Glass manufacturing – Processes – Sequentially forming – reheating – and working
Patent
1991-12-16
1993-02-23
Lindsay, Robert L.
Glass manufacturing
Processes
Sequentially forming, reheating, and working
65 77, 65102, 65104, 425808, C03B 2300
Patent
active
051886502
ABSTRACT:
Molding is effected while pressing pressure is continuously or stepwise controlled so that at the initial stage in which the temperature distribution of a glass blank is not sufficiently uniformized, molding may be effected with relatively low pressing pessure and in a state in which the whole of the glass blank is uniformly increased in temperature, press molding may be effected with the pressing pressure increased. In a press molding apparatus for an optical element, during press molding, the glass blank is press-molded while the pressing pressure is continuously or stepwise varied so that at a temperature whereat the glass viscosity of the glass blank corresponds to 10.sup.21 -10.sup.11 poise, molding may be started with pressing pressure of 10 kg/cm.sup.2 -100 kg/cm.sup.2, and thereafter in a temperature range in which the glass viscosity x of the central portion of the glass blank corresponds to 10.sup.11 -10.sup.10 poise, pressing pressure in the range of 10.times.(10.sup.11-x)-100+10.times.(10.sup.11-x) kg/cm.sup.2 may be applied, and further at a temperature whereat the glass viscosity corresponds to 10.sup.10 or less, pressing pressure of 100 kg/cm.sup.2 or greater may be applied.
REFERENCES:
patent: 4591373 (1986-05-01), Sato
patent: 4734118 (1988-03-01), Marechal et al.
patent: 4921519 (1990-05-01), Schinker et al.
Canon Kabushiki Kaisha
Lindsay Robert L.
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