EP0414956A1

EP0414956A1 - Face mask

Info

Publication number: EP0414956A1
Application number: EP89116217A
Authority: EP
Inventors: Amad Tayebi
Original assignee: NEW ENGLAND THERMOPLASTICS Inc
Current assignee: NEW ENGLAND THERMOPLASTICS Inc
Priority date: 1989-04-06
Filing date: 1989-09-01
Publication date: 1991-03-06
Also published as: DE8915900U1; JPH02268772A

Abstract

A face mask (10) which may be disposed after one use or reused which filters particulate matter and/or noxious or poisonous gases from inhaled air. The mask (10) has a shell (11) formed of polymeric closed cell foam which is air impervious, which has good flexibility and shape retention qualities, enabling a secure sealing against the face of the mask user. The mask shell (11) has one or more holes (12) through a central portion thereof and a filter (17) mounted to cover said holes (12). A one-way valve (16) is mounted through the wall of the mask shell (11) to provide an exhaust for exhaled air.

Description

Background of the Invention:

Many different varieties of face masks are known to the art, said masks which may be generally be divided into two categories, namely, those of the "disposable" type, and those which include replaceable cartridge respiration filters.
In the majority of disposable masks known to the art, the masks are constructed of a permeable fibrous media formed to fit the contour of the face of the wearer and cover the nose and mouth. Such masks function as air is inhaled through the fibrous media by the mask wearer; the flow of particulates or mists is inhibited by the fibrous filtering media, which acts to entrain the undesired particulates or mists from passing therethrough and entering into the nose or mouth of the wearer. The large amount of filtration material which must be utilized in the contruction of these masks, and the generally poor seal about the nose and mouth of the wearer are factors which effect their utility, yet the large amount of filtration media provides the benefit of a generally lower pressure drop per unit area of filter media for each unit volume of air which passes therethrough. As such, in selected applications, such filter masks remain an effective means of air filtration.
Masks of the second type, of the multiple-use variety, are those which include replaceable cartridge respiration filters are generally not directed to "throw-away" use, i.e. to be used once and subsequently disposed of. Face masks of this type generally include a face piece comprising an elastomaric material which may be fitted to the face of the user and which achieves an air-tight against the wearer's face, a detachably attached cartridge for treatment of the air to be inhaled, and very frequently, a one-way exhalation valve for allowing for rapid exit of exhaled air. For their effective operation, the face pieces of such masks are stiffened either through the use of ribbing or by the inclusion of addition elastomeric material thickness, particularly about the cartridge receiving opening so that the mask remains durable, and provides an effective seal. To provide such a seal, such masks are further provided with a one or two elastic straps or bands which pass about the head of the user, and which provide sufficient force so to deform the face piece of the mask by compressing it against the face of the mask wearer so to provide an effective seal. The provision of such an effective further allows that the replaceable cartridge respiration filters include an impregnated agent, or an additional filter layer which may be used to absorb or entrain undesired materials, such as particular gases. As a consequence, in contrast to the face masks of the first "disposable" type, the instant type of mask has a substantially less amount of filter area, and the replaceable cartridge respiration filters are often generally thicker so to provide an effective equivalent of the filtration medium.

Summary of the Invention:

The present invention as defined in the appended claims is directed to face masks which cover the nose and mouth while filtering inhaled air and in particular face masks which include both a molded or thermoformed, non-porous or porous shells, and filter cartridges one or more layers of a fibrous, or other filter material which may be impregnated with a substance to remove noxious or other material including gases from the breathed air. The face mask according to the instant invention may be disposable or of the multiple-use variety, and includes an outer shell whis if thermoformed of cross-linked, closed-cell foam sheet material. The foam shell is impermeable to air, has good shape retention and elasticity, and yet remains soft and flexible so to provide a comfortable, yet secure seal against the face of the wearer. The center area of the foam shell is perforated with a plurality of holes to permit inhaled air to pass therethrough, and a filter disposed either inside or outside of the mask so to cover said holes. The mask shell is sufficiently rigid to a support a variety of filters. The filters may be simple, single layer fibrous materials which might be applicable for filtering dust or other particulates, or filters consisting of a plurality of layers which layers might be impregnated with an active agent directed as the removal or neutralization of noxious or toxic gases or vapors. The filter may be removably retained on the interior or exterior of the mask, by a force or friction fit, clips, or other means allowing for the removable installation of a filter. Alternately, the filter may be permanently bonded to the foam shell and thus produce a "disposable" embodiment of the present invention. Additionally, a one-way exhaust valve may be provided in the foam mask shell to provide a vent for exhaled air.
These, and further embodiments of the face mask according to the invention will be more precicely explained with reference to the following detailed description of the invention, and the accompanying drawings.

Brief Description of the Drawings:

Figure 1. is a front view of a mask having a filter mounted in the interior of the mask.
Figure 2. is a side cross-sectional view of a mask having a filter attached to the front of the mask.
Figure 3. is a side cross-sectional view of a mask which has a filter mounted in the interior of the mask.
Figure 4. is isometric sectional view of a snap-in plastic retainer used for holding a filter in the interior of the mask.
Figure 4a. is a cross-sectional view of the mask shown in Fig.4 which shows a sectional view of the plastic retainer in conjunction with the mask.
Figure 5. shows a filter retainer arrangement used with a mask that has both an external pre-filter and an internal post-filter.
Figure 6. is a view of filter showing different layers thereof.
Figure 7. is a cross-sectional view of a foam shell mask having only one filter which is replaceably mounted on the outside of the mask by means of an adhesive strip.
Figure 8. is a cross-sectional view of a foam shell mask according to the present invention which utilizes one or more filter cartridges detachably fastened to collars that mount through and are fastened to the foam shell.

Detailed Description of the Invention:

Turning to Figure 1. is shown a front view of a mask 10 having a filter mounted in the interior of the mask 10. The mask 10 includes an outer shell 11 through which a plurality of holes 12 are provided to provide for the passage of inhaled air from the "exterior" of the mask, i.e. the side of the mask 10 which in use, does not face the wearer and the "interior", which in use, faces the wearer's nose and mouth. The outer shell 11 of the mask is fabricated from a single-layer sheeet of cross-linked, closed-cell foam which is impermeable to air. Such a sheet may be of an polymeric foam material which is impermeable to the flow of gases and liquids, wherein the mass density of the foam material is less than the product of the standard mass density of water (1 kg/litre; 62,4 lb/ft³) and the specific gravity of the solid consitency of the polymer or combination of polymers from which the mask shell medium is to be made. For example, an impermeable polyethylene foam shall have a density lower than 1 kg/litre x 0,91 = 0,91 kg/litre (62,4 lb/ft³ x 0,91 = 56,784 lb/ft³), and similarly a Nylon-66 foam shell shall have a density lower than 1 kg/litre x 1,14 = 1,14 kg/litre (62,4 lb/ft³ x 1,14 = 71,136 lb/ft³) An initially permeable fibrous sheet or open cell foam sheet coated or sealed on one or both sides in order to be impermeable to the flow of gases and liquids may be defined as an impermeable foam. Other materials may also be used to make the mask according to the instant invention, including combinations of laminates of polymeric sheets or films, fibrous webs, fabrics, open cell and/or closed cell foams. The use of laminates provides for the construction of a mask shell 11 which may satisfy particular color requirements, texture characteristics, "tack" characteristics (i.e. the tendency to cling to the skin of the mask wearer) on either the interior or exterior of the mask shell 11. The density of the mask shell medium may be as low as 0,002 g/cm³ (4 oz/ft³), but an exemplary (though not necessary optimal) embodiment is a density of 0,065 g/cm³ (4 lb/ft³). Preferable embodiments of the invention may be attained when a factor "R", defined to be the ratio of the weight of the filter media to the total weight of the mask with the filter media approaches the value of 1, thus assuring that the weight of the mask is relatively minimized when compared to the weight of the filter media to be used.
The use of such lower density foams allows for the production of a thick, yet light flexible face mask shell 11 which provides comfort to the mask wearer and yet retains sufficient security to the wearer. The use of such foams also allows for the production of a thicker shell offering greater stiffness which enables the mask to retain its shape while being able to carry a large mass of filtration or other air treatment media without sacrificing the ease of surface deformability of the shell, without increasing the mass, and appendant discomfort of the mask wearer.
The use of such lower density foams also provides for improved fabricability (cutting, peforating) when compared to uniform phase polymeric mateial. The forming of masks according to the invention may be achieved by any suitable means, including thermoforming, injection molding, rotational molding, compression molding, blow molding, or other technique. In the example, the mask 10 was constructed from a single-layer sheet of cross-linked, closed cell foam having a thickness of about 0,5 cm (3/16 inch) thick. It is preferred to provide a plurality of holes 12 with a diameter of about 1 cm (1/4 inch). The mask shell 11 is futher provided with two elastic straps 13,14 of sufficient length to pass about the head of the wearer when the mask is in use, to hold the mask 10 when the rim 15 of the mask 10 is pressed against the face of the wearer. Further, a one-way valve 16 of the type well known to the art is included. The valve 16 permits the wearer to inhale through the hole 16, and exhale through the valve 16.
Figure 2. is a side cross-sectional view of an embodiment of a mask 10 having an external filter 18 externally attached to the front of the mask 10. In a disposable version of such an embodiment, the external filter 18 is permanently bonded to the mask 10 by use of thermobonding, adhesives, or other fastening means. In a multi-use version, the outside of the mask shell 11 may be provided with a retainer arrangement, such as later described with reference to Fig.5. The mask further includes a valve 16 to facilitate the withdrawal of exhaled air, which is affixed to the lower wall of the shell 11 so as to not obstruct the wearer.
Figure 3. is a side cross-sectional view of a further alternative embodiment of a mask 10 which has a filter 17 mounted in the interior of the mask 10, wherein the filter 17 may be permanently affixed to the shell 11 by means as disclosed with reference to Fig.2, or by use of a snap-in retainer 19, which is to be further discussed with reference to Fig. 4. Such an arrangement may be used with a single or multilayer filter 17, wherein a multilayer filter may include a layer of activated charcoal, and comprise any additional layers of suitable filtering material to form a composite, or filter 17 of laminar layered arrangement.
Figure 4. is an isometric sectional view of a snap-in plastic retainer 19 used for holding a filter 17 in the interior of the mask 10, and Figure 4a. is a cross-sectional view a detailed portion of the mask 10 shown in Fig.4 which shows a sectional view of the plastic retainer 19 in conjunction with the mask 10. Retainer 19 is molded of a slightly flexible material which can be slightly bent so to be fitted into the mask 10 and yet remain its ridgidity so to provide a suitable support for the filter 17 being retained against the holes 12. The retainer 19 includes an outer edge 20 which cooperatively may be retained by a groove 22 in the mask 10, so to retentitively assure the filter's 17 position and which may be readily removed to allow the insertion or replacement of the filter 17 when desired. The retainer 19 may further include transverse supports 21 such as ribs, or parallel beams which lends further structural stability to the retainer 19 while not substantially impeding the flow of inhaled air.
Figure 5. shows a filter retainer arrangement used with a mask 10 that has both an external filter 18 and an internal filter 17 wherein an altenative retainer assembly 23 is shown. The retainer assembly 23 comprises a frame 24 which may be generally rectangular or of another shape and include a snap in retainer assembly similar to the retainer 19, and peripheral rods 25 which extend through rod holes 28 in the mask 10 and may be affixed to a second frame 26. The frames 24,26 are preferably of like or similar configuration and may include transverse supports 21. The dimensions of the peripheral rods 25 and the frames 24,26 are designed to assure that the external filter 18 and the internal filter 17 are retentitively retained to cover the holes 12 in the mask 10. Retainer clips 29 are provided to secure the retainer assembly 23. These retainer clips 29 provided may be reusable to allow for the changing of the internal and external filters 17,18 when desired.
Figure 6. is a view of filter 17,18 showing different layers thereof, wherein a first layer 27 of fibrous material for filtering dust or particulates, a second layer 30 of a fibrous material impregnated with activated charcoal, and a net like third layer 31 which is to seen from the exterior side of the mask 10 which is provided for aesthetic appearances and which does not substantially inhibit air flow.
Figure 7. is a cross-sectional view of a foam shell mask 10 having only one filter 18 which is replaceably mounted on the outside of the mask 10 by means of a self adhesive strip 32 wherein a mounting piece 33 on the front of the mask 10 is provided. To install or replace a filter 18, a cover strip (not illustrated) is peeled off the adhesive strip 18 which comprises part of a filter 18, and presses it onto the mounting piece 33. Alternatively, the mounting piece may be placed on the inside of the mask, or to both the inside and outside surfaces of the mask 10, allowing for a variety of filters 17,18 to be utilized to provide selective filtering, although this embodiment is not illustrated.
Figure 8. is a cross-sectional view of a foam shell mask 10 according to the present invention which utilizes one or more filter cartridges 40 detachably fastened to collars 38 that mount through and are fastened to the foam shell 11. In such an embodiment, a hole 37 is provided and a peripheral collar 38 is affixed. The collar 38 may by of any geometry and requires only to effect an airtight seal between the shell 11 and the exterior 41 of a filter cartridge 40 so that no unfiltered air passes at this juncture 39. Although not shown, a plurality of filter cartridges 40 might be incorporated into a mask 10 according to the invention, although only a single cartridge 40 is disclosed in Fig. 8 for ease of representation. As with the other embodiments discussed above, the cartridge 40 may be permanently or removably mounted in the mask 10.

