GB1044579A - Method of producing precision bore glass tubing of uniform wall thickness - Google Patents

Abstract

To produce glass tubing of uniform bore and wall thickness and of true circularity, the glass at a temperature above its softening point is centrifuged on a layer of molten tin inside a hollow cylindrical container, the container then being cooled and the glass tube withdrawn. The inner bore of the molten tin will not have the irregularities of the container. The tin and glass may be introduced together as a powdered mixture, the denser tin forming the outer layer, or the tin tube may be preformed and the glass added separately as a powder or as molten glass. Ply or composite glass tubing may be made by the introduction of a second glass after the first glass tube is formed, the container being cooled before significant diffusion of the two glasses takes place. With suitable modification a continuous process can be achieved with molten glass fed from a glass tank into the rotating container and molten tin, the glass being solidified in its passage along the metal float by a temperature gradient along the container and the solidified tube being rotated as it is withdrawn. Induction heating of the container is preferably used and heating of the container is in an atmosphere, for example, of forming gas. The container may be of graphite, metal or ceramic.