GB2308743A

GB2308743A - Liquid heating vessels

Info

Publication number: GB2308743A
Application number: GB9706143A
Authority: GB
Inventors: John Crawshaw Taylor
Original assignee: Strix Ltd
Current assignee: Strix Ltd
Priority date: 1994-06-09
Filing date: 1995-06-09
Publication date: 1997-07-02
Anticipated expiration: 2015-06-09
Also published as: GB9706143D0; GB2308743B

Description

Liquid Heating Vessels The present invention relates to liquid heating vessels having electrical heating elements, and in particular in certain aspects to liquid heating vessels having a liquid receiving container and an electrical heating element provided on the base of the container or secured in good thermal contact to the underside of the container. An example of such an arrangement is shown in GB-A-2042269.

Such types of vessel are popular in certain areas of the world, for example in continental Europe, for boiling water for making hot beverages such as tea and coffee. Typically, the liquid receiving container has a base portion at least which is made from a corrosion resistant metal such as stainless steel, which gives the interior of the vessel an attractive appearance and makes it easier to clean. The rest of the vessel may also be of this metal, but could possibly also be of for example a plastics material suitably joined to the base portion. The container conventionally has an external base plate made of a high thermal conductivity metal such as aluminium, to which the element is secured and through which heat is conducted into the container.

The invention from one aspect seeks to provide an improved vessel of the above type.

From a first aspect therefore, the invention provides a liquid heating vessel comprising: a liquid receiving container; an electrical heating element provided on the base of the container or arranged below and in thermal contact with, said container; a thermally sensitive overheat control arranged to operate in the event of said element overheating so as to interrupt or reduce the supply of electrical energy to the element; and a manually-resettable boiling control operable to interrupt the supply of electrical energy in the event of liquid in said vessel boiling; said overheat and boiling controls being located in a compartment arranged below, and substantially within the footprint of said container.

The heating element may be of a traditional sheathed construction, connected directly to a vessel base or to a heat diffusion plate attached thereto as is well known in the art, or indeed a printed heating element provided on the vessel base.

In accordance with the invention, for the first time, a vessel of the type described earlier is provided with a overheat control operable in the event the element overheats, for example if the vessel is switched on dry or boils dry (a "primary" overheat protector) and a manually resettable boiling control in a compact arrangement.

Preferably the vessel also comprises a thermally sensitive "back-up" overheat control operable should said primary overheat control fail to interrupt or reduce the supply of electrical energy to said element in the event of said element overheating, which is also arranged in the base compartment. Thus in preferred embodiments the vessel has both primary and back-up overheat protectors in the base compartment. The "back up" protector may be arranged to operate at a higher temperature than the primary protector, or at substantially the same temperature, and could be provided in the other pole of the electrical supply to the element, to provide double pole protection.

The primary overheat, back-up overheat and boiling controls may be integrated into a combined unit, but they may also be discrete units, suitably electrically connected, and mounted in the compartment.

Preferably a 'cordless' electrical connector is also provided in the base compartment, most preferably of the type which will allow engagement of the connector with a corresponding connector in a base unit on which the vessel stands in use and through which electrical energy will be conducted to the vessel irrespective of their relative angular orientation.

Preferably the base portion at least of the container is of a corrosion resistant metal such as stainless steel, and the heating element is attached to a thermally conductive base plate of the container which is of a material such as aluminium.

Preferably the respective controls are spaced laterally from one another, being positioned under different portions of the container base.

This is an advantageous feature in that it will allow the depth of the base compartment to be minimised, thereby reducing the overall height of the vessel, contributing to the stability of the vessel and enhancing its appearance.

In accordance with a second broad aspect therefore, the invention provides a liquid heating vessel having a liquid receiving container, comprising a first, primary overheat protector and a secondary, back-up overheat protector, said protectors being arranged in a compartment under the base of said container and being spaced laterally from one another.

Preferably the primary and back-up overheat protectors are separate units mounted separately in thermal contact within the base of the container, although they may be integrated into a combined unit.

