Patent Description:
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 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. These face masks range from basic dust masks that merely filter out relatively large dust particles, to more complex air-purifying respirators that require that the air pass through a filter element or cartridge. However, as these face masks typically cover at least the users mouth and nose they can make normal breathing more laborious and can also cause problems with the user's ability to speak to others, such that there is some reluctance to make use of such face masks on a day-to-day basis despite the potential benefits.

As a consequence, there have been various attempts to develop air purifiers that can be worn by the user but that do not require the user'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 user and that create a jet of air that is directed upwards towards the user's mouth and nose. Whilst these may be more socially acceptable, they are generally less effective at limiting the user's exposure to airborne pollutants than some of the best performing face-worn filters. This is largely due to the lack of accuracy with which they deliver the jet of air to the user's mouth and nose and to the fact that flows of unfiltered air that can still reach the user's mouth and nose.

<CIT>, <CIT>, <CIT> and <CIT> all describe head-worn purifiers that provide an alternative to both face masks and neck-worn purifiers. Each of <CIT>, <CIT> and <CIT> describe a headset having a pair of earphones on opposite sides of a headband and a microphone provided on the end of an arm that extends from one of the earphones.

In <CIT> a separate air filtering unit (<NUM>) is connected by a pipe (<NUM>) to an air outlet (<NUM>) provided on the arm that supports the microphone (<NUM>). Filtered air is generated by the air filtering unit (<NUM>) and pumped through the pipe (<NUM>) to be discharged from the air outlet (<NUM>). This head-worn purifier takes the form of a conventional head-set, and does not completely cover the user's mouth and nose, and is therefore likely to be more socially acceptable then a face mask. In addition, by providing the air delivery outlet on the end of a conventional microphone arm, this head-worn purifier should be capable of providing more accurate delivery of purified air to the user's nose and/or mouth than a neck-worn purifier. However, this head-worn purifier will still allow a not insignificant amount of unfiltered air to reach the user's mouth and nose. Furthermore, the requirement for a separate air filtering unit makes the purifier more complex and more cumbersome for the user.

In CN103949017A a fan (<NUM>) is incorporated into one of the earphones (<NUM>), with this fan (<NUM>) being used to pump air through a duct (<NUM>) to an air purifying device (<NUM>) provided on the end of the arm that supports the microphone (<NUM>). Whilst this head-worn purifier has incorporated the air purification functionality into the headset, the air purification and delivery performance will be limited due to the small space available for both filtering pollutants from the air supplied by the fan and for delivering filtered air to the user. In particular, the small space available will significantly limit both the maximum flow rate and the filtering efficiency due to the small filter area available. Furthermore, as with the head-worn purifier described in <CIT>, this head-worn purifier will still allow a significant amount of unfiltered air to reach the user's mouth and nose.

<CIT> describes an air filtering device that includes a filtering device shell and a filtering unit. The filtering unit includes a blower assembly in fluid communication with a filter assembly via a duct. The blower assembly is vibrationally isolated from the filtering device shell by being only attached to the filtering device shell by the duct.

It is an object of the present invention to provide a wearable air purifier that provides improved air purification and air delivery performance when compared with prior wearable air purifiers.

According to a first aspect there is provided a head wearable air purifier. The head wearable air purifier comprises a first speaker assembly arranged to be worn over a first ear of a user and a second speaker assembly arranged to be worn over a second ear of the user; wherein the first speaker assembly comprises a speaker, a filter assembly, an impeller for creating an airflow through the filter assembly, a motor arranged to drive the impeller, and an air outlet downstream from the filter assembly for emitting the filtered airflow from the speaker assembly. The impeller and the motor are disposed within an impeller casing. The first speaker assembly further comprises a housing containing the speaker, the filter assembly and the impeller casing, and the impeller casing is suspended/supported within the housing by a plurality of resilient supports or isolation mounts that extend between the impeller casing and the housing.

Preferably, the resilient supports are angularly spaced about the impeller casing. Preferably, two or more of the resilient supports extend radially between an outer surface of the impeller casing and an inner surface of the housing. These two or more resilient supports may each comprise a profile damper, preferably comprise a radially damping profile damper and more preferably comprise a radial tube damper. These two or more resilient supports may each be attached to the inner surface of the housing and compressed against the outer surface of the impeller casing. Preferably, one of the resilient supports is provided by a resilient duct that is sealed around and extends from an air outlet of the impeller casing towards the air outlet of the speaker assembly.

Preferably, the filter assembly is disposed over the impeller casing and two or more of the resilient supports extend radially between an outer surface of the impeller casing and an inner surface of the filter assembly. These two or more resilient supports may each comprise a profile damper, preferably comprise a radially damping profile damper and more preferably comprise a radial tube damper. These two or more resilient supports may be attached to an inner collar that is disposed over the impeller casing and to an outer collar that contacts the inner surface of the filter assembly.

The impeller casing may be generally frusto-conical in shape. The impeller casing may comprise a generally frusto-conical impeller housing surrounding the impeller and an annular volute fludically connected to the base of the impeller housing that is arranged to receive the air exhausted from the impeller housing and to guide the air to the air outlet of the speaker assembly. The impeller housing may be provided with an air inlet through which air can be drawn by the impeller and an air outlet through which the air is emitted from the impeller housing into the annular volute. The air inlet of the impeller housing may be provided by an aperture at a smallest diameter end of the impeller housing and the air outlet is provided by an annular slot formed around a base of the impeller housing. Preferably, two or more of the resilient supports are spaced angularly around a base of the impeller casing. These two or more of the resilient supports may be spaced angularly around a periphery of the annular volute.

Preferably, two or more of the resilient supports are spaced angularly around a top of the impeller casing. These two or more of the resilient supports may be spaced angularly around a top of the impeller housing.

The head wearable air purifier may further comprise a nozzle arranged to receive a filtered airflow from the air outlet of the first speaker assembly, the nozzle comprising an air outlet arranged to emit the received filtered airflow from the head wearable air purifier.

Preferably, the first speaker assembly and the second speaker assembly are substantially the same. The second speaker assembly may comprise a speaker, a filter assembly, an impeller for creating an airflow through the filter assembly, a motor arranged to drive the impeller, and an air outlet downstream from the filter assembly for emitting the filtered airflow from the speaker assembly, wherein the impeller and the motor are disposed within an impeller casing, and the second speaker assembly then further comprises a housing containing the speaker, the filter assembly and the impeller casing, and the impeller casing is suspended/supported within the housing by a plurality of resilient supports.

The head wearable air purifier may then further comprise a nozzle arranged to receive a filtered airflow from the air outlets of both the first speaker assembly and the second speaker assembly, the nozzle comprising an air outlet arranged to emit the received filtered airflows from the head wearable air purifier.

Preferably, the head wearable air purifier comprise a headphone system such that the first speaker assembly is mounted on a first end of a headband and the second speaker assembly mounted on an opposite, second end of the headband, the headband being arranged to be worn on the head of a user.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:.

There will now be described a head wearable air purifier that provides several advantages over conventional wearable air purifiers. The term "air purifier" as used herein refers to a device or system capable of removing contaminants from air and emitting a supply of purified or filtered air. The term "head wearable" is used herein to define an item as being capable of or suitable for being worn on the head of a user.

The head wearable air purifier comprises a headphone system comprising a pair of speaker assemblies mounted on a headband. A first speaker assembly is mounted on a first end of the headband and a second speaker assembly is mounted on an opposite, second end of the headband. One or both of the first speaker assembly and the second speaker assembly then comprise a filter assembly, an impeller for creating an airflow through the filter assembly, a motor arranged to drive the impeller and an air outlet downstream from the filter assembly for emitting the filtered airflow from the speaker assembly. The impeller is a mixed flow impeller that has a generally conical or frusto-conical shape, and both the impeller and the motor are disposed within an impeller casing that is generally frusto-conical in shape. The head wearable air purifier then further comprises a nozzle arranged to receive the filtered airflow from one or both of the first speaker assembly and the second speaker assembly, the nozzle comprising an air outlet arranged to emit the received filtered airflow from the head wearable air purifier.

The term "headphones" as used herein refers to a pair of small loudspeakers, or speakers, joined by a headband that is designed to be worn on or around the head of a user. Typically, the speakers are provided by electroacoustic transducers that convert an electrical signal to a corresponding sound. Circumaural headphones, often referred to as full-size or over-ear headphones, have earpads whose shape is that of a closed loop (e.g. circular, elliptical etc.) so that they encompass the entire ear. Because these headphones completely surround the ear, circumaural headphones can be designed to fully seal against the head to attenuate external noise. Supra-aural headphones, often referred to as on-ear headphones, have earpads that press against the ears, rather than around them. This type of headphone generally tends to be smaller and lighter than circumaural headphones, resulting in less attenuation of outside noise.

