GB247148A - Improvements in electric incandescent lamps - Google Patents

Abstract

247,148. General Electric Co., Ltd., (Assignees of Patent Treuhand Ges. f³r Elektrische Gl³hlampen). Feb. 5, 1925, [Convention date]. Bulbs.-To enable electric lamp bulbs to provide a light source that can be accurately located, for example when used with reflectors or for projection purposes, the envelope is made of a material, or is provided with a coating, such that the light proceeding from the filament is diffusely reflected by the greater part of the internal surface and emerges equally in all directions through a small window in the bulb, whereby the window may be utilized as the source of light. The filament d may be level with the window b, as shown in full lines, or located away from the window, as shown in broken lines in Fig. 3. In the case of bulbs composed of an internal layer a, Fig. 3, of clear glass and an external layer f of opal glass, the window may be formed by grinding away the opal glass. In tubular lamps, windows b, Figs. 4 and 5, may extend along the bulb as shown, and may be associated with external reflectors g, h of a width not exceeding that of the bulb. Light may be transmitted from the window to an object through a glass rod, in known manner.