Abstract:
Filtration method and device for filtering solid contaminants from a stream of a flowing fluid such as internal combustion engine intake air. An imperforate housing has a tubular inlet exiting at its downstream end into a conically divergent first wall section terminating in a maximum diameter apex. A convergent second wall section terminates at a housing outlet opening of greater diameter than that of the housing inlet. A perforate filter element disposed within the housing conical portions has an exterior configuration generally complimental to the housing interior, and thus has a first generally conical divergent section, and a second generally conical downstream section convergent from a maximum diameter apex of the filter element and defining the filter device outlet. The housing and filter element define therebetween first and second frustoconical annular fluid flow chambers of successively diminishing cross-sectional radial thickness in the direction of downstream fluid flow.

Description:
This is a United States regular utility patent application filed pursuant to 35 U.S.C. §111 (a) and claiming the benefit under the provisions of 35 U.S.C. §119 (e) (1) of the priority of U.S. provisional patent application Ser. No. 60/329,342 filed Oct. 15, 2001 pursuant to 35 U.S.C. §111 (b). 
    
    
     FIELD OF THE INVENTION 
     This invention relates to fluid filtration devices of the type wherein a fluid-permeable filter media is operably disposed in flow-through filtering relationship with a fluid medium, and more particularly to an air filtration device constructed for use with the air intake manifold of an internal combustion engine such as reciprocating piston and rotary engines, such as those used in automobiles, trucks, motorcycles, small engine vehicles and lawn and garden engine-powered appliances, as well as larger turbine engines used on tanks, helicopters and the like, and power generating station gas turbines. 
     BACKGROUND OF THE INVENTION 
     There are many types of air filtration devices for internal combustion engines on the market today. One example is an automotive air filtration unit offered on the Ford Mustang model year 2000 in which a rectangular cross section housing is provided at the upstream inlet end of the engine air intake manifold located on the left side fender well under the hood of the vehicle. This box-like housing has disposed within it an air filtration element in the form of a frustoconically shaped filter media with a blunt, imperforate nose of say three inches in diameter at its leading end. This filter media diverges from its nose in a conical shape with a straight taper to a diameter of about four or five inches at its rear end, and is approximately six to seven inches long. The conical surface of this filter is pleated, and the smaller diameter, blunt nose of the filter media is oriented as the leading end of the filter, thus facing upstream in the air flow stream being engine-drawn into the intake manifold. 
     One of the problems discovered with this prior art filter is caused by the nonconformance geometrically between the general conical shape of the filter media versus the generally rectangular shape of the enclosing housing. This configuration presents a relatively high level of air deflection and creates turbulence and eddies that also contribute to deposit collection of contaminating particles in certain areas of the housing, thereby reducing the efficiency of the filter relative to air flow capacity. Also, the audible noise level associated with such air filtration devices is objectionably high in some instances and under certain conditions. The aforementioned filter-housing configuration also reduces the air flow velocity through the filter due to the air flow deflections and turbulence effects. Conditions of velocity changes in air flow, depending on the engine demand, also typically change the interface angle between the impinging air and the filter surface, further reducing optimum performance of the filter. 
     Other examples of prior art automotive air filtering devices are those shown in the U.S. design patents DES. No. 401,597; DES. No. 401,942; DES. No. 403,414 and DES. No. 403,416. 
     OBJECTS OF THE INVENTION 
