FR3111633A1 - Ceramic filter tablet for respiratory protection mask. - Google Patents

Abstract

PRECISE France, SAINT-GOBAIN CENTER FOR RESEARCH AND EUROPEAN STUDIES, and NANOCERAM BOUVERAT-PERNAT "Ceramic filter pellet for respiratory protection mask." The invention relates to a sintered ceramic part in the form of a pellet (6; 6.1, 6.2), intended to be implanted in a respiratory protection mask (1), the part having a total porosity greater than 40%. The invention also relates to a filtration cartridge incorporating such a pellet. Figure 10

Description

Filtering ceramic pellet for respiratory protection mask.

The present invention relates to a sintered ceramic part, more particularly intended to be implanted in a respiratory protection mask.

The applications of the invention are numerous, including the medical and paramedical sector, health security services (ambulance, firefighters, civil security, etc.), the general public, in particular the elderly, businesses, deaf people or hard of hearing.

The technological development of the ^20th century was accompanied by the introduction of a range of respiratory protection masks adapted to risk environments.

Thus, in a hospital environment, surgical protective masks are used. Such a mask consists of one or more layers of textile or paper held on the face of the wearer by elastic bands or straps. Typically, a surgical mask comprises a stack consisting of a non-woven polypropylene (PP) outer layer / a PP microfiber filter layer / an acrylic backing / a non-woven PP inner layer. Fine particles suspended in an aerosol that can be filtered by surgical masks can be of the order of 3µm ± 0.3 µm (D50 by volume), with an efficiency of up to 98%

A major drawback of these masks is that they are dedicated to single use, and thus generate a significant amount of waste because they cannot be recycled.

In addition, these masks are designed to filter only bacteria and viruses. Even if they de facto filter certain pollutants and/or certain particles of matter, they are not designed for this.

Also, the intrinsic quality of protection of these masks is relatively low, because they are mainly intended to avoid the projections of the wearers on the close environment and not the reverse.

In addition, in use, the nursing staff who wear such masks cannot really communicate with the patients, because the textile layer(s) on the one hand, form a sound barrier and on the other hand, are opaque, which prohibits lip reading by patients.

In the context of the coronavirus epidemic, designated COVID-19, washable textile masks have been produced. These washable masks have the same inherent limitations as surgical masks. Effective cleaning requires compliance with specific conditions, in particular drying at high temperature and/or ironing. In addition, they are often thick and therefore relatively heavy and uncomfortable for some users, with in particular the frequent risk of the glasses fogging up. The manufacture of such textile masks is also difficult to automate, since it requires sewing operations.

Finally, as with surgical masks, the seal between a mask and its wearer is non-existent, which is harmful in environments where aerosols circulate which may be contaminated, for example with viruses of the COVID-19 type.

In dusty environments, such as construction sites, or those with the additional presence of harmful gases, different technologies for the realization of respiratory protection masks can be implemented.

Thus, there are masks with a preformed shell with one or more housings in which filtering materials are housed. These masks in principle have an improved filtering power, for example FFP2 or FFP3 according to the NF EN 149 and NF EN 13724-7 standards.

In particular, FPP3 type shell masks are known designed to filter fine and very fine particles, and up to 99% of fine particles of the order of 0.06 to 0.1 μm (D50 by volume).

Shell military masks are intended exclusively to filter gaseous pollutants, such as CO ₂ or nitrogen oxide.

These shell masks are for the most part quite heavy, to the point that wearing them for a long time cannot reasonably be considered.

In addition, their relative rigidity means that the interface with the skin is often imperfect, especially for certain face morphologies, with here again the frequent risk of fogging of wearers' glasses.

To improve the interface with the skin, it is common to add a metal insert to conform to the shape of the nose or a foam gasket. However, these elements complicate the manufacture of masks and their recycling.

In the emergency of the COVID-19 epidemic, some plastic masks were made by additive manufacturing. These masks comprise a flexible part forming a skirt connected to a central rigid part in the form of a shell which houses one or more layers of filtering material between two grids including a cap which can be removed to allow replacement of the layers of filter material. The masks offered are also relatively heavy and uncomfortable to wear over a long period. In addition, the proposed additive manufacturing is incompatible with mass production likely to meet strong demand in times of health crisis.

Also, when a user is wearing a goggle, they are usually inaudible.

