EP3612278B1

EP3612278B1 - A filter cartridge and a method of manufacturing a filter cartridge

Info

Publication number: EP3612278B1
Application number: EP18721445.7A
Authority: EP
Inventors: Stephen Sanders; Gavin Shaw; Matthew JUDSON; Clive Johnstone
Original assignee: JSP Ltd
Current assignee: JSP Ltd
Priority date: 2017-04-19
Filing date: 2018-04-19
Publication date: 2023-10-11
Anticipated expiration: 2038-04-19
Also published as: PL3612278T3; GB2561586A; ES2968275T3; EP3612278A1; GB201706201D0; WO2018193256A1; GB2561586B

Description

This invention relates to a filter cartridge for a respiratory mask, to be used in areas and/or work where there is a high level of pollution and/or hazardous environment, and a method of manufacturing such a filter cartridge.
Respiratory masks for protecting the wearer against potentially hazardous contaminants in the air, such as particles, gases and vapours, are well known and are becoming an increasingly important item of personal protection equipment (PPE) in some workplaces to protect personnel against such contaminants that might otherwise endanger their health and safety at work, if inhaled.
Respiratory masks which are more suited to long-term use, and are more comfortable to wear, have a face-piece made from moulded rubber which is held over the wearer's nose and mouth by means of an adjustable head strap, or plurality of straps, conventionally made from an elasticated fabric or rubber. The face-piece forms a hermetic seal against the wearers face. Such respiratory masks have at least one opening on the side of the face-piece to which a filter cartridge can be fitted, often by engaging corresponding screw threaded attachment means on both the filter cartridge and the respiratory mask.
A number of different types of filter cartridges are known in the art, and vary in properties of weight, size, longevity and filterability. Single-, or few-, use cartridges are known which are advantageously smaller and lighter, but have a much shorter lifespan than more robust filter cartridges and/or may not be suitable for all types of hazardous environments. Such filter cartridges are known as 'pancake' or disc-filters and typically have the filter media exposed on the outer wall of the filter frame.
For more dangerous environments, fully encased filter cartridges are preferred, and typically comprise a hard outer casing in which the filter media is provided.
It is important to ensure the respiratory mask and filter are fitted correctly before, and periodically during, the wearer's time in a hazardous environment, and in fact currently, health and safety regulations require a pre-use fit check each time a face-piece is worn and before entering the hazardous environment. Inadequate fit will cause a significant reduction in the protection afforded to the wearer, and will allow airborne contaminants and particulates to leak into the mask.
Pre-use fit procedures vary according to the specific configuration of the respiratory mask and/or filter cartridge, For the type described above, wherein the mask itself requires at least one filter cartridge or disc filter to be fitted thereto, the procedure generally involves temporarily sealing the respiratory airflow which is defined through the filter cartridge at the location at which the filter cartridge is attached to the mask.
Typically, a generally tubular connecting member is provided on the filter device that carries the means to attach the filter device over the opening in a face mask. In order to provide a seal between the connecting member and the edge defining the opening in the face mask, a foam gasket seal is typically provided around the connecting member or around the opening in the face mask. This provides a deformable layer between the filter cartridge and the respiratory mask. When the filter cartridge is attached to the respiratory mask, the foam gasket seal is compressed in some areas, but able to expand into other areas where there may be a gap due to uneven surfaces, thus providing the required seal. Additionally, it is known to provide a foam gasket seal on the upper part of a filter cartridge or around the breathing aperture of a disc-filter, in order to provide a good seal when the negative pressure fit check is performed.
However, this solution presents a number of difficulties, firstly, the manufacturer must purchase and stock the foam material needed for producing the individual foam gasket seals. Cutting and aligning foam, or other material, gasket seals and fitting them correctly on the filter cartridge and/or respiratory mask is labour-intensive, as well as having a high margin of error. Furthermore, waste material is produced when cutting the foam gasket seals which will need to be stored, and disposed of or recycled, adding to the overall labour, and therefore cost, of the foam gasket seal.
Foam gasket seals must be attached to the filter cartridge material and/or respiratory mask by means of an adhesive. However, it is known for the adhesive to fail and the foam gasket seal to become loose, dislodged or broken, thus rendering the filter cartridge and/or respiratory mask unusable. Furthermore, foam can become brittle and permanently deformed over time, and, depending on where it is fitted, can reduce the lifetime of the respiratory mask and/or filter cartridge.
WO 2012/100116 discloses a low-profile filter frame for maintaining an open filter plenum configuration during normal operation, and for enabling quick and reliable negative pressure testing. The frame has upper and lower halves. A breathing tube in the lower half connects to a respirator port. The upper and lower halves snap together to maintain the structure in an assembled configuration. The halves also include features that bias the halves apart when the device is in the assembled configuration, thereby maintaining the breathing tube open. To perform a fit test, a force is applied to an outer surface of the upper half, which moves the halves together, in opposition to the bias, so that the upper half seals against the breathing tube. The frame can be provided in as a single-piece, with a living hinge connecting upper and lower halves, or the upper and lower halves can be separate pieces.
