WO2007021528A1 - Heaters with perforated bus bars - Google Patents

Heaters with perforated bus bars Download PDF

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Publication number
WO2007021528A1
WO2007021528A1 PCT/US2006/029850 US2006029850W WO2007021528A1 WO 2007021528 A1 WO2007021528 A1 WO 2007021528A1 US 2006029850 W US2006029850 W US 2006029850W WO 2007021528 A1 WO2007021528 A1 WO 2007021528A1
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WO
WIPO (PCT)
Prior art keywords
bus bars
heating element
electrically conductive
metal
alloy
Prior art date
Application number
PCT/US2006/029850
Other languages
French (fr)
Inventor
Alan D. Gardner
Peter J.A. Marsh
Clive W. Leah
Original Assignee
Thermion Systems International
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thermion Systems International filed Critical Thermion Systems International
Publication of WO2007021528A1 publication Critical patent/WO2007021528A1/en

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/02—Details
    • H05B3/06—Heater elements structurally combined with coupling elements or holders

Definitions

  • the present invention is directed to the field of electrical resistance heating. Specifically, the present invention is directed to a method for manufacturing an electrically conductive heater having perforated bus bars.
  • Electrical resistance heaters are used to provide localized heating for various applications. Because of their light weight and even heat distribution characteristics, certain types of resistance heaters have found great utility. In the aerospace industry, for example, electrical resistance heaters are used for deicing structures such as airplane wings, jet engine inlets, and antenna dishes; in the buildings industry for heating solid structures such as floors, countertops, pipes, and tanks; in the food industry for heating food receptacles; and in the shipping industry and marine structures for preventing biofouling. See for example: US 5,344,696; US 5,925,275; US 5,932,124; US 5,942,140; US 5,954,977; US 5,966,501; and US 5,981,911.
  • US 6,483,087 provides a laminated fabric heater comprising a consolidated electrically conductive fabric layer, two bus bars, and two thermoplastic layers. Each bus bar contacts opposing edges of the conductive fabric layer without an adhesive, and the conductive fabric layer and the bus bars are laminated between the thermoplastic layers or other composite laminates to form a single sheet.
  • NASA Report TM-8888 discloses a surface heater using a graphite fiber-epoxy composite as the heating element.
  • Nickel foil contacts the end portions of the composite and is partially exposed beyond the composite for electrical contact.
  • a perforated nickel foil is used in certain embodiments of the heater.
  • the present invention provides for a flexible or non-flexible electrically conductive heater comprising a resistive heating element; a pair of plated, perforated, electrically conductive bus bars; and a conductive adhesive affixing the bus bars to the heating element.
  • the conductive heater is generally thin, porous, and provides a uniform distribution of heat to the article(s) to which it is applied.
  • the conductive heater provides uniform heating, as compared to prior art heaters which can produce hot spots or cool spots or uneven heat patterns.
  • the conductive heater can be used to warm any particular article or any surface of an article.
  • the heater can be placed on or inside an aircraft wing structure to heat its outer surface for de-icing applications.
  • the heater can be used in high- altitude conditions, such as 45,000 feet.
  • the heater can also be used inside an article, such as in a floor covering to heat the floor.
  • Flexible heaters can be fitted to any particular surface or application.
  • the present invention also provides a method for manufacturing the electrically conductive heater of this invention. Specifically, the method comprises, but is not restricted to, the following steps: perforating a pair of electrically conductive bus bars; plating the bus bars with a metal or a metal alloy; and affixing the bus bars to a resistive heating element with a conductive adhesive.
  • the perforated bus bars form a strong attachment to the resistive heating element, and permit an efficient flow of electrical current to the heating element.
  • the perforations in the bus bars can be formed by any convenient means.
  • the bus bars can be drilled or punched using a metal punch to form the perforations, or they can be prepared by acid etching.
  • the perforations can have any suitable dimension, diameter or shape without limitation.
  • the perforations can be circular, triangular, or square. Li an embodiment of the invention, the perforations have a diameter in the range of 0.5-2 mm.
  • the bus bars can be perforated with a single perforation, or they may be perforated with a plurality of perforations.
  • the perforations can be placed randomly on or at any convenient position on the bus bars, such as on the ends of the bus bars.
  • the perforations can optionally form a linear, nonlinear, or circular array on the bus bars, depending upon the desired end use and the current carrying capacity required.
  • the bus bars can be formed of any conductive material which can transfer electrical current to the heater element. Examples of suitable materials are metals such as copper or silver.
  • the bus bars can also be formed from alloys such as copper alloys, hi one embodiment, the bus bars comprise a beryllium/copper alloy. In general, two bus bars will be used for each resistive element, although in certain embodiments, more than two bus bars can be used for a given resistive element.
  • the bus bars are plated before or after they have been perforated and prior to being affixed to the heater element.
  • the bus bars can optionally be surface-treated prior to affixing the bus bars to the heating element or prior to plating, hi accordance with another embodiment, the bus bars may be pre-plated with a base metal before the final plating layer is applied.
