EP0848576A2 - Elektrischer Heizvorrichtung - Google Patents

Elektrischer Heizvorrichtung Download PDF

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Publication number
EP0848576A2
EP0848576A2 EP97309917A EP97309917A EP0848576A2 EP 0848576 A2 EP0848576 A2 EP 0848576A2 EP 97309917 A EP97309917 A EP 97309917A EP 97309917 A EP97309917 A EP 97309917A EP 0848576 A2 EP0848576 A2 EP 0848576A2
Authority
EP
European Patent Office
Prior art keywords
heating element
diffusion layer
heat diffusion
heating
base plate
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.)
Withdrawn
Application number
EP97309917A
Other languages
English (en)
French (fr)
Other versions
EP0848576A3 (de
Inventor
Michael Chorlton
Andrew Hunt
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.)
Sheathed Heating Elements Ltd
Original Assignee
Sheathed Heating Elements Ltd
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 Sheathed Heating Elements Ltd filed Critical Sheathed Heating Elements Ltd
Publication of EP0848576A2 publication Critical patent/EP0848576A2/de
Publication of EP0848576A3 publication Critical patent/EP0848576A3/de
Withdrawn legal-status Critical Current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
    • H05B3/78—Heating arrangements specially adapted for immersion heating
    • H05B3/82—Fixedly-mounted immersion 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
    • H05B3/00—Ohmic-resistance heating
    • H05B3/40—Heating elements having the shape of rods or tubes
    • H05B3/42—Heating elements having the shape of rods or tubes non-flexible
    • H05B3/48—Heating elements having the shape of rods or tubes non-flexible heating conductor embedded in insulating material
    • H05B3/50—Heating elements having the shape of rods or tubes non-flexible heating conductor embedded in insulating material heating conductor arranged in metal tubes, the radiating surface having heat-conducting fins

