The present invention relates to controls for controlling a liquid heating apparatus, e.g. to switch off the apparatus when water is boiling or to prevent overheating, and to assemblies and appliances incorporating such controls.

A traditional liquid heating apparatus such as an electric kettle or hot water jug is equipped with a boiling control which, when liquid in the vessel boils, operates to disconnect the power supply to the heater of the vessel so to discontinue boiling. Similarly an overheat control can be provided which disconnects the power supply when the heater exceeds a safe operating temperature.

Commonly such controls employ copper alloy leaf springs as moveable contacts to make or break the electrical power circuit with the leaf springs carrying current as part of the circuit. Typically the leaf springs are acted on via a push-rod by a thermally sensitive bimetallic actuator which operates when the liquid in the vessel boils or the heater overheats. Often these controls rely on cantilevered leaf springs that flex freely when acted upon by an actuator to move apart the contacts.

Electrical power is supplied to a cordless liquid heating apparatus when it is engaged with a base connector. Another set of contacts is provided in the base connector so that the electrical circuit is broken when the apparatus is separated from the base.

It is an object of the present invention to provide an improved control and control assembly for a liquid heating apparatus.

When viewed from a first aspect the present invention provides a control assembly for a cordless liquid heating apparatus comprising a control for mounting to the liquid heating apparatus to control the supply of electrical power thereto, a cordless base connector adapted to supply electrical power to the control when engaged therewith, and a switch arrangement for making or breaking an electrical circuit for supplying electrical power to the liquid heating apparatus, the switch arrangement comprising a fixed electrical contact provided on the cordless base connector and a moveable electrical contact for engagement with the fixed electrical contact,

wherein the moveable electrical contact is mounted at a free end of a resilient member that is fixed at one point and can be flexed to effect movement of the electrical contact, the resilient member being constrained in its movement at another point between the fixed point and the free end so as to control the movement of the electrical contact that results from flexing of the resilient member. This aspect of the invention extends to a control for a cordless liquid heating apparatus comprising a switch arrangement for making or breaking an electrical circuit for supplying electrical power to the liquid heating apparatus, the switch arrangement comprising a moveable electrical contact mounted at a free end of a resilient member that is fixed at one point and can be flexed to effect movement of the electrical contact, the resilient member being constrained in its movement at another point between the fixed point and the free end so as to control the movement of the electrical contact that results from flexing of the resilient member.

Such a control may be arranged to bring the moveable electrical contact into

engagement with a fixed contact provided inside the control but preferably, as in accordance with the first aspect of the invention, the moveable electrical contact is brought into engagement with a fixed contact provided by a cordless base connector.

It will be appreciated that compared to arrangements that employ a freely flexing leaf spring to move a contact to make or break the electrical circuit in a control, e.g. a cantilever arrangement, the resilient member is constrained such that movement of the contact may be limited. Such a switch arrangement can be more accurate and predictable in its operation. For example, it can be important to control movement of one contact relative to another so as to ensure there is achieved good electrical contact, on the one hand, and controlled separation of the contacts on the other hand. In particular, when the moveable contact is moving into or out of electrical contact with a fixed contact e.g. provided on a cordless base connector then the space available around the fixed contact (e.g. as dictated by the cordless base connector) may be limited.

Furthermore, when making or breaking the electrical circuit at a fixed contact provided on a cordless base connector, a considerable advantage can be achieved in that fewer current- carrying contact pairs may be required overall. In conventional arrangements there are contacts between the two cordless connector parts (the base connector and a connector provided by the control) and also another set of contacts in the control for switching power - e.g. to prevent the element overheating. Instead the switch arrangement recited herein can carry out the dual function of switching power to the apparatus and the necessary separable electrical connection between the control mounted to the liquid heating apparatus and the cordless base connector. It is therefore preferable that the control assembly consists of a single switch arrangement for making or breaking the electrical circuit supplying electrical power to the liquid heating apparatus. This is advantageous as electrical contacts typically require a silver contact surface and this gives rise to a significant proportion of the manufacturing cost of the control. The elimination of a set of contacts is also beneficial in reducing the number of moving parts in the control which improves reliability. Moreover, since the resilient member in the control of the invention can provide the necessary contact pressure, it is not necessary to provide a resiliently biased contact in the cordless base connector which makes it more robust as well as allowing more cost-effective manufacture.

It will be understood that the resilient member is arranged so as to be flexed by an external force to effect movement of the electrical contact mounted thereto. The switch arrangement preferably comprises an actuator, for example a moveable push member, arranged to act on the resilient member at another point away from its constrained point. The actuator can act on the resilient member at any point spaced from the constrained point. In one set of embodiments the actuator acts on the resilient member at a point between its fixed point and its constrained point. Rather than flexing freely from its fixed point in the form of a cantilever, the resilient member can only flex within the constrained bounds that are imposed. The degree of movement of the free end carrying the electrical contact therefore depends on the constrained point as well as the force applied by the actuator. Independent movement control is achieved in addition to the elastic response of the resilient member. This can be contrasted with arrangements in which an electrical contact is mounted to a bimetallic member, for example a creep action bimetallic actuator, that deflects itself when heated. The resilient member is not itself a bimetallic actuator although it may be acted upon, directly or indirectly, by a bimetallic actuator (as will be discussed in more detail below).

