Field of Invention

The present application is in the field of respirators. Specifically said respirators may be used in settings such as clinical settings such as hospitals, to protect the user from airborne hazards such as pathogens. This application in particular concerns the impeller used to generate airflow within the respirator device.

Background

Personal protective equipment is used in environments in which there are hazards to humans. The personal protective equipment allows a user to move through said environment whilst minimising the risks posed by said hazards. Examples of such environments include hospitals and clinical settings where there are likely to be airborne pathogens. For example, the air in wards containing covid-19 positive patients will likely contain particulates such as aerosols carrying the Covid-19 virus - and thus putting the staff in the ward at risk.

There have been many attempts to develop sufficient personal protective equipment to reduce the risk of the user effectively. However, these solutions either insufficiently alleviate the problem, or produce other problems. For example, many such devices are difficult to wear, heavy, bulky, or make the user's task more difficult. For example, face masks are often used by clinicians but these can be noisy if they are powered devices, or ineffective if they are not. Clinicians often have to speak with the patient and so the noise of the personal protective device can hinder this communication. Therefore, there is a need to provide an effective piece of personal protective equipment that does not induce other problems to the user. In particular, there is a need for a device to be worn on the user's head in order to reduce the risk on breathing in contaminated air containing pathogens or other hazards.

There is also a need to make it easy to remove the device, and to be able to do so without contamination. It may be beneficial for any non-disposable elements to be readily cleanable, and for the device to not be overly bulky.

There are particular problems relating to the production of air flow within the respirator. The respirator has to produce sufficient air flow, whilst not creating too much noise or heat for the user. Moreover, the impeller must be reliable and not draw too much energy so that users can complete a task whilst wearing it that may take a great deal of time (e.g. surgical procedures). As such there are numerous related problems for the impeller in a respirator to overcome. of Invention

Aspects of the invention are set out in the independent claims. Optional features are set out in the dependent claims.

In accordance with a first aspect there is provided herewith an impeller for use in a powered air purifying respirator, the respirator comprising a collar and a hood configured to be detachably coupled, and wherein the impeller is configured to sit within the collar and provide air flow into the hood, the impeller comprising: an outer shell comprising a first air inlet, a first air outlet, and an inner volume; a rotating component housed within the outer shell, the rotating component comprising a first disc and a second disc fused together with a plurality of blades situated in a plane between, wherein the first disc comprises a second air inlet configured to intake air from the first air inlet, and wherein the blades are positioned with a proximal end extending towards the second air inlet, and with a distal end positioned adjacent the outer circumference of the first and second discs, and wherein the blades are curved from the proximal end to the distal end; wherein the impeller further comprises a motor configured to rotate the rotating component on receipt of electrical energy; wherein the rotating component is positioned within the outer shell such that an air pathway is formed around the rotating component, such that air exiting the rotating component is channelled into the air pathway around the rotating component and then out of the first air outlet. Optionally the direction of air flow out of the first air outlet is perpendicular to the first and second air inlets. It has been found that this impeller arrangement is particularly advantageous because the rotating component and the outer shell work together to create air flow efficiently whilst generating less noise than other arrangements.

Optionally, the proximal end of the blades are shaped to be atraumatic. This reduces the turbulence generated by the blades and therefore reduces the noise created, whilst also increasing the air flow generated by the impeller.

Optionally, the proximal end of the blades are shaped as an aerofoil. This channels the air as the rotating component rotates, bringing the air under the aerofoil so as to speed up the air flow and to create strong air flow paths that discourage turbulence. Optionally, the curve of the blades creates a backward curved spiral. This has an effect of increasing the efficiency of the impeller.

Optionally, the rotating component rotates counter clockwise when viewed from between the two discs and viewing out through the first disc.

Optionally, wherein the sides of the rotating component are open. This advantageously allows a large surface for the air to flow through, and therefore allows the air to join the air flow channel around the rotating component with minimal turbulence.

Optionally, the second air inlet sits within the second air inlet, with a gap of 1mm- 2mm between first air inlet and the second air inlet at their closest point. This gap has been found to be particularly advantageous. If the gap is too small then as the user moves the second air inlet can contact the air inlet (for example due to conservation of angular momentum if the user twists suddenly). If the gap is too large then there is considerable air leakage, turbulence and loss of air flow. Therefore, considerable time has been spent optimising the distance of this gap.

Optionally, wherein the gap between the first air inlet and second air inlet is 1.25mm at the closest point. It has been found that this value of 1.25mm is the optimal distance that reduces noise, and increases efficiency whilst also reducing the amount of contact between the first air inlet and the second air inlet. Whilst this is not fully prohibited this is believed to be the most usable value and so offers great benefits to the user.

Optionally, wherein the closest point comprises an annulus of the second air inlet sitting within the first air inlet. This creates a symmetrical ring with the same air gap so that the air flow remains symmetrical- which reduces wear in the system.

Optionally, the rotating component has a depth that is less than the depth of the inner volume of the outer shell. This may provide a plane in which air can be forced up into. This can create a more balanced air flow speed.

Optionally, the depth of the rotating component is less than the depth of the inner volume by 5mm. This value has been found to be particularly advantageous as smaller values may lead to the rotating component touching the inside of the outer shell as the user moves.

Optionally, the depth of the rotating component being less than the depth of the inner volume forces air output of the side of the rotating component to be vertically displaced on exit of the rotating component. Optionally, the air pathway around the rotating element increases in width towards the air outlet. As there is more air flow the closer to the air outlet this may advantageously reduce the turbulence in the air pathway.

Optionally, the width of the air pathway increases linearly as the angle increases from the point with the smallest width. The linear increase may be advantageous as the resulting volume change enables the increase in air in the air pathway to not induce too much turbulence.

Optionally, the width of the air pathway increases by 2-3 times the change of the angle in radians, preferably wherein the width of the air pathway increases by 2.25 times the change of the angle in radians. This increase has been found to be particularly advantageous for efficient air flow.

Optionally, the first and second discs of the rotating component are fused by ultrasonic welding. This may advantageously create a strong bond to provide a long device lifetime and prevent failure.

Optionally, at least one blade comprises a protrusion along its spine. This may allow stronger mating between the blades and the second disc (or first disc if the blades are mounted on the second disc).

Optionally, the protrusion is along the entire length of the blade. This may increase the contact length and so increase the strength of the bond.

