WO2022253609A1

WO2022253609A1 - Protective respiratory mask and check valve for the same

Info

Publication number: WO2022253609A1
Application number: PCT/EP2022/063865
Authority: WO
Inventors: Zhongchi LUO; Weizhong Chen; Haiyong Huang
Original assignee: Koninklijke Philips N.V.
Priority date: 2021-06-04
Filing date: 2022-05-23
Publication date: 2022-12-08
Also published as: JP2024522296A; EP4347055A1; CN117412792A

Abstract

The present invention provides a protective respiratory mask and a check valve for the same. The check valve comprises a first housing having a substantially flat substrate, a first approximately semicircular passage portion and a second approximately semicircular passage portion being formed in the substrate and separated by a central beam positioned to extend through a diameter of the first approximately semicircular passage portion and the second approximately semicircular passage portion; a first diaphragm having a semicircular shape and covering the first passage portion; a second diaphragm having a semicircular shape and covering the second passage portion; and a second housing having an open passage, the second housing being mounted to the first housing so as to retain the first diaphragm and the second diaphragm between the first housing and the second housing such that the first diaphragm and the second diaphragm are each hinged at a part opposite the central beam to deflect outwardly so as to open the first passage portion and the second passage portion and to allow the exhaled airflow to be discharged through the first passage portion, the second passage portion and the passage when a wearer of the protective respiratory mask exhales. The check valve of the present invention may improve comfort to the wearer.

Description

PROTECTIVE RESPIRATORY MASK AND CHECK VALVE FOR THE SAME

FIELD OF THE INVENTION

The invention relates to a protective respiratory mask, and particularly to a check valve for a protective respiratory mask.

BACKGROUND OF THE INVENTION

Protective respiratory masks that cover the nose and mouth of a wearer are often worn to filter airborne particles such as pollutants, pathogens and allergens from ambient air. Atypical protective respiratory mask includes a main body formed from a filtering material. The main body forms a seal with the face of the wearer at its periphery to define an enclosed mask cavity between the main body and the face of the wearer when the protective respiratory mask is worn. A check valve (also often called “exhaling valve”) may be disposed in the main body. The check valve opens to promote the exhaled gas to discharge from the enclosed mask cavity through the check valve when the wearer exhales and closes to block unfiltered ambient air from directly entering the enclosed mask cavity through the check valve when the wearer inhales. The check valve allows exhaled gas to discharge from the mask cavity with less resistance than the filtering material of the main body. In addition, to further improve the comfort and effectiveness, an exhaling fan may be disposed at the outlet of the check valve. In general, more effective exhaling ventilation or lower resistance filtering material makes the wearer more comfortable while breathing. However, more powerful fan often requires either more power taken from a battery or a bigger fan size, and an increased permeability of the filtering material often reduces the filtering efficiency for the airborne particles. Further, the existing check valves have a small effective area of the opening through which the exhaled gas passes, resulting in less efficiently discharging of the exhaled gas from the mask cavity and discomfort to the wearer when the wearer exhales.

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

SUMMARY OF THE INVENTION

According to one aspect of the present invention, it is to provide a check valve for a protective respiratory mask comprising: a first housing having a substantially flat substrate, a first approximately semicircular passage portion and a second approximately semicircular passage portion being formed in the substrate and separated by a central beam positioned to extend through a diameter of the first approximately semicircular passage portion and the second approximately semicircular passage portion; a first diaphragm having a semicircular shape and covering the first passage portion; a second diaphragm having a semicircular shape and covering the second passage portion; and a second housing having an open passage, the second housing being mounted to the first housing so as to retain the first diaphragm and the second diaphragm between the first housing and the second housing such that the first diaphragm and the second diaphragm are each hinged at a part opposite the central beam to deflect outwardly so as to open the first passage portion and the second passage portion and to allow the exhaled airflow to be discharged through the first passage portion, the second passage portion and the passage when a wearer of the protective respiratory mask exhales.

