Power base for a removable appliance part

Abstract

A power base 4 for receiving a removable appliance 6 preferably a liquid heating vessel, comprising of an upper part 8, a lower part 10 preferably having cable receiving portion (26, fig 4) integrally formed, a weight sensor 34 arranged between upper and lower part preferably having sub-sensors 34A-34D evenly distributed and / or maybe a strain gauge or preferably an indicator means 16, a power supply cable (12, fig 4) and its securing means (28, fig 4) preferably formed integral to hold power cable or may have clamps. Base further comprises a cordless electrical connector 14 for electrical connection to the appliance with a cordless electrical adaptor 48. Base Further comprises a control circuit 35 to detect the removal and amount of liquid maybe if below threshold in the appliance, may also send signal / user-alert (378, fig 12) for threshold warning.

Description

The present invention relates to a power base and to an electrical appliance comprising such a power base. Some prior art countertop water heating appliances comprise a means for measuring the weight of the water contained in the appliance. The measured weight can be used to provide an indication to a user as to how much water is in the appliance. This may allow a user to determine whether the appliance needs to be refilled, for example prior to operation. Some water heating appliances are in the form of cordless liquid heating appliances which comprise a removable appliance part, e.g. a liquid heating vessel, which is removably seated on a power base. In such examples, the power base may comprise a weight sensor capable of measuring the weight of the removable appliance part when it is seated thereon. Through knowledge of the weight of the removable appliance part without any contents therein, the weight of the contents may be determined. The Applicant has recognized that in some prior art examples, the weight sensor may not always accurately measure the weight of the removable appliance part, and as a result may provide an inaccurate indication of the contents of the removable appliance part. Specifically, the Applicant has recognized that in prior art appliances various forces can act to distort the measured weight. For example, cordless appliances typically comprise cordless electrical connector in the power base and a corresponding cordless electrical adaptor in the removable appliance part. Such connectors and adaptors typically comprise resiliently biased electrical contacts which apply a force to the other of the connector and the adaptor when they are mated together. Such forces can impact the weight measured by the weight sensor, depending on the positioning of the removable appliance part relative to the power base. In a similar manner, the power supply cable which typically extends from the power base may be relatively inflexible and thus, when arranged in at least some positions, it may apply a vertical force to the power base, which may distort the measurement obtained from a weight sensor arranged in the power base. The present invention aims to address, or at least mitigate, at least one of the problems outlined above. When viewed from a first aspect, the present invention provides a power base for receiving a removable appliance part thereon, the power base comprising: an upper part configured to receive, in use, the removable appliance part thereon; a lower part, separate to the upper part, arranged below the upper part; a weight sensor arranged between the upper part and the lower part; a power supply cable configured to supply the power base with electrical power; and a cable securing means configured to secure the power supply cable to the lower part. The Applicant has appreciated that the specific structure of the power base according to the first aspect of the present invention may facilitate more accurate measurement of the weight of a removable appliance part received, in use, on the power base. The power base may thus be able to determine the weight of the contents of the removable appliance part more accurately. Specifically, the cable securing means, which functions to secure the power supply cable to the lower part, may advantageously prevent any forces from the power supply cable from being transferred to the weight sensor which would otherwise impact the weight measured by the weight sensor. When the removable appliance part is seated on the upper part, the weight of the removable appliance part is transferred through the upper part to the weight sensor arranged between the upper and lower parts. As the power supply cable is secured to the lower part, any forces applied by the power supply cable will be applied to the lower part and may not impact the output of the weight sensor, as this is arranged between the lower part and the upper part. Securing the power supply cable in this manner thus isolates any forces which it applies to the power base. As the power base is configured to receive the removable appliance part in use, the removable appliance part may be considered to be a physically separate component to the power base, which can be placed onto the power base during use. The power base may be a power base for supplying power to any suitable removable appliance part. The power base may be configured to supply inductive power to a removable appliance part. As such, the power base may comprise an inductive heater, e.g. in the form of induction coil. In such embodiments, the removable appliance part may comprise a susceptor configured to generate heat when experiencing a magnetic field generated by the inductive heater. However, in set of embodiments, the power base comprises a cordless electrical connector for providing an electrical connection to the removable appliance part when seated on the power base, wherein the cordless electrical connector extends from the upper part and is positioned so as to mate with a corresponding cordless electrical adaptor on the removable appliance part when it is received thereon. As discussed above, the cordless electrical connector, and indeed the corresponding adaptor in the removable appliance part, may comprise at least one resiliently biased component that acts between the connector and the adaptor. The resiliently biased component may, for example, be a resiliently biased electrical contact. When the removable appliance part is seated on the power base, the at least one resiliently biased component may generate a force acting between the connector and the adaptor. The arrangement of the weight sensor between the upper part and the lower part, in combination with the cordless connector extending from the upper part, advantageously means that forces that arise between the connector and the adaptor when the appliance part is seated on the upper part do not impact the weight measured by the weight sensor. The power base may thus be able to more accurately measure the weight of the removable appliance part. In embodiments in which the cordless electrical connector is configured to mate with a corresponding cordless electrical adaptor on an appliance part, the power base may be considered to be a cordless power base as it provides an electrical connection to the appliance part in a cordless manner. As a removable appliance part may be received, i.e. seated or stood on, the power base during use, the power base may be considered to be a power base stand. The power base may be configured to receive any suitable removable appliance part. In some embodiments, the removable appliance part is a liquid heating vessel. The liquid heating vessel may comprise a chamber for receiving a liquid, e.g. water. Measurement of the weight of the removable appliance part may thus be indicative of the weight of the liquid contained within the chamber. In such embodiments, the liquid heating vessel may comprise a heating element configured to heat the contents thereof, e.g. of the chamber. The cable securing means which secures the power supply cable to the lower part may take any suitable form. In a set of embodiments, the cable securing means is integrally formed with the lower part. For example, the cable securing means may comprise at least one cable securing feature which is integrally moulded with the lower part. The cable securing feature may, for example, comprise a latch which may act to hold the power supply cable against the lower part. The provision of an integrally formed cable securing means may reduce the overall number of parts required to manufacture the power base and may simplify assembly of the power base. However, it is not essential for the cable securing means to be integrally formed with the lower part. Thus, in an alternative set of embodiments, the cable securing means comprises a clamping element configured to be attached to the lower part so as to secure the power supply cable to the lower part. The clamping element may be attached to the lower part in any suitable manner. The clamping element may, for example, be attached to the lower part using at least one, e.g. two, screw(s). In a set