the surface of the precious stone. This fastening belt is formed in a groove hollowed in the stone and at least partially encroaches on the frontal part of the stone (i.e., the crown).
Publication WO 2014/030068 A2 relates to a frame that comprises a precious stone, a mounting surface and a brazed joint. The brazed joint is formed from a reactive metal alloy, this alloy allowing the adhesion of certain points on the surface of the precious stone directly to the mounting surface. However, the fastening techniques described in this publication risk not providing sufficiently reliable or effective maintenance of the stone, and the described brazing method requires high temperatures, generally exceeding 800° C., which consume considerable energy and may potentially damage a delicate mounting surface of a mount for a top-of-the-line piece.
The problems raised by fastening jewelry stones on a mount consist both of ensuring effective and reliable maintenance of the stone while not requiring high process temperatures for fastening, and performing this fastening practically invisibly, so as not to undermine the shine of the stone. The known techniques do not provide a satisfactory solution to these problems.
The present invention aims to overcome the above drawbacks by proposing a jewelry stone arranged to be able to be fastened on its mount invisibly and a method for fastening the stone on its mount, the obtained fastening being effective, reliable, durable and invisible.
To that end, the invention relates to a jewelry stone as defined in the preamble, characterized in that said connecting zone is located on part or all of a peripheral sector with a limited width of said pavilion, in which the incident rays on the crown penetrating the stone by an air/stone interface, are either reflected by a first pavilion/air interface on a point of the pavilion lower than said connecting zone or completely reflected by said first pavilion/air interface of said stone in the peripheral sector including said connecting zone, and are refracted to the outside of said stone, behind said pavilion, through at least one second pavilion/air interface of said stone.
According to one preferred embodiment, said peripheral sector is situated on said pavilion near said girdle. Said peripheral sector can preferably include a so-called invisible zone in which no incident ray refracted at the air/crown interface is reflected by the first pavilion/air interface. Said peripheral sector can advantageously include a band extending over 360° around the pavilion. Said band preferably covers a zone corresponding at least approximately to about 20 to 35% of the surface of said pavilion.
Particularly advantageously, the metal fastening means can comprise a plurality of metal layers deposited in a sandwich. The plurality of metal layers preferably comprises an inner layer forming a layer of carbide with the stone. According to one advantageous embodiment, said inner layer comprises titanium, tantalum, hafnium or niobium.
The plurality of metal layers also preferably comprises an outer layer comprising the same material as that of the mount intended to receive the stone. Preferably, the outer layer and said mount comprise gold. According to another embodiment, the plurality of metal layers comprises an intermediate layer forming a diffusion barrier between said inner layer and said outer layer. The intermediate layer can comprise platinum. Advantageously, the metal fastening means are deposited using a PVD method.
Also to this end, the invention relates to a fastening method as defined in the preamble, characterized in that said connecting zone is deposited over part or all of a peripheral sector of limited width of said pavilion, in which the incident rays on the crown penetrating the stone via an air/stone interface, are either reflected by a first pavilion/air interface on a point of the pavilion lower than said connecting zone or are completely reflected by said first pavilion/air interface of said stone in the peripheral sector including said connecting zone, and are refracted outside said stone, behind said pavilion, through at least one second pavilion/air interface of said stone.
In the context of this method, said peripheral sector is advantageously defined at said pavilion near said girdle. Advantageously, a band is deposited in said peripheral sector that covers a zone corresponding to at least approximately 20 to 35% of the surface of said pavilion. The band advantageously covers a zone corresponding to at least approximately 20 to 35% of the surface of said pavilion.
In the context of the method, it is possible to deposit a plurality of metal layers in a sandwich to form the metal fastening means. It is also possible to deposit an inner layer forming a layer of carbide with the stone, this inner layer comprising titanium, tantalum, hafnium or niobium. It is also possible to deposit an outer layer comprising the same material as that of the mount intended to receive the stone before the fastening of said stone.
