CN117412792A - Protective respiratory mask and check valve thereof - Google Patents

Abstract

The invention provides a protective respiratory mask and a check valve thereof. The check valve includes a first housing having a substantially planar base plate, an approximately semicircular first channel portion, and an approximately semicircular second channel portion formed in the base plate and separated by a center beam positioned to extend through the diameters of the approximately semicircular first channel portion and the approximately semicircular second channel portion; a first diaphragm having a semicircular shape and covering the first channel portion; a second diaphragm having a semicircular shape and covering the second channel portion; and a second housing having an open channel, the second housing mounted to the first housing so as to retain the first and second diaphragms therebetween such that when a wearer of the protective respiratory mask exhales, the first and second diaphragms each hinge at a portion opposite the central beam to deflect outwardly so as to open the first and second channel portions and allow the flow of exhaled air to exit through the first, second channel portions and the channel. The check valve of the present invention may improve the comfort of the wearer.

Description

Protective respiratory mask and check valve thereof

Technical Field

The present invention relates to protective respiratory masks, and more particularly to a check valve for protective respiratory masks.

Background

Wearers often wear protective respiratory masks that cover the wearer's mouth and nose to filter airborne particulates such as pollutants, pathogens, and allergens in the ambient air. A typical protective respiratory mask includes a body formed of a filtering material. The body forms a seal with the wearer's face at its perimeter to define a closed mask cavity between the body and the wearer's face when the protective respiratory mask is worn. A check valve (also commonly referred to as an "exhalation valve") may be provided in the main body. The check valve opens to facilitate the removal of exhaled air from the closed mask cavity through the check valve when the wearer exhales, and closes to prevent unfiltered ambient air from directly entering the closed mask cavity through the check valve when the wearer inhales. The check valve allows exhaled gas to escape from the mask cavity with less resistance than the filtering material of the body. In addition, an exhalation fan may be provided at the outlet of the check valve for further improved comfort and effectiveness. Generally, more efficient exhalation ventilation or lower resistance filter materials provide more comfort to the wearer when breathing. However, more powerful fans typically require more power from the battery or larger fan sizes, and increased permeability of the filter material typically reduces the filtration efficiency of airborne particulates. Furthermore, existing check valves have a small open effective area through which exhaled air passes, resulting in less efficient exhalation of exhaled air from the mask cavity and discomfort to the wearer when exhaling.

Accordingly, there is a need for an improved check valve for a protective respiratory mask.

Disclosure of Invention

According to one aspect of the present invention, there is provided a check valve for a protective respiratory mask, the check valve comprising:

a first housing having a substantially planar base plate, an approximately semicircular first channel portion and an approximately semicircular second channel portion formed in the base plate and separated by a central beam positioned to extend through the diameters of the approximately semicircular first channel portion and the approximately semicircular second channel portion;

a first diaphragm having a semicircular shape and covering the first channel portion;

a second diaphragm having a semicircular shape and covering the second channel portion; and

a second housing having an open channel, the second housing being mounted to the first housing so as to retain the first and second diaphragms therebetween such that when a wearer of the protective respiratory mask exhales, the first and second diaphragms each hinge at a portion opposite the central beam to deflect outwardly so as to open the first and second channel portions and allow the flow of exhaled air to exit through the first, second channel portions and channels.

According to another aspect of the present invention, there is provided a protective respiratory mask comprising a body formed of a filtering material and a check valve disposed in the body, wherein the check valve is a check valve as described above.

The check valve for a protective respiratory mask according to the present invention can maximize the effective area of the opening through which the flow of exhaled air passes and minimize resistance when the flow of exhaled air is exhausted, at a certain overall size, thereby significantly improving the comfort of the wearer.