The term "conical" as used herein refers to an object having the shape of a cone. The term "cone" as used herein refers to a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. The term "cone" therefore encompasses a a right circular cone that has a circular base and an axis that passes through the centre of the base at right angles to its plane. The perimeter of the base of a cone is called the "directrix", and each line between the directrix and apex is a "generatrix" or "generating line" of the conical surface of the cone. The term "frusto-conical" as used herein refers to an object having the shape of a frustocone, The term "frustocone" as used herein refers to the portion of a cone that remains when a region including its apex is cut off by a truncation plane that is parallel to the base of the cone. The term "frustocone" is synonymous with the terms "conical frustum" and encompasses a right circular conical frustum that has a circular base end and a circular top end, the diameter of the circular base end being greater than that of the circular top end, and a truncated conical surface extending between the base end and the top end.

<FIG>, <FIG> and <FIG> are external views of an embodiment of a head wearable air purifier <NUM>. The head wearable air purifier <NUM> comprises a pair of generally cylindrical speaker assemblies 1100a, 1100b connected by an arcuate headband <NUM>, and a nozzle <NUM> that extends between and is connected at opposite ends to both speaker assemblies 1100a, 1100b. <FIG> is a cross-sectional view of the air purifier <NUM> taken along the axis of the headband <NUM> and also shows a cross-section through the axis of the arcuate nozzle <NUM>, wherein the axis of a curve is the straight line that bisects the curve at right angles and divides the curve into two symmetrical portions. <FIG> then shows a side view of a speaker assembly <NUM> of the air purifier <NUM> of <FIG>, whilst <FIG> shows a perspective view of a speaker assembly <NUM> of the air purifier <NUM> of <FIG>, and <FIG> is a cross-sectional view through the speaker assembly <NUM> of <FIG> taken along line A-A.

In the illustrated embodiment, each end of the headband <NUM> is provided with an arcuate support arm 1201a, 1201b that is perpendicular to the headband <NUM> (i.e. such that the plane that is parallel to the length of the arcuate headband <NUM> is perpendicular to the plane that is parallel to the length of the arcuate support arm <NUM>). A first end of each support arm 1201a, 1201b is attached to a rear surface of the headband <NUM> such that the support arm 1201a, 1201b extends rearward and downward from the headband <NUM>. An opposite, second end of each support arm 1201a, 1201b is then provided with a socket or gudgeon 1202a, 1202b that faces forward.

As shown in <FIG>, each of the cylindrical speaker assemblies <NUM> are then provided with a mounting projection or pintle <NUM> that projects from an outer surface of the speaker assembly <NUM>. The socket/gudgeon 1202a, 1202b provided on each of the support arms <NUM> is configured to receive and retain the projection/pintle <NUM> that projects from the outer surface of the corresponding speaker assembly <NUM>. The engagement of the projections <NUM> within the sockets <NUM> provided on the support arms <NUM> therefore forms a gimbal or hinge that pivotally supports the speaker assemblies <NUM> when attached to the ends of headband <NUM>.

As shown in <FIG>, each of the pair of speaker assemblies <NUM> further comprises a speaker housing or enclosure <NUM> having an air inlet <NUM> and an air outlet or discharge port <NUM>, a speaker or driver unit <NUM> within the housing <NUM>, and an earpad <NUM> arranged to enclose the speaker <NUM> and to encompass or press against an ear of a user. In addition, each of the pair of speaker assemblies <NUM> further comprises a filter assembly <NUM> within speaker housing <NUM> and an impeller casing <NUM> within the speaker housing <NUM>. Disposed within the impeller casing <NUM> is an impeller <NUM> for creating an airflow through the filter assembly <NUM> and a motor <NUM> arranged to drive the impeller <NUM>. The air outlet or discharge port <NUM> is downstream (i.e. relative to the airflow generated by the impeller <NUM>) from the filter assembly <NUM> and is arranged to emit the filtered/purified airflow from the speaker assembly <NUM>. In the illustrated embodiment, the air outlet or discharge port <NUM> of each speaker assembly <NUM> is provided in a side of the speaker assembly <NUM>, with the air outlet or discharge port <NUM> of both speaker assemblies 1100a, 1100b being generally parallel with one another when attached to the ends of headband <NUM>.

<FIG> are perspective views of the speaker assembly of <FIG> at various levels of construction. As shown in <FIG> and <FIG>, the speaker housing <NUM> comprises a speaker chassis <NUM> upon which the speaker/driver unit <NUM> is mounted and a generally frusto-conical speaker cover <NUM> mounted on the speaker chassis <NUM> over the speaker <NUM>. In the illustrated embodiment, the speaker chassis <NUM> comprises a generally circular base 1111a that is surrounded by a cylindrical outer side wall 1111b and an arcuate inner side wall 1111c located concentrically within and adjacent to the outer side wall 1111b such that an arcuate slot is defined between the arcuate inner side wall 1111c and an adjacent portion of the cylindrical outer side wall 1111b. The air outlet or discharge port <NUM> is then defined by corresponding, aligned apertures formed in both the arcuate inner side wall 1111c and the cylindrical outer side wall 1111b.

A central portion of the base 1111a provides a driver support plate 1111d upon which the speaker/driver unit <NUM> can be located. The driver support plate 1111d of the speaker chassis <NUM> is provided with an array of apertures for allowing sound generated by the speaker/driver unit <NUM> to pass through the speaker chassis <NUM> into the space enclosed by earpad <NUM>. In addition, the driver support plate 1111d is angled or tilted relative to the peripheral portion of the base 1111a of the speaker chassis <NUM>. The angle or tilt of the driver support plate 1111d is chosen so that the speaker/driver unit <NUM> is substantially parallel with the ears when the head wearable air purifier <NUM> is worn on the head of a user with the speaker assembly <NUM> over the user's ear. For example, in the illustrated embodiment, the angle of the driver support plate 1111d relative to the peripheral portion of the base 1111a is from <NUM> to <NUM> degrees.

The speaker chassis <NUM> can also be provided with a number of ports 1111e that are configured to allow a small volume of air to pass between the outside of the speaker assembly <NUM> and the space behind the speaker/driver unit <NUM>. In the illustrated embodiment, the ports 1111e are provided in the base 1111a of the speaker chassis <NUM> and extend through the base 1111a from a point within the speaker chassis <NUM> that is adjacent to the central portion that provides the driver support plate 1111d to an outer surface of the cylindrical outer side wall 1111b.

In addition, a feedback microphone <NUM> for active noise cancellation (ANC) can be provided on the speaker chassis <NUM>. The feedback microphone <NUM> is arranged to provide data to a control circuit <NUM>, with the control circuit <NUM> then being configured to implement active noise cancellation (ANC) when controlling the speaker/driver unit <NUM>. In the illustrated embodiment, the feedback microphone <NUM> is disposed within a corresponding aperture 1111f provided in the driver support plate 1111c. For active noise cancellation (ANC) applications, a feedback microphone <NUM> is provided in the interior of the ear pad <NUM>, adjacent to the speaker/driver unit <NUM>, in order to acquire the sounds that are reaching the user so that any unwanted noise can be identified and cancelled out. A feedback microphone is therefore often referred to as an error microphone. Providing the speaker assembly <NUM> with a feedback microphone <NUM> is particular useful, as it provides that noise generated by the motor <NUM> and/or the impeller <NUM> can be detected by the feedback microphone <NUM> and cancelled out along with any other unwanted background or ambient noise.

In the illustrated embodiment, a control circuit <NUM> is disposed on or mounted to the peripheral portion of the speaker chassis <NUM>. The control circuit <NUM> therefore at least partially encircles the speaker/driver unit <NUM> (i.e. is disposed outside/around a periphery of the speaker/driver unit <NUM>)when the speaker/driver unit <NUM> is mounted on to the driver support plate 1111d. In the illustrated embodiment, the control circuit <NUM> comprises two arcuate circuit boards 1114a, 1114b; however, in alternative arrangements the control circuit <NUM> could equally comprise more than two arcuate circuit boards or a single arcuate or annular circuit board.

The control circuit <NUM> controls both the motor <NUM> and the speaker/driver unit <NUM> based on control inputs received from a user. The control circuit <NUM> also provides one or more wireless communication modules that allows the purifier <NUM> to connect to one or more wireless networks using Wi-Fi, Bluetooth or some other form of wireless personal area network (WPAN). A user of the purifier <NUM> can then wirelessly connect to and communicate with the purifier <NUM> using a personal computer device so that they can send and receive data to and from the purifier <NUM>, provide user inputs etc. The control circuit <NUM> may also have a wired connection (not shown) to a touch screen and/or one or more physical user control devices (not shown) that are provided on the purifier <NUM> and/or that are accessible to the user.

The speaker assembly <NUM> is also provided with a hollow, rigid outlet duct <NUM> that extends from the speaker housing <NUM> and that is arranged to connect the air outlet <NUM> of the speaker assembly <NUM> to an air inlet of the nozzle <NUM>. The rigid outlet duct <NUM> is further arranged so that it can revolve relative to the speaker housing <NUM>, around at least a portion of the periphery of the speaker housing <NUM>, so that the angle between the nozzle <NUM> and the headband <NUM> can be changed and so that the nozzle <NUM> can be stowed over the headband <NUM> when not in use, as illustrated in <FIG>.

