WO2024116010A1

WO2024116010A1 - A wearable air purifier

Info

Publication number: WO2024116010A1
Application number: PCT/IB2023/061675
Authority: WO
Inventors: Philip Reilly; James Nelson; William Jasper
Original assignee: Dyson Technology Limited
Priority date: 2022-11-30
Filing date: 2023-11-20
Publication date: 2024-06-06
Also published as: GB2624920A; GB202218023D0

Abstract

A wearable air purifier (101) is disclosed. The wearable air purifier comprises a helmet (102) for wearing on a wearer's head, a fan assembly (103) mounted to the helmet and operable to generate an airflow, a duct assembly to duct airflow generated by the fan assembly, a nozzle (105) connectable to the helmet to receive airflow from the duct assembly and depend downward from the helmet to direct the airflow towards a wearer's face, wherein the fan assembly is mounted rearwards of a point of connection of the nozzle to the helmet, and the duct assembly extends between the fan assembly and the point of connection.

Description

A WEARABLE AIR PURIFIER

Field of the Disclosure

The present disclosure relates to a wearable air purifier.

Background of the Disclosure

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 a filtered airflow towards a wearer’s face.

Summary of the Disclosure

A first aspect of the present disclosure provides a wearable air purifier, comprising: a helmet for wearing on a wearer’s head, a fan assembly mounted to the helmet and operable to generate an airflow, a duct to duct airflow generated by the fan assembly, a nozzle connectable to the helmet to receive airflow from the duct and depend downward from the helmet to direct the airflow towards a wearer’s face, wherein the fan assembly is mounted rearwards of a point of connection of the nozzle to the helmet, and the duct extends between the fan assembly and the point of connection.

The fan assembly may thus be located towards a rear of the helmet, which may confer desirable mass distribution and/or acoustic isolation characteristics, . However, it may be undesirable for the nozzle to similarly connect to a rear of the helmet, as the nozzle may thus inhibit fitting and/or removal of the helmet from a wearer’s head. The duct thus desirably facilitates mounting of the fan assembly to a rearward portion of the helmet whilst allowing the nozzle to connect to a forward portion of the helmet.

In an implementation, the duct is covered by an exterior wall of the helmet. The duct may thus be protected from impacts by the exterior wall. Additionally, the exterior wall may present an aerodynamic surface. In an implementation, the duct extends along a side of the helmet between the fan assembly and the point of connection. Consequently, an integrity of a top region of the helmet is not impaired by the duct.

In an implementation, the duct is arranged to discharge airflow to the nozzle on a downward trajectory. Consequently the nozzle is not required to turn the airflow to direct it from the helmet towards a wearer’s lower nasal/mouth region.

In an implementation, the nozzle comprises at least a section formed wholly of one or more elastomer materials, the elastomer materials thereby extending about a full circumference of a passage for carrying airflow defined by the section. The elastomer material may thus deform in the event of an impact, reducing a risk of injury being caused to a wearer by the nozzle being displaced towards the volume.

In an implementation, the section defines a passage extending from an inlet of the nozzle to an outlet of the nozzle. In other words, a full length of duct between the inlet and outlet may be formed from elastomer material, thereby further reducing a risk of injury being caused to a wearer.

In an implementation, the helmet comprises compressible material for absorbing impact energy defining a volume for accommodating at least a part of the wearer’s head, and the compressible material defines a wall of at least a section of the duct assembly. In other words, the duct may be formed by the compressible material, such that the compressible material defines a wall of the duct that is exposed to airflow. This avoids the need to provide an additional dedicated duct structure to form the wall. This may reduce mass and/or complexity. Additionally, for a given depth of the helmet, excluding a dedicated duct structure may desirably allow a depth of the compressible material to be increased, and thereby energy absorbing characteristics of the helmet may be improved. Further, removal of a dedicated duct structure reduces a risk of the duct structure contacting a wearer’s head in the event of an impact resulting from a fall or collision. Consequently, a risk of injury being caused to the wearer’s head may be reduced. In an implementation, the compressible material comprises air-impermeable material forming the wall. Consequently airflow within the duct may be well contained, and leakage reduced.