Drawings

These and/or other aspects, features and advantages of the present invention will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings, in which:

fig. 1 schematically illustrates a first housing of a check valve for a protective respiratory mask according to a first embodiment of the present invention;

fig. 2 schematically illustrates a second housing of a check valve for a protective respiratory mask according to a first embodiment of the present invention;

fig. 3 schematically illustrates two diaphragms of a check valve for a protective respiratory mask according to a first embodiment of the present invention;

FIG. 4 schematically illustrates an alternative embodiment of the two diaphragms shown in FIG. 3;

FIG. 5 is a top view of the first housing shown in FIG. 1 equipped with the diaphragm shown in FIG. 3;

fig. 6 schematically illustrates a check valve for a protective respiratory mask according to a first embodiment of the present invention;

fig. 7 schematically illustrates a first housing of a check valve for a protective respiratory mask according to a second embodiment of the present invention;

fig. 8 schematically illustrates a first housing of a check valve for a protective respiratory mask according to a third embodiment of the present invention; and is also provided with

Fig. 9 schematically illustrates a second housing of a check valve for a protective respiratory mask according to a third embodiment of the present invention.

Detailed Description

Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below to explain the present invention by referring to the figures.

Fig. 1 schematically illustrates a first housing of a check valve for a protective respiratory mask according to a first embodiment of the present invention. As shown in fig. 1, a check valve 1 for a protective respiratory mask according to the present invention includes a first housing 3, the first housing 3 including a substantially planar base plate 5. An annular flange 7 projects from one side of the base plate 5 to define an annular region 9 on the base plate 5. An air flow channel 11 is formed in the annular region 9. The air flow channels 11 are separated by a central beam 13, the central beam 13 extending through the diameter of the annular region into an approximately semicircular first channel portion 11a and an approximately semicircular second channel portion 11b. The center beam 13 forms long straight sides of the approximately semicircular first channel portion 11a and the approximately semicircular second channel portion 11b, respectively. The first and second channel portions 11a and 11b are formed in an approximately semicircular shape because portions of the annular region 9 directly opposite to the center beam 13 are held to form the first and second diaphragm mounting regions 9a and 9b of the check valve. The first diaphragm holding portion 15a protrudes from the first diaphragm mounting area 9a, and the second diaphragm holding portion 15b protrudes from the second diaphragm mounting area 9b. In the preferred embodiment, the first and second diaphragm retaining portions 15a, 15b are elongate protrusions, but it should be appreciated that the first and second diaphragm retaining portions 15a, 15b may be one or more protruding posts. In the case where the first diaphragm holding portion 15a and the second diaphragm holding portion 15b are protruding posts, it is preferable that at least two protruding posts are provided to prevent displacement of the diaphragm during assembly. The portion of the center beam 13 adjacent to the first channel portion 11a, the portion 12a of the annular region 9 between the center beam 13 and the first membrane mounting region 9a, and the portion 16a of the first membrane mounting region 9a between the first membrane holding portion 15a and the first channel portion 11 together form a first membrane mating region, and the portion of the center beam 13 adjacent to the second channel portion 11b, the portion 12b of the annular region 9 between the center beam 13 and the second membrane mounting region 9b, and the portion 16b of the second membrane mounting region 9b between the second membrane holding portion 15b and the second channel portion 11b together form a second membrane mating region. That is, the first diaphragm-engaging region surrounds the first channel portion 11a, and the second diaphragm-engaging region surrounds the second channel portion 11b. Two first notches 17a and two second notches 17b are formed in the annular flange 7 near the first diaphragm holding portion 15a and the second diaphragm holding portion 15b, respectively. Further, an annular groove 19 is formed on the outer side of the annular flange 7 close to the base plate 5.

