EP0715483A2 - Elément de chauffage électrique - Google Patents

Elément de chauffage électrique Download PDF

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Publication number
EP0715483A2
EP0715483A2 EP95308639A EP95308639A EP0715483A2 EP 0715483 A2 EP0715483 A2 EP 0715483A2 EP 95308639 A EP95308639 A EP 95308639A EP 95308639 A EP95308639 A EP 95308639A EP 0715483 A2 EP0715483 A2 EP 0715483A2
Authority
EP
European Patent Office
Prior art keywords
heater
plate heater
track
vessel
overheating
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Withdrawn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
EP95308639A
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German (de)
English (en)
Other versions
EP0715483A3 (fr
Inventor
Dominic Michael Anthony Oughton
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.)
Strix Ltd
Original Assignee
Strix 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 Strix Ltd filed Critical Strix Ltd
Publication of EP0715483A2 publication Critical patent/EP0715483A2/fr
Publication of EP0715483A3 publication Critical patent/EP0715483A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/74—Switches in which only the opening movement or only the closing movement of a contact is effected by heating or cooling
    • H01H37/76—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material
    • H01H37/761—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material with a fusible element forming part of the switched circuit
    • 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

Definitions

  • This invention relates to electric heaters, and in particular, electric heaters for use in domestic appliances such as electric water heating vessels.
  • One very common type of domestic electric water heating vessel is the electric kettle or the more recent variant the electric water heating jug.
  • an immersion heater is located within a water receiving portion formed by the metal or plastics body of the vessel.
  • the heater has an element which is bent into a tortuous shape in order to provide sufficient length within the confines of the jug.
  • Each end of the element is attached to the heater head which is clamped in place through an opening in the side of the vessel, thereby securing the heater in position.
  • On the far side of the head are provided the so-called cold tails which are the electrical connections to the element.
  • an integrated control for example one of the type described in GB 2181598 is mounted directly to the back of the head by means of studs or screws.
  • control provides convenient electrical connection to the element and also contains apparatus to cut off the supply of current in the event that overheating occurs, for example as a result of the vessel being allowed to boil dry.
  • control may also have a steam operated switch which may be used to switch of the kettle or jug automatically when it boils.
  • Mounting the heater in this position also has the advantage that an integrated control may be provided in the base of the vessel. This allows for much greater flexibility in the design of the outward appearance of the vessel and also may simplify manufacture, particularly if it is desired to produce a vessel of the well known "cordless" type in which the vessel mates with a base unit.
  • An example of a control unit which provides these benefits is illustrated in co-pending patent application No. GB 9417243.4.
  • Plate heaters generally have a low thermal inertia as a result of the comparatively small mass of metal which they employ. This has the advantage that they heat up more quickly, but unfortunately it also has the side effect that if, for any reason, overheating occurs, for example as a result of a vessel boiling dry, the overheating may be particularly rapid and this may lead to difficulties in providing sufficiently fast-acting overheat protection devices.
  • overheat protection devices as a means of disconnecting the electrical supply from the heater of an electric water heating vessel in the event of its overheating.
  • this is provided by means of a Dry Switch On (DSO) thermal actuator (typically a bimetal) inside the control which is held against the heater head.
  • DSO Dry Switch On
  • the heater head is in thermal contact with a raised portion of the element called the hot return which ensures that the bimetallic actuator is triggered soon after the element starts to be uncovered.
  • DSO Dry Switch On
  • the heater will quickly reach its normal operating temperature, but in the event of serious overheating, its resistance will increase to the extent that its power output will reduce and thereby at least reduce the rate of overheating to a manageable level.
  • This arrangement is described in EP 0286217, for example.
  • Each of the resistive tracks of EP 0286217 is arranged in a tortuous path extending over much of the surface of the element, and only those regions of each track corresponding to the exposed part of the heater will experience a significant temperature rise. Consequently, only those regions of track will experience an increase in resistance. Unless the exposed part of the heater comprises a large part of its total surface area, the overall increase in resistance may be small compared to the total resistance of the tracks. Therefore there may be a relatively small effect on the total resistance of the tracks. Consequently, since the supply voltage will be constant, the current flowing through the heater tracks will not be significantly changed, and neither will the heat output from the major part of the heater.
