Electrical heating cable with temperature self-limiting heating elements

Claim 1

A temperature self-limiting electrical heating cable or tape to provide heat to pipes, tanks and the like, comprising: (a) first conductor means and second conductor means extending in proximity to each other along the length of the cable for conveying electrical current; (b) insulating means, comprising: (1) insulating material mounted between said first and second conductor means along the length of the cable for insulating said first and second conductor means from each other; (2) said insulating material mounted between said first and second conductor means having portions thereof removed at spaced intervals thereof to form pockets; (3) said pockets being spaced from each other along the length of the cable in accordance with the heat to be generated by the cable; and (4) insulating material enclosing said first and second conductor means and serving as a protective covering therefor; and (c) heating means comprising a plurality of chips of variable resistance heating material mounted in said pockets in said insulating material and being electrically connected between said first and second conductor means for producing heat when current flows therethrough, said variable resistance chips substantially increasing in resistance when a temperature limit is reached to reduce the current flowing through said heating means and control the heat output of the cable.