초록 ▼

In an injection compression molding method of a lens, in which a mold is closed to preserve a predetermined compressing margin in a cavity 3 for a lens, molten resin is injected and fed into the cavity 3 for the lens, and compressed for the aforementioned predetermined compressing margin before or a

In an injection compression molding method of a lens, in which a mold is closed to preserve a predetermined compressing margin in a cavity 3 for a lens, molten resin is injected and fed into the cavity 3 for the lens, and compressed for the aforementioned predetermined compressing margin before or after the injection and the feed of the molten resin is completed, the predetermined compressing margin (the degree of slightly opening S.sub.(-)) for producing a minus lens is molded is defined to be larger than the predetermined compressing margin (the degree of slightly opening S.sub.(+)) for producing a plus lens is molded. As a result, even when the minus lens is molded, the larger area of the cavity can be ensure and a flow property of the molten resin in the cavity is improved, so that the molten resin reached the inside of the cavity 3 flow through the central portion of the cavity 3 into the peripheral portion, with the result that the appearance of a weld mark in the central portion is avoided.

대표청구항 ▼

[ What is claimed is:] [1.] A method of injection compression molding a spectacle lens using an injection molding machine having: a stationary die; a movable die that is opened and closed relative to the stationary die, the movable die including a die fitting member and a die body separate from the

[ What is claimed is:] [1.] A method of injection compression molding a spectacle lens using an injection molding machine having: a stationary die; a movable die that is opened and closed relative to the stationary die, the movable die including a die fitting member and a die body separate from the die fitting member that are movable toward the stationary die, the die body positioned to close against the stationary die; an insert guide provided inside the die body; an exchangeable insert movably positionable in the insert guide; a cavity for molding the lens, the cavity being formed by the stationary die, the die body and the insert; a sprue and a runner through which molten resin is supplied into the cavity; a holding member for holding the insert; a resilient member for constantly biasing the holding member in a direction opposite to the stationary die so that the holding member abuts the die fitting member; and an eject pin that is selectively insertable in the die fitting member against the holding member for moving the holding member and the insert towards the stationary die, the method comprising the steps of:closing the mold by advancing the die fitting member to the stationary die so that the die body of the movable die closes against the stationary die;simultaneously with said mold closing step or after completion of said mold closing step, setting a predetermined compression margin in the cavity by setting the position of the insert;injecting the molten resin through the sprue and the runner to fill the cavity;compressing the molten resin by advancing the die fitting member toward the stationary die to form the lens, wherein:when a minus-lens having a thinner central portion than a peripheral portion is molded, said compressing step is started before completion of said molten resin injection step; andwhen a plus-lens having a thicker central portion than a peripheral portion is molded, said compressing step is started simultaneously with or after completion of said molten resin injection step; andseparating the movable die from the stationary die by retracting the die fitting member; andafter said step of separating the movable die, ejecting the lens molding by pushing the holding member toward the stationary member with the eject pin, wherein:when the minus-lens is molded, the predetermined compression margin is set larger than the predetermined compression margin for molding a plus-lens, and said step of setting the predetermined compression margin for molding the minus-lens is performed by advancing the die fitting member from an initial position having a maximum compression margin to a position where the predetermined compression margin is less than the maximum compression margin; andwhen the plus-lens is molded, said step of setting the predetermined compression margin is performed by advancing the die fitting member from the initial position where the compression margin is at the maximum, to a position at which there is no compression margin and by then retracting the die fitting member a distance equal to the predetermined compression margin; and,the predetermined compression margin is defined in accordance with a lens factor of the lens.