GB2251986A - Switched electrical contacts for cordless appliances - Google Patents

Abstract

A cordless electrical appliance such as a hot water jug or kettle (2) has terminal pins (13,14,15) engageable with contacts (4, 5, 6) a socket connector in a base (3). The pins (13, 15) are mounted such that they may be moved away from the corresponding base contacts (4, 6) by a spring mechanism (42) in response to operation of a bimetallic actuator (31) when the heater of the appliance overheats. This avoids the need for further contacts within the control. <IMAGE>

Description

CORDLESS ELECTRICAL APPLIANCES The present invention relates to cordless electrical heating appliances such as hot water jugs and kettles. Such appliances are provided with a base or stand upon which the appliance may be placed for the supply of electrical power to the appliance. The base is normally provided with a female socket connector which is connected to the mains electrical supply and with which a male pin connector of the appliance engages when the appliance is placed on the base, to supply power to the appliance.

It is also normal to provide cordless liquid heating vessels with a thermally sensitive control including a set of switch contacts which control operates to open the set of switch contacts in the event that for example, liquid within the vessel boils, or the electric heater element of the appliance overheats should the appliance boil dry or be switched on dry thereby to interrupt the electrical supply to the heater element. Such controls are often self contained units which are mounted to the appliance and which, for maximum manufacturing flexibility may be used in either corded or cordless appliances. An example of such a control is shown in GB 2181598.

In cordless appliances, the male pin connector may conveniently be formed by a terminal pin connector of the thermally responsive control or by a terminal pin connector, serving as an adaptor, mounted on the male pin connector of a thermal control unit.

Thus there are at least two sets of contacts which have to be provided in a cordless appliance as described above: namely between the male pin and female socket connector, and in the thermally responsive control.

This results in complicated and costly construction, and the present invention seeks to provide a simpler cordless appliance.

The invention is based on the concept of using the contact connections between the male pin connector of the appliance and female socket connector of the base also for the thermally responsive control.

Thus from a first aspect, the present invention provides a cordless electrical appliance and a corresponding base therefor, the base comprising first contact means connected, in use, to a power supply, and the appliance having a second contact means for engagement with the first contact means when the appliance is placed on the base to supply power to the appliance, and further including a thermally responsive control which comprises a thermally sensitive actuator which operates at a certain predetermined temperature, one of the contact means being operatively connected with the actuator and being mounted so as to be movable with respect to the other contact means, whereby when the actuator operates, the said one of said contact means is moved away from and out of contact with the other said contact means to interrupt the electrical supply to the appliance.

The present invention, therefore, does not attempt to adapt known corded appliances and thermally responsive controls to a cordless application as has been done up to now, but utilises the electrical contacts provided between the appliance and the base also as part of a thermal control of the appliance.

While it is possible by suitable linkage, that the first contact means (i.e. the base contact) could be moved upon operation of the actuator it is preferred that it is the second contact means (i.e. the appliance contact) which is so moved.

In one embodiment, the first contact means may include a contact formed within a socket provided on the base and the second contact means may include a pin extending from the appliance for engagement within the socket. The movement of the appliance contact means is preferably substantially vertical, so typically a contact pin may extend substantially vertically downwardly from the appliance to engage inside an upwardly open socket in the base. Although a single movable contact means e.g. a pin may be provided on either the line or the neutral side of the electrical supply to the appliance, preferably both line and neutral movable contact means are provided in accordance with the invention so that two pole protection is provided.It is not, however, necessary for an earth contact means, where provided, to be so movable and indeed it is preferred that the earth connection between appliance and base, if provided, be maintained when the appliance is on its base irrespective of the state of the thermal control.

To obtain a satisfactory contact pressure between the appliance and base contact means, the contact means are preferably resiliently biased together in the normal operating condition of the appliance. For example, a base contact means may be fixedly mounted in the base and the corresponding appliance contact means, for example a pin, resiliently biased against the base contact means. In a preferred construction such a pin is mounted at one end of an electrically conductive spring member, the other end of which is electrically connected, preferably directly, to the cold tail i.e.

the low resistance terminal of a heating element of the appliance. The spring member may be formed from a strip of resilient conductive material, such as beryllium copper, which is bent at its end mounting the pin into a series of resilient folds and which at is other end clips directly over the cold tail of the element although other forms of spring member will be readily apparent to those skilled in the art. This is a particularly simple arrangement which allows a single component to be used both to bias the pin into contact with the base contact and to form the conductive path from the pin to the element of the appliance and which can permit a substantial movement of the pin, when the thermally sensitive control operates, as will be described below.

