B - Operations – Transporting – 29 – C
Patent
B - Operations, Transporting
29
C
18/104, 88/38
B29C 1/00 (1980.01)
Patent
CA 1113290
ABSTRACT A mold for casting a resin ophthalmic lens is comprised of a glass disc defining a principal casting surface on one face thereof. The casting surface is a portion of a surface of revolution which has a first axis of symmetry and which has, at a location along such axis, an effective center of curvature. The principal casting surface has, in a selected portion thereof, a bottom surface defining in the mold a minor casting surface which is a portion of a surface of revolution having a second axis of symmetry. The first and second axes, if they intersect at all, intersect at a location on the first axis other than at substantially the center of curvature of the principal casting surface. The mold is made by forming in one face of a first glass blank an optically finished surface which has a curvature identical to that of the bottom surface of the mold recess. A second glass blank is provided, and has characteristics sufficiently compatible with those of the first blank that the first and second blanks may be stably adhered together. The second blank, as initially provided, has formed at least partially therethrough a recess which has a perimetral shape at least partially congruent to the perimetral shape of the mold recess. The mold making procedure includes forming in one side of the second blank a second surface which is essentially reversely curved to that of the finished surface in the first blank. The second surface is formed on the second blank so that, upon completion of the second surface, the recess extends through the second blank. The first and second blanks are registered with each other with the formed surfaces thereof in opposition. The registered blanks are adhered together to define a resulting blank. The mold making procedure further includes forming in the face of the resulting blank to which the recess opens an optically finished third surface having a curvature identical to the curvature of the mold principal casting surface; this step is performed without eliminating the recess entirely from the resulting blank.
332690
Hirons & Rogers
Signet Optical Corporation
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