Optionally, four blades comprise the protrusion. This may ensure adequate strength.

Optionally, all of the blades comprise the protrusion. This may enable the rotating to component to have maximum strength.

Optionally, the four blades with the protrusion are equally spaced. This may enable the rotation to be balanced.

Optionally, the protrusion along the blades enables fusing of the first disc and the second disc.

Optionally, the first and second discs are each formed by injection moulding. This may enable efficient manufacture of the impeller.

Optionally, there are 13 blades within the rotating component. This has been found to maximise air flow whilst keeping drag, noise etc. to a minimum. Optionally, the blades are equally spaced from one another. This may allow rotation to be balanced.

Optionally, the blades are mounted on to the second disc. This may be particularly advantageous. This brings the strength of the blades on to the disc nearest the motor. This means that vibrations from the motor may be more effectively damped, and may improve the overall balance of the device. Indeed, in such embodiments a washer may not improve the noise - as the rotating component may already be sufficiently damped. Therefore, manufacturing may also be made more efficient.

Optionally, each blade is 1.5mm in width. This may advantageously be the minimum width achievable without deformation of the blade during manufacture. The narrower blade reduces drag in the system.

Optionally, the blades curve in accordance with graph 1. Optionally wherein this curvature is a deltoid function or alternatively where this function is a cubic spline fit. This curve may advantageously promote efficient air flow with low drag.

Optionally, wherein the frequency of noise produced by the rotating component is outside of the range of 500Hz to 2000Hz. This makes the device more user friendly as such frequencies may interfere either with the user, or with other nearby medical equipment that operate at such frequencies.

Optionally, the impeller may further comprise a balancing ring around one of the first or second discs of the rotating component. This may allow for efficient manufacture with more allowed error in the injection moulding phase.

Optionally, the balancing ring is configured such that mass of the balancing ring may be removed to aid with weight balancing of the rotating component. This may allow unintended errors to be corrected and allow balanced rotation.

Optionally, the impeller may further comprise two or more pins to aid with orientation of the first and second discs during fusion, preferably wherein four pins are present. This may allow the first and second discs to be correctly matched during fusion such that they are in the correct positon next to each other.

Optionally, the second air inlet comprises a rounded surface. This may be particularly advantageous. It has been found that where a step or square ridge (that is simpler to manufacture) is used this drastically affects air flow, and causes a reduction in efficiency, air flow layers to become separated, and much greater noise and turbulence inside the impeller. Optionally, the second air inlet comprises a taper between the external surface of the first disc and the internal surface of the first disc comprising the rounded surface of the air inlet. This taper may be a particularly advantageous rounded edge.

Optionally, the rounded surface of the air inlet comprises a rounded fillet. This aids with reducing turbulence as above, but is the most preferred way of doing so as it is the most efficient. The fillet may be formed integrally, or may be an insert to be added after initial moulding.

Optionally, the first air inlet further comprises a cylindrical air intake with open ends.

Optionally, the cylindrical air intake is sized to match an air filter of the collar of the respirator. This may reduce any boundaries for the air flow to negotiate, thus reducing turbulence created.

Optionally, the motor is positioned outside of the outer shell and is in mechanical communication with the rotating component through the outer shell. This may drive the rotating component efficiently.

Optionally, the motor is positioned at the centre of the outer shell and the rotating component. This may allow for balanced rotation.

Optionally, a washer is positioned between the outside of the outer shell and the motor. This may advantageously damp the vibrations from the motor.

Optionally, an indent is provided on the outer surface of the outer shell in which the washer is configured to be positioned. This may allow the washer to sit flush with the outer shell to reduce vibration.

Optionally, the washer has a depth greater than the width of the indent such that for the motor to be flush with the outer shell the connection is overtightened. Overtightening may be particularly effective at damping vibration.

Optionally, the washer has a hardness that is less than the hardness of the outer shell. This may mean that the outer shells lifetime is not limited by the washer. The washer nay be an easier part to replace in routine maintenance.

Optionally, wherein the hardness of the washer is in the range of 50D to 70D, and preferably wherein the hardness is 55D. This value has been found to be particularly effective at damping. Optionally, the motor is powered by a 5.2v power source. This is a particularly advantageous feature. This may be in the range of 5.1v to 5.4v. The voltage is specific because any more power may increase the noise generated and so reduce user comfort (and make it harder for the user to communicate). Any less power and the level of air flow generated may not be sufficient. This voltage has been found to be particularly effective.

Optionally, the impeller produces an airflow of at least 1701 of airflow per minute.

In accordance with a second aspect there is provided a powered air purifying respirator comprising: a hood; a collar; wherein the hood is detachably coupled to the collar; the impeller of the first aspect, wherein the impeller is situated within the collar; wherein the collar further comprises a filter feeding the first air inlet of the impeller; wherein the collar comprises an air outlet outputting air flow from the impeller, wherein the air outlet is situated within the hood. This may be advantageous as such a respirator benefits from all the advantages of the impeller above in the first aspect.

Optionally, the hood comprises a first aperture for the user's head to pass through. This may aid usability.

Optionally, the hood comprises a second aperture positioned adjacent the air inlet. This may allow an easy access for air that does not increase the length of the air pathway.

Optionally, the hood comprises one or more valves for air to exit the hood. This may promote circulation of air and reduce retained carbon dioxide.

Optionally, an indicator is positioned within the collar and is configured to sense if airflow from the impeller drops below a predetermined level. This may allow a user to know if there has been failure for safety reasons.

Brief Description of Figures

Figure 1 shows a perspective view of a hood to be used with the device.

Figure 2 shows the template for the hood in manufacture. Figure 3 shows a template for the visor of the hood in manufacture.

Figure 4 shows an exploded view of the components of the collar of the respirator.

Figure 5 shows a plan view of the bottom half of the collar.

Figure 6a shows a cross section of the bottom half of the collar.

Figure 6b shows a further cross section of the bottom half of the collar.

Figure 6C shows a close up of the portion of the collar configured to house the indicator.

Figure 7 shows a perspective view of the bottom half of the collar.

Figure 8a shows a close up of the air outlet from above.

Figure 8b shows a close up of the air outlet in partial cut-away.

Figure 9 shows a plan view of the top half of the collar.

Figure 10a shows a cross section of the top half of the collar.

Figure 10b shows a close up of the portion of the top half of the collar configured to house the indicator.