As stated above, preferably the appliance contact means are operatively connected to a thermally responsive actuator of the thermally-sensitive control of the appliance. The actuator may comprise a thermally responsive bimetallic element, preferable a snap-acting bimetallic actuator. Such snap-acting actuators are well known in the art and are described for example in GB 1542252 and GB 657434.

The movement of the actuator per se, particularly a snap-acting bimetallic actuator, may not be sufficient to move the appliance contact means by the necessary amount. In a preferred embodiment, therefore, the operative connection between the actuator and the appliance contact means comprises means for amplifying the movement of the actuator. Advantageously the amplification means comprises a spring mechanism which can be pre-loaded by the user e.g. in switching the appliance on and which is tripped by the operation of the actuator. Where the appliance contact means are spring loaded, as described above, the spring force exerted by the movement amplification means should of course be greater than that exerted by the biasing means for the appliance contact means so as to allow the appliance contact means to be moved out of contact with the base contact means upon operation of the control.

In a preferred embodiment, the appliance may comprise a link of high thermal conductivity, one end of which engages with a portion of a heating element of the appliance, and the other end of which supports engages or mounts the thermally responsive actuator which is preferably a snap-active bimetallic actuator as described above. In the event that the element overheats, heat is transferred along the link to the actuator which will operate at a predetermined temperature, to move the appliance contact means out of contact with the base contact means to disconnect the power supply to the element.

Preferably the link is arranged generally horizontally, and supports engages or mounts horizontally a snap-acting bimetallic actuator which produces a generally vertical movement on operation.

This is a convenient arrangement for producing a vertical movement of the appliance contact means without the need for bell crank levers or the like. An earth pin of the appliance may be connected to the link and preferably also serves to mount the actuator to the link. Preferably the movable portion of the bimetallic actuator co-operates with a movable actuating member forming part of a pre-loaded over-centre spring mechanism, whereby when the actuator operates, the spring mechanism is moved over centre and then moves the actuating member through a sufficiently large distance to move the appliance contact means out of contact with the base contact means.The spring mechanism may operate only once, but where, for example, the actuator is associated with a thermally responsive boiling control to switch off the appliance when the contents have boiled means are provided to reset the mechanism after operation.

Conveniently the appliance contact means are supported on a carrier member which is resiliently biased towards the base contact means, by, for example, the contact means biasing spring arrangement described earlier. Preferably there is a lost motion connection between the actuator or actuating member and the carrier member such that the over-centre spring mechanism may be tripped by the actuator and develop a substantial spring force before the actuating member engages the carrier member.

The appliance may be provided with more than one thermally responsive control each serving a different function, each having a thermally sensitive actuator operatively and independently connected with the second i.e. the appliance, contact means. Alternatively a multi-purpose thermally responsive control may be provided including more than one thermally-sensitive actuator, each actuator however acting e.g. through common actuating means on a common pre-loaded spring mechanism which when tripped by the operation of one or other of said actuators moves the appliance contact means out of contact with the base contact means.

As stated above, the control may perform one or more of a number of functions. The above description refers to a dry switch-on" control or overheat protector. However a boiling control may be provided such that when liquid in the appliance boils the appliance is disconnected from the electrical supply.

Furthermore, a control serving as back-up protector may be provided which would operate in the event that the switch-on-dry control fails. Advantageously a control in the form of a thermally deformable fuse member may be provided which in the embodiment referred to above is spring biased into thermal contact with the thermally conductive link referred to above. Should the dry switch on control fail, for example by failure of the bimetallic actuator, the temperature of the thermally conductive link will continue to rise to the point where the fuse member will deform, and move towards the link under the spring biasing force. This movement may be used to move the appliance contact means away from the base contact means. In a preferred arrangement, the fuse member has lugs which engage with the carrier member to move the contact means to disable the appliance.This movement may be sufficient to move the carrier into contact with and move the actuating member to a point where the over-centre spring mechanism trips, and, in cases where no lost motion is provided between the carrier and the spring mechanism, the movement of the fuse member may merely trigger the overcentre mechanism.