In an implementation, the compressible material comprises closed cell foam material. Closed-cell foam material may be a good energy absorber, whilst also being relatively impermeable to air.

In an implementation, the compressible material comprises a recess defining the wall of the duct, and the wearable air purifier further comprises a cap extending across the recess and sealed against the compressible material to define a further wall of the section of the duct assembly. The duct may thereby be conveniently formed.

In an implementation, the recess is on an opposite side of the compressible material to the volume such that a portion of the compressible material is located between the recess and the volume. Consequently, the portion of the compressible material may mechanically, thermally, and/our acoustically insulate a wearer’s head from airflow within the duct.

In an implementation, the helmet comprises a hard outer shell extending over the compressible material and the recess, the hard outer shell forming the cap to the recess.

In an implementation, the compressible material comprises a bore defining the wall of the section of the duct assembly, the wall surrounding a full circumference of the section of the duct assembly. Such a bore may be desirably mechanically simple.

In an implementation, the compressible material forms a first part defining the volume and the wall, and a second part shaped to define a further volume in which the first part is located, the second part defining a further wall of the section of the duct assembly, such that the section of the duct assembly is formed between the wall of the first part and the further wall of the second part. Brief Description of the Drawings

In order that the present disclosure may be more readily understood, embodiments of the disclosure will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic perspective view of a first wearable air purifier embodying the present disclosure;

Figure 2 is a schematic side elevation view of the wearable purifier;

Figure 3 is a schematic front elevation view of the wearable air purifier;

Figure 4 is a schematic top plan view of the wearable air purifier;

Figure 5 is a further schematic side elevation view of the wearable air purifier,

Figure 6 is a further schematic side elevation view of the wearable air purifier;

Figure 7 is a schematic side cross-sectional view of the wearable air purifier;

Figure 8 is a further schematic side cross-sectional view of the wearable air purifier;

Figure 9 is a schematic front cross-sectional view of the wearable air purifier, taken through the plane depicted by the line A- A in Figure 7;

Figure 10 is a further schematic front cross-sectional view of the wearable air purifier, taken through the plane depicted by the line B-B in Figure 7;

Figure 11 is a schematic top cross-sectional view of the wearable air purifier; Figure 12 is a further schematic front cross-sectional view of the wearable air purifier;

Figure 13 is a schematic front cross-sectional view of a second wearable air purifier embodying the present disclosure;

Figure 14 is a schematic front cross-sectional view of a third wearable air purifier embodying the present disclosure;

Figure 15 is a schematic depicting an example fan controller for the wearable air purifiers embodying the present disclosure; and

Figure 16 is a flow diagram depicting an example control process performed by the fan controller.

Detailed Description of the Disclosure

A wearable air purifier 101, embodying aspects of the present disclosure, is shown schematically in the Figures. 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 environmental air pollution may desirably be reduced.

Referring firstly to Figures 1 to 4, the wearable air purifier 101 comprises headgear 102 for mounting on a wearer’s head, a pair of fan assemblies, indicated generally at 103 and 104, for generating filtered airflows, a nozzle 105 for directing the filtered airflows from the fan assemblies 103, 104 towards the lower nasal and mouth region of the wearer’s face, and an eye shield 106 for shielding a wearer’s eyes.

The headgear 102 forms a protective helmet for wearing on a wearer’s head, to cover a top and sides of the wearers’ head, to protect the wearer’s head from injury caused by impacting objects. In the examples described herein, the headgear 102 is configured as a cycling helmet for protecting the wearer’ s head by absorbing energy of impacting obj ects, e.g., the ground or vehicles, as may result from a fall or collision. As will be described in further detail herein, the helmet 102 utilises energy-absorbing materials for this purpose. In other examples the headgear 102 could be configured as an alternative form of helmet, for example, as a motorcycling helmet, or an action sports helmet. Fan assemblies 103, 104 are mounted to a rear of the helmet 102 to left and right sides respectively of a sagittal plane of the wearer’s head in use

The nozzle 105 functions as an air guide for receiving filtered airflows from the fan assemblies 103, 104, and discharging the airflows towards the lower nasal and mouth region of the wearer’s face. The nozzle 105 is coupled at left and rights ends to left and right sides respectively of the helmet 102, and is configured in use to depend downwardly from the helmet 102 and extends width-wise across the wearer’s face, such that a mouthpiece portion of the nozzle from which airflow is discharged is supported in use in front of the wearer’s lower nasal and mouth region. In examples, the nozzle 105 is configured to not contact the wearer’s face, such that it is supported by the helmet 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. The nozzle 105 may be formed of an elastomer material, such as a rubber material, to avoid a risk of injury being caused to a wearer in the event of a frontal impact resulting in the nozzle being pushed rearwards towards the wearer’s face.

