Method of verifying a porous article made out of glass soot and furnace for carrying out the method

US4842628A · kind A · utility

Assignee

• Heraeus Quarzschmelze GmbH · DE

Inventors

• Karl Kreutzer · Leverkusen, DE
• Fritz Simmat · Gelnhausen, DE
• Anton Steinkohl · Grundau, DE
• Wolfgang Englisch · Kelkheim, DE

Key dates

• Filing date: Mar 2, 1988
• Grant date: Jun 27, 1989
• Expiry date: Mar 2, 2008

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C03B37/0146
• WIPO field: Other special machines
• WIPO sector: Mechanical engineering

Abstract

A method of vitrifying a porous cylindrical article made out of glass soot, especially for manufacturing a preliminary blank for optical fibers. The article is heat-treated in a furnace in a vacuum or in an atmosphere that contains helium. The porous article is placed in a horizontal graphite tube in the furnace, is sintered therein for 20 to 40 minutes in a vacuum or in a helium atmosphere with reduced pressure at 1250.degree. to 1400.degree. C., and is subsequently vitrified by heat-treating the sintered article at first in the sintering atmosphere, while slowly rotating it in the hot graphite tube for 20 to 40 minutes at approximately 1450.degree. to 1600.degree. C. and then while rotating it in the graphite tube more rapidly than in the first stage for 10 to 30 minutes at approximately 1650.degree. to 1750.degree. C.