Figure 11 shows an exploded view of the components of the impeller.

Figure 12a shows a perspective view of the rotating component.

Figure 12b shows an exploded view of the rotating component.

Figure 12c shows a plan view of the first disc of the rotating component (the blades may be situated on either disc).

Figure 13a shows a side view of the rotating component.

Figure 13b shows a plan view of the outside of the first disc.

Figure 14 shows both sides of the second disc.

Figure 15 shows a portion of the outer shell with the first air inlet.

Figure 16a shows a cross section of the outer shell of the impeller.

Figure 16b shows various cross sections of Figure 15a showing the widths of the air pathway at various points along the angular rotation of the air pathway. Figure 17a shows a side view of the outer shell of the impeller.

Figure 17b shows a perspective view of the half of the outer casing without the air inlet.

Figure 18a shows a perspective view of half of the outer shell of the impeller with the first air inlet.

Figure 18b shows a cross section of the impeller.

Figure 18C shows a plan view of the half of the impeller with the air inlet.

Figure 19 shows an exploded view of the indicator.

Figure 20 shows a plan view of the base plate of the indicator.

Figure 21 shows a plan view of the spring of the indicator.

Figure 22a shows a plan view of the axis of the rotor in the indicator.

Figure 22b shows a pattern of the central portion of the axis.

Figure 23a shows a plan view of the rotor of the indicator.

Figure 23b shows a cross section of the rotor showing various cut through.

Figure 23c is a first cut through showing a cross section of the rotor.

Figure 24a shows a plan view along section G-G of Figure 22b.

Figure 24b shows a plan view along section H-H of Figure 22b.

Figure 24c shows a plan view along section I-I of Figure 22b.

Figure 24d shows a plan view along section J-J of Figure 22b.

Figure 25a shows the portion of the rotor that mates with the base plate.

Figure 25b shows this same portion in perspective view.

Figure 26a shows the front of the rotor for attachment to the spring.

Figure 26b shows the front of the rotor for attachment to the spring in perspective view.

Figure 27a shows a perspective view of a cable end with a locking pattern to prevent inadvertent decoupling of the cable from the power source.

RECTIFIED SHEET (RULE 91) ISA/EP Figure 27b shows a plan view of the end of the cable with the locking pattern.

Detailed Description of Figures

Figure 1 shows a hood. The hood comprises a skirt portion 3, a visor portion 2 and a hood body. The hood body comprises two hemispheres separated by a central seam. The central seam may extend to the visor portion 2, or may end (as shown) before the visor portion. The visor portion is free from the central seam. Also shown in Figure 1 are two valves 1. The valves are configured to allow air to be expelled from the hood. The hood may be configured to contain a positive pressure (i.e. the hood may contain air at a pressure above atmospheric or local pressure). Therefore, the valves may allow air to exit from the hood. However, the valves do not allow air to enter into the hood via the valves. The valves may be configured in this manner, or alternatively the valves may be two way valves, and the positive pressure may be sufficient to stop air from entering through the valves during use.

The central seem provides a shape and structure to the hood. The seam may comprise a raised ridge. This may provide structural support to the hood to prevent sagging of the hood. The central seam in some embodiments is punctuated by an air inlet. The air inlet may be positioned at the rear of the device on the opposite side to the visor portion. The air inlet may comprise a reinforced ring to provide stability and to prevent the air inlet from being weakened to cause potential damage to the hood during use.

The valves may be positioned either side of the central seam. In use this creates two portions for air outlets at points air is directed by flow from the air outlet of the collar. This therefore reduces the linger time of air within the hood, which reduces build-up of carbon dioxide. It has been found that having two or more valves is particularly advantageous as one valve provides a single exit point for air. One exit point is not as efficient as two with the same capacity because user movement, or movement of the air flow can reduce the amount of air exiting through a single valve, but is less likely to affect two or more valves in the same way.

Moreover, it is advantageous for the valves to be positioned symmetrically apart from the seam so that air flow is symmetrical around the hood. If one valve is used then either it must be positioned symmetrically (in which case it further weakens the central seam) or it is offset and so creates an unequal distribution of air flow. This may create discomfort for the user, increase air linger time within the hood, or increase drag in the air (increasing noise). Therefore, two valves are particularly advantageous. Figure 1 also shows three connectors at the base of the visor portion. These connectors are for connection to the collar portion of the device. The three connectors comprise a central connector, a right most connector and a left most connector. The connectors provide a secure connection to ensure the hood and collar do not decouple during use, as the user may be in a hazardous environment. The connectors may serve a dual purpose. The central connector in particular may reduce the flex that propagates from the hood body into the visor portion. Flex in the visor portion may cause visual distortions for the user as the flex may change the effective thickness of the visor portion in the user's eye line, and therefore the effect of light travelling a different distance through the material may cause distortion. As the hood may be used for example in surgical procedures visual accuracy is important. The connectors may be manufactured from the same material as the rest of the visor (this may improve the recyclability of the visor), and may be integral to the structure of the visor in order to reduce flex of the visor.

Also shown in Figure 1 are the apron connectors. These are situated in the right hand and left hand corner of the visor portion. These comprise tabs that may be manipulated or folded along a diagonal score line that separates the apron connector from the remainder of the visor portion. The apron connector comprises a slot for an apron (or other PPE item) worn by a user to fit within. This joins the respirator to the other PPE item and therefore combines to form an effective protection. The slot in this particular example has a zig-zag pattern. This zig-zag pattern has been found to be particularly beneficial at restraining an apron strap, and therefore creates a secure attachment. The placement of the apron connector in the corner of the visor portion greatly increases efficiency of manufacture. This is because the apron connector can be formed in a single step with the formation of the visor portion. No welding or other attachment is needed. The visor portion is also not weakened and so no additional visor flex is induced (or minimal additional flex dependent on the exact arrangement). Indeed, the corner can simply be created by scoring or bending the visor portion appropriately rather than any more time consuming, costly or complex technique.

The skirt portion may comprise a side hole. One side hole may be placed on either side of the skirt (either side defined as one side or other of the central seam). These side holes may allow the strap to fit therethrough. The strap may then be used to contain the skirt to remove the skirt from being in the way of any user activity. The side holes shown here each comprise a slot that the strap threads through. This is shown by the rectangular portion over the strap on each side of the skirt. The side holes are beneficial as it is efficient to manufacture. The side holes may be created by stamping the skirt during the cutting of the material for the hood, and therefore add very little time or expense to the manufacture process.