The eye shield 106 is transparent and functions to shield a wearer’s eyes from headwinds and impacting objects, such as airborne insects, and further functions to exclude unfiltered ambient air from the wearer’s nasal/mouth region and contain filtered airflow. The eye shield 106 is coupled at left and right ends to left and right sides respectively of the helmet 102, and is configured in use to extend width- wise across the wearer’s face. In examples, the transparent eye shield is formed of transparent plastic material, such as acrylic, which is desirably low mass and highly impact-resistant. In other examples the eye shield is formed of glass, or another transparent material. Referring next in particular to Figures 5 and 6, in examples each of the nozzle 105 and eye shield 106 is hingedly coupled to the headgear 102.

For this purpose, each of the left and right ends of the nozzle 105 is provided with a hinged coupling 501 for hingedly fixing the respective end to the helmet 102. The nozzle 105 is thus movable by a wearer in use from the operative position shown in Figures 1 to 4 downwards to the inoperative position shown in Figures 5 and 6. As will be described in further detail with reference to later Figures, in the operative position airflow inlets of the nozzle 105 mate with airflow outlets on the helmet 102, such that the nozzle 105 may receive airflow from the fan assemblies 103, 104 via the helmet 102 and direct the airflow towards the wearer’s lower nasal/mouth region. The eye shield 106 is also hingedly coupled at left and right sides to the helmet 102, to enable the wearer to similarly move the eye shield from the operative, lowered, position depicted in Figure 5 to the inoperative, raised position depicted in Figure 6. The nozzle 105 and eye shield 106 are relatively arranged to mate with and seal against one another when both the nozzle 105 and the eye shield 106 are in the operative positions, as depicted in Figures 1 to 4. The mating of the nozzle 105 and the eye shield 106 has the effect of better containing filtered airflows discharged by the fan assemblies 103, 104 via the nozzle 105 in front of the wearer’s face, and unfiltered ambient air may be better excluded from the wearer’s face.

In some examples, the coupling between the nozzle 105 and helmet 102, and/or the eye shield 106 and the helmet 102, is releasable, to allow the nozzle and/or the eye shield to be detached from the helmet. The releasable coupling 2 allows the wearer to conveniently detach the nozzle 105 or the eye shield 106 from the helmet 102. This may advantageously allow easier cleaning of the nozzle and eye shield separately from the helmet, and/or enable more dimensionally compact stowage of the helmet 102, nozzle 105, and eye shield 106.

Referring next to Figures 7 to 12 collectively, in examples the helmet 102 comprises compressible material 701 for absorbing impact energy, and a hard outer shell 702. The compressible material 701 and hard outer shell 702 house a source of electrical power, namely battery assembly 703, and a sensor 704 for sensing a position of the eye shield 106.

The compressible material 701 is generally dome shaped having a concave inner surface which bounds a top and sides of a volume 705 for partially accommodating the wearer’s head. The compressible material 701 is configured to deform under load to thereby absorb energy associated with objects impacting the helmet, to protect the wearer’s head from injury caused by excessive force. Compressible material 701 is shaped to define a frontal void 706 between the compressible material 701 and the hard outer shell 102, positioned to accommodate the eye shield 106 when the eye shield is located in the raised position. Compressible material 701 defines a recess 1201 to the external surface in which the battery assembly 703 is located, formed on a top portion of the helmet. In examples, the compressible material is a plastically deformable material, such as expanded polystyrene, foam, or a plastic honeycomb structure. In some examples, the compressible material 701 comprises air-impermeable material, such as a closed-cell polystyrene foam. Such an air- impermeable construction has an advantage where ducts for ducting filtered airflows from the fan assemblies 103, 104 are formed by the compressible material 701, as will be described in further detail with reference to later Figures.

