The present invention relates to cordless electrical appliances, and particularly to the mounting of a cordless electrical connector part in the base unit of a cordless electrical appliance.

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, the connector part typically stands in the centre of such a base unit. The base unit is assembled by fitting the connector part in a central aperture of a moulded portion that forms the upper surface of the base unit. This upper portion is typically fitted to a lower portion that is intended to rest on a horizontal surface that supports the base unit in use, so that the bottom of the connector part is hidden between the two moulded portions. A channel may be provided for a power supply cable to be led out from the base connector part. The base unit is generally closed with the connector part and the moulded portions being securely fixed together.

It has been recognised that manufacturing tolerances in the cordless 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 resiliently 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. In WO 03/094307 it is proposed to replace a conventional cordless connector set with one in which the terminal contact(s) in the base connector part are not resiliently mounted but fixedly positioned therein. The base connector part is instead adapted to be resiliently mounted in the base unit so that a floating movement of the entire base connector part is capable of accommodating a degree of misalignment between the connector parts. The moulded assembly of the base connector part is able to move vertically and also to tilt from side to side so that the plane of its upper surface can rotate away from horizontal in any direction. However, such a proposal may not be suitable for all types of fixed contacts in the base connector part and assumes that the channels in the 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. Non-vertical alignment may be difficult especially with connector parts that are made smaller than is conventional, for example a base connector part that is less than 30 mm, or even less than 25 mm, in diameter. The Applicant has developed a new generation of cordless electrical connectors which are significantly smaller than those previously known for domestic cordless electrical appliances. In turn, the reduced size of these cordless electrical connectors allows for the appliance itself to be reduced in size so that it will have a smaller footprint on a horizontal surface on which it rests in use. It has been found that the reduced size of a base unit can make it more susceptible to distortion during manufacture and so the tolerances may increase. A reduced size for the connector parts means that they also need to be brought into

engagement more precisely, but vertical alignment is made difficult if one of the connector parts is tilted. Furthermore, the type and arrangement of the electrical contacts in the base connector part, and in the corresponding connector part in the cordless appliance, may also impact on the tolerances that can be accommodated while ensuring that electrical connection and switching is achieved reliably. This can especially be an issue 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 contact in the base connector part. Such a switching arrangement can conveniently reduce the number of contact pairs in the power supply circuit, but requires the contacts to be reliably brought together and separated despite manufacturing tolerances in the appliance and/or base unit.

The present invention seeks to provide an improved approach to mounting a cordless electrical connector part in a base unit for a cordless appliance.

According to a first aspect of the present invention there is provided a base unit for a cordless electrical appliance comprising: a base connector part for supplying electrical power to a corresponding connector part of a cordless appliance when the cordless appliance is seated on the base unit so as to engage the connector parts; and a base portion arranged to rest on a horizontal surface which supports the base unit in use; wherein the base connector part is resiliently mounted to the base portion so as to be biased away from the base portion and further into engagement with a corresponding connector part; and wherein resiliently-biased movement of the base connector part relative to the base portion is guided so that the connector part can only move vertically relative to said horizontal surface.

It will be appreciated that the base connector part is not resiliently mounted to the base portion so as to float freely, but is constrained to vertical movement alone by virtue of a guiding function. This ensures that the base connector part is not able to tilt away from the vertical direction. If the base portion is distorted during manufacture or during use, the base connector part can move up or down so as to ensure that it is always at the same level relative to the horizontal surface on which the base unit is resting. If the cordless appliance is supported at a predetermined height from the same horizontal surface then it can be ensured that there is a constant spacing between the electrical contact(s) in the base connector part and the electrical contact(s) provided by a corresponding connector part in the cordless appliance. 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 base connector part may be directly or indirectly mounted to the base portion of the base unit. Preferably the base unit comprises at least one set of cooperating features shared by the base portion and base connector part to guide the resiliently-biased movement. If the connector part is directly mounted to the base portion then its movement may be guided by features on the connector part that cooperate with features of the base portion. For example, protruding ribs running vertically down the side of the connector part may cooperate with corresponding grooves provided by the base portion (or vice versa) so that the connector part can move up and down relative to the base portion in the vertical direction. However, it will be appreciated that any distortions of the base portion may then interfere with the guided movement of the connector part so that it becomes difficult to ensure freedom of movement. Thus in a preferred set of embodiments the base connector part is indirectly mounted to the base portion by a coupling portion. The coupling portion may be significantly larger in diameter than the base connector part and act as a buffer that prevents distortions of the base portion from affecting the vertical movement of the connector part. Preferably the coupling portion is fixed to the base connector part so that the coupling portion and connector part move together as a single unit. The base connector part may, for example, be fixed to the coupling portion during assembly e.g. using a bayonet or snap-fit connection. In one set of embodiments the coupling portion comprises an annular member with the base connector part fixed in a central aperture thereof. The coupling portion is preferably arranged to cooperate with the base portion so as to guide the resiliently-biased movement of the base connector part.