of embodiments, the clamping element and / or the lower part, may comprise at least one retention feature configured to attach the clamping element to the lower part. For example, the clamping element may comprise a latch feature configured to engage the lower part in a manner in which holds the clamping element against the lower part. The use of such a retention feature may reduce the number of parts required to manufacture the power base and may also reduce the time required to assemble the power base. In addition to the above, through the use of a separate clamping element, the moulding of the lower part may be less complex, as compared to an integrally formed cable securing means, which may thus reduce the cost of the lower part and potentially the power base. In some embodiments, the cable securing means may be shaped to suitably secure the power supply cable against the lower part. For example, the clamping element may be shaped to receive the power supply cable therein. For example, the clamping element may comprise a curved portion shaped to extend at least partially around the power supply cable. Such a curved portion may increase the amount of contact between the clamping element and the power supply cable, which may hold the power supply cable in a more secure manner. In a set of embodiments, the lower part comprises a cable receiving portion, integrally formed therein, shaped to receive the power supply cable. The cable receiving portion may have a shape that corresponds to the shape of the power supply cable. For example, if the power supply cable has a generally circular, e.g. circular, cross-section, the cable receiving portion may be circularly shaped, or at least have a curved portion which follows the profile of a circle. The cable receiving portion may comprise an opening in a wall of the lower part into which the power supply cable can be inserted. The cable receiving portion may be dimensioned so as to be substantially the same, e.g. the same, size as the power supply cable. The provision of a cable receiving portion may minimize the amount to which the power supply cable can move relative to the lower part and thus prevent the transmission of forces from the power supply cable to other parts of the power base. The cable securing means may secure the power supply cable in any suitable manner. In a set of embodiments, the cable securing means is configured to hold the power supply cable against the lower part. The cable securing means is configured to secure the power supply cable to the lower part of the power base. In a set of embodiments, the cable securing means is configured to secure the power supply cable to the lower part in a manner in which at least at the portion of the power supply cable which is secured to the lower part cannot be moved relative to the lower part. This arrangement may help to ensure that any forces that are applied through the power supply cable, e.g. due to bending of the power supply cable, are substantially, e.g. only, applied to the lower part, rather than any other part of the power base. The lower part, to which the power supply cable is secured, is arranged below the upper part. The lower part may be arranged to rest, in use, on a work surface. The lower part may be arranged to rest directly on a work surface. The work surface may, for example, comprise a countertop. In other embodiments, the lower part may be an intermediate part arranged between the upper part and a further lower part which is arranged below the lower part. In any case, by securing the power supply cable to the lower part, which is separate to the upper part, forces applied by the power supply cable may be prevented from being transferred to the upper part. The lower part may comprise a single moulded body. However, in some embodiments, the lower part comprises a first sub-part, arranged to rest on a work surface, and a second sub-part attached to the first sub-part. The first sub-part may be shaped to receive the upper part and allow the upper part to move relative to the second sub-part. The second sub-part may function to enclose a bottom of the lower part, and may thus be considered to be a lower cover. The provision of a first and second sub-parts may facilitate assembly of the power base. The cordless electrical connector may be integrally formed with the upper part. However, in a set of embodiments, the cordless electrical connector is mounted to the upper part. The cordless electrical connector may be arranged such that there is a minimum clearance, e.g. 8mm, beneath the cordless electrical connector and a surface, e.g. of the lower part, facing an underside of the cordless electrical connector. This minimum clearance may prevent an electrical short circuit occurring within the cordless electrical connector in the situation in which water enters a space between the upper and lower parts. This may therefore improve the safety of the power base. The minimum clearance required may depend on the type of connector used within the power base as well as the power base design. In other embodiments, the minimum clearance may, for example be 6 mm or 10 mm. The weight sensor may have any suitable form. In a set of embodiments, the weight sensor comprises a plurality of sub-sensors spatially distributed between the upper part and lower part. The plurality of sub-sensors may be spatially distributed around an axis extending through the upper part and lower part. In embodiments comprising a cordless electrical connector, the axis may extend through a centre of the cordless electrical connector. The plurality of sub-sensors may, for example, comprise at least three, e.g. at least four, sub-sensors. The plurality of sub-sensors may be spatially distributed in any suitable manner. In a set of embodiments, the plurality of sub-sensors are evenly spatially distributed between the upper part and the lower part. For example, the plurality of subsensors may be equiangularly distributed around an axis extending through the lower part and upper part. The axis may be a central axis, for example an axis extending through the cordless electrical connector, where included. Evenly distributing the sub-sensors in this manner may mean that, in embodiments wherein the power base is configured to receive the appliance part irrespective of angular orientation, it is still possible to accurately measure the weight of the removable appliance part. Such an arrangement may also advantageously account for embodiments in which a centre of mass of the appliance part is not aligned with the axis extending through a centre of the cordless electrical adaptor of the removable appliance part. In an alternative set of embodiments, the weight sensor comprises a single weight sensor arranged between the upper part and the lower part. The single weight sensor may, for example, be arranged centrally between the upper part and the lower part. For example, the single weight sensor may be arranged beneath, and in line with, the cordless electrical connector (where included). The provision of a single weight sensor may reduce the overall cost of the power base. The use of a single weight sensor may reduce the accuracy of measurement of the weight of the appliance part, however this arrangement may nonetheless still be useful in embodiments wherein an approximate number of cups of water are required, rather than an exact volume. The weight sensor may take any suitable form that is capable of measuring the weight of the removable appliance part. In a set of embodiments, the weight sensor comprises at least one strain gauge. In embodiments in which the weight sensor comprises a plurality of sub-sensors, each of the sub-sensors may comprise a strain gauge. An output of the strain gauge may indicate the weight of the appliance part when seated on the power base during use. In other embodiments, any other suitable means for measuring the weight may be employed. For example, a force-sensitive resistor may be utilized. The Applicant has also recognized that the weight sensor need not be electrical / electronic. As such, in some embodiments, the weight sensor may be non-electrical and may, for example comprise a mechanical scale. Such a mechanical scale may comprise a resilient element, e.g. a spring, in combination with a weight indicator, e.g. a dial. The weight sensor may be arranged in any suitable position between the upper part and lower part. In a set of embodiments, the weight sensor is arranged between the upper part and lower part in a manner such that all downward vertical force applied to the upper part is applied through the weight sensor. The upper part and lower part may have any suitable form / arrangement with respect to one another such that the vertical force is applied in this manner. In being arranged to apply all downward vertical force through the weight sensor, the upper part may be considered to be floating / resting on the weight sensor. In other words, the upper part may be seated on the weight sensor such that all downward vertical force is applied through the weight sensor. The upper