US3719796A - Heating unit having a ptc heating resistor - Google Patents

Heating unit having a ptc heating resistor Download PDF

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Publication number
US3719796A
US3719796A US3719796DA US3719796A US 3719796 A US3719796 A US 3719796A US 3719796D A US3719796D A US 3719796DA US 3719796 A US3719796 A US 3719796A
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United States
Prior art keywords
resistor
case
ptc
body
walls
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Expired - Lifetime
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J Abildtrup
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Danfoss AS
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Danfoss AS
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01CRESISTORS
    • H01C7/00Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/02Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
    • H01C7/022Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient mainly consisting of non-metallic substances
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05DSYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00Control of temperature
    • G05D23/19Control of temperature characterised by the use of electric means
    • G05D23/20Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
    • G05D23/24Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element having a resistance varying with temperature, e.g. a thermistor
    • G05D23/2401Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element having a resistance varying with temperature, e.g. a thermistor using a heating element as a sensing element

Abstract

The invention relates to an electrical heating unit for appliance such as coffee makers, hot plates and the like. The heating unit includes a PTC resistor which is mounted so as to be completely surrounded by a liquid medium so that a uniform temperature is maintained for the external surface of the resistor. This uniform temperature prevents cracking of the resistor due to unevenly distributed thermal strains.

Description

United States Patent my Abildtrup HEATING NIT'IIAVING A PTC HEATING RESISTOR I Denmark [73] Assignee: Danfoss A/Sl, Nordborg,'Denmark [22] Filed: July 21, 1971 211 Appl.No.: 164,627 9 [30] I Foreign Application Priority Data 9 Aug. 14, 1970 Germany ..P 20 40 523.6

[451 March 6, 1973 2,236,837 4/1941 Rimmel ..219/440 X 3,029,331 4/1962 Kowarik ..338/22 R X 3,044,968 7/ 1962 lchikawa ..252/520 3,073,940 1/1963 Brandl ..219/438 X 3,214,719 10/1965 Turner ..338/22 R 3,274,360 .9/1966 Brand] ..219/331 X 3,489,884 1/1970 Waseleski, Jr.. ....338/22 R X 3,51 1,970 5/ 1970 Kjellberg .219] 331 3,551,644 12/1970 Sano et a1 ..219/441 FOREIGN PATENTS OR APPUCATIONS 258,804 5/ 1949 Switzerland ..219/439 470,827 8/ 1937 Great Britain .,.2 1 9/442 Primary Examiner-Volod'ymyr Y. Mayewsky Attorney-Wayne B. Easton 1-v ABSTRACT mounted so as to be completely surrounded by aliquid medium so that a uniform temperature is maintained for the external surface of the resistor. This uniformtemperature prevents cracking of the resistor due to unevenly distributed thermal strains.

1 Claim, 2 Drawing Figures HEATING UNIT HAVING A PTC HEATING RESISTOR The invention I relates to a heating or regulating device comprising a FTC-resistor.

Resistors, the resistance of which increases with temperature (FTC-resistors), are frequently used in industry, for example as temperature-responsive resistors, as the starting resistors of single-phase asynchronous mo- I tors, or as heating resistors. in all cases, their currentliquid, e.g., coffee. For this purpose, one or more PTC- V resistor bodies in disc form are enclosed in a fluid-tight manner in a casing,-tw faces of the casing being in heat-conducting contact with the faces of the discs, and an electrically insulating layer of mica being fitted between the faces of the casing and the discs. In an arrangement of this kind, the current-carrying capacity of the FTC-resistors is still lower.-

The object of the invention is to provide a heating device comprising a FTC-resistor, which device can be more heavily loaded than previously as regards electrical power or temperature.

According tothe invention, this object is achieved by completely immersing the FTC-resistor in a fluid which undergoes a flow movement when differences in the surface temperature of the FTC-body occur.

The fluid surrounding the FTC-resistor is a uniform good conductor of heat, since the fluid is kept continuously in circulation, and as long as the PTC-resistor is heated, the fluid is warmed on the PTC-body and cooled on the case. A heating element of this kind can be sealed off in a fluid-tight manner and can be used for heating a fluid. It can also be incorporated in a hotplate or attached to its underside.

substance which. is also kept in circulation by differences in temperature. Consequently, all the surface zones of the FTC-body are at approximately the same temperature at each moment. When the surface temperature is uniform, the danger of cracking due to ther- 'mal stresses is very much reduced, since cracking of this kind is usually initiated at the surface of the body.

