Improvements in or relating to electric lighting arrangements for producing light resembling daylight

Abstract

Abstract 798,884. Lighting fittings. GENERAL ELECTRIC CO., Ltd. Nov. 12, 1956 [Dec. 15, 1955], No. 36017/55. Classes 75(4) A daylight lighting fitting for colour comparison purposes of the kind comprising a combination of two or more electric lamps, such as low pressure mercury vapour fluorescent electric discharge lamps combined with tungsten filament lamps, is provided with means for generating ultra-violet radiation so that of the resultant total radiation of wavelengths between 3200A and 7000A, at least 5 per cent comprises wavelengths between 3200A and 4000A. The ultra-violet radiation may be obtained from a phosphor coating of barium strontium disilicate actuated by lead in the fluorescent lamps which provide part of the visible light. As shown the fitting comprises two filament lamps 4, 5 combined, in a trough reflector 1 closed by a diffusing glass 3, with two low-pressure mercury vapour fluorescent discharge lamps 6, 7 which have magnesium tungstate coatings. Two additional low pressure mercury vapour fluorescent discharge lamps 8, 9, having coatings of barium strontium disilicate activated by lead, provide the desired ultra-violet component in the range 3200Š to 4000A, each lamp 8, 9 being surrounded by a filter 10, 11 respectively to absorb the visible radiation from the lamps. The internal surface 12 of the trough is made diffusely reflecting for wavelengths down to 3200A. Fig. 2 shows the control circuit of the fitting, the pair of filament lamps 4, 5, which may be 75 watt 240 volt, being connected in parallel with each other, and in series with a 100 ohm, variable resistance 14 for control of the contribution of the filament lamps. Each pair of discharge lamps 6, 7 and 8, 9, are connected in series with each other and with a ballast choke 17, 22 respectively, each lamp having its electrodes connected through a thermal starterswitch of the resistance heated type. Fig. 3 shows, by the full line A, the spectral energy distribution of the resultant light, curve B showing that of overcast daylight. The curve A<SP>11</SP> shows the ultra-violet contribution of lamps 8, 9 which produces the distortion of curve A into closer approximation with curve B, the line A<SP>1</SP> showing the distribution which would result in the absence of lamps 8, 9. Specification 734,426 [Group XL(a)] is referred to.

Inventors

• 👤 Edward Ernest Miles
• 👤 Derek Charles Peach

Bibliographic Details