Method and assembly for molding optical lenses

A method of molding anoptical lens comprising the steps of:

• arranging a first generally disc shaped mold part with an outer surface thereof supported by a shelf of a retainer ring,
• arranging on the inner surface of the first mold part opposite the said surface and near the periphery thereof a pair of adjacent gaskets, one of which is a hard spacer which maintains its shape at elevated temperatures under load, except for elastic deformation, and the other is a soft gasket having the property of softening so as to creep under load at elevated temperatures, and arranging the two gaskets adjacent to each other so that the inside diameter of each forms a part of the cavity,
• arranging a second generally disc shape mold part with an inner surface thereof against the gasket so as to define an enclosed cavity with the inside diameter of the gasket and the said inner surface of the first mold part,
• exerting a resilient force to urge the two mold parts toward each other, so as to hold the two mold parts and the gasket together as they form said cavity by a means which is positively located relative to the retainer means to exert the force precisely centered along the axis of the retainer ring,
• filling said cavity with a liquid capable of being converted into a state in which, upon being heated, it shrinks in volume and becomes hard and insoluble at room temperature,
• heating the mold assembly with the said liquid filling the said cavity,
• and wherein the magnitude of the resilient force and the creeping characteristic of the gasket are such that as the liquid shrinks during the heating step, the two mold parts move toward each other to maintain contact with the liquid throughout the said conversion and hardening of the liquid in the cavity.