GB2627433A

GB2627433A - One-way valve

Info

Publication number: GB2627433A
Application number: GB2301316.2A
Authority: GB
Inventors: Crawshaw Taylor John
Original assignee: Fromanteel Ltd
Current assignee: Fromanteel Ltd
Priority date: 2023-01-30
Filing date: 2023-01-30
Publication date: 2024-08-28
Also published as: WO2024161114A1

Abstract

One-way valve 10 for use in an item of personal protective equipment (PPE) and comprising a travelling valve member 40 that moves between a normally closed position and an open position, a compliant seal member 30 that engages the valve member in its closed position, a resilient member 50 that urges the valve member into engagement with the compliant seal member to close the valve, a base member 20 that locates the seal member within the valve, and a housing member 60 that holds and retains the valve, seal, resilient and base members. The valve comprises one or more tracks 22 that guide the valve member between its closed and open positions, where the valve member slides or translates along the tracks from its closed position to its open positions due to pressure differentials caused by a user breathing. The valve member may be rigid and plate-like, having a sealing surface around its periphery for engaging the seal member, and one or more stiffening ribs comprising a single, annular rib separating the peripheral sealing surface from a central interior region. The resilient member may be a thin strip-like member or a thin wire compression or tension coil spring. The tracks may comprise pillars 21 on the base member. The PPE item may be a face mask.

Description

ONE-WAY VALVE

Field

This invention relates to a valve, for general use and in particular for use in personal protective equipment ("PPE"), for example face masks and other types of PPE.

Background

One-way valves are used in situations where it is desired to allow gas to flow in one direction with minimum obstruction, whilst substantially preventing the gas moving back in the other direction. They are particularly common in various types of PPE, as safety critical items that control the airflow into and out of a breathing volume. For example, face masks have often incorporated a one-way valve mounted directly onto the filter surface. These one-way valves are usually fixed onto the face mask permanently, with no way to service the one-way valve or replace it easily, if at all. The whole face mask is then discarded after use, with substantial cumulative cost as well as disposal problems (PPE is often manufactured from non-biodegradable plastic).

Typically, one-way valves incorporated into PPE operate on the pressure difference created by the user inhaling or exhaling. That is, the energy required to operate such valves comes from the user's breath. It is desired to keep the energy required to open such valves to a minimum, particularly for extended periods of time, and/or so that the effort in opening the valve on inhalation and/or exhalation does not become unnecessarily tiring to the user.

It has been common practice to provide a one-way valve having a circular, flexing diaphragm mounted centrally, and engaging a fixed, substantially circular sealing rim. The diaphragm in these valves has to stretch in order to move symmetrically to open the valve. Commonly this is not achieved, and the diaphragm tends to flex or bend open on a semi-diameter instead. Accordingly the valve requires an increased pressure difference to operate, which can be tiring especially in the medium to long term.

It is desired, therefore, to improve the construction of a one-way valve, to make it easier to use and incorporate into various types of PPE in a sustainable manner.

Summary

In accordance with various aspects of the invention, there is provided a one-way valve, in particular but not exclusively for use in an item of personal protective equipment ("PPE").

Such PPE typically has a means to filter out, trap or kill (Inactivate") pathogens in the air, for example using a physical filter or UV light. Throughout this disclosure we may refer to such means collectively as a "filter" (for brevity), but this is not intended to limit the means to a physical filter. One-way valves may be used to ensure that a user of the PPE, upon inhalation, only receives air that has passed through a filter (e.g., an inlet filter). Similarly, a one-way valve may also make it easier for the user to exhale, whilst protecting the user from any back-flow of air from the external environment.

In designing the one-way valve described herein, it was found to be advantageous that the pressure to open the valve is kept to a minimum. This pressure depends, in part, on the physiology of any particular user. For example, and as will become apparent, the valve of the invention progressively opens to cater for progressively increasing volumes of air. This means that the one-way valve performs equally well for a user with a large lung capacity as it does for a user with a smaller one.

The one-way valve according to various embodiments may include features ensuring any or all of the following advantages:- * The valve is normally closed with sufficient closing force to ensure it remains closed when subjected to the head movements of the user in normal life.

* The valve is opened by the start of the user's inhalation or exhalation but the pressure across the valve to achieve such opening is designed to be kept to a minimum.

* The valve progressively opens, for example dependant on the depth and speed of the user's inhalation or exhalation.

* The increase in pressure drop across the valve as the flow of inhalation or exhalation air increases is kept as low as practicable.

