Appliance to Which One of a Plurality of Magnetic Attachments Is Attachable

The present invention relates to an appliance to which one of a plurality of magnetic attachments is attachable.

An appliance may have a main unit to which one of a plurality of attachments is attachable. For example, a hair appliance may comprise different attachments for achieving different styling results. In some instances, it may be desirable for the appliance to determine which of the attachments is attached to the main unit.

According to a first aspect of the present invention, there is provided an appliance comprising: a main unit to which one of a plurality of magnetic attachments is attachable in any one of a plurality of rotational positions relative to the main unit about an axis; a magnetometer; and a control module operable to determine which of the plurality of attachments is attached to the main unit based on data output by the magnetometer; wherein the appliance comprises one or more of the following features: (i) the magnetometer is located on the axis; (ii) the appliance comprises the plurality of magnetic attachments, where each magnetic attachment comprises a plurality of magnetic regions distributed about the axis in a rotationally symmetric arrangement, and the magnetometer is located radially inwardly of the plurality of magnetic regions when the attachment is attached to the main unit; and/or (iii) the appliance comprises the plurality of magnetic attachments and wherein each magnetic attachment comprises a magnetic region located on the axis when the attachment is attached to the main unit.

Any one (or indeed combination) of features (i) to (iii) allows for the control module to determine which attachment is attached to the main unit regardless of the rotational position of the attachment. This may, in turn, provide for robust identification of the attachment and/or for flexible use of the attachment. For example, different magnetic attachments may be configured to produce different magnetic fields. However, in each one (or combination) of features (i) to (iii), at least a component of the magnetic field produced by each magnetic attachment in a direction parallel to the axis will be invariant (or nearly so) with respect to the rotational position of the attachment about the axis. This rotationally invariant component may be measured, and different attachments accordingly discriminated, regardless of the rotational position of the attachment. This allows for a robust identification of the attachment, while at the same time allowing for the benefits associated with an attachment that can be attached to the main unit in any one of a plurality of rotational positions (including infinitely many), such as flexibility of use.

Alternatively or additionally to the above benefits, use of the magnetometer according to any one or more of features (i) to (iii) may allow the remote and/or automatic determination of which attachment is attached to the main unit. For example, use of the magnetometer according to any one or more of features (i) to (iii) may allow the determination of which attachment is attached to the main unit to be made remotely from the attachment interface. For example, the magnetic field produced by each attachment (or at least a portion of that magnetic field) may be measurable remotely from the magnetic attachment itself, e.g. at the magnetometer. The attachment interface may otherwise be an undesirable location for sensors to be located due to e.g. packaging constraints and/or harsh conditions such as high temperatures. Therefore, being able to determine, remotely from the attachment interface, which attachment is attached to the attachment interface, may allow for such packaging constraints and/or harsh conditions to be mitigated. Further, use of the magnetometer may allow the determination of which attachment is attached to the main unit to be made automatically, for example as compared to that information being input by a user on a user interface, which may improve user experience.

Optionally, the appliance comprises an electric component and the control module is operable to control the electric component in response to the determination. This may allow for the control module to control the electric component differently for different attachments. This has the benefit that operation of the appliance may be controlled automatically on the basis of the attachment that is in use.

Optionally, the electric component comprises an electric motor or a heater, and the control module is operable to control a speed of the electric motor or a temperature of the heater in response to the determination. The performance of the appliance may be improved by operating the electric motor at different speeds and/or by operating the heater at different temperatures based on the attachment that is in use. For example, the appliance may be a hair appliance, the electric motor may be used to generate an airflow, and the heater may be used to heat the airflow. Different attachments may then provide better drying or styling results at different flow rates and/or at different heat settings. In another example, the appliance may be a vacuum cleaner and the electric motor may be used to generate suction. Different attachments may then perform better at different suctions.

Optionally, the electric component comprises a sensor, and the control module is operable to control a setting of the sensor in response to the determination. Sensors of the appliance may operate more effectively if calibrated according to the attachment being used with the main unit. For example, different attachments for a hair appliance, such as a diffuser and a concentrator, may have different lengths. A ranging sensor, such as a Time-of-Flight sensor, included in the main unit and used to determine the distance from the appliance to a user's head may therefore, for example, be calibrated differently according to which attachment is being used. For example, the distance at which hair is to be detected by the ranging sensor when a diffuser attachment is in use may be set or calibrated differently to that when a concentrator is being used.