It is an object of aspects of the present invention to address at least some of these issues and, in accordance with a first aspect of the present invention, there is provided a filter cartridge for a respiratory mask, the filter cartridge comprising a first and second frame member pivotally connected together at one end, said first frame member comprising a connecting member configured to connect said filter cartridge to a respiratory mask for use and defining a breathing aperture therethrough which extends through said first frame member and defines a respiratory flow path when said filter cartridge is in a first configuration, said filter cartridge being configured to receive a filter media therein or thereon to filter air, in use, flowing along said respiratory flow path, said first and second frame members being selectively pivotally moveable relative to each other from said first configuration to a second configuration in which a seal is formed between said first and second frame members and said respiratory flow path is blocked, characterised in that said filter cartridge further comprises a double-sided gasket seal comprising a first seal portion that provides said seal between said first and second frame members in said second configuration, and a second seal portion on said connecting member configured to form a seal between said filter cartridge and a respiratory mask, in use, wherein said first and second seal portions are formed integrally with each other by means of a single over-moulding process.
In a first exemplary embodiment, the filter cartridge may comprise a disc-filter frame, wherein said first frame member comprises a generally planar base and said second frame member comprises an elongate lever pivotally mounted at one end to said first frame member. In this case, the connecting member may be a generally tubular member having a lower end portion that extends outwardly from a breathing aperture provided in said base, and the second seal portion may be provided around said lower end portion of said connecting member, at or adjacent to said base. The lever may include a cover portion configured to cover said breathing aperture to block said respiratory flow path in said second configuration, and wherein said first seal portion is provided around the periphery of said breathing aperture. Alternatively, the connecting member may be a generally tubular member that extends through a breathing aperture provided in said base and has a lower end portion and an upper end portion, and the lever may include a cover portion configured to cover the end of said upper end portion of said connecting member to block said respiratory flow path in said second configuration, and wherein said first seal portion is provided around the peripheral end of said upper end portion.
The first and second seal portions may be connected by an integral joining strip that extends through a channel in said first frame member, and the gasket seal may be formed of a rubber resin material such as thermoplastic elastomer (TPE) rubber resin.
In a second exemplary embodiment of the invention, the filter cartridge may comprise an encased filter cartridge, wherein said first frame member comprises an at least partially open-topped base receptacle configured to receive therein a filter media, in use, and said second frame member comprises a cover pivotally mounted at one end to said base receptacle for selective pivotal movement between a first configuration, in which there is a gap between the upper edges of the base receptacle and the inner surface of the cover, said gap defining said respiratory air flow path, and a second configuration in which the inner surface of the cover covers the open top of the base receptacle and blocks the respiratory flow path. In this case, the first seal portion may extend around said upper edges of said base receptacle. A generally planar mesh cover may be provided across said open top of said base receptacle.
The connecting member may be a generally tubular member that extends from or through a breathing aperture provided in said base receptacle and has a lower end portion, said second seal portion being provided around said lower end portion of said connecting member, at or adjacent to said base receptacle.
Once again, the first and second seal portions may be connected by an integral joining strip that extends through a channel in said base receptacle.
A second breathing aperture may be provided in said cover, at or adjacent the end thereof opposite to the end at which it is pivotally connected to said base receptacle.
Once again, the gasket seal may be formed of a rubber resin material such as a thermoplastic elastomer rubber resin.
The breathing aperture may be provided longitudinally off-centre in said first frame member, nearer to the end at which the second frame member is pivotally connected to the first frame member than to the opposing end.
In accordance with a second aspect of the present invention, there is provided a method of manufacturing a filter cartridge according to any of the preceding claims, comprising the steps of:

moulding said first frame member, said first frame member comprising a channel therethrough and defining a first recess around an opening in or of said first frame member forming said respiratory flow path and a second recess around said connecting member, said first and second recesses and said channel together defining a fluid flow path therethrough;
performing an over-moulding process in respect of said first frame member by injecting into said fluid flow path a molten rubber resin to form said double-sided gasket seal, wherein rubber resin flowing into said first recess forms said first seal portion and rubber resin flowing into said second recess forms said second seal portion;
moulding said second frame member; and
assembling said first and second frame member to form a filter cartridge according to any of the preceding claims.

