Layered self-regulating heating article

• US 4,330,703 A
• Filed: 09/24/1979
• Issued: 05/18/1982
• Est. Priority Date: 08/04/1975
• Status: Expired due to Term

• Current Assignee: Raychem Limited (TE Connectivity Limited)
• Original Assignee: Raychem Limited (TE Connectivity Limited)
• Inventors: Lyons, Bernard J., Horsma, David A., Smith-Johannsen, Robert
• Primary Examiner(s): Mayewsky, Volodymyr Y.
• Application Number:
  US06/078,386
• Time in Patent Office: 967 Days
• Field of Search: 219/504, 219/505, 219/510, 219/528, 219/549, 219/543, 219/548, 219/552, 219/553, 174/DIG. 8, 174/91, 174/92, 174/93, 338/7, 338/9, 338/20, 338/22 R, 338/22 SD, 338/23, 338/24, 338/211, 338/212, 338/322, 338/320, 264/25, 264/104, 264/105, 252/510, 252/511, 252/512, 361/106
• US Class Current: 219/553
• CPC Class Codes: B29C 65/342 comprising at least a single wire, e.g. in the form of a winding
• CPC Class Codes: B29C 65/3428 said at least a single wire having a waveform, e.g. a sinusoidal form
• CPC Class Codes: B29C 65/3432 comprising several wires, e.g. in the form of several independent windings B29C65/3436, B29C65/344 take precedence
• CPC Class Codes: B29C 65/3468 characterised by the means for supplying heat to said heated elements which remain in the join, e.g. special electrical connectors of windings B29C65/3668 takes precedence
• CPC Class Codes: B29C 65/3488 being an electrically conductive polymer
• CPC Class Codes: B29C 66/91218 using colour change, e.g. using separate colour indicators
• CPC Class Codes: B29C 66/91411 of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account
• CPC Class Codes: B29C 66/91431 the temperature being kept constant over time
• CPC Class Codes: B29C 66/91651 by controlling or regulating the heat generated by Joule heating or induction heating
• CPC Class Codes: B29C 66/91653 by controlling or regulating the voltage, i.e. the electric potential difference or electric tension
• CPC Class Codes: B29C 66/91655 by controlling or regulating the current intensity
• CPC Class Codes: B29C 66/919 characterised by specific temperature, heat or thermal flux values or ranges specific electrical resistance values B29C66/81262
• CPC Class Codes: B29C 66/9192 in explicit relation to another variable, e.g. temperature diagrams
• CPC Class Codes: B29C 66/949 characterised by specific time values or ranges
• CPC Class Codes: B29C 66/9592 in explicit relation to another variable, e.g. X-Y diagrams
• CPC Class Codes: B29K 2995/0005 Conductive
• CPC Class Codes: B29K 2995/0049 Heat shrinkable
• CPC Class Codes: H01C 1/1406 Terminals or electrodes formed on resistive elements having positive temperature coefficient
• CPC Class Codes: H01C 7/027 consisting of conducting or semi-conducting material dispersed in a non-conductive organic material
• CPC Class Codes: H05B 3/146 Conductive polymers, e.g. polyethylene, thermoplastics
• CPC Class Codes: H05B 3/56 : Heating cables
• CPC Class Codes: Y10S 174/08 : Shrinkable tubes

Abstract

A self-regulating heating article comprising a layer of material exhibiting a positive temperature coefficient of resistance (PTC) and said PTC layer having at least partially contiguous therewith at least one layer of constant wattage output material. The article operates such that when connected to an electric power source, the current flows through at least a portion of the thickness of the PTC layer and of the constant wattage layer. In a preferred embodiment, upon heating the article, a change in dimensions as well as activation of an adhesive occurs.

Claims

1. A self-regulating electrical heating article adapted for connection to a source of electrical power comprising a first layer of material, said first layer exhibiting a positive temperature coefficient of resistance with an associated anomaly temperature T_s and having at least partially contiguous therewith a second layer of constant wattage material having an associated resistance, said article being connectable to an electric power input source whereby current flow is through at least a portion of said first layer and through at least a portion of said second layer, whereby there is both direct electrical and thermal coupling between said first and second layers, and whereby at a temperature which is the higher of the temperature at which the resistance of said first layer exceeds the resistance of said second layer or the anomaly temperature of said first layer, current flow predominantly follows the directionally shortest path through said first layer.

2. An article in accordance with claim 1 wherein at least one of said first and second layers comprises a polymeric layer which is heat-recoverable within the operating range of the heating article.

3. The article of claim 1 having at least one exterior surface layer which is an adhesive that is activatable within the operating temperature range of said article.

4. The article of claim 1 wherein the constant wattage layer is an adhesive that is activatable within the operating temperature range of the article.

5. The article of claim 1 wherein at least one of said first and second layers comprises a polymeric composition.

6. The article of claim 5 wherein said constant wattage layer comprises a polymer having dispersed therein particulate carbon black.

7. The article of claim 5 wherein said constant wattage layer comprises a polymer having dispersed therein a highly conductive member selected from the group consisting of fibers and fibrils.