The hard outer shell 702 is similarly generally dome shaped, and is arranged to cover the compressible material 701, such that a concave interior surface of the hard outer shell 702 contacts the exterior surface of the compressible material 701, and a convex exterior surface of the hard outer shell 702 forms an exterior surface of the helmet 102. The hard outer shell 702 is configured to be substantially non-deformable. A function of the hard outer shell 702 is to spread force of impacting objects over a relatively greater area of the compressible material 701, to thereby reduce point-loading of the compressible material 701, with the object of enabling the compressible material 701 to better absorb impact energy and thereby better protect the wearer’s head. The hard outer shell is further functional to support the nozzle 105, eye shield 106, and fan assemblies 103, 104. In examples, the hard outer shell 702 is formed of a durable plastic material, such as polycarbonate or acrylonitrile butadiene styrene. The fan assemblies 103, 104 are mounted to the hard outer shell 702 at a rear of the helmet 102. Fan assemblies 103, 104 are substantially like, and for brevity therefore only fan assembly 103 will be described in detail herein, on the understanding that substantially the same description applies to the fan assembly 104.

Fan assembly 103 comprises housing 707, air filter 708, fan 709 and fan controller 710. The housing 707 defines inlet 711 and outlet 712 and an airflow path therebetween. Fan 709 comprises a mixed-flow impeller in the airflow path between the inlet 711 and outlet 712, driven by an electric motor. The electric motor is supplied with electrical power by battery assembly 703, via conductors, not shown in the drawings, and fan controller 710. Fan 709 is controllable by fan controller 710 to draw air in through inlet 711, via filter 708, and discharge the filtered airflow via the outlet 712. Housing 707 is configured to seal against the exterior surface of the hard outer shell 702, to inhibit uncontrolled ingress of air, liquids and/or dust from the external environment.

Sensor 704 is for sensing whether the eye shield 106 is in the operative, mating position, depicted in Figure 7, or the inoperative, non-mating, position, shown in Figure 8. In examples, the sensor 704 is configured to be acted on by the eye shield 106 when the eye shield 106 is in a position other than the mating position depicted in Figure 7. For example, the sensor 704 could be a momentary push-to-break switch with an open-circuit state and a closed-circuit state, whereby the switch 704 is pushed by the eye shield 106 when the eye shield 106 is in any position other than the mating position depicted in Figure 7, such as when the eye shield 106 is in the raised, non-mating, position depicted in Figure 8. As a result, breaking of the sensor circuit by the sensor 704 is indicative of the eye shield 106 being in a position other than the mating position, for example, in the non-mating position depicted in Figure 8.

In examples, the compressible material 701 and the hard outer shell 703 together define ducts for ducting airflows to and from the inlets 711 and outlets 712 respectively of the fan assemblies 103, 104. That is to say, in examples, one or both of the compressible material 701 and the hard outer shell 702 define walls of ducts for ducting airflows to and/or from the fan assemblies 103, 104. In such examples, the compressible material 701 may be formed of an air-impermeable material to ensure adequate containment of air flowing through the duct. A closed-cell foam, such as expanded polystyrene, is a good material for such examples, as it is desirably air impermeable and a good energy absorber.

In the example depicted in Figures 7 to 12, the compressible material 701 defines walls of inlet ducts 713, 714, for ducting influent airflows to the inlets 711 of the fan assemblies 103, 104 respectively, and the compressible material 701 and hard outer shell 702 together define outlet ducts 901, 902 for ducting effluent airflows from the outlets 712 of the fan assemblies 103, 104 to a respective inlet of the nozzle 105. Inlet ducts 713, 714 are substantially like, as are outlet ducts 901, 902. Again, for brevity therefore, only inlet duct 713 and outlet duct 901, associated with fan assembly 103, will be described in detail herein.