Fig. 2 schematically illustrates a second housing of a check valve for a protective respiratory mask according to a first embodiment of the present invention. As shown in fig. 2, the check valve 1 for a protective respiratory mask according to the present invention further includes a second housing 21, the second housing 21 being for mounting to the first housing 3 to hold the diaphragm of the check valve in place. The second housing 21 includes an annular or frustoconical hollow body 23, and in the hollow body 23, opposed first and second diaphragm regulating portions 25a and 25b are integrally formed with the hollow body 23. The intermediate portions of the first and second diaphragm limiting portions 25a, 25b are substantially straight, but the ends of the first and second diaphragm limiting portions 25a, 25b are curved and extend toward the inner wall of the hollow body 23. In this way, when the second housing 21 is mounted to the first housing 3, the first diaphragm regulating portion 25a and the second diaphragm regulating portion 25b regulate the positions of the diaphragms while the ends of the first diaphragm regulating portion 25a and the second diaphragm regulating member 25b are respectively accommodated in the two first recesses 17a and the two second recesses 17b in the annular flange 7 of the first housing 3. The first and second lugs 27a and 27b may be formed on the first and second diaphragm limiting portions 25a and 25b, respectively. The first lug 27a has a recess for accommodating the first diaphragm holding portion 15a on the first housing 3, and the second lug 27b has a recess for accommodating the second diaphragm holding portion 15b on the first housing 3. An open passage 29 is formed in the second housing 21 between the first diaphragm regulating portion 25a and the second diaphragm regulating portion 25 b. At least one blocking beam 31 may be disposed in the open channel 29 between the first and second diaphragm limiting portions 25a, 25 b. In the preferred embodiment, two barrier beams 31 are shown connecting the first diaphragm limiting portion 25a and the second diaphragm limiting portion 25 b. The barrier beam 31 may prevent excessive deflection of the diaphragm. If the exhalation fan is mounted downstream of the check valve, excessive deflection of the diaphragm may result in the diaphragm failing to return to a closed position or contact the blades of the exhalation fan. The rib 33 is provided on the hollow body 23 such that the rib 33 is received in the annular groove 19 on the outer side of the annular flange 7 of the first housing 3 to fix the second housing 21 to the first housing 3 when the second housing 21 is mounted to the first housing 3.

Fig. 3 schematically shows two diaphragms of a check valve for a protective breathing mask according to a first embodiment of the invention. As shown in fig. 3, the check valve 1 for a protective respiratory mask according to the present invention further includes a first diaphragm 35a and a second diaphragm 35b that are separated from each other. The first diaphragm 35a and the second diaphragm 35b each have a semicircular shape. The first and second diaphragms 35a and 35b are provided with first and second mounting holes 37a and 37b, respectively, near the diametrically opposed arcuate edges. The shape and size of the first and second mounting holes 37a and 37b correspond to those of the first and second diaphragm holding portions 15a and 15b such that the first and second diaphragm holding portions 15a and 15b pass through the first and second mounting holes 37a and 37b, respectively. For example, when the first diaphragm holding portion 15a and the second diaphragm holding portion 15b are elongated protrusions as shown in fig. 1, the first mounting hole 37a and the second mounting hole 37b are designed as elongated holes to match the elongated protrusions. When the first diaphragm holding portion 15a and the second diaphragm holding portion 15b are two cylinders, the first mounting hole 37a and the second mounting hole 37b are two circular holes to match the two cylinders, as shown in fig. 4. The first and second diaphragms 35a, 35b are sized such that when the first and second diaphragms 35a, 35b are mounted on the first and second diaphragm retaining portions 15a, 15b, respectively, the first and second diaphragms 35a, 35b cover a first diaphragm mating region surrounding the first channel portion 11a and a second diaphragm mating region surrounding the second channel portion 11b. The corner 39a of the first diaphragm 35a and the corner 39b of the second diaphragm 35b may be rounded corresponding to the corner of the first channel portion 11a and the apex angle of the second channel portion 11b, respectively. The diaphragm may be made of a flexible elastomeric material such as rubber, silicone, plastic, or any other type. The diaphragm may deflect under positive pressure to open the airflow passage 11 of the check valve. In the absence of positive or negative pressure, the diaphragms may return to their position against the diaphragm mating area to close the airflow passage 11 of the check valve.

