Electrical resistance heater

An electrical heating device comprising:

• a substrate having an electrically-insulating surface
• a semi-conductor pattern carried on said surface of said substrate, said pattern including a pair of generally continuous pattern portions extending longitudinally of said device and generally parallel to and spaced apart from each other, and other pattern portion between and electrically connected to said continuous pattern portions, said other pattern portion being arranged so as to provide portions of said substrate intermediate said continuous pattern portions and closely adjacent to and spaced along the adjacent longitudinally-extending edges of said continuous pattern portions that are free from said semi-conductor pattern;
• a pair of elongated conductors, each of said conductors having a resistivity less than that of said continuous pattern portions and overlying and in direct electrical engagement with one of said pair of said continuous pattern portions;
• and
• an electrically-insulating sealing sheet overlying at least one of said conductors and the one of said pair of continuous pattern portions associated therewith, said sheet being sealed at one side of said one conductor to said portions of said substrate intermediate said continuous pattern portions that are free from said semi-conductor pattern, whereby said sheet holds said one conductor in tight face-to-face engagement with the associated one of said continuous pattern portions.

An electrical heating device comprising:

• a substrate having an electrically insulating surface;
• a semi-conductor pattern carried on said electrically insulating surface of said substrate, said pattern including a plurality of substantially identical and identically oriented bars spaced apart from each other and extending generally transversely of said substrate between and electrically connected to said stripes and, at each end of each of said bars, a semi-conductor portion abutting said bar and extending longitudinally of said device beyond at least one of the side edges of said bar such that the length of such longitudinally-extending portion is greater than the width of the said bar with which it is associated;
• a pair of elongated conductors, each of said conductors having a resistivity less than that of said bars and said longitudinally-extending semi-conductor portions and overlying and in direct electrical engagement with the said longitudinally-extending semi-conductor portion at one end of each of said bars;
• and
• an electrically insulating sealing sheet overlying at least one of said conductors and the said longitudinally-extending semi-conductor portions associated therewith, said semi-conductor pattern being arranged so as to provide portions of said substrate intermediate adjacent ones of said bars and closely adjacent to and spaced along the longitudinally-extending edges of said one conductor that are free from said semi-conductor pattern, and said sheet being sealed at one side of said one conductor to portions of said substrate closely adjacent said one conductor that are free from said semi-conductor pattern and at the opposite side of said one conductor to portions of said substrate closely adjacent the other longitudinal edge of said one conductor that are free from said semi-conductor pattern, whereby said sealing sheet holds said one conductor in tight face-to-face engagement with said longitudinally-extending semi-conductor portions underlying said one conductor.