Where the appliance is for example a hot water jug or kettle, the movable contact means may be operatively connected to a boiling control of the appliance, such that when the boiling control operates, the contacts are opened to disconnect the power supply to the appliance.

From a second aspect the invention extends to a cordless electrical appliance for engagement with a corresponding base, comprising a terminal pin extending for engagement with a contact member provided in said base, and a thermally responsive control comprising a thermally responsive actuator operatively connected to said pin of said appliance such that when said actuator operates in use, said terminal pin is moved away from the base contact.

From a third aspect the invention extends to a thermally sensitive control for a cordless electrical heating appliance comprising a terminal pin extending for engagement with a contact provided in use in a base for the appliance, and a thermally responsive actuator operatively connected to said pin such that when said actuator operates, said pin is moved in such a direction that in use it will become disengaged from said base contact.

A control as above may be assembled into a unit with a heating element of the appliance, the unit being mountable as a unit from the outside into an opening provided in a wall of an electrical appliance.

Of course the appliance and control as referred to above may comprise the preferred features of the invention as earlier described.

Preferred embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings in which Figure 1 shows a schematic vertical section of an appliance in accordance with the invention taken in the direction of arrow A of Figure 2, with certain components removed for clarity, and showing two operative conditions of the control; Figure 2 is a schematic vertical section taken along the line B-B of Figure 1; and Figure 3 is a schematic view taken along the line C-C of Figure 2.

Figure 4 is an enlarged schematic view along line D-D of Figure 2.

Figure 5 is an enlarged view of detail E in Figure 1.

Figure 6 is a schematic view of a further embodiment.

Figure 7 is a schematic view of a further embodiment.

With reference to the Figures, a cordless hot water jug 1 comprises a jug body 1 and a corresponding base 3.

The jug has an electric immersion heater element 26 which is controlled by a thermally sensitive multifunction control 19 mounted in the lower part of the appliance. The base 3 is formed with live, earth and neutral contacts 4,5,6 respectively within a socket 7.

Live and neutral contacts 4,6 are fixedly mounted in the base 3, while earth contact 5 is vertically movable in a bore 8 in the socket 7 against the action of a coil spring 9. The contacts 4,5,6 are connected to a power supply cable, not shown and are of a standard silver faced, copper backed construction.

The socket 7 is provided with upwardly facing openings 10, 11, 12 to accept line, earth and neutral pins 13, 14, 15 of the thermally sensitive control 19 of the jug. The relative disposition of the pins and contacts is such that the earth pin 19 and contact 5 make first and break last as the jug 2 is placed on and removed from the base 3.

To facilitate location of the appliance 2 on the base 3, a location cone 16 is provided on the base 3 which engages in an aperture 17 formed in the base of the appliance, below a handle 18 formed on the jug body 2.

The line and neutral pins 13, 15 are formed of copper and are provided with silver faced contacts at their lower ends for engagement with the base contacts 4,6. At their upper ends, the pins 13,15 are connected to biasing springs 20,21 which are suitably located in a control housing 101,102. The springs 20,21 are formed from strips of resilient conductive material such as beryllium copper, which are, at their ends adjacent the pins 4,6, formed into resilient serpentine loops 22,23.

At their other ends, they are connected directly to the cold tails 24, 25 of the element 26 of the appliance 2 i.e. the low resistance connecting pins to the resistive heating wire of the element 26. This may conveniently be effected, for example, by providing two parallel slits in the end region of each strip, compressing the end region of the end strip to deform the material between the slits into a loop which may then be pushed over the respective cold tails 24,25. As can be seen from Figure 3, the free ends of the cold tails 24,25 are supported in the cover plate 102 of the control housing when the control is assembled.

For economy of manufacture the pins 13,14,15 are square or rectangular in section, so that they may be stamped out from a sheet of material of appropriate thickness. To facilitate attachment to the springs 20,21, the upper ends of the pins 13,15 may be provided with projections 25 which may extend through corresponding holes in the springs 20,21 and be riveted over to secure the pins to the springs.

The line and neutral pins 13,15 are mounted, with an interference fit, in a carrier or yoke 27, which is biased downwardly by the springs 20,21. The yoke 27 is movable vertically relative to the control housing and also has a limited facility to rock from side to side.