The present invention and its advantages will better appear in the following description of one embodiment provided as a non-limiting example, in reference to the appended drawings, in which:
The present invention relates to a jewelry stone, which will be referred to hereinafter as “stone” 10. The stone 10 according to the invention can be natural or synthetic, and may in particular consist of a faceted diamond, but may also consist of an emerald, a sapphire, a ruby or another type of stone. In the illustrated examples, the stone 10 is a round diamond having multiple cut facets 11. This example embodiment is of course not limiting, and the present invention refers to various shapes of stones.
In reference to figures, the stone 10, as shown, includes a frontal part that is commonly called crown 12, visible when the stone 10 is fastened on a mount (not shown). It is common for it to be cut so as to have multiple facets 11. Behind the crown 12, the stone 10 includes a dorsal part, commonly called pavilion 13, that is defined relative to the crown 12 by an intermediate part, commonly called girdle 14. The pavilion 13 is generally cut in a point and can also have multiple facets 11. Typically, the pavilion 13 is at least partially hidden when the stone is mounted on its mount. Indeed, the pavilion 13 is typically used to allow fastening of the stone 10 on a mount such that only the crown 12 is visible, while making sure that the fastening of the stone 10 is as invisible as possible. One aim sought by jewelers is to hide the manner in which the stone 10 is fastened while ensuring that is fastened reliably and with optimal shine or brilliancy of the stone 10, irrespective of the application, therefore independently of the type of mount, which may for example consist of a timepiece or a piece of jewelry.
As shown in particular in
n
1 sin(i1)=n2 sin(i2)
The refracted ray R′1 is deviated by an angle i2 relative to the normal HA1, this angle i2 being smaller than the incident angle i1 of the incident ray R1, since the refraction index n1 of the air is lower than the refraction index n2 of the stone 10. This refracted ray R′1 travels inside the stone 10 and strikes the wall of the pavilion 13, more specifically the first pavilion/air interface, at a point B1, on which it undergoes a complete reflection. Indeed, the refracted ray R′1 forms an angle ir relative to the normal HB1 at the point B1 which is larger than the limit angle il beyond which there is a total reflection and which obeys the law:
I
l=arcsin(n1/n2).
For example, for a diamond stone 10 with a refraction index n2=2.42 and a refraction index of the air n1 equal to 1, the limit angle il is substantially equal to 24°. The reflected ray R′1, along an angle ir at the point B1, is next sent onto a second pavilion/air interface point C1, where it undergoes a new total reflection, before being returned onto a third crown/air interface at a point D1. It undergoes a refraction such that the exit angle i4 is larger than the incident angle i3 at the point D1. It will be noted that the incident light at the point A1 of the crown 12 is returned to the point D1 of the crown 12 in the form of a ray R″1, such that the stone 10 shines with all its brilliance, when the above conditions are met.
A second incident light beam R2 is shown in
Under the aforementioned conditions and assuming that the surface of the pavilion 13 is metallized or covered in part or in whole with an opaque coating, in order to arrange fastening means for fastening the stone 10 on a mount, at least part of the light having passed through the stone 10 and having been reflected by the surface provided with said opaque coating, returns the image of this opaque coating and undermines the desired brilliance of the stone 10, which one is seeking to avoid.
To that end, the stone 10 according to the invention, as shown by
As an example and as shown in
A second ray R4 shown in
As illustrated by
As a result, the particular optical properties of the peripheral sector 131 make it possible to deposit the connecting zone 21 on part or all of this peripheral sector 131, such that they are made invisible for a viewer looking at the stone 10 via the crown 12. It has been observed in faceted round diamonds that the peripheral sector 131 is situated directly below the girdle 14 and extends over a surface smaller than the total surface of the pavilion 13.
According to one embodiment of the present invention, the metal fastening means 20 are deposited on the surface of the stone using a PVD (Physical Vapor Deposition) method. The use of PVD makes it possible to form the connecting zone 21 in a controlled and precise manner on the surface of the stone. The PVD deposition step can be preceded by a step for cleaning the surface of the stone, as well as, optionally, depositing an adherence layer. Preferably, the PVD deposition step takes place in a chamber comprising an inert gas, such as argon, at a pressure between 10−4 to 10−2 mbar.
