REVERSE FLOW AIR FILTER ARRANGEMENT AND METHOD

Abstract: A reverse flow air filter arrangement is provided. The arrangement includes a filter element (21) having first and second end caps (23, 24), the second end cap (24) having a central drainage aperture (96). A funnel shape on an interior surface (94) of second end cap is used to direct moisture flow to the drainage aperture. The arrangement includes a housing (2) in which the filter element is positioned, operatively, during use. Certain features in the housing facilitate moisture withdrawal from the filter element while also inhibiting interference with sealing between the filter element and the housing.

Description: REVERSE FLOW AIR FILTER ARRANGEMENT AND METHOD Field of the Invention The present invention relates to reverse flow air cleaner arrangements. That is, the invention concerns air cleaner arrangements wherein filtering flow is in a direction with the "clean" side of the air filter being around an exterior thereof, and the "dirty" side of the air filter being along an interior thereof. The invention particularly concerns such air cleaner arrangements having drainage systems for water accumulating in an interior of associated air filter elements. The invention also concerns provision of preferred components, such as air filter elements, for use with such arrangements; and, to methods involving the use of such arrangements. Background of the Invention In general, air cleaner arrangements include a housing and an air filter element. The housing is configured such that air is directed through the air filter element, for filtering. Various geometric configurations of the air cleaner housing, the air filter element, and related seal arrangements are used to effect this. Many air cleaner arrangements include generally cylindrical air filter elements. Such elements typically include filter media arranged in a cylindrical pattern, with end caps. Seal arrangements are used either on or in conjunction with the end caps, to provide appropriate sealing with the housing or other portions of the air cleaner, and to control the direction of air flow. Reverse air flow air cleaner arrangements are generally those in which air is directed to an interior of the air filter element before it is filtered, and the air is filtered as it passes through the air filter element from the interior to the exterior. If the air filter element is cylindrical, this means that the unfiltered air is directed into the interior of the cylinder, and then through the filter media, to an exterior, during filtering. Material entrained in the air directed into the air filter, then, is left along an interior of the cylindrical filter media. Consider for example, a reverse flow air cleaner arrangement, having a cylindrical air filter element, utilized on an over the highway truck. Air directed into the interior of the cylindrical element may include dust, leaves, large particulates, and even moisture entrained therein. This material will tend to build up in the interior of the air filter element, in time. If the water depth inside the air filter becomes significant, the water, alone or with fine particulates or salt in suspension, can permeate filter media. This has the potential to damage engine components. It is would be preferred that arrangements be provided to drain the water from the interior of the filter element. In those arrangements wherein the filter element is operationally oriented such that the longitudinal axis of the cylindrical air filter is substantially vertical, drainage arrangements involving drainage apertures in one of the end caps have been used. In general, these have involved offset (from a central location) apertures in one end cap, and unless the air filter element is oriented nearly perfectly vertically, drainage is inefficient. Also, in such arrangements debris can sometimes collect along interior surfaces of the housing when the arrangement is opened and the element is removed; and, unless the housing is thoroughly cleaned before the element is reinserted into the housing, the debris can interfere with attainment of a good seal at critical locations. g .mnna-y n-F the Invention According to the present invention an air filter arrangement is provided. The air filter arrangement includes a housing and an air filter element having first and second opposite end caps, filter media and an open filter interior. The first end cap has an air inlet opening therein, for air to be passed into the arrangement to be filtered. The second end cap has a central drainage aperture and an interior surface constructed and arranged to funnel moisture that collects on the second end cap interior surface to the central drainage aperture, and outwardly from the filter element. The central drainage aperture is preferably positioned at a center of the second end cap, with a longitudinal axis of the air filter element passing therethrough. The air filter arrangement also includes an air flow direction arrangement constructed and arranged to direct air flow into the housing, into the open filter interior, through the filter media for filtering and then outwardly from the housing, as filtered air. The air flow direction arrangement generally comprises various features of the housing, seals and filter element. Preferably, the interior surface of the second end cap is circular. In