EP1177708A1 - Improvements relating to heating elements, particularly in the field of thick film heatiing elements - Google Patents

Improvements relating to heating elements, particularly in the field of thick film heatiing elements

Info

Publication number
EP1177708A1
EP1177708A1 EP00927490A EP00927490A EP1177708A1 EP 1177708 A1 EP1177708 A1 EP 1177708A1 EP 00927490 A EP00927490 A EP 00927490A EP 00927490 A EP00927490 A EP 00927490A EP 1177708 A1 EP1177708 A1 EP 1177708A1
Authority
EP
European Patent Office
Prior art keywords
heating element
thick film
vessel
element assembly
assembly
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
EP00927490A
Other languages
German (de)
French (fr)
Other versions
EP1177708B1 (en
EP1177708B2 (en
Inventor
Robert Andrew O'neill
Robin Keith Moore
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.)
Otter Controls Ltd
Original Assignee
Otter Controls 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
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Application filed by Otter Controls Ltd filed Critical Otter Controls Ltd
Priority to DE60024253T priority Critical patent/DE60024253T3/en
Publication of EP1177708A1 publication Critical patent/EP1177708A1/en
Publication of EP1177708B1 publication Critical patent/EP1177708B1/en
Application granted granted Critical
Publication of EP1177708B2 publication Critical patent/EP1177708B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

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
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
    • H05B3/26—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base
    • H05B3/262—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base the insulating base being an insulated metal plate
    • 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
    • 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

Definitions

  • This invention concerns improvements relating to electric heating
  • thick film type comprising a substrate, commonly formed of stainless steel,
  • the substrate may be formed on an electrically-insulating
  • electrically-insulating layer may be provided over the resistance heating track
  • Thick film heating elements are employed in
  • immersion heating element of metal sheathed construction has aesthetic
  • a further layer of glass may then be provided over the
  • the domed thick film heating element onto the planar surface.
  • the joining process may be the same as or similar to any of the
  • Blitzkocher type elements i.e. impact pressure bonding, welding or brazing
  • dispersion layer to the vessel may be done first, for example by impact
  • the heating element may be induction brazed separately, giving the opportunity of inspecting the quality of the vessel/dispersion layer joint.
  • Vents could be left in the part of the dispersion layer which extends beyond
  • the heating element to allow the escape of flux and fumes generated during
  • the assembly is desirably pressed
  • Figure 1 is a schematic side elevation view of a thick film heating
  • FIGS. 2 A and 2B show alternative constructions of the peripheral
  • Figure 3 is a plan elevation view of the thick film heating element of
  • the illustrated embodiment comprises a thick film heating element 1
  • Figures 2A and 2B are, respectively, intended to provide a
  • the dispersion layer will spread the
  • heating element of an effective diameter of 80mm.
  • the heater track power density is
  • the heater can be reduced still further
  • a disc of 77mm diameter has half the area of one of 110mm,
  • the thin substrate becomes possible because of the support
  • the vessel wall which is preferably formed of a 300 series
  • the heating surface is not more than that of a conventionally made thick
  • the complete heating element sandwich can be made as an "Easifix"
  • plastic securing ring as was developed for the Millennium kettle. Examples of
  • hotplate element which may have a raised heating surface surrounded by a
  • the diameter of the element four times as many may be printed and processed
  • the small diameter element has an additional operational advantage
  • the dispersion layer will ensure that, as liquid boils away, the exposed area of
  • the heater is cooled to some extent by the remaining liquid until a protector
  • any thermal protector will tend to cover a larger
  • sheathed heating element is secured to a heat transfer plate which in turn is
  • thermal conductivity of the ceramic substrate and are only suitable for low

Landscapes

  • Cookers (AREA)
  • Resistance Heating (AREA)

Abstract

A thick film heating element for a water boiling vessel is secured to the bottom of the vessel with a heat dispersion layer of copper or aluminium between the vessel bottom and the thick film heating element and extending laterally beyond the edges of the thick film heating element. The thick film heating element is about half the size of a conventional thick film heating element (about 60mm as compared to 110mm) with a corresponding cost reduction, and has at least twice as high a power density (60W/cm<SP>2</SP> as compared to 30W/cm<SP>2</SP>) and yet does not generate excessive noise in operation.