In addition to all the aforementioned drawbacks, most of the existing respiratory protection masks are designed for a type of species to be filtered which is fixed (fine particles or gaseous pollutants or viruses and bacteria) and/or for a given level of efficiency. (FFP1 or FFP2 or FFP3).

Above all, none of the existing masks is imperishable.

Finally, none of them really benefited from an aesthetic design.

There is therefore a need to improve respiratory protection masks, in particular so that they are comfortable, efficient in terms of filtration, scalable as to the nature of the species to be filtered or the level of efficiency sought, easy to clean without risk contamination, reusable or even imperishable, recyclable, aesthetic, and that they allow their users (wearers) to be easily audible.

An additional need is for the manufacture of these masks to be compatible with mass production, in particular if it has to be done in a short time.

The object of the invention is to meet at least in part this (these) need(s).

To do this, the invention firstly relates to a respiratory protection mask, comprising:

- a rigid frame to be placed on a user's face;

• a sealing envelope, fixed or formed integrally with at least the rear of the frame, shaped to match the shape of the face by surrounding an area comprising the nose and the mouth, the sealing envelope comprising in its rear part a flexible sealing lip shaped to be in contact with the face by delimiting the zone;
• a transparent interface wall, fixed or formed integrally with the front of the frame, so as to make the mouth visible;
• a first filtration cartridge housing at least one filtering material, the first filtration cartridge being removably fixed to the envelope, to allow the air to pass by filtering it from outside the mask by inspiration from the user and the if necessary outwards by user expiration.

Advantageously, the sealing lip is made with a flexible wall thickness which may be thick, over at least part of its length. This guarantees all the more both the comfort of the user of the mask and the tightness of the volume imprisoning the mouth and nose vis-à-vis the outside.

According to an advantageous embodiment, the mask comprises a second filtration cartridge housing at least one filtering material, the second filtration cartridge being removably fixed to the envelope, to allow air to pass by filtering it from the outside by inspiration from the user and if necessary outwards by expiration from the user.

Preferably, the first and second filter cartridges are identical. Thus, in addition to the standardization of the cartridges, one can have the same flow of air inspired by cartridge, which makes it possible to have a balanced filtration and a homogeneous air circulation in the volume in contact with the user, imprisoned by the mask.

According to an advantageous embodiment, the mask comprises:

• a third filter cartridge housing at least one filter material, the third filter cartridge being removably attached to the casing;
• at least one exhaust valve fixed in the frame in front of the third filtration cartridge, the exhaust valve being configured to allow air to pass by filtering it only from the inside towards the outside of the mask by exhalation of the user.

Advantageously, the exhaust valve consists of a flexible blade extended by a stud, the blade being held by being inserted into the frame with the stud mounted in a through hole of the frame, so that a exhalation of air from inside the mask deflects the blade, freeing the pin from the hole at least partially, while inhaling air from inside the mask deflects the blade, closing the hole with the pin.

Advantageously, the exhaust valve is configured to amplify the speech sounds of the user.

Preferably, the exhaust valve is made of elastomer, more preferably of silicone.

According to this mode, the mask is advantageously symmetrical with respect to a longitudinal median plane, the first and second cartridges being fixed symmetrically on either side of the median plane, each through one of the side edges of the envelope, while that the third cartridge is fixed through one of the longitudinal edges of the casing around the longitudinal median plane. The first, possibly the second, possibly the third cartridge being fixed to the envelope by a snap-fastening.

Thus, in this mode with a third cartridge, the air is inspired only through the first and second cartridges, because the valve prevents any inspiration by the third cartridge which is therefore dedicated to the filtration only of the air exhaled by the mask user.

According to an advantageous example of implementation of removable fastening by snap-fastening, the first, optionally the second, optionally the third filtration cartridge is provided with a continuous snap-in groove or bead on its periphery to snap in with respectively a bead or a continuous snap groove on a periphery of the casing so as to achieve a sealed attachment. We thus obtain a fixing that is simple and quick to implement with perfectly controlled sealing.

According to a variant embodiment, the casing is fixed to the frame by a snap-fastening.

The transparent interface wall can be fixed to the frame by gluing.

Advantageously, the rigid frame is made of plastic material(s), preferably polycarbonate (PC). The envelope being made of elastomer, preferably silicone.

To attach the mask to the head of a user in a simple and effective manner, the rigid frame advantageously comprises at least two lugs formed integrally therewith, for the attachment of at least one elastic band with holes, forming a tether to the user's head.