  • the plating can be conducted using any conventional plating process which applies a coating of a metal or metal alloy to the surface of the bus bars.
  • a single coating of the metal or metal alloy can be plated on the bus bars.
  • a plurality of coatings can be plated onto the bus bars in order to build up a thicker coating layer, hi one embodiment, the bus bars are plated with silver or a silver alloy.
  • the heating element itself may optionally be plated before the bus bars are affixed.
  • One or more flash coats can also be applied to the bus bars before they are plated.
  • the flash coat can comprise any suitable material, such as nickel or a nickel alloy.
  • a conductive adhesive is used to affix the perforated bus bars to the heating element.
  • the conductive adhesive wets out the heating element and the perforated bus bars, and thereby significantly increases the surface area of these components which are in contact with the conductive adhesive. In this manner, an especially effective electrical contact between the bus bars and the heating element is obtained.
  • the conductive adhesive can be any substance which cures to securely bond the bus bars to the heating element and which allows the flow of electrical current between the bus bars and the heating element.
  • the composition of the conductive adhesive is not critical as long as it allows efficient flow of electrical current.
  • the conductive adhesive may be cured using means known in the art, such as heat, ultraviolet or visible light curing.
  • the conductive adhesive comprises metallic or carbon particles.
  • the conductive adhesive can comprise silver particles.
  • An example of a suitable conductive adhesive is a silver-loaded epoxy material.
  • the conductive adhesive and the plating on the bus bars can contain the same or different metal or alloy. In certain applications, using the same metal or alloy can improve the mutual chemical affinity of these materials and reduce problems that may be associated with the use of dissimilar materials and improve the current carrying capacity of the bus bar/adhesive/heating element interface.
  • the heating element used in the present invention may comprise a woven or non- woven mat of electrically conductive fibers.
  • the fibers in the mat may be randomly arranged or they may be in an array.
  • suitable conductive fibers are carbon fibers and metallic fibers.
  • the electrically conductive fibers may be uncoated, or they may be coated with an electrically conductive metal, layer of metals, or alloys. Examples of suitable coatings include nickel, silver, copper, gold, palladium, platinum, ruthenium, aluminum, other electrically conductive metals, layers of metals, and alloys of any of the foregoing metals.
  • the heating element itself may be coated with a metal such as nickel, silver, copper, gold, palladium, platinum, ruthenium, other electrically conductive metals, layers of metals, and alloys of any of the foregoing metals.
  • a metal such as nickel, silver, copper, gold, palladium, platinum, ruthenium, other electrically conductive metals, layers of metals, and alloys of any of the foregoing metals.
  • the resistive element is non- woven and comprises uncoated or metal-coated coated carbon fibers.
  • An example of a commercially available heating element which can be used in the invention is a nickel-coated carbon fiber grade of ThermionTM (Thermion Systems International, Stratford, CT). Different kinds of fibers can also be used in the same element, such as a combination of metal-coated and uncoated fibers.
  • a single conductive heater can be replaced by several heaters to provide zoned heating, and each zone heater can be powered independently so that the arrangement uses lower power levels.
  • the electrically conductive heater does not require complex equipment to obtain power as an AC or DC power supply is generally sufficient.
  • the current can pass along the length or width of the heater, depending on the particular application.
  • the size or shape of the conductive heater will depend on the particular application. In general, the heater will be manufactured to a specific size for a predetermined end use.
  • the conductive heater can comprise a single heater, or a plurality of heaters can be used for a particular application. If a plurality of heaters are used, e.g. for zone heating, each heater can have different physical or mechanical properties, such as different shapes, heat output, porosity or density, in order to obtain optimum zone heating characteristics.
  • the amount of heat produced by the heater, and the corresponding elevated temperatures obtained, will depend upon the particular characteristics of the heater. Typical operating temperatures are envisioned to be in the range of 20 0 C to 250°C (68°F to 482°F), although the operating temperature can be higher or lower than this range depending on individual circumstances. For example, for ice protection and ice protection systems equipment temperature protection, a useful operating temperature range can be in the range of -85 0 C (corresponding to flight at 45,000 feet) to 150 0 C (corresponding to temperatures after standing on an airport apron).
  • the resistivity of the heater can be tailored by adjusting, for example, the metal content or the mass per unit area of the base fabric when using metal or metal-coated fabrics or fibers. In such an embodiment, the design flexibility of the heater is increased and the output capacity and the temperature distribution can be controlled more easily and precisely compared to prior art methods.
  • the conductive heater can optionally be encapsulated in a thermoset or thermoplastic material which may be a polymer or another non-electrically conductive material. Encapsulation allows the heater to be more easily handled in industrial applications.