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

With a certain overall size, the check valve for the protective respiratory mask according to the present invention is capable of maximizing an effective area of the opening through which the exhaled airflow passes and minimizing the resistance when the exhaled airflow is discharged, thereby significantly improving comfort to the wearer.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

FIG. 4 schematically shows 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 shows a check valve for a protective respiratory mask according to a first embodiment of the present invention; FIG. 7 schematically shows a first housing of a check valve for a protective respiratory mask according to a second embodiment of the present invention;

FIG. 8 schematically shows a first housing of a check valve for a protective respiratory mask according to a third embodiment of the present invention; and

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

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Reference will now be made in detail to 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. Exemplary embodiments are described below to explain the present invention by referring to the figures.

Figure 1 schematically shows 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 comprises a first housing 3 comprising a substantially flat substrate 5 An annular flange 7 protrudes from one side of the substrate 5 to define an annular area 9 on the substrate 5. An airflow passage 11 is formed in the annular area 9. The airflow passage 11 is separated by a central beam 13 extending through a diameter of the annular area into a first approximately semicircular passage portion 11a and a second approximately semicircular passage portion 1 lb. The central beam 13 forms a long straight side of the first approximately semicircular passage portion 11a and the second approximately semicircular passage portion 1 lb respectively. The first passage portion 11a and the second passage portion l ib are formed as being approximately semicircular because the portions of the annular area 9 directly opposite the central beam 13 are retained to form the first diaphragm mounting area 9a and the second diaphragm mounting area 9b of the check valve. A first diaphragm holding portion 15a projects from the first diaphragm mounting region 9a and a second diaphragm holding portion 15b projects from the second diaphragm mounting region 9b. In a preferred embodiment, the first diaphragm holding portion 15a and the second diaphragm holding portion 15b are elongated projections, but it should be understood that the first diaphragm holding portion 15a and the second diaphragm holding portion 15b may be one or more projecting columns. In the case that the first diaphragm holding portion 15a and the second diaphragm holding portion 15b are projecting column, at least two projecting columns are preferably provided to prevent the diaphragm from shifting during assembly. A portion of the center beam 13 adjacent to the first passage portion 11a, a portion 12a of the annular area 9 between the center beam 13 and the first diaphragm mounting area 9a, and a portion 16a of the first diaphragm mounting area 9a between the first diaphragm holding portion 15a and the first passage portion 11a together form a first diaphragm mating area, and a portion of the center beam 13 adjacent to the second passage portion lib, a portion 12b of the annular area 9 between the center beam 13 and the second diaphragm mounting area 9b and a portion 16b of the second diaphragm mounting area 9b between the second diaphragm holding portion 15b and the second passage portion lib together form a second diaphragm mating area. That is, the first diaphragm mating area surrounds the first passage portion 11a and the second diaphragm mating area surrounds the second passage portion lib. 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 recess 19 is formed on an outer side of the annular flange 7 near the substrate 5.