In one set of embodiments the base connector part is fixed to a coupling portion that takes the form of an inner annular member and the base portion takes the form of an outer annular member. Preferably the inner annular member fits inside the outer annular member so that together they form an upper surface of the base unit. However, unlike a conventional base unit whose upper surface is fixed, it will be appreciated that the inner annular member undergoes resiliently-biased movement together with the base connector part and therefore moves vertically relative to the outer annular member. An advantage of this arrangement is that the base connector part and inner annular member may be fixed in size while the outer annular member may have an outer diameter that is variable and can be changed by an appliance designer without affecting the guided movement that is a key feature of the invention. In order to guide the resiliently-biased movement of the base connector part, the inner annular member is preferably arranged to slidingly cooperate with the outer annular member. Rather than tilting, the inner annular member may slide horizontally and/or vertically within the annulus defined by the outer annular member. The inner annular member can thereby translate any changes in the base portion into a movement that is always vertical. The inner annular member may be provided with one or more cooperating surfaces that are arranged to slide against a

corresponding surface of the outer annular member. The cooperating surface(s) may be horizontal, vertical, or at an angle therebetween.

As will be described in more detail below, the coupling portion may provide a conical surface leading radially inwardly and upwardly to the base connector part. This conical surface may be arranged to mate with a bottom surface of the cordless appliance unit that provides a corresponding conical surface portion leading radially inwardly and upwardly to the cordless connector part. Mating of such conical surfaces can assist with alignment of the connector parts.

The base connector part may be resiliently mounted to the base portion by any suitable resilient means. In one set of embodiments a resilient member is arranged between the base connector part and the base portion. In various of the examples described above, the resilient member is arranged to act on the base connector part and/or the coupling portion e.g. inner annular member (where provided). The resilient member may be any elastic member e.g. a block, pad, dome or column of elastic material such as natural or synthetic rubber. The resilient member may be a spring member, for example one or more leaf springs or compression springs. A compression spring may take the form of a compressible rubber block or metal coil. In a set of embodiments the resilient member preferably comprises one or more metal coil springs, which have the advantage of being relatively stiff with a well-defined spring constant. The more reliable the spring constant of the resilient member(s), the narrower the tolerances involved in the resiliently-biased movement of the connector part. Metal coil springs have been found to reliably provide the desired 2-3 mm range of movement. In fact it is an advantage of providing a dedicated resilient member that this part can be chosen for its spring properties independently of the other parts of the base unit.

In another set of embodiments the base connector part is resiliently mounted by a resilient coupling portion e.g. that combines the function of coupling the connector part to the base portion with the function of a resilient bias. This can avoid the need for a separate resilient member and potentially reduce the number of parts required for the base unit. This can result in greater efficiency during assembly and reduced costs. The coupling portion may be resilient as a result of its material, e.g. formed of an elastic material such as rubber, and/or because it is formed to have a resilient structure. This may be achieved, for example, by moulding the coupling portion from a plastics material with an overall construction that is elastically deformable. The coupling portion may take the form of an inner annular member that is resiliently deformable out of its plane. In a set of embodiments the coupling portion is mounted to the base portion by one or more resilient struts. This means that the coupling portion can be mainly made of a relatively stiff material while the strut(s) provide a resilient bias to enable compression of the base unit. A plurality of struts may be arranged to extend radially outwardly from the coupling portion e.g. like a spider's legs. The struts may slidingly cooperate with the base portion, for example by sliding in corresponding grooves e.g. provided by a lower cover portion of the base unit.