  • an electric heater comprising a substrate and a plurality of discrete heater cells electrically interconnected in parallel and distributed about the surface of the substrate, each cell having an electrically resistive element with a positive temperature coefficient of resistance.
  • the value of the PTC be at least 0.003 or 0.005/°C and preferably in excess of 0.006/°C. Higher values will produce a more significant effect, but the choice of such materials is presently limited. The maximum practical would be around 0.01/°C - higher values might draw excessive current when cold.
  • the invention will provide advantages with the heater divided into a comparatively small number of heater cells, such as eight or sixteen, larger numbers of smaller cells, such as up to two hundred, would produce a better effect.
  • the cells should be distributed in two dimensions. This is because, in the situation described above, a smaller proportion of the cells will be on the boundary between the normal and the overheated parts of the vessel. Additionally, smaller cells are less likely to have a significant temperature differential across the length of their element which could lead to localised heating in a manner analogous to that described in relation to the prior art. Moreover, any such overheating which did occur for this reason would be limited to a small cell, and so could be accommodated by the substrate acting as a heat sink.
  • a further advantage provided by having a large number of resistors in parallel is that it greatly reduces the chance of a heater having to be rejected during production, since if there is a break in the track in one of the resistors it will have little effect on the overall power output of the heater. Thus, the failure of a small number of heater cells may be tolerated.
  • the precise arrangement of the cells is not critical to the operation of the device, but preferably they are shaped and arranged such that if the vessel in which the heater is mounted is tipped in any direction, as small a proportion of the cells as possible will be located in positions corresponding to the boundary between the immersed and exposed regions. Thus, significantly elongate cells which extend across a large part of the area of heater should be avoided.
  • One particularly effective arrangement which is appropriate for use with disc shaped heaters, is to arrange the cells in a generally ring-like configuration, for example disposed radially between a pair of concentric conductors. Preferably, more concentric conductors are provided with further cells extending between them. The most preferred arrangement is for the conductive rings to alternate between being connected to the live and neutral supplies.
  • a heater according to the invention may be provided by mounting thin sheets or strips of metal or resistive material against a suitable insulator on a substrate.
  • An alternative option is to use thick film printed circuit technology.
  • a steel or stainless steel substrate may be coated with a number of insulating material layers of ceramic, enamel, glass etc. onto which the conductors and elements may be screen printed using conductive and resistive inks. Inks are available in a wide range of resistivities, for example from the order of 1m ⁇ /square up 10,000 ⁇ /square and higher.
  • the precise configuration of the resistors forming the elements within each cell is dependent upon the resistivity of the ink employed. For example, if a low resistivity ink is used, it will be necessary to provide a long length of track in each cell by arranging the resistor in a tortuous path. Alternatively, if a high resistivity ink is used, a simple shape, such as a rectangle of ink covering most of the cell may be more convenient.
  • the DSO thermal actuator is held against the part of the heater head which is adjacent the hot return part of the element. Since the hot return is the highest part of the element it will generally become uncovered first if the vessel starts to boil dry and so, in such a situation, it is normally the hottest part of the heater. This ensures that the thermal actuator will trip rapidly.
  • plate heaters are preferably generally planar, it is not desirable to provide a raised portion analogous to the hot return. However, it is still desirable to provide a single region on the heater which is likely to overheat first in order to provide a reliable trigger for the DSO bimetal.
  • a so-called "hot spot" on the surface of the heater which has a higher output power density, and will therefore experience a faster temperature rise than the remainder of the heater.
  • This may be provided either by using a resistance ink for this portion of the track in series with the rest of the heater, by providing a narrower track, and/or by increasing the density of resistor tracks in the area.
  • the hot spot is arranged adjacent a thermal actuator such as the known type of DSO bimetal in order to provide a rapid control response.
  • the invention provides a combination of a plate heater and a thermal actuator, the plate heater having a region of track which in use has a higher output power density than the remainder of the plate heater, wherein the thermal actuator is located adjacent said region and the arrangement is such that in the event of the plate heater overheating, the thermal actuator operates switch means to disconnect the supply of electrical current before any part of the plate heater track is ruptured.
