Method and apparatus for producing a quartz glass cylinder

• Main Authors: WHIPPEY NIGEL, LEBER HELMUT, BERG RAINER
• Format: Patent
• Language: English
• Published: 24.12.2013
• Subjects: CHEMISTRY; GLASS; MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES; METALLURGY; MINERAL OR SLAG WOOL

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. In order to provide a method starting from this which facilitates the production of homogeneous quartz glass cylinders, even if the lateral dimensions thereof are in the range of the inside diameters of conventional melting crucibles (1), according to the invention the viscous quartz glass mass is drawn over a flow constriction (12; 32) provided in an upper region of the die (4; 34) and leading downward into the outlet (25; 36) via a flow channel, said region facing the crucible interior, wherein the outlet has an opening width that is larger than the width of the flow constriction (12; 32), and wherein a first minimum circumscribed circle around the flow constriction (12; 32) has a diameter that is a maximum of 30% of the diameter of a second minimum circumscribed circle around the quartz glass strand (5; 33) to be drawn. The invention further relates to a corresponding apparatus.