part may be seated directly on the weight sensor. However, in some embodiments, at least one intermediate member may be arranged between the upper part and the weight sensor. In other embodiments, only part of the weight of the removable appliance part is transferred into the weight sensor. The power base may be configured to take this into account, e.g. using suitable control circuitry, when providing an indication as to the weight of the removable appliance part. In some embodiments, the upper part and lower part may be resiliently biased towards one another, or resiliently biased away from one another. In some embodiments, at least one resiliently biased (e.g. spring) member may be arranged between the upper part and the lower part The at least one resiliently biased member may be arranged to push the upper part in a direction away from the lower part, or pull the upper part in a direction towards the lower part. As such, the at least one resiliently biased member may prevent the upper part from being able to move freely with respect to the lower part (at least when there is no removable appliance part seated on the power base), which may help to prevent rattling within the power base. As the force from the at least one resiliently biased member acts between the upper part and lower part, this may not be impacted by forces applied through the power supply cable and so may not impact the accuracy of the measurement performed by the weight sensor. In embodiments wherein the at least one resiliently biased member is arranged to push the upper part in a direction away from the lower part, a spring force provided by the at least one resiliently member may be set to be lower than the weight of the upper part plus the minimum weight of the appliance. As such, when the appliance part is seated on the upper part, it will overcome the spring force provided by the at least one resiliently biased member and apply a force to the weight sensor. The at least one resiliently biased member may be integrally formed with at least one of the upper part and lower part. In other embodiments, the at least one resiliently biased member may be a separate part to the upper part and lower part. In some embodiments, the at least one resiliently biased member comprises a plurality of resiliently biased members. The at least one resiliently biased member may, for example, be in the form of a leaf spring, or a coil spring. The weight sensor, or control circuitry connected thereto, may be configured to take into account the spring force applied by the at least one resilient member, when measuring the weight of the removable appliance part. In a set of embodiments, the upper part and lower part together comprise a retention arrangement configured such that in at least one angular position of the upper part relative to the lower part, the upper part is able to move vertically with respect to the lower part and is also prevented from being separated from the lower part when moving in the vertical direction only. For example, the retention arrangement may comprise a bayonet fitting comprising at least one protruding pin and at least one corresponding slot, e.g. an L-shaped slot, arranged to receive the protruding pin. The L-shaped slot and pin may be dimensioned so as to facilitate a small range of vertical movement between the upper part and lower part during use of the power base. This may allow the upper part to move vertically thereby applying a force to the weight sensor during use. The amount of vertical movement may, for example, be 1.5-2.5 mm, e.g. 2 mm. The vertical movement of the upper part may help to avoid interference between the parts of the power base. In a set of embodiments, the upper part and lower part together define a housing of the power base. The upper part may, for example, define a top-portion of the housing and the lower part may define a side, e.g. peripheral, and bottom portion of the housing. In any of the embodiments herein, the upper part and lower part may be moulded, e.g. injection moulded, plastic bodies. In some embodiments, in which the upper and lower part together define a housing, the power supply cable extends from the housing. For example, the power supply cable may extend out through a side wall of the housing. The side wall may, for example, be defined by the lower part of the power base. Of course, in other embodiments, the power supply cable may enter the power base, e.g. the housing thereof, on an underside thereof. The lower part may be configured to rest directly on a work surface. In a set of embodiments, the lower part comprises a plurality of feet arranged to rest on a work surface. The plurality of feet may be integrally formed with, or attached to, the lower part. The plurality of feet may comprise a contact portion which has a high coefficient of friction, so as to prevent the lower part from sliding on the work surface. For example, the plurality of feet may comprise a rubber portion arranged to contact the work surface. Through the presence of the weight sensor in the power base, it may be possible to indicate to a user the volume of a liquid within the removable appliance part. In a set of embodiments, the power base further comprises an indicator means configured to provide an indication relating to the weight measured by the weight sensor. The indicator means may, for example, comprise an electronic display, e.g. a liquid crystal display (LCD), or an light emitting diode (LED) display. The electronic display may, for example, provide an indication as to the volume of liquid within the appliance part. The volume may be indicated as a number of cups of a predefined volume, or an actual measure of volume, e.g. in millilitres, litres, fluid ounces etc. The volume may be determined based on the weight measured by the weight sensor. The power base may comprise control circuitry, e.g. in the form of an electronic controller. The electronic controller may be connected to the weight sensor and the indicator means (where included). The electronic controller may be configured to determine the weight of the contents (e.g. a liquid) of the removable appliance part, and may convert this weight into a volume. This conversion may be based on an expected density of the material contained within the removable appliance part. Determination of the weight of the contents of the removable appliance part may be achieved through suitable calibration of the electronic controller, which may involve measuring the weight of the removable appliance part when it is empty of its contents, e.g. empty of water. This calibration may be performed in a factory, using a single removable appliance part, and the empty weight of the removable appliance part may then be used in electronic control circuitry for a plurality of power bases. In addition, or alternatively, the calibration may be performed by a user of the power base. In order to determine the weight of the contents of the removable appliance part, the power base, e.g. electronic control circuitry therein, may be configured to subtract the weight of the removable appliance part when empty from the measured weight of the removable appliance part when it is received on the power base. The difference is the weight of the contents (e.g. liquid) within the removable appliance part. The provision of the weight sensor may also allow for more sophisticated indications to be provided. This may be particularly relevant when the removable appliance part is in the form of a liquid heating vessel. In a set of embodiments, the power base is for receiving a removable appliance part in the form of a liquid heating vessel, and wherein the power base further comprises a control circuit configured to: determine, using the weight sensor, a first amount of liquid within the removable appliance part when the removable appliance part is positioned on the power base; detect when the removable appliance part has been removed from the power base and subsequently placed back on the power base; and after said detection, determine, using the weight sensor, a second amount of liquid within the removable appliance part. Determination of the amount of liquid within the removable appliance part at different points in time when the removable appliance part is seated on the power base may allow for analysis of how a user is operating an appliance comprising the power base. In a further set of embodiments, the control circuit is further configured to determine whether the difference between the first amount of liquid and the second amount of liquid is less than a threshold. When the difference is less than a threshold, this may indicate that a user has only dispensed a small volume of liquid from the removable appliance part. The dispensing of a small amount of liquid may be considered to be uneconomical use of the appliance. In a further set of embodiments, the control circuit is configured, in response to determining that the difference is less than the threshold, to send a signal for triggering a user-alerting means arranged to alert a user that an over-fill has