Electric heated soldering tool

Claim 1

An electrically heated soldering iron comprising; a generally cylindrical hollow heating element core, an electrical heating coil surrounding said core, an electrically conductive metal soldering iron tip having a working end portion and a rear end portion, attachment means on said tip for releasably attaching said tip to said core in heat-transfer relationship so that said tip is heated by conduction of heat from said core to said tip when said coil is energized, said attachment means comprising screw threads on said rear end portion of said tip, said rear end portion of said tip having a centrally located bore therein, said bore having a bottom within the body of said tip and spaced rearward from said working end portion, an elongated electrically conductive metal rod having a diameter smaller than said bore, said rod having a front end portion received in said bore in centrally located position, said rod having a front end brazed to said bottom of said bore, insulating material in said bore surrounding said rod, said rod being of a different metal than said tip and extending axially rearward therefrom, a metal electrical conductor secured to said tip in spaced relationship to said rod and extending axially rearward therefrom, said electrical conductor being formed of a metal different than said rod, said tip itself forming part of the hot junction of a thermocouple and defining the sole connection between said rod and said electrical conductor, said rod and said electrical conductor having rear end portions axially spaced from said tip, electrical insulating material insulating said rod and said electrical conductor from one another and covering said rod and said Electrical conductor from said rear end portion of said tip to points spaced from said rear end portions of said rod and electrical conductor, said rod and said electrical conductor having their rear end portions exposed and free of covering insulating material in axially spaced electrically insulated relationship to one another, said soldering iron including hollow handle means attached to said core opposite said tip, said handle means having a pair of first and second electrical connections therein, said rod and said electrical conductor extending through said core and into said handle means and having said rear end portions thereof in quick-releasable sliding frictional engagement with said electrical connections, a pair of third and fourth electrical connections in said handle means separate from said first and second connections for connecting said heating coil to a voltage source, and means on said handle for connecting said first, second, third and fourth electrical connections with control means for interrupting flow of current to said coil when the temperature sensed by the thermocouple defined by said rod, tip and electrical conductor reaches a predetermined value.