GB224164A - Process for the manufacture of articles in silica glass - Google Patents

Abstract

224,164. Quartz et Silice. Nov. 2, 1923, [Convention clate]. Forming silica - glass articles.-A process of manufacturing articles of fused silica, or of glass having a high silica content, consists in melting the silica in a crucible of refractorv and conducting material by the induction of high-frequency electric current, expelling the plastic silica from the crucible either by pressure or by drawing, and then shaping the mass by pressure or by other suitable mechanical treatment. The charge a of sand, rock crystal or other suitable material is placed in a crucible b, made of graphite, which is closed at its upper end by a tightly fitted cover c with an inlet tube d. The bottom of the crucible is closed by a removable plug e of graphite. The furnace comprises a tube f, of copper or aluminium, wound on a cylinder g of insulating material. Water is circulated through the tube, and the space around the crucible is packed with a heat-insulator h, such as lampblack. High-frequency electric currents, produced by known means such as a highfrequency alternator, spark or arc generator, or thermionic valves, is passed through the tube f, and the crucible is raised to a high temperature by induction. When the material is fused, the plug e is removed and the plastic silica is expelled by means of gas under pressure admitted through the tube d. If the silica is to be made into rod, the plug e is replaced by a graphite draw-plate, and the silica. is extruded by the gas pressure, an external drawing device being also used if necessary. In making tubing, a tube is used to form a core for the extrusion aperture and for permitting the introduction of blowing air into the interior of the silica mass. The melting can be carried out in vacuo or in an atmosphere of a suitable gas introduced into the crucible through the tube d.