Fluorescent lamp having integral mercury-vapor pressure control means

Abstract

The mercury-vapor pressure within an operating fluorescent lamp is regulated by several discrete bodies or bits of a suitable amalgamative metal (such as indium or an indium alloy) that are placed into the lamp envelope before it is sealed. The metal bodies are not secured to any of the structural parts of the lamp and are thus free to move about within the envelope. When they subsequently combine with the dosed mercury in the finished lamp, they form a plurality of mobile amalgam bodies that are distributed at random locations within the lamp and release controlled amounts of mercury vapor when the lamp is energized and the amalgam bodies are heated. The amalgamative metal is preferably dispensed into the envelope in the form of spherical pellets that are provided with a porous non-stick coating to prevent them from becoming accidentally attached to each other or to the lamp electrodes. The amalgamative metal pellets may also be combined with the mercury outside the lamp to form pellets of preformed amalgam which, when dispensed into the envelope, simultaneously doses the lamp with predetermined amounts of both mercury and amalgamative metal. The introduction of a measured amount of an amalgamative metal into the lamp, either separately or in combination with a predetermined dosage of mercury, can thus be achieved in a very simple and economical manner during the normal sequence of operations required to manufacture the lamp.