certain embodiments it includes a plurality of radially directed troughs which terminate in the central drainage aperture. The troughs can be used to help funnel and direct moisture collected on an interior surface of the air filter element in use (i.e. "when operationally" or "operatively' 1 assembled) . In certain preferred arrangements, the second end cap includes an outer annular compressible portion and the housing includes an annular sealing surface against which the second end cap outer annular compressible portion is sealed, when the air filter arrangement is operatively assembled for use. Such a seal is referred to herein as a peripheral or annular radial seal, around the second end cap. That is, in this context the term "annular" refers to a sealing portion around the outside of the end cap, which seals under radial compression. In a preferred embodiment, the housing includes a base having a central, preferably recessed, pan and a sealing bead circumferentially positioned around the central recessed pan. A drainage aperture is provided in the central pan, so that water collected in the pan can be removed from the housing. With such an arrangement, preferably the second end cap is constructed and arranged to form a secondary seal with the sealing bead in the base, when the air filter element is operatively positioned within the housing. Preferably the manner of engagement with the seal bead is by provision of a mating "trough" in the second end cap outer surface. Preferably the second end cap outer surface has an outer edge or lip; and, the second end cap outer surface is recessed (or depressed) in extension between the outer edge and the trough which engages the sealing bead and the base. In this manner, in a preferred manner a gap or space is provided between the filter element second end cap, and the housing base, in the region between the sealing bead of the base and an outer peripheral area of the base. A space in this location accommodates debris that may collect in the housing, without interference with the seal between the second end cap and the housing. This is facilitated by those arrangements involving provision of the seal along an annular portion of the end cap,- as a radial seal, rather than as an end or axial seal. Preferably the second end cap outer surface is configured to provide a funnel surface having a declination angle of at least about 1°, and preferably 1° to 3°, in the region of extension between the outer edge of the second end cap and the portion of the end cap which engages the seal bead in the base. In preferred arrangements, an evacuation valve is mounted in the drainage aperture of the recessed pan in the base. This provides for a preferred, controlled, drainage of moisture from the system. In preferred embodiments, a soft polymeric material is utilized for the first and second end caps. Preferably each of the polymeric end caps comprise polyurethane. For the end caps, a polyurethane foam material having an "as molded" density of about 14-22 lbs per ft 3 will be preferred (most preferably about 18.4) . In some embodiments, the same material can be utilized for both end caps. In preferred constructions, an air inlet tube is provided in the housing, which is configured to generate a radial seal with the first end cap of the filter element. In an alternate embodiment, an arrangement having a sheet metal end cap as the second end cap is provided. This arrangement is preferably axially sealed, by provision of a primary seal gasket axially compressed between the second end cap and the base, when the air filter arrangement is operationally assembled. A secondary gasket can also be provided in such arrangements between a selected portion of the second end cap and the housing base. According to the present invention, a preferred filter element is provided. The preferred filter element comprises a generally cylindrical extension of filter media. The filter media may be, for example, a pleated paper filter media. Preferably, an inner support liner and an outer support liner are provided, for the cylindrical extension of filter media. Preferably the arrangement has first and second end caps, the first end cap including an air inlet opening therein. The second end cap preferably has a central drainage aperture and an interior surface constructed and arranged to funnel moisture, collected on the interior surface of the second end cap, to the central drainage aperture. The central drainage aperture is preferably located at an approximate center of the end cap, on a longitudinal axis of the cylindrical extension of filter media. A preferred configuration for the interior surface of the second end cap, is as an interior of a funnel. In some embodiments, the second end cap interior surface includes a plurality of radially directed troughs therein, which terminate at the central drainage aperture. Other preferred features for the preferred air filter element include: a circular sealing trough on an outer surface of the second end cap; and, a recess between an outer edge of the end cap outer surface, and the circular trough. Also, a compressible region providing for a radial seal along an annular portion of the second end cap is preferred. According to the present invention, a method of operating a reverse flow air filter arrangement is provided. In general, the method