Patent Application
20110067700
The present invention pertains to a flat-fold filtering face-piece respirator that has a weld pattern disposed on its front surface, which weld pattern assists in providing a collapse resistant structure to the mask body.
Respirators are commonly worn over the breathing passages of a person for at least one of two common purposes: (1) to prevent impurities or contaminants from entering the wearer's breathing track; and (2) to protect other persons or things from being exposed to pathogens and other contaminants exhaled by the wearer. In the first situation, the respirator is worn in an environment where the air contains particles that are harmful to the wearer, for example, in an auto body shop. In the second situation, the respirator is worn in an environment where there is risk of contamination to other persons or things, for example, in an operating room or a clean room.
A variety of respirators have been designed to meet either (or both) of these purposes. Some respirators have been categorized as being “filtering face-pieces” because the mask body itself functions as the filtering mechanism. Unlike respirators that use rubber or elastomeric mask bodies in conjunction with attachable filter cartridges (see, e.g., U.S. Pat. RE39,493 to Yuschak et al.) or insert-molded filter elements (see, e.g., U.S. Pat. No. 4,790,306 to Braun), filtering face-piece respirators are designed to have the filter media cover much of the whole mask body so that there is no need for installing or replacing a filter cartridge. Filtering face-piece respirators commonly come in one of two configurations: molded respirators and flat-fold respirators.
Molded filtering face piece respirators have regularly comprised non-woven webs of thermally-bonded fibers or open-work plastic meshes to furnish the mask body with its cup-shaped configuration. Molded respirators tend to maintain the same shape during both use and storage. Examples of patents that disclose molded, filtering, face-piece respirators include U.S. Pat. Nos. 7,131,442 to Kronzer et al, 6,923,182, 6,041,782 to Angadjivand et al., 4,850,347 to Skov, 4,807,619 to Dyrud et al., 4,536,440 to Berg, and Des. 285,374 to Huber et al. Flat-fold respirators—as their name implies—can be folded flat for shipping and storage. Examples of flat-fold respirators are shown in U.S. Pat. Nos. 6,568,392 and 6,484,722 to Bostock et al. and in U.S. Pat. No. 6,394,090 to Chen.
During use, filtering face-piece respirators should maintain their intended cup-shaped configuration. After being worn numerous times and being subjected to high quantities of moisture from a wearer's exhalations, in conjunction with having the mask bump into other objects while being worn on a person's face, known masks can be susceptible to collapsing or having an indentation pressed into the shell. The wearer can remove this indentation by displacing the mask from their face and pressing on the indentation from the mask interior. To preclude masks from collapsing during use, additional layers have been added to the mask body structure to improve its structural integrity. U.S. Pat. No. 6,923,182 to Angadjivand et al., for example, uses first and second adhesive layers between the filtration layer and first and second shaping layers to provide a crush-resistant molded filtering face mask. To preserve the structural integrity of a flat-fold respirator, U.S. Pat. No. 6,394,090 to Chen provides first and second lines of demarcation on the mask body to assist in preventing collapse during use.
The present invention provides a new flat-fold filtering face-piece respirator construction that assists in preventing mask body collapse during use. The respirator of the present invention comprises a mask body and a harness. The mask body has a transversely-extending line of demarcation, a longitudinal axis and first and second weld patterns disposed above and not traversing the line of demarcation on each side of the longitudinal axis, respectively. Third and forth weld patterns are disposed below and not crossing the line of demarcation on each side of the longitudinal axis, respectively. Each of the first, second, third, and fourth weld patterns is a two-dimensional enclosed pattern.
The present invention is directed to providing a flat-fold filtering face-piece respirator that possesses crush resistant properties that minimize mask shape deformation caused by extended use or rough handling. The respirator also is less likely to lose its structural integrity from particle loading and/or moisture build-up. Because the filtering face-piece respirator is less likely to collapse during use, it therefore presents the benefit of improving wearer comfort and convenience. Further, there is less need for additional layers or heavier layers to provide collapse resistant qualities. The use of additional layers can result in increased breathing resistance and product cost. The present invention therefore presents the benefit of preserving the intended in-use shape of the mask body in conjunction with improving wearer comfort without the added cost of additional or heavier layers.