The primary and backup overheat protectors may comprise thermally responsive actuators of any known type, for example, bimetallic actuators. As an example, the primary overheat protector may comprise a snapacting thermally sensitive bimetallic actuator, such as described in GB 1542242, which is mounted in thermal contact with the base of the liquid receiving container and which, when it reaches a predetermined temperature operates to open a set of switch contacts in the supply to the heater.

The back-up protector may also, for example, comprise an actuator as described above, set to operate for example at a higher temperature, or may even comprise a creep bimetal, which upon heating a certain predetermined amount deflects sufficiently to open a set of switch contacts. It may alternatively comprise a fusible member, for example a plastics push rod, biased into thermal contact with the base of the vessel and which, in its solid condition maintains closed a sprung set of contacts. When the vessel base overheats the fusible member melts or thermally deforms so as to allow the contacts to open.

The primary overheat protector is preferably arranged so as to reset automatically once the element has cooled to a safe temperature, but if deemed desirable in the particular application, it may be such that it either requires manual resetting, or replacement, after operation. Similarly, the back-up protector may be such as to reset automatically, to require manual resetting or replacement after operation.

Commercially available "one-shot" thermal protectors may therefore be used as the overheat protectors.

From a yet further broad aspect, the invention provides a liquid heating vessel having a liquid receiving container, electrical heating means attached to an external, bottom surface of said container, and a boiling control arranged in a compartment below said container and spaced inwardly from the edge thereof, and means for directing vapour from said vessel to said control.

The boiling control may comprise a thermally sensitive actuator such as a bimetallic actuator, more particularly a snap-acting bimetallic actuator as described above, which is exposed in use to vapour produced in the vessel as the liquid boils. The vapour is conveniently directed onto the actuator by a pipe leading into the base compartment, for example through a passage extending from an aperture formed in an upper part of the vessel wall or through the vessel base.

The actuator preferably operates to trip a bistable spring loaded mechanism to open a set of switch contacts in the supply to the element. The spring loaded mechanism may comprise a pivotally mounted lever arm which is movable between two stable positions against the action of an over-centre spring mechanism.

One end of the lever may form, or be connected to, a knob or the like, by which a user may re-set the switch once it has operated to re-boil the liquid in the vessel, or by which the user may switch the vessel on or off.

Preferably the primary and back-up overheat protectors and the boiling control are arranged around the periphery of the container base, that is away from the central area, so as to leave the central area of the base free for the provision, if required, of a cordless connector in the base compartment.

From a yet further broad aspect, therefore, the invention provides a liquid heating vessel with a liquid receiving container and an electrical heating element mounted therein or externally thereof but in thermal contact with the base of said container, a cordless connector arranged generally centrally of the base, and a primary overheat protector arranged laterally displaced from said connector in a base compartment of the vessel.

Preferably the connector is of the type which will allow engagement with a corresponding connector provided in a base unit for the vessel irrespective of the relative rotational orientation of the vessel and the base. Such a connector is described in our international application WO 95/08524.

Preferably the connector is provided with a contact carrying conductive strip projecting laterally therefrom, the strip being connected to a terminal member of the connector.

In this way the connector may be connected directly to a switch in the vessel, the contact on the strip for example forming a fixed contact of a switch in the primary overheat protector.

From a yet further broad aspect, therefore, the invention provides a cordless electrical connector having an electrically conductive strip extending laterally therefrom said strip being provided with an electrical contact and being connected to a terminal member of said connector.

The contact may for example be a separate contact member, such as a silver contact, mounted on the strip or it could be formed by plating all, or a selected part, of the strip with a contact forming material such as silver.

In the preferred embodiment of the invention, where the electrical heating means are arranged below the bottom of the liquid receiving container, it will be appreciated that the temperature in the base compartment of the vessel may be quite high. This may mean that traditional electrical wiring which is plastics coated, may soften, sag, or even catch fire, particularly if it is arranged too close to the element itself.From a yet further aspect, therefore, to alleviate this potential problem, the invention provides a liquid heating vessel having a liquid receiving container and an electrical heating element in thermal contact with the underside of said container, a base compartment below said container and housing switch means of a control of the vessel, plug means having terminals for connection to an external electrical supply, and communicating with the interior of the base compartment, said terminals being connected to said switch means by electrically conductive strips extending laterally therefrom through the base compartment.

