Abstract: In a known method for drawing a tubular quartz glass strand, SiO2-containing starting material is fed to a melting crucible, softened therein into a viscous quartz glass mass (27), and said mass is pulled vertically downward as a cylindrical quartz glass strand (5; 33) through a die (4; 34) provided in the bottom region of the melting crucible (1), said die having a gap-shaped outlet (25; 36), which is defined by a bottom opening and a die inside part, and thereafter the quartz glass cylinder is cut to length.

Abstract: The invention relates to a process for the production of internally-hardened glass tubes, in which in a tube-drawing process for the production of glass tubes that is known in the art, a coated drawing tool, for example in the process according to Danner a coated mandrel or in the process according to Vello or in A-drawing process a coated needle, is used, whose coating releases coating material upon contact with the inside surface of the tube that is produced and accumulates on the inside glass surface. The chemical resistance is increased by this internal hardening. The invention also relates to devices for implementing this process and uses of the tubes that are produced according to these processes.

Abstract: A method and apparatus are provided for drawing a self-aligned core fiber free of surface contamination and inserting the core fiber into a cladding material to make an optical fiber preform. Single or multi-mode optical fibers having high quality core-clad interfaces can be directly drawn from the preforms described herein.

Abstract: Methods of an apparatus for producing profiled glass tubing utilizing the Danner process comprise flowing the molten glass over profiled blowpipe heads which are "super-profiled" in that the angles of ridges and grooves are more acute than the ridges and grooves resulting in the glass tubing. The particular profiles of the glass tubing are controlled by selecting the necessary drawing speed, viscosity of the glass, internal air pressure at the blowpipe head and throughput rate of the glass melt.

Abstract: A process is described for manufacturing vertically withdrawn pipes from quartz glass or glasses having a high content of silica with only minor diameter deviation. In an electrically heated furnace, the initial material is heated up to the softening point. A pipe is formed in a deformation zone and is downwardly withdrawn. In this deformation zone, a constant pressure difference is maintained between the pressure in the pipe interior and the pressure in a chamber and/or heating chamber. The pressure is continuously measured and controlled so as to be at a constant difference. In order to maintain a higher pressure in the pipe interior as opposed to the pressure in the chamber and/or the heating chamber, the withdrawn pipe end of the pipe to be manufactured is sealed.