Method and apparatus for making optical preforms with controlled peripheral edge wall geometry and preforms made therewith

摘要

Optical glass preforms for use in subsequent molding processes for the production of lenses are produced which have a controlled peripheral edge wall geometry. Gobs of molten glass of predetermined weight and volume are dripped onto a lower mold surface. A pressing head including a sleeve and a plunger are lowered such that the sleeve surrounds the gob. The plunger is then depressed such that the upper mold surface of the plunger resides in a predetermined elevation above the lower mold surface thereby forcing the gob to conform to the cavity created within the sleeve and between the upper and lower mold surfaces. In such manner the sleeve serves as a form or exterior boundary for the resultant preform such that a preform is produced which requires no grinding or polishing prior to its use in subsequent molding operations. <IMAGE>