GB648115A - Improved apparatus for coiling elongated vitreous tubing - Google Patents

Abstract

648,115. Glass. BRITISH THOMSONHOUSTON CO., Ltd. Nov. 25, 1948, No. 30619. Convention date, Nov. 25, 1947. [Class 56] Comprises means for bending a preformed length of glass tubing, e.g. for a fluorescent lamp, into a double helix which may be of the form shown in Fig. 4 or may comprise a conical or flat double spiral. After the tube has been uniformly heated it is engaged at its mid-section and both ends are then helically coiled in the same direction about a common axis. In the apparatus shown in Fig. 2 the tubing 2 is supported upon two elongated driven rollers 4, 5 carried by a frame 23 tiltable as a whole about the axis of the roller 4. When the frame is in the vertical position shown, it registers with an electric oven 7 carried on pivoted arms 10; when the glass is sufficiently soft the oven is raised and the frame 23 is swung counter-clockwise so that the tubing rolls off the rollers and down an inclined guide plate 40 until it lies across the horizontal upper end of a vertical drum 3 with its mid-section riding into a transverse groove 43<SP>1</SP> between the ends of opposite raised guide lips 43 on the drum, and its ends projecting beyond the periphery of the drum and resting on a tray 41 level with the upper end of the drum, a circular aperture being provided in the tray concentric with the drum. The lips 43 are at the ends of a pair of parallel helical grooves 77, 77<SP>1</SP> formed in and alternately spaced around the drum. The drum is now rotated and simultaneously raised along its axis and the ends of the tubing contact and are guided and pressed by rollers 75, 76 so that the tubing engages and is held in the grooves and assumes the double helical shape as the drum rotates and rises. After cooling, the drum is rotated reversely whereby the coiled tube can be unwound from the drum. Air under pressure may be blown into the tubing towards the end of the coiling to maintain its circular cross-section. In the form shown in Fig. 8 a completed straight fluorescent lamp 92 may be coiled, the ends of the lamps being connected to chucks 96 through which neutral gas is passed for protecting the fluorescent coating during heating. The tray 41 is replaced by a pair of oppositelydriven endless belts 105, 106 which positively assist the movement of the ends of the tube towards the guide and pressure rollers 75, 76 and the drum 3 thereby reducing any strain on the chucks and associated parts. Fig. 12 shows the shape of the former 3" used when a conical double spiral tube is required. Such spiral may be converted into a flat spiral by reheating and compressing it axially. The guide and pressure rollers 76<SP>11</SP>, Fig. 12, are mounted so that they may follow the conical grooves of the former.