occurred. The power base may thus be capable of providing feedback to a user on how efficiently they are using the appliance, which the power base forms part of. The indicator means, where provided, may be the user-alerting means. In some embodiments, the user-alerting means is separate to the indicator means. In another set of embodiments, the power base is for receiving a removable appliance part in the form of a liquid heating vessel, and wherein the power base further comprises a control circuit configured to: determine that the removable appliance part has been operated whilst being seated on the power base; detect when the removable appliance part has been removed from the power base and subsequently placed back on the power base; after said detection, determine, using the weight sensor, a remaining amount of liquid within the removable appliance part; compare the remaining amount of liquid to a first threshold; and wherein if the remaining amount of liquid is greater than the first threshold, to send a signal for triggering a user-alerting means arranged to alert a user that an over-fill has occurred. The determination that the removable appliance part has been operated may be a determination that the removable appliance part has been operated to heat the contents of the liquid therein. Detection of this may be determined by detecting the transfer of electrical power through a cordless electrical connector, which may be indicative of the removable appliance part having been operated. Of course, any other means for detecting operation of the removable appliance part may be used. The first threshold may, for example, correspond to 200 ml. The exact threshold amount may, of course, depend on the volume of the removable appliance part and so may be more or less than 200 ml. In other embodiments, the threshold may be based on a percentage change in the liquid within the removable appliance part. In the most economical situation, following operation and removal of the removable appliance part from the power base, the entire contents thereof will be used and thus the amount of liquid in the removable appliance part when it is subsequently put back on the power base may be zero. However, in reality, as it is often difficult to fill the removable appliance part with the exact amount of liquid required, it is expected that even when a user fills the removable appliance part in an economical manner, there may still be a small amount of liquid within the removable appliance part. As such, the first threshold being non-zero, but still relatively small, may prevent the repeated indication of an over-fill, when only a small amount of liquid remains in the removable appliance part. The above embodiment may nonetheless provide an indication to a user when they have overfilled the removable appliance part during use with more water than they actually needed. Whilst the above has been described in the context of a liquid, the power base may be used with removable appliance parts which contain a material other than a liquid, e.g. a food product. As such, the embodiments described above may equally be used to determine a weight of a food material within the removable appliance part, rather than a liquid. In a set of embodiments, a control circuit is configured to use the weight sensor to determine when the removable appliance part has been removed from, and placed back on, the power base. Use of the weight sensor as a means for detecting when the removable appliance part has been removed from the power base may reduce the number of components required to perform the steps set out above. In some embodiments, the power base comprises a control circuit configured to control operation of the power base. The control circuit may perform the functions set out above. In a further set of embodiments, the control circuit is configured to: determine the weight of the contents of the removable appliance part using the weight sensor; compare the weight to a maximum fill threshold; and if the weight is greater than the maximum fill threshold, to send a signal for triggering a user-alerting means arranged to alert a user than an over-fill has occurred. In this context, the power base may be capable of providing an indication that too much material, e.g. water, has been inserted into the removable appliance part. This may prevent the user from operating the removable appliance part in a manner which may cause damage to the removable appliance part and / or cause a safety hazard. In another set of embodiments, the control circuit is configured to: determine the weight of the contents of the removable appliance part using the weight sensor; compare the weight to a minimum fill threshold; and if the weight is less than the minimum fill threshold, to send a signal for triggering a user-alerting means arranged to alert a user than an under-fill has occurred. In this context, the power base may be capable of providing an indication that too little material, e.g. water, has been inserted into the removable appliance part. This may prevent the user from operating the removable appliance part in a manner which may cause damage to the removable appliance part and / or cause a safety hazard. The power base may have any suitable form. In some embodiments, the power base may be suitable for receiving an appliance part in a single orientation. However, in a set of embodiments, the power base is configured to receive a removable appliance part substantially irrespective, e.g. irrespective, of the angular orientation of the removable appliance part relative to the power base. In such embodiments, the appliance part may have a generally circular cross-section. As such, the upper part of the power base may have a substantially circular, e.g. circular, cross section. Such an upper part may define an upper circular receiving portion on which the appliance part may be seated. The lower part may have any shape capable of receiving the upper part. In further embodiments, wherein the power base comprises a cordless electrical connector, the cordless connector may comprise a 360-degree cordless connector arranged to mate with a corresponding adaptor at any angular orientation. The cordless power cable may be directly connected to the cordless electrical connector (where included). For example, the power supply cable may comprise a live, neutral and an earth (where provided) core which may be connected to respective live, neutral and earth terminals on the cordless electrical connector. In other embodiments, the cordless power cable may be connected indirectly to the cordless electrical connector, via at least one electrical component within the power base. The weight sensor may be connected to the electrical component. The electrical component may comprise a control circuit, e.g. an electronic controller. The present invention is not limited to the provision of just a power base. Accordingly, when viewed from a second aspect, the present invention provides an electrical appliance comprising: a power base of any preceding claim; and a removable appliance part configured to be seated on the power base. The removable appliance part may comprise any suitable appliance part in which it is desirable to measure the weight of the contents thereof. For example, the removable appliance part may comprise a food mixer or blender in which it is desirable to know the amount of food / liquid within the mixer or blender. The electrical appliance may be a domestic electrical appliance. The electrical appliance may be a countertop electrical appliance. In a set of embodiments, the removable appliance part is a liquid heating vessel. In such embodiments, the electrical appliance may be a cordless electrical kettle suitable for heating water. In other embodiments, the liquid heating vessel may be a milk frother, which is configured to heat and froth milk. The removable appliance part may be seated on the power base and removed therefrom (e.g. for filling of the removable appliance part with water) by a user of the appliance. The power base and removable appliance part are thus physically separate components. As set out above with respect to the power base, an indicating means may be arranged on the power base so as to provide an indication relating to the weight measured by the weight sensor. In some embodiments, the removable appliance part comprises an indicating means configured to provide an indication relating to the weight measured by the weight sensor. In such embodiments, there may be a data connection between the power base and the removable appliance part which facilitates the transfer of data therebetween. The data connection may facilitate the transfer of data including the weight measured by the weight sensor from the power base to the removable appliance part, for indication on the indicating means. As discussed previously, the power base may comprise a weight sensor which comprises a plurality of sub-sensors which are suitably spaced so as to accurately indicate the weight of the removable appliance part when its centre of mass is not necessarily