The method may further comprise the step of transporting said assembled filter cartridge to a conveyor belt and applying, at said conveyor belt, a filter media on or to said filter cartridge.
Optionally, the first frame member may be moulded in a first cavity and said second filter member may be moulded separately in a second cavity, and automated transport means may be used to move at least one of said frame members to the same location as the other of said frame members for assembly. Automated transport means may also be used to transport said assembled filter frame to said conveyor belt. Such automated transport means may comprise one or more robotic devices.
The rubber resin may be a thermoplastic elastomer (TPE) rubber resin.
These and other aspects of the present invention will be apparent from the following specific description, in which embodiments of the present invention are described, by way of examples only, and with reference to the accompanying drawings, in which:

Figure 1A is a schematic perspective cross-sectional view of a disc-filter according to a first exemplary embodiment of the present invention;
Figure 1B is a schematic side cross-sectional view of the disc-filter of Figure 1A;
Figure 1C is a schematic perspective view of the frame member of the disc-filter of Figures 1A and 1B;
Figure 2 is a schematic perspective view of the double-sided gasket seal of the disc-filter of Figure 1A;
Figure 3 is a schematic partial close-up view of the connecting member and gasket seal of the disc-filter of Figure 1A;
Figure 4 is a top view of the housing base of an encased filter style cartridge according to a second exemplary embodiment of the invention;
Figure 5 is a bottom view of the housing base of Figure 4;
Figure 6 is a schematic side view of an encased filter cartridge according to a second exemplary embodiment of the present invention;
Figure 7 is a schematic cut-away view of the filter cartridge of Figure 6; and
Figures 8A to 8D are schematic diagrams showing some of the steps of a method of manufacturing a disc-filter according to a first exemplary embodiment of the present invention.