Tests have shown that a FTC-resistor, known per se, can in this way be loaded several times more heavily; for example, a FTC-resistor that can normally carry only 25 W can now carry 225 W. Furthermore, it is possible to keep the PTC-resistor at a point on the straight part of the characteristic curve, whereas hitherto the working point often moved to the upper or lower terminal point.

Expediently, the fluid is not electrically conductive. Then the FTC-resistor can be directly immersed in the fluid.

If however a' conductive fluid is used, the FTC-body should be provided with a coating of electrically insulating material. In this connection, it suffices to apply very thin coatings that neither adversely affect the thermal conductivity nor apply any forces at all to the PTC- body.

In a preferred embodiment, the FTC-body and the fluid are placed in a closed case. Since the FTC-body is completely surrounded by fluid, its surface is virtually not in contact with this case at any point. Nevertheless,

- a heating element is obtainedthat can be used in large instead of this, the PTC-body can also be fitted directly in a fluid-medium that is to, be heated. Thus, the fluid to be heated, e.g., water or coffee, can be used directly for evening out the surface temperature. In some instances the FTC-resistor must be provided with a thin, electrically insulating protective coating, e.g., of glass or plastics material, in order to meet safety requirements. This arrangement is also suitable when a FTC-heating resistor is to be fitted directly in the water.

compartment of a washing machine.

When a case is used for the FTC-body and the fluid,

it is expedient for the case to be provided with a device for compensating the differences in the volume of the fluid governed by temperature. A device of this kindcan be agas-cushion, a resilient wall or the like. It is then unnecessary to ensure'that the fluid has the smallest possible coefficient of thermal expansion.

In all the applications of. the heating device in accordance with the invention, the FTC-resistor is not only used to provide a predetermined amount of heat;

it is also enabled to keep the temperature of the medi um to be heated at a constant level, since it automatically reduces the supply of power when the temperature rises.

The invention will now be described in more detail by reference to embodiments illustrated in the drawing, in which:

FIG. I is a schematic section through a hot-plate constructed in accordance with the invention, and

FIG. 2 is a schematic section through a water heater constructed in accordance with the invention.

Referring to FIG. l,'a PTC-body l andthe oil 2 surrounding it are contained in a metal case 3. Leads 4 and 5 run through lead-through passages in insulations 6 and 7 to the end-faces of the body 1. The top of the metal case 3 is in heat-conducting contact with the bottom of a metal plate 8, on whicha cooking vessel for example can be placed. The bottom of the case 3 contains an opening 9 which is covered by a resilient sheetmetal element 10.

When current is passed to the PTC-body 1, it and the surrounding oil 2 are heated up. Flow movement is imparted to the oil which passes heat to the case 3. Apart from that portion lost by radiation to the surrounding air, this heat is passed to the metal plate 8. The oil 2 ensures that the entire surface of the body 1 is at the same temperature at any moment. Changesin volume of the oil 2 are compensated by deflection of the sheet-metal part 10. When the heating device has acquired a predetermined temperature, the resistance of the body 1 will have risen to an extent such that the power supplied is reduced. The hot-plate is thenenabled to maintain this predetermined temperature at a substantially constant level. After the system has been switched off, the entire arrangement gradually cools down, and the entire surface of the body [again has substantially the same temperature at any moment.

In the arrangement shown in FIG. 2, a FTC-body 13, having the form of an annular disc, is fitted in a con tainer l2 filled with water 11. The PTC-body has a thin electrode coating 14 and 15 on each of its two faces, and'leads l6 and 17 are secured to these coatings and pass through lead-through passages in insulations 18 and 19 upwards through the base of the container. The FTC-body l3 and electrodes 14 and 15 are surrounded by a thin electrically insulating coating 20 which, as in the case of the electrodes 14 and 15, possess good thermal conductivity and apply no external stresses to the body 13.

In this construction, the water 11 that is to be heated is used for keeping the surface temperature of the PTC- body 13 uniform. Provision should therefore be made for the body 13 also to be covered by the water during the cooling period. This can be achieved for example by fitting a water-intake cock 21, incorporating a valve 22, in the wall of the container and at a point just above the FTC-body 13.

If the principle illustrated in FIG. 2 is applied to a washing machine, the PTC-body can be fitted in a recess in the base, in which recess residual water is always present.

I claim:

1. A heating unit comprising a sealed metal case for a liquid, said case having top, sides and bottom walls, a PTC heating resistor mounted in said case in spaced relation to said walls, a heat conductive liquid in said case in substantially complete surrounding relation to said resistor, said top wall being in contact with a heat conductive state for conducting heat thereto, electrical leads for said resistor extending through one of said walls and electrically insulated therefrom, said one of walls having an opening, and a resilient sheet portion closing said opening and being outwardly expandable in response to the liquid inner pressure applied thereto.