Figure 1 also shows perforations in a score line situated at the rear of the device. This score line may be used to tar the hood along the score line. When the user comes to remove the hood at the end of use there is a technical problem as to how to remove the hood whilst minimising contact between the user (or any other surface) and the outside surface of the hood as the hood may be contaminated. By tearing the score line the hood can simply be lifted off of the collar and so no other surface touches the outside of the hood (aside from a user's hands which should be clad in PPE or gloves). The hood can then be appropriately disposed of. The perforations - and gaps between the perforations are of a certain size to make tearing simple for a user. These sizes are shown in Figure 2. However, it has been found that having the perforations longer than the gaps between the perforations is advantageous in making the tearing easy enough for a user - even when fully clad in PPE.

There is also an annular contact portion situated below the connectors at the top of the skirt portion. The annular contact portion is an annulus that is configured to come into contact with the collar of the device when the respirator is in use. The annular contact region is the ring that forms a seal with the collar. This seal may be one of two types. Firstly, the seal formed between the annular contact ring and the collar may be airtight. This means that no air can enter or exit the hood via the seal between the hood and the collar. This can be achieved by having a close fit between the hood and the collar. In some instances, the annular contact portion may be formed of a ring of hardened, or thicker material (potentially even rigid material in some instances) that fits around the collar. This may be a friction fit or there may be a snap fit, or other mechanical fit at this point. In this example however the annular contact portion is simply a ring of material that contacts the collar - and is not physically different to regions around it. This is because a positive pressure seal is used. This means that air can exit between the hood and the collar, but it cannot enter the hood in this way. This is because of the higher pressure within the hood. This therefore requires a looser fit between the annular contact region and the collar. What is important in this embodiment however (and to an extent in the airtight embodiment too) is that the connectors shown are situated to be offset from the annular contact region. This means that the connectors (and the bulging structure that facilitates them) does not interfere with the seal created at the annular contact region. This therefore improves the seal, and means that less air can travel between the hood and outside of the hood. This offset may ideally be 6 mm (as this provides a sufficient distance to create an improved seal). However, the offset may be in the range of 2- 20mm to get at least a portion of this effect. The 6mm offset may be more ergonomic for use, as no part of the user's view may be obstructed by the connector.

Figure 2 shows a template used in the manufacture of the hood. On the left hand side is a zoomed in view of the perforations showing that the perforations in the score line are 5.5mm long, and the gaps between the perforations are 3mm long. The perforations are therefore longer than the gap between the perforations. The perforations may be any length between 5mm and 6mm. The tear strength needed to tear these perforations varies between 15N and 30N dependent on the exact length of the perforations. It is noted that handles may be added to the hood body adjacent the score line and the perforations, such that the user may grip the handles in order to tear the score line in order to remove the device. This may make the removal of the hood easier for the user as the handles may be easier to grasp.

The template shows the visor portion and the hood portion. In this example the apron connectors are not shown. The central seam will be formed by connection the two sides of the hood body together to form an encapsulating hood. It is noted that the hood body and the visor portion may be made from the same material - e.g. PVC in order to make the hood more readily recyclable. In this example the visor portion is made of the same material - but is thicker (around 500 microns in thickness) in order to reduce the flex of the visor portion. The hood body on the other hand has a thickness of 150 microns - and so allows for greater user movement.

A valve hole is also shown either side of the template. The valve hole may be undersized such that it is smaller than the diameter of the valves - so that the seal formed from the valve entering the valve hole is tight. This may mean that no adhesive is required for the valve to be situated correctly. A two-part valve connecting together with the valve whole between the two portions of the valve may allow for such a tight connection.

The air inlet is shown as two hemispherical cut-outs at the periphery of either side of the template. The perforations may be formed adjacent the edge of either or both sides of the hood - below the hemispherical cut-out for the air inlet.

Figure 3 shows a template for the visor portion. This shows the apron connectors and a curved top edge of the visor. This is so that when the visor is bent in use (as shown in Figure 1) the top edge becomes flat. Alternatively, the top edge may be flat or otherwise curved in the template and may be curved during use. This may however complicate the join between the visor and the hood body, which then maybe reinforced. The dimensions of the connectors in this embodiment are also shown - as are the approximate dimensions of the visor itself.

Figure 4 shows an exploded view of the collar (a perspective non-exploded view is also shown for completeness). The collar comprises a top portion, a bottom portion, an impeller, a cable to connect the impeller to a power source, an indicator, connection pins, a weighting element and not shown is a filter element. The top portion and bottom portions are configured to connect together. Together the top portion and bottom potion form a collar body. This is approximately a torus in shape. In some embodiments the diameter of this torus may be 32mm, whilst the diameter of the collar body may have the diameter just greater than a human head (around 30cm). Other sizes may be used. In use the collar body is worn around a user's neck. On the front of the collar body (on the top portion of the collar in this example - but they could be on either portion) are connection points. These three connection points (other number of connection points may be used in other embodiments) may connect to the connectors of the hood to connect the hood and the collar together.

The hood body may be weighted. This is an entirely optional feature. The weighting may provide a more ergonomic weight distribution so that the collar body is front heavy. This means that when a user bends for instance the rear of the collar is not raising the front of the collar body into the user's chin - and so improves the user experience.

The impeller is used to provide air flow into the hood. This air flow is provided through an air pathway situated between (or encapsulated within one or both) of the portions of the collar body. The air is then outlet from an opening (the air outlet) on the top portion of the collar body. The impeller may be any impeller. A particularly effective impeller is described later with respect to later Figures.

The cable passes through a hole in the collar boy. This hole is approximately circular and is 4mm in diameter. This makes the fit between the cable and the hole tight. This reduces dirt ingress and makes cleaning the collar after use simpler. After the cable enters the hole to pass through a U-shaped bend channel before reaching the void that houses the impeller. This U-bend channel may secure the cable in position and prevent the cable from being inadvertently removed from the impeller during use.

An indicator is also shown. This indicator sits in the air flow path and indicates if the air flow drops below a pre-determined level. This level may correspond to an amount of air flow that is safe for a user. Any indicator may be used. A particularly effective indicator in one embodiment is described with reference to later Figures. The shape of the collar portions is advantageous. The upper portion comprises a bulge to house a void in which the impeller sits. A channel protrudes from this void. This is the air pathway for air exiting the impeller. At the proximal end of the air pathway the air pathway is fully encapsulated within the top portion of the collar body. This then joins the remainder of the air pathway that sits in both the top and bottom portions of the collar boy, before exiting at the air outlet in the top portion of the collar body.

