Heraeus Quarzglas Gmbh & Co Kg

Udo Peper

Steffen Zwarg

Sven Schmidt

Hans-Georg Fritsche

Martin Trommer

Hartwig Schaper

Juergen Roeper

Rene Sowa

René Sowa

Anke Schuster

Thomas Krause

Frank Hoff

Michael Muschler

Andreas Helm

J&uuml;rgen R&ouml;per

Frank Neubauer

In a known process for producing a quartz glass cylinder, a porous soot tube, which is sintered to form the quartz glass cylinder, is produced by depositing SiOparticles on an outer cylindrical surface of a support, which rotates about the longitudinal axis thereof and has a layer of silicon carbide (SiC layer). In order on this basis to specify a support having a high resistance to fracture, which firstly can easily be removed and which secondly presents a low risk of contamination for the soot body, the invention proposes that the SiC layer is treated at a high temperature in an oxygen-containing atmosphere before the SiOparticles are deposited, in such a manner that an SiOprotective layer having a thickness of at least 0.1 &#x3bc;m is produced by oxidation.

Process for producing a quartz glass cylinder and also support for carrying out the process

The invention relates to a known method for the production of a cylinder from quartz glass, comprising a step, wherein an SiObody which comprises a porous SiOsoot layer and has a lower end, an upper end, and an outer casing, is sintered to form said quartz glass cylinder in a vitrification furnace, and is being held in a vertical orientation by means of a retaining device, which comprises an upper retaining element connected at the upper end of the SiObody, and a lower retaining element disposed on the lower end. In order to provide a method based thereon, by means of which even heavy bodies made of porous SiOcan be safely retained during vitrification, the invention provides that the retaining device has a dimensionally stable connecting part, which extends inside the vitrification furnace along the outer casing of the SiObody and which connects the upper and the lower retaining elements to each other.

Method for the production of a cylinder made from quartz glass using a retaining device, and retaining device

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

Method for producing a semifinished product from synthetic quartz glass Methods for producing a semifinished product from synthetic quartz glass by plastic deformation of a softened SiOmass in a melt mold are known. Starting from this, to avoid fusion defects as much as possible and to obtain semifinished products of quartz glass in a reproducibly high quality, a method is suggested that comprises the following steps: (a) providing a porous SiOsoot body, (b) zonewise sintering of the SiOsoot body in the melt mold at a sintering temperature and during a sintering period with formation of a completely sintered transparent quartz glass body, and directly thereafter (c) shaping the sintered quartz glass body by softening in the melt mold with formation of a viscous quartz glass mass which fills the volume of the melt mold entirely or partly, and (d) cooling the quartz glass mass and removing the mass from the melt mold with formation of the semifinished product.

Method for producing a semifinished product from synthetic quartz glass

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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Halle/Saale, Germany

Udo Peper