Claims (1)

1. A heating unit comprising a sealed metal case for a liquid, said case having top, sides and bottom walls, a PTC heating resistor mounted in said case in spaced relation to said walls, a heat conductive liquid in said case in substantially complete surrounding relation to said resistor, said top wall being in contact with a heat conductive state for conducting heat thereto, electrical leads for said resistor extending through one of said walls and electrically insulated therefrom, said one of walls having an opening, and a resilient sheet portion closing said opening and being outwardly expandable in response to the liquid inner pressure applied thereto.
US3719796D 1970-08-14 1971-07-21 Heating unit having a ptc heating resistor Expired - Lifetime US3719796A (en)

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Application Number Priority Date Filing Date Title
DE19702040523 DE2040523C3 (en) 1970-08-14 1970-08-14

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US3719796A true US3719796A (en) 1973-03-06

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US3719796D Expired - Lifetime US3719796A (en) 1970-08-14 1971-07-21 Heating unit having a ptc heating resistor

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US (1) US3719796A (en)
JP (1) JPS52142251U (en)
BR (1) BR7105227D0 (en)
CA (1) CA936576A (en)
CH (1) CH526247A (en)
DE (1) DE2040523C3 (en)
DK (1) DK129070B (en)
ES (1) ES393611A1 (en)
FR (1) FR2104247A5 (en)
GB (1) GB1306907A (en)
NL (1) NL7111206A (en)
NO (1) NO133296C (en)

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3885129A (en) * 1974-02-28 1975-05-20 Sprague Electric Co Positive temperature coefficient resistor heater
US4007684A (en) * 1973-09-26 1977-02-15 Nippon Telegraph And Telephone Public Corporation Ink liquid warmer for ink jet system printer
US4029941A (en) * 1975-10-20 1977-06-14 Gould Inc. Electric heater assembly
US4068115A (en) * 1974-05-09 1978-01-10 Sweetheart Plastics, Inc. Food serving tray
US4086467A (en) * 1976-07-19 1978-04-25 Texas Instruments Incorporated Electronic heater for high voltage applications
US4141327A (en) * 1976-09-09 1979-02-27 Texas Instruments Incorporated Early fuel evaporation carburetion system
US4147927A (en) * 1975-04-07 1979-04-03 U.S. Philips Corporation Self-regulating heating element
FR2417234A1 (en) * 1978-02-14 1979-09-07 Siemens Ag immersion
US4177375A (en) * 1977-09-29 1979-12-04 Siemens Aktiengesellschaft Heating device having an optimized heating element of PTC thermistor material
US4210800A (en) * 1977-02-21 1980-07-01 U.S. Philips Corporation Heating element comprising a PTC-resistor body
US4336444A (en) * 1980-01-14 1982-06-22 Gust, Irish, Jeffers & Hoffman Apparatus and method for converting electrical energy into heat energy
US4387291A (en) * 1980-11-28 1983-06-07 Texas Instruments Incorporated Fuel heater system and self-regulating heater therefor
US4394646A (en) * 1979-10-31 1983-07-19 Goessler Gerhard Temperature indicator for a glass ceramic cooking surface
US4459466A (en) * 1980-11-26 1984-07-10 Nippon Soken, Inc. Dual air passage heating apparatus with ceramic heater element
US4639818A (en) * 1985-09-17 1987-01-27 Raychem Corporation Vent hole assembly
US4797534A (en) * 1987-06-08 1989-01-10 Gte Products Corporation PTC thermistor heating device
US5025133A (en) * 1989-04-04 1991-06-18 Mitsubishi Denki Kabushiki Kaisha Semiconductor wafer heating device
US5073699A (en) * 1988-02-05 1991-12-17 V. Dardanella Austin Device for warming food and beverage containers having support plate and perimeter skirt structure
US6094129A (en) * 1994-11-19 2000-07-25 Daimlerchrysler Ag PTC thermistor and a current limiter device having at least one PTC thermistor
GB2397237A (en) * 2003-01-18 2004-07-21 Draeger Medical Ag Heated incubator hood and incubator temperature control
US20050281547A1 (en) * 2004-06-16 2005-12-22 Yvan Sauvageau Surface heating system
US20110064394A1 (en) * 2009-09-11 2011-03-17 Elkamet Kunststofftechnik Gmbh Heatable liquid container made from plastic material and production method therefor

