The present invention relates to respirator masks, particularly with a non-collapsible chassis, yet retaining a sufficiently flexible conformation, and a method of manufacturing such respirator masks.

Background to the Invention

Respirator masks are designed to protect the wearer from inhaling hazardous fumes, vapours, gases and particulate matter such as dust and air borne microorganisms. Respirator masks are also used to prevent the wearer from passing on infection to others by air borne transmission such as can occur during a pandemic like the 2020 Covid-19 pandemic. All respirator masks have some kind of facepiece held to the wearer’s head with straps, a cloth harness or some other mode of clasping. The mask facepieces are designed in different styles and sizes so as to accommodate all types of face shapes. The differences in respirator masks designs impact their assigned protection factors, i.e., the degree of protection from one or more kinds of hazards.

One essential concern about respirator masks is their fit on wearer’s face. An adequate fit would be when there is a good seal between the respirator body and the face of the wearer. A poor fit can have an overall negative impact on the filtering effectiveness of the respirator mask. However, a trade-off here is the maintenance of a minimum air space or oxygen level to ensure that the wearer does not face a deficit of oxygen and does not experience difficulty in breathing.

Filtering facepiece (FFP) standards are mechanical filter standards used for protective respirator masks certified by the European Union. Based on performance requirements, there are three classes of particle filtering respirator masks, namely FFP1 , FFP2 and FFP3. The most filtering masks of the three are FFP3 respirator masks which offer the highest aerosol filtration percentage of not less than 99% and lowest internal leak rate of not more than 2%. The respirator masks according to the present invention are specifically designed in compliance with FFP3 standards. US2009/0078265A1 provides a filtering face-piece respirator that is capable of expanding and contracting in the longitudinal direction to accommodate wearer jaw movement. This respirator mask has a “concertina” type geometry allowing flexibility in one orientation with adjustability while remaining very stiff in the other orientation. Moreover, the filter fabric is adhered to the inside of the mask chassis with nothing otherwise to prevent it from being pushed in the direction of the wearer’s mouth in case of an accident.

US2016/0199676A1 provides a respiratory protection device comprising a flexible and contoured gasket creating an adaptable structure that conforms easily and fully to the facial features of the wearer. The ridge in the gasket enables accurate positioning of the same across the nose and cheekbones, preventing inward leakage of air during use. The gasket has a tailored profile and thickness to permit it to conform to facial features and its inner sections pivot or flex in a very flexible and collapsible way around a high ridge of mainly “V” profile.

A limitation with currently available respirator masks is that they rely upon a thick preformed carrier to which filtration layers and other functional components of the mask are adhered. Such preformed carrier has been inevitably required to provide a structure and dimension to the respirator mask. However, the drawback with the thick preformed carrier is, firstly, that it creates an additional barrier to airflow, thereby reducing breathability when such masks are worn by a user and, secondly, it impedes the mask from changing shape to suit the fit on a wearer’s face.

Accordingly, the respirator mask of the present invention has been specifically constructed to alleviate the aforesaid drawbacks of the known masks and at the same time ensure an optimum air flow when the mask is worn by a user.

Object of the Invention

It is, therefore, an object of the invention to provide a respirator mask specifically designed to have a non-collapsible mask chassis bearing sufficient compression strength from crushing forces and maintaining shear rigidity to prevent the mask from twisting and causing asymmetry while maintaining sufficient flexibility to conform to the wearer’s face. At the same time, the respirator mask according to the present invention uses thin filtration materials without the requirement of a formed fibrous carrier preform to render a structure to the mask. Moreover, since multiple sheets of filter material are loosely placed over one another, the present respirator mask ensures alternate airflow pathways between surfaces of the filter material, thus, increasing path length and potentially adding to filtration efficiency.

Hence, the present respirator mask alleviates the drawbacks of the existing ones while still offering an excellent fit on a wearer’s face and highly efficient protection against hazardous substances or gases or emissions or microbes.

Another object of the invention is to provide an efficient method of forming the two- dimensional filter sheets on to the said respirator masks.

Summary of the Invention

The present invention provides a respirator mask comprising a mask chassis, on the exterior of which a mask fabric is welded to or fitted on, and includes band clasps and a face seal, the mask being adjustable to fit an individual in a comfortable arrangement.

In one embodiment of the invention, the respirator mask chassis is a single unit framework having a nose ridge situated at the frontal end and projecting outwards from the periphery of the chassis.

