Abstract:
Fluted filter media includes filter material having a plurality of flutes formed therein having alternating ends of adjacent flutes closed to force fluid through filter material. A first embodiment of the filter media includes tapered flutes which have the open ends of the flutes larger in cross-section than the closed flutes, wherein the upstream open flutes converge toward the downstream end and the upstream closed end flutes diverge toward the downstream end. A second embodiment includes filter media which is asymmetric formed with dissimilar upstream and downstream flute cross-sections with larger flute openings to the upstream side of the filter. A third embodiment includes filter media with an upstream edge crushed to improve flow at the upstream edge. A fourth embodiment includes filter media with the upstream sealing material recessed from the upstream edge for reducing effects from blockages at the upstream edge of the filter.

Description:
CROSS REFERENCE RELATED APPLICATION 
     The present application is a continuation of application Ser. No. 12/069,660, now U.S. Pat. No. 8,268,053 filed Feb. 11, 2008. Application Ser. No. 12/069,660 is a divisional of application Ser. No. 10/371,825, filed Feb. 21, 2003, that issued as U.S. Pat. No. 7,329,326. Application Ser. No. 10/371,825 is a divisional of application Ser. No. 09/580,091, now abandoned, filed May 30, 2000, which is a divisional of application Ser. No. 08/639,220, now abandoned, filed Apr. 26, 1996. The disclosures of application Ser. Nos. 12/069,660, 10/371,825, 09/580,091, and 08/639,220 are incorporated herein by reference 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to fluted filter media, and in particular, to fluted filter media having flutes which minimize restriction across the filter. 
     2. Prior Art 
     Pleated filters which utilize filter media to remove contaminants from fluids are commonly known and take on many configurations. 
     A common problem with filters is inadequate filter surface area. Prior attempts to improve filtering surface area for a given filter volume have not been entirely successful. Pleated filters are commonly used which utilize a pleated filter media in an attempt to overcome this shortcoming. Although pleated filter material may increase the filter area, as the pleats are placed closer and closer together, thereby placing more and more filter media in a given volume, the pleats are pressed tighter and tighter together, thereby restricting the flow. This restriction may cause the velocity of flow to increase in order to pass through the filtering media, thereby increasing the pressure differential across the filter which may cause additional problems in the system. 
     Most permeable filter media does not provide structural support so that the filters require housings for supporting the filtering material. This increases manufacturing costs as well as the mass and size of the filter. 
     To improve restriction and provide increased media area, as well as filter efficiency, fluted filter configurations may be utilized. Fluted filters have the capability of increased media area per unit volume, as well as less restriction and substantially straight-through flow. 
     Although fluted filters provide improved flow characteristics and efficiency over prior filter designs, fluted filters have the possibility of greater efficiency and improved flow characteristics. The sealed upstream ends of flutes provide a substantial blockage of the flow, and when combined with the filter material, more than half of the available cross sectional area of the fluid flow is blocked. Filter designs which have greater cross sectional area transverse to the flow provide improved flow and restriction characteristics. 
     It can be seen that new and improved filters are needed which provide self support, improved restriction, improved flow characteristics, and greater efficiency. In particular, fluted filters should have a leading edge which provides less resistance and takes up less of the cross-sectional flow area than standard flute designs. In addition, the cross-sectional area of the filter media and the closed ends of the flutes at the upstream edge should be smaller than the opening area at the upstream edge of the flutes. Such improved filter designs should also be easily manufactured without undue additional steps. The present invention addresses these as well as other problems associated with filter designs. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a fluted filter device, and in particular, to fluted filter media with improved flow characteristics. 
     According to a first embodiment of the present invention, fluted filter media includes a fluting center sheet intermediate a top and bottom layer. It can be appreciated that the filter media may be wound or otherwise stacked so that only a single sheet need be attached to a fluting sheet, as adjacent layers will serve as either the top or bottom sheet of the next adjacent layer. In addition, the layers may be wound in a spiral configuration. Alternating ends of adjacent chambers formed by the fluted material are blocked on either the upstream or downstream side. The first embodiment has tapered flutes which widen from one end to the other. The fluted chambers having their upstream end closed widen to an open downstream end. Conversely, the downstream closed fluted chambers widen to an open upstream end. 
