Process for making reinforcing layers on inner surfaces of complicated cavities

Claim 1

Process for reinforcing inner surfaces of complicated and inaccessible cavities of a unitary molded plastic article with metallic or ceramic material, comprising the steps of: (a) making a core member having outer surfaces of complicated and irregular configurations complementary to said complicated and inaccessible cavities of the molded plastic article to be obtained from water-soluble or heat-meltable inert material, said core member being of a length between its end surfaces greater than the length of a mold cavity to be used, (b) applying metallic or ceramic reinforcing material onto said complicated and irregular outer surfaces of said core member except said end surfaces at temperature above the degradation temperature of the plastic material subsequently used to form said molded plastic article to form a reinforcing layer of sufficient thickness to impart desired mechanical strength and resistance to abrasion and chemicals to the molded plastic article, (c) placing said core member covered with said reinforcing layer into a mold cavity formed by two mold halves for injection or transfer molding in such a manner that a continuous spacing necessary to form the molded plastic article is left between said reinforcing layer and the inner surface of said mold cavity, and securing end portions of said core member extending beyond said mold cavity between said mold halves by closing the same, (d) injecting molten plastic material into said continuous spacing to form a unitary plastic body around and integrally with said reinforcing layer, and (e) removing said plastic body containing therein said reinforcing layer and said core member from said mold cavity, and then applying water or heat to said core member thereby to fluidize and remove said inert material from said plastic body to leave said reinforcing layer therein integral with said plastic body, thus producing the unitary molded plastic article having on its complicated and inaccessible cavity surfaces the reinforcing metallic or ceramic layer.