aligned with its centerline. In other embodiments, the removable appliance part is configured such that its centre of gravity is substantially aligned with a centerline extending through the removable appliance part and wherein the weight sensor in the power base comprises a single weight sensor. In such embodiments, as the centre of gravity is substantially aligned with a centerline extending through the appliance, the angular position of the removable appliance part relative to the power base may have less of an impact on the weight measurement, and thus it may be possible to only utilize a single weight sensor, as opposed to a weight sensor comprising a plurality of sub-sensors. The removable appliance part may be configured in any suitable manner such that its centre of gravity is substantially aligned with its centerline. For example, components within the removable appliance part may be suitably arranged so as to shift the centre of gravity accordingly. For example, in embodiments wherein the removable appliance part is in the form of a liquid heating appliance, the removable appliance part may include a heating element, e.g. a resistive heating element, and a heat diffuser plate. The heating element may be shaped such that there is a void at one end thereof. The heating element may be arranged in the removable appliance part such that the void is on a side of the removable appliance part which is otherwise heavier than an opposing side of the removable appliance part. For example, the void may be arranged on a side of the removable appliance part which comprises a handle, which otherwise moves the centre of gravity away from the centre of the removable appliance part. The void may be arranged between cold tails of the heating element, i.e. the terminals of the heating element. Similarly, the heat diffuser plate may comprise a cut-away, and again this may be arranged such that the cut-away is on a side of removable appliance part which is otherwise heavier than the opposite side. This is just one example of how the removable appliance part may be configured such that its centre of gravity is substantially aligned with the centerline. In some embodiments, the centre of mass is fully aligned with the centerline. The centerline of the removable appliance part may extend through a centre of a cordless electrical adaptor arranged on the base of the removable appliance part. In embodiments of the second aspect of the invention, the removable appliance may comprise a cordless electrical adaptor configured to mate with the cordless electrical connector on the power base (where provided). In other embodiments, the removable appliance part may be configured to be seated on the power base, but an electrical connection may not be formed therebetween. Instead, the power base may comprise an inductive heater, and the removable appliance part may comprise a susceptor arranged to heat the contents thereof. According to a third aspect of the present invention there is provided a power base for receiving a removable appliance part thereon, the power base comprising: an upper part configured to receive, in use, the removable appliance part thereon; a lower part, separate to the upper part, arranged below the upper part and arranged to rest, in use, on a work surface; a weight sensor arranged between the upper part and the lower part; a power supply cable configured to supply the power base with electrical power; and a cable securing means configured to secure the power supply cable to the lower part. Features of any of the embodiments of the first and second aspects of the invention may equally be applied to this third aspect of the invention. In any of the embodiments described above, where a liquid is described, the liquid may comprise water, milk, or any other liquid which may be heated or processed in any other suitable manner by the removable appliance part. Some preferred embodiments of the present invention will now be described, by way of example, only, and with reference to the accompanying drawings, in which: Fig. 1 shows a perspective view of a cordless electrical appliance in accordance with an embodiment of the present invention, including a power base in accordance with an embodiment of the present invention; Fig. 2 shows a perspective view of the power base shown in Fig. 1 in isolation; Fig. 3 shows an exploded view of the power base shown in earlier Figs.; Fig. 4 shows an underside view of the power base shown in earlier Figs.; Fig. 5 shows a cross-sectional view of the cordless electrical appliance shown in Fig. 1; Fig. 6 shows a cross-sectional view of a cordless electrical appliance in accordance with another embodiment of the present invention, including a power base in accordance with another embodiment of the present invention; Fig. 7 shows a view of an underside of a heat diffuser plate and heating element included in the removable appliance part of the appliance shown in Fig. 6; Fig. 8 shows a view of the underside of the power base shown in Fig. 6; Fig. 9 shows a perspective view of the power base shown in Fig. 6 with the upper part separated therefrom; Fig. 10 shows a perspective view of a lower part of a power base including an integrated cable securing means; Fig. 11 shows the steps that may be performed by control circuitry in the power base; Fig. 12 shows an embodiment of a power base including a user-alerting means; Fig. 13 shows a perspective view of a cordless electrical appliance, in accordance with another embodiment of the present invention, in which the removable appliance part comprises an indicator means; Fig. 14 shows a sectional view of a cordless electrical appliance, in accordance with an embodiment of the present invention, comprising an inductive heater and a susceptor; and Fig. 15 shows an exploded view of another embodiment of a power base which comprises a resiliently biased member acting between the upper part and lower part thereof. Figure 1 shows a perspective view of a cordless electrical appliance 2 in accordance with an embodiment of the present invention. In the embodiment depicted, the cordless electrical appliance 2 comprises a power base 4 in accordance with an embodiment of the present invention, as well as a removable appliance part 6. In the embodiment depicted the removable appliance part 6 is in the form of a liquid heating vessel, although any other suitable removable appliance part may be utilised. Figure 2 shows the power base 4, shown in Figure 1, in isolation. As shown in this Figure, the power base 4 comprises an upper part 8 and a lower part 10 which together define a main housing of the power base 4. A power supply cable 12 extends into the main housing defined by the upper and lower parts 8, 10. A cordless electrical connector 14 extends upwards from the upper part 8 so as to mate with a corresponding adaptor (not yet shown) in the removable appliance part 8 shown in Figure 1. The cordless electrical connector 14 may be mounted to the upper part 8. In other embodiments, the cordless electrical connector 16 may be integrally formed with the upper part 8. In some embodiments, as shown, the power base 4 comprises an indicator means 16, e.g. in the form of an LCD or LED display. The indicator means 16 may be used to provide an indication regarding a weight measured by a weight sensor providing within the power base 4. The weight may be indicated as a volume of liquid contained within the removable appliance part 6. The indicator means 16 may also be used to indicate an operational mode or state of the removable appliance part 6, when seated on the power base 4. Figure 3 shows an exploded view of the power base 4 discussed above and shown in earlier Figures. The upper part 8, of the power base 4, has a circular crosssection so as to suitably receive the removable appliance part 6, the bottom of which, at least, also has a corresponding circular cross section. The upper part 8 comprises an aperture 18 in its centre for receiving the cordless electrical connector 14. The upper part 8 comprises a circumferentially extending skirt 20 extending around its periphery. The skirt 20 comprises at least one L-shaped slot 22 therein. The L-shaped slot 22 is dimensioned to receive a pin (not visible in this Figure) protruding radially inwards on the lower part 10. Engagement between the pin and the L-shaped slot 22 prevents the upper part 8 from separating from the lower part 10 during typical use of the power base 4. The L-shaped slot 22 also permits vertical movement of the upper part 8 relative to the lower part 10. The L-shaped slot 22 and pin (not shown) form a retention arrangement. The cordless electrical connector 14 is secured to the upper part 8 using a bracket 24. The lower part 10 comprises a first sub-part 10A and a second sub-part 10B. The second sub-part 10B functions to close the underside of the power base 4 and may thus be considered to be a lower cover. The first and second sub-parts 10A, 10B may be attached together by any suitable means, e.g. by a friction fitting. As visible in Figure 3, the first sub-part 10A