Method for forming self-regulating heat trace cable

Claim 1

A method of making a flexible heating cable comprising the steps of notching the sides of a pair of insulated power leads at spaced locations alternately along the length of the pair to alternately expose the power leads, helically wrapping heating wire along the length of the insulated power leads and in contact with first one power lead and then the other only at the notches to establish resistive heating segments between successive pairs of notches, then, for each heating segment, fixing a thermistor chip, having a lead at least at its outer-face, against the pair of power leads with the inner-face of the chip mechanically and electrically connected with said heating wire to establish both a first heating wire hold-down and an inner-face electrical connection, and with the chip lead from the outer-face of the chip also mechanically and electrically connected, across a lengthwise gap, with said heating wire to establish both a second heating wire hold-down and an outer-face electrical connection, severing said heating wire at a location within said lengthwise gap between said inner-face and outer-face connections to establish, for the heating segment associated with the chip, an electrically serial relationship between the chip and the heating wire, and forming an insulating casing around the parts so assembled.

Claim 2

A method of making a flexible heating cable comprising the steps of notching the sides of a pair of insulated power leads at spaced locations alternately along the length of the pair to alternately expose the power leads, helically wrapping heating wire along the length of the insulated power leads and in contact with first one power lead and then the other only at the notches to establish resistive heating segments between successive pairs of notches, then, for each heating segment, fixing a thermistor chip, having a lead at least at its outer-face, against the pair of power leads with the inner-face of the chip mechanically and electrically connected with said heating wire to establish both a first heating wire hold-down and an inner-face electrical connection, and with the chip lead from the outer-face of the chip also mechanically and electrically connected, across a lengthwise gap, with said heating wire to establish both a second heating wire hold-down and an outer-face electrical connection, severing said heating wire at a location within said lengthwise gap between said inner-face and outer-face connections to establish, for the heating segment associated with the chip, an electrically serial relationship between the chip and the heating wire, and forming an insulating casing around the parts so assembled.