comprises collecting moisture within the filter element and draining the moisture from the filter element through a central aperture in the end cap, by funneling the moisture to the central aperture. Brief Description of the Drawings Fig. 1 is a side elevational view of an air cleaner arrangement according to the present invention. Fig. 2 is a top plan view of the arrangement shown in Fig. 1. Fig. 3 is an exploded plan view of the arrangement shown in Fig. 1. Fig. 4 is an enlarged fragmentary side cross- sectional view of a portion of the arrangement shown in Fig. 1; Fig. 4 being generally taken along line 4-4, Fig. 1. Fig. 5 is a fragmentary cross-sectional view of a portion of the arrangement shown in Fig. 1; Fig. 5 generally being taken along line 5-5, Fig. 1. Fig. 6 is a fragmentary exploded view of a portion of the arrangement shown in Fig. 5. Fig. 7 is a fragmentary top plan view of a portion of the arrangement shown in Fig. 6. Fig. 8 is a fragmentary cross-sectional view of an alternate embodiment to that shown in Figs. 1-7. Detailed Description of the Invention The reference numeral 1, Fig. 1, generally designates an air cleaner assembly according to the present invention. Fig. 1 is a side elevational view of air cleaner assembly 1. In the Figure, housing 2 is depicted generally. The housing 2 includes an inlet construction 3 and a filter element receiver or can 4. Can 4 includes outlet 7. In use, air to be filtered passes through inlet construction 3, and is directed to an interior of can 4. Within can 4, the air is directed through a filter element, not viewable in Fig. 1. After being filtered by the filter element, the air passes outwardly through outlet 7 and is directed to the air intake of the engine, not shown. Herein, the term "air flow direction arrangement" is used to generally refer to these features of an air filter arrangement which direct air flow in the preferred manner or along a preferred path. The term may refer to a variety of features, and typically refers to internal configurations of the housing and filter element, as well as the various seals. Still referring to Fig. 1, inlet construction 3 is mounted on can 4, and is secured thereto by bolts 8 and nuts 9. Access to the interior of can 4, and a filter element positioned therein, is obtained by loosening bolts 8 and separating inlet construction 3 from can 4. For the particular construction shown, inlet construction 3 includes an upper dome 12, perforated air inlet screen 13 and an inlet tube 14 (the inlet tube not being viewable in Fig. 1, but being shown in Fig. 4 in cross-section) . Still referring to Fig. 1, can 4 includes a drainage aperture therein the drainage aperture not being viewable in Fig. 1, but being shown at reference numeral 18 in Fig. 5. The drainage aperture is covered by an evacuation valve 19. The evacuation valve 19 may be, for example, as described in U.S. Patent 3,429,108, the disclosure of which is incorporated herein by reference. In general, the drainage aperture 18 is positioned in a portion of can 4 which will be, when assembly 1 is operatively installed, positioned at the bottom of the assembly 1. Thus, water will tend to collect near aperture 18, and be drained therefrom, in use. This will be more readily apparent from further descriptions wherein internal details of air cleaner assembly 1 are presented. Referring to Fig. 2, air cleaner assembly 1 includes four bolts and nuts 9 for securing the inlet construction 3 to the filter can 4. While the number of bolts used may be varied, depending on the particular application, it is an advantage of constructions according to- the present invention that filter assemblies as large as about 15 inches in outside diameter can be reliably secured closed, with as few as about three to five bolts. Features which facilitate this, will be apparent from further descriptions. An exploded view of air cleaner assembly 1 is depicted in Fig. 3. In Fig. 3, air cleaner assembly 1 is shown with inlet construction 3 separated from filter can 4, and with air cleaner element 21 removed from can 4. For the particular arrangement shown, air cleaner element 21 is generally cylindrical. Element 21 includes first and second end caps 23 and 24; filter media 25; inner support 26 (Fig. 4) ; and, outer support 27. For the particular embodiment shown, filter media 25 comprises a pleated paper construction 30. In general, pleated paper construction 30 comprises a cylinder 31 of fluted paper with the flutes running in a direction longitudinally along, and generally parallel to, a central axis 33 of the element 21. It will be understood that alternate filter media constructions could be utilized. In general, the filter media 25 extends between the end caps 23 and 24. For assembly 1 depicted, end caps 23 and 24 comprise polymeric material as described below, in which opposite ends of the filter media 25 are set or potted. In Fig. 4 a fragmentary cross-sectional view of air cleaner assembly 1 is depicted. In Fig. 4, the inlet construction 3 and portions of air cleaner assembly 1, in association therewith, are depicted. In general, the filter media 25 is positioned between inner support 26 and outer support 27. Each support generally comprises a tubular or cylindrical extension of perforated metal or expanded metal, opposite ends of which are also set in,- or potted in, end caps 