Abstract

A method for manufacturing a flexible or non flexible electrically conductive heater is provided. The method comprises perforating a pair of electrically conductive bus bars; plating the bus bars with a metal or a metal alloy; and affixing the bus bars to a resistive heating element with an electrically conductive adhesive. The heating element can be a conductive woven or non-woven fabric, film, or mesh, and can be formed of nickel-coated carbon fibers. The bus bars can be plated with an electrically conductive metal or metal alloy, such as silver or a silver-containing alloy. Advantageously, the perforated bus bars enable the conductive adhesive to wet through to form a strong attachment to the resistive heating element and permit an efficient flow of electrical current to the heating element.

Description

HEATERS WITH PERFORATED BUS BARS
[0001] This application claims the priority benefit of U.S. provisional patent application serial no. 60/709,030, filed August 17, 2005.
FIELD OF THE INVENTION
[0002] The present invention is directed to the field of electrical resistance heating. Specifically, the present invention is directed to a method for manufacturing an electrically conductive heater having perforated bus bars.
BACKGROUND OF THE INVENTION
[0003] Electrical resistance heaters are used to provide localized heating for various applications. Because of their light weight and even heat distribution characteristics, certain types of resistance heaters have found great utility. In the aerospace industry, for example, electrical resistance heaters are used for deicing structures such as airplane wings, jet engine inlets, and antenna dishes; in the buildings industry for heating solid structures such as floors, countertops, pipes, and tanks; in the food industry for heating food receptacles; and in the shipping industry and marine structures for preventing biofouling. See for example: US 5,344,696; US 5,925,275; US 5,932,124; US 5,942,140; US 5,954,977; US 5,966,501; and US 5,981,911.
[0004] US 6,483,087 provides a laminated fabric heater comprising a consolidated electrically conductive fabric layer, two bus bars, and two thermoplastic layers. Each bus bar contacts opposing edges of the conductive fabric layer without an adhesive, and the conductive fabric layer and the bus bars are laminated between the thermoplastic layers or other composite laminates to form a single sheet.
[0005] NASA Report TM-8888 discloses a surface heater using a graphite fiber-epoxy composite as the heating element. Nickel foil contacts the end portions of the composite and is partially exposed beyond the composite for electrical contact. A perforated nickel foil is used in certain embodiments of the heater.
[0006] Although such heaters are useful, further advances in the field of resistance heating are still desirable. DESCRIPTION OFTHE INVENTION
[0007] The present invention provides for a flexible or non-flexible electrically conductive heater comprising a resistive heating element; a pair of plated, perforated, electrically conductive bus bars; and a conductive adhesive affixing the bus bars to the heating element. The conductive heater is generally thin, porous, and provides a uniform distribution of heat to the article(s) to which it is applied. Advantageously, the conductive heater provides uniform heating, as compared to prior art heaters which can produce hot spots or cool spots or uneven heat patterns.
[0008] The conductive heater can be used to warm any particular article or any surface of an article. For example, the heater can be placed on or inside an aircraft wing structure to heat its outer surface for de-icing applications. In this regard, the heater can be used in high- altitude conditions, such as 45,000 feet. The heater can also be used inside an article, such as in a floor covering to heat the floor. Flexible heaters can be fitted to any particular surface or application.
