EP0320862A2 - Thermistorheizeinheit mit positivem Temperaturkoeffizienten - Google Patents

Thermistorheizeinheit mit positivem Temperaturkoeffizienten Download PDF

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Publication number
EP0320862A2
EP0320862A2 EP88120760A EP88120760A EP0320862A2 EP 0320862 A2 EP0320862 A2 EP 0320862A2 EP 88120760 A EP88120760 A EP 88120760A EP 88120760 A EP88120760 A EP 88120760A EP 0320862 A2 EP0320862 A2 EP 0320862A2
Authority
EP
European Patent Office
Prior art keywords
heating pad
heating
conductor means
thermistors
pad
Prior art date
Legal status (The legal status 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 status listed.)
Granted
Application number
EP88120760A
Other languages
English (en)
French (fr)
Other versions
EP0320862A3 (en
EP0320862B1 (de
Inventor
David C. Goss
Chandrakant M. Yagnik
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thermon Manufacturing Co
Original Assignee
Thermon Manufacturing Co
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 Thermon Manufacturing Co filed Critical Thermon Manufacturing Co
Publication of EP0320862A2 publication Critical patent/EP0320862A2/de
Publication of EP0320862A3 publication Critical patent/EP0320862A3/en
Application granted granted Critical
Publication of EP0320862B1 publication Critical patent/EP0320862B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
    • H05B3/14—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
    • H05B3/141—Conductive ceramics, e.g. metal oxides, metal carbides, barium titanate, ferrites, zirconia, vitrous compounds
    • 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
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional [2D] plane, e.g. plate-heater
    • H05B3/34—Heating elements having extended surface area substantially in a two-dimensional [2D] plane, e.g. plate-heater flexible, e.g. heating nets or webs
    • 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
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/002—Heaters using a particular layout for the resistive material or resistive elements
    • H05B2203/005—Heaters using a particular layout for the resistive material or resistive elements using multiple resistive elements or resistive zones isolated from each other
    • 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
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/009—Heaters using conductive material in contact with opposing surfaces of the resistive element or resistive layer
    • 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
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/013—Heaters using resistive films or coatings
    • 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
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/017—Manufacturing methods or apparatus for heaters
    • 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
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/02—Heaters using heating elements having a positive temperature coefficient

