Abstract:
A fluid filter assembly having a relief valve for visually indicating when a filter element may be replaced. The fluid filter assembly of the present invention provides a vertical, transparent housing having a fluid inlet for communicating a fluid into the housing and a fluid outlet for communicating fluid downstream of the housing. A filter element is disposed within the housing between the fluid inlet and the fluid outlet for filtering the fluid.

Description:
[0001]     The following patent application is a continuation of U.S. patent application Ser. No. 10/301,946, filed Nov. 22, 2002, which is a continuation of U.S. patent application Ser. No. 09/800,982, filed Mar. 7, 2001, which is a formalization of Provisional Patent Application Ser. No. 60/220,540, filed Jul. 25, 2000. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to fluid filters, and more particularly, a fluid filter having a pressure relief valve to provide an accurate visual indicator as to the remaining life of a filter element.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is well known to utilize fuel filter assemblies to filter fuel for a combustible engine of a motor vehicle. Such fuel filter assemblies comprise a variety of different orientations of the fuel filter assembly. For example, it is known to utilize sideways, downwardly, and upwardly mounted canisters having a paper filter media enclosed in the canister. With respect to upwardly mounted fuel assemblies, prior art filtration devices have been known to draw fuel into the filter assembly by use of a pump on the outlet side of the filter assembly. The fuel is directed downward into a lower chamber of the filter assembly wherein the fuel flow proceeds upward into an upper filter chamber of the filter assembly. The fuel may then be contained and sealed by a transparent filter cover or closure and a filter mount which may separate the lower chamber from the upper chamber.  
         [0004]     Within the filter chamber of the filter assembly, the filter assembly may provide a filter canister comprised of a filter media circling a central filter tube that is contained by filter end caps at the top and bottom of the filter media. The end caps are sealed to the edges of the filter media to preclude any possible leak paths at the ends of the filter canister. The filter media typically comprises a porous paper material that may be pleated or concentrically wound so as to direct the fluid through the filter media. The filter media removes and retains undesirable contaminants within and on the media.  
         [0005]     As fluid enters the filter chamber, the fuel level rises and passes through from the outside to the inside of the filter media. The fuel then flows downward into a central passage located along the central axis of the canister. The central passageway is in communication with a fuel outlet wherein the fuel passes outwardly from the filter assembly.  
         [0006]     During the filtering process, the fuel is either drawn into the filter chamber by a vacuum or pushed into the filter chamber by pressure until the fuel finds a path through the filter media. As the fuel flows through the filter, dirt and other contaminants larger than the porous openings in the filter media, are trapped and retained by the filter media. These contaminants plug or clog the porous holes in the filter media and restrict or close the paths used by the flowing fuel. The fuel is then forced to seek other open and less restrictive flow openings which are available above the level of the fuel by climbing the height of the filter and accessing the clean areas of the filter media. This process of clogging and climbing continues until the filter media is completely immersed in the flowing fuel.  
         [0007]     Even though the filter media may be completely immersed in the flowing fluid, the incoming fuel continues to pass through the filter media. It is not until the filter media becomes greatly clogged that the filter media needs to be replaced. This is a problem since the user generally views the height of the fuel in the filter chamber to see if the filter media is clogged. If the filter media is completely immersed in fuel, the user generally believes that the filter media needs to be replaced. Therefore, this type of system may lead to premature replacement of the filter media.  
         [0008]     It would be desirable to provide a fuel filter assembly that provides an accurate indication as to the remaining usefulness of the filter media.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention provides a fluid filter assembly that provides an accurate indication of the remaining usefulness of a filter element. The present invention provides a vertical, transparent housing having a fuel inlet for communicating fluid into the housing and a fluid outlet for communicating fluid downstream of said housing. A filter element is disposed within the housing between the fluid inlet and the fluid outlet for filtering the fluid. A means for maintaining and relieving a predetermined level of pressure across the filter element provides an accurate visual indicator as to whether the filter element needs replacement.  
         [0010]     Preferably, the maintaining and relieving means provides a divider that is connected to the filter element and extends between a housing wall and an unfiltered side of the filter element. The divider divides the housing into an outer region and an inner region, wherein the outer and inner regions are in communication at a lower portion of the housing. A relief valve is in communication with a filtered side and the unfiltered side of the filter element and is located in the top of the filter element in the outer region of the housing. The relief valve opens when the pressure across the filter element exceeds the predetermined pressure level thereby raising the level of fluid in the outer region of the housing and indicating that the filter element needs replacement. A segment of filter media may be adjacently mounted to the relief valve to filter any unfiltered fluid that passes through the relief valve to the filtered side of the filter element.  
