Abstract:
Filter elements are described. In an example embodiment, the filter element has a support framework and media defining a closed end and an open end. A non-circular radial seal is depicted, in an example. Variations for particular applications are described.

Description:
[0001]    This application is a continuing application of U.S. Ser. No. 13/412,076, filed Mar. 5, 2012. U.S. Ser. No. 13/412,076 is a continuation of U.S. Ser. No. 12/386,482, filed Apr. 16, 2009, which has issued as U.S. Pat. No. 8,128,724. U.S. Ser. No. 12/386,482 is a continuing application of Ser. No. 11/275,904, filed Feb. 2, 2006, which has issued as U.S. Pat. No. 7,520,913. U.S. Ser. No. 11/275,904 claimed priority to U.S. Ser. No. 60/650,019, filed Feb. 4, 2005 and U.S. Ser. No. 60/733,978, filed Nov. 3, 2005. A claim of priority is made to each of U.S. Ser. No. 13/412,076; U.S. Ser. No. 12/386,182; U.S. Ser. No. 11/275,904; U.S. Ser. No. 60/650,019; and, U.S. Ser. No. 60/733,978. The complete disclosures of applications U.S. Ser. No. 13/412,076; U.S. Ser. No. 12/386,482; U.S. Ser. No. 11/275,904; U.S. Ser. No. 60/650,019 and U.S. Ser. No. 60/733,978 are incorporated by reference herein. 
     
