Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles
Reexamination Certificate
1999-05-19
2001-10-30
Theisen, Mary Lynn (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
C419S036000
Reexamination Certificate
active
06309573
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for shaping metal parts from powders and molding compositions therefor. More particularly, the invention is directed to molding processes and molding compositions for forming long, thin sections and complex-shaped cross sections that can be readily fired to produce near netshape articles without the need for machining or other shaping and finishing operations.
BACKGROUND OF THE INVENTION
There are many different techniques used in the art of fabricating flat stainless steel tableware. One process is known as forging, in which the flat tableware is formed by a series of high pressure and force impacts until the desired shape is obtained. This process entails numerous steps from start to the finished product, taking a relatively long time and requiring the use of large, expensive machinery. The first step is known as the upset in which the rod material is heated and a ball is formed on the end to create enough material in the bolster area during forging. The second step is known as the breakdown forge in which the rod is heated in a furnace to approximately 1300° F. and forged into a generally flat article. The third step is called the drop forge in which the preformed article is forged again to its rough finished shape. The fourth step is known as the trim step in which the forging is trimmed to the actual outline of the flatware. The fifth step is known as the “kp” tumble in which the flatware is tumbled with stone media to remove burrs. The sixth step is known as the notch step in which the circular part of the flatware outline is machined. The seventh step is known as the mill step in which the flat surfaces of the flatware are milled. The eighth step is the heat treatment in which the flatware is furnace hardened. The ninth step is known as the line finish in which the parts are buffed with a very aggressive coated roll to remove forging scale. The tenth step entails vibratory tumbling of the flatware to prepare them for additional buffing. The eleventh step is the finish buffing step in which the flatware is buffed to a mirror finish. The final step is the inspection step.
In order to overcome some of the shortcomings of the prior art method of manufacturing flat tableware, injection molding techniques have been found to be ideally suited for high volume manufacturing of near net-shape flatware. This process produces flatware that has the desired physical properties and visual appearance without the need to perform costly finishing operations. The process is relatively inexpensive and offers considerable advantages over multiple step processes that require additional machining and finishing operations to produce acceptable finished product. Low pressures and temperatures are employed to shape the finished flatware using aqueous feedstocks made from metal powders.
BRIEF SUMMARY OF THE INVENTION
The invention is directed to a process for forming a long, thin cross section article having a complex shape comprising the steps of forming a mixture comprising a metal powder, a gel-forming material and an aqueous gel-forming material solvent; and molding the mixture in a mold under conditions of temperature and pressure sufficient to produce a self-supporting article.
The invention also provides an injection molding process for forming a flat tableware article comprising the steps of forming a mixture comprising a metal powder, a gel-forming material selected from the group of polysaccharides consisting of agaroids and an aqueous gel-forming material solvent; supplying the mixture to an injection molding machine having a mold containing a cavity for shaping the article therein, the mixture being maintained during the supply step at a first temperature above the gel point of the gel-forming material; and cooling the mixture in the mold to a second temperature below the gel point of the gel-forming material to form the tableware article.
The tableware is molded at low temperatures of approximately 85° C. and low pressures of approximately 400 to 1000 psi (hydraulic). The tableware is cooled in the mold to approximately 37° C.
REFERENCES:
patent: 5250254 (1993-10-01), Achikita et al.
patent: 5258155 (1993-11-01), Sekido et al.
patent: 5746957 (1998-05-01), Fanelli et al.
R.L. Whistler, et al. “Industrial Gums”, Academic Press, New York and London, 1973.
Schoonover James
Sesny Steve
Zedalis Michael Sean
Criss Roger H.
Rutgers The State University of New Jersey
Theisen Mary Lynn
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