This aspect of the invention is of course applicable to cordless arrangements as discussed above, or indeed to conventional corded arrangements wherein the terminal pins engage in a socket connector provided on the end of a power lead for the vessel. Furthermore, as discussed above, the strips may carry switch contacts of the switch means.

If for any reason the liquid heating vessel is required to heat water to a temperature lower than boiling, for example to 80"-90"C, which is a temperature appropriate to making coffee, the boiling control of the invention may be replaced with, or supplemented by, a thermally sensitive control which operates to interrupt or reduce the power to the element at a water temperature lower than 1000C. This control may be of the type that needs re-setting manually after its operation, but preferably is of the type that will cycle to keep the liquid in the vessel simmering at the desired temperature.

Such "simmer" controls are known, in principle, from for example EP-A-528656 and EP-A-510863.

In the arrangements described in the above applications, the boiling control and the simmer control are connected in series with one another. A user selects a "boil" or "simmer" setting in accordance with his or her needs. In the "boil" setting, the liquid in the vessel will be heated to boiling, whereupon the vessel is automatically switched off by the boiling control. In this condition, however, the "simmer" control must be by-passed such that it will not operate to interrupt the electrical supply at a temperature below boiling. In the "simmer" setting, the simmer control is enabled and operates to cycle the electrical supply to the vessel once the liquid in the vessel has reached the required temperature.

In certain parts of the world, for example in the Far East, water is frequently required, for example for culinary purposes, at a temperature below boiling point.

However, because the water supply may not be entirely clean, it is common practice to boil the water first.

In water heaters commercially available for this purpose, there are provided two separately controlled heating elements, one of which is used exclusively to boil the water and the other of which is used exclusively to simmer the water at a desired temperature.

It might be thought that single element arrangements as described above would be suitable for this task, but if it is desired to simmer water after boiling, and thus after the boiling control has operated, it is necessary firstly to re-enable the simmer control, and then switch the boiling control on again.

This requires positive action on behalf of a user after the water in the vessel has boiled and means that the vessel cannot be left automatically to boil and then simmer water. The invention, in yet another aspect, seeks to overcome this problem, and provides a liquid heating vessel having an electric heating element, a manually re-settable boiling control operable in the event of liquid boiling in the vessel and a simmer control for maintaining liquid in the vessel at a desired temperature at or below boiling, said controls being connected electrically in parallel with each other.

With such an arrangement, as the liquid in the vessel is heated, when it reaches the "simmer" temperature, the simmer control will operate. However, since that control is electrically in parallel with the boiling control, which has not yet operated, power will continue to be supplied to the heating element so that the liquid will continue to be heated up to boiling, at which point the boiling control will operate to interrupt the power supply to the element. Although the boiling control switch will remain open until the control is reset manually as the liquid in the vessel cools, when it reaches the "simmer" temperature, the simmer control will operate to maintain the liquid at that temperature. Thus a fully automatic operation is achieved.

In a preferred embodiment, means may be provided for selectively enabling or disabling the simmer control, so that if desired the vessel may be used just to boil water. A manually operated switch in series with the simmer control may be provided for the purpose.

Similarly, in preferred embodiments the boiling control may be switched on or off to allow the vessel to be used purely to simmer water without first boiling it. In the most preferred embodiment, switches are provided selectively to enable or disable both the controls in which case the vessel may, depending on the settings of the switches be used to boil only, simmer only, or boil and then simmer.

It will be clear that this aspect of the invention is not limited to liquid heating vessels having electrical heating elements secured to the external base of a liquid containing container, but is equally applicable to conventional vessels, such as those disclosed in the aforementioned European and UK patent applications in which the element is arranged within the vessel.

