Patent ID: 8025819

Claim:
A method of manufacturing a plastic lens in which a rotatable disc is provided and a plurality of cylinders which allow molds to pass therethrough are provided along an inner circumference of the rotatable disc, a piston shaft which includes a mold holding portion being arranged on a center axis of the cylinder, the molds having a planned combination, the method comprising: placing two respective ones of the molds which have the planned combination on a transport base; heating the two molds in a state that a one of the two molds having a convex forming surface is heated with the forming surface directed upwardly and the mold having a concave forming surface is heated with the forming surface directed downwardly; holding one of the two molds in the inside of the cylinder; controlling the piston shaft using at least one pre-controlled automatic transport device and/or manually such that the forming surface of said one of the two molds having the convex forming surface assumes substantially a same height as an upper surface of an opening portion of the cylinder or slightly projects from the upper surface of the opening portion thus arranging the mold in a fixed manner; causing an optical thermoplastic resin molten material having no agitation flow or having negligible agitation flow to flow out from a nozzle of an extruding machine so as to be placed on the one of the two molds, the resin molten material which flows out from the nozzle of the extruding machine along with the rotation of the disc being placed in a direction of the rotation so as to create a band of said resin molten material which extends continuously from a first region of a top surface of said rotatable disc adjacent to a first side of said one of the two molds, entirely across said one of the two molds, to a second region of the top surface of said rotatable disc adjacent to a second side of said one of the two molds, the resin molten material being extruded in such manner that said band is produced with a gradually increased volume per a unit length in a region thereof corresponding to a center of said one of the two molds as compared to a corresponding volume per unit length of the band of resin molten material corresponding to a peripheral region of said one of the two molds; subsequently placing an other of the two molds having the concave forming surface on the resin molten material with the forming surface directed downwardly; and urging both of said two molds towards one another in the inside of the cylinder until a given distance is defined so as to form a plastic lens by pressing the resin molten material.