GB983465A - A microminiature electric incandescent lamp - Google Patents

Abstract

983,465. Electric incandescent lamps. PATENT-TREUHAND - GES. FUR ELEKTRISCHE GLUHLAMPEN. June 1, 1962 [June 2, 1961], No. 21198/62. Heading H1F. A very small incandescent lamp, e.g. having a tubular envelope of about 0.6 mm. diameter and a filament the diameter of which is less than 10 microns, has a single wire of high melting point metal, e.g. tungsten, constituting both the filament and the leading-in wires, the portion serving as the filament having a smaller cross-sectional area than that forming the leading-in wires. The difference may be produced by etching away part of a uniform wire of the cross-section required for the leading-in wires to produce a filament wire of smaller cross-section or by starting with a wire of cross-section appropriate to the filament and producing thickened portions for the lead-in wires by electrodeposition. The deposited metal may be tungsten or another metal such as gold or copper. The lead-in portions 3 may be fixed into a glass bead 7 and inserted in a tube 4 closed at one end. After evacuation, the tube is sealed to the bead. To ensure accuracy in the finished length of the lamp, the glass tube may be relatively long and is sealed at the open end after evacuation. The tube can then be sealed off at the required part, the end with the initial closure being removed. Specification 659,992 is referred to.