Furthermore, the simmer control may take any convenient form, for example a thermally sensitive actuator, such as a bimetallic actuator, in thermal contact with the liquid in the vessel.

In a particularly preferred embodiment the simmer control comprises a bimetallic actuator, preferably a creep bimetal, mounted in good thermal contact with the base of the vessel, the temperature of which will during normal operation, reflect the water temperature.

In a particularly preferred embodiment, the bimetal acts on a snap-operating microswitch, which constitutes a simmer switch.

The creep bimetal may also function as an actuator for a thermal protector, for example a back-up protector, as discussed above. If the vessel is switched on dry or the liquid therein evaporates away the temperature of the base plate will rise, causing the bimetal to move beyond its normal range at which point it will operate the protector. This in itself is a novel arrangement and from a yet further aspect, the invention provides a liquid heating vessel comprising a switch unit arranged in the electrical supply to the element and having a bimetallic actuator in thermal contact with the vessel and operating under normal conditions as a thermostat to maintain the liquid within the vessel at a predetermined temperature through opening and closing a first set of contact and in an overheat condition to open a second set of contacts.

As mentioned above, the boiling control and the simmer control are arranged electrically in parallel.

In the preferred embodiment, the boiling control comprises a switch, one contact of which is formed on one fork of a bifurcated supply strip, the other fork of which carries a contact of a simmer enable/disable switch. The simmer enable/disable switch can be generally similar to the boiling switch, having a manually operable, bistable, lever, although of course without a bimetallic actuator. Preferably the levers of the respective switches are arranged side by side.

Some preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a rear view of a vessel in accordance with the invention; Figure 2 is an underneath view of the vessel of Figure 1 with the base cover removed; Figure 3 is a schematic section along the line III III of Figure 2; Figure 4 is a schematic section along the line IV IV of Figure 2; Figure 5 is a scrap section view along the line V-V of Figure 2; Figure 6 is a view similar to Figure 2, but showing a cordless vessel; Figure 7 is a schematic composite view showing the positions of a cordless or plug terminal in the base compartment; Figure 8 is a schematic circuit diagram for the vessel.

With reference to Figure 1, a water boiling vessel in accordance with a preferred embodiment of the invention comprises a stainless steel water receiving container 2, to the external base of which is brazed an aluminium base plate 4. An electrical heating element 6 is secured to the base plate 4, in a standard manner. A cover 8 forms a base compartment 10 below the base plate 4. A back cover 12 is arranged at the back of the vessel to provide a steam passage 14, as will be described later. A standard plug inlet 16, with line, neutral and earth pins 18, 20, 22 is arranged at the rear of the base compartment 10, and is flanked by two user operable knobs 24, 26 the first of which 24 is a "boiling" knob and the second of which 26 is a "simmer" knob. The functions of these will be described in detail later.

With reference to Figure 2, the vessel comprises a number of controls, distributed around the base plate 4.

These may be designated generally as a boiling control 28, a primary overheat protector 30, and a combined simmer control and back up overheat protector 32. In addition there is a simmer on/off switch 34. All these are arranged within the base compartment 10.

These controls are essentially separate units connected electrically to one other, as shown schematically in Figure 8 from which it will be seen that the boiling control 28 and simmer control 32 are connected in parallel to each other in the line side of the supply and the overheat protector in the neutral side of the supply.

The boiling control 28 comprises a thermally responsive bimetallic actuator 36 of the type described in GB 1542252 which is mounted on a lever arm 38 the end of which extending out from the rear of the base compartment 10 forms the boiling knob 24. The tongue 39 of the actuator abuts a fixed spigot 40. The lever arm 38 is pivotally mounted in a knife edge 41 provided in a housing 42, and is biassed between two stable positions (shown in Figure 3) by a C spring 44, one end of which is supported in a groove in the housing 42 and the other in a groove in the lever arm 38.