In the following description, directional descriptors such as upper, lower, inner, outer, vertical, horizontal, etc. are used to describe the exemplary embodiments of the invention when the embodiment is in the preferred orientation. It will be understood by those skilled in the art that the embodiments described below can change their orientation during use, and therefore the corresponding descriptors will change.
Referring to Figures 1A to 1C of the drawings, a disc filter style filter device according to a first exemplary embodiment of the present invention is illustrated, and comprises a lever 10 and frame member 12.
The frame member 12 comprises a single piece of moulded plastic, of generally rectangular shape, with peripheral cut-out portions 11 to reduce the material used and the overall weight of the device. A generally circular breathing aperture is provided in the frame member 12, the breathing aperture being located off-centre, i.e. nearer one end (hereinafter referred to as the 'front' end 12a) than the other.
A generally tubular connecting member 16 extends through the breathing aperture, having an 'inner' end 14a extending beyond the inner side of the frame member 12 and an opposing 'outer' end 14b extending beyond the opposing 'outer' side of the frame member 12. A peripheral flange 18 extends radially outwardly from the connecting member 16, immediately below the above-mentioned outer side of the frame member 12. An extension portion 32 extends from the outer edge of the peripheral flange 18, toward the 'front' end 12a, and from the outer to the inner side, of the frame member 12. Struts 21 extend radially across the breathing aperture and meet at a generally central location therein, wherein a pin 23 is provided for receiving and supporting a rubber diaphragm (not shown). Connecting member 16 carries attachment means for attaching the filter device over an opening in a respiratory face mask. Such attachment means may be a twist-lock mechanism, as illustrated, but it will be understood by a person skilled in the art that other types of attachment means may be provided, and the present invention is not necessarily intended to be limited in this regard.
It will be appreciated by a person skilled in the art that the frame member 12, connecting member 16, peripheral flange 18, extension portion 32, struts and pin 23 are integrally formed in this exemplary embodiment of the present invention and, as such, are all part of the same piece of moulded plastic.
A channel 19 extends through the peripheral flange 18 nearest the front end 12a, from the inner to the outer side of the frame member 12.
The lever 10 is pivotally mounted to the frame member 12 adjacent the 'front' end 12a, such that it extends longitudinally, and spaced apart from, the inner side of the frame member 12. The lever 10 comprises an elongate piece of moulded plastic, again generally rectangular in shape, but shorter and narrower than the frame member 12. At one end, there is provided a mechanism for pivotally mounting it to the frame member 12, in this case the mechanism comprising a pair of stepped feet 25 which are received in respective openings 27 in the frame member 12. The mechanism, thus assembled, allows the lever 10 to be pivoted under manual force toward the frame member 12.
A generally circular cap region 20, defined by a protruding rim 20a is formed on the 'inner' surface of the lever 10 such that, when assembled, the location of the cap region 20 corresponds to the location of the 'inner' end 14a of the connecting member 16. The lever 10 is biased away from the frame member 12 such that, at rest, it extends at an angle from the pivot point 22 away from the frame member 12. In use, to perform a fit check, a user grips the frame member 12 at the 'rear' end 12b and the free end of the lever 10 between their thumb and forefinger, squeezing them together, to pivot the lever 10 toward the frame member 12 such that the protruding rim 20a of the cap region 20 covers the breathing aperture defined at the 'inner' end of the connecting member 16.
As explained above, in prior art arrangements, a foam gasket seal would be provided around the periphery of the breathing aperture within the filter frame to provide a good seal between the cap region on the lever 10 and the breathing aperture. Prior art manufacturing techniques would not permit for the connecting member 16 to extend into the filter frame because it is not possible, using known techniques, to provide a foam gasket seal thereon. A second, separate foam gasket seal would be provided around the connecting member, immediately below the peripheral flange, to provide a good seal between the filter cartridge and the face mask, in use. In contrast, the present invention comprises a unique, double-sided, overmoulded gasket seal, as described hereinafter.
Thus, referring back to Figures 1A to 1C of the drawings, a disc filter according to a first exemplary embodiment of the present invention, comprises a gasket seal comprising a first seal portion 24 that extends around the periphery of the 'inner' end of the connecting member 16, and a second seal portion 26 that extends around the connecting member 16, immediately below the peripheral flange 18. The seal portions 24, 26 are connected by a narrow joining strip 28 that extends through the channel 19 through the peripheral flange 18. The double-sided gasket seal 30, comprising the first and second seal portions 24, 26 and the joining strip 28 is integrally formed of rubber resin such as, for example, thermoplastic elastomer (TPE) rubber, e.g. Dryflex ^®. However, other suitable rubber resin that can be used in an overmoulding process will be known to a person skilled in the art, and the present invention is not necessarily intended to be limited in this regard. A significant advantage of using rubber, compared with the foam used in prior art devices, is that it lasts longer and is much less susceptible to breakage or deformation, thus further ensuring the effectiveness of the negative pressure fit check, in use, as described hereinafter.