Definitions

  • the present invention relates to electrical heating devices that use positive temperature coefficient thermistors as self-regulating heaters.
  • Heating cables as disclosed in U.S. Patent No. 4,072,848 based their temperature control on the use of variable resistance heating materials which provide a self-regulating feature.
  • the heating materials are generally formed into chips made of barium titanate or solid solutions of barium and strontium titanate which are made semiconductive by the inclusion of various dopants. These chips are referred to as positive temperature coefficient thermistors and have a relatively low temperature coefficient of resistance at low temperatures. As the temperature of the thermistor rises, a sharp rise in the resistance occurs at a point termed the "Curie point". The transition from low resistivity to high resistivity occurs at a relatively sharp point as shown in U.S. Patent No. 4,072,848. As these chips are well known to those skilled in the art, no further discussion of their construction is necessary.
  • the thermistor As a voltage is applied to the thermistor, the thermistor generates heat due to resistance effects. This heat is then transferred to the environment, such as the pipe to which the cable is attached. As the temperature of the thermistor and the surrounding environment increases, the thermistor temperature reaches the Curie point, the heat producing capability of the thermistor is reduced and the thermistor cools down. Thus the thermistor temperature settles on or near the Curie point, with the temperature of the surrounding environment being based on the thermal conductivities of the various materials in contact with the thermistor.
  • Prior art thermistor-based devices were cables and other similar devices which covered only small lateral areas, even though they could be extended for long distances. While the prior art cables could be shaped in serpentine patterns to cover larger lateral areas, this often resulted in uneven temperature distributions over the surface area and was hard to manufacture.
  • U.S. Patent No. 4,330,703 shows several examples of prior art cables utilizing heat generating layers of materials and having electrical conductors formed of metal sheets, grid of meshes.
  • the heat generating materials are located over the entire area of the cable, not in discrete and separated areas as is the practice in thermistor-based cables. Additionally, the electrical conductors are thin, utilized only to supply electrical current to the heat generating materials and not utilized to conduct appreciable amounts of heat.
  • the heating pad of the present invention has substantially flat, preferably woven, electrical conductors disposed in overlying parallel relationship and having a plurality of spaced thermistors electrically connected thereto, wherein the electrical conductors serve as the primary heat transfer means by dissipating heat produced by the thermistors away from them.
  • the thermistors are spaced in a grid or substantially uniform pattern over the area of the heating pad.
  • Such construction results in an efficient heat transfer between the conductors and the thermistors, thus allowing heat to be removed from the thermistors. Also such construction enables the thermistor to produce high power levels with a given applied voltage before the thermistor reaches the self-limiting temperature or Curie point.
  • Such heat transfer using the electrical conductors improves the temperature distribution over the surface of the pad because the heat is transferred in all directions along the electrical conductors, which are good thermal conductors, and away from the thermistors, limiting the amount of local heat and improving the heat balance of the pad.
  • the construction of a heating pad of the present invention allows ease of manufacture because complex serpentine paths are not required.
  • the use of the woven electrical conductors significantly decreases the thermal or mechanical stresses which occur at the connections between the conductors and thermistors because of the dispersed multidirectional forces which are exerted because of the small size and great number of wire strands in the material.
  • the letter P generally designates a heating pad according to the present invention.
  • Fig. 1 illustrates the preferred embodiment of a heating pad P constructed according to the present invention.
  • a plurality of thermistors 10 are inserted into a separating dielectric insulator 12.
  • the separating dielectric 12 contains a series of holes or cavities 14 in which the thermistors 10 are installed.
  • the spacing between the holes 14 is varied depending upon the specific size of the thermistors 10 and the number of thermistors 10 required for a given desired thermal output of the heating pad P.
  • the holes 14 are slightly smaller than the size of the thermistors 10 so that the thermistors 10 are positively retained in the separating dielectric 12.
  • the thermistors 10 are shown as being circular in cross-section, but any desired shape can be used, with the holes 14 have corresponding shapes.
  • the dielectric material may be rubber, thermoplastic resins such as polyethylene or polytetrafluoroethylene, asbestos fiber, or any satisfactory material which is an electrical insulating material and is capable of withstanding the temperatures of the thermistors 10, while conducting sufficient heat as desired and being flexible to allow the heating pad P to be flexed as desired.
  • Conductive sheets 16, 18 are installed parallel to each other and on opposite sides of the separating dielectric 12 to provide the source of electrical energy converted by the thermistors 10 to heat.
  • the conductive sheets 16, 18 are attached to the thermistors 10 by soldering, brazing, welding or otherwise electrically and mechanically connecting the conductive sheets 16, 18 to the surfaces of the thermistors 10.
