GB764944A - Improvements in or relating to electric incandescent lamps for vehicle lighting - Google Patents

Abstract

764,944. Electric incandescent lamps. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Feb. 25, 1955 [March 2, 1954], No. 5703/55. Class 39(2) In an electric lamp for use in motor vehicle headlamps, comprising a filament 1 surrounded in part by a screen 2 extending substantially in the axial direction of the lamp, the concave surface of the screen is rendered dull black over the area of the end 12 adjacent the lamp cap and has light-reflecting properties throughout the remaining portion of the concave surface, the object of the black area being to cut out the upwardly inclined rays emanating from a dipped beam when the lamp is associated with a parabolic reflector. The provision of the black area 12 allows the distance "a" between the projection of the end turn 13a of the filament upon the axis X-X of the lamp, and the corresponding projection of the part 14a of the edge of the screen upon the axis to exceed 0.5 mm. thereby reducing the risk of short circuit between the edge of the screen and the oblique end part of the filament which is secured to an adjacent pole wire 4. The other end 5 of the filament is secured to the horizontal lateral edge 6 of the screen below which is secured a second pole wire 3 supporting the screen. The dull black surface is obtained by coating the area 12 with a thin layer of graphite, zirconium, or .zirconium compound, the last mentioned materials also having a "getter" effect. A main filament may be supported between the pole wire 3 and another pole wire (not shown), and positioned so that when the lamp is mounted in a parabolic reflector the main filament is at the focus F.