Importance

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Abstract

A mold assembly for forming a lens blank which gives a contact lens includes an upper and a lower mold half which cooperate with each other to define a substantially fluid-tight mold cavity when the two halves are assembled together. The mold cavity is filled with a monomer liquid which is polymerized to provide the lens blank that is to be subjected to a cutting operation for forming a base and a front curved surface of the contact lens. The upper mold half includes a flexible thin-walled portion which has a downwardly convex shape and which partially defines the mold cavity. The thin-walled portion is deformable to absorb expansion or shrinkage of the monomer liquid during polymerization thereof in the mold cavity. The lower mold half includes a base portion at which the lower mold half is clamped by a chuck of a lathe during the cutting operation. A mold portion of the lower mold half has a molding surface which is provided with a recess or protrusion for holding the lens blank on the lower mold half. The lens blank is formed in the mold cavity defined by and between the upper and lower mold halves.

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First Claim