In either case it is preferable for the resilient means, whether a separate resilient member or integrally provided by a coupling portion for the connector part, to be arranged symmetrically with respect to the base connector part. For example, a plurality of resilient members such as metal coil springs may be arranged circumferentially to surround the base connector part at a constant distance. However it may be preferred to provide a single resilient member, such as a metal coil spring, that is arranged directly beneath the base connector part so as to provide an upwards thrust in line with the electrical contact(s) housed therein. Of course it will be appreciated that the resilient means is provided to physically bias the base connector part, rather than to form any part of an electrical connection between the connector parts, and can therefore be differentiated from a current-carrying leaf spring or the like found in conventional connector parts.

It will be appreciated that the base unit may include one or more further portions, for example an upper cover portion arranged at least partially over the top of the base portion and/or a lower cover portion arranged beneath the base portion. Preferably the upper and/or lower cover portion is fixedly attached to the base portion. Only part of the base portion may rest on the horizontal surface that supports the base unit, for example a peripheral rim of the base portion. A lower cover portion may be fixed underneath the base portion. The lower cover portion may rest directly on the horizontal surface which supports the base unit, but it is instead preferable for the lower cover portion to be provided with a plurality of supporting feet, as this can allow any liquid spilled under the base portion to drain away. Such a lower cover portion may be provided to support a resilient member acting between the base portion and the base connector part. The lower cover portion may be formed from a thicker and/or stronger plastic material that can resist the spring forces.

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 vertical position of the fixed electrical contact(s) in the base connector part can be particularly important when the corresponding electrical contact(s) in the connector part of the cordless appliance are moveable so as to form a switch arrangement with the fixed contact(s) in the base connector part. This switch arrangement preferably makes or breaks an electrical circuit for supplying power to the cordless electrical appliance. 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.

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 arranged to engage with a base connector part of the base unit 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 which supports the cordless electrical appliance in use and the base connector part is resiliently mounted to the base unit so as to be biased away from the base unit and further into engagement with the appliance connector part, and wherein 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 said horizontal surface. In a preferred set of embodiments that particularly takes advantage of the present invention, 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 Applicant has recognised that whenever the base connector part is resiliently mounted to the base unit it can assist in absorbing manufacturing tolerances so that an electrical circuit can more reliably be switched using a contact pair shared between the base connector part and the cordless connector part of the appliance unit. This may be particularly beneficial where the base connector part has a smaller diameter than is conventional.

Thus according to a further 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 arranged to engage with a base connector part of the base unit 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 which supports the cordless electrical appliance in use and the base connector part is resiliently 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 appliance further comprising 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.

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. It is therefore preferable that the switch arrangement comprises a single contact pair for making or breaking the electrical circuit for supplying power to the cordless appliance unit. Where the electrical power supply is mains power, the single contact pair may be arranged to switch the live pole of the electrical power supply circuit. Of course another similar switch arrangement could be provided to switch the neutral pole of the electrical power supply circuit, in addition or alternatively.

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 corresponding 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 corresponding 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.

In such a switch arrangement, the moveable contact member may be mounted on a switch lever with resilient means, separate from and acting on the switch lever, arranged so as to bias the moveable contact member into electrical contact with the fixed contact. The switch arrangement may cause the switch lever to move the moveable contact member away from the fixed contact when the cordless appliance unit reaches a predetermined temperature condition, for example when liquid in the cordless appliance unit reaches a predetermined temperature condition such as boiling. The switch arrangement may therefore comprise a temperature- sensitive actuator arranged to act on the switch lever.

Preferably the connector part of the base unit, and any corresponding connector part of a cordless electrical appliance, is of the type which allows 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. Where the base connector part is a 360 ° connector part, it is preferable for the connector part to be arranged centrally on the base unit.

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 an entirely circular geometry, and it can 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 substantially circular, and further preferably the base connector part is located centrally in 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. The base connector part may have a diameter of about 20 mm.

