Abstract:
A fluid filter has an outer case with a side wall, a closed first end wall, and a second end wall defining fluid inlet and outlet openings, as well as a filter cartridge received within the outer case. The filter cartridge includes a substantially cylindrical full flow filter element, providing for passage of a major portion of fluid entering the filter, and a substantially cylindrical bypass filter element, providing for passage of a minor portion of fluid entering the filter and disposed radially within and surrounded circumferentially by the full flow filter element. By way of the particular fluid filter configuration disclosed, a simple alternative to known filters having full flow and bypass filters located in common housings is provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    A simple alternative to known filters having full flow and bypass filters located in common housings is described and claimed. 
         [0003]    2. Description of Related Art 
         [0004]    Known filter systems for automotive or other applications commonly utilize one of two full flow filter and bypass filter configurations. One such configuration is an arrangement having two separate filtering systems, with a full flow system, which may include more than one filter, depending on flow requirements, and a bypass filter system, which processes only a small percentage of the full fluid volume. In such a configuration, an in-line, series approach is often utilized, with a full flow filter provided downstream of a bypass filter. These systems typically introduce additional costs and components for the automotive assembler and service industry to handle and manage. Vehicle weight is increased as well. U.S. Patent application publication 2008/0078716 to Farmer discloses one such in-line, series approach to filtering. 
         [0005]    Evolutions of this configuration include systems having filters with full flow and bypass media stacked upon each other in the same filter housing. Examples of filters having stacked media include apparatuses disclosed by U.S. Patent application publication 2005/0252838 to Fisher and U.S. Pat. Nos. 5,447,627 to Loafman et al., 6,319,402 to Schwandt et al., and 6,350,379 to Roll et al. These sorts of arrangements, however, can reduce the overall capacity for the full flow and bypass filter media. 
         [0006]    Further developments have provided increased filtering capacity in the same or smaller footprint, while also offering high efficiency bypass filtration to “polish” the fluid system and provide integral soot filtration, by fitting bypass filters concentrically within full flow filters. U.S. Pat. Nos. 6,666,968 to Smith et al., 6,787,033 to Beard et al., 7,014,761 to Merritt et al., and 7,090,773 to Meddock et al. provide examples of such developments. The disclosure of each of these U.S. patents is incorporated herein by reference in its entirety as non-essential subject matter. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a simple alternative to known filters having full flow and bypass filters located in common housings. According to the invention, a fluid filter includes an outer case with a side wall, a closed first end wall, and a second end wall defining fluid inlet and outlet openings, and a filter cartridge received within the outer case. The filter cartridge includes a substantially cylindrical full flow filter element, providing for passage of a major portion of fluid entering the filter, and a substantially cylindrical bypass filter element, providing for passage of a minor portion of fluid entering the filter and disposed radially within and surrounded circumferentially by the full flow filter element. 
         [0008]    Also included as parts of the cartridge are a first annular end cap, which has a first solid wall to which adjacent first ends of both the full flow filter element and the bypass filter element are secured and which surrounds an inlet to an inner bypass filter volume, and a second annular end cap, including a second solid wall adapted to surround a filter discharge opening. A second end of the full flow filter element is secured to the second solid wall. 
         [0009]    The cartridge further includes a bypass filter end cap, disposed at an intermediate location between the first and second annular end caps, to which a second end of the bypass filter element is secured. The bypass filter end cap may be formed by either a solid disc closing off the second end of the bypass filter element or by a cap structure permitting one way fluid flow therethrough for pressure relief. By way of the fluid filter configuration claimed, fluid flow into the bypass filter volume occurs through a space defined between the closed first end wall of the outer case and the first annular end cap, and through the inlet to the inner bypass filter volume surrounded by the first annular end cap. 
         [0010]    In the illustrated fluid filter configuration, the first annular end cap includes radially inner and outer flanges depending from the first solid wall to facilitate positioning of the full flow and bypass filter elements. The second annular end cap includes a radially outer flange depending from the second solid wall to facilitate positioning of the full flow filter element. 
         [0011]    A spacer acts between the solid wall of the first annular end cap and the closed end wall of the outer case. 
         [0012]    Finally, the filter may be provided with a perforated support tube located around a surface of at least one of the full flow and bypass filter elements. In the particular embodiment of the invention illustrated, that surface can be a circumferential outer or a circumferential inner surface. 
         [0013]    A design according to the present invention, in a simplified manner, incorporates maximized full flow and bypass media surface areas while housing the bypass medium within an area that is commonly located downstream of the full flow medium. Media for both full flow and bypass flow are bonded or otherwise secured to a common, open end cap, and both media are supported by center tubes to resist crushing of the elements in cold weather startup conditions. The bypass medium is bonded to either a closed end cap or an end cap incorporating a conventional relief valve to allow flow to bypass both filters if they are clogged up or if the system is over-pressurized due to pressure regulator failure or cold temperature start up. 