    
     FIELD 
       [0002]    The present invention relates to a fluid filter for removing contaminants from a gaseous stream, such as an air stream. 
       BACKGROUND 
       [0003]    Filter elements are used in many industries to remove airborne contaminants to protect people, the environment, and often, a critical manufacturing process or the products that are manufactured by the process. 
         [0004]    There is always a need to design different filter elements. 
       SUMMARY OF THE INVENTION 
       [0005]    Non-cylindrical filter elements are provided. Preferably, the filter elements have at least two flat or planar filtration panels. Fluid, such as air, to be filtered enters the filter element through the panels, preferably through each of the panels. An outlet aperture is provided, which has generally the same shape as the cross-sectional shape of the filter. A filter element having three filter elements will be generally triangular in shape and have a generally triangular outlet aperture. 
         [0006]    The design of the present filter element can be such that both axial and radial seals are formed between the outlet aperture and any outlet duct or piping. The filter element can include an integrally molded outlet flange or collar for connecting to an outlet duct. 
         [0007]    Various problems are solved by the design of the present disclosure. The filter element of the present disclosure, by having a non-circular outlet aperture, increases the outlet area to thus decrease outlet velocity and decrease pressure drop. The non-circular cross-section limits the possible orientations for adjoining ductwork, which is desired for some installations; a circular outlet has infinite orientations, which may be a non-preferred configuration for some installations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Referring now to the drawings, wherein like reference numerals and letters indicate corresponding structure throughout the several views: 
           [0009]      FIG. 1  is a perspective view of a filter element according to the present invention; 
           [0010]      FIG. 2  a perspective view of the filter element of  FIG. 1  operably connected to an outlet duct; 
           [0011]      FIG. 3A  is an end view of the filter element of  FIG. 1 ; 
           [0012]      FIG. 3B  is similar to  FIG. 3A ; 
           [0013]      FIG. 4A  is a cross-sectional view of the filter element taken along line  4 - 4  of  FIG. 3A , the filter element including the outlet duct thereon; 
           [0014]      FIG. 4B  is an enlarged section of a portion of  FIG. 4A  detailing the outlet seal; 
           [0015]      FIG. 5  is a perspective view of a second embodiment of a filter element according to the present invention; 
           [0016]      FIG. 6A  is an end view of the filter element of  FIG. 5 ; 
           [0017]      FIG. 6B  is similar to  FIG. 6A ; and 
           [0018]      FIG. 6C  is a cross-sectional view of a portion of the filter element of  FIG. 6A  taken along line  6 - 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Referring now to the Figures, a filter element according to the present invention is shown at  10  in  FIGS. 1 through 4B . Filter element  10  is a fluid filter; that is, filter element  10  filters out or removes contaminants from a fluid stream. In many embodiments, filter element  10  is a gas filter, configured for removal of contaminants from a gas stream. In most embodiments, the gas being filtered is air. Filter element  10  is particularly suitable for use in an aircraft or other lightweight vehicle, for filtering cabin air. In a passenger aircraft, filter element  10  would generally be located in a cargo hold, below the passenger cabin. 
         [0020]    In use, filter element  10 , in many embodiments, is removably positioned in a housing, duct, or other structure. The housing, duct or other structure may or may not complete enclose or envelope filter element  10 . 
         [0021]    Filter element  10  has a first end  12  and an opposite second end  14 . Filter element includes filtration panels  16  and support structure  18 , which will be described below. Together, panels  16  and support structure  18 , between first end  12  and second end  14 , define a filter interior  15 . Panels  16  provide fluid access into and out from interior  15 . Second end  14  includes an aperture  20 , which provides fluid access to and from interior  15 . In  FIGS. 2 ,  4 A and  4 B, a duct  44  is attached to aperture  20 . In the preferred configuration, panels  16  provide fluid access into interior  15 , and are thus the inlet into interior  15  of filter  10 . Thus, fluid to be filtered passes through panels  16  and panels  16  provide filtration. In line with panels  16  being the inlet into filter  10 , aperture  20  provides access out from interior  15 , and thus is the outlet from interior  15  of filter  10 . Panels  16  are radially positioned in relation to interior  15 , and aperture  20  is axially positioned in relation to interior  15 . With such a configuration, the fluid being filtered changes direction, e.g., turns, when moving from panels  16  (e.g., the inlet) to aperture  20  (e.g., the outlet). Generally, no air or other fluid passes out from interior  15  through panels  16 . 