8. The article of claim 5 wherein both said first and second layers comprise polymeric compositions.

9. The article of claim 8 wherein both said layers contain particulate carbon black.

10. The article of claim 8 wherein said second layer is positioned adjacent a first surface of said first layer and a third layer of constant wattage polymeric material is positioned adjacent the other surface of said first layer and wherein at least one of said second and third layers is in conductive contact with metal electrodes.

11. The article of claim 10 having additionally a layer of heat activated adhesive, said adhesive being activatable within the operating temperature range of the article.

12. The article of claim 10 wherein said electrodes are embedded in the constant wattage layers.

13. The article of claim 10 wherein at least one of the layers is heat recoverable within the operating temperature range of the article.

14. The article of claim 1 wherein said directionally shortest path does not dimensionally exceed the thickness of said first layer by more than about 50%.

15. The article of claim 1 wherein the constant wattage layer is sufficiently conductive to act as an electrode.

16. The article of claim 1 wherein said positive temperature coefficient of resistance layer has two substantially planar surfaces and has a constant wattage layer at least partially contiguous with each of said planar surfaces.

17. The article of claim 16 wherein both said constant wattage layers are sufficiently conductive to act as electrodes.

18. The article of claim 1 wherein at least the constant wattage layer is in contact with at least one metal electrode.

19. The article of claim 18 wherein said electrode is at least partly contiguous with the surface of the constant wattage layer opposite that surface of the constant wattage layer which is adjacent the positive temperature coefficient of resistance layer.

20. The article of claim 18 wherein said metal electrode is at the interface between a positive temperature coefficient of resistance layer and a constant wattage layer.

21. The article of claim 18 wherein said metal electrode is embedded in a constant wattage layer.

22. The article of claim 18 wherein said metal electrode is of a form selected from the group consisting of fabric, braid, grid, wire, strip and sheet.

23. The article of claim 18 wherein said metal electrode is a wire conductor having a concentric layer of electrical insulation, segments of which have been removed intermittently along the length of the conductor.

24. The article of claim 1 wherein at least said positive temperature coefficient of resistance layer is in contact with at least one metal electrode.

25. The article of claim 24 wherein said positive temperature coefficient of resistance layer has at least one metal electrode embedded therein.

26. The article of claim 24 wherein said metal electrode is of a form selected from the group consisting of fabric, grid, wire, strip and sheet.

27. The article of claim 24 wherein said metal electrode is a wire conductor having a concentric layer of electrical insulation, segments of which have been removed intermittently along the length of the conductor.

28. The article of claim 1 having at least one electrode comprising a highly conductive fiber.

29. The article of claim 1 having at least one electrode comprising a conductor which is partially insulated from at least one of said layers.

30. The article of claim 1 wherein one of said first and said second layers is encompassed in cross section by the other of said layers.

31. The article of claim 30 wherein said first layer encompasses said second layer.

32. The article of claim 30 wherein said layers are concentrically disposed about an electrode.

33. The article of claim 1 wherein said article includes a plurality of electrodes at least one of which is embedded in said positive coefficient of resistance layer.

34. The article of claim 1 wherein said first and second layers are each disposed around electrodes.

35. The article of claim 1 wherein both said first and second layers are polymeric compositions and wherein a plurality of substantially elongate electrodes are in conductive contact with said layers and wherein the axes of the electrodes in contact with said first layer are non-parallel in at least one plane with the axes of the electrodes in contact with said second layer.

36. The article of claim 35 wherein the interfacing surfaces of said first and second layers are nonparallel with the non-interfacing surface of at least one of said layers.

37. The article of claim 1 wherein said article is conformed about an electrically conductive substrate whereby said current flow is at least partially through said substrate.

38. The article of claim 1 wherein said positive temperature coefficient of resistance layer has a plurality of electrodes of opposite polarity embedded therein.

39. The article of claim 1 wherein said constant wattage layer has a plurality of electrodes of opposite polarity embedded therein.

40. The article of claim 1 wherein said first layer comprises barium titanate.

41. The article of claim 1 wherein said article has an effective T_s in excess of 90°

C. and said T_s is in excess of the inherent T_s of said first layer.

42. The article of claim 41 wherein said first layer comprises an organic polymer and wherein the effective T_s exceeds the melting point of said polymer.

43. The article of claim 1 wherein said second layer is a positive temperature coefficient of resistance material having an anomaly temperature T_s above the T_s of said first layer.

44. The article of claim 1 wherein the resistivity ratio of said first layer to said second layer ranges from about 0.1 to about 20.

45. The article of claim 1 wherein said second layer is not fully contiguous with said first layer.

46. The article of claim 45 wherein the surface area of said first layer is greater than the surface area of said second layer.

47. The article of claim 45 wherein the surface area of said second layer is greater than the surface area of said first layer.

48. The article of claim 1 wherein the Joule heat output of said article is substantially unaffected by a change in the temperature of said article up to about the effective T_s of said article.

49. The article of claim 1 wherein said first layer exhibits an increase in resistance of at least a factor of six (6) for a temperature increase of 30°

C. or less starting at T_s.

50. The article of claim 1 wherein the material of said second layer has resistivity of at least about 1 ohm-cm at 25°

C.

51. The article of claim 1 in the form of an elongate flexible strip.