Mold for making contact lenses, either the male or female mold sections being relatively more flexible
AssigneeMia Lens Production A/S
InventorHans-Ole Larsen
Life of this patent
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Abstract
A plastic mold assembly comprising a male and female section for casting soft contact lenses from a polymerizable feed material wherein compensation for polymerization shrinkage is attained and disengagement of the male and female mold sections is facilitated by providing one flexible and one rigid mold section. Good optical properties of the mold surfaces are obtained by forming the mold sections entirely from a thermoplastic material such as polystyrene that will not crystallize when cooled from a melt. In one embodiment a plurality of flexible male sections having convex molding surfaces and a plurality of rigid female sections having concave molding surfaces are supported on frames to attain an increased production rate of finished soft contact lenses.
Claims10
A lens mold assembly comprising a plurality of female mold sections having a concave optical surface terminating in a peripherally extending annular flange, the surface of said flange forming a sharp edge at the intersection with said concave optical surface;
- a plurality of male mold sections having a substantially spherical convex optical surface terminating in a peripherally extending annular flange;
- the maximum outside diameter of the convex surface of said male mold section being greater than the maximum inside diameter of the concave surface of said female mold section whereby said sharp edge of said female mold section impinges on said convex surface of said male mold section to form a mold cavity in said mold assembly with the facing surfaces of said peripherally extending annular flanges of said female and male mold sections being spaced apart;
- one of said female or male mold sections having relatively greater flexibility than the other section whereby compensation for shrinkage during polymerization of monomers within the mold cavity is afforded by said relatively more flexible mold section;
- and each of said female mold sections being attached to a supporting frame by a tab or bar extending between said female mold sections and said supporting frame, and each of said male mold sections being individually centered on a respective female mold section to define said mold cavity.
Dependencies are inferred from the claim text.