Patent ID: 6451227
Filing Date: 2002-09-17
Classification: B29D

Abstract:
A method of making an eye glass lens having a preselected prescription strength from a thermoplastic material comprising;selecting a concave mold half from a series of concave mold halves; said series of concave molds halves having three (3) to six (6) different radii of curvature; said series of concave mold halves comprising: a first concave mold half having a radius of curvature less than about 2 diopters; each different radius of curvature of said mold halves being 1 to 3 diopters greater than the radius of curvature of the concave mold half having the next lower radius of curvature; selecting a preform from a group of preforms having a convex bottom and a flat substantially flat, or concave top for use with said selected concave mold half; said group of preforms having the same number of different radii of curvature as said concave mold halves each different radii of curvature preform having from one (1) to three (3) different preselected weights; said group of preforms made from a thermoplastic material; said selected preform having a radius of curvature on said convex bottom of from 1 to 5 diopters greater than the radius of curvature of said selected concave mold half; selecting a convex mold half from a series of convex mold halves for mating with the selected concave mold half to form a lens of said preselected prescription strength; placing said selected preform in said concave mold halve; heating said selected preform said concave mold half and said convex mold half to a temperature above the softening temperature of said thermoplastic material; placing said mold halves in a press either before or after heating; closing said press and pushing said mold halves toward each other until said mold halves are a preselected distance apart to form a lens having a preselected center thickness; said center thickness variable depending on prescription strength and the weight of the selected preform.