Mold and a method of hot-forming a thermoplastic lens

摘要

The mold comprises two dies mounted in a sheath to slide along the axis of the sheath and each presenting a forming face facing the other. The two dies and the sheath are provided with intrinsic heat transfer means. A parison or preform of said thermoplastic material is placed between the two dies and the assembly is enclosed in the sheath; the dies and the sheath are heated by their intrinsic heat transfer means up to a forming temperature; The dies are moved towards each other to shape the material by plastic deformation until a predetermined relative position is reached corresponding to the thickness desired for the lens; the dies and the sheath are cooled by their intrinsic heat transfer means down to an unmolding temperature; and the finished lens is extracted from the mold.