Description

IMPROVEMENTS RELATING TO HEATING ELEMENTS, PARTICULARLY IN THE FIELD OF THICK FILM HEATING
ELEMENTS
Field of the Invention:
This invention concerns improvements relating to electric heating
elements and, more particularly, concerns heating elements of the so-called
thick film type comprising a substrate, commonly formed of stainless steel,
carrying a resistance heating track or layer which, as appropriate having regard
to the nature of the substrate, may be formed on an electrically-insulating
layer, commonly of glass, provided on the substrate. An additional
electrically-insulating layer may be provided over the resistance heating track
or layer as a protective measure. Thick film heating elements are employed in
a variety of applications and are currently becoming popular in the field of
electrically-heated water boiling vessels, domestic kettles and hot water jugs
for example, where their clean appearance as compared to the conventional
immersion heating element of metal sheathed construction has aesthetic
advantages. In addition it is possible with a thick film heating element to
accommodate a greater power density than is readily accommodated with
conventional sheathed heating elements, leading to more rapid boiling times.
Background of the Invention:
As mentioned above, thick film heating elements are commonly
formed on a stainless steel substrate, for example by first providing an
electrically-insulating layer of glass on one or both surfaces of a stainless steel plate or disc and then screen-printing a resistance heating track onto the glass
surface using electrically conductive inks which are then fired. As
abovementioned, a further layer of glass may then be provided over the
resistive track. It is known that the manufacture of thick film heating
elements by this process can give rise to problems of distortion of the heating
element out of its normal planar configuration and that distortions can arise
furthermore in use of the heating element on account of differential thermal
expansion effects. In order to at least alleviate these problems, it has been
proposed to select the materials deposited onto the stainless steel substrate to
have compatible thermal expansion coefficients insofar as is possible and it
has been proposed furthermore to provide layers on both sides of the stainless
steel substrate so as to subject it to similar thermal expansion and contraction
effects from both sides. All of these solutions give rise to cost implications
which, when added to the basic cost of appropriate quality stainless steel
substrates as are required for water boiling vessels, tend to render the product
unattractive on considerations of cost irrespective of its other clear
advantages.
To overcome or at least substantially reduce the distortion problem
abovementioned, the invention of our British Patent Application No.
9908918.7 proposed to form the substrate of a thick film heating element with
a slightly domed curvature, form the heating element track or layer on the
convex surface of the domed substrate, and bond the thus formed thick film heating element to a planar surface to be heated by a process which flattens
the domed thick film heating element onto the planar surface.
Whilst the invention of our British Patent Application No. 9908918.7
promises to overcome the distortion problem, there are a number of other
problems in the manufacture and use of thick film heating elements which
tend to limit their wider adoption, namely:
(i) The materials used are relatively expensive. Anything that can
be done to reduce material content is desirable. This includes a
reduction in thickness of the substrate, and a reduction in size
of the substrate and printed area.
(ii) The usable power density is limited by the noise generated by
such heaters during heating water. The noise principally arises
from local formation of steam bubbles, which rapidly collapse,
because the power density is too high to allow convection
currents to become established close to the element surface,
and especially directly opposite the location of the heater track.
(iii) The limiting power density leads to heaters that are of relatively
large area, leading not only to increased costs but also to an
inability to operate on more than a very small angle of slope. To overcome this problem it has been conventional to employ
costly solutions of multiple protectors or electronics.
(iv) At present the only steel substrate which is successfully used is
400 series stainless steels. These materials have poor
resistance to corrosion and give a low quality cosmetic surface.
To overcome this various coatings have been proposed, which
increases the cost and raises the running temperature of the
heater tracks.
(v) In order to withstand thermal and mechanical shock arising
from abuse of the appliance, it has normally been necessary to
employ relatively thick steel substrates, which increases costs.
(vi) The screen printing techniques presently employed can only be
applied to flat surfaces, with no rims or other projections above
the printing surface. This limits the applications which can
make use of such elements.
(vii) To overcome the limitations of the flat printing process it might
be possible to fabricate the plate into a separate vessel.
However the materials from which such vessels are commonly made (typically 300 series stainless steel) are not sufficiently
compatible to allow straightforward and inexpensive direct
assembly and joining.
Summary of the Invention
To overcome or at least substantially reduce these problems we
propose to use a relatively small heater mounted to a larger vessel, with a
layer of material of relatively high thermal conductivity between the steel
substrate of the heater and the material of the vessel to act to spread the heat
from the heater over a wider area of the liquid heating surface.
Any material may be used for the intermediate heat dispersion layer,
provided it has a thermal conductivity significantly greater than the stainless
steels used, i.e. about 20W/sqM/°C. Preferred materials are copper and
aluminium, chosen for their thermal conductivity, relatively low cost and
compatibility with the proposed assembly processes.