The assembly process of the check valve 1 for a protective breathing mask according to the present invention will be described below. First, as shown in fig. 5, the first diaphragm holding portion 15a on the first housing 3 passes through the first mounting hole 37a in the first diaphragm 35a such that the first diaphragm 35a covers the first passage portion 11a in the first housing 3, and the second diaphragm holding portion 15b on the first housing 3 passes through the second mounting hole 37b in the second diaphragm 35b such that the second diaphragm 35b covers the second passage portion 11b in the first housing 3. Fig. 5 is a top view of the first housing shown in fig. 1 equipped with the diaphragm shown in fig. 3. Next, the second housing is mounted to the first housing 3 by aligning the recess of the first lug 27a on the second housing 21 with the first diaphragm holding portion 15a on the first housing 3, and aligning the recess of the second lug 27b on the second housing 21 with the second diaphragm holding portion 15 on the first housing 3. At this time, as shown in fig. 6, the first diaphragm holding portion 15a on the first housing 3 is received in the first boss 27a on the second housing 21, the second diaphragm holding portion 15b on the first housing 3 is received in the second boss 27b on the second housing 21, the first diaphragm regulating portion 25a of the second housing 21 regulates the first diaphragm 35a to the first diaphragm mounting area 9a of the first housing 3 near the first passage portion 11a, the end of the first diaphragm regulating portion 25a is received in the two first recesses 17a in the annular flange 7 of the first housing 3, the second diaphragm regulating portion 25b of the second housing 21 regulates the second diaphragm 35b to the second diaphragm mounting area 9b of the first housing 3 near the second passage portion 11b, the end of the second diaphragm regulating portion 25b is received in the two second recesses 17b in the annular flange 7 of the first housing 3, and the rib 33 on the second housing 21 is received in the two second recesses 17b in the annular flange 7 of the first housing 3, thereby holding the second diaphragm 35b precisely and securing the first diaphragm 35a in place. Of course, the second housing and the first housing may be secured together by other snap-fit means. The portion of the first diaphragm 35a that is restrained by the first diaphragm restraining portion 25a forms a first hinge about which the first diaphragm 35a can deflect and the portion of the second diaphragm 35b that is restrained by the second diaphragm restraining portion 25b forms a second hinge about which the second diaphragm 35b can deflect. It should be noted that the first diaphragm regulating portion 25a and the second diaphragm regulating portion 25b regulate the positions of the first diaphragm 35a and the second diaphragm 35b, respectively, but it is not necessary that the first diaphragm 35b and the second diaphragm 35b be firmly pressed against the first diaphragm mounting area 9a and the second diaphragm mounting area 9b, respectively. The first and second lugs 27a and 27b further serve to limit the position of the first and second diaphragms 35a and 35b, respectively.

When wearing a protective respiratory mask with a check valve 1 (not shown) according to the present invention, the first housing 3 faces the wearer's face and the second housing 21 faces the external environment. When the wearer exhales, the first and second diaphragms 35a and 35b deflect outwardly about the first and second hinges, respectively, under positive pressure generated by the flow of exhaled air to open the first and second channel portions 11a and 11b, allowing the flow of exhaled air to flow smoothly. When the wearer inhales, the first and second diaphragms 35a, 35b deflect inwardly under the negative pressure generated by the inhaled air flow, respectively, to abut the first and second diaphragm mating regions to close the first and second channel portions 11a, 11b, thereby preventing unfiltered air from entering the mask cavity through the check valve 1 and being inhaled by the wearer. Thus, the first diaphragm mating region and the second diaphragm mating region in the present invention refer to regions of the first housing that are in sealing contact with the first diaphragm and the second diaphragm, respectively. The check valve 1 for a protective respiratory mask according to the present invention has an approximately semicircular first channel portion 11a and an approximately semicircular second channel portion 11b separated by a center beam 13 extending through the diameter of the airflow channel 11, and a first diaphragm 35a and a second diaphragm 35b separated from each other and mated with the first channel portion 11a and the second channel portion 11b, respectively. The check valve 1 of the protective breathing mask has a larger movable portion of the first and second diaphragms 35a, 35b at a certain overall size to provide a longer outward moment arm and increase its deflection moment, maximizing the effective area of the opening through which the exhaled airflow passes and minimizing the resistance to the exhaled airflow to be expelled, thereby significantly improving the comfort of the wearer. Furthermore, the non-return valve 1 according to the invention is particularly useful for guiding the flow of exhalation air to the centre of the exhalation fan in case the exhalation fan is arranged at the outlet of the non-return valve, so that the flow of exhalation air is discharged as fast as possible.

