Fluorescent light source with a plurality of sequentially energized electrodes

Claim 1

A low-pressure positive coluMn discharge lamp adapted for operation from a two-line current circuit comprising a discharge space defined by two elongated concentric tubular envelopes of vitreous material hermetically sealed together at their ends leaving an annular space forming at least part of the discharge space, an ionizable medium including an inert starting gas at low pressure and a small quantity of mercury sealed within said discharge space, a multiplicity of at least four sequentially operable electrodes arranged at one end of said annular space, and an electrode of opposite polarity arranged to be effective at the other end of said discharge space, the inside of the outer tubular envelope and the outside of the inner tubular envelope each being provided with a phosphor coating, and means adapted to allow sequential energization of said multiplicity of electrodes. CM,2-pressure positive column discharge lamp according to claim 1 wherein two elongated concentric tubular envelopes are hermetically sealed against the atmosphere at one of their ends and the outer one of said tubular envelopes is effectively hermetically sealed against the atmosphere at its other end, while the other end of the inner tubular envelope communicates with the annular space between the said tubular envelopes to form an elongated discharge space inside the inner one of said envelopes serially connected with the annular discharge space between said two envelopes, a multiplicity of at least four sequentially operated electrodes in the annular space at the first mentioned ends and an electrode of opposite polarity at the adjacent end in the inner one of said envelopes, the inside of the outer tubular envelope and the outside and inside of the inner tubular envelope being each provided with a phosphor coating.