An apparatus for forming glass tubing is described. The apparatus for forming glass tubing comprises an endless former with an outer surface and an inner passage defining an inner surface. The apparatus for forming glass tubing further comprises two chambers from which molten glass may flow. One chamber flows molten glass to the outer surface of the endless former and another chamber flows molten glass to the inner surface of the endless former. The two flows of molten glass meet at the bottom of the former to form glass tubing.

The present invention is directed to methods for making high quality glass tubes, and apparatuses for making high quality glass tubes. Because glass tubes made using the methods and apparatuses disclosed herein are substantially free from the optical defect known as paneling, the glass tubes may be used in displays for consumer electronic devices. The glass tubes are made by a continuous process in which a flow of molten glass is provided on an inner surface of a hollow, rotating mandrel such that the glass coats the inner surface of the mandrel and flows downstream on the inner surface of the mandrel, during which it is cooled to provide a higher viscosity. The glass is then removed from the mandrel and drawn to obtain a glass tube. A flow of molten glass may also be provided on the outer surface of the mandrel and joined with the glass flow on the inner surface of the mandrel when the glass flows exit the mandrel. The apparatuses presented herein are configured to provide high quality glass tubes using this method.

The present invention is directed to methods for making high quality glass tubes, and apparatuses for making high quality glass tubes. Because glass tubes made using the methods and apparatuses disclosed herein are substantially free from the optical defect known as paneling, the glass tubes may be used in displays for consumer electronic devices. The glass tubes are made by a continuous process in which a flow of molten glass is provided on an inner surface of a hollow, rotating mandrel such that the glass coats the inner surface of the mandrel and flows downstream on the inner surface of the mandrel, during which it is cooled to provide a higher viscosity. The glass is then removed from the mandrel and drawn to obtain a glass tube. A flow of molten glass may also be provided on the outer surface of the mandrel and joined with the glass flow on the inner surface of the mandrel when the glass flows exit the mandrel. The apparatuses presented herein are configured to provide high quality glass tubes using this method.

One or more glass articles include an aluminum oxide containing silicate glass matrix. The glass matrix has less than 1 SiO.sub.2-enriched glassy sphere of compositional inhomogeneities per 15 g of glass.

One or more glass articles include an aluminum oxide containing silicate glass matrix. The glass matrix has less than 1 SiO.sub.2-enriched glassy sphere of compositional inhomogeneities per 15 g of glass.

Provided is a sleeve for glass tube molding, the sleeve being capable of: preventing the weakening of clamping force between a metal tip and a metal holding fixture even if the distance between the metal tip and the metal holding fixture increases due to the thermal expansion of a sleeve shaft; and ensuring the coaxiality, on the sleeve shaft, of the metal tip, the metal holding fixture and a refractory tube. This sleeve for glass tube molding comprises: a sleeve shaft; a refractory tube into which the sleeve shaft is inserted in a coaxial manner; a metal tip which is at one end of the refractory tube, and is fixed to the tip of the sleeve shaft; and a metal holding fixture which, at the other end of the refractory tube, is slidably inserted in the sleeve shaft, and clamps and holds the sleeve shaft together with the metal tip. A part of the inner circumferential surface of a through-hole, which is in the metal holding fixture and through which the sleeve shaft is inserted, is in close contact with the outer circumferential surface of the sleeve shaft.

Provided is a sleeve for glass tube molding, the sleeve being capable of: preventing the weakening of clamping force between a metal tip and a metal holding fixture even if the distance between the metal tip and the metal holding fixture increases due to the thermal expansion of a sleeve shaft; and ensuring the coaxiality, on the sleeve shaft, of the metal tip, the metal holding fixture and a refractory tube. This sleeve for glass tube molding comprises: a sleeve shaft; a refractory tube into which the sleeve shaft is inserted in a coaxial manner; a metal tip which is at one end of the refractory tube, and is fixed to the tip of the sleeve shaft; and a metal holding fixture which, at the other end of the refractory tube, is slidably inserted in the sleeve shaft, and clamps and holds the sleeve shaft together with the metal tip. A part of the inner circumferential surface of a through-hole, which is in the metal holding fixture and through which the sleeve shaft is inserted, is in close contact with the outer circumferential surface of the sleeve shaft.

A bell assembly for a glass tubing manufacturing apparatus includes a bell head and a support connected to the bell head. The support includes a bell shaft with an inner bore and an outer surface, and a liner positioned in the inner bore of the bell shaft. A thermal shield extends along the outer surface of the bell shaft and reduces temperature variation across a width of the bell shaft during glass tubing manufacturing.

A bell assembly for a glass tubing manufacturing apparatus includes a bell head and a support connected to the bell head. The support includes a bell shaft with an inner bore and an outer surface, and a liner positioned in the inner bore of the bell shaft. A thermal shield extends along the outer surface of the bell shaft and reduces temperature variation across a width of the bell shaft during glass tubing manufacturing.

At least one glass tube has an azimuthal wall thickness deviation WTD of not more than 6.0%, the azimuthal wall thickness deviation being determined based on a lowest wall thickness value and a highest wall thickness value measured within a cross-section of the at least one glass tube, the azimuthal wall thickness deviation WTD being calculated according to the following formula:

[00001]$WTD=100-\left(\frac{\mathrm{lowest}\mathrm{wall}\mathrm{thickness}\mathrm{value}}{\mathrm{highest}\mathrm{wall}\mathrm{thickness}\mathrm{value}}*100\right)\%.$