The present invention finds its ground in the demand triggered by a segment of consumers who, although of little extent from a numerical point of view, are particularly refined in their tastes, to the point that they desire to be able to have at their disposal, also for the everyday use, objects that are made of precious materials.

It therefore is a first purpose of the present invention to meet such a demand by providing objects, such as cutlery and table vessels, which, as processed according to an industrial process aimed at making use of precious stones, have an inherent value that is even greater than the one of the same objects made of silver and gold which are have been marketed since the most remote ages.

It is a generally known fact that, on objects made of silver alloys, atmospheric agents can be the cause of a surface opacification, which is better known under the term of tarnishing in the art, which extends also below the precious stones that may be set therein. It is also widely known that the aggressiveness of some foodstuffs or beverages (such as for instance vinegar, tomatoes, mayonnaise, juices of citrus fruits) gives rise to darkening and oxidation reactions whose effect adds to the afore cited tarnishing one. The usual detergent substances, even if used in a spray form, are in fact not capable of fully and evenly penetrating under the precious stones, in direct contact with the silver, and so ensuring a perfect cleaning of these inner surfaces.

A second purpose of the present invention is to keep the desired characteristics of glossiness, ease of cleaning and hygiene unaltered in collections of cutlery and vessels adorned with precious stones, during the practical utilization thereof.

It therefore is the main subject of the present invention to provide an industrial process having the characteristics as recited in the appended claims and adapted to decorate and embellish with precious stones objects that are at least prevailingly made of metal, and more particularly of a noble metal, used to take food and beverages, such as cutlery and vessels. The scope of the present invention extends to also cover objects that are manufactured in accordance with this technical process.

In view of a better understanding of the invention, as well as the features and advantages thereof, the description is given in the following, by way of non-limiting example, of a preferred embodiment of a process to embellish a cutlery piece made of a silver alloy (generally an alloy with a fineness of 800/°°° or an alloy with a fineness of 925/°°°). All processing steps mentioned below shall be understood as being performed after the phases of formng, deburring and polishing of the piece.

1. Preliminary processing of the cutlers piece This processing step is completed through following operations: 1. a-With the use of sharp-pointed tools, in the pre-established zones of the surface of the cutlery piece, which normally do not come into contact with the mouth, there are made a plurality of round conical recesses to accommodate the precious stones, with diameters and depths that are proportionally correlated to the diameter and depth size of the same stones that are to be set there. These accommodating recesses may be carried out also through the use of dedicated graphic software as well as CAM software for managing and routing the tools in numerical-control milling machines. In this case, the possibility is given of obtaining a great degree of precision in making the recesses to their exact dimensions and locating them in their correct position in the stone setting zone. After this step, the surface around each such recess is split in view of forming approx. four clasps.

1. b-As an alternative thereto, in the case that the setting of the precious stones is to be carried out under utilization of a"plug" (as this will be described in greater detail further on), the recesses can be made either manually, with the use of appropriate tools, or with the use of numerical-control milling machines.

1. c-Fine polishing of the inner surfaces of the recesses, preferably by means of micro- brushes and polishing pastes.

2. Processing of the precious stones In order to not only ensure the best possible visual impact, but also to do away with the risks of the precious stones coming off the seats in which they are set, the

present invention provides for making preferably use of such natural precious gems as diamonds, emeralds, sapphires and rubies, wherein the stones are processed solely by workshops that are specialized in cutting the stones to a very high precision degree, i. e. to a precision that is generally defined as"watchmaking grade"in the art. The most frequently used cut is the so-called brilliant cut, which calls for thirty-two facets in the upper zone (crown) and twenty-four facets in the lower zone (pavilion), with a girdle provided between the two zones. In the case of diamonds-considering the so-called Tolkowsky shape as an ideal reference example-the high-precision cut is assured by following dimensions: assuming that the largest diameter of the girdle is equal to 100, the height of the crown shall correspond to a value between 15% and 16% of said diameter, the height of the pavilion shall amount to anywhere between 40% and 45%, the height of the girdle shall be situated between 2% and 4%, the width of the upper table shall range between 52% and 56% of the above mentioned diameter. It is only in the case of coloured stones, either cuts with twenty-four facets on the crown and sixteen facets on the pavilion or cuts with eight facets on both the crown and the pavilion, may be taken into consideration.

