The present invention relates to cordless electrical appliances, and in particular to the stability of a cordless appliance unit on a base unit.

In cordless electrical appliances, such as domestic kettles, it is typical for the base unit to be provided with an upstanding base connector part that supplies electrical power to a corresponding connector part in the cordless appliance unit when it is seated on the base unit. If the cordless connector parts are of the so called 360° type, i.e. that allow the cordless appliance unit to be seated on the base unit in any rotational position, then the base connector part typically stands in the centre of the base unit and the corresponding connector part is recessed in the centre of a base cover of the cordless appliance unit. When the connector parts are fully engaged, the cordless appliance unit comes to rest on the upper surface of the base unit but can be swivelled around by up to 360°. The plastics mouldings typically used for the base cover of the appliance unit and for the upper surface of the base unit need to be relatively robust as any distortion can cause the appliance unit to rock unstably when seated on the base unit.

It has been recognised that manufacturing tolerances in a cordless electrical appliance, and in particular its base unit, may affect the degree of engagement between the cordless connector parts. In many cordless connector systems, such as Strix P72 (described in WO 95/08204) or Strix P76 (described in WO 01/28294), the electrical contacts in the base connector part are resiliency mounted on leaf springs that are designed to take up the likely tolerances so that electrical connection is always made even if the connector parts are brought into

engagement with a degree of misalignment and/or disengagement. However the Applicant has developed a new generation of cordless electrical connectors comprising fixed electrical contacts, which can be made significantly smaller than those previously known for domestic cordless electrical appliances. Such a base connector part is described in WO 2012/164317.

It is increasingly desirable to reduce the size of cordless electrical appliances, for example to save on material costs and minimise carbon footprint. This means that appliances and their base units are being made smaller in diameter and

consequently the base connector part becomes taller as compared to the diameter of the base unit. The smaller the diameter of the base unit, the larger the angle of approach for the cordless appliance unit and the more care must be taken to ensure that the appliance unit is seated with its corresponding cordless connector part aligned vertically over the base connector part. This can be a particular problem when the base connector part is also small and provides only relatively narrow channels for terminals of the corresponding connector part to access a set of fixed contacts housed therein. Furthermore it has been found that the reduced size of a base unit can make it more susceptible to distortion during manufacture and so tolerances may increase. In turn, this can lead to the appliance unit being unstable when seated on the base unit and affect electrical connection between the cordless connector parts. The present invention seeks to mitigate the problems outlined above.

According to a first aspect of the present invention there is provided a cordless electrical appliance comprising a cordless appliance unit and a base unit, the cordless appliance unit comprising a cordless connector part and the base unit comprising a base connector part arranged to engage with the cordless connector part to supply electrical power to the cordless appliance unit when it is seated on the base unit, wherein the base unit is arranged to rest on a horizontal surface that supports the cordless electrical appliance with a footprint that is smaller than that of the cordless appliance unit and the cordless appliance unit comprises a peripheral portion that is arranged to rest on the horizontal surface radially outward of the base unit.

Accordingly there is provided a cordless electrical appliance with a cordless appliance unit which has a peripheral portion to additionally support itself directly on the horizontal surface, rather than only being indirectly supported via the base portion. Even if the base unit is or becomes distorted, the appliance unit can use the peripheral portion to right itself and stand level on the supporting surface. The appliance unit is therefore uncoupled from distortions in the base unit that might otherwise make it unstable and prone to rock from side to side. In order to facilitate the peripheral portion of the cordless appliance unit coming into contact with the horizontal surface without interference from the base unit, it is preferable for the peripheral portion to be provided in areas that do not overlap with the footprint of the base unit. The peripheral portion may take any suitable form, such as a continuous or semi-continuous peripheral rim, or a number of separate peripheral portions e.g. spaced around the periphery. In a preferred set of embodiments the peripheral portion comprises a plurality of feet. Preferably there are at least three feet spaced equally around the periphery of the appliance unit, e.g. in the form of a tripod. A tripod arrangement is particularly helpful for ensuring that the appliance unit supports itself stably on the horizontal surface. The tripod feet may be arranged to contact the horizontal surface radially outside the footprint of the base unit while leaving a large degree of design freedom for the shape of the base unit. Of course the peripheral portion may be separated into any suitable number of feet spaced (evenly or unevenly) around the periphery of the cordless appliance unit.