Advantageously, the speaker assembly <NUM> is arranged so that the revolution of the rigid outlet duct <NUM> around the periphery of the speaker housing <NUM> is independent of the impeller casing <NUM>, such that it can revolve relative to both the speaker housing <NUM> and to the impeller casing <NUM>. This arrangement provides that the nozzle <NUM> can be rotated towards and stowed over the headband <NUM> when not in use without the need for any of the components that are internal to the speaker housing <NUM> to be rotatable relative to the speaker housing <NUM>, which would complicate the construction of the speaker assembly <NUM>.

In addition, the speaker assembly <NUM> is arranged so that the revolution of the rigid outlet duct <NUM> around the periphery of the speaker housing <NUM> causes the rigid outlet duct <NUM> to move away from the earpad <NUM>. This arrangement provides when the nozzle <NUM> is rotated towards the headband <NUM> the rigid outlet ducts <NUM> that extend from each of the first speaker assembly 1100a and the second speaker assembly 1100b move away from each other such that the opposing ends of the nozzle <NUM> are splayed/spread apart to enable nozzle <NUM> fit over the headband <NUM> when in the stowed position. Preferably, the speaker assembly <NUM> is arranged so that the revolution of the rigid outlet duct <NUM> around the periphery of the speaker housing <NUM> also causes the rigid outlet duct <NUM> to roll around its longitudinal axis to further spread the opposing ends of the nozzle <NUM>. This spreading of the nozzle <NUM> when revolved is advantageous as it allows the nozzle <NUM> to be fit more closely to the user's face when in use and then expand as it moves into the stowed position to enable nozzle <NUM> fit over the headband <NUM>.

In the illustrated embodiment, the rigid outlet duct <NUM> is arranged so that it can revolve between a first end position and a second end position. In the first end position the rigid outlet duct <NUM> is generally aligned with the air outlet <NUM> of the speaker assembly <NUM>, as illustrated in <FIG>. Specifically, in the first end position, a first open end of the rigid outlet duct <NUM> (i.e. that is proximal/adjacent to the air outlet <NUM> of the speaker assembly <NUM>) is generally aligned with the air outlet <NUM> of the speaker assembly <NUM> such that any air flow emitted from the air outlet <NUM> of the speaker assembly <NUM> will pass into the rigid outlet duct <NUM>. In the second end position, the rigid outlet duct <NUM> is generally parallel with the headband <NUM> and will therefore not be aligned with the air outlet <NUM> of the speaker assembly <NUM>, as illustrated in <FIG>. The purifier <NUM> is therefore also provided with a sensor (not shown) that detects when the rigid outlet duct <NUM> of one or both of the first speaker assembly 1100a and the second speaker assembly 1100b is not aligned with the corresponding air outlet <NUM> and automatically turns off the motor <NUM>.

In order to allow for the position of the nozzle <NUM> relative to the headband <NUM> to be adjusted whilst maintaining the flow of purified air from the speaker assemblies 1100a, 1100b, the angular extension of the first open end of the rigid outlet duct <NUM> is greater than that of the air outlet <NUM> of the speaker assembly <NUM>. This allows the fluidic connection between the rigid outlet duct <NUM> and the air outlet <NUM> of the speaker assembly <NUM> to be maintained even when the rigid outlet duct <NUM> is revolved away from the first end position by a small angle/distance. For example, in the illustrated embodiment a central angle of the arcuate first open end of the rigid outlet duct <NUM> is from <NUM> to <NUM> degrees greater than a central angle of the arcuate air outlet <NUM> of the speaker assembly <NUM>.

In the illustrated embodiment, the first open end of the rigid outlet duct <NUM> is provided with a flange (not shown) that projects around the periphery of the first open end of the rigid outlet duct <NUM> and that is arranged to fit and slide within the arcuate slot defined between the arcuate inner side wall 1111c and an adjacent portion of the cylindrical outer side wall 1111b. The sliding of the rigid outlet duct <NUM> within the arcuate slot therefore results in the revolution of the rigid outlet duct <NUM> around a portion of the periphery of the speaker housing <NUM> without any corresponding rotation of the impeller casing <NUM>.

The aperture formed in the cylindrical outer side wall 1111b that partially defines the air outlet <NUM> therefore extends partially around the circumference of the speaker housing <NUM> in order to define a track <NUM> that guides the revolution of the rigid outlet duct <NUM> around a portion of the periphery of the speaker housing <NUM>. The track <NUM> is arranged so that as it extends from the first end position to the second end position it moves away from the earpad <NUM> so that when the nozzle <NUM> is rotated towards the headband <NUM> the rigid outlet ducts <NUM> that extend from each of the first speaker assembly 1100a and the second speaker assembly 1100b move away from each other. Consequently, this rotation of the nozzle <NUM> towards the headband <NUM> causes the opposing ends of the nozzle <NUM> to splay/spread apart to enable nozzle <NUM> fit over the headband <NUM> when in the stowed position, as illustrated in <FIG>.

The generally frusto-conical speaker cover <NUM> is then mounted on the speaker chassis <NUM> over the entirety of the driver support plate 1111c such that the speaker/driver unit <NUM> is covered by the speaker cover <NUM>. In the illustrated embodiment, the speaker cover <NUM> is arranged so as to only cover the driver support plate 1111c, such that the peripheral portion of the base 1111a and the two arcuate circuit boards 1114a, 1114b mounted thereon are not covered by the speaker cover <NUM>, but such that the inner ends of the ports 1111e are covered by the speaker cover <NUM>. In the illustrated embodiment, the speaker cover <NUM> is formed with a number of concave depressions or dimples 112a that increase the rigidity of the speaker cover <NUM> to minimize vibration of the speaker cover <NUM>.

As shown in <FIG>, <FIG>, the generally frusto-conical impeller casing <NUM> containing both the impeller <NUM> and the motor <NUM> is then disposed over the speaker cover <NUM> so that speaker/driver unit <NUM> is nested within a recess or cavity defined by a back/rear of the impeller casing <NUM>. The speaker cover <NUM> and the speaker/driver unit <NUM> are therefore both partially disposed within the recess defined by the back/rear of the impeller casing <NUM>.

<FIG> shows a perspective view of the impeller casing <NUM> without the impeller <NUM> and the motor <NUM>, and <FIG> is a cross-sectional view of <FIG>. <FIG> is then a cross-sectional side view through the impeller casing <NUM> without the impeller <NUM> and the motor <NUM>, whilst <FIG> is a cross-sectional side view through the impeller casing <NUM> with both the impeller <NUM> and the motor <NUM> disposed inside. The impeller casing <NUM> is generally frusto-conical and the rear/back side of the impeller casing <NUM> defines a generally frusto-conical recess <NUM> having an open large diameter end and a closed small diameter end. The open large diameter end of the recess <NUM> is proximate to the trailing edge of the impeller <NUM> whilst the closed small diameter end of the recess <NUM> is proximate to the leading edge of the impeller <NUM>.

Specifically, in the illustrated embodiment, the impeller <NUM> is a mixed flow, unshrouded impeller, and the motor <NUM> is disposed within the hub of the impeller <NUM>. The impeller casing <NUM> then provides an impeller housing <NUM> surrounding the impeller <NUM> and the motor <NUM>, and a vaneless diffuser that fluidically connects a base of the impeller housing <NUM> to an annular volute <NUM> that is arranged to receive the air exhausted from the impeller housing <NUM>. The rear/back side of the impeller housing <NUM> defines an inner portion of the generally frusto-conical recess <NUM> and comprises the closed small diameter end of the recess <NUM>. The impeller housing <NUM> is provided with an air inlet <NUM> through which air can be drawn by the impeller <NUM> and an air outlet <NUM> through which the air is emitted from the impeller housing <NUM> into the annular volute <NUM>. The air inlet <NUM> of the impeller housing <NUM> is provided by an aperture/opening at the small diameter end of the impeller housing <NUM> and the air outlet <NUM> is provided by an annular slot formed around a large diameter end or base of the impeller housing <NUM>. In the illustrated embodiment, the angle (θ<NUM>) between the air outlet <NUM> of the impeller housing <NUM> and a central axis (X) of the impeller housing <NUM> is approximately <NUM> degrees; however, this angle (θ<NUM>) could be from <NUM> to <NUM> degrees, is preferably from <NUM> to <NUM> degrees, and is more preferably from <NUM> to <NUM> degrees.

