Abstract:
Diamonds are marked by applying apertured stencils bearing identifying indicia to the girdles, applying a fusible coating material over the apertured stencils, and then heating the coating material to fuse the material on the girdles. The stencils can be eliminated, and the indicia can be formed by directing a source of radiant energy at the coating material, and by moving the source and/or the girdle relative to each other.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of application Ser. No. 09/909,174, filed Jul. 19, 2001, now U.S. Pat. No. 6,593,543 and claims the benefit of U.S. Provisional Application Serial No. 60/219,475, filed Jul. 20, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to marking and inscribing gemstones, particularly diamonds, with indicia identifying the gemstones by heating surface portions of the gemstones upon exposure to radiant energy in a fused marking pattern corresponding to the identifying indicia. 
     2. Description of the Related Art 
     Laser etching or inscribing of a diamond surface for the purpose of permanently identifying a diamond is well known. U.S. Pat. No. 4,392,476; No. 4,467,172; No. 5,753,887; No. 5,932,119; No. 6,211,484; No. 5,149,938; No. 5,410,125; No. 5,573,684 and U.S. patent application Ser. No. 09/785,631 filed Feb. 16, 2001 are representative of known laser marking systems that employ lasers, beam delivery and imaging components, gemstone fixtures, servomotors, optical encoders, and programmed computers for controlling the marking procedure. 
     Such marking systems not only occupy a large volume of space to accommodate all of their various components, but also are costly to purchase and operate. As a result, such systems are typically installed at one or more authorized sites, such as a gemological laboratory or institute. Jewelers and like customers desiring gemstones to be marked send the gemstones to the site of the marking system, and wait for the marked gemstones to be returned. 
     Many jewelers dislike sending precious items out of their hands and, hence, out of their sight and control, but perhaps, more importantly, dislike having to wait for their return. Yet, the size and cost of laser marking systems dictate against any one jeweler&#39;s purchasing and installing such a system at the jeweler&#39;s premises. Such systems also require skilled, trained personnel to operate the system. This requirement is typically difficult for the average jeweler to meet. 
     Another U.S. patent application Ser. No. 09/858,846 filed May 16, 2001, etches a diamond by igniting a flammable substance applied in a burn pattern to the diamond. This technique requires close monitoring of the flame produced after ignition to avoid the risk of fire. 
     SUMMARY OF THE INVENTION 
     OBJECTS OF THE INVENTION 
     One object of this invention is to enable gemstones to be marked with identifying indicia without using large sized, costly laser marking systems or flame etching systems. 
     Another object of this invention is to reduce the skill level required for personnel to mark gemstones. 
     Still another object of this invention is to enable gemstone marking on-site at a jeweler&#39;s premises. 
     Yet another object of this invention is to increase the use of gemstone marking by making the procedure more available and affordable and safer to jewelers. 
     FEATURES OF THE INVENTION 
     In keeping with these objects, one feature of this invention resides in a gemstone marking system and method that apply a fusible coating on a surface of a gemstone, for example, on a diamond girdle. The coating may be applied over the entire surface, or only over selected areas of the surface by use of a stencil having cutouts corresponding to identifying indicia for the diamond. A high melting point substance or mixture having a melting point greater than that of the diamond may be used for the coating. The substance or mixture is exposed to a radiant energy source and heated to fuse the coating on the surface in a marking pattern corresponding to the indicia. When the stencil is used, the substance or mixture filling all the cutouts is preferably simultaneously heated. When the stencil is not used, the energy source, preferably a laser, emits a laser beam and directs the laser beam and/or the energy source to move along the marking pattern. The marking can be performed at a jeweler&#39;s premises. 
     The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a marked gemstone according to this invention; 
     FIG. 2 is a sectional view of the process for marking the gemstone of FIG. 1 using a stencil according to this invention; 
     FIGS. 3A,  3 B and  3 C are sectional, enlarged views of the marked areas of the gemstone; and 
     FIG. 4 is a sectional view of the process for marking the gemstone of FIG. 1 without using a stencil according to this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference numeral  10  in FIG. 1 schematically depicts a diamond having a crown  12 , a girdle  14 , and a pavilion  16 . The girdle  14  is a peripheral band between the crown and the pavilion and, in the preferred embodiment, an identifying indicium or mark  18  is formed on the girdle. The mark  18  can be a machine-readable indicium, such as a one- or a two-dimensional bar code symbol, or can be a human-readable indicium, such as an alphabetical and/or numerical indicium, or can be a logo or image, for example, a certification mark of quality or of source of origin. The mark is permanent and is substantially imperceptible to the naked eye, although clearly visible under magnification such as by a ten power loupe. 