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, which means that the base connector part becomes taller when 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 on the base connector part. In a set of embodiments the base unit includes a (preferably convex) conical surface portion leading radially inwardly to the base connector part. The bottom surface of the cordless appliance unit may include a corresponding (preferably concave) 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. In embodiments where the base connector part is mounted to the base portion by a coupling portion, e.g. taking the form of an annular member, the coupling portion may provide the conical surface portion leading radially inwardly to the base connector part.

The Applicant has recognised that when a cordless appliance unit is seated on a base unit that may be, or may become, distorted, there is a risk that the appliance itself is not seated level with the horizontal surface on which the base unit is resting. This can result in the appliance being tilted so that the electrical contact(s) provided by a corresponding connector part are not aligned vertically in the way intended. Even though the base connector part in the base unit is resiliently mounted so that it can move vertically and correct for distortions of the base portion, there may still exist a problem with the electrical contacts in the two connector parts being incorrectly aligned if the corresponding connector part in the cordless appliance unit is tilted at an angle to the horizontal surface. In a set of embodiments it is therefore preferable for the base unit to be mated with a cordless appliance unit that also comprises a peripheral portion arranged to rest on the horizontal surface which supports the base unit in use.

Accordingly there is provided a cordless electrical appliance which is itself directly supported by the horizontal surface, rather than only indirectly via the base portion. By providing the cordless appliance unit with such a peripheral portion, it is ensured that any electrical contact(s) carried by the appliance are at a constant height from the horizontal surface. 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.

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 base unit to have a footprint that is reduced in size compared to that of the cordless appliance unit. The peripheral portion may therefore be provided in areas that do not overlap with the footprint of the base unit. This is described in more detail in the Applicant's co-pending application. The peripheral portion may take any suitable form, such as a peripheral rim or a number of feet spaced around the periphery. In a preferred set of embodiments the peripheral portion comprises at least three feet spaced around the periphery of the appliance, e.g. in the form of a tripod. If the three feet are spaced inwardly of the periphery then they may rest on the base unit (e.g. on its upper surface) rather than on the horizontal surface.

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;

Figures 2a and 2b show a first embodiment of the cordless electrical appliance in cross- section, where it can be seen that in Fig. 2a the base connector part of the base unit is in a lower position and in Fig. 2b it has moved to a higher position;

Figures 3a and 3b provide perspective views of the base unit of the first embodiment in an exploded form;

Figure 4 is another perspective view showing two members of the base unit that are guided for movement relative to one another; Figure 5a is a cross-sectional view of the base unit showing the base connector part in a lower position and Figure 5b shows the base connector part in a higher position;

Figures 6a and 6b show a second embodiment of the cordless electrical appliance in cross-section, where it can be seen that in Fig. 6a the base connector part is in a higher position than in Fig. 6b;

Figs. 7a and 7b provide perspective views of the base unit of the second embodiment in an exploded form;

Figure 8 is another perspective view showing a member of the base unit from its underside;

Fig. 9a is a cross-sectional view of the base unit showing the base connector part in a higher position and Fig. 9b is a cross-sectional view of the base unit showing the base connector part in a lower position;

Figure 10 is an exploded view of a cordless appliance unit (Fig. 10a) and base unit (Fig. 10b) of a cordless electrical appliance according to a further embodiment; and

Figure 1 1 is an exploded view of a cordless appliance unit (Fig. 1 1 a) and base unit (Fig. 1 1 b) of a cordless electrical appliance according to a yet further embodiment.

There is seen in Figure 1 a cordless electrical appliance 1 that generally comprises a cordless appliance unit 2 and a corresponding a base unit 4 that is connected to the mains electrical power supply by a cable 6. The base unit 4 includes a base connector part 8a that can be engaged with a corresponding connector part 8b on the underside of the cordless appliance unit 2 when it is seated on the base unit 4. The two connector parts 8a, 8b provide a 360 ° type connector set. 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.