Optionally, the appliance comprises an airflow generator for drawing an airflow through the appliance, and the control module is operable to control a characteristic of the airflow in response to the determination. Different attachments may deliver better results for different airflows. For example, the appliance may be a hair appliance and the attachments may comprise a diffuser and a concentrator. The diffuser may deliver better results when the airflow has lower flow rate. This is because the hair is moved less by the airflow and thus curls are better defined. By contrast, a concentrator may deliver better results when the airflow has a higher flow rate. For example, by employing a higher flow rate, drying and/or styling of the hair may be achieved more rapidly. In another example, the appliance may be a vacuum cleaner and the attachments may comprise a first suction nozzle for use on floors, and a second suction nozzle for use on upholstery. When used on floors, a higher suction may be beneficial to draw in more of the dirt. However, when used on upholstery, a higher suction may cause the upholstery to be sucked into and block the suction nozzle. Accordingly, better results may be achieved on upholstery with a lower suction.

Optionally, the control module is operable to control one or more of a flow rate and a temperature of the airflow. Similar to that mentioned above, by controlling the flow rate and/or the temperature of the airflow in response to the attachment in use, better overall styling and/or cleaning results may be achieved.

Optionally, the appliance is a hair appliance comprising a plurality of flow and heat settings, and the control module is operable to select one of the settings based on the determination. As noted above, different attachments may deliver better results for different flow and/or heat settings. Accordingly, by selecting one of the plurality of settings based on the attachment in use, better drying and/or styling results may be achieved.

Optionally, the appliance comprises the plurality of magnetic attachments, and the magnetic attachments differ in the magnetic field that each magnetic attachment produces at the magnetometer when the attachment is attached to the main unit. This may allow for a cost-effective means to determine which of the attachments is attached to the main unit. For example, the attachments may anyway comprise magnetic components as a means by which the attachments are attached to the main unit. In other words, a magnetic component of the attachment that is used to attach the attachment to the main unit may also be used by the main unit to determine which attachment it is. Tailoring these magnetic components on each attachment so that they produce different magnetic fields (e.g. net strength and/or direction) at the magnetometer may therefore allow the main unit to identify the attachment without necessarily adding components to the attachments or otherwise requiring adaptation of the form or functionality of the attachments.

Optionally, the magnetic field that each magnetic attachment produces at the magnetometer has a component parallel to the axis, and the component differs for different magnetic attachments. This may allow for a relatively efficient and/or robust means by which to determine the attachment attached to the main unit. For example, the component of the magnetic field parallel to (e.g. along) the axis may be independent of the rotational position of the attachment relative to the main unit, and the attachment may be identified from a relatively simple measurement of the magnetic field in this direction, e.g. by a single axis magnetometer, regardless of the rotational orientation of the attachment.

Optionally, the magnetic attachments each comprise a plurality of magnetic regions, each magnetic region has a positive or negative polarity in the direction of the magnetometer when the magnetic attachment is attached to the main unit, and the magnetic attachments differ in the arrangement of magnetic regions having positive and negative polarities. For example, the arrangement of the magnetic regions having positive and negative polarities may correspond to the number of positive polarity magnetic regions and/or negative polarity magnetic regions, the ratio of positive polarity magnetic regions to negative polarity magnetic regions, the size of the positive polarity magnetic regions and/or negative polarity magnetic regions, and/or the distribution or order of the positive polarity magnetic regions and/or negative polarity magnetic regions. For example, the differing arrangements of magnetic regions between attachments may comprise a differing ratio of magnetic regions having a positive polarity in the direction of the magnetometer when the magnetic attachment is attached to the main unit to magnetic regions having a negative polarity in the direction of the magnetometer when the magnetic attachment is attached to the main unit. Providing different magnetic fields by differing the arrangement of positive and negative polarity magnetic regions may allow for the different attachments to be identified without necessarily altering the magnetic force by which different attachments are attached to the main unit. This may allow for consistency in the attachment and detachment operation across different attachments, which may improve user experience.

