GB1451810A - Heated fluorescent lamp - Google Patents

Abstract

1451810 Fluorescent discharge lamps XEROX CORP 21 Dec 1973 59535/73 Heading H1D A fluorescent lamp has a resistive coating 4 to which a heating current can be applied to maintain the lamp at an optimum operating temperature. In one embodiment, Fig. 1, the coating 4 is applied to the exterior of the glass envelope 1 which is coated internally with a phosphor layer 2 and a white translucent reflective coating 3, the coatings being applied to define an aperture 5. The resistive coating 4 may comprise conductive particles e.g. of a metal such as Ag, Al, Ni, Cu or mixtures thereof dispersed in an insulating carrier e.g. a solution of an insulating resin or polymer in either oil or water. Connection to the resistive coating 4 is effected through spring clips 6, Fig. 2, which may also serve to hold the lamp in a fixture. Current is supplied to the lamp through contacts 7. The coating 4 may be applied to only half of the lamp circumference, and the reflective coating 3 may be omitted Fig. 3 (not shown). In an alternative embodiment Fig. 5 (not shown) the coating 4 is applied to the inside of the envelope and is separated from an internal phosphor coating by an insulating layer of varnish, shellac, cellulose, polypropylene, cellulose acetate or mixtures thereof. The resistive coating 4 may act as its own thermostat or a thermocouple may be attached to the lamp Fig. 4, (not shown) to control the heating current to a value which maintains the lamp temperature constant at about 38‹C, corresponding to a mercury-vapour pressure of about 6À5 X 10<SP>-3</SP> torr.