The annular volute <NUM> comprises a spiral (i.e. gradually widening) duct that is arranged to receive the air exhausted from the impeller housing <NUM> and to guide the air to an air outlet <NUM> of the volute <NUM>. The air outlet <NUM> of the volute <NUM> is then fluidically connected to the air outlet <NUM> of the speaker assembly <NUM>. The term "volute" as used herein refers to a spiral funnel that receives the fluid being pumped by an impeller and increases in area as it approaches a discharge port. The air outlet <NUM> of the volute <NUM> therefore provides an efficient and quiet means for collecting the air that is exhausted from the circumferential annular slot that that forms the air outlet <NUM> of the impeller housing <NUM>. In the illustrated embodiment, the annular volute <NUM> comprises a partially planar front surface 1118a and an angle of the planar portion of the front surface 1118a of the volute relative to the central axis of the impeller housing <NUM> is acute. The annular volute <NUM> therefore has a non-circular cross-section. In the illustrated embodiment, the angle (Θs) between the planar portion of the front surface of the volute <NUM> and the central axis (X) of the impeller housing <NUM> is approximately <NUM> degrees; however, this angle (Θs) could be from <NUM> to <NUM> degrees, is preferably from <NUM> to <NUM> degrees, and is more preferably from <NUM> to <NUM> degrees. In the illustrated embodiment, the annular volute <NUM> further comprises a partially planar rear/back surface 1118b wherein the planar portion of the rear/back surface 1118b is generally perpendicular to the central axis (X) of the impeller housing <NUM>.

In the embodiment illustrated in <FIG>, the impeller casing <NUM> comprises a front casing section <NUM> that is attached to a rear/back casing section <NUM>, such that the impeller housing <NUM> and the volute <NUM> are integrally formed with one another. <FIG> therefore shows a perspective view of the rear/back casing section <NUM>, whilst <FIG> shows a perspective view of the front casing section <NUM>.

As shown in <FIG>, the impeller <NUM> and the motor <NUM> are disposed between the front casing section <NUM> and the rear/back casing section <NUM>, such that the impeller <NUM> and the motor <NUM> are housed/accommodated within a space defined between the front casing section <NUM> and the rear/back casing section <NUM>. The front casing section <NUM> is therefore arranged to be disposed over a front of the impeller <NUM> and the rear/back casing section <NUM> is arranged to be disposed over the back of the impeller <NUM> and the motor <NUM>. In particular, both the front casing section <NUM> and the rear casing section <NUM> have a generally frusto-conical shape with the front casing section <NUM> being configured to fit closely over the front of the impeller <NUM>, whilst the rear casing section <NUM> then generally conforms to the back of the impeller <NUM> whilst also providing space to accommodate the motor <NUM>. The front casing section <NUM> therefore also comprises the aperture that provides the air inlet <NUM> of the impeller casing <NUM>, whilst the rear casing section <NUM> forms the rear/back side of the impeller casing <NUM> that defines the generally frusto-conical recess <NUM>.

As shown in <FIG>, the rear casing section <NUM> is generally circular and comprises a generally frustoconical raised central portion <NUM> that has a circular through hole <NUM> provided at the centre. The rear casing section <NUM> is also provided with a raised rim <NUM> that extends around approximately three quarters of the periphery of the rear casing section <NUM> such that there is a gap between a first end of the rim <NUM> and an opposite, second end of the rim <NUM>. The raised central portion <NUM> and the raised rim <NUM> therefore define a depression or trough <NUM> between them that spirals outwardly (i.e. gradually widens) towards an opening provided by the gap between the first end of the rim <NUM> and the second end of the rim <NUM>.

As shown in <FIG>, the front casing section <NUM> is also generally circular and comprises a generally frustoconical raised central portion <NUM> that has a circular through-hole <NUM> provided at the centre. The front casing section <NUM> is then provided with an impression or indentation <NUM> that spirals outwardly (i.e. gradually widens) around the raised central portion <NUM> towards an opening provided by a gap in a rim <NUM> formed around the periphery of the front casing section <NUM> by the spiral indentation <NUM>. The rim <NUM> extends around approximately three quarters of the periphery of the front casing section <NUM>, such that the gap is formed between a first end of the rim <NUM> and an opposite, second end of the rim <NUM>.

As described above, the impeller housing <NUM> formed by the front casing section <NUM> and the rear casing section <NUM> houses the the impeller <NUM> and the motor <NUM>. In the illustrated embodiment, the impeller <NUM> and the motor <NUM> are therefore housed within the impeller housing <NUM> that is defined by the frustoconical raised central portion <NUM> of the rear casing section <NUM> and the frustoconical raised central portion <NUM> of the front casing section <NUM>. The space between the frustoconical raised central portion <NUM> of rear casing section <NUM> and the frustoconical raised central portion <NUM> of the front casing section <NUM> is sufficient to house the impeller <NUM> and the motor <NUM>, and is shaped so that the impeller <NUM> is in close proximity to, but does not contact, an inner surface of the frustoconical raised central portion <NUM> of the front casing section <NUM>. The centre of the frustoconical raised central portion <NUM> of the rear casing section <NUM> therefore provides a motor support seat upon which the motor <NUM> is disposed, whilst the circular through-hole <NUM> provided at the centre of the front casing section <NUM> provides the air inlet <NUM> through which air can be drawn into the impeller casing <NUM> by the impeller <NUM>.

The gaps formed in the rims <NUM>, <NUM> of the front casing section <NUM> and the rear casing section <NUM> respectively are then aligned with one another when the front casing section <NUM> and the rear casing section <NUM> are connected together so as to form the air outlet <NUM> of the volute <NUM>, which is then fluidically connected to the air outlet <NUM> of the speaker assembly <NUM>. In addition, when the front casing section <NUM> and the rear casing section <NUM> are connected together, the spiral depression <NUM> formed in the rear casing section <NUM> and the spiral impression <NUM> formed in the front casing section <NUM> together define the spiral duct of the volute <NUM> that is arranged to receive the air exhausted from the impeller housing <NUM> and to guide the air to the air outlet <NUM> of the volute <NUM>.

As described above, the impeller <NUM> is a mixed flow impeller that has a generally conical or frusto-conical shape. The impeller <NUM> is hollow such that a rear/back side of the impeller <NUM> defines a generally frusto-conical recess <NUM> having an open large diameter end and a closed small diameter end. The open large diameter end of the recess <NUM> is proximate to the trailing edge of the impeller <NUM> whilst the closed small diameter end of the recess is proximate to the leading edge of the impeller <NUM>. The motor <NUM> is then nested/disposed within the closed small diameter end of the recess <NUM>. Preferably, the impeller <NUM> is a semi-open/semi-closed mixed flow impeller i.e. having a back shroud <NUM> only. The back shroud <NUM> of the impeller then defines the recess <NUM> within which the motor <NUM> is nested/disposed. In the illustrated embodiment, the motor <NUM> is a DC brushless motor having a speed which is variable by the control circuit <NUM>.

In the illustrated embodiment, the angle between the trailing edge of the impeller <NUM> and a central axis (X) of the impeller <NUM> corresponds to/is the same as the angle (θ<NUM>) defined between the air outlet <NUM> of the impeller housing <NUM> and the central axis (X) of the impeller housing <NUM>. The angle (θ<NUM>) between the trailing edge of the impeller <NUM> and the central axis (X) of the impeller <NUM> is therefore approximately <NUM> degrees; however, this angle (θ<NUM>) could be from <NUM> to <NUM> degrees, is preferably from <NUM> to <NUM> degrees, and is more preferably from <NUM> to <NUM> degrees.

In the illustrated embodiment, the back shroud <NUM> of the impeller <NUM> is curved so that it widens or flares outwardly from the the leading edge to the trailing edge. In particular, in the illustrated embodiment, the closed small diameter end of the back shroud <NUM> of the impeller <NUM> is generally cylindrical in shape so that this fits closely over the generally cylindrical motor <NUM>. Consequently, the portion of the back shroud <NUM> of the impeller <NUM> that is adjacent to the closed small diameter end is generally parallel with the central axis (X) of the impeller <NUM> so as to define a generally cylindrical small diameter end. The back shroud <NUM> of the impeller <NUM> then curves outwardly so that angle of the back shroud <NUM> of the impeller <NUM> relative to the central axis (X) gradually increases towards the trailing edge of the impeller <NUM>.

The impeller casing <NUM> is then supported/suspended within the speaker housing <NUM> by a plurality of resilient supports <NUM> that reduce the transmission of vibrations from the impeller casing <NUM> to the speaker housing <NUM>. To do so, the plurality of resilient supports <NUM> each comprise a resilient material such as an elastomeric or rubber material. In particular, it is preferable that the resilient supports <NUM> each have a Shore A hardness of <NUM> or less, preferably <NUM> or less, and more preferably of from <NUM> to <NUM>. In the illustrated embodiments, the only direct connection between the speaker housing <NUM> and the impeller casing <NUM> is provided by the resilient supports <NUM>.

<FIG>, <FIG> illustrate a first embodiment of the plurality of resilient supports <NUM> that support/suspend the impeller casing <NUM> within the speaker housing <NUM>. <FIG>, <FIG> then illustrate an alternative, second embodiment of the plurality of resilient supports <NUM> that support/suspend the impeller casing <NUM> within the speaker housing <NUM>.

In the embodiment illustrated in <FIG>, <FIG>, the plurality of resilient supports <NUM> comprise three lower resilient supports 1134a, 1134b and three upper resilient supports 1134c. The three lower resilient supports 1134a, 1134b extend radially between an inner surface/side wall of the speaker housing <NUM> and an outer surface of the impeller casing <NUM>. Specifically, the three lower resilient supports 1134a, 1134b extend radially between an inner surface/side wall of the speaker housing <NUM> and an outer peripheral surface of the annular volute <NUM>. The three upper resilient supports 1134c then extend radially between an outer surface of the impeller casing <NUM> and a lower surface of the filter assembly <NUM> that is disposed over the impeller casing <NUM>, and which will be described in more detail below. Specifically, the three upper resilient supports 1134c extend radially between an outer surface of the impeller housing <NUM> and a lower surface of the filter assembly <NUM>.

