Abstract:
A fuel filter assembly for a combustion engine, including a two-part filter housing, a filter element, and a restriction sensor, including an external visual display apparatus for indicating when to replace the filter element. As fluid pressure increases within the filter housing, the visual display apparatus correspondingly displays the increase in pressure. When the pressure sensor detects an amount of pressure at or in excess of a predetermined amount, the visual display apparatus indicates replacement of the filter element. A modified embodiment including an electronic pressure sensor and a remote display unit is also described.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fuel filter apparatus for filtering contaminants from liquid fuel for combustion engines, including an indicator for displaying the condition of the filter media contained therein, and to methods of using the described apparatus. More particularly, the present invention relates to a fuel filter including a restriction indicator gauge with a visual display, for identifying when a fuel filter needs to be replaced, and to methods of using the described filter. 
     2. Description of the Background Art 
     The use of fluid filters to protect the downstream components of a machine is well known. Several different fluids associated with internal combustion engines require filtration, i.e. fuel and oil. In particular, fuel filters protect the engine from contaminants, such as dirt and water which, if left unfiltered, could result in inefficient combustion, reduced engine performance and premature engine wear. Fluid filters need to be replaced, at regular intervals, to ensure continued proper filtration. 
     Known fuel filters for combustion engines generally include a housing, filter, and connective conduits to provide an inlet and outlet. Known filters may also include an optional drain valve (typically a threaded plug, removable from the housing, to allow fuel or coalesced water drainage therefrom). Often, the housing is almost entirely transparent (or includes a sight glass) to permit an individual to view the condition of the fuel filter, and then determine whether replacement of the fuel filter is necessary. However, visually determining when to replace a filter, based upon this known method is subjective, given that filter replacement depends on the opinion and/or experience of the individual viewing the filter. Moreover, a plugged filter element does not always appear visually different from a clean one. 
     Accordingly, concerns arise on both sides as to when a fuel filter should be replaced; premature replacement of a fuel filter gives rise to cost, disposal, and environmental concerns, while delayed replacement of a fuel filter gives rise to concerns of diminished engine performance, reduced efficiency and premature wear. As a result, a number of methods and equipment for detecting deterioration and contamination of engine fuel have been developed. 
     Some examples of known fuel filters are illustrated in U.S. Pat. No. 4,981,584 issued to Nunes; U.S. Pat. No. 5,776,332 issued to Hurner; U.S. Pat. Nos. 5,507,942 and 5,766,449 issued to Davis, and; U.S. Pat. Nos. 5,916,442 and 6,203,698 issued to Goodrich. 
     The use of pressure sensors to monitor fluid pressure within fluid filters is taught by U.S. Pat. No. 4,654,140 to Chen, U.S. Pat. No. 4,818,385 to Medley, U.S. Pat. No. 5,132,009 to Futa, Jr. and U.S. Pat. No. 5,702,592 to Suri et al. 
     While the known devices have shown some utility for their intended purposes, a need still exists in the art for an apparatus that provides a simple, cost-effective, visual indication of the filter&#39;s condition, to reduce the subjectivity inherent in visually determining filter replacement, while still maintaining effective fuel filtration. 
     SUMMARY OF THE INVENTION 
     The present invention has been developed to overcome limitations and disadvantages of known fuel filters, and to generally fill a need in the art for a fuel filter which combines cost-effective and reliable fuel filtration with an accurate and objective visual condition indicator. 
     The present invention provides a method and apparatus for filtering liquid fuel for a combustion engine, in which the apparatus includes a restriction indicator gauge to visually indicate when the filter requires replacement. The fuel filter hereof can be serviced or changed by non-expert service personnel or by a vehicle owner, if desired, when the filter visually indicates the need for replacement. 
     In accordance with a particular embodiment hereof, the present invention provides a fuel filter assembly including a two-part filter housing, a filter element, and a restriction indicator gauge. The restriction indicator gauge includes a sensor that attaches to the housing, and includes a probe for insertion into the center of the filter element. 
     A filter element according to the invention may include a hydrophobic filter media, to remove fuel contaminants from fuel, and to reduce or eliminate microbial growth within the downstream components of a vehicle&#39;s fuel system. 
     Additionally, the fuel filter hereof may also contain one or more fuel additives, for slow release over time, to stabilize fuel quality, improve combustion, reduce emissions, clean fuel injectors, etc. Examples of some fuel additives which may be associated with the fuel filter hererof include antioxidants, cetane improvers, corrosion inhibitors, demulsifiers, dispersants, lubricating agents, metal detergents, and metal deactivators coated with a hydrocarbon-insoluble material. 