23 and 24. In general, end cap 23 is open and end cap 24 is closed. That is, end cap 23 includes a large inlet aperture 28 (Fig. 4) therein, for introduction of air to be filtered into filter element interior 35. End cap 24, on the other hand, is generally closed, but for a drainage aperture extending therethrough as described below. Still referring to Fig. 4, it can be seen that inlet construction 3 includes inlet tube 14. When assembled, inlet tube 14 extends into aperture 28 in end cap 23. At least in this location, end cap 23 is preferably formed of a soft compressible material. When inlet tube 14 is not inserted into aperture 28, at least a portion of aperture 28 in its uncompressed state will generally have an inside diameter slightly larger than an outside diameter of section 39 of inlet tube 14; i.e. the portion of tube 14 which engages end cap 23 when arrangement 1 is operatively assembled. Thus, when inlet tube 14 is inserted through aperture 28, end cap material in region 40 will be compressed. In this manner a seal is formed at region 41. Such seals are described, for example, in conjunction with air cleaner assemblies in U.S. Patent B2 4,720,292, the disclosure of which are incorporated herein by reference. It is noted that the arrangement of U.S. Patent 4,720,282 is not necessarily a reverse flow arrangement; however, the principles relating to the formation of the seal are basically the same. Such seals are sometimes referred to as "radial" or"radial-type" seals, since the forces maintaining sealing are directed radially around a central longitudinal axis 33 (Fig. 3) of the tube and element, rather than co-extensively or coaxially therewith. For the particular arrangement shown in Figs. 1-7, material at region 40 is compressed between and against both inlet tube 14 and inner support 26; that is, inner support 26 is set sufficiently deeply into end cap 23 that a portion of it is positioned behind compressible region 40, to provide support. Thus, a good seal is effected. The shape of aperture 28 in region 41 will preferably be as a ribbed or stepped funnel (or tapered), to facilitate engagement. Such a ribbed arrangement is shown in 5,238,474, incorporated herein by reference. In U.S. 4,720,292 a similarly tapered surface without ribs is shown. Preferably, 3 equally, sized steps from a region of diameter about the same as the inlet tube O.D. are used, with the amount of total compression of the smallest diameter rib (i.e. region of most compression) being about 21.4% (20% ± 3%) . The size of each step will depend in part on the diameter of the inlet tube. In general, for an element used with an inlet tube having an O.D. of 175-200 mm, a total compression thereacross of 2.7 mm (or 1.35 mm for any location since any location compresses about one-half of the total compression) for the smallest rib would be used. It will be understood, then, that for the arrangement shown in Figs. 1-7, seal 41 prevents air directed into filter interior 35 through inlet tube 14 from bypassing filter media 25 and getting into clean air plenum 44. In general, the various portions of the arrangement 4 cooperate as an air flow direction arrangement to direct air flow: into the housing, into the filter interior, through the filter media and outwardly from the housing. Another point of potential leakage of unfiltered air into clean air plenum 44 is presented by the location whereat inlet construction 3 engages filter can 4. This region is located generally at 50; i.e. where bolts 8 secure inlet construction 3 to filter can 4. At region 50, inlet construction 3 is provided with an outwardly extending flange 52; and, can 4 is provided with an outwardly extending flange 53. Seal ring 54 is provided in extension around can 4, between flanges 52 and 53. Seal ring 54 is positioned at a location between bolts 8 and filter element 21. When bolts 8 are tightened, seal ring 54 will be compressed between flanges 52 and 53, i.e. at a location between inlet construction 3 and filter can 4, providing a seal. Thus, air leakage into plenum 44, by passage between portions of can 4 and inlet construction 3 is inhibited. Filter ring 54 may be a conventional O-ring type gasket. Attention is now directed to Fig. 5, which is a cross-sectional view showing the "bottom half" or "opposite end" of assembly 1 from the end whereat inlet construction 3 is located. Referring to Fig. 5, reference numeral 60 generally designates an end of can wall 61. Within end 60 is positioned a cover or base 63 of can 4. Base 63 is configured in a preferred manner, to advantage. For the particular embodiment shown, base 63 is circular, to conform to the cross-sectional configuration of can wall 61 at end 60. For the particular embodiment shown, base 63 is also radially symmetric. That is, the features of base 63 are configured radially symmetrically about central axis 33. Base 63 includes end flange 65 for engagement with end 60, for example by means of welds. Progressing inwardly from flange 65 toward its center 66, the features of the preferred base 63 depicted are as follows: an annular circumferential sealing surface 67 is provided; a bend or corner 68; an end surface 69; a secondary seal bead or ridge 70; and, a central pan 71. In the center 66 of pan 71, drainage aperture 18 is provided. The arrangement shown in Figs. 1-7 is configured preferentially