In one embodiment, the metal fastening means 20 comprise a plurality of metal layers deposited in a sandwich on the surface of the stone. According to one privileged alternative, an inner metal layer of titanium (or a titanium-based alloy) is deposited first on the stone, followed by an intermediate layer made from platinum (or a platinum-based alloy), then an outer layer of gold (or a gold-based alloy). Here, the layer of titanium, which preferably has a thickness of 40-500 nm, plays an adherence role, the titanium forming a layer of carbide with the stone. Other materials capable of forming a carbide layer with the stone (such as tantalum, hafnium or niobium) can alternatively be used in place of titanium as inner layer. The outer layer of gold, which preferably has a thickness of 100-2000 nm, allows fastening to a gold mount by welding or by thermocompression, as described below. Of course, if the mount intended to receive the stone is made from another material, the material of the outer layer can be adapted accordingly. The platinum layer, which preferably has a thickness of 60-500 nm, forms a diffusion barrier between the layer of titanium and the layer of gold, but other materials can also be used as intermediate layers. Other layers aside from those that have been mentioned may also be present in the fastening means 20.
After the formation of the metal fastening means 20 on the surface of the stone, a chemical cleaning step can take place to eliminate any metal material present in unwanted locations in order to ensure that the connecting zone 21 is positioned correctly and is not discernible, as explained in detail above.
After metallization, the stone including the metal fastening means 20 can be fastened to a corresponding mount using different techniques, but is preferably fastened by thermocompression or welding. In the context of thermocompression, and preferably also in the context of welding, a metal layer is also formed by a PVD method on the part of the surface of the mount intended to receive the stone (and in particular the metal fastening means 20). In particular, for a gold mount, the metal layer deposited on the mount is preferably also made from gold. This deposition of a metal layer on the mount can also be preceded by a step for cleaning the surface of the mount in question.
According to one alternative, the stone is fastened to the mount by thermocompression, and the metal fastening means 20 comprising a gold outer layer are compressed against a gold layer deposited on the mount. In one example, a compression machine, operating at a force of 2-20 kg/mm2 and at a temperature of 100-600° C. (or more preferably 200-450° C.) for a duration from 20 seconds to 60 minutes, is used for this step.
According to another alternative, the stone is fastened to the mount by a welding machine under a force of 5-50 g/mm2 and a temperature of 280-350° C. for a duration from 1 second to 5 minutes. As indicated above, in this case, a pre-form of an appropriate material and having an appropriate shape (for example, a conical ring made from gold-tin) is used, and the mount preferably has a gold layer deposited beforehand on its surface. A chemical cleaning step can take place after the welding to eliminate any remaining debris.
This description clearly shows that either the metal band 22 is not discernible because it is found in the invisible zone ZI just below the girdle, or all of the incident rays R3 that are reflected by the peripheral sector 131, at a first pavilion/air interface, in which the metal band 22 is situated, are returned on a second pavilion/air interface under an angle smaller than the total reflection limit angle il, such that they are refracted and evacuated at the rear of the pavilion 13 of the stone 10 without being seen. The invention makes it possible to achieve the desired aims, i.e., making the connecting zone 21 of the stone 10 invisible when it is fastened to its mount.
Depositing metal fastening means 20 on the pavilion using a PVD method allows the formation of a metal connecting zone 21 with a controlled size and precise position. Preferably, this connecting zone 21 extends like a metal band 22 over 360° around the pavilion, which allows reliable and robust fastening to a mount, even if the stone is small and the band 22 has a relatively thin width. Furthermore, the stone including the metal fastening means 20 can advantageously be fastened to the mount according to conditions where the temperatures do not exceed 600° C., and more preferably do not exceed 450° C.
The present invention is not limited to the described example embodiment, but extends to any modifications and alternatives obvious for one skilled in the art.
Number | Date | Country | Kind |
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01856/14 | Dec 2014 | CH | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CH2015/000175 | 11/30/2015 | WO | 00 |