Overflow downdraw glass tube forming apparatus

An apparatus for forming glass tubing comprising:

• an endless former, a first molten glass hold, and a second molten glass hold,
• wherein the endless former is positioned substantially vertically and comprises an upper portion, an outer surface, and a first inner passage with a first inner surface, the upper portion of the endless former comprises an extension configured to be fixed in order to fix the endless former in a substantially vertical position;
• wherein the first molten glass hold comprises a first floor, the first floor comprises a first opening configured for positioning of the endless former;
• the first molten glass hold is positioned so that the first floor is spaced below the extension of the endless former and the endless former is positioned within the opening in the first floor defining a glass flow gap between the endless former and the first floor of the first molten glass hold;
• the first floor is configured to permit the flow of molten glass toward the endless former such that molten glass may pass through the glass flow gap and down along the outer surface of the endless former;
• and
• wherein the second molten glass hold comprises a second floor spaced above the first floor and above the extension of the endless former, the second floor comprises a second opening and a first neck extending downwardly from the second opening;
• the first neck comprises a second inner passage with a second inner surface;
• the second floor is configured to permit the flow of molten glass toward the second opening such that the molten glass may flow into the second opening and down along the second inner surface of the first neck;
• the second molten glass hold is positioned such that the molten glass flowing into the second opening and the down along the second inner surface of the first neck will flow down along the first inner surface of the endless former to meet the molten glass flowing down along the outer surface of the endless former to form glass tubing.