The end of the lever arm 38 within the base compartment is bifurcated into two arms 45, 46. The first arm 45 acts to open a set of boiling contacts 48, 50 in the line side of the supply to the element 6. A fixed contact 48 is formed on a conductive strip 52 electrically connected to an spade terminal 53 which is for connection to the line side of the element 4, while a movable contact 50 is provided on one limb 56 of a Tshaped conductive strip 54, typically of beryllium copper, which is riveted to the line terminal pin 18 inside the base compartment 10. The function of the other arm 58 of the strip 54 will be described later.

The bimetallic actuator 36 is arranged so as to lie under a pipe 60 connected to the bottom of the steam passage 14, such that when liquid in the vessel boils, steam will be exhausted onto the actuator. This will cause the actuator to reverse its curvature with a snap action, the reaction of the actuator tongue 39 on the reaction spigot 40 causing the right-hand end of the lever arm 38 to move upwardly, to the point where the C spring 44 moves over centre, causing the lever arm to move to the OFF position and be retained in the position shown in Figure 3. In this position, the first arm 45 of the lever arm 38 opens the contacts 48, 50, thereby breaking one electrical path into the spade terminal 53.

The other arm 58 of the T shaped strip 54 forms part of the simmer on/off switch 34, and carries a movable contact 62 of a simmer on/off contact pair 62, 64, the other, fixed contact 64 of which is mounted on the end of a conductive strip 66 connected to the simmer control, as will be described later.

The simmer on/off switch 36 is operated by a pivotally mounted spring lever arm 70.

The lever arm 70 extends out of the base compartment to provide the simmer knob 26 for operation by a user. The lever arm 70 is biassed into two stable positions (as shown in Figure 4) by a C spring 72, in a manner identical to that for the "boiling" lever arm 38.

However, there is no bimetallic actuator mounted on the lever arm 70 so that its operation is entirely manual.

When the lever arm 70 is in the "on" position as shown in Figure 4, the contacts 62, 64 are closed, whereby the electrical supply will pass to the simmer control 32.

When, however, the lever is in the "off" position, the contacts 62, 64 are opened, which effectively disables the simmer control 32.

It will be seen, therefore, that the line side supply to the element 6 through spade connector 53 is split by the T shaped strip 54, which leads the supply in parallel through the simmer on/off switch 34 and simmer control 32 and the boiling control 28. If it is desired to boil water in the vessel then the boiling knob 24 must be set to its "on" position so that line current can flow to the element via the strip 54, the boiling switch contacts 48, 50, strip 52 and connector 53. When water in the vessel boils, the lever arm 38 will be tripped by the actuator 36 to open the contacts 48, 50, thereby breaking this path.

If the "simmer" knob 22 is in the "off" position, the simmer on/off contacts 62, 64 will be open, so that the vessel will be switched off by the operation of the boiling control 28, and if water in the vessel is to be re-boiled, the lever arm 38 must be reset manually by the knob 24. If, however, the simmer knob 22 is in the "on" position, the contacts 62, 64 will be closed, which means that line side of the supply can still reach the element 4 via the simmer control 32, so that the subsequent operation of the vessel will be determined by the simmer control 32. Unlike earlier proposals, where boiling is required before simmering, no manual intervention is required after the boiling has occurred.

Turning now to the simmer control 32, this can be seen schematically in Figures 2, 3 and 4. The switch is shown schematically in a housing 80 mounted to the base plate 4. A creep bimetal strip 82 is supported in the housing 80 and positioned in good thermal contact with a boss 84 formed on the base plate 4. Also supported in the housing 80 is a conductive strip 86 mounting a fixed simmer contact 88 on its end. (In Figures 3 and 4, this is shown as being supported in the wall of the housing supporting the bimetal 82.) However, this is schematic as will be seen from Figure 2, it is in fact supported in another wall. The strip 86 is integral with or coupled to the strip 52 leading from the boiling control 28 and the line side element connector 53.

