Patent Publication Number: US-6705114-B2

Title: Decorative stone made of glass

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a decorative stone made from glass with a facetted front, and a mirrored rear converging from the periphery of the stone to a point provided with an adhesive. 
     2. Description of Related Art 
     It has long been known (see GB 1 325 293) to provide glass decorative stones with an adhesive on the rear, so that they can be ironed individually or in the form of a pattern applied to transfer foils onto a textile substrate. In areas of application where ironing is inadvisable, for imitation tattoos in particular, a pressure-sensitive adhesive is used instead of the usual hot-melt adhesive. 
     Decorative stones coated with adhesives basically have a planar rear, and the corresponding stone shape is known commercially as a rose. In exceptional cases, stones with a concave rear have even been proposed in order to improve adhesion (see WO 97/41746 and DE 26 46 727). 
     There is a need to configure stones of the type described in the Background such that they can be attached to a substrate using an adhesive. In particular, this is the case when the stones have a planar central area (table) on the front and their type of cut (“chaton”) thus resembles a diamond. 
     In the case of diamonds, a chaton normally has an angle between 96° and 98° at the point of the stone. In spite of the substantially different refractive index, with a glass stone, an optical behavior comparable to diamonds of a similar size is obtained. This is possible because the total reflection occurring on the rear of diamonds is replaced by mirroring. The term mirroring, as used herein, means treating a surface of an object, such as with silvering, to create a more reflective surface. 
     Chatons with a standard angle have already been used occasionally on textile substrates, but these are limited to very small stones with a diameter of less than 2.5 mm, and particularly soft substrates, because the gap between the periphery of the stone and substrate is otherwise too large. 
     If required, a certain increase in the diameter of adhesive chatons would be obtainable if the flattest of the chatons previously proposed were to be used, as have been described with an angle of 130°, and claimed for with an angle of up to 150° in AT 393 597. Larger stones have actually been used, however, configured with a flat rear, that is to say in rose form. In contrast to rivoli stones, when stones are chaton-cut, that is to say with a front table, this results in a central part that gives a less lively impression. Stones with a substantially increased brilliance are unexpectedly produced when the rear angle is made large enough for the adhesion of the stones no longer to be obstructed by the corresponding slight unevenness of the rear side of the stone. 
     SUMMARY OF THE INVENTION 
     The decorative stone made of glass of the present invention has a facetted front and a mirrored facetted rear converging from the periphery of the stone to a point, and the rear of the stone is provided with an adhesive. The decorative stone is provided with an angle of more than 150° between opposing surfaces of the rear of the stone. 
     In another aspect of the present invention, the decorative stone is provided with an angle of more than 160° between the two opposing surfaces of the rear of the stone. 
     In yet another aspect of the present invention, the decorative stone is provided with an angle between 170° and 175° between the two opposing surfaces of the rear of the stone. 
     Further, the front of the decorative stone of the present invention is provided in the central area of the stone with a planar surface, and the rear of the adhesive coated stone is planar. 
    
    
     Further details of the invention will be explained with reference to the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 to  3  illustrate the flattest chaton described until now from the rear, side and front views, respectively. 
     FIGS. 4 to  6  illustrate a first embodiment of a stone according to the present invention from the rear, side and front views, respectively. 
     FIGS. 7 to  9  illustrate a second embodiment represented in a manner similar to FIGS. 1 to  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The known stone  1  as shown in FIGS. 1-3 is made of glass, preferably of glass with a high refractive index. As is usual in the case of stones that are sold commercially under the description of chatons, eight planar surfaces  8  come together to a point, from the circular girdle  4 , which can be somewhat flattened into a culet  9 . From the girdle  4 , eight planar surfaces  2  extend forwards, terminating in the planar table  3  configured as a regular octagon. 
     What is unusual about the stone  1  shown in FIGS. 1-3 is 130° the angle between opposing surfaces  8  of the rear of the stone. Such an angle results in a completely different optical path for the incident light than is sought in conventional diamond cutting. It has been proved, however, that when the stone shown is used for manufacturing cup chains, the type of refraction of the light normally incident upon the table  3  is not vitally important. In contrast to an individual decorative stone that is worn perhaps as a pendant or ring, there are no preferred orientations for the mutual relationship of light source, stone and observer with a cup chain. This results in the individual stones always being in a position in which light already dispersed is reflected towards the observer. 
     With the stones according to the present invention, however, which are designed for adhesion onto a substrate, it has to be assumed that the direction of observation is normal to the stones. The observer of a stone with a front table and planar rear (rose with chaton cut) thus sees less dispersed light, as, with a large diameter, the stone has relatively little brilliance. The present invention provides facetting of the mirrored rear of the stone with an extremely large angle and thus an extremely low point on the rear of the stone, which is unexpectedly sufficient for substantially enlivening the stone. By means of this low point, it is possible to make the delimitation surface of the glue completely, or almost completely flat, and thus make the adhesive invisible along the periphery of the stone. If a thickness of the adhesive is 0.3 mm in the proximity of the periphery of the stone, the rear of the glue is completely planar. With a stone with a 2 mm diameter, an angular field of approximately 150° and a peripheral angle of the facets of approximately 15° is provided. Further, with a stone diameter of 7 mm, an angular field of approximately 170° with a peripheral angle of approximately 5° is provided. Accordingly, due to the above-described angular fields and peripheral angles, the angle between opposing surfaces of the rear of the stone are provided to be an angle of more than 150° and up to 175°. In the embodiment according to FIGS. 4 to  6 , the stone has only one set of mirrored facets  8  on the rear that are inclined at an angle of approximately 5° to the central plane of the stone. These facets are covered with an adhesive  10 , the thickness of which decreases towards the center, so that the rear of the coated stone is completely planar and the peak, the low point extending outward from the rear of the stone to which the facetted surfaces of the rear of the stone converge outwardly to, does not protrude the adhesive layer. As the angle of inclination of the facets  8  is so slight, it would also be possible to use an adhesive  10  of constant thickness (for example, of 0.3 mm). 
     The embodiment according to FIGS. 7 to  9  differs from the embodiment according to FIGS. 4-6 in that second set of facets  8 ′ is provided that are opposite the facets  8 . The large number of the surfaces ( 8  and  8 ′) largely compensates for a disadvantage caused by the slight inclination of the different facetted surfaces. The angle between opposing surfaces  8  and  8 ′ of the rear of the stone is more than 150° and may also be more than 160°. Further, with a stone diameter of 7 mm and an angular field of approximately 170° with a peripheral angle of approximately 5°, the angle between opposing surfaces  8  and  8 ′ of the rear of the stone may be between 170° and 175°.