     It can be appreciated that with this configuration, the area of the filter media transverse to the upstream flow includes a large portion open to the chambers for receiving the flow. As the flow filters through the various filter material sheets, the filtered fluid passes through an enlarged downstream end as well. In this manner, the restriction due to the filter is substantially decreased over standard fluted filter materials. In addition, the percentage of bead material and the upstream edge of the filter sheets is substantially less than the open area receiving the upstream flow. 
     According to a second embodiment of the present invention, fluted filter media includes asymmetric flutes which have a substantially sharp peak and a widened trough. The area above the trough is open to the upstream flow. In this manner, the upstream openings at the edge of the filter media have a larger cross sectional area transverse to the flow than the area of the closed flutes and the upstream edge of the filter material. This configuration provides improved flow with greater filter efficiency and reduced restriction across the filter. 
     According to a third embodiment of the present invention, fluted filter media includes a crushed upstream edge providing for improved flow. According to the third embodiment, the leading edge of the filter media includes beads blocking alternating chambers of the filter flutes. The upstream edge of the bead and fluting sheet are angled so that a widened edge intercepts the flow and angles toward the downstream end. As the flow intercepts the upstream edge, only the leading sheeting edge contacts the upstream flow and the bead and fluting sheet angle rearward. With this configuration, the resistance and proportion of the filter media intercepting the upstream flow at the leading edge of the filter is reduced. Therefore, improved flow is attained which provides for increased efficiency and reduced restriction across the filter. 
     These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, wherein like reference letters and numerals designate corresponding elements throughout the several views: 
         FIG. 1  shows a perspective view of a first embodiment of double-faced fluted filter media having tapered flutes according to the principles of the present invention; 
         FIGS. 2A-2B  show diagrammatic views of the process of manufacturing the filter media shown in  FIG. 1 ; 
         FIG. 3  shows an end elevational view of the filter media shown in  FIG. 1 ; 
         FIG. 4  shows an end elevational view of a roller for forming the filter media shown in  FIG. 1 ; 
         FIG. 5  shows a detailed end view of the teeth for the roller shown in  FIG. 4 ; 
         FIG. 6  shows a perspective view of a second embodiment of filter media having asymmetric flutes according to the principles of the present invention; 
         FIG. 7  shows an end elevational view of the filter media shown in  FIG. 6 ; 
         FIG. 8  shows an end elevational view of a roller for forming the filter media shown in  FIG. 6 ; 
         FIG. 9  shows a perspective view of a third embodiment of filter media having crushed leading flute edges according to the principles of the present invention; 
         FIG. 10  shows an end elevational view of the filter media shown in  FIG. 9 ; 
         FIG. 11  shows a side sectional view of the leading edge of the filter media shown in  FIG. 9 ; 
         FIG. 12  shows a graph of pressure drop across the filter versus airflow through the filter for various fluted filter media designs; 
         FIG. 13  shows a graph of pressure drop versus dust loading for various fluted filter media designs; 
         FIG. 14  shows a sectional view of a fourth embodiment of filter media having upstream sealed flutes with a sealed portion recessed from the upstream edge of the filter media according to the principles of the present invention; 
         FIG. 15  shows a side elevational view of a method of forming the leading edge of the filter media shown in  FIGS. 9-11 ; and, 
         FIG. 16  shows a side elevational view of a sheet of filter media cut into strips utilizing the method shown in  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and in particular to  FIG. 1 , there is shown a portion of a layer of double-faced permeable fluted filter media, generally designated  100 . The first embodiment of the fluted filter media  100  includes a multiplicity of tapered flute chambers  102 . The flute chambers  102  are formed by a center fluting sheet  108  forming alternating peaks  104  and troughs  106  between facing sheets  110 , including a first facing sheet  112  and a second facing sheet  114 . The troughs  106  and peaks  104  divide the flutes  102  into an upper row and lower row. In the configuration shown in  FIG. 1 , the upper flutes form flute chambers  122  closed at the downstream end, while upstream closed end flute chambers  120  are the lower row of flute chambers. The fluted chambers  120  are closed by first end bead  124  completely filling a section of the upstream end of the flute between the center fluting sheet  108  and the second facing sheet  114 . Similarly, a second end bead  126  closes the downstream end of alternating flutes  102 . Adhesive tacks connect the peaks  104  and troughs  106  of the flutes  102  to the facing sheets  112  and  114 . The flutes  102  and end beads  124  and  126  provide a filter element which is structurally self-supporting without a housing. 
