Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles
Reexamination Certificate
1999-08-26
2001-11-13
Theisen, Mary Lynn (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
C264S621000, C264S328200, C419S036000
Reexamination Certificate
active
06315935
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 cross sections that can be readily fired to produce near net-shape articles without the need for machining or other shaping and finishing operations.
BACKGROUND OF THE INVENTION
There are several different techniques used to make knife blades in the art known as bladesmithing. One process is forging, in which the steel blade is formed by a series of high pressure and force impacts until the desired shape is obtained. This process takes a relatively long time and requires the use of large, expensive machinery. Another process used to fabricate thinner blades is known as fine blanking, in which a strip of steel is uncoiled, straightened, flattened and moved into position where a die grips the steel while a punch forces the material into a cavity and counter punches perforate any holes required in the blade. This process is slower and more costly than conventional blanking. Prior to employing either of these processes, a precisely controlled tempering operation must be performed in order to produce hardened steel blades that are capable of maintaining a sharp edge. Following either of these processes, a final step must be performed to hollow grind the finished cutting edge on the blade.
In order to overcome some of the shortcomings of these prior art methods of making knife blades, injection molding techniques have been found to be ideally suited for high volume manufacturing of near net-shape blades. This process produces knife blades that have desired physical properties without the need to perform costly finishing operations. The process is relatively inexpensive and offers considerable advantages over processes that require additional machining and finishing operations to produce acceptable blades. Low pressures and temperatures are employed to shape the finished blades using aqueous feedstocks made from metal powders.
BRIEF SUMMARY OF THE INVENTION
The invention is directed to a process for forming a knife blade 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 knife blade 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 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 knife blade.
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Whistler, Roy L., et al., “Industrial Gums”, Second Edition, Academic Press, New York and London, 1973.
Schoonover James
Snow Brian
Zedalis Michael Sean
Allied-Signal Inc.
Criss Roger H.
Theisen Mary Lynn
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