The switch arrangement may be shared between the control and the cordless base connector. However it is preferable that at least the moveable electrical contact is associated with the control and therefore mounted in a cordless liquid heating apparatus in use. When the control is engaged with the cordless base connector it is preferable that the moveable contact is automatically engaged with the fixed contact, e.g. power is supplied as soon as the apparatus is placed on a base unit carrying the cordless base connector. The resilient member may therefore be arranged to provide a resilient bias that urges the moveable contact into engagement with the fixed contact. Flexing of the resilient member must overcome such a bias to move the electrical contact away from the fixed contact. In a set of embodiments a latch may be provided to keep the resilient member in a flexed configuration to hold open the switch arrangement until the apparatus is manually switched on. A latch may act directly on the resilient member to hold it in a flexed configuration with the moveable electrical contact separated from the fixed electrical contact. Or a latch may interact with the actuator, where provided, to hold it in a position that acts on the resilient member to put it into a flexed configuration.

As is mentioned above, it is preferable that flexing of the resilient member results in movement of the moveable electrical contact away from the fixed electrical contact to thereby break the electrical circuit for supplying electrical power to the liquid heating apparatus. The moveable electrical contact may be brought into engagement with the fixed contact in any direction - e.g. vertically or horizontally - depending on the orientation of the fixed contact in the control assembly, and the resilient member may therefore be arranged to move the moveable contact in one of these particular directions. In a set of embodiments the moveable electrical contact may be mounted at a free end of the resilient member that extends substantially in the plane of the control assembly. Flexing of the resilient member may then effect movement in a direction substantially out of the plane of the control assembly. However such arrangements may require a clearance height to be provided in the control assembly that can prevent its vertical extent from being minimised.

In other sets of embodiments the moveable electrical contact may be mounted at a free end of the resilient member that extends out of the plane of the control assembly. Flexing of the resilient member may then effect movement in a direction substantially in the plane of the control assembly, i.e. a lateral movement of the electrical contact. In such embodiments a sliding engagement of the contacts (i.e. a side-swipe action) may be achieved when the control is engaged with the cordless base connector. A sideways approach relative to the fixed contact may help to minimise the vertical height of the control assembly as the free end of the resilient member mounting the moveable contact may extend so as to overlap with the depth of the cordless base connector. In such embodiments the switch arrangement may comprise a resilient member having a portion between the fixed point and the constrained point that extends substantially laterally in the control assembly. A portion of the resilient member between the constrained point and the free end mounting the moveable electrical contact may extend parallel to the cordless base connector e.g. substantially out of the plane of the control assembly. Preferably the resilient member is bent at an angle, which may be between 0° and 180°, but is preferably around 90°, between the two portions extending from the constrained point, e.g. a substantially J-shaped, L-shaped or T-shaped member. The bend in the resilient member may conveniently provide a point to be constrained.

There are many different ways in which the resilient member may be constrained in its movement. What is meant by the movement being constrained is that at least one degree of freedom is reduced or removed. In one example the resilient member may be constrained from translational movement in any direction but left with the freedom to pivot, for instance a fixed pivot point may pass through the resilient member (e.g. at a bend in the member, where one is provided). However a problem with constraining the movement to pivoting only is that the free end of the resilient member is then forced to trace an arcuate path and this can make it harder to ensure accurate engagement of the moveable contact with the fixed contact. In a preferred set of embodiments the resilient member is constrained from translational movement only in a direction out of its plane e.g. in a z-direction. This limits the flexing motion of the member but ensures that it can slide backwards/forwards in its plane as well as pivoting around the constrained point. This combination of sliding and pivoting can help the free end carrying the moveable electrical contact to move substantially linearly rather than along an arcuate path.

The resilient member may be caused to flex and move the electrical contact away from the fixed contact when acted on at more than one point. In particular, the Applicant has recognised that providing the constrained point somewhere between two arms of the resilient member, while another arm of the member is fixed, means that movement may be effected from either side of the constrained point. Two actuators may therefore be arranged to act independently on the resilient member from different sides of the constrained point. The resilient member may comprise a member with three arms, for example a T-shaped member. A first arm may comprise the fixed point while a second arm may be fixed, semi-fixed or free. A third arm may comprise the free end carrying the moveable electrical contact. The constrained point is provided between the three arms. When either the first or second arm is caused to flex, preferably when acted upon by a respective actuator, this results in a controlled movement of the electrical contact carried by the third arm (as dictated by the constrained point between the three arms). Four or more arms may be employed, albeit with increasing complexity for the switch arrangement.

In a set of embodiments the resilient member comprises a first arm with the moveable electrical contact mounted at a free end and two further arms with the constrained point at a junction between the three arms. The second arm is arranged to be acted upon by a first actuator, such as a temperature-sensitive actuator, so as to flex and move the electrical contact away from the fixed contact. The third arm is arranged to be acted upon by a second actuator, such as an overheat actuator, so as to flex and move the electrical contact away from the fixed contact. The first and second actuators preferably act on the second and third arms, respectively, in opposite directions so as to result in movement of the first arm in the same direction (i.e. moving the electrical contact away from the fixed contact). Such embodiments conveniently enable two independent levels of protection to be provided using a single resilient member. Furthermore the operation of the first and second actuators in opposite directions can contribute to efficient use of space in the control assembly and help to keep the assembly compact while maximising functionality.

So that the resilient member returns to its original configuration after flexing, it preferably comprises a spring member. The resilient member could be made of a suitable plastics material, for example an elastomer moulded around a current-carrying wire, but preferably the resilient member comprises an electrically conductive material so that it can carry current to the moveable electrical contact itself. In a set of embodiments the resilient member comprises a metallic material, preferably a metallic material providing relatively high electrical conductivity, for example copper or a copper alloy. The resilient member preferably comprises a leaf spring member. A conductive leaf spring member acts as a particularly convenient and economical way to supply current to the moveable electrical contact while also providing the resilience required to flex and move the contact.

