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1. WO2020109960 - DIAMOND CUT

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

Diamond cut

The present invention relates to a cut diamond.

The quality and value of cut and polished diamonds for use as a jewel is often described by the four C's:

- Carat

- Clarity

- Colour

- Cut

Carat is the unit of weight of diamonds, whereby one carat equals 200 mg. Traditionally, the value of a diamond is determined by its size or weight, expressed in carat. The bigger the stone, the higher the value.

Clarity refers to the imperfections and intrinsic impurities already present in the rough stone.

The colour is also determined by the rough stone. Colourless and transparent stones are scarcer and therefore more valuable .

Cut refers to the cutting and polishing of the stone in a specific form with numerous facets. The manner a stone is cut determines the path the light, which enters the stone, will travel. Almost all the light that enters the stone will also leave it again . The reflections, refraction and dispersion along the light path will determine the brilliance and fire of the stone .

Colour and clarity are intrinsic properties of the stone for which gradation scales have been defined. Their values cannot be changed to increase the value of the stone.

Traditionally, the stones are cut and polished in such a way as to retain their maximum weight during the method, while any defective spots, such as points or granules, could be removed. Because the play of the light in the stone was not co-ordinated, the light did not produce much fire or brilliance in the stone.

The last centuries the cut diamond’s brilliance and fire have become more valued than merely the weight of the stone.

Even with modern techniques, cutting and polishing a diamond crystal always leads to a drastic loss of weight: said loss is rarely less than fifty percent.

If the crystal is an octahedron, the round brilliant cut is usually preferred because often two stones can be cut from one crystal then. As its name suggests, the brilliant cut is characterised by a lot of brilliance and fire.

In the mid-seventeenth century the first diamonds were cut in a form that was a precursor of the current brilliant cut, the so-called mazarins or double-cut brilliants. Since then the design of the brilliant cut has developed further .

The different dimensions and angles of a brilliant cut to maximise the brilliance were determined more by skill than by science. In 1912, Marcel Tolkowsky published his book "Diamond design, A study of Reflection and Refraction in Diamond" . This book contains a mathematical study to determine the optimal angles and dimensions for achieving the maximum brilliance with the brilliant cut.

Tolkowsky' s ideal model did not consider all aspects; it was a two-dimensional model and did not take into account the effects of the girdle. The model has been somewhat refined since. Nevertheless, study of diamonds that were supposed to be very well cut and polished, obtained by pure skill, showed that they have almost the same dimensions as predicted by Tolkowsky 1 s ideal model . An example can be found in EP 1.181.875. An alternative construction for the traditional ideally cut brilliant can be found in US 20060086143 in which eight extra facets on the crown and sixteen extra facets on the pavilion are described.

We can conclude that the value of a stone with a given size can be influenced by changing the way it is cut. The goal is to obtain a maximum brilliance and fire in the stone while retaining the highest possible weight. The problem is that these are contradictory requirements .

It is therefore a purpose of the present invention to provide a solution which at least diminishes the aforementioned and other disadvantages .

To this end the present invention provides a cut diamond characterised in that it is a convex polyhedron and has fifty-six facets, which is one less than the fifty-seven facets of an ideally cut diamond brilliant when no culet is present.

In particular, the crown has 24 facets, namely eight girdle cross-facets, eight big kite facets and eight crown star facets .

The girdle is provided with 48 facets, but can also be executed cylindrically .

The pavilion consists of a lower star pavilion with eight pavilion star facets, surrounded by eight small kite facets, in turn surrounded by eight larger kite facets, which border eight girdle facets, or 32 facets together.

The eight pavilion star facets come together in the culet or in the apex of the pavilion such that a symmetrical eight-pointed star shape is formed when viewed from below.

The eight crown star facets come together in the apex of the crown, which apex can optionally be replaced by a small table, forming a fifty-seventh facet .

A cut diamond according to the invention strengthens the brilliance and the fire of the rough stone, with maximum retention of the weight.

A special aspect of the invention is the aspect that the cut diamond, viewed from above, creates a light effect like that of a rotating wheel. For this reason, the cut was called Dream Catcher, by analogy with spiral-shaped amulets from Indian culture to which effects on dream and sleep behaviour were attributed.