Two of the three lower resilient supports then each comprise a radially damping profile damper 1134a. The term "profile damper" as used herein refers to a device that is arranged to dissipate kinetic energy and particularly vibrations by deformation of the profile of the device. A radially damping profile damper is therefore a profile damper that is arranged to deform radially, whilst an axially damping profile damper is a profile damper that is arranged to deform axially.

In the embodiment illustrated in <FIG>, <FIG>, each radially damping profile damper 1134a comprises a tube of resilient material that is connected/attached to an inner surface/side wall of the speaker housing <NUM> and that then presses/compresses against an outer surface of the impeller casing <NUM>. In particular, the tube of resilient material is connected/attached to an inner surface/side wall of the speaker housing <NUM> at a first location on an outer surface the tube and then presses/compresses against an outer surface of the impeller casing <NUM> at a diametrically opposed, second location on the outer surface of the tube. In the illustrated embodiment, each radially damping profile damper 1134a comprises a non-circular tube of resilient material that has a rectangular cross section; however, each profile damper could alternatively comprise a tube of resilient material having a circular or other quadrilateral cross section.

As illustrated in <FIG> and <FIG>, the third of the lower resilient supports is then provided by a resilient duct 1134b that is sealed around the air outlet <NUM> of the impeller casing <NUM> (e.g. is sealed to or against a surface surrounding the air outlet <NUM> of the impeller casing <NUM>) and extends from the air outlet <NUM> of the impeller casing <NUM> towards the air outlet <NUM> of the speaker housing <NUM>. The resilient duct 1134b then also forms a seal around the air outlet <NUM> of the speaker housing <NUM> so that the airflow generated by impeller <NUM> is conveyed from the impeller casing <NUM> and out through the air outlet <NUM> of the speaker housing <NUM>. In the illustrated embodiment, the resilient duct 1134b comprises a connecting portion 1134b1 that is connected around the air outlet <NUM> of the impeller casing <NUM> and a skirt portion 1134b2 that is arranged to contact the surface surrounding the air outlet <NUM> of the speaker housing <NUM> to form the seal around the air outlet <NUM> of the speaker housing <NUM>. In addition, the resilient duct 1134b further comprises a damping portion 1134b3 that is configured to further reduce the transmission of vibrations from the impeller casing <NUM> to the speaker housing <NUM>. This damping portion 1134b3 comprises an integral axially damping profile damper that is provided by a bulge or dilation formed around a circumference of the resilient duct 1134b.

In the embodiment illustrated in <FIG>, the plurality of resilient supports <NUM> comprise three lower resilient supports 1134d, 1134e and four upper resilient supports 1134c. The three lower resilient supports 1134d, 1134e extend radially between an inner surface/side wall of the speaker housing <NUM> and an outer surface of the impeller casing <NUM>. Specifically, the three lower resilient supports 1134d, 1134e extend radially between an inner surface/side wall of the speaker housing <NUM> and an outer peripheral surface of the annular volute <NUM>. The four upper resilient supports 1134c then extend radially between an outer surface of the impeller casing <NUM> and a lower surface of the filter assembly <NUM> that is disposed over the impeller casing <NUM>, and which will be described in more detail below. Specifically, the four upper resilient supports 1134c extend radially between an outer surface of the impeller housing <NUM> and a lower surface of the filter assembly <NUM>.

In the embodiment illustrated in <FIG>, the three lower resilient supports 1134d, 1134e are mounted to a jacket or cover <NUM> that is mounted/disposed over a lower portion of the impeller casing <NUM>. Preferably the jacket <NUM> is formed of a resilient material thereby providing that the lower resilient supports 1134d, 1134e can be mounted to the impeller casing <NUM> merely by stretching the jacket <NUM> over the lower portion of the impeller casing <NUM>. In addition, where impeller casing <NUM> is formed from two separate parts, forming the jacket <NUM> from a resilient material also provides that the jacket <NUM> can act as a seal around the joint (i.e. act as a joint sleeve) between the two parts. In the illustrated embodiment, the three lower resilient supports 1134d, 1134e are integrally formed with the jacket <NUM>, which ensures that the three lower resilient supports 1134d, 1134e are securely mounted on the impeller casing <NUM>. However, the lower resilient supports 1134d, 1134e and the jacket <NUM> could be formed separately, with the lower resilient supports 1134d, 1134e then being attached to the jacket <NUM>, e.g. using an adhesive.

In the embodiment illustrated in <FIG>, the jacket <NUM> is disposed over the outer peripheral surface of the annular volute <NUM> and the air outlet <NUM>. Two of the three lower resilient supports 1134d then each comprise a multi-directional damper. In particular, two of the three lower resilient supports 1134d each comprise a connector portion that is arranged to connect to an inner surface/side wall of the speaker housing <NUM> and a damping portion that extends between the connector portion and the jacket <NUM>. The damping portion is formed with a narrow neck or intermediate portion. Specifically, the damping portion tapers in two-dimensions from the distal ends of the damping portion to form the narrow neck intermediate between the distal ends of the damping portion. The narrow neck of the damping portion provides for multi-directional damping of vibrations but also provide that the stiffness of the damping portion increases as the deflection increases so as to prevent the impeller casing <NUM> from contacting the sides of the speaker housing <NUM> when exposed to significant 'shock' (i.e. from being dropped).

As illustrated in <FIG>, <FIG>, the third of the lower resilient supports 1134e is then provided by a resilient duct that is sealed around the air outlet <NUM> of the impeller casing <NUM> (e.g. is sealed to or against a surface surrounding the air outlet <NUM> of the impeller casing <NUM>) and extends from the air outlet <NUM> of the impeller casing <NUM> towards the air outlet <NUM> of the speaker housing <NUM>. The resilient duct then also forms a seal around the air outlet <NUM> of the speaker housing <NUM> so that the airflow generated by impeller <NUM> is conveyed from the impeller casing <NUM> and out through the air outlet <NUM> of the speaker housing <NUM>. In the embodiment illustrated in <FIG>, the resilient duct 1134e comprises a connecting portion 1134b1 that is connected around the air outlet <NUM> of the impeller casing <NUM> and a skirt portion 1134b2 that is arranged to contact the surface surrounding the air outlet <NUM> of the speaker housing <NUM> to form the seal around the air outlet <NUM> of the speaker housing <NUM>. In addition, the resilient duct 1134b further comprises a damping portion 1134b3 that is configured to further reduce the transmission of vibrations from the impeller casing <NUM> to the speaker housing <NUM>. This damping portion 1134b3 comprises an integral axially damping profile damper that is provided by a bulge or dilation formed around a circumference of the resilient duct 1134b.

The filter assembly <NUM> is then mounted to the speaker chassis <NUM> so that the filter assembly <NUM> is provided upstream of the impeller <NUM> and is arranged to be nested over the impeller casing <NUM>. The filter assembly <NUM> comprises a filter seat <NUM> supporting one or more filter elements <NUM>, <NUM>. The filter seat <NUM> is provided with a plurality of apertures <NUM> that allow air to pass from a front surface of the filter seat <NUM> to a rear/back surface of the filter seat <NUM>, with the front surface being arranged to support the filter elements <NUM>, <NUM> over the plurality of apertures <NUM>. The filter seat <NUM> then further defines an air passageway or channel <NUM> between the rear/back surface of the filter seat <NUM> and the air inlet <NUM> of the impeller casing <NUM> that is arranged to guide air to the air inlet <NUM> of the impeller casing <NUM>. This air passageway <NUM> is provided by a cavity defined between the rear/back surface of the filter seat <NUM> and a front surface of the impeller casing <NUM>. Air must therefore pass through the filter elements <NUM>, <NUM> before it can pass through the apertures <NUM> in the filter seat <NUM> and into the air passageway <NUM> that leads to the air inlet <NUM> of the impeller casing <NUM>.

In the illustrated embodiment, the filter seat <NUM> is mounted to the speaker chassis <NUM> and located over the impeller housing <NUM>, with the impeller housing <NUM> partially disposed within a volume defined by a back of the filter seat <NUM>. In particular, the filter seat <NUM> comprises a generally frusto-conical peripheral portion 1135a and a generally cylindrical central portion 1135b. The generally frusto-conical peripheral portion 1135a of the filter seat <NUM> is provided with the plurality of apertures <NUM> and is arranged to support one or more generally frusto-conical filter elements <NUM>, <NUM> over the plurality of apertures <NUM>. The impeller housing <NUM> is then at least partially disposed within the generally cylindrical central portion 1135b of the filter seat <NUM>. In particular, the air inlet <NUM> of impeller housing <NUM> is disposed within a volume defined by a back of the cylindrical central portion 1135b of the filter seat <NUM>.