Definitions

  • the present invention relates to an electric heating device.
  • One such device which is mounted in the base of the water chamber in an electric kettle, includes a pair of aluminium plates with an electric heating element crimped between them, the electric heating element comprising a resistance heating wire surrounded by and electrically insulated from a stainless steel sheath.
  • the electric heating element comprising a resistance heating wire surrounded by and electrically insulated from a stainless steel sheath.
  • Another previously known kettle element assembly ameliorates these problems and comprises an aluminium plate, one side of which is brazed to an aluminium sheathed electric heating element.
  • the opposite side of the plate is brazed to a second plate of stainless steel, which provides the surface that contacts the medium to be heated (normally water) within the kettle.
  • the thermal conductivity of aluminium is, however, low compared with that of certain other metals, resulting in a relatively localised, inefficient heating of the water in the kettle and difficulties in efficiently controlling the kettle element assembly by way of a temperature sensitive electrical cut-out mounted on the aluminium plate.
  • the present invention seeks to overcome these disadvantages by providing a more efficient pathway of thermal conduction between the heating element and the steel plate, and preferably also a better compatibility of the materials of the contact surfaces via which the heating element is mounted in the device.
  • the present invention provides a heating device comprising a heating element including a resistance heating wire surrounded by and electrically insulated from a metal sheath, the heating element being carried directly or indirectly on a metal base plate for transferring heat from the heating element to a medium to be heated by the device, wherein the heating element is in thermally conductive communication with the base plate via a heat diffusion layer, wherein the heat diffusion layer is of a metal comprising copper.
  • the base plate is of ferrous metal, e.g. stainless steel.
  • the invention encompasses devices in which the heat diffusion layer is preferably made of copper per se or alternatively may be made of an alloy or mixture of copper with one or more other suitable components. Such other suitable components may be selected for example from zinc, phosphorus, nickel or chromium. An example of a copper alloy that may be used as the heat diffusion layer is brass.
  • the invention further encompasses devices in which the heat diffusion layer is made of a laminate including at least one layer which is of copper or a copper alloy.
  • Copper which is used according to the invention as or in the heating diffusing layer, has a significantly higher thermal conductivity than aluminium, resulting in several advantages over the previously known devices. Firstly, the transfer of thermal energy from the heating element to the base plate is faster and less localised, resulting in faster, more efficient energy transfer to the medium to be heated. Secondly, the better distribution of thermal energy away from the element extends the lifetime of the element, and means that it may be better protected from burn-out on occasions when the vessel in which the device is incorporated is empty. Protection against the latter is typically afforded by a temperature sensitive electrical cut-out, which may be mounted on the base plate, or on the heat diffusion layer or on the heating element itself. The degree of protection is enhanced due to the increased rate of heat transfer from the element to the electrical cut-out, which is a function of the relationship between thermal mass and thermal conductivity of the material of the heat diffusion layer. The optimum relationship is found with copper and its alloys.
  • the heat diffusion layer and the sheath of the heating element are of the same material or at least are of different metals having relative standard electrode potentials such that galvanic corrosion is eliminated or minimised, especially in heating devices in which the heat diffusion layer and the sheath of the element are in direct contact.
  • This same relationship may also apply to the heat diffusion layer and the base plate, and/or also to the sheath of the heating element and the base plate, where those respective pairs of components are in contact.
  • Such corrosion may be a problem when the device is located in a humid environment such as often occurs within the casing of an electric kettle.
  • the metal or metals used in the heat diffusion layer have substantially the same or closely similar coefficient of expansion to the metal of the base plate, such that bending or other deformation of the device is prevented as its temperature changes.
  • copper used according to the invention as or in the heat diffusion layer, having an advantageously high thermal conductivity
  • copper is also particularly advantageous over aluminium of the prior art in that it is a better material for attaching a heating element by brazing, since heating elements are commonly sheathed in copper. The attachment of such a heating element to the heat diffusion layer may thus be even further facilitated, and a simple solder connection may suffice instead of brazing or welding as in the prior art.
  • the heat diffusion layer and the base plate constitute the two layers of a bimetallic plate.
  • the base plate of the device may have any suitable shape, depending for instance on the shape or configuration of the heating element itself and the practical application for which the device is intended for use, e.g. depending on the shape of the base of a heating appliance in which the device is to be mounted.
  • the heating element may be configured and arranged on the device so as to follow the line of an arc of a circle or so as to be coiled or otherwise of a convoluted shape.
  • the element is generally circular (i.e. toroidal), with the terminal portions of the element lying out of register with one another and overlapping one another by a short distance, e.g. by a few percent (e.g. 1 to 10 or 15%) of the total length of the element, such as by about 1 to 5 cm in a typical practical example.
