Patent ID: 6755996
Filing Date: 2004-06-29
Classification: B29C,B29D,B29L

Abstract:
A method for making a preform from thermoplastic material for use in making a compression molded optical product comprising:a) placing a convex and a concave mold in a press; b) heating a thermoplastic material in a reservoir to form a fluid; c) heating said molds to a temperature above room temperature; d) said reservoir having a fluid outlet located in close proximity to said concave mold; e) dispensing a predetermined amount of said fluid thermoplastic material from said outlet onto the outside edge of concave mold at a point spaced one-half (Â½) the radius or greater from the center of said heated concave mold prior to said fluid solidifying so that said fluid makes point or line contact as it contacts the concave mold and flows into said concave mold to form a blob of thermoplastic material having a greater thickness at the center of said concave mold and a smaller diameter than the resulting molded article; f) allowing said blob to cool to below its melting temperature thereby converting the material to a monolithic preform mass having a skin and having a flat to slightly convex surface which will make point contact with the convex mold to preclude the entrapment of air and formation of air bubbles in a finished compression molded final finished product.