The inherent resilience of the resilient member may be relied upon to provide a contact pressure between the moveable electrical contact and the fixed electrical contact. However, the Applicant has recognised that it can be important to ensure that there is adequate contact pressure between the electrical contacts, especially when making or breaking the live pole of the electrical circuit i.e. switching the current of the power supply. In a set of embodiment it is therefore preferable that the control assembly or control further comprises means arranged relative to the fixed contact to bear on the resilient member such that its free end is resiliently biased to move the electrical contact into engagement with the fixed electrical contact. This "rating" means ensures that the resilient member is at least slightly stressed when the electrical contacts are in engagement and the member therefore applies a certain contact pressure. The position of the rating means relative to the position of the fixed contact can be chosen to provide a desired degree of deflection at the free end and hence a desired contact pressure as a result of the resilient bias.

In at least some embodiments the "rating" means may be provided by, or combined with, the constrained point. Especially where the resilient member is bent between two portions extending from the constrained point, the constrainment applied to the bend can be arranged to pre-stress a portion of the resilient member carrying the moveable contact so that its free end is resiliently biased to move the electrical contact into engagement with the fixed electrical contact. Flexing of the resilient member to move the electrical contact away from the fixed electrical contact might release the stress on the resilient member. However, in another set of embodiments the "rating" means is provided separately from the constrained point. This keeps the forces on the resilient member independent. In particular, to attain full benefit from the "rating" means it can be important for it to be arranged relative to the fixed electrical contact provided on the cordless base connector. Given that parts of the control assembly are moveable relative to the cordless base connector, and the control part of the assembly can be disengaged from the cordless base connector, it may be preferable for the "rating" means to be provided on the cordless base connector as well. The "rating" means may be in a fixed position on the cordless base connector relative to the fixed electrical contact.

The resilient member can complete the electrical circuit for supplying power to the liquid heating apparatus, in use, when the control is engaged with the cordless base connector and the contacts are engaged. The resilient member may be provided with a terminal for electrical connection to the liquid heating apparatus. A single switch arrangement of the type described could be provided, e.g. for switching the live side of the power supply only, with the other electrical contacts, e.g. for connection to the neutral and earth terminals (where provided), connected differently, e.g. hard wired. However in a set of embodiments the control comprises at least two such switch arrangements, e.g. for switching both the live and neutral poles.

However, as is mentioned above, it is preferable that only one of the switch arrangements is arranged to make or break the electrical circuit supplying electrical power to the liquid heating apparatus (i.e. the primary switch arrangement). While the contact(s) in the primary switch arrangement may have a silver contact surface for this purpose, the contact pair in other of the switch arrangements may be less silvered or un-silvered as it is not used to switch any current.

Where two (or more) switch arrangements are provided, the same resilient member could be used to mount the respective contact pairs (e.g. live and neutral). However, in a set of embodiments separate resilient members are provided for each contact pair. This makes it easier for the respective switching arrangements to be operated independently, for example by being acted upon by independent actuators. The Applicant has recognised that increasing the number of switch arrangements can increase the space required by a control assembly for its moving parts. However it is desirable to make a control assembly as compact as possible so as to reduce the space it takes up in a liquid heating apparatus, together with the associated materials and carbon footprint for transportation etc. In a preferred set of embodiments the switch arrangement comprises two resilient members each mounting a moveable electrical contact for engagement with a respective fixed electrical contact, the resilient members being arranged substantially side by side and extending in opposite directions from their respective fixed points such that flexing of one resilient member results in movement of its electrical contact in a direction opposed to the movement of the electrical contact that results from flexing of the other resilient member.

This is considered novel and inventive in its own right and thus when viewed from a second aspect the present invention provides a control assembly for a cordless liquid heating apparatus comprising a control for mounting to the liquid heating apparatus to control the supply of electrical power thereto, a cordless base connector adapted to supply electrical power to the control when engaged therewith, and a switch arrangement for making or breaking an electrical circuit for supplying electrical power to the liquid heating apparatus, the switch arrangement comprising first and second fixed electrical contacts provided on the cordless base connector and respective first and second moveable electrical contacts for engagement with the fixed electrical contacts, each of the first and second moveable electrical contacts being mounted at a free end of respective first and second resilient members that can be flexed to effect movement of the electrical contacts, wherein the first and second resilient members are arranged substantially side by side and extend in opposite directions from respective fixed points such that flexing of the first resilient member results in movement of the first electrical contact in a direction opposed to the movement of the second electrical contact that results from flexing of the second resilient member.

This aspect of the invention also extends to a control for mounting to a liquid heating apparatus, the control comprising a switch arrangement for making or breaking an electrical circuit for supplying power to the liquid heating apparatus, the switch arrangement comprising first and second moveable electrical contacts, each of the first and second moveable electrical contacts being mounted at a free end of respective first and second resilient members that can be flexed to effect movement of the electrical contacts, wherein the first and second resilient members are arranged substantially side by side and extend in opposite directions from respective fixed points such that flexing of the first resilient member results in movement of the first electrical contact in a direction opposed to the movement of the second electrical contact that results from flexing of the second resilient member. Such a control may be arranged to bring the moveable electrical contacts into engagement with respective first and second fixed electrical contacts. The fixed contacts could be provided inside the control but preferably, as in accordance with the first aspect of the invention, they are provided by a cordless base connector.