     Accordingly, among the objects of the present invention are to provide an improved air filtration method and device for performing such method, and an improved method of making such devices for use with internal combustion engines that achieves increasing air flow and air velocity through the air filtering system while maintaining a high level of air filtration, that operates with a lower level of air deflection in the air stream presented to the filter media due to unique and cooperative geometrical shapes of the filter media and the enclosing housing, wherein such cooperative shapes also create several thousand direct paths for the air to flow through the filter media without deflection, that enhances proper air flow direction and obtains higher operating air velocities than conventional air filtration devices, that reduces the audible noise level from that associated with prior air filtration devices, and which is simple and economical in construction, reliable in operation which provides a long service life. 
     SUMMARY OF THE INVENTION 
     In general, and by way of summary description and not by way of limitation, the present invention accomplishes one or more of the foregoing objects by providing an improved air filtration method and device for filtering solid contaminants from a stream of flowing fluid wherein a housing is provided having a tubular inlet exiting at its downstream end into a conically divergent first wall section having a first taper angle of divergence and terminating in a maximum diameter apex. The housing wall taper then reverses and thus continues in a convergent second wall section having a second angle of taper. The second wall section terminates at a housing outlet opening of greater diameter than the diameter of the inlet opening at the tubular inlet. A filter element is disposed within the interior chamber defined by the conical portions of the housing and has an exterior configuration generally complimental to that of the interior of the housing. The filter element thus has a first generally conical section divergent at a third taper angle greater than the first taper angle of the housing and a second generally conical downstream section convergent at a fourth taper angle from a maximum diameter apex of the filter to an outlet at an angle of convergence less than the second taper angle. 
     The filter housing and filter element thereby define first and second frustoconical annular chambers of successively diminishing cross-sectional radial thickness in the direction of downstream fluid flow. 
     In one embodiment the housing is constructed of flexible material such as rubber or the like and is molded as a one-piece unit. 
     In another embodiment the housing comprises a two-piece unit with half sections that mate together along mounting flanges provided at the side edges of each of the half sections. The housing is made of a plastic material having at least semi-rigid characteristics with sufficient strength to withstand in operation substantial pressure differences between that of the interior air stream and the exterior ambient atmosphere. 
     In both embodiments the filter element is radially corrugated to provide axially extending corrugations spaced generally uniformly around the entire circumference of the filter element and extending substantially for its entire axial length. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further objects, features and advantages of the present invention will become apparent from the following detailed description of the best mode presently known to the inventor for making and using the invention, from the appended claims and from the accompanying drawings (which are to engineering scale unless otherwise indicated) wherein: 
     FIG. 1 is an exploded perspective view of a first embodiment of an air filtration device constructed for use with an automotive internal combustion engine in performing the method of the invention. 
     FIG. 2 is a perspective view of the improved filter element itself employed in the air filtration device of FIG. 1, looking from a point upstream of the filter leading end. 
     FIG. 3 is a side view of the air filter, housing and other components of the assembly shown in FIG. 1 shown in assembled condition and with the housing cut away to better illustrate the filter element therein. 
     FIG. 4 is a perspective view of a second embodiment encapsulating housing for use in the filter assembly of FIG. 1 in place of the housing shown in FIGS. 1 and 3. 
     FIG. 5 is a view similar to FIG. 3 but showing the modified housing of FIG. 4 in assembly with the remaining components of the air filtration device illustrated in FIGS. 1 and 2. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring in more detail to the accompanying drawings, FIG. 1 illustrates in exploded perspective simplified format a first embodiment of an air filtration device  8  in accordance with the invention that comprises in assembly the following components: 
     
