Abstract:
A filter media including a gathered sheet of porous filter material, is provided, together with an apparatus and method for fabricating such a gathered sheet of porous filter material. An improved filter apparatus incorporating such gathered porous filter material is also provided. By gathering the porous filter material, rather than forming convolutions through corrugating or pleating, as was done in the past, a desirable convoluted shape is achieved with little or no compression of the filter media.

Description:
FIELD OF THE INVENTION 
     This invention relates to fluid filters for removing particulate matter from a flow of fluid in liquid or gaseous form, including filters of the type used for filtering inlet air supplied to machinery such as engines and compressors. 
     BACKGROUND OF THE INVENTION 
     Filters of the type used for filtering particulate matter from engine intake air sometimes include one or more layers of a porous filter material that is formed into a convoluted pattern, often referred to in the industry as fluted filter media. One type of porous filter material commonly used for such filters is a cardboard or paper-type material having a thickness in the range of 0.006 to 0.008 inches. This material is somewhat stiff, and not easily bent or formed, without special provisions being made to prevent tearing or breaking the material. Although it is desirable to use a media of this type having a greater thickness, in the range of 0.012 to 0.018 inches for example, such thicker media has not been used in the past due to difficulties inherent in forming such stiff materials into a compact convoluted shape. 
     In the past, such fluted filter media was typically formed by processes which required, or resulted in the porous filter material being at least locally compressed during the process of forming the convolutions. Compression of the porous filter media is undesirable because it reduces the filtering efficiency and particulate holding capacity of the fluted filter media below what it could be if the porous filter media could be formed into a convoluted shape without compression of the media. The degree and unavoidability of such compression in the past would have essentially negated any advantage gained by using a thicker media, even if the problem of breakage or tearing could have been resolved. 
     In one widely utilized prior approach to forming a convoluted media, the porous filter material is fed through a corrugating machine, between a pair of rollers having intermeshing wavy surfaces which pinch and crimp the porous media in a manner that compresses and permanently deforms the filter media into a convoluted shape that is generally self supporting, and able to maintain the convoluted shape following corrugation, regardless of whether or not the corrugations are constrained. United States patent application number US 2003/0121845 A1, to Wagner, et al, discloses such an approach. 
     Corrugation typically compresses the porous filter material by 25 to 40 percent from its thickness prior to being corrugated, resulting in a significant reduction in efficiency and effectiveness, particularly where the media prior to corrugating has a thickness only in the range of 0.006 to 0.008 inches. It is also typically necessary, for paper filter media of the type often used in air filters, to expose the porous filter media to a water spray, steam, and heat, during the corrugation process in order to achieve a corrugated product that is self supporting. These additional processing requirements add undesirable cost and complexity to the manufacture of corrugated filter media, and exacerbate compression of the filter media during corrugation. 
     In another widely utilized prior approach to forming a fluted filter media, the porous material is pleated, rather than corrugated, by first feeding a sheet of porous media between a pair of cylinders or toothed belts having ridges which locally compress the porous material at periodic intervals, to thereby crease or score the material. The scored material is then fed through a folding mechanism which causes the scored media to fold at the scoring into a pleated shape. Such pleated shapes are not generally as self supporting as corrugated media, requiring that the pleats be constrained and held in an equally spaced relationship by a spacing mechanism, until they can be joined to a face sheet or secured to a support structure. U.S. Pat. Nos. 4,798,575 and 4,976,677 to Siversson, U.S. Pat. No. 5,389,175 to Wenz, and U.S. Pat. No. 6,022,305 to Choi, et al, disclose such pleated methods and pleated filter media. Where it is desired to set the pleats into a self supporting form, liquids sprayed onto the porous media, and sequentially applied heating and cooling are sometimes utilized, in the same manner described above in relation to corrugated filter media. 
     As was the case with corrugated media, in pleated media the scoring undesirably reduces the thickness of the porous media, thereby reducing its filtering effectiveness and efficiency. Also, the mechanisms required for sequentially scoring, forming, spacing, spraying, heating and cooling the pleated media undesirably increase the complexity and cost of manufacturing the pleated media. 
