초록 ▼

An electrical heating cable in which at least two elongate conductors are separated by an insulating spacer and are contacted by at least one elongate resistive heating strip. The heating strip, which contacts alternately the first conductor and the second conductor at contact points which are longi

An electrical heating cable in which at least two elongate conductors are separated by an insulating spacer and are contacted by at least one elongate resistive heating strip. The heating strip, which contacts alternately the first conductor and the second conductor at contact points which are longitudinally spaced apart along the length of the strip and along the length of each of the conductors, is made from a conductive polymer composition which exhibits PTC behavior. The conductors are concentric stranded wires having a lay length L of at most 20 mm or a lay angle .beta. of at least 11.degree., or a lay length L of at most 20 mm and a lay angle .beta. of at least 10.degree..

대표청구항 ▼

[ What is claimed is:] [12.] An electrical heating cable which comprises(1) first and second elongate, spaced-apart, conductors which can be connected to a source of electrical power, each of said first and second conductors comprising a concentric stranded wires having a lay length L of at most 20

[ What is claimed is:] [12.] An electrical heating cable which comprises(1) first and second elongate, spaced-apart, conductors which can be connected to a source of electrical power, each of said first and second conductors comprising a concentric stranded wires having a lay length L of at most 20 mm (0.8 inch) and a lay angle .beta. of at least 10.degree.;(2) an elongate resistive heating strip which(a) comprises an elongate PTC component which (i) runs the length of the heating strip and (ii) is composed of a conductive polymer composition which exhibits PTC behavior, and(b) is in electrical contact alternately with the first conductor and the second conductor at contact points which are longitudinally spaced apart along the length of the strip and along the length of each of the conductors; and(3) a strip of insulating material which lies between the conductors so that, when the conductors are connected to a power source, all the current passing between the conductors passes through the heating strip.