       
         
               
               
             
           
               
                   
               
               
                 Reference 
                   
               
               
                 Numeral 
                 Name of Component 
               
               
                   
               
             
             
               
                 10 
                 Air filter element 
               
               
                 12 
                 Filter housing 
               
               
                 14 
                 Upstream gasket 
               
               
                 16 
                 Downstream gasket 
               
               
                 18 
                 Mounting plate/collar 
               
               
                 20 
                 Hose clamp 
               
               
                   
               
             
          
         
       
     
     Air filter element  10  is shown by itself in FIG. 2 in a view enlarged over that of FIG. 1, and also appears in side elevation in FIG.  3 . In accordance with one principal feature of the present invention, filter element  10  has a generally conical configuration made up of a perforate pointed nose section  22  that is divergent from its leading apex edge  24  that faces upstream into the air flow stream. Nose section  22  merges with a generally straight tapered conical mid-section  26  that is again divergent in the downstream direction relative to air flow. Mid-section  26  terminates at its maximum diameter at an apex junction  28  where it is integrally joined to an oppositely tapered trailing section  30  that in turn terminates at its downstream end in a radially outwardly extending mounting flange  32 . The entire axial length of filter  10  from nose  24  to flange  32  is perforate (air pervious) and radially corrugated, i.e., it is preferably made up of angularly evenly spaced corrugations each of generally V-shaped cross-section as schematically represented in FIGS. 1-3 by a root apex  34  and corresponding peak apex  36 . 
     As will be evident from the foregoing and as best seen in FIGS. 2 and 3, filter element  10 , instead of having a straight taper from nose  24  to its downstream exit end at the junction with mounting flange  32 , has a bulbous configuration reaching a maximum diameter at apex  28  which is located approximately two thirds of the axial length of filter element  10  downstream from the leading edge or nose  24 . Preferably, filter  10  is made of conventional cotton perforate filter media for essentially its entire axial length including the nose section  22 . 
     Mounting flange  32  of filter element  10  is imperforate and may be made separately from the conical sections  22 / 26 / 30  of the filter element and bonded to the downstream edge of the same via suitable adhesive material. Alternatively, flange  32  may be formed in the manufacture of the perforate conical corrugated sections  22 / 26 / 30  so as to be joined integrally with the trailing edge of the trailing conical section  30 , as described in more detail hereinafter. 
     In accordance with another principal feature of the present invention, filter housing  12  of the first embodiment device  8  is made of an imperforate flexible rubber material that offers a relatively high level of flexibility and shock resistance, and is primarily intended for use in naturally aspirated applications that typically have minimal pressure differentials between internal and ambient air pressure. The flexibility of housing  12  easily accommodates mounting variations encountered in vehicle installation of filtration device  8  when coupling to the mating elements in the vehicle, thereby readily accommodating such loose intake component location tolerances during factory installation of the filtration device. 
     Housing  12  comprises a cylindrical imperforate tubular wall inlet section  40  designed to telescopically receive the outlet end of the tubular conduit that is connected to a vehicle air intake scoop or the like, and is to be clamped on inlet  40  by hose clamp  20 . The downstream end of tubular inlet  40  is integrally joined to a generally straight taper conical imperforate wall section  42  divergent in the downstream direction. Wall section  42  terminates at its outlet end at a maximum diameter apex  44  where it is integrally joined to a convergent trailing imperforate wall section  46  that, at its downstream end, is joined to a radially outwardly extending annular mounting flange portion  48 . 
     Mounting collar  18  comprises a radially outwardly extending circular mounting flange portion  50  seamlessly joined either integrally or by a suitable adhesive to a flexible annular collar boot section  52  that terminates at its downstream end in an annular mounting rib  54  adapted to be sealably abutted to the inlet of the engine intake manifold port. Gaskets  14  and  16  are flat rings made of suitable conventional gasket material. Gasket  14  is dimensioned at its I.D. to encircle the outlet end of filter section  30  in assembly when held clamped between housing flange  48  and filter element flange  32 . Gasket ring  16  is clamped between filter flange  32  and collar flange  50  in assembly, and its I.D. is designed to match that of flange  50  and flange  32 , and likewise as to its O.D. A pair of headed fasteners  56  and  58  and cooperative threaded nuts  60  and  62  are inserted through associated mounting holes in flange  48 , gasket  14 , flange  32 , gasket  16  and flange  50  to thereby clamp these components of the filter device  8  in assembled operative relationship as shown in FIG.  3 . 
     In accordance with another one of the principal features of the present invention, the surface shape of filter element  10 , with its maximum diameter bulge located at apex  28 , provides a greater surface area than a straight tapered conical shape having the same entrance and exit diameters, thereby increasing the total surface area so that the total air flow capacity of the filter element is significantly increased. This bulbous surface shape and consequent increase in surface area exposed to air flow combine to provide less flow resistance to the air passing through the filter media, and hence greater overall flow capacity for the filter device. 
