Metal treatment – Stock – Noble metal base
Reexamination Certificate
2000-02-14
2002-04-16
Wyszomierski, George (Department: 1742)
Metal treatment
Stock
Noble metal base
C420S466000, C420S555000
Reexamination Certificate
active
06372060
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solder composition and, more particularly, to a solder composition for assembling, repairing and/or sizing jewelry having a platinum content of up to about 95% by weight.
2. Description of the Related Art
A variety of solder compositions are known in the art for repairing platinum jewelry. These prior art compositions arc characterized by melting temperatures ranging from about 1000° C. to about 1700° C. and consist essentially of varying relative amounts by weight of gold, silver and/or palladium. The higher melting temperature solder compositions (16000 and 1700° C.) are difficult to work with and have melting temperatures that are not significantly lower than the melting temperature of pure platinum (1769° C.). While the lower melting temperature compositions are easier to work with than the higher melting temperature compositions, all of the compositions are problematic when used to repair platinum jewelry having a platinum content of at least 90% by weight. Specifically, the color of the solder composition does not match the color of the high platinum content jewelry. This results in an unsightly dark seam or spot of solder that must be temporarily masked by plating the seam or spot with rhodium. In addition to adding to the cost and complexity of the jewelry repair, the rhodium plating is also subject to wear over time, whereupon the color difference between the platinum jewelry and the solder composition becomes visible again. Moreover, pitting of the solder at its point of application to the jewelry is often observed, thus further detracting from the appearance of the repaired jewelry.
It is known to add minor amounts of platinum (up to about 5% by weight) to the above-noted solder compositions, but the problems of color matching and pitting still persist. Solder compositions combining palladium and up to 75% by weight platinum have also been employed, but such compositions are characterized by high melting temperatures (1600° to 1700° C.) that are not significantly lower than the 1769° C. melting temperature of platinum itself and make the compositions difficult to work with. Additionally, color matching and pitting problems still occur.
Various high platinum content jewelry materials are known in the art. For example, U.S. Pat. No. 4,165,983 discloses an alloy for fabricating jewelry containing at least 95% by weight platinum, 1.5% to 3.5% by weight gallium, and a balance of at least one of indium, gold, palladium, silver, copper, cobalt, nickel, ruthenium, iridium and rhodium. U.S. Pat. No. 5,846,352 discloses a heat-treated platinum-gallium alloy for fabricating jewelry containing 1% to 9% by weight gallium and a small amount of palladium. However, such alloys are intended for fabricating the jewelry itself. Neither of these patents disclose or suggest particular solder compositions that would be useful for repairing platinum jewelry, and particularly platinum jewelry having a platinum content of up to about 95% by weight.
Currently, there are no known solder compositions or platinum alloys with low flow temperatures that can be used for repairing jewelry having a platinum content of at least 90% by weight without incurring the above-mcntioned problems. Accordingly, the development of a solder composition for such platinum jewelry that does not involve the aforementioned problems would be a significant advance in the art.
SUMMARY OF THE PREFERRED EMBODIMENTS
The present invention is directed to a solder composition that can be used for assembling, repairing, and/or sizing jewelry having a platinum content of up to about 95% by weight. In accordance with the invention, such a solder composition consists essentially of about 90% to about 95% by weight platinum and about 5% to about 10% by weight of an alloy that provides the solder composition with a melting temperature in a range from about 1300° C. to about 1500° C.
In accordance with one preferred aspect of the present invention, a solder composition for assembling, repairing, and/or sizing jewelry consists essentially of about 90% to about 95% by weight platinum, about 3% to about 6% by weight gallium, about 1.5% to about 3% by weight indium, and about 0.5% to about 1.0% by weight copper. In accordance with another preferred aspect of the present invention, a solder composition for assembling, repairing and/or sizing jewelry consists essentially of about 90% to about 95% by weight platinum and about 5% to about 10% by weight of an alloy consisting of gallium, indium and copper in a respective weight ratio of approximately 6:3:1. In accordance with yet another preferred aspect of the present invention, there is provided an alloy for lowering the melting point of platinum when combined therewith to provide a solder composition having a reduced melting temperature, the alloy consisting essentially of about 60% by weight gallium, about 30% by weight indium and about 10% by weight copper.
Further in accordance with the present invention, there is also provided a method of soldering jewelry containing up to about 95% by weight platinum. The method comprises the step of soldering a piece of jewelry containing up to about 95% by weight platinum with a solder composition consisting essentially of about 90% to about 95% by weight platinum and about 5% to about 10% by weight of an alloy that provides the solder composition with a melting temperature in a range from about 1300° C. to about 1500° C. In a preferred aspect of the inventive method, the solder composition consists essentially of about 90% to about 95% by weight platinum, about 3% to about 6% by weight gallium, about 1.5% to about 3% by weight indium, and about 0.5% to about 1.0% by weight copper.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a solder that is not only easy and safe to use, due to a relatively low flow temperature of 1300° C. to 1500° C. in relation to the melting temperature of platinum (1769° C.), but that also, in use, matches the color of platinum jewelry having a platinum content up to about 95% by weight. These advantages have not previously been found together in a solder composition for platinum jewelry.
In accordance with the present invention, a solder composition containing about 90% to about 95% by weight platinum combined with an alloy that reduces the melting temperature of the solder composition to about 1300° C. to about 1500° C. eliminates the disadvantages associated with prior art solder compositions for platinum jewelry.
The preferred solder compositions of the present invention contain about 90% to about 95% by weight platinum. The platinum content of the solder composition insures a color match with platinum jewelry containing up to about 95% by weight platinum. It has been found that solder compositions having a platinum content of about 87.5% by weight are unsatisfactory for use in the present invention. In this regard, solder compositions with a platinum content of about 87.5% by weight are too brittle or “ceramic” to roll and fabricate into useful solders. They turn to dust. Conversely, it has been found that solder compositions having a platinum content above 95% by weight can result in useful solders. However, such compositions arc extremely hard and possessed of higher melting temperatures, which increase the risk of damage to the platinum jewelry they are used in conjunction with.
The preferred solder compositions of the present invention also contain about 5% to about 10% by weight of an alloy that reduces the melting temperature of the solder composition to about 1300° C. to about 1500° C. In this regard, the melting temperature of pure platinum is 1769° C. Accordingly, the alloy reduces the melting temperature of the solder composition sufficiently to facilitate its use while avoiding potential damage to the platinum jewelry.
It has been found that a suitable alloy for use in the present invention is an alloy consisting essentially of about 3% to about 6% gallium, about 1.5% to about 3% indium
Oppenheimer Wolff & Donnelly LLP
Weinstein Keith
Wyszomierski George
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