The double-sided gasket seal 30 is formed by a single overmoulding process, as described later, wherein the molten rubber resin is injected at point B at the end of the extension portion 32 that extends from the outer edge of the peripheral flange 18 to the 'inner' surface of the frame member 12, such that it flows through a recess located around the periphery of the 'inner' end of the connecting member 16, through the channel 19 and through a recess located around the connecting member 16 immediately below the peripheral flange 18, so as to create the double-sided gasket seal 30 illustrated in Figure 2. Thus, and referring additionally to Figure 3 of the drawings, a unique, double-sided, rubber gasket seal 30 is provided on both the inside and the outside of the frame member 12, that extends through the frame member 12 (via the channel 19).
Thus, in use, the filter frame (comprising the frame member 12, the lever 10 and the double-sided gasket seal 30) is encased within a filter media 13, with the 'outer' end 14b of the connecting member 16 extending through an aperture or hole in the filter media 13. The assembly is attached to a respiratory face mask by locking the 'outer' end of the connecting member 16 within an opening in the face mask, such that the 'front' end 12a of the frame member faces forward (i.e. the general direction in which the user is facing) and the 'rear' end 12b is directed rearwardly accordingly. The second seal portion 26 of the gasket seal 30 provides an airtight seal between the connecting member 16 and the face mask. To perform a negative pressure fit check, the user squeezes the free end of the lever 10 (through the filter media 13) toward the frame member 12 using their thumb and forefinger, as described above, to bring the cap region 20 down over the first seal portion 24 around the 'inner' end of the connecting member 16, thereby sealing the breathing aperture. If the user tries to breathe, there should be no respiratory path at all if the filter device is fitted and operating correctly.
Referring to Figures 4 to 7 of the drawings, an encased filter cartridge according to a second exemplary embodiment of the invention is illustrated. The assembled filter cartridge comprises a housing cover 50, filter media 14, a housing base 52, and a unique double-sided gasket seal 30'; and the encased filter cartridge , thus assembled, can be fitted to the face-piece of a respiratory mask (not shown), via an opening therein, as before. The filter media 14 is held within the housing base 52 and covered by the housing cover 50. The housing cover has an intake aperture 58 at one end thereof, and side walls that extends down over the side edges of the housing base 52.
As in the first exemplary embodiment of the present invention, as described with reference to Figures 1 to 3 of the drawings, a connecting member 16' extends from the bottom of the filter cartridge and is formed integrally with the housing base 52. As before, the connecting member 16' of the present exemplary embodiment is shown to be a twist-lock mechanism, which engages with a corresponding aperture in the face-piece of a respiratory mask (not shown) to connect the filter cartridge within an opening in the respiratory mask, as and when required. It will be understood by those skilled in the art that other types of attachment mechanisms, such as co-operative mating threads on the connecting member 16' and the aperture in the respiratory mask, or snap- or interference-fit, may be used. It is important that the connection between the filter cartridge 2 and the face-piece of the respiratory mask is strong enough to withstand accidental knocks or blows, and that the filter cartridge is only removed when the user desires to remove it.
A breathing aperture 18' is provided through the bottom surface of the housing base 52 and the connecting member 16' extends outward therefrom. A respiratory airway is defined through the aperture 58 in the housing cover 50, through the filter media 14 held within the housing base 52, through the breathing aperture 18' and into a face-piece of the respiratory mask, when the filter cartridge is attached to a respiratory mask for use.
Struts 22 extend radially inwardly across the breathing aperture 18' and meet in a generally central point. The struts 22 may provide support for a rubber circular diaphragm, as before.
The inner surface of the housing cover 50 is provided, at the end opposite to that having therein the breathing aperture 58, with a pivot pin (not shown) which is cooperatively engaged with a pivot loop provided on an outer wall of the housing base 52. The pivot pin and pivot loop together form a fixed pivotal connected between the housing cover 50 and the housing base 52. When no external forces are acting on the filter cartridge, there is a gap between the upper edges of the housing base 52 and the inner surface of the housing cover 50, providing a further respiratory airway. In order to perform a negative pressure fit check, application of pressure in the direction of arrows A pushes the housing cover 50 and housing base 52 together such that the inner surface of the housing cover 50 engages with the upper edges of the housing base 52, covering the opening defined thereby, and thus sealing the respiratory airways.