FIG. 2 schematically shows 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 the protective respiratory mask according to the present invention further comprises a second housing 21 for mounting to the first housing 3 to retain the diaphragms of the check valve in place. The second housing 21 comprises an annular or truncated conical hollow body 23. Within the hollow body 23, opposing first diaphragm limiting portions 25a and second diaphragm limiting portions 25b are formed integrally with the hollow body 23. The middle portions of the first diaphragm limiting portion 25a and the second diaphragm limiting portion 25b are substantially straight but the ends thereof are curved and extend toward an 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 limiting portion 25a and the second diaphragm limiting portion 25b limit the position of the diaphragms while the ends of the first diaphragm limiting portion 25a and the second diaphragm limiting portion 25b are respectively received in the two first notches 17a and the two second notches 17b in the annular flange 7 of the first housing 3. A first lug 27a and a second lug 27b may be formed on the first diaphragm limiting portion 25a and the second diaphragm limiting portion 25b respectively. The first lug 27a has a concave portion for receiving the first diaphragm holding portion 15a on the first housing 3 and the second lug 27b has a concave portion for receiving 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 limiting portion 25a and the second diaphragm limiting portion 25b. At least one blocking beam 31 may be disposed in the open passage 29 between the first diaphragm limiting portion 25a and the second diaphragm limiting portion 25b. In a preferred embodiment, two blocking beams 31 connecting the first diaphragm limiting portion 25a and the second diaphragm limiting portion 25b are shown. The blocking beams 31 may prevent the diaphragms from excessively deflecting. Excessively deflecting of the diaphragms may result in the diaphragms not returning to the closed position or touching the blades of an exhaling fan if the exhaling fan is installed downstream of the check valve. Ribs 33 are provided on the hollow body 23 so that the ribs 33 are received in the annular recess 19 on the outer side of the annular flange 7 of the first housing 3 to secure 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 respiratory mask according to a first embodiment of the present invention. As shown in FIG. 3, the check valve 1 for a protective respiratory mask according to the present invention further comprises a first diaphragm 35a and a second diaphragm 35b which are separate from each other. The first diaphragm 35a and the second diaphragm 35b are each in a semicircular shape. The first diaphragm 35a and the second diaphragm 35b are respectively provided with a first mounting hole 37a and a second mounting hole 37b near an arcuate edge opposite to the diameter. The shape and size of the first mounting hole 37a and the second mounting hole 37b correspond to the shape and size of the first diaphragm holding portion 15a and the second diaphragm holding portion 15b so that the first diaphragm holding portion 15a and the second diaphragm holding portion 15b pass through the first mounting hole 37a and the second mounting hole 37b respectively. For example, when the first diaphragm holding portion 15a and the second diaphragm holding portion 15b are elongated projections as shown in Fig. 1, the first mounting hole 37a and the second mounting hole 37b are designed as elongated holes to match with the elongated projection. When the first diaphragm retaining part 15a and the second diaphragm retaining part 15b are two cylindrical columns, the first mounting hole 37a and the second mounting hole 37b are two circular holes to match with the two cylindrical columns, as shown in Fig. 4. The first diaphragm 35a and the second diaphragm 35b are sized such that the first diaphragm 35a and the second diaphragm 35b cover the first diaphragm mating area surrounding the first passage portion 11a and the second diaphragm mating area surrounding the second passage portion lib respectively when the first diaphragm 35a and the second diaphragm 35b are mounted on the first diaphragm holding portion 15a and the second diaphragm holding portion 15b respectively. The corners 39a of the first diaphragm 35a and the corners 39b of the second diaphragm 35b may be rounded corresponding to the corners of the first passage portion 11a and the top angle of the second passage portion lib respectively. The diaphragms may be made of a flexible elastomeric material such as rubber, silicone, plastic or any other type. The diaphragms may deflect under positive pressure to open the airflow passage 11 of the check valve. Without positive pressure or under negative pressure, the diaphragms may return to a position at which they abut against the diaphragm mating areas to close the airflow passage 11 of the check valve.