According to one embodiment, the mask comprises a visor removably attached to the rigid frame. This visor protects the eyes, especially in an environment where splashes occur. The visor can be perfectly integrated into both the ergonomics and the aesthetics of the mask.

Advantageously, the visor is fixed to the rigid frame by a snap-fastening. According to this mode and an advantageous variant embodiment, the visor comprises at least two snap-in tabs or at least two snap-in notches to be snapped individually with respectively at least two snap-in notches or at least two snap-in tabs of the armature.

Preferably, the transparent interface wall and/or, where applicable, the visor is (are) made of plastic material(s), preferably polycarbonate (PC) or poly(methyl methacrylate) (PMMA). These materials have both very good optical characteristics and mechanical and thermal resistance. In particular, PMMA can be easily thermoformed while retaining very good optical transparency.

It is possible to envisage that the interface wall and/or, where appropriate, the visor be mass-tinted while being transparent. Thus, depending on the environments and the wishes of the users, one can either have a colorless or colored wall.

For aesthetic and ergonomic reasons, the transparent interface wall and/or, where applicable, the visor can be curved, preferably in the form of a spherical portion.

According to an advantageous variant, the rigid frame supports at least one identification plate on which are engraved at least one alphanumeric and/or bar code. Each mask according to the invention can be individually identified.

According to another advantageous variant, the mask can comprise at least one housing for at least one radio-identification tag (RFID) and/or at least one electronic wireless communication chip of the wifi or Bluetooth® type. It is thus possible to carry out a precise follow-up of the user. For example, in environments highly exposed to contaminants, information can be recorded in real time, in particular the user's exposure time, location, etc.

A further subject of the invention is a filtration cartridge, intended to be removably attached to a health protection mask according to one of the preceding claims, comprising:

- a body in two parts assembled to one another defining a housing, each of the two parts being pierced with at least one through hole opening into the housing;

- a holding and sealing support, housed in the housing of the body;

- at least one filter material maintained with sealing in the support.

Alternatively, the two parts of the body can be screwed together.

The invention finally relates to a sintered ceramic part in the form of a pellet, intended to be implanted in a respiratory protection mask, the ceramic part having a total porosity greater than 40%, preferably greater than 50%, preferably greater than 55%, or even greater than 60%, or even greater than 70% and preferably less than 90%, or even less than 85%, or even less than 80%, preferably between 55 and 85%.

Such total porosity offers a microstructure perfectly suited to the treatment of pathogens.

A ceramic pellet also has the advantage of being able to be cleaned and/or purified to be reused. It therefore generates little waste.

By “ceramic” is meant in the context of the invention, any non-metallic and non-organic material.

The term "sintering" means the consolidation by heat treatment at over 1100°C of a preform, possibly with partial or total melting of some of its constituents (but not all of its constituents, so that the preform is not transformed into a liquid mass).

By "recrystallized silicon carbide" is meant silicon carbide recrystallized by high temperature treatment of the ceramic part, and in particular of the ceramic foam. Recrystallization is a well-known phenomenon corresponding to a consolidation by evaporation of the smallest grains of silicon carbide then condensation to form the bond with the largest grains.

The total porosity, in percentage, is typically equal to 100 x (1 - the ratio of the geometric density divided by the absolute density).

Geometric density is measured according to ISO 5016:1997 or EN 1094-4 and expressed in g/cm3. It is conventionally equal to the ratio of the mass of the sample divided by the apparent volume.

The absolute density value, expressed in g/cm ³ , is conventionally measured by dividing the mass of a sample by the volume of this ground sample so as to substantially eliminate the porosity.

The ceramic part is made of silicon carbide or cordierite or aluminum titanate or zirconia or alumina or mullite or silica or their mixtures. According to a variant, the ceramic part comprises more than 80% by mass of silicon carbide (SiC), or even more than 90% of silicon carbide, or even more than 95% of silicon carbide, or even consists essentially of silicon carbide . According to a variant, the silicon carbide is recrystallized silicon carbide, in particular in the alpha form. Recrystallized silicon carbide is particularly interesting, because it makes it possible to obtain parts with a microstructure whose pores are almost exclusively open and highly interconnected.