The joining process may be the same as or similar to any of the
existing known methods of attaching aluminium mounting plates as for
Blitzkocher type elements, i.e. impact pressure bonding, welding or brazing,
with any of the known sources of heat. However the preferred method,
because of its controllability, is induction brazing. This technique claims to
give a good quality, repeatable, joint with few voids. The join of the heat
dispersion layer to the vessel may be done first, for example by impact
bonding, and the heating element may be induction brazed separately, giving the opportunity of inspecting the quality of the vessel/dispersion layer joint.
Vents could be left in the part of the dispersion layer which extends beyond
the heating element to allow the escape of flux and fumes generated during
brazing. During the brazing process, the assembly is desirably pressed
together with a clamping force, possibly as much as 4 tons, to ensure that the
plates are flattened together without any gaps in the joint area. This clamping
force enables the invention of our British Patent Application No. 9908918.7 to
be utilized in the practice of the present invention.
The above and further features of the present invention are set forth in
the appended claims and will be explained in the following by reference to an
exemplary embodiment which is illustrated in the accompanying drawings.
Description of the Drawings:
Figure 1 is a schematic side elevation view of a thick film heating
element embodying the present invention;
Figures 2 A and 2B show alternative constructions of the peripheral
edge of the thick film heating element of Figure 1 ; and
Figure 3 is a plan elevation view of the thick film heating element of
Figure 1.
Detailed Description of the Embodiment:
The illustrated embodiment comprises a thick film heating element 1
of relatively small diameter which is bonded to a heat dispersion plate 2,
formed of aluminium or copper for example and having a diameter greater than that of the thick film heating element 1, which in turn is bonded to a
heating surface 3 shown in the example as a thin metal plate adapted to be
fitted into the bottom of a water heating appliance, the alternative edge details
shown in Figures 2A and 2B are, respectively, intended to provide a
water-retaining well around the heating element periphery to facilitate sealing
of the element into a vessel body by providing a cooler sealing environment
and to facilitate interfacing with the vessel body; other edge configurations are
of course possible.
It is conventionally considered that a thick film heating element having
a power density of more than 30W/cm" will give rise to unacceptable noise.
This equates to an overall power output of about 3kW on an element formed
on a 120mm diameter disc with a plain sealing area left all round. It is
proposed according to the teachings of the present invention to use a
significantly higher power density heating element formed on a disc of around
60mm, for example. It is proposed that the dispersion layer will spread the
heat over an area extending about 10mm beyond the disc, thus giving a
heating element of an effective diameter of 80mm. Bearing in mind that the
material costs of a thick film heating element are proportion to its area
(thickness being constant), a conventional 80mm diameter element would use
78% more material than one of 60mm diameter constructed according to the
present invention, which represents a significant saving. There are, of course, approximations in the above, since the power
density of the embodiment will fall rapidly outside the disc region 1, and will
tend to be concentrated towards the centre. However, examination of a
conventional thick film heater on a stainless steel substrate shows that the heat
is not spread evenly over the surface, but is closely concentrated directly
above the tracks with little heating occurring between the tracks. The true
power density is much greater than simply dividing the power by the disc area
would suggest. It is believed that this is the cause of the excessive noise
generation. This effect is caused by the low thermal conductivity of the
stainless steel substrate, which forces the heat to flow perpendicularly to the
plane of the heater, through the thickness, and significantly limits lateral heat
flow. By the addition of the dispersion layer taught by the present invention,
heat can flow laterally as well as transversely, so that a more uniform heat
distribution is obtained on the liquid heating surface. Thus the power density
on the liquid heating surface is close to the calculated value of the power
divided by the surface area, rather than to the value of the power divided by
the (much smaller) heater track area. The result is a lower effective power
density and a significant reduction in noise generated.
As an example of the improvements that can be made, the following
values are taken from present production elements. For a conventional
element of around 110mm diameter, the heater track power density is
68W/cm2. Thus, if the dispersion layer is fully effective, the area of the heater could be reduced to less than half, whilst maintaining the same power density
on the liquid heating surface. By adding the further gain in surface area
around the periphery of the heater disc, the heater can be reduced still further
in size. The net result of this is a major reduction in the cost of the materials
of the element. A disc of 77mm diameter has half the area of one of 110mm,
and taking into account the dispersion layer, this gives an element diameter of
approximately 60mm, the value used in the example above. Thus
theoretically it should be possible, with an element of only 60mm diameter, to
achieve approximately the same power density at the liquid heating surface as
is presently achieved with a conventional 110mm diameter element. This is a
reduction to just over one third of the area. The material cost of the element
makes up over 80% of the total element cost, when fully automated. We
believe that the track power density can be still further increased to in excess
of lOOW/cm , leading to still further cost reduction. In the end the limit is
likely to be caused by the loss of area caused by the need to make electrical
