Tubular electrical heating element with a segmented helical fin

Claim 1

A tubular electrical heating element comprising: a cylindrical sheath having a heating wire disposed within the interior of said sheath and a quantity of insulating material compacted between said wire and said sheath; a fin fabricated from a strip of sheet metal comprising a base formed along a longitudinal edge of the strip, and a plurality of blades formed by cutting a plurality of lateral slits longitudinally spaced along the strip, said blades subtending an included angle with respect to said base, the base of the fin extending around the cylindrical surface of the sheath in a continuous helix with the blades extending radially outward from said sheath, the width of each blade is narrower than the diameter of said sheath to permit the base to lie flush with the cylindrical surface of the sheath without having the blade crimp, said blades subtend an incLuded angle of approximately 90* from said base; and weld means extending along the length of the base for bonding said base to the cylindrical surface of said sheath.