GB329399A - Improvements in combined reflectors and diffusers for electric lamps - Google Patents

Abstract

329,399. Swift, A. G. Feb. 22, 1929. Street and like overhead lamps.-In a combined reflector and diffuser for a street-lighting or other overhead electric lamp, the lower edge of the reflector a lies in the horizontal plane Y Z containing the filament c of an electric lamp bulb b and the reflector is formed from an arc o, c<2> of radius r struck from a centre X at a distance from the centre of the filament and rotated about an axis 1-2 passing through the centre of the filament. When a more distributed light is required the radius is increased and the centre X is disposed beneath the plane Y Z. The reflector may be produced by spinning from a single piece of aluminium alloy or other metallic sheet, the central portion being removed to provide an aperture or being formed or fitted with an upstanding perforated cone or bowl g to accommodate the bulb d. The reflector may have a polished, mirrored, or other reflecting inner surface, or a bright matt surface, and it may be tinted to produce a daylight or other colour effect. The reflector may form part of the lamp casing or be a glass or other lining for an outer casing e. The diffusing bowl d may be made of the material known under the registered Trade Mark " Opalite " and may be of similar shape to the reflector. The diameter of the diffuser may be equal to or smaller than that of the reflector, and it may be attached to the reflector as by means of a globe ring f, a bayonet joint, or a spring wire locking ring taking into a recess around the rim of the reflector. Instead of being completely circular in plan the lamp may be in the form of any section or segment of a circle, and when used for street-lighting purposes several such lamps may be mounted within a single lantern, for example, one vertically and two inclined in opposite directions to each other.