     During filtration, unfiltered fluid enters the flute chambers  122  which have their upstream ends open, as indicated by the shaded arrows. Upon entering the flute chambers  122 , the unfiltered fluid flow is closed off by the second end bead  126  at the downstream end. Therefore, the fluid is forced to proceed through the fluting sheet  108  or face sheets  110 . As the unfiltered fluid passes through the fluting sheet  108  or face sheets  110 , the fluid is filtered through the filter media layers, as indicated by the unshaded arrow. The fluid is then free to pass through the flute chambers  120 , which have their upstream end closed and to flow out the open downstream end out the filter media  100 . With the configuration shown, the unfiltered fluid can filter through the fluted sheet  108 , the upper facing sheet  112  or lower facing sheet  114 , and into a flute chamber  120  blocked on its upstream side. 
     Referring now to  FIGS. 2A-2B , the manufacturing process for fluted filter media, which may be stacked or rolled to form filter elements, as explained hereinafter, is shown. It can be appreciated that when the filter media is layered or spiraled, with adjacent layers contacting one another, only one facing sheet  110  is required as it can serve as the top for one fluted layer and the bottom sheet for another fluted layer. Therefore, it can be appreciated that the fluted sheet  108  need be applied to only one facing sheet  110  when the layers are stacked or rolled. 
     As shown in  FIG. 2A , a first filtering media sheet  30  is delivered from a series of rollers to opposed crimping rollers  44  forming a nip. The rollers  44  have intermeshing wavy surfaces to crimp the first sheet  30  as it is pinched between the rollers  44 . As shown in  FIG. 2B , the first now corrugated sheet  30 , and a second flat sheet of filter media  32  are fed together to a second nip formed between one of the crimping rollers  44  and an opposed roller  45 . A sealant applicator  47  applies a sealant  46  along the upper surface of the second sheet  32  prior to engagement between the crimping roller  44  and the opposed roller  45 . At the beginning of a manufacturing run, as the first sheet  30  and second sheet  32  pass through the rollers  44  and  45 , the sheets fall away. However as sealant  46  is applied, the sealant  46  forms first end bead  38  between the fluted sheet  30  and the facing sheet  32 . The peaks  26  and troughs  28  have tacking beads  42  applied at spaced intervals along their apex or are otherwise attached to the facing sheet  32  to form flute chambers  34 . The resultant structure of the facing sheet  32  sealed at one edge to the fluted sheet  30  is single-faced layerable filter media. If the layers are stacked or spiraled, a second bead is applied at an opposite edge to the fluted sheet  30 . If the layers are not stacked or spiraled, a second bead is applied at an opposite edge and a second facing sheet is applied. 
     Referring again to  FIG. 1 , it can be appreciated that the flutes  102  taper. The fluted chambers  120  having their upstream end closed, widen along the trough to an enlarged downstream opening, as shown in  FIG. 3 . Similarly, chambers  122  have a large upstream opening, also shown in  FIG. 3 , and taper to a narrowed closed end. In this manner, the portion of the filter media intercepting the upstream flow that is open is substantially increased. In addition, as the fluid flows along the flutes and passes through the walls of the filter media, either center sheet  108  or facing sheets  112  or  114 , the fluid will flow out an enlarged open end on the downstream side of the filter. 
