GB354509A - A method of and apparatus for drawing glass tubes - Google Patents

Abstract

354,509. Making glass tubing. HADDAN, R., 31, Bedford Street, Strand, London.-(Corning Glass Works ; Walnut Street, Corning, New York, U.S.A.) July 2, 1930, No. 20111. [Class 56.1 Relates to a method of making glass tubing, particularly lens-fronted thermometer tubing having the bore backed by a coloured stripe. The invention consists in forming a narrow layer of coloured glass on a bath of molten clear glass, and in drawing a tube vertically upwards from the two glasses through a shaping device situated above a cooled nipple immersed below the surface of the glass. The glass from which the tube is drawn is contained in a pot 2, Fig. 5, housed in a -furnace structure 3 and filled from time to time with fresh glass by ladling through an aperture 4 in the roof of the furnace. A hollow nipple 5 is inserted in the bottom of the pot and is cooled, if required, by a jet of air from a pipe 6. The drawing mechanism consists of a pair of wheels situated above the roof of the furnace. A cylindrical casing or boot 10 is fitted in an aperture in the roof above the nipple 5, and its lower end supports a shaping-member 12 which dips into the molten glass and gives the required shape to the glass tube as it is drawn. A perforated pipe 15<1> surrounding the tube is supplied with air and enables the temperature within the boot to be controlled. In operating the device, the pot is filled with glass until its surface is above the lower edge of the shaper 12. Drawing is started with a bait and is continued by the drawing wheels. The shaper 12 gives the desired cross-sectional shape to the tube which is drawn from the cooled glass over the nipple 5. Air may be allowed to pass through an opening 27 in the head of the nipple. to maintain the bore of the glass tube. When a coloured stripe is to be inserted in the tube, the lower edge of the shaper is cut away at 14, Figs. 5 and 8, and a floating frame 17 is placed in contact with it. The floater is divided into two compartments 24, 26 by a transverse bridge 22, and slots 23; 25 are formed in the lower edges of the bridge and the wall 20 which is in contact with the shaper. Coloured glass is introduced into the compartment 24 and floats on the surface of the clear glass in the pot; and clear glass is introduced into the compartment 26. As the draw takes place, the coloured glass is drawn along beneath the surface of the glass in the compartment 26 and forms a coloured stripe '28 behind the bore. of the glass tube.