comprises a cable receiving portion 26 which is integrally formed therewith. The cable receiving portion 26 is shaped and dimensioned to receive the power supply cable 12. A cable securing means 28, in the form of a clamping element, is also included. In the embodiment depicted, the cable securing means 28 is configured so as to be attached to the first sub-part 10A, thereby securing the power supply cable 12 in place, using two screws. The first sub-part 10A comprises a plurality of feet 30. The second sub-part 10B comprises a plurality of openings 32, shaped to receive the feet 30 such that they extend therethrough. As such, when assembled, the feet 30 are positioned to rest on a work surface, e.g. a countertop. In the embodiment depicted, the power supply cable 12 comprises three cores, a live core 12A, a neutral core 12B and an earth core 12C. Each of the cores 12A, 12B, 12C may be connected directly to corresponding terminals on the cordless electrical connector 14. In other embodiments, whilst not shown, the power supply cable 12 may be connected to an intermediate electrical component, e.g. an electronic controller. In the embodiment depicted, the power base 4 comprises a weight sensor 34 comprising four sub-sensors 34A, 34B, 34C, 34D. Whilst four sub-sensors are shown, it will be appreciated that any suitable number of sub-sensors may be utilised. The first sub-part 10A of the lower part 10 comprises sensor receiving portions 36 on to which the four sub-sensors 34A-34D are seated. In the embodiment shown, the feet 30 are positioned directly below the sensor receiving portions 36. This may help to ensure that the first part 10, specifically the first subpart 10A is sufficiently rigid when the removable appliance part 6 is seated thereon. This may help to ensure that the sub-sensors 34A-34D provide an accurate weight measurement. The first sub part 10A may also comprise an opening 38 into which the indicator means 16 may be mounted. The indictor means 16 may be configured to output a measurement of the volume of the contents of the removable appliance part 6, when seated on the power base 4. The volume may be determined directly from the weight measured by the weight sensor 34. Suitably electronic control circuitry (not shown) may be provided to determine the weight, and thus the volume of the contents of the removable appliance part, and provide a suitable output on the indicator means 16. Figure 4 shows an underside view of the assembled power base 4, with the second sub-part 10B removed. This view more clearly shows each of the four feet 30 of the first sub-part 10A. An outer wall 40 of the first sub-part 10A comprises a cut-out 42 through which the power supply cable 12 extends. As shown in Figure 4, when assembled, the power supply cable 12 is received in the cable receiving portion 26 and is secured in position using the cable securing means 28. As shown in this Figure, the power supply cable 12, e.g. the live, neutral and earth cores 12A, 12B, 12C may be connected directly to the cordless electrical connector 14. As will be appreciated by those skilled in the art, by securing the power supply cable 12 to the lower part 10, i.e. the first sub-part 10A, forces applied through the cable portion 44 outside of the power base 4 are not transferred to the cable portion 46 which is inside the power base. Instead, the forces are applied directly to the first sub-part 10A, i.e. the lower part. As a result, the forces may have less, or no, impact on any readings by the weight sensor 34. The portion of the power supply cable 12 beneath the cable securing means 28, within the cable receiving portion 26, may be held therein such that it cannot move relative to the lower part 10. This arrangement may serve to prevent the transfer of force from the power supply cable 12 to any part of the power base 4, other than the lower part 10. Figure 5 shows a side-on cross-sectional view of the removable appliance part 6 and power base 4. As visible in this cross-section, the removable appliance part 6 comprises a cordless electrical adaptor 48 which is configured to mate with the cordless electrical connector 14 on the power base 4 when it is seated thereon during use. In the embodiment depicted, the removable appliance part 6 is in the form of a liquid heating vessel which comprises a liquid receiving chamber 50 which is heated by a heating element 52, e.g. a sheathed electrical heating element. The heating element 52 is electrically connected to the cordless electrical adaptor 48 such that when the removable appliance 6 is seated on the power base 4 it is in electrical connection therewith. As visible in Figure 5, the skirt 20 of the upper part 8 rests on each of the subsensors 34A-34D, although only sub-sensors 34A, 34C are visible in this Figure. The upper part 8 is dimensioned such that there is a small gap 54 between, i.e. around, the skirt 20 and the first sub-part 10A. As such, the upper part 8 can freely move vertically with respect to the first sub-part 10A of the lower part 10. As will be appreciated by those skilled in the art, in the embodiment shown in this Figure, the upper part 8 rests entirely on the weight sensor 34, specifically the subsensors 34A-34D. As such, when the removable appliance part 6 is seated on the upper part 8, all of the weight of the removable appliance part 6 is transferred down through the weight sensor 34. In other words, all vertical downward force is transferred through the weight sensor 34. Any forces which interact between the cordless electrical connector 14 and cordless electrical adaptor 48 will have negligible, or no, impact on the weight measured. The power base 4 may comprise a control circuit 35, as shown in Figure 5. The control circuit 35 may be connected to the weight sensor 34 and the indicator means 16. The control circuit 35 may be in the form of a controller comprising a processor. The control circuit 35 may process the measurement from the weight sensor 34 and convert this measurement into a volume of liquid contained within the removable appliance part 5. As will be appreciated by those skilled in the art, the power base 4 of the embodiments set out above may advantageously provide a more accurate measurement of the weight of the removable appliance part 6, and thus the contents thereof. Figure 6 shows an embodiment of a cordless appliance 102 in accordance with another embodiment of the present invention. A power base 104 in accordance with another embodiment of the present invention is also depicted. Unlike the previous embodiment described above wherein the power base 4 comprises a weight sensor 34 including a plurality of sub-sensors 34A-34D, in the embodiment shown in Figure 6 the power base 104 includes a single weight sensor 134. The single weight sensor 134 is nonetheless arranged between the upper part 108 and the lower part 110, specifically the first sub-part 110A thereof. The upper part 108 comprises a skirt 120 similar to the embodiment set out above. However, as there is only a single weight sensor 134, the skirt 120 comprises tabs 156 which rest on a rim 158 on the first sub-part 110A. As such, when the removable appliance part 106 is seated on the power base 106, some of the force transferred through the upper part 108 will be transferred directly into the lower part 110, specifically the first sub-part 110A, rather than through the weight sensor 134. However, the control circuitry / electronics to which the weight sensor 134 may be connected may be configured to take this into account. For example, the skirt 120 may be configured and the weight sensor 134 arranged such that, for example, 20% of the force is transferred through the weight sensor 134. Any measured force may then be scaled up to reflect the actual force and thus weight of the removable appliance part 106. However, this may not work particularly well when the removable appliance part 106 has a centre of gravity that is not substantially aligned with a centreline of the removable appliance part 106. Thus, in some embodiments, the removable appliance part 106 may be specifically configured to have a centre of gravity that is aligned with its centreline. With continued reference to Figure 6, the centre of gravity of a typical removable appliance part 106, in the form of a liquid heating appliance, is typically located away from the centreline (indicated by dashed line 164) and towards the handle 166 of the removable appliance part 106. The black cross 160 indicates the typical centre of gravity of such a removable appliance part. However, in the embodiment depicted, the removable appliance part 106 is modified so as to bring the centre of gravity closer to the centreline 164. In the embodiment depicted, the centre of gravity of the removable appliance part 106 is indicated by the black cross 162, which is substantially aligned with the centreline 164. Shifting of this centre of gravity 162 of the removable appliance part 106 is achieved by a number of modifications in the embodiment depicted. Firstly, control electronics 168 in the removable appliance part 106 