Molding arrangement to achieve short mold cycle time

A molding apparatus for producing at least one mold half which is used for subsequently molding a soft contact lens therewith, comprising:

• first and second reciprocating blocks, having opposing faces, said blocks reciprocating relative to one another so that the opposing faces meet and separate in a regular repetitive molding cycle;
• at least one first structure, mounted within said first reciprocating block, said first structure including a hollow cylindrical bushing and a power insert disposed therein, said power insert defining a convex curved surface which protrudes from the face of said first reciprocating block and a flat annular surface surrounding the convex surface, said convex curved surface and said flat annular surface establishing an interface, said interface comprising a discontinuous profile so as to provide a sharp edge in the mold half produced thereby, said discontinuous profile being provided entirely by said insert;
• at least one corresponding second structure, mounted within said second reciprocating block, said second structure having a concave curved surface which forms a recession in the face of said second block, wherein said convex curved surface of said first structure and said concave curved surface of said second structure are disposed in proximal spaced relation to one another and define therebetween a volume wherein a mold half is formed when said opposing faces meet;
• said convex curved surface being an optical quality curved surface for imparting an optical quality to a concave surface of the mold half formed thereby;
• a hot runner system connected to the volume between said first and second structures for delivering a quantity of molten material of which the mold half is to be formed, wherein said at least one first structure having the optical quality surface is positioned further from the heated hot runner system than said at least one second structure;
• and
• wherein the positioning of the optical quality curved surface further away from the heated hot runner system provides for faster cooling of molten material which forms the concave optical quality surface of the mold half than the other surface of the mold half to allow quicker setting so that minimal residual stresses remain in the material which forms the optical quality curved surface of the mold half, and also provides faster molding cycle.

A molding apparatus for producing at least one mold half which is used for subsequently molding a soft contact lens therewith, comprising:

• first and second reciprocating blocks, having opposing faces, said blocks reciprocating relative to one another so that the opposing faces meet and separate in a regular repetitive molding cycle;
• at least one first structure, mounted within said first reciprocating block, said first structure including:
• a hollow cylindrical bushing having annular flat surface recession at one end thereof, and
• a power insert disposed within said bushing having a convex curved surface which protrudes from the face of said first reciprocating block, and an annular flat surface surrounding said convex curved surface, the interface of said annular flat surface thereof and said convex curved surface defining a discontinuous profile, said power insert comprising a thermally conductive material selected from the group comprising brass, copper-nickel-silicon-chromium, or cobalt and nickel alloyed martensitic steel, said power insert further comprising a chrome nitride coating on at least a portion of said convex curved surface;
• whereby an annular flat flange portion of said mold half may be formed simultaneously with the formation of the mold half by the annular flat surfaces of said bushing and said power insert;
• at least one corresponding second structure, mounted within said second reciprocating block, said second structure having a concave curved surface which forms a recession in the face of said second block, wherein said convex curved surface of said first structure and said concave curved surface of said second structure are disposed in proximal spaced relation to one another and define therebetween at least a portion of a volume wherein a mold half is formed when said opposing faces meet;
• said convex curved surface being an optical quality curved surface for imparting an optical quality to a concave surface of the mold half formed thereby;
• a hot runner system connected to the volume between said first and second structures for delivering a quantity of molten material of which the mold half is to be formed.

A molding apparatus for producing at least one mold half which is used for subsequently molding a soft contact lens therewith, comprising:

• first and second reciprocating blocks, having opposing faces, said blocks reciprocating relative to one another so that the opposing faces meet and separate in a regular repetitive molding cycle;
• at least one first structure, mounted within said first reciprocating block, said first structure including a hollow cylindrical bushing and a power insert disposed therein, said power insert defining a convex curved surface which protrudes from the face of said first reciprocating block and a flat annular surface surrounding the convex surface, said convex curved surface and said flat annular surface establishing an interface, said interface comprising a discontinuous profile so as to provide a sharp edge in the mold half produced thereby, said discontinuous profile being provided entirely by said insert and having a radius of 10 to 40 micrometers;
• at least one corresponding second structure, mounted within said second reciprocating block, said second structure having a concave curved surface which forms a recession in the face of said second block, wherein said convex curved surface of said first structure and said concave curved surface of said second structure are disposed in proximal spaced relation to one another and define therebetween a volume wherein a mold half is formed when said opposing faces meet;
• said convex curved being an optical quality curved surface for imparting an optical quality to a concave surface of the mold half formed thereby;
• a hot runner system connected to the volume between said first and second structures for delivering a quantity of molten material of which the mold half is to be formed, wherein said at least one first structure having the optical quality surface is positioned further from the heated hot runner system than said at least on second structure;
• and
• wherein the positioning of the optical quality curved surface further away from the heated hot runner system provides for faster cooling of molten material which forms the concave optical quality surface of the mold half than the other surface of the mold half to allow quicker setting so that minimal residual stresses remain in the material which forms the optical quality curved surface of the mold half, and also provides faster molding cycle.

A molding apparatus for producing at least one mold half which is used for subsequently molding a soft contact lens therewith, comprising:

• first and second reciprocating blocks, having opposing faces, said blocks reciprocating relative to one another so that the opposing faces meet and separate in a regular repetitive molding cycle;
• at least one first structure, mounted within said first reciprocating block, said first structure including a hollow cylindrical bushing and a power insert disposed therein, said power insert defining a convex curved surface which protrudes from the face of said first reciprocating block and a flat annular surface surrounding the convex surface, said convex curved surface and said flat annular surface establishing an interface, said interface comprising a discontinuous profile including an annular tapered wall having a taper of 2.degree. to 10.degree. to provide a sharp edge in the mold half produced by said apparatus;
• at least one corresponding second structure, mounted within said second reciprocating block, said second structure having a concave curved surface which forms a recession in the face of said second block, wherein said convex curved surface of said first structure and said concave curved surface of said second structure are disposed in proximal spaced relation to one another and define therebetween a volume wherein a mold half is formed when said opposing faces meet;
• said convex curved being an optical quality curved surface for imparting an optical quality to a concave surface of the mold half formed thereby;
• a hot runner system connected to the volume between said first and second structures for delivering a quantity of molten material of which the mold half is to be formed, wherein said at least one first structure having the optical quality surface is positioned further from the heated hot runner system than said at least on second structure;
• and
• wherein the positioning of the optical quality curved surface further away from the heated hot runner system provides for faster cooling of molten material which forms the concave optical quality surface of the mold half than the other surface of the mold half to allow quicker setting so that minimal residual stresses remain in the material which forms the optical quality curved surface of the mold half, and also provides faster molding cycle.

A molding apparatus for producing at least one mold half which is used for subsequently molding a soft contact lens therewith, comprising:

• first and second reciprocating blocks, having opposing faces, said blocks reciprocating relative to one another so that the opposing faces meet and separate in a regular repetitive molding cycle;
• at least one first structure, mounted within said first reciprocating block, said first structure including:
• a hollow cylindrical bushing having annular flat surface recession at one end thereof, and
• a power insert disposed within said bushing having a convex curved surface which protrudes from the face of said first reciprocating block, and an annular flat surface surrounding said convex curved surface, the interface of said annular flat surface thereof and said convex curved surface defining a discontinuous profile, said power insert comprising a thermally conductive material selected from the group comprising brass, copper-nickel-silicon-chromium, or cobalt and nickel alloyed martensitic steel, said power insert further comprising a silicone oxide coating on at least a portion of said convex curved surface;
• whereby in annular flat flange portion of said mold half may be formed simultaneously with the formation of the mold half by the annular flat surfaces of said bushing and said power insert;
• at least one corresponding second structure, mounted within said second reciprocating block, said second structure having a concave curved surface which forms a recession in the face of said second block, wherein said convex curved surface of said first structure and said concave curved surface of said second structure are disposed in proximal spaced relation to one another and define therebetween at least a portion of a volume wherein a mold half is formed when said opposing faces meet;
• said convex curved surface being an optical quality curved surface for imparting an optical quality to a concave surface of the mold half formed thereby;
• a hot runner system connected to the volume between said first and second structures for delivering a quantity of molten material of which the mold half is to be formed.