The base unit may have a footprint that is at least 10%, 20%, 30%, 40% or 50% smaller than that of the cordless appliance unit. This can be measured by comparing the area of a horizontal surface that is covered by the respective footprints when the cordless appliance is supported thereon. It will be understood that only the peripheral portion of the cordless appliance unit is in physical contact with the horizontal surface. The base unit may be in physical contact with the horizontal surface at various points across its footprint, e.g. having a circular base that is provided with three, four or more feet that are in contact with the surface. The base unit may then provide a central contact point for the cordless appliance while the appliance unit provides peripheral contact with the horizontal surface. This ensures that the appliance as a whole is seated stably.

It is desirable for the base unit to be able to rest stably on a surface in its own right, so that it does not rock when a cordless appliance unit is placed down on top of it. Thus in a set of embodiments it is preferable for the base unit to rest on the horizontal surface with a central portion and a peripheral portion spaced radially outwardly of the central portion. The design of the base unit may therefore be similar to a conventional base unit except its footprint is reduced. The peripheral portion of the base unit may comprise a plurality of feet, e.g. spaced around its a double tripod arrangement, with preferably both the base unit and the cordless appliance unit supported by a respective tripod arrangement of feet. This further increases the stability of the cordless appliance on a horizontal surface which supports it.

By providing the cordless appliance unit with a peripheral portion that contacts the horizontal surface radially outward of the base unit, it can be ensured that the electrical contact(s) carried by the appliance connector part are at a constant height from the horizontal surface. If the base connector part comprises one or more fixed electrical contacts then this can help to maintain a constant spacing between each contact pair, which can be particularly important if such a contact pair provides a switch arrangement for making or breaking an electrical circuit that supplies electrical power to the cordless appliance unit. However, it has been appreciated that manufacturing tolerances and/or distortions in the base unit may interfere with the position of the electrical contact(s) in the base connector part. In a preferred set of embodiments the base connector part is resiliency mounted to the base unit so as to be biased away from the base unit and further into engagement with the appliance connector part. The resilient mounting of the connector part in the base unit then allows the base connector part to move up and down so that its electrical contact(s) can be maintained at a fixed separation from those in the cordless appliance unit. Manufacturing tolerances and any distortions of the base unit are therefore absorbed so that the electrical contacts in the two connector parts are always the same distance apart. The base connector part may be mounted so as to undergo resiliently-biased movement in any direction. In other words, the base connector part may be mounted so as to effectively "float" with tilting and/or vertical movement relative to the base unit. However, the Applicant has recognised that a rocking movement of the base connector part may not be suitable for all types of fixed contacts and/or where the channels in the base connector part are wide enough to accommodate downward movement of the terminals of a corresponding connector part at a range of angles from the vertical. It is therefore preferable that the resiliently-biased movement of the base connector part relative to the base unit is guided so that the connector part can only move vertically relative to the horizontal surface. By ensuring that the base connector part is resiliently biased into a vertical alignment, it can be easier to engage the connector parts even if they are smaller than is conventional, for example a base connector part that is less than 30 mm, or even less than 25 mm, in diameter. This is described in more detail in the Applicant's copending application.

It is mentioned above that a resilient mounting may be particularly beneficial when the base connector part carries one or more electrical contacts that are fixed contacts, that is, contacts that are not resiliently mounted e.g. on a leaf spring, as is conventional. Accordingly the base connector part preferably comprises one or more fixed electrical contacts. Such fixed contacts may be permanently attached to respective conductors in a mains power supply cable attached to the base connector part, e.g. in the manner described in WO 2012/164137, the contents of which are hereby incorporated by reference. The resiliently-biased movement of the base connector part is preferably chosen to be in the range of 1-5 mm, further preferably 2-3 mm, and in particular around 2.5 mm.