connections, with their associated creepage and clearances, and by the area
needed to accommodate any necessary element protector controls as
schematically shown in Figure 3.
This significant reduction in area may be accompanied by a similar
reduction in substrate thickness. At present, substrates of between 1.2 and
1.5mm are used to achieve satisfactory mechanical rigidity and resistance to
thermal and mechanical shock. We propose to reduce the substrate thickness, for example to 0.3mm, to allow the use of high power density without a
penalty in increased track running temperatures. We anticipate that the
improved heat transfer efficiency afforded by the dispersion layer will reduce
the track running temperature to acceptable values, but this will only be
possible by reducing the thermal resistance of the whole sandwich to values
similar to those at present, taking into account the narrow thermal path of the
present designs. The thin substrate becomes possible because of the support
and cushioning of the dispersion layer, further supported by the water treating
plate and/or vessel wall. Thus the complete assembly will be able to
withstand mechanical impact and thermal shock better than an element with a
unitary substrate of the present thickness. To further improve the heat transfer
we propose that the vessel wall, which is preferably formed of a 300 series
stainless steel commonly used in stainless steel cooking vessels like
saucepans, is also reduced to around 0.3mm. This compares with 0.5mm
normally found in stainless steel kettles. The arrangement of the sandwich is
preferably such that the thermal resistance between the printed heater tracks
and the heating surface is not more than that of a conventionally made thick
film heating element on a 1.2mm substrate of 400 series (S430D or S444)
stainless steel, with a dielectric thickness of no more than lOOμ.
The complete heating element sandwich can be made as an "Easifix"
(GB 2330064A) type element or as a Strix "Sure Seal" (WO 96/18331) for
fitting to a moulded vessel, or it may be made directly onto the base of a stainless steel vessel. This latter is a very cost effective method of fitting a
thick film heater to a stainless steel appliance, something that, so far as we are
aware, has only been done by Pifco - Russell Hobbs by using the same (costly)
plastic securing ring as was developed for the Millennium kettle. Examples of
such mountings are in Pifco's GB 2 291 324 and GB 2 319 154 which show
the complexity of the method. It is possible to attach the small thick film
element 1 into a depression, which would otherwise prevent screen printing,
and this gives further advantages in that it allows a well to be formed around
the periphery of the element to retain some water in the event of boiling dry,
which will give protection to any adjacent seals or cosmetic mouldings. Such
protection is given at present by providing an area free of heating element
track around the element periphery, which increases the diameter and hence
the cost of the heating element. An example of such a well is shown in
Sunbeam, CA 1 202 659, applied to a mechanical embedded element. The
ability to attach the element within a depression will allow a thick film printed
element to be used where previously it was not possible. An example is a
hotplate element which may have a raised heating surface surrounded by a
mounting flange, so that the heating surface is above the general level of the
top of the appliance.
A further advantage of the small element proposed by the present
invention, which gives rise to savings in the manufacturing cost of the
elements, is that they may be processed several at a time. The number of elements which can be printed simultaneously is limited by the area of the
screen printer and by the width of the processing ovens. Clearly, by halving
the diameter of the element, four times as many may be printed and processed
together on the same equipment. Depending on the type of equipment used,
this may be achieved by carrying the elements in a strip and separating them
on completion, or by automated handling, placing individual discs into
location jigs for printing and onto the oven belts for drying and firing. It is
believed that retaining the discs in a strip for processing will lead to reduced
distortion, as a result of the support of the strip. In any case, measures such as
this may be desirable to reduce the effects of distortion.
The small diameter element has an additional operational advantage,
in that it is less sensitive to being operated on a slope whilst heating liquids.
The dispersion layer will ensure that, as liquid boils away, the exposed area of
the heater is cooled to some extent by the remaining liquid until a protector
can operate. In addition, any thermal protector will tend to cover a larger
proportion of the heating element and give protection over a wider area.
The proposal of the invention may be considered to be similar in
principle to the Blitzkocher type of heating element construction, where a
sheathed heating element is secured to a heat transfer plate which in turn is
secured to a steel plate which is part of a liquid heating vessel. However the
power density available from a sheathed heating element is limited by the
insulation of the mineral filling of the sheath and by the robustness of the joint between the sheath and the heat dispersion mateπal. If the power density of a
Blitzkocher heating element is too great, the thermal expansion of the sheath
causes it to peel away from its support, leading to further overheating and
subsequent premature failure. We are also aware of thick film ceramic heaters
secured by conductive cement to the base of water heating vessels, such as the
Hywel egg boiler. Such arrangements are limited by the relatively poor
thermal conductivity of the ceramic substrate and are only suitable for low
power density applications.
While the invention has been described in the foregoing with
particular reference to water boiling vessels such as kettles and hot water jugs,
the invention is not limited to such applications and, in particular, could be
used in electric cooker hobs and hotplates for example.