     It is desirable, therefore, to provide an improved filter media, together with an apparatus and method for manufacturing such an improved media. It is also desirable to provide an improved filter apparatus incorporating such an improved filter media. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides a filter media including a gathered sheet of porous filter material, together with an apparatus and method for fabricating such a gathered sheet of porous filter material, and an improved filter apparatus incorporating such gathered porous filter material. By gathering the porous filter material, rather than forming convolutions through corrugating of pleating, as was done in the past, a desirable convoluted shape is achieved with little or no compression of the filter media, thereby resulting in improved filtering efficiency and effectiveness, and reduced complexity and cost of manufacture. It is also generally not necessary to expose the porous media to heat, steam, or liquid sprays or immersion during the process of forming a gathered media, according to the invention. The invention also allows porous materials to be used for forming the media that are considerably thicker than those which could be used in the past. 
     In one form of the invention, a filter media having a gathered sheet of porous material is provided. The thickness of the porous material in the gathered sheet may be the same as the thickness of the porous sheet prior to gathering. The filter media may also include a face sheet attached to the gathered sheet, for retaining the gathered sheet of porous material in a gathered state. 
     A filter apparatus, according to the invention, has one or more layers of a filter media including a gathered sheet of porous filter material. The filter apparatus may comprise a filter cartridge, adapted for attachment to a filter assembly, but not including the filter assembly. Such a filter cartridge may comprise a coil of the gathered media. 
     A filter apparatus, according to the invention, may alternatively take the form of a filter assembly adapted for attachment thereto of a filter cartridge, and a filter cartridge including one or more layers of a filter media comprising a gathered sheet of porous filter material. The filter cartridge, in such a filter apparatus, may comprise a coil of the gathered porous filter material. 
     An apparatus and method, according to the invention, include forming a filter media having a gathered sheet of porous filter material, by feeding a sheet of porous filter material between a first and a second gathering roller of an apparatus wherein the first and the second gathering rollers each include an outer periphery thereof having a plurality of circumferentially spaced protrusions extending radially therefrom. The first and second gathering rollers are mounted for rotation in a spaced and timed relationship to one another such that the protrusions of one gathering roller are disposed between adjacent protrusions of the other gathering roller for forming gathers in the sheet of porous filter material as it is fed between the first and second gathering rollers. The protrusions and outer peripheries of the first and second gathering rollers are configured and spaced from one another such that the sheet of porous material is not compressed between any portion of the outer periphery or protrusions of the first gathering roller and any portion of the outer periphery or protrusions of the second gathering rollers. 
     An apparatus and method, according to the invention, may also constrain the gathers of a gathered portion of the sheet of porous filter material within the spaces between adjacent protrusions of one of the gathering rollers after the gathered portion of the sheet has passed between the gathering rollers, and provide for attachment of a face sheet to the gathered sheet of porous filter material. 
     Other aspects, objectives and advantages of the invention will be apparent from the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a first exemplary embodiment of the invention, in the form of a filter media including a gathered sheet of porous filter material. 
         FIG. 2  is an enlarged cross section of the filter media of the first exemplary embodiment of  FIG. 1 . 
         FIG. 3  is a perspective view of a coil of gathered filter media, according to the invention. 
         FIG. 4  is a perspective view showing a method of constructing the coil of filter material of  FIG. 3 . 
         FIG. 5  is a cross section of a second exemplary embodiment of the invention, in the form of a filter cartridge, adapted for attachment to a filter assembly, but not including the filter assembly. 
         FIG. 6  is a cross sectional view of a third exemplary embodiment of the invention in the form of a filter apparatus, according to the invention, including a filter assembly and a filter cartridge attached to the filter assembly. 
         FIG. 7  is a schematic side view of a fourth embodiment of the invention, in the form of an apparatus for forming a filter media including a gathered sheet of porous filter material. 
       FIGS.  8  and  10 - 12  are enlarged side views of portions of the apparatus of  FIG. 7 , taken in areas as indicated in  FIGS. 7 and 9 . 
         FIG. 9  is a top view of the apparatus of  FIG. 7 . 
