APARELHO E METODO PROPRIOS PARA FORNECER UMA CORRENTE DE VIDRO ENCAMISADO

Apparatus for forming a cased glass stream having an inner core glass surrounded by an outer casing glass includes a first orifice (22) for receiving core glass from a first source (12), and an orifice ring (26) forming a second orifice (28) vertically spaced beneath and aligned with the first orifice. A chamber (30) surrounds the second orifice and communicates with the second orifice through a metering gap (56) between the first and second orifices. Casing glass is delivered from a second source (42) to the chamber, such that glass flows by gravity from the first and second sources through the orifices to form the cased glass stream. A heater ring (46) of refractory material is disposed beneath the orifice ring, and includes at least one electrical heater (48) embedded in the refractory material of the heaterring. The electrical heater is thus disposed external to the casing glass chamber for adding heat to casing glass flowing through the chamber to the metering gap. The heater ring in the preferred embodiment of the invention underlies and is contoured for facing engagement with the entire undersurface of the orifice ring for transferring heat energy through the orifice ring to glass in the casing glass chamber.