Patent Publication Number: US-2007107734-A1

Title: Face Mask and Method of Manufacturing the Same

Description:
PRIORITY  
      This patent application is a divisional application of U.S. patent application Ser. No. 10,423,382, filed Apr. 15, 2003, naming Robert A. Brunell and George A. Snow as inventors, which claims priority from provisional U.S. patent application 60/386,297, filed Jun. 5, 2002, naming Robert A. Brunell and George A. Snow as inventors. The disclosure of each of the above-described applications are incorporated herein, in their entirety, by reference. 
    
    
     FIELD OF THE INVENTION  
      The invention relates generally to face masks and, more particularly, the invention relates to face masks used to filter air breathed by people wearing such face masks.  
     BACKGROUND OF THE INVENTION  
      Air filtration masks (referred to herein as “filter masks”) are widely used to protect people from air borne contaminants and gasses. For example, air borne dust particles are a known hazard commonly on work sites. Consequently, such workers normally wear filter masks to avoid inhaling the dust particles. To that end, filter masks used in this application are manufactured with a filter material specified to prevent, among other things, a substantial majority of dust particles from being inhaled by the worker.  
      In addition to primarily protecting inhaled air, some filter masks are specifically manufactured to filter both inhaled and exhaled air. For example, hospital staff often wear filter masks to prevent both their germs from infecting patients, and patients&#39; germs from infecting them.  
      There is a need in the art to improve the filtration efficiency of filter masks. Accordingly, filter masks with multiple filter layers have been developed for that purpose. Multiple filter layer filter masks typically filter particles and gasses more efficiently than many types of single filter layer filter masks. Use of multiple filter layers, however, undesirably increases the air resistance through the filter mask. Consequently, a person wearing the filter mask may have a more difficult time breathing. In fact, due to reduced amount of breathable air, some people can become dizzy when wearing multiple layer masks.  
      To overcome this problem while still providing improved filtration efficiency, filter masks have been developed to increase filter area, thus improving performance. Manufacture of such filter masks, however, can be more complex than filter masks with multiple filter layers. Sometimes, increasing the area can cause portions of the single layer filter layer to overlap. Overlap effectively increases the thickness of the filter layer, thus causing the same air resistance problem as discussed above.  
     SUMMARY OF THE INVENTION  
      In accordance with one aspect of the invention, a method of manufacturing a mask folds a sheet of filter material into a set of sections that each has two ends. The two ends of each of the sections then are reshaped to form two reshape lines common to all of the set of sections. The sections then are connected along the two reshape lines to form a primary assembly. Note that the two reshape lines are not connected together. The primary assembly is folded inside-out to form a secondary assembly, and then coupled to a support base. The set of sections illustratively includes at least four sections.  
      In some embodiments, each of the set of sections includes a first side and a second side, where the first side and the second side of each section are the two ends noted above. The two ends of each of the sections thus are reshaped by making first and second cuts along the folded sheet of filter material. The first cut cuts the first side of each section, while the second cut cuts the second side of each section. In other embodiments, the set of sections may be connected along the two reshape lines by a number of ways known in the art, such as by at least one of bonding, welding, sewing, gluing, fastening, and heating along either of the two reshape lines,  
      The primary assembly may have the form of a trapezoid, and may be substantially flat. In addition, the set of sections may be formed to include two end sections anti two middle sections, where the middle sections are between the two end sections. Each of the two middle sections illustratively has a smaller area than the area of either of the two end sections.  
      The secondary assembly may include a rim forming an opening. The secondary assembly thus may be coupled to the support base by bonding the rim to the support base. In yet other embodiments, the secondary assembly forms a concave portion, and the support base has a corresponding convex portion. To couple the secondary assembly, the convex portion may be placed into the concave portion before coupling the secondary assembly to the support base. The secondary assembly further may include at least one pleat.  
      In accordance with another aspect of the invention, a mask includes a filter layer and a support base supporting the filter layer. The filter layer has first and second complimentary portions that together form a rim, where the first portion is connected to the second portion at first and second seams. The first seam extends from the rim to a first pleat, while the second seam extends from the rim to a second pleat. The first pleat is connected to the second pleat by an unpleated central portion. The first pleat, second pleat and unpleated central portion are formed by the first and second portions of the filter layer.  