The unique double-sided gasket seal 30' extends around the upper edges of the housing base 52 and also around the connecting member 16', immediately below the bottom surface of the housing base 52, to provide the dual functions of providing a seal between the upper edges of the housing base 52 and the inner surface of the housing cover 50 (during a negative pressure fit check) and also to seal the connecting member 16' against the edges of the opening in the face mask. As before, the double-sided gasket seal 30' is formed by an overmoulding process using rubber resin. The housing base 52 is formed with a planar grid 52' across its upper edges and, during manufacture, molten rubber resin is injected at a point adjacent the end at which the pivotal connection between the cover 50 and the base 52 is located and flows through a recess provided around the upper edges of the housing base 52 and also through a recess provided around the connecting member 16', immediately below the housing base 52. A channel (not shown) extends through the housing base 52, at or near the injection point, such that the first seal portion 30a' (around the upper edges of the base 52) and the second seal portion 30b' (around the connecting member 16') are integrally formed, in a single over-moulding process, with a joining strip (not shown) therebetween.
The exemplary embodiments of the invention described above are advantageous for a number of reasons. Due to the manufacturing process, which will be described hereinafter, the cost per filter cartridge is reduced. When manufacturing multiple millions for sale with respiratory masks and/or as spares, this cost saving amounts to a significant increase in profit margins for the manufacturer, or ultimately a saving by the end user. Additionally, since the rubber gasket seals are more effective at creating a seal between two surfaces the cost saving represents an improvement in the quality and effectiveness of the end product. Rubber is more durable than foam, therefore the lifetime of the filter cartridges is extended and the quality of the seal is increased, with less material and labour expense to achieve it.
Referring now to Figures 8A-8D of the drawings, a novel, fully automated, method of manufacturing filter cartridges having the unique double-sided gasket seals 30, 30' of the filter devices described above begins by separately moulding the two parts of the filter cartridge frame/housing. In the following description of the manufacturing method, the disc-filter style cartridge of the first exemplary embodiment described above will be referenced by way of example only; however, it will be clear to the person skilled in the art that the manufacturing process can be modified to make the encased filter cartridge of the second exemplary embodiment described above.
The frame member12 of the filter cartridge is moulded in a first cavity 100. When complete, a robotic arm 102 moves the frame member 12 from a first cavity 100 to a second cavity 104, where a rubber resin (not shown) is over-moulded into and through the frame member 12, the injection point of the rubber resin being shown in Figure 1A of the drawings indicated at arrow B. Meanwhile a separate tool moulds the lever 10 (not shown).
Robotic arms bring the lever 10 and the frame member 12 together for assembly. Once assembled the frame member 12 and lever 10, complete with over-moulded double-sided gasket seal 30, 30', form the main filter frame 112 of the disc-filter cartridge.
The filter frames 112 are then deposited onto a conveyor belt 116 on which a continuous roll of fibrous filter media 110 is prepared with pre-punched holes. The pre-punched holes are equal in diameter to the connecting member 16 of the frame member 12. The connecting member 16 of each filter frame 112 is aligned with a pre-punched hole by a pair of robotic arms 106, 108. A series of manoeuvers by the robotic arms fold the filter media 110 over the filter frame 112. The filter media 110 is then secured in place by ultrasonically welding the filter media 110 around the perimeter of the filter frame 112, and also around the connecting member 16. Excess filter media 110 is removed by any suitable method known in the art, in this exemplary embodiment the completed disc-filter style cartridge is separated from the roll of filter media 110 by a fast-moving downward-acting cutter 114.
It will be apparent to those skilled in the art that modifications to this method of manufacturing can be made in order to enable the process to be used for encased filter cartridges of the type described above with reference to a second exemplary embodiment of the present invention, and indeed other filter cartridges to which a gasket seal needs to be fitted both inside and outside the main filter cartridge frame. The method of manufacturing is fully-automated and therefore reduces labour costs and waste while improving uniformity and quality of the end product. The unique double-sided gasket seal 30, 30' present on the frame member 12 or housing base 52 presents a unique improvement over the prior art foam gasket seals. In addition to the advantages listed throughout this specific description, by including a portion of the unique double-sided gasket seal 30, 30' on the connecting member of filter cartridge itself (rather than around the opening in the face mask), the gasket seal is replaced every time the filter cartridge is replaced and therefore very little wear builds up on the gasket seal during the lifetime of the filter cartridge, thereby improving safety and reliability.
It will be apparent to someone skilled in the art, from the foregoing description that modifications and varieties can be made to the described embodiments, without departing from the scope of the invention as defined by the appended claims.