so that when oriented for use, pan 71 is at a lowermost or recessed location, so that water will drain to pan 71 under gravity influence. As the water drains into pan 71, it will be drained outwardly from air cleaner assembly 1 through drainage aperture 18. Particular features described herein are provided, for a preferred manner of debris collection within assembly 1 and drainage of collected moisture to aperture 18. Still referring to Fig. 5, filter element 21 includes end cap 24 thereon. End cap 24 is of an appropriate material, and of appropriate size, so that when it is pushed into and against base 63, an outer circumferential surface 75 of the end cap 24 engages surface 67 of base 63 in a sealing manner. That is, an annular seal 76 is formed in region 77, circumferentially around end cap 24. This is facilitated by preferably providing surface 67 in a cylindrical configuration extending generally parallel to axis 33. The seal prevents unfiltered air from reaching clean air plenum 44. As a result of the circumferential seal 76, sealing against flow of air is not required between any other portions of filter element 21 and base 63. A secondary seal 80, described herein below, is provided, however, between end cap 24 and base 63. The secondary seal 80 is generally provided to inhibit movement of debris or water into region 81, between element 21 and base 63, rather than to necessarily prevent flow of air therebetween. Thus, while seal 76 should be in a form sufficient to withstand a pressure differential thereacross of up to about 40 inches of H 2 0, secondary seal 80 will generally be sufficient if it can maintain at pressure differential thereacross of up to about 2 inches (and typically only up to about 2-4 inches) of H 2 0. Still referring to Fig. 5, end cap 24 includes a circular recess or trough 85 therein. Trough 85 is sized and configured to receive and sealingly engage bead 70. Trough 85 should be sized, relative to bead 70, such that when element 21 is pressed against base 63, bead 70 is pushed into trough 85 to form a seal therewith, capable of holding a pressure differential of up to about 2-4 inches of H 2 0. This could be readily accomplished by forming the related region 86 of end cap 24 of an appropriately soft compressible polymeric material into which rigid bead 70 can be pressed, for engagement. Referring to Figs. 5 and 6, it is noted that for the preferred embodiment depicted surface 90 of end cap 24 is recessed from outer edge 91 to region 92, so that a space between surface 90 and end surface 69 is provided, when filter element 21 is operatively positioned within can 4. The amount of recess can be varied, depending upon the size of the arrangement. In general, an engle of inclination from edge 91 to region 92 on the order of about 1° to 3° will be sufficient. Advantages which result from this inclination, will be apparent from further descriptions herein below. In general, the space between surface4 90 and end surface 69 ensures that there will not be interference with easy formation of the annular, radial, seal. Still referring to Figs. 5 and 6, internal surface 94 of end cap 24 is configured to incline downwardly, when the assembly 1 is oriented as shown in Figs. 5 and 6, in extension from outer region 95 toward central aperture 96. Preferably, internal surface 95 is conical or funnel shaped in this region. Thus, any water which collects on internal surface 94 will tend to flow toward central aperture 96 and therethrough, into recessed pan 71. In some embodiments recessed, radial troughs extending outwardly and upwardly from central aperture 96 can be used to facilitate this flow. Such an arrangement is shown, for example, in Fig. 7 (a top plan view of element 21) wherein four evenly (radially) spaced, recessed, troughs 99 are depicted. It will be understood that each of troughs 99 generally inclines downwardly as it extends from region 95 toward central aperture 96, to facilitate collection of water within interior 35 and direction of the collected water to central aperture 96. An -advantage to troughs 99 is that should a leaf or other large particulate material become positioned over central aperture 96, water can still flow into and through the aperture 96 by means of the troughs 99, since the troughs 99 can generally direct water flow underneath debris collected on top of internal surface 94. Numerous advantages result from the preferred features described. As assembly 1 is used for a filtering operation, air will generally flow through inlet tube 14 into interior 35, carrying within it moisture and/or debris. The moisture and debris will tend to collect within interior 35, on internal surface 94 of end cap 24, since arrangement 1 will generally be configured with end cap 24 positioned beneath inlet tube 14. Water collecting on internal surface 95 will generally be directed toward central aperture 96, for drainage into recessed pan 71 and eventually drainage outwardly from assembly 1 through drainage aperture 18. Evacuation valve 19, if used, will facilitate this. Because sealing between end cap 24 and housing 2 is positioned along annular circular sealing surface 67, i.e. at region 77, the critical sealing is not located at a surface where debris is likely to be spread or collect, as element 21 is removed from and replaced into housing 2, during typical maintenance