     
    
    
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a first exemplary embodiment of the invention in the form of a filter media  10  comprising, a gathered sheet  12  of relatively stiff, paper-like, porous filter material of the type typically used for air filters. Such relatively stiff, paper-like porous filter materials are available in various thicknesses from suppliers including Ahlstrom Engine Filtration, LLC, of Madisonville, Ky. Specifically, it is contemplated that filter materials marketed by Ahlstrom, such as Ahlstrom part numbers 19N-1 or 23N-3, or other filter materials having physical characteristics similar to those tabulated in below, can be used with efficacy, according to the invention in providing an embodiment of the invention for use in a typical air filter of the type used for engine air intakes. 
     Ahlstrom 19N-1 Filter Media 
     100% cellulose fibers 
     Basis weight=70 pounds per 3000 square feet 
     Flat sheet caliper=14.5 mils 
     Grooved sheet caliper=18 mils 
     Frazier (CFM) 11-19, preferably 14 
     SD Gurley Stiffness (mg)=3000 
     Ahlstrom 23N-3 Filter Media 
     100% cellulose fibers 
     Basis weight=55 pounds per 3000 square feet 
     Flat sheet caliper=13 mils 
     Non-grooved sheet 
     Frazier (CFM) 11-19 
     SD Gurley Stiffness (mg)=1300 
     The Ahlstrom 19N-1 product is available with small grooves cut into the media for improving dirt holding capability. Theses grooves run the length of a roll of the filter media and, as will be apparent from the description below, are thus preferably, but not necessarily, oriented perpendicular to the direction of the peaks and valleys of the gathers in a gathered sheet of media, according to the invention. 
     As used herein, the term “gathered” is intended to mean that the sheet of porous material is guided into a final undulating or convoluted form, primarily by pulling the sheet of porous material over a series of protrusions extending from rotating gathering rollers, in such a manner that the porous filter material preferably experiences little or no compression, and in any event, substantially less compression than was typically required for forming prior corrugated or pleated filter medias. Because the undulating form of the gathered sheet of porous filter media is achieved by pulling the sheet of material over a series of protrusions, in a manner described in more detail below, the sheet of porous material has a thickness t prior to gathering, and a thickness t after gathering that is both substantially uniform throughout and substantially equal to the thickness t of the porous material prior to gathering. 
     Those having skill in the art will recognize that various embodiments of the invention, including all exemplary embodiments thereof specifically disclosed herein, may include a filter media including a gathered sheet of relatively stiff, paper-like, porous filter material of the type described in relation to the first embodiment. Those having skill in the art will also recognize that because the filter material is gathered, according to the present invention, rather than being pleated or corrugated as was the case for prior filter medias, the present invention allows relatively stiff, paper-like, porous filter materials of the type typically used for air filters to be utilized for forming undulating or convoluted filter medias in a manner that is more efficient and effective than prior forming methods. 
     As shown in an enlarged cross section in  FIG. 2 , the gathered sheet  12  forms a plurality of contiguous adjacent gathers  14 , each having a generally V-shaped cross section with substantially straight side walls  16  joined by radiused bights  18  to form alternating peaks  20  and valleys  22 . The peaks  20  and valleys  22  formed by the gathers  14  of the exemplary embodiment of the filter media  10  are substantially equal in size and equally spaced but, in other embodiments of the invention, this need not necessarily be the case. 
     As shown in  FIGS. 1 and 2 , the filter media  10  of the exemplary embodiment includes a face sheet  24  attached to the gathered sheet  12 , for retaining the gathered sheet  12  of porous filter material in a gathered state. The face sheet  24  may be attached to the gathered sheet  12  in any appropriate manner, such as by beads of adhesive  26 , applied at the juncture of the gathered sheet  12  and the face sheet  24 , as shown in  FIG. 1 . In the exemplary embodiment of the filter media  10 , the face sheet  24  is also made of a porous filter material. 
     As shown in  FIG. 1 , the space between the peaks  20  of the gathers  14  and the face sheet  24 , along one edge  28  of the filter media  10  have a sealant  30  disposed in them, to thereby form a sealed portion  32  of the gathers  14  that blocks a flow of fluid through the sealed portion  32 . In the exemplary embodiment of the filter media  10 , this sealed portion extends all along the one edge  28  of the filter media  10 , blocking flow through all of the peaks  20  along the edge  28 . 
