Apparatuses and methods for continuous production of glass tubing

An apparatus for producing glass tubing, the apparatus comprising:

• an inner cylindrical container including an inner delivery ring extending from a bottom of the inner cylindrical container, the inner delivery ring defining a central opening in the bottom of the inner cylindrical container;
• an outer cylindrical container concentrically arranged to surround the inner cylindrical container, the outer cylindrical container comprising a side wall and a bottom wall extending radially inward from the side wall to an outer delivery ring extending downward from the bottom wall, the outer delivery ring defining a central opening in the bottom wall of the outer cylindrical container, wherein the outer cylindrical container is spaced apart from the inner cylindrical container to define an annular chamber, a flow control region downstream of the annular chamber, and an annular flow channel extending from the flow control region to the outer delivery ring;
• at least one flow control valve disposed within the annular chamber and translatable relative to the outer cylindrical container, wherein translation of the at least one flow control valve is operable to change an impedance to flow of a molten glass composition through the flow control region;
• and
• a blow tube disposed within the inner cylindrical container and operable to deliver a gas flow proximate the inner delivery ring.