     It can be appreciated that to manufacture the tapered flutes  102 , a special roller  144  is required, shown in  FIG. 4 . The roller  144  includes a peripheral surface having a multiplicity of aligned teeth  146  formed thereon. The tapering teeth  146  taper from a narrow first end to a widened second end, as shown more clearly in  FIG. 5 . It can be appreciated that complementary teeth  147  on an opposing roller  145  taper from a narrowed second end to a widened first end. Therefore, as the facing sheet of the center sheet  108  is fed through the nip of the complementary rollers  144 , the filter media is crimped to form peaks  104  and troughs  106  which taper in alternate directions along their length. It can be appreciated that the beads  124  and  126  provide filter media which is structurally self-supporting. 
     As shown in  FIG. 3 , the resulting filter media  100  includes tapered flute chambers  120  which have a closed upstream end and flute chambers  122  which have an open upstream end. It can be appreciated that with tapered flutes  102 , flute chambers  122  have a larger cross sectional area transverse to the flow than the chambers  122  which have their upstream ends closed. It can also be appreciated that the cross sectional area transverse to the flow of the fluted chambers  120  is larger than the cross sectional area of the closed chambers  122  and the edges of the sheets  108 ,  112  and  114 . In this manner, the filter media  100  intercepts greater flow with less resistance. As the flute chambers  120  and  122  taper inversely to one another, the ends of the chambers are reversed in size at the downstream edge. With this configuration, it can be appreciated that the flute chambers  120  have a much smaller cross section at the closed downstream end of the filter media  100  and the flute chambers  122  have a much larger cross sectional area. Therefore, the flow passes in through the larger openings of chambers  120  and out through the enlarged open downstream ends of flute chambers  122 . With this configuration, flow passes through filter material having much greater open space with less resistance, while still providing sufficient filter media area in the same volume. 
     Referring now to  FIG. 6 , there is shown a second embodiment of filter media, generally designated  200 , having asymmetric flutes according to the principles of the present invention. The filter media  200  includes asymmetric flutes  202  forming substantially narrower peaks  204  and widened arcing troughs  206 . The radius of the arc of the peaks  204  is less than the radius of the arc of the troughs  206  of the asymmetric flutes  202 . The filter media  200  includes a center sheet  208  and facing sheets  210 , including a first upper facing sheet  212  and a second lower facing sheet  214 . 
     The facing sheets  210  are connected by upstream beads  224  and downstream beads  226 . In this manner, the sheets  208 ,  212  and  214  form chambers  220  having their upstream ends closed and chambers  222  having their downstream ends closed. 
     It can be appreciated that with the configuration shown in  FIG. 6 , the upstream portion of the filter media  200  intercepting flow includes an enlarged opening for the chambers  222 . In this manner, increased flow is intercepted by the fluted chambers  222  which then flow through the sheets  208 ,  212  and  214  and through the chambers  220 . In addition, the asymmetric fluted filter media  200  provides for a self-supporting filter structure. 
     Referring now to  FIG. 7 , the open end of the chambers  222  is substantially larger than the bead  224  at the upstream end and the surface area transverse to the flow of the sheets  208 ,  212  and  214 . This arrangement decreases the restriction at the filter inlet and provides for improved flow and dust loading capacity. 
     Referring now to  FIG. 8 , roller  244  for forming the asymmetric fluted filter media  200  includes a multiplicity of teeth  246  along its periphery. The teeth  246  of a first roller  244  will have a widened outer surface with a narrow trough formed therebetween. The complementary roller would have narrowed teeth with a widened trough formed therebetween for intermeshing with the teeth  246 . It can be appreciated that as the rollers engage filter material fed therebetween, asymmetric peaks and troughs are formed in the fluted filter material. 
     Referring now to  FIG. 9 , there is shown another embodiment of the present invention having crushed filter media, generally designated  300 . The crushed filter media includes flutes  302  having a crushed upstream edge  316 . The flutes include peaks  304  and troughs  306  formed by a fluted center sheet  308 . Facing sheets  310  sandwich the center sheet  308  to form fluted chambers  320  and  322 . A first facing sheet  312  contacts the upper surface of the flutes, while a lower facing sheet  314  contacts the bottom of the flutes. The filter media  300  includes an upstream bead  324  and a downstream bead  326 . The cross section of the flutes from the downstream end appears as in  FIG. 10 . The cross sectional view from the upstream ends would be reversed from that shown with the open and closed portions being opposite. 