[0009] The present invention also provides a method for manufacturing the electrically conductive heater of this invention. Specifically, the method comprises, but is not restricted to, the following steps: perforating a pair of electrically conductive bus bars; plating the bus bars with a metal or a metal alloy; and affixing the bus bars to a resistive heating element with a conductive adhesive. Advantageously, the perforated bus bars form a strong attachment to the resistive heating element, and permit an efficient flow of electrical current to the heating element.
[0010] The perforations in the bus bars can be formed by any convenient means. For example, the bus bars can be drilled or punched using a metal punch to form the perforations, or they can be prepared by acid etching. The perforations can have any suitable dimension, diameter or shape without limitation. For example, the perforations can be circular, triangular, or square. Li an embodiment of the invention, the perforations have a diameter in the range of 0.5-2 mm.
[0011] The bus bars can be perforated with a single perforation, or they may be perforated with a plurality of perforations. The perforations can be placed randomly on or at any convenient position on the bus bars, such as on the ends of the bus bars. The perforations can optionally form a linear, nonlinear, or circular array on the bus bars, depending upon the desired end use and the current carrying capacity required.
[0012] The bus bars can be formed of any conductive material which can transfer electrical current to the heater element. Examples of suitable materials are metals such as copper or silver. The bus bars can also be formed from alloys such as copper alloys, hi one embodiment, the bus bars comprise a beryllium/copper alloy. In general, two bus bars will be used for each resistive element, although in certain embodiments, more than two bus bars can be used for a given resistive element.
[0013] The bus bars are plated before or after they have been perforated and prior to being affixed to the heater element. The bus bars can optionally be surface-treated prior to affixing the bus bars to the heating element or prior to plating, hi accordance with another embodiment, the bus bars may be pre-plated with a base metal before the final plating layer is applied.
[0014] The plating can be conducted using any conventional plating process which applies a coating of a metal or metal alloy to the surface of the bus bars. A single coating of the metal or metal alloy can be plated on the bus bars. Alternatively, a plurality of coatings can be plated onto the bus bars in order to build up a thicker coating layer, hi one embodiment, the bus bars are plated with silver or a silver alloy. In addition, the heating element itself may optionally be plated before the bus bars are affixed. One or more flash coats can also be applied to the bus bars before they are plated. The flash coat can comprise any suitable material, such as nickel or a nickel alloy.
[0015] A conductive adhesive is used to affix the perforated bus bars to the heating element. The conductive adhesive wets out the heating element and the perforated bus bars, and thereby significantly increases the surface area of these components which are in contact with the conductive adhesive. In this manner, an especially effective electrical contact between the bus bars and the heating element is obtained.
[0016] The conductive adhesive can be any substance which cures to securely bond the bus bars to the heating element and which allows the flow of electrical current between the bus bars and the heating element. The composition of the conductive adhesive is not critical as long as it allows efficient flow of electrical current. The conductive adhesive may be cured using means known in the art, such as heat, ultraviolet or visible light curing. In one embodiment, the conductive adhesive comprises metallic or carbon particles. For example, the conductive adhesive can comprise silver particles. An example of a suitable conductive adhesive is a silver-loaded epoxy material. The conductive adhesive and the plating on the bus bars can contain the same or different metal or alloy. In certain applications, using the same metal or alloy can improve the mutual chemical affinity of these materials and reduce problems that may be associated with the use of dissimilar materials and improve the current carrying capacity of the bus bar/adhesive/heating element interface.