It will be appreciated that in switch arrangements comprising (at least) two contact pairs that are opened/closed in opposite directions by respective resilient members, the control or control assembly can potentially be made more compact by arranging for the opposed movements to overlap in the same plane. This benefit may be enhanced in embodiments, such as described above, where the free end of each resilient member, which mounts the moveable electrical contact, extends out of the plane of the control assembly. Preferably the first and second resilient members are arranged side by side so as to flex and effect movement in opposed directions that are substantially in the plane of the control assembly, i.e. opposite lateral movements of the electrical contacts. Such a dual sideways approach relative to the fixed contacts can minimise the vertical height of the control assembly as the free ends of the resilient members mounting the moveable contacts may both extend so as to overlap with the depth of the cordless base connector but without interference between their movements.

Preferably the resilient members are bent at an angle, which may be between 0° and 180°, but is preferably around 90°, between their respective fixed points and free ends, e.g. they are substantially J-shaped, L-shaped or T-shaped members. A compact switch arrangement may be particularly suited to a control for a liquid heating apparatus comprising a relatively low power heater e.g. 1.5 kW and having a small base area to accommodate the control.

While the resilient members may flex freely from their fixed points, it is preferable that they are constrained in their movements at another point between the fixed point and the free end, so as to provide control over the movement of the electrical contact that results from flexing of the resilient member, as in accordance with the first aspect of the present invention. Any of the other features described hereinabove may equally be applied to this second aspect of the invention. There will now be described features and embodiments that apply to either of the foregoing aspects of the invention.

The moveable electrical contact preferably comprises a material which is a good electrical conductor, e.g. copper. In a set of embodiments the moveable contact comprises a silver coating or tip. Silver is chosen for its high electrical conductivity which reduces the tendency for deterioration of the contact surface through oxidation, but preferably it is only provided as a coating or at the tip, i.e. where physical contact with the fixed contact is made, in order to reduce the cost of the contact while maximising the effectiveness of the silver. It is similarly preferred that the contact surface of the fixed contact comprises silver. However the Applicant has found that using silver on one side only, i.e. on either the moveable contact or the fixed contact, when the opposing side is copper, provides an adequate performance. This is because the plasma generated during arcing, as the contacts open, causes the silver on the one contact to melt, resulting in a layer of silver being deposited on the opposite contact.

In the set of embodiments in which two moveable contacts are provided, e.g. for switching separate poles, it may be that only one of them comprises a silver coating or tip, preferably that used to switch the live (primary) pole. The control can advantageously be arranged such that in normal use the electrical contact with the silver contact surface preferentially makes or breaks contact first. This maximises the benefit of the small amount of silver whilst allowing other contact pairs to be un-silvered or less silvered.

In a set of embodiments the switch arrangement comprises a resilient member that is arranged to move the moveable contact mounted thereon away from its corresponding fixed contact when the liquid heating apparatus reaches a predetermined temperature condition. Where multiple electrical contacts are provided (e.g. live and neutral) then this preferably breaks the electrical circuit for the live pole of the power supply. It could be that the liquid in the apparatus reaches a predetermined temperature, e.g. boiling, or that the electric heating element reaches a predetermined temperature, e.g. to indicate boiling or overheating. In a set of embodiments the control comprises a temperature-sensitive actuator, e.g. a bimetallic actuator, arranged to act on the resilient member. The actuator may act directly or indirectly on the resilient member. The actuator may comprise a boiling sensor (e.g. a steam sensor) or an overheat sensor. The control may further comprise means for transmitting the movement of the actuator to the resilient member, for example a push rod or lever acted upon by the actuator. A snap action bimetallic actuator may be used to ensure a rapid response at a desired

temperature. Where a temperature-sensitive actuator, such as a snap-acting bimetallic actuator, acts on the resilient member to separate the contacts, the nature of a lever can be exploited. For example, by arranging for the actuator to act on the resilient member at a distance from the constrained point (or fixed point, where a constrained point is not necessarily provided in accordance with the second aspect) that is closer than the distance to the moveable contact, the movement of the actuator is amplified by the flexing of the resilient member. The lever effect can also be exploited to allow a relatively small force exerted by the actuator to be amplified in order to open the moveable contact against the resilient bias force, so that a relatively high resilient bias can be used to ensure a high contact pressure. This creates a safer control as the relatively small distance of travel of an actuator such as a snap-acting bimetallic actuator can be amplified into a larger distance of travel of the moveable contact, ensuring that there is adequate separation from the fixed contact to meet safety standards.

In a preferred set of embodiments a temperature-sensitive actuator is mounted on the control such that when the control is mounted to a liquid heating apparatus the temperature- sensitive actuator makes thermal contact with and is sensitive to the temperature of the liquid heating apparatus, the temperature-sensitive actuator being arranged to act on the resilient member (directly or indirectly) such that the resilient member moves the moveable contact away from the fixed contact when the liquid heating apparatus reaches a predetermined temperature condition. The temperature-sensitive actuator is preferably a snap acting bimetallic actuator.