Inlet duct 713 is defined by the compressible material 701 in the form of a passage extending through the compressible material 701 between the internal concave surface and the external convex surface. An inlet 715 of the inlet duct 713 opens into the volume 705. A rim of the inlet 715 is chamfered to aid smooth airflow into the inlet duct 713. An outlet 716 of the inlet duct 713 opens outside of the volume 705 and is in fluid communication with the inlet 711 of the fan assembly 103 via an aperture 717 formed in the outer shell 702. The inlet duct 713 thus functions to guide air from within the volume 705 to the inlet 711 of the fan assembly 103, such that the fan assembly 103 may draw airflow from within the volume 704 via the inlet duct 713. Inlet duct 714 similarly extends through the compressible material 702 to allow the fan assembly 104 to draw air from within the volume 705. In other examples, a single inlet duct, such as inlet duct 713 could be configured to be shared by the fan assemblies 103, 104, such that each of the fan assemblies 103, 104 may draw airflow from the volume 705 via a common inlet duct, such as inlet duct 713. Or indeed, in other examples only a single fan assembly, such as fan assembly 103, may be employed. Referring in particular to Figures 9 to 11, outlet duct 901 is defined by the compressible material 701 and the hard outer shell 702. The compressible material 701 is shaped to define a recess 903 extending inwardly from the external convex surface part of the depth of the compressible material 701, and along the compressible material 701 from the outlet 712 of the fan assembly 103 at the rear forwardly to a duct outlet 1001, located at the point of connection of the nozzle 105 to the helmet 102. The recess 903 thus defines an open channel having a generally U-shaped cross-sectional form. The hard outer shell 702 overlies the recess 903 and seals against the compressible material 701, thereby capping the channel formed by the recess 903 to form the duct 901 that is capable of ducting airflow from the outlet 712 of the fan assembly 103 to the inlet 1002 of the nozzle 105. The recess 903 is formed on a side of the compressible material 701. Thereby the impactabsorbing properties of top, front and rear regions of the compressible material 701 are unaffected by the recess 903.

Inlet 1002 of nozzle 105 mates with outlet 1001 of outlet duct 901 when the nozzle 105 is in the operative, raised, position to thereby receive airflow from the outlet duct 901 for delivery via the nozzle outlet 1003 to the breathing region 1004 between the nozzle 105 and the wearer’s face.

Outlet duct 902 is similarly formed by a recess in the compressible material 701 capped by the hard outer shell 702, and functions to guide filtered airflow from the fan assembly 104 to an opposite inlet of the nozzle 105. Outlet duct 902 is formed on the opposite side of the compressible material 701 to outlet duct 901. In other examples, a single outlet duct, such as outlet duct 901 could be configured to be shared by the fan assemblies 103, 104, such that each of the fan assemblies 103, 104 discharge filtered airflows via the common outlet duct. Or, where only a single fan assembly is employed, helmet 102 may comprise only one outlet duct, such as outlet duct 901.

Battery assembly 703 is provided for supplying electrical power to the motors of the fan assemblies 103, 104, and for powering the fan controller 710. The battery assembly 703 is located in the recess 1201 formed by the compressible material 701, separated from the volume 703 by an underlying portion 718 of the compressible material 701 that forms a floor to the recess 1201. Battery assembly 703 comprises a cylindrical electrochemical cell 719 located in a load spreading body 720.

A function of the load-spreading body 720 is to spread load applied by the battery assembly 703 in a direction normal to the volume 705, as might occur in the event of a fall or collision, over a relatively large area of the compressible material 701. Consequently, point loading of the compressible material 701 may be reduced, and the compressible material 701 may better absorb impact energy of the battery assembly 703. Thereby a risk of the battery assembly 703 penetrating through the compressible material 701 into the volume 705 is reduced, along with an associated risk of injury being caused to the wearer’s head by the battery assembly 703 in the event of a fall or collision.

For this purpose, the load spreading body 720 is relatively non-deformable, and is sized and shaped to present a relatively greater frontal area to the volume 905 than a corresponding area of the electrochemical cell 719. As a result, the area of the portion

718 of the compressible material 701 that is located between the battery assembly 703 and the volume 705, i.e. the area of the compressible material 701 that is intersected by a projection of the area of the load spreading body 729 onto a plane tangential to the concave internal surface of the compressible material at a centre point of the projected area, is relatively larger than the area of compressible material 701 between the electrochemical cell 719 and the volume 705, i.e., the area of compressible material 701 intersected by a projection of the area of the electrochemical cell 719 onto the same tangent plane.