The vertical position of the electrical contact(s) in the base connector part can be particularly important when an electrical circuit supplying power to the cordless appliance unit is made or broken by controllably moving a contact member towards and away from a fixed contact in the base connector part. In a set of embodiments that takes particular advantage of a base connector part that is guided to adjust its vertical height relative to the base unit, the cordless electrical appliance comprises a switch arrangement for making or breaking an electrical circuit for supplying power to the cordless appliance unit, the switch arrangement comprising a fixed contact provided on the base connector part and a moveable contact member mounted in the cordless appliance unit. The resilient mounting of the base connector part can act to ensure that such a switch arrangement performs reliably despite manufacturing tolerances and/or distortions of the base unit that could have an effect.

An advantage of moving a contact member into or out of electrical contact with a fixed electrical contact in the base connector part, so as to make or break the electrical power circuit, is that an additional set of switching contacts is not necessarily required. Therefore fewer current-carrying contact pairs may be used than in more conventional arrangements e.g. where there is a set of contacts between the two cordless connector parts and also another set of switch contacts in the cordless electrical appliance for making or breaking the power supply circuit. Instead the same switch arrangement can carry out the function of selectively removing power from the cordless appliance unit as well as the necessary separable connection between the cordless appliance unit and the base unit. This is advantageous as each contact pair typically requires silver on each side and this gives rise to a significant proportion of the manufacturing cost involved. The elimination of a set of current-carrying contacts is also beneficial for reducing the number of moving parts in the appliance as a whole and potentially improving reliability.

Preferably the fixed contact(s) in the base connector part are end-point contacts, i.e. providing an end-point contact surface adapted to engage with a corresponding contact on a distal end of a current-carrying contact member, rather than an extended surface contact such as an annular ring. Preferably the base connector part comprises at least two end-point contacts, e.g. for the live and neutral poles of the electrical power supply. The corresponding connector part in the cordless appliance unit may provide at least one corresponding end-point contact carried by a moveable member such as a pin. The end-point contact may be carried by a contact member that takes the form of an upstanding pin, for example formed from copper. The end-point contact surface, at least for the live contact, may be coated, plated or otherwise provided with a surface layer of silver to improve conductivity and integrity at the point of electrical connection. Where the base connector part is designed for use with a corresponding connector part in a cordless connector set that always intends to make or break the electrical connection at the live contact pair, then the neutral contact may not be provided with a silver layer on its end-point surface, or at least a thinner layer of silver.

Either the fixed contact in the base connector part and/or the moveable contact member in the corresponding appliance connector part may comprise a silver coating or tip. Silver is chosen for its high electrical connectivity, which reduces a tendency for deterioration of the contact surface through oxidation or electric arc erosion. Preferably silver is only provided as a coating or at the tip, i.e. where physical contact is made, in order to reduce the costs involved whilst maximising electrical effectiveness. However the Applicant has found that using a silver contact on one side only, i.e. on either the moveable contact member or the fixed contact, when the opposing side is copper, provides an adequate performance. This is because the plasma provided during arcing, as the contact pair opens, causes the silver on the one contact to melt, resulting in a layer of silver being deposited on the opposite contact. When making or breaking an electrical power supply circuit using end-point contacts, it becomes even more important to ensure a constant spacing between the contacts so that a predetermined movement of the moveable contact member can be relied upon to make electrical contact and apply a predictable contact pressure.

