GB605329A - Manufacture of cold electrode fluorescent discharge lamps - Google Patents

Abstract

605,329. Fluorescent lamps. HERZOG, C. June 7, 1945, No. 14395. Convention date, Jan. 25, 1944. [Class 39 (i)] In the manufacture of a cold electrode fluorescent discharge lamp, the envelope is coated internally with fluorescent material leaving an uncoated zone at each end, one shorter than the other, one electrode being introduced at the shorter zone end which is heated and collapsed to form a vacuum - tight seal, the second electrode introduced at the other zone and the envelope evacuated to the desired stage before being' heated and collapsed and that part of the uncoated zone beyond the seal removed. Fig. 9 shows the sealing head 45 with a water cooling jacket 48, a mercury supply port 51 whose rotary valve supplies a measured amount, a port 56 leading to a twoway valve controlling a source of vacuum and a source of inert gas. The tube end is clamped by a packing member 61 and nut cap 63, and a metal clamp 65 whose end passes through an insulating sleeve 70 to an outside terminal 72, engages the lead of the electrode when the latter is in position. Heat is applied from burners 75, jaws 77 compress the softened ends and reciprocating blades 79 sever the upper portion of the tube. Glass blades of varying shapes may be formed on the lead-in wire to aid sealing of large diameter tubes. The closed ends have metallic end caps mounted thereon with leads attached. In alternative forms, e.g. as shown in Fig. 20, a retainer member 85 of larger diameter than the electrode 25a is provided, being separate from or integral with the tubular electrode. The assembly is press-fitted into the glass envelope before sealing. Centring devices for holding the electrodes in position comprise hexagonally interconnected slotted mica strips 28, Fig. 14, or two mica strips through slots in which project metal lugs attached to the cylindrical external wall of the electrode.