It is noted that the bottom half and the top half of the collar body may be joined in some embodiments by a double sided adhesive gasket. This gasket may replace other adhesive such as glue. The use of the gasket may therefore both simplify manufacture (As the gasket can simply be positioned in place rather than needing to be applied or spread) and may also reduce the amount of excess adhesive used. This reduction may limit detritus adhered to the device, and may aid cleaning. The gasket may be shaped in a ring to match the torus shape of the collar body. The gasket may avoid covering the air pathway situated within the collar body. The double sided adhesive gasket may be formed from 3M tape. The gasket may be coated in an adhesive on both sides. The adhesive may be acrylate. The adhesive layer may be 0.05mm to 0.1mm thick, in particular the adhesive may be 0.076mm thick. This thickness range may be particularly effective t providing the needed adherence, but in limiting the amount of excess adhesive.

Figure 5 shows a plan view of the bottom half of the collar. This shows a space for the indicator (indicated "L"), a space for the impeller, a space for the filter (attached to the impeller), and an air pathway.

The impeller is configured to sit in the void within the bottom half of the collar body. The impeller is configured to be attached to the filter. The filter is also configured to sit within the collar body. In particular, the filter sits in the air inlet at the rear of the collar body. The filter feeds the air to the impeller. The impeller therefore draws air in through the air inlet, through the air filter, and then directs the air into the air pathway within the collar body.

The air filter may be any air filter suitable for filtering the air. For example, in a clinical setting the air filter may be suitable for filtering air borne pathogens out of the air.

The air pathway shown in Figure 5 is non-continuous. This is because the air pathway directly connected to the impeller is housed within the upper portion of the collar body (as opposed to the bottom half of the collar body shown in Figure 5). Having the proximal end of the air pathway (connected to the impeller) allows the void in the collar for the impeller to be enlarged to accept a larger impeller (with the associated higher air flow).

Wings are also shown at the rear of the collar body These wings protect the air filter (and to an extent the impeller) from any knocks or forces as a user collides into other objects. The wings are shaped to be triangular (although this is not essential), and the vertices and edge of the wings may be atraumatic in some embodiments.

The air flow path then re-appears in this bottom half of the collar body. The indicator sits in the air flow path. As shown in figure 5 a groove in the collar body adjacent the top surface of the bottom of the collar body (i.e. adjacent the point at which the bottom half will join to the top half) comprises an indent configured to accept an alignment nodule of the indicator. The position of this means that the indicator may be put into either the top or bottom half of the collar body during assembly, making the assembly of the collar more flexible. Collars may also be situated within the collar body at the point at which the indicator may be positioned. These collars may aide the alignment of the indicator when the collar is being assembled.

Figure 6a shows a cross section of the bottom half of the collar. This viewpoint is from the rear of the collar body. This shows the air inlet and the position at which the filter will sit from a rear view.

Figure 6b shows a further cross section of the bottom half of the collar. This shows that the rear portion and front portion of the bottom half of the collar body are deeper than the central portion. This is because impeller is at the rear portion of the bottom half of the collar body. The front is deeper to accommodate the weighting element positioned at the front of the bottom half of the collar body.

Figure 6C shows a close up of the portion of the collar configured to house the indicator. This shows the cavity in which the indicator is configured to sit. The two collars at the edge of the cavity are shown. This helps guide the assembly of the indicator within the collar body. Also shown is a groove at the top surface of the bottom half of the collar for accepting an outdent of the indicator.

Figure 7 shows a perspective view of the bottom half of the collar. In this example the weighting element is positioned in the bottom half of the collar, and so the depth of the front portion of the collar is expanded. The void for the impeller, and the air flow path described above are also shown.

Figure 8a shows a close up of the air outlet from above. This is positioned on the top surface of the top half of the collar body. The front of the collar body is shown at the point at which the central connection (which is extending from the torus). The air outlet is positioned offset from the front of collar body. This means that air is angled away from the user's nose and mouth. This decreases user discomfort whilst using the device. In this example the air outlet is positioned 20 degrees to 40 degrees along the torus away from the front of the collar body. In particular, this offset is 30 degrees. In distance this offset is approximately 30 mm from the centre of the torus. This also helps create a helix of air around the user's head as air flow straight from the air outlet is not impeded by the user's facial features.

Figure 8b shows a close up of the air outlet in partial cut-away. This shows that the outlet is angled at an angle from the plane of the collar body. The air outlet is angled at 38 degrees in this example. However, a range of between 25 to 60 degrees, and more preferably 30 to 45 degrees may be used. 38 degrees has been found to be the optimal angle. This angle (and the associated ranges) are angled acutely so that air does not blow up into a user's face. Instead air blows (at least partially) across so that the air forms a helical flow path around the user's face within the hood. The hood is relatively cylindrical so the volume around the user's head permits air flow. By increasing the number of turns in a helical air flow path around the user's head this decreases the number (or proportion) of dead spots within the hood. Dead spots may have little or lower air flow, and so carbon dioxide may gather there. Increasing the number of turns in the helix by reducing the angle eradicates at least some of these dead spots, and therefore promotes a high turnover of air within the hood. However, if the angle is too low then air will interact with the collar itself, and turbulence will therefore be created. The range of angles (and 38 degrees in particular) has been found to balance these concerns.

Figure 9 shows a plan view of the top half of the collar. This is almost a mirror image of the plan of the bottom half of the collar. The portion for the indicator for the instance is the same as the bottom half, allowing flexibility as to which portion of the collar the indicator is first placed in to during assembly.

The main difference concerns the portion of the air pathway connected to the void configured to house the impeller. A fully encapsulated channel exists between this void and the visible section of the air pathway that can be seen.

Figure 10a shows a cross section of the top half of the collar. This cross section shows not just a bulbous portion for hosing the void to house the impeller, but also an elongate extremity extending from this void. This is the fully encapsulated section of the air pathway that is directly connected to the void housing the impeller. In this section air only flows through the top portion of the collar. When the air flow path reaches the point on both Figure 9 and Figure 5 where the air flow path can be seen the air flow path is then in both the top and the bottom portions of the collar body.

