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US 6,521,146 B1Granted
Compression molding of optical lenses
AssigneeMead Ophthalmics
InventorVandenberg Mead
Life of this patent
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Abstract
A lens molding system which uses glass molds to mold polycarbonate blanks. The blanks are preheated, then additionally surface heated, molded, and cooled under pressure.
Claims12
A polycarbonate lens forming device, comprising:
- an oven, which is programmed to first heat a polycarbonate blank to a specified first temperature below a deformation point of the polycarbonate material and then to heat by an amount effective to raise a temperature of only an outer surface of the polycarbonate material to a second higher temperature, above the first temperature but below a glass transition point of the polycarbonate material;
- and
- a heated pressurized mold, heated to a third temperature higher than said second temperature, and after said outer surface of said polycarbonate material is heated to said second temperature, pressing against surfaces of said polycarbonate material at a pressure less then 450 pounds per square inch.
A polycarbonate lens molding apparatus, comprising:
- first and second glass molds, including a bottom glass mold and a top glass mold, one of said glass molds being concave, and the other of said glass molds being convex, each of said glass molds being in contact with a heat conductance medium which heats the molds to a specified temperature;
- and
- said top glass mold including a holding mechanism, rigidly coupled to said lens molding apparatus, having surfaces which hold the top mold in place and limit its downward motion, but which allows the top mold to be pressurized upwards during pressurization.
A method of forming a polycarbonate lens, comprising:
- obtaining a polycarbonate blank, and heating the polycarbonate blank to a temperature above its glass transition point;
- further heating surfaces of the polycarbonate blank to further soften said surfaces more than a middle part thereof;
- and
- bringing the heated polycarbonate blank into contact with upper and lower heated molds, which are heated to a temperature higher than the surface of the blank, where the molds include a lower mold, where the polycarbonate blank rests against the lower mold, and
- pressing the upper mold, pressed against the polycarbonate blank.
2 more elements
Dependencies are inferred from the claim text.