may be moved to a position whereby they are as far away as possible from the handle 166, within the constraints of the removable appliance part 106. As visible in Figure 6, the control electronics 168 are situated on the far right-hand side of removable appliance part, distal from the handle 166. Secondly, the heating element 152 and heat diffuser plate 170 may be configured so as to reduce the amount of weight on the side of the centreline 164 proximal to the handle 166. Figure 7 shows the heating element 152 and heat diffuser plate 170, of the removable appliance part 106, in isolation. As shown here, the heating element 152 follows a circular shape with a void 174 where cold tails 172 are provided for electrical connection to the heating element 152. In the space adjacent the void 174, the heat diffuser plate comprises a corresponding cut-out 176. The result of this arrangement is that the weight of the heating element 152 and heat diffuser plate 170 assembly is less on the left-hand side of Figure 7 than on the right-hand side. With reference back to Figure 6, by arranging the heating element 152 and heat diffuser plate 170 in a manner in which the void 174 and cut-out 176 are on the side of the centreline 164 proximal to the handle 166, the weight of the removable appliance part on the left-hand side of the centreline 164 shown in Figure 6 may be reduced. The result is that the centre of gravity 162 may be moved closer to the centreline 164. Of course, any other components of the removable appliance part 106 may be rearranged so as to align the centre of gravity 162 more closely with the centreline 162. Bringing the centre of gravity 162 as close as possible to the centreline 162 of the removable appliance part 106 may allow the power base 104 to include a single weight sensor 134, as irrespective of the angular orientation of the removable appliance 106 relative to the power base, the amount of force applied through the upper part 108 onto the weight sensor 134 will be substantially the same. Figure 8 shows a view of the underside of the power base 104 shown in Figure 6. The power base 104 is the same as the power base 4 of the first embodiment set out above, except for the provision of a single weight sensor 134, as opposed to a plurality of sub-sensors. As such, the power supply cable 112 of this embodiment is secured in an identical manner to the first sub-part 110A using a cable securing means. Figure 9 shows a view of the power base 104 described above. As can be seen more clearly in this Figure, the upper part 108 comprises a plurality of tabs 156 which, when assembled, rest on the rim 158 of the lower part 10. The single weight sensor 134 can also be seen. The tabs 156 and single weight sensor 134 may be equiangularly distributed around the rim 158. Figure 10 shows an underside view of a lower part 210 in accordance with another embodiment of the present invention. As depicted, unlike the previous embodiments in which the cable securing means is in the form of a separate clamping element attached to the lower part, in this embodiment the cable securing means 228 is integrally formed with the lower part 210. The cable securing means 228 may take any suitable form. In the embodiment depicted, as will be appreciated by those skilled in the art, when a power supply cable is pushed against the cable securing means 228, the cable securing means 228 will initially displace allowing the power supply cable to move into the cable receiving portion 226. Once in the cable receiving portion 226, the cable securing means 228 may press against the power supply cable and hold it therein. Integrally forming the cable securing means 228 with the lower part may reduce the number of separate components which have to be both manufactured and assembled. Figure 11 shows a flow chart of steps which may be performed by control circuitry which may be present in any of the embodiments described herein. For ease of reference, the steps will be described with reference to the electrical appliance 2 shown in Figures 1 to 5. In step S1, the control electronics determine, using the weight sensor 34, a first amount of liquid within the removable appliance part 6. Then, in step S2, the control electronics detect when the removable appliance part 6 has been removed from, e.g. so as to pour heated liquid from the removable appliance part 6, and subsequently placed back on the power base 4. After this detection, in step S3, a determination is made, using the weight sensor 34, of a second amount, i.e. the remaining amount, of liquid within the removable appliance part 6. Following this, at step S4, a determination may be made as to the difference between the first and second amounts, and this difference may be compared to a threshold. If the amount is less than a threshold, i.e. only a small amount has been poured out, in step S5 a signal may be sent to a user alerting means to indicate an overfill having occurred. In step S2, detection of the removable appliance part 6 being lifted away, and placed back on, the power base 4 may be achieved using the weight sensor 34. Figure 12 shows a perspective view of a power base 302 in accordance with another embodiment. The power base 302 is substantially the same as the first embodiment set out above, except that the power base 302 further comprises useralerting means 378. The user alerting means 378 may comprise, for example, three lights, e.g. three light emitting diodes (LEDs). Each of the LEDs may have a different colour, e.g. red, yellow and green. The user-alerting means 378 may be in addition to the indicator means 316. The user-alerting means 378 may be used to provide an output relating to the steps according to Figure 11, described above. For example, if it is determined that an over-fill has occurred. A red user-alerting means 378 may be illuminated. In contrast, if no over-fill is detected, a green useralerting means 378 may be illuminated. Figure 13 shows a perspective view of an electrical appliance 402 in which in addition, or alternatively, to an indicator means 416 arranged on the power base 404, an indicator means 480 may be arranged on the removable appliance part 406. The indicator means 480 may similarly comprise an LCD display or LED display. The indicator means 480 may also provide an indication relating to a weight, e.g. a volume of liquid within the removable appliance part 406, measured by a weight sensor in the power base 404. Otherwise, the electrical appliance 402 is identical to the appliance 2 described above. Figure 14 shows a side cross-sectional view through an electrical appliance 502 in accordance with another embodiment of the present invention. In this embodiment, the power base 504 comprises an inductive heater 582 and the removable appliance part 506 comprises a susceptor 584. The susceptor 584 is arranged to heat the contents of the liquid chamber 550. The inductive heater 582 may comprise an inductor coil. With the exception of the cordless electrical connector being removed, the power base 504 is otherwise identical to the power base 2 described above in relation to its inclusion of weight sensors and the relative arrangement of the upper part and lower part. When the removable appliance part 506 is seated on the power base 504, specifically the upper part 508 thereof, the weight force is transferred down to the weight sensors 534. Whilst not shown in this Figure, the power base 504 comprises a power supply cable secured to the lower part 510 of the power base 504. Figure 15 shows an exploded view of a power base 604 in accordance with another embodiment of the present invention. The power base 604 is identical to the power base 4 described above, except for the power base 604 shown in this embodiment comprises at least one resiliently biased member 635A, e.g. a plurality of resiliently biased members 635A-635D arranged between the upper part 608 and lower part 610. The at least one resiliently biased member 635A-365D may act to push the upper part 608 away from the lower part 610. The upper part 608 may be prevented from separating completely from the lower part 10 due to the engagement between the L-shaped slot 622 and pin. The at least one resiliently biased member 635A-635D may function to prevent the upper part 608 from rattling with respect to the lower part 610. Whilst resiliently biased members 635A-635D are depicted which act to push the upper part 608 away from the lower part 610, it is envisaged that alternative resiliently biased members may act to pull the upper part 608 towards the lower part 610. The at least one resiliently biased member 635A-635D may be integrally formed with at least one of the upper part 608 or lower part 610. As depicted, the at least one resiliently biased member 635A-635D may be in the form of a coiled spring. However, the at least one resiliently biased member 635A-635D may take any other suitable form. Whilst four resiliently biased members 635A-635D are shown, any number of resiliently biased members may be utilised. While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims. 5