[0017] The heating element used in the present invention may comprise a woven or non- woven mat of electrically conductive fibers. The fibers in the mat may be randomly arranged or they may be in an array. Non-exhaustive examples of suitable conductive fibers are carbon fibers and metallic fibers. The electrically conductive fibers may be uncoated, or they may be coated with an electrically conductive metal, layer of metals, or alloys. Examples of suitable coatings include nickel, silver, copper, gold, palladium, platinum, ruthenium, aluminum, other electrically conductive metals, layers of metals, and alloys of any of the foregoing metals.
[0018] Alternatively, the heating element itself may be coated with a metal such as nickel, silver, copper, gold, palladium, platinum, ruthenium, other electrically conductive metals, layers of metals, and alloys of any of the foregoing metals.
[0019] In one embodiment of the invention, the resistive element is non- woven and comprises uncoated or metal-coated coated carbon fibers. An example of a commercially available heating element which can be used in the invention is a nickel-coated carbon fiber grade of Thermion™ (Thermion Systems International, Stratford, CT). Different kinds of fibers can also be used in the same element, such as a combination of metal-coated and uncoated fibers.
[0020] In an embodiment of the invention, a single conductive heater can be replaced by several heaters to provide zoned heating, and each zone heater can be powered independently so that the arrangement uses lower power levels.
[0021] The electrically conductive heater does not require complex equipment to obtain power as an AC or DC power supply is generally sufficient. The current can pass along the length or width of the heater, depending on the particular application. [0022] The size or shape of the conductive heater will depend on the particular application. In general, the heater will be manufactured to a specific size for a predetermined end use. The conductive heater can comprise a single heater, or a plurality of heaters can be used for a particular application. If a plurality of heaters are used, e.g. for zone heating, each heater can have different physical or mechanical properties, such as different shapes, heat output, porosity or density, in order to obtain optimum zone heating characteristics.
[0023] The amount of heat produced by the heater, and the corresponding elevated temperatures obtained, will depend upon the particular characteristics of the heater. Typical operating temperatures are envisioned to be in the range of 200C to 250°C (68°F to 482°F), although the operating temperature can be higher or lower than this range depending on individual circumstances. For example, for ice protection and ice protection systems equipment temperature protection, a useful operating temperature range can be in the range of -850C (corresponding to flight at 45,000 feet) to 1500C (corresponding to temperatures after standing on an airport apron). The resistivity of the heater can be tailored by adjusting, for example, the metal content or the mass per unit area of the base fabric when using metal or metal-coated fabrics or fibers. In such an embodiment, the design flexibility of the heater is increased and the output capacity and the temperature distribution can be controlled more easily and precisely compared to prior art methods.
[0024] After manufacture, the conductive heater can optionally be encapsulated in a thermoset or thermoplastic material which may be a polymer or another non-electrically conductive material. Encapsulation allows the heater to be more easily handled in industrial applications.
[0025] Numerous modifications and variations of the present invention are possible in light of the above teachings, and therefore, within the scope of the appended claims, the invention may be practiced otherwise than as particularly described.

