초록 ▼

An apparatus for molding polystyrene mold halves which are used, for subsequent molding of a soft contact lens. The apparatus is designed with superior heat conduction capacity so as to minimize the molding cycle time, while simultaneously producing uniformly precise and accurate optical quality sur

An apparatus for molding polystyrene mold halves which are used, for subsequent molding of a soft contact lens. The apparatus is designed with superior heat conduction capacity so as to minimize the molding cycle time, while simultaneously producing uniformly precise and accurate optical quality surfaces. Molten polystyrene is provided via a hot runner system to a plurality of mold cavities. In a specific variation, the convex surface provides the optical quality surface to the concave surface of the mold half produced thereby. The structural element which defines the convex surface includes a hollow cylindrical bushing and a removable power insert mounted therein, which may be changed so that the prescription strength of the contact lens to be formed by the mold may be varied. In a first embodiment, the power insert includes only a convex surface at its operational end. In a second embodiment, the power insert includes an annular flat surface surrounding the convex surface, defining at the junction therebetween a discontinuity of curvature, which imparts a sharp edge to the mold half formed thereby. The power insert may be constructed of pure steel, or alternatively, it may be made of brass, copper chromium, or cobalt-nickel alloyed martensitic steel. The power insert may be coated with a surface layer of nickel phosphor or silicone oxide, or chrome nitride. These layers may be turned to their proper thicknesses and dimensions by diamond cutters, and they may be thermally hardened.

대표청구항 ▼

A molding apparatus for producing at least one mold half which is used for subsequently molding a soft contact lens therewith, comprising: at least one first structure having a convex curved surface defining an optical quality curved surface; at least one corresponding second structure having a conc

A molding apparatus for producing at least one mold half which is used for subsequently molding a soft contact lens therewith, comprising: at least one first structure having a convex curved surface defining an optical quality curved surface; at least one corresponding second structure having a concave curved surface disposed in proximal spaced relation to said convex surface, said first and second structures defining therebetween a volume wherein a mold half is formed; a hot runner system connected to the volume between said first and second structures for delivering a quantity of molten material of which the mold half is to be formed; said optical quality curved surface of said first structure being positioned further away from said hot runner system than said concave curved surface of said at least one second structure, such that the subsequently molded mold half comprises a concave optical quality lens forming surface; said at least one first structure comprising a bushing having a hollow cylindrical shape and a power insert, said insert being positioned within said bushing and having an end surface protruding from one end of said bushing wherein said end surface comprises said optical quality curved surface, said insert further comprising a flat annular surface surrounding said optical quality curved surface; and a cooling system for cooling at least one of said first and second structures, wherein the positioning of the optical quality curved surface further away from the heated hot runner system, and the cooling system, provide for faster cooling of molten material which forms the mold half at the optical quality surface than the other surface of the mold half to allow quicker setting so that minimal residual stresses remain in the material which forms the optical quality curved surface of the mold half, and also provides faster molding and cycling time.