  • the hot spot may have a higher PTC than the remainder of the heater. As discussed above, when in series with the heater such a region may enhance localised heating.
  • the heater is designed for use in combination with an integrated control such as that described in our patent application No. GB 9417243.4 which incorporates a thermal actuator.
  • an integrated control such as that described in our patent application No. GB 9417243.4 which incorporates a thermal actuator.
  • mounting arrangements such as screw holes or studs would be provided on the heater to cooperate with those on the control.
  • the hot spot is arranged adjacent these mountings to align with the thermal actuator on the control.
  • a thermal fuse on the heater itself.
  • a gap may be provided in a track which may be bridged by an easily meltable conductor, such as solder or solder paste which will melt when it reaches a certain temperature due to the heater overheating, and break the circuit.
  • a leaf spring may be bent into an arc and soldered whilst in tension across the gap. If the temperature becomes sufficiently high for the solder to melt, this will release one end of the spring and thereby break the circuit.
  • thermal fuse Although a single such thermal fuse may be provided on the heater, it is preferred to have a number of them connected in series and distributed about its surface. As well as providing a backup if one of them fails to operate, such an arrangement is sensitive to different regions of the heater becoming seriously overheated.
  • the fuses are arranged around the outside of the heater so that in the event of serious overheating taking place with the heater partially covered by water at least one fuse will blow. The situation of an exposed part becoming dangerously hot after the DSO protection has not operated, whilst the thermal fuse also does not operate because of the adjacent part of the heater being covered by the water, is therefore avoided.
  • This arrangement is, in itself, believed to be inventive, and therefore from a third aspect the invention provides a plate heater having an overheat protection arrangement provided around its periphery, the arrangement being such that overheating of any substantial part of the periphery of the plate heater will break the supply of current to the plate heater.
  • the overheat protection arrangement preferably comprises a long single thermal fuse (eg. a narrow portion of track) extending around the heater perifery, or one of the arrangements discussed above.
  • a heater according to the invention may be mounted in the base of a water heating jug or kettle as a direct replacement for that in WO 94/18807.
  • a further application which is thought to be particularly significant is to use a heater according to the invention to produce an example of the European type of water heating vessels known as "wasserkochers". These traditionally have a metal body with a fairly thick base into the outside of which an immersion heater is pressed. Although this design results in less effective transfer of heat from the element to the water within a vessel, it does produce a more attractive vessel since a need for an exposed immersion heater is avoided. This also makes the vessel much easier to clean than a traditional kettle or jug.
  • the heater of the present invention may be incorporated in such a vessel in a number of ways.
  • it may be mounted through the base in a manner similar to that described above in relation to a kettle or water heating jug.
  • it could be mounted on the outside of a vessel, preferably having a comparatively thin base to allow efficient conduction of heat.
  • the presently preferred arrangement is to use the heater itself to form a major part of the base of the vessel. This may most conveniently be achieved if the heater is disposed with the side on which the tracks are provided facing downwards. This arrangement avoids any problems regarding the insulation of the heater since the live parts are in a permanently dry region.
  • a vessel of this type incorporating a heater according to the invention could comprise a generally cylindrical body having a flange at its lower end against which the circumference of a heater could be clamped, welded etc. It is thought that clamping the heater would be most convenient in order to avoid the risk of damage to the heater itself.
  • an annular seal is provided to prevent water escaping at the joint between the heater and the vessel.
  • an unheated region of the element adjacent the seal for example in the form of an annulus around the outermost part of the track.
  • the provision of such a region has a further advantage in that it may be used for mounting the thermal fuses so that they are distanced from the heater cells, thereby reducing the risk of their being unnecessarily tripped in the event of slight overheating.
  • the region where they are located will be heated by conduction sufficiently to cause a fuse to blow. Since the fuses are interposed between the cells and the vessel walls, a fuse will blow before sufficient heat reaches the vessel walls to cause serious damage.
  • the invention provides an electric water heating vessel having a body and a plate heater, there being provided an array of overheat protection devices disposed between a heated region of the plate heater and a region of the vessel which is to be protected from overheating.