Claims

1. A power base for receiving a removable appliance part thereon, the power base comprising:an upper part configured to receive, in use, the removable appliance part thereon;a lower part, separate to the upper part, arranged below the upper part;a weight sensor arranged between the upper part and the lower part;a power supply cable configured to supply the power base with electrical power; anda cable securing means configured to secure the power supply cable to the lower part.

2. The power base of claim 1, a cordless electrical connector for providing an electrical connection to the removable appliance part when seated on the power base, wherein the cordless electrical connector extends from the upper part and is positioned so as to mate with a corresponding cordless electrical adaptor on the removable appliance part when it is received thereon.

3. The power base of any preceding claim, wherein the cable securing means is integrally formed with the lower part.

4. The power base of claim 1 or 2, wherein the cable securing means comprises a clamping element configured to be attached to the lower part so as to secure the power supply cable to the lower part.

5. The power base of any preceding claim, wherein the lower part comprises a cable receiving portion, integrally formed therein, shaped to receive the power supply cable.

6. The power base of any preceding claim, wherein the cable securing means is configured to hold the power supply cable against the lower part.

7. The power base of any preceding claim, wherein the cable securing means is configured to secure the power supply cable to the lower part in a manner inwhich at least at the portion of the power supply cable which is secured to the lower part cannot be moved relative to the lower part.

8. The power base of any preceding claim, wherein the weight sensor comprises a plurality of sub-sensors spatially distributed between the upper part and lower part.

9. The power base of claim 8, wherein the plurality of sub-sensors are evenly spatially distributed between the upper part and the lower part.

10. The power base of any preceding claim, wherein the weight sensor comprises at least one strain gauge.

11. The power base of any preceding claim, wherein the weight sensor is arranged between the upper part and lower part in a manner such that all downward vertical force applied to the upper part is applied through the weight sensor.

12. The power base of any preceding claim, wherein the upper part and lower part together define a housing of the power base.

13. The power base of claim 12, wherein the power supply cable extends from the housing.

14. The power base of any preceding claim, further comprising an indicator means configured to provide an indication relating to the weight measured by the weight sensor.

15. The power base of any preceding claim, wherein the power base is for receiving a removable appliance part in the form of a liquid heating vessel, and wherein the power base further comprises a control circuit configured to: determine, using the weight sensor, a first amount of liquid within the removable appliance part when the removable appliance part is positioned on the power base;detect when the removable appliance part has been removed from the power base and subsequently placed back on the power base; andafter said detection, determine, using the weight sensor, a second amount of liquid within the removable appliance part.

16. The power base of claim 15, wherein the control circuit is further configured to determine whether the difference between the first amount of liquid and the second amount of liquid is less than a threshold.

17. The power base of claim 16, wherein the control circuit is configured, in response to determining that the difference is less than the threshold, to send a signal for triggering a user-alerting means arranged to alert a user that an over-fill has occurred.

18. The power base of any preceding claim, wherein a control circuit is configured to use the weight sensor to determine when the removable appliance part has been removed from, and placed back on, the power base.

19. The power base of any preceding claim, wherein the power base is configured to receive a removable appliance part substantially irrespective of the angular orientation of the removable appliance part relative to the power base.

20. An electrical appliance comprising:a power base of any preceding claim; anda removable appliance part configured to be seated on the power base.

21. The electrical appliance of claim 20, wherein the removable appliance part is a liquid heating vessel.

22. The electrical appliance of claim 20 or 21, wherein the removable appliance part comprises an indicating means configured to provide an indication relating to the weight measured by the weight sensor.

23. The electrical appliance of claim 20, 21 or 22, wherein the removable appliance part is configured such that its centre of gravity is substantially alignedwith a centerline extending through the removable appliance part and wherein the weight sensor in the power base comprises a single weight sensor.33

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