      In some embodiments, the filter layer has an effective center line that bisects the filter layer in a longitudinal direction. The first and second seams are substantially coincident with the effective center line. Moreover, the first and second pleats may be substantially bisected by the effective center line. The filter layer may form a concave inner surface, and the support base may form a convex outer surface. The concave inner surface of the filter layer may face the convex outer surface of the support base, and the concave inner surface of the filter layer may be free to move relative to the convex outer surface of the support base.  
      The filter layer may form a filter rim and the support base may form a base rim. Consequently, the filter rim may be secured to the base rim for form the rim. The filter illustratively is normally substantially free of overlap. The mask also may include a valve extending through both the filter layer and the support base. Porous polyester is one exemplary material used for the support base, while the filter layer may be manufactured from polypropylene. The surface area of the filter layer illustratively is greater than the surface area of the support base. The filter layer normally forms an opening. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing and advantages of the invention will be appreciated more fully from the following further description thereof with reference to the accompanying drawings wherein:  
       FIG. 1  schematically shows an exemplary filter mask constructed in accordance with illustrative embodiments of the invention.  
       FIG. 2  schematically shows a person wearing the mask shown in  FIG. 1 .  
       FIG. 3  shows a process of manufacturing the mask shown in  FIG. 1  in accordance with illustrative embodiments of the invention.  
       FIG. 4  schematically shows a sheet of filter material folded in an illustrative manner for the process shown in  FIG. 3 .  
       FIG. 5  schematically shows the folded filter material of  FIG. 4 .  
       FIG. 6  schematically shows a first assembly laid flat.  
       FIG. 7  schematically shows a partially cut-away second assembly produced from the first assembly shown in  FIG. 6 .  
       FIG. 8A  schematically shows a plan view of a support base used in illustrative embodiments of the invention.  
       FIG. 8B  schematically shows a bottom view of the support base shown in  FIG. 8A .  
       FIG. 9  schematically shows the second assembly of  FIG. 7  after it is coupled with the support base of  FIGS. 8A and 8B . 
    
    
     DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS  
      In illustrative embodiments of the invention, an air filtration mask hereinafter “filter mask  10 ” or “mask  10 ”) is constructed to have an increased filtration area by incorporating two pleats into its filter layer. Moreover, manufacturing, is simplified because, among other things, much of the process of manufacturing the filter layer may be completed while such filter layer is laid flat. Details of illustrative embodiments are discussed below.  
       FIG. 1  schematically shows an exemplary filter mask  10  constructed in accordance with illustrative embodiments of the invention. Specifically, the filter mask  10  includes a specially constructed filter layer  12  that is supported on a porous, but relatively more rigid, molded support base  14 . In illustrative embodiments, the filter layer  12  and support base  14  are sufficiently resilient so that the filter mask  10  has a normally open concave area for sealingly receiving a user&#39;s nose and mouth (see  FIG. 2 ).  
      The filter mask  10  shown in  FIGS. 1 and 2  also includes a nose piece  16  to properly position the mask  10  against the user&#39;s nose, straps  18  to secure the mask  10  to the user&#39;s face, and a peripheral rim  20  that contours to the user&#39;s face when worn. The filter mask  10  also includes a one-way valve  22  that more freely permits air to be exhaled. Of course, illustrative embodiments permit air to be freely inhale through the filter layer  12  and support base  14 . The valve  22  may be any valve known in the art conventionally used for these purposes, such as a one-way flapper valve.  
      The straps  18  may be constructed from a resilient rubber material, or other conventionally known material (e.g. a non-resilient fabric), that permits a secure and snug fit between the user&#39;s face and the rim  20 . The straps  18  thus apply an inwardly directed force for those purposes. At a minimum, this force should be sufficient at least to hold the mask  10  to the user&#39;s face. Moreover, it is preferred that the rim  20  have a contoured surface that contours to the user&#39;s face. Accordingly, when the straps  18  apply the noted inwardly directed force to the mask  10 , the contoured surface should be sufficiently flexible and resilient to shape to the user&#39;s face. This ensures that the substantial majority of the user&#39;s air is inhaled and exhaled through the filter mask  10 . In some embodiments, the rim  20  includes additional material (e.g., rubber) to provide an effective seal against the user&#39;s face.  