In a preferred set of embodiments the cordless connector part in the cordless appliance unit comprises a moveable contact member mounted on a switch lever that is itself resiliently biased to move the contact member into electrical contact with a fixed contact in the base connector part, e.g. as is described in WO

2012/164318 and WO 2012/164319, the contents of both of which are hereby incorporated by reference. The switch arrangement may or may not be part of a control, for example a thermally responsive control, that is mounted in a cordless appliance unit that takes the form of a liquid heating apparatus. In at least some embodiments the cordless connector part in the cordless appliance unit may be integrated with a power supply circuit and the switch arrangement may be arranged to make or break the power supply circuit. This power supply circuit can be provided by a standalone cordless electrical connector unit or by a thermally responsive control means. Means for operating the switch arrangement may be provided so that the power supply circuit can be opened or closed independently of engagement or separation of the cordless connector parts. The switch

arrangement may be operated manually and/or by a thermally responsive actuator.

The Applicant has recognised that when the base unit of a cordless electrical appliance has a smaller footprint than that of the appliance unit, it becomes possible to utilise the bottom of the appliance unit for visual effect(s). For example, a base cover of the appliance unit may now be visible from the underside even when the appliance unit is seated on the base unit. Such a base cover may therefore be coloured or decorated for aesthetic purposes. In a preferred set of embodiments the cordless appliance unit comprises a base cover that is provided with one or more light emitters. The emitters) can shine light out from underneath the appliance unit to illuminate an area of the horizontal surface outwardly of the base unit. This may not only provide an aesthetic effect, but also serve a purpose of informing a user about an operational state of the cordless appliance, e.g.

emitting one or more different light colours to indicate a particular operational state.

This feature is considered novel and inventive in its own right, regardless of whether the appliance unit includes a peripheral portion that rests on the horizontal surface radially outward of the base unit. Thus according to a second aspect of the present invention there is provided a cordless electrical appliance comprising a cordless appliance unit and a base unit, the cordless appliance unit comprising a cordless connector part and the base unit comprising a base connector part arranged to engage with the cordless connector part to supply electrical power to the cordless appliance unit when it is seated on the base unit, wherein the cordless appliance unit comprises a base cover that is provided with one or more light emitters, and wherein the base unit is arranged to rest on a horizontal surface that supports the cordless electrical appliance with a footprint that is smaller than that of the cordless appliance unit.

It will be appreciated that the smaller footprint of the base unit allows light emitted from the base cover of the cordless appliance unit to not only shine onto the base unit but also to shine onto the horizontal surface aligned beneath the larger footprint of the appliance unit. As is mentioned above, the one or more light emitters may be arranged to illuminate an area of the horizontal surface outwardly of the footprint of the base unit. Such a lighting effect can be enhanced by the light emitter(s) of the base cover preferably directing light substantially downwardly e.g. towards the horizontal surface. This may also be assisted by the base cover only having light emitter(s) in its lower surface. It may be preferred that no light is emitted sideways from the base cover. To take advantage of the under lighting effect, the base unit may have a footprint that is only 5%, 10%, 20%, 30%, 40%, or less than 50%, smaller than that of the cordless appliance unit. This can help to ensure that the appliance unit is relatively stable when seated on the base unit and not unduly prone to rock from side to side. To increase the stability of the cordless appliance unit, it may preferably comprise a peripheral portion that is arranged to rest on the horizontal surface radially outward of the base unit, e.g. as is described above. The peripheral portion of the cordless appliance unit may be arranged so as not interfere with visibility of the under lighting effect. For example, the peripheral portion may comprise a number of separate feet (e.g. a tripod arrangement as described above) or a peripheral rim with windows and/or the peripheral portion may be at least partially transparent or translucent to light from the emitter(s).

In a set of embodiments the base cover of the cordless appliance unit is provided with one or more individual light emitters, for example one or more light emitting diodes mounted in the base cover. In another set of embodiments the base cover of the cordless appliance unit is provided with one or more light emitting portions coupled to an individual light emitter such as a light emitting diode. The light emitting portions may be provided by a light guide coupled to the light emitter. The light guide may be a transparent or translucent light carrier that is fitted in the base portion. A light guide can be a convenient way to spread the light from a single emitter to different light emitting portions spaced around the base cover. Of course one or more light guides and/or light emitters may be used together to provide a desired lighting pattern. The light emitter(s) and/or light emitting portion(s) may be arranged to protrude through a corresponding aperture in the bottom surface of the base cover.