       FIGS. 3-5  show a second exemplary embodiment of the invention in the form of a filter cartridge  34 , including a coil  35  ( FIG. 3 ) of a gathered filter media, according to the invention. In the second exemplary embodiment, the filter media shown in  FIG. 3  is the gathered filter media  10 , as described above in regard to  FIGS. 1 and 2 . In other embodiments of a filter cartridge, according to the invention, however, it will be understood that other forms of gathered filter media could be used. It will also be understood that the gathered filter media, in other embodiments of filter cartridges according to the invention, need not be coiled, but could be formed in other ways, such as by stacking or otherwise laminating layers of gathered filter media. 
     As shown in  FIGS. 3-5 , the exemplary embodiment of a filter cartridge  34  is formed by winding the gathered filter media  10  around a central mandrel  36 . As shown in  FIG. 4 , as the gathered filter media  10  is wound onto the mandrel  36 , a second bead of sealant  38  is applied in the valleys  22  along the second edge  40  of the gathered filter media  10 . As illustrated in  FIG. 1 , as the gathered filter material  10  is coiled, the face sheet  24 ′ of each subsequent layer  15  of the media  10  is sequentially wrapped over the tops of the peaks  20  of the previously coiled layer  13  of gathered filter media  10 . As noted above, the first bead of sealant  30  closes the flow areas bounded by the face sheet  24  and the peaks  20  of the gathered filter media  10 , at one edge  28  of the gathered filter media  10 . The second bead of sealant  38  closes the flow area bounded by the face sheet  24  and the valleys  22  of the gathered filter media  10  at the other edge  40  of the gathered filter media  10 . 
     By virtue of this construction, one end  42  of the filter cartridge  34  is formed by the first edge  28  of the coiled gathered filter media  10 , and the other end  44  of the filter cartridge  34  is formed by the second edge  40  of the coiled gathered filter media  10 . As a result, at the one end  42  of the filter cartridge  10 , the air passages formed by the face sheet  24  and the valleys  22  are open for receiving air flow, as shown by inflow arrows  46  in  FIG. 1 , and the air passages formed by the peaks  20  are blocked by the first bead of sealant  30 . At the other end  44  of the filter cartridge  10 , however, the air passages formed by the face sheet  24 ′ of the subsequent layer  15  of media  10  and the valleys  22  of the preceding layer  13  of media  10  are blocked by the second bead of sealant  38 , and the air passages formed in the preceding layer  13  by the peaks  20  of the and the face sheet  24  are open to allow flow, as shown by outflow arrows  48  in  FIG. 1 . As shown by crossover arrows  50 , in  FIG. 1 , the airflow must pass through the gathers  14  of the gathered filter media  10  in order to flow through the filter cartridge  34 . 
     As shown in  FIG. 5 , the exemplary embodiment of the filter cartridge  34  also includes a bolting ring  52  fastened to the one end  42  of the filter cartridge  34 . A seal support ring  54  is fastened to the other end  44  of the filter cartridge  34 , and supports a resilient seal  56 . The bolting ring  52 , seal support ring  54  and resilient seal  56  are provided to adapt the filter cartridge  34  for attachment to a filter assembly. 
     It will be understood, however, by those having skill in the art, that the first exemplary embodiment of a filter apparatus, according to the invention, in the form of the filter cartridge  34 , does not include the filter assembly, but is intentionally limited to a filter apparatus including only a filter cartridge in accordance with the invention, as defined in the appended claims. 
