Sola Usa, Inc.

Jeffrey M Kingsbury

David P Spector

A method and apparatus for molding and casting ophthalmic lenses includes a front surface die and a back surface die slidably and removably received in the bore of a molding or casting apparatus. Molding or casting compound is introduced by conventional means between the two dies, and the dies are urged together to impress the die surfaces on the compound as the compound is cured by thermal or chemical means. At least one of the dies includes at least one gate channel formed in the edge thereof parallel to the axis of the bore and extending from the optical forming surface to a point adjacent to the opposite, external die surface. In compression molding, the gate channel comprises a vent through which excess molding compound is discharged from the molding cavity as the dies are urged together. As the gated die is fully inserted in the bore, the gate channel opening to the exterior is sealed, thus limiting the discharge effect and controlling the thickness of the molded part. In casting, the dies are partially inserted in the bore, and the gate channel serves as an injection channel to introduce the casting compound into the casting cavity. The dies are urged together in the bore, the gate channel first serves to vent excess casting compound from the casting cavity. Full die insertion in the bore causes the gate channel opening to the exterior to be sealed, thus limiting the discharge effect and controlling the thickness of the cast part.

Method of molding using gated dies

A method and apparatus for the fabrication of optical lenses by injection/compression molding of thermoplastic includes a plurality of sleeves, each having a bore therethrough, and a plurality of mold inserts dimensioned to be received in the bore with minimal clearance for sliding fit. The mold inserts each include a precision optical surface adapted to form a front or back surface of a lens. A selected pair of mold inserts are placed in the bore of a sleeve with front and back surface forming optical surfaces in confronting relationship to define a mold cavity, and the assembly is heated to a temperature above the glass transition temperature of the thermoplastic to be molded. An injection port extends through the sleeve to the bore, and is positioned to inject thermoplastic that has been heated to a fluid state into the cavity. After injection of the thermoplastic, the mold inserts are compressed together, and excess thermoplastic is forced out of the mold cavity. The mold inserts are then translated together relative to the sleeve to uncouple the injection port from the cavity. Compressive pressure is then maintained on the mold inserts while the mold assembly is cooled below the glass transition temperature. The mold inserts are pulled from the sleeve, and the finished lens is removed.

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Santa Rosa, CA, United States of America

Jeffrey M Kingsbury