Figure 10b shows a close up of the portion of the top half of the collar configured to house the indicator. This is identical to Figure 6b, with the exception that the air outlet is positons next to the indicator.

Figure 11 shows an exploded view of the components of the impeller. The impeller comprises a cable for providing power to a motor, a motor, a washer, an outer shell comprising a first portion adjacent the motor and a second portion, and a rotating component. The second portion of the outer shell comprises a first air inlet. A second air inlet is situated on the rotating component adjacent the first air inlet. The rotating component sits within the outer shell. The outer shell also comprises an air outlet, which is perpendicular to the first air inlet and the second air inlet.

The motor may be any suitable motor for rotating the rotating component. The motor may however transmit vibrations to the rotating component. Therefore, the washer may in some embodiments damp these vibrations effectively. In some embodiments the washer may be housed in an indent positioned on the outside of the second disc around the hole for the motor to access through the outer shell. In some preferable embodiments the washer may have a greater depth than the indent such that the motor, washer outer shell assembly must be overtightened to get the arrangement flush at the outer shell. This may damp vibrations particularly effectively. The washer r may in some embodiments be softer in hardness than the outer shell so as to not damage the outer shell. For example, the washer may have a hardness between 50D and 70D, and in particular may be 55D. The washer is however entirely optional.

Figure 12a shows a perspective view of the rotating component. This shows that the rotating component comprises a first disc, a second disc, and blades sandwiched there between. The sides of the rotating component are open. The rotating component forms a cylinder whereby the base is significantly wider in diameter than the cylinder is long in length.

Figure 12b shows an exploded view of the rotating component. This shows that the blades are attached to the first disc of the rotating element, and that the first disc comprises the second air inlet, configured to feed air into the rotating component.

It is noted however that the blades may alternatively be positioned on the second disc (the disc without the air inlet, and the disc that is positioned closet to the motor). Indeed, this arrangement may be highly advantageous. As the blades are then attached to the second disc this is the disc that is directly connected to the shaft that receives drive from the motor. Therefore, the second disc is exposed to vibrations of the motor. The blades being attached to the second disc advantageously may damp the vibrations transmitted from the motor, and therefore ensure more even rotation, and less vibration, and therefore a greater produced air flow, and less turbulence within the air flow created. In such embodiments a washer may not be used.

The air inlet of the rotating component comprises a rounded entry. This rounded edge may lessen the drag of the air entering the rotating component. This rounded edge may comprise a tapered edge tapering from the outside edge of the first disc to the inside edge of the first disc. The rounded edge may avoid sharp edges that may create turbulence. The rounded edge may comprise a rounded fillet. Said fillet may be formed in the injection moulding process as a single piece with the remainder of the first disc. Alternatively the fillet may be added after the first disc is formed.

Figure 12c shows a plan view of the first disc of the rotating component (the blades may be situated on either disc). It is noted that in this embodiment the disc has 13 blades attached thereto. In this embodiment this number of blades has been found to be advantageous in the efficient creation of air flow. It is also noted that the blades are equidistant. This may be the case even if the number of blades is changed.

The blades themselves are approximately 1.5mm in length for the majority of the length of the blade. At the distal end (that end closest the circumference of the disc) the blades may be slightly flared. At the proximal end (that nearest the air inlet) the blades are shaped to be rounded at the end. The blades in some embodiments are atraumatic. This reduces the turbulence caused when the air flow from the air inlet hits the proximal end of the blades. In some embodiments the proximal end of the blades may be shaped as an aerofoil with one side of the proximal end of the blade having a longer air flow path than the other side of the blade. This therefore creates an imbalance in the air flow either side of the aerofoil. This may also reduce turbulence formed as air progresses along the blade, as the air may act as a single sheet between each blade, with minimal turbulence.

Four blades are shown highlighted with black. This is because these blades have a fusion element along the spine of the blade. The spine of the blade may be defined as the longitudinal line in the centre of the blade. These spine protrusions may help the blades be fused to the second disc (or to the first disc if the blades are already positioned on the first disc). It is noted that every blade may comprise such a protrusion. In this embodiment the protrusions are evenly spaced and four blades with protrusions are present. The curve of the blades creates a backward curved spiral which has been found to generate efficient air flow. Moreover, in the viewpoint shown in this figure (viewing from between the first and second disc through the air inlet of the first disc) the rotating component is configured to rotate counter clockwise. This has been found in combination with the backward spiral, to be particularly efficient at air flow generation.

It is noted that the depth of the rotating component may be less than the depth of the void within the outer shell. In particular, the depth of the rotating component may be 5m less than the depth of the void. This may reduce any contact between the rotating component and the outer shell (which may create noise, and reduce air flow) and may also provide a vertical space for the air to exit the rotating component, and therefore reduce turbulence as the exiting air ions the air flow pathway around the rotating component.

The curve of each blade is shown in graph 1.

This graph shows that the curve of the blade may be approximated by a deltoid function, or by a cubic spline fit. This plots the co-ordinates of the centre point of the blade.

Figure 13a shows a side view of the rotating component. This shows that the sides of the rotating component are open. This allows air flow to exit the rotating component via the sides when the impeller is in use.

Figure 13b shows a plan view of the outside of the first disc. This shows the air inlet that is used to draw air into the rotating component.

Figure 14 shows both sides of the second disc. The left most side in the Figure shows the inside of the second disc. This is mostly flat. Four pin holes are situated around the outer edge of the disc. These pin holes may correspond with pins on the inside of the first disc. This pins may be used to align the discs together accurately when the two discs are being fused together. The outside of the second disc is shown in the rightmost part of the Figure. This shows that the central portion of the second disc is configured to be driven by the motor, causing rotation of the rotating component.

Either of the two discs may also comprise a balancing ring. This is a ring of material at a position around the disc (typically on the outer side of the disc). This ring of material may be removed to weight balance the rotating component. Weight balancing ensures that the rotating component is weighted neutrally, and so rotate freely (with

RECTIFIED SHEET (RULE 91) ISA/EP an equal weight distribution). Due to manufacturing errors there can be slight unevenness in the weight distribution of the rotating component. The balancing ring can then be trimmed appropriately to remove material at regions where there is additional mass to correct for the errors in manufacture and create a neutrally weighted rotating component.