         [0011]     Alternatively, the maintaining and relieving means may provide a restrictive filter media integrally connected to the filter element. The restrictive filter media prevents the flow of fluid through the restrictive filter media until the pressure across the filter element reaches the predetermined pressure level thereby causing the fluid in the housing to rise and indicating that the filter element needs replacement. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The description herein makes reference to the accompanying drawings wherein like referenced numerals refer to like parts throughout several views and wherein:  
         [0013]      FIG. 1  is a schematic drawing showing the fluid flow path and the normal rising fluid path of a prior art fuel filter assembly.  
         [0014]      FIG. 2  is a schematic drawing showing the rising fluid level in the fluid filter assembly of the present invention.  
         [0015]      FIG. 3  is a schematic drawing showing a segment of filter media being utilized above a relief valve of the present invention.  
         [0016]      FIG. 4  is a schematic drawing showing a segment of filter media being utilized underneath the relief valve of the present invention.  
         [0017]      FIG. 5  is a schematic drawing of a hang down fluid filter assembly of the present invention.  
         [0018]      FIG. 6  is a schematic drawing showing a restrictive media being utilized as a relief valve in the fluid filter assembly of the present invention.  
         [0019]      FIG. 7  is a bottom view of the filter element of the present invention.  
         [0020]      FIG. 8  is a sectional view of the filter element of the present invention taken in the direction of arrows  9 - 9  in  FIG. 8 .  
         [0021]      FIG. 9  is an exploded view of the relief valve shown in the top of the filter element of the present invention.  
         [0022]      FIG. 10  is a sectioned perspective view of the relief valve shown in the top of the filter element of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]     Referring to the drawings, the present invention will now be described in detail with reference to the preferred embodiment.  
         [0024]      FIG. 2  shows a fluid filter assembly  10  of the present invention in its preferred form. The fluid filter assembly  10  is best suited for filtering and processing diesel fuel, but the fluid filter assembly  10  may also be utilized with other fluids, such as gasoline, oil, water, antifreeze, etc. The fluid filter assembly  10  is mounted vertically upright and provides a closed housing  12 , a lower fluid storage chamber  16 , and an upper filter chamber  17 . A fluid inlet  14  is in communication with the lower fluid storage chamber  16 , which is in communication with the upper chamber  17  through a passageway  15 . A filter element  20  is housed within the upper chamber  17  of the housing  12  for filtering a fluid  19  to a fluid outlet  18 . The fluid inlet  14  delivers fluid  19  into the housing  12  so that the fluid  19  may pass through the filter element  20  and out the fluid outlet  18 . A relief valve  38  mounted in the top of the filter element  20  opens when the pressure level across the filter element  20  reaches a predetermined level. A relief valve filter  40  filters fluid  19  that passes through the relief valve  38 . Preferably, the relief valve filter  40  is mounted below the relief valve  38 , as shown in  FIG. 4 , but alternatively, the relief valve filter may be mounted above the relief valve  38 , as shown in  FIG. 3 .  
         [0025]     To filter contaminants from the fluid  19 , the filter element  20  is fabricated from a pleated porous paper material. The filter element  20  encircles a central filter tube  22  and is contained by a top and bottom end cap  24 ,  26 , respectively, as seen in  FIGS. 2 and 7 - 11 . The top and bottom end caps,  24 ,  26  are sealed to the edges of the filter element  20  to preclude any possible leak paths at the ends of the filter element  20 . A flexible seal  28  is provided on the bottom end cap  26  of the filter element  20  to create a seal between the central filter tube  22  and an inner core  43  of the filter element  20  and ensure that unfiltered fluid  19  does not leak into or escape through the fluid outlet  18 . The filter element  20  is preferably pleated or concentrically wound but may also be arranged in any of the ways known to one familiar with filtration construction so as to direct the fluid  19  through the filter element  20 . In addition, the filter element  20  may be fabricated from a hydrophobic filter material to filter out water from the fluid  19 .  
