Electric heating elements

Claim 1

An electric heating element for a water tank, comprising a mounting flange and a metal tubular sheath of hairpin formation, said flange having a pair of openings in which the ends of the legs of the sheath are securely fixed, said flange being securable to the exterior of the wall of a water tank with the sheath extending through an opening in said tank wall to dispose said legs and the bight connecting the same within said tank, a dielectric terminal block secured to said mounting flange and an electric switch carried by said terminal block, a helically coiled resistance wire of hairpin shape, having its bight held within said sheath inwardly of the end of one leg thereof, the legs of said wire extending through said one sheath leg, through the sheath bight and through the other sheath leg and having terminal pins extending respectively from the leg ends of the wire and outwardly of said other sheath leg for electrical connection to terminals carried by said terminal block and said switch, said switch also having another terminal, and its terminals being connectable to a source of electrical energy, the switch controlling flow of electrical energy to said resistance wire, a metal rod within said sheath, having one end fixed to said sheath adjacent to said wire bight and its other end extending outwardly of said one sheath leg and in position to operate a switching member of said electric switch, said rod and sheath being formed of metals having different thermal expansion properties whereby when a preselected temperature is reached, the differential expansion is sufficient to operate said switch.