The terms set forth below will have the meanings as defined:
“bisect(s)” means to divide into two generally equal parts;
“comprises (or comprising)” means its definition as is standard in patent terminology, being an open-ended term that is generally synonymous with “includes”, “having”, or “containing”. Although “comprises”, “includes”, “having”, and “containing” and variations thereof are commonly-used, open-ended terms, this invention also may be suitably described using narrower terms such as “consists essentially of”, which is a semi open-ended term in that it excludes only those things or elements that would have a deleterious effect on the performance of the inventive respirator in serving its intended function;
“clean air” means a volume of atmospheric ambient air that has been filtered to remove contaminants;
“contaminants” means particles (including dusts, mists, and fumes) and/or other substances that generally may not be considered to be particles (e.g., organic vapors, et cetera) but which may be suspended in air;
“crosswise dimension” is the dimension that extends laterally across the respirator from side-to-side when the respirator is viewed from the front;
“cup-shaped configuration” means any vessel-type shape that is capable of adequately covering the nose and mouth of a person;
“exterior gas space” means the ambient atmospheric gas space into which exhaled gas enters after passing through and beyond the mask body and/or exhalation valve;
“filtering face-piece” means that the mask body itself is designed to filter air that passes through it; there are no separately identifiable filter cartridges or insert-molded filter elements attached to or molded into the mask body to achieve this purpose;
“filter” or “filtration layer” means one or more layers of air-permeable material, which layer(s) is adapted for the primary purpose of removing contaminants (such as particles) from an air stream that passes through it;
“filter media” means an air-permeable structure that is designed to remove contaminants from air that passes through it;
“filtering structure” means a construction that includes a filter media or a filtration layer;
“first side” means an area of the mask body that is located on one side of a plane that bisects the mask body normal to the cross-wise dimension;
“fitment” means any one or combination of donning, doffing, or the adjusting mask body;
“flange” means a protruding part that has sufficient surface area to be grasped by a person;
“frontally” means extending away from the mask body perimeter when the mask body is in a folded condition;
“harness” means a structure or combination of parts that assists in supporting the mask body on a wearer's face;
“indicia” means an identifying mark(s), pattern(s), image(s), opening(s), or combination thereof;
“integral” means being manufactured together at the same time; that is, being made together as one part and not two separately manufactured parts that are subsequently joined together;
“interior gas space” means the space between a mask body and a person's face;
“laterally” means extending away from a plane that bisects the mask body normal to the cross-wise dimension when the mask body is in a folded condition;
“line of demarcation” means a fold, seam, weld line, bond line, stitch line, hinge line, and/or any combination thereof;
“longitudinal axis” means a line that bisects the mask body normal to the cross-wise dimension;
“mask body” means an air-permeable structure that is designed to fit over the nose and mouth of a person and that helps define an interior gas space separated from an exterior gas space (including the seams and bonds that join layers and parts thereof together);
“nose clip” means a mechanical device (other than a nose foam), which device is adapted for use on a mask body to improve the seal at least around a wearer's nose;
“perimeter” means the outer edge of the mask body, which outer edge would be disposed generally proximate to a wearer's face when the respirator is being donned by a person;
“pleat” means a portion that is designed to be or is folded back upon itself;
“polymeric” and “plastic” each mean a material that mainly includes one or more polymers and that may contain other ingredients as well;
“plurality” means two or more;
“respirator” means an air filtration device that is worn by a person to provide the wearer with clean air to breathe;
“second side” means an area of the mask body that is located on one side of a plane that bisects the mask body normal to the cross-wise dimension (the second side being opposite the first side);
“snug fit” or “fit snugly” means that an essentially air-tight (or substantially leak-free) fit is provided (between the mask body and the wearer's face);
“tab” means a part that exhibits sufficient surface area for attachment of another component; and
“transversely extending” means extending generally in the crosswise dimension.
In practicing the present invention, a flat-fold, filtering face-piece respirator is provided that has a weld pattern disposed on the mask body to help improve collapse resistance.
