Adjustable mold for direct casting of plastic multifocal lenses

Static molds – Providing substitution of alternatively used parts

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249155, 249159, 425808, B29D 1100

Patent

active

039469824

ABSTRACT:
Apparatus for finish casting of bifocal ophthalmic lenses from plastic material is described. No further surface grinding or polishing of the lens is required. The portion of the bifocal segment of the lens may be adjusted to any desired location relative to the optical center of the distance field of the lens. The apparatus comprises a power mold having a predetermined spherical or sphero-cylindrical surface, a bifocal mold having a predetermined optical curvature with a bifocal segment having a different optical curvature countersunk in the face thereof, and an annular gasket coupling the power and bifocal molds. The bifocal segment is adjusted relative to the optical center of the cast lens by use of a wedge member. An illustrative calculation to determine placement and thickness of the wedge for a given ophthalmic prescription is set forth. Alternative means for adjusting the bifocal segment by sliding the assembled power mold and gasket relative to the bifocal mold is also described, as is a means for introducing corrective prism into a cast lens.

REFERENCES:
patent: 3056166 (1962-10-01), Weinberg
patent: 3297422 (1967-01-01), Emerson et al.
patent: 3460928 (1969-08-01), Casko
patent: 3555611 (1971-01-01), Reiterman
patent: 3605195 (1970-08-01), Campbell
patent: 3674587 (1972-07-01), Laliberte

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