Abstract:
An engine is equipped with a filter assembly with a structure that prevents assembly without a filter element in place. In addition, one can choose between a cleanable metallic screen filter element or a replaceable conventional pleated paper filter element. Depending upon the circumstances, the engine user can switch between the two different filter types throughout the working life of the engine.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates generally to screen filter assemblies, and more particularly to a cleanable filter assembly for an engine that may be substituted in place of a conventional paper filter element.  
       BACKGROUND  
       [0002]     Filter assemblies for filtering liquids such as engine oil, hydraulic oil and fuel are well known in the art. A fuel filter assembly is installed in the engine fuel lines to remove grit and other contaminants from the fuel or other fluids to increase the service life of the fluid system and associated components. Disposable or “throw-away” type of fluid filters, such as those including paper filter elements, are also known in the art. For instance, co-owned U.S. Patent Application Publication No. U.S. 2003/0019809 shows a fuel filter assembly that includes a disposable paper filter element. Depending on the application, the paper filter element should be replaced on some predetermined frequency, such as every so many hundreds of hours of engine operation. Problems can sometimes arise in instances where the filter is actually in need of replacement before the prescribed time period due to excessive filtering of unexpectedly dirty fuel. In addition, problems can sometimes arise in instances where a replacement filter element may not be readily available.  
         [0003]     Another reoccurring problem that sometimes occurs with prior art filter assemblies is when a filter assembly is reattached to an engine with the filter element mistakenly omitted. In other words, the owner of the vehicle and/or the maintenance technician may dispose of a used filter element, but unknowingly fail to replace the filter element, or replace the filter element with a substandard will-fit filter. Thus, in some prior art fuel filter assemblies, a threaded reusable housing attaches to a filter head, but it is possible to attach the housing to the head without the correct replacement filter installed, or reattach without any filter installed. Those skilled in the art will appreciate that operation of a fluid system without a filter in place, or without the correct filter element, can jeopardize the integrity of the filtering system, possibly resulting in serious consequences, such as engine damage and/or fuel injector clogging.  
         [0004]     The present invention is directed to overcoming one or more of the problems identified above.  
       SUMMARY OF THE INVENTION  
       [0005]     In one aspect, a filter assembly includes a center support having a filter head attachment adjacent one end, a bowl attachment adjacent an opposite end, and a plurality of radial openings located between the ends. A metallic screen filter element is mounted around the center support.  
         [0006]     In another aspect, a method of servicing a filtration portion of a fluid system for an engine includes a step of detaching a center support from a filter head and a bowl. If a paper filter element is mounted on the center support, then a new filter element is substituted for the paper filter element. If a metallic screen filter element is mounted on the center support, then the metallic screen filter element is washed. The center support is then reattached to the bowl, and to the filter head. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a schematic view of a pair of engines, one having a metallic screen filter element and the other having a paper filter element;  
         [0008]      FIG. 2  is a perspective view of a bowl and center support for a filter assembly according to the present invention;  
         [0009]      FIG. 3  is an enlarged partial sectioned perspective view of one end of a screen filter element assembly according to one aspect of the present invention;  
         [0010]      FIG. 4  is an enlarged sectioned partial perspective view of a screen filter element assembly according to another aspect of the present invention;  
         [0011]      FIG. 5  is an enlarged sectioned partial perspective view of a filter element assembly according to still another aspect of the present invention; and  
         [0012]      FIG. 6  in an enlarged sectioned partial perspective view of a screen filter element assembly according to still another aspect of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0013]     Referring to  FIG. 1 , a pair of engines  10  each include a fuel filter assembly  12 . The engines are identical except that the filter assembly  12  on the left includes a screen filter element  20 , whereas the engine on the right has a paper filter element  74 . The present invention allows for an engine buyer or/and user to choose between a washable screen filter element  20  or a replaceable paper filter element  74 . Preferably, the filter assembly of the present invention is a pre-filter for removing relatively large particulate matter. In other words, an engine according to the present invention would likely include a pre-filter according to the present invention, and later down stream include a fine filter for removing small particles so that only finely filtered fuel is injected into the engine. When in operation, fuel enters filter assembly  12  at an inlet  30 , passes through the filter element  20 ,  74  and then exits the filter assembly at an outlet  32  for later supply to a combustion portion of engine  10  in a conventional manner.  