The assembly process of the check valve 1 for the protective respiratory mask according to the present invention will be described below. Firstly, the first diaphragm holding portion 15a on the first housing 3 passes through the first mounting hole 37a in the first diaphragm 35a so 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 so that the second diaphragm 35b covers the second passage portion lib in the first housing 3, as shown in Figure 5. FIG. 5 is a top view of the first housing shown in FIG. 1 equipped with the diaphragms shown in FIG. 3. Next, with the concave portion of the first lug 27a on the second housing 21 aligned with the first diaphragm holding portion 15a on the first housing 3 and the concave portion of the second lug 27b on the second housing 21 aligned with the second diaphragm holding portion 15b on the first housing 3, the second housing 21 is mounted to the first housing 3. At this time, the first diaphragm holding portion 15a on the first housing 3 is received in the first lug 27a on the second housing 21, the second diaphragm holding portion 15b on the first housing 3 is received in the second lug 27b on the second housing 21, the first diaphragm limiting portion 25a of the second housing 21 limits the first diaphragm 35a onto the first diaphragm mounting area 9a of the first housing 3 near the first passage portion 11a, the ends of the first diaphragm limiting portion 25a are received in two first notches 17a in the annular flange 7 of the first housing 3, the second diaphragm limiting portion 25b of the second housing 21 limits the second diaphragm 35b onto the second diaphragm mounting area 9b of the first housing 3 near the second passage portion lib, the ends of the second diaphragm limiting portion 25b are received in two second notches 17b in the annular flange 7 of the first housing 3, and the ribs 33 on the second housing 21 are received in the annular recesses 19 on the outer side of the annular flange 7 of the first housing 3, thereby securing the second housing 21 to the first housing 3 and precisely and reliably holding the first diaphragm 35a and the second diaphragm 35b in place, as shown in Fig. 6. Of course, the second housing and the first housing can be secured together by other snap-fit means. A portion of the first diaphragm 35a limited by the first diaphragm limit portion 25a forms a first hinge around which the first diaphragm 35a can deflect, and a portion of the second diaphragm 35b limited by the second diaphragm limit portion 25b forms a second hinge around which the second diaphragm 35b can deflect. It should be noted that the first diaphragm limiting portion 25a and the second diaphragm limiting portion 25b limit the position of the first diaphragm 35a and the second diaphragm 35b respectively, but it is not necessary to press firmly the first diaphragm 35a and the second diaphragm 35b against the first diaphragm mounting area 9a and the second diaphragm mounting area 9b respectively. The first lug 27a and the second lug 27b further serve to limit the position of the first diaphragm 35a and the second diaphragm 35b respectively.

When the protective respiratory mask with the check valve 1 according to the present invention (not shown) is worn, the first housing 3 faces the wearer's face and the second housing 21 faces the external environment. When the wearer exhales, the first diaphragm 35a and the second diaphragm 35b deflect outwardly around the first hinge and the second hinge under the positive pressure generated by the exhalation airflow respectively to open the first passage portion 11a and the second passage portion lib, thereby allowing the exhaled airflow to smoothly flow out. When the wearer inhales, the first diaphragm 35a and the second diaphragm 35b deflect inwardly under the negative pressure generated by the inhaled airflow respectively to abut against the first diaphragm mating area and the second diaphragm mating area to close the first passage portion 11a and the second passage portion l ib, thereby preventing unfiltered gas from entering the mask cavity through the check valve 1 and being inhaled by the wearer. Thus, the first diaphragm mating area and the second diaphragm mating area in the present invention refer to the areas of the first housing that form a sealed contact with the first diaphragm and the second diaphragm respectively. The check valve 1 for the protective respiratory masks according to the present invention has the first approximate semicircle passage portion 11a and the second approximate semicircle passage portion lib separated by the central beam 13 extending through the diameter of the airflow passage 11 as well as the first diaphragms 35a and the second diaphragms 35b which are separate from each other and match the first passage portion 11a and the second passage portion lib respectively. With a certain overall size, the check valve 1 of the protective respiratory mask makes the first diaphragm 35a and the second diaphragm 35b to have a larger movable portion so as to provide a longer outward force arm and increase its deflection moment, so that the effective area of the opening through which the exhaled airflow passes is maximized and the resistance to the exhaled airflow to be discharged is minimized, thereby significantly improving comfort to the wearer. Further, in the case that an exhaling fan is disposed at the outlet of the check valve, the check valve 1 according to the present invention is particularly useful for directing the exhaled airflow to the center of the exhaling fan so that the exhaled airflow is discharged as quickly as possible.

