One Piece, Light-Weight Vitreous Articles such as Telescope Mirror Blanks.

摘要

1,167,892. Mirror blanks. OWENS-ILLINOIS Inc. March 7, 1966 [March 5, 1965; July 1, 1965], No. 9810/66. Heading G2J. [Also in Division C1] A one-piece, vitreous telescopic mirror blank is provided with cavities 19 which communicate via openings 18 with one surface of the blank, each opening 18 having a smaller cross-sectional area than the cavity itself. The blank is formed of a thermally crystallizable glass which is poured in a molten state into a graphite mould. Open-cell type amorphous fused silica foam formers are immersed in the molten mass so that after treatment of the mass to produce the blank (see Division C1) they may be removed by chipping or scraping to provide the cavities 19.