         [0026]     The portion of the housing  12  between the filter element  20  and an outer wall  37  of the upper filter chamber  17  of the housing  12  is preferably divided by a substantially frusto-conical divider  30 . The divider  30  has a top portion  32  that is either integrally or sealingly connected to the top end cap  24  of the filter element  20 . The divider  30  also has a bottom portion  33  that extends downward toward the bottom of the filter element  20 , while also tapering or flaring outward away from the filter element  20 . It should be noted that the present invention is not limited to a frusto-conical divider  30 , but rather, the divider may also be substantially cylindrical wherein the bottom portion of the divider may extend downward substantially parallel to the filter element  20 . In both embodiments, the divider  30  essentially divides the upper chamber  17  of the housing  12  into an inner portion or region  34  and an outer portion or region  36 . The inner portion  34  is the space contained between the outside or unfiltered side of the filter element  20  and the inner surface of the divider  30 . The outer portion  36  is the space contained between the outer surface of the divider  30  and the inner surface of the outer wall  37  of the upper chamber  17  of the housing  12 . The inner and outer portions  34 ,  36  remain in fluid communication at the bottom portion of the upper filter chamber  17  of the housing  12 .  
         [0027]     In order to maintain and relieve the pressure in the upper chamber  17  of the housing  12 , a relief valve  38  is mounted in the top end cap  24  of the filter element  20 . The top end cap  24  is fabricated from a thin metallic material having a shape complementary to the top of the filter element  20 . The top end cap  24  has a substantially circular configuration with sidewalls  39  that extend downward from its periphery to sealingly connect to and cover the top of the filter element  20 . The top end cap  24  also has a centrally located recessed portion  41  which is received by and complementarily engages the inner core  43  of the filter element  20 .  
         [0028]     The recessed portion  41  of the top end cap  24  is formed by two layers of thin metallic material. A first inner layer  45  is integrally connected to the sidewalls  39  and the portion of the top end cap  24  that extends over the top of the filter element  20 . A second outer layer of the recessed portion  41  is formed by a substantially cylindrical cup that is connected to and complementarily engages the inner layer  45  of the recessed portion  41 . The inner layer  45  of the recessed portion  41  has a raised portion  49  relative to the outer layer  47 . The outer layer  47  has four apertures  51  that extend therethrough and align directly under the raised portion  49  of the inner layer  45  of the recessed portion  41 . A sheet of filter media  53  lies between the inner layer  45  and the outer layer  47  of the recessed portion  41  so as to cover the four apertures  51  extending through the outer layer  47 .  
         [0029]     The raised portion  49  of the inner layer  45  provides two apertures  55 ,  57  extending therethrough. The larger of the two apertures  55  receives a flexible valve member  58  having an inverted mushroom-shaped configuration. The stem portion  59  of the mushroom-shaped, configuration is disposed within the larger aperture  55 . The head portion  61  of the flexible member  58  extends across the underside of the raised portion  49  of the inner layer  45  such that the head portion  61  of the flexible member  58  covers the smaller aperture  57 . The smaller aperture  57  acts as a port such that when the pressure level across the filter element  20  reaches a predetermined level, the head portion  61  of the flexible member  58  flexes away from the smaller aperture  57  thereby allowing fluid  19  and/or air/vapor from the unfiltered side of the filter element  20  to pass through the smaller aperture  57 . Fluid  19  will only pass through the smaller aperture  57  after all of the air/vapor has first passed through the smaller aperture  57 . The fluid  19  and/or air/vapor passes through the sheet of filter media  53  and through the four apertures  51  in the outer layer  47  of the recessed portion  41  to the filtered side of the filter element  20 . Although the patentable subject matter may be limited to a relief valve  38  having the structure defined above, Applicants consider the invention to include any relief valve  38  having a structure that provides for the release of fluid  19  and/or air/vapor at a predetermined pressure level.  
         [0030]     The relief valve  38  is normally closed until the pressure level across the filter element  20  exceeds a predetermined level. When the relief valve  38  is closed, the air/vapor within the outer portion  36  of the housing  12  is trapped thereby forcing the fluid level in the outer portion  36  to be lower than the fluid level in the inner portion  34 . This occurs because as long as the filter element  20  is not clogged, air/vapor and fluid  19  within the inner portion  34  will pass through the filter element  20  at a pressure less than the pressure level in which the relief valve  38  is to open. Once the pressure across the filter element  20  exceeds the predetermined level due to the filter element being sufficiently clogged, the relief valve  38  opens and allows air/vapor and/or fluid  19  to pass from the outer portion  36  of the housing  12  to the inner core  43  of the filter element  20 .  