  • This particular arrangement of the element allows a greater length of element to be carried on a base plate of a given size and hence results in the element having a decreased watts density and a longer lifetime.
  • the means of attachment of any one of the heat diffusion layer, the heating element and the metal base plate to one or more other of those components may be selected from any suitable means of attachment known in the art, eg. brazing, welding, soldering, glueing, cementing, metal spraying, or even mechanical attachment by a simple pressure connection, eg. crimping. In certain instances a unitary connection between components may not be necessary and a simple surface to surface contact may suffice.
  • an underside of the heating element contacts, or is directly attached to, eg. by brazing, the metal base plate.
  • the heat diffusion layer which is preferably brazed to the base plate is shaped so as to wholly or partially overlie the element, with the contacting surfaces optionally being bonded such as by brazing.
  • the heating element is attached, e.g. by brazing or soldering, to the heat diffusion layer which is in turn attached, eg. by brazing, to the base plate.
  • the present invention provides a heating vessel or appliance including a heating device according to the first aspect of the invention.
  • one exemplary heating device of the invention which in practice is mounted in the base of the water chamber of an electric kettle, includes a stainless steel base plate (1), substantially covered by and brazed to a copper heat diffusion layer (2), onto which a copper sheathed electric heating element (3) is soldered.
  • the stainless steel base plate (1) is shaped so as to be cooperative with the shape of the casing of the kettle in the region in which the device is mounted.
  • the heating element (3) comprises a coiled resistance heating wire (4) surrounded by a copper sheath (5).
  • the ends of the resistance heating wire (4) are connected to metal pins (7) which project from the end of the sheath and serve to make the electrical connections to the resistance wire (4).
  • Both the wire (4) and the pins (7) are electrically insulated from the surrounding sheath (5) by a layer of magnesium oxide (6).
  • a plug (8) located at each end of the element (3) holds the pins (7) in position and seals the magnesium oxide (6) inside the sheath (8).
  • the heat diffusion layer of copper (2) provides for a faster, and less localised transfer of thermal energy from the element (3) to the water in the kettle when compared to a heating device in which the heat diffusion layer is absent and the only thermally conductive pathway between the element and the water in the kettle is via a base plate made entirely of stainless steel, or is a stainless steel plate brazed to an aluminium plate: stainless steel and aluminium both have lower thermal conductivities than copper.
  • the enhanced transfer of thermal energy from the element (3) via the copper heat diffusion layer (2) also extends the lifetime of the element (3).
  • a temperature sensitive electrical cut-out may be mounted on the copper heat diffusion layer (3), for example at position (9) in Figure 1.
  • the means for mounting the electrical cut-out on the heat diffusion layer may for example comprise a U-shaped slot cut into the heat diffusion layer, the portion of the heat diffusion layer surrounded by the slot being folded along a line between the ends of the slot so as to project away from the base plate.
  • the electrical cut-out may then be mounted on this upstanding projection of the heat diffusion layer.
  • the means for mounting the electrical cut-out on the heating device may comprise a rivet. The head of the rivet is mounted on the metal base plate and the rivet projects through a circular aperture in the heat diffusion layer. The electrical cut-out may then be mounted on the rivet.
  • the rapid heat transfer from the element (3) to the cut-out via the copper heat diffusion layer (2) ensures that the element (3) is better protected from burn-out on the occasions when the kettle is operated empty, than if the heat diffusion layer (2) were absent.
  • a heating element (3) of similar construction to that in the first embodiment of Figure 1 is brazed directly to a stainless steel base plate (1).
  • a copper heat diffusion layer (2), a portion of which is brazed to the base plate (1), is shaped so as to lose contact with the base plate (1) in the vicinity of the heating element (3) and to make contact with the sheath (5) of the element (3), thereby establishing a thermally conductive pathway from the heating element (3) to remote parts of the steel base plate (1).
  • a heating element (3) again of similar construction to that in the first embodiment of Figure 1 is brazed directly to a stainless steel base plate (1).
  • a copper heat diffusion layer (2) brazed to the base plate (1) is shaped so as to lose contact with the base plate (1) in the vicinity of the heating element (3), to make contact with the sheath (5) of the heating element (3), and to maintain this contact as it bends over the element (3).
  • the contact between the element (3) and the copper heat diffusion layer (2) is lost on the other side of the element (3) where the copper heat diffusion layer (2) again lies against and is brazed to the stainless steel base plate (1).
  • the heating element (3) thus becomes encased in the copper heat diffusion layer (2), and an efficient indirect thermal conductive pathway from the element (3) to the base plate (1) is once again established.
  • Figure 5 shows a preferred conformation for the heating element (3) in which the element is generally circular (i.e. toroidal) with the thermal portions of the element overlapping.
  • This configuration allows a greater length of element to be accommodated on a base plate of a given size and hence results in the element having a decreased watts density and an increased lifetime.
  • This preferred conformation of the element may be used in any of the embodiments of the invention previously described and shown in Figures 1 to 4.