* The size (e.g., aspect ratio) of the one-way valve is such that a user's visage can be maintained, and not blocked by the valve (when used in PPE).

According to an aspect of the invention there is provided one-way valve. The valve may be for use in an item of personal protective equipment ("PPE"), although the valve is considered inventive in its own right, and could be used to control airflow through any body (e.g., into or out from an interior volume).

The valve comprises a travelling valve member configured to move between a normally closed position that prevents airflow through the valve and open positions that allow airflow through the valve. The valve further comprises a compliant seal member configured to engage the valve member in its closed position, and a resilient member configured to urge the valve member into engagement with the compliant seal member to close the valve. The valve further comprises a base member configured to locate the seal member within the valve, and a housing member to hold and retain the valve member, seal member, resilient member and base member. The valve may be affixed to a surface of a body (e.g. PPE), for example by affixing the housing member or base member thereto (suitable means are described herein).

Advantageously, the valve (e.g., base member or housing member) comprises one or more tracks configured to guide the valve member between its closed position and its open positions. The valve member may be configured to translate progressively (e.g., as a single piece) along the tracks from its closed position to its open positions as a result of pressure differentials caused by a user breathing and developing a slight pressure gradient across the valve. The valve member may substantially retain its shape (e.g., without bending or flexing) throughout its range of translation from its closed position to its open positions.

Accordingly, in response to the user's rate and depth of breathing the valve member can progressively move to open positions that allow progressively more airflow through the valve for the user, whilst minimising the backpressure to the airflow.

The valve member is urged into contact with the seal member in its closed position by the resilient member, which may have a relatively low spring rate. This means the valve may be closed preferably with a small force. The housing member combines with the base member to locate, align and retain the various parts of the valve.

A small millibar pressure drop (e.g., less than about 0.6 millibar, and preferably less than about 0.5 millibar) across the valve (e.g., the face area of the valve member) may be sufficient to cause the valve member to move away from the seal member to open the valve, against the action of the resilient member. The resilient member may lightly urge the valve member to its closed position even when there is a very small pressure drop across the valve (e.g., below the values disclosed above).

The valve mechanism described above avoids the use of flexing, bending or hinged valve members. These require, for example, the utmost precision of alignment of the valve member to the valve seal when its position is controlled by a fixed alignment mechanism.

The use of a travelling/translating valve member that is free to move without restriction other than a resilient member (e.g., by a further requirement for the valve member to flex, bend or operate using a hinge) means that the valve can respond better to small pressure differentials, for example a user breathing in and out. This solves the above-described problems with existing valves, in particular those that are incorporated into PPE. Of course, the -4 -valve described herein could be useful in any situation involving a relatively small pressure differential.

The valve member may not substantially flex or bend in use, e.g., could be rigid/hard. The valve member could be a plate-like member having a sealing surface around its periphery, such sealing surface being configured to engage a corresponding sealing surface of the seal member.

The valve member is typically configured with a low mass (e.g., it is thin and plate-like) thereby reducing the effect of any acceleration force from the movement of the user of the PPE.

The valve member may include a peripheral sealing surface, and optionally stiffened using a central region on a slightly different plane. This stiffening allows a reduction in the mass of the valve member as compared, for example, to a completely flat plate. Such a valve member then only requires a light spring force from the resilient member to retain the contact with the sealing surface of the seal member, e.g. during any acceleration forces caused by head movements of the user of the PPE.

The sealing surface of the seal member may comprise a rim configured to engage the sealing surface of the valve member, the rim being peripheral (e.g., annular) and preferably configured as a compliant lip seal. A body of the seal member could progressively reduce in thickness towards and including the rim.

The rim of the seal member may form part of a peripheral (e.g., annular) wall that defines a passage for gas to flow through the valve. As the sealing surface of the valve member lifts off the rim in use (i.e., to open the valve), gases may pass through the gap formed between the rim and the sealing surface, and then through the passage formed by the peripheral wall. Due to the progressive nature of the valve opening, the gap formed between the rim and the sealing surface increases proportional to the user's rate and depth of breathing.

The wall defining the passage for gas to flow through the valve may also extend around a longitudinal axis. The valve member may be configured to translate along the tracks in a first direction to open the valve, wherein the first direction is parallel to this longitudinal axis. The valve may have a height defined by a distance along/in the first direction, and a length defined by a distance perpendicular to the first direction, wherein a maximum height of the valve is at least twice as small as a maximum length, or wherein the maximum height of the valve is at least five times as small as the maximum length.

