Wearable air purifier

Abstract

A filter module 151, 152 for housing a filter (171, Fig 5), the filter module being releasably attachable to an airflow generating assembly of a wearable air purifier 101, the airflow generating assembly comprising a headgear 102 for wearing on a wearer’s head, and an airflow generator 103, 104, such as a fan assembly, coupled to the headgear and adapted to generate an airflow for inhalation by the wearer. The headgear may be configured as headphones, with the filter module coupled to a ear cup 109, 110. Left and right filter modules may be provided, for releasably attaching to left and right housings of a head wearable purifier. Each of the filter modules are provided with a mechanical coupling, with the left filter module coupled to the left housing by rotating the module in a first direction, and the right filter module coupled to the right housing by rotating the module in a second direction opposite the first direction. A wearable air purifier comprising a filter module is also disclosed.

Description

B ACKGROUND Exposure to air pollution such as pollutant gases or airborne particulates presents a risk of harm to human health. An approach to reducing a person’s exposure to air pollution is to use a wearable air purifier to discharge filtered air towards a wearer’s face. SUMMARY According to a first aspect of the invention, there is provided a wearable air purifier, comprising: an airflow generating assembly comprising: headgear for wearing on a wearer’s head, and an airflow generator coupled to the headgear and adapted to generate an airflow for inhalation by the wearer. The wearable air purifier comprises: a filter module for retaining a filter, the filter for filtering the airflow, wherein the filter module is releasably attachable to the airflow generating assembly. The filter may be loosely or fixedly retained within the filter module. When loosely retained, movement of the filter relative to the filter module may be unrestricted within the filter module. When fixedly retained, movement of the filter relative to the filter module may be restricted within the filter module. The filter may be releasably fixedly retrained within the filter module. A component or components, other than a casing of the filter module, may fixedly retain the filter within the filter module. The filter module is reversibly attachable and detachable by the wearer from the airflow generating assembly. The filter module may be releasably attachable to the airflow generator of the airflow generating assembly. The wearer may attach the filter module to the airflow generating assembly when the provision of filtered airflow by the airflow generating assembly is desired, and detach the filter module from the airflow generating assembly when the filtered airflow is not desired. The headgear may thus be wom without the filter module attached, and thus without the additional mass and bulk of the filter module. This may be useful as the wearer may desire to wear the headgear, which may in some cases be headphones, without the filter module in scenarios where filtered airflow is not desired, such as in environments with low levels of air pollution. Whereas in environments with high levels of air pollution the wearer may desire to also receive the filtered airflow to reduce their exposure to the air pollution. The headgear and components coupled thereto may thus have dual functionality, which may desirably reduce a perceived need for the wearer to have separate air purifying and non-air purifying headgears, e.g., separate air purifying and non-air purifying headphones. The airflow generator may be a fan assembly. The airflow generator, which may comprise a radial fan, is operable to generate airflow to be discharged from the wearable air purifier for inhalation by the wearer. The airflow generating assembly or the filter module may comprise an outlet for discharging the filtered airflow directly out of the wearable air purifier for inhalation by the wearer. The discharged filtered airflow may be directed towards the wearer’s face, past the wearer’s face and / or generally towards the vicinity of the wearer's face. The filter module may be releasably attachable to the airflow generating assembly at an air inlet of the airflow generating assembly or an air of the outlet airflow generating assembly. For example, airflow generated by the airflow generator may be drawn through the filter module, and the filter contained therein, from the environment and then discharged from the airflow generating assembly via an outlet in the airflow generating assembly, such as an outlet in the airflow generator, or the filter module for inhalation by the user. For example, air may pass from the environment into the filter module, through the filter, from the filter module into the airflow generator and from the airflow generator to an outlet in the airflow generator. In another example, air may pass from the environment into the filter module, through the filter, from the filter module into the airflow generator and from the airflow generator to an outlet in the filter module. In other words, the filter module may fluidly couple with the airflow generator when releasably attached thereto. The filter media may be pleated. The filter media may comprise any of a particulate filter element and a chemical filter element. The particulate filter element may comprise a pleated particulate filter media that may be arranged to be annular and / or frustoconical in shape. Folds (e.g. fold lines) of the pleated filter media may be at an acute angle relative to a central axis of the particulate filter element. Both inner and outer edges of the pleated filter media may be parallel to a central axis of the filter. The entirety of the inner edge of the pleated filter media may then be disposed within a seal of resilient material, and the entirety of the outer edge of the pleated filter media disposed within another seal of resilient material. The wearable air purifier may further comprise a nozzle connected to the airflow generating assembly to receive airflow generated by the airflow generator and discharge the airflow towards the wearer’s face. The nozzle may thus function to carry airflow from the airflow generating assembly, an in particular an outlet of the airflow generating assembly, closer to the wearer’s face, e.g., closer to the nose / mouth region of the wearer’s face. Thus, the airflow generator may be attached to the headgear at a location relatively remote from the wearer’s face, for example, at the side, top, or rear of the wearer’s head, thereby avoiding obstructing the wearer’s face, e.g., obstructing the wearer’s vision. Whereas, notwithstanding that the airflow generator may be relatively remote from the wearer’s face, the filtered airflow may still be provided relatively directly to the wearer’s nose and / or mouth via the nozzle, thereby reducing dilution of the filtered airflow by unfiltered ambient air prior to inhalation. The nozzle may, for example, be arranged to extend from an outlet of the airflow generating assembly in front of the wearer’s face, to thereby duct airflow from the airflow generating assembly to the front of the wearer’s face, e.g., to the wearer’s lower nasal and mouth region. When the headgear comprises an outlet for discharging the airflow for inhalation by the user, the nozzle may be releasably attachable to the headgear at the outlet. When the airflow generator comprises an outlet for discharging the airflow for inhalation by the user, the nozzle may be releasably attachable to the airflow generator at the outlet. Alternatively, when the airflow generator comprises an outlet for discharging the airflow for inhalation by the user, the nozzle may be integrally formed with the airflow generator. In this case, the airflow generator may be releasably attached to the headgear. The wearable air purifier may further comprise a nozzle connected to the filter module to receive airflow generated by the airflow generator and discharge the airflow towards the wearer’s face. The nozzle may thus function to carry airflow from the filter module, and in particular form an outlet in the filter module, closer to the wearer’s face, e.g., closer to the nose / mouth region of the wearer’s face. Thus, the filter module may be attached to the airflow generating assembly, such as to the airflow generator, at a location relatively remote from the wearer’s face, for example, at the side, top, or rear of the wearer’s head, thereby avoiding obstructing the wearer’s face, e.g., obstructing the wearer’s vision. Whereas, notwithstanding that the filter module may be relatively remote from the wearer’s face, the filtered airflow may still be provided relatively directly to the wearer’s nose and / or mouth via the nozzle, thereby reducing dilution of the filtered airflow by unfiltered ambient air prior to inhalation. The nozzle may, for example, be arranged to extend from the filter module in front of the wearer’s face, to thereby duct airflow from the filter module to the front of the wearer’s face, e.g., to the wearer’s lower nasal and mouth region. The nozzle may be integrated with the filter module. In other words, the filter module and nozzle may form a single integrated unit that is releasably attachable to the airflow generating assembly. In this way, the process of attaching and detaching the nozzle and filter module to the airflow generating assembly may be simplified for the wearer as there is only a single attachment and detachment action to perform. The nozzle may be releasably attachable to the filter module. In other words, the filter module and nozzle may form separate units that are releasably attachable to the airflow generating assembly and each other. In this way, the wearer may be provided with a greater number of configuration options for the wearable air purifier. For example, the wearer may wear the airflow generating assembly only, the airflow generating assembly with the filter module attached or the airflow generating assembly with the filter module and the nozzle attached. A shape of the filter module may comprise a major sector of an annulus. In other words, the shape of the filter module may be a portion of a ring shape. Put another way, the filter module may be C-shaped. The filter may be shaped appropriately to be received within the filter module. The outlet for discharging the filtered airflow from the wearable air purifier may be provided in a gap defined by the major sector of the annulus, i.e., within the minor sector of the annulus not occupied by the filter module. The shape of the filter module may be an annulus. In other words, the filter module may be substantially ring-shaped. The filter may be shaped appropriately to be received within the filter module. A portion of the airflow generator may be receivable in a recess of the filter module. In other words, the filter module may be provided around a portion of the airflow generator, for example the portion of the airflow generator that houses the fan. Put another way, the portion of the airflow generator may define a protruding portion receivable in an intruding portion, defined by the recess, of the filter module. The recess of the filter module may be defined by the shape of the filter module, i.e., by the annular or part-annular shape of the filter module. The portion of the airflow generator cooperates with the recess of the filter module to function as a locating feature. This may desirably aid correct positioning of the filter module relative to the airflow generator during attachment of the filter module by the wearer. Correct positioning of the filter module relative to the airflow generator during attachment may be particularly complicated in a scenario where the wearer attaches the filter module to the airflow generator in use, whilst the headgear is worn on the wearer’s head, in which case the airflow generator may be outside of the wearer’s field of view. Forming the male locating feature of the airflow generator has the advantage that such a protruding portion is dual functional. In addition to acting as a male locating feature, a protruding portion is usable to accommodate at least a part of the airflow generator, such as the fan. Thus, the volume of such a protruding portion may be efficiently used, which may thereby desirably allow a reduction in overall size of the airflow generating assembly. The filter module may be releasably attachable to the airflow generating assembly by way of a magnet coupling or a mechanical coupling. By providing a magnet coupling as the means of releasably attaching the filter module to the headgear, the process of attaching the filter module to the airflow generating assembly is greatly simplified for the wearer. For example, to attach the filter module to the airflow generating assembly, the wearer may simply bring the filter module into close proximity with the airflow generating assembly in order to engage the magnet coupling and is not required to rotate or actuate a locking mechanism separately Similarly, to detach the filter module from the airflow generating assembly, the wearer may simply pull the filter module away from the airflow generating assembly in order to disengage the magnet coupling and is not required to rotate or actuate a locking mechanism separately. Further, as magnet couplings do not require direct contact in order to attach to each other, the filter module may attach to the airflow generating assembly in a variety of different orientations without reducing the attachment strength of the magnet coupling. The magnet coupling may comprise: a first attachment feature provided in and / or on the airflow generating assembly; and a second attachment feature provided in and / or on the filter module. In other words, the magnet coupling may comprise a plurality of attachment features distributed across both the filter module and the airflow generating assembly. The attachments features may be realised in a number of ways, which are discussed in further detail below. Due to the magnetic nature of the magnet coupling, the first and second attachment features do not require direct contact in order to attach to each other. Accordingly, the first and second attachment features may be provided within the airflow generating assembly and the filter module, respectively. Alternatively, the first and second attachment features may be provided on the airflow generating assembly and the filter module, respectively, for example on a surface of the airflow generating assembly and the filter module. The first attachment feature may comprise an airflow generating assembly magnet. In other words, the airflow generating assembly may comprise a magnet forming part of the magnet coupling between the airflow generating assembly and the filter module. The airflow generating assembly magnet may comprise a plurality of airflow generating assembly magnets. Tn other words, the airflow generating assembly may comprise a plurality of magnets forming part of the magnet coupling between the airflow generating assembly and the filter module. The provision of a plurality of magnets in the airflow generating assembly may improve the strength of the magnet coupling between the airflow generating assembly and the filter module. Further, the provision of a plurality of magnets in the airflow generating assembly may provide multiple different attachment points and / or orientations between the airflow generating assembly and the filter module. In addition, the plurality of magnets may comprise a plurality of the same type of magnets or a plurality of different types of magnets. The plurality of airflow generating assembly magnets may be arranged in an annular array, and optionally wherein the airflow generating assembly magnets are spaced from each other uniformly within the annular array. In other words, the plurality of magnets in the airflow generating assembly may be arranged in an annular array within, or on, the airflow generating assembly. The annular array may be a complete annulus or a partial annulus. The annular array may be substantially annular and may comprise one or more concentric annular arrangements of magnets. The annular array may enable the airflow generating assembly to be indexed in a plurality of positions about a centre of the annular array. This may increase flexibility for a wearer by allowing the airflow generating assembly to be rotated to a number of different rotational positions relative to the headgear. The airflow generating assembly magnet may comprise one or more ring-shaped magnets. In other words, the magnet in the airflow generating assembly may be provided in the shape of a ring. In this way, the magnet may be arranged concentrically with substantially circular features or components of the airflow generating assembly. The second attachment feature may comprise a filter module ferromagnetic element. In other words, the filter module may include an element that a magnet provided in the airflow generating assembly may attract. Thus, the magnet coupling may comprise a magnetferromagnetic element coupling. The first attachment feature may comprise an airflow generating assembly ferromagnetic element. In other words, the airflow generating assembly may include an element that a magnet in the filter module may attract. Thus, the magnet coupling may comprise a magnet-ferromagnetic element coupling. The second attachment feature may comprise a filter module magnet. In other words, the filter module may comprise a magnet forming part of the magnet coupling between the airflow generating assembly and the filter module. The filter module magnet may comprise a plurality of filter module magnets. In other words, the filter module may comprise a plurality of magnets forming part of the magnet coupling between the airflow generating assembly and the filter module. The provision of a plurality of magnets in the filter module may improve the strength of the magnet coupling between the airflow generating assembly and the filter module. Further, the provision of a plurality of magnets in the filter module may provide multiple different attachment points and / or orientations between the airflow generating assembly and the filter module. The plurality of filter module magnets may be arranged in an annular array or a partially annular array, according to the shape of the filter module, and optionally wherein the filter module magnets are spaced from each other uniformly about the array. In other words, the plurality of magnets in the filter module may be arranged in an annular or partially annular array within, or on, the filter module. The array may be a complete annulus or a partial annulus. The annular array may be substantially annular and may comprise one or more concentric annular arrangements of magnets. The filter module magnet may comprise one or more ring-shaped magnets. In other words, the magnet in the filter module may be provided in the shape of a ring, or a major segment of an annulus. In this way, the magnet may be arranged concentrically with substantially circular features or components of the filter module. The magnet coupling may comprise a magnet-magnet coupling where both the airflow generating assembly and the filter module comprise a magnet. The magnet coupling may comprise a magnet-ferromagnetic coupling where one of the airflow generating assembly and the filter module comprises a magnet and the other comprises a ferromagnetic element. The magnet coupling may comprise a mixed magnet coupling, where both the filter module and the airflow generating assembly comprise both magnets and ferromagnetic elements. The magnet coupling may comprise a partially mixed magnet coupling, where one of the airflow generating assembly and the filter module comprises a magnet and the other comprises both magnets and ferromagnetic elements. The mechanical coupling may comprise a rotational locking mechanism, such as a threaded assembly or a bayonet assembly. In other words, the mechanical coupling may comprise an assembly that inhibits the axial movement of the filter module relative to the airflow generating assembly. In this way, the filter module may be securely held to the airflow generating assembly. The bayonet assembly may comprise: a bayonet projection provided on the filter module; and a cavity provided on the airflow generating assembly adapted to receive the bayonet projection, the cavity having an opening and a securing end at an end of the cavity opposite the opening, wherein the cavity is adapted to receive the bayonet projection at the opening, and wherein the bayonet projection is moved from the opening to the securing end by the rotation of the filter module with respect to the airflow generating assembly in order to attach the filter module to the airflow generating assembly. In other words, the bayonet assembly may comprise a cavity adapted to receive the bayonet projection at one end and releasably secure it at another end after the wearer has rotated the filter module. Accordingly, the process of attaching the filter module to the airflow generating assembly is greatly simplified for the wearer. For example, to attach the filter module to the airflow generating assembly, the wearer may simply bring the filter module to the airflow generating assembly such that the bayonet projection of the bayonet assembly is received in the cavity and rotate the filter module in a predetermined direction in order to releasably attach the filter module to the airflow generating assembly. Accordingly, the wearer is not required to actuate a locking mechanism separately. Similarly, to detach the filter module from the airflow generating assembly, the wearer may simply rotate the filter module in the opposite direction and pull the filter module away from the airflow generating assembly in order to disengage the mechanical coupling and is not required to actuate a locking mechanism separately. Alternatively, the bayonet projection may be provided on the airflow generating assembly and the cavity may be provided on the filter module. The mechanical coupling may comprise a plurality of bayonet assemblies, and optionally wherein the plurality of bayonet assemblies comprises two bayonet assemblies arranged at least 90° (for example, arranged at 180°) from each other about an axis of rotation of the filter module. In other words, the mechanical coupling of the filter module to the airflow generating assembly may be made more secure by providing multiple attachment points around the connection between the filter module and the airflow generating assembly. The mechanical coupling may further comprise a sloped portion adapted to contact the bayonet as it is received in the cavity. Tn other words, the mechanical coupling may comprise a means of aligning the depth of the bayonet within the cavity, thereby ensuring that the bayonet engages correctly with the securing end of the cavity. The mechanical coupling may comprise a locking assembly. In other words, the mechanical coupling may comprise a means of releasably rotationally locking the filter module to the airflow generating assembly when attached. Accordingly, the mechanical coupling of the filter module to the airflow generating assembly may be made more secure by preventing unintended rotation of the filter module, which would otherwise release the filter module from the airflow generating assembly. The locking assembly may comprise: a resilient arm provided on the filter module comprising a projection; and a receiving portion provided on the airflow generating assembly, the receiving portion comprising a track having a ridge section connected to a seat section, wherein relative rotation of the filter module and the airflow generating assembly (i) forces the resilient arm to deflect so that the projection passes over the ridge section and (ii) permits the resilient arm to return towards a rest state as the projection enters the seat section so as to releasably rotationally inhibit rotation of the filter module and the airflow generating assembly together. In other words, the resilient arm may have a strength sufficiently high enough to prevent unwanted rotation of the filter module with respect to the airflow generating assembly; whilst still allowing the wearer to overcome the retaining force of the resilient arm and rotate the filter module to release the mechanical coupling and detach the filter module from the airflow generating assembly, without requiring the user to perform any additional actions. The track may further comprise a stop section connected to the seat section, wherein the stop section is adapted to engage with the projection when the projection is in the seat section to inhibit rotation of the filter module relative to the airflow generating assembly in the direction. Tn other words, the wearer may be prevented from over-rotating the filter module with respect to the airflow generating assembly, which may otherwise release the locking mechanism or damage the mechanical coupling. The locking assembly may further comprise a sloped portion adapted to contact the resilient arm as it is received in the track. In other words, the locking assembly may comprise a means of aligning the resilient arm along the track, thereby ensuring that the projection engages correctly with the seat. The mechanical coupling may comprise a plurality of locking assemblies, and optionally wherein the plurality of locking assemblies comprises two locking assemblies arranged at least 90° (for example, arranged at 180°) from each other about an axis of rotation of the filter module. In other words, the mechanical coupling of the filter module to the airflow generating assembly may be made more secure by providing multiple locking assembly around the connection between the filter module and the airflow generating assembly. The plurality of bayonet assemblies and the plurality of locking assemblies may be arranged in an alternating order about an axis of rotation of the filter module. In other words, the components of the mechanical coupling may be distributed about the filter module and the airflow generating assembly in order to prevent excess mechanical stress being applied to a specific portion of the mechanical coupling. Further, the airflow generator may be releasably attachable to the headgear, for example by way of a magnet coupling or a mechanical coupling in a manner similar to that described above. The wearable air purifier may further comprise a speaker housing supported on a side of the wearer’s head by the headgear, wherein the airflow generator is coupled to the speaker housing. The airflow generator may be releasably attachable to the speaker housing. The headgear thus forms headphones, which may be used for audio playback. The filter module is reversibly attachable and detachable by the wearer from the headphones. The airflow generator may be reversibly attachable and detachable by the wearer from the headphones. The speaker housing may be supported on a side of the wearer’s head by the airflow generating assembly. The speaker housing may form part of the airflow generating assembly and may therefore be provided with an outlet for discharging the filtered airflow for inhalation by the wearer, to which a nozzle may be releasably attached as described above. The wearable air purifier may comprise a left housing to be supported by the headgear at a left side of the wearer’s head, a right housing to be supported by the headgear at a right side of the wearer’s head, optionally a speaker located in one of the left and right housings, and a filter arrangement comprising a left filter module releasably attachable to the left housing by way of a first mechanical coupling by rotating the left filter module with respect to the left housing in a first direction, a right filter module releasably attachable to the right housing by way of a second mechanical coupling by rotating the right filter module with respect to the right housing in a second direction opposite the first direction. When the wearable air purifier comprises the speaker, the headgear thus forms headphones, which may be used for audio playback. The left and right filter module assemblies are reversibly attachable and detachable by the wearer from the headphones. The wearer may attach the left and right filter module assemblies to the headgear when the provision of filtered airflow (for example, by the fan) is desired, and detach the left and right filter module assemblies from the headgear when the airflow is not desired. The headgear may thus be used without the left and right filter module assemblies attached, and thus without the additional mass and bulk of the left and right filter module assemblies. This may be useful as the wearer may desire to wear the headgear, i.e., the headphones, without the left and right filter module assemblies in scenarios where the filtered airflow is not desired, such as in environments with low levels of air pollution. Whereas in environments with high levels of air pollution the wearer may desire to also receive the filtered airflow to reduce their exposure to the air pollution. The headgear and components thereof may thus have dual functionality, which may desirably reduce a perceived need for the wearer to have separate air purifying and non-air purifying headgears, i.e., separate air purifying and non-air purifying headphones. The mechanical couplings are provided on opposite sides of the headgear, i.e., the first mechanical coupling being provided on the left housing and left filter module and the second mechanical coupling being provided of the right housing and the right filter module. By providing mechanical couplings that engage by rotating the left and right filter module assemblies in opposite directions relative to the respective housings, the user may attach both assemblies by performing the same rotating action. Put another way, by providing mechanical couplings that are engaged through opposing rotations, the left and right assemblies are given a handedness in the way they releasable attach to the left and right housings. For example, the left and right filter module assemblies may both be attached by rotating both of them forwards (from the wearer’s perspective) and may both be detached by rotating both of them backwards (from the wearer’s perspective). In another embodiment, attachment may be via backwards rotation and detachment may be via forwards rotation. The first direction may be clockwise and the second direction may be anti-clockwise. In other words, when wearing the headgear, the wearer may releasably attach the assemblies to the housings by rotating the assemblies in a direction that travels from the bottom of the wearer’s face to the top of the wearer's face. The first mechanical coupling may comprise a first bayonet assembly. In other words, the first mechanical coupling may comprise an assembly that inhibits the axial movement of the left filter module relative to the left housing. In this way, the left filter module may be securely held to the left housing. The first bayonet assembly may comprise: a bayonet projection provided on the left filter module; and a cavity provided on the left housing adapted to receive the bayonet projection, the cavity having an opening and a securing end at an end of the cavity opposite the opening, wherein the cavity is adapted to receive the bayonet projection at the opening, and wherein the bayonet projection is moved from the opening to the securing end by the rotation of the left filter module with respect to the left housing in the first direction in order to attach the left filter module to the left housing. In other words, the first bayonet assembly may comprise a cavity adapted to receive the bayonet projection at one end and releasably secure it at another end after the wearer has rotated the left filter module in the first direction. Accordingly, the process of attaching the left filter module to the left housing is greatly simplified for the wearer. For example, to attach the left filter module to the left housing, the wearer may simply bring the left filter module to the left housing such that the bayonet projection of the first bayonet assembly is received in the cavity and rotate the left filter module in the first direction in order to releasably attach the left filter module to the left housing. Accordingly, the wearer is not required to actuate a locking mechanism separately. Similarly, to detach the left filter module from the left housing, the wearer may simply rotate the left filter module in the second direction and pull the left filter module away from the left housing in order to disengage the mechanical coupling and is not required to actuate a locking mechanism separately. The second mechanical coupling may comprise a second bayonet assembly. In other words, the second mechanical coupling may comprise an assembly that inhibits the axial movement of the right filter module relative to the right housing. In this way, the right filter module may be securely held to the right housing. The second bayonet assembly may comprise: a bayonet projection provided on the right filter module; and a cavity provided on the right housing adapted to receive the bayonet projection, the cavity having an opening and a securing end at an end of the cavity opposite the opening, wherein the cavity is adapted to receive the bayonet projection at the opening, and wherein the bayonet projection is moved from the opening to the securing end by the rotation of the right filter module with respect to the right housing in the second direction in order to attach the right filter module to the right housing. Accordingly, the process of attaching the right filter module to the right housing is greatly simplified for the wearer. For example, to attach the right filter module to the right housing, the wearer may simply bring the right filter module to the right housing such that the bayonet projection of the second bayonet assembly is received in the cavity and rotate the right filter module in the second direction in order to releasably attach the right filter module to the right housing. Accordingly, the wearer is not required to actuate a locking mechanism separately. Similarly, to detach the right filter module from the right housing, the wearer may simply rotate the left filter module in the first direction and pull the right filter module away from the right housing in order to disengage the mechanical coupling and is not required to actuate a locking mechanism separately. According to a further aspect, a filter module is provided. The filter module is for housing a filter, the filter for filtering an airflow for inhalation by a wearer, wherein the filter module is releasably attachable to an airflow generating assembly. The airflow generating assembly comprising: headgear for wearing on a wearer’s head; and an airflow generator coupled to the headgear and adapted to generate the airflow for inhalation by the wearer. The filter module may be releasably attachable to an ear cup of the headgear. The filter module may be releasably attachable to the airflow generating assembly by way of a magnet coupling or a mechanical coupling. The mechanical coupling may comprise a rotational locking mechanism, such as a threaded assembly or a bayonet assembly. According to yet a further aspect, a filter arrangement is provided. The filter arrangement comprising: a left filter module releasably attachable to a left housing of a head wearable purifier by way of a first mechanical coupling by rotating the left filter module with respect to the left housing in a first direction, and a right filter module releasably attachable to a right housing of the head wearable purifier by way of a second mechanical coupling by rotating the right filter module with respect to the right housing in a second direction opposite the first direction; wherein the left and right filter modules are for housing a respective filter, the respective filter for filtering an airflow for inhalation by a wearer of the head wearable purifier. Any feature(s) of the filter module or filter arrangement of any aspect may be incorporated by the filter module or filter arrangement of any other aspect. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic perspective view of a wearable air purifier embodying the present disclosure; Figure 2 is a schematic front elevation view of the wearable purifier; Figure 3 is a schematic partially exploded perspective view of the wearable air purifier; Figure 4 is a schematic partially exploded front perspective of the wearable air purifier; Figure 5 is a schematic front cross-sectional view of a portion of the wearable air purifier, Figures 6A to 6F show different views of the filter module attached to and removed from the airflow generating assembly; Figure 7 is a schematic perspective view of the filter module; Figure 8 is a schematic exploded perspective view of a filter module; Figure 9 is a schematic front elevation view of the wearable purifier. DETAILED DESCRIPTION A wearable air purifier 101, embodying aspects of the present disclosure, is shown schematically in Figures 1 and 2. As will be described in further detail herein, the wearable air purifier 101 is configured to be worn on a wearer’s head and deliver a filtered airflow towards a lower nasal and mouth region of a wearer’s face. Consequently, the wearer’s exposure to ambient air pollution may desirably be reduced. The wearable air purifier 101 comprises an airflow generating assembly that includes headgear 102 for mounting on a wearer’s head and a pair of airflow generators, in the form of fan assemblies 103, 104, for generating airflows. Releasably attached to the fan assemblies are filter modules 151 and 152. A nozzle 105 for directing the airflows from the filter modules 151, 152 towards the lower nasal and mouth region of the wearer’s face is shown connected to an outlet the filter modules. The headgear 102 has the form of over-the-ear headphones, and comprises a headband 106 and left and right ear cups 109, 110 connected to respective ends of the headband 106. The headband 106 is arcuate, and is configured to overlie a top and sides of the wearer’s head in use, to thereby support the earcups 109,110 over the wearer’s left and right ears respectively. The headband 106 is formed to resiliently hold the earcups 109, 110 against opposite sides, i.e., left and right sides respectively, of the wearer’s head, to thereby firmly retain the headgear 102 mounted on the wearer’s head. The headband 106 is resiliently flexible to accommodate differing distances between the ear cups, and so differing head widths. The earcups 109, 110 are pivotally mounted to the ends of headband 106, to facilitate pivoting of the ear cups 109, 110 to accommodate different head shapes. The left and right earcups 109, 110 comprise fan assemblies 103, 104 and respective speaker housings for housing components, such as respective speakers. The speakers in the earcups 109, 110 may thus be supported by the headgear 102 over the wearer’s ears, e.g., to facilitate use of the headgear 102 as headphones. The earcups 109, 110 comprise respective annular cushions for cushioning against the wearer’s head. The fan assemblies 103, 104 are releasably attachable to a respective one of the earcups 109, 110, such that the headgear 102 may releasably support the fan assemblies 103, 104 at left and right sides respectively of the wearer’s head. The releasable attachment of the fan assemblies 103, 104 to the ear cups 109, 110 may be realised by way of a magnet coupling or a mechanical coupling. The nozzle 105 is attachable at left and right ends 111, 112 to a respective one of the filter modules 151, 152 of the headgear 102. The nozzle 105 defines air inlets at the left and right ends 111, 112, to mate with respective air outlets of the filter modules 151, 152, to thereby receive filtered airflow from the filter modules 151, 152 when so attached. The nozzle 105 is configured to extend from the left and right ends 111, 112 width-wise across the wearer’s face. The nozzle 105 comprises an air outlet at a central region approximately mid-way between the left and right ends 111, 112, to be positioned approximately directly in front of and facing the wearer’s lower nasal and mouth region, in use. The nozzle 105 thus functions to duct filtered airflows from the filter modules 151, 152, supported at the sides of the wearer’s head, to the central outlet of the nozzle 105, and for discharging the airflows therefrom towards the lower nasal and mouth region of the wearer’s face. In use, when the filter modules 151, 152 are attached to the earcups 109, 110 respectively, the headgear 102 thereby supports the nozzle 105 in front of the wearer’s face. In particular, in result of the nozzle 105 being attached to the headgear 102, via the filter modules 151, 152 4, on opposite, left and right, sides of the wearer’s head, the nozzle 105 is well supported and less prone to unintended movement, e.g., vibration of the nozzle 105 in use. In comparison, coupling of the nozzle 105 to the headgear 102 at only one side of the wearer’s head, for example, at the left end 111 only, may result in a torque being exerted on the single coupling by the mass of the nozzle, and may result in excessive undesired movement of the nozzle in use. Like the headband 102, the nozzle 105 is configured to be flexible in a width dimension, i.e., parallel to the width dimension of the wearer’s head, so as to allow a distance between the point of coupling of the nozzle 105 to the headgear 102 to be varied. This flexibility advantageously allows the nozzle 105 also to accommodate differing distances between the filter modules 151, 152. This may advantageously accommodate differing distances between the ear cups 109, 110, and thus differing widths of wearers’ heads. Additionally, the flexibility of the nozzle 105 may desirably aid attachment and detachment of the filter modules 151, 152 to the ear cups 109, 110 respectively. In examples, the nozzle 105 is configured to not contact the wearer’s face, such that it is supported by the headgear 102 a short distance in front of the wearer’s face. This non-contact configuration may advantageously improve wearer comfort, inasmuch that the potential for skin irritation or other discomfort caused by contact of the nozzle 105 with the wearer’s face is reduced. Referring next in particular to Figure 3, because the filter modules 151, 152 are releasably attachable to a respective one of the earcups 109, 110 of the headgear 102, and in particular to the fan assemblies 103, 104, the filter modules 151, 152, and the nozzle 105 attached thereto, may be releasably attached and detached from the headgear 102 by the wearer. In examples, the filter modules 151, 152 and the nozzle 105 are integral with each other and are configured to be attachable to and detachable from the headgear as an assembly, in which the nozzle 105 remains attached to the filter modules 151, 152 during attachment / detachment of the filter modules 151, 152 to / from the airflow generating assembly. When attached, the filter modules 151, 152 may fluidly couple to the fan assemblies 103, 104 by way of fluid coupling ports 153, 154. In the example shown in Figure 4, the filter modules 151, 152 and the nozzle 105 are not integral with each other and the nozzle 105 is reliably attachable to the filter modules 151, 152 at outlets 155 and 156. The filter modules 151, 152 and the nozzle 105 are therefore configured to be attachable to and detachable from the headgear as individual components, in which the nozzle 105 may remain detached from the filter modules 151, 152 during attachment / detachment of the filter modules 151, 152 to / from the airflow generating assembly. Thus the wearer may attach the filter modules 151, 152 to the headgear 102 when the wearer desires the provision of filtered airflow, such as when the wearer is in an environment with relatively high levels of environmental air pollution, and the wearer may detach the filter modules 151, 152 from the headgear 102 when the filtered airflow is not desired, such as when the wearer is in an environment with relatively low levels of environmental air pollution. The headgear 102 may thus be used in the latter scenario without the filter modules 151, 152 attached, and thus without the additional mass and bulk of the filter modules 151, 152. For example, the headgear may be used by the wearer simply as headphones for audio playback. The headgear 102 and components thereof may thus have dual functionality, which may desirably reduce a perceived need for the wearer to have separate air purifying and non-air purifying headphones. To assist the wearer with the releasable attachment of the filter modules 151, 152 to the fan assemblies 103, 104 respectively, each of the fan assemblies 103, 104 is provided with a male locating feature, in the form of a protruding portion 301, and each of the filter modules 151, 152 is provided with a corresponding female locating feature in the form of recess, or intruding portion 302. The protruding portion 301 of each fan assembly 103, 104 cooperates with the intruding portion 302 of the respective filter modules 151, 152 to function as a locating feature. This may desirably aid correct positioning of the filter modules 151, 152 relative to the airflow generating assembly during attachment of the filter modules 151, 152 by the wearer. Each of the fan assemblies 103, 104 defines a mating surface 304, that is flat and generally annular and extends around the circumference of the protruding portion 301. The fan filter modules 151, 152 each similarly define a flat and generally annular mating surface 303 extending around the circumference of the intruding portion 302. The mating surfaces 303, 304 of the fan assemblies 103, 104 and the filter modules 151, 152 are arranged to contact when the filter modules 151, 152 are attached to the respective fan assemblies 103, 104, to thereby stably support the filter modules 151, 152 relative to the headgear 102. Figure 5 shows a cross sectional view of a filter module 151, comprising a filter 171, detached from an ear cup 109 comprising a fan assembly 103, including a radial fan 173, and a speaker housing 181, including a speaker 183. The filter 171 includes filter media 171a held by a filter frame 171b. The filter media 171a may be pleated particulate filter media. The fan assembly 103 comprises a radial fan 173 that has a rotational axis oriented such that when the ear cup 109 is worn, the rotational axis is substantially normal to the side of a wearer’s head (i.e. it extends laterally in a direction away from / towards the wearer’s ear). The filter module 151 may be retained on the fan assembly 103 by e.g. a bayonet connection, screw connection, or magnetic connection, etc. The speaker housing 181 is operatively (i.e. electrically) connected to the fan assembly 103 as shown by the dotted lines. The fan assembly, and / or the speaker housing may be operatively connected to a power supply 190 (e.g. a rechargeable battery) housed in the headgear for supply of power to the speaker 183 and the radial fan 173. The fan assembly 103 also houses a controller 191 for controlling the supply of power to the radial fan 173. Likewise, the controller 191 controls the supply of power to the speaker 183 (although in other embodiments, separate controllers may be provided for each of the speaker 183and the radial fan 173). In some embodiments, the controller may be provided in the speaker housing 181, or elsewhere in the headgear. In use, the radial fan 173 is operated to draw air into the external inlet 157 of the filter module 151. The air is drawn through the filter 171, which is upstream of the radial fan 173, such that the air received by the fan (by way of a fluid coupling between the filter module 151 and the fan assembly 103 not shown in Figure 5) is filtered. The radial fan 173 then discharges (filtered) air from the wearable air purifier via fluid couplings 153, 154 and the outlet 155. Figures 6A to 6F show various views of the ear cup 109 with the filter module 151 attached to the fan assembly 103 (Figures 6A, 6B and 6E) or the filter module 151 removed from the fan assembly 103 (Figures 6C, 6D and 6F). In the examples shown in Figures 6A to 6F, the filter module 151 is annular and the protruding portion 301 of fan assembly 103 is receivable in the recess defined by the annular shape of the filter module 151. The filter 171 contained within the filter module 151 shown in Figures 6A to 6F may be annular or partially annular, as shown in Figure 7. Figure 7 shows an example of a filter in the shape of a major section of an annulus, or a C-shape. The filter module 151 to receive such a filter 171 may be annular or may also be in the shape of a major section of an annulus, i.e., a C-shape. Figure 7 further illustrates the position of the radial fan 173 with respect to the filter 171 when the filter module 151 is attached to the fan assembly 103 such that the protruding portion 301, which houses the radial fan 173, is received in the recess, or intruding portion, of the filter module 151. Figure 8 shows an exploded view of an annular frustoconical filter 175 provided within a filter module 201 comprising an upper casing 203 and a lower casing 207. The upper casing 203 and the lower casing 207 may be releasably coupled to each other to facilitate replacement of the filter 175. The annular filter 175 comprises filter media 209 and a filter frame 205 providing structural support to the filter media 209. In this example, the filter media 209 is pleated and is for filtering particulates. In some examples, the upper and lower casing 203, 207 may additionally or alternatively (to the filter frame 205) provide structural 5 support to the filter media 209. Any of the filter modules described above may comprise a similar arrangement. Figure 9 shows a wearable air purifier 401 where the outlets 455, 456, which may define releasable attachment points for the nozzle 405, are provided on the airflow generating 10 assembly, and in particular on the fan assemblies 403, 404, rather than the filter modules 451, 452.

Claims

1. A wearable air purifier, comprising:an airflow generating assembly comprising:a headgear for wearing on a wearer’s head; andan airflow generator coupled to the headgear and adapted to generate an airflow for inhalation by the wearer; anda filter module for retaining a filter for filtering the airflow, wherein the filter module is releasably attachable to the airflow generating assembly.

2. The wearable air purifier as claimed in claim 1, the wearable air purifier further comprising a nozzle connected to the airflow generating assembly to receive airflow generated by the airflow generator and discharge the airflow towards the wearer’s face.

3. The wearable air purifier as claimed in claim 1, the wearable air purifier further comprising a nozzle connected to the filter module to receive airflow generated by the airflow generator and discharge the airflow towards the wearer’s face.

4. The wearable air purifier as claimed in claim 3, wherein the nozzle is integrated with the filter module.

5. The wearable air purifier as claimed in claim 3, wherein the nozzle is releasably attachable to the filter module.

6. The wearable air purifier as claimed in any of claims 1 to 5, wherein a shape of the filter module comprises a major sector of an annulus.

7. The wearable air purifier as claimed in claim 6, wherein the shape of the filter module is an annulus.

8. The wearable air purifier as claimed in any of claims 6 to 7, wherein a portion of the airflow generator is receivable in a recess of the filter module.

9. The wearable air purifier as claimed in any of claims 1 to 8, wherein the filter module is releasably attachable to the airflow generating assembly by way of a magnet coupling or a mechanical coupling.

10. The wearable air purifier as claimed in any of claims 1 to 9, wherein the wearable air purifier further comprises a speaker housing supported on a side of the wearer’s head by the headgear, wherein the airflow generator is coupled to the speaker housing.

11. A filter module for housing a filter, the filter for filtering an airflow for inhalation by a wearer, wherein the filter module is releasably attachable to an airflow generating assembly comprising:headgear for wearing on a wearer’s head; andan airflow generator coupled to the headgear and adapted to generate the airflow for inhalation by the wearer.

12. The filter module as claimed in claim 11, wherein the filter module is releasably attachable to an ear cup of the headgear.

13. The filter module as claimed in claim 11 or claim 12, wherein the filter module is releasably attachable to the airflow generating assembly by way of a magnet coupling.

14. The filter module as claimed in claim 11 or claim 12, wherein the filter module is releasably attachable to the airflow generating assembly by way of a mechanical coupling.

15. A filter arrangement comprising:a left filter module releasably attachable to a left housing of a head wearable purifier by way of a first mechanical coupling by rotating the left filter module with respect to the left housing in a first direction, anda right filter module releasably attachable to a right housing of the head wearable purifier by way of a second mechanical coupling by rotating the right filter module with respect to the right housing in a second direction opposite the first direction;wherein the left and right filter modules are for housing a respective filter, the respective filter for filtering an airflow for inhalation by a wearer of the head wearable purifier.

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