Line protector having arrester and fail-safe circuit bypassing the arrester

A line protector comprising means forming a circuit that comprises in series a surge arrester of the cold cathode gas tube type having coaxial electrodes, first conductor means for connection to a line to be protected, and second conductor means for connection to ground such that an overvoltage surge of short duration at the line will pass current through said series circuit for discharge to ground;

• fusible means normally preventing said first and second conductor means from being in contact, spring means for bringing said first and second conductor means into contact exteriorly of said surge arrester upon melting of said fusible means due to an overvoltage surge of longer duration across said series circuit to provide a direct metallic path from said line to ground bypassing said arrester, and means forming an arc gap between said first and second conductor means for providing a discharge path to ground in the event of failure of said surge arrester due to leakage of gas therefrom, said last-named means comprising a perforated insulating member defining said arc gap between portions of said first and second conductor means that are radially outwardly of the electrode axis.

A line protector comprising a cap, a metallic shunt member within the cap and being slidable relative thereto, a tubular insulating sleeve within the shunt member, a metallic disc member within the shunt member, a metallic cup within the sleeve and being slidable relative thereto, said sleeve being perforated to provide an air gap between the cup and the shunt member, a meltable pellet within the cup, a cold cathode surge arrester tube within the cup and having spaced electrodes respectively in electrical contact with the solder pellet and the disc, said electrodes providing a sealed arc gap within the tube that is greater in width than the width of said air gap, the environment within said tube being such that the arc-over voltage is less than the arc-over voltage at said air gap, and a spring within said cap for moving an assembly comprising said shunt, said disc, said arrester, and said sleeve upon melting of said pellet to cause said disc to engage said cup.

A line protector comprising first conductive means that includes a tubular cap and structure slidably telescoped within the cap coaxial therewith, second conductive means coaxial with said cap, a surge arrester having opposed conductor elements, said first and second conductive means being respectively connected to said conductor elements to provide a current path through said arrester from one conductive means to the other conductive means upon an overvoltage surge of short duration across said surge arrester, spring means in said cap urging said slidable structure toward said second conductive means, and a fusible element preventing engagement of said movable structure with said second conductive means except on melting of said fusible element due to an overvoltage surge of longer duration across said arrester, the engagement of said movable structure and said second conductive means forming a metallic current path bypassing said arrester , and an insulating sleeve interposed between and spacing said first and second conductive means, said sleeve having at least one perforation constituting an air gap between said first and second conductive means.

A line protector comprising means forming a circuit that comprises in series a fusible solder pellet, spaced electrodes forming an arc gap, first conductor means for connection to a line to be protected, and second conductor means for connection to ground such that an overvoltage surge of short duration at said line will pass current through said series circuit for discharge to ground;

• said arc gap being sealed in a cold cathode gas tube of which said electrodes form a part;
• means including said solder pellet normally preventing said first and second conductor means being in contact, and spring means for bringing said first and second conductor means into contact exteriorly of said tube to bypass said arc gap upon melting of said solder pellet due to an overvoltage surge of longer duration across said series circuit and thereby provide a direct metallic path from said line to ground, and in which one of said conductor means includes a cup, said solder pellet and said tube are in said cup, an insulating sleeve surrounds said cup, and the other conductor means surrounds said insulating sleeve.