     It will be further understood that, in other embodiments of a filter apparatus comprising only a filter cartridge, according to the invention, the construction of such embodiments of filter cartridges may differ considerably from the exemplary embodiment of the filter cartridge  34  disclosed herein. For example, the cartridge  34  may have other shapes, such as oblong, square, or rectangular. In some embodiments, a filter cartridge according to the invention may include only a coiled or otherwise laminated structure formed from a gathered porous filter media according to the invention, without attachment and sealing features, such as the bolting ring  52 , seal support ring  54  and resilient seal  56  of the exemplary embodiment of the filter cartridge  34  disclosed herein. Where a coiled construction is used, the central mandrel  36  may be eliminated, and the winding may be carried out around a central crushed portion of the gathered filter media  10 , in a manner similar to that used in the past for filters having corrugated filter medias. Many arrangements for adapting the filter cartridge for attachment to the filter assembly, other than those disclosed with regard to the exemplary embodiment of the filter cartridge  34 , may be used in other embodiments 
       FIG. 6  shows a third exemplary embodiment of the invention, in the form of a filter apparatus  58 , including a filter assembly  59  in the form of a filter housing  60  and a boot  62 , adapted for attachment thereto of a filter cartridge  64  having one or more layers of a filter media  66  comprising a gathered sheet of porous filter material. The filter cartridge  64  includes a coil of gathered porous filter material, in the same manner as the filter cartridge  54  of the second exemplary embodiment of the invention described above. In contrast to the second exemplary embodiment of the invention, in which the filter apparatus included only the filter cartridge  10 , and not the filter assembly to which the cartridge is adapted to be attached, the third exemplary embodiment of the invention includes both the filter cartridge  64  and the filter assembly  59  formed by the housing  60  and the boot  62 . It should be further noted that the filter apparatus  58  of the third exemplary embodiment also includes a safety filter  68 , mounted in the filter housing  60  at a point in the airflow path downstream from the filter cartridge  64 . 
       FIGS. 7-12  show a fourth exemplary embodiment of the invention in the form of a gathering apparatus  70  for forming a filter media  72  including a gathered sheet  74  of porous filter material  76 . As shown in  FIG. 7 , the gathering apparatus  70  includes a first gathering roller  78  and a second gathering roller  80 , each including an outer periphery  82 ,  84  thereof having a plurality of circumferentially spaced protrusions  86 ,  88  extending radially outward from the outer peripheries  82 ,  84  of the gathering rollers  78 ,  80 . 
     As shown in  FIGS. 7 and 8 , the first and second gathering rollers  78 ,  80  are mounted in a frame  81  for rotation in a spaced and timed relationship to one another such that the protrusions  88  of the second gathering roller  80  are disposed between adjacent protrusions  86  of the first gathering roller  78 , and vice versa, for forming gathers  90  in the sheet of porous filter material  76  as it is fed between the first and second gathering rollers  78 ,  80 . The protrusions  86 ,  88  and outer peripheries  82 ,  84  of the first and second gathering rollers  78 ,  80  are configured and spaced from one another such that the sheet of porous filter material  76  is not compressed between any portion of the outer periphery  82  or protrusions  86  of the first gathering roller  78  and any portion of the outer periphery  84  or protrusions  88  of the second gathering roller  80 . Specifically, the gathering rollers  78 ,  80  are configured and spaced from one another such that the thickness “t” of the porous filter material  76  is not compressed between the protrusions  86 ,  88  or outer periphery  82 ,  84  of either one of the gathering rollers  78 ,  80  and the outer periphery  84 ,  82  or the protrusions  88 ,  86  of the other gathering roller  80 ,  78 . 
     In the exemplary embodiments of the invention described herein, it is contemplated that the thickness of the porous filter material  76  would fall within the range of 0.006 to 0.020 inches, with a preferred thickness for many applications being 0.014 inches. In other embodiments, however, a porous media having a thickness that is greater or less than the above stated range of 0.006 to 0.020 inches may also be used, with the actual selection of the thickness t being dependent upon the application and desired performance of the filter media. 
     As shown in  FIGS. 7-12 , the gathering apparatus  70  also includes a pair of guides  92  adapted for maintaining the sheet  76  in a gathered state after the gathers  90  are formed by passage of the sheet  76  between the first and second gathering rollers  78 ,  80 . As shown in  FIG. 10 , for both the first and second gathering rollers  78 ,  80 , adjacent protrusions and a portion of the outer periphery of the gathering roller joining the adjacent protrusions define a space between the adjacent protrusions. For example, as shown in  FIG. 10 , adjacent protrusions  88  from the second gathering roller  80 , and a portion of the outer periphery  84  of the second gathering roller  80  define a space  94  (as indicated by dashed lines) between the adjacent protrusions  88 . The guides  92  constrain gathers  90  of a gathered portion  96  (as indicated in  FIG. 7 ) of the sheet of porous filter material  76  within the spaces  94  between adjacent protrusions  88  of the second gathering roller  80  after the gathered portion  96  of the sheet  76  has passed between the gathering rollers  78 ,  80 . 
