Method of manufacture of a nonuniform heating element

Abstract

A flexible elongated resistance heating element of improved uniformity and ease of termination has a continuous strip of resistance wire formed about a flexible elongated strand of insulating material in a generally helical pattern of nonuniform pitch with regions of increased pitch and correspondingly reduced turns density which regions experience little increase in temperature when the element is energized. The pitch of the helical resistance wire pattern varies as it approaches each of the ends of the element to provide a region of increased pitch followed by a region of decreased pitch at each end. Shorting wires may thereby be eliminated. An insulating coating surrounds the resistance wire and strand and electrical terminals are connected by crimping to the regions of decreased pitch of the resistance wire at the ends. The heating element may be bonded to a support member in a serpentine pattern with the cool end regions extending freely from the support member. Intermediate regions of increased pitch may be provided in portions of the heating element when it is desired to have those regions experience reduced heating. A method of fabricating such a heating element is also disclosed.