         [0022]    Filter element  10  is generally a non-cylindrical element. In the particular embodiment illustrated, filter element  10  is a three-sided filter element  11 , composed of three panels  16 , which are generally flat or planar. By the terms “generally flat” or “generally planar”, what is intended it that the panel may not be completely flat or planar (i.e., having a surface angle of 0 degrees), but may include a slight dip, indentation variation, bend, or the like on its surface or structure; overall, the overall surface angle of a “generally planar” or “generally flat” panel, from end-to-end, is no more than 10 degrees, preferably no more than 5 degrees. In some embodiments, filter element  10  has no rounded or curved surfaces, e.g., panels  16 , that provide filtration. 
         [0023]    Filter element  10  includes at least two filtration portions or panels  16 ; preferably filter element  10  includes at least three filtration panels  16 . For three-sided filter element  11 , panels  16  are indicated as first panel  16   a,  second panel  16   b,  and third panel  16   b.  It is understood that filter element  10  could have any number of panels  16 , however, as the number of panels  16  increases the cost of designing and assembling such a filter  10  generally increases, thus, less panels  16  are preferred. Preferred numbers of panels  16  include three, four, six, and eight. 
         [0024]    The at least two panels  16  are positioned angled to other or they may be opposite each other. The at least two panels  16  may be evenly spaced. For example, a filter element having two panels  16  may have the panels  16  opposite to and parallel to each other. As another example, filter element  10  has three panels  16   a,    16   b,    16   c  spaced apart approximately 120 degrees. Alternately, a filter element having two panels  16  may have panels  16  angled with respect to each other, for example, at an angle of 90 degrees. It is understood that other degrees, other than 0 degrees (i.e., having the panels  16  planar to or co-planar with each other), are suitable. 
         [0025]    Preferably, each of panels  16   a,    16   b,    16   c  is the same size, shape and filtration material, although it is not necessary that all panels have the same size, shape and/or filtration material. Panels  16  are planar or flat; that is, they are not rounded or curved. The planar or flat characteristic is due to the rigid material used for panels  16 . In future embodiments, it may be possible to provide non-planar or curved panels, however, the present application is directed to using planar, non-curved filtration panels  16 . 
         [0026]    Panels  16  are held together by a support structure  18 , which can be any combination of suitable frames, pieces, and materials to provide support to panels  16  and define interior  15  and aperture  20 . Examples of suitable materials for any portion of support structure  18  include metals (e.g., aluminum, titanium), polymeric or plastic materials (e.g., polyethylene, polyethylene terephthalate, polypropylene, polycarbonate, urethane or polyurethane), composite materials, or any combinations thereof. 
         [0027]    In one embodiment, support structure  18  includes aluminum metal bent as a frame to support panels  16  and a hard polymer material molded to engulf the metal frame and seal interior  15  from the exterior of element  10 . In another embodiment, support structure  18  includes hard plastic molded as a frame to support panels  16  and a soft polymer material molded to engulf the hard plastic frame and seal interior  15  from the exterior of element  10 . Support structure  18  may include details and features to attach filter  10  to mounting brackets or other supporting structures. 
         [0028]    Panels  16  of filter element  10  (or, for the specific embodiment illustrated, panels  16   a,    16   b,    16   c  of filter element  11 ) filter particulate and chemical contaminants from the fluid passing therethrough. Panels  16  may include a single feature or layer that accomplishes both chemical and particulate removal from the fluid passing therethrough. However, as in a preferred embodiment, panels  16  include multiple features or layers. Referring to  FIG. 4A , panel  16   c  is illustrated having four layers, first media layer  22 , second media layer  24 , third medial layer  26  and fourth media layer  28 . 
         [0029]    A first example of a suitable layer, for any of media layers  22 ,  24 ,  26 ,  28  is a low pressure drop, rigid article having a plurality of passages therethrough, the passages having surfaces with adsorptive material. Fluid passes through the passages following the direction of the passage, which is generally in a straight line. Contaminants present in the fluid are adsorbed, absorbed, trapped, retained, reacted, or otherwise removed from the fluid by the adsorptive material. The rigid article can be configured for removal of specific contaminants. For example, the article can be designed for the removal of acidic materials, of basic materials, organic materials, or any combination thereof. 
         [0030]    Examples of such rigid articles are taught in U.S. Pat. No. 6,645,271 (Sequin et al.), the entire disclosure of which is incorporated herein by reference. Pending U.S. patent application having Ser. No. 10/947,732 (Ding et al.), filed Sep. 23, 2004 entitled “Adsorptive Filter Element and Methods” provides rigid elements specifically designed for the removal of carbonyl-containing compounds; this application is incorporated herein by reference. It is understood that the rigid elements, or any of the filtration elements described herein, can be modified from their original design to obtain the desired properties for this application. For example, at anytime during the manufacturing process of rigid articles, the substrate of the articles may be treated to obtain the desired final characteristics for the articles. For example, an aluminum substrate may be etched or otherwise treated to increase the adhesion of a binder to the surface, or for other reasons. 