  • the overheat protectors are thermal fuses formed integrally with the heater as discussed above, but alternatively, re-settable overheat protectors, such as bimetallic actuators may be used, for example held against the dry side of the plate heater.
  • the overheat protectors are ideally located adjacent the heater perifery. However, if a central part of the heater is sealed to the floor of the vessel, as in WO94/18807, then the overheat protectors may be provided towards the centre of the plate heater, adjacent the seal.
  • the invention also extends to a vessel, for example a water heating jug, kettle or wasserkocher incorporating a heater according to the invention.
  • FIG. 1 there is illustrated a water heating vessel 1 having a water receiving portion formed by a generally cylindrical stainless steel body 2 which forms the sides and a disc shaped printed circuit heater 3 which forms the bottom.
  • the heater 3 is clamped to the body 2 and the joint is made water tight by the provision of an annular seal 4.
  • a thermally sensitive control 5, for example of the type described in co-pending patent application No. GB 9417243.4 is clamped against the underside of the heater 3 using screws or by means of studs projecting from the bottom of the heater.
  • the control provides electrical connection to the heater 3 and has means to disconnect the supply of current from the heater in the event of its overheating.
  • the control may also serve to switch off the vessel when water within it boils, in which case a steam channel is provided between the inside of the vessel and a steam operated actuator within the control 5.
  • the vessel is completed by providing a cup-like housing (not shown) over the bottom of the vessel to cover the electrically live components and provide a suitable base to the vessel. If required, a handle may also be attached to the side of the vessel.
  • the heater 3 comprises a stainless steel disc on which four or five layers of ceramic material are deposited by printing, spraying or dipping. Alternatively, enamel may be deposited by spraying or dipping. These processes form an insulating layer over the steel.
  • the conductive and resistive tracks through which electrical current will flow and which form the heater elements, are printed onto the insulating layer.
  • the configuration of these will be discussed in detail below.
  • the element is fired and then a layer of silicate or low temperature glass is deposited on the heater and fired in order to provide an insulating outer surface. Gaps are provided at certain points in this layer in order to permit electrical connection to the printed tracks.
  • FIG. 1 The side of the heater 3 on which the tracks are provided faces downwardly (as viewed in Figure 1) so that the other, plain, side forms the visible bottom surface of the water receiving portion.
  • an unheated region 6 which has no heater elements is provided around the outside of the heated region 8, as shown in Figure 2a. This prevents the sealing region 7 around the circumference of the heater from becoming as hot as the remainder of the heater so that the seal 4 is not damaged.
  • Figure 2b is a graph showing the approximate temperature distribution in the radial direction X-X across the heater. It will be noted that there is a significant temperature drop across the unheated region 6. This is because steel has a relatively low thermal conductivity and the water in the vessel acts as heat sink.
  • Figure 3 illustrates the arrangement of tracks on the underside of a first embodiment of heater 10.
  • Towards the centre of the heater are provided exposed areas of conductive track which form the live 11 and neutral 12 terminals respectively.
  • a short piece of conductive track leads from the live terminal 11 to a "hot spot" 13 which is a small region of track arranged in a tortuous path.
  • the track in this region is formed from the same ink as the conductive track, but it is narrower with a result that localised heating occurs when the heater is energised.
  • the resistance and density of the track forming the hot spot are chosen in order to make this region the hottest part of the heater in use.
  • the hot spot 13 is located against the overheat protection mechanism (bimetallic actuator) (not shown) of the control 5, and this ensures that the electrical supply is disconnected rapidly in the event that, for example, the vessel boils dry.
  • the heater temperature should not greatly exceed 100°C except for the hot spot which should not exceed about 130°C.
  • the bimetallic actuator in the control is arranged to disconnect the electrical supply when the hot spot exceeds its normal temperature during boiling by more than about 20°C.
  • a further piece of conductive track 14 Leading from the hot spot 13 is a further piece of conductive track 14 which leads to an unheated conductive ring 15 located towards the circumference of the heater.
  • the ring 15 connects eight discrete thermal fuses 16 in series so that if any one of them blows, the supply of current to the heater will be cut off.
  • the thermal fuses 16 are located in the unheated region 6 of the heater so that they are not triggered by the normal action of the heated part of the element, rather, they are triggered by heat conducted through the substrate caused by serious overheating.
  • the fuses are designed to blow if they reach about 180°C. Because they are located between the heated part of the element and the seal 4, in the event of serious overheating (ie.
