Patent Publication Number: US-2001000400-A1

Title: Fuel filter including slow release additive

Description:
FIELD OF THE INVENTION  
       1. The present invention relates generally to a fuel filter for use with internal combustion engines, for example, but not limited to diesel engines in commercial vehicles. More specifically, the present invention is directed to a fuel filter containing a fuel additive that can be released into fuel and a method of releasing the additive into the fuel.  
       BACKGROUND OF THE INVENTION  
       2. Fuel filters are necessary components used to protect combustion engines by filtering out contaminants and thereby preventing damage to the engine and other downstream components such as valves, fuel injectors, fuel lines and related components. Fuel can entrain a wide variety of contaminants from a number of sources. Frequently fuel oxidizes and forms resinous materials such as asphaltenes commonly referred to as varnishes. Bacteria can grow in fuel, particularly fuel that contains moisture. The growing bacteria forms a “slime” on inner surfaces of fuel tanks, fuel lines and fuel filters. The slime often sloughs off the surfaces and fuel transports the free slime through the fuel lines. The fuel filter filters out the varnishes and bacteria; however, in the process the varnish and bacteria block the fuel filter element. The blocked filter exhibits a reduced fuel flow and increases the pressure differential across the filter element, thereby reducing engine performance and fuel efficiency. To maintain engine performance and reliability, the fuel filters must be replaced, often as frequently as every 2,000 to 4,000 vehicle miles. For many vehicles, particularly commercial trucks that travel hundreds or even thousands of miles a month, this significantly increases vehicle maintenance and operating costs and can reduce reliability.  
       3. Fortunately, the formation of varnishes and bacteria growth can be inhibited by adding fuel additives such as antioxidants and biocides to the fuel. Dispersants can be added to break up and dissolve some of the existing material clogging the filters and other fuel related components. To be effective, the additives must be constantly maintained in the fuel. This is often difficult. Unlike other fluid systems, such as the coolant and oil systems, the fuel system does not re-circulate all of the fluid. Therefore, the additives must be continuously added to the fuel at a controlled rate.  
       4. It is difficult to maintain a constant or desired level of an additive in the fuel. Typically an operator adds a bottled additive to the vehicle fuel tank with each fuel fill-up. While many bottled fuel additives are commercially available, often operators do not consistently add the additive with each fill-up. The additive might not be readily available or the operator may forget to include the additive. When the additive is added to the fuel tank, it does not always form a homogeneous mixture with the fuel. Fuel tanks do not include reliable methods for mixing fuel. Generally operators rely upon the turbulence created during a fill-up and by vehicle motion to mix the additive and fuel. Furthermore, the additive concentration in the fuel may vary, depending upon the amount of fuel added-assuming a set amount of additive is added with each fill-up.  
       5. The following references provide a background for filters in general that contain additives.  
       6. Davis in U.S. Pat. No. 5,372,942 describes a pressurized fuel filter having an additive embedded in wax; the wax/additive composition dissolves when contacted with fuel. Additional additive is only added when a portion of the fuel becomes clogged and the fuel level in the filter rises to contact and dissolve additional amounts of the wax/additive composition.  
       7. Lefebvre in U.S. Pat. No. 5,591,330 discloses an oil filter that includes a thermoplastic material having oil oxidation and acidification additives. The hot oil recirculating through the engine and the filter dissolves that thermoplastic material thereby releasing the additives into the oil.  
       8. Hudgens in U.S. Pat. No. 5,662,799 discloses a coolant filter for recirculating coolant. The coolant filter includes a supplemental coolant additive (SCA) and a release means to maintain the concentration of SCA already dissolved in the recirculating coolant fluid.  
       9. One of the design challenges addressed by the present invention is how to control the release of fuel additive into the fuel. The present invention solves this challenge in several ways, each of which is believed to be a novel and unobvious solution. The solution avoids the undesirable side effects, which have already been described and can be exploited to increase the maintenance interval, increase the fuel filter life span and enhance engine performance and fuel efficiency.  
       SUMMARY OF THE INVENTION  
       10. In one form the present invention provides a fuel filter for filtering fuel and adapted to release a fuel additive into the fuel at a controlled rate. The fuel filter comprises a housing assembly including an inlet and an outlet for fuel and defining an interior chamber; a filter element disposed within the interior chamber; a source of fuel additive disposed within the interior chamber; and a slow release means for controlling the rate of release of the fuel additive into the fuel. The slow release means is positioned between the source of fuel additive and the fuel outlet.  