The earth pin 14 which may be of the same material as the line and neutral pins 13,15 is fixedly relative to the control housing. The upper end of the pin 14 is riveted to a copper strip 28 (Fig. 2) which at one end is supported in the cover plate 102 and at its other end is wrapped around a return portion 29 of the element 26, and retained in position by a spring clip 30. The copper strip thus acts as an earth link between the earth pin 14 and the element 26.

The copper strip 28 extends through a seal member 100 and a plastics head member 101 of the control housing which, in use, seal the opening in the vessel wall 83, and mounts, adjacent its other end a snapacting bimetallic actuator 31. The bimetallic actuator is of a type well known in the art comprising a generally U-shaped cut out 32 (Fig. 3) which releases a tongue 33, which tongue 33 will move upwardly when the actuator 31 operates. The copper strip 28 therefore also acts as a thermally conductive link, and should the element overheat, for example in the event that the jug is switched on dry or boils dry, heat will be transmitted to the bimetallic actuator 31 which will operate at a predetermined temperature, which is chosen to be greater than the temperature the actuator experiences during normal operation of the jug.

The bimetallic actuator 31 is operatively connected with the yoke 27 by means of an actuating member 34.

The actuating member 34 has a rearwardly projecting nose portion 35 which freely engages the upper surface of the tongue 33 of the bimetallic actuator 31. The nose portion 35 also extends underneath the cross member 36 of the yoke 27, with a clearance between its upper surface and the under surface of the cross member 36.

The upper portion 37 of the actuating member 34 receives the lower end of a rail 38 of a steam control as will be described later, and is provided at its uppermost region with grooves 39 which engage with the respective control tongues 40,41 of an over centre "B" spring 42 which is supported at its ends in the head member 101.

The operation of this part of the control will now be described. Should the element 26 overheat, heat will be transmitted along the thermal link 28 to cause operation of the bimetallic actuator 31. This results in a small upward movement of the actuating member 34, from the position shown in the left side of Figure 1 sufficient to move the tongues 40,41 of the "B" spring 42 overcentre, whereupon the force of the spring 42 continues to move the member 34 upwardly, so that the nose portion 35 will engage the yoke cross member 36.

The spring force of the "B" spring 42 is greater than that of the biasing springs 20,21 whereby the actuating member 34 will be moved to the position shown at the right side of Fig 1 so as to move the pins 13,15 out of contact with the base contacts 4,6 and so interrupt the power supply to the element 26. The yoke 27, as stated above, is mounted so as to be able to rock from side to side in the plane of Fig. 1. This allows one contact pin to be lifted by the mechanism should the other pin become welded to its base contact.

To reset the control, the steam control rail 38 is moved downwardly to cause the "B" spring to go over centre in the opposite direction, causing the actuating member 34 to return to its original position and the pins 13,15 to move back into contact with the base contacts 4,6 under the biasing force of the springs 20,21. Of course, where a steam control is not provided, means other than the member 38 could be provided to reset the B-spring.

The control shown in Figures 1 to 5 also comprises back-up protection which operates to disconnect the power supply to the element 26 in the event that the "dry switch-on control" described above fails to operate. The back-up protector comprises an thermallyresponsive actuator in the form of a thermal fuse 50 (Fig. 2) which has a hollow body portion 51 and a projection 52. The projection 52, at least, is made from a thermally deformable material and abuts the under side of the copper strip 28. The body portion is provided, at its lower end, with sidewardly extending lugs 53 (Fig. 1) which in the inoperative condition lie below inwardly projecting lugs 54 provided on the yoke 27. A pre-stressed coil spring 55 is arranged within the hollow body portion 51 so as to bias the projection into engagement with the copper strip 28.

In the event that the dry switch on control fails to operate e.g. by failure of the bimetallic actuator 31 the temperature of the copper strip 28 will rise to such an extent that the projection 52 will soften and deform under the effect of heat. The body of the fuse 51 will move upwardly under the force of the spring 55 as the projection 52 deforms so as to bring the lugs 53 into engagement with the lugs 54 on the yoke 26. The spring force of the coil spring 55 is greater than that of the pin biasing springs 20,21 whereby continued movement of the lugs 53 consequent upon progressive collapse of the projection 52 will cause the yoke 26 to move upwardly so as to disengage the pins 13,15 from the base contacts 4,6.It will be clear that once the back-up protector has operated, the control 19 may not be reset since the spring force of the compression coil spring 55 is greater than that of the biasing spring 20,21.