On the bottom surface of the cordless appliance unit 2 there is provided three feet 5 that bear against an upper surface of the base unit 4 when the appliance unit is seated thereon. The three feet 5 are arranged to form a tripod for stability. It will be understood that if the upper surface of the base unit 4 is or becomes distorted then the appliance unit 2 may not be level and this can effect the separation distance between the two connector parts 8a, 8b. It can also be seen that the bottom surface of the cordless appliance unit 2 has a conical portion 9b leading radially inwardly to the appliance connector part 8b. On the upper surface of the base unit 4 there is a corresponding conical surface portion 9a leading radially inwardly to the base connector part 8a. When the cordless appliance unit 2 is placed on the base unit 4, the two conical surface portions 9a, 9b cooperate so as to bring the connector parts 8a, 8b into vertical alignment with one another so that the appliance connector part 8b can drop cleanly down into engagement with the base connector part 8a without any tilting. Further details of such an arrangement are described in the Applicant's co-pending application GB 1220679.3. The cross-sectional view seen in Figures 2a and 2b shows the two connector parts 8a, 8b in engagement when the cordless appliance unit 2 is seated on the base unit 4. The corresponding connector part 8b in the cordless appliance unit 2 may be integrated with a power supply circuit in a cordless electrical connector unit provided with a manually operable switch or as part of a thermally responsive control that is mounted to a heater 10 of the appliance unit 2. The electrical power supply to the cordless appliance unit 2 can be connected and disconnected by separating the two connector parts 8a, 8b. Where at least one of the connector parts 8a, 8b includes one or more fixed contacts and the other connector part has a corresponding contact carried by a moveable member, it is important for the connector parts 8a, 8b to be brought into the same degree of engagement despite the presence of manufacturing tolerances or distortion in the base unit 4, which is typically moulded from a plastics material. It can be seen that this is achieved by resiliently mounting the base connector part 8a so that it is guided to move vertically up and down relative to a main portion of the base unit 4.

A first embodiment of a base unit 4 will now be described with reference to Figures 2 to 5. The exploded views of Figures 3a and 3b show that the base unit 4 has the base connector part 8a with its associated power supply cable 6 fitted in a central aperture of an inner annular member 12. The base connector part 8a may be permanently attached to the inner annular member 12 upon initial assembly of the base unit 4, e.g. using a bayonet fitting, snap-fit or even welding. The inner annular member 12 acts as a coupling portion between the base connector part 8a and the rest of the base unit 4. The inner annular member 12 is mounted within a central aperture of an outer annular member 14, which accommodates the power cable 6 so that it can be led out from the base unit 4. The outer annular member 14 provides a moulded plastics base portion that forms the majority of the surface on which the cordless appliance unit 2 is seated and which has a peripheral rim 16 extending downwardly to contact a horizontal surface which supports the base unit 4 in use.

Distortions of the outer annular member 14 can adversely effect the engagement of the base connector part 8a with the corresponding connector part 8b in the cordless appliance unit 2. So as to accommodate such distortions, the inner annular member 12 that carries the base connector part 8a is resiliently mounted on a metal coil spring 18 located directly beneath the base connector part 8a. The metal coil spring 18 is itself supported on a base cover plate 20 that is fixedly attached to the under side of the outer annular member 14, e.g. by screws or rivets. The inner annular member 12 can bounce up and down on top of the coil spring 18.

It can be seen from Figures 3a, 3b and 4 that the inner annular member 12 and outer annular member 14 are each provided with various features that provide a guiding function that results in vertical movement of the inner annular member 12. It can be seen that the inner annular member 12 has a downwardly depending outer peripheral wall 22 that is moulded with three sets of features involved in guiding the sliding cooperation of the inner annular member 12 within the aperture provided by the outer annular member 14. The outer annular member 14 has a downwardly depending inner peripheral wall 23 that carries some cooperating features. Firstly, there is provided a number (e.g. three as shown) of U-shaped slots 24 cut into the outer peripheral wall 22 of the inner annular member 12 so as to be open from the underside. Each of the slots 24 engages over a corresponding rib 26 that protrudes radially inwardly from the inner peripheral wall 23 of the outer annular member 14. It can be seen that the ribs 26 also carry a boss into which a screw can be inserted to attach the base cover plate 20. The slots 24 have straight vertical sides that cooperate with the ribs 26 so that the inner annular member 12 can move up and down only vertically relative to the outer annular member 14. Secondly, on the inside of the outer peripheral wall 22 there are a number (e.g. three as shown) of triangular tabs 28 that extend radially inwardly and engage against an upstanding rim 30 provided on the upper side of the base cover plate 20. Thirdly, around the outside of the outer peripheral wall