      In accordance with illustrative embodiments, the filter layer  12  is constructed to have complimentary top and bottom portions  24  and  26  that together both 1) a filter layer rim  28 , and 2) a pair of pleats  30 A and  30 B. As known by those in the art, pleats are formed by a portion of the filter material that is normally folded. Although the pleats may be single pleats (one fold), illustrative embodiments include double pleats (two folds). The pleats  30 A and  30 B desirably increase the surface area of the filter layer  12 , consequently improving filtering efficiency without requiring multiple filter layers or heavier single layers. In illustrative embodiments, other than portions of the pleats  30 A and  30 B, the entire filter layer  12  is substantially free of overlap. In other words, portions of the filter layer  12  do not overlap other portions. As known by those skilled in the art, being substantially free of overlap is beneficial because they typically increase air resistance through the filter mask  10 . Details of the manufacturing process that forms the pleats  30 A and  30 B are discussed below with reference to  FIG. 3 .  
      The complimentary top and bottom portions  24  and  26  of the filter layer  12  illustratively are mirror images or each other. Accordingly, the tops portion  24  and bottom portion  26  are considered to meet along an effective center line that bisects the entire filter layer  12 . This effective center line also is substantially coincident with a pair of seams  32 A and  32 B that each extend from the filter layer rim  28  to one of the pleats  30 A and  30 B. The pleats  30 A and  30 B are bridged via an unpleated central portion  34  of the filter layer  12  that also is bisected by the effective center line. In a similar manner, the effective center line also bisects both pleats  30 A and  30 B. In practice, however, it is expected that manufacturing tolerances may not permit every filter mask  10  to have exactly bisected/coincident filter layer portions. Those filter masks having filter layer portions that are not exactly bisected/coincident, but very close to being bisected/coincident, also should be considered to be within the scope of various embodiments of the invention.  
       FIG. 3  shows a process of manufacturing the filter mask  1  shown in  FIGS. 1 and 2 . The process begins at step  300 , in which a sheet of filter material  36  is folded into four sections. In particular, as shown in  FIG. 4 , the sheet of filter material  36  illustratively has a rectangular shape, and is folded to have two end sections  38 A and  38 B and two middle sections  40 A and  40 B. Both of the end sections  38 A and  38 B have a substantially equal area, while both of the middle sections  40 A and  40 B similarly have a substantially equal area. The area of each of the middle sections  40 A and  40 B, however, is smaller than that of either of the two end sections  38 A and  38 B.  
      The sheet of filter material  30  may be folded in any number of ways to obtain the configuration shown in  FIG. 4 . In illustrative embodiments, the sheet  36  first is folded along its longitudinal center  42  (i.e., parallel to the Y-axis shown in  FIG. 4 ). Then, parallel second and third fold lines  44 A and  44 B are calculated about one inch from each side of the noted first fold. The sheet of filter material  36  then is folded along the second and third fold lines  44 A and  44 B to obtain the configuration shown in  FIG. 4 .  
      The filter layer  42  may be manufactured from any conventionally known filter material used for such purposes. The appropriate filter material, however, is selected based upon the intended use of the mask  10 . Specifically, the filter material is selected based upon the material characteristics (i.e., porosity, rigidity, etc . . . ) required for the intended use. For example, the filter layer  12  may be constructed from polypropylene manufactured to comply with the well known P100 NIOSH (National Institute of Safety and Health) standard. Details of the P100 NIOSH standard can be obtained from NIOSH, which has a World Wide Web site address of http://www.ede.gov/niosh/homepage.html.  
      As another example, the filter layer  12  may be constructed from polypropylene manufactured to comply with the well known P3SL CE (Community European) standard. Of course, other types of materials may be used. Accordingly, discussion of specific types of materials is exemplary for many embodiments and thus, not intended to limit all embodiments of the invention. Those skilled in the art should understand which other types of materials may be used.  
      After the sheet of filter material  36  is folded (step  300 ),the entire folded sheet is laid flat on a surface. Once flat, the process continues to step  302 , in which the ends  46 A and  46 B of the folded sheet of filter material are reshaped. Specifically, while folded, the two ends  46 A and  46 B of the folded sheet are cut in a predetermined manner. In illustrative embodiments, the two ends  46 A and  46 B are cut along the two taper lines identified by reference number  48  in  FIG. 5 . The taper lines  48  illustratively converge toward the center fold, which is shown in  FIG. 4 . Cutting along these lines effectively reshapes the two ends of each of the end and middle sections  38 A,  38 B,  40 A, and  40 B of the folded filter sheet discussed above. In alternative embodiments, the ends  46 A and  46 B of the folded filter material are reshaped in a different manner, such as in a non-converging manner. For example, the ends  46 A and  46 B may be left in their original form.  