operations. Because surface 90 is recessed from end surface 69, in extension between edge 91 and region 92, any debris which may spread along end surface 69 during operations involving removal and insertion of filter elements into housing 2, will not likely interfere with sufficient insertion of the element 21 into can 4 for the development of a good seal at region 77. That is, some debris buildup along the bottom of base 63 is well tolerated. Also, secondary seal- 80 will inhibit the likelihood of debris or moisture moving from pan 71 into surface 69, or region 77. This will also help facilitate removal of moisture from assembly 1, since the moisture will tend to concentrate near drainage aperture 18. In Fig. 6, the arrangement of Fig. 5 is shown exploded. From this, a preferred configuration for surface 75, relative to circular (annular) sealing surface 67 will be understood. In particular, surface 75 includes steps 101, 102 and 103, with extensions 105 and 106 therebetween. Step 103 is approximately the same diameter as circular sealing surface 67, and facilitates guidance of air cleaner element 21 into engagement with base 63, during assembly. Step 102 is preferably slightly larger in diameter than circular sealing surface 67, and step 101 is preferably slightly larger in diameter than step 102, to enhance compression of end cap material in region 77, as element 21 is inserted into base 63, during assembly. In this manner, a good seal is formed. In general, for preferred embodiments the actual amount of compression of the end cap in region or step 102 is 3 mm ± 1 mm on diameter (or 1.5 mm at any location) . The diameter of step 102 is preferably about 1.5 mm greater than step 101, and about 3 mm greater than step 103. The amount of compression in step 102 would preferably be about 21.4% (20% ± 3%) . As indicated, the arrangement described with respect to Figs. 1-7 generally utilizes a radial seal engagement in region 77. Alternate sealing arrangements may be utilized. An example of such an arrangement is illustrated in the alternate embodiment of Fig. 8. Alternate Embodiment-A-xiallv Sealing System In Fig. 8 an alternate application of principles according to the present invention is provided. Fig. 8 illustrates an engagement between an air cleaner assembly base and a filter element, to provide advantages according to the present invention, in an arrangement which utilizes an "axial seal" between the filter element and the housing, at least at this location. In general, an axial seal is a seal which is maintained by forces directed along an axis of the filter element, as opposed to radial seal arrangements described with respect to Figs. 1-7 which use forces directed radially around an axis. Axial seal arrangements have been widely utilized in filter elements in a variety of manners. Often a central yoke or axle is provided, along which forces are directed between the housing in the element . In other systems a bolt engagement between portions of the housing are used to compress the element against one end or both ends of the housing. The O-ring 54 in the embodiment of Figs. 1-7, for example, provides sealing by axial compression. Fig. 8 is a fragmentary cross-sectional view of an alternate air cleaner assembly 115 according to the present invention. The air cleaner assembly 115 is also a reverse flow arrangement . Assembly 115 includes housing 116 and air filter element 117. An inlet arrangement, not depicted, would be utilized to direct air flow into interior 118. Air flow would then be through filter element 117 into clean air plenum 120, and outwardly through a conventional outlet, not shown, into an air intake for an engine. In Fig. 8 the outer wall of the housing 116 or can, is generally shown at 121. The housing end or base 123 is configured to perform functions generally analogous to those for base 63, Figs. 1-7. Still referring to Fig. 8, filter element 117 has a sheet metal end cap, such as end cap 125. The filter element 117 includes filter media 126 potted within the end cap 125 (the opposite end cap not being shown in Fig. 8) . Element 117 includes inner and- outer liners 127 and 128 respectively. Sealing between element 117 and base 123, against air flow therebetween, is provided by gasket 130. That is, an appropriate mechanism to apply axial forces in the direction of arrow 131 against element 117 should be provided, to compress gasket 130 between end cap 125 and base 123 and form a seal. This can be accomplished with bolts used to drive an end cover or inlet construction against an opposite end of element 117. Preferably appropriate sizes and configurations of the element 117, base 123 and gasket 130 are selected, so that the seal of gasket 130 will be sufficient to hold a pressure differential at least about 40 inches of H 2 0 thereacross. In this manner, unfiltered air in region 132 is prevented from reaching clean air plenum 120, in use. In general, the features of the preferred base 123 depicted are as follows. Base 123 is radially symmetric and includes outer flange 135, for securement to can wall 121, such as by welding. Base or recess area 136 is provided for a receipt of gasket 130 therein, during sealing. This is accommodated, by recessed area 136 forming a trough 137. Region 138, of base 123, is raised above trough 137, and provides a raised surface 139 for