GB2252875A - Liquid boiling vessels - Google Patents

Abstract

An electrically heated liquid boiling vessel (1) comprises a thermally sensitive control arranged in a lower part of the vessel and responsive to overheating of the heater element (26) to open a set of electrical contacts to interrupt the power to the heater (26). A bimetallic actuator (80) which is responsive to steam is arranged at an upper part of the vessel and is mounted on a first elongate member (84). A movable part of the actuator (80) co-operates with a second elongate member (38) slidable relative to the first elongate member (84) and connected to a preloaded spring mechanism such that when the actuator (80) operates, the spring mechanism trips to open the set of contacts to interrupt the electrical supply to the heater element (26). In a cordless appliance, the openable contacts comprise the terminal pins of the appliance and in a corded appliance the contacts comprise leaf springs engageable with the terminal pins. Upon actuation of the bimetallic actuator (80), a closure is moved to prevent further vapour from reaching the actuator (80). An on-off knob 95 cannot be moved from the off to the on position unless a lid is properly positioned on the vessel. If a bimetallic actuator (31) responsive to overheating of the heater (26) fails, a back up protector (50) including thermally deformable material operates. <IMAGE>

Description

LIQUID BOILING VESSELS The present invention relates to electrically heated liquid boiling vessels such as electric hot water jugs and kettles, and in particular to liquid boiling controls for such vessels.

It is common practice in electric kettles and hot water jugs, for example, to provide a boiling control whereby when water in the kettle or jug boils, steam impinging on a steam-sensitive actuator, such as a snapacting bimetallic actuator, causes operation of the actuator so as to open a set of switch contacts in the power supply to the electric heater element of the kettle or jug and so interrupt the power supply to the element.

In older style kettles which are relatively squat, and which have a handle extending across the top of the kettle, the steam-sensitive actuator is mounted at the upper rear portion of the kettle and acts on one end of a sprung pivotally mounted rocker arm, which at its other end cooperates with a set of switch contacts of a control situated at the lower rear part of the kettle.

Operation of the steam-sensitive bimetallic actuator pivots the rocker arm to open the contacts. This control also comprises thermally sensitive means which act to disconnect the power supply to the element in the event that the element should overheat e.g. should the kettle be switched on without being filled i.e. dry.

Such an arrangement is disclosed in GB 1470367, for example.

It has also been proposed to conduct steam from an upper part of a kettle via a steam pipe which extends through the head mount of the heating element of an immersion heater and which opens onto a steam-sensitive bimetallic actuator which is provided in a control at the lower part of the kettle. Such an arrangement is disclosed, for example, in GB-A-2111754.

In the more modern, jug type, kettles which are taller than older style kettles and have a handle provided along the rear of the jug, because of lack of space and the nature of the jug material, which is usually plastics, it has become normal practice to mount a steam-sensitive switch at an upper part of the jug rear wall and to connect this switch electrically in series with the dry-switch-on control of the jug which is situated at the lower rear part of the jug, adjacent the heater head.

The present invention seeks to obviate the need for the provision of a separate steam-sensitive switch in the upper part of a jug kettle.

According to a first aspect of the invention, there is provided an electrically heated liquid boiling vessel comprising a thermally-responsive control associated with the electric heater of the vessel for interrupting the electrical supply to the heater in the event that the heater element overheats, said control being disposed at a lower part of said vessel, a pre-loadable spring mechanism for opening a set of electrical contacts associated with said control, a thermally responsive bimetallic actuator arranged at an upper part of said vessel and in fluid communication with a liquid boiling chamber of said vessel, a first elongate member mounted off said control, and a second elongate member slidable with respect to said first elongate member and operatively connected to said spring mechanism, said bimetallic actuator being mounted to said first and second members such that operation of the actuator in response to liquid boiling in said vessel causes said second elongate member to move relative to said first elongate member so as to trip said spring mechanism and open said set of contacts to interrupt the electrical power supply to the heater.