      After the ends are reshaped, the edges of the filter material are connected along the reshape lines as shown in  FIG. 6  (step  304 ). Any known connecting method may be used. For example, the edges may be bonded, welded, sewn, glued, fastened, and/or heated to connect the edges. Note that, as shown in  FIG. 6 , the two edges of each section are not connected together. When the edges are connected, they form first and second borders  50 A and  50 B. At this point in the process, the filter material is considered to be a “primary assembly  52 ,” which illustratively is normally in the form of a substantially flat trapezoid (see  FIG. 6 ).  
      After the primary assembly  52  is produced, the process continues to step  306 , in which the primary assembly  52  is folded inside-out to form a “secondary assembly  54 ,” which is shown in  FIG. 7  and described in detail above with regard to  FIGS. 1 and 2  and referred to as the filter layer  12 . Accordingly, among other things, the secondary assembly  54  includes the noted top and bottom portions  24  and  26 , pleats  30 A and  30 B, seams  32 A and  32 B, and central portion  34 . In addition, the secondary assembly  54  is normally open.  
      The process then continues to step  308 , in which the secondary assembly  54  is coupled with the support base  14 . To that end, the secondary assembly  54  has a concave portion  55  that is placed over a convex portion  56  of the support base  14 .  FIG. 8A  schematically shows a perspective top view of the support base  14  and its convex portion  56 , while  FIG. 8B  schematically shows a bottom view of the support base  14  (i.e., a concave portion  58  formed by the convex portion). In some embodiments, the inner surface of the concave portion  55  of the secondary assembly  54  is substantially flush against the outer surface of the convex portion  56  of the support base  44 .  
      The secondary assembly  54  may be coupled with the support base  41  in a number of ways. In some embodiments, the filter layer rim  28  of the secondary assembly  54  is welded to a corresponding area of the support base  14 . It should be noted that in a manner similar to the reshape lines (discussed above with regard to  FIG. 304 ), any manner known in the art coupling the support base  14  to the secondary assembly  54  should suffice. Other than at the valve, no other portions of the secondary assembly  54  (in this embodiment) are coupled with the support base  14 . Accordingly, this permits the secondary assembly  54  to move relative to the support base  14 . Such movement may be caused by, normal breathing.  
      The support base  14  illustratively is manufactured from a porous polyester that more resilient than the filter material. In other embodiments, this relative resilience is not necessary. The support base  14  material illustratively introduces no more than a negligible air resistance to the overall filter mask  10 .  
      The process then continues to step  310 , in which the final manufacturing steps are completed. In particular, excess material is removed from the support base  14  along the line identified by reference number  60  in  FIG. 9 . In illustrative embodiments, about ⅛ of an inch of base material extends beyond the area that connects the secondary assembly  54  to the support base  14 . This extra material and the connection area together form the above noted rim  20 , which has a surface that is flexible enough to contour to a user&#39;s face. In addition to removing excess material, the straps  18 , nose piece  16 , and valve  22  may be added, thus completing the process.  
      When in use, as shown in  FIG. 2 , the mask  10  is placed over a person&#39;s nose and mouth. The straps  18  may tie together behind the person&#39;s head, thus providing the necessary force to both hold the mask  10  to the person&#39;s face and contour the rim  20  to such person&#39;s face. The person may breath normally and without stress (caused by the mask  10 ). When not in use, the rim  20  is normally open and thus, ready to be easily positioned on a person&#39;s face. Manufacturing is simplified because, among other reasons, the cutting/connecting steps of the filter layer  12  (i.e., those discussed above with regard to steps  302  and  304 ) may be performed while the mask  10  is flat.  
      Although various exemplary embodiments of the invention have been disclosed, it should be apparent to those skilled in the art that various changes and modifications can be made that will achieve some of the advantages of the invention without departing from the true scope of the invention. These and other obvious modifications are intended to be covered by the appended claims.