As shown in <FIG> and <FIG>, the generally frusto-conical filter elements <NUM>, <NUM> are arranged to fit over and be supported upon the filter seat <NUM>. To do so, the one or more generally frusto-conical filter elements <NUM>, <NUM> are open. In other words, the filter elements <NUM>, <NUM> are provided as hollow frustacones with open ends, such that the filter elements <NUM>, <NUM> each have an open large diameter end and an open small diameter end that forms a central opening in the filter elements <NUM>, <NUM>. In addition, the angle (θ<NUM>) between the frusto-conical peripheral portion 1135a and the central axis (Y) of the filter seat <NUM> is the same as the angle (θ<NUM>) between the upper and lower surfaces of each of the generally frusto-conical filter elements <NUM>, <NUM> and the central axis (Y) of the generally frusto-conical filter elements <NUM>, <NUM>.

In the illustrated embodiment, the angle (θ<NUM>) between the frusto-conical peripheral portion 1135a and the central axis (Y) of the filter seat <NUM> is approximately the same as the angle (Θs) between the planar portion of the front surface of the volute <NUM> and the central axis (X) of the impeller housing <NUM>. Consequently, the angle (θ<NUM>) between the frusto-conical peripheral portion 1135a and the central axis (Y) of the filter seat <NUM> is approximately <NUM> degrees; however, this angle (θ<NUM>) could be from <NUM> to <NUM> degrees, is preferably from <NUM> to <NUM> degrees, and is more preferably from <NUM> to <NUM> degrees.

In the illustrated embodiment, the filter assembly <NUM> comprises both a particulate filter element <NUM> and a chemical filter element <NUM>, with the particulate filter element <NUM> located upstream relative to the chemical filter element <NUM>. The generally frusto-conical particulate filter element <NUM> comprises a pleated particulate filter media 1136a that is arranged to be frustoconical in shape with the pleats/folds of the pleated filter media 1136a at an acute angle (θ<NUM>) relative to a central axis (Y) of the particulate filter element <NUM> and both the inner and outer ends/edges of the pleated filter media 1136a parallel to the central axis (Y) of the particulate filter element <NUM>. The entirety of both ends/edges of the pleated filter media 1136a are then disposed within a seal 1136b of resilient material that extends parallel to the central axis (Y) of the particulate filter element <NUM>. For example, the resilient material could be any of synthetic rubber, polyurethane, silicone rubber, ethylene-vinyl acetate (EVA), polyolefins (PO) etc..

As shown in <FIG> and <FIG>, the speaker housing <NUM> further comprises an outer cover <NUM> that is mounted onto the speaker chassis <NUM>. This outer cover <NUM> is arranged to fit over (and therefore generally conforms to) the filter assembly <NUM> and is provided with an array of apertures <NUM> that allow air to pass through the outer cover <NUM> and that therefore define an air inlet of the outer cover <NUM>. These apertures <NUM> are sized to prevent larger particles from passing through to the filter assembly <NUM> and blocking, or otherwise damaging, the filter elements <NUM>, <NUM>. Alternatively, in order to allow air to pass through, the outer cover <NUM> could comprise one or more grilles or meshes mounted within windows in the outer cover <NUM>. It will also be clear that alternative patterns of arrays are envisaged within the scope of the present invention.

The outer cover <NUM> is releasably attached to the speaker chassis <NUM> so as to cover the filter assembly <NUM>. For example, the outer cover <NUM> could be attached to the speaker chassis <NUM> using cooperating screw threads provided on the outer cover <NUM> and the speaker chassis <NUM> and/or using some catch mechanism. When mounted on speaker chassis <NUM>, the outer cover <NUM> protects the filter elements <NUM>, <NUM> from damage, for example during transit, and also provides a visually appealing outer surface covering the filter assembly <NUM>, which is in keeping with the overall appearance of the purifier <NUM>. In addition, the outer cover <NUM> is arranged such that, when attached to the speaker chassis <NUM>, the outer cover <NUM> compresses the resilient edge seals 1136b that encompass the ends/edges of the pleated filter media 1136a of the particulate filter element <NUM> against the filter seat <NUM>. The compression of these edge seals 1136b prevents air from reaching the apertures <NUM> provided in the filter seat <NUM> without first passing through the filter elements <NUM>, <NUM>.

In the illustrated embodiment, the outer cover <NUM> is provided as a hollow frustacone with open ends. The open large diameter end of the outer cover <NUM> is arranged to fit over the periphery of the large diameter end of the filter assembly <NUM>, whilst the open small diameter end of the outer cover <NUM> is arranged fit over both the periphery of the small diameter end of the filter assembly <NUM> and the generally cylindrical central portion 1135b of the filter seat <NUM>. A circular front surface 1135c of the generally cylindrical central portion 1135b of the filter seat <NUM> is therefore exposed within the open small diameter end of the outer cover <NUM> and thereby forms a portion of the outer surface of the speaker assembly <NUM>. Preferably, the circular front surface 1135c of the filter seat <NUM> is transparent and thereby forms a window through which the user to see the spinning of the impeller <NUM> through the air inlet <NUM> of the impeller casing <NUM>. This allows the user to visually check the speed of the impeller <NUM> and to confirm that the impeller <NUM> is functioning appropriately.

In addition, in the illustrated embodiment a feedforward microphone <NUM> for active noise cancellation (ANC) is provided on the inner surface of the circular front surface 1135c of the filter seat <NUM>. The feedforward microphone <NUM> is arranged to provide data to the control circuit <NUM>, with the control circuit <NUM> then being configured to implement active noise cancellation (ANC) when controlling the speaker/driver unit <NUM>. For active noise cancellation (ANC) applications, a feedforward microphone is provided towards the exterior of the speaker assembly in order to detect any background or ambient noise so that this can be cancelled out using the sound generated by the speaker. A feedforward microphone is therefore often referred to as a reference microphone. Providing the speaker assembly <NUM> with a feedforward microphone <NUM> is particular useful, as it provides that noise generated by the motor <NUM> and/or the impeller <NUM> can be detected by the feedforward microphone <NUM> and cancelled out along with any other unwanted background or ambient noise. When both a feedback microphone <NUM> and a feedforward microphone <NUM> are present, it is possible to combine both the feedforward and feedback approaches and implement hybrid ANC, which exhibits a synergistic performance improvement over the independent feedforward and feedback approaches.

As described above, the impeller casing <NUM> is supported/suspended within the speaker housing <NUM> by a plurality of resilient supports <NUM> that, in the illustrated embodiment, comprise three lower resilient supports 1134a, 1134b and three upper resilient supports 1134c. The three upper resilient supports 1134c extend radially between an outer surface of the impeller casing <NUM> and a rear/back surface of the filter assembly <NUM> that is disposed over the impeller casing <NUM>.

The three upper resilient supports 1134c each comprise a radially damping profile damper. Each of these radially damping profile dampers 1134c comprises a tube of resilient material that is mounted between the outer surface of the impeller casing <NUM> and the lower/inner surface of the filter assembly <NUM>. In the illustrated embodiment, each radially damping profile damper 1134c comprises a tube of resilient material that has a circular cross section; however, each profile damper could alternatively comprise a tube of resilient material having a non-circular cross section.

In the illustrated embodiment, each of the tubes 1134c of resilient material is connected between an inner collar/ring <NUM> that is disposed over the front surface of the impeller casing <NUM> and an outer collar/ring <NUM> that contacts the rear/back surface of the filter assembly <NUM>. In particular, each tube of resilient material 1134c is connected to the inner ring <NUM> at a first location on a periphery of the tube and connected to the outer ring <NUM> at a diametrically opposed, second location on the periphery of the tube. The inner ring <NUM> is disposed within a recess <NUM> formed around the periphery of the impeller casing <NUM>, specifically around the periphery of the frustoconical raised central portion <NUM> of the impeller casing <NUM>, and is thereby retained on the front surface of the impeller casing <NUM>. The recess <NUM> is configured to receive and contain at least a substantial proportion of the inner ring <NUM> so that this does not obstruct the flow of air through the air passageway <NUM>.

A hollow nozzle <NUM> is then attached to both the first speaker assembly 1100a and the second speaker assembly 1100b and is arranged so that it can receive both the filtered airflow generated by the first speaker assembly 1100a and the filtered airflow generated by the second speaker assembly 1100b. The air purifier <NUM> is therefore arranged so that the attached nozzle <NUM> can be fluidically connected to both the air outlet 1104a of the first speaker assembly 1100a and the air outlet 1104b of the second speaker assembly 1100b.

<FIG> shows a perspective view of the nozzle <NUM> when detached from the speaker assemblies 1100a, 1100b. In the illustrated embodiment, the nozzle <NUM> essentially comprises an elongate, hollow tube that is arranged so that it can be fluidically connected between the air outlet 1104a of the first speaker assembly 1100a and the air outlet 1104b of the second speaker assembly 1100b, with a first air inlet or ingress port <NUM> being provided by a first open end of the nozzle <NUM> and a second air inlet or ingress port <NUM> being provided by an opposite, second open end of the nozzle <NUM>. The first air inlet or ingress port <NUM> of the nozzle <NUM> is therefore arranged to be able to receive the filtered airflow emitted from the air outlet 1104a of the first speaker assembly 1100a and the second air inlet or ingress port <NUM> of the nozzle <NUM> is arranged to be able to the receive the filtered airflow emitted from the air outlet 1104b of the second speaker assembly 1100b.

