Electrical resistance heater

• US 4,485,297 A
• Filed: 08/21/1981
• Issued: 11/27/1984
• Est. Priority Date: 08/28/1980
• Status: Expired due to Term

• Current Assignee: Calorique Limited
• Original Assignee: Flexwatt Corporation
• Inventors: Stumphauzer, William C., Grise, Frederick G. J.
• Primary Examiner(s): Mayewsky, Volodymyr Y.
• Application Number:
  US06/295,000
• Time in Patent Office: 1,194 Days
• Field of Search: 219/203, 219/301, 219/345, 219/522, 219/528, 219/529, 219/541, 219/543, 219/544, 219/548, 219/549, 219/552, 219/553, 338/217, 338/211, 338/212, 338/293, 338/300, 338/309, 338/319, 338/320, 338/330, 174/68.5
• US Class Current: 219/528
• CPC Class Codes: H05B 3/56 Heating cables
• CPC Class Codes: H05B 3/565 flat cables

Abstract

The heater of the present invention includes a paper or plastic substrate on which is printed a semi-conductor pattern (typically a colloidal graphite ink) having (a) a pair of longitudinal stripes extending parallel to and spaced apart from each other and (b) a plurality of identical bars spaced apart from each other and extending between and electrically connected to the stripes. A metallic conductor (typically copper stripping) overlies each of the longitudinal stripes in face-to-face engagement therewith, and the conductors are held in tight engagement with the stripes by a sealing layer that overlies the metallic conductors and is sealed, at opposite sides of the semi-conductor stripe associated with the particular metallic conductor, to portions of the substrate that are free from the printed semi-conductor pattern.

Claims

1. 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 pair of stripes extending longitudinally of said device generally parallel to and spaced apart from each other, and a plurality of bars spaced apart from each other and extending between and electrically connected to said stripes, all of said plurality of bars being identical to each other and being identically oriented relative to said stripes and said bars and stripes being arranged so as to provide portions of said substrate intermediate said stripes and adjacent ones of said bars and closely adjacent to and spaced along the longitudinally-extending edges of said stripes 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 bars and said strips and overlying and in direct electrical engagement with one of said pair of stripes; and

an electrically insulating sealing sheet overlying at least one of said conductors and the said one of said pair of stripes associated therewith, said sheet being sealed at one side of said one conductor to said 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 one stripe.

2. The electrical heating device of claim 1 wherein said sealing sheet extends from adjacent said other longitudinal edge of one of said strips to the far side of the other of said stripes and is sealed to portions of said substrate intermediate adjacent ones of said bars, and adjacent the far sides of the other of said stripes.

3. The electrical heating device of claim 1 wherein said bars extend between said stripes in straight lines portions oblique to said stripes.

4. The electrical heating device of claim 1 wherein each of said conductors is a metallic strip slightly curved transverse cross-section and positioned with the convex surface thereof facing away from said substrate.

5. The heating device of claim 1 wherein each of said bar portions comprises a straight line extending from one of said stripes toward the other of said stripes and forming a predetermined oblique angle with a line extending perpendicularly between said stripes.

6. The electrical heating device of claim 1 wherein said pattern includes a third said stripe spaced from and parallel to said pair of stripes and a plurality of further bars spaced apart from each other and extending from said third stripe to one of said pair of first stripes, and comprising also a said conductor overlying and engaging said third stripe.

7. The electrical heating device of claim 6 wherein said further bars are substantially identical to said first-mentioned bars and are oriented relative to said third stripe identically to the orientation of said first-mentioned bars relative to one of said pair of stripes.

8. The electrical heating device of claim 1 wherein the resistivity of said conductors is at least an order of magnitude less than that of said bars.

9. The electrical heating device of claim 1 wherein said bars are of substantially uniform thickness, said stripes are of substantially uniform thickness, and the thickness of said stripes is greater than that of said bars.

