Fremgangsmåder og apparat til opvarmning af et aflangt glassubstrat

摘要

A glass tube (31) from which optical fiber is to be drawn is heated by a torch assembly comprising a plurality of nozzles (54-54) disposed on a carriage. In order to avoid contamination of the tube by particles of the torch assembly resulting from thermal degradation, the nozzles are disposed in a plane which is normal to an axis (36) of the tube with each nozzle axis inclined so that flame fronts associated with the nozzles are substantially closer to the tube than to the torch assembly. Reaction of materials which are flowed into the tube is enhanced by including a second row of nozzles (91-91) which are inclined within a plane which is inclined to the longitudinal axis of the tube. In order to collapse the tube into a rod, a muffle member (100) preferably is caused to be disposed about the tube with an opening in the periphery of the muffle member to allow portions of the gas flows to converge and to allow heat energy to be transferred from the flame fronts to the tube.