Patent ID: 6071111
Filing Date: 2000-06-06
Classification: B29C,B29D,Y10S

Abstract:
A mold assembly for forming a lens blank which gives a contact lens, said mold assembly comprising an upper mold half and a lower mold half which cooperate with each other to define a substantially fluid-tight mold cavity when said upper and lower mold halves are assembled together, said mold cavity being filled with a monomer liquid which is polymerized to provide said lens blank that is to be subjected to a cutting operation for forming a base curved surface and a front curved surface of said contact lens, wherein the improvement comprises:said upper mold half including a flexible thin-walled portion which has a downwardly convex shape and which partially defines said mold cavity, said thin-walled portion being deformable so as to absorb expansion or shrinkage of said monomer liquid during polymerization thereof in said mold cavity; andsaid lower mold half including a base portion at which said lower mold half is clamped by a chuck of a lathe during said cutting operation, and a mold portion having a molding surface which is provided with lens blank holding means for holding said lens blank on said lower mold half, said lens blank being formed in said mold cavity defined by and between said upper and lower mold halves wherein said base portion of said lower mold half is a hollow cylindrical member which includes reinforcing means provided in said hollow cylindrical member.