GB861032A - Improvements in electric incandescent lamps - Google Patents

Abstract

861,032. Incandescent electric projection lamps. SYLVANIA ELECTRIC PRODUCTS Inc. Dec. 8, 1958 [Dec. 9, 1957 (2); Jan. 9, 1958], No. 39557/58. Class 39 (2). [Also in Group XX]. In an incandescent projection lamp having a sealed light transmitting bulb and a filament and reflector mounted within the bulb on a common header, the reflector is in the form of a concave shell with a substantially circular perimeter cut off along two generally parallel chords at opposite ends of the diameter and the filament is an elongated filament mounted with its longitudinal axis substantially parallel to the diameter and at right angles to the chords. The reflector is carried by the filament support so that the two can be arranged in correct relationship before the filament mount is sealed into the bulb. The reflector is preferably made of pressed metal e.g. pressed and polished copper coated with nickel and then silvered. Alternatively, a curved glass plate having a reflecting coating of silver or aluminium deposited on the concave surface e.g. by evaporation or condensation in a vacuum may be used. In one form, four lead-in wires 9, 11, Fig. 2, and 10, 12 (not shown) are sealed into a glass disc 4. Support wires, 27, 29 and 28, 30 (not shown) are gelded to short wires 23, 25 and 24, 26 (not shown) on the back of the reflector 17, the wires 27, 28 being welded to the wires 9, 10 and the wires 29, 30 being brought together and welded to a cross wire 31 extending between the wires 11, 12. The filament 3 is of non-sag construction and is connected at the ends by wires 33 (not shown) and 34 spaced apart by transverse, wires carried by an insulating glass bead and welded to the lower ends of the wires 27, 28. A metal cap 43 having an outwardly projecting part 45 covering the sealed exhaust tube and provided with a keyway for centering the lamp is connected to the neck 5 of the bulb. The cap has holes through which wires 9-12 pass, being insulated from the cap by small glass projections on the disc 4. The reflector may be spherical or ellipsoidal. The lamp is filled with nitrogen at a pressure of about 100‹ millimetres of mercury and the upper part of the bulb is provided with a coating 8 of coloured or black enamel glaze. In a modified form, the filament is supported by two wires passing through a ceramic button mounted in a slot in the reflector, the assembly being attached to the header of the lamp by four support wires, two of which act as lead-in wires, all four wires being welded to contact pins in the header. The ceramic button may be composed of 86% talc, 8% feldspar and 6% ball clay.