provision of a secondary seal, as described below. Base 123 then defines pan 145, by downwardly extending or declining wall 146, towards a recessed central aperture 147. With respect to the filter element, end cap 125 includes a downwardly slanted surface 149 toward central pan 150 having drainage aperture 151 therein. A secondary seal between end cap 125 and surface 139 is provided by secondary seal gasket 155. This gasket 155 is intended to inhibit the migration of moisture and debris from recessed pan 145 into region 137, whereat it could interfere with seal gasket- 130. Secondary gasket 155 need only provide a seal sufficient to inhibit substantial migration of moisture and debris, and does not need to be a primary air seal. Thus, gasket 155 need only be compressed sufficiently to withstand a pressure differential of up to about 2-4 inches of H 2 0 thereacross. Operation of assembly 115 will now be apparent. When assembled, sufficient axial pressure is applied along the direction of arrow 131, to provide an air seal end at gasket 130 and a secondary seal at gasket 155. Debris and moisture directed into interior 118 will generally collect in pan 150. In general, moisture collecting along recessed surfaces 149 will be directed downwardly toward and through aperture 151, into pan 145 of base 123, and eventually through drainage aperture 147 and outwardly from assembly 115. It will be understood that a trough system (analogous to that described for Figs. 1-7) may be utilized in pan 150, if desired, to inhibit the likelihood of drainage aperture 151 becoming closed or plugged by debris. Materials While a wide variety of materials may be utilized in constructions according to the present invention, the principles described herein were particularly developed for use, to advantage, with systems constructed from certain preferred materials. In general, the constructions were designed for utilization with sheet metal housing systems, or stainless steel housing systems; i.e. arrangements wherein the housing, in particular the inlet assembly, the can and the base, are formed from sheet metal or stainless steel parts which are secured to one another as by welding. Materials useful for such fabrication include 0.75-.0.25 inches thick stainless steel or sheet metal, although other thickness are useable. Plastics can also be used. For the arrangement of Figs. 1-7, the preferred end cap material for forming the regions in the end cap that need to be compressed to form a seal is a soft polymeric material such as foamed polyurethane. Such materials include the following polyurethane, processed to an end product having an as molded density of 14-22 pounds per cubic foot (lbs/ft 3 ) . The preferred polyurethane comprises a material made with I35453R resin and I305OU isocyanate. The materials should be mixed in a mix ratio of 100 parts 135453 resin to 36.2 parts I3050U isocyanate (by weight) . The specific gravity of the resin is 1.04 (8.7 lbs/gallon) and for the isocyanate it is 1.20 (10 lbs/gallon) . The materials are typically mixed with a high dynamic shear mixer. The component temperatures should be 70-95°F. The mold temperatures should be 115-135°F. The resin material I35453R has the following description: (a) Average molecular weight 1) Base polyether polyol = 500-15,000 2) Diols = 60-10,000 3) Triols = 500-15,000 (b) Average functionality 1) total system = 1.5-3.2 (c) Hydroxyl number 1) total systems = 100-300 (d) Catalysts 1) a ine = Air Products 0.1-3.0 PPH 2) tin = Witco 0.01-0.5 PPH (e) Surfactants 1) total system = 0.1-2.0 PPH (f) Water 1) total system = 0.03-3.0 PPH (g) Pigments/dyes 1) total system = 1-5% carbon black (h) Blowing agent 1) 0.1-6.0% HFC 134A. The I3050U isocyanate description is as follows: (a) NCO content - 22 .4 -23 .4 wt% (b) Viscosity, cps at 25°C = 600 -800 (c) Density = 1 .21 g/cm 3 at 25°C (d) Initial boiling pt. - 190°C at 5mm Hg (e) Vapor pressure = 0.0002 Hg at 25°C (f) Appearance - colorless liquid (g) Flash point (Densky-Martins closed cup) = 200°C. The materials I35453R and I3050U are available from BASF Corporation, Wyandotte, Michigan 48192. For the arrangement shown in Fig. 8, the filter element includes sheet metal end caps with a fluted filter paper media element potted therein. Conventional arrangements such as potted in plastisol may be used. Dimensions of a Typical Embodiment Consider an air cleaner arrangement such as depicted in Fig. 1 used on a over the highway truck (heavy duty truck) . The housing would be about 13-15 inches in diameter and about 32 inches long. The element would be about 11-13 inches in diameter and about 23-26 inches long. The I.D. of the smallest rib on the sealing portion of the end cap with the inlet tube (prior to compression) would be about 6.78-7.44 inches. The I.D. of the annular surface in the housing base whereat the radial seal with second end cap occurs would be about 11.28-19.94 inches. The O.D. of the largest step on the second end cap, for sealing with the base, would be about 11.4-13.06 inches. The bead on the base for engagement with the second end cap would be large enough to extend into the trough on the end cap about 0.35 inches. The declination angle in the second end cap from its outer rim to the recess engaging the bead would be about 1.75°. The declination angle on the inside of the second end cap would be about 4°±2°.

