Method for extruding articles

Abstract

A gas head extrusion apparatus (10), having upper (12) and lower (13) chambers, is arranged to feed glass particulate (60) into the upper chamber (12). The particulate (60) is heated to consolidate the particulate (60) into a first viscous melt (71) as an elevated gas pressure is simultaneously applied within the chamber (12). The first viscous melt (71) is urged through a narrow opening (16) in the bottom (14) of the upper chamber (12) into the lower chamber (13) to form a second viscous melt (73). The lower chamber (13) is pressurized to a second pressure, P.sub.2, where P.sub.1 >P.sub.2. Gas bubbles, having an internal pressure, P.sub.1, formed during the consolidation process in the upper chamber (12), will expand in the lower chamber (13) to facilitate removal thereof from the melt (73). The lower pressure, P.sub.2, also causes the melt (73) in the lower chamber (13) to be extruded through an annular opening (29), in the bottom of the lower chamber (13), to form a substantially bubble-free hollow glass tube (74).

Dependencies are inferred from the claim text.