GB772550A - Improvements in or relating to electric incandescent lamps - Google Patents

Abstract

772,550. Electric incandescent lamgs. SCARBOROUGH ASSOCIATES, Inc. Dec. 31, 1954 [Jan. 14, 1954], No. 37781/54. Class 39(2) An electric incandescent lamp comprises a concave reflector 5 with a transparent closure 2 covering it to provide a sealed envelope enclosing a light-emitting element 4 of electrically conductive, high melting-point, sheet material, e.g. tungsten, having the outline of an area to be illuminated and having one of its faces directed towards said reflector, the light emitting element being arranged at a focalpoint of the reflector so that an image of it is produced at a predetermined distance from the reflector. By employing a Mangin mirror as the reflector the reflected light rays are corrected against distortion. A silver coating 6 on the rear surface of the mirror may have a protective coating of paint. The front closure 2 of glass or other transparent material is sealed, as by fusion, to the periphery of the mirror, and the sheet metal element 4 is supported within the resultant enclosure on leading- ing wires 12, 14. The front closure glass 2 may have a spherical curvature and, in order to prevent rays from the front face of the element 4 from passing directly out of the lamp, an opaque shield 17<SP>1</SP>, which may be of circular outline of a diameter slightly larger than the maximum dimension of the element 4, may be formed on, or applied to the central outer portion of the front glass 2. The sheet metal element 4 may be of rectangular outline to produce an illuminated area a, b, c, d, Fig. 3, of corresponding outline, or elements of other shapes may be used. To increase the flatness of the image of the element 4, the latter is preferably curved, as shown in Fig. 1, substantially to the same curvature as the rear reflecting surface 6. Instead of forming the reflecting mirror 5 as a diverging meniscus with spherical surfaces of different curvatures, as in the example, it may consist of concentric front and rear surfaces, with a front glass or lens having the same curvatures, Fig. 2 (not shown). The lamp is provided with the usual exhaust tube 17 which may be sealed after exhausting the air therefrom, or an inert gas such as argon or nitrogen may be admitted prior to sealing.