The valve member may comprise one or more stiffening ribs. The one or more stiffening ribs may comprise a single, annular rib separating the peripheral sealing surface from the central region interior of the annular rib. Thus, the central region may be depressed into the valve member from the plane of the peripheral sealing surface, with the annular stiffening rib interconnecting the depressed central region with the peripheral sealing surface. This means -5 -that a flat sealing surface is maintained around the periphery of the valve member, which is on a slightly different plane to the flat central region. The rib may form a slope between the two flat areas that contributes to the overall stiffness of the valve member, which helps maintain the flatness of the sealing surface in use.

The seal between the two members may be distinct from, e.g., compression (or hermetic) seals that require a large force to close the seal. The travelling valve member does not require such a seal since it only needs to close during relatively small pressure differentials, such as breathing. This is advantageous because the compliance achieved using a lip seal is enough to connect the whole periphery even if the seal rim or valve member are not perfectly planar. The use of the compliant lip seal advantageously accommodates such minor imperfections as well as helping seal over dust and other small contaminants.

The use of a compliant lip seal also assists the Bernoulli effect of the valve. That is, any slight leak of moving air is at a lower pressure to the static air on the other side of the seal, and the small leak has a tendency to close off the valve.

Advantageously the valve member is retained in contact with the rim of the compliant lip seal by the resilient member with sufficient spring force to maintain the valve in a closed position, even without the pressure of the breathing acting over the active area of the valve member, such that the acceleration forces by the movement of the user's head do not disrupt the sealing of the valve.

The resilient member may be a thin strip-like member (it does not have to exert a particularly strong closing force). For example, the resilient member could be a strip affixed to the housing at its centre, comprising two opposed cantilevered arms extending from the centre, and biased towards the valve member to urge it against the seal member. The resilient member could alternatively be a coil spring biased in the same manner (e.g., a thin wire formed into a compression or tension coil spring).

The housing member or seal member may comprise at least two pillars extending in the direction of opening of the valve member (i.e., the first direction defined above), wherein each pillar includes one of the tracks (formed in each of the pillars) along which the valve member translates. This provides a particularly simple and effective guide for the valve member, by maintaining the orientation of the valve member as it translates between its open and closed positions. This ensures, along with the resilient member, that the sealing surface of the valve member remains parallel to the opposing sealing surface of the seal member throughout translation of the valve member in use.

In an optimised arrangement, two pillars are preferably located on opposed sides of the housing, and most preferably near the maximum dimension across (breadth of) the valve member, and opposed tabs of the valve member are retained in two opposed tracks in each -6 -pillar. In such an arrangement, and where the resilient member is a cantilevered strip as aforesaid, the opposed arms of the resilient member could contact the valve member on a surface thereof adjacent to the opposed tabs. This permits a desired low spring force and low spring rate, as discussed.

The valve may comprise a housing formed from the base member and housing member as a single piece, or separate pieces that interconnect with each other to hold and retain the seal member, resilient member and valve member therebetween. The housing, valve member, seal member and resilient member may assemble to form a single assembly that can be manufactured, tested, packed, installed, cleaned, transported, replaced, etc. as a single unit.

The assembly process may include placing the seal member, resilient member and valve member between the base member and the housing member, and enclosing the base member and housing member together to form the valve (e.g., as a replaceable unit). An aspect of the invention, which may be claimed independently, includes a method of assembling the valve in this manner.

The housing member may comprise a plurality of stiffening arms configured to connect with the base member and extending over and across the valve to protect the valve member in use. These arms can extend in a bridge-like fashion across the housing member and base member (when connected) to protect the valve member from accidental damage, for example when the valve is being assembled or cleaned or during use.

The valve (e.g., housing and/or base member) may be configured to affix to an opposing surface of the item of PPE. This affixing could use permanent means such as glue, rivets or fasteners, or semi-permanent means such as screws, or spring fasteners to mount the valve as a single unit. The housing and/or base member could comprise clips that extend downward (e.g., away from the valve member towards an opposing surface of the item of PPE) and configured to clip onto the opposing surface. This means the valve can be easily installed or replaced as a single unit as described above.

