EP0201394A1 - Process for cutting a diamond to otain an invisible setting, polishing process and device for producing it - Google Patents

Abstract

The present invention relates to a diamond cutting method for producing an invisible setting using notches located under the sheet in which the frame can engage. According to the invention the notches (7) have the shape of a dihedral (4) whose two surfaces (5-6) are located on either side of the plane of the natural table according to which the polished table is oriented (1), the two surfaces (5-6) of each dihedron being themselves polished using a sawing machine in which the diamond holder is mounted movable in a direction parallel to the plane of the disc and driven in an alternating movement according to this direction, the surface of the disc being coated with a mixture of evened and gum arabic diluted with water, the speed of polishing of the surface of the disc relative to the diamond being between 2500 and 3200 m / min. with, per minute, about ten passes of the diamond in contact with the surface of the disc.

Description

In FR-A-802.327, it has been proposed to mount precious stones on a mount by practicing notches or notches in the stones, in fact on each edge of the pyramid which constitutes its lower part or cylinder head. It is said that the notches of the stones described in the form of grooves in saw cuts could be different.

If the lessons of this patent prove to be sufficient in the case of colored stones, they do not allow a setting of the diamond which is really invisible. The notches or notches, whatever their shape and their position on the edge, give the polished table gray reflections, which makes the use for the diamond of the assembly described in FR-A-802.367 absolutely impossible.

The object of the present invention is to remedy these drawbacks and its purpose is to cut a diamond to allow the edges of its cylinder head to be fitted under the laminate with notches or notches in which the frame can engage, characterized in that the notches have the shape of a dihedral whose two surfaces are located on either side of the plane of the natural table according to which the polished table is oriented, the two surfaces of each dihedron being themselves polished.

The inventor has indeed found that when the two surfaces of the dihedral were polished, the crimping, both the metal part engaged in the notch and the notch itself, was completely invisible and did not modify the fires of the stone.

We know that it is impossible to polish a diamond according to the cubic crystallization planes called table of four points parallel to the plane passing through the four coplanar vertices of the octahedron, table of three points parallel to the plane passing through three coplanar vertices of l octahedron and table of two points which passes through two vertices, that is to say an edge, of the octahedron.

Consequently, when the stone is said to be full stone or with a sawn point with the polished table cut according to the table of the four points, the polished table being inclined by at least 7 ° relative to the table of the four points, the notches are made on the table of two points and the surfaces of each dihedral forming a notch are, one, substantially parallel to the polished table and, the other, inclined at an angle of at least 30 ° relative to the first.

When the polished table is placed on the table of three points, the notches are made on the table of four points.

When the polished table is tilted on the table of two points, the notches are made on the table of two points.

The cuts are made using a sawing machine or laser then the dihedral surfaces, one of which is substantially parallel to the polished table and the other inclined at an angle of at least 30 ° to the first, are polished using a sawing machine whose carriage carrying the diamond has been made mobile in a direction parallel to the plane of the sawing disc, the surface of the disc being coated with a mixture of shredded and gum arabic diluted with water, the speed of polishing of the surface of the disc with respect to the diamond being between 2500 and 3200 m / min ., preferably 2750 to 2900 m / min., with about ten passes of the diamond per minute in contact with the surface of the disc and a speed of passage of 2 m / min.

The nature of the abrasive, namely a mixture of embroidered and gum arabic is essential to avoid frosting the facets of the laminate and the table during the polishing of the dihedral surfaces.

The relative speed of the surface of the polishing disc with respect to the diamond must be greater than a minimum speed of 2500 m / min. below which there is no polishing but remain below at a maximum speed of 3200 m / min. above which there is combustion of the diamond. In addition, the polishing times must be short and separated by periods of cooling, which is why the carriage carrying the diamond should preferably make about five reciprocating movements per minute with a speed of passage of the diamond. about 2 m / min.

• La figure 1 est une vue par dessous d'un diamant muni d'encoches conformes à l'invention: la figure 2 en est une vue en élévation et figure 3 une vue en perspective; la figure 4 est une vue de l'octaèdre de cristallisation naturelle du diamant destinée à expliquer l'orientation des tables; la figure 5 est une vue illustrant la position des crans sur un diamant taillé en pleine pierre; la figure 6 est une vue ccrrcspon- dante d'un diamant taillé sur une pointe sciée; la figure 7 est une vue correspondante dans le cas d'un diamant taillé en brut de clivage et la figure 8 une vue correspondante dans le cas d'un diamant en pierre basculée.'

