Apparatus for and method of forming ophthalmic lenses and/or semi-finished lens blanks including those of the eye contact type. The apparatus includes molds having cooperating first and second members each of which includes a longitudinal axis and a mold surface which is symmetrical with respect to such axis. In one embodiment these mold members or halves also include cooperating surfaces which, in operation and in cooperation with the selected lens material, both align the respective mold axes and axially position the mold surface of the first member with respect to the mold surface of the second member to thereby form the desired lens mold cavity. Further, each of the assembled molds also includes an annular reservoir which surrounds the mold cavity and is defined by surfaces provided on the first and second mold members. This reservoir is connected to the mold cavity via an annular restriction. In one embodiment this restriction is defined by the cooperating aligning surfaces provided on the first and second mold members. In operation, the reservoir holds a volume of lens material which, during the polymer forming reaction, is kept in a flowable state longer than the lens material in the mold cavity. This arrangement permits the transfer of lens material between the reservoir and the mold cavity during curing. Apparatus is also provided for removing selected portions of the cast lens in those instances where removal is either necessary or expedient.
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of both application Ser. No. 564,403, filed Apr. 8, 1975 and now abandoned, and application Ser. No. 693,402 filed June 7, 1976 and now abandoned. Application Ser. No. 693,402 is a division of application Ser. No. 564,403 which, is, in turn, a continuation-in-part of application Ser. No. 466,933, filed May 6, 1974, and now abandoned.
The invention relates to a novel process for the manufacture of mouldings, especially contact lenses, in which a soluble prepolymer comprising crosslinkable groups is crosslinked in solution, and also to mouldings, especially contact lenses, obtainable in accordance with that process. The present invention relates also to novel prepolymers that can be used in the process according to the invention, especially derivatives of a polyvinyl alcohol having a molecular weight of at least about 2000 that, based on the number of hydroxy groups of the polyvinyl alcohol, comprise from approximately 0.5 to approximately 80% of units of formula I ##STR1## wherein R is lower alkylene having up to 8 carbon atoms, R.sup.1 is hydrogen or lower alkyl and R.sup.2 is an olefinically unsaturated, electron-attracting, copolymerisable radical preferably having up to 25 carbon atoms, to crosslinked polymers, either homo- or co-polymers of those novel prepolymers, to processes for the preparation of the novel prepolymers and the homo- and co-polymers obtainable therefrom, to mouldings made from the said homo- or co-polymers, especially contact lenses made from those homo- or co-polymers, and to processes for the manufacture of contact lenses using the said homo- or co-polymers.
Plastic lenses are cast from thermohardening resins using two mating mold halves positioned in a tubular sleeve which is provided with a fluid compensating reservoir that retains excess resin. As the mold is heated to polymerize the resin the monomer first expands in volume and flows into the reservoir, then as the polymerizing resin contracts additional resin flows out of the reservoir into the mold until the gel stage is reached. Polymerization is completed by moving the mold halves towards each other.
A method of controlling the polymerization of spin cast hydrogel contact lenses by controlling the shape of the ultraviolet light beam across the rotating surface of the spin cast lens. To provide polymerization which progresses smoothly from the center to edge of the rotating lens.
A two piece contact lens mold having a pair of blunt, continuous mating surfaces extending around the periphery of the mold cavity is disclosed. Parameters for mold materials and important dimensions are also disclosed. The mold can produce finished contact lenses which do not require further machining.