The base member may comprise a peripheral (e.g., annular) wall defining a through-hole, through which the seal member extends. The seal member could be configured to span across opposed sides of the base member (i.e., on either side of the through-hole), such that one side of the seal member is configured to contact the valve member facing one side of the base member (to close the valve in use, urged by the resilient member), and the other side is configured to contact a surface (e.g., of PPE) facing the other, opposed side of the base member. The seal member on the latter (i.e., PPE) side could be configured as a compression seal, for example compressed by fastening the base member to the surface. Adequate compression could be achieved by use of a thin wall protruding from the base member towards the surface, providing localised seal compression between the surface and the base member. -7 -

Fastening the valve assembly to an opposed surface can be achieved using snap fit features. The seal member can also be used to create an airtight seal around these snap fit features. For example, the seal member could comprise extensions on the PPE side thereof, which are configured to extend around the snap fit features to create an airtight seal.

The valve may comprise a generally elliptical profile. For example, a periphery of the valve could be generally elliptical or oval. This is in comparison, for example, to a rectangle with rounded corners. The term "generally" is used to indicate that the profile may not be a perfect ellipse, and it may also have small indentations or protrusions, but is generally elliptical as opposed to circular, etc. The valve member may define an axis along which it moves, which axis is parallel with the direction of translation thereof (i.e., the first direction referred to above). The valve may have a height defined by a distance along this movement axis, and a length defined by the longest dimension of the valve perpendicular to this axis. The valve may also have a width, perpendicular to the length on the same plane. Taking an elliptical valve as an example, the major axis would correspond to the length, and the minor axis corresponding to the width, with the movement axis corresponding to the height.

It may be advantageous to provide the maximum height at least 2, 3, 4 or even 5 times as small than the maximum length or width. This means the valve is particularly shallow/thin and can be incorporated easily into items of PPE, such as a face mask or helmet. Additionally, or alternatively the valve may have a length that is at least 2, 3, 4 or even 5 times as large as its width.

Using the above described aspect ratios (e.g., a larger length than width, or generally elliptical profile, especially combined with a shallow height) means that the valve could be incorporated into a narrow housing, for example an item of PPE. This could be particularly important, for example, if the valve is to be positioned with the length, or major axis running parallel and close to the long axis of a user's lips, or above the user's forehead (for example, as described in the Applicant's co-pending international (PCT) publication number WO 2022/008539, which is incorporated herein by reference in its entirety).

In accordance with an aspect of the invention there is provided an item of PPE incorporating one or more one-way valves as described in any of the aspects or embodiments above. For example, the item of PPE may be configured to fit onto a user's head to enclose a breathable volume of air (e.g., a face mask or helmet), wherein one or more one-way valves as described are configured to control airflow into or out from the enclosed volume of air.

The invention is particularly suitable for use in a helmet-type device that fits around a user's head to enclose a breathable volume of air between the user's head and the device, for -8 -example further comprising a seal around the user's neck. Therefore an embodiment of the invention incudes the item of PPE being such a device.

The item of PPE could include a plurality of one-way valves as described in any of the aspects or embodiments above. One or more inlet valves could be configured to permit airflow into the enclosed volume of air, and optionally having passed through a filter such as that described in the Applicant's co-pending international (PCT) publication number WO 2022/008539 (see Figs. 5A-5F thereof), and one or more outlet valves could be configured to permit airflow out from the enclosed volume of air.

The invention also extends to a method of manufacturing a valve or item of PPE as described above. A particularly useful technique for manufacturing the constituent parts of the valve (including the housing, valve member and optionally the seal member) is additive manufacturing, otherwise known as 3D printing. This is the construction of a three-dimensional object from a computer-aided design ("CAD") model or other suitable type of digital 3D model, and can include a variety of processes in which material is deposited, joined or solidified under computer control to create a three-dimensional object, with material being added together (such as plastics, liquids or powder grains being fused together), typically layer by layer.

In accordance with an aspect of the invention there is provided a system comprising an additive manufacturing device configured to construct one or more (or all) of these constituent parts of the valve.

The invention also extends to a computer program comprising instructions which, when the program is executed by a computer of an additive manufacturing device (e.g., as described above), cause the additive manufacturing device to additively manufacture one or more (or all) of these constituent parts of the valve.

The invention also extends to a computer readable storage medium comprising instructions which, when executed by a computer of an additive manufacturing device (e.g., as described above), cause the additive manufacturing device to additively manufacture one or more (or all) of these constituent parts of the valve.

The instructions in any of the aspects described above including a computer program or computer readable storage medium may include a CAD model or other digital 3D printable model.

Brief description of the drawings

Fig. 1 shows an exploded view of a valve in accordance with the invention (e.g., prior to assembly). -9 -

Fig. 2 shows a cross-section through the combination of a seal member and base of the valve of Fig. 1, in an assembled state.