In another embodiment of the invention, the respirator mask chassis is a single unit ring frame without projecting into a nose ridge so as to further enhance the comfort of the mask by reducing a stiffening component.

Preferably, the mask chassis is substantially circular in shape and the ridge, if present, is an elliptical protrusion from the frontal periphery of the chassis.

Preferably, the length of the horizontal axis of the mask chassis is approximately 136mm and that of the vertical axis is approximately 140mm. Preferably, the mask chassis is injected moulded in thermoplastic with variable thicknesses to provide flexibility in some areas and stiffness in others.

The mask chassis further comprises a plurality of ribs aligned in a suitable configuration so as to create a space inside and ensure optimum air pocket when the respirator mask is worn by a person. The shape of the said space may vary depending upon the configuration of the ribs.

Preferably, a plurality of ribs can be aligned in a curved configuration. However, variants with different configurations of ribs, for example, coiled configuration, are also possible.

Preferably, the ribs are attached to the periphery of the mask chassis in an “X” pattern, thereby dividing the space formed in the chassis into several smaller areas. However, the “X” pattern of ribs is not limiting and the same can be aligned in alternative formations.

Advantageously, the “X” pattern of ribs provides a flexibility of the chassis in the horizontal and vertical bending planes to aid conformity to numerous facial sizes, while retaining sufficient compression strength from crushing forces and maintaining shear rigidity to prevent the mask from twisting and causing asymmetry during the use.

Preferably, the mask fabric or filtering material is attached on the external convex side of the chassis along its periphery. However, alternate formations of the mask with the mask fabric or filtering material being welded at single or multiple positions on the X-patterned ribs are also possible. Particularly, in an alternate embodiment of the invention, the mask fabric or filtering material is welded to the point of intersection of the X-patterned ribs.

Preferably, numerous layers of filter fabric or material are attached on the external convex periphery of the mask chassis to offer sufficient filtration and protection. More preferably, the layers of the filter fabric or material are loosely laid on top of one another to maximize the surface area of the filters and enhance breathability when the mask is worn by a user.

Since there is no stiff or formed filter fabric layer to act as a mask frame, the filter fabric layers take the shape of the mask chassis or framework as the layers are affixed or welded on to it.

Preferably, the curved configuration of ribs in the respirator mask chassis and/or the filter fabric or material or sheets attached or welded on to it form a cup-shaped or dome-shaped structure inside the mask chassis. In a preferred embodiment, the depth of the said cup-shaped or dome-shaped structure is approximately 80mm and it comprises an air pocket within itself.

Advantageously, the multiple smaller unsupported areas formed by the alignment of ribs on the mask chassis can accommodate creased filter fabric or material which provides an enhancement in surface area of the filter fabric, thereby increasing breathability.

A face seal having nearly constant thickness is attached to the peripheral frame of the respirator mask chassis. The shape, geometry and dimension of the face seal is adapted in proportion with that of the peripheral frame of the mask chassis so that it perfectly fixes on to the same. Similar to the mask chassis or framework, the face seal is circular in shape with an elliptical ridge protruding from the frontal periphery of the face seal. The elliptical ridge of the face seal creates an underlying cut out space so that the respirator mask sits comfortably around the nose of the wearer.

In one preferred embodiment, the face seal has an elliptical profile which creates a straightforward compression around a tangent of the mask chassis and does not flex or collapse on its inner side.

Preferably, the face seal element comprises a radially inwards extending flange capable of being formed into a three-dimensional configuration. ln another preferred embodiment, the face seal has a flat, punched profile attached to the peripheral frame of the mask chassis.

Preferably, the face seal is made up of a thermoplastic elastomer to ensure proper grip around the nose and mouth of the wearer when the respirator mask is in use. The grip of the face seal ensures preventing hazardous gases or substances or microbes from entering the respirator mask.

More preferably, the thermoplastic elastomer for forming face seal can be selected from SEBS (Styrene-ethylene-butylene-styrene), metallocene and combinations thereof.

Since the respirator mask according to the invention does not derive any form or structure from the filter fabric or material, the face seal works in conjunction with the mask chassis or framework to provide sufficient structural rigidity and handleability of the respirator mask product.

Preferably, the face seal is attached to the peripheral frame of the mask chassis by ultrasonic welding.

A clasp arrangement comprising multiple clasps is welded on either side of the peripheral frame of the respirator mask chassis. The whole arrangement comprising the mask chassis and the clasps constitutes a single unit. Clasps are small rectangular or square shaped frames perforated to receive and pass elastic headbands through them. Elastic headbands run across the clasps either in a semicircular or criss-cross alignment with respect to the respirator mask chassis or framework. The headbands can be tightened or loosened depending upon the wearer’s head size by a hinge mechanism whereby pulling action results in tightening of the bands and pushing the inner part of the clasp allows the release of the band for loosening.

