Patent GB-808284-A (GB)
Title: Improvements in or relating to methods of, and apparatus for, severing glass tubing
Inventor: HOUGHTON ROY WELLESLEY
IPC: C03B33/085
Filed: 1955-10-14
Abstract: 808,284. Glass cutting. GENERAL ELECTRIC CO. Ltd. Oct. 15, 1956 [Oct. 14, 1955], No. 29401/55. Class 56. In severing a length of glass tubing into a plurality of separate sections while it is being fed continuously in the direction of its length, an annular zone of the tubing is preheated by means arranged to travel along with the tubing during the preheating so as to reduce the electrical resistance in the zone and an electric current is passed round a circumferential path in the preheated zone so as to raise the temperature of the glass along that path to a value sufficient to melt the glass and sever the tubing, the spacing between successive preheated zones along the axis of the tubing being arranged to produce sections of tubing of the required length. The tubing 2 is drawn from a glass furnace by endless belts 3 lined with asbestos pads 7 and passed through a ring burner 8, fed with coal gas or oxygen, on a carriage 9 slidably mounted on guide rails 10 secured on main supports 14 to reciprocate between stops 17 on a cross rod 18 in bearings 19 on the main support, one end carrying a piston sliding in an air cylinder 20 to act as a shock absorber. Reciprocation is effected by an endless chain 11 carried by sprockets 12 and having a roller 15 free to slide in a groove 16 in the carriage 9, the chain 11 and belts 3 being driven from an electric motor and geared so that the carriage 9 travels in the forward direction at the same speed as the tubing 2. The burner 8 is mounted on a support 21 rotatably mounted within a bearing 22 on carriage 9, the bearing 22 also carying an air cylinder 23 containing a piston connected by rod 24 to the end 25 of the support 21 to rotate the support and burner through approximately 80 degrees during its forward travel and return it to its original position on the return stroke. The burner 8 has a large number of burners uniformly spaced on an inner ring and two burners 30 at opposite sides which extend inwardly to almost touch the tubing 2, which is centred by grooved rollers 32, the two burners 30 acting as electrodes. The burners 30 are insulated and connected by leads 33 to the secondary winding 34 of a step-up transformer 35, the primary winding 36 of which is connected to alternating current supply through a variable resistance 38 and switch 37, the switch 37 being operated towards the end of the forward stroke of carriage 9 by a cam 39 rotated from the motor driving belts 3 and chain 11. The leading end of the tubing 2 just before severing is picked up by endless belts 40, with asbestos pads 41, arranged to be driven from the same motor as belts 3 but geared to rotate at a slightly greater speed so as to feed the severed length of tubing axially away from the main tubing. The ends of the severed tubing may then be annealed immediately. The burner 8 is formed from annular sections of channel shape bolted together to hold the inner ring of burners with a hollow ring between for the passage of the combustible gas. As shown in Fig. 3, an alternative form of burner comprises annular metal sections 43, 44, the section 44 not shown, forming a closed annular shell into which the gas is fed through a feed pipe 51, the sections being bolted through an annular plate 46 lying over section 43, which carries the burner jets 45 arranged in two arcs. Support members 47 on the section 43 carry electrode supports 48 of conducting material which pass radially through the members 47 and then are bent over to extend into the ring of burners 45 where they carry the electrode 30 which consist of tungsten rods. The electrodes 30 are mounted so that their points be adjacent the tubing 2 and inclined to be into the direction of rotation 50. The support members 47 may be hinged so that the electrodes or supports 48 may ride over any bulges in the tubing. Instead of being incorporated in the burner 8, the electrodes 30 may be in a fixed position, such as on the support 14 at the forward end of the apparatus, and may comprise gas jets with the gas flames conducting the current into and out of the tubing.