Thus a bimetallic actuator is mounted at the upper end of two elongate members, one of which is slidable along the other so as to operate a spring mechanism to open a set of contacts in the power supply to the heater of the vessel. This arrangement is much simpler and more compact than one in which a spring rocker arm is used to open switch contacts as was previously known and is thus particularly suitable in vessels where space is limited and where the height of the vessel is such that a single rocker arm is not practical, such as in jug type kettles. Furthermore, since the bimetallic actuator is mounted to the elongate members rather than the vessel body, the expansion of the vessel body as it is heated, which may be considerable, for example in plastics hot water jugs, does not affect operation of the boiling control.

The invention also extends in a second aspect to a control for an electrically heated liquid boiling vessel comprising a thermally-responsive control mountable in an opening in a lower part of a wall of said vessel and operable to interrupt the electrical supply to the heater of said vessel in the event that the heater element overheats, a pre-loadable spring mechanism for opening a set of electrical contacts associated with said control, a thermally responsive bimetallic actuator arranged at an upper part of said vessel and in fluid communication with a liquid boiling chamber of said vessel, a first elongate member mounted off said control, and a second elongate member slidable with respect to said first elongate member and operatively connected to said spring mechanism, said bimetallic actuator being mounted to said first and second members such that operation of the actuator in response to liquid boiling in said vessel causes said second elongate member to move relative to said first elongate member so as to trip said spring mechanism and open said set of contacts to interrupt the electrical power supply to the heater.

Preferably the bimetallic actuator is of the snap acting type although a creep bimetal actuator could be used.

In a preferred embodiment the bimetallic actuator is arranged generally horizontally such that upon operation, a generally vertical movement is produced which is transmitted to the second elongate member to cause movement thereof, operation of the spring mechanism and opening of the contacts.

Conveniently the set of contacts opened by the steam-sensitive actuator is also used for the thermallyresponsive control providing dry switch on protection since this helps to avoid unnecessary duplication of components.

Preferably the spring mechanism is an over-centre spring mechanism, for example a "B" spring type mechanism. It is also desirable for the spring mechanism to be provided as part of a dry-switch-on control unit and to be tripped by operation of said dryswitch-on control to open said set of contacts.

The elongate members may be of any form so long as they are slidable relative to one another. Thus, for example, a Bowden cable could be employed, the inner cable constituting the second, movable, elongate member and the outer sleeve constituting the first member which is mounted off the control. Such an arrangement has the advantage that the cable is fully flexible and may be bent to give an operating movement in any desired direction at the control. Preferably, however, the elongate members are semi-rigid. In a particularly preferred arrangement, the first member is formed by a channel-shaped member and the second member formed by a rail which is slidably mounted within the channel. The rail may itself be channel shaped in section. Both members may be of, for example, stainless steel. Thisarrangement provides a substantial degree of rigidity to the assembled control.

It is particularly preferred to use a snap-action bimetallic actuator of the type comprising for example, a rectangular blank with a generally U-shaped cut out which releases a tongue from the blank, and which is prestressed, such that when it reaches a critical temperature, it reverses its curvature with a snap action, so as to move the tongue with a snap action from one position to another. Actuators of this type are well known in the art and are described, for example, in GB 1542252 and GB 657434. The actuator may be mounted on the channel member by lugs extending into the Ushaped cut out adjacent the free end of the tongue, which co-operate with open slots formed in the channel sides. The free end of the tongue then co-operates with the slidable rail member.

Alternatively, the bimetallic actuator may be mounted in a carrier which is mounted to an elongate member.

The present invention is applicable both to socalled corded and cordless liquid vessels. In the former electrical power is supplied through a corded electrical connector to an electrical connector usually a male pin connector on the vessel and usually being an integral part of a switch-on-dry control mounted on the vessel. In a cordless vessel power is supplied to a base for the vessel, electrical connectors being provided in the vessel and base which interconnect when the vessel is stood on its base. In a preferred construction the electrical connections between base and vessel also act as the openable contacts of the switchon-dry and boiling controls. Conventionally this is not so and a further set of contacts are provided for this purpose. This invention is applicable to either arrangement.