3. Application of the precious stones onto the cutlerv piece The cutlery piece is then adorned with the natural precious stones that are set thereonto in view of providing a pave-like decoration pattern and/or various chromatic decoration patterns.

3. a-The application of the precious stones directly onto the surface of the cutlery piece can be carried out according to any of the traditional methods of stone-setting; in this case, each stone is inserted directly in its own conical recess, which will have been previously provided as above described in connection with the step 1. a, and is fastened thereto in a definitive manner by the clasps being closed against the facets of the crown.

3. b-An alternative manufacturing technique calls for the precious stones to be set not directly in the central surface of the cutlery piece, but rather in a single plug, which is made separately and is only at a later stage applied in an own seat that will have been established in advance in the central surface of the cutlery piece. On the plug there is provided a plurality of conical recesses for the precious stones as in the afore described step 1. a. The seat for the plug is obtained through a highest-precision milling operation and subsequent removal of material in the pre-defined central zone. The plug-which may be made of a silver alloy with the same fineness of the alloy of the cutlery piece, i. e.

800/°°° or 925/°°°-has first of all a purpose of granting a considerable extent of easiness and convenience in carrying out the manufacturing phases of the cutlery piece. During the manufacturing cycle, in fact, the reduced size of the plug with respect to the actual size of

the cutlery piece makes it more practical and convenient to handle the workpiece when making the recesses, setting the stones and carrying out the finishing steps (rhodium- treatment and final brightening) that will be described further on. Therefore, the need arises to provide for a specific plug to be provided for each type of articles to be manufactured. This of course applies also to other objects differing from the cutlery pieces considered in the herein described example. The plugs may be produced by hot coining, cold coining or casting. Coining gives better results from a point of view of material quality, since cast surfaces may show the presence of impurities or small inclusions in the metal.

The application of the plug may be carried out in two different modes, namely : a definitive mode, in which the plug is applied perfectly in its central seat by means of internal screws and micro-welds ; once these processing phases are concluded, the plug cannot be removed from the cutlery piece any more; a temporary mode, in which the plug carrying the precious stones set therein is applied in the central seat of the cutlery piece by snap-type fastening means. In this case, the usefulness of the plug, which was only considered under a technical- manufacturing point of view in the previous case, acquires an important role also in practical use. As a matter of fact, the plug can in this case be removed from the cutlery piece after the latter has been used at table and either washed with some special liquid detergent available for cleaning precious stones or immersed in an ultrasound cleaning bath. The all-metal cutlery piece, with the plug so removed therefrom, can in turn undergo a periodical cleaning with the use of the traditional liquid or creamy products available for cleaning oxidized surfaces, without any risk of damaging or losing-even inadvertently-the precious stones. A further advantage deriving from the use of this application of a plug lies in the possibility of making available, for a same cutlery piece, a plurality of equally sized plugs, which are however decorated with different precious stones. In this manner, it is possible for more plugs to be periodically replaced in a same cutlery set so as to be able to present on the table, on different occasions, alternative chromatic decorations.

4. Finishing operations on the metal parts of the cutlery piece 4. a-The clasps are finely polished by means of special polishing disks (e. g. of the type Cambric with a diameter of orientatively 100 mm) under utilization of an appropriate paste (e. g. supplied by the company Mérard-Cauillaudin S. A. sited at Villefranche, France) and using buffing felts (which may have a diameter of orientatively 60 mm), with the use of red polishing paste based on alumina and iron or cerium oxide (as for instance of the type Menzerna supplied by the firm Karl Ulrich of Bolzano, Italy) or some other suitable paste (as for instance the one supplied by the firm Bula Techno-Finish at Henniez, Switzerland).

4. b-The cutlery piece is initially caused to undergo a first ultrasonic cleaning with an alkaline cleaner to remove even the slightest traces of polishing paste; it is then degreased in a cathodic electrolytic bath (eg, containing the degreasing agent of the type Brenton R. 61), and is finally allowed to undergo a further rinse, followed by a drying step by means of a flow of hot air.

4. c-The surface zones of the cutlery piece differing from the ones that are designed to accommodate the setting of the precious stones, are appropriately and accurately coated with a special resist lacquer (e. g. of the type Lechleroid Metalloid Red supplied by the firm Lechler of Chiasso, Switzerland), which is preferably applied manually with a brush.