The control 19 described also operates in response to liquid boiling in the jug 2. A further snap-acting bimetallic actuator 80 is arranged in a chamber 81 at the upper part of the jug body 2. The chamber 81 communicates with the interior space of the jug 2 through an aperture 82 formed in the upper part of the jug wall 83. The bimetallic actuator 80 is supported on an elongate channel-shaped section 84 of stainless steel in a manner which will be described later, and locates in the horizontal plane, against a shoulder 85 in the jug body. The rail 38 is of elongate, rectangular section and made of stainless steel and is slidably mounted in the channel of the section 84, as can be seen from Figure 4.

The channel section 84 is provided, at its lower end, with a spring tang 86 which locates behind a shoulder formed in a boss 87 of the head member 101.

The lower end of the channel section locates against a fixed surface 200 of the head member to locate the channel member 84 vertically in position with respect to the control housing. The lower end of the rail 38 is also provided with a spring tang 88 which locates behind a shoulder formed in a boss 89 at the upper part of the actuating member 34 and in which grooves 39 for the tongues and B-spring 42 are provided. The lower end of the rail 38 engages a surface 201 of the actuating member 34. The lead-in to each boss 87,89 is tapered to facilitate insertion of the ends of the channel section 84 and rail 38 respectively.

The nested channel section 84 and rail 38 are located laterally by means of a complementarily shaped passage 90 in the chamber housing. The passage should be of sufficient size to allow the section 84 and rail 38 to move freely vertically within the passage.

As can be seen from Figures 4 & 5, at its upper end the channel section 84 is provided with two lateral open slots 91 for supporting the bimetallic actuator 80 as will be described below. The upper end of the rail 38 is provided with an axially extending closed elongate slot 92 and a smaller opening 93 above it. A projection 94 of a pivotally mounted "on-off" knob 95 engages the opening 93, as can be seen in Figure 2.

With reference to Figure 4, the bimetallic actuator 80 is generally rectangular in shape, having a generally U shaped cut out to define two outer limbs 96,97 joined by a cross member 98, and a tongue 99. The limbs 96,97 are provided with opposed inwardly facing, lugs 211 which engage within the slots 91 formed in the channel section 84, so as to mount the bimetallic actuator, by its outer limbs 96,97 on the channel section 84.

When the bimetallic actuator 80 is mounted on the channel section 84, the tip 205 of the tongue 9 extends through the slot 92 in the rail 38, with a clearance between the tip 205 and the top of the slot 92. The channel section 84 is provided with an upwardly open slot 206 to accommodate the tip 205.

The bimetallic actuator 80 may be easily mounted on the channel member 84 by sliding it down over the nested channel section 84 and rail 38 with the cross section 98 pressed against the back of the channel section 84 until the lugs 211 are opposite the slots 91 in the channel section 84. The bimetallic actuator 80 is then pushed towards the channel section 84 so that the lugs 211 engage in the slots 91 and the tip 205 of the tongue 99 engages in the slot 92 of the rail 38. The shoulder formed at the base of the tip 225 and the shoulder 85 locate the bimetallic actuator 80 laterally.

It will be apparent that since the bimetallic actuator 80 is mounted directly on the channel section 84 rather than the jug housing, and since the rail 38 is also independent of the jug housing, operation of the steam control will not be influenced by for example thermal expansion of the jug mouldings or manufacturing or assembly tolerances.

The operation of the steam control will now be described. When liquid in the jug 2 boils, steam will enter chamber 81 through the aperture 82 in the jug wall 83. The bimetallic actuator 80 will be heated by the steam and operates to move the tongue 99 upwardly with a snap action. The tip of the tongue therefore moves towards the top of the slot 92 in the rail 38, the clearance between the two allowing the tip 205 to impact upon the top of the slot 92. The movement of the tongue 99 is greater than the clearance, so the rail 38 will slide in the channel section 84 lifted by the tongue 99.