It is noted that rotation of the rotation component, and use of the impeller as a whole produces noise, but without significant noise in the range of 500Hz to 2000Hz. This is advantageous because other medical equipment and systems use sound in this frequency, and so avoiding this frequency limits any interference between the devices.

Figure 15 shows a portion of the outer shell with the first air inlet. This is the second portion of the outer shell. The air inlet is configured to be attached to the air filter that is also positioned within the collar body. The air passing through the air filter then enters the first air inlet, and then enters the void within the outer shell. This is the void in which the rotating component is housed.

Figure 16a shows a cross section of the outer shell of the impeller. This shows that the outer shell of the impeller comprises a central void in which the rotating component is housed. Around the rotating component is an air pathway. This air pathway starts at a narrow point (around the cross section B-B as marked). The air pathway then widens as it approaches the air outlet at the end (in a similar manner to the enlarging compartments in a nautilus shell). This widening may be by any amount. In this particular example the width of the channel widens in a linear manner as compared to the radians of rotation (starting from the point B-B). A graph plotting the radians of rotation with respect to the width of the channel is shown in graph 2.

Radians are plotted on the X axis, and the width of the channel on the y axis. The width therefore multiplies by two to three times per doubling of the rotation in radians. Specifically, the width multiplies by 2.25 (and more specifically 2.2263).

Figure 16b shows various cross sections of Figure 15a showing the widths of the air pathway at various points along the angular rotation of the air pathway. This shows the widths of each of the cross sections shown in Figure 16a, and these widths are then plotted on the graph shown above.

Figure 17a shows a side view of the outer shell of the impeller. This shows the air outlet from the outer shell of the impeller.

RECTIFIED SHEET (RULE 91) ISA/EP Figure 17b shows a perspective view of the half of the outer casing without the air inlet.

RECTIFIED SHEET (RULE 91) ISA/EP Figure 18a shows a perspective view of half of the outer shell of the impeller with the first air inlet, inlet This shows that the casing for the air flow path is formed in this half of the outer shell. The air inlet forms a cylindrical inlet that may mate with the air filter such that there is join such that air passes seamlessly from the air filter to the first air inlet. This may reduce turbulence.

Figure 18b shows a plan view of the half of the impeller with the air inlet.

Figure 18c shows a cross section of the impeller. This shows the first air inlet feeding air into the void within the outer shell. This also shows the second air inlet feeding air into the rotating component. There is a l-2mm gap between the first air inlet and the second air inlet. This is highlighted by an arrow. Optimally this gap may be 1.25mm. A gap between the first air inlet and the second air inlet is necessary to prevent friction, and to prevent noise from the surfaces contacting whilst the rotating component is rotating. However, the gap must not be too large as this allows air to escape and may induce turbulence and even lead to air layers disassociating from one another. It has been found that a l-2mm reduces the drag and reduction in air flow - whilst also minimising the amount of contact between the first and second air inlets during use. Indeed, it has been found that only sharp rotations of the head by the user may induce such contact at the gap of 1.25mm, whilst air turbulence is suitably reduced.

This gap may be between the closest point on the second air inlet and closest point on the first air inlet. In some embodiments this closest point may constitute an annulus on both air inlets, as the first and second air inlets may be positioned concentrically to produce an even flow of air through the rotating component.

Figure 19 shows an exploded view of the indicator. This shows the indicator spring, the outer housing, the rotor element, the rotor backing, and the base plate. The indicator spring may be in the form of a clock spring as shown.

The housing outer is sized to receive the rotor element therein. The rotor element may have a central axle aligned with the longitudinal central axis of the rotor element. The rotor backing comprises inwardly extending spokes supporting a central hub configured to receive one end of the axle. Although not shown in this Figure the outer housing may comprise a corresponding set of spokes supporting a central hub (not shown) configured to receive the opposite end of the central axle. The outer housing and the rotor backing thereby support the rotor element for rotation within the housing. The spring is a spiral shaped spring comprising an attachment element in the shape of a U or L-shaped hook positioned at the outside terminal end of the spiral and a hub positioned at the inner terminal end of the spiral. The hook of the clock spring is connectable to the outer housing and the hub of the spring is connectable to the central axle of the rotor element. The rotor element and the outer housing are is generally hollow such that air can pass from one side of the indicator (which may be referred to as a flow rate meter) to the other. As such, the rotor element and the outer housing form part of the air flow pathway.

The rotor element comprises a number of rotors (or baffle elements) extending across the centre of the rotor element. The rotors are inclined relative to the direction of flow through the rotor element such that incident air causes the rotor element to rotate about the central axle against the action of the spring.

Figure 20 shows a plan view of the base plate of the indicator. This is a thin circular disc with two holes at the top for mating the base plate to the rotor backing.

Figure 21 shows a plan view of the spring of the indicator. This spring is configured to invert at a force that is equal to the force provided by the air flow at a predetermined level. Therefore, the spring can indicate that the air flow is not being provided at the predetermined level. If the air flow is not sufficient this can be a hazard to the user. So the use of this spring offers a safety indicator to the user. The spring comprises an L-shaped, or U-shaped attachment means. This attachment means may be used to attach the spring to a protuberance on a co-operating member of the indicator. For example, said protuberance may be on the outer housing, or any other suitable portion of the indicator to keep the spring of the indicator in place. The U or L- shaped attachment means may be particularly simple to assemble as it reduces complex or fiddly spring attachment, and so saves time in the assembly of the indicator.

Figure 22a shows a plan view of the central axle in the indicator. The axle may be attached to the rotor backing, through the rotor element (and therefore also through the outer housing within which the rotor element sits), and the other end of the axle is then connected to the spring. This axle is generally tubular, and is elongate. The axle comprises a proximal portion, a distal potion and a central portion. The central portion is covered with a resistive pattern. The central potion is the portion that may be in contact with the rotor of the indicator. Therefore, the central portion is covered in a resistive pattern to provide greater contact between the rotor and the axle. Figure 22b shows a pattern of the central portion of the axle. This is the resistive pattern shown in Figure 22a. The resistive pattern may be any resistive pattern that is suitable. However, this example may be particularly advantageous. In this example the resistive pattern is a knurling pattern. This is formed from interlocked elongate hexagonal elements, that when locked together leave central gaps in the pattern, wherein these gaps are diamond shaped (as in the four sided shape, rather than a cut of a stone diamond). This means that the contact surface on the knurling pattern varies, and this helps to give greater grip to the axle.