Figs. 3a and 3b show different cross-section views of the seal member and base of Fig. 2, again in an assembled state.

Fig. 4 is a graph showing a comparison between a valve according to the invention, and a valve of the prior art.

Detailed description

A valve 10 in accordance with an embodiment is provided, for attachment to a body (e.g., an item of PPE) and to control airflow into or out therefrom.

The valve 10 comprises a base member 20 that is provided in the form of a generally elliptical ring, although various types of shape may be used (e.g., circular). The base member 20 has various features that allow it to connect to the remainder of the apparatus. These features include diametrically opposed pillars 21, that each extend upwards with a U-shaped cross-section to form tracks 22. In addition to the pillars 21, the base member 20 comprises notches 23 spaced around its outer periphery. The base member 20 further comprises holes 24, which may also be diametrically opposed at substantially the same peripheral location as the pillars 21 (although that is not essential). These features will be described in more detail below.

The base member 20 comprises an inner peripheral wall 25, which in the illustrated case is the shape of an ellipse. The inner peripheral wall 25 defines a through-hole, fitted into which is a seal member 30. The seal member 30 is preferably elastomeric and straddles the inner peripheral wall 25 so that it is able to contact sealing surfaces on either side of the base member 20. The seal member 30 itself comprises an inner peripheral wall 31 that defines a passage for gas to flow through the valve 10.

Fig. 2 shows the seal member 30 in more detail (and in cross-section), which comprises an annular member 32 that comprises two annular flanges 33 and 34 extending radially away therefrom and parallel to each other. The two flanges and the annular member optionally form a U-shaped trough that extends around the entire peripheral surface of the seal member 30. Flanges 33 and 34 extend radially outward from the peripheral surface of the member 32, and straddle the inner peripheral wall 25 of the base member 20.

The seal member 30 comprises substantially opposing (e.g., opposite facing) surfaces 35 and 36, which are configured to contact respective sealing surfaces on the item of PPE and on the valve member 40 (which sit on opposed sides of the seal member 30 in use). The thickness of the sealing surface 36 abutting the valve member 40 may reduce towards a rim 37.

-10 -The valve 10 further comprises a movable valve member 40 configured to contact the seal member 30 in order to open and close the valve 10. In accordance with the invention, the valve member 40 is configured to translate, as opposed to (for example) flex around a periphery or pivot about a hinge. This means that the force required to open it is reduced as compared to conventional arrangements. The valve member 40 comprises a sealing surface 41 that faces the seal member 30 when the valve 10 is assembled. The sealing surface 41 is configured to contact the rim 37 of the seal member 30, acting as a compliant lip seal to close the valve 10.

The valve member 40 overlies the seal member 30 and has generally a similar shape to the base member 20 (in this case an ellipse). The valve member 40 may be a lightweight, rigid member, for example made from a thin, rigid, lightweight sheet material with a central rib 44 and folded edges 45. Tabs 42 are located at diametrically opposed ends of the valve member 40, which are configured to align with the tracks 22 formed by the U-shaped pillars 21 (see arrows 100). In use the tabs 42 are configured to ride along the tracks 22 as the valve member 40 moves to open and close the valve 10.

The valve 10 further comprises a resilient member 50 configured to urge the valve member 40 to its closed position, that is towards and against the seal member 30.

In the illustrated embodiment the surface of the valve member 40 adjacent the tabs 42 is flat, so as to form diametrically opposed contact surfaces 43 for the resilient member 50. Here, the resilient member 50 is a simple torsion spring in the form of a thin metal strip. The strip comprises two opposed arms 51 bent and extending from a central mounting portion 52. The arms 51 are configured to press against the contact surfaces 43 to urge the valve member 40 towards the seal member 30 (see arrows 101). The ends of the arms 51 preferably contact the valve member 40 adjacent to the outer periphery thereof. This can assist in maintaining the orientation of the valve member 40 as it translates to open and close the valve 10 in use.

Other types of resilient member 50 may be used in the present invention, as will be appreciated by a person of skill in the art. The resilient member 50 could comprise any suitable type of compression or tension spring. For example, the resilient member 50 could be formed by a wire or wires formed into a compression or tension spring, for example as a coil spring. If formed as a tension spring, the resilient member 50 could be biased between the valve member 40 and the base member 20.

The valve 10 further comprises a housing member 60 configured to cap the valve 10 and hold the various parts together. In the illustrated embodiment the resilient member 50 is biased between the valve member 40 and a housing member 60.