In order to prevent unfiltered gas from entering the mask cavity through a gap between the first diaphragm 35a and the first diaphragm mating area and between the second diaphragm 35b and the second diaphragm mating area when the wearer inhales, the surfaces of the first diaphragm mating area and the second diaphragm mating area can be treated so that they have a smooth surface finish. To simplify the surface treatment of the first diaphragm mating area and the second diaphragm mating area, the entire surface of the annular area 9 can be treated to have a smooth surface finish. To further improve the ability to prevent unfiltered gas from entering the mask cavity, the portion of the first diaphragm 35a in contact with the first diaphragm mating area and the portion of the second diaphragm 35b in contact with 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 diaphragms may reduce the efficiency during assembly of the check valve. To this end, the portions of the first diaphragm 35a not in contact with the first diaphragm mating area and the portions of the second diaphragm 35b not in contact with the second diaphragm mating area are also surface-treated to roughen their surfaces to prevent the diaphragms from sticking to each other. In Figures 3 and 4, the reference numerals 41a and 41b represent the portion of the first diaphragm 35a in contact with the first diaphragm mating area and the portion of the second diaphragm 35b in contact with the second diaphragm mating area respectively while the reference numerals 43 a and 43b represent the portions of the first diaphragm 35a not in contact with the first diaphragm mating area and the portions of the second diaphragm 35b not in contact with the second diaphragm mating area respectively.

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

FIG. 7 schematically shows 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 those in FIG. 1 is omitted. The first housing shown in

FIG. 7 differs from the first housing shown in FIG. 1 in that a first contact rim 47a protruding from the annular area 9 is formed along the periphery of the first passage portion 11a and a second annular contact rim 47b protruding from the annular area 9 is formed along the periphery of the second passage portion lib. In this way, the first annular contact rim 47a is in an approximately trapezoidal shape and the first diaphragm holding portion 15a is located outside of the first annular contact rim 47a. The second annular contact rim 47b is also in an approximately trapezoidal shape and the second diaphragm holding portion 15b is located outside of the second annular contact rim 47b. The first annular contact rim 47a constitutes the first diaphragm mating area in contact with the first diaphragm 35a, and the second annular contact rim 47b constitutes the second diaphragm mating area in contact with the second diaphragm 35b. The first annular contact rim 47a and the second annular contact rim 47b may be surface-treated so that they have a smooth surface finish. Preferably, the two first side portions 49a of the first annular contact rim 47a may be arcuately and gradually raised from its ends near the first diaphragm holding portion 15a toward the center beam 13 and the two second side portions 49b of the second annular contact rim 47b may be arcuately and gradually raised from its ends near the second diaphragm holding portion 15b toward the center beam 13. In this way, when the first diaphragm 35a and the second diaphragm 35b rest on the first annular contact rim 47a and the second annular contact rim 47b, a pre-tension may be applied to the first diaphragm 35a and the second diaphragm 35b to prevent the first diaphragm 35a and the second diaphragm 35b from accidentally opening when the wearer bends over.

FIG. 8 schematically shows 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 annular contact rim 47a and the second annular contact rim 47b are formed in a substantially semicircular shape respectively such that the first diaphragm holding portion 15a and the second diaphragm holding portion 15b are located inside of the first annular contact rim 47a and the second annular contact rim 47b respectively. FIG. 9 schematically shows a second housing for 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 depressions 51a for receiving the first annular contact rim 47a are formed in the first diaphragm limiting portion 25a and two second receiving depressions 5 lb for receiving the second annular contact rim 47b are formed in the second diaphragm limiting portion 25b.

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

1. A check valve for a protective respiratory mask comprising. a first housing (3) having a substantially flat substrate (5), a first approximately semicircular passage portion (11a) and a second approximately semicircular passage portion (lib) being formed in the substrate (5) and separated by a central beam (13) positioned to extend through a diameter of the first approximately semicircular passage portion (11a) and the second approximately semicircular passage portion (lib); a first diaphragm (35a) having a semicircular shape and covering the first passage portion (11a); a second diaphragm (35b) having a semicircular shape and covering the second passage portion (lib); and a second housing (21) having an open passage (29), the second housing (21) being mounted to the first housing (3) so as to retain the first diaphragm (35a) and the second diaphragm (35b) between the first housing (3) and the second housing (21) such that the first diaphragm (35a) and the second diaphragm (35b) are each hinged at a part opposite the central beam (13) to deflect outwardly so as to open the first passage portion (11a) and the second passage portion (lib) and to allow the exhaled airflow to be discharged through the first passage portion (11a), the second passage portion (lib) and the passage (29) when a wearer of the protective respiratory mask exhales.