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0001542A1 (en) * 1977-09-27 1979-04-18 Jules Eeckhout Method for the temperature control of a bimetallic heating element serving as a thermocouple between the terminals of the electric heating current, and electric apparatus utilizing this method
DE3063162D1 (en) * 1979-11-15 1983-06-16 Landis & Gyr Ag Control device for an oil burner with an oil preheating device
US5058197A (en) * 1990-04-02 1991-10-15 Emerson Electric Co. Heater apparatus for fluid medium in a hermetically sealed chamber

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4421744Y1 (en) * 1965-06-14 1969-09-13

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4007684A (en) * 1973-09-26 1977-02-15 Nippon Telegraph And Telephone Public Corporation Ink liquid warmer for ink jet system printer
US3885129A (en) * 1974-02-28 1975-05-20 Sprague Electric Co Positive temperature coefficient resistor heater
US4068115A (en) * 1974-05-09 1978-01-10 Sweetheart Plastics, Inc. Food serving tray
US4147927A (en) * 1975-04-07 1979-04-03 U.S. Philips Corporation Self-regulating heating element
US4029941A (en) * 1975-10-20 1977-06-14 Gould Inc. Electric heater assembly
US4086467A (en) * 1976-07-19 1978-04-25 Texas Instruments Incorporated Electronic heater for high voltage applications
US4141327A (en) * 1976-09-09 1979-02-27 Texas Instruments Incorporated Early fuel evaporation carburetion system
US4210800A (en) * 1977-02-21 1980-07-01 U.S. Philips Corporation Heating element comprising a PTC-resistor body
US4177375A (en) * 1977-09-29 1979-12-04 Siemens Aktiengesellschaft Heating device having an optimized heating element of PTC thermistor material
FR2417234A1 (en) * 1978-02-14 1979-09-07 Siemens Ag immersion
US4230935A (en) * 1978-02-14 1980-10-28 Siemens Aktiengesellschaft Immersion heater
US4394646A (en) * 1979-10-31 1983-07-19 Goessler Gerhard Temperature indicator for a glass ceramic cooking surface
US4336444A (en) * 1980-01-14 1982-06-22 Gust, Irish, Jeffers & Hoffman Apparatus and method for converting electrical energy into heat energy
US4459466A (en) * 1980-11-26 1984-07-10 Nippon Soken, Inc. Dual air passage heating apparatus with ceramic heater element
US4387291A (en) * 1980-11-28 1983-06-07 Texas Instruments Incorporated Fuel heater system and self-regulating heater therefor
US4639818A (en) * 1985-09-17 1987-01-27 Raychem Corporation Vent hole assembly
US4797534A (en) * 1987-06-08 1989-01-10 Gte Products Corporation PTC thermistor heating device
US5073699A (en) * 1988-02-05 1991-12-17 V. Dardanella Austin Device for warming food and beverage containers having support plate and perimeter skirt structure
US5025133A (en) * 1989-04-04 1991-06-18 Mitsubishi Denki Kabushiki Kaisha Semiconductor wafer heating device
US6094129A (en) * 1994-11-19 2000-07-25 Daimlerchrysler Ag PTC thermistor and a current limiter device having at least one PTC thermistor
GB2397237A (en) * 2003-01-18 2004-07-21 Draeger Medical Ag Heated incubator hood and incubator temperature control
GB2397237B (en) * 2003-01-18 2005-03-09 Draeger Medical Ag Method for regulating the temperature of an incubator hood
US20050281547A1 (en) * 2004-06-16 2005-12-22 Yvan Sauvageau Surface heating system
US7187854B2 (en) * 2004-06-16 2007-03-06 Yvan Sauvageau Heating tiles
US20110064394A1 (en) * 2009-09-11 2011-03-17 Elkamet Kunststofftechnik Gmbh Heatable liquid container made from plastic material and production method therefor
US8768153B2 (en) * 2009-09-11 2014-07-01 Elkamet Kunstsofftechnik GmbH Heatable liquid container made from plastic material and production method therefor

Also Published As

Publication number Publication date
FR2104247A5 (en) 1972-04-14
CA936576A1 (en)
NL7111206A (en) 1972-02-16
GB1306907A (en) 1973-02-14
ES393611A1 (en) 1973-08-16
BR7105227D0 (en) 1973-04-17
DK129070B (en) 1974-08-12
CH526247A (en) 1972-07-31
DE2040523A1 (en) 1972-02-17
JPS52142251U (en) 1977-10-28
NO133296C (en) 1976-04-07
DE2040523B2 (en) 1973-03-01
NO133296B (en) 1975-12-29
CA936576A (en) 1973-11-06
DE2040523C3 (en) 1973-09-20

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