The housing member 60 is skeletal and comprises a lower, elliptical rim 61 in substantially the same shape as the base member 20. The outer rim 61 comprises clips 62 spaced around its outer periphery, which align with the notches 23 located on the base member 20 (see arrows 102). In the illustrated embodiment the resilient member 50 is attached to a central portion 63 and held in place by any suitable means (e.g., a pin, rivet or other mechanism; see arrow 103).

Upon assembly of the valve 10, the housing member 60 is pushed onto the base member 20, with the seal member 30, valve member 40 and resilient member 50 therebetween. As it is pushed, the clips 62 ride over the notches 23 to clip onto the housing member 60, which holds it firmly against the base member 20. In this position, and absent any force to open the valve (e.g., caused by breathing), the resilient member 50 is configured to urge the valve member 40 against the seal member 30 to close the valve 10.

In order to open the valve 10, a pressure differential may be created across the seal between the valve member 40 and the seal member 30. Where the valve 10 is used in a PPE device, this pressure differential is created by the user inhaling or exhaling. Once the pressure differential is sufficient, the valve member 40 will translate along the tracks 22 and against the action of the resilient member 50. As noted above, this requires no rotation, flex or expansion (etc.) of the valve member 40. This means that the pressure differential need not be as high as in conventional arrangements. In the case of PPE, this means that a user does not need to exert as much energy in order to open and close the valve 10. As will be appreciated, this technical effect is equally applicable to other situations in which a valve is required to open and close in an efficient manner. In other words, whilst the valve 10 of the invention as illustrated is particularly advantageous for use in PPE devices, the valve 10 is inventive in its own right. As such the broadest aspects of the invention are not limited to any particular use.

Moving back to the particular construction of the valve 10 as illustrated, the housing member 60 may be stiffened by various arms 64 that extend in a bridge-like fashion across it. These arms 64 also form a cover for the valve 10, protecting the various parts from accidental damage, for example when cleaning the valve 10. The arms 64 may extend to the central portion 63 of the housing member 60. The combination of the base member 20 and housing member 60 may form a shell, with the arms 64 forming part of the shell and increasing the rigidity of the valve 10.

As noted above, the tabs 42 of the valve member 40 cooperate with the tracks 22 to maintain the correct orientation of the valve member 40 as it moves between open and closed positions. This ensures the sealing surface 41 of the valve member 40 properly engages the seal member 30 as the valve 10 closes. The resilient member 50 may help to locate the valve member 40 as well.

It will be appreciated that various modifications to the illustrated embodiment may be made, without departing from the scope of the invention as defined by the claims.

For example, the pillars 21 are shown as being incorporated on the base member 20 and locate into suitable recesses 65 of the housing member 60. Instead, they may be incorporated -12_ on the housing member 60 and could, for example, hang from the arms 64 at similar, diametrically opposed locations and locate onto suitable recesses in the base member 20. In other words, and more generally, the tracks along which the valve member moves could be located on the housing member instead of the base member.

The base member 20 and seal member 30 are shown as separate pieces, but in some embodiments they may be integrally formed as a single piece. It may however be preferable to press a separate seal member 30 into a harder, more rigid base member 20.

Fig. 2 and Fig. 3 show section views of the base member 20 and seal member 30 for clarification of further detail.

The seal member 30 is illustrated as straddling the inner peripheral wall 25 of the base member 20, so that it can seal against both the valve member 40, as well as a surface of the body to which the valve 10 is attached. The illustrated seal member 30 therefore performs three functions. A first, compliant lip seal is formed against the valve member 40 using rim 37 of sealing surface 36. A second, compression seal using sealing surface 35 is formed between the base member 20 and the PPE. This is not essential and the seal member 30 could be configured to seal against only the valve member 40. In such a case an additional seal member could be provided between the base member 20 and the PPE. Third, an airtight seal may optionally be provided around any fastening features of the base member 20 to the PPE, for example using sealing features 38 configured to provide a sealing, interference fit around any such fastening features.

Additional location features 39 may be used in order to locate the seal member 30 within the base member 20 using features such as pips/pedestals 26, prior to instillation of the valve 10 into/on the item of PPE.

The valve 10 may be mounted to a portion of a PPE device, and the seal member(s) 30 used to achieve an airtight seal in the interface between the base member 20 and the PPE device. Adequate compression could be achieved by use of a thin, annular wall 27 protruding from the base member 20 towards the item of PPE, providing localised seal compression between the item of PPE and the base member 20. This wall 27 could hang from a lower surface of the base member 20 and adjacent to the inner peripheral wall 25.