According to another variant, the ceramic part consists, in mass percentage on the basis of the crystallized phases, of 25 to 55% mullite (3Al ₂ O ₃ -2SiO ₂ ), 20 to 65% corundum (Al ₂ O ₃ under alpha crystalline form), 10 to 40% zirconia (ZrO ₂ ), mullite, corundum and zirconia together representing more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 98 % of the mass of the crystallized phases.

Forming processes by strip casting or by foaming are particularly suitable for the production of parts with complex shapes, in particular pellets, before firing to avoid/limit the machining steps.

Advantageously, a ceramic part according to the invention has a thickness of between 1 and 20 mm, preferably greater than 2 mm, or even greater than 3 mm and/or less than 15 mm, or even less than 10 mm.

Preferably, the ceramic part also has one or more of the following characteristics:

- the median pore size (D50 by volume, measured by mercury porosity) is greater than 1 µm, or even greater than 5 µm, or greater than 10 µm, or greater than 20 µm, or greater than 30 µm, or greater than 40 µm and less than 400 μm, or even less than 300 μm, or even less than 200 μm, or even less than 160 μm, or even less than 150 μm;

- pores larger than 300 μm represent less than 10% by volume, or even less than 5% by volume;

- tortuosity is greater than 1, or even greater than 1.1, or greater than 1.2, or greater than 1.3, or greater than 1.4 and less than 2, or greater than 1.9, or greater than 1.8, or even less than 1.7. The tortuosity is measured by nanotomography. The images have a resolution suitable for binarization. The use of software such as iMorph© makes it possible to obtain a geometric characterization in three dimensions and to calculate the tortuosity. The tortuosity is defined as the ratio between the shortest route allowing the sample to cross in the direction of its thickness, within its porosity, and the distance or the line segment joining the starting point and the starting point. arrival corresponding to this route.

According to a first advantageous embodiment, the ceramic part is a ceramic foam having a plurality of cells, the majority of these cells being connected to other adjacent cells by cellular windows or pores. A cell on the surface of the ceramic foam also generally has one or more openings to the outside. The walls delimiting the cells have a so-called “intergranular” porosity. They are in fact formed by agglomeration of particles, this agglomeration leaving interstices or “intergranular pores” between the particles. An example of ceramic foam according to this embodiment is described in EP1778601.

According to this first mode, the ceramic foam advantageously has one or more of the following characteristics:

• the intergranular porosity is at least 5%, preferably at least 8%, more preferably at least 10% and/or less than 25%, or even less than 20%;
• the median size of the intergranular pores is less than 25 μm, or even less than 20 μm and greater than 4 μm, or even greater than 7 μm;
• the median size of the cellular pores is less than 400 μm, even less than 300 μm, even less than 200 μm, even less than 180 μm, even less than 160 μm and greater than 40 μm, even greater than 50 μm, even greater than 80μm;
• the pore size distribution is bimodal;
• the total porosity is greater than 55%, or even greater than 60%, or even greater than 70%.

An analysis using a mercury prosimeter makes it possible to highlight several porosity characteristics: a distribution of the size of the pores showing two distinct peaks representative of the two families of pores, the median size of the pores of each of the families being given by the position of the apex of each peak.

A ceramic foam advantageously has an essentially open porosity, which makes it accessible and allows a high filtration capacity.

A ceramic foam advantageously makes it possible to filter particles whose size is up to 30 times smaller than the median pore size, which makes it possible to limit the pressure drop.

A ceramic foam advantageously presents an excellent compromise between the pressure drop and the filtration capacity, which makes it possible to form a mask having both good breathability and effective filtration.

According to a second advantageous embodiment, the ceramic part consists of several superposed ceramic layers having different respective total porosities. Preferably, the total porosity and the median pore size of the layer constituting the air inlet face to be filtered are lower than those of the other layer(s). The different layers can result from the impregnation of part of the ceramic part.

In particular when the ceramic part is a ceramic foam of recrystallized silicon carbide, a layer can be obtained by impregnating part of the thickness of the part with a slip based on silicon carbide and optionally comprising pore-forming agents; the slip then fills both the cellular pores and the intergranular porosity constituting a differentiated layer in the ceramic piece. Preferably, the impregnated part is the air inlet face to be filtered.

Preferably, this impregnated part has:

• a total porosity less than the total porosity of the non-impregnated part. Preferably the total porosity of the impregnated part is greater than 30%, or even greater than 35% and preferably less than 70%, or even less than 60%, or even less than 50%; and or
• pores whose median size is greater than 1 μm, or even greater than 2 μm, or even greater than 3 μm and less than 20 μm, or even less than 10 μm, or even less than 5 μm; and or
• a thickness of between 5 and 500 μm, preferably greater than 10 μm and/or less than 400 μm, or even less than 200 μm, or even less than 100 μm.