Landscapes

  • Cookers (AREA)
  • Surface Heating Bodies (AREA)
EP97309917A 1996-12-09 1997-12-09 Elektrischer Heizvorrichtung Withdrawn EP0848576A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9625507 1996-12-09
GBGB9625507.0A GB9625507D0 (en) 1996-12-09 1996-12-09 Electric heating device

Publications (2)

Publication Number Publication Date
EP0848576A2 true EP0848576A2 (de) 1998-06-17
EP0848576A3 EP0848576A3 (de) 1998-11-25

Family

ID=10804138

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97309917A Withdrawn EP0848576A3 (de) 1996-12-09 1997-12-09 Elektrischer Heizvorrichtung

Country Status (2)

Country Link
EP (1) EP0848576A3 (de)
GB (1) GB9625507D0 (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2876535A1 (fr) * 2004-10-13 2006-04-14 Seb Sa Element chauffant
CN104080213A (zh) * 2013-03-29 2014-10-01 宁波吉毅电器有限公司 一种铝板式快速散热电加热器
CN104797020A (zh) * 2015-02-12 2015-07-22 厦门华业新电热电器有限公司 用于空调及送风型电加热领域的螺旋翅片管
CN105455654A (zh) * 2015-06-10 2016-04-06 高要市金田电热有限公司 一种咖啡机用双通铝管加热器装置
US20160109152A1 (en) * 2014-10-21 2016-04-21 Bleckmann Gmbh & Co. Kg Heating system component and method for producing same

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1503896A (fr) * 1966-10-18 1967-12-01 Thomson Houston Comp Francaise Perfectionnements aux plaques chauffantes et procédés de réalisation
CH658356A5 (de) * 1982-12-08 1986-10-31 Jura Elektroapparate Fab Heizvorrichtung und verfahren zur herstellung derselben.
DE3718836A1 (de) * 1987-06-05 1989-01-12 Ego Elektro Blanc & Fischer Heizvorrichtung mit einem elektrischen heizkoerper
DE3830327A1 (de) * 1988-09-07 1990-03-15 Dieter Schanuel Elektrisch beheizbarer behaelter, wie friteuse, und verfahren zu seiner herstellung
FR2708407B1 (fr) * 1993-07-26 1995-09-08 Seb Sa Bouilloire électrique comportant un moyen de chauffe simplifié.

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2876535A1 (fr) * 2004-10-13 2006-04-14 Seb Sa Element chauffant
WO2006040476A1 (fr) * 2004-10-13 2006-04-20 Seb S.A. Element chauffant, notamment destine aux bouilloires
CN104080213A (zh) * 2013-03-29 2014-10-01 宁波吉毅电器有限公司 一种铝板式快速散热电加热器
US20160109152A1 (en) * 2014-10-21 2016-04-21 Bleckmann Gmbh & Co. Kg Heating system component and method for producing same
CN105526702A (zh) * 2014-10-21 2016-04-27 布莱克曼两合公司 加热系统组件及其制造方法
EP3013116A1 (de) * 2014-10-21 2016-04-27 Bleckmann GmbH & Co. KG Heizungssystemkomponente und Verfahren zur Herstellung davon
EP3013117A1 (de) * 2014-10-21 2016-04-27 Bleckmann GmbH & Co. KG Heizungssystemkomponente und verfahren zur herstellung davon
KR20160046741A (ko) * 2014-10-21 2016-04-29 블랙만 게엠베하 코. 카게 가열 시스템 구성 요소 및 이의 제조 방법
US10941962B2 (en) 2014-10-21 2021-03-09 Bleckmann Gmbh & Co. Kg Heating system component and method for producing same
CN104797020A (zh) * 2015-02-12 2015-07-22 厦门华业新电热电器有限公司 用于空调及送风型电加热领域的螺旋翅片管
CN105455654A (zh) * 2015-06-10 2016-04-06 高要市金田电热有限公司 一种咖啡机用双通铝管加热器装置

Also Published As

Publication number Publication date
GB9625507D0 (en) 1997-01-29
EP0848576A3 (de) 1998-11-25

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