The mask body that is used in connection with the present invention may take on a variety of different shapes and configurations. Generally the shape and configuration of the filtering structure corresponds to the general shape of the mask body. Although a filtering structure has been illustrated with multiple layers that include a filtration layer and two cover webs, the filtering structure may simply comprise a filtration layer or a combination of filtration layers. For example, a pre-filter may be disposed upstream to a more refined and selective downstream filtration layer. Additionally, sorptive materials such as activated carbon may be disposed between the fibers and/or various layers that comprise the filtering structure. Further, separate particulate filtration layers may be used in conjunction with sorptive layers to provide filtration for both particulates and vapors. The filtering structure may include one or more stiffening layers that assist in providing a cup-shaped configuration. The filtering structure also could have one or more horizontal and/or vertical lines of demarcation that contribute to its structural integrity. Using the first and second flanges in accordance with the present invention, however, may make unnecessary the need for such stiffening layers and lines of demarcation.
The filtering structure that is used in a mask body of the invention can be of a particle capture or gas and vapor type filter. The filtering structure also may be a barrier layer that prevents the transfer of liquid from one side of the filter layer to another to prevent, for instance, liquid aerosols or liquid splashes (e.g. blood) from penetrating the filter layer. Multiple layers of similar or dissimilar filter media may be used to construct the filtering structure of the invention as the application requires. Filters that may be beneficially employed in a layered mask body of the invention are generally low in pressure drop (for example, less than about 195 to 295 Pascals at a face velocity of 13.8 centimeters per second) to minimize the breathing work of the mask wearer. Filtration layers additionally are flexible and have sufficient shear strength so that they generally retain their structure under the expected use conditions. Examples of particle capture filters include one or more webs of fine inorganic fibers (such as fiberglass) or polymeric synthetic fibers. Synthetic fiber webs may include electret-charged polymeric microfibers that are produced from processes such as meltblowing. Polyolefin microfibers formed from polypropylene that has been electrically charged provide particular utility for particulate capture applications. An alternate filter layer may comprise a sorbent component for removing hazardous or odorous gases from the breathing air. Sorbents may include powders or granules that are bound in a filter layer by adhesives, binders, or fibrous structures—see U.S. Pat. Nos. 6,334,671 to Springett et al. and 3,971,373 to Braun. A sorbent layer can be formed by coating a substrate, such as fibrous or reticulated foam, to form a thin coherent layer. Sorbent materials may include activated carbons that are chemically treated or not, porous alumna-silica catalyst substrates, and alumna particles. An example of a sorptive filtration structure that may be conformed into various configurations is described in U.S. Pat. No. 6,391,429 to Senkus et al.
The filtration layer is typically chosen to achieve a desired filtering effect. The filtration layer generally will remove a high percentage of particles and/or or other contaminants from the gaseous stream that passes through it. For fibrous filter layers, the fibers selected depend upon the kind of substance to be filtered and, typically, are chosen so that they do not become bonded together during the molding operation. As indicated, the filtration layer may come in a variety of shapes and forms and typically has a thickness of about 0.2 millimeters (mm) to 1 centimeter (cm), more typically about 0.3 mm to 0.5 cm, and it could be a generally planar web or it could be corrugated to provide an expanded surface area—see, for example, U.S. Pat. Nos. 5,804,295 and 5,656,368 to Braun et al. The filtration layer also may include multiple filtration layers joined together by an adhesive or any other means. Essentially any suitable material that is known (or later developed) for forming a filtering layer may be used as the filtering material. Webs of melt-blown fibers, such as those taught in Wente, Van A., Superfine Thermoplastic Fibers, 48 Indus. Engn. Chem., 1342 et seq. (1956), especially when in a persistent electrically charged (electret) form are especially useful (see, for example, U.S. Pat. No. 4,215,682 to Kubik et al.). These melt-blown fibers may be microfibers that have an effective fiber diameter less than about 20 micrometers (μm) (referred to as BMF for “blown microfiber”), typically about 1 to 12 μm. Effective fiber diameter may be determined according to Davies, C. N., The Separation Of Airborne Dust