It has never previously been proposed for a cordless appliance unit to overhang a base unit with the former having a larger footprint than the latter. The present invention therefore extends to a cordless electrical appliance comprising a cordless appliance unit and a base unit, the cordless appliance unit comprising a cordless connector part and the base unit comprising a base connector part arranged to engage with the cordless connector part to supply electrical power to the cordless appliance unit when it is seated on the base unit, wherein the base unit is arranged to rest on a horizontal surface that supports the cordless electrical appliance with a footprint that is smaller than that of the cordless appliance unit. As is mentioned above, the footprint is not necessarily the area of the base unit that physically contacts the horizontal surface but the area of the horizontal surface that is covered by the base unit when viewed from above. There will now be described some general features that apply to embodiments of any of the aspects of the invention defined hereinabove.

It is increasingly desirable to reduce the size of cordless electrical appliances, for example to save on material costs and minimise carbon footprint. The smaller the diameter of the base unit, the larger the angle of approach for the cordless appliance unit and the more care must be taken to ensure that the appliance unit is seated with its cordless connector part aligned vertically over the base connector part. In a set of embodiments the base unit preferably includes a conical surface portion leading radially inwardly to the base connector part e.g. on its upper surface and preferably the base cover of the cordless appliance unit includes a

corresponding conical surface portion leading radially inwardly to the corresponding connector part. These conical portions can help to ensure that the cordless appliance unit locates correctly over the base connector part and comes down vertically onto the base unit. Further details of such an arrangement are described in the Applicant's co-pending application GB 1220679.3.

Preferably the cordless connector part and base connector part are of the type which allow electrical connection to be made substantially irrespective of the relative rotational orientation between the two connector parts i.e. a so called 360° connector set. However it will be appreciated that in at least some embodiments the connector parts may not allow for full 360° rotation, but while still allowing electrical connection to be made substantially irrespective of rotational position, e.g. through a range of 345° or greater.

A base connector part of the 360° type has a circular geometry and preferably a cylindrical annular wall. Of course it is not necessary for the base unit to also have a circular geometry. For example, it may take the overall form of a tripod. The base unit can even take advantage of a 360° cordless connection while itself being non-rotationally symmetric, for example having an oval, rectangular, square or other shape when seen in plan view. However, in a preferred set of embodiments the base unit is rotationally symmetric, and further preferably the base connector part is located centrally on the base unit. The base connector part may be smaller in diameter than in a conventional connector set such as a Strix P72. In a set of embodiments the diameter of the base connector part is less than 30 mm and preferably less than 25 mm.

Some preferred embodiments of the present invention will now be described, by way of example, and with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a cordless electrical appliance according to a first embodiment;

Figure 2 is an exploded view of the cordless appliance unit (Fig. 2a) and base unit (Fig. 2b) of the cordless electrical appliance of Figure 1 ;

Figure 3 is another perspective view of the base unit of Fig. 2b;

Figure 4 shows a first version of a base cover for the appliance unit of Fig. 2a; Figure 5 shows a second version of a base cover for the appliance unit of Fig. 2a; Figure 6 is a perspective view of a cordless electrical appliance according to a second embodiment;

Figure 7 shows the underside of the cordless electrical appliance of Figure 6; and Figure 8 is an exploded view of the cordless appliance unit (Fig. 8a) and base unit (Fig. 8b) of the cordless electrical appliance of Figure 6.