Optionally, the magnetic regions are distributed around the circumference of a circle that is centred on the axis when the magnetic attachment is attached to the main unit. This may allow for the attachments to be rotatable about the axis when the attachment is attached to the main unit, whilst still allowing for the attachment to be identified. This may improve flexibility of use of the attachments and/or ease of use of the appliance.

Optionally, the magnetic regions are provided by polarised portions of a bonded magnet. A bonded magnet may, for example, be formed of magnetic particles bound in a binder material. Providing the magnetic regions by polarised portions of a bonded magnet may allow for the magnetic regions to be provided without increasing the magnet part count. For example, the same isotropic bonded magnet part may be used for each attachment, but the isotropic bonded magnet of different attachments may be magnetised according to different polarisation patterns. This may allow for a cost-effective way to provide the magnetic regions.

Optionally, where the magnetometer is located on the axis as per feature (i), the distribution of the polarities of the magnetic regions may be rotationally asymmetric about the axis. This may allow that the rotational position of the magnetic attachment relative to the main unit can be determined, for example by the control module. For example, having a rotationally asymmetric distribution of polarities of magnetic regions may provide that there is a component of the magnetic field at the magnetometer perpendicular to the axis. This may, for example, be measured by the magnetometer, and the control module may determine the rotational position of the attachment based on the angle of the perpendicular component about the axis. Having the distribution of the polarities of the magnetic regions being rotationally asymmetric about the axis may allow for the rotational position to be determined precisely without necessarily altering the magnetic force by which different attachments are attached to the main unit. This may allow for consistency in the attachment and detachment operation across different attachments, which may improve user experience.

Optionally, where the magnetometer is located on the axis as per feature (i), and when one of plurality of magnetic attachments is attached to the main unit, the control module may be operable to additionally determine a rotational position of the magnetic attachment relative to the main unit based on data output by the magnetometer. Use of the magnetometer located on the axis may, for example, allow the rotational position of the attachment to be determined remotely from the attachment interface, which may otherwise be an undesirable location for sensors to be located due to e.g. packaging constraints and/or harsh conditions. This may also allow the rotational position to be determined automatically, for example as compared to being input by a user on a user interface, which may improve user experience. Accordingly, this may allow the rotational position of an attachment relative to the main unit to be automatically and remotely determined.

Optionally, where the magnetometer is located on the axis as per feature (i), the magnetic field produced by the magnetic attachment at the magnetometer when attached to the main unit may have a component perpendicular to the axis, and the control module may be operable to determine the rotational position of the magnetic attachment relative to the main unit based on an angle of the perpendicular component about the axis. This may allow for a cost-effective means to determine the rotational position of the attachment. For example, the attachment may anyway comprise magnetic elements as a means by which the attachments are attached to the main unit. Tailoring these magnetic elements so that they produce a net magnetic field that has a component perpendicular to the axis at the magnetometer may therefore allow the main unit to determine the rotational placement of the attachment without necessarily adding components to the attachment or otherwise requiring adaptation of the form or functionality of the attachments. Moreover, since the perpendicular component is orthogonal to the component parallel to (e.g. along) the axis, the magnetic field produced by the magnetic attachment may serve the dual purpose of allowing the identification of the attachment and allowing the rotational position of the attachment to be determined. This may be cost effective, for example as compared to providing separate means for these separate functions.

Optionally, the appliance comprises an electric component, and the control module is operable to control the electric component according to the determined rotational position. For example, this may be the same electric component as mentioned above, such as a heater or air flow generator. This may allow for the control module to control the electric component differently for rotational positions of an attachment. This has the benefit that operation of the appliance may be controlled automatically on the basis of the rotational position of the attachment relative to the main unit. For example, the rotational position of the attachment relative to the unit may be changed manually by a user and thereby provide a means by which the user may control the appliance to operate in a particular mode. As another example, an attachment orientated at different rotational positions relative to the main unit (and hence relative to e.g. a handle of the main unit) may provide for optimal styling when the appliance is operated differently. Accordingly, this may provide for improved styling.

Optionally, the main unit comprises a barrel section having a central bore, the one of a plurality of attachments is attachable to an end of the barrel section, and the magnetometer is located within the bore. Locating the magnetometer in the bore may allow for the magnetometer to be relatively isolated from heated components of the appliance and/or from other components that may otherwise interfere with the magnetometer. A robust determination of the attachment and/or rotational position of an attachment may therefore be provided. Furthermore, for appliances that already have an existing bore, the magnetometer may be incorporated without increasing the overall size of the appliance or without having to significantly alter the existing packaging of the components in the main unit.

