Heraeus Quarzglas Gmbh & Co Kg

Hans-Georg Fritsche

Udo Peper

Hartwig Schaper

Steffen Zwarg

Sven Schmidt

Michael Muschler

Frank Neubauer

Frank Hoff

J&uuml;rgen R&ouml;per

A known method for producing a cylinder of quartz glass comprises a method step in which a porous SiObody comprising a central inner bore, a lower end and an upper end is sintered in a sintering furnace zone by zone, starting from the upper end, to obtain the quartz glass cylinder, a holding device being used by means of which the SiObody is held standing in vertical orientation during a first sintering phase and suspended in a second sintering phase. Starting therefrom, to indicate a method by means of which even heavy bodies of porous SiOcan be reliably held during sintering, it is suggested according to the invention that the holding device comprises a fusion body of quartz glass which is arranged in the area of the upper end in the inner bore and which in the course of the first sintering phase fuses with the quartz glass of the SiObody and which during the second sintering phase is in operative interaction with a holding element of the holding device and together with said element contributes to a suspended holding of the SiObody to be sintered.

Method for producing a cylinder of quartz glass using a holding device and appropriate holding device for performing the method

In a known process for the manufacture of an elongated porous SiO,preform, SiO,particles are deposited on the mantle surface of a cylindrical carrier rotating about its longitudinal axis. The SiO,particles are formed by means of a plurality of deposition burners which are arranged, at a distance from one another, in at least one burner row extending parallel to the longitudinal axis of the carrier. The burners are moved in a repeated cycle back and forth along the forming preform and between turnaround points where the direction of their motion is reversed. Measures are taken in the process to prevent or reduce overheating of the preform in the turnaround point regions. These measures can lead to variations in the rate of deposition. In order to prevent this it is proposed according to the invention that the measures comprise localized removal of heat from the turnaround points (,), or a localized heat shielding of the regions (,) around the turnaround points (,), and that these measures be kept time-constant within a motion cycle. As far as concerns an apparatus suitable for implementation for the manufacture of a porous SiO,preform, with a cylindrical carrier rotatable about its longitudinal axis, with a plurality of deposition burners arranged in at least one burner row extending parallel to the carrier's longitudinal axis, connected with one another and at a distance from one another and with a jogging device which moves the deposition burners along the carrier and between turnaround points where the direction of the motion is reversed and by means of which burners SiO,particles are deposited on the carrier, forming the preform, it is proposed that heat sinks (,) be provided in the regions (,) around the turnaround points (,).

Process and apparatus for manufacturing a porous SiO2 preform

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Bobbau, Germany

Hans-Georg Fritsche