22 the inner annular member 12 is provided with a number (e.g. three as shown) of vertically cut out tabs 32 that extend lower than the peripheral wall 22 and terminate with an outwardly depending lip 33. Each of these tabs 32 is aligned with a slot 34 in the bottom of the inner peripheral wall 23 of the surrounding outer annular member 14. Each lip 33 hooks underneath its corresponding slot 34 so as to limit the vertical movement of the inner annular member 12. Finally, for stability, the inner annular member 12 also has a pair of downwardly depending legs 36 moulded on its underside to surround the base connector part 8a and rest on the upper surface of the base cover plate 20.

The resiliently-biased vertical movement of the inner annular member 12 relative to the outer annular member 14 may be seen by comparing Figures 5a and 5b. In the lower position seen in Figure 5a, the tabs 32 are spaced from the upper limit provided by the slots 34 and therefore the inner annular member 12 is free to move vertically upwards under the resilient bias of the coil spring 18. This vertical movement is guided by the slots 24 sliding up and down over the corresponding ribs 26. In its lower position, the triangular tabs 28 rest against the rim 30 on top of the base cover plate 20 such that the inner annular member 12 is seated vertically and level with the horizontal surface on which the base unit 4 is resting. In Figure 5b it can be seen that tolerances or distortions have been accommodated by the inner annular member 12 moving vertically upwards away from the base cover plate 20 so as to stand proud of the outer annular member 14. The resiliently-biased upwards movement is limited by the tabs 32 as their lips 33 come to rest against the upper limit of the slots 34 provided in the inner peripheral wall

23 of the outer annular member 14. While the moulding of the outer annular member 14 may be twisted or otherwise distorted, it can be seen that the inner annular member 12 carrying the base connector part 8a is guided to move vertically so as to maintain the base connector part spaced level with the horizontal surface.

In other embodiments it is envisaged that the inner annular member 12 may not be constrained to move solely vertically relative to the fixed outer annular member 14. For example, there may be a degree of clearance between the inner annular member 12 and the inner peripheral wall 23 of the outer annular member 14 that allows the inner annular member 12 to slightly tilt or rock from side to side in addition to sliding vertically up and down.

An alternative embodiment of a base unit 40 is shown in Figures 6 to 9. In this embodiment the cordless appliance unit 2 is the same as previously described (e.g. with reference to Figure 1 ), but the base unit 40 has a different type of resilient mounting for the base connector part 8a. Vertical movement of the base connector 8a relative to the base unit 40 is generally seen from the cross-sectional views of Figures 6a and 6b. The exploded views of Figures 7a and 7b show the main components of the base unit 40. Again the base connector part 8a is fixed in an aperture in the centre of an inner annular member 42, but this inner annular member 42 has a greater diameter and therefore provides the majority of the upper surface of the base unit 40. The inner annular member 42 is slidingly mounted inside an aperture of an outer annular member 44, which is moulded with a peripheral outer wall and three horizontal spokes 46 extending radially to a base plate 45 to form a surface-engaging base for the base unit 40. It is an advantage of this embodiment that in addition to the base connector part 8a and its power supply cable (not shown), the base unit 40 comprises only two moulded parts that need to be assembled together during manufacture. However, a further lower base cover may of course be provided where desired.

The structure of the underside of the inner annular member 42 is seen in more detail from the view of Figure 8. It can be seen that a number (e.g. three as shown) of radially extending elongate struts 48 are arranged to stand proud of the inner annular member 42 so as to be able to engage in corresponding grooves 50 provided on the upper side of the spokes 46. The struts 48 act to resiliently bias the inner annular member 42 as they undergo elastic defamation under vertical loading. The struts 48 therefore act to resist compression of the base unit 40 when a cordless appliance unit is placed thereon. As well as being pressed closer to the inner annular member 42, the struts 48 can slide radially in and out along the corresponding grooves 50.