Optionally, at least one of the plurality of attachments is rotatable relative to the main unit about the axis whilst attached to the main unit. This may allow for the user to change the rotational position of the attachment relative to the main unit, which may allow for more flexible use, and further to do so without necessarily removing the attachment from the main unit, which may improve ease of use and overall user experience. In such an appliance it may be particularly useful to allow for attachment identification independent of rotational placement of the attachment and/or remote determination of the rotational placement of the attachment.

Optionally, the appliance is a hair appliance. However, it will be understood that in other examples the appliance may be another type of appliance, such as a vacuum cleaner.

Like reference signs denote like features. The axes x, y, z indicated in the Figures correspond amongst the Figures.

Referring to, there is illustrated an applianceaccording to an example. In broad overview, the appliancecomprises a main unitto which one of a plurality of magnetic attachments,is attachable. Each magnetic attachment,is attachable to the main unitin any one of a plurality of rotational positionsrelative to the main unitabout an axis A. The appliancecomprises a magnetometerlocated on the axis A. The appliancecomprises a control moduleoperable to determine which of the plurality of magnetic attachments,is attached to the main unitbased on data output by the magnetometer. For example, as described in more detail below, the magnetic attachments,may differ in the magnetic field that each magnetic attachment,produces at the magnetometerwhen the attachment,is attached to the main unit. The magnetometermay measure or otherwise sense this magnetic field and output data indicative of the sensed magnetic field. The control modulemay map the output data indicative of the sensed magnetic field onto an identifier of one of the plurality of attachments,, thereby to determine which of the plurality of attachments,is attached to the main unit.

Locating the magnetometeron the axis A, about which the magnetic attachments,may have any one of a plurality of rotational positions(including infinitely many) relative to the main unit, allows for the control moduleto determine which attachment,is attached to the main unitregardless of the rotational positionof the attachment,. This may, in turn, provide for robust identification of the attachment,and/or for flexible use of the attachment,. For example, different magnetic attachments,may be configured to produce different magnetic fields. However, at least a component of the magnetic field produced by each magnetic attachment,along the axis A will be invariant with respect to the rotational positionof the attachment,about the axis A. Locating the magnetometeron the axis A may allow this rotationally invariant component to be measured, and different attachments,to be accordingly discriminated, regardless of the rotational position of the attachment,. This may allow for a robust identification of the attachment,, while at the same time allowing for benefits associated with an attachment,that can be attached to the main unitin any one of a plurality of rotational positions, such as flexibility of use.

Alternatively or additionally to the above benefits, use of the magnetometerlocated on the axis A may allow the remote and/or automatic determination of which attachment,is attached to the main unit. For example, use of the magnetometerlocated on the axis A may allow the determination of which attachment,is attached to the main unit to be made remotely from an attachment interface. For example, the magnetic field produced by each attachment,(or at least a portion of that magnetic field) may be measurable remotely from the magnetic attachment,itself, e.g. at the magnetometerlocated on the axis A. The attachment interfacemay otherwise be an undesirable location for sensors to be located due to e.g. packaging constraints and/or harsh conditions such as high temperatures. Therefore, being able to determine, remotely from the attachment interface, which attachment,is attached to the main unit, may allow for such packaging constraints and/or harsh conditions to be mitigated. Further, use of the magnetometermay allow the determination of which attachment,is attached to the main unitto be made automatically, for example as compared to that information being input by a user on a user interface (not shown), which may improve user experience.

In this example, the applianceis a haircare appliance, and the attachments,comprise a concentratorand a diffuser(see e.g.).

In some examples, the appliance may comprise an electric component,,and the control modulemay be operable to control the electric component,,in response to the determination of which attachment,is attached to the main unit. This may allow for the control moduleto control the electric component,,differently for different attachments,. This has the benefit that operation of the appliancemay be controlled automatically on the basis of the attachment,that is in use.

As one example, the electric component,,may comprises an electric motor(e.g. used to generate an airflow) or a heater(e.g. used to heat the airflow), and the control modulemay be operable to control a speed of the electric motoror a temperature of the heaterin response to the determination of which attachment,is attached. For example, different attachments,may provide better drying or styling results at different flow rates and/or at different heat settings. For example, the appliancemay comprise an airflow generatorfor drawing an airflow through the appliance, and the control modulemay be operable to control a characteristic of the airflow in response to the determination. Different attachments may deliver better results for different airflows. For example, the diffusermay deliver better results when the airflow has lower flow rate. This is because the hair is moved less by the airflow and thus curls are better defined. By contrast, the concentratormay deliver better results when the airflow has a higher flow rate. In some examples, the control moduleis operable to control one or more of a flow rate and a temperature of the airflow. For example, the hair appliancemay comprise a plurality of flow and heat settings, and the control moduleis operable to select one of the settings based on the determination of which attachment,is attached to the main unit. For example, the control modulemay store a default flow and temperature setting for each of the attachments,. Additionally, or alternatively, the control modulemay store the flow and temperature setting selected by a user when last using a particular attachment,. As noted above, different attachments may deliver better results for different flow and/or heat settings. Accordingly, by selecting one of the plurality of settings based on the attachment in use, better drying and/or styling results may be achieved. As another example, the control modulemay be operable to map different user selectable settings onto different operation of the hair appliancebased on the determination of which attachment,is attached to the main unit. For example, in a default mode, user selection of certain settings of flow rate and/or temperature (e.g. ‘low’, ‘medium’ and ‘high’) may correspond to operation of the hair applianceat certain flow rates and/or airflow temperatures. However, the control modulemay be configured to change the flow rates and/or airflow temperatures to which the selectable settings correspond based on the attachment,attached to the main unit. For example, the change may be implemented as applying an offset in flow rate and/or temperature to those in the default mode. For example, if the control moduledetermines that a given attachment,is attached to the main unit(which attachment is, say, associated with use close to a user's skin so that use with default mode temperatures may be uncomfortable for a user), the control modulemay be configured to reduce the temperatures at which the heateris controlled to operate (e.g. via reducing the heater duty cycle and/or reducing a target value for a PID control, for example). More generally, in some examples, the control modulemay determine the range of temperatures and/or flow rates (or other operation of the hair appliance) selectable by a user (i.e. that are able to be selected by a user) based on the attachment,that the control moduledetermines to be attached to the main unit. For example, so that the range of selectable operation is optimised for the identified attachment,.

As another example, the electric component may be or comprise a sensor, and the control modulemay be operable to control a setting of the sensor in response to the determination. Sensorsof the appliancemay operate more effectively if calibrated according to the attachment,being used with the main unit. For example, as shown in, the appliancemay comprise a ranging sensor, such as a Time-of-Flight sensor, included in the main unitand used to determine the distance from the applianceto a user's head or hair. The different attachments,for the hair appliance, such as the diffuserand the concentrator, may have different lengths. Accordingly, the Time-of-flight sensormay therefore, for example, be calibrated differently according to which attachment,is being used. For example, the distance at which hair is to be detected by the ranging sensorwhen a diffuser attachmentis in use may be set or calibrated differently to that when a concentratoris being used.

In some examples, the control modulemay be operable to set a responsiveness with which the heaterand/or airflow generatoris turned on or off (or an operating mode thereof adjusted) in response to the determination of which attachment,is attached. For example, the responsiveness may be set by altering an algorithmic smoothing applied to the output of the sensor, a low pass filter applied to the output of the sensor, and/or a delay applied to the change in operating mode of the heaterand/or airflow generator. For example, some attachmentsmay be typically used in rough drying where the applianceis moved around relatively vigorously during use. In this case (i.e. when it is determined that such an attachment,is attached to the main unit), it may be desirable to increase an algorithmic smoothing applied to the output of the sensor, lower a low pass filter applied to the output of the sensor, and/or increase a delay applied to a change in the operating mode of the heaterand/or airflow generator. This may reduce the chances that said vigorous movement (and hence rapid change in the output of the sensor) is erroneously interpreted by the control moduleas the appliancebeing moved away entirely from the hair of the user.

In either case, the control modulemay be operable to control the electric component,,in response to the determination of which attachment,is attached to the main unit, which may allow for the operation of the applianceto be controlled automatically on the basis of the attachment,that is in use.

In the example illustrated in, the main unitcomprises a handle sectionand a barrel section. The handle sectionis generally cylindrical in shape and comprises a housingthat houses the airflow generator. The housing comprises an inletthrough which an airflow is drawn into the handle sectionby the airflow generator, and an outletthrough which the airflow is discharged into the barrel section. The airflow generatormay comprise, for example, a fan driven by an electric motor.

The barrel sectionis likewise generally cylindrical in shape, but is shorter in length and wider in diameter than the handle section. The barrel sectionis attached to an end of the handle sectionand is oriented such that the longitudinal axes of the handle sectionand the barrel sectionare orthogonal. As a result, the shape of the main unitresembles a gavel or mallet.

The barrel sectioncomprises a housingthat houses the heaterand the control module. The housingcomprises an outer walla and an inner wallthat are generally concentric and define a chamber within which the heaterand the control moduleare housed. The housingcomprises an inletthrough which airflow from the handle sectionenters the chamber, and an outletat an end of the barrel sectionthrough which the airflow is discharged. The heateris located between the inletand the outletand, when powered, heats the airflow. The inner walldefines a borethat extends through the centre of the barrel section.

As best seen in, the main unitfurther comprises user controls,,,. The user controls,,,are provided on both the handle sectionand the barrel section, and comprise a first buttonor slider to power on and off the appliance, a second buttonto momentarily power off the heatersuch that the appliancedelivers a cold shot of air, a third buttonto control the flow rate of the airflow, and a fourth buttonto control the temperature of the airflow. Alternatively or additionally to the control provided by the control modulein response to the determination of which attachment,is attached, the control modulemay control electric components,,in response to user controls. For example, in response to inputs from the user controls,,,, the control modulemay power on and off the airflow generatorand/or the heater. Additionally, the control modulemay control the power or speed of the airflow generatorin order to vary the flow rate of the airflow. For example, repeatedly pressing the third buttonmay cause the control moduleto cycle through different flow rates (e.g., low, medium and high). Similarly, the control modulemay control the power of the heaterin order to vary the temperature of the airflow. For example, repeatedly pressing the fourth buttonmay cause the control moduleto cycle through different temperature settings (e.g., cold, warm, hot).

Each of the attachments,may be attached to an end of the barrel sectionof the main unit. When attached, each of the attachments,may be free to rotate relative to the main unitabout the central longitudinal axis A of the barrel section. The free rotation of the attachments,has the advantage that a user is able to achieve a desired direction and angle of airflow without having to hold or manipulate the applianceat uncomfortable angles. In this example, each of the attachments,comprises an annular magnet, and the barrel section comprises a ferrous ringto which the magnetis attracted to secure the attachment,in place. It will be appreciated that the ringneed not necessarily be ferrous and may be made of another material to which the magnetis attracted. In this example, when the attachment,is attached to the main unit, a portion or bungof the attachment,is received into the bore. In this example, when the attachmentis attached to the main unit, an airflow expelled from the outletof the barrel sectionflows through the attachment and is in turn expelled from an outletof the attachment.

In this example, the magnetometeris located within the boreof the barrel section. Specifically, in this example, the magnetometeris provided in a capsulethat is located generally centrally of the bore. In this example, the capsuleis elongate and lies along the axis A. The capsuleis connected to the inner wallof the barrel sectionby a member or fin. In this example, the capsulealso houses the ranging sensor. Locating the magnetometerin the boreand/or in the capsulelocated within the boremay allow for the magnetometerto be relatively isolated from heated componentsof the applianceand/or from other components that may otherwise interfere with the magnetometer. A robust determination of the attachment,may therefore be provided. Furthermore, for appliances that already have an existing bore, the magnetometermay be incorporated without increasing the overall size of the applianceor without having to significantly alter the existing packaging of the components in the main unit.

As described in more detail below, in some examples the magnetometeris configured to measure or otherwise sense a strength and/or direction of a magnetic field at the magnetometer. For example, the magnetometermay be configured to output data indicative of the magnitude and/or direction of the magnetic field at the magnetometer. For example, the magnetometermay be configured to output a magnitude of each of one or more components of the magnetic field at the magnetometerin one or more respective directions, such as along the x, y and/or z axes as indicated in the Figures. The magnetometermay, for example, be provided by one or more Hall effect sensors, although other magnetometers may be used. For example, the magnetometermay be provided by a three axis Hall-effect sensor, for example provided on an integrated chip. The control modulemay be configured to receive the output data from the magnetometer, and determine which attachment,is attached to the main unitbased on this data. In some examples, the magnetometerand/or the control modulemay apply a low pass filter and/or averaging to the data output of by magnetometerin order to remove high frequency noise, such as may be produced by components of the appliancesuch as the heateror the airflow generator, or indeed by other electrical devices external to the appliance. This may improve the reliability of the determination of which magnetic attachment,is attached to the main unit.

In this example, the magnetometeris set reasonably far back in the boreof the barrel section. In this example, the distance between the magnetometer and the end of the barrel section(i.e., that end to which the attachments,attach) is around 45 mm. The magnetometerbeing set back from the magnetic attachment,along the axis A, and specifically set back from the magnetof the magnetic attachment,, may allow for the magnetto produce a magnetic field at the magnetometerthat has a non-zero component along the axis A, which as described in more detail below allow for effective identification of different attachments,by the control module.

As mentioned, the magnetic attachments,may differ in the magnetic field that each magnetic attachment,produces at the magnetometerwhen the attachment,is attached to the main unit. In the present example, the magnetic field is produced by the magnet. That is, the magnetof the attachment,that is used to attach the attachment,to the main unitis also used to produce the magnetic field that is sensed by the magnetometerand hence on the basis of which the control moduledetermines which attachment,is attached to the main unit. by the main unit to determine which attachment it is. Tailoring the magneton each attachment,so that they produce different magnetic fields (e.g. net strength and/or direction) at the magnetometerwhen the attachment,is attached to the main unitmay therefore allow the main unitto identify the attachment without necessarily adding components to the attachments,or otherwise requiring adaptation of the form or functionality of the attachments,. This may allow for a cost-effective means to determine which of the attachments,is attached to the main unit.

In some examples, the magnetic field that each magnetic attachment,produces at the magnetometerhas a component parallel to (e.g. along) the axis A, and this component differs for different magnetic attachments,. This may allow for a relatively efficient and/or robust means by which to determine the attachment attached to the main unit. For example, the component of the magnetic field parallel to (e.g. along) the axis A will be independent of the rotational position of the attachment,relative to the main unit, and the attachment may be identified from a relatively simple measurement of the magnetic field regardless of the rotational orientation of the attachment.

As an example, the magnetof different attachments,may be of different strengths, which may accordingly result in a magnetic fields at the magnetometerhaving a component along the axis A of different magnitudes. Alternatively or additionally, the magnetof different attachments,may be of different polarities, which may accordingly result in magnetic fields at the magnetometer having a component along the axis A in one direction or an opposite direction and/or with different magnitudes in those directions. Alternatively or additionally, the magnetof different attachments,may differ in the direction or angle of polarisation, which may accordingly result in magnetic fields at the magnetometer having a component along the axis A in one direction or an opposite direction and/or with different magnitudes in those directions.

In some examples, the magnetic attachments,may each comprise a plurality of magnetic regions. For example, the magnetof each attachment,may be made up of a plurality of magnetic regions. In the example of, each magnetic regionis provided by an individual magnetic component, such as a bipolar magnet. In the example of, there are 24 such magnetic regionsdistributed in a circle centred on the axis A. In this example, the 24 magnetic regionsare distributed evenly around the circle centred on the axis A. Distribution of the magnetic regionsin a circle centred on the axis A may allow for the attachmentsto be rotatable about the axis A when the attachment,is attached to the main unit, whilst still allowing for the attachment,to be identified. This may improve flexibility of use of the attachments,and/or ease of use of the appliance.

In some examples, each magnetic regionmay have a positive or negative polarity (e.g. its North or South pole, respectively) in the direction of the magnetometerwhen the magnetic attachment,is attached to the main unit, and the magnetic attachments,differ in the arrangement of magnetic regionshaving positive and negative polarities. For example, the arrangement of the magnetic regionshaving positive and negative polarities may correspond to the number of positive polarity magnetic regionsand/or negative polarity magnetic regions, the ratio of positive polarity magnetic regionsto negative polarity magnetic regions, the size of the positive polarity magnetic regionsand/or negative polarity magnetic regions, and/or the distribution or order of the positive polarity magnetic regionsand/or negative polarity magnetic regions.