The load spreading body 720 comprises a container 721 in which the electrochemical cell

719 is located, and a filler material 722. The container 721 has a profile closest to the volume 705 that curves with a curvature of the internal concave surface of the compressible material 710. Consequently, the portion 718 of the compressible material 701 has a relatively uniform thickness across its area, and thus impact energy may be absorbed uniformly across the area of the portion 718 of compressible material, reducing the risk of excessive point loading of the portion 718 of compressible material. The container 721 may be formed of a rigid plastic, such as acrylonitrile butadiene, or another relatively rigid/non-deformable material, such as plastic or metal.

The filler material 722 fills a volume between an exterior of the electrochemical cell 719 and an interior of the container 721. The filler material 722 is solid, and thereby functions to rigidly fix the electrochemical cell 719 within the container 721, to inhibit movement of the electrochemical cell 719 relative to the load-spreading body 720. Consequently, the risk of the electrochemical cell 719 impacting the container 721 is reduced, along with an associated risk of damage occurring to the electrochemical cell 719. In examples, the filler material 722 comprises a curing material, such as a thermosetting polymer, that is introduced into the container 721 in a liquid state, thereby achieving a close conformance to substantially all of the exterior of the electrochemical cell 719 and the interior of the container 721, and which subsequently hardens in-situ.

The electrochemical cell 719 is cylindrical in form, and arranged to extend within the container 721 such that its longitudinal axis extends in a front-to-rear direction of the helmet 102. Consequently, the greater, length, dimension of the electrochemical cell 719 can be more easily accommodated by the relatively lower curvature of the compressible material 701 in the front-to-rear direction compared to the relatively greater curvature of the compressible material 701 in the side-to-side direction. As a result, a thickness of the portion 718 of compressible material 701 remains relatively uniform along the length of the battery assembly 703.

Referring in particular to Figure 12, in examples, the helmet 102 is configured such that the battery assembly 703 is accessible, and optionally removable, by the wearer. For this purpose, the hard outer shell 702 is provided with an openable hatch 1202 overlying the battery assembly 703 to permit access to the battery assembly 703, for example, to allow inspection or maintenance of the battery assembly by the wearer. In examples, the battery assembly 703 is adapted to be removable by the wearer, and the hatch 1202 is sized and configured to permit removal of the battery assembly 703, for example, to enable replacement of the battery assembly, or ex-situ charging of the electrochemical cell 719. In the examples previously described with reference to Figures 9 to 12, the outlet ducts 901, 902 are formed jointly by the compressible material 701 and the hard outer shell 702, each of which is exposed to airflow within the duct. In other examples, either or both of the outlet ducts 901, 902 could instead be formed solely by the compressible material 701. Alternative example configurations in which the outlet ducts 901, 902 are each formed solely by the compressible material 701 are depicted schematically in Figures 13 and 14. The example helmets depicted in Figures 13 and 14 are substantially the same as helmet 102, except in relation to the outlet ducts, and like features will be denoted using like reference numerals.

Referring to Figure 13, in examples outlet ducts 1301, 1302, which like outlet ducts 901, 902 are provided for ducting filtered airflows from the fan assemblies 103, 104 to the nozzle 105, are formed by respective bores formed by the compressible material 701. The bores formed by the compressible material 701 thus form closed ducts whereby the compressible material 701 forms a wall extending about a full circumference of each duct. The bores in the compressible material 701 could be formed, for example, during an initial process of forming the compressible material 701 into the dome shape, e.g., the bores could be integrally moulded with the compressible material 701 where the compressible material is a mouldable material. Alternatively, the bores could be formed, for example, by a post-production step of machining the bores out of the pre-formed compressible material 701, or by another suitable forming process.