The lower end of the rail 38 is connected to the actuating member 34 which will therefore also be moved upwardly a short distance past the point where the "B" spring 42 goes over-centre, which, as described earlier causes the actuating member 34 to engage the yoke 27 to disengage the pins 13,15 from their respective base contacts 4,6 to interrupt the power supply to the jug element 26.

Since the rail 38 moves with the actuating member 34, it will continue to move to the position shown in Fig 4. The slot 92 is sufficiently long to accommodate such movement without the base of the slot 92 engaging the tip 205 of the tongue 99. The upward movement of the rail 38 also causes the knob 95 to pivot to an "off" position.

When it is desired to operate the jug again the knob 95 neèd only be pivoted back to its "on" position so as to move the rail 38 downwardly to its original position, and so re-cock the over centre "B" spring as described earlier.

The assembly of the complete control will now be described in broad terms. The control 19 and the element 26 are assembled as a unit and the element is introduced from the outside, through the aperture formed in the lower part of the jug wall 83. The aperture is sealed by the seal member 100 which also seals around the end regions of the element 26 and the copper strip 28 to prevent ingress of water into the control. The heater and control unit is secured to the jug wall 83 by means of screws (not shown) passing through registering apertures in the cover 102 and head member 101 and engaging in bosses on the jug wall 83. It will be seen from Fig. 3 that the cover plate 102 also acts to locate the free ends of the copper strip 28 and the cold tails 24,25 of the element 26. This provides a very satisfactory location for the element 26.

Once the heater and control unit have been mounted to the jug body 7, the steam control may be added. The channel section 84 and rail 38 are first nested together, and the bimetallic actuator 80 mounted on the assembly as described above. The lower ends of channel section 84 and rail 38 are then inserted into their respective bosses 87,89 on the head member 101 of the control housing and actuating member 34 respectively so as to locate the bimetallic actuator 80 with the respect to the control.

It will be seen that, at least in its preferred embodiments, a substantial vertical movement of the contact pins 143,15 can be achieved. The control may thus in its "off" condition be properly termed "off" within the definition of the I.E.C. regulations, which requires disconnection on two poles with a 3mm gap between the contacts. A gap of at least twice that is achievable with the present invention whilst maintaining the earth connection.

With reference to Figure 6, the operation of the steam control may also cause the aperture 82 to be closed to prevent entry of further steam into the chamber 81, so allowing the bimetallic actuator to reset quickly and to prevent steam venting possibly to burn a user. In this embodiment, a knob 206 is provided with a forwardly projecting extension 207 which has a flap member 208 formed at the end thereof. When the steam control operates, the knob 206 will be pivoted to an "off" position as described earlier, the flap 208 thus being pivoted to cover the aperture 82 from the inside.

It is also possible to provide an interlock whereby the jug 2 may not be switched on until its lid is properly in position on the jug. One possible arrangement is shown in Figure 7. In this embodiment, a pivotally mounted on-off knob 250 is provided with a laterally extending lug 251. A spring member 252 is mounted to the jug body 253 such that its upper end engages the underside of the lug 251. The knob cannot be depressed to switch the jug or until the spring 252 is deflected out of the way by suitable means provided on the lid.

Claims (35)

Claims

1. A cordless electrical appliance and a corresponding base therefor, the base comprising first contact means connected, in use, to a power supply, and the appliance having a second contact means for engagement with the first contact means when the appliance is placed on the base to supply power to the appliance, and further including a thermally responsive control which comprises a thermally sensitive actuator which operates at a certain predetermined temperature, one of the contact means being operatively connected with the actuator and being mounted so as to be movable with respect to the other contact means, whereby when the actuator operates, the said one of said contact means is moved away from and out of contact with the other said contact means to interrupt the electrical supply to the appliance.

2. An appliance and base as claimed in claim 1 wherein the second contact means is moved in response to operation of the actuator.

3. An appliance and base as claimed in claim 1 or 2 wherein said second contact means comprises a pin extending from the appliance for engagement with a socket.

4. An appliance and base as claimed in claim 3 wherein the movement of the appliance contact means is preferably substantially vertical.

5. An appliance and base as claimed in any preceding claim wherein contact means on both the line and neutral sides of the electrical supply are movable upon operation of the actuator.

6. An appliance and base as claimed in any preceding claim wherein said first and second contact means are resiliently biased together in the normal operating condition of the appliance.