         [0031]     In a secondary embodiment of the fluid filter assembly  10 ′, a restrictive filter media section  42  of the filter media  20 ′ is either integrally formed on the top of the filter media  20 ′ or is attached to the upper portion of the filter media  20 ′, as shown in  FIG. 6 . The restrictive section  42  of the filter media  20 ′ acts in the same manner as the relief valve  38  and the relief valve filter  40  of the preferred embodiment, but the secondary embodiment does not require the divider  30 . The restrictive section  42  of the filter media  20 ′ only allows air/vapor and/or fluid  19  to pass through the restrictive section  42  once the pressure level across the filter element  20  exceeds a predetermined level. This ensures that the fluid level within the housing  12  will remain at a level below the restrictive filter media  42 . Once the predetermined pressure level is reached, air/vapor and/or fluid is allowed to pass through the restrictive filter media  42  thereby raising the fluid level and providing a visual indicator that the filter element  20 ′ needs replacement.  
         [0032]     In yet another embodiment of the present invention, a divider  30 ″ and a relief valve  38 ″ may be utilized in conjunction with a hang down fluid filter assembly  10 ″, as shown in  FIG. 5 . The structure in this embodiment is similar to that of the preferred embodiment in that the divider  30 ″ is sealingly connected to a top end cap  24 ″. The divider  30 ″ extends downward along the bottom portion of the filter element  20  while flaring outward from the filter element  20 . A relief valve filter (although not shown in  FIG. 5  but similar to that shown in  FIGS. 3 and 4 ) is mounted in a portion of the central filter tube  22 . The relief valve filter is incorporated with the relief valve  38 ″ to prevent any unfiltered fluid  19  from entering fluid outlet  18 ″. The relief valve  38 ″ in the hang down fluid filter assembly  10 ″ works in the same manner as the preferred embodiment. The divider  30 ″ forms an outer portion  34 ″ and an inner portion  32 ″ of the housing  12 ″ wherein the trapped air in the outer portion  34 ″ forces the fluid level in the outer portion  34 ″ to be lower than the fluid level in the inner portion  32 ″. This allows the filter element  20  to become completely clogged before reaching the predetermined pressure level that will open the relief valve  38 ″. Once the relief valve  38 ″ opens, air/vapor passes through the relief valve  38 ″ thereby allowing the fluid level in the outer portion  34 ″ to rise and provide a visual indicator that the filter element  20  needs replacement.  
         [0033]     In operation, the prior art device functions as depicted in  FIG. 1 . Fluid  19  enters the fluid inlet  14  of the fluid filter assembly  10  and accumulates within the lower chamber  16  of the housing  12 . Fluid flows through the passageway  15  leading to the upper filter chamber  17  wherein an unfiltered fluid level is established within the upper filter chamber  17 . The fluid  19  is drawn into the filter chamber  17  by vacuum (as most commonly occurs in diesel fuel filters) or forced by low pressure (as seen in oil, antifreeze or many other filters) until it finds a path through the filter element  20 . As the filter element  20  becomes partially clogged, the restriction increases temporarily overcoming the surface tension of fluid covering the unused pores of the filter  20  element and causing a temporary flow of air/vapor through the filter element  20 . As the air/vapor passes, it creates a void on the outside of the filter element  20 , and the fluid level rises to fill the void. The new fluid level allows flow through clean and unused pores of the filter element  20 , and the restriction through the filter element  20  reestablishes itself at a fluid level as previously described. Once the fluid level establishes itself, the surface tension of the fluid  19  across the remaining pores of the filter media  20  prevents the flow of air/vapor through the filter element  20  until, once again, the restriction increases to a level in which air/vapor is forced through the filter element  20 . This process continues as dirt and other contaminants in the fluid  19 , larger than the openings in the filter element  20 , are trapped and retained by the filter element  20  as the fluid  19  passes through the filter element  20 . These contaminants plug or clog the holes in the filter media  20  and restrict and/or close the paths used by the flowing fluid  19 . The fluid  19  is forced to seek other open and less restrictive fluid openings that are above the level of the fluid  19 , and therefore, the fluid  19  climbs up the height of the filter element  20  and uses the clean areas of the filter element  20 . The process of clogging and climbing continues until the filter element  20  is completely immersed in the flowing fluid  19 . When the fluid level reaches the top of the upper filter chamber  17 , this has generally been a visible indication to the user to change the filter element  20 . The problem with changing the filter element  20  at this point is that the filter element  20  still allows for the passage of fluid  19  through the filter element  20  even when the fluid level has risen to the top of the filter chamber  17 . Therefore, if the filter element  20  is changed immediately upon the fluid level rising to the top of the filter chamber  17 , then the filter element  20  is being replaced prematurely.  
