GB301281A - - Google Patents

Abstract

301,281. Dorey, W. A. Jan. 24, 1928, [Convention date.]. Lighting, systems of; ceiling lamps, - A lighting apparatus for producing illumination of high intensity over a predetermined area and a moderate illumination over surrounding areas comprises a group of lenses 15 and light sources 7 disposed above and offset from the axes of the lenses, so that the beams emitted from the lenses overlap. As shown applied to the illumination of an operating table 9, the light sources are enclosed in a chamber 10 recessed above the ceiling line 11. The interior of the chamber 10 has a matt white surface and the light sources have translucent specular reflectors 8 with their axes inclined towards the operating table. A frame 13 supports the lens sections 15 by mullions 14 arranged in squares, each lens section being a quarter of a complete condensing lens of the Fresnel type, and the light sources are. offset from the lens centres in varying degrees so that the beams from the lenses are directed towards a small space 31 above the centre of the operating table. The: interaction between the various light sources and the diffuse reflecting interior of the chamber 10 give general illumination. Curve 22, Fig. 1, shoe's the total horizontal illumination at the table level and curves 17, 18, 20 show the distribution of intensity from the various lenses. The end lenses 19 are tilted to obtain greater intensity along the, beam axis. To ensure that the lens sections 15 are positioned properly in the frame 13 the exterior corners 25, Fig. 5. of the lenses are bevelled and fit against inclined slugs 24 fastened in the mullion at its intersections, but the interior corners 26 - - 28 are not bevelled, nor are the corresponding mullion intersections fitted with slugs. The lamps may be connected together in groups and wired to separate switches permitting of selective control so that the direction and intensiy of the beams may be adjusted. The end lenses may be tilted upward from the main line of the frame 13 or the whole frame may be divided into two flat tilted sections. Figs. 11 and 15 show a modification adapted for lighting a vertical surface such as a blackboard 42 in which a number of light sources 33 are mounted in a recess 34 covered by a hinged lens-holding frame 35 flush with the ceiling. The light sources are offset from the axes 39 of the lens combinations which comprise an inner plate 47 having concentric prisms 48 and an outer plate 49 having parallel prisms 50. Each lamp 33 is provided with a spherical reflector 43 reflecting light back to the particular lens cooperating with that lamp. A part 45 of the recess 34 forms a wiring channel and the interior of the recess has a white matt surface except the wall 53, which may be finished black to reduce illumination of the wall 41 above the blackboard.