Process and furnace for heat application

Abstract

Control of speed and uniformity of the heating of the working zone of the preform in a glass drawing operation in which the softening heat is applied by forced convection (13), using a separate fluid heating zone to introduce temperature and velocity controlled fluid. The size of the working zone is further controlled by changing (18) the configuration of a movable exit sleeve. Uniformity and accuracy of temperature is enhanced by normalization (10) of the temperature of the preform close to a preselected value before the preform enters the furnace. A glass drawing apparatus embodies the preferred means to carry out the process, providing a two-chamber furnace having an air heating chamber (44) connected by air delivery channels (51) to a drawing chamber (43). The drawing chamber has preform inlet (41) and a drawn product outlet (56). Each of the latter preferably has an adjustable opening diameter. The inlet is provided with a pre-cooling collar (35). The outlet has an insulated, movable sleeve (62) controlling the effective distance from the inlet to the outlet by modifying the temperature gradient. The latter provides means for controlling the length and shape of the working zone (55).

Dependencies are inferred from the claim text.