The invention extends to switch-on-dry and boiling controls aforesaid constructed as a control unit mountable to a liquid boiling vessel. For a cordless vessel one of the set of contacts of at least the boiling control may be provided on the base for the vessel as abovementioned.

Preferably the first and second elongate members are readily mountable on the control so that they can be supplied detached from a control unit to which they belong. This facilitates packing and transport of control units and yet enables simple assembly of the complete control at the time it is mounted to a liquid boiling vessel. Preferably the thermally sensitive control together with the heating element of the appliance is mountable as a unit to the vessel, and the elongate members mounted to the control unit after it has been so mounted.

Preferably as mounted to the vessel the movable elongate member is directly connected to the spring mechanism which opens the switch contacts, such that it too is moved when the spring mechanism is tripped. Thus the movement of the second elongate member may be much greater than that of the bimetallic actuator and lost motion means may be incorporated between the two, for example a slot formed in a rail as described above. The movement of the second elongate member may thus be used to perform a number of tasks if desired.

In one embodiment the second elongate member is connected, preferably at its upper end, to a manually operable 'on-off' knob, such that as it is moved, for example upwardly, upon operation of the steam control, it moves the knob from the 'on' to the 'off' position.

The knob may be pivotally mounted. When it is desired to re-boil liquid in the vessel, the knob is moved from its 'off' to its 'on' position to move the member against the spring mechanism so as to pre-load the spring mechanism and close the set of contacts.

The second elongate member may also be connected to a flap member which acts selectively to open and close the fluid communication path between the vessel and the bimetallic actuator, such that when the boiling control operates, the flap member is moved by the second elongate member to close the fluid communication path.

In a particularly preferred arrangement, the flap is formed as part of or an extension of the 'on-off' knob such that when this moves to the 'off' position, fluid communication between the vessel and the actuator is cut off.

Provision of means which close the communication between the vessel and actuator when the liquid in the vessel boils allows the actuator to reset itself quickly. Without such a feature, vapour will still impinge upon the actuator after the liquid has boiled, which means that it will not be possible quickly to reboil liquid in the vessel as is sometimes desirable.

Furthermore it is normal to provide the actuator inside a chamber which is vented to the outside atmosphere to allow vapour to escape. There is thus a risk of scalding a user with vapour, particularly when the vessel is tilted so as to pour its contents. This feature of the invention has therefore wider application than the particular arrangement described.

Thus from a third aspect of the invention there is provided an electrically heated liquid boiling vessel comprising an opening in an upper part of a wall thereof, said opening being in fluid communication with a thermally-sensitive actuator of a boil control for the vessel, and closure means arranged so as selectively to block said communication, said closure means being operatively connected to said actuator such that when said actuator operates in response to vapour impinging thereon, said closure means is moved to a position where it blocks fluid communication between said opening and said actuator so as to prevent further vapour from reaching said actuator.

In preferred arrangements as described above, the closure member may be operated by a spring mechanism which is tripped by operation of the actuator, which is preferably a snap acting bimetallic actuator, preferably arranged closely adjacent the opening to allow rapid operation when liquid boils. The closure means may simply be a flap, advantageously pivotally mounted, and arranged to cover the opening, perhaps forming part of an on-off knob of the vessel.

In the preferred embodiments of the invention described above it is also possible to incorporate a safety feature whereby it is not possible to turn on the heating element of the heating vessel until the lid of the vessel has been properly positioned. In one preferred embodiment, a member is provided which, when the lid is not properly engaged prevents rotation of the on-off knob from the "off" to the "on" position, but which is deflected by suitable means on the lid when it is placed in position to allow movement of the knob.

This member is preferably resiliently biased such that when the knob is in the 'off' position and the lid is removed, it is urged back to its blocking position. A particularly simple arrangement would be the provision of a leaf spring in a suitable position.

Again this safety feature has broader application than to the preferred arrangements described above.

Thus, from a fourth broad aspect, the present invention provides a liquid boiling vessel comprising means arranged in an upper part of said vessel for cooperating, in use, with a lid of said vessel, said means being associated with an on-off knob of said vessel such that unless said lid is properly positioned on said vessel, said knob cannot be moved from an 'off' position to an 'on' position, whereby power may not be supplied to the heater of said vessel.