         [0031]    Another example of a suitable layer for any of media layers  22 ,  24 ,  26 ,  28  is a low pressure drop fibrous article having a plurality of passages therethrough, the fibrous material having been impregnated with various materials to adsorb, absorb, or react with contaminants. Pending U.S. patent application having Ser. No. 10/928,776 (Dallas et al.), filed Aug. 27, 2004 entitled “Acidic Impregnated Filter Element, and Methods” provides impregnated porous elements specifically designed for the removal of basic or alkaline compounds; this application is incorporated herein by reference. Pending U.S. patent application having Ser. No. 10/927,708 (Dallas et al.), filed Aug. 27, 2004 entitled “Alkaline Impregnated Filter Element, and Methods” provides impregnated porous elements specifically designed for the removal of acidic compounds; this application is incorporated herein by reference. Pending U.S. patent application having Ser. No. 11/016,013 (Ding et al.), filed Dec. 17, 2004 entitled “Impregnated Filter Element, and Methods” provides impregnated porous elements specifically designed for the removal of carbonyl-containing compounds; this application is incorporated herein by reference. Additional details regarding removal of alkaline materials, acidic materials, carbonyl-containing compounds, and organics, are provided in pending PCT application having serial number US05/30577, filed Aug. 25, 2005. 
         [0032]    A third example for a suitable layer for any of media layers  22 ,  24 ,  26 ,  28  is a fibrous or particulate filtration layer. Suitable examples of a particulate layer include mats of randomly placed non-woven fibers, thin layers of conventional filtration media, and pleated conventional filtration media. A preferred filtration media to use is HEPA media. 
         [0033]    HEPA filters are known in the art of filters as “high-efficiency particulate air” filters. HEPA media is the media of the filter that provides the filtration efficiency. HEPA media has a minimum efficiency of 99.97% removal when tested with essentially monodispersed 0.3 micron particles. The media may be any suitable HEPA media and may be made from cellulose, polymeric materials (e.g., viscose, polypropylene, polycarbonate, etc.), glass or fiberglass, or natural materials (e.g., cotton). Other HEPA media materials are known. Microfibrous glass is a preferred material for HEPA media. A suitable HEPA media for aircraft applications is that commercially available as H&amp;V “HB-7633”. 
         [0034]    Any of the fibrous or media materials may be electrostatically treated and/or include one or more layers of material. One or more layers of fine fiber, such as taught by U.S. Pat. No. 6,673,136 (Gillingham et al.), may be included. 
         [0035]    Any or all of these various media layers may be provided in any order to provide panel  16 . 
         [0036]    Referring again to  FIG. 4A , panel  16  is illustrated as having first media layer  22 , second media layer  24 , third media layer  26  and fourth media layer  28 . In a preferred construction, first media layer  22  is a pleated HEPA filter element configured for particulate removal, second media layer  24  is a rigid media having impregnated absorbent materials (such as taught by U.S. Pat. No. 6,645,271), third media layer  26  is a rigid media having impregnated absorbent material (such as taught by U.S. Pat. No. 6,645,271), and fourth media layer  28  is a rigid media configured for carbonyl-containing compound removal, particularly for aldehyde removal (such as taught by U.S. patent application Ser. No. 10/947,732). Thus, in use, fluid to be filtered would first pass through the HEPA filter, then through two rigid layers to remove acids and bases, and then through a layer to remove aldehydes. It is understood that this is an exemplary configuration for the media layers, and that other arrangements are suitable. For example, none, one, two, or any number of the media layers may be rigid and/or impregnated, or the various layers may be impregnated with different materials and/or arranged to provide a different path through the layers. 
         [0037]    The filtered fluid, such as air, arrives in interior  15  of filter element  10 . From interior  15 , the fluid exits filter element  10  via aperture  20 . 
         [0038]    Aperture  20  is present at second end  14  of element  10 . Aperture  20  includes an outlet aperture  30  that provides access into and out from interior  15 . In the particular embodiment, outlet aperture  30  is a three-sided outlet aperture  31 , as will be further described below. Surrounding aperture  30  is an outlet collar or flange  32 . Collar  32  preferably has a circular outer perimeter, for reasons which will be described later. 
         [0039]    Outlet aperture  30  preferably has the same number of sides as there are number of panels  16 . For three-sided filter element  11 , the aperture is a three-sided outlet aperture  31 . Aperture  31 , and any non-round aperture  30 , need not be a true polygon, but can include rounded or curved sides and/or corners. See for example,  FIG. 3A . Aperture  31  has a general triangular shaped, but with rounded angles or corners and curved sides; aperture  31  could be referred to as having a tri-oval or a tri-lobal shape. 
