still for framstellning of fototropa flerfokala glasogonglas

摘要

1396059 Multifocal glass lenses CARL ZEISS-STIFTUNG [trading as CARL ZEISS] 16 April 1973 [2 May 1972] 18174/73 Heading C1M [Also in Division G2] In the manufacture of a fused multifocal lens of photochromic glass, a reading glass segment 2, Fig. 9 or Fig. 3 and photochromic glass major lens 4 or 7 are brought into position for fusing, heated together to a heat treatment temperature range in which separation areas determining the photochromic properties of the glass are formed, 550‹ C. to 650‹ C., thereby fusing the parts together and subsequently cooling the parts rapidly so that the retention time in the heat treatment range is less than about 10 hours, the time sufficient to produce a turbidity in the glass. The reading segment may be of non-photochromic glass and both glasses may be of previous non-heat-treated photochromic glass and the photochromic areas of the glass are fully established by a further heating and cooling cycle. The reading segment 2 with polished surface 3 may be positioned on a support 1 in a metal ring 6 and the lower melting point glass 4 pressed downwardly after the heating step by a ram 2. Alternatively, the glass 7 may be provided with a polished recess 8 and the segment 9 of lower melting point glass positioned thereover by a metal alloy ring 10 which melts at about the temperature of softening of the segment 9 to flow off the convex surface of the glass 7 as the segment 9 sinks into the recess 8.