         [0014]     Each filter assembly  12  includes a filter head  14 , a bowl  16 , a center support  18  and a filter element  19 , which can either be a screen  20  or a pleated paper filter element  74 . Center support  18  is shown as a center tube which is preferably nonmetallic and formed from rigid polymer material to include a plurality of radial openings  29 . Center tube  18  includes a head attachment end  21  that includes features to facilitate attachment to filter head  14 . In this illustrated embodiment, head attachment end  21  includes internal threads  22  that mate to external threads  24  on a threaded stud portion of filter head  14 . Those skilled in the art will recognize that any suitable attachment structure could be substituted for the threaded attachment. Center tube  18  also includes a bowl attachment end  33  with a female locking mechanism  38  that mates to a male locking member  36  that is attached to, and positioned inside of, bowl  16 . Although center support  18  is shown as a tube, those skilled in the art will appreciate that any center support having a filter head attachment located at one end and a bowl attachment located at an opposite end could fall within the intended scope of the present invention. For instance, the two attachment ends could simply be separated by a plurality of posts or the like. Although not preferred, the opposite attachment ends could be supported by the filter element itself. In any event, by utilizing the illustrated structure, the bowl  16  cannot be mated to the filter head  14  without center support  18  being present. Preferably, the filter element  19  is permanently affixed to the center support in some suitable manner. This aspect of the invention prevents the filter head assembly  12  from being inadvertently reassembled without a filter element in place. Nevertheless, the invention also contemplates a structure in which the center support can be disconnected from the filter element.  
         [0015]     Referring in addition to  FIG. 2 , the male/female locking structure that allows the center support  18  to be attached to the bowl  16  is illustrated disconnected from one another. Bowl  16  is preferably constructed from a rigid polymer material that can be clear or opaque, depending upon the filter application. The open end of bowl  16  has an annular sealing groove  27  that receives an O-Ring seal  28 . The opposite end may include a valve to facilitate evacuation of water trapped in the filter assembly  12 . As seen in  FIGS. 1 and 2 , the O-Ring  28  prevents leakage between filter head  14  and bowl  16 . By preferably utilizing a nonmetallic center tube or support  18  along with a nonmetallic bowl  16 , one potential source of undesirable metal particles or other contaminants may be prevented from entering the fluid system. Bowl  16  is preferably molded to include a male stem  37  that includes a male locking member  36 . Male locking member  36  is preferably keyed to be received in a similar shaped opening toward the bowl attachment end  33  of center support  18 . Center support  18  is attached to bowl  16  by mating the male locking member  36  with the female locking mechanism  38  until the male stem  37  engages tangs  34 . After being rotated through an angle of 90 degrees, ledges  35  prevent separation of the center support  18  from bowl  16 . Preferably, a stop surface formed adjacent tangs  34  prevent the bowl from being rotated beyond the 90 degree rotation lock position. The bowl is locked axially in place until the ledges  35  are rotated back into alignment with the keyed opening of the female locking mechanism  38 .  
         [0016]     In the prior art filter assembly  12  shown in the right side of  FIG. 1 , the filter element assembly  19  includes a conventional paper filter element  74  attached between end caps  72  and  75 . End caps  72  and  75  are also attached via grooves  73  and  76  to center support  18  in a conventional manner, such as via adhesives, sonic welding, overmolding techniques or any other suitable manner known in the art. The filter element assembly  12  shown in the left hand side of  FIG. 1  includes a filter element assembly  19  that includes a metallic screen mesh tube  20  that is mounted between end caps  40  and  42 . As best shown in  FIG. 3 , end caps  40  and  42  are preferably plastic and are overmolded to include an annular groove  55  that receives the annular edge of metallic screen  20 . The end cap  42  can be attached to center support  18  in any suitable manner, such as by sonically welding an inner surface  56  of the end cap to an outer surface or end of center support  18 . Likewise, the end cap  40  can be attached to the opposite end  41  of center support  18  in a like manner. In the preferred embodiment, screen  20  is a metallic mesh that can be coated with a suitable hydrophobic coating, such as Teflon, to assist in separating water from fuel, if the filter assembly is being used as a fuel filter as in the illustrated embodiments. In a preferred embodiment, the screen mesh would be at least a 40 micron mesh, which would be suitable for use as a pre-filter in a fuel system for a diesel engine. In the preferred versions of the invention, the filter element assembly  19  is irreversibly attached to the center support  18 .  