A snap-acting microswitch 90 is mounted in the housing 80. It will be apparent to the skilled person from Figures 3 and 4 that this microswitch is of a standard construction, having a movable simmer contact 92 mounted at the end of a contact arm 94, which is moved downwardly by a push rod 96 coupled to the bimetal 82. The arm moves with a snap action due to the overcentre "C" spring mechanism 98 as is well known in the art. The contact arm 94 is either integrally formed with or joined to a mounting strip 100 mounted in the housing 80, as is a calibration screw 102 which is used to adjust the set point of the switch in a known manner, and thereby vary the simmer temperature. The strip 100 is integral with or joined to the strip 66 mounting the fixed simmer on/off contact 64.

It will thus be seen that when the simmer on/off contacts 62, 64 are closed, the line side of the supply will be connected to the spade terminal 53 through the strip 54, arm 58, simmer on/off contacts 62, 64, strip 66 mounting strip 100, contact arm 94, simmer contacts 88, 92 and strip 86. Since the simmer control 32 is arranged electrically in parallel with the boiling control 28, even if the latter is in an "off" condition, current will still be supplied to the element 6, in dependence on the condition of the simmer contacts.

This is controlled by the position of the bimetal 82 which is in good thermal contact with the base plate 4.

The base plate temperature will reflect the water temperature in the vessel, and as the water heats, the base plate temperature will rise causing the bimetal to deflect downwardly, in the sense of Figure 4. When the base plate temperature reaches a given temperature corresponding to a desired water temperature, the bimetal 82 will have moved to the extent that the C spring mechanism 98 moves over-centre causing the simmer contacts 86, 92 to open with a snap action.This disconnects the electrical supply to the element, which then cools, the water in the vessel cooling to the point that the bimetal 82 moves upwardly again to point the C spring mechanism 98 moves over-centre in the other direction, causing the simmer contacts 88, 92 to snap shut again, and so the cycle repeats until the simmer on/off knob 26 is switched to an off position, thereby opening the contacts 62, 64 so isolating the simmer control 32.

The simmer control 32 also acts as a back-up overheat protector. In this regard, an extension portion 104 of the bimetal 82 overlies the arm 46 of the steam control lever arm 38. A push rod 106 is mounted with a lost motion between the portion 104 of the bimetal 82 and the arm 46. Should the primary overheat protector 30 (to be described below) fail to operate and the base plate 4 continue to rise in temperature, the bimetal 82 will continue to deflect downwardly at its end 104 beyond the point at which the simmer contacts 88, 92 snap open to the point that the lost motion in the pin 106 is taken up and it then moves the arm 46 of the lever arm 38 downwardly to the extent that it trips the over centre mechanism 44, to open the boiling contacts 48, 50.In this way the switch contacts both arms of the line side supply to the element will be opened so that the power to the element will be disconnected.

With reference to Figures 5 and 8, the primary overheat protector 30 is arranged in the neutral side of the element supply. It comprises a bimetallic actuator 110 of the same type as the boiling actuator 36, which is mounted in good thermal contact with a boss 112 on the base plate 4. The actuator 110 acts to open and close a set of contacts 114, 116 through a push rod 118.

A fixed contact 114 is formed at the end of a conductive strip 120 on whose other end is provided a spade connector 122 for connection to the neutral side of the element 6. The movable contact 116 is formed on the end of a conductive strip 124, whose other end is riveted to the end of the neutral terminal pin 20 in a manner similar to the strip 54 being riveted to the line pin 18.

Should the boiling control 28 fail to operate, for example if the vessel boils dry or is switched on without any water in it, the temperature of the base plate 4 will rise to the point at which the bimetallic blade 110 will change curvature with a snap action, so opening the contacts 114, 116, thereby opening the neutral side of the supply to the element. The base will eventually cool and the actuator snap back, causing the contacts 114, 116 to reclose, so that unless the user switches the vessel off using the simmer and boiling knobs 22, 24, the element will cycle.

As mentioned above, the members carrying current from the line and neutral terminal pins 18, 20 are in the form of metal strips, which gives the advantage of heat resistance and rigidity. The earth connection is also made through a strip 130 riveted to the base of the earth pin 22 inside the base compartment 10. An earth strap (not shown) may lead to an earth connection provided on the base 4.