Preferably said means comprises a resilient member acted upon by the lid. The knob is provided with an abutment surface which, if the lid is not properly in position will co-operate with the resilient member to prevent its movement.

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.

Figure 8 is a schematic view of a further steam bimetal mounting arrangement.

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 need 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.

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.

Referring to Fig. 8, an alternative form of bimetallic actuator mounting is shown.

A moulded plastics holder 300 supports a known snap-action bimetallic actuator blade 301 of the type having a U-shaped cut out 301 defining a tongue 303, by which the actuator 301 is retained in the holder 300.

The holder is provided with resilient lugs 304 which engage behind the sides of a channel shaped member 305 which in use is mounted to the thermally sensitive control unit as described above. The member 305 has a tongue 306 which engages in an opening 307 provided in the holder. The holder 300 and thus the blade 301 are thus located with respect to the channel member 305.

A channel shaped rail member 308 has a tongue 309 extending through an opening 310 in the holder 310 so that it may be acted upon by a movable portion of the actuator 301.

The members 305,308 are held together by two T shaped tongues 311 released from the member 305, and engaging through T shaped slots 312 provided in the rail 308. This arrangement allows relative movement between the two members 305,308.

A tongue 313 co-operates with the base of the lower slot 312 to limit the upward movement of the rail member 308 with respect to the channel member 305.

It will be appreciated that the invention is not limited to cordless appliances but is also applicable to so called "corded" appliances. In a corded adaptation of the preferred embodiment described above, a conventional three pin male connector may be provided to extend horizontally from the rear of the control to replace the pins 13,14,15. The serpentine biasing spring 20,21 can be dispensed with, and, for example leaf springs mounted to the respective cold tails 24,25, each leaf spring having a contact at its other end of example for engagement with a contact surface provided on the line and neutral pins of the connector. The yoke 27 may then be provided with means for engaging the respective leaf springs such that upon operation of the control, the contacts thereon are moved out of contact with the respective pin contacts to interrupt the supply of energy to the heater. Rather than acting upon the yoke 27 in such an embodiment the lugs of thermal fuse member 50 could alternatively act directly on the leaf springs.

Claims (26)

Claims

1. An electrically heated liquid boiling vessel comprising a thermally-responsive control associated with the electric heater of the vessel for interrupting the electrical supply to the heater in the event that the heater element overheats, said control being disposed at a lower part of said vessel, a pre-loadable spring mechanism for opening a set of electrical contacts associated with said control, a thermally responsive bimetallic actuator arranged at an upper part of said vessel and in fluid communication with a liquid boiling chamber of said vessel, a first elongate member mounted off said control, and a second elongate member slidable with respect to said first elongate member and operatively connected to said spring mechanism, said bimetallic actuator being mounted to said first and second members such that operation of the actuator in response to liquid boiling in said vessel causes said second elongate member to move relative to said first elongate member so as to trip said spring mechanism and open said set of contacts to interrupt the electrical power supply to the heater.

2. An electrically heated liquid boiling vessel as claimed in claim 1 wherein the bimetallic actuator is snap-acting type.

3. An electrically heated liquid boiling vessel as claimed in claims 1 or 2 wherein the bimetallic actuator is arranged generally horizontally such that upon operation, a generally vertical movement is produced which is transmitted to the second elongate member to cause movement thereof.

4. An electrically heated liquid boiling vessel as claimed in any preceding claim wherein the set of contacts opened by the steam-sensitive actuator is also used for the thermally-responsive control.

5. An electrically heated liquid boiling vessel as claimed in any preceding claim wherein the spring mechanism is an over-centre spring mechanism.

6. An electrically heated liquid boiling vessel as claimed in any preceding claim wherein the elongate members are semi-rigid.

7. An electrically heated liquid boiling vessel as claimed in claim 6 wherein the first member is formed by a channel-shaped member and the second member formed by a rail which is slidably mounted within the channel.