Fastening the base member 20 to the PPE can be achieved using any suitable means, for example snap fit features/clips 66. Optional features of the seal member 30, such as sealing features 38, may be configured to create an airtight seal around these snap fit features 66.

The valve (e.g., housing member or base member) may be affixed to a body by any suitable means, for example using downwardly extending clips 66. These have the effect of enabling the valve 10 to be removed as a complete unit, enabling easy replacement and/or inspection of the valve 10. Alternative mounting arrangements could include glue, rivets or -13 -fasteners, each of which could be configured to mount the valve 10 to the body. Semipermanent means such as screws or spring fasteners may additionally, or alternatively be used and configured to mount the valve 10 to a body. The seal member 30 may be adapted to extend around any such alternative mountings, for example using sealing features 38 within or extending from lower surface 34 and configured to form a compression or interference sealing fit around such mountings. For example, the seal member 30 could extend around any screw holes to prevent gas leakage bypassing the valve 10.

The valve 10 as illustrated in Fig. 1 (e.g., the periphery thereof) has an elliptical shape, with the tracks 22 and tabs 42 located in substantially the same diametrically opposite locations, namely at the vertices of the ellipse. This provides a particularly useful arrangement for inserting within a PPE device, since it has a narrow profile whilst providing an effective and easy way for the valve to move between open and closed positions (as discussed above). One type of PPE device that would benefit from the valve described herein is described in the Applicant's co-pending international (PCT) publication number WO 2022/008539 (which is incorporated herein by reference in its entirety), or other helmet-type device, which would benefit, for example, from the more efficient opening/closing of the valve, as well as the narrow profile.

Once assembled, the valve 10 is intended to form a unit that can be replaced, transported, etc. with all its constituent parts without any disassembly. In the illustrated embodiment the valve 10 can be clipped into place (using the downwardly extending clips 66) to replace an existing, similar valve. In other words, the valve 10 may be replaceable as a single unit.

Fig. 4 is a graph showing the results of testing valves according to the illustrated embodiment ("WellMet") as compared to valves of the prior art ("FFP3"). The prior art valves were each of the type having a circular diaphragm mounted centrally, which flex to engage an opposing, fixed circular sealing rim.

A housing was constructed for each set of valves, each housing being substantially identical and forming an enclosed volume with an air inlet/outlet opening. Two prior art valves were mounted to one housing, and two valves of the invention were mounted to the other. In each case, one of the valves was an inlet one-way valve, permitting airflow into the enclosed volume, and the other was an outlet one-way valve, permitting airflow out from the enclosed volume. A 12V radial fan was connected to the air inlet/outlet opening. A BME680 pressure sensor was fitted to each housing to measure internal pressure, from which could be calculated a pressure difference across the valve. A high precision camera was used to monitor movement of the valve, and calculate the open area.

Upon operation of the fan in one direction, air was pushed by the fan into the enclosed volume, and then flowed out through the outlet valve (the inlet valve remaining shut). Upon operation of the fan in the opposite direction air was drawn into the enclosed volume through -14 -the inlet valve (the outlet valve remaining shut) and then flowed out through the air inlet/outlet opening.

Fig. 4 shows a graph of valve open area in mm2 versus pressure difference (drop) across the valve in millibar. The graph illustrates a number of advantages associated with the valve according to the invention. Firstly, the valve according to the invention opens at a lower pressure difference, which improves the response of the valve (for example, to sudden/fast changes in breathing). Second, the valve opening area increases at a much faster rate than the prior art valve as the pressure difference increases, meaning a lower pressure difference is required to achieve a given opening area. This also means that resistance to flow is lower for the valve of the invention. When incorporated into an item of PPE, these advantages improve the ease and feel of the valve (and PPE) as a user breathes in and out.

Some prior art ("FFP3") face masks are configured with dual exhaust valves, for example that overlie each cheek. Whilst this may help exhalation, it significantly reduces the space available for the filter media on the mask. This, in turn, increases the pressure difference required during inhalation. The exhaust valve described herein would, for a given type of PPE, assist both exhalation and inhalation, for the reasons provided above.