The invention may be applied to corded vessels such as shown in Figure 2 where a lead is plugged into an inlet provided on the vessel, to fixed cord vessels, in which a power lead is introduced directly into the base compartment 10 for connection to the controls, or a cordless appliance, such as shown in Figures 6 and 7 where the vessel sits on a base through which power is transferred to the vessel.

In Figures 6 and 7 there is shown a vessel having a cordless connector 200 arranged centrally in its base compartment 10. The connector 200 is of the type described in our International patent application WO 95/08524, and is such as to allow electrical connection with the base connector 202 to be made irrespective of other relative angular disposition. The vessel connector 200 has a central line pin 204, the top of which has two connection means for engagement with a bifurcated "line in" conductive strip 206 which is arranged to extend down the sides of the connector 202 and which has on its respective ends the movable contacts of the boiling control 28 and the simmer on/off switch 34, in the same manner as in the embodiment of Figures 1 to 5.

The connector 200 has an annular neutral terminal 212, which has a connector at its upper end for receiving, or indeed forming, a conductive strip 214 mounting at its other end a contact of the primary overheat protector 30, as in the earlier embodiment.

The neutral connector may be formed, for example in a slot in the upper surface of the connector 200.

Finally, the connector has an annular earth terminal 218, at whose upper end is formed a spade terminal 220 for connection to an earth strap.

This type of connector is particularly advantageous since it has a relatively low profile. Furthermore, since the various controls are displaced laterally from the connector, rather than arranged on to of it as in existing designs, the depth of the base compartment 10 may be kept low to improve stability of the vessel.

The functions and detail of the various controls in this embodiment are the same as those in the earlier described embodiment, and it is just the electrical connections which essentially differ.

It will be appreciated that while the above embodiments have been described with reference to vessels having a standard, sheathed electrical heating element attached to the base of the vessel, the invention is equally applicable to vessels provided with printed heating elements on their bases.

Claims

1. A liquid heating vessel having a liquid receiving container and an electrical heating element arranged below, but in thermal contact with said container or provided on a base of said container and comprising a first, primary, overheat protector and a second, backup, overheat protector, said protectors being arranged in a compartment under the base of said container and being spaced laterally from one another.

2. A liquid heating vessel as claimed in claim 1 wherein said first and second protectors are separate units mounted in thermal contact with said vessel base.

3. A liquid heating vessel as claimed in claim 1 or 2 wherein said first protector resets automatically once the element has cooled to a predetermined temperature.

4. A liquid heating vessel as claimed in any of claims 1 to 3 wherein said first protector comprises a bimetallic actuator in thermal contact with the vessel base.

5. A liquid heating vessel as claimed in any preceding claim wherein said second protector comprises a bimetallic actuator in thermal contact with the vessel base.

6. A liquid heating vessel as claimed in any of claims 1 to 4 wherein said second protector comprises a fusible member biased into thermal contact with the vessel base.

7. A liquid heating vessel as claimed in any preceding claim wherein said primary and secondary protectors are arranged around the periphery of the vessel.

8. A liquid heating vessel as claimed in any preceding claim further comprising a cordless electrical connector.

9. A liquid heating vessel as claimed in claim 8 wherein said connector is arranged generally centrally of said base compartment.

10. A liquid heating vessel as claimed in claim 8, wherein the connector is of the type which will allow engagement with a corresponding connector provided in a base unit for the vessel irrespective of the relative rotational orientation of the vessel and the base.

11. A liquid heating vessel as claimed in claim 8, 9 or 10, wherein the connector is provided with a contact carrying conductive strip projecting laterally therefrom, the strip being connected to a terminal member of the connector.

12. A liquid heating vessel as claimed in any preceding claim further comprising a boiling control.

13. A liquid heating vessel as claimed in claim 12 wherein said boiling control is arranged in a compartment below said container and spaced inwardly from the edge thereof, and wherein means are provided for directing vapour from said vessel to said control.

14. A liquid heating vessel as claimed in any preceding claim wherein said element is a printed element provided on the underside of the vessel base.