Preferably, the clasp arrangement comprises four clasps, two on each side of the peripheral frame of the mask chassis or framework. More preferably, the two clasps on the same side of the mask chassis are aligned at an angle of 40° with respect to each other.

Preferably, the width of each clasp is approximately 20mm.

Advantageously, it is possible to mount valves and sensors on the chassis of the respirator mask further enhancement of the functionality of the mask.

A further aspect of the invention provides a method of forming two-dimensional flat sheets of filter material or fabric into the cup-shaped or dome-shaped structure of the mask, whilst at the same time controlling the inevitable wrinkling of these sheets which occurs as they pressed into a three-dimensional shape.

The said method includes forcing filter sheets into the cup-shaped or dome-shaped structure of the respirator mask chassis, yet having optimally spaced creases over the filter sheet around the base of the cup or dome. The optimally spaced creases on the filter sheet result in a very tidy appearance and enhance the aesthetic appeal of the respirator mask, alleviating the need of topping the same with a smooth and stiff filter sheet. This also allows for flexibility of the mask filter during movement for the wearer’s comfort and would even reduce the weight of the mask making it more comfortable for the wearer.

Preferably, the method of forming optimally spaced creases on the two-dimensional filter sheets utilizes a plunger and cavity set-up. The plunger part of the set-up comprises two components, a circular hollow frame and a solid three-dimensional cast, to fit in the cavity cast, having a small handle over and above the centre of the cast. The cavity cast is a three-dimensional frame, circular in shape and includes a depression analogous to the shape and dimensions of the mask chassis.

Advantageously, the plunger and cavity set-up is designed and constructed in such a way that the peripheries of the inner side of the circular hollow frame of the plunger part and the outer side of the cavity cast comprise optimally spaced creases. Optionally, the method of forming creases on the two-dimensional filter sheets utilizing a plunger and cavity configuration, involves another heavy cut-out frame which is used for inserting further weight and pressing down even more upon the plunger during the process of forming creases on the filter sheets.

Thus, the method of forming two-dimensional flat sheets of filter material or fabric into the cup-shaped or dome-shaped structure of the mask while creating optimally spaced creases on the filter sheets, according to the invention, comprises the steps of:

1. Placing the filter material or fabric sheets over the cavity cast such that multiple sheets are aligned parallel on top of one another;

2. Placing and pressing the plunger frame on the top of the filter sheets such that creases on the inside of plunger frame sit over the corresponding creases on the periphery of the cavity cast so as to trap the filter sheets in between the two;

3. Placing and pressing a solid three-dimensional cast over the central portion of the filter sheets and pushing the sheets inwards to create a cup-shaped or dome-shaped structure, thereby taking the form of the mask while simultaneously creating optimally spaced creases along the periphery of the sheets;

4. Optionally placing a cut-out frame over the plunger frame to enhance the thrust exerted over the filter sheets;

5. Removing the plunger frame, the three-dimensional solid cast and the metal cut-out frame to retain formed filter sheets having shape and dimensions proportionate to the mask with optimally spaced creases along its periphery;

6. Attaching the formed filter sheets to the external convex frame of the mask chassis, preferably by welding. The respirator mask, according to the invention, having optimally spaced creases in the filter sheet has an aesthetic appeal in itself due to the symmetry of the creases and does not require an additional smooth filter layer to be fixed on it. Such arrangement of filter sheets also works in concert with the mask chassis to provide sufficient structural integrity. Also, having multiple layers of filters sheets on top of one another imparts the present mask an ability to expand under tension to permit movement when worn by a person. Thus, the method, according to the invention, offers competitive advantage over the existing methods of forming a respirator mask.

The scope of the present invention is not limited to just the preferred embodiments but includes all the plausible variants notably those concerning the materials used for the construction and assembly of the respirator masks.