According to an advantageous variant, whatever the type of ceramic part, the ceramic part is provided with a coating for inactivating one or more pathogens.

The inactivation coating is tailored to the pathogens to be inactivated.

In particular, the inactivation coating can be a coating eliminating one or more pathogenic agents, for example bactericidal and/or virucidal. The inactivation coating may in particular consist of nanoparticles, in particular based on silver and/or copper.

The coating can be deposited by impregnation directly in the porous structure, in particular when it is a ceramic foam, directly on the walls of the foam,

The coating can be deposited on one of the outer faces of the ceramic part, preferably the air inlet face to be filtered.

The very porous microstructure, and in particular the microstructure of a ceramic foam, advantageously offers a very large exchange surface with the inactivation coating.

The invention also relates to the use of a sintered ceramic part as described above for filtering the air intended to circulate in a respiratory protection mask.

The advantages of a mask according to the invention are numerous, among which we can mention:

• very effective respiratory protection, the flow of air inspired and exhaled by a wearer of the mask being guided to cross only the filter material cartridge(s) because the lip envelope ensures perfect sealing of the internal volume of the mask surrounding the mouth and the nose ;
• the possibility of making the mask very easily and quickly upgradeable, by carrying out a removable assembly/disassembly of cartridges configured according to the desired level of filtration FMP1, FMP2, FMP3 relates to the masks and, where appropriate, virucidal and/or bactericidal properties;
• comfort for the wearer due to the lightness of the possible materials for the various components of the mask and the flow of air to be inhaled, which can be well calibrated;
• a very long lifespan or even imperishability through the use of resistant and stable materials over time, in particular for ceramics which can be used to guarantee effective filtration;
• the possibility of recycling all the components of the mask;
• a very aesthetic appearance by the implementation of a transparent wall preferably curved to match the shape of a face, which also allows lip reading;
• the absence of fogging on a wearer's glasses because the sealing lip guarantees that no air exhaled by the wearer can come in the direction of the eyes;
• the implementation of a sound amplification function by a suitable configuration of the air exhaust valve;
• effective eye protection with a visor that can be quickly and easily integrated into the mask;
• a manufacturing process compatible with mass production in a short time, all the components being able to be produced by perfectly mastered processes, such as injection molding or thermoforming of plastic or elastomer material, for the rigid frame, the casing, the exhaust valve, the visor, the attachment straps, or the cutting for the cartridges, the foaming or the sintering of the ceramic pellets as filter materials;
• easy cleaning of all components, in particular by going through the dishwasher, or even sterilization in an autoclave. Ceramic pellets, particularly in recrystallized silicon carbide, are perfectly suited to being washed and reintegrated into the mask multiple times. The chemical and temperature resistance of recrystallized silicon carbide makes it very well suited and resistant to multiple washing agents, even when hot;
• traceability of the mask wearer, particularly useful in very restrictive environments, such as hospital environments, dusty environments, with harmful gas atmospheres, etc.

Other advantages and characteristics of the invention will emerge better on reading the detailed description of examples of implementation of the invention given by way of illustration and not limitation with reference to the following figures.

FIG. 1 is a perspective view from the front of an example of a respiratory protection mask according to the invention.

Figure 2 is a perspective view from the rear of the mask example according to Figure 1.

Figure 3 is an exploded view of a mask according to Figures 1 and 2.

FIG. 4 shows a front view of another example of respiratory protection according to the invention as it is in the configuration worn by a user.

Figure 5 is a side view of Figure 4.

Figure 6 is a front view of the example of Figures 4 and 5, the removable visor having been removed.

FIG. 7 is a front perspective view of an example of a filtration cartridge with filtering material according to the invention to be removably attached to a mask according to the invention.

Figure 8 is a rear perspective view of a removable filter cartridge according to Figure 7.

Figure 9 is a longitudinal sectional view of the filter cartridge according to Figures 7 and 8.

FIG. 10 represents in longitudinal section a variant of a filtration cartridge according to the invention.

FIG. 11 is a schematic view of the filtration principle of a mask according to the invention, both on inspiration and on expiration of the user.