Claims

1. A face mask for filtering air comprising:
characterized by:
a mask shell (11) formed of a flexible, air impermeable polymeric closed cell foam that has physical properties that provide shape retention to said mask shell and elasticity that enables the edge of said mask shell (11) to conform and seal to the face of a wearer around their nose and mouth said mask shell having one or more holes (12) through the central portion thereof, and
a removable filter (17,18) mounted to cover said hole(s) to thereby filter all inhaled air passing through said holes (12).

2. The face mask according to claim 1 further
characterized by:
a polymeric foam material which is impermeable to the flow of gases and liquids, wherein the mass density of the foam material is less than the product of the standard mass density of water (1 kg/litre; 62,4 lb/ft³) and the specific gravity of the solid consitency of the polymer or combination of polymers from which the mask shell medium is to be made.

3. The face mask according to claim 1 or 2 further characterized by:
a groove (22) formed in the interior of said shell (11) and a filter (17) is retentively mounted by a retainer (19) which may be retentitively fitted into said groove (22) for retaining the filter (18) against the holes (12) provided in the shell (11).

4. The face mask according to claims 1,2 or 3 further characterized by:
the filter (17,18) includes a plurality of filter layers.

5. The face mask according to any of claims 1 to 4, further characterized by:
the filter (17,18) includes a filter layers including activated carbon.

6. The face mask according to any of claims 1 to 5 further characterized in:
that the filter (17,18) is a removable cartridge filter (40).

7. The face mask according to claim 1 which is further characterized in that:
it includes a one-way exhaust valve (16) mounted through the wall of said mask for venting exhaled air.

8. The face mask according to claim 1 which is further characterized by:
including one or more elastic straps (13,14) attached to the rim (15) of said mask shell (11) and being used to hold the face mask (10) over the nose and mouth of a mask wearer by passing around the head of the wearer.