         [0014]    The customer will receive a price benefit resulting from the provision of a less complex system and elimination of extra material from the filtering system. Reduction of required storage space also results from reduced inventories of multiple filters conventionally needed with separate in-line media configurations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic, cut away perspective view of a fluid filter showing flow paths according to the present invention. 
           [0016]      FIG. 2  is a more detailed, side sectional view of a fluid filter according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    The liquid filter  10  shown in  FIG. 1  includes an outer case  12  composed of an approximately cylindrical side wall  14 , a top formed by an end wall  16 , and an annular end wall  18  forming part of a bottom assembly  20 . The terms “fluid,” “liquid,” and “oil” will be used interchangeably throughout this description, but it should be understood that it is possible to use the filter  10  of the invention in connection with fluids or liquids other than oil when desired. The annular wall  18  is provided with an oil filter discharge opening  24  as well as a hole, slot, perforation, or other such opening  22 , or a plurality of holes, slots, perforations, or other such openings, circumferentially surrounding the discharge opening. The discharge opening  24  is typically threaded for connection to a correspondingly threaded fitting attached to or forming part of a vehicle engine, so that oil leaving the filter  10  through the discharge opening enters the engine oil circulating system. 
         [0018]    A filter cartridge  26  disposed within the outer case  12  is composed of a substantially cylindrical full flow filter element  28 , a substantially cylindrical bypass filter element  30  surrounded circumferentially by the full flow filter element, a first, annular, top end cap  32 , a second, annular, bottom end cap  34 , and a bypass filter end cap  33 . The first end cap  32  shown in  FIG. 1  is formed by a solid, substantially flat wall  36  having a radially inner flange  38  and a radially outer flange  40  depending from that flat wall. The flanges  38  and  40  are shown as oriented in the same direction, and, in combination with the solid wall  36 , act to provide the first end cap  32  with an approximately “C” or “U” shaped cross-section. Adjacent first ends of both the full flow filter element  28  and the bypass filter element  30  are bonded or otherwise secured to the flat wall  36  of the first end cap  32 . The flanges  38  and  40  facilitate initial positioning of the bypass and full flow filter elements  30  and  28 , respectively, with respect to the end cap  32 . 
         [0019]    The second end cap  34  of the filter cartridge  26 , as shown, is formed by a solid, substantially flat wall  42  having both a radially inner flange  44  and a radially outer flange  46  depending from that flat wall. The flanges  44  and  46  shown are oriented in opposite directions, and, in combination with the solid wall  42 , act to provide the bottom end cap  34  with an approximately “Z” shaped cross-section. The flange  46  facilitates initial positioning of the full flow filter element  28  on the second end cap  34 . The flange  44  acts as a spacer between the solid wall  42  and the annular end wall  18  of the outer case, and assures that a clearance between the openings  22  and the solid wall  42  is maintained so as to permit fluid to flow in a way to be described. The spacer could alternatively be formed as part of the end wall  18  of the bottom assembly  20  rather than as part of the bottom end cap  34  of the filter cartridge. In this case, the second end cap  34  would have an approximately “L” shaped cross-section. A second end of the full flow filter element  28  is bonded or otherwise secured to the solid wall  42 . 
         [0020]    The bypass filter end cap  33 , shown in  FIG. 1  in its simplest configuration, can be formed by a solid disc, bonded or otherwise secured to a second end of the bypass filter element  30  and closing off an end of the inner bypass filter volume  35  as illustrated. In a preferred embodiment, the end cap  33  may have a relief valve incorporated therein, as shown in  FIG. 2  and described below, to permit oil to flow around both the full flow filter element  28  and the bypass filter element  30  if those elements  28  and  30  are clogged or the system becomes over-pressurized due to pressure regulator failure or cold temperature start up. 
         [0021]    As illustrated in  FIG. 1 , the circumferential inner side or surface of the full flow filter element  28  is provided with a perforated support tube  50  composed of a suitably rigid plastic, metal, or metal alloy material. Similarly, as illustrated, the circumferential inner side or surface of the bypass filter element  30  is provided with a perforated support tube  52 , again composed of a suitably rigid plastic, metal, or metal alloy material. The tubes  50  and  52  may be formed, for example, by joining ends of a sheet of support material together at an appropriate joint or seam after cutting the sheet to an appropriate length. One such joint or seam  54  is shown in  FIG. 1 . 
         [0022]    Fluid flow paths represented in  FIG. 1  will now be described. During engine operation, liquid enters the filter  10  through the openings  22 , passes through the space delimited by the flange  44  between the underside of the end cap  34  and the annular end wall  18 , and travels into an annular volume  60  defined between an outer circumferential side of the full flow filter element  28  and an inner circumferential side of the outer case side wall  14 . A major portion of the liquid entering the filter  10  will pass through the full flow filter element  28  in a manner that is schematically represented by an arrow “A,” and will thus be subjected to coarse filtering. However, a minor portion of the liquid entering the filter  10  will pass entirely through the annular volume  60 , into a volume  62  defined between the end wall  16  and the top end cap  32 , through an inlet to the inner bypass filter volume  35  that, as illustrated, is defined by the radially inner end cap flange  38 , and into the inner bypass filter volume  35  in a manner that is schematically represented by an arrow “B.” The cap  32  is kept spaced from the end wall  16  by a guide element or guide elements, or a spring, as will become apparent from the description of  FIG. 2 . Such a guide element or spring is not shown in  FIG. 1 . 