Claims

What is claimed is:
1. A method for manufacturing an electrically conductive heater, the method comprising the steps of: perforating a pair of electrically conductive bus bars; plating the bus bars with a metal or a metal alloy; and affixing the plated bus bars to a resistive heating element with a conductive adhesive.
2. The method according to claim 1 , wherein the perforations have a width in the range of 0.5-2 mm.
3. The method according to claim 1, wherein the perforations are randomly placed on the bus bars.
4. The method according to claim 1, wherein the perforations form a linear, nonlinear, or circular array on the bus bars.
5. The method according to claim 1, wherein the bus bars are perforated before or after the plating step.
6. The method according to claim 1, wherein the bus bars are plated with an electrically conductive metal or alloy.
7. The method according to claim 1, wherein the bus bars are plated with silver or a silver alloy.
8. The method according to claim 1, further comprising the step of surface-treating the bus bars prior to affixing the bus bars to the heating element.
9. The method according to claim 1, further comprising pre-plating the bus bars with a base metal prior to the plating step.
10. The method according to claim 1, wherein the bus bars comprise copper, a copper alloy, silver, or a silver alloy.
11. The method according to claim 1, wherein the bus bars comprise a beryllium/copper alloy.
12. The method according to claim 1, wherein the conductive adhesive comprises metallic or carbon particles.
13. The method according to claim 1, wherein the conductive adhesive comprises silver particles.
14. The method according to claim 1, wherein the conductive adhesive and the plating on the bus bars contain the same metal or metal alloy.
15. The method according to claim 1, wherein the heating element is a woven or non-woven fabric, film, or mesh.
16. The method according to claim 1, wherein the heating element comprises coated or uncoated carbon fibers.
17. The method according to claim 16, wherein the heating element or the carbon fibers are coated with an electrically conductive metal or alloy, or electrically conductive layers of metals or alloys.
18. The method according to claim 17, wherein the metal coating of the heating element or the carbon fibers is selected from the group consisting of nickel, brass, silver, gold, palladium, platinum, ruthenium, and aluminum.
19. The method according to claim 1, wherein the heating element comprises nickel-coated carbon fibers.
20. An electrically conductive heater prepared according to the method of any one of claims 1-19.
21. An electrically conductive heater comprising: a resistive heating element; a pair of plated, perforated, electrically conductive bus bars; and a conductive adhesive affixing the bus bars to the heating element.
PCT/US2006/029850 2005-08-17 2006-07-31 Heaters with perforated bus bars WO2007021528A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US70903005P 2005-08-17 2005-08-17
US60/709,030 2005-08-17

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WO2007021528A1 true WO2007021528A1 (en) 2007-02-22

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014024165A2 (en) 2012-08-08 2014-02-13 Centi - Centro De Nanotecnologia E Materiais Técnicos Funcionais E Inteligentes Heating device, respective printing and using methods
CN111056017A (en) * 2018-10-16 2020-04-24 古德里奇公司 Method of transferring power to a heated component using a printed highly flexible conductive ink bus bar

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05275205A (en) * 1992-03-26 1993-10-22 Murata Mfg Co Ltd Manufacture of positive temperature coefficient thermistor element
JPH06244007A (en) * 1993-02-19 1994-09-02 Tdk Corp Composite type ptc thermistor device
US6104587A (en) * 1997-07-25 2000-08-15 Banich; Ann Electrical device comprising a conductive polymer
US6531950B1 (en) * 2000-06-28 2003-03-11 Tyco Electronics Corporation Electrical devices containing conductive polymers
US6570483B1 (en) * 1994-06-08 2003-05-27 Tyco Electronics Corporation Electrically resistive PTC devices containing conductive polymers

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05275205A (en) * 1992-03-26 1993-10-22 Murata Mfg Co Ltd Manufacture of positive temperature coefficient thermistor element
JPH06244007A (en) * 1993-02-19 1994-09-02 Tdk Corp Composite type ptc thermistor device
US6570483B1 (en) * 1994-06-08 2003-05-27 Tyco Electronics Corporation Electrically resistive PTC devices containing conductive polymers
US6104587A (en) * 1997-07-25 2000-08-15 Banich; Ann Electrical device comprising a conductive polymer
US6531950B1 (en) * 2000-06-28 2003-03-11 Tyco Electronics Corporation Electrical devices containing conductive polymers

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014024165A2 (en) 2012-08-08 2014-02-13 Centi - Centro De Nanotecnologia E Materiais Técnicos Funcionais E Inteligentes Heating device, respective printing and using methods
CN111056017A (en) * 2018-10-16 2020-04-24 古德里奇公司 Method of transferring power to a heated component using a printed highly flexible conductive ink bus bar

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