As shown in <FIG>, the first open end <NUM> of the nozzle <NUM> is connected to the rigid outlet duct <NUM> that extends from the speaker housing <NUM> of the first speaker assembly 1100a. The nozzle <NUM> then extends away from the first speaker assembly 1100a and assumes an arcuate shape so that the opposite, second end <NUM> of the nozzle <NUM> connects to the rigid outlet duct <NUM> that extends from the speaker housing <NUM> of the second speaker assembly 1100b. It is therefore preferable that at least a portion of the nozzle <NUM> is formed of a flexible/resilient material so that the nozzle <NUM> can bend and flex as the first and second speaker assemblies 1100a, 1100b move relative to one another. For example, in the illustrated embodiment, a central portion <NUM> (i.e. a portion located around the midpoint of the length of the nozzle <NUM>) is made from a flexible, transparent plastic such as a polyurethane, whilst the two end portions <NUM>, <NUM> are each made from a rigid, transparent plastic such as a polyethylene terephthalate glycol-modified (PETG). Alternatively, the entire nozzle <NUM> could be formed from one or more flexible/resilient materials.

As described above, in the illustrated embodiment, the rigid outlet ducts <NUM> are arranged so that they can revolve between a first end position in which a first open end of the rigid outlet duct <NUM> is aligned with the air outlet <NUM> of the corresponding speaker assembly <NUM> and a second end position in which the rigid outlet duct <NUM> is not aligned with the air outlet <NUM> of the speaker assembly <NUM>. The attached nozzle <NUM> can therefore move between a first end position in which it is fluidically connected to both the air outlet 1104a of the first speaker assembly 1100a and the air outlet 1104b of the second speaker assembly 1100b and a second end position in which it is not fluidically connected to either the air outlet 1104a of the first speaker assembly 1100a or the air outlet 1104b of the second speaker assembly 1100b.

The nozzle <NUM> is arranged such that, when the purifier <NUM> is worn by a user with the first speaker assembly 1100a over a first ear of the user and the second speaker assembly 1100b over a second ear of the user and with the nozzle <NUM> in the first end position, the nozzle <NUM> will extend around a face of the user, from one side to the other, and in front of a mouth of the user. In particular, the nozzle <NUM> extends around the jaw of the user, from adjacent to one cheek to adjacent the other cheek, without making contact with the mouth, nose or surrounding regions of the user's face. It is therefore preferable that the at least a portion of the nozzle <NUM> is formed of a transparent or partially transparent material so that the user's mouth is visible through the nozzle <NUM> so as to avoid limiting the user's ability to clearly speak to others. For example, in the illustrated embodiment, the central portion <NUM> is made from a flexible, transparent plastic such as a polyurethane, whilst the two end portions <NUM>, <NUM> are each made from a stiff, transparent plastic such as a polyethylene terephthalate glycol-modified (PETG). Alternatively, the entire nozzle <NUM> could be formed from a single transparent or partially transparent material.

The air purifier <NUM> is arranged to so that, when in the first end position, the nozzle <NUM> will extend away from the air outlets 1104a, 1104b of the speaker assemblies 1100a, 1100b at an angle (θ<NUM>) of from <NUM> to <NUM> degrees relative to the headband <NUM> (i.e. such that the angle between a plane that is parallel to the length of the nozzle and the plane that is parallel to the length of the arcuate headband is from <NUM> to <NUM> degrees). In this regard, it has been found that an angle from <NUM> to <NUM> degrees is appropriate for locating the nozzle <NUM> in front of at least the mouth of the user when the purifier <NUM> is worn by a user with the first speaker assembly 1100a over a first ear of the user and the second speaker assembly 1100b over a second ear of the user. The mounting projections <NUM> and the air outlets <NUM> of the speaker assemblies <NUM> are therefore located so that the the angle (θ<NUM>) between the headband <NUM> and the nozzle <NUM> is within the range of <NUM> to <NUM> degrees.

In order to achieve a desired pressure drop within the nozzle <NUM>, the cross-sectional area of an interior passage <NUM> defined by the hollow nozzle <NUM> is preferably from <NUM><NUM> to <NUM><NUM>, and is preferably around <NUM><NUM>. In addition, it is preferable that the height (H) of the nozzle <NUM> is from <NUM> to <NUM>, and is more preferably from <NUM> to <NUM> in order to ensure that the nozzle <NUM> will adequately deliver air to the user's mouth and nose whilst also providing protection from external airflows. Consequently, the height of the nozzle <NUM> may vary along its length provided that at least the portion of the nozzle <NUM> that extends around a face of the user from one side to the other has a minimum height from <NUM> to <NUM>. In this regard, the height of the nozzle <NUM> is the distance between a top edge and a bottom edge of the nozzle <NUM>, wherein the top edge is that which faces generally upwards when the headband <NUM> is worn on the head of a user and the bottom edge is that which faces generally downwards when the headband <NUM> is worn on the head of a user.

As shown in <FIG>, the nozzle <NUM> has a generally D-shaped cross-section comprising a generally flat first outer surface <NUM> and a second outer surface <NUM> that comprises a generally flat mid-portion and edge portions that curve to meet the edges of the first outer surface <NUM>. When connected between the first speaker assembly 1100a and the second speaker assembly 1100b, the first outer surface <NUM> faces outwardly away from the first speaker assembly 1100a and the second speaker assembly 1100b, whilst the second outer surface <NUM> faces inwardly towards the first speaker assembly 1100a and the second speaker assembly 1100b.

The nozzle <NUM> is provided with an air outlet <NUM> for emitting/delivering the filtered air to a user. In the illustrated embodiment, the air outlet <NUM> of the nozzle <NUM> comprises an array of apertures formed in a section of the nozzle <NUM>, with these apertures extending from the interior passage <NUM> defined by the nozzle <NUM> to an exterior surface of the nozzle <NUM>. Alternatively, the air outlet <NUM> of the nozzle <NUM> may comprise one or more grilles or meshes mounted within windows in the nozzle <NUM>. It will also be clear that alternative patterns of air outlet arrays are envisaged within the scope of the present invention.

The array of apertures that provide the air outlet <NUM> are formed in a section of the nozzle <NUM> that is centred at the centre of the second outer surface <NUM> of the nozzle <NUM> that faces towards the speaker assemblies 1100a, 1100b. The apertures are therefore only present in in a section of the nozzle <NUM> that, when the purifier <NUM> is worn by a user, faces towards the mouth and nose of the user. In the illustrated embodiment, the section of the nozzle <NUM> that is provided with the array of apertures extends at least partially over the generally flat mid-portion of the second outer surface <NUM> of the nozzle <NUM> and partially over one of curved edge portions of the second outer surface <NUM>.

In use, the purifier <NUM> is worn by a user with the first speaker assembly 1100a over a first ear of the user and the second speaker assembly 1100b over a second ear of the user such that, when in the first end position, the nozzle <NUM> will extend around a face of the user, from one ear to the other, and over at least the mouth of the user. Within each speaker assembly 1100a, 1100b, the rotation of the impeller <NUM> by the motor <NUM> will cause an airflow to be generated through the impeller casing <NUM> that draws air into the speaker assembly <NUM> through the apertures <NUM> in the outer cover <NUM>. This flow of air will then pass through the filter elements <NUM>, <NUM> disposed between the outer cover <NUM> and the filter seat <NUM> thereby filtering and/or purifying the airflow. The resulting filtered airflow will then pass through the apertures <NUM> provided in the frustoconical portion 1135a of the filter seat <NUM> into the air passageway <NUM> provided by the space between the impeller casing <NUM> and the opposing surface of the filter seat <NUM>, with the air passageway <NUM> then guiding the airflow to the air inlet <NUM> of the impeller casing <NUM>. The impeller <NUM> will then force the filtered airflow out through the annular slot that provides the air outlet <NUM> of the impeller housing <NUM> and into the volute <NUM> of the impeller casing <NUM>. The volute <NUM> then guides the filtered airflow through the air outlet <NUM> of the speaker assembly <NUM> and into the nozzle <NUM> through an air inlet <NUM>, <NUM> provided by one of the open ends of the nozzle <NUM>.

As the first open end of the nozzle <NUM> providing the first air inlet <NUM> is connected to the first speaker assembly 1100a and the second open end of the nozzle <NUM> providing the second air inlet <NUM> is connected to the second speaker assembly 1100b, a first filtered airflow generated by the first speaker assembly 1100a and a second filtered airflow generated by the second speaker assembly 1100b will enter the nozzle <NUM> from opposite ends. The first and second filtered airflows will therefore travel in opposite directions within the interior passage <NUM> of the nozzle <NUM> until they collide in the vicinity of/towards the centre of the nozzle <NUM> (i.e. the midpoint of the length of the nozzle <NUM>). The collision between the first filtered airflow and the second filtered airflow will cause both airflows to change direction and will result in the formation a combined filtered airflow that is directed out through the apertures formed in the nozzle <NUM> that provide the air outlet <NUM> and towards the mouth and nose of the user.