Referring to Figure 14, in another example, the compressible material 701 could be formed in two distinct parts, and the outlet ducts 1401, 1402 could be defined between the two parts. In this alternative configuration, the compressible material 701 is formed in two generally dome-shaped parts 701a, 701b. The inner part 701a has a concave internal surface defining the internal volume 705 and a convex external surface defining recesses at left and right sides, such as left recess 1403. The outer part 701b has a concave inner surface similarly defining recesses at left and right sides, such as left recess 1404, and a convex external surface. The outer part 701b is over-sized compared to the inner part 701a, and the inner part 701a is located within the outer part 701b, such that the convex external surface of the inner part 701a abuts and seals against the concave internal surface of the outer part 701b, and the recesses 1403 of the inner part 1403 mate with the recesses 1404 respectively of the outer part 701b to form a duct capable of ducting the filtered airflows from the fan assemblies. In this configuration, the recesses 1403, 1404 of the inner part 701a and the outer part 701b respectively define walls forming outlet duct 1401.

Referring next to Figure 15, in examples, fan controller 710 comprises input/output interface 1501, memory 1502, processor 1503, motor driver 1504, and system bus 1505. The fan controller 710 is configured to control the operation of the fan assemblies 103, 104 based on a position of the eye shield 106, sensed by sensor 704. In examples, fan controller 710 located with fan assembly 103 is employed for controlling each of the fan assemblies 103, 104.

Input/output interface 1501 is provided for connection of the sensor 704, the electrochemical cell 719, and the motors of the fan assemblies 103, 104. Memory 1502 stores a computer program, comprising machine-readable instructions, for controlling motor speeds of the fan assemblies 103, 104 based on a state of the sensor 704. Memory 1502 further stores a lookup table, defining motor speed settings associated with respective states of the sensor 704. Processor 1503 is configured for receiving and processing a signal from the sensor 704, executing instructions of a computer program for determining a motor speed setting for the motors of the fan assemblies based on the signal from the sensor, and generating a motor control signal for use by motor driver 1504. Motor driver 1504 regulates the power supplied to the motors of the fan assemblies 103, 104, and so the speed of the motors, in dependence on the motor control signal output by the processor 1503. The components 1501 to 1504 of the fan controller 710 are in communication via system bus 1505.

The fan controller 710 is thus configured, in accordance with instructions of the computer program stored on memory 1502, to: sense a state of the sensor 704 (and thus determine a position of the eye shield 106); consult the lookup table stored on memory 1502 to identify a motor speed setting associated with the sensed state of the sensor 704; and supply power to the motors of the fan assemblies 103, 104 in dependence on the identified motor speed setting. The speed of the motors, and so the flow rates of the airflows generated by the fan assemblies 103, 104 is thus controlled in dependence on the state of the sensor 704.

The rate of filtered airflow provided by the fan assemblies 103, 104 to the nozzle 105 may thereby be varied depending on whether the eye shield 106 is in the mating position, depicted in Figure 7, or the non-mating position, depicted in Figure 8.

This control scheme advantageously enables the rate of filtered airflow to be varied to compensate for changes to airflow dynamics in the breathing region 1004 between the outlet 1003 of the nozzle 105 and the wearer’s face that vary with the position of the eye shield 106. For example, the propensity of unfiltered ambient air to enter the breathing region may be greater when the eye shield 106 is in the non-mating position than when the eye shield 106 is in the mating position, sealingly mated against the nozzle 105. To compensate for this, and reduce the ingress of unfiltered ambient air into the wearer’s breathing region, the fan controller 710 may increase the airflow rate of the fan assemblies 103, 104 when the eye shield 106 is not in the mating position, such that an excess of filtered airflow displaces unfiltered airflow away from the breathing region, thereby reducing the wearer’s exposure to environmental air pollution. Conversely, when the eye shield 106 is in the mating position, sealed against the nozzle 105, the eye shield 106 functions to exclude unfiltered ambient air from the breathing region, and thus excess filtered airflow into the breathing region to counter ingress of unfiltered airflow may not be not needed. Rather, in this scenario, the fan controller 710 may set the airflow rate of the fan assemblies 103, 104 to be relatively lower, thereby reducing power consumption of the fan assemblies, and so prolonging the state of charge of the electrochemical cell 719, and reducing generation of acoustic noise by the fan assemblies 103, 104. Referring finally to Figure 16, in examples the computer program for controlling the operation of the fan assemblies 103, 104 based on the position of the eye shield 106 comprises four stages.

