Importance

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Abstract

A method of manufacturing a prescription lens, for eyeglasses on site by compression molding, in a pair of upper and lower molds having a mold surfaces from a thermoplastic preformed lens blank having opposite surfaces and a periphery, comprising the steps of: preheating a preform blank at a first temperature and preheating the upper and lower molds to a second higher temperature; positioning the preheated preform between the upper and lower preheated molds such that the preform makes a single point or line contact with each of the mold surfaces; initially compressing the preformed at a first fixed rate of speed regardless of pressure exerted on the preform, with the preform being compressed to about 4 mm of a predetermined lens thickness desired for the prescription lens; finally compressing the preform to a substantially finished prescription lens at a second fixed rate of speed substantially higher than the first fixed rate of speed regardless of pressure exerted on the preform while substantially maintaining the predetermined temperature, and shutting off the heating to the molds, and stopping travel of the molds with respect to each other upon reaching the predetermined lens thickness; and cooling the molds to another, but lower predetermined temperature; and thereafter opening the molds so as to remove the finished prescription lens.

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First Claim