FIG. 12 is a detail sectional view of a mask according to the invention produced at the level of a removable filtration cartridge arranged on one of the side edges.

FIG. 13 is a detail sectional view of a mask according to the invention produced at the level of a removable cartridge arranged at the level of the plane of symmetry of the mask.

FIG. 14 is a perspective view of an example of an exhaust valve mounted in a mask according to the invention.

FIG. 15 is a perspective view from the front of another example of a respiratory protection mask according to the invention.

figure 16 is a perspective view from the rear of the other example of mask according to figure 15.

detailed description

Throughout the application, the terms "top", "bottom", "above", "below", "upper" and "lower" are to be understood by reference in the configuration worn by a user in a standing position. with the head vertical.

Likewise, the terms “front” and “rear” are to be understood by reference to this configuration.

An example of mask 1 according to the invention is shown in Figures 1 to 3.

In this illustrated example, the mask 1 is symmetrical with respect to a longitudinal median plane.

The mask 1 firstly comprises a rigid frame 2 to be placed on the face of a user. This rigid reinforcement 2 is for example made of polycarbonate (PC) by injection molding.

A sealing envelope 3 is fixed by snap-fastening with at least the rear of the frame 2. As can be seen in FIGS. 4 to 6, this sealing envelope 3 is shaped to match the shape of the face by surrounding an area comprising nose and mouth. More specifically, the sealing envelope 3 comprising, in its rear part 30, a flexible sealing lip 31 shaped to be in contact with the face by delimiting the area. The rear part 30 notably comprises a narrower zone 300 projecting, intended to match the shape of the bridge of the nose. The sealing envelope 3 is for example made of silicone, a flexible material which allows a perfect seal in contact with the skin but also brings lightness to the mask and wearing comfort for the user.

A transparent interface wall 4 is glued to the front of the frame, so as to make the mouth visible, as can be seen in FIGS. 4 to 6. This transparent interface wall 4 is for example made of polycarbonate ( PC) or poly(methyl methacrylate) (PMMA). As illustrated in Figures 4 to 6, this wall 4, like the rigid frame 2, is curved in the form of a spherical portion for the aesthetics of the mask and to best match the contour of the wearer's face.

The mask 1 further comprises two identical cartridges 5 fixed symmetrically on either side of the median plane of the mask. Each of these two cartridges 5 is removably attached to the casing 3, through one of the side edges of the casing. More precisely, each of the cartridges 5 is snapped onto the sealing casing 3 by passing through through openings 40, 20, 32 aligned, made respectively in the transparent wall 4, in the rigid reinforcement 2 and in the casing of sealing 3.

Each of the two removable side cartridges 5 houses at least one filter material 6; 6.1,6.2. More specifically, as illustrated in Figures 7 to 10, a removable cartridge 5 comprises a body 50 in two parts 51, 52 assembled together to define a housing. Each of the two parts 51, 52 is pierced with a plurality of through holes 510, 520 opening into the housing of the body 50. A support 53 housed in the housing of the body 50 maintains with sealing, at least one filter material 6; 6.1,6.2 in the form of a pellet. As illustrated in FIG. 9, two pellets of filtering material 6.1, 6.2, which may be of different materials, are held parallel by the support. In Figure 10, a single pellet 6 is held by the support 53. As also illustrated in Figures 9 and 10, the two parts 51, 52 of the body can be screwed together to complete their assembly. For example, the part 51 forming the lid comprises an internal thread 511 which cooperates with the external thread 521 of the part 52 forming the bottom of the body 50.

The parts 51, 52 of the body are for example made of aluminium, a light material which is easy to machine.

The support 53 is for example made of flexible material(s) and with a shock-absorbing function. Preferably, support 53 is made of elastomer, typically silicone, rubber, etc.

A particularly advantageous embodiment of a pellet 6 of filtering material consists of a sintered ceramic part having a total porosity of greater than 40%.

Pellets 6 in sintered ceramic have an enhanced filtration power, for example of the FMP1, FMP2 or even FMP3 type.

The mask 1 comprises another cartridge 7 removably attached to a front part 33 of the casing 3, which is arranged so that in the configuration worn by the user, this cartridge 7 is substantially facing the chin. This central cartridge 7 also houses at least one pellet of filtering material 6, preferably identical to that of the side cartridges 5.

One or two exhaust valves 8 is (are) fixed in the frame 2 in front of the central cartridge 7.