Claims

A filter cartridge for a respiratory mask, the filter cartridge comprising a first (12) and second (10) frame member pivotally connected together at one end (12a), said first frame member (12) comprising a connecting member (16) configured to connect said filter cartridge to a respiratory mask for use and defining a breathing aperture therethrough which extends through said first frame member (12) and defines a respiratory flow path when said filter cartridge is in a first configuration, said filter cartridge being configured to receive a filter media (14) therein or thereon to filter air, in use, flowing along said respiratory flow path, said first and second frame members (12, 10) being selectively pivotally moveable relative to each other from said first configuration to a second configuration in which a seal is formed between said first and second frame members (12, 10) and said respiratory flow path is blocked, characterised in that said filter cartridge further comprises a double-sided gasket seal (30) comprising a first seal portion (24) that provides said seal between said first and second frame members (12, 10) in said second configuration, and a second seal portion (26) on said connecting member (16) configured to form a seal between said filter cartridge and a respiratory mask, in use, wherein said first and second seal portions (24, 26) are formed integrally with each other by means of a single over-moulding process.
A filter cartridge according to claim 1, comprising a disc-filter frame, wherein said first frame member (12) comprises a generally planar base and said second frame member (10) comprises an elongate lever pivotally mounted at one end (12a) to said first frame member (12).
A filter cartridge according to claim 2, wherein said connecting member (16) is a generally tubular member having a lower end portion (14b) that extends outwardly from a breathing aperture provided in said base (12); optionally wherein said second seal portion (26) is provided around said lower end portion (14b) of said connecting member (16), at or adjacent to said base (12).
A filter cartridge according to claim 3, wherein said lever (10) includes a cover portion (20) configured to cover said breathing aperture to block said respiratory flow path in said second configuration, and wherein said first seal portion (24) is provided around the periphery of said breathing aperture.
A filter cartridge according to claim 3, wherein said connecting member (16) is a generally tubular member that extends through a breathing aperture provided in said base (12) and has a lower end portion (14b) and an upper end portion (14a); optionally wherein said lever (10) includes a cover portion (20) configured to cover the end of said upper end portion (14a) of said connecting member (16) to block said respiratory flow path in said second configuration, and wherein said first seal portion (24) is provided around the peripheral end of said upper end portion (14a).
A filter cartridge according to any of the preceding claims, wherein said first and second seal portions (24, 26) are connected by an integral joining strip (28) that extends through a channel in said first frame member (12).
A filter cartridge according to claim 1, comprising an encased filter cartridge, wherein said first frame member (12) comprises an at least partially open-topped base receptacle (52) configured to receive therein a filter media (14), in use, and said second frame member (10) comprises a cover (50) pivotally mounted at one end (12a) to said base receptacle (52) for selective pivotal movement between a first configuration, in which there is a gap between the upper edges of the base receptacle (52) and the inner surface of the cover (50), said gap defining said respiratory air flow path, and a second configuration in which the inner surface of the cover (50) covers the open top of the base receptacle (52) and blocks the respiratory flow path; optionally wherein said first seal portion (30a') extends around said upper edges of said base receptacle (52).
A filter cartridge according to claim 7, wherein said connecting member (16') is a generally tubular member that extends from or through a breathing aperture (18') provided in said base receptacle (52) and has a lower end portion, said second seal portion (30b') being provided around said lower end portion of said connecting member (16'), at or adjacent to said base receptacle (52).
A filter cartridge according to claim 7 or 8, wherein said first and second seal portions (30a', 30b') are connected by an integral joining strip that extends through a channel in said base receptacle (52).
A filter cartridge according to any of claims 7 to 9, wherein a second breathing aperture (58) is provided in said cover (50), at or adjacent the end thereof opposite to the end at which it is pivotally connected to said base receptacle (52).
A filter cartridge according to any preceding claim, wherein said gasket seal (30, 30') is formed of a rubber resin material; optionally wherein said rubber resin material is a thermoplastic elastomer rubber resin.
A filter cartridge according to any of the preceding claims, wherein said breathing aperture is provided longitudinally off-centre in said first frame member (12), nearer to the end (12a) at which the second frame member (10) is pivotally connected to the first frame member (12) than to the opposing end (12b).
A method of manufacturing a filter cartridge according to any of the preceding claims, comprising the steps of:
- moulding said first frame member (12), said first frame member comprising a channel therethrough and defining a first recess around an opening in or of said first frame member forming said respiratory flow path and a second recess around said connecting member, said first and second recesses and said channel together defining a fluid flow path therethrough;

- performing an over-moulding process in respect of said first frame member by injecting into said fluid flow path a molten rubber resin, such as a thermoplastic elastomer (TPE) rubber resin, to form said double-sided gasket seal (30), wherein rubber resin flowing into said first recess forms said first seal portion (24) and rubber resin flowing into said second recess forms said second seal portion (26);

- moulding said second frame member (10); and

- assembling said first and second frame member (12, 10) to form a filter cartridge (112) according to any of the preceding claims;
the method optionally further comprising the step of transporting said assembled filter cartridge to a conveyor belt (116) and applying, at said conveyor belt, a filter media (110) on or to said filter cartridge (112).
A method according to claim 13, wherein said first frame member (12) is moulded in a first cavity (100) and said second frame member (10) is moulded separately in a second cavity, and automated transport means are used to move at least one of said frame members to the same location as the other of said frame members for assembly.
A method according to claim 13 or 14, wherein automated transport means are used to transport said assembled filter frame (112) to said conveyor belt (116); optionally wherein said automated transport means comprises one or more robotic devices.