  • the thermal fuses will be heated sufficient to cause them to blow before enough heat reaches the seal to potentially set fire to the seal or vessel or otherwise constitute a serious safety hazard.
  • the thermal fuses are equally radially spaced around the heater so that if the vessel is tipped away from the horizontal whilst energised sufficiently to expose one edge of the heated part of the heater, thereby causing it to overheat, regardless of the direction in which the vessel is tipped, there will always be a fuse sufficiently close to the overheated portion to blow before a safety hazard arises.
  • a further piece of conductive track 17 links the ring 15 to another almost ring-shaped conductor 18 located within it. Extending radially on either side of this conductor are seventy-two heater cells. These are illustrated as each comprising a rectangle of resistive track of 1000 ⁇ /square resistivity forming an element 22. However, since at present inks with this resistivity are only available with a relatively low PTC, the rectangles may be replaced with a tortuous track of lower resistivity (eg. 10 ⁇ /square) in order to take advantage of the higher PTC inks available with low resistivity.
  • Two further concentric conductors, an outer ring 19 and an inner ring 20 are provided on opposite sides of the ring 18.
  • the resistive ink used to form the elements 22 is chosen to have as high a positive temperature coefficient of resistance as possible.
  • an element becomes overheated, for example due to there being no water in contact with the corresponding part of the heater surface, its resistance will increase as the temperature increases. Consequently, the flow of current through the element is reduced and therefore the power produced by it is also reduced. This at least reduces the rate of overheating. Since a large number of discrete resistors are provided, each covering only a small area of the heater, localised heating will cause the resistance of the elements in that area to increase and thereby reduce their output power as discussed above.
  • a second embodiment of heater 30 is illustrated in Figure 4. This is of generally similar configuration to the first embodiment but does differ in several significant respects which mainly result from its being designed for use with resistive inks having much lower resistivity. The use of such inks is desirable since they are presently available with much larger positive temperature coefficients of resistance than the higher resistivity inks.
  • This embodiment uses ink having a resistivity of 10 ⁇ /square and a temperature coefficient of resistance of approximately 0.007/°C.
  • the live terminal 31 is connected to a hot spot 32 which is formed from a small area of resistive material having a resistance of about 2 ⁇ . This is connected by a radially extending piece of conductive track to a circumferential thermal fuse 33. This is formed from a low resistance ink having a high PTC.
  • the track is of just sufficient width to carry the normal flow of current. However, if a region of the substrate on which the track lies is heated significantly, eg. in the event of the vessel boiling dry, this will increase the resistance of the track and thereby cause it to heat further. In the event of serious overheating, the track will be heated to such an extent that it will rupture and cut the supply of current to the heater.
  • each cell 40 Since the resistivity of the ink used in this heater is low it is necessary for each cell 40 to comprise an element having a tortuous path, rather than a single block of resistive material.
  • FIG. 5a A third embodiment of heater 45 is illustrated in Figures 5a and 5b. It will be noted that this is generally similar to the previously described embodiment, but there are certain differences.
  • An additional ring of elements 40 has been provided (reference numerals correspond to those used in the second embodiment), together with an additional conductive ring 46 to provide electrical connection to the live terminal.
  • the elements 40 are shown schematically in Fig. 5a. In fact, each of these is a tortuous track of low resistivity material similar to those of Figure 4.
  • Fig. 5b illustrates one such element 40.
  • this embodiment provides still greater protection against overheating caused by a partially uncovered element.
  • This heater also differs from the second embodiment in that it has the thermal fuse arrangement of the first embodiment, ie. an array of discrete fuses 33'.
  • the discrete tracks connected to each side of the hot spot have been dispensed with. Instead the hot spot directly abuts terminal 39 and track 36.
  • thermal fuse Although the second embodiment incorporates a different type of thermal fuse from the other embodiments, these fuses are, in fact, interchangeable. With regard to the discrete thermal fuses, various methods of producing these are possible, as illustrated in Figures 6a to 8b. In general, they comprise a break 50 in the conductive track 51 which is bridged by some form of heat sensitive material. An alternative form of fuse which is not illustrated in these figures is to provide a short narrow region of track.
  • solder paste is replaced by solder wire 54.
  • the wire may be attached by means of soldering, compression or discharge welding or using conductive epoxy. Again, overheating of the fuse leads to the wire melting at which time surface tension again results in the solder accumulating around the conductors at opposite sides of the break in the track, again breaking the bridge between the two pieces of track (Fig. 6b).