     As shown in  FIG. 11 , the upstream side of the filter media  300  includes a crushed edge  316  along the upstream bead  324 . This forms a sloping surface  328  of the bead  324  and center sheet  308  which engages the flow. The slope provides less resistance while greater flow is achieved, so that the restriction across the filter media is reduced. It can be appreciated that the filter material and bead engaging the flow at the edge  330  is less than the open area intercepting the flow, improving efficiency and flow. 
     The sloped edge can be formed by a number of methods, however a preferred method is shown in  FIGS. 15 and 16 . An arced or round forming member  350  is pressed against the upstream bead  324  before the sealing material of the beads is set to provide a quick and easy method of forming an sloping surface  328 , as shown in  FIG. 15 . The forming tool  350  may be a ball which is rolled along the upstream bead  324  or a rounded member which is pressed onto the media  300 . After the depression is made, the media  300  is cut with a blade  360  or other cutting tool at the upstream bead  324 , thereby forming two strips of filter media  300  having a sloping upstream edge  330 , as shown in  FIG. 16 . It can be appreciated that a number sets of widened alternating beads  324  and  326  may be applied to a sheet of media  300 . The upstream beads  324  are then crushed as shown in  FIG. 15 . When the sealing material of the beads  324  and  326  sets, the sheet of filter media  300  is cut at beads  324  and  326  to form multiple sheets of filter media  300  having crushed upstream edges  300 . 
     Referring now to  FIG. 14 , there is shown a fourth embodiment of the present invention with fluted filter media  400 . The fluted filter media  400  is similar to other fluted filter media, but the fluted filter media  400  has a modified upstream edge and bead configuration, as explained hereinafter. As shown in  FIG. 14 , the fluted filter media  400  includes flutes  402  having peaks and troughs with flutes  420  closed upstream and flutes  422  closed downstream. However, unlike other fluted filters having alternating chambers sealed at the extreme upstream face of the filter media, the flutes  420  include a bead  424  sealing off the flute chamber which is recessed from the upstream edge of the filter media  400 . The flutes  422  have beads  426  which are at the downstream end. 
     The filter media  400  provides performance advantages as it can be appreciated that large particles  1000  may accumulate at the upstream face of the filter media. As shown in  FIG. 14 , if the particles  1000  are large enough, some of the flutes  402  may become completely blocked off. For prior filter media, if several flutes are blocked off, the blockage  1000  has greater impact as alternating surrounding flutes are sealed at their upstream side, creating increased flow redirection around the blocked flutes. However, as shown in  FIG. 14 , when the flutes  420  are sealed at their upstream side at  424  and recessed from the upstream edge, a blockage  1000  of an adjacent downstream closed flute  422  allows the flow to pass into the upstream end of the flutes  420  and through the fluting sheet or other filter material upstream of the seal  424 . In this manner, the fluid flows into flute  422  where it is forced back through the filtering material into the flutes  420  which are open to the downstream side of the filter. This reduces clogging and provides for better flow without pressure buildup or otherwise adversely affecting filter performance. In a preferred embodiment, the upstream sealing beads  424  are recessed from approximately ¼″ to 1″ from the upstream edge. In this manner, the fluted material is still self supporting while decreasing the effects of clogging at the upstream face of the filter media  400 . 
     As shown in  FIG. 12 , the pressure drop for air flow compares fluted filter media having standard B size flutes to the tapered filter media  100  also having a B size flute. In addition, a standard A size fluted filter media is compared to the crushed filter media  300  having an A size flute. It can be appreciated that the pressure drop across the filter, in both instances, is reduced as compared to the standard fluted filter configuration while having the same filter volume and nominal flute size. 
     In addition, as shown in  FIG. 13 , as the filter media becomes loaded with dust, it can be appreciated that a standard B flute has a much higher pressure drop than a B flute with tapered filter media  100 . In addition, a size A flute for filter media  300  with a crushed leading edge has a significantly lower initial pressure drop than a standard A flute. 
     It can be appreciated that with the present invention, filter media is provided which has a substantially greater open area transverse to the flow which intercepts the flow. This provides for increased efficiency with decreased restriction. 
     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.