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US 6,156,242 AGranted
Method of injection molding plastic lens
AssigneeHoya Corporation
InventorsKiyohiro Saito, Hiroshi Asami
Life of this patent
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Abstract
A cavity 22 in an injection molding assembly includes a lower mold insert 21 for shaping a lens convex surface and an upper mold insert 20 for shaping a lens concave surface. When the heated injection molding assembly is cooled and a lens is ejected after a molten resin is pressurized by the upper mold insert 20, the temperature of the lower mold insert 21 is lowered below the temperature of the upper mold insert 20, which prevents the molded lens from bending at a central portion and enable high transfer precision of insert shapes.
Claims12
A method of injection molding a plastic lens, comprising the steps of;
- providing a cavity for molding the lens including a pair of cavity forming members for shaping a convex surface and a concave surface of the lens disposed oppositely with each other inside an injection molding assembly;
- heating the injection molding assembly;
- filling a molten resin in the cavity for molding the lens;
- pressurizing the molten resin;
- cooling the injection molding assembly to cool and solidify the molten resin to mold the lens in the cavity;
- and ejecting the lens from the cavity,
- wherein the temperature of the cavity forming member for shaping the convex surface is lowered below the temperature of the cavity forming member for shaping the concave surface.
4 more elements
Dependencies are inferred from the claim text.