7. An appliance and base as claimed in claim 6 as dependent directly, or indirectly upon claim 3 wherein said pin is mounted at one end of an electrically conductive spring member, the other end of which is electrically connected to a cold tail of an electric heating element of the appliance.

8. An appliance and base as claimed in any preceding claim wherein said actuator comprises a snap-action bimetallic actuator.

9. An appliance and base as claimed in any preceding claim wherein the operative connection between the actuator and the movable contact means comprises a preloaded spring mechanism for moving said contact means.

10. An appliance and base as claimed in claim 9 wherein said operative connection further comprises a lost motion connection between said spring mechanism and said second contact means.

11. An appliance and base as claimed in any preceding claim wherein said second contact means are supported on a carrier member which is resiliently biased towards the base contact means.

12. An appliance and base as claimed in claim 11 wherein said carrier allows limited pivotal movement of said contact means.

13. An appliance and base as claimed in any preceding claim comprising a link of high thermal conductivity, one end of which engages with a portion of a heating element of the appliance, and the other end of which supports engages or mounts the thermally responsive actuator.

14. An appliance and base as claimed in claim 13 wherein said link is arranged generally horizontally, and supports or mounts horizontally a snap-acting bimetallic actuator which produces a generally vertical movement on operation.

15. An appliance and base as claimed in claim 13 or 14 wherein an earth pin of said appliance is connected to said thermal link.

16. An appliance and base as claimed in claim 15 wherein said earth pin mounts said actuator to said link.

17. An appliance and base as claimed in any preceding claim comprising at least one further thermally sensitive actuator operatively connected to said movable contact means.

18. An appliance and base as claimed in claim 17 wherein said at least one further actuator comprises a thermally deformable fuse member, operatively connected to said movable contact means.

19. An appliance and base as claimed in claim 18 and any of claims 13 to 15 wherein said fuse member is resiliently biased into contact with said thermally conductive link.

20. An appliance and base as claimed in any preceding claim wherein said appliance is a liquid heating vessel and said movable contact means is operatively connected to a steam activated actuator such that it is moved in response to liquid in the vessel boiling.

21. A cordless electrical appliance for engagement with a corresponding base, comprising a terminal pin extending from the appliance for engagement with a contact member provided in said base, and a thermally responsive control comprising a thermally responsive actuator operatively connected to said pin of said appliance such that in use when said actuator operates, said terminal pin is moved away from the base contact.

22. A thermally sensitive control for a cordless electrical heating appliance comprising a terminal pin extending for engagement with a contact provided in use in a base for the appliance and a thermally responsive actuator operatively connected to said pin such that in use when said actuator operates, said pin is moved away from said base contact.

23. An appliance or control as claimed in claim 21 or 22 wherein said pin is resiliently mounted.

24. An appliance or control as claimed in claim 23 wherein said pin is mounted at one end of an electrically conductive spring member, the other end of which is in use electrically connected to a terminal of an electric heating element of the appliance.

25. An appliance or control as claimed in any of claims 21 to 24 comprising a pre-loaded spring mechanism for moving said pin, operation of said actuator tripping said mechanism to move the pin.

26. An appliance or control as claimed in any of claims 21 to 25 comprising a link of high thermal conductivity, one end of which engages with a portion of a heating element of the appliance, and the other end of which supports engages or mounts the thermally responsive actuator.

27. An appliance or control as claimed in claim 26, wherein said link is arranged generally horizontally, and supports or mounts horizontally a snap-acting bimetallic actuator which produces a generally vertical movement on operation.

28. An appliance or control as claimed in claim 25 or 26 wherein an earth pin of said appliance is connected to said thermal link.

29. An appliance or control as claimed in claim 28 wherein said earth pin mounts said actuator to said link.

30. An appliance or control as claimed in any of claims 22 to 29 comprising at least one further thermally sensitive actuator operatively connected to said pin.

31. An appliance or control as claimed in claim 30 wherein said further actuator comprises a thermally deformable fuse member.

32. A control as claimed in any of claims 22 to 31 in combination with an electrical heating element, said combination being mountable as a unit from the outside into an opening provided in a wall of an electrical appliance.

33. An appliance and base substantially as hereinbefore described with reference to the drawings.

34. An appliance substantially as hereinbefore described with reference to the drawings.

35. A control substantially as hereinbefore described with reference to the drawings.