Preferably the temperature-sensitive actuator is mounted on an outer face of the control. The control could comprise more than one actuator, e.g. one to sense boiling and one to sense overheating. In one set of embodiments the control comprises a temperature-sensitive actuator arranged to detect boiling of the liquid in the liquid heating apparatus, e.g. a steam switch which could comprise a bimetallic actuator, arranged to act on the resilient member so as to separate the moveable and fixed contacts. In another, not mutually exclusive, set of embodiments, the control comprises a temperature-sensitive actuator arranged to detect overheating of the liquid heating apparatus, e.g. which could comprise a bimetallic actuator or a thermal fuse mounted on or against the electric heating element, arranged to act on the resilient member (directly or indirectly) so as to separate the moveable and fixed contacts. In embodiments where two different actuators act on the same resilient member, for example acting on different arms of the resilient member as described above, one actuator may comprise a bimetallic actuator arranged to detect liquid temperature while the other actuator may comprise a thermal fuse arranged to detect an overheat condition. Multiple actuators may be used to provide additional levels of back-up protection for safety.

In the set of embodiments in which two moveable switch arrangements are provided, e.g. for the live and neutral poles, preferably the control comprises independent temperature- sensitive actuators arranged to act on each respective resilient member. Alternatively, or in addition, the control could comprise both boiling and overheat actuators arranged to act on the same resilient member. In a set of embodiments the control comprises at least two

independent temperature sensitive actuators for detecting overheating of the liquid heating apparatus which are arranged to act on the resilient members associated with the live and neutral poles respectively, and an actuator to detect boiling of the liquid in the liquid heating apparatus also arranged to act on the resilient member associated with the live pole. The actuators could act directly on the respective resilient members or by means of an intermediate mechanism - e.g. a lever. In a set of embodiments, for example, the boiling actuator is arranged to act on an on/off slider which in turn acts on the resilient member carrying the contact for the live pole. This arrangement is advantageous as it allows in some embodiments for the "on" mechanism to over-ride the action of the boiling actuator and thus permits the user to re-boil when desired.

As mentioned previously, in a set of embodiments where overheat actuators are provided to act on both the live and neutral poles, the actuator associated with the live pole (primary) is arranged preferentially to act first in an overheat situation - e.g. because this allows only the live contact to have a silver contact surface, or else a thicker layer of silver on its contact surface. This can be done by, for example, arranging the overheat actuator associated with the live pole to be closer to a sheathed heating element of the apparatus than the overheat actuator associated with the neutral pole (secondary). In a set of embodiments the overheat actuator associated with the live pole comprises a bimetallic actuator mounted on or adjacent the sheathed heating element. In a set of embodiments the overheat actuator associated with the neutral pole comprises a bimetallic actuator mounted more thermally remote from the sheathed heating element, e.g. between the cold tails of the sheathed element mounted. The control may be mounted to a liquid heating apparatus comprising a sheathed electrical heating element beneath the base of a liquid heating chamber (i.e. an underfloor heater).

In a set of embodiments this neutral pole or secondary overheat actuator is arranged not to be able to be reset if it operates, i.e. it permanently holds the associated contacts open. This provides an additional level of safety. A latching mechanism associated with this secondary actuator could be provided to hold open the respective contacts and/or to retain the actuator in an operated state. However, the Applicant has observed that even a remotely located secondary actuator can operate after the live pole or primary actuator (i.e. the actuator mounted closer to the sheathed heating element) has operated owing to the residual thermal energy dissipating through the heated base, e.g. via a diffuser plate - i.e. thermal overshoot. To prevent this from happening, in a set of embodiments the control is mounted in a liquid heating apparatus comprising a heater or diffuser plate which comprises means to disrupt the direct thermal path from the sheathed heating element to the secondary overheat actuator. The disrupting means could comprise holes, gaps, slots, walls, baffles, etc, formed in the heater or diffuser plate, or additional thermal masses in thermal contact with the heater or diffuser plate.

However the Applicant has also devised a further approach which addresses the thermal overshoot issue in the control itself (i.e. without requiring any particular measures on a heating element diffuser plate etc.). Thus in a set of embodiments the control comprises a primary overheat actuator for interrupting the supply of power to a heating element in the liquid heating apparatus by opening a first (primary) switch arrangement in the event of said heating element overheating and a secondary overheat actuator for interrupting the supply of power to the heating element by opening a second (secondary) switch arrangement in the event of said primary actuator failing to operate, wherein the primary actuator is arranged in normal use to operate before the secondary actuator in the event of the heating element overheating and wherein the first and second switch arrangements have a relationship which is such that if the second switch arrangement independently opens before the first switch arrangement a latch is engaged which prevents one or both of said first and second switch arrangements from re- closing to supply power to the heating element but, if the first switch arrangement opens before the second switch arrangement, the latch is not engaged.

To further improve the safety of the control and the apparatus, in a set of embodiments the control is arranged so that the switch arrangement cannot be re-closed once the resilient member has been acted on by an overheat actuator before a further predetermined temperature condition is reached. Thus, once overheating has been detected, the temperature-sensitive actuator has to cool down to a certain temperature before operation of the apparatus is possible again. This protects the apparatus and/or the heating element from being re-energised too soon after overheating has been detected. Furthermore it is not possible for this safety function to be over-ridden by a user attempting to re-energise the apparatus. The apparatus and/or the heating element therefore has to cool down to a safe temperature before a repeat operation is possible.

In contrast, in a set of embodiments the control is arranged so that the switch

arrangement can be re-closed manually - e.g. with an 'on' button - after the resilient member has been acted on by a temperature-sensitive actuator that detects boiling or a desired temperature condition. This allows for liquid to be re-boiled or re-heated shortly after boiling (or another temperature condition) has previously been reached.

