Resistance heater with improved thermocouple

Claim 1

A thermocouple junction in a cartridge heater structure having an elongate tubular outer metal sheath having open ends, means sealing the ends of the sheath, a filler of dielectric insulating material in the sheath and a resistance heating element supported in and clear of the sheath by said filler and having contact leads extending through and from one end of the sheath, said filler being compacted tight in the sheath and about said heating element by radially inward swaging of the sheath during manufacture of the heater, said junction comprising a pair of substantially radially extending conical disc in tight peripheral bearing contact with the sheath, in electric isolation from the heating element and in partial nested axial spaced relationship with each other, a pair of thermocouple wires entering the sheath at said one end and extending axially in the sheath in electric isolation from the heating element and each having a connector portion extending substantially radially and in tight pressure contact between the discs, the connector portions last contacting and extending from the disc at predetermined spaced points on said discs, said conical discs being of obtuse angle and in pressure contact with the connector portions and the sheath before the sheath is swaged and being reformed to a less obtuse angle and into increased pressure and heat conducting contact therewith when the sheath is swaged and said discs are re-formed radially inwardly.