     In accordance with another feature of the present invention, housing  12  has an interior surface configuration which, although generally complimental to the exterior surface configuration of filter element  10 , (i.e., being bulbous and maximizing its diameter at apex  44  in general radial alignment with apex  28  of the filter element  10 ), nevertheless has a taper angle in wall section  42  that is slightly convergent downstream with the taper angle of media wall sections  22  and  26  of filter element  10 . Then, downstream of housing apex  44 , the trailing housing wall section  46  is convergent in the downstream direction. Note also that housing wall section  46  has a taper angle convergent with that of filter wall section  30 , with the incremental degree of convergence of the housing convergent with that of section  46  relative to filter section  30  being greater than that of the upstream housing section  42  relative to filter sections  22  and  26 . As will be evident from FIG. 3, nose  24  of filter element  10  is spaced sufficiently downstream from the outlet of tubular housing section  40  to maintain this complimentary surrounding convergent annular chamber relationship with housing  12 . 
     Due to this geometric complimental configuration between the perforate exterior surface of filter element  10  and the imperforate interior wall surface of housing  12 , the air flow entering from inlet tube section  40  into the generally conical expanding annular air space chamber  64  (defined between sections  22  and  26  of filter element  10  and wall section  42  of housing  12 ) is allowed to pass through the filter media throughout the axial extent of chamber  64 . The slightly convergent relationship of the housing wall section  42  relative to the wall section  22  and  26  of filter  10  tends to maintain the air pressure outside the filter element substantially constant as it travels axially even though the chamber volume is increasing because it is diverging, and even though air is being lost from this chamber by passage through the filter media in the downstream direction. This effect is augmented downstream of the maximum diameter apex  28 ,  44  travel point due to the convergent air chamber  66  and the increasing convergence of the housing downstream wall section  46  relative to the filter element downstream wall section  30 . 
     As is well known in the art, the volumetric mass air flow through an automotive air filter typically changes with engine rpm, and also pulsates in accordance with engine cylinder intake sequence cycles. This variable air flow typically causes changes in the interface incidence angles relative to the filter media surface of filter element  10  at different flow velocities. In accordance with a further feature of the invention, the foregoing geometrical variation between the exterior surfaces of the filter element  10  and the inside surfaces of housing  12  are specifically designed to accept multiple changes in flow direction under air flow velocity and pressure changes. The non-parallel cavity walls of the filter element  10  and housing  12  correct the path of the air flow during such fluctuation to thereby ensure maximum air flow at multiple velocities and interface angles, thereby greatly enhancing the operational efficiency of filter device  8 . Due to these features, filter device  8  accomplishes an increasing air flow and air velocity compared to prior art devices, while maintaining a high level of air filtration. In operation the air filtration device  8  of the invention offers a lower level of air deflection due to the foregoing unique geometrical shape that creates several thousand direct paths for the air to flow through the filter media without significant deflection. Additionally, the filter housing shape enhances proper flow direction and thereby makes it possible to achieve higher flow-through air velocities than conventional air filtration devices. For example, the filter element  10  when configured by way of example as shown in FIGS. 1-3 and as described hereinabove, provides an approximately 20% increase in surface area to thereby provide the potential for approximately 20% more air flow in cubic feet per minute through device  8 . This enhanced air flow capacity of filter device  8  also reduces the audible noise level associated with the air filtration device in operation because of the elimination of incorrect air to filter interface angles found in prior art devices. 
     Preferably filter element  10  is made from a layout on a flat sheet blank that has a maximum radius arc at the downstream peripheral edge and a minimum radius arc at the upstream peripheral edge that when unrolled, is similar to an unrolled tapered megaphone. The flat layout blank is then formed through cooperative meshing tapered forming dies that are suitably corrugated with a tighter pattern on the pointed end and a wider pattern on the exit end. When the sheet is rolled between these forming dies, the blank is progressively curved until the leading side edge is brought into registry with the trailing side edge to provide a generally conical shape in the overall form. These two side edges are suitably joined or seamed together. The corrugations are preferably V-shaped with rounded root and peak apices. The rolling dies can also be shaped to form the radially extending flange portion  32  of filter  10  as an integral downstream portion of the roll form. Rolling dies are, of course, suitably shaped to provide the finished bulbous configuration of the filter element illustrated in FIGS. 1-3. 
     The flexible rubber material of housing  12  offers a higher level of flexibility and shock resistance. This rubber based housing  12  is primarily used in a filter device  8  that is intended for naturally aspirated engine applications that typically have minimal negative internal air pressures relative to external ambient pressures. The flexibility of the rubber housing  12  makes it more easily adaptable to tolerance variations in the upstream and downstream mounting components of the vehicle to which it is to be attached. 
     The increased air flow capacity of unit  8  for filtering air is augmented by the streamlined shape of filter element  10  with its pointed nose  24  facing upstream so that the angle of incidence of the air stream is a very shallow angle relative to the exterior surface of filter element  10 . Hence, a maximum extent of volumetric air flow-through can be accommodated with a minimum noise level and with less pressure drop through the filter media, thereby further contributing to the operational efficiency of the filter device  8 . The increased surface area contributed by the bulbous shape and diametrical enlargement at the apex of the bulb provide less flow resistance and greater flow capacity in performance of the unit. The generally complimental shape of the confining interior surface of housing  12  also enhances air flow and decreases turbulence in the air stream, further enhancing efficiency. Air velocity in the air stream is thereby increased and hence the flow rate through the filter likewise is increased. Turbulence and eddies also are reduced in the air stream as it impinges the surface of the filter element. 