Claims

Claims:
1. A heating element assembly comprising a heating element proper of
thick film construction secured to a surface to be heated with a heat dispersion
layer between the heating element proper and the surface to be heated, the heat
dispersion layer extending laterally beyond the periphery of the heating
element proper.
2. A heating element assembly as claimed in claim 1 wherein the heating
element proper comprises a substrate of stainless steel.
3. A heating element assembly as claimed in claim 2 wherein said
substrate has a thickness of less than 0.5mm.
4. A heating element assembly as claimed in any preceding claim
wherein said heat dispersion layer comprises copper or aluminium.
5. A heating element assembly as claimed in any of the preceding claims
wherein the power density of the thick film heating element, measured over its
total area, is substantially greater than 30W/cm .
6. A heating element assembly as claimed in claim 5 wherein the power
density if the thick film heating element, measured over its total area, is at
least 60W/cm2.
7. A heating element assembly as claimed in any of the preceding claims
wherein the area of the thick film heating element is of the order of one third
to one half of the area of the surface to be heated.
8. A heating element assembly as claimed in claim 7 wherein the surface
to be heated is a disc of diameter of around 100 or 110mm and the thick film
heating element is a disc of diameter around 60 to 80mm.
9. A heating element assembly as claimed in any of the preceding claims
wherein the heat dispersion layer extends at least 10mm beyond the periphery
of the thick film heating element.
10. A heating element assembly as claimed in any of the preceding claims
wherein the surface to be heated comprises a heater plate adapted to be
assembled into a plastic bodied liquid heating vessel.
11. A heating element assembly as claimed in claim 10 wherein the heater
plate is formed around its periphery with a well.
12 A heating element assembly as claimed in any of claims 1 to 9 wherein
the surface to be heated compπses the bottom of a liquid heating vessel
13 A heating element assembly as claimed in claim 12 wherein said liquid
heating vessel bottom is formed of stainless steel, preferably 300 seπes
stainless steel.
14 A heating element assembly as claimed in claim 13 wherein said
stainless steel has a thickness of less than 0 5mm, preferably 0 3mm.
15. A heating element assembly as claimed m any of claims 10 to 14
wherein the surface to be heated, viewed from the side to which the thick film
heating element is affixed, has a depression into which the thick film heating
element is affixed
16 A liquid heating vessel having a thick film heating element of such a
high power density that excessive noise generation would occur in operation
were it not for the provision of a heat dispersion layer between the thick film
heating element and the vessel to provide more uniform heat distπbution and
so avoid excessive noise generation
17. A liquid heating vessel having a bottom surface to which there is
attached a thick film heating element, the thick film heating element being
significantly smaller than said bottom surface (e.g. less than half the diameter
thereof) and a heat dispersion layer of high thermal conductivity material (e.g.
copper or aluminium) being interposed between the thick heating element and
said bottom surface, said heat dispersion layer being significantly larger than
the thick film heating element (e.g. approaching twice the diameter thereof).
18. A heater assembly comprising a thick film heating element constructed
so as in itself to provide an output having a predetermined power density (e.g.
greater than 60W/cm2) and, affixed thereto, a heat dispersion member of
greater surface area than the thick film heating element, the power density of
the overall assembly thereby being substantially less than that of the thick film
heating element itself (e.g. only about 30W/cm2).
19. A heating element assembly as claimed in any of claims 1 to 15 and 18
in or for a liquid heating vessel and wherein the thick film heating element is
located in a depression in the bottom of the vessel (as viewed from the outside
thereof).
20. A heating element assembly substantially as herein described with
reference to the accompanying drawings.
21. A liquid heating vessel including a heating element assembly as
claimed in any of claims 1 to 15, 18, 19 and 20.
EP00927490A 1999-05-04 2000-05-04 Improvements relating to heating elements, particularly in the field of thick film heatiing elements Expired - Lifetime EP1177708B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE60024253T DE60024253T3 (en) 1999-05-04 2000-05-04 IMPROVEMENTS FOR HEATING ELEMENTS, ESPECIALLY FOR THICK HEATING ELEMENTS