2. A check valve according to claim 1, wherein a first support beam (45a) thinner than the central beam (13) is disposed in the first passage portion (11a), a second support beam (45b) thinner than the central beam (13) is disposed in the second passage portion (lib), the first support beam (45a) and the second support beam (45b) are recessed relative to a surface of the first housing (3) supporting the first diaphragm (35a) and the second diaphragm (35b).

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

4. A check valve according to claim 1, wherein a portion of the substrate (5) surrounding the first passage portion (11a) and in contact with the first diaphragm (35a) constitutes a first diaphragm mating area, a portion of the substrate (5) surrounding the second passage portion (lib) and in contact with the second diaphragm (35b) constitutes a second diaphragm mating area, the first diaphragm mating area and the second diaphragm mating area are surface-treated to have a smooth surface finish.

5. A check valve according to claim 1, wherein a first annular contact rim (47a) protruding from the substrate (5) is formed around the first passage portion (11a) and a second annular contact rim (47b) protruding from the substrate (5) is formed around the second passage portion (l ib), the first annular contact rim (47a) at least in part constitutes a first diaphragm mating area in contact with the first diaphragm (35a), the second annular contact rim (47b) at least in part constitutes a second diaphragm mating area in contact with the second diaphragm (35b).

6. A check valve according to claim 5, wherein the first annular contact rim (47a) and the second annular contact rim (47b) are surface-treated to have a smooth surface finish.

7. A check valve according to claim 5, wherein the first annular contact rim (47a) is formed near the first passage portion (11a) and the second annular contact rim (47b) is formed near the second passage portion (lib).

8. A check valve according to claim 7, wherein two first side portions (49a) of the first contact rim (47a) are arcuately and gradually raised from one end away from the central beam (13) toward one end near the central beam (13) and two second side portions (49b) of the second annular contact rim (47b) are arcuately and gradually raised from one end away from the central beam (13) toward one end near the central beam (13).

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

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

11. A check valve according to claim 1, wherein a first diaphragm holding portion (15a) is disposed on the substrate (5) at a side of the first passage portion (11a) opposite to the central beam (13), a second diaphragm holding portion (15b) is disposed on the substrate (5) at a side of the second passage portion (lib) opposite to the central beam (13), the first diaphragm holding portion (15a) passes through a first mounting hole 37a in the first diaphragm (35a), the second diaphragm holding portion (15b) passes through a second mounting hole (37b) in the second diaphragm (35b) to rest the first diaphragm (35a) and the second diaphragm (35b) on the first housing (3).

12. A check valve according to claim 11, wherein an annular flange (7) is formed on the substrate (5) around the first passage portion (11a), the second passage portion (lib), the first diaphragm holding portion (15a) and the second diaphragm holding portion (15b), the annular flange (7) and a hollow body (23) of the second housing (21) are secured together by a snap fit.

13. A check valve according to claim 11 , wherein there are opposing first diaphragm limiting portion (25a) and second diaphragm limiting portion (25b) formed integrally with and within the hollow body (23) of the second housing (21), the passage (29) is between the first diaphragm limiting portion (25a) and the second diaphragm limiting portion (25b), a portion of the first diaphragm (35a) limited by the first diaphragm limit portion (25a) forms a first hinge around which the first diaphragm (35a) deflects, and a portion of the second diaphragm (35b) limited by the second diaphragm limit portion (25b) forms a second hinge around which the second diaphragm (35b) deflects.

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

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