     The increasing convergence in annular chamber  66  between the downstream section  46  of housing  12  and section  30  of filter  10  tends to force the diminished volume of air through the filter and reduces the bounce-back or reversal effect which might otherwise occur absent this relationship. In other words, in terms of what is dynamically occurring in the air flow incrementally, axially in the downstream direction, as the air stream progressively goes through the filter media, the higher volumetric flow rate goes from annular chamber  64 , through the first and second conically divergent sections  22  and  26  of the filter media. Then the air stream remaining that flows back around and past apex  28  of filter  10  has less volume, but this is compensated for by the increasing convergence in the annular surrounding space of chamber  66  to thereby maintain force-through pressure in the air stream. The result of the effect of these compound convergent angles in the annular space flow chambers  64  and  66  defined between housing walls  42  and  46  and filter element  10  is to thereby get as much air through the filter as quickly as possible. In addition, the non-parallel cavities  64  and  66  between filter  10  and housing  12  operate to correct the path of the air flow during pressure fluctuations to maintain a more uniform angle of incidence for entry of the air stream through the filter media despite mass volumetric air flow rate variations as well as pulsating effects. In this manner, the geometrical variation between the surface of filter  10  and the inside surface of housing  12  are specifically designed to accept multiple changes in flow direction under velocity pressure changes. 
     It is to be noted that the volume of the chambers  64  and  66  on the scale shown in FIGS. 3 and 5 of the drawings is about 16 to 17% greater than the volume contained within filter  10 . However, this ratio may be increased somewhat up to say about 20% greater volume of chambers  64  and  66  than the volume of filter  10 . It is also to be understood that the geometric shape of housing  12 ,  70  is that of a venturi to achieve a pressure drop in the air filter of the housing, and the generally complemental shape of filter  10  enhances this effect while substantially reducing turbulence within the chambers  64  and  66 . 
     It is also to be understood that confining the filter  10  within the complemental housing  12  with its entrance duct  40  facilitates conducting an air flow stream from one of several sources. Thus housing  12 , in addition to enhancing the filtration performance of filter  10  while providing a protective enclosure for the same, also provides a convenient structure having sufficient strength to support the coupling or mounting via tubular inlet  40  to a variety of intake air duct configurations. Housing  12  with its tubular inlet  40  also provides a place to mount the typical mass air flow sensor associated with the typical electronic control unit (ECU) in an automotive installation. Conventional practice is to locate and mount such a mass air flow sensor downstream from an air filter. However in such locations the sensor is receptive to contamination from the oil swept by the filtered air stream from the oil coating conventionally provided on the filter media. This coating oil tends to migrate with the air stream off of the filter and then deposit onto the mass air flow sensor and thereby adversely affect the same. When this occurs it adversely alters the calibration of the mass air flow sensor, thereby causing a performance deterioration in the mass air flow sensor and its associated sensing and control system. However, with the strength, size and space provided by inlet  40  of housings  10  or  70  it is a relatively simple matter to provide a suitable mounting of a conventional mass air flow sensor unit in this tubular inlet where it is both housed and protected. Moreover, because the sensor is now upstream of the associated filter media  10 , it is not subject to filter oil contamination. For example, a mass air flow sensor unit of typical construction is generally made in a flat, thin planar form and may be dimensioned so as to have its transverse dimension sized for slip or press fit inside of tubular inlet  40  so as to be supported by the wall of the tubular inlet  40  while presenting a minimum obstruction to air flow by having its major plane coincident with the axis of inlet  40 . In such cases the exit sleeve of the feed duct to the filter unit would be sized to telescope onto the outside of inlet  40  and be held thereon by hose clamp  20 , as described previously. 
     From the foregoing description and accompanying drawings, it will now be apparent to those of ordinary skill in the art that the improved air filtration device of the present invention amply fulfills and accomplishes one or more of the aforestated objects of the invention and provides many features and advantages over the prior art. 
     Second Embodiment 
     FIGS. 4 and 5 illustrate a second embodiment of a housing  70  that can be substituted for housing  12  in the assembly of filter unit  8 . Housing  70  is a two-piece housing made up of identical but mirror image half sections  72  and  74 , each provided with a radially outwardly extending flange  76  extending axially along one of the side edges  78  of half section  74  and a similar flange  80  extending axially along and radially outwardly from the other side edge  82  of section  74 , as shown in FIG.  5 . Similar flanges  84  and  86  are provided along the side edges of the other half section  72  of housing  70  (FIG.  4 ). The edge flanges  76 ,  80 ,  84  and  86  are provided with suitable fastener mounting openings and  88  and  90  are fastened together with suitable fasteners (not shown). Housing  70  may be injection molded from suitable plastic composition material designed for automotive under-the-hood applications so as to be rigid or semi-rigid and have a high temperature resistance. Housing  70  thus has the capability to handle a higher level of internal air pressures, whether negative or positive, relative to ambient pressure, such as is encountered in supercharged applications. 
     Except for the nature of the plastic material versus the flexible rubber material, housing  70  and housing  12  have the same geometrical configuration, same function and same mode of operation in cooperation with filter element  10  as described hereinabove. 
     From the foregoing description and accompanying drawings, it will now be evident that the improved air filtration method and device of the invention offers many advantages and can be applied to internal combustion engines of various types, such as those used in automobiles and trucks as well as smaller engines used on motorcycles and small engine vehicles, as well as marine craft, jet skis and the like. Moreover, the principles of the present invention are applicable more generally to filtering a variety of different types of gaseous fluids and even liquid fluids with corresponding improved results relative to prior art methods and devices employed for these purposes.