Figure 23a shows a plan view of the rotor of the indicator. This shows three rotors that are housed within a cylindrical member. These rotors form the shape of a marine propeller (a type of screw propeller). The rotors comprise curved blades that sweep across an angular range of 68-78 degrees (optimally 73 degrees). This angular range is highly specific. It has been found that the force at which the spring of the indicator flips from one state (e.g. showing the device to be in a safe condition) to a second state (e.g. showing the device to be in an unsafe position) is different for going from state one to state two, than for going from state two to state one. The spring is therefore calibrated such that false negatives (where the user is erroneously informed that the device is not functioning as intended) are minimised, whilst true failures are still detected. It has been found that this calibration is enhanced by having the curved blades sweep across the above angular range.

Figure 23b shows a cross section of the rotor showing various cut through.

Figure 23c is a first cut through showing a cross section of the rotor. This is along the E-E section of Figure 23b. This shows that one rotor in cross section (of the right of the Figure) extending outwardly towards the circumference of the cylindrical member towards the base of the cylindrical member. This also shows that each rotor is thin and so forms a curved plane. A second rotor (on the left of the figure) is also shown. This rotor is shown in plan view (as the rotors are different positions so are at different views in this cross section). Therefore, this rotor appears to be a flat plane (although in practice it is curved in the same manner as the other rotor shown).

Figure 24a shows a plan view along section G-G of Figure 22b. This shows that at section G-G the three rotors all form straight lines in cross-section.

Figure 24b shows a plan view along section H-H of Figure 22b. This shows that at section H-H the cross section of the rotors is beginning the curve. It is noted that this curve is perpendicular to the curve shown in Figure 23c, and show that the rotor blades each curve in two directions. This curvature forms the marine propeller shape o screw propeller shape) of the rotor blades.

Figure 24c shows a plan view along section I-I of Figure 22b. This shows that at section I-I that rotor is at its maximum curvature.

Figure 25a shows a plan view along section J-J of Figure 22b. This shows that at section J-J the rotors are back to being relatively straight in cross section, but are displaced relative with the cross section at G-G.

Figure 25a shows the portion of the rotor that mates with the base plate. The two pins are configured to mate with the base plate. It is noted that this element is optional. This element anchors the axle of Figure 22 and positions it within the centre of the rotor element. The division into three segments may also help with air flow in some embodiments. This same division may also be present on the front of the rotor arrangement (where the spring is attached)

Figure 25b shows this same portion in perspective view.

Figure 26a shows the front of the outer casing. This end of the outer casing is suitable for attachment to the spring. This shows an air divisor (similar to that shown in Figure 25) at the front of the outer casing. This divisor may also aid with air flow. As well as the divisor also shown is a protuberance that is located adjacent one of the arms of the divisor (it is noted that the protuberance may be situated on the casing away from one of the arms but that this may increase drag and turbulence). This protuberance is used for attaching the U or L-shaped hook of the spring to such that the spring is attached to the indicator. The axle may also pass through the spring in some embodiments to keep the spring centralised.

A second protuberance is also shown - situated outside the circumference of the rotor assembly. This may help the user in assembling the collar as this protuberance may be inserted into a groove n the collar that is situated adjacent the flat portion of both the top and bottom half of the collar - such that the indicator may be positioned in either side of the collar body during assembly to aid with flexibility.

Figure 26b shows the front of the rotor for attachment to the spring in perspective view. This shows the side protuberance attached to the outer casing. This shows the extent of the protuberance in this embodiment. This gives an indication of how this may be slotted into a groove on the collar.

Figure 27a shows a perspective view of a cable end with a locking pattern to prevent inadvertent decoupling of the cable from the power source. In this case the locking pattern comprises two atraumatic nodules located either side of the cable at the point the cable attaches to the power unit. The cable can therefore be inserted into the power unit and then rotated by the user. The nodules then lock into coupling voids situated in the power unit (or a casing surrounding the power unit so the system is compatible with multiple power units). Once rotated the cable cannot be removed from the power unit without further rotation being applied to return the cable to its original position with the nodules no longer aligned with the coupling voids. This rotation therefore prevents the cable from inadvertently decoupling with the power unit during use (for example due to the cable snagging on surface whilst the user is within the respirator.

Figure 27b shows a plan view of the end of the cable with the locking pattern. This also shows the elements of the cable in cross section with the outer casing of the cable surrounding a conducting element. The end of the cable comprises an over moulded portion to which the nodules are attached/integrally formed.

It is noted that regardless of the locking pattern a voltage may preferably be provided that is within the range of 5.1v to 5.4v and that comprises direct current. This voltage range may be particularly advantageous. The only powered element in this embodiment is the impeller. Providing a voltage in this range for the impeller enables the impeller to provide sufficient air flow for various applications. In some embodiments this may be 1701 of air flow per minute. However, more power may also significantly increase the noise produced by the impeller and by the resultant air flow. Noise has been found to be a great problem for respirators, especially in clinical settings where the user of the respirator often has to communicate with others such as patients and colleagues. The lower level of noise provided by using a 5.1v to 5.4 DC voltage means that the respirator is improved whilst still providing sufficient air flow for the intended use. In particular, the voltage range 5.2 to 5.3v has been found to be extremely beneficial, and a voltage of 5.25v has been found to be optimal.

It is noted that features of each of the embodiments described above, specifically the embodiment shown as well as those optional features described in the text above may be combined with the features of the other embodiments. For example, the hood described may be combined with any suitable collar, but it may be preferably combined with the collar also described herein. The impeller described herein may be particularly well adapted for use with the collar, and in some embodiments with the hood. However, the impeller may also be used on its own in separate applications. The indicator may be particularly suited to both the collar and to the impeller, but again may be used in separate applications. Each of these elements descried are intended to be combined together to form a single respirator that is particularly advantageous as it is effective at preventing the ingress of hazards from the outside environment, and is designed to provide required air flow, and to reduce the amount of noise generated, whilst being comfortable to wear for the user. The respirator as a whole is therefore highly advantageous over those that have come before, and the components are even more beneficial when used together as a respirator as a whole than when used apart. For example, the hood shape and the air outlet of the collar are designed together to create optimal air flow within the hood that avoids facial features of the user. Either hood or collar used without the other may provide some benefits but may not be as beneficial as when used together in the respirator as described above.