     As shown in  FIG. 7 , the first gathering roller  78  is rotatable about an axis  98  of the first gathering roller  78  and the second gathering roller  80  is rotatable about an axis  100  of the second gathering roller  80 , with the respective axes  98 ,  100  of the first and second gathering rollers  78 ,  80  being oriented parallel to one another (i.e. extending perpendicularly into and out of the paper in  FIG. 7 ) and intersected by a common centerline  102  extending generally orthogonally to the axes  98 ,  100  of the first and second gathering rollers  78 ,  80 . 
     The first and second gathering rollers are rotatable in opposite directions about their respective axes, as shown in  FIG. 7  with the protrusions  86 ,  88  of each gathering roller  78 ,  80  extending into the spaces between adjacent protrusions  88 ,  86  of the other gathering roller  80 ,  78  to define a gathering zone  104 , as shown in  FIG. 7 , having an infeed side  106  and an outfeed side  108  with respect to the common centerline  102 . The protrusions  86 ,  88  on both the first and second gathering rollers  78 ,  80  enter into the gathering zone  104  from the infeed side  106 , and exit the gathering zone  104  from the outfeed side  108 , as the first and second gathering rollers  78 ,  80  are rotated in opposite directions, as illustrated in  FIG. 7 , about their respective axes  98 ,  100 . 
     As shown in  FIGS. 7 and 10 , the protrusions  86 ,  88  on the first and second gathering rollers  78 ,  80  each define a distal end thereof, with the distal ends of the protrusions  86 ,  88  of each of the first and second gathering rollers  78 ,  80  respectively defining a maximum radius R 1  of the first and second gathering rollers  78 ,  80  respectively. It should be noted that in the exemplary embodiment of the gathering apparatus  70 , the first and second gathering rollers are identical, and therefore have identical maximum radii R 1 , but in other embodiments of the invention this need not be the case. 
     The guides  92  each define a generally C-shaped guide surface  110  of the guide  92  disposed primarily on the outfeed side  108  of the second gathering roller  80  and having a radius R 2  centered on the axis  100  of the second gathering roller  80 , with the radius R 2  of the guide surfaces  92  (see  FIGS. 7 and 10 ) substantially matching the maximum radius R 1  of the second gathering roller  80  plus the thickness t of the sheet of porous filter material  76 . In the Exemplary embodiment of the gathering apparatus  70 , the radius R 2  of the guide surfaces  92  also includes a clearance distance (not shown) to ensure that the thickness t of the porous filter material  76  is not compressed by the guide surface  110 . 
     As best seen in  FIGS. 9 and 10 , in the exemplary embodiment of the apparatus  70 , for forming a filter media  72  including a gathered sheet  74  of porous filter material  76 , the first gathering roller  78  defines a pair of circumferentially oriented grooves  112  therein for receiving a portion of the guides  92 . As best seen in  FIGS. 7 and 10 , the guides  92  each define a leading edge  114  thereof, extending into the gathering zone  104  from the outfeed side  108 , and past the common centerline  102 . The guides  92  also each include a trailing edge  116  thereof, as best seen in  FIGS. 7 and 11 , disposed on the outfeed side  108  of the common centerline  102 . 
     In the exemplary embodiment of the gathering apparatus  70  for forming a filter media  72  including a gathered sheet  74  of porous filter material  76 , the guide surfaces  110  extend substantially half way around the second gathering roll  80 , for constraining the gathers between the second gathering roll  80  and the guide surfaces  110 . In other embodiments, however, the guide surfaces  110  may be shorter or longer than those of the exemplary embodiment of the apparatus  70 . 