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9910286A GB2351894B (en) 1999-05-04 1999-05-04 Improvements relating to heating elements
GB9910286 1999-05-04
PCT/GB2000/001695 WO2000067527A1 (en) 1999-05-04 2000-05-04 Improvements relating to heating elements, particularly in the field of thick film heating elements

Publications (3)

Publication Number Publication Date
EP1177708A1 true EP1177708A1 (en) 2002-02-06
EP1177708B1 EP1177708B1 (en) 2005-11-23
EP1177708B2 EP1177708B2 (en) 2012-12-12

Family

ID=10852772

Family Applications (1)

Application Number Title Priority Date Filing Date
EP00927490A Expired - Lifetime EP1177708B2 (en) 1999-05-04 2000-05-04 Improvements relating to heating elements, particularly in the field of thick film heatiing elements

Country Status (6)

Country Link
EP (1) EP1177708B2 (en)
CN (1) CN1162044C (en)
AT (1) ATE311083T1 (en)
DE (1) DE60024253T3 (en)
GB (1) GB2351894B (en)
WO (1) WO2000067527A1 (en)

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GB2481217B (en) 2010-06-15 2017-06-07 Otter Controls Ltd Thick film heaters
TWI503903B (en) * 2011-10-26 2015-10-11 矽品精密工業股份有限公司 Heating equipment for a wiring machine
WO2015161120A1 (en) * 2014-04-16 2015-10-22 Spectrum Brands, Inc. Portable container system for heating a beverage
EP3132654A4 (en) 2014-04-16 2018-01-31 Spectrum Brands, Inc. Cooking appliance using thin-film heating element
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GB2351894B (en) 2003-10-15
CN1162044C (en) 2004-08-11
WO2000067527A1 (en) 2000-11-09
DE60024253D1 (en) 2005-12-29
ATE311083T1 (en) 2005-12-15
EP1177708B1 (en) 2005-11-23
GB9910286D0 (en) 1999-06-30
DE60024253T2 (en) 2006-08-24
GB2351894A (en) 2001-01-10
EP1177708B2 (en) 2012-12-12
CN1358402A (en) 2002-07-10
DE60024253T3 (en) 2013-05-29

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