In a set of embodiments the control comprises a user-operated actuator arranged to move the moveable contact away from the fixed contact against the biasing force of the resilient member, e.g. an "off" button to break the electrical power circuit. Preferably the user-operated actuator acts on the resilient member carrying the moveable contact associated with the live (primary) pole of the electrical circuit, where provided. In a set of embodiments the actuator acts directly on the resilient member. In a set of embodiments the control comprises a latching mechanism arranged to hold the moveable contact away from the fixed contact, i.e. when it is acted on by the user-operated actuator. This may be necessary because the resilient member is likely to be mono-stable, i.e. when the user-operated actuator is released, the moveable contact would be biased back towards the fixed contact. In general, providing a resilient member which is mono-stable allows a simpler actuating mechanism to be used either for the user-operated actuator or the temperature-sensitive actuators in combination with a latching mechanism described below as a further movement is no longer needed, e.g. as would be for a bi-stable or over-centre mechanism. A further user-operated actuator, e.g. an "on" button, could be provided to release the resilient member from the latching mechanism. In one set of embodiments the "on" and "off" buttons could comprise a linking mechanism, e.g. so that only one of them can be actuated at any one time. In a set of embodiments, only an "on" button is provided with the user able to switch the apparatus off in another way - e.g. by momentarily lifting it from its base. This reduces the number of components and so increases reliability.

In embodiments in which a cordless appliance comprising the control is provided, the control may comprise a mechanism arranged to act on the resilient member so as to move the moveable contact away from the fixed contact against the biasing force when the appliance is placed on the cordless base. This prevents the appliance being inadvertently re-energised when it is placed on the base after being lifted off, e.g. to pour heated liquid out of the appliance. It also provides a mechanism whereby the apparatus can be switched off without having to provide an "off" switch. The resilient member carrying the moveable contact could be latched in its flexed configuration with the contact moved away from the fixed contact when acted on by the mechanism, or the mechanism itself could be latched by the action of placing the appliance on the cordless base thus holding the resilient member in a flexed configuration with the moveable contact separated from the fixed contact. In a set of embodiments the mechanism comprises a physical blocking member arranged so that when the moveable contact is separated from the fixed contact, the blocking member moves automatically to a blocking position in which it prevents the resilient member from flexing under its own bias so that the moveable contact can not make electrical contact with the fixed contact. The action of placing the appliance on the cordless base may provide the force necessary to overcome the biasing force of the resilient member, with the free end carrying the moveable contact being moved by the blocking mechanism. In a set of embodiments the control comprises a user- operated actuator, e.g. an "on" switch arranged to disengage the blocking mechanism. This acts to release the resilient member carrying the moveable contact from its flexed configuration where it is held open by the blocking mechanism, allowing it to re-make contact with the fixed contact.

In embodiments of the present invention the control or control assembly is preferably mounted in good thermal contact with a heater of the liquid heating apparatus. The electrical circuit controlled by the switch arrangement supplies electrical power to the heater in use. The switch arrangement may operate to disconnect electrical power from the heater in the event of a predetermined temperature condition being reached and/or in the event that the heater overheats.

In embodiments of the present invention the control or control assembly may comprise a connector part for engagement with the cordless base connector. However this is not essential and the moveable electrical contact(s) may be brought into engagement with fixed contact(s) provided on the base connector without any other parts coming into physical engagement.

The cordless base connector is preferably of the type which allows electrical connection to be made substantially irrespective of the relative angular orientation between it and the control - i.e. a so-called 360° connector. However in some embodiments the base connector may not allow full 360° relative to the orientation of the control, but while still allowing electrical connection to be made substantially irrespective of this orientation, e.g. through a range of 345° or greater.

As is mentioned above, the control is particularly well-suited for use with a cordless electrical appliance comprising a connector part of the 360°-type, that is, an appliance connector part that can be brought into engagement with a corresponding base connector provided by a power base unit regardless, or substantially regardless, of the relative angular orientation of the two parts. The cordless connector system may include two or three electrical terminals (e.g. live, neutral and optionally earth) for basic power connection. In particular, the appliance connector part may be in the form of a connector plug part comprising a central terminal pin (e.g. earth) and outer spring terminals (e.g. carrying live and neutral electrical contacts), while the base connector may be in the form of a connector socket part comprising a central recess with a spring contact finger and concentrically arranged electrical contact rings.

Where, as is preferred, the liquid heating apparatus is of the so-called cordless type, comprising a cordless base for connection to the mains supply and an appliance proper for mating therewith, the control of the invention could be provided in the cordless base, but in a set of preferred embodiments the control is mainly in the appliance proper - e.g. electrically connected to an electric heating element. However, as mentioned above, the fixed contact of the switch arrangement may be provided in the cordless base connector while its other components are provided in the appliance part. The electric heating element will typically be arranged in good thermal contact with the liquid to be heated in the apparatus. The electric heating element could comprise a sheathed heating element, e.g. immersed or mounted on the underside of a heater plate on the liquid heating apparatus, or a thick film heating element.

The present invention also extends to a cordless electrical appliance comprising a cordless liquid heating apparatus comprising a control or control assembly as described above, and a power base comprising the base connector part adapted to supply electrical power to the control when the cordless liquid heating apparatus is engaged with the power base.

