Line protector

Claim 1

A line protector comprising a tubular cap, a metallic cage telescoped within the cap coaxial therewith and being axially slidable relative thereto, said cage comprising: an end wall and a series of axially extending circumferentially spaced fingers projecting from the periphery of said end wall, a sealed cold cathode gas tube having axially spaced electrodes separated by a dielectric tubular insulator and so jointed thereto as to form a sealed gas filled primary arc gap within the gas tube, said electrodes also having exposed conductive electrode flanges at the opposite ends of the tubular insulator, an electrically conductive tubular structure telescoped within said cage, said gas tube being telescoped within the tubular structure, one electrode flange being in electrically conductive connection with said tubular structure and with said cage, an end portion of said tubular structure and said other electrode flange being spaced to provide an annular secondary arc gap in electrical parallel with said primary arc gap, an insulator adjacent to said other electrode flange and projecting axially therebeyond, said insulator being surrounded by said end portion and having an outer wall portion that is greater in diameter than the outer diameter of said other electrode flange, said end portion being confined between said outer wall portion and said fingers such that said outer wall portion prevents radially inward movement of said end portion to prevent closing of said secondary arc gap, and a member in electrical contact with said other electrode flange and projecting through said insulator, the breakdown voltage across the secondary gap being less than the breakdown voltage across the primary arc gap if the gas tube seal fails and the primary arc gap becomes exposed to ambient atmosphere.