       11. In another form the present invention provides a fuel filter for filtering fuel and adapted to release a fuel additive into the fuel. The fuel filter comprises an outer housing assembly defining a filter chamber, an inlet and an outlet for fuel; a filter element disposed within the filter chamber and positioned between the inlet and the outlet for fuel; an inner housing assembly positioned within the filter chamber, the inner housing assembly defining an inner chamber in fluid communication with the filter chamber; a source of a fuel additive disposed within the inner chamber; and a diffusion controlled orifice positioned between the source of fuel additive and the fuel outlet.  
       12. In another form the present invention provides a method of releasing a fuel additive into fuel. The method comprises: providing a fuel filter containing a fuel additive, the fuel filter positioned between a source of fuel and an internal combustion engine; contacting a portion of the fuel additive with a portion of the fuel to provide a fuel composition comprising fuel additive; and allowing the fuel composition to admix with the fuel.  
       13. One object of the present invention is to provide an improved fuel filter containing a fuel additive.  
       14. Further objects, features and advantages of the present invention shall become apparent from the detailed drawing and the descriptions provided herein.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     15.FIG. 1 is a front elevational view in full section of one form of a fuel filter according to the present invention.  
     16.FIG. 2 is a top plan view of a baffle plate for use with the fuel filter of FIG. 1.  
     17.FIG. 3 is a front elevational view in full section of an alternative embodiment of a fuel filter comprising a thermostat according to the present invention.  
     18.FIG. 4 is a front elevational view in full section of an alternative embodiment of a fuel filter comprising a semipermeable membrane according to the present invention.  
     19.FIG. 5 is a front elevational view in full section of another embodiment of a fuel filter according to the present invention.  
     20.FIG. 6 is a front elevational view in full section of yet another embodiment of a fuel filter comprising a fuel additive briquette according to the present invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     21. For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will, nevertheless, be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described processes, systems, or devices and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.  
     22. Referring to FIG. 1, there is illustrated a fuel filter  10  according to one embodiment of the present invention. The illustrated embodiment of filter  10  is intended to include basic components in a construction that is typical of such fuel filters with the exception of the fuel additive and the slow-release means associated with the fuel additive. The basic components of filter  10  include housing  12  defining a filter chamber  14 , filter element  16  disposed within the filter chamber  14 , drain opening  18  having an externally threaded wall  19 , and cap  20  having internal threads adapted to matingly engage externally threaded wall  19 .  
     23. Housing  12  includes a closed base end  22  and an open outlet end  24 , which is crimped to the outer edge periphery of nut plate  26 . The crimped combination creates a filter house assembly  23 . Nut plate  26  provides the inlet openings  28  for fuel to enter filter  10 . Internally threaded outlet aperture  30 , which is defined by nut plate  26 , provides the flow exit for the filtered fuel.  
     24. Filter element  16  is supported on one end by outlet end plate  32  and on an opposite end by base plate  34 . Filter element  16  is bonded to end plate  32  to form a fluid tight seal. Fuel enters filter chamber  14  through inlet  28  and flows to annular space  35 . From annular space  35 , fuel flows radially inward through filter element  16  into an interior region  37 , then out through opening  39  of outlet  30 . From outlet  30 , fuel flows to a combustion engine, which can include an carburetor system or fuel injection system (not shown).  
     25. Base end plate  34  provides a support and a seat for filter element  16 , as well as for the components associated with the present invention, including the filter additive which is provided in the form of a plurality of tablets or pellets  42 . In the embodiment illustrated by filter  10  base plate  34  is spaced from housing  12  by spring  41 .  
     26. The foregoing description of the basic filter components and construction of fuel filter  10  is provided with regard to FIG. 1 and is applicable to the filter elements depicted in FIGS. 3-6. Accordingly the same reference numerals will be used for the same components. The differences between filters illustrated in FIGS. 1 and 3- 6  are embodied in the structures that house a plurality of coated pellet tablets  42 .  
