GB891437A - Improvements in or relating to electric filament lamps - Google Patents

Abstract

891,437. Incandescent electric lamps. PATENT-TREUHAND-GESELLSCHAFT FUR ELEKTRISCHE GLUHLAMPEN. April 6, 1960 [April 10, 1959], No. 12214/60. Drawings to Specification. Class 39(2) In a gas filled electric lamp of the type for general or domestic use having a coiled-coil tungsten filament mounted on support wires and having a voltage rating between 100 and 250 volts and a wattage rating between 15 and 200 watts, the filament being designed for a life of not less than 800 hours and an operating temperature of not less than 2000‹C. at the rated voltage, the filament is formed so that its primary core factor (defined as the ratio of the diameter of the mandrel on which the filament is wound to the diameter of the tungsten wire) and secondary core factor (defined as the ratio of the diameter of the mandrel on which the primary helix is wound to the diameter of the primary helix) both lie between 1À78 and 20, one of these core factors being greater than 3, the filament having no intermediate support unless the voltage rating is greater than 135 in which case a single intermediate support may be used. Preferably the primary core factor is between 3 and 12 and the secondary core factor is less than 2À5. During manufacture, the initial flashing of the filament may be effected in an atmosphere of or containing hydrogen and thereafter the filament is kept out of contact with oxygen or with any gas containing oxygen e.g. by connecting the bulb during processing continuously to the pump or by continuous flushing with oxygen free gas. The final gas filling may be a mixture of argon or argon and nitrogen with one per cent to five per cent by volume of hydrogen. Zirconium with or without aluminium may be used as a getter. The resulting lamps are stated to have an improved light output with a reduced tendency of the filament to sag.