10. The electrical heating device of claim 1 wherein said semi-conductor pattern comprises colloidal graphite and a binder.

11. The heating device of claim 1 wherein each of said bars comprises two straight line portions each of which is oblique to one of said conductors and which form an obtuse angle with each other.

12. The heating device of claim 1 wherein said substrate is paper.

13. The heating device of claim 1 wherein said substrate is organic plastic.

14. The heating device of claim 1 wherein each of said bars comprises a plurality of parallel spaced thin lines of semi-conductor material, the distance between adjacent ones of said lines of a said bar being less than half the distance between adjacent ones of said bars.

15. The heating device of claim 14 wherein the distance between each of said lines of a said bar is greater than the width of the lines of said bar.

16. The heating device of claim 1 wherein the width of each of said bars is about twice the width of the space between adjacent ones of said bars.

17. The heating device of claim 1 wherein said pattern is printed on said substrate such that the resistivity of the portion of said pattern defining said bars is not less than about 1000 ohms per square.

18. The heating device of claim 1 wherein said sealing is water-impervious and including a second sheet of water-impervious material on the side of said conductors and semi-conductor pattern opposite said sealing sheet, each of said sheets extending transversely of said device from beyond the outer edge of one of said conductors to beyond the outer edge of the other of said conductors, and said sheets being sealed together along respective lines extending longitudinally of said device adjacent the outer edges of said conductors.

19. The heating device of claim 18 wherein said conductors, substrate and semi-conductor pattern are between said sealing sheet and said second sheet and said sheets extend beyond the side edges of said substrate.

20. The heating device of claim 18 wherein each of said sealing sheet and said second sheet is a sheet of organic plastic.

21. The heating device of claim 1 wherein said sealing sheet comprises an organic plastic sheet overlying said substrate and attached to portions of said substrate closely adjacent said conductors and not covered by said semi-conductor pattern or said conductors.

22. The electrical heating device of claim 1 wherein said sealing sheet is a sheet of organic plastic material and is sealed at the side of said one conductor opposite the other of said conductors to a second sheet of organic plastic material, said second sheet of organic plastic material being on the side of said semi-conductor pattern opposite said first-mentioned sheet.

23. The electrical heating device of claim 1 wherein the length of the junctions between the ends of said bars and the longitudinally-extending edges of said stripes, measured parallel to said stripes, is in the range of not more than 1/2 inch.

24. The electrical heating device of claim 23 wherein said range is 1/4 inch to 1/2 inch.

25. The electrical heating device of claim 1 wherein the length of the junctions between the ends of the spaces between adjacent one of said bars and the longitudinally-extending edges of said stripes, measured parallel to said stripes, is in the range of not less than 1/8 inch.

26. The electrical heating device of claim 25 wherein said range is 1/8 to 1/4 inch.

27. The electrical heating device of claim 1 wherein about two thirds of the area bounded by said stripes and the most longitudinally spaced of said bars is coated with said semi-conductor material.

28. 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.

29. The electrical heating device of claim 28 wherein portions of said substrate closely adjacent the side of each of said continuous pattern portions opposite the other of said continuous pattern portions are free from said semi-conductor pattern, and said sealing sheet is sealed at opposite sides of said one conductor to portions of said substrate that are closely adjacent said opposite sides of said one conductor and free from said semi-conductor pattern.

30. The electrical heating device of claim 28 wherein the distance between adjacent ones of said portions that are free from said semi-conductor pattern, measured longitudinally of said device, is in the range of not more than 1/2 inch.

31. The electrical heating device of claim 30 wherein said range is 1/4 to 1/2 inch.

32. The electrical heating device of claim 28 wherein the length of the junctions between said portions that are free from said semi-conductor pattern and the longitudinally-extending edges of said continuous pattern portions, measured longitudinally of said device, is in the range of not less than 1/8 inch.

33. The electrical heating device of claim 32 wherein said range is 1/8 inch to 1/4 inch.

34. 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.