Gas tube protector having an internal fuse link

Claim 1

A protective device for use in combination with a circuit including a protected station, and a line subject to carrying normal electrical current levels, occasional excessive current levels, and occasional excessive voltage pulses, said protective device comprising an electrically conductive housing, means for coupling said housing to ground potential, an electrode disposed within and spaced apart from said housing, a fuse link disposed within said housing and connected to one end of said electrode, an ionizable inert gas substantially filling the space within said housing about said electrode and fuse link, means for connecting said electrode and fuse link in series with said line and said protected station, electrically insulative means for providing a substantially gas tight seal between said housing and said connecting means, said inert gas being responsive to the application of an excessive voltage pulse to said electrode to ionize and provide a conductive path between said electrode and said grounded housing, and said fuse link having an electrical current carrying capacity in the presence of said inert gas which is sufficient to carry said normal current level, and being responsive to the application of an excessive current level to melt and thereby open the circuit between said line and said protected station.