     In accordance with this invention, the mark is formed as follows: First, as depicted in FIG. 2, a generally planar stencil  20  having cutouts  22  is mounted on the girdle. One or both sides of the stencil may bear an adhesive layer to adhere the stencil in place on the girdle. The cutouts  22  have the same pattern as the mark  18 . 
     The manufacture of the stencil is preferably performed not by the jeweler or ultimate user, but instead, by an authorized stencil supplier who has the facilities and equipment to make the stencil with the cutouts. Thus, a jeweler may pre-order a supply of apertured stencils, for example, with sequential numbers in a series, or with a logo, from the stencil supplier. 
     With the supply of apertured stencils on hand at the jeweler&#39;s premises, the jeweler selects a stencil and applies it along the girdle of a gemstone to be marked. Preferably, the stencil has an adhesive surface that adheres to the girdle. 
     Next, the cutouts of the stencil are filled with a fusible coating or layer  24 , preferably of a high melting point material or mixture having a melting point exceeding that of the gemstone, e.g., diamond, to be marked. Preferably, the high melting point material is a metal such as tungsten, or a metal oxide material, or a ceramic material, or an alloy of such materials. The material layer may be sprayed, painted, dusted, or otherwise applied over the stencil to fill each cutout. The material layer  24  is preferably covered with a cover layer  26  that is preferably light-transmissive. 
     The jeweler then heats the material layer  24 , typically by directing a source of radiant energy, such as a laser  28 , at the cover layer  26 . The laser  28  emits a laser beam  30  that is directed to the cover layer  26 . The cover layer  26 , if present, simply allows the emitted laser beam  30  to pass therethrough. The material layer  24  is heated and alters the girdle in dependence upon the energy level of the laser beam as adjusted by an energy controller  32 . 
     At a relatively low energy level as depicted in FIG. 3A, the material layer  24  forms a raised bump and is fused with concomitant sublimation of the material layer  24  to the girdle  14  which may have cracks or fractures under the bump. A gel may be applied over the bump to help secure its position. At a medium energy level as depicted in FIG. 3B, there is concomitant sublimation of the material layer  24 . The heat is so intense that a cavity  34  is formed in the girdle, and the material layer  24  flows into, is fused to, and substantially fills the cavity until its upper surface is generally flush with the outer surface of the girdle. At the highest energy level as depicted in FIG. 3C, a much larger cavity or crater  36  is formed by the heat from the laser beam  30 , and the material layer  24  flows into, is fused to, and substantially lines or coats the interior surface of the crater. In all cases, the fused material layer  24  has a marking pattern which matches the shape of the cutouts which, of course, matches the shape of the identifying indicia or mark  18  desired. 
     The radiant energy source is preferably a laser, such as an excimer laser, but can by any type of laser or even a radio frequency or microwave source of radiation. 
     When tungsten is used for the material layer, the material layer  24  turns black after exposure to the radiation. The black or dark-colored layer  24  presents a sharp contrast against the essentially colorless diamond. Other colors are obtainable when different metal oxide materials are used in the material layer. 
     Rather than using a stencil, an entire exterior surface portion of the girdle can be applied or coated with the material layer  24 , and be overcoated with the optional cover layer  26 . Thereupon, as shown in FIG. 4, the laser beam  30  and/or the girdle  14  can be moved in the directions of the four-headed arrows  38  to directly trace the pattern of the indicia on the girdle surface portion. As before, the laser beam heats the material layer  24  at each spot where the laser beam impinges on the material layer, preferably after being focused by a focusing lens  40 . The energy level of the laser beam dictates whether the girdle surface is altered as shown in FIGS. 3A, B or C. 
     Once the gemstone is marked, a final heating step by baking the gemstone in an oven, or by exposing the gemstone to a finishing laser, may be needed. 
     The next step is to clean the gemstone, preferably in an acetone or acid wash. If a stencil is used, it is removed before cleaning. The resulting marked gemstone conforms to that shown in FIG.  1 . 
     The marking can be performed on any outer surface of the gemstone, and not necessarily on the girdle. The gemstone need not necessarily be a diamond. 
     Thus, marking is achieved at a jeweler&#39;s premises. The skill involved in applying a stencil, then applying the high melting point material layer, then heating the material layer, and cleaning the marked gemstone, or alternatively, the skill involved in applying the material layer without a stencil, is well within the expertise of the jeweler. 
     It will be understood that each of the elements described above, or two or more together, also may find a useful application in other types of constructions differing from the types described above. 
     While the invention has been illustrated and described as embodied in a gemstone marking system and method, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims. 
     What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.