Particles, Institution Of Mechanical Engineers, London, Proceedings 1B, 1952. Particularly preferred are BMF webs that contain fibers formed from polypropylene, poly(4-methyl-1-pentene), and combinations thereof. Electrically charged fibrillated-film fibers as taught in van Turnhout, U.S. Pat. Re. 31,285, also may be suitable, as well as rosin-wool fibrous webs and webs of glass fibers or solution-blown, or electrostatically sprayed fibers, especially in microfilm form. Electric charge can be imparted to the fibers by contacting the fibers with water as disclosed in U.S. Pat. Nos. 6,824,718 to Eitzman et al., 6,783,574 to Angadjivand et al., 6,743,464 to Insley et al., 6,454,986 and 6,406,657 to Eitzman et al., and 6,375,886 and 5,496,507 to Angadjivand et al. Electric charge also may be imparted to the fibers by corona charging as disclosed in U.S. Pat. No. 4,588,537 to Klasse et al. or by tribocharging as disclosed in U.S. Pat. No. 4,798,850 to Brown. Also, additives can be included in the fibers to enhance the filtration performance of webs produced through the hydro-charging process (see U.S. Pat. No. 5,908,598 to Rousseau et al.). Fluorine atoms, in particular, can be disposed at the surface of the fibers in the filter layer to improve filtration performance in an oily mist environment—see U.S. Pat. Nos. 6,398,847 B1, 6,397,458 B1, and 6,409,806 B1 to Jones et al. Typical basis weights for electret BMF filtration layers are about 10 to 100 grams per square meter. When electrically charged according to techniques described in, for example, the '507 Angadjivand et al. patent, and when including fluorine atoms as mentioned in the Jones et al. patents, the basis weight may be about 20 to 40 g/m2 and about 10 to 30 g/m2, respectively.
An inner cover web can be used to provide a smooth surface for contacting the wearer's face, and an outer cover web can be used to entrap loose fibers in the mask body or for aesthetic reasons. The cover web typically does not provide any substantial filtering benefits to the filtering structure, although it can act as a pre-filter when disposed on the exterior (or upstream to) the filtration layer. To obtain a suitable degree of comfort, an inner cover web preferably has a comparatively low basis weight and is formed from comparatively fine fibers. More particularly, the cover web may be fashioned to have a basis weight of about 5 to 50 g/m2 (typically 10 to 30 g/m2), and the fibers may be less than 3.5 denier (typically less than 2 denier, and more typically less than 1 denier but greater than 0.1). Fibers used in the cover web often have an average fiber diameter of about 5 to 24 micrometers, typically of about 7 to 18 micrometers, and more typically of about 8 to 12 micrometers. The cover web material may have a degree of elasticity (typically, but not necessarily, 100 to 200% at break) and may be plastically deformable.
Suitable materials for the cover web may be blown microfiber (BMF) materials, particularly polyolefin BMF materials, for example polypropylene BMF materials (including polypropylene blends and also blends of polypropylene and polyethylene). A suitable process for producing BMF materials for a cover web is described in U.S. Pat. No. 4,013,816 to Sabee et al. The web may be formed by collecting the fibers on a smooth surface, typically a smooth-surfaced drum or a rotating collector—see U.S. Pat. No. 6,492,286 to Berrigan et al. Spun-bond fibers also may be used.
A typical cover web may be made from polypropylene or a polypropylene/polyolefin blend that contains 50 weight percent or more polypropylene. These materials have been found to offer high degrees of softness and comfort to the wearer and also, when the filter material is a polypropylene BMF material, to remain secured to the filter material without requiring an adhesive between the layers. Polyolefin materials that are suitable for use in a cover web may include, for example, a single polypropylene, blends of two polypropylenes, and blends of polypropylene and polyethylene, blends of polypropylene and poly(4-methyl-1-pentene), and/or blends of polypropylene and polybutylene. One example of a fiber for the cover web is a polypropylene BMF made from the polypropylene resin “Escorene 3505G” from Exxon Corporation, providing a basis weight of about 25 g/m2 and having a fiber denier in the range 0.2 to 3.1 (with an average, measured over 100 fibers of about 0.8). Another suitable fiber is a polypropylene/polyethylene BMF (produced from a mixture comprising 85 percent of the resin “Escorene 3505G” and 15 percent of the ethylene/alpha-olefin copolymer “Exact 4023” also from Exxon Corporation) providing a basis weight of about 25 g/m2 and having an average fiber denier of about 0.8. Suitable spunbond materials are available, under the trade designations “Corosoft Plus 20”, “Corosoft Classic 20” and “Corovin PP-S-14”, from Corovin GmbH of Peine, Germany, and a carded polypropylene/viscose material available, under the trade designation “370/15”, from J. W. Suominen OY of Nakila, Finland.
Cover webs that are used in the invention preferably have very few fibers protruding from the web surface after processing and therefore have a smooth outer surface. Examples of cover webs that may be used in the present invention are disclosed, for example, in U.S. Pat. No. 6,041,782 to Angadjivand, U.S. Pat. No. 6,123,077 to Bostock et al., and WO 96/28216A to Bostock et al.
The strap(s) that are used in the harness may be made from a variety of materials, such as thermoset rubbers, thermoplastic elastomers, braided or knitted yarn/rubber combinations, inelastic braided components, and the like. The strap(s) may be made from an elastic material such as an elastic braided material. The strap preferably can be expanded to greater than twice its total length and be returned to its relaxed state. The strap also could possibly be increased to three or four times its relaxed state length and can be returned to its original condition without any damage thereto when the tensile forces are removed. The elastic limit thus is preferably not less than two, three, or four times the length of the strap when in its relaxed state. Typically, the strap(s) are about 20 to 30 cm long, 3 to 10 mm wide, and about 0.9 to 1.5 mm thick. The strap(s) may extend from the first tab to the second tab as a continuous strap or the strap may have a plurality of parts, which can be joined together by further fasteners or buckles. For example, the strap may have first and second parts that are joined together by a fastener that can be quickly uncoupled by the wearer when removing the mask body from the face. An example of a strap that may be used in connection with the present invention is shown in U.S. Pat. No. 6,332,465 to Xue et al. Examples of fastening or clasping mechanism that may be used to joint one or more parts of the strap together is shown, for example, in the following U.S. Pat. Nos. 6,062,221 to Brostrom et al., 5,237,986 to Seppala, and EP1,495,785A1 to Chien.
As indicated, an exhalation valve may be attached to the mask body to facilitate purging exhaled air from the interior gas space. The use of an exhalation valve may improve wearer comfort by rapidly removing the warm moist exhaled air from the mask interior. See, for example, U.S. Pat. Nos. 7,188,622, 7,028,689, and 7,013,895 to Martin et al.; 7,428,903, 7,311,104, 7,117,868, 6,854,463, 6,843,248, and 5,325,892 to Japuntich et al.; 6,883,518 to Mittelstadt et al.; and RE37,974 to Bowers. Essentially any exhalation valve that provides a suitable pressure drop and that can be properly secured to the mask body may be used in connection with the present invention to rapidly deliver exhaled air from the interior gas space to the exterior gas space.
This invention may take on various modifications and alterations without departing from its spirit and scope. Accordingly, this invention is not limited to the above-described but is to be controlled by the limitations set forth in the following claims and any equivalents thereof.
This invention also may be suitably practiced in the absence of any element not specifically disclosed herein.
All patents and patent applications cited above, including those in the Background section, are incorporated by reference into this document in total. To the extent there is a conflict or discrepancy between the disclosure in such incorporated document and the above specification, the above specification will control.
A respirator filtering structure was formed from three layers of nonwoven material and other respirator components. The inventive mask was assembled in two operations—preform making and mask finishing. The preform making stage included the steps of lamination and fixing of nonwoven fibrous webs, formation of pleat crease lines and attachment of perimeter web material and nose clip. The mask finishing operation included folding of pleats along embossed crease lines, fusing both the lateral mask edges and reinforced flange material, cutting the final form, and attaching a headband.
In the preform making stage, three layers of nonwoven material were plied in face to face orientation. In the example, individual materials that formed the layers were assembled in the following order:
1. outer scrim
2. filter material
3. inner cover web
The outer scrim (indicated as 60 in
In the mask finishing operation, pleats were folded along crease lines as shown in
Design of flat-fold respirators with the best fit and highest comfort level for a spectrum of wearers of diverse anthropometry can be augmented with the use of headforms adapted for measuring the collapse of the respirator when subjected to a simulated breathing load. This method simulated the interaction between a respirator and a headform. Head-strap forces, headform shape, mask positioning; breathing cycle volume and rate play roles in determining the collapse resistance performance of a flat-fold respirator.
The headform used in this test method was adapted with a breathing opening and contact load pad positioned on the face of the headform. Anthropometric feature dimensions of the headform are given in Table 1; these features are those outlined for characterizing head and face dimensions in respirator performance analysis described in a National Institute for Occupational Safety and Health (NIOSH) study titled “A HEAD-AND-FACE ANTHROPOMETRICSURVEY OF U.S. RESPIRATOR USERS”, May 2004. A simulated breathing opening, having a 13 mm diameter round outlet on the face of the headform, was located 15.9 mm above and centered over the human analog of the Menton position—the inferior point of the mandible in the midsagittal plane (bottom of the chin). The contact load pad, with a contact activation threshold of 6.9 kPa, was in the shape of an elliptical annular ring positioned around the simulated breathing opening. The pad extended radially from the edge of the simulated breathing opening and had a thickness of 5 mm. Orientation of the contact load pad was such that the ellipse major axis was transverse to the headform, with the major axis length being 66 mm and the minor axis length being 48 mm. During testing, when contact between the mask was made with the contact load pad, a light would illuminate indicating collapse of the mask.
Masks for evaluation were fitted to the headform using two elastic bands—one that generally followed the Bitragion Subnasale Arc around to the back of the headform above the ear and a second that traversed the back of the headform under the ear. The force exerted on the mast from extending from each of four attachment points was nominally 2 Newtons (N). The mask was positioned on the headform so that the intersection of the center fold transversely-extending line of demarcation and the longitudinal axis was aligned with the center of the breathing opening. With the mask properly positioned for evaluation, the breathing cycle of the test apparatus was initiated.
A Dynamic Breathing Machine, Warwick Technology Limited, Warwick, United Kingdom was used in conjunction with the previously described headform to simulate human respiration as it would be delivered to a respirator. The test apparatus was configured such that air was channeled from the breathing machine to the back of the headform through a 30 cm long 2.54 cm inner diameter hose. The breathing machine provided a breathing sine wave waveform with a flow rate, given in liters/minute (1/min) that was varied over the duration of the test. The breathing machine was operated at a respiratory frequency of 20 cycles/minute, with a tidal volume of 1 liter, and at room conditions of 25 deg C. and relative humidity of 50%.
Respirator evaluations were conducted by placing a respirator on the headform, as described in the Headform section above, and initiating the breathing apparatus at a flow rate of 20 l/min. The flow rate was then gradually increasing by increments of 5 l/min every 3 minutes until the load cell was triggered. Triggering of the load cell indicated collapse of the respirator, and the test was ended. The flow rate at which the respirator collapsed was recorded as the measure of collapse resistance and recorded in 1/m.
A respirator was constructed by the procedures detailed in the General Mask Making Procedure using a reinforcing weld pattern in the form of an isosceles triangle with two nested isosceles triangles located in corners opposite the equal-length sides of the larger triangle, as is generally depicted in
A mask was formed and tested as described in Example 1 except that no reinforcing pattern was used. Test results are given in Table 2.
A mask was formed and tested as described in Example 1 except that a 34 gsm inner cover web and outer scrim of polypropylene spun-bonded nonwoven, available from Shandong Kangjie Nonwovens Co. Ltd., Jinan, China were used in the Preform Making Stage. Test results are given in Table 2.
A mask was formed and tested as described in Comparative Example 1 except that a 34 gsm inner cover web and outer scrim were used in the Preform Making Stage. Test results are given in Table 2.
The masks were tested according to the Simulated Breathing Apparatus and Collapse Resistance Test protocol. Test results and testing parameters are given in Table 2:
The test results indicate that the collapse resistance of masks, formed with weld reinforcing patterns, had a greater effect on lighter-weight constructions than heavier constructions. The truss-type weld pattern provided improvement of collapse resistance for the lighter-weight mask construction relative to a mask of that construction with no weld pattern.
This invention may take on various modifications and alterations without departing from its spirit and scope. Accordingly, this invention is not limited to the above-described but is to be controlled by the limitations set forth in the following claims and any equivalents thereof.
This invention also may be suitably practiced in the absence of any element not specifically disclosed herein.
All patents and patent applications cited above, including those in the Background section, are incorporated by reference into this document in total. To the extent there is a conflict or discrepancy between the disclosure in such incorporated document and the above specification, the above specification will control.