We will now describe with reference to Figure 11, the principle of filtration of the mask 1 thanks to the different filtration cartridges 5, 7.

The air, possibly contaminated, inspired by the wearer of the mask 1 passes through the side filtration cartridges 5 while being filtered by their pellets 6 of filtering material. The exhaust valve(s) 8 is (are) configured to block off the central part of the mask, so that no air flow can pass during an inspiration.

The air exhaled by the user is filtered by the filtering material 6 of the central cartridge 7 then evacuated by the exhaust valve 8 which lets the air pass in this direction of flow circulation. Due to the very good seal obtained by the lip 32, no air leak is present between the mask 1 and the user. Thus, the filtration cartridges 5, 7 constitute the only filtration barrier between the respiratory tract of the user and the external environment.

The snap-fastening of a lateral filtration cartridge 5 is shown in more detail in FIG. 12. The body 50 of the cartridge 5 is provided with a continuous groove 500 on its periphery which, on inserting the cartridge 5 into the side opening 32 of the casing 3 snaps into a continuous bead 300 made on a periphery of the latter. This assembly is easy, fast and guarantees a tight fixing.

The snap-fastening of a central filter cartridge 7 is carried out in a similar manner, as shown in more detail in FIG. 13. The body 70 of the central cartridge 7 is provided with a continuous bead 700 on its periphery which, at insertion of the cartridge 7 in the central opening 33 of the casing 3, snaps into a continuous groove 301 made on a periphery of the latter. It is noted in this figure 13 that the central cartridge 7 is not made with a housing and a support for maintaining and sealing as for a side cartridge 5. The sealing at the level of the body 70 of the cartridge 7 is much less critical than for a side cartridge 5 because its operation is not permanent. The exhaust valve(s) 8 prevent(s) the passage of the air inspired by this cartridge 7.

An advantageous embodiment of an exhaust valve 8 made of silicone is shown in FIG. 14. The valve 8 consists of a flexible blade 80 extended by a stud 81. The blade 80 is kept inserted in the armature 2 with the pin 81 mounted in a through hole 210 of the frame. When the user of the mask exhales air, the blade 80 is deflected and thus releases the stud 81 from the hole 210, which allows the exhaled air to pass. On the contrary, during an inspiration of air, the blade 80 is deflected by closing the hole 210 by the pin 81.

By optimizing the shape of the valve 8 and its arrangement in the frame, it can be configured to amplify the sounds of the user's speech.

The mask 1 is held on the user's head by one or two elastic bands 9, each forming a fastening strap, as shown in Figure 5. For attaching a strap 9 to the frame 2, each strap 9 is pierced with at least a hole 90 at each end in which is housed a lug 22 projecting outwards, formed integrally in the frame 2. Preferably, each side edge of the frame 2 comprises two lugs 22 remote from each other. These two lugs 22 form points of traction of a strap 9 on the frame on each side edge. This arrangement allows a well-distributed traction and therefore a uniform pressure between the periphery of the sealing lip 31 and the wearer's face, which further reduces the risk of creating an air passage between the envelope 3 and face.

When the environment requires eye protection, a visor 10 can be fixed by snap-fastening onto the frame 2. To do this, as visible in FIG. 3, the frame 2 comprises at least two tabs 200 which are snapped individually into at least two indentations 100 of the frame 2. Preferably, to guarantee optimal support, a number of three tabs 200 are provided, one of which is on each of the side edges and one arranged in the median plane of the mask. Like the wall 4, the visor 10 is made of polycarbonate (PC) or poly (methyl methacrylate) (PMMA). For aesthetic reasons, the visor 10 is curved, and preferably in the form of a spherical portion of the same radius or homothetic to that of the wall 4.

To individually identify each mask 1, it is possible to fix on the frame 2 at least one identification plate 11 on which are engraved at least one alphanumeric and/or bar code. This plate 11 is for example made of aluminum and preferably arranged inside the mask so as not to be visible from the outside as shown in FIG. 2.

Also, in the event of required traceability, at least one radio-identification tag (RFID) and/or at least one electronic wireless communication chip 12, 13 of the wifi or Bluetooth® type can be housed in housings afferents made in the frame.

It is easy to regularly clean the surfaces of the components of the mask 1 without however cleaning the filter cartridges 5 which, in particular with pellets 6 of sintered ceramic, have a very long service life.

