LENS THICKNESS ADJUSTMENT IN PLASTIC INJECTION MOLD

摘要

Method and apparatus for lens thickness adjustment in injection molding of thermoplastic vision-corrective spectacle lenses without manual addition or removal of shims, of inserts or of any other mold part. Thickness adjustment can be made quickly while the lens mold is kept at very hot operating temperatures, yet minimal risk of burning the operator. A rotatable adjustment head is mounted externally onto the mold's operator side, and manually-driven rotation turns a threaded screw which moves one wedge block of a slideably mated pair of opposing wedge blocks in a plane parallel to the parting line, thus moving the opposing wedge block axially forward or back perpendicular to the parting line, but always retaining proper alignment and loadbearing support of optical inserts, even in multicavity injection-compression molding. After many re-polishings of inserts, lens thickness specifications are still maintained without needing shims. This permits use of circulating heat transfer fluids internally within the inserts, to greatly reduce cycle times, yet have minimal fluid leakage problems.