The invention will be described in more detail below with reference to the attached drawing in which:

• Figure 1 is a bottom view of a diamond provided with notches according to the invention: Figure 2 is an elevational view and Figure 3 a perspective view; FIG. 4 is a view of the octahedron of natural crystallization of the diamond intended to explain the orientation of the tables; Figure 5 is a view illustrating the position of the notches on a diamond cut in solid stone; Figure 6 is a view ccrrcspon- dante of a diamond cut on a sawn point; FIG. 7 is a corresponding view in the case of a diamond cut in the rough of cleavage and FIG. 8 a corresponding view in the case of a diamond in tilted stone.

In the drawings, the reference 1 designates the table of the cut diamond, the reference 2 the facets of the laminate and the reference 3 the cylinder head.

In accordance with the invention, notches 7 are produced in the edges of the cylinder head. These notches are dihedrons with an edge 4 orthogonal to the edge of the cylinder head with the two surfaces of the dihedral polished, one of the surfaces 5 being substantially parallel to the table 1 and the other 6 making an angle with the surface 5 of about 30 °.

In the octahedron of crystallization of the dihedral represented in FIG. 4, the plane passing through the four points 10 of the base of the pyramids and the planes parallel to it is called a table of four points. We call the table of three points the surface 12 passing through two points 10 and a vertex 11 of a pyramid and the table of two points a surface passing through an edge 13 of the tetrahedron. Natural tables can not practically be polished because of their hardness, the facets of the cut diamond and in particular table 1 must make a minimum angle of about 7 ° with the natural table according to which is cut the facet.

In Figure 5 the diamond is cut full stone and the table 1 is inclined at an angle of at least 7 ° on the table of the four points, the notches for priming the notches 7 are made in the tables of two points and the facets of the dihedrons are then polished, the facets 5 being substantially parallel to the table 1, that is to say inclined by about 7 ° on the table of the four points. The facets 6 are inclined by about 30 °.

In the case of a diamond cut on a sawn point shown in Figure 6, the notch formation rules are the same as for a full stone diamond.

In the case, illustrated in FIG. 7, of a so-called rough cleavage diamond, the table 1 is also inclined by at least 7 ° on the table of the three points 10-11. The starting notches of the notches 7 are sawn on the table of four points and the surfaces polished according to the same rules by making an angle of at least 7 ° with the table of four points.

In the case, illustrated in FIG. 8, of a diamond with a table tilted on the table of two points, the notches of the notches are made on the tables of two points and the polished facets 5 and 6 are respectively parallel to the table 1 and inclined by about 30 ° with respect thereto.

The notches of the notches are either sawed by successive passes of 4 / 1000th of a mm, or cut with laser. The faces of the dihedral constituting the notch are then polished on a sawing machine the diamond holder of which is mounted on a carriage driven in an alternating movement along a parallel to the plane of the machine disc. This reciprocating movement has an amplitude of approximately 20 cm and a frequency of 12 seconds, which gives a speed of 2 m / minute and a frequency of passage of the diamond in contact with the disc of 10 per minute.

The disc having a diameter of 15 cm is driven at a speed of 6000 revolutions / minute and its surface is coated with a mixture of equalizer and gum arabic diluted with water.

Claims (8)

1. A method of cutting a diamond to make an invisible setting using notches located under the laminate in which the frame can engage, characterized in that the notches (7) have the shape of a dihedral (4 ) whose two surfaces (5-6) are located on either side of the plane of the natural table along which the polished table (1) is oriented, the two surfaces (5-6) of each dihedron being themselves polished. 2. Method according to claim 1, characterized in that the surfaces of each dihedral forming a notch are, one, substantially parallel to the polished table and, the other, inclined at an angle of at least 30 ° by compared to the first. 3. Method according to any one of claims 1 and 2 applied to a stone called full stone or sawn point with the polished table (1) cut according to the table of four points, the polished table being inclined by at least 7 ° with respect to the table of four points, characterized in that the notches are made on the table of two points. 4. Method according to any one of claims 1 and 2 applied to a stone called rough cleavage or placed on the table of three points, characterized in that the notches are made on the table of four points. 5. Method according to any one of claims 1 and 2 applied to a stone called tilted on the table of two points, characterized in that the notches are made on the table of two points. 6. A method according to any one of claims 3 to 5, characterized in that the cuts are sawn or cut by laser and are then shaped and their surfaces polished by polishing. 7. A sawing machine modified for the implementation of the method according to any one of claims 1 to 6, characterized in that the diamond holder is mounted movable in a direction parallel to the plane of the disc and driven by a movement alternative in this direction. 8. A polishing process for implementing the cutting process according to any one of claims 1 to 6 with a machine according to claim 7, characterized in that the surface of the disc is coated with a mixture of even and gum arabic diluted with water, the polishing speed of the surface of the disc with respect to the diamond being between 2,500 and 3,200 m / min., preferably 2,750 to 2,900 m / min. with, per minute, about ten passages of the diamond in contact with the surface of the disc and a speed of passage of 2 m / min.

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