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Cookers (AREA)
  • Resistance Heating (AREA)
EP95308639A 1994-11-30 1995-11-30 Elément de chauffage électrique Withdrawn EP0715483A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9424173A GB2296847B (en) 1994-11-30 1994-11-30 Electric heaters
GB9424173 1994-11-30

Publications (2)

Publication Number Publication Date
EP0715483A2 true EP0715483A2 (fr) 1996-06-05
EP0715483A3 EP0715483A3 (fr) 1997-01-15

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EP95308639A Withdrawn EP0715483A3 (fr) 1994-11-30 1995-11-30 Elément de chauffage électrique

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GB (1) GB2296847B (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997014269A1 (fr) * 1995-10-11 1997-04-17 Strix Limited Dispositifs de chauffage electriques
DE19645095A1 (de) * 1996-11-01 1998-05-07 Ego Elektro Geraetebau Gmbh Beheizung
WO1998019499A1 (fr) * 1996-10-31 1998-05-07 Delta Theta Limited Elements chauffants ayant une pluralite de pistes paralleles montees sur un substrat
WO1999029140A1 (fr) * 1997-11-28 1999-06-10 Koninklijke Philips Electronics N.V. Element chauffant pour recipient de chauffage de liquide
WO2000010364A2 (fr) * 1998-08-12 2000-02-24 Otter Controls Limited Amelioration d'elements de chauffage electriques
WO2000007410A3 (fr) * 1998-07-30 2002-08-22 Otter Controls Ltd Ameliorations apportees a des bouilloires electriques
WO2008116685A1 (fr) * 2007-03-26 2008-10-02 Robert Bosch Gmbh Fusible thermique
EP2523529A3 (fr) * 2006-10-31 2013-02-13 Leach International Corporation Régulateur de puissance avec fil fusible
EP3764739A1 (fr) * 2019-07-11 2021-01-13 Vorwerk & Co. Interholding GmbH Dispositif de préparation des aliments pourvu de résistances à coefficient de température positive électriques montées en parallèle

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0992110A (ja) * 1995-09-26 1997-04-04 Denso Corp 温度ヒューズ付抵抗器
GB2333901B (en) * 1997-09-25 2000-06-14 Otter Controls Ltd Improvements relating to electrically heated water boiling vessels
GB2336481B (en) * 1998-04-06 2002-10-16 Otter Controls Ltd Improvements relating to control of electric heating elements
GB2353457B (en) * 1999-08-13 2004-08-25 Strix Ltd Electric heaters
US8289122B2 (en) * 2009-03-24 2012-10-16 Tyco Electronics Corporation Reflowable thermal fuse

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2181598A (en) 1985-10-04 1987-04-23 Strix Ltd Thermally-sensitive controls
EP0286217A1 (fr) 1987-02-25 1988-10-12 THORN EMI plc Bandes en film épais, à résistance électrique
WO1994018807A1 (fr) 1993-02-15 1994-08-18 Strix Limited Thermoplongeurs