     27. Referring to FIG. 1, fuel filter  10  includes cap  36  and base plate  34 , which matingly join together to form inner chamber  40 . Cap  36  is substantially cylindrical and includes an upper portion  43  sized to have an outside diameter smaller than the inside diameter of filter chamber  14 . Cap  36  includes an annular shelf  45  and an upper wall portion  62 . Annular shelf  45  provides support for filter element  16  and is adapted to form a fluid tight seal with the lower portion of filter element  16 . Upper wall portion  62  includes orifice  44 , which provides fluid communication between inner chamber  40  and inner region  37 . The upper wall portion can also include at least one, preferably two, vent openings  46 . Upper wall  62  includes an axially protruding tapered diffusion tube  48 . Diffusion tube  48  defines a tapered diffusion passageway for orifice  44 , which extends therethrough and establishes a passageway of fluid communication between the inner chamber  40  and inner region  37 .  
     28. Referring additionally to FIG. 2, there is illustrated a typical baffle plate  50  for use with the present invention. Cap  36  can include, but is not required to include, at least one, preferably a plurality, of baffle plates  50 . Each baffle plate  50  includes a plurality of openings  51  formed therethrough. Baffle plate  50  is spaced from diffusion tube  48 . In preferred embodiments, cap  36  includes three baffle plates  50  spaced from each other; each baffle plate individually bonded about its peripheral edge to inner surface  52  of cap  36 . It will be appreciated that in alternative forms cap  36 , which includes at least one baffle plate  50 , need not include a diffusion control orifice or the diffusion tube  48 . When thus provided, cap  36  has an opening providing fluid communication with filter chamber  12  and includes a sufficient number of baffle plates  50  to slow the flow of fuel into inner chamber  40  and/or to control the rate of release of the fuel additive. Further, a plurality of baffle plates  50  can be provided to reduce turbulence in inner chamber  44 . Preferably, each baffle plate  50  is spaced from an adjacent baffle plate to misalign the plurality of openings  51  in the adjacent baffle plates.  
     29. As is illustrated in FIG. 1, cap  36  seats on base plate  34  and forms an inner housing  43  assembly that defines inner chamber  40 . The only openings into inner chamber  40  are the diffusion orifice  44  and vent openings  46 . Inner chamber  40  is substantially filled with a fuel additive composition, which is illustrated in a form of a tablet  42 . It is understood that the fuel additive composition can be provided in a variety of shapes and sizes, including cubic, cylindrical, and spherical. Typically, tablets  42  are provided in a cubic shape to fill the inner chamber  40 .  
     30. Fuel from filter chamber  12  in filter  10  migrates through the diffusion orifice  44  into an inner chamber  40 . Fuel in inner chamber  40  contacts the outer coating  47  of fuel additive tablet  42 . Fuel then diffuses through the coating  47  to contact the fuel additive composition, which dissolves in the fuel to provide a fuel composition comprising the dissolved additive. The fuel composition diffuses back through coating  47  into inner chamber  40 . The fuel composition mixes with fuel in inner chamber  40 .  
     31. The fuel system is unlike the coolant and oil systems used with internal combustion engines because in some duty cycles the fuel system does not recirculate a significant portion of fluid. Therefore, under these conditions, the majority of fuel entering into filter chamber  14  has not been recirculated through filter  10  and for all practical purposes does not include any dissolved additive. While not intending to be bound by any theory, it is believed that the concentration of dissolved additive in the fuel composition in inner chamber  40  is vastly greater than the concentration of dissolved additive in the fuel in filter chamber  14  outside inner chamber  40 . This concentration difference is significantly greater than would be expected in a recirculating fluid system. This concentration difference creates a stronger driving force for the fuel composition to migrate from inner chamber  40  into filter chamber  40 . In preferred embodiments, baffle plate  50  and/or diffusion orifice  44  are provided to inhibit or reduce the flow of fuel into and out from inner chamber  40 . This increases the useful lifespan of fuel filter  10  and controls the rate of release of the fuel additive composition into the fuel.  
     32. Inner chamber  40  provides a substantially quiescent region inside filter chamber  12  that does not experience the currents created by fuel flowing through filter  10 . As the concentration of dissolved fuel additive in inner chamber  40  increases relative to concentration of the fuel additive in filter chamber  12 , the fuel composition migrates or diffuses from inner chamber  40  into filter chamber  12  in an effort to achieve equilibrium. The fuel composition comