GB2625560A

GB2625560A - Head wearable air purifier

Info

Publication number: GB2625560A
Application number: GB2219273.6A
Authority: GB
Inventors: Murray Orchard James; Scott Middleton Thomas; David Eaton George
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2022-12-20
Filing date: 2022-12-20
Publication date: 2024-06-26
Also published as: GB202219273D0; WO2024134377A1

Abstract

A head wearable air purifier 10 comprises an air purifier assembly 14 configured to generate a purified airflow and a nozzle 24 defining a duct configured to receive the purified airflow from the air purifier assembly and discharge the purified airflow via an outlet towards a wearer’s face. The air purifier further comprises a conduit 42 that defines a passage distinct from the duct and a pressure sensor 40 which is arranged for sensing air pressure in the duct via the conduit. The air purifier may comprise a controller that controls a rate of generation of purified airflow in dependence on the sensed air pressure. The conduit or a coupling assembly may redirect an incident airflow by 90 degrees onto the pressure sensor. Also disclosed is a headgear 12 for a head wearable air purifier comprising an air purifier assembly, duct, conduit, and pressure sensor, wherein the pressure sensor senses air pressure in the duct via the conduit.

Description

HEAD WEARABLE AIR PURIFIER

Technical Field

The present invention relates to a head wearable air purifier and a headgear for a head wearable air purifier.

Background

Air pollution is an increasing problem and a variety of air pollutants have known or suspected harmful effects on human health. The adverse effects that can be caused by air pollution depend upon the pollutant type and concentration, and the length of exposure to the polluted air. For example, high air pollution levels can cause immediate health problems such as aggravated cardiovascular and respiratory illness, whereas long-term exposure to polluted air can have permanent health effects such as loss of lung capacity and decreased lung function, and the development of diseases such as asthma, bronchitis, emphysema, and possibly cancer.

In locations with particularly high levels of air pollution, many individuals have recognised the benefits of minimising their exposure to these pollutants and have therefore taken to wearing face masks with the aim of filtering out at least a portion of the pollutants present in the air before it reaches the mouth and nose. There have also been various attempts to develop air purifiers that can be worn by the wearer but that do not require the wearer's mouth and nose to be covered. For example, there are various designs for wearable air purifiers that are worn around the neck of the wearer and that create a jet of air that is directed upwards towards the wearer's mouth and nose.

There is a general desire for wearable air purifiers to provide effective air purification.

Summary

According to a first aspect of the present invention, there is provided a head wearable air purifier comprising: an air purifier assembly configured to generate a purified airflow; a nozzle assembly defining a duct configured to receive the purified airflow from the air purifier assembly and discharge the purified airflow via an outlet towards a wearer's face; a conduit defining a passage distinct from the duct: and a pressure sensor, wherein the pressure sensor is arranged for sensing air pressure in the duct via the conduit.

The pressure sensor senses pressure in the duct via the conduit. This for example allows the pressure sensor to be located remotely of the duct. Disposing the pressure sensor remotely of the duct in this manner for example allows the mass of the nozzle to be reduced and can allow the mass of the pressure sensor to be positioned closer to the centre of gravity of the head. This may improve the stability of the head wearable air purifier on the wearer's head. This can in turn improve performance by reducing unintended movement of the head wearable air purifier during use. Furthermore, the nozzle may be easier to clean than otherwise. For example, the pressure sensor may be disposed remotely from a face mask of the nozzle, which can reduce moisture damage to the pressure sensor compared to disposing the pressure sensor within the face mask, where it may be exposed to a large volume of exhaled air of the wearer, with a high moisture content. Disposing the pressure sensor remotely from the face mask may also allow a less complex face mask to be used, which can simplify construction of the head wearable air purifier.

Because the passage is distinct from the duct, and is separated from the duct by a wall of the conduit, for example, the passage is isolated from turbulence in airflow in the duct, and thus the pressure sensor reading may be less noisy. For example, breathing of the wearer of the head wearable air purifier can cause airflow within the duct to be turbulent. In particular, as the wearer breathes out, a high velocity stream of air can escape the mouth, which is typically incident on a relatively small region of the face mask. This effect is known is jetting, and can lead to large variations in a flow rate of air incident on the face mask, and hence within the duct, depending on the position of the face mask relative to the mouth and nose of the wearer. The air pressure sensed via the conduit, which defines a passage distinct from the duct, may be less sensitive to large signal strength variations such as this. The air pressure sensed by the pressure sensor may thus more accurately reflect the air pressure in the duct, and may be less sensitive to variations in positioning of the head wearable air purifier on the head. In addition, such a pressure sensor may also be more robust to other sources of noise, such as wind.

In particular, the passage may fluidly communicate with a downstream region of the duct to the remote location of the pressure sensor, thereby exposing the pressure sensor to the airflow in the downstream region, where the air pressure may be more representative of the pressure of the airflow to which the wearer is subjected, and less affected by sources of noise. With this approach, the air pressure in the duct may be sensed indirectly, via the conduit, for example by detecting the air pressure of a back pressure wave within the conduit, caused by the breathing of the wearer.

The air pressure sensed in this manner can be used for a number of different purposes. For example, it could be used to control the rate of generation of the purified airflow, e.g. to maintain constant air pressure within the duct, or to detect breathing of the wearer, and so on.

In some examples, the pressure sensor is in a fluidly sealed arrangement with the passage. This for example allows the air pressure from the duct to be efficiently transferred to the pressure sensor, which can improve the pressure sensor response to changes in air pressure in the duct. The pressure sensor can be fluidly sealed with the passage in various different manners. For example, the pressure sensor could be sealed to the conduit (e.g. so that an outlet of the pressure sensor is fluidly sealed to an inlet of the conduit). Alternatively, the pressure sensor may be located within a housing, such as a housing of an air purifier of the air purifier assembly, with the housing sealed to the conduit (e.g so that an outlet of the housing is fluidly sealed to the inlet of the conduit).

In some examples, the head wearable air purifier comprises a controller configured to control a rate of generation of the purified airflow by the air purifier assembly in dependence on the air pressure sensed by the pressure sensor. This for example allows the rate of generation of the purified airflow to be adapted based on the breathing of the wearer (as indicated by the air pressure) For example, as the activity level of the wearer increases, this may cause a corresponding change to the breathing of the wearer and hence to the air pressure sensed by the pressure sensor. In response to this change to the air pressure, a greater quantity of purified air can be provided by the air purifier assembly to compensate for the increased activity of the wearer. Adjusting the purified airflow in this manner for example provides improved protection from air pollution.

The purified airflow may be more comfortable for the wearer, as it can be provided at an appropriate level for the wearer and their current activity level. Moreover, with this approach, the purified airflow can be controlled for example to limit the intensity of the provided airflow to a level that is appropriate for a particular wearer. This can for example increase a lifetime of components of the head wearable air purifier, such as a filter of the air purifier assembly and a power source for providing power to the air purifier assembly, such as a battery.

At least one of the conduit or a coupling assembly coupling the conduit to the pressure sensor may be configured to redirect an incident airflow flowing therethrough onto the pressure sensor. Redirecting the incident airflow in this manner can reduce turbulence of the incident airflow so that the air pressure sensed by the pressure sensor is more robust, and is less sensitive to fluctuations due to turbulence The at least one of the conduit or the coupling assembly may be configured to redirect the incident airflow by approximately 90 degrees. A redirection of the incident airflow by approximately 90 degrees, such as 90 degrees within manufacturing tolerances, can for example cause the airflow incident on the pressure sensor to be relatively static, so as to further reduce turbulence.

The at least one of the conduit or the coupling assembly may comprise at least one bend to redirect the incident airflow. This for example allows the incident airflow to be redirected in a relatively simple manner.

In some examples, a moisture-impermeable and gas-permeable component is disposed over an inlet of the conduit. For example, this component may be or comprise a mesh, which may comprise a hydrophobic material to repel moisture. This can increase the robustness of the head wearable air purifier by reducing moisture damage to the conduit and pressure sensor that may otherwise be caused by flow of moisture, e.g. in the wearer's breath or in an ambient environment, through the conduit and onto the pressure sensor.

In some examples, an outlet of the conduit is coupled to a sensing surface of the pressure sensor with an area which is substantially the same size as an area of the outlet of the conduit. For example, the area of the sensing surface may be within 5% or 10% of the area of the outlet of the conduit. This for example improves sensitivity compared to other approaches in which there is a mismatch in size between the area of the sensing surface and the area of the outlet of the conduit.

In some examples, the head wearable air purifier comprises a headgear supporting the air purifier assembly, wherein a side of the headgear comprises an elongate connecting portion having an end coupled to the nozzle, and the conduit extends along part of a length of the elongate connecting portion and terminates prior to the end of the elongate connecting portion. In this way, the conduit does not pass through a coupling location at which the end of the elongate connecting portion is coupled to the nozzle. This can reduce loss of air through the coupling location, which may otherwise occur. Accuracy of the air pressure sensed by the pressure sensor can thus be improved. This arrangement for example allows the components used for pressure sensing to be located remotely from the nozzle, such as within the headgear. This can simplify the structure of the nozzle, as electronic circuitry and components for pressure sensing need not be included within the nozzle. In such cases, the nozzle can for example be cleaned more straightforwardly, without risking damage to electronic circuitry and components that may otherwise occur during cleaning.

In some of these examples, the nozzle is at least one of: hingedly, detachably or adjustably coupled to the side of the headgear. In such cases, terminating the conduit prior to the end of the elongate connecting portion obviates the need to provide a disconnection or adjustment point within the conduit at the coupling location, which for example allows a less complex conduit to be used, with a lower susceptibility to air loss that may otherwise occur at the coupling location. This can further simplify cleaning of the nozzle, as the nozzle can simply be detached and cleaned, for example in a dishwasher, without damage to components for pressure sensing In some examples, the head wearable air purifier comprises a headgear supporting the air purifier assembly, wherein the nozzle comprises: a side section coupled to a side of the headgear; and a central section coupled to the side section and comprising the outlet, wherein the conduit extends along the side section and at least part of the central section. In these examples, the conduit may thus sample the air pressure from closer to a breathing zone of the wearer, in use, which may improve accuracy. For example, the conduit may be arranged such that an inlet to the passage is located in front of a wearer' s face in use.

In some examples, the conduit is a first conduit extending along a first side of the head wearable air purifier, the passage is a first passage, the head wearable air purifier comprises a second conduit defining a second passage distinct from the duct, the second conduit extending along a second side of the head wearable air purifier, opposite to the first side of the head wearable air purifier, and the pressure sensor is arranged for sensing the air pressure in the duct via the first conduit and the second conduit. With this approach, two pressure waves, on opposite sides of the head wearable air purifier, can be sampled at two different sampling locations due to the two different conduits. Such an arrangement can further improve accuracy. For example, if the head wearable air purifier is being used in windy conditions, the effects of the wind can be compensated for by the use of the two conduits. As an example, if there is a crosswind directed onto an inlet of the first conduit, the air pressure sensed by the pressure sensor based on the pressure wave travelling through the first conduit may be less accurate than otherwise, as it may include a component due to the crosswind. However, the crosswind may have a lesser effect on the second conduit, as the wind may flow in a direction away from, rather than into, the inlet of the second conduit. The air pressure sensed by the pressure sensor from the second conduit may thus be more accurate and may thus be combined with or used instead of the air pressure sensed via the wind-affected first conduit to improve the overall accuracy.

In some examples, a or the headgear of the head wearable air purifier supports an air purifier of the air purifier assembly, and the pressure sensor is disposed within a housing of the air purifier. The housing of the air purifier can protect the pressure sensor from the ambient environment without requiring an additional protective component, which can reduce the weight and bulk added to the head wearable air purifier due to the inclusion of the pressure sensor. Moreover, mounting the pressure sensor on the headgear for example allows a mass of the pressure sensor to be positioned closer to a centre of gravity of the head, with the head wearable air purifier in use, which can improve the stability of the head wearable air purifier on the head.

A controller, or the controller referred to in previous examples, may be disposed within the housing of the air purifier. In this way, electronics for pressure sensing and controlling the rate of generation of the purified airflow based on the air pressure sensed by the pressure sensor can be contained within the same component (the housing of the air purifier). This for example reduces the complexity of the head wearable air purifier by obviating the need for electronic circuitry and components to be disposed in other elements such as in the nozzle. The head wearable air purifier can thus have a simpler structure than if, for example, electronics are included in the nozzle and pass through a coupling location between the nozzle and the headgear, and may be easier to clean.

In some examples, the head wearable air purifier comprises a headgear supporting the air purifier assembly, wherein a side of the headgear comprises an elongate connecting portion coupled to the nozzle, and the pressure sensor is disposed within the elongate connecting portion. Disposing the pressure sensor within the elongate connecting portion for example allows a simpler nozzle to be provided than otherwise, as the nozzle need not include a pressure sensor. Mass of the pressure sensor in this case may be located closer to a centre of gravity of the head, in use, than if the pressure sensor is disposed within the nozzle, which can improve stability of the head wearable air purifier on the head In these examples, a controller, or the controller of previous examples, may be disposed within a housing of an air purifier of the air purifier assembly. Similarly to other examples above, this for example allows electronic components and circuitry, including the controller, to be included within the headgear and omitted from the nozzle, which can reduce the complexity of the nozzle, e.g. by obviating the need to pass wiring through a coupling location between the nozzle and headgear, which may be relatively complex e.g. if the elongate connecting portion is hingedly, detachably and/or adjustably coupled to the nozzle (as it is in some of these examples).

In some examples, the pressure sensor is a first pressure sensor arranged at a or the first side of the head wearable air purifier, the conduit is a first conduit extending along a first side of the head wearable air purifier, the passage is a first passage, and the head wearable air purifier comprises: a second conduit defining a second passage distinct from the duct, the second conduit extending along a or the second side of the head wearable air purifier, opposite to the first side of the head wearable air purifier; and a second pressure sensor, wherein the second pressure sensor is arranged for sensing the air pressure in the duct via the second conduit. This can further improve robustness of the head wearable air purifier, for example in windy conditions, e.g. in a similar manner to that described above for examples in which two conduits are coupled to the same pressure sensor. Including two pressure sensors for example provides for redundancy, so that the air pressure in the duct can be sensed even if one of the pressure sensors fails or is working sub-optimally. In addition, by arranging the first and second pressure sensors on opposite sides of the head, the weight of the first and second pressure sensors is for example more evenly distributed across the head, in use. This can improve the stability and comfort of the head wearable air purifier, when mounted on the head.

According to a second aspect of the present invention, there is provided a headgear for a head wearable air purifier, the headgear comprising: an air purifier assembly configured to generate a purified airflow; a duct to receive the purified airflow from the air purifier assembly for providing to a wearer; a conduit defining a passage distinct from the duct; and a pressure sensor, wherein the pressure sensor is arranged for sensing air pressure in the duct via the conduit. As explained with respect to the first aspect, this for example provides for remote sensing of the air pressure via the conduit, which is for example most robust than direct sensing of the air pressure in the duct. For example, the pressure sensor of the headgear may be able to more accurately sense the air pressure in the duct, via the conduit, and may be less susceptible to moisture damage. In addition, mounting the pressure sensor on the headgear for example allows the weight and bulk associated with the pressure sensor to be placed closer to the centre of gravity of a head wearable air purifier comprising the headgear, improving stability and comfort for the wearer. Plus, a less complex nozzle can be provided for use with the headgear than if the nozzle comprises the pressure sensor instead of the headgear. Such a nozzle can for example be cleaned more straightforwardly than a nozzle comprising a pressure sensor (which may be susceptible to water damage during cleaning).

In some examples, the pressure sensor is in a fluidly sealed arrangement with the passage. This can improve the efficiency with which pressure from the duct is transferred to the pressure sensor, as explained with respect to the first aspect In some examples, the headgear comprises a controller configured to control a rate of generation of the purified airflow by the air purifier assembly in dependence on the air pressure sensed by the pressure sensor. As explained with respect to the first aspect, this for example allows the rate of generation of the purified airflow to be controlled based on breathing of the wearer, which can improve protection from air pollution for the wearer, improve wearer comfort and increase a lifetime of the headgear.

In some examples, the air purifier assembly comprises an air purifier comprising a housing, and the pressure sensor is disposed within the housing. The housing can for example protect the pressure sensor without adding extra weight and bulk to the headgear, using an existing component of the headgear.

In some examples, the conduit is a first conduit extending along a first side of the headgear, the passage is a first passage, the headgear comprises a second conduit defining a second passage distinct from the duct, the second conduit extending along a second side of the headgear, opposite to the first side of the headgear, and the pressure sensor is arranged for sensing the air pressure in the duct via the first conduit arid the second conduit. As explained with respect to the first aspect, this can improve robustness in air pressure sensing in noisy conditions, e.g. in the presence of high winds In some examples, the pressure sensor is a first pressure sensor arranged at a first side of the headgear, the conduit is a first conduit extending along a first side of the headgear, the passage is a first passage, and the headgear comprises: a second conduit defining a second passage distinct from the duct, the second conduit extending along a or the second side of the headgear, opposite to the first side of the headgear; and a second pressure sensor, wherein the second pressure sensor is arranged for sensing the air pressure in the duct via the second conduit. As explained with respect to the first aspect, this can also for example improve the robustness of the head wearable air purifier, e.g. in windy conditions, while providing for redundancy and improved weight distribution of the weight of the first and second pressure sensors across the headgear.

Optional features of aspects of the present invention may be equally applied to other aspects of the present invention, where appropriate.

Brief Description of the Drawings

Figure 1 is a schematic side view of a head wearable air purifier according to examples; Figure 2 is a schematic front view of the head wearable air purifier of Figure 1; Figure 3 is a schematic side view of the first air purifier and side cutaway view of the first end section of the head wearable air purifier of Figure 1, Figure 4 is a schematic front view of the first air purifier of the head wearable air purifier of Figure]; Figure 5 is a schematic view of certain internal components of an air purifier according

to examples;

Figure 6 is a schematic side view of the pressure sensor housing of Figure 5; Figure 7 is a schematic side view of a head wearable air purifier according to examples; Figure 8 is a schematic side view of a head wearable air purifier according to examples; Figure 9 is a schematic left side view of a head wearable air purifier according to examples; Figure 10 is a schematic front view of the head wearable air purifier of Figure 9; Figure 11 is a schematic right side view of the head wearable air purifier of Figure 9; Figure 12 is a schematic left side view of a head wearable air purifier according to examples; Figure 13 is a schematic right side view of the head wearable air purifier of Figure 12; Figure 14 is a plot of air pressure versus time for two different sensor positions; and Figure 15 is a schematic block diagram of internal control components of an air purifier according to examples.

Detailed Description

A head wearable air purifier, generally designated 10, is shown schematically in Figures 1 to 2, mounted on a head 50 of a wearer.

The head wearable air purifier comprises a headgear 12, first and second air purifiers 14, 16, which together form an air purifier assembly for generating a purified airflow, and a nozzle assembly 24. The nozzle assembly 24 is an example of a nozzle.

The headgear 12 comprises a headband 60, which is generally elongate and arcuate in form. The headband 60 is arranged to be placed on the forehead of the wearer, so that the headband 60 wraps around the wearer's head, from one side of the head 50, across the forehead and around the other side of the head 50. Hence, rather than being arranged longitudinally on the head 50, the headband 60 is instead configured to circumferentially surround part of the head 50, in use, by wrapping around part of a circumference of the wearer's head 50 from one side of the head to the other The headgear 12 further comprises a connecting portion 68, which, in Figures 1 and 2, forms a crown of the headgear 12, which overlies the top of the head 50, in use. The connecting portion 68 in this case rests on an upper surface of the head 50, to aid in supporting the head wearable air purifier 10 on the head 50. Various materials may be used for the connecting portion 68. For example, the connecting portion 68 may be formed of fabric, for wearer comfort, and may be or comprise flexible material to conform to heads of different shapes and sizes. The connecting portion 68 is connected around a circumference of the headband 60, along an elongate upper section of the headband 60. In other examples, though, a connecting portion 68 may be connected to a smaller extent of the headband 60, e.g. to form a strip connecting one side of the headband 60 to the other, and may not overlie the entirety of the crown of the head 50 in use, or a connecting portion 68 may be omitted.

The headgear 12 of Figures 1 and 2 includes a peak 70, which is connected to the front of the headband 60 (arranged to be positioned on the wearer's forehead, in use). The peak 70 acts to provide shade to the wearer, for example to partially shield the wearer's eyes from sunlight. In this case, the headgear 12 takes the general form of a peaked cap, but this is merely an example.

A first and second battery compartment 72, 74 are arranged on opposite sides of the headband 60, to be located along opposite sides of the head 50 in use. The first and second battery compartments 72, 74 are each hollow housings for receiving one or more batteries therein. It will be appreciated that batteries may be removable from the first and/or second battery compartments 72, 74, or may be intended to be retained within the first and/or second battery compartments 72, 74 during normal use. Where the batteries are replaceable and intended to be removable from the first and/or second battery compartments 72, 74, the first and/or second battery compartments 72, 74 may, for example, comprise a releasable door or cover to enable access to the interior of the first and/or second battery compartments 72, 74. Where batteries are rechargeable and intended to be retained within the first and/or second battery compartments 72, 74 in normal use, the first and/or second battery compartments 72, 74, or indeed other components of the head wearable air purifier 10, may comprise at least one charge port to enable recharging of batteries.

The first and second air purifiers 14, 16 are coupled to opposite sides of the headband 60 so that the first and second air purifiers 14, 16 are disposed rearwards of the first and second battery compartments 72, 74 when the head wearable air purifier 10 is mounted on the head 50. To enable electrical connection of batteries contained within the first and second battery compartments 72,74 to components internal of the first and second air purifiers 14, 16, the headband 60 may include a cavity, for example to allow electrical wiring or the like to pass therethrough.

The first and second air purifiers 14, 16 are arranged to generate purified air to be provided to the wearer via the nozzle assembly 24. The first and second air purifiers 14, 16 each include respective hollow housings, to house internal components such as a filter assembly to filter incoming air, and an airflow generator.

The airflow generators of the first and second air purifiers 14, 16 are configured to receive power from the batteries housed by the first and second battery compartments 72, 74. In this example, the airflow generator of the first air purifier 14 is configured to be powered by at least one battery within the first battery compartment 72, whilst the airflow generator of the second air purifier 16 is configured to be powered by at least one battery within the second battery compartment 74. In this way, purified air can be generated by the first and second air purifiers 14, 16, to be provided to the nozzle assembly 24.

The nozzle assembly 24 has a first side section 26, a second side section 28 and a central section 30 between the first and second side sections 26, 28. Opposite ends of the central section 30 are coupled to ends of the first and second side sections 26, 28, respectively.

The opposite ends of the first and second side sections 26, 28 to those coupled to the central section 30 include teeth to engage with first and second elongate connecting portions 32, 34 of the headgear 12 at coupling locations 31, 33 respectively. This forms a ratchet mechanism that enables adjustment of the length of the first and second elongate connecting portions 32, 34. To this end, the teeth, a spacing between the teeth and an opposing internal wall of the first and second side sections 26, 28 may be sufficiently resilient to provide the required retention.

The nozzle assembly 24 is curved between the first and second side sections 26, 28 such that the nozzle assembly 24 is generally arcuate in form. The first and second end sections 26, 28 are connected to the first and second air purifiers 14, 16, respectively, to receive a purified airflow therefrom, via the first and second elongate connecting portions 32, 34. The first and second side sections 26, 28 and the central section 30 are generally hollow in form, to receive the purified airflow therethrough. In this example, the first and second elongate connecting portions 32, 34 extend from the first and second air purifiers 14, 16 respectively and curve around each side of the wearer's lower face, in use, to generally follow the shape of the face. The first and second elongate connecting portions 32, 34 are configured to be placed beneath the first and second ears 78, 80 respectively, in use, to reduce interference in the wearer's hearing and discomfort that may otherwise occur if they instead passed over the ears.

The nozzle assembly 24 defines a duct to receive the purified and discharge the purified airflow to the wearer. In this example, the duct of the nozzle assembly 24 is an arcuate duct, formed by the first side section 26, the central section 30 and the second side section 28, via which purified air flows from the first and second air purifiers 14, 26 to the outlet within the face mask 36. In other examples, though, a duct may be located at a single side of the wearer's head, in use, rather than extending from one side to the other side of the head as shown in the example of Figures I and 2.

As explained above, the first and second side sections 26, 28 are coupled to the first and second elongate connecting portions 32, 34 via respective ratchet mechanisms, which each form an adjustable coupling between the nozzle assembly 24 and a respective side of the headgear 12. The ratchet mechanisms in this case are detachable, so that the nozzle assembly 24 can be disconnected from the headgear 12. In other examples, though, a different mechanism may be used to adjustably and/or detachably couple the nozzle assembly to the headgear. In further examples, the nozzle assembly may also or instead be hingedly connected to the headgear, for example using a mechanism at one or both of the coupling locations 31, 33 to connect respective ends of the first and second side sections 26, 28 to corresponding ends of the first and second elongate connecting portions 32, 34.

When the nozzle assembly 24 is connected to the first and second air purifiers 14, 16, and the head wearable air purifier 10 is worn by a wearer, the nozzle assembly 24 is configured to extend in front of the face of the wearer, and particularly the mouth and lower nasal region of the wearer, without contacting the face of the wearer. The midsection 30 of the nozzle assembly 24 includes a face mask 36 to be placed over the wearer's mouth and nose, in use. In other examples, though, a face mask may cover a different extent of a wearer's face, such as just the mouth or just the nose, and/or the face mask may be configured to contact the face of the wearer, in use. The head wearable air purifier 10 can be removed and mounted on the head 50 for example by opening up the back of the headgear 12 so that the head 50 can be moved away from or towards the face mask 36 and out of or into the head wearable air purifier 10, respectively. Alternatively, the nozzle assembly 24 can be disconnected from the headgear 12 at the coupling locations 31, 33 so that the wearer can for example lift the head wearable air purifier 10 down onto their head, or up and away from their head.

The face mask 36 includes an air outlet to emit the purified airflow. The air outlet may be in the form of a mesh, which is defined by an array of holes between adjacent fibres or sections of the material of the mesh for the purified airflow to pass through The face mask 36 defines a breathing zone 38. The breathing zone 38 defined by the face mask 36 is for example a three-dimensional region of space bound by, and at a rear-facing side of, the face mask 36 (which is for example a side of the face mask 36 to face towards the wearer, in use). The arrow labelled 38 to indicate the breathing zone in Figures 1 and 2 thus indicates the region behind the face mask 36, between the face mask 36 and the face. In use, the breathing zone 38 is adjacent a mouth and nasal region of the wearer in this example. Upper and lower surfaces of the central section 30 may comprise flow guides that extend rearwardly, to reduce the entrance of unfiltered air into the breathing zone, in use, particularly in conditions where the head wearable air purifier 10 is worn outside in a cross wind.

The head wearable air purifier 10 comprises a pressure sensor 40, which is disposed remotely from the face mask 36. In this case, the pressure sensor 40 is arranged within a housing of the first air purifier 14. As the pressure sensor 40 is within the housing of the first air purifier 14, it is shown in dotted lines in Figure 1. The headgear 12 thus comprises the pressure sensor 40 in this example. The pressure sensor 40 is configured to sense air pressure in the duct via a conduit 42, which defines a passage distinct from the duct. The air pressure sensed by the pressure sensor 40 can be used for various purposes, such as by a controller of the head wearable air purifier 10 to control the rate of generation of the purified airflow generated by the air purifier assembly.

In the example of Figures 1 and 2, the conduit 42 guides a back pressure wave which depends on the air pressure within the duct towards the pressure sensor 40, for sensing. For example, as the wearer breathes out, this will push air into the conduit 42, increasing the air pressure within the conduit 42. The air pushed into the conduit 42, which may be referred to as an incident airflow, flows through the conduit 42 and onto the pressure sensor 40 and causes an increase in the air pressure detected by the pressure sensor 40. The conduit 42 in this example has the form of an elongate, hollow tube, such as a silicon tube, which extends along the first elongate connecting portion 32 of the headgear 12 so as to extend from the first air purifier 14 towards the breathing zone 38, along the side of the face, in use. The first elongate connecting portion 32 forms a channel between the first air purifier 14 and the nozzle assembly 24. This channel comprises the conduit 42, so the conduit 42 is also shown with dotted lines as it is an internal component of the head wearable air purifier 10 in this example. However, in other cases, the conduit 42 may be disposed in a separate component so that it is not housed by the first elongate connecting portion 32. For example, the conduit 42 may be provided as a separate component that is arranged along an upper surface of the first elongate connecting portion 32. In this example, the channel forms an extension of the duct defined by the nozzle, so that the duct itself may be considered to extend from the outlet in the face mask 36, along the first side of the head wearable air purifier 10 and to the first air purifier 14. In other words, the channel may itself be considered to form a duct (or a portion of a duct) for providing the purified airflow to the wearer.

The conduit 42 in this case connects to the pressure sensor 40 within the housing of the first air purifier 14 (as shown in more detail in Figure 5, discussed further below). The conduit 42 then extends out of the housing of the first air purifier 14, through an aperture in the housing of the first air purifier 14, and along part of the length of the first elongate connecting portion 32. In this case, the conduit 42 terminates prior to the end of the first elongate connecting portion 32, before the coupling location 31 at which the first elongate connecting portion 32 is coupled to the nozzle assembly 24. In other words, an inlet 44 of the conduit 42, which is a closest end of the conduit 42 to the breathing zone 38, is positioned within the elongate connecting portion 32, rather than extending through the coupling location 31 and into the nozzle assembly 24.

A hydrophobic mesh is disposed over, and in this example covers, the inlet 44 of the conduit 42. The hydrophobic mesh is an example of a moisture-impermeable and gas-permeable, and acts to repel moisture incident on the conduit 42, such as moisture in the wearer's breath or in the atmosphere which is travelled through the nozzle assembly 24 and into the first elongate connecting portion 32. Entry of moisture into the conduit 42 is thus reduced. However, as the hydrophobic mesh includes holes between adjacent hydrophobic fibres, the airflow into the conduit 42 can continue without substantial interruption, for example so that the signal sensed by the pressure sensor 40 is substantially unaffected by the presence of the mesh (e.g. unaffected within measurement uncertainties).

The first air purifier 14 is shown in more detail in Figures 3 and 4. It is to be appreciated that the second air purifier 16 of Figures 1 and 2 includes the same components as the first air purifier 14, although in other examples the first and second air purifiers may have a different structure than each other.

As can be seen in Figure 3, a housing 81 of the first air purifier 14 includes an ambient air inlet 82 through which ambient air 84 may be drawn into the interior of the housing 81. The ambient air inlet 82 is an elongate slot in a lower section of the housing 81 of the first air purifier 14. The housing 81 of the first air purifier 14 has a generally circular cross-section, with a generally circular inner face 83 to be arranged on the head of the wearer and an opposing outer face 85 to face the ambient environment, in use. The inner face 83 is concave to conform to the head 50 of the wearer. In other words, the inner face 83 curves inwardly, in a generally dished shape, so as to approximately match the outward, convex curvature of the head 50. The elongate aperture is elongate along a side wall section 87 of the housing 81 joining the inner and outer faces 83, 85 of the housing In other cases, though, the ambient air inlet 82 may include a plurality of apertures and/or at least one aperture of a different shape or location than that shown in Figures 3 and 4 The first air purifier 14 includes a filter assembly (not shown) disposed within the housing 81 between the ambient air inlet 82 and an airflow generator (not shown). The filter assembly includes a filter material chosen to provide a desired degree of filtration of air to be provided to a wearer in use. In this example, the airflow generator comprises a motor driven impeller to draw air from the ambient air inlet 82, through the filter assembly, and output air through an outlet aperture 89 of the first air purifier 14, which is an outlet of the housing 81 of the first air purifier 14 to be connected to an air inlet 91 of the nozzle assembly 24 to provide a purified airflow to the nozzle assembly 24.

The outlet aperture 89 of the first air purifier 14 is shown in Figure 4. In this example, the outlet aperture 89 is an elongate aperture in the side wall portion 87 of the housing 81 for connection to the nozzle assembly 24. The outlet aperture 89 in this example is wider and shorter than the ambient air inlet 82, and is located at an angle with respect to the ambient air inlet 82. The location of the outlet aperture 89 with respect to the ambient air inlet 82 is selected so that the nozzle assembly 24 can be connected to the outlet aperture 89 without impeding a flow of ambient air into the ambient air inlet 82.

The outlet aperture 89 is connected to the air inlet 91 of the nozzle assembly 24 (shown in Figure 3) to receive a purified airflow 93 from the first air purifier 14.

In this example, as explained with reference to Figures 1 and 2, the first air purifier 14 is connected to a first elongate connecting portion 32 of the headgear. As can be seen in Figure 3, the first elongate connecting portion 32 includes a partition wall 46, which divides the first elongate connecting portion 32 into a first channel 48 and a second channel 52. The first and second channels 48, 52, which are separated from each other by the partition wall 46 in this case. The purified airflow 93 flows from the first air purifier 14 through the first channel 48 and into the nozzle assembly 24, to be provided to the air outlet of the face mask 36. The first channel 48 may therefore be considered to be, or form part of, a duct for providing the purified airflow 93 to the wearer. The second channel 52 includes the conduit 42, which is connected to the pressure sensor (not shown in Figure 3). As can be seen, the conduit 42 is distinct from the first channel 48 within which the purified airflow 93 flows, and thus defines a distinct passage for air to flow therethrough than that within which the purified airflow 93 is provided to the wearer. In other examples, though, the first elongate connecting portion need not include a partition wall but may nevertheless include the conduit 42, located within a channel for providing the purified airflow 93 to the nozzle assembly 24. In such cases, the passage defined by the conduit 42 is nevertheless distinct from the channel for providing the purified airflow 93 (which may be or form part of a duct) in that the conduit 42 is not in fluid communication with the channel.

Figure 5 is a schematic view of certain internal components of an air purifier 114, which may be similar to or the same as the first and second air purifiers 14, 16 of Figures 1 to 4. It is to be appreciated that the air purifier 114 may include other internal components than those shown in Figure 5. The air purifier 114 includes a housing 181, within which is disposed a mounting component 154 fin the form of a cylindrical component in this example) for use in mounting the air purifier 114 to a headgear of a head wearable air purifier, such as the headgear 12 of Figures 1 and 2. Within the housing 181, there is controller circuitry to implement a controller for controlling the rate of generation of the purified airflow generated by the air purifier 114 based on the air pressure sensed generated by a pressure sensor, also disposed within the housing 181 of the air purifier 114 and electrically connected to the controller circuitry. In this example, the controller circuitry is in the form of a printed circuit board (PCB) 158 within the housing 181 of the air purifier 114.

A button 162 is connected to the controller circuitry and protrudes through a slot in the side wall of the housing 181 so it is pressable by a wearer of the head wearable air purifier. The wearer can press or release the button 162 to cause the air purifier 114 to begin or cease purifying incoming air entering into the housing 181 (e.g. via an ambient air inlet 82 as shown in Figures 3 and 4). In other examples, a button similar to the button 162 of Figure 5 may also be used to adjust the rate of air purification provided by the air purifier 114, or a head wearable air purifier may include a further component, such as a slider component, for adjusting the rate of air purification.

The pressure sensor housing 141, which includes the pressure sensor, is shown in Figure 5. In this example, the pressure sensor housing 141 is mechanically coupled to a conduit 142 for receiving an incident airflow from closer to a wearer's face, in use. As explained above, the incident airflow depends on airflow within the duct, so that the air pressure sensed by the pressure sensor in dependence on the incident airflow is also reflective of the air pressure within the duct. The conduit 142 is disposed within a channel 152, which may be similar to the channel 52 of Figures 1 and 2. The channel 152 may thus be disposed within an elongate connecting portion of the headgear, for connection to a nozzle assembly (not shown in Figure 5).

In this case, the conduit 142, which is in the shape of a hollow tube, has an outlet 164 which has a slightly wider diameter than a diameter of an inlet 166 of the pressure sensor housing 141 for connection to the conduit 142. The outlet 164 of the conduit 142 is opposite to an inlet of the conduit 142 (not shown in Figure 5 but discussed above with reference to Figures 1 and 2) which is the closest end of the conduit 142 to the breathing zone. The inlet 166 of the pressure sensor housing 141 snugly fits within the outlet 164 of the conduit 142 so as to securely connect the pressure sensor to the conduit 142.

The connection between the pressure sensor housing 141 and the conduit 142 is shown in more detail in Figure 6, which shows a schematic side view of the pressure sensor housing 141 of Figure 5, showing internal components of the pressure sensor housing 141. An incident airflow flows through the conduit 142 and into the pressure sensing housing 141 via a join between the outlet 164 of the conduit 142 and inlet 166 of the pressure sensor housing 141, and onto the pressure sensor 140, which is within the pressure sensor housing 141. As the pressure sensing housing 141 is fluidly sealed to the conduit 142, the pressure sensor 140 is thus in a fluidly sealed arrangement with the passage defined by the conduit 142. The portion of the pressure sensor housing 141 surrounding the pressure sensor 140 and connected to the conduit 142, as well as the outlet 164 of the conduit 142 which is received within the inlet 166 of the pressure sensor housing 141, may be considered to form a coupling assembly coupling the conduit 142 to the pressure sensor 140 In Figure 6, the coupling assembly redirects the incident airflow received from the conduit 142 onto the pressure sensor 140, as the pressure sensor housing 141 includes a bend 176, which causes the direction of the incident airflow to change. In this case, rather than continuing to flow straight onto the pressure sensor 140 in the direction of a length of the conduit 142, the bend 176 causes the incident airflow to change direction by 90 degrees before it is then incident on the pressure sensor 140. As explained above, this for example provides a less turbulent airflow to the pressure sensor 140, which for example allows air pressure to be sensed more robustly by the pressure sensor 140. In other examples, the conduit 142 may instead or also redirect the incident airflow, e.g. by including at least one bend or at least one additional bend.

The pressure sensor 140 has a sensing surface 178, which is for example a surface of the pressure sensor 140 which is sensitive to the air pressure of an incident airflow and over which the air pressure of the incident airflow is sampled. For example, the sensing surface 178 may include an array of sensing elements for sensing the air pressure of the incident airflow. An area of the sensing surface 178 is substantially the same as an area of the outlet 164 of the conduit 142. This for example improves accuracy compared to other implementations in which the sensing surface has a notably larger area than the area of the outlet 164 of the conduit 142 because distribution of the incident airflow over a larger sensing surface for example reduces accuracy. In Figure 6, the thickness of the walls of the pressure sensor housing 141 are exaggerated for ease of illustration.

However, in practice, the walls of the pressure sensor housing 141 may be relatively thin so that the change in diameter between the outlet 164 of the conduit 142 and an interior diameter of the inlet 166 of the pressure sensing housing 141 is relatively insignificant, such as less than 10%, 5% or 1%. Furthermore, the interior volume of the pressure sensor housing 141 is also exaggerated for ease of illustration in Figure 6 and may, in practice, be smaller relative to a diameter of the outlet 164 of the conduit 142 than that shown in Figure 6.

A seal 186 surrounds the pressure sensor 140 and seals the pressure sensor housing 141 closed so as to limit the escape of air from the pressure sensor housing 141. Screws 188a, 188b on opposite sides of the pressure sensor 140 pass through holes in the pressure sensor housing 141 to couple the pressure sensor housing 141 to the PCB 158 of the control circuitry. It is to be appreciated that the pressure sensor 140 is connected to at least one other electronic component of the control circuitry via electrical connection(s), not shown in Figure 6. The screws 188a, 188b also pass through the PCB 158 and into corresponding receptacles 190a, 190b of the housing 181 of the air purifier 114, which protrude upwards from a lower surface of the housing 181 and are arranged to receive the screws 188a, 188b therein. With the screws 188a, 1886 screwed into place within the receptacles 190a, 190b, the PCB 158 and the pressure sensor housing 141 are affixed to an interior of the housing 181 of the air purifier 114.

Figure 7 is a schematic side view of a head wearable air purifier 210 according to further examples. The head wearable air purifier 210 of Figure 7 is the same as the head wearable air purifier 10 of Figures 1 and 2 except for the conduit 242. Features of Figure 7 that are the same as corresponding features of Figures 1 and 2 are labelled with the same reference numerals but incremented by 200; corresponding descriptions are to be taken to apply.

In Figure 7, rather than the conduit 242 terminating within the first elongate connecting portion 232, the conduit 242 instead extends along the first elongate connecting portion 232, through the coupling location 231, along the first side section 226 of the nozzle assembly 224 and into and along part of the central section 230 of the nozzle assembly 224. In this example, the conduit 242 terminates within the face mask 236 of the central section 230. In other words, an inlet to the passage defined by the conduit 242 is located in front of the face of the wearer, in use, in this example. However, in other examples, a similar conduit may instead terminate within the first side section or with a part of the central section prior to the face mask 236. As the inlet 244 of the conduit 242 is disposed within the face mask 236, the conduit 232 thus terminates within the breathing zone 238 defined by the face mask 236. In this way, the conduit 232 can sample an airflow within the breathing zone 238, so as to provide this airflow to the pressure sensor 240 connected to the conduit 232. The pressure sensor 240 in this case is the same as the pressure sensor 40 of Figures 1 and 2, and is disposed within the first air purifier 214 Figure 8 is a schematic side view of a head wearable air purifier 310 according to further examples. The head wearable air purifier 310 of Figure 8 is the same as the head wearable air purifier 10 of Figures 1 and 2 except for the location of the pressure sensor 340. Features of Figure 8 that are the same as corresponding features of Figures 1 and 2 are labelled with the same reference numerals but incremented by 300; corresponding

descriptions are to be taken to apply.

In Figure 8, the pressure sensor 340 is disposed within the first elongate connecting portion 332 of the headgear 332 rather than within the first air purifier 314. A conduit 332 is extends within and along the first elongate connecting portion 332 and is fluidly sealed to the pressure sensor 340. An inlet 344 of the conduit 342 is within the first elongate connecting portion 332, such that the conduit 342 terminates prior to the coupling location 331 at which the headgear 312 is coupled to the nozzle assembly 324.

In this example, the controller is disposed within the housing of the air purifier 314, like the controller in the example of Figures 1 and 2 and like the control circuitry of Figures and 6. An electrical connector 392, such as wiring, is disposed within the first elongate connecting portion 332 (e.g. within the second channel, if present) to electrically connect the pressure sensor 340 to the controller, so as to provide a signal generated by the pressure sensor 340 to the controller. The signal is representative of the air pressure sensed by the pressure sensor 340, via the conduit 342, which is indicative of the air pressure within the duct defined by the nozzle assembly 342. In this case, the duct defined by the nozzle assembly 342 is formed by the first side section 326, the central section 330 and the second side section (not shown in Figure 8), similarly to the duct of Figures] and 2.

As the pressure sensor 340 and the electrical connector 392 do not pass through the coupling location 331, the first elongate connecting portion 332 may be hingedly, detachably and/or adjustably coupled to the nozzle assembly 324 without interfering with the pressure sensing apparatus. In this case, the first elongate connecting portion 332 is adjustably coupled to the nozzle assembly 324 via the ratchet mechanism described with reference to Figures 1 and 2.

Figures 9, 10 and 11 are schematic left side, front and right side views of a head wearable air purifier 410 according to further examples. The head wearable air purifier 410 of Figures 9, 10 and 11 is the same as the head wearable air purifier 10 of Figures 1 and 2 except that the pressure sensor disposed within the first air purifier 414 of Figures 9, 10 and 11 is a first pressure sensor 440a, and the head wearable air purifier 410 also includes a second pressure sensor 440b. Features of Figures 9, 10 and 11 that are the same as corresponding features of Figures 1 and 2 are labelled with the same reference numerals but incremented by 400; corresponding descriptions are to be taken to apply.

The first pressure sensor 440a and the second pressure sensor 440b are the same as each other, but disposed in the first and second air purifiers 414, 416 at opposite sides of the headgear 412. They are connected to the first and second conduits 440a, 440b within the first and second elongate connecting portions 432, 434 of the headgear 412, respectively. The first and second conduits 440a, 440b are otherwise the same as the conduit 40 of Figures 1 and 2, and include inlets 444a, 444b that are located within the first and second elongate connecting portions 432, 434, respectively.

In this example, the second pressure sensor 440b is electrically connected to the controller disposed within the housing of the first air purifier 414 via wiring that passes from the second pressure sensor 440b within the housing of the second air purifier 416, out of the second air purifier 416, through the headband 460, into the housing of the first air purifier 416 and into contact with the controller. The controller can hence use an air pressure sensed by the first pressure sensor 440a and/or the air pressure sensed by the second pressure sensor 440b to control the rate at which the purified airflow is generated by the first and second air purifiers 414, 416. In other examples, though, each of the pressure sensors 440a, 440b may be connected to a separate controller, which may interact, via a suitable electrical connection, to control the rate at which the purified airflow is generated by the first and second air purifiers 414, 416, or which may independently control the rate at which the purified airflow is generated by the first and second air purifiers 414, 416 respectively. For example, the first pressure sensor 440a may be connected to a first controller within the housing of the first air purifier 414, whereas the second pressure sensor 440b may be connected to a second controller within the housing of the second air purifier.

Figures 12 and 13 are schematic left side and right side views of a head wearable air purifier 510 according to further examples. The head wearable air purifier 510 of Figures 12 and 13 is the same as the head wearable air purifier 10 of Figures 1 and 2 except that there is a first conduit 542a and a second conduit 542b connected to the pressure sensor 540. Features of Figures 12 and 13 that are the same as corresponding features of Figures 1 and 2 are labelled with the same reference numerals but incremented by 500; corresponding descriptions are to be taken to apply.

The first conduit 542a is the same as the conduit 42 of Figures 1 and 2, and extends along a first side of the head wearable air purifier 510 to provide a first incident airflow to a pressure sensor 540 disposed within a housing of a first air purifier 514. The first incident airflow is caused by air within the breathing zone 538 forcing air between the breathing zone 538 and a first inlet 544a of the first conduit 542a, which is the closest end of the first conduit 542a to the breathing zone 538, into and through the first conduit 542 and onto the pressure sensor 540. The first conduit 542a of Figures 12 and 13 extends along, and is within, a first elongate connecting portion 532 of a headgear 512 of the head wearable air purifier 510. The first inlet 544a of the first conduit 542a is within the first elongate connecting portion 532.

The second conduit 542b is elongate, like the first conduit 542, and in this example is a tube that extends towards the breathing zone 538 along a second side of the head wearable air purifier 510, opposite to the first side. In Figures 12 and 13, the second conduit 542b is connected to the pressure sensor 540 within the first air purifier 514 in a similar manner to the first conduit 542a. The second conduit 542b extends from the pressure sensor 540, along a lower edge of the housing of the first air purifier 514 and into the headband 560. The second conduit 542b is disposed along, and within, the headband 560, from the first air purifier 514 to the second air purifier 516 on the opposite side of the head wearable air purifier 510. In this case, the second conduit 542b is located beneath the first and second battery compartments 572, 574, inside the headband 560, and is thus indicated with dotted lines in Figures 12 and 13 as it is an internal component. As shown in Figure 13, upon reaching the second air purifier 516, the second conduit 542b enters the housing of the second air purifier 516, extends along a lower edge of the housing of the second air purifier 516 and bends into the second elongate connecting portion 534 at the second side of the head wearable air purifier 510. The second conduit 5426 then extends within and along the second elongate connecting portion 534, towards the breathing zone 538. A first inlet 544b of the second conduit 542b, which is the closest end of the second conduit 542b to the breathing zone 538, is located within the second elongate connecting portion 534. The second conduit 542b provides a second incident airflow to the pressure sensor 540, caused by air within the breathing zone 538 forcing air between the breathing zone 538 and the first inlet 544b of the second conduit 542b into and through the second conduit 542b and onto the pressure sensor 540. In this way, the pressure sensor 540 can sense the air pressure in the duct defined by the nozzle assembly 524, via the first and second conduits 542a, 542b. In this case, the duct defined by the nozzle assembly 542 is formed by the first side section 526, the central section 530 and the second side section 528, similarly to the duct of Figures 1 and 2.

Various different arrangements of pressure sensor(s) and conduit(s) have been described in examples herein. A difference in air pressure detected by the pressure sensor(s) in each of these arrangements may be negligible, such that any of these arrangements may be used to produce a sufficiently accurate signal related to the air pressure within the breathing zone, with substantially the same accuracy as via a pressure sensor within a face mask in still, indoor conditions, but with greater robustness in turbulent conditions and an increased lifetime, for example. This is indicated in Figure 14, which is a plot 600 of air pressure fin hectopascals (hPa)) versus time (in milliseconds (ms)) for two different pressure sensor positions. A first trace 602 indicates the air pressure versus time for a comparative head wearable air purifier with a pressure sensor within a face mask, and a second trace 604 indicates the air pressure versus time for a head wearable air purifier 210 in accordance with the example of Figure 7, with each of the head wearable air purifiers mounted on the head of a test mannequin configured to inhale and exhale regularly, to mimic breathing of a wearer.

The first and second traces 602, 604 each show a time-varying air pressure with a wave-shape form over time, with peaks in the air pressure corresponding to exhalations of the wearer and troughs in the air pressure corresponding to inhalations of the wearer. As can be seen, the first and second traces 602, 604 are substantially the same, indicating that the pressure sensor in a duct (which e.g. corresponds to the air pressure within the face mask) can be sensed via a conduit without unduly affecting the accuracy of the air pressure measurement obtained by the pressure sensor. Further experiments have also shown that the air pressure detected by the pressure sensor is not substantially affected by the length of a conduit connected to the pressure sensor, by the breathing intensity of the wearer, or by the flow rate of the purified airflow provided by the head wearable air purifier.

Figure 15 is a schematic block diagram of an air purifier 614 including a pressure sensor 640, which may be similar to or the same as air purifiers that include a pressure sensor as described in other examples herein. The pressure sensor 640 detects air pressure in a duct for providing purified airflow to a wearer of a head wearable air purifier comprising the air purifier 614 via a conduit, such as the conduits of other examples herein. A control unit 695 of the air purifier 614 includes a controller 696 and a motor control unit 697. The controller 696 is electrically connected to the pressure sensor 640 and receives a signal from the pressure sensor 640 indicative of an air pressure sensed by the pressure sensor 640 within the conduit, which is, in turn, related to the air pressure in the duct. The controller 695 generates a control signal, based on the signal received from the pressure sensor 640, to control driving of the motor control unit 697. The motor control unit 697 controls an electric motor 698 of the air purifier 640. More specifically, the motor control unit 697 generates a drive signal for controlling the speed of the electric motor 698 based on the control signal received from the controller 695. An impeller 699 of the air purifier 614 is driven by the electric motor 698 and, when driven, causes air to be drawn into the air purifier 614 via an ambient air inlet of the air purifier 614 (as discussed further with respect to Figures 3 and 4), and through a filter assembly of the air purifier 614 to purify the air. As the drive signal generated by the motor control unit 697 depends on the control signal generated by the controller 696, which in turn depends on the signal generated by the pressure sensor 640, the speed of driving the motor 698, and hence the flow rate of air through the air purifier 614, can be controlled based on the signal generated by the pressure sensor 640, and thus in dependence on the air pressure within the duct, as sensed via the conduit.

Similar internal components to those shown in Figure 15 may be used for control of a head wearable air purifier with a plurality of pressure sensors. For example, the controller 696 may receive signals from a plurality of pressure sensors. In other cases, though, each pressure sensor may be connected to a separate control unit. For example, there may be a plurality of air purifiers, each including a separate pressure sensor and each including the components shown in Figure 15. Furthermore, in examples in which the pressure sensor is comprised by a different component than an air purifier (such as the example of Figure 8), similar components as those shown in Figure 15 may be used for control of the air purifier. However, in this case, the pressure sensor is comprised by the different component rather than the air purifier.

While examples have thus far been described, it should be understood that these are illustrative only and that various modifications may be made without departing from the scope of the accompanying claims.

Claims

CLAIMSI. A head wearable air purifier comprising: an air purifier assembly configured to generate a purified airflow; a nozzle defining a duct configured to receive the purified airflow from the air purifier assembly and discharge the purified airflow via an outlet towards a wearer' s face; a conduit defining a passage distinct from the duct; and a pressure sensor, wherein the pressure sensor is arranged for sensing air pressure in the duct via the conduit.
2. The head wearable air purifier of claim 1, wherein the pressure sensor is in a fluidly sealed arrangement with the passage.
3. The head wearable air purifier of claim 1 or claim 2, comprising a controller configured to control a rate of generation of the purified airflow by the air purifier assembly in dependence on the air pressure sensed by the pressure sensor.
4. The head wearable air purifier of any one of claims t to 3, wherein at least one of the conduit or a coupling assembly coupling the conduit to the pressure sensor is configured to redirect an incident airflow flowing therethrough onto the pressure sensor.
5. The head wearable air purifier of claim 4, wherein the at least one of the conduit or the coupling assembly is configured to redirect the incident airflow by approximately degrees.
6. The head wearable air purifier of claim 4 or claim 5, wherein the at least one of the conduit or the coupling assembly comprises at least one bend to redirect the incident airflow.
7. The head wearable air purifier of any one of claims 1 to 6, wherein a moisture-impermeable and gas-permeable component is disposed over an inlet of the conduit.
8. The head wearable air purifier of any one of claims 1 to 7, wherein an outlet of the conduit is coupled to a sensing surface of the pressure sensor with an area which is substantially the same size as an area of the outlet of the conduit.
9. The head wearable air purifier of any one of claims 1 to 8, comprising a headgear supporting the air purifier assembly, wherein a side of the headgear comprises an elongate connecting portion having an end coupled to the nozzle, and the conduit extends along part of a length of the elongate connecting portion and terminates prior to the end of the elongate connecting portion.
10. The head wearable air purifier of any one of claims 1 to 9, comprising a headgear supporting the air purifier assembly, wherein the nozzle comprises: a side section coupled to a side of the headgear; and a central section coupled to the side section and comprising the outlet, wherein the conduit extends along the side section and at least part of the central section.
11. The head wearable air purifier of claim 10, wherein the conduit is arranged such that an inlet to the passage is located in front of a wearer's face in use.
12. The head wearable air purifier of claim 10 or claim 11, wherein the nozzle is at least one of hingedly, detachably or adjustably coupled to the side of the headgear. 25
13. The head wearable air purifier of any one of claims 1 to 12, wherein the conduit is a first conduit extending along a first side of the head wearable air purifier, the passage is a first passage, the head wearable air purifier comprises a second conduit defining a second passage distinct from the duct, the second conduit extending along a second side of the head wearable air purifier, opposite to the first side of the head wearable air purifier, and the pressure sensor is arranged for sensing the air pressure in the duct via the first conduit and the second conduit.
14. The head wearable air purifier of any one of claims 1 to 13, wherein a or the headgear of the head wearable air purifier supports an air purifier of the air purifier assembly, and the pressure sensor is disposed within a housing of the air purifier.
15. The head wearable air purifier of claim 14, wherein a or the controller of the head wearable air purifier is disposed within the housing of the air purifier.
16. The head wearable air purifier of any one of claims 1 to 8, comprising a headgear supporting the air purifier assembly, wherein a side of the headgear comprises an elongate connecting portion coupled to the nozzle, and the pressure sensor is disposed within the elongate connecting portion.
17 The head wearable air purifier of claim 16, wherein a or the controller disposed within a housing of an air purifier of the air purifier assembly.
18. The head wearable air purifier of claim 16 or claim 17, wherein the elongate connecting portion is at least one of: hingedly, detachably or adjustably coupled to the nozzle.
19. The head wearable air purifier of any one of claims 1 to 18, wherein the pressure sensor is a first pressure sensor, the conduit is a first conduit extending along a first side of the head wearable air purifier, the passage is a first passage, and the head wearable air purifier comprises: a second conduit defining a second passage distinct from the duct, the second conduit extending along a or the second side of the head wearable air purifier, opposite to the first side of the head wearable air purifier; and a second pressure sensor, wherein the second pressure sensor is arranged for sensing the air pressure in the duct via the second conduit.
20. A headgear for a head wearable air purifier, the headgear comprising: an air purifier assembly configured to generate a purified airflow; a duct to receive the purified airflow from the air purifier assembly for providing to a wearer; a conduit defining a passage distinct from the duct; and a pressure sensor, wherein the pressure sensor is arranged for sensing air pressure in the duct via the conduit.
21. The headgear of claim 20, wherein the pressure sensor is in a fluidly sealed arrangement with the passage.
22. The headgear of claim 20 or claim 21, comprising a controller configured to control a rate of generation of the purified airflow by the air purifier assembly in dependence on the air pressure sensed by the pressure sensor.
23. The headgear of any one of claims 20 to 22, wherein the air purifier assembly comprises an air purifier comprising a housing, and the pressure sensor is disposed within the housing
24. The headgear of any one of claims 20 to 23, wherein the conduit is a first conduit extending along a first side of the headgear, the passage is a first passage, the headgear comprises a second conduit defining a second passage distinct from the duct, the second conduit extending along a second side of the headgear, opposite to the first side of the headgear, and the pressure sensor is arranged for sensing the air pressure in the duct via the first conduit and the second conduit.
25. The headgear of any one of claims 20 to 23, wherein the pressure sensor is a first pressure sensor, the conduit is a first conduit extending along a first side of the headgear, the passage is a first passage, and the headgear comprises: a second conduit defining a second passage distinct from the duct, the second conduit extending along a or the second side of the headgear, opposite to the first side of the headgear; and a second pressure sensor, wherein the second pressure sensor is arranged for sensing the air pressure in the duct via the second conduit.