  • Conductors 17, 19 are attached to the conductive sheets 16, 18 and to the voltage source (not shown) used to supply electrical energy to the heating pad P.
  • an insulating layer 20 is provided to protect the heating pad P from the environment. In this way, short circuit and potential shock conditions are prevented.
  • a metallic sheath 22 can be formed over the insulating layer 20 of the heating pad P.
  • the metallic sheath 22 may be aluminum, stainless steel, copper or any satisfactory metal or metal alloy that can be formed about the pad.
  • the conductive sheets 16, 18 are preferably formed of copper wire cloth approximately the same size and shape as the heating pad P.
  • the conductive sheets 16, 18 can alternately be formed of wire cloth made of aluminum, stainless steel or other metallic conductors.
  • carbon or graphite fibers, conductively coated fiberglass yarn or other similar materials of known construction as are commonly used in automotive ignition cables and as disclosed in U.S. Patent No. 4,369,423 may be used.
  • the fibers can be electroplated with nickel to further improve the conductivity of the fibers. Sufficient numbers of the fibers are woven to provide a conductive sheet which is capable of carrying the necessary electrical and thermal loads.
  • the conductive sheets could be solid metallic sheets of materials such as copper, aluminum or other suitable materials.
  • An exemplary copper cloth is comprised of 0.011 inch diameter copper wire formed into a mesh having 16 wires per inch in either direction.
  • the individual copper strands may be coated with a tin, silver, aluminum or nickel plated finish.
  • the conductive sheet construction according to the present invention is preferably formed with a large number of smaller wires which are woven into sheets.
  • the increased number of contacts of smaller wire and the mesh or woven pattern developed by the woven conductors decreases the thermal and mechanical stresses which occur at the connection between the conductive sheets 16, 18 and the thermistor 10.
  • the thermal stresses arise due to differing expansion rates and other reasons and the mechanical stresses occur due to the flexible nature of the heating pad P. Because the woven wires are small and are arranged in several different directions, the forces exerted on each strand or wire are low, thereby increasing the reliability of the heating pad P.
  • a heating pad P according to the present invention can be cut or formed into almost any desired shape.
  • the exemplary embodiment shown in Fig. 1 is formed into a square, but the heating pad P can be formed into circular shapes irregular shapes or regular or irregular polygons as desired. Because the thermistors 10 are relatively small, and the other materials used in the present invention are preferably flexible, the heating pad P is adapted to be flexed so as to substantially conform to an item such as a vessel or pipe to be heated.
  • a heating pad P was constructed of copper wire cloth according to Fig. 1 with Curie temperature 124-128° C. thermistors 10.
  • a one foot square separating dielectric layer 12 of coated fiberglass having a thickness of 0.07 inches was used. Twelve thermistors 10 were placed in openings 14 distributed evenly over the area of the separating dielectric layer 12. Copper wire cloth having a 16 by 16 mesh and formed of 0.011 inch diameter wires was formed into sheets one foot square which were then soldered to pre-tinned thermistors 10 with a silver bearing, high temperature solder alloy.
  • This heating pad P was then insulated with high temperature RTV silicone to form the insulating layer 20.
  • the completed heating pad P thus formed had a resistance of 90 ohms at room temperature of approximately 77°F.
  • This heating pad P was then placed in an environmental chamber, and tested as equilibrium temperatures of -35°F, 0°F., 50°F., 100°F., and 200°F. and energized at voltages ranging from 0 to 300 volts.
  • the power consumption at the various voltages and temperatures was recorded and the results are shown in Figs. 2 and 3. It can thus be seen that the present invention provides a construction which produces high power levels with a given applied voltage before the thermistors reach the self-limiting temperature.
  • the same heating pad P was energized by approximately 120 volts while the heating pad P was suspended in a free air environment having a temperature of 76°F. Temperature measurements were taken at a series of locations on the surface of the heating pad P. The maximum and minimum temperatures at positions directly over the thermistors 10 were 199°F and 178°F. The average temperature directly over the termistors was approximately 183°F. The outer edges of the heating pad P had temperatures of 111°F, 116°F, 112 °F and 102°F. The average temperature on the surface area at locations between the thermistors 10 was approximately 121°F, with a maximum of 134°F and a minimum of 108°F. Such results indicate the efficient heat transfer from the thermistors 10 to the conductive sheets 16, 18 and the good thermal conduction of the conductive sheets 16, 18.
  • the pad may be selectively formed or cut into any desired shape while still retaining approximately the same watts per square foot capability for the selected area, assuming an equal area of remaining heating pad per thermistor.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Resistance Heating (AREA)
  • Surface Heating Bodies (AREA)
  • Thermistors And Varistors (AREA)
  • Control Of Resistance Heating (AREA)
  • Thermotherapy And Cooling Therapy Devices (AREA)
EP88120760A 1987-12-14 1988-12-13 Thermistorheizeinheit mit positivem Temperaturkoeffizienten Expired - Lifetime EP0320862B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US13247987A 1987-12-14 1987-12-14
US132479 1993-10-06

