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US 6,284,162 B1Granted
Molding method for manufacturing thin thermoplastic lenses
AssigneeSola International, Inc.
InventorsJeffrey M. Kingsbury, Michael J. Tuhtan, Robert H. Juul, Martin P. Rolph
Life of this patent
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Abstract
Disclosed are novel molding methods for manufacturing thin thermoplastic lenses and, in particular, minus ophthalmic lenses that have thickness of about 1 mm or less at the thinnest point thereof. The molding methods disclosed provide for lenses which lack any abrasion or polishing artifacts on the surface and also lack any negative fining marks below the nominal surface.
Claims24
A method for manufacturing a thermoplastic lens which comprises:
- (a) providing a mold comprising a male mold half and a female mold half wherein said mold halves, when closed against one another, close a parting line of the mold, said mold further comprising a male mold member disposed within said male mold half and a female mold member disposed within said female mold half, wherein said mold members define, when said mold halves are closed, a mold cavity in the shape of a lens;
- (b) closing said mold halves of the mold so as to close the parting line of the mold, the distance between said mold members being greater than a final thickness of the to-be-formed lens;
- (c) after step (b), introducing into the mold cavity a molten thermoplastic material in a quantity at least sufficient to form a lens;
- (d) moving at least one of said male and female mold members to a predetermined hard stop point and stopping said at least one mold member at said predetermined hard stop point prior to freezing of the thermoplastic material at the thinnest point of the to-be-formed lens, the distance between the mold members at the predetermined hard stop point being substantially equal to the final thickness of the to-be-formed lens;
- (e) maintaining said mold members in a stationary position at said predetermined hard stop point while applying expansive pressure to the mold cavity;
- and
- (f) permitting the thermoplastic material to freeze thereby forming the thermoplastic lens.
4 more elements
A method for manufacturing a thermoplastic ophthalmic lens which comprises:
- (a) providing a mold comprising male and female mold halves wherein said mold halves, when closed, define a mold cavity in the form of a thermoplastic lens;
- (b) introducing into the mold cavity a molten thermoplastic polycarbonate material in a quantity at least sufficient to form the lens wherein said thermoplastic polycarbonate material is maintained at a temperature above about 575° F. which permits the material to flow;
- (c) moving at least one of said male and female mold halves to a pre-determined hard stop point wherein the mold cavity has a center thickness of less than 1 mm and stopping said at least one mold half at said hard stop point prior to freezing of the thermoplastic material at the thinnest point of the to-be-formed lens;
- (d) maintaining said mold halves in a stationary position at said hard stop point while applying expansive pressure in the mold cavity by use of an injector or injectors to maintain a constant volume within the mold;
- and
- (e) permitting the thermoplastic polycarbonate material to freeze thereby forming the thermoplastic ophthalmic lens.
3 more elements
Dependencies are inferred from the claim text.