4. d-The cutlery piece is allowed to undergo a second ultrasonic cleaning, followed by a treatment of cathodic degreasing at a lower current density than the one used in the preceding phase 4. b (usually lower than 0.3 A/dm2) in view of maintaining a perfect adhesion of the previously applied layer of resist lacquer.

4. e-The cutlery piece is immersed in an acid neutralization bath, e. g. in a 3 to 10% aqueous solution of sulphuric acid.

4. f-When the cutlery piece is made of a silver alloy, such as in the example being considered here, in order to obtain a sufficiently thick protective layer against the atmospheric oxidizing agents and the aggressive substances that are present in foodstuffs and beverages, the present invention at this stage provides for a galvanic treatment with a white-hued metal, which is carried out only in correspondence of the surface zones of the piece, in which the precious stones are to be set. The cutlery piece is immersed in a galvanic bath adapted to deposit electrolytically a metal belonging to the eighth group of the periodic table of the elements, having an atomic number that is either just lower than the one of silver- in practice a bath of rhodium (as supplied for instance under the designation 5503W by the Swiss firm Metalor) or palladium-or higher, such as a bath of platinum. The immersion time has a duration ranging from 60 to 120 seconds, in particular approx. 80 seconds in the case that said element is rhodium, which is a preferred option for reasons of both technical and aesthetical nature. The surface intended to receive the precious stones, i. e. in which the latter have to be set, is first coated with a finishing rhodium layer, deriving from a sulfate/phosphate solution, in view of obtaining a final colour that is as white and bright as possible (very close to the colour of silver) and, at the same time, a very high level of hardness in the formation of the protective layer. The overall thickness of the deposited rhodium layer shall preferably amount to approx. 0.5 micrometers. In the case that the objects are made of alloys of yellow and pink gold, this rhodium-plating phase to protective purposes shall not be carried out.

4. g-The resist lacquer that had been previously applied during the afore described phase 4. c is at his point removed with the use of an appropriate solvent, which may for example be acetone.

4. h-The cutlery piece is then rinsed and allowed to dry under the action of a flow of hot air.

4. i-The cutlery piece is finally brightened over its whole surface according to the usual methods that find application in the field of silverware.

4. j-In the case of cutlery pieces made of silver alloys for which there can be expected quite long periods of storage, especially under climatic conditions characterized by high temperatures associated with a high relative humidity, the method according to the present invention provides for a last phase of chemical passivation, generally known as antitarnishing treatment in the art, in which the passivating agent may for example be the type Tarniban 51 supplied by the company Technic Inc.

Further to the ones that are specifically connected with and deriving from the application of the precious stones, the advantages offered by the present invention may be summarized as follows : The embellishment with precious stones confers an indisputably high extent of refinedness and valuableness to the herein considered objects. a An effective and appropriate protection is ensured to said objects against the oxidizing action of atmospheric agents, as well as against the aggressiveness of the afore cited food and beverage substances, thereby allowing for very high standards of cleanness and hygiene.

In the case of objects made of silver alloys, the surfaces of the piece that are not intended to accommodate the setting of precious stones, and which are therefore not subject to rhodium-plating-i. e. a treatment that, as already mentioned earlier in this description, solely involves the stone setting zone of the piece-retain the peculiar milky tone of silver, as well as the level of brightness that is particularly acknowledged and appreciated by the consumers whom the present invention is aimed at.

The additional deposition of a rhodium layer (or of any other one among the afore cited metals of the eighth group of the periodic table of the elements) on the surface in which the precious stones are to be set, before the same precious stones are definitively applied thereto, further improves the protection of the silver.

Although the above given description refers to a currently preferred embodiment, it will be appreciated that the present invention may be embodied according to a number of variants and be the subject of a number of modifications without departing from the scope thereof, as defined in the appended claims.

A first variant may for instance provide for an additional electrolytic deposition of rhodium (or of any other one among the afore cited metals of the eighth group of the periodic table of the elements) over the entire surface of the objects in advance of the definitive application of the precious stoned. The method used to carry out such a further plating phase is substantially the same as the one described in connection with phase 4. f above. This gives a further advantage in that, with an overall thickness of the rhodium layer in excess of 0.5 micrometers, the protection of the surface zones is improved to a superlative effectiveness.

It should on the other hand be noticed that, in the case that the above cited objects are made of gold alloys, these phases of electrolytic deposition are not required.

Furthermore, the plugs used on objects made of alloys of such a kind are themselves made of white, yellow and pink gold alloys.