The head wearable air purifier therefore provides a nozzle that blocks most, if not all, unfiltered ambient or external airflows from reaching the user's mouth and nose area. In doing so, not only does the head wearable air purifier reduce the volume of unfiltered air that is inhaled by the user's but it also prevents these external airflows from interfering with the airflow delivered by the air purifier, which would otherwise hinder the effective delivery of the purified airflow to the user. In addition, in embodiments in which at least a portion of the nozzle is formed of a transparent material the head wearable air purifier assembly also provides that, despite covering the user's mouth so as to block unfiltered external or ambient airflows, the user's mouth is still visible through the nozzle so as to avoid limiting the user's ability to clearly speak to others.

Furthermore, the use of single nozzle that causes the two air flows of purified air to collide to thereby generate a combined airflow that is directed to the user does away with the need for the nozzle to be provided with structures (e.g. vanes, baffles etc.) within the interior passage of the nozzle that would otherwise be necessary in order to change the direction of the airflow. Providing such structures within the nozzle reduces the pressure of the airflow that can be delivered to the user and limits the potential for transparency of the nozzle.

Moreover, by making use of two separate purifiers, one in each speaker, to deliver purified airflows into each end of the nozzle, the head wearable air purifier described herein does away with the need for any additional ducting that would otherwise be necessary if a single air purifier were to be used to deliver both airflows into the nozzle. Additionally, using two separate purifiers, one in each speaker, provides that each purifier can be made as small as possible, so as to be suitable to be comfortably incorporated into headphones, without sacrificing performance. In particular, using two separate purifiers provides an improved flow rate and improved filtering efficiency due to the increase in available filter area.

In a preferred embodiment, the control circuit <NUM> of the speaker assemblies 1100a, 1100b is arranged to control a rotational speed of the motor <NUM> such that the maximum rotational speed of the impeller <NUM> is from <NUM> to <NUM>,<NUM> RPM, is preferably from <NUM>,<NUM> to <NUM>,<NUM> RPM, and is more preferably from <NUM>,<NUM> to <NUM>,<NUM> RPM. These ranges of rotational speeds equate to frequency ranges that it has been found can be effectively cancelled by a typical active noise cancellation (ANC) system thereby improving the extent to which noise generated by the motor <NUM> and/or the impeller <NUM> can be cancelled out. However, limiting the maximum rotational speed of motor <NUM> and the impeller <NUM> to within these ranges also places limitations on the size of the impeller <NUM> that must be used in order to generate an air flow having a sufficient flow rate.

In this regard, in order to effectively deliver purified air to the user, it has been found that the flow rate of the air flow generated by the air purifier should be at least <NUM> litres per second such that each of the speaker assemblies 1100a, 1100b are required to deliver at least <NUM> litres per second. Furthermore, in order for each of the speaker assemblies 1100a, 1100b to deliver an air flow of at least <NUM> litres per second when their impeller speeds are limited to the above ranges, it has been found that the impeller <NUM> of each of the speaker assemblies 1100a, 1100b preferably has a tip diameter (i.e. a distance between the mid-point of the trailing edges of opposing impeller blades) of no less than <NUM>. However, when the speaker assemblies 1100a, 1100b make use of highly efficient particulate filters (e.g. <NUM>% and above) and are sealed so as to prevent any significant amount of air from bypassing the filter assembly <NUM>, then it has been found that the impeller <NUM> of each of the speaker assemblies 1100a, 1100b should preferably have a tip diameter of no less than <NUM>, and preferably no less than <NUM>.

In another preferred embodiment, each of the speaker assemblies 1100a, 1100b comprises an earpad <NUM> that has an asymmetric cross-section. In this regard, circumaural and supra-aural headphones have earpads whose shape is that of a closed loop so that they encompass the entire ear or just the opening to the ear canal, and a conventional earpad has a symmetric cross-section wherein the depth of the earpad is continuous around its circumference, as illustrated in the above described embodiment. In this alternative embodiment, the earpad <NUM> is arranged such that the depth/thickness (D) of the earpad <NUM> varies gradually around the circumference of the earpad <NUM>, with a deepest/thickest portion 2106a of the earpad <NUM> being diametrically opposed to a thinnest/shallowest portion 2106b of the earpad <NUM>, as illustrated in <FIG>. In the embodiment illustrated in <FIG>, the outer surface of the earpad <NUM> therefore defines an angle (Θs) relative to the inner surface of the earpad <NUM> that is attached to the speaker housing <NUM> (and therefore relative to the base of the speaker housing <NUM>) of approximately <NUM> degrees; however, this angle (Θs) could be anything from <NUM> to <NUM> degrees. This has several advantages.

Firstly, it is preferable that the speaker/drive unit <NUM> is parallel with the user's ear, which typically requires that the speaker/driver unit <NUM> is mounted at an angle of <NUM> to <NUM> degrees relative to the base of the speaker housing <NUM> to which it is attached, as illustrated in the above described embodiment. This angle provides that when the speaker assembly <NUM> rotates due to the tapered shape of the user's head the speaker/driver unit <NUM> will then be generally parallel with the user's ear. The use of an earpad <NUM> that has an asymmetric cross-section provides that the angle of the speaker/driver unit <NUM> relative to the base of the speaker housing <NUM> can be reduced to less than <NUM> degrees and, depending on the angle of the outer surface of the earpad <NUM> relative to the base of the speaker housing <NUM>, can even eliminate the need to angle the speaker/driver unit <NUM> relative to the speaker housing <NUM>. This is particular advantageous in the head wearable air purifier <NUM> described herein, as a reduction in the angle of the speaker/driver unit <NUM> relative to the speaker housing <NUM> reduces the space required behind the speaker/driver unit <NUM> and thereby reduces the overall volume required to house the internal components of the speaker assembly <NUM>.

Secondly, circumaural and supra-aural headphones require that the headband is configured to apply pressure to against the sides of the user's head in order to seal the earpads around or onto the user's ear. This pressure can reduce the comfort of the headphones for the user. The use of an earpad <NUM> that has an asymmetric cross-section also provides that the pressure applied by the headband that is required in order to seal the earpads <NUM> around or onto the user's ear can be reduced, thereby improving the comfort for the user.

It will be appreciated that individual items described above may be used on their own or in combination with other items shown in the drawings or described in the description and that items mentioned in the same passage as each other or the same drawing as each other need not be used in combination with each other. In addition, the expression "means" may be replaced by actuator or system or device as may be desirable. In addition, any reference to "comprising" or "consisting" is not intended to be limiting in any way whatsoever and the reader should interpret the description and claims accordingly.

Furthermore, although the invention has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims. For example, in the above described embodiment the head wearable air purifier comprises a headphone system in which the two speaker assemblies are provided on opposite ends of a headband. However, the head wearable air purifier could equally comprise any head wearable article that could be used to support an air flow generator and a filter assembly on the head of a user. For example, the head wearable air purifier could comprise any type of headgear, such as a hat or a helmet, including safety hats and helmets, bicycle helmets, motorcycle helmets etc. In particular, the head wearable air purifier could comprise a headgear, such as a bicycle helmet or motorcycle helmet, which supports an air purifier assembly such as that described herein either with or without a speaker or acoustic driver unit. In this example, if the air purifier assembly were not arranged to be worn over an ear of a user, then the inclusion of a speaker or acoustic driver unit would be optional.

In addition, whilst in the above described embodiments both speaker assemblies include motor-driven impellers and filter assemblies, with both speaker assemblies then providing filtered/purified air to the nozzle, it is also possible that only one of the two speaker assemblies include a motor-driven impeller and a filter assembly, such that only a single speaker assembly then provides filtered/purified air to the nozzle. However, such an arrangement would not be as effective as those of the above described embodiments.

Claim 1:
A head wearable air purifier (<NUM>) comprising:
a first speaker assembly (1100a) arranged to be worn over a first ear of a user and a second speaker assembly (1100b) arranged to be worn over a second ear of the user;
wherein the first speaker assembly (1100a) comprises a speaker (<NUM>), a filter assembly (<NUM>), an impeller (<NUM>) for creating an airflow through the filter assembly (<NUM>), a motor (<NUM>) arranged to drive the impeller (<NUM>), and an air outlet (<NUM>) downstream from the filter assembly (<NUM>) for emitting the filtered airflow from the first speaker assembly (1100a); and characterized in that:
the impeller (<NUM>) and the motor (<NUM>) are disposed within an impeller casing (<NUM>);
the first speaker assembly (1100a) further comprises a housing (<NUM>) containing the speaker (<NUM>), the filter assembly (<NUM>) and the impeller casing (<NUM>); and
the impeller casing (<NUM>) is supported within the housing (<NUM>) by a plurality of resilient supports (<NUM>) that extend between the impeller casing (<NUM>) and the housing (<NUM>).