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2258594B1 (fr) * 1974-01-23 1977-09-23 Scholtes Ets Eugen
US3995141A (en) * 1975-10-31 1976-11-30 Texas Instruments Incorporated Food warming device
GB1548406A (en) * 1976-04-13 1979-07-11 Husqvarna Ab Cooking pan with electronic control of temperature and a method for the manufacture of the same
US4286377A (en) * 1978-07-03 1981-09-01 General Electric Company Method of manufacture for a resistance heater and temperature sensor
US4574187A (en) * 1980-08-29 1986-03-04 Sprague Electric Company Self regulating PTCR heater
GB2153190B (en) * 1984-01-14 1987-09-09 Emi Ltd Improvements in or relating to heaters for water vessels
SE8505911L (sv) * 1985-12-13 1987-06-14 Kanthal Ab Folieelement
DE3545445A1 (de) * 1985-12-20 1987-06-25 Bosch Siemens Hausgeraete Heizelement insb. fuer kochstellen
GB8704467D0 (en) * 1987-02-25 1987-04-01 Thorn Emi Appliances Electrically resistive tracks
DE3869773C5 (de) * 1988-07-15 2010-06-24 Dbk David + Baader Gmbh Radiator.
GB2228396A (en) * 1989-02-20 1990-08-22 Emaco Electric hotplate
GB2269980B (en) * 1992-08-13 1996-07-03 Ist Lab Ltd Apparatus for heating liquid
IT1267672B1 (it) * 1994-01-17 1997-02-07 Hydor Srl Composto resistivo termosensibile, suo metodo di realizzazione ed uso

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2181598A (en) 1985-10-04 1987-04-23 Strix Ltd Thermally-sensitive controls
EP0286217A1 (fr) 1987-02-25 1988-10-12 THORN EMI plc Bandes en film épais, à résistance électrique
WO1994018807A1 (fr) 1993-02-15 1994-08-18 Strix Limited Thermoplongeurs

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997014269A1 (fr) * 1995-10-11 1997-04-17 Strix Limited Dispositifs de chauffage electriques
GB2321579A (en) * 1995-10-11 1998-07-29 Strix Ltd Electric heaters
GB2321579B (en) * 1995-10-11 2000-07-26 Strix Ltd Electric heaters
WO1998019499A1 (fr) * 1996-10-31 1998-05-07 Delta Theta Limited Elements chauffants ayant une pluralite de pistes paralleles montees sur un substrat
DE19645095A1 (de) * 1996-11-01 1998-05-07 Ego Elektro Geraetebau Gmbh Beheizung
WO1999029140A1 (fr) * 1997-11-28 1999-06-10 Koninklijke Philips Electronics N.V. Element chauffant pour recipient de chauffage de liquide
US6180925B1 (en) 1997-11-28 2001-01-30 U.S. Philips Corporation Heating element with regions of high/low density
WO2000007410A3 (fr) * 1998-07-30 2002-08-22 Otter Controls Ltd Ameliorations apportees a des bouilloires electriques
WO2000010364A3 (fr) * 1998-08-12 2001-11-08 Otter Controls Ltd Amelioration d'elements de chauffage electriques
WO2000010364A2 (fr) * 1998-08-12 2000-02-24 Otter Controls Limited Amelioration d'elements de chauffage electriques
EP2523529A3 (fr) * 2006-10-31 2013-02-13 Leach International Corporation Régulateur de puissance avec fil fusible
WO2008116685A1 (fr) * 2007-03-26 2008-10-02 Robert Bosch Gmbh Fusible thermique
CN101647081B (zh) * 2007-03-26 2013-06-19 罗伯特.博世有限公司 热熔断器
US8633795B2 (en) 2007-03-26 2014-01-21 Robert Bosch Gmbh Thermal fuse
EP3764739A1 (fr) * 2019-07-11 2021-01-13 Vorwerk & Co. Interholding GmbH Dispositif de préparation des aliments pourvu de résistances à coefficient de température positive électriques montées en parallèle
CN114081358A (zh) * 2019-07-11 2022-02-25 德国福维克控股公司 具有并联电冷导体的食物制备装置
US11638330B2 (en) 2019-07-11 2023-04-25 Vorwerk & Co. Interholding Gmbh Food preparation apparatus with electrical PTC thermistors connected in parallel
US11997765B2 (en) 2019-07-11 2024-05-28 Vorwerk & Co. Interholding Gmbh Food preparation device with parallel electrical cold conductors

Also Published As

Publication number Publication date
GB9424173D0 (en) 1995-01-18
EP0715483A3 (fr) 1997-01-15
GB2296847A (en) 1996-07-10
GB2296847B (en) 1999-03-24

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