Claims

-15 -CLAIMS: 1. A one-way valve for use in an item of personal protective equipment ("PPE") and configured to control airflow into or out from an enclosed volume, the valve comprising: a travelling valve member configured to move between a normally closed position that prevents airflow through the valve and open positions that allow airflow through the valve; a compliant seal member configured to engage the valve member in its closed position; a resilient member configured to urge the valve member into engagement with the compliant seal member to close the valve; and a base member configured to locate the seal member within the valve; and a housing member to hold and retain the valve member, seal member, resilient member and base member, characterised in that the valve comprises one or more tracks configured to guide the valve member between its closed position and its open positions, and in that the valve member is configured to translate progressively along the tracks from its closed position to its open positions as a result of pressure differentials caused by a user breathing.
2. A valve as claimed in claim 1, wherein the valve member is a lightweight, rigid member that does not flex or bend in use.
3. A valve as claimed in claim 1 or 2, wherein the valve member is a plate-like member having a sealing surface around its periphery, which sealing surface is configured to engage the seal member.
4. A valve as claimed in claim 1, 2 or 3, wherein the valve member comprises one or more stiffening ribs.
5. A valve as claimed in claims 3 and 4, wherein the one or more stiffening ribs comprise a single, annular rib separating the peripheral sealing surface from a central region interior of the annular rib.
6. A valve as claimed in claim 5, wherein the central region is depressed into the valve member from the plane of the peripheral sealing surface, with the annular stiffening rib interconnecting the depressed central region with the peripheral sealing surface.
-16 - 7. A valve as claimed in any preceding claim, wherein the seal member comprises a sealing rim configured to engage the sealing surface of the valve member, the sealing rim configured as a compliant seal.
8. A valve as claimed in claim 7, wherein the sealing rim of the seal member forms part of a peripheral wall that defines a passage for gas to flow through the valve, and as the sealing surface of the valve member lifts off the rim to open the valve in use, gases are permitted to pass through the gap formed between the rim and the sealing surface, and then through the passage formed by the peripheral wall.
9. A valve as claimed in claim 8, wherein the peripheral wall extends around a longitudinal axis, and the valve member is configured to translate along the tracks in a first direction to open the valve, wherein the first direction is parallel to the longitudinal axis of the peripheral wall.
10. A valve as claimed in any preceding claim, wherein the resilient member is a thin strip-like member.
11. A valve as claimed in any of claims 1-9, wherein the resilient member is a thin wire formed into a compression or tension coil spring.
12. A valve as claimed in any preceding claim, wherein the valve member is configured to slide along the track in use between its open and closed positions, without bending or flexing.
13. A valve as claimed in any preceding claim, wherein the housing comprises at least two pillars extending in the direction of translation of the valve member, each pillar comprising one of the tracks along which the valve member slides.
14. A valve as claimed in any preceding claim, wherein the housing comprises a base member and housing member that interconnect with each other to hold and retain the seal member, resilient member and valve member between the base member and the housing member.
15. A valve as claimed in any preceding claim, wherein the housing, valve member, seal member and resilient member assemble to form a single unit that can be replaced, transported, etc. as a single unit.
16. A valve as claimed in any preceding claim, wherein the valve comprises a generally elliptical profile.
-17 - 17. A valve as claimed in any preceding claim, wherein the direction of movement of the valve member defines a first direction, and the valve has a height defined by a distance in the first direction, and a length defined by a distance perpendicular to the first direction, wherein a maximum height of the valve is at least twice as small as a maximum length.
18. A valve as claimed in any preceding claim, wherein the maximum height of the valve is at least five times as small as the maximum length.
19. An item of PPE including at least one one-way valve as claimed in any preceding claim.
20. An item of PPE as claimed in claim 19 and configured to fit onto a user's head to enclose a breathable volume of air, wherein the one-way valve is configured to control airflow into or out from the enclosed volume of air.
21. An item of PPE as claimed in claim 19 and configured to fit onto a user's head to enclose a breathable volume of air, wherein a first of the one-way valves is configured to control airflow into the enclosed volume of air, and a second of the one-way valve is configured to control airflow out from the enclosed volume of air.
22. An item of PPE as claimed in claim 19, 20 or 21, wherein the item is a helmet-type device that fits around a user's head and seals around the user's neck to enclose a breathable volume of air between the user's head and the device.
23. An item of PPE as claimed in claim 22, wherein the item of PPE includes at least two one-way valves as claimed in any of claims 1-18, a first of the one-way valves being an inlet valve configured to control airflow into the enclosed volume of air (e.g., via a filter), and a second of the one-way valves being an outlet valve configured to control airflow out from the enclosed volume of air.