To prevent unfiltered gas from entering the mask cavity through the gaps between the first diaphragm 35a and the first diaphragm mating region and between the second diaphragm 35b and the second diaphragm mating region when the wearer inhales, the surfaces of the first diaphragm mating region and the second diaphragm mating region may be treated so that they have a smooth surface finish. In order to simplify the surface treatment of the first and second diaphragm mating areas, the entire surface of the annular area 9 may be treated to have a smooth surface finish. To further improve the ability to prevent unfiltered gases from entering the mask cavity, the portions of the first diaphragm 35a that contact the first diaphragm mating area and the portions of the second diaphragm 35b that contact the second diaphragm mating area may also be surface treated so that they have a smooth surface finish. The diaphragms often stick together. The operation of separating the diaphragm may reduce efficiency during assembly of the check valve. For this reason, the portion of the first diaphragm 35a not in contact with the first diaphragm mating region and the portion of the second diaphragm 35b not in contact with the second diaphragm mating region are also surface-treated to roughen their surfaces to prevent the diaphragms from adhering to each other. In fig. 3 and 4, reference numerals 41a and 41b denote a portion of the first diaphragm 35a in contact with the first diaphragm fitting region and a portion of the second diaphragm 35b in contact with the second diaphragm fitting region, respectively, and reference numerals 43a and 43b denote a portion of the first diaphragm 35a not in contact with the first diaphragm fitting region and a portion of the second diaphragm 35b not in contact with the second diaphragm fitting region, respectively.

The first and second support beams 45a and 45b may be provided in the first and second passage portions 11a and 11b, respectively. The first and second support beams 45a, 45b are used to support the first and second diaphragms 35a, 35b to prevent the first and second diaphragms 35b, 35b from being sucked into the mask cavity due to excessive suction when the wearer inhales. The first support beam 45a and the second support beam 45b only function as a barrier and thus can be significantly thinner than the center beam 13. Although the first and second support beams 45a, 45b may be disposed substantially perpendicular or oblique to the center beam 13, preferably they are disposed substantially parallel to the center beam 13 so that the suction arm may be divided into two smaller moment arms, thereby reducing the moment of sucking the first and second diaphragms 35a, 35b inward. Preferably, the first and second support beams 45a, 45b are recessed inwardly relative to the first and second diaphragm mating regions, respectively, so as to allow but limit inward strain in the first and second diaphragms 35a, 35b in response to tension when the wearer inhales.