         [0023]    The fraction of liquid entering the filter  10  that passes into the inner bypass filter volume will, of course, depend on a number of parameters, including the relative porosities of the full flow filter element  28  and the bypass filter element  30 , although, as mentioned, commonly, about 10 percent of the liquid passes into the volume  35  in the manner described. 
         [0024]    After entering the inner bypass filter volume  35 , the fraction of liquid that does not pass through the full flow filter element  28  proceeds through the bypass filter element  30 , in a manner that is schematically represented by an arrow “C,” and is subjected to the fine filtering process provided by the bypass filter element. The liquid flow passing through the full flow filter element  28  and the liquid flow passing through the bypass filter element  30  both exit the liquid filter through the discharge opening  24  in the annular wall  18 . 
         [0025]    In the arrangement shown in  FIG. 2 , many features are the same as or similar to features described in connection with the configuration shown in  FIG. 1 , and an unnecessary, repetitive description of those features is not provided here. Any feature shown in  FIG. 2  that is essentially the same as a corresponding feature shown in  FIG. 1  is indicated by the same reference number used in  FIG. 1  but with the letter “a” added. The arrangement shown in  FIG. 2  includes a filter cartridge  26   a  having a full flow filter element  28   a  surrounding a bypass flow filter element  30   a , a first, annular, top end cap  32   a , a second, annular bottom end cap  34   a , and a bypass filter end cap  33   a .  FIG. 2  shows the top end cap  32   a  as having guide elements  37   a  formed thereon or attached thereto. These guide elements  37   a  help to guide the filter cartridge  26   a  into the outer case  12   a  as the filter  10   a  is being assembled, and act to keep the cap  32   a  spaced from the end wall  16   a  after the filter is assembled, as mentioned in the description of  FIG. 1 . Inner and outer flanges  38   a  and  40   a  of the solid end cap wall  36   a  are also indicated in  FIG. 2 . In the arrangement shown in  FIG. 2 , the perforated support tube  52   a  is provided on the circumferential outer side of the bypass flow filter element  30   a  rather than on the circumferential inner side thereof. 
         [0026]    The bottom assembly  20   a  of the arrangement shown in  FIG. 2  includes an annular wall  18   a  having fluid inlet openings  22   a  circumferentially surrounding a discharge opening  24   a . As with the configuration illustrated in  FIG. 1 , the second, annular bottom end cap  34   a  is formed by a solid wall  42   a  having both a radially inner flange  44   a  and a radially outer flange  46   a  extending from the wall  42   a . An end  45   a  of the inner flange  44   a  is bent over radially inwardly so that it can rest on an axial end  70   a  of a tube  72   a  defining the discharge opening  24   a . Abutment of the end  45   a  and the axial end  70   a  operates, similarly to abutment of the flange  44  and the wall  18  in the arrangement shown in  FIG. 1 , to assure that a clearance between the openings  22   a  and the wall  42   a  is maintained to permit the necessary fluid flow. 
         [0027]      FIG. 2  also illustrates the seal structure surrounding the discharge opening  24   a  that cooperates with an adjacent part of a vehicle engine or engine fitting. The seal structure shown is composed of a gasket  80   a  and a retainer  82   a  that is rolled onto or otherwise secured to the side wall  14   a  of the outer case  12   a . The gasket  80   a  may be of a suitable elastomeric material, while the retainer  82   a  may be of a suitable metallic or plastic material. 
         [0028]    The end cap  33   a  is shown with a relief valve incorporated therein. As mentioned above, such a relief valve permits oil to flow around both the full flow filter element  28   a  and the bypass filter element  30   a  if those elements are clogged or the system becomes over-pressurized due to pressure regulator failure or cold temperature start up. The end cap  33   a , in this configuration, defines a valve seat with a central opening therein, which is closable by a disc or plate, a piston, a ball, or some other appropriate valve element  90   a . The valve element  90  is biased by a spring  92   a  toward the valve seat and into a position in which it closes the central opening in the cap  33   a . In this manner, the relief valve permits one-way fluid passage through the end cap  33   a  out of the inner bypass filter volume  35   a , but precludes return flow from the full flow filter volume  96   a  back into the inner bypass filter volume  35   a . In the arrangement shown, the spring  92   a  is retained in position relative to the end cap  33   a  by a retainer cage  94   a  mounted on the end cap  33   a . Other relief valve configurations could be used if desired. In other respects, flow proceeds through the filter  10   a  shown in  FIG. 2  in the same way as through the filter  10  shown in  FIG. 1 . 
         [0029]    The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.