         [0040]    The shape of outlet aperture  30  is selected to correspond to the overall shape of filter element  10 , which is dependent on the number of panels  16 . Outlet aperture  30  preferably follows the same general shape as interior  15 , formed by panels  16  and support structure  18 . Having outlet aperture  30  generally correspond to the shape of interior  15  allows a larger outlet aperture area than if a circular outlet were used. For example, for aperture  31 , the three corners extend farther out than would a circular outlet, thus obtaining more outlet area. Increased outlet area is desired as it decreases the velocity of the exiting fluid, thus decreasing pressure losses. 
         [0041]    Collar  32  is configured to receive duct  44  (see  FIGS. 2 and 4A ) and provide a leak-free seal therebetween. The particular configuration of collar  32  provides both axial and radial sealing to duct  44 . As best seen in  FIGS. 3A and 4B , collar  32  includes an inner perimeter surface  34 , a stop or longitudinal surface  36 , a chamfered edge  38  on the inner surface  34 , and outer perimeter surface  40  opposite inner surface  34 , and a retaining lip  42  at outer surface  40 . Inner surface  34 , stop  36  and chambered edge  38  have the same general shape as aperture  30 , which in the illustrated embodiment, is aperture  31 . Outer perimeter surface  40  and retaining lip  42  have a generally circular shape. 
         [0042]    Collar  32  can be formed, typically molded, together with support structure  18 ; collar  32  may be integral with support structure  18 . Such a configuration eliminates the need for a separate flange to be attached to filter element  10 . 
         [0043]    Referring to  FIGS. 2 and 4A , duct  44  is configured to fit within collar  32  and specifically, within inner perimeter surface  34 . Duct  44  is specifically configured to fit with the tri-oval or tri-lobal shape of aperture  31 . By having duct  44  formed to the same shape as aperture  31 , only three proper orientations of duct  44  are available, which in some configurations is more preferable than an infinite number of orientations, which would be the case if the duct was circular and formed to a circular outlet aperture. Duct  44  includes a transition region  46 , which changes from tri-oval or tri-lobal to circular, thus allowing filter element  11  to be connected to circular ductwork. 
         [0044]    To connect duct  44  to filter element  10  via aperture  20 , as illustrated in  FIGS. 4A and 4B , duct  44  is slid into collar  30 , facilitated by chamfered surface  38 . Duct  44  is pushed in to seal against both inner surface  34  and stop  36 . A radial seal is formed between duct  44  and inner surface  34  and an axial seal is formed between duct  44  and stop  36 . A band clamp  50  (seen in  FIG. 4B ) is used to tighten against collar  30  and duct  44 . Band clamp  50  is positioned on collar  32  against outer surface  40 , between retaining lip  42  of collar  32  and bead  48  on duct  44 . Positioning between lip  42  and bead  48  improves the stability of clamp  50  and reduces the chance of it pulling off. 
         [0045]    As stated above, collar  32  has a circular outer perimeter. When band clamp  50  is positioned on collar  32  behind retaining lip  42 , band clamp  50  contacts collar  32  continuously around the perimeter and, thus, the pressure exerted by band clamp  50  is a uniformly distributed load around collar  32  and duct  44 . 
         [0046]    Referring to  FIGS. 5 and 6A ,  6 B,  6 C, a second embodiment of a filter element  10  according to the present invention is illustrated. The particular embodiment of filter element  10  of these figures is filter element  100 . It is to be understood that any of the features from filter element  10  could be used for filter element  100 , in any combination, and vice versa. Filter element  100  has a first end  112  and an opposite second end  114 . Filter element includes filtration panels  116  and support structure  118 . Together, panels  116  and support structure  118 , between first end  112  and second end  114 , define a filter interior  115 . Panels  116  provide fluid access into and out from interior  115 , thus providing an inlet into interior  115 . Second end  114  includes an aperture  120 , which provides fluid access to and from interior  115 , and thus providing and outlet from interior  115 . In this embodiment, first end  112  includes indicia thereon; it is understood that any filter element embodiment may include indicia, or, no indicia may be present. Such indicia can be used to identify the manufacturer of filter element  100 , or to convey, for example, installation instructions. 
         [0047]    Filter element  100  is a non-cylindrical element, particularly, a three-sided filter element composed of three planar or flat panels  116 . Filter element  100  has no rounded or curved surfaces that provide filtration. 
         [0048]    Filter element  100  includes at least two filtration portions or panels  116 ; in this embodiment, filter element  100  has three panels  116 , which are indicated as first panel  116   a,  second panel  116   b,  and third panel  116   b.  Preferably, each of panels  116   a,    116   b,    116   c  is the same size, shape and filtration material, although it is not necessary that all panels have the same size, shape and/or filtration material. Panels  116  are preferably planar or flat; that is, they are not rounded or curved. 
