Patent GB-687922-A (GB)
Title: Improvements in and relating to a method for fusing an electric lamp foot into a tubular end of a glass lamp envelope
IPC: H01J9/38
Filed: 1948-12-06
Abstract: 687,922. Making tubular electric lamps. LUMALAMPAN AKTIEBOLAG. Dec. 6, 1948 [Dec. 6, 1947], No. 31515/48. Class 39(ii) [Also in Group XL(a)] In fusing or welding a foot or mount to the end of a tubular lamp envelope, e.g. a fluorescent discharge tube, the foot and the envelope are mounted in separate, axially spaced, and relatively movable carriers, and the circumferential edge of the foot and the edge of the tubular envelope are heated separately and simultaneously to a fusible condition and then brought together by relative movement of the carriers, so that they are welded without deformation other than at, or adjacent to, the resulting welded edge. whereupon the respective carriers are at once pulled further apart very slightly before the lamp foot holder releases its grip. A further local heating is next given to the welded edge to fuse it circumferentially. The tubular envelopes may be supported either horizontally or vertically during the operations. In a horizontal arrangement, Figs. 1 and 3, both ends of a tube 8 are supported on chain conveyers 4 with links provided at intervals with lobes 6 carrying asbestos plates 7 to receive the tube. The upper runs of the chains are supported by longitudinally arranged U-sectioned rails 5. The lamp foot, comprising a glass disc 20 with an electrode 19 supported on leading-in wires, and an exhausting-tube 24, is held by clamping the latter in automatically operated jaws in a holder 23 which is mounted at the end of a rod 27 slidable within a supporting-bracket 31. The rear end of the rod 27 has a pin-and-slot connection with a lever arm 30 controlled by a cam 40 at the other end, whereby the foot-holder 23 is moved inwardly towards the end of the tube. The driving-shaft 39 of 'the cam 40 also carries a cam 38 which operates a vertical rack-bar 32 driving a pinion 15 controlling a compressed-air valve and regulating the admission of air to a cylinder containing a piston linked to jaws for gripping the exhausting- tube 24. Burners 10 for heating the end 12 of the tube 8 extend radially from a fixed pipe 11 which is concentric with the tube when the latter is in the heatingposition; burners 21 are mounted similarly around the edge of the foot disc 20. In the example both ends of the tube 8, and the glass foot discs for the respective ends, are operated on simultaneously, the foot gripping devices, and means for advancing and retracting them, being duplicated. The foot discs having been welded, their gripping devices are immediately moved outwardly a short distance before opening to release them, and the lamp is then carried to the next position where fusion of the welded edge is effected by burners 48 which are rotated by a cam-operated rack and pinion 46, 47. At further positions 50 the ends are subjected to diminishing heating. Heating may be effected by high frequency or other known methods as alternatives to gaseous fuel. The jaws 85, Fig. 6, which grip the exhausting-tube of a foot disc are pivotally mounted within a foot-holder 23 consisting of a cylinder provided with a peripheral slot or groove dividing it into two parts that are held together by three internal sectors 87, the jaws being formed by a corner of each of two triangular plates 79, and 89 carried on pivots 80, 88 respectively, and an offset end of a plate 86 pivoted at 84. The three plates are interconnected by two links 78, 82, and their movement is effected by an offset arm 75 on plate 79 engaging within a transverse aperture in a rod 74 carried by a piston in a cylinder 93 connected by a flexible tube 16 to the compressed air valve which is controlled by pinion 15. This valve is operatively associated with, although not connected to, a series of gaseous fuel control valves, formed by radial passages in an otherwise solid cylinder 58, Fig. 5 (not shown), which is rotated within a cylindrical casing provided with radial inlet and outlet passages that are connected to the passages of the cylinder 58 in a predertermined sequence.