Thus, after a certain number of uses, the user can dismantle all the filter cartridges 5, 7 by unclipping. Then, the mask subassembly consisting of the frame 2, the envelope 3 and of the transparent wall 4 can be cleaned in particular in a dishwasher. If necessary, the elastic strap or straps 9 can be removed before placing the aforementioned subassembly in the dishwasher.

Depending on the recommendations and/or the more or less severe constraints of the environment(s) encountered during the use of the mask 1, the replacement of the filtration cartridges 5, 7 can be carried out easily by any user.

Another example of a mask 1 according to the invention is illustrated in FIGS. 15 and 16. Here, a single lateral filtration cartridge 5 is fixed in the envelope 3. The principle of filtration remains the same as that previously indicated: the air breathed in by the user passes only through the single lateral cartridge 5, the valve 8 keeping the central opening 210 closed, and the exhaled air is expelled by the latter by crossing the central cartridge 7.

Of course, the invention is not limited to the examples of implementation which have just been described.

Other variants and improvements can be considered without departing from the scope of the invention.

In particular, it is possible to consider implanting a single filtration cartridge through which both the air inspired and that expired by the user of the mask would pass. Such an embodiment can for example be envisaged for environments that are not very restrictive in terms of particles, gases, viruses or bacteria to be filtered.

Also, in the examples shown, for aesthetic reasons, the side and front cartridges are arranged to leave the largest visible area of the mouth and around it. It is of course possible to provide other arrangements in the mask, in particular for applications where lip reading is not essential and/or in dusty work environments where the flow of aerosol carrying contaminated material mainly reaches the front of the mask.

If the nature of the filtering materials imposed by the level of filtration sought generates excessive pressure drops through the filtration cartridge(s), it is possible to consider installing a fan within the mask to compensate for said pressure drops.

If in the examples illustrated, the interface wall and the visor are preferably transparent while being colorless, it is possible to consider tinting one and/or the other in the mass while keeping them transparent. This may for example be the case when looking for sun protection for the face, especially the eyes.

Claims (15)

Sintered ceramic part in the form of a pellet (6; 6.1, 6.2), intended to be implanted in a respiratory protection mask (1), the part having a total porosity greater than 40%. Ceramic part (6; 6.1, 6.2) according to claim 1, consisting of silicon carbide or cordierite or aluminum titanate or zirconia or alumina or mullite or silica or mixtures thereof. Ceramic part (6; 6.1, 6.2) according to claim 1, comprising more than 80% by mass of silicon carbide. Ceramic part (6; 6.1, 6.2) according to one of Claims 1 to 3, having a thickness of between 1 and 20 mm. Ceramic part (6; 6.1, 6.2) according to one of the preceding claims, the median pore size being greater than 1 µm and less than 400 µm. Ceramic part (6; 6.1, 6.2) according to one of the preceding claims, the pores of size greater than 300 µm representing less than 10% by volume, or even less than 5% by volume. Ceramic part (6; 6.1, 6.2) according to one of the preceding claims, the tortuosity being greater than 1.1 and less than 1.7. Ceramic part (6; 6.1, 6.2) according to one of the preceding claims, consisting of a ceramic foam. Ceramic foam according to claim 8, having a total porosity greater than 50%, preferably greater than 60%, or even greater than 70%. Ceramic foam according to claim 8 or 9, the intergranular porosity being at least 5%, preferably at least 8%, more preferably at least 10% and/or less than 25%. Ceramic foam according to one of Claims 8 to 10, the median size of the intergranular pores being less than 25 μm, or even less than 20 μm and greater than 4 μm, or even greater than 7 μm. Ceramic foam according to one of Claims 8 to 11, the median size of the cell pores being less than 400 μm, or even less than 200 μm. Ceramic foam according to one of Claims 8 to 12, the pore size distribution being bimodal. Ceramic part (6; 6.1, 6.2) according to one of claims 1 to 7, the ceramic part consisting of several superposed ceramic layers having different respective total porosities. Filtration cartridge (5), intended to be removably attached to a health protection mask, comprising:

• a body (50) in two parts (51, 52) assembled together to define a housing, each of the two parts being pierced with at least one through hole (510, 520) opening into the housing;
• a support (53) for maintaining and sealing, housed in the housing of the body;
• at least one sintered ceramic part (6; 6.1, 6.2) according to one of the preceding claims, held with sealing in the support.