8. An electrically heated liquid boiling vessel as claimed in claim 7 wherein the rail is channel shaped.

9. An electrically heated liquid boiling vessel as claimed in any preceding claim wherein said actuator is mounted directly to one of said elongate members.

10. An electrically heated liquid boiling vessel as claimed in claim 7 or 8 and 9 wherein said bimetallic actuator comprises a blade having a generally U shaped cut out defining a tongue, and is mounted to the channel member by lugs extending into the U-shaped cut out adjacent the free end of the tongue, which co-operate with open slots formed in the channel sides, the tongue co-operating with the rail member.

11. An electrically heated liquid boiling vessel as claimed in any of claims 1 to 8 wherein said actuator is mounted in a carrier which is mounted to an elongate member.

12. An electrically heated liquid boiling vessel as claimed in any preceding claim wherein said first and second elongate members are readily mountable with respect to the control.

13. An electrically heated liquid boiling vessel as claimed in any preceding claim wherein the movable elongate member moves with the spring mechanism.

14. An electrically heated liquid boiling vessel as claimed in claim 13 wherein lost motion means is provided between the bimetallic actuator and the movable elongate member.

15. An electrically heated liquid boiling vessel as claimed in any preceding claim wherein said movable elongate member is connected to an 'on-off' knob of the vessel.

16. An electrically heated liquid boiling vessel as claimed in any preceding claim wherein said movable elongate member is connected to a flap member which acts selectively to open and close the fluid communication path between the vessel and the bimetallic actuator, such that when the boiling control operates, the flap member is moved by the second elongate member to close the fluid communication path.

17. An electrically heated liquid boiling vessel comprising an opening in an upper part of a wall thereof, said opening being in fluid communication with a thermally-sensitive actuator of a boil control for the vessel, and closure means arranged so as selectively to block said communication, said closure means being operatively connected to said actuator such that when said actuator operates in response to vapour impinging thereon, said closure means is moved to a position where it blocks fluid communication between said opening and said actuator so as to prevent further vapour from reaching said actuator.

18. An electrically heated liquid boiling vessel as claimed in claim 16 or 17 wherein said closure member is operated by a spring mechanism which is tripped by operation of the actuator.

19. An electrically heated liquid boiling vessel as claimed in claim 16, 17 or 18 wherein said actuator is arranged closely adjacent the opening.

20. An electrically heated liquid boiling vessel as claimed in any of claims 16 to 19 wherein said closure means comprises a pivotally mounted flap.

21. An electrically heated liquid boiling vessel as claimed in claim 20 wherein said flap forms part of an on-off knob of the vessel.

22. A liquid boiling vessel comprising means arranged in an upper part of said vessel for co-operating, in use, with a lid of said vessel, said means being associated with an on-off knob of said vessel such that unless said lid is properly positioned on said vessel, said knob cannot be moved from an 'off' position to an 'on' position, whereby power may not be supplied to the heater of said vessel.

23. A liquid boiling vessel as claimed in claim 22 wherein said means comprises a resilient member acted upon by said lid.

24. A control for an electrically heated liquid boiling vessel comprising a thermally-responsive control mountable in an opening in a lower part of a wall of said vessel and operable to interrupt the electrical supply to the heater of said vessel in the event that the heater element overheats, a pre-loadable spring mechanism for opening a set of electrical contacts associated with said control, a thermally responsive bimetallic actuator arranged at an upper part of said vessel and in fluid communication with a liquid boiling chamber of said vessel, a first elongate member mounted off said control, and a second elongate member slidable with respect to said first elongate member and operatively connected to said spring mechanism, said bimetallic actuator being mounted to said first and second members such that operation of the actuator in response to liquid boiling in said vessel causes said second elongate member to move relative to said first elongate member so as to trip said spring mechanism and open said set of contacts to interrupt the electrical power supply to the heater.

25. An electrically heated liquid boiling vessel, substantially as hereinbefore described with reference to the accompanying drawings.

26. A control for an electrically heated liquid boiling vessel, substantially as hereinbefore described with reference to the accompanying drawings.