     The fuel filter according to the invention may include a restriction indicator gauge for fuel flow through in-situ analysis. In-situ analysis visually and beneficially indicates the actual level of restriction applied to fuel flowing to the engine. Such an in-situ fuel flow restriction indicating device is advantageous because the indicator may also be retrofitted on to a conventional fuel filter housing equipped with a drain plug. This capability permits vehicle owners of nearly all makes and models to reap the benefits of visual fuel restriction detection, which helps preserve the life of a vehicle&#39;s engine. This feature of the device also affords a cost-effective mechanism for sensing fuel restriction, as it requires no specifically designated mounting area and no separate maintenance. A worn system may be replaced with a new system as part of a new fuel filter installation, as required. 
     For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a fuel filter assembly in accordance with a first embodiment of the invention; 
         FIG. 2  is a partially exploded sectional view of the fuel filter assembly of  FIG. 1 ; 
         FIG. 3  is partially exploded sectional view of a modified fuel filter assembly in accordance with a second embodiment of the invention; and 
         FIG. 4  is a front plan view of a digital gauge which is usable in the apparatus of  FIGS. 1–2 . 
     
    
    
     DETAILED DESCRIPTION 
     Overview—First Embodiment 
     Referring now to  FIGS. 1–2 , a fuel filter assembly and restriction indicating system, in accordance with the present invention, is shown generally at  10 . The assembly  10  includes a two-part housing  12  ( FIG. 2 ), a filter element  20  disposed within the housing, and a restriction indicator gauge  22 , which fits into a threaded opening in the housing, as will be further described. Other secondary parts are also included, as will be further described herein. 
     The Filter Housing 
     The housing  12  includes a base  14  having a plurality of channels formed therein, and a housing cover  16 , which fits threadably and rotatably on top of the base. A lower O-ring seal  17  is provided for sealing placement between the base  14  and the housing cover  16 . 
     The housing cover  16  may be constructed from material similar to conventional, transparent fuel filter housings; however, since the housing cover need not be transparent, it may be constructed from any material suitable for contact with fuel, namely various types of fuel-tolerant plastic or metal. 
     The housing cover  16  includes an enlarged diameter skirt  19  at the bottom edge thereof, which is internally threaded to allow the housing cover to be threadably installed on the base  14 . 
     The housing cover  16  also has a threaded cylindrical aperture  18  formed in a top center portion thereof, to receive a threaded base portion  23  of the restriction indicator gauge  22  therein. An upper o-ring seal  24  is provided to fit around the base portion  23  of the restriction indicator gauge, and to form a fluid-resistant seal between the restriction indicator gauge  22  and the top of the housing cover  16 . 
     The top of the housing cover  16  also includes an integral dependent boss  25  extending downwardly thereon, as shown. A tension spring  27  is located between the housing cover  16  and the filter element  20 , surrounding the dependent boss  25 . The spring  27  acts to put constant downward pressure on the filter element  20 , thereby forming a seal between the filter element and the housing base  14 . More specifically, the seal is formed between a lower end cap  42  on the filter element  20 , and a central boss  32  of the housing base. 
     The housing base  14  has an inlet passage  30  formed therein ( FIG. 2 ), which feeds fuel into the housing  12 , to an area outside of the filter element  20 . The housing base  14  may have a hollow inlet tube  31  extending outwardly from the inlet passage  30 , as shown. 
     The housing base  14  also has a raised central boss  32  with an outlet feed tube  33  located centrally thereon. As seen in  FIG. 2 , the filter element  20  rests on the central boss  32  of the housing base  14 , leaving the outer portion of the filter element elevated above the floor of the base, and allowing fuel to flow therearound as it leaves the inlet passage  30 . 
     The housing base  14  further has an outlet passage  34  formed therein, in fluid communication with the centrally located outlet feed tube  33 . The housing base  14  may also have a hollow outlet tube  36  extending outwardly from the outlet passage  34 , as shown. 
     In this manner, the unfiltered fuel travels through the inlet tube  31  of the housing base  14 , into a chamber  35  between the housing cover  16  and the filter element  20 , through the filter element  20  and into the internal cavity  47  thereof, ultimately exiting through the outlet tube  36  of the housing base. 
     The Filter Element 
     The filter element  20  has resilient upper and lower end caps  40 ,  42  respectively, thereon. The end caps  40 ,  42  are formed from a ble, fuel-tolerant material, which may be steel, plastic or a suitable elastomer. The upper end cap  40  includes a hollow central collar  41  having a central opening  45  formed vertically therethrough to receive a probe  29  of the restriction indicator  22 . 