         [0017]     Referring to  FIG. 4 , an alternative embodiment of the present invention includes a snap attachment of the filter element assembly  119  to the center support  118 . In particular, an end cap  142  is overmolded around screen  120  to include an annular groove  155  that receives the annular end of screen  120 . In addition, the end cap  142  includes an annular groove  145  that receives an annular seal  146  that sealingly engages the outer surface  143  of center support  118 . Finally, end cap  142  is molded to include an annular protrusion  143  that snaps into an annular indentation  122  formed on the outer surface of center support  118 . Annular groove  142  preferably has a locking action that preferably inhibits later disengagement of the filter element  119  from the center support  118 . Those skilled in the art will appreciate that the structure of  FIG. 4  could be blended with the structure of  FIG. 3  such that the assembly process initially slides the filter element assembly  119  onto a center support  118  until the annular protrusion  143  comes in locking engagement with annular groove  122 . Thereafter, the other end cap, which could have a structure of the type shown in  FIG. 3  is sonically welded to the center support to both complete the attachment and to seal against leakage between the inner surface of the end cap and the outer surface of the center support.  
         [0018]     Referring now to  FIG. 5 , still another attachment strategy is illustrated. In this embodiment, a rubber end cap  242  is over molded to include a groove  246  that receives an annular end  243  of center support  218 , and a second groove  247  that receives the annular end of metallic screen  220 . By appropriately sizing the grooves, the respective center support  218  and metallic screen  220  can be press-fit attached to the end cap  242 . Alternatively, the end cap could be overmolded around both of the center support  218  and screen  220 . As shown in  FIG. 1 , center support  218  includes internal threads  22  that allow for attachment to the filter head  14 .  
         [0019]     Referring now to  FIG. 6 , still another embodiment of the present invention includes an end cap  342 , which could be made from any suitable elastomer, that includes a plurality of sealing protrusions  346  that engage the outer surface  343  of center support  318 . Like a couple of the previous embodiments, end cap  342  is over molded to include a groove  355  that allows for attachment to one end of metallic screen  320 . In this embodiment, the filter element assembly  319  is slid onto the outer surface of center support  318 , and thus may be later separated to help facilitate cleaning.  
       Industrial Applicability  
       [0020]     The present invention allows an engine buyer to choose between a fuel filter assembly with a replaceable paper filter element or a cleanable metallic screen filter element according to the present invention. In addition, and users of the engine can, during the life of the engine, substitute a washable screen filter element assembly  19  according to the present invention for a used paper filter element  74  at time of servicing. For instance, at time of servicing, an engine having a paper filter element that is in need of replacement could either have another paper filter element installed or have a washable filter element according to the present invention installed. If the engine already has a metallic screen filter element according to the present invention, the filter element can be washed in a conventional manner and then reinstalled for filtering until the next scheduled maintenance.  
         [0021]     In the preferred embodiment, the filter assembly  12  is assembled by first securing a screen filter element  20  to a center support  18  in a conventional manner, such as one of the ways illustrated before. Preferably, the screen filter element  20  comes preassembled as a filter element assembly  19  with the center support  18  permanently attached thereto. The filter element assembly  19  is then advanced over the male locking stem  37  of the bowl and then twisted to its locked position as shown in  FIG. 1 . Next, the bowl and filter element subassembly is mated to the filter head  14  by inserting the threaded stud  26  into the open end of center support  18 . Next, the subassembly is rotated with respect to filter head  14  so that the internal threads  22  engage the external threads  24 . The subassembly is then rotated until the bowl  16  advances into the filter head sufficiently far so that the O-Ring  28  is sealingly engaged between the outer surface of bowl  16  and the inner surface of filter head  14  as shown in  FIG. 1 . When properly coupled, the bowl  16  cannot be actually removed due to the presence of the stopping mechanism that engages the keyed male locking member  36 . This same feature also allows for the subassembly of the bowl  16  and filter element assembly  119  to be threadably attached to the filter head.  
         [0022]     The present invention is advantageous in that it gives an engine buyer or user a choice between a replaceable filter element or a cleanable and reusable filter element. The washable metallic screen filter element of the present invention can be preferred in some applications, such as use in remote locations where replacement filters are not available and/or fuel quality is relatively poor in that it may include an excessive amount of contaminants. In such situations, the filter element can be quickly disengaged from the filter head washed and replaced even when a heavily contaminated fuel source is used. In addition, the filter element can be quickly cleaned and reused over the life of an engine to save on cost and promote maintaining a clean fuel supply to the engine.  
         [0023]     It should be further understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present invention in any way. Thus, those skilled in the art will appreciate that other aspects, objects, and advantages of the invention can be obtained from a study of the drawings, the disclosure and the appended claims.