Brief Description of the Drawings

Figure 1 is a perspective view of a respirator mask chassis for use in an embodiment of a mask according to the invention;

Figure 2 is a perspective view of a formed respirator mask with face seal, filter sheets and elastic headbands attached to it;

Figure 3 is a cross-sectional view of the respirator mask;

Figures 4 and 5 are side views of the respirator mask;

Figures 6 to 12 are perspective drawings illustrating steps in a method of forming two- dimensional flat filter sheets into shape and dimensions proportionate to the three- dimensional cup-shaped or dome-shaped structure of a respirator mask, with optimally spaced creases around the periphery of the filter sheet;

Figure 13 is a perspective top view of an elliptical face seal having a flange extending radially inwards;

Figure 14 is a perspective inside view of an elliptical face seal; Figure 15 is a closer view along the nose ridge of the elliptical face seal depicting diaphragm at the bridge of the nose;

Figure 16 is a perspective view of a flat, punched face seal attached to the peripheral frame of a mask chassis; and

Figure 17 is a perspective view of a respirator mask chassis without a nose ridge, for use in an alternate embodiment of the respirator mask according to the invention.

Detailed Description

The invention will hereafter be more particularly described with reference to the accompanying drawings, which describe the invention by way of example only.

In the first embodiment of the invention, a respirator mask 10 is provided, comprising a mask chassis 20, a seal 30, formed filter sheets 40 and a cup-shaped or domeshaped support structure 50.

The mask chassis 20 comprises a circular structural framework 22 having a protrusion or nose ridge 24 at the frontal periphery of the structural framework, a pair of ribs 26 aligned in a curved “X” pattern within the circular structural framework 22, a clasp arrangement 28 with four clasps 27, two attached on either side of the structural framework 22, the two clasps on same side aligned at an approximate angle of 40° with respect to one another. Elastic headbands 25 run from end to end between two corresponding clasps 27 on either side. These elastic headbands 25 can be tightened or loosened depending upon the wearer’s head size by a hinge mechanism 29 whereby pulling action results in tightening of the bands 25 and pushing the inner part of the clasp 27 allows the release of the band for loosening.

A face seal 30 is attached to the framework 22 of the mask chassis 20, having an elliptical profile comprising a radially inwards extending flange 32. However, referring to Figure 16, the face seal 30 can also have a flat, punched profile. The face seal 30 is typically made up of a thermoplastic elastomer which is capable of forming a sufficient grip around the nose and mouth of the wearer when the mask is in use. Formed filter sheets 40 are attached or welded to the external convex periphery of the mask chassis 20 thereby sitting across the exterior of the structural framework 22 and pair of ribs 26.

A cup-shaped or dome-shaped structure 50 is created within the mask chassis 20 owing to the configuration of the ribs 26 and/or formed filter sheets 40 attached or welded on to the ribs 26. The cup-shaped or dome-shaped structure 50 retains an air pocket sufficient to prevent deficit of oxygen when a person is wearing the respirator mask.

Since the layer of filter sheets is attached to the exterior of the mask chassis 20 which is a support structure, the filter sheets do not tend to be pushed into the mouth of the user in case of any accidents or such. The mask chassis together with the formed sheets on the exterior side and an optimum air pocket being maintained inside the mask chassis, without the requirement of a thick preformed carrier for attachment of filter sheets and other mask components, offer competitive advantage over respirator masks known in the art.

The second aspect of the invention provides a method of forming two-dimensional flat sheets of filter material or fabric into the cup-shaped or dome-shaped structure of the mask while creating optimally spaced creases on the filter sheets, thereby producing formed filter sheets (40), comprising the steps of:

1 . Placing the filter material or fabric sheets (41) over the cavity cast (60) of the plunger and cavity set-up such that multiple sheets are aligned on top of one another;

2. Placing and pressing the plunger frame (80) on the filter sheets such that creases on the inside of plunger frame (80) sit over the corresponding creases on the periphery of the cavity cast (60) so as to trap the filter sheets in between the two;

3. Placing and pressing a solid three-dimensional cast (100) on the central portion of the filter sheets, thereby pushing the sheets inwards to create a cup-shaped or dome-shaped structure (50) thereby taking the form of the mask chassis (20) while simultaneously creating optimally spaced creases (42) on the peripheral portion of the sheets;

4. Optionally placing a cut-out (120) frame over the plunger frame (80) to enhance the thrust exerted over the filter sheets;

5. Removing the plunger frame (80), the three-dimensional solid cast (100) and the cut-out frame (120) to retain formed filter sheets (40) having shape and dimensions proportionate to the mask chassis with optimally spaced creases (42) along the periphery; 6. Attaching the formed filter sheets (40) to the external convex frame of the mask chassis (20), preferably by welding.

It is to be understood that the invention is not limited to the specific details described herein, which are given by way of examples only and various modifications and alterations are possible without departing from the scope of the invention as defined in the appended claims.