Certain embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 provides a partial perspective view of some of the operational parts of a control and a cordless base connector in accordance with a first embodiment, with Fig. 1a showing the control in an unoperated configuration and Fig. 1 b showing the control in an operated configuration; Fig. 2 is a plan view of the control and cordless base connector of Fig. 1a;

Fig. 3 provides a partial perspective view of some of the operational parts of a control and a cordless base connector in accordance with a second embodiment, with Fig. 3a showing the control in an unoperated configuration and Fig. 3b showing the control in an operated configuration;

Fig. 4 provides a schematic of the basic operation of a control and a fixed contact in accordance with a third embodiment, with Fig. 4a showing the control in an unoperated configuration and Fig. 4b showing the control in an operated configuration;

Figs. 5a and 5b schematically show a fourth embodiment in which movement of a contact- carrying member releases a resilient bias resulting from a stop associated with a fixed member; and

Figs. 6a and 6b schematically show a fifth embodiment in which movement of a contact-carrying member releases a resilient bias resulting from another stop associated with a fixed member.

There is seen in Figs. 1 and 2 some of the components of a control 2 in engagement with a base connector 4. The control 2 may be mounted in a cordless liquid heating apparatus such as a kettle or hot water jug (not shown). The base connector 4 is a 360° cordless connector that allows for engagement with the control 2 regardless of their relative angular orientation. The base connector 4 may be provided on a power base (not shown) for the cordless apparatus. The base connector 4 comprises two concentrically arranged electrical contact rings 6, 8 that provide fixed electrical contacts. The contact rings 6, 8 may be formed of copper or copper alloy and may be provided with an outer surface coating or plating of silver or a silver alloy.

The base connector 4 may be in the form of a connector socket part such as is seen, for example, in WO 94/06185. The other components of the base connector 4, such as a moulded plastics housing, shutter and spiral spring, and spring finger for the earth contact in a central hollow post, are not shown. As is clearly seen from Fig. 2, the base connector 4 has rotational symmetry in a plane transverse to the axial direction of the contact rings 6, 8, which

corresponds to the direction in which the parts of the control 2 and base connector 4 are brought into engagement. Each of the contact rings 6, 8 is electrically connected by a wire 7, 9 to the mains power supply (e.g. by a cable not shown).

The control 2 comprises a first resilient leaf spring member 10 carrying an electrical contact 12 (e.g. live) at its free end and a second resilient leaf spring member 14 carrying an electrical contact 16 (e.g. neutral) at its free end. The two leaf springs 10, 14 are each L- shaped, fixed at one end to extend in the plane of the control 2 before bending into respective arms 18, 20 that extend parallel to the axial direction of the contact rings 6, 8 and terminate in the free end carrying a respective contact 12, 16. The leaf springs 10, 14 are electrically connected to a power supply circuit for the liquid heating apparatus by respective wires 11 , 15 crimped onto the fixed ends. Of course the wires 1 1 , 15 may be soldered rather than crimped. Where desired, a 'Faston' connector, blade connector or other push-on connector may be attached directly to the fixed end instead of a wire. It can be seen from the plan view of Fig. 2 that the leaf springs 10, 14 extend side by side in opposite directions from their respective fixed ends.

The leaf springs 10, 14 are not freely cantilevered from their fixed ends as each of them has tabs 22 that extend laterally in the vicinity of the bend that forms the arms 18, 20 and are mounted on a surface (not shown) in the control. As the tabs 22 rest on a surface, the leaf springs 10, 14 are constrained from movement in the axial direction at this point. However the leaf springs 10, 14 are free to slide along the surface in the plane of the control 2 and the arms 18, 20 are free to pivot. The position of the tabs 22 bearing against this surface is arranged so that the arms 18, 20 are resiliently biased to move the electrical contacts 12, 16 into

engagement with the fixed electrical contacts 6, 8 when the lateral portions of the leaf springs 10, 14 are not flexed (as seen in Fig. 1 a). The arms 18, 20 are under a bending stress that tends to push the electrical contacts 12, 16 against the fixed contact rings 6, 8, thereby providing a contact pressure.

The control 2 also includes an actuator, in the form of a push rod 24, 26, that is arranged to bear axially on a respective leaf spring 10, 14 between its fixed end and the tabs 22 that form a constrained point. When the push rod 24, 26 is moved axially towards the base connector 4 the leaf spring 10, 14 is flexed, resulting in pivotal movement of the arm 18, 20 carrying the electrical contact 12, 16 so as to release the stress in the leaf springs 10, 14 and move the contacts 12, 16 away from the contact rings 6, 8 in the base connector 4. Each push rod 24, 26 may be actuated by a temperature-sensitive actuator (not shown) such as a bimetallic actuator arranged in thermal contact with the liquid heating apparatus. Operation of the control will be understood by comparing Figs. 1 a and 1 b. When either of the push rods 24, 26 moves axially towards the base connector 4, the corresponding leaf spring 10, 14 is not free to move in a cantilever fashion but flexes in a manner controlled by the constrained tabs 22. The tabs 22 may slide along associated supporting surface(s) while also providing a pivot point for the arms 18, 20 carrying the contacts 12, 16. The flexing of the leaf springs 10, 14 is therefore converted into a controlled lateral movement of each electrical contact 12, 16. Flexing of the leaf springs 10, 14 and pivoting of the arms 18, 20 releases the bending stress and allows the arms 18, 20 to straighten as they move out laterally. Furthermore it can be seen that the side by side arrangement of the two L-shaped leaf springs 10, 14, with lateral movement of the electrical contacts 12, 16 within the height of the base connector 4, allows the vertical extent of the control 2 to be minimised.

Operation of either of the push rods 24, 26 can result in the corresponding leaf spring 10, 14 flexing to move its electrical contact 12, 16 out of contact with the associated contact ring 6, 8 of the base connector 4. In practice one of the leaf springs 10, 14 is designated as a "primary" switch arrangement with its associated push rod 24, 26 actuated e.g. by an overheat condition to operate before the other. The primary switch arrangement is the one that makes or breaks the electrical circuit for supplying electrical power to the liquid heating apparatus, and the electrical contacts involved in this switch arrangement have at least one silvered contact surface. Other electrical contacts in the control and base connector may be less silvered or un- silvered.

