Apparatus for supporting lenses during heat treatment

A fixture for heat sinking a selected portion of an ophthalmic quality lens or lens blank to produce a reversible, progressive local variation in photochromic behavior with a continuous variation in transmissivity from a lens or lens blank which is composed of a potentially phototropic glass containing all the necessary ingredients therein to develop photochromic behavior at a temperature of development of photochromic behavior during heat treatment thereof, during which heat treatment said apparatus maintains a selected portion of said lens or lens blank at a temperature to substantially inhibit the development of photochromic behavior and to produce a progressive gradient transmissivity comprising:

• a base portion, sidewalls fixedly secured to said base portion and extending generally upwardly therefrom and enclosing a cavity portion;
• divider means extending upwardly from said base portion between generally opposite sidewalls and separating said cavity portion into two portions;
• flange means disposed on said sidewalls intermediate said base portion and top of said sidewalls and adapted to receive said lens or lens blank;
• heat-sinking material disposed in one of said cavity portions, said heat-sinking material having at least one phase transition temperature below the temperature of development of photochromic behavior;
• and a heat-conducting cover disposed over said one of said cavity portions, one side of said cover being in contact with said heat-sinking material and the other side of said cover being in contact with the selected portion of the lens or lens blank.