Publications (3)

Publication Number Publication Date
EP0320862A2 true EP0320862A2 (de) 1989-06-21
EP0320862A3 EP0320862A3 (en) 1990-06-13
EP0320862B1 EP0320862B1 (de) 1995-02-15

Family

ID=22454243

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88120760A Expired - Lifetime EP0320862B1 (de) 1987-12-14 1988-12-13 Thermistorheizeinheit mit positivem Temperaturkoeffizienten

Country Status (8)

Country Link
EP (1) EP0320862B1 (de)
JP (1) JPH025390A (de)
AT (1) ATE118664T1 (de)
AU (1) AU611237B2 (de)
CA (1) CA1298338C (de)
DE (1) DE3853056T2 (de)
IN (1) IN171935B (de)
MX (1) MX170020B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0554459A4 (de) * 1991-08-26 1994-03-18 Nippon Tungsten Ptc-thermistor verwendenden heizapparat.
FR2722937A1 (fr) * 1994-05-06 1996-01-26 Michel Jean Francois Dispositif de chauffage permettant d'economiser de l'energie
CN105376878A (zh) * 2014-08-26 2016-03-02 许少君 一种自供发电导热面料
DE102017130508A1 (de) 2017-12-19 2019-06-19 Dbk David + Baader Gmbh Flexibler flächiger Heizer und Verfahren zu dessen Herstellung

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06168774A (ja) * 1991-01-22 1994-06-14 Ube Ind Ltd セラミックヒータユニット
JPH0755836Y2 (ja) * 1992-03-26 1995-12-20 積水化成品工業株式会社 ヒーター
JP2008546945A (ja) * 2005-06-22 2008-12-25 エアバス・フランス 抵抗マットを有する航空機エンジン室用の防氷および除氷システム
DE102015203114A1 (de) * 2015-02-20 2016-08-25 Mahle International Gmbh PTC-Thermistor
JP7380243B2 (ja) * 2020-01-23 2023-11-15 株式会社デンソーウェーブ センサ収容装置

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4330703A (en) * 1975-08-04 1982-05-18 Raychem Corporation Layered self-regulating heating article
JPS6046789B2 (ja) * 1976-08-04 1985-10-17 レイケム、コ−ポレ−シヨン 電気加熱装置
US4242567A (en) * 1978-06-05 1980-12-30 General Electric Company Electrically heated hair straightener and PTC heater assembly therefor
CH630456A5 (fr) * 1979-06-01 1982-06-15 Hotel Du Rhone Societe Pour L Installation comportant au moins une armoire frigorifique, pour chambres d'hotel.
JPS6316156Y2 (de) * 1980-10-08 1988-05-09
DE3042420A1 (de) * 1980-11-11 1982-06-24 Fritz Eichenauer GmbH & Co KG, 6744 Kandel Elektrischer heizkoerper mit ein oder mehreren flachen, quaderfoermigen heizelementen
GB2091070B (en) * 1980-12-13 1984-10-10 Fudickar Kg C S An electrical heating device
DE3046995C2 (de) * 1980-12-13 1988-09-08 C.S. Fudickar Kg, 5600 Wuppertal Elektrische Heizvorrichtung für beheizte Apparate, Haushaltsgeräte u.dgl.
US4728779A (en) * 1985-09-27 1988-03-01 Tdk Corporation PTC heating device
US4794229A (en) * 1987-04-24 1988-12-27 Thermon Manufacturing Company Flexible, elongated thermistor heating cable

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0554459A4 (de) * 1991-08-26 1994-03-18 Nippon Tungsten Ptc-thermistor verwendenden heizapparat.
FR2722937A1 (fr) * 1994-05-06 1996-01-26 Michel Jean Francois Dispositif de chauffage permettant d'economiser de l'energie
CN105376878A (zh) * 2014-08-26 2016-03-02 许少君 一种自供发电导热面料
DE102017130508A1 (de) 2017-12-19 2019-06-19 Dbk David + Baader Gmbh Flexibler flächiger Heizer und Verfahren zu dessen Herstellung
WO2019121772A1 (de) 2017-12-19 2019-06-27 Dbk David + Baader Gmbh Flexibler flächiger heizer und verfahren zu dessen herstellung

Also Published As

Publication number Publication date
JPH025390A (ja) 1990-01-10
MX170020B (es) 1993-08-04
EP0320862A3 (en) 1990-06-13
ATE118664T1 (de) 1995-03-15
CA1298338C (en) 1992-03-31
DE3853056T2 (de) 1995-07-27
EP0320862B1 (de) 1995-02-15
DE3853056D1 (de) 1995-03-23
AU2680988A (en) 1989-06-15
AU611237B2 (en) 1991-06-06
IN171935B (de) 1993-02-13

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