Fig. 7 schematically illustrates a first housing of a check valve for a protective respiratory mask according to a second embodiment of the present invention. For simplicity, the description of the same parts of the first housing in fig. 7 as in fig. 1 is omitted. The first housing shown in fig. 7 is different from the first housing shown in fig. 1 in that a first contact rim 47a protruding from the annular region 9 is formed along the periphery of the first channel portion 11a, and a second annular contact rim 47b protruding from the annular region 9 is formed along the periphery of the second channel portion 11b. In this way, the first annular contact edge 47a has an approximately trapezoidal shape, and the first diaphragm holding portion 15a is located outside the first annular contact edge 47 a. The second annular contact edge 47b is also approximately trapezoidal, and the second diaphragm holding portion 15b is located outside the second annular contact edge 47b. The first annular contact edge 47a constitutes a first diaphragm mating region that contacts the first diaphragm 35a, and the second annular contact edge 47b constitutes a second diaphragm mating region that contacts the second diaphragm 35b. The first annular contact edge 47a and the second annular contact edge 47 may be surface treated so that they have a smooth surface finish. Preferably, the two first sides 49a of the first annular contact rim 47a may rise arcuately and gradually from their ends proximate to the first diaphragm retaining portion 15a towards the central beam 13, and the two second sides 49b of the second annular contact rim 47 may rise arcuately and gradually from their ends proximate to the second diaphragm retaining portion 15b towards the central beam 13. In this way, when the first and second diaphragms 35a, 35b rest on the first and second annular contact edges 47a, 47b, a pretension may be applied to the first and second diaphragms 35a, 35b to prevent the first and second diaphragms 35a, 35b from accidentally opening when the wearer bends over.

Fig. 8 schematically illustrates a first housing of a check valve for a protective respiratory mask according to a third embodiment of the present invention. The first housing shown in fig. 8 is substantially similar to the housing shown in fig. 7 except that the first and second annular contact rims 47a and 47 are formed in substantially semicircular shapes, respectively, such that the first and second diaphragm holding portions 15a and 15 are located inside the first and second annular contact flanges 47a and 47b, respectively. Fig. 9 schematically illustrates a second housing of a check valve for a protective respiratory mask according to a third embodiment of the present invention. The second housing shown in fig. 9 is mounted to the first housing shown in fig. 8. The second housing shown in fig. 9 is substantially similar to the second housing shown in fig. 2 except that two first receiving recesses 51a for accommodating the first annular contact rim 47a are formed in the first diaphragm limiting portion 25a, and two second receiving recesses 51b for accommodating the second annular contact rim 47 are formed in the second diaphragm limiting portion 25.

Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims.

Claims (15)

1. A check valve for a protective respiratory mask, comprising:

a first housing (3) having a substantially flat base plate (5), an approximately semicircular first channel portion (11 a) and an approximately semicircular second channel portion (11 b), the approximately semicircular first channel portion (11 a) and the approximately semicircular second channel portion (11 b) being formed in the base plate (5) and separated by a central beam (13), the central beam (13) being positioned to extend through the diameters of the approximately semicircular first channel portion (11 a) and the approximately semicircular second channel portion (11 b);

a first diaphragm (35 a) having a semicircular shape and covering the first passage portion (11 a);

a second diaphragm (35 b) having a semicircular shape and covering the second channel portion (11 b); and

-a second housing (21) having an open channel (29), the second housing (21) being mounted to the first housing (3) so as to hold the first and second diaphragms (35 a, 35 b) between the first and second housings (3, 21) such that when a wearer of the protective respiratory mask exhales, the first and second diaphragms (35 a, 35 b) each hinge at a portion opposite the central beam (13) to deflect outwardly so as to open the first and second channel portions (11 a, 11 b) and allow an exhaled air flow to exit through the first, second and channel portions (11 a, 11b, 29).

2. The check valve according to claim 1, wherein a first support beam (45 a) thinner than the center beam (13) is provided in the first channel portion (11 a), a second support beam (45 b) thinner than the center beam (13) is provided in the second channel portion (11 b), the first support beam (45 a) and the second support beam (45 b) being recessed with respect to a surface of the first housing (3) supporting the first diaphragm (35 a) and the second diaphragm (35 b).

3. The check valve according to claim 2, wherein the first support beam (45 a) and the second support beam (45 b) are arranged substantially parallel to the central beam (13).

4. The check valve according to claim 1, wherein a portion of the base plate (5) surrounding the first channel portion (11 a) and in contact with the first diaphragm (35 a) constitutes a first diaphragm mating region, and a portion of the base plate (5) surrounding the second channel portion (11 b) and in contact with the second diaphragm (35 b) constitutes a second diaphragm mating region, the first and second diaphragm mating regions being surface treated to have a smooth surface finish.