There is shown in Figure 1 a cordless electrical appliance 1 comprising a cordless appliance unit 2 seated on a base unit 4. The cordless appliance unit 2 is shown in the form of a liquid heating vessel e.g. a kettle, but this is merely for illustrative purposes. The mains electrical power cable 6 connected to the base unit 4 has been omitted from this view for clarity (but is visible in Figs. 2b and 3). It can be seen that the base unit 4 has a footprint which is smaller than that of the appliance unit 2. The appliance unit 2 therefore overhangs the base unit 4. When the appliance 1 is supported on a horizontal surface, the base unit 4 rests on the surface with a main central portion 8 (provided with four small feet) and three tripod legs 10. Radially outward of the base unit 4, the appliance unit 2 also rests on the surface with three feet 12 that are spaced around its periphery to form a tripod for stability. It may also be seen that three light emitters 14 protrude downwardly through the base cover 16 of the appliance unit 2 to shine light onto the surface outside the base unit 4.

From Figure 2 it is seen how the cordless appliance unit 2 is separable from the base unit 4. The appliance unit 2 houses a cordless connector part 20a e.g. exposed through a central aperture in the base cover 16. A conical portion 22a of the base cover 16 leads inwardly and upwardly to the connector part 20a. As seen in both Figures 2 and 3, the base unit 4 carries an upstanding base connector part 20b that is connected to a power supply cable 6. A corresponding conical portion 22b on the upper surface of the base unit 4 leads radially inwardly to the base connector part 20b. When the appliance unit 2 is seated on the base unit 4, the conical portions 22a, 22b help to bring the two connector parts 20a, 20b into vertical alignment before they are engaged together. The base connector part 20b may be fixed in position on the base unit 4 or it may be resiliently mounted, e.g. biased away from the base unit 4 by a spring, so as to adjust its position in response to any distortion of the base unit. The two connector parts 20a, 20b provide a 360° type connector set.

Figures 4 and 5 illustrate two different ways in which the light emitters 14 may be mounted in the base cover 16 of the appliance unit 2. In Figure 4 there is shown three separate light emitting diodes 14 (connected in series by an electrical wire) that protrude through respective apertures in the base cover 16. In Figure 5 it is shown how a single light emitting diode 14 may be optically coupled to a light guide 15 that carries light to three emitting portions 14' which are exposed through the base cover 16. In either case the light emitting diode(s) 14 is/are electrically connected to a power supply circuit for the appliance that is fed by the cordless connector part 20a.

In another embodiment seen in Figures 6 to 8, there is again a cordless appliance unit 2' seated on a base unit 4' which has a smaller footprint. Three light emitters 14 (which may instead be replaced by light emitting portions 14' as described above) protrude from the base cover 16 of the appliance unit 2' to shine light down onto a surface surrounding the base unit 4'. The main difference is that the appliance unit 2' is provided with a peripheral rim 24, rather than separate feet, to support itself on the surface. This rim 24 may be formed from a semi-transparent or transparent (or semi-translucent or translucent) material so that light shining down from the base cover 16 can be seen from the outside. The rim 24 may be made of plastics or glass. The base unit 4' also has a different shape, without any tripod legs, which is more like a conventional base unit. As before, the base connector part 20b may be resiliently mounted to the base unit 4'. This may be an indirect mounting if the base connector part 20b is fixed to a conical surface portion 22b which is itself resiliently coupled to the rest of the base unit 4' for resiliently-biased vertical and/or tilting movement. Other features which are substantially the same as previously described have been given the same reference numbers.

While certain embodiments have been described in the context of a cordless electrical appliance that comprises a cordless appliance unit in the form of a liquid heating vessel such as a kettle, it will be appreciated that the invention may be applied to any type of cordless electrical appliance such as, for instance: cordless steam irons, steam cleaners, steam cookers, or other steam generating appliances; cordless liquid heating and boiling appliances such as infusion beverage makers (e.g. for tea and/or coffee), baby milk formula preparation appliances, etc.; cordless liquid cooling appliances such as water chillers; and any other cordless electrical appliance requiring a separable connection to the mains power supply.