GB1362364A - Electric lamps - Google Patents

Abstract

1362364 Vehicle lamps W L GILLER 11 Oct 1971 [9 July 1970] 33457/70 Heading F4R [Also in Division H1] An electric lamp, e.g. for vehicle headlights, comprises an envelope 20 formed by a window 21 with the remainder of the envelope being formed as an ellipsoidal member 22, and a source of light within the envelope 20 at a focus of the ellipsoid, wherein part 31 of the ellipsoidal member is reflecting, while the remaining part 32 thereof is non-reflecting. The arrangement focuses the light at the second focus of the ellipsoid outside the envelope and if only the upper half of the ellipsoidal member 22 is reflecting the emitted beam has a sharp upper cut-off to prevent dazzling on-coming drivers. The reflecting part 31 and the light-absorbing part 32 may be provided as coatings on the glass envelope. The ellipsoidal part of the envelope may be closed by a flat or slightly curved window 21 which may be formed integrally therewith or sealed thereto by a bezel ring. The point light source may comprise a filament lamp bulb or it may be a tungsten ball 23 forming an anode between which and an adjacent cathode 26 an arc is struck. A shield may be provided to prevent direct radiation from the source through the window, and as shown the cathode 26 may provide this shield.