         [0034]     During the operation of the preferred embodiment of the present invention, fluid  19  enters the fluid filter assembly  10  and the upper filter chamber  17  in the same way as described in the prior art. However, by employing the divider  30  and incorporating the preset relief valve  38  in the top end cap  24 , the fluid level can be made to rise approximately in proportion to the plugging rate of the fuel element  20 . This gives an accurate visual indicator as to the remaining life of the filter element  20 . In so doing, the incoming fluid  19  and air/vapor initially behave as similarly described in the prior art. When the fluid level approaches the bottom of the divider  30 , the fluid  19  continues to rise between the filter element  20  and the inside surface of the divider  30 , which was previously defined as the inner portion of the housing  12 , but the fluid  19  does not rise between the outer surface of the divider  30  and the outer wall of the housing  12 , which was previously defined as the outer portion of the housing  12 . This is because the trapped air/vapor in the outer portion  36  of the housing  12  prevents the rise of fluid  19  into the outer portion of the housing  12 .  
         [0035]     As to the inner portion  34  of the housing  12 , fluid  19  and air/vapor move through the filter element  20  in a usual manner. The fluid level continues to rise between the filter element  20  and the inside surface of the divider  30  as the filter element  20  becomes more clogged. This continues until the fluid  19  has risen to the full or nearly full height of the filter element  20 , as previously described. Once the filter element  20  is completely saturated, the pressure differential across the filter element  20  begins to increase with the increased clogging of the filter element  20 . Once this pressure differential reaches a predetermined level, preferably 5″ Hg, the relief valve  38  may open, and vapor/air may flow through the relief valve  38  while fluid flows through the filter element  20  since both present the same amount of resistance to flow. As the pressure differential across the filter media  22  begins to exceed the 5″ Hg point, the relief valve  38  becomes the preferred flow path since its pressure differential is fixed at 5″ Hg. Since air/vapor is closest to the relief valve  38 , the air/vapor flows through the relief valve  38  first, and the fluid  19  follows. The fluid level begins to rise in the outer portion  36  of the housing  12 , thereby providing a visual indicator to the operator that the filter element  22  is plugged. The relief valve filter  40  provided in the fluid path of the relief valve  38  ensures that the fluid  19  that passes through the relief valve  38  is filtered. Once the user sees that the fluid level in the outer portion  36  of the housing  12  has risen to the top of the upper filter chamber  17 , the user knows to replace the filter element  20 .  
         [0036]     In operation, the secondary embodiment, as depicted in  FIG. 4 , works in a similar manner as described in the preferred embodiment. The fluid level rises within the filter chamber  17 , until it reaches the restrictive filter media  42  on the filter media  20 . When the fluid level reaches the restrictive media  42 , the pressure differential across the filter media  20 ′ must rise to a preferred level of 5″ Hg in order for the air/vapor and fluid  19  to pass through the restrictive media  42 . The fluid level stops at a point just below the restrictive media  42  until the filter media  20 ′ becomes so clogged that the pressure differential reaches the 5″ Hg level. At that point, air/vapor and fluid  19  pass through the restrictive media  42 , thus allowing the fluid level to rise within the filter chamber  17  of the fluid filter assembly  10 ′. The user may then use the risen fluid level as an indicator that the filter media  20 ′ needs to be replaced.  
         [0037]     In operation, the alternative embodiment depicted in  FIG. 5  works in exactly the same manner as described in the preferred embodiment. The only difference in the embodiment depicted in  FIG. 5  is that the housing  12 ″ is upside down, but the fluid level responds in the same manner as described in the preferred embodiment.  
         [0038]     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, the scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.