5. The check valve according to claim 1, wherein a first annular contact rim (47 a) protruding from the base plate (5) is formed around the first channel portion (11 a) and a second annular contact rim (47 b) protruding from the base plate (5) is formed around the second channel portion (11), the first annular contact rim (47 a) at least partially constituting a first diaphragm mating area in contact with the first diaphragm (35 a) and the second annular contact rim (47 b) at least partially constituting a second diaphragm mating area in contact with the second diaphragm (35 b).

6. The check valve of claim 5, wherein the first annular contact edge (47 a) and the second annular contact edge (47 b) are surface treated to have a smooth surface finish.

7. The check valve of claim 5, wherein the first annular contact edge (47 a) is formed proximate the first channel portion (11 a) and the second annular contact edge (47 b) is formed proximate the second channel portion (11 b).

8. The non-return valve according to claim 7, wherein the two first sides (49 a) of the first contact rim (47 a) are arcuately and gradually raised from an end remote from the central beam (13) towards an end proximal to the central beam (13), and the two second sides (49 b) of the second annular contact rim (47 b) are arcuately and gradually raised from an end remote from the central beam (13) towards an end proximal to the central beam (13).

9. The check valve according to claim 1, wherein a first diaphragm mating region in contact with the first diaphragm (35 a) is defined on the first housing (3) around the first passage portion (11 a), a second diaphragm mating region in contact with the second diaphragm (35 b) is defined on the first housing (3) around the second passage portion (11 b), and a portion (41 a) of the first diaphragm (35 a) in contact with the first diaphragm mating region and a portion (41 b) of the second diaphragm (35 b) in contact with the second diaphragm mating region are surface treated to have a smooth surface finish.

10. The check valve according to claim 9, wherein the remaining portions of the first diaphragm (35 a) and the second diaphragm (35 b) are surface treated to roughen their surfaces.

11. The check valve according to claim 1, wherein a first diaphragm holding portion (15 a) is provided on the base plate (5) at a side of the first passage portion (11 a) opposite to the center beam (13), a second diaphragm holding portion (15 b) is provided on the base plate (5) at a side of the second passage portion (11 b) opposite to the center beam (13), the first diaphragm holding portion (15 a) passes through a first mounting hole 37a in the first diaphragm (35 a), and the second diaphragm holding portion (15 b) passes through a second mounting hole (37 b) in the second diaphragm (35 b) to put the first diaphragm (35 a) and the second diaphragm (35 b) on the first housing (3).

12. A check valve according to claim 11, wherein an annular flange (7) is formed on the base plate (5) around the first channel portion (11 a), the second channel portion (11 b), the first diaphragm retaining portion (15 a) and the second diaphragm retaining portion (15 b), the annular flange (7) and the hollow body (23) of the second housing (21) being fixed together by snap-fitting.

13. The check valve according to claim 11, wherein there are opposing first and second diaphragm limiting portions (25 a, 25 b), the first and second diaphragm limiting portions (25 a, 25 b) being integrally formed with the hollow body (23) of the second housing (21), and the first and second diaphragm limiting portions (25 a, 25 b) being formed within the hollow body (23), the channel (29) being between the first and second diaphragm limiting portions (25 a, 25 b), the portion of the first diaphragm (35 a) being limited by the first diaphragm limiting portion (25 a) forming a first hinge about which the first diaphragm (35 a) deflects, and the portion of the second diaphragm (35 b) being limited by the second diaphragm limiting portion (25 b) forming a second hinge about which the second diaphragm (35 b) deflects.

14. A check valve according to claim 13, wherein at least one blocking beam (31) is provided in the channel (29) between the first diaphragm limiting portion (25 a) and the second diaphragm limiting portion (25 b).

15. A protective respiratory mask comprising a body formed of a filter material and a check valve disposed in the body, wherein the check valve is the check valve of any one of claims 1-14.