As described in more detail below, the differing arrangements of magnetic regionsbetween attachments,may comprise a differing ratio of magnetic regionshaving a positive polarity in the direction of the magnetometerwhen the magnetic attachment,is attached to the main unitto magnetic regionshaving a negative polarity in the direction of the magnetometerwhen the magnetic attachment is attached to the main unit. For example, each magnetic regionmay have the same individual magnetic strength, but the arrangement or distribution of polarities of these magnetic regions may differ between attachments,. Providing different magnetic fields by differing the arrangement of positive and negative polarity magnetic regionsmay allow for the different attachments,to be identified without necessarily altering the magnetic force by which different attachments are attached to the main unit. For example, this attachment force may be in the range 10 N to 100 N, for example 50 N. This may allow for consistency in the attachment and detachment operation across different attachments,, which may improve user experience.

Referring to, there is illustrated schematically different arrangements of magnetic regions, according to one example. As per the magnetic regionsof, in each arrangement there are 24 magnetic regions distributed in a circle. In the example of, there are eight different arrangements,,,,,,of magnetic regions. Each different arrangement may, for example, be implemented on a different attachment,. Accordingly, in this example, the control modulemay determine which one of eight different attachments,is attached to the main unit. In, each magnetic region is represented by circle. A filled in circle represents that a negative polarity (i.e. South pole, S) is facing towards the magnetometer (not shown) when the attachment (not shown) is attached to the main unit (not shown), and an empty circle represents that a positive polarity (i.e. North pole, N) is facing towards the magnetometer (not shown) when the attachment (not shown) is attached to the main unit (not shown).

In this example, each arrangement,,,,,,has a different number of magnetic regions having a positive polarity N facing towards the magnetometer and a different number of magnetic regions having a negative polarity S facing towards the magnetometer. More particularly, in this example, each arrangement,,,,,,has a different ratio of magnetic regions having a positive polarity N facing towards the magnetometer to magnetic regions having a negative polarity S facing towards the magnetometer. Specifically, in a first arrangementthere are 8 N and 16 S (giving a ratio of 8:16), in a second arrangementthere are 6 N and 18 S (giving a ratio of 6:18), in a third arrangementthere are 3 N and 21 S (giving a ratio of 3:21), in a fourth arrangementthere are 0 N and 24 S (giving a ratio of (0:24 ), in a fifth arrangementthere are 16 N and 8 S (giving a ratio of 16:8), in a sixth arrangementthere are 18 N and 6 S (giving a ratio of 18:6), in a seventh arrangementthere are 21 N and 3 S (giving a ratio of 21:3), and in an eighth arrangementthere are 24 N and OS (giving a ratio of 24:0). It is noted that in this example, the distribution of the polarities N,S of the magnetic regions is rotationally symmetric about the axis A, that is, the distribution of the polarities N,S of the magnetic regions of each arrangement,,,,,,has a rotational symmetry of more than one. Specifically, in this example the rotational symmetries of arrangements,,,,,,are 8, 6, 3, 24, 8, 6, 3, and 24 respectively.

Each arrangement,,,,,,produces a different magnetic field at the magnetometer. As indicated in, the relative magnetic field strength of the eight arrangements,,,,,,at the magnetometer will be −25,−50, −75, −100, +25, +50, +75, and +100, respectively. In this example, references to ‘+’ and ‘−’ correspond to magnetic field strengths in one direction (e.g. along the axis A in one direction) and an opposite direction (e.g. along the axis A in the opposite direction) respectively.illustrates a plot of magnetic field strength as measured at the magnetometeras a function of attachments,being attached to the main unithaving the different arrangements,,,,,,illustrated in. Specifically, the plateaus,,,,,,,in the magnetic field measurement correspond to attachments being attached to the main unit having the arrangements,,,,,,, respectively. As is evident, the eight attachments can be readily discriminated on the basis of the magnetic field. For example, the control modulemay store eight attachment identifiers each in association with a respective one of these eight magnetic field values. The control modulemay be configured to determine to which of these eight magnetic field values a current magnetic field value output by the magnetometercorresponds, and accordingly retrieve the associated attachment identifier, thereby to determine which of the plurality of attachments,is attached to the main unit.