     As best seen in  FIGS. 7 and 11 , the exemplary embodiment of the forming apparatus  70  further includes a second guide surface  117 , formed by a second guide surface roller  118  and a second stationary guide surface  119 , that are positioned adjacent the trailing edges  116  of the guide surfaces  110  of the guides  92 , for receiving the gathered filter media  76  from the second gathering roller  80 . The second guide surface  117  is spaced from the distal ends of the protrusions  88  on the second gathering roller  80  a distance substantially equal to the thickness t of the porous filter material  76  plus the thickness t 2  of a face sheet  120 , that is joined to the gathered sheet  74  of porous filter material  76 , to form part of the filter media  72  and to retain the sheet  74  in a gathered condition. 
     By virtue of the construction recited above, the second gathering roller  80  is adapted for feeding the gathered sheet  72  of porous filter material  76  onto the second guide surface  117  at an outfeed speed, and the gathering apparatus  70  further comprises a face sheet feeder  122  adapted for feeding a face sheet  120  onto the second guide surface  117  at a speed substantially matching the outfeed speed of the gathered sheet  72  of porous filter material  76 . 
     As shown in  FIG. 7 , the exemplary embodiment of the gathering apparatus  70 , for forming a filter media  72  including a gathered sheet  74  of porous filter material  76 , further includes both an adhesive feeder  124 , and a sealant feeder  126 . The adhesive feeder  124  is adapted for feeding an adhesive into a juncture of the face sheet  120  with the gathered sheet  72  of porous filter material  76 , for bonding the face sheet  120  and gathered sheet  72  to one another. The sealant feeder  126  is adapted for feeding a sealant  128  onto the gathered sheet  72  of porous filter material  76 , to form a sealed portion  130  thereof, as shown in  FIG. 12 . 
     It will also be noted that in the exemplary embodiment of the gathering apparatus  70 , as shown in  FIG. 7 , the porous filter material  76  is wrapped around the first gathering roller  78 , and fed into the gathering zone  104  by allowing it to slide across the distal ends of the protrusions  86  on the first gathering roller  78 . It will be recognized that, by virtue of the gathering, the porous material  76  entering the gathering zone  104  slides across the distal ends of the protrusions  86 ,  88  on both the first and second gathering rollers  78 ,  80  at a speed greater than the peripheral tip speed of the distal ends of the protrusions  86 ,  88 . This sliding motion of the porous material  76  entering the gathering zone  104  facilitates gathering of the porous material  76  in a manner that does not cause compression of the porous filter material  76 . Feeding the porous material  76  around the distal ends of the protrusions  86  on the first gathering roller  78  also facilitates maintaining a proper tension on the porous filter material  76 , so that no compression occurs due to excessive pulling on the material  76  as it is gathered. 
     Those having skill in the art will thus recognize that the present invention provides a number of advantages over prior corrugated and/or pleated filter medias, and the apparatuses and methods used to manufacture them. One particular advantage is that, in many embodiments of the invention, the gathered media of the present invention can be formed without having to expose the porous media to heat, steam, liquid spray or immersion, to facilitate formation of convolutions, as was the case in prior corrugated and pleated medias. 
     Those having skill in the art will also recognize that, although invention has been described herein with reference to several exemplary embodiments, many other embodiments of the invention are possible. 
     For example, although all of the exemplary embodiments of the apparatus and methods described herein have focused on gathered medias, it will be recognized that the apparatus and method for forming a media, according to the invention can be adapted for forming other types of convoluted filter media having some degree of compression of the porous media, by simply reducing the clearances between the elements of the gathering rollers to the point that some compression occurs. Although some of the effectiveness and efficiency of the media is lost where compression is allowed, those having skill in the art will recognize that the method and apparatus for forming the convolutions, and for guiding and constraining the formed convolutions in a preferred spacing, according to the invention, is considerably more straightforward than the methods and apparatuses that were previously available. 
     It will be further recognized that, although all of the exemplary embodiments or the apparatus and methods described herein have focused on a gathered media having first and second beads of sealant  32 ,  38  disposed at opposite edges  30 ,  40  of the media, the apparatus and method for forming a media, according to the invention can be adapted for forming other types of convoluted filter media having an intermediate seal, as disclosed in a US patent application bearing the Ser. No. 10/979,453, which is filed concurrently herewith and incorporated herein by reference. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventor for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventor intends for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.