Method and apparatus for the dry release of a compliant ophthalmic article from a mold surface
View Patent ↗An apparatus for releasing a molded lens from a deformable mold includes a shear ring for temporarily retaining an annular portion of the deformable mold outside a periphery of the lens and a plunger for deforming an annular section of the deformable mold within the periphery of the lens. The apparatus can be employed to release a non-hydrated hydrogel lens from a deformable mold section.
1. A method for releasing an ophthalmic molded lens from a mold cavity of a deformable mold, the deformable mold having an anterior molding surface and an opposite curved posterior surface, the method comprising:
a) distorting the anterior molding surface by
i) pressing against the curved posterior surface along a first annulus; and
ii) pressing against the anterior molding surface along a second annulus comprising a shear ring;
b) the first and second annuli being generally concentric with the molded lens with the first annulus being within a perimeter of the molded lens and the second annulus being radially spaced from the perimeter of the molded lens; and
c) the distorting of the molding surface creating sufficient shear between the molded lens and the molding surface to effect a peeling of the molded lens from the molding surface.
2. The method of claim 1 , wherein the peeling progresses radially inward from the perimeter of the molded lens.
3. The method of claim 1 , wherein pressing against the curved posterior surface is continuous along the first annulus.
4. The method of claim 1 , further comprising forming the first annulus of a rounded surface.
5. The method of claim 1 , wherein pressing against the curved posterior surface is intermittent along the first annulus.
6. The method of claim 1 , wherein pressing against the anterior molding surface is continuous along the second annulus.
7. The method of claim 1 , wherein pressing against the anterior molding surface is intermittent along the second annulus.
8. The method of claim 1 , further comprising forming the shear ring to include a knife edge.
9. The method of claim 8 , further comprising forming the knife edge from facets intersecting at an acute included angle.
10. The method of claim 8 , further comprising forming the knife edge from facets intersecting at an obtuse included angle.
11. The method of claim 1 , further comprising hydrating the molded lens after peeling of the molded lens from the molding surface.
12. The method of claim 1 , further comprising releasing an ophthalmic molded lens having a hydrated modulus less than 70 gm/mm 2 .