     The central portion of the filter element  20  contains the filter media, which is in the general shape of a hollow cylinder defining a hollow internal cavity  47  therein. The filter media may be formed from pleated filter paper, porous sintered metal or plastic, or other suitable filter material. 
     The filter media  44  may be formed from a paper material which has been coated with a hydrophobic substance, to resist decomposition when in contact with fuel. Depending on the filtration material, a retaining cage surrounding may be used around the filter media  44  for added support, if desired. Additionally, the filter media  44  may also be coated with, or the filter  10  may otherwise include a detergent or other fuel additive, provided for time release, to consistently disperse the additive or detergent throughout the life of the filter. 
     Although the fuel filter media  44  is shown in an accordion configuration, alternative configurations may be implemented; by way of example, such alternative configurations may include a honeycomb configuration, or another alternative configuration. 
     The Restriction Indicator Gauge 
     The restriction indicator gauge  22  may be described as one type of restriction sensor. 
     In the embodiment of  FIGS. 1–2 , the restriction indicator gauge  22  includes the threaded base section  23 , a display face  26 , and an indicator needle  28 , which is movably mounted on the display face. The restriction indicator gauge  22  further includes a restriction-monitoring probe  29  having a first pressure sensor  56  at the lower tip end thereof. A second pressure sensor may be located inside the threaded base section  23  of the gauge  22 . 
     Alternatively, the gauge  22  may include a sealed internal fluid coil, which uses fluid pressure from outside of the filter element  20  to move the needle  28 . 
     The gauge  22  preferably senses the level of restriction as a pressure differential between fluid pressure outside and inside of the filter element  20 . As the level of restriction increases, the increase is reflected by movement of the needle  28  on the display face  26 . When the level of restriction exceeds a predetermined limit, such as twelve inches of mercury, the indicator display illustrates the need to replace the filter element  20 , by moving the needle  28  into the area marked “Change”, which may be color-coded in red or another suitable color. 
     The embodiment of the invention shown in  FIGS. 1–2  utilizes a three-field condition range to indicate the condition of the fuel filter. However, alternative embodiments indicating the need to replace the fuel filter may include a color changing display or an increasing numeric scale. Additionally, the display indicator may include an audible indicator as well. 
     While a first embodiment of the present invention is illustrated in  FIGS. 1 and 2 , alternative embodiments are conceivable. While the gauge  22  shown in  FIGS. 1–2  is an analog gauge with a dial indicator, it will be understood that in an alternative embodiment, as shown in  FIG. 4 , the gauge used could be a digital gauge  222  with an electronic readout. The gauge  222  of  FIG. 4  could be substituted in place of the analog gauge  22  in the apparatus of  FIGS. 1–2 . 
     By way of example, the collar  41  is shown integrally secured to the fuel filter; however, the collar may be secured to the fuel filter housing, or may be independent of both the filter and the housing. Further, the restriction indicator probe  29  may be replaced with a hollow tube through which filtered fuel travels to a restriction indicator gauge external from the filter housing  12 . In another modified version of the first embodiment, the restriction indicator gauge may be completely contained within the filter housing, with a transparent housing cover  16 . 
     Second Embodiment 
     Referring now to  FIG. 3 , a modified fuel filter assembly according to a second embodiment of the invention is shown generally at  100 . The filter assembly  100  according to this embodiment shares many features with the first embodiment. Unless specifically described as different herein, it will be understood that the filter assembly  100  is similar to the filter assembly  10  as previously described. 
     The filter assembly  100  according to the second embodiment includes a restriction sensor  122  in place of the gauge  22  used in the first embodiment. The sensor  122  includes electrical contacts  130  for connecting to a plug connector  132 , to send a signal to a remote location. 
     If desired, the plug connector may place the sensor  122  into communication with the main vehicle computer, such as the powertrain control module or the like. 
     Preferably, the signal from the sensor  122  is sent as a digital signal, and the wire(s)  133  going to the connector  132  either carry no current, or else do not carry current in an amount sufficient to create a spark. Current-carrying wires are avoided in this context, in order to reduce or eliminate any likelihood of a stray spark igniting fuel and starting a fire. 
     In the embodiment of  FIG. 3 , the sensor  122  includes both an external pressure sensor  124  and an internal pressure sensor  125 , so that the pressure differential (restriction) can be displayed on a remote gauge, warning light or other display. Preferably, such a remote gauge or display will be provided inside of a vehicle, such as on the dashboard. 
     Although the present invention has been described herein with respect to a preferred embodiment thereof, the foregoing description is intended to be illustrative, and not restrictive. Those skilled in the art will realize that many modifications of the preferred embodiment could be made which would be operable. All such modifications which are within the scope of the claims are intended to be within the scope and spirit of the present invention.