Primary dry cell with fail-safe vent

Claim 1

A primary dry cell comprising, in combination, a cylindrical metal container having an open end, a central carbon electrode rod protruding beyond the open end of said container and a seal closure for sealing the open end of said container, said closure comprising an annular insulating cover having its inner peripheral surface fitting tightly around the protruding end of said carbon electrode rod forming a juncture therebetween which is tightly sealed except for a gas-venting passageway extending through said juncture for releasing high internal gas pressure at a predetermined hiGh temperature level, said gas-venting passageway being defined by an indentation within at least one of said cover and said carbon electrode rod located at said juncture and by a portion of the other of said cover and said carbon electrode rod which coincides with said indentation whereby part of the walls of said passageway are formed by said carbon electrode rod which is thermally stable at said predetermined high temperature level, said gas-venting passageway being closed by a normally solid fusible sealant having a softening or melting point which substantially corresponds to said predetermined high temperature level.