Patent ID: 6074579
Filing Date: 2000-06-13
Classification: B29C,B29D,B29L

Abstract:
A method of substantially manufacturing instantly a prescription lens, for eyeglasses on site by compression molding, in a pair of upper and lower molds having mold surfaces from a thermoplastic preform lens blank, having opposite surfaces and a periphery, comprising the steps of:preheating said preform at a first temperature and preheating said upper and lower molds to a second higher temperature;positioning said preheated preform between said upper and lower preheated molds such that said preform makes a single point or line contact with each of said mold surfaces;initially compressing said preformed at a first fixed rate of speed regardless of pressure exerted on said preform, with said preform being compressed to about 4 mm of a predetermined lens thickness desired for said prescription lens;finally compressing said preform to a substantially finished prescription lens at a second fixed rate of speed substantially higher than said first fixed rate of speed regardless of pressure exerted on the preform while substantially maintaining a predetermined temperature on said preform, and shutting off heating of said molds, and stopping travel of said molds with respect to each other upon reaching said predetermined lens thickness; andcooling said molds to another temperature lower than said predetermined temperature; and thereafter opening said molds so as to remove said finished prescription lens;whereby said prescription lens is made within minutes without any air bubbles or entrapped air, leaving only flashing to be removed prior to fitting said prescription lens to an eyeglass frame.