At stage 1601, the computer program causes the processor 1503 to initiate the fan assembly control procedure. The initiation stage could be triggered, for example, by a wearer’s input, such as wearer pressing an ‘ON’ button connected to the input/output interface 1501 of the fan controller 710. As an example alternative, the computer program could cause the processor 1503 to initiate the control procedure in response to a change of state of the sensor 704.

At stage 1602, the computer program causes the processor 1503 to sense the state of the sensor 704. Stage 1602 could, for example, involve the processor supplying power to the sensor circuit to detect whether the sensor is the open-circuit or closed-circuit state. For example, at stage 1602, the processor 1503 could sense that the sensor 604 is in the opencircuit state, indicating that the eye shield 106 is in the non-mating position depicted in Figure 8. Stage 1602 could also involve the processor 1503 storing the sensed sensor state to memory 1502.

At stage 1603, the computer program causes the processor 1503 to retrieve the lookup table from the memory 1502 and identify a motor speed setting associated in the lookup table with the state of the sensor 604, as sensed at stage 1602. For example, where the sensor 604 was sensed to be in the open-circuit state at stage 1602, at stage 1603 the processor 1503 could consult the lookup table to identify a fan speed setting associated with the sensor open-circuit state.

At stage 1604, the computer program causes the processor 1503 to trigger the motor driver 1504 to drive the motors of the fan assemblies 103, 104 at the motor speed identified at stage 1603. The control process depicted in Figure 16 could be repeated, such that following stage 1604, the control routine returns to sensing the sensor state at stage 1602, and in the event of a change in the sensor state proceeds with later stages 1603 and 1604.

Claims

1. A wearable air purifier, comprising: a helmet for wearing on a wearer’ s head, a fan assembly mounted to the helmet and operable to generate an airflow, a duct to duct airflow generated by the fan assembly, a nozzle connectable to the helmet to receive airflow from the duct and depend downward from the helmet to direct the airflow towards a wearer’ s face, wherein the fan assembly is mounted rearwards of a point of connection of the nozzle to the helmet, and the duct extends between the fan assembly and the point of connection.

2. The wearable air purifier of claim 1, wherein the duct is covered by an exterior wall of the helmet.

3. The wearable air purifier of claim 1 or claim 2, wherein the duct extends along a side of the helmet between the fan assembly and the point of connection.

4. The wearable air purifier of any one of the preceding claims, wherein the duct is arranged to discharge airflow to the nozzle on a downward trajectory.

5. The wearable air purifier of any one of the preceding claims, wherein the nozzle comprises at least a section formed wholly of one or more elastomer materials, the elastomer materials thereby extending about a full circumference of a passage for carrying airflow defined by the section.

6. The wearable air purifier of claim 5, wherein the section defines a passage extending from an inlet of the nozzle to an outlet of the nozzle.

7. The wearable air purifier of any one of the preceding claims, wherein the helmet comprises compressible material for absorbing impact energy defining a volume for accommodating at least a part of the wearer’ s head, and the compressible material defines a wall of at least a section of the duct assembly.

8. The wearable air purifier of claim 7, wherein the compressible material comprises air-impermeable material forming the wall.

9. The wearable air purifier of claim 7 or claim 8, wherein the compressible material comprises closed cell foam material.

10. The wearable air purifier of any one of claims 7 to 9, wherein the compressible material comprises a recess defining the wall of the duct, and the wearable air purifier further comprises a cap extending across the recess and sealed against the compressible material to define a further wall of the section of the duct assembly.

11. The wearable air purifier of claim 10, wherein the recess is on an opposite side of the compressible material to the volume such that a portion of the compressible material is located between the recess and the volume.

12. The wearable air purifier of claim 10 of claim 11, wherein the helmet comprises a hard outer shell extending over the compressible material and the recess, the hard outer shell forming the cap to the recess.

13. The wearable air purifier of any one of claims 7 to 12, wherein the compressible material comprises a bore defining the wall of the section of the duct assembly, the wall surrounding a full circumference of the section of the duct assembly.

14. The wearable air purifier of any one of claims 7 to 13, wherein the compressible material forms a first part defining the volume and the wall, and a second part shaped to define a further volume in which the first part is located, the second part defining a further wall of the section of the duct assembly, such that the section of the duct assembly is formed between the wall of the first part and the further wall of the second part.