The control 2 may further comprise a central terminal pin (not shown) that extends axially to contact a spring contact finger in a central hollow (not shown) of the base connector 4 to provide a third electrical connection e.g. earth, where desired.

There is seen in Figs. 3a and 3b another embodiment that basically operates in the same way as already described. Like components are provided with the same reference numbers as before. In this control 2', each leaf spring 10', 14' is modified so that the tabs are replaced with a further arm 28, 30 extending laterally from the point at which the leaf spring 10', 14' bends to form its axially extending arm 18, 20. The leaf springs 10', 14' are therefore T- shaped rather than L-shaped. The junction between the arms 18, 20, 28, 30 rests on a surface (not shown) provided by the control so it is constrained against movement in the axial direction. As before, the constrained point bears on the leaf springs 10', 14' such that the axially extending arms 18, 20 are resiliently biased with the contacts 12, 16 pressed against the contact rings 6, 8.

The purpose of the laterally extending arms 28, 30 is to provide an additional means of flexing the leaf springs 10', 14' and moving the electrical contacts 12, 16 relative to the contact rings 6, 8 in the base connector 4. Each leaf spring 10', 14' may be flexed when acted upon by a respective push rod 24, 26 as previously described. In addition, the further arms 28, 30 are acted upon by a spring 32, 34 from one side with the spring 32, 34 held in a compressed state by a thermal fuse 36, 38 acting on the arms 28, 30 from the opposite side. In normal use the further arms 28, 30 are fixed at their ends with an equilibrium maintained between the thermal fuse 36, 38 and the compressed spring 32, 34. The push rods 24, 26 can act to flex the leaf springs 10', 14' and pivot the arms 18, 20 that carry the electrical contacts 12, 16 in the manner seen in Fig. 1 b. Alternatively, the springs 32, 34 can act on the leaf springs 10' 14' instead.

Operation of the control 2' in response to an overheat condition will be understood by comparing Figs. 3a and 3b. If either of the thermal fuses 36, 38 collapses then the associated spring 32, 34 becomes free to expand and pushes on the lateral arm 28, 30 of the leaf spring 10', 14'. Independently of its associated push rod 24, 26, the leaf spring 10', 14' then flexes with the contact-carrying arm 18, 20 pivoting at the constrained junction to move the electrical contact 12, 16 laterally away from the associated contact ring 6, 8 of the base connector 4, as shown in Fig. 3b. Flexing of the leaf springs 10', 14' to move the contacts 12, 16 also releases the bending stress in the arms 18, 20.

In other embodiments the leaf springs may not be bent into an L-shape or T-shape. It is shown schematically in Figs. 4a and 4b how a substantially straight leaf spring 10" may be fixed at one end and mount an electrical contact 12 at its free end. The electrical contact 12 is biased into engagement with a fixed contact 8'. Again, instead of being freely cantilevered the leaf spring 10" is constrained by resting on a surface 40 between its fixed end and its free end. When the leaf spring 10" is acted on by a push rod 24 (or other actuator) it flexes but the lateral movement of the electrical contact 12 is controlled by the constraining surface 40. This basic principle may be applied in any of the embodiments described above.

A further feature that may be applied to any of the embodiments described above is that of an independent "rating" stop arranged relative to a fixed contact to bear on the leaf spring (or other resilient member) such that it is resiliently biased to move its electrical contact into engagement with the fixed electrical contact. In the embodiment seen in Figs. 5a and 5b, a leaf spring 10" is mounted in the same away as described with respect to Figs. 4a and 4b except that now the free end of the leaf spring 10" carrying the contact 12 interacts with a stop 42 that has a fixed position relative to the contact 8'. Like components are provided with the same reference numbers as before.

In the unoperated configuration seen in Fig. 5a the stop 42 bears against the free end of the leaf spring 10" so that it presses the contact 12 against the fixed contact 8' with a resilient bias. This can ensure that a desired contact pressure is achieved. When the leaf spring 10" flexes, as seen in Fig. 5b, its free end is moved away from the stop 42 and the resilient bias is released. In a further embodiment illustrated by Figs. 6a and 6b, the stop 42' has a different position relative to the fixed contact 8' but is still arranged to bear on the leaf spring 10" when the contacts 8', 12 are engaged. The leaf spring 10" now has a hooked end to enable interaction with the stop 42'. As before, the stop 42' causes the leaf spring 10" to resiliently bias the contacts 8', 12 into engagement in the configuration seen in Fig. 6a whereas the leaf spring 10" can relax when flexed into the configuration seen in Fig. 6b.

While the illustrated embodiments have been described as using leaf springs as resilient members, it will be apparent to the skilled person that these members may take another form, for example a resilient plastic member that carries an electrical lead or the like.

It will be appreciated that various other features and components commonly found in a control and cordless base connector have not been described with reference to the illustrated embodiments but will be apparent to a person skilled in the art. For example, the push rods may be operated by a suitable thermally sensitive actuator such as a bimetallic actuator or thermal fuse. Indeed the push rods are merely exemplary and may be replaced by any other suitable actuating mechanism. A thermally sensitive actuator may be arranged to act directly or indirectly on the leaf springs. Further features such as a latching mechanism, manual ON and/or OFF switch, etc. may be integrated into the control as desired.