Further guidance of the vertical movement of the inner annular member 42 is provided by two other sets of cooperating features shared between the inner annular member 42 and the outer annular member 44. It can be seen that the inner annular member 42 is provided with an outer peripheral rim 52, which may be split into pairs of resilient tabs 54 either side of each of the struts 48 so as to facilitate assembly of the base unit 40. After assembly, this rim 52 and its tabs 54 engage underneath the outer annular member 44 and therefore limit the range of vertical movement available to the inner annular member 42. Furthermore, formed on the underside of the inner annular member 42 is a pair of support legs 56 arranged either side of the aperture receiving the base connector 8a and these are received in corresponding guide bores 58 formed on the upper surface of the base plate 45. As the inner annular member 42 moves up and down under the resilient bias of the struts 48, these support legs 56 slide in the bores 58 so as to constrain the movement to being vertical.

Movement of the inner annular member 42 relative to the outer annular member 44 can be seen by comparing the cross-sectional views of Figures 9a and 9b. It is also conveniently seen from the cross-sectional views that the base connector part 8a has a centrally located contact member in the form of a fixed contact pin 60. The corresponding connector part 8b in the cordless appliance unit 2 may include a moveable contact member which is brought into engagement with the contact pin 60 when the two connector parts 8a, 8b are engaged together. For example, the moveable contact member in the appliance unit 2 may be moved by a resiliently-biased lever to make or break electrical contact within the base connector part 8a. For this to be achieved reliably, there must be a predictable separation between the fixed contact pin and the position of the moveable contact member. This is achieved even if there are distortions in the base unit 40, as the inner annular member 42 can move to adjust the height of the cordless base connector part 8a.

In this embodiment the three struts 48 are designed to provide the necessary resilient bias that provides for movement of the inner annular member 42. However, it is envisaged that another resilient member, such as a metal coil spring, could also be used e.g. located underneath the base connector part 8a where a higher spring force is required. Of course, in either of the described embodiments the resilient mounting may instead be provided in an alternative way, for example using rubber pads or the like underneath the inner annular member in either of the embodiments.

In the further embodiment of Figure 10, there is seen a cordless appliance unit 2' seated on a base unit 4' which has a smaller footprint. The appliance unit 2' therefore overhangs the base unit 4'. When the appliance 2' is supported on a horizontal surface, the base unit 4' rests on the surface and, radially outward of the base unit 4', a peripheral rim 24 of the appliance unit 2' also rests on the surface. Optionally, two or 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'. The peripheral 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. As seen in Figure 10a, 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 Figure 10b, 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 two connector parts 20a, 20b provide a 360° type connector set. In a similar manner to Figures 1 to 5 describe above, the base connector part 20b is resiliently mounted to the base unit 4', 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. This may be achieved by an indirect mounting, the base connector part 20b being fixed to the 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.

In an alternative embodiment seen in Figures 1 1 a and 1 1 b, the peripheral rim has been replaced with three feet 12 that are spaced around its periphery to form a tripod for stability. This appliance unit 2' is again separated from a base unit 4' having a footprint which is smaller than that of the appliance unit 2'. As before, the appliance unit 2' therefore overhangs the base unit 4'. Radially outward of the base unit 4', the appliance unit 2' also rests on the surface with the three feet 12. 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'. The connector parts 20a, 20b and conical portions 22a, 22b are the same as described above. As before, the base connector part 20b is resiliently mounted to the base unit 4' for vertical and/or tilting movement.

In any of the embodiments described above, the cordless connector part 8b, 20a in the cordless appliance unit 2, 2' may be brought into engagement with the corresponding base connector part 8a, 20b so that a moveable contact member mounted on switch lever makes electrical contact with a fixed contact in the base connector part 8a, 20b. By operating the switch lever, the electrical power supply circuit can be opened or closed independently of engagement or separation of the connector parts. In such embodiments, the moveable contact member may be mounted on a switch lever that is resiliently biased to move the contact member into electrical contact with the fixed contact. This is described in more detail in WO 2012/164318 and WO 2012/164319, the contents of both of which are hereby incorporated by reference.

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.