With the intention of better showing the characteristics of the invention, a preferred embodiment of a cut diamond according to the invention is shown hereinafter by way of an example without any limiting nature, with reference to the accompanying drawings, wherein:

figure 1 schematically shows a frontal view of an ideally cut brilliant;

figure 2 is a top view of the crown of the diamond of figure 1;

figure 3 is a bottom view of the pavilion of the diamond of figure 1;

figure 4 schematically shows a frontal view of a cut diamond according to the invention;

figure 5 shows a top view of the crown of the diamond of figure 4 whereby the rotating wheel- light effect typical of the diamond according to the invention is emphasised;

figure 6 shows a bottom view of the pavilion of the diamond of figure 4;

As the shape of a cut diamond according to the invention can most easily be explained based on the shape of an ideally cut diamond, we will first explain the geometry of such an ideally cut diamond.

An ideally cut brilliant 1 consists of fifty-seven facets when no culet is present. The shape of such diamond can be derived from the figures 1 to 3.

An ideally cut brilliant 1 consists of an upper part, called the crown 2, and a lower part, called the pavilion 3. These two parts are separated by a proportionally thin disk, called the girdle 4. For the purpose of the invention it is not necessary the girdle 4 is present . If no girdle is present, the horizontal plane that the crown 2 and the pavilion 3 have in common can still be called the girdle plane. The girdle 4 itself may or may not have facets, but this is not relevant for the present invention.

The crown 2 comprises thirty-three facets. The top facet of the crown 2 lies in a horizontal plane and is called the table 5. There are eight crown kite facets 6, eight crown star facets 7 and sixteen upper half facets 8.

The pavilion 3 comprises sixteen lower half facets 9 and eight lower main facets 10. The pavilion 3 may also contain a culet facet, which is a facet that is located near the apex of the pavilion 3 and is parallel to the table 5.

In an ideally cut brilliant 1, the axis through the middle of the table 5 and through the apex of the pavilion 3, or through the middle of the culet, if present, is an eightfold symmetrical axis .

The shape of an ideally cut brilliant 1 can be described by eight independent parameters . Other ratios can be easily calculated from the independent parameters . The following table 1 summarises the most important parameters in the known way, whereby their planes and a reference are indicated in the drawings .

Table I Parameters of an ideally cut brilliant diamond.

Less important is the size g, which indicates the minimum height of the girdle 4, as is shown in figure 1. In the drawings an ideally cut brilliant 1 without culet is shown .

A diamond cut 11 according to the invention without a culet facet is also a convex polyhedron, but has fifty-six facets, of which three series of eight facets on the crown side and four series of eight facets on the pavilion side, whereby the top of the crown side is also pointed and forms an apex, like the pavilion below. Optionally, the pointed apex of the crown can be replaced with a small table, forming a fifty-seventh facet.

The three series of eight facets on the crown side consist of eight crown star facets, eight crown kite facets and eight girdle facets which border the girdle.

The four series of eight facets on the pavilion side consist of eight pavilion star facets, eight big pavilion kite facets, eight smaller pavilion kite facets which touch the girdle and eight girdle facets which border the girdle.

Optionally, the girdle can be provided with girdle facets of a desired number, for example of eight times six girdle facets in the plane of the girdle, forty-eight facets together. Optionally, a culet facet can be present on the pavilion side.

Preferably, the axis running through the middle of the crown 2 and through the apex of the pavilion 3, or through the middle of the culet, if present, is an eight-fold symmetrical axis .

The following table II summarises the most important parameters of a preferred embodiment of a cut diamond 11 according to the invention, whereby their planes and their reference are indicated in the drawings.

Table II: parameters of the Dream Catcher cut according to the invention.

Light that enters the crown cross in the diamond is dispersed and refracted. The refracted light falls on the thirty-six facets of the pavilion and is reflected. The pavilion 3 of a diamond cut according to the invention is usually deeper than that of an ideally cut brilliant 1, the effect being that such a diamond holds the light in the diamond longer. Viewed from above the reflections form a rotating wheel pattern (see figure 5) , said pattern being characteristic for a diamond cut according to the present invention.

A diamond according to the invention may or may not have a faceted girdle 4. Both are seen as alternatives that fall under the protection of the present invention. In the case of a faceted girdle 4, the number of girdle facets is hereby determined in practice according to the state of the art.

In another alternative embodiment, a culet facet can be added to the underside of the pavilion 3 of a diamond cut according to the invention.

In yet another alternative embodiment, a table facet can be added at the top of the crown of a diamond cut according to the invention without losing the optical effect with the formation of a rotating wheel pattern.

The axis running through the middle of the crown 2 and through the apex of the pavilion 3, or through the middle of the culet , if present, is preferably an eight-fold symmetrical axis.

The present invention is by no means limited to the embodiments described as an example and shown in the figures, but a diamond cut according to the invention can be realised in all kinds of forms without departing from the scope of the invention, as it is defined in the following claims .