Patent GB-319361-A (GB)
Title: Method and apparatus for continuously drawing glass tubes or rods
IPC: C03B17/04
Filed: 1929-09-18
Abstract: 319,361. Favre, P. A. Sept. 22. 1928, [Convention date]. Drawing; forming glass tubes.-Relates to the method of making glass tubing, described in Specification 300,646, in which one or more cylindrical glass blanks 1, Fig. 4, are threaded on a tubular mandrel 5 having a conical extension 7 at its lower end to support the blanks. The lowest blank is heated by gas flames, and the glass as it melts runs over the enlargement 7 and is drawn off by a suitable drawing device. The present invention consists mainly of modifications of the apparatus described in the prior specifications. The glass blanks 1, Fig. 4, are made by casting or pressing, and have recesses on their lower faces and projections on their upper faces, so that they pile easily on one another. The mandrel 5 is fitted with a tubular sleeve 2, and with a fireclay cone 7 which is kept in place by a disc 8 of refractory metal. The sleeve 2 is formed with grooves 3, 4 which are engaged by hinged supporting-clamps 9<1>, 9<2>. The heating-device preferably consists of a ring 13, Fig. 5, fitted with gas burners 11 and mounted, coaxial with the mandrel 5, on ball bearings on a plate 12. The ring is oscillated on its axis by suitable means so that the heat from the burners is distributed evenly over the lower part of the pile of glass blanks. Alternatively, the mandrel may be suspended in a tubular furnace, open at the top and bottom, which may be heated by gas, oil, or electricity. Coaxial sleeves 16, 17 surround the mandrel above and below the conical end, and their position can be adjusted to regulate the flow of the glass on to the cone and the thickness of the tube that is drawn away. The apparatus for drawing the tube consists of three pairs of opposed wheels 21, 28, Fig. 8, of equal diameter, which are rotated in the same direction and speed and grip the glass tube T, as shown. The wheels 21 are journaled in a frame 25<1> while the wheels are carried by counterweighted bellcrank levers 27. The Specification, as open to inspection under Sect. 91 (3) (a), describes a modified construction in which the tubing is drawn vertically upwards from molten glass contained in an annular trough surrounding a mandrel similar to the mandrel 5. The trough is heated to keep the molten glass at the proper temperature for drawing. This subject-matter does not appear in the Specification as accepted. Glass, cutting or dividing.-The device for .dividing the tube into lengths preferably consists of a pair of rotating metal discs 30, Fig. 10, mounted on opposite sides of the drawn tube T and carried by pivoted arms 49 which are linked together. The device is carried by a frame 31 which is reciprocated vertically and is counterbalanced by weights 33. On the down. ward movement of the frame, a latch connected to one of the levers 49 engages a fixed cam 58 and swings the cutters 30 into contact with the glass tube. A movable support 73 is moved at the same time into contact with the tube and, in conjunction with a fixed member 71, supports the tube while the lower section is being cut off. In another construction, the severing- device consists of a pair of grippers which are kept cold and are brought into contact with the hot tube to cause it to crack. Alternatively, the grippers may be heated electrically and may be brought into contact with the glass tube after it has cooled.