         [0049]    Panels  116  filter particulate and chemical contaminants from the fluid passing therethrough. Panels  116  may include a single feature or layer that accomplishes both chemical and particulate removal from the fluid passing therethrough. Although not specifically illustrated, each panel  116  of this embodiment is composed of multiple layers, similar to filter element  11 . The same materials suitable for panels  16  are suitable for panels  116 . 
         [0050]    Aperture  120  of filter element  100  provides access into and out from interior  115 . In the particular embodiment, aperture  120  is a three-sided outlet aperture, as will be further described below, defined by structure  122 , which is similar to collar  32  of filter element  11  in many aspects. Structure  122  includes an outer surface  124  and an inner perimeter surface  134 . In this embodiment, outer surface  124  and inner surface  134  of structure  122  have generally the same shape, i.e., they are both generally triangular, unlike for filter element  11  wherein outer surface  40  is generally circular and inner surface  34  is generally triangular. 
         [0051]    Aperture  120  and structure  122  have the same number of sides as there are number of panels  116 , i.e., three for this embodiment. Aperture  120  and structure  122  have a generally triangular shape, but with rounded angles or corners. The shape of aperture  120 , and in this embodiment, of structure  122 , is selected to correspond to the overall shape of filter element  100 . 
         [0052]    Referring to  FIG. 6C , an enlarged of a portion of structure  122  is illustrated, in close proximity to a mounting bracket  150 , onto which filter element  100  will be seated. As provided above, structure  122  is similar to collar  32  of filter element  11 , except that, for example, structure  122  does not extend away from structure  118  in the same manner that collar  32  extends away from structure  18 . Structure  122  includes a channel, trough, or other recessed area which retains a seal  136 . 
         [0053]    Structure  122 , in particular seal  136 , has a low or no-clearance; that is, structure  122  extends no more than about 1 cm, preferably no more than about 0.5 cm, past support structure  118  of filter element  100 . In preferred embodiments, structure  122  is flush with or recessed in toward end  114 . 
         [0054]    In use, filter element  100  will be operably sealed against bracket  150  at structure  122 , in particular at seal  136 , to provide a leak-free seal. Bracket  150  includes a protrusion  155  extending toward filter element  100 . Protrusion  155  can be a radiused or sloped bead, and have a height of at least about 0.1 cm (1 mm), or at least about 0.25 cm. 
         [0055]    Prior to use, filter element  100  is slid into placed against bracket  150 . Having structure  122  with a low or no-clearance facilitates sliding filter element  100  into its position, with minimal clearance needed between bracket  150  and filter element  100 . 
         [0056]    When properly seated, filter element  100 , via seal  136 , forms an axial seal with bracket  150 . Depending on the configuration of protrusion  155 , a radial seal may also be formed. Seal  136  is sufficiently deformable, flexible and/or resilient to allow protrusion  155  to embed into seal  136 ; seal  136  is generally a low-durometer material. Examples of suitable material for seal  136  include urethanes, polyethylenes, silicone, rubbers, and other similar materials. Seal  136  may be, for example, a rolled seal, may be formed-in-place, such as by a one-component or multiple-component foam or gel that is poured into place. The engagement of seal  136  with protrusion  155  and bracket  150  should be a continuous seal, with no breaks. 
         [0057]    Filter element  100  may be seated in a generally horizontal position, as illustrated in the figures, with the outlet being generally horizontal out from interior  115 , or, filter element  100  may be seated in a generally vertical position, with the outlet being generally vertical above or below interior  115 . 
         [0058]    Filter element  100  includes three mounting elements  140  and three mounting elements  145 . In this embodiment, mounting elements  140  function both as handles, to facilitate moving and lifting of filter element  100 , and as mounting mechanisms, to mount and lock filter element in a desired position, for example, for use. Mounting elements  145  also mount and lock filter element  100  in the desired position. It is not necessary that all three mounting elements  140  and three mounting elements  145  are used; this will depend on the housing, duct, or other structure to which filter element  100  is mounted. For example, only two mounting elements  140  together with all three mounting elements  145  may be used. Other configurations of mounting elements can also be used. 
         [0059]    It is understood that mounting elements  140  may be used for mounting of element  100  and a separate structure can be used to facilitate moving and lifting of the filter element, or, mounting elements  140  may be used solely as handles. 
         [0060]    Referring to the reference numerals in  FIGS. 3B ,  4 A,  6 A and  6 B, the following properties and dimensions are suitable examples for filter elements  10 ,  100 . 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Filter element 10 
                 filter element 100 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Panel size 
                 17.5 × 25 inches 
                   
