GB315114A - Improvements in illuminating appliances - Google Patents

Abstract

315,114. Holophane, Ltd., and English, S. July 31, 1928. Reflectors.- In a prismatic glass lampshade provided with a. smooth outer surface 1 and with internal prisms 6 which cause a single total reflection of the incident light rays. the faces 7 of the prisms are substantially parallel with the axis of the shade whilst the faces 8 are substantially parallel with the directions of the incident light rays. The prisms may all be of the same height, and they may be divided into groups, all the faces 8 in any one group having the same angle. The lower edge of the shade may be provided with a beaded rim 9 to which is clipped the rim 10 of a glass plate which forms a dust-proof cover for the open mouth of the shade. The cover plate may be formed on its exterior with radial flutes 15 and on its interior with outer and inner circumferential flutes 16, 17. The rims 9, 10 may be formed with vertical flutes and the centre of the cover plate may be formed as a small hollow pipe 18 with internal vertical flutes 19. The interior of the shade and cover plate mav be lightly satin finished, and a daylight-blue glass filter may be interposed between the mouth of the shade and the cover plate. The top of the shade may be provided with a metal reflector or it may be formed integrally with a portion 3 formed with external doubly-reflecting radial prisms 4. The portion 3 may be spherical about the light source 2 as centre or it may comprise a surface of revolution generated by rotating about the axis of the shade a circular are struck from any point on a circular filament arranged concentrically about the axis of the shade.