Claims: WHAT IS CLAIMED IS: 1. An air filter arrangement comprising: (a) a housing; (b) air filter element having: first and second, opposite, end caps; filter media; and, an open filter interior; (i) said first end cap having an air inlet opening therein; (ii) said second end cap having: (A) a central drainage aperture; and, (B) an interior surface constructed and arranged to funnel moisture on said second end cap interior surface to said central drainage aperture; and, (c) an air flow direction arrangement constructed and arranged to direct air flow: into said housing; into said open filter interior; through said filter media; and, outwardly from said housing. 2. An air filter arrangement according to claim 1 wherein: (a) said second end cap interior surface includes a plurality of radially directed troughs therein which terminate at said central drainage .apertur . 3. An air filter arrangement according to claim 1 wherein: (a) said second end cap includes an outer, annular, compressible portion; and, (b) said housing includes an annular sealing surface against which said second end cap outer, annular, compressible portion is sealed, when said air filter arrangement is operatively assembled, for use. An air filter arrangement according to claim wherein: (a) said housing includes a base; said base including: a central pan; and, a sealing bead arranged circumferentially around said central recessed pan; (i) said central pan including a central drainage aperture; (b) said second end cap being constructed and arranged to form a secondary seal with said sealing bead in said base, when said air filter element is operatively positioned within said housing. 5. An air filter arrangement according to claim wherein: (a) said second end cap has an outer surface including a circular trough therein, sized and positioned for sealing engagement with said sealing bead in said base. 6. An air filter arrangement according to claim wherein: (a) said second end cap outer surface includes an outer edge; and, (b) said second end cap outer surface is recessed in extension between said outer edge and said circular trough. 7. An air filter arrangement according to claim 6 wherein: (a) said second end cap outer surface recess is a funnel region in said outer surface having an angle of declination of at least about 1° in extension from said outer edge to said circular trough. 8. An air filter arrangement according to claim 7 wherein: (a) said second end cap interior surface includes a plurality of radially directed troughs therein which terminate at said central drainage aperture. 9. An air filter arrangement according to claim 4 including: (a) an evacuation valve mounted in said drainage aperture of said central recessed pan in said base. 10. An air filter arrangement according to claim 1 wherein: (a) said second end cap of said filter element comprises a soft foamed polymeric material having an "as molded" density of 15-22 lbs per square ft. 11. An air filter arrangement according to claim 1 wherein: (a) said first and second end caps of said filter element each comprise soft polymeric material. 12. An air filter element according to claim 11 including: (a) an air inlet tube constructed and arranged to form a radially directed seal with said air inlet opening in said first end cap, when said filter element is operationally positioned within said housing. 13. An air filter arrangement according to claim 1 wherein: (a) said filter element second end cap is a sheet metal end cap; (b) said housing includes a base having a central pan with a central drainage aperture; and, (c) a primary seal gasket is axially compressed between said second end cap and said base, when said air filter arrangement is operationally assembled. 14. An air filter arrangement according to claim 13 wherein: (a) said base includes a secondary seal surface oriented higher than said central recessed pan, and between said central pan and said primary seal gasket, when said air filter arrangement is operationally assembled; and, (b) a secondary seal gasket is compressed between said filter element second end cap and said secondary seal surface of said base, when said air filter arrangement is operationally assembled. 15. An air filter element comprising: (a) a cylindrical extension of filter media defining an open filter interior; (b) an inner support liner; (c) an outer support liner; (d) a first end cap having an air inlet opening therein; (e) a second end cap having: (i) a central drainage aperture; and, (ii) an interior funnel surface constructed and arranged to funnel moisture, collected on said second end cap interior surface, to said central drainage aperture. 16. An air filter element according to claim 15 wherein: (a) said second end cap interior surface includes a plurality of radially directed troughs therein which terminate at said central drainage aperture. 17. An air filter element according to claim 16 wherein: (a) said second end cap has an outer surface including a circular sealing trough therein. 18. An air filter element according to claim 17 wherein: (a) said second end cap outer surface includes an outer edge; and, (b) said end cap outer surface is recessed in extension between said outer edge and said circular trough. 19. An air filter element according to claim 18 wherein: (a) said end cap outer surface recess is a funnel region in said outer surface having an angle of declination of at least about 1° in extension from said outer edge to said circular trough. 20. A method of operating a reverse flow air filter arrangement including a cylindrical filter element therein; the filter element having a lower end cap with a central aperture; said method including a step of: (a) collecting moisture within said cylindrical filter element and draining the moisture from the filter element through the lower end cap central aperture, by funneling the moisture along a funnel surface to the central aperture.

Inventors: ENGEL DONALD F, ENGEL, DONALD, F.
Applicants: DONALDSON CO INC, DONALDSON COMPANY, INC.
Application year: 1995
Main classification: B01D46
IPC codes: B01D46