               
               
                 # of panels 16 
                 3 
                 3 
               
               
                 panel thickness 
                 4.6 inches 
               
               
                 # layers in 
                 4 
               
               
                 panel 16 
               
               
                 layer 1 
                 pleated HEPA filter (having a 
                 pleated HEPA filter 
               
               
                   
                 thickness of about 1.5 inches) with 
                 (having a thickness 
               
               
                   
                 hot melt adhesive spacer beads 
                 of about 1.5 
               
               
                   
                 between the pleats 
                 inches) 
               
               
                 layer 2 
                 rigid absorption filtration media 
               
               
                   
                 layer (having a thickness of about 
               
               
                   
                 1.04 inches) 
               
               
                 layer 3 
                 rigid absorption filtration media 
               
               
                   
                 layer (having a thickness of about 
               
               
                   
                 1.04 inches) 
               
               
                 layer 4 
                 rigid absorption filtration media 
               
               
                   
                 layer (having a thickness of about 
               
               
                   
                 1.04 inches) 
               
               
                 A 
                 25.31 inches 
                 25.96 inch 
               
               
                 B 
                 22.75 inches 
                 22.53 inches 
               
               
                 C 
                 17.00 inches 
                 17.14 inches 
               
               
                 D 
                 3.80 inch radius 
               
               
                 E 
                 2.75 inch radius 
               
               
                 F 
                 16.00 inch radius 
               
               
                 G 
                 15.25 inch radius 
               
               
                 H 
                 15.00 inch diameter 
               
               
                 I 
                 25.00 inches 
                 25.00 inches 
               
               
                 J 
                   
                 11.56 inches 
               
               
                   
               
             
          
         
       
     
         [0061]    Additionally, for an embodiment of filter element  10 , the widest dimension, in one direction, is about 26.3 inches, and, in another direction, is about 22.8 inches. Additionally, in this embodiment, collar  32  extend pasts panels  16  by about 2 inches. The approximate diameter of aperture  31  is 15.25 inches, with the corners of aperture  31  being radiused to 2.75 inches. Such an outlet aperture has an area of about 94.7 square inches; a comparable circular outlet would have an area of about 38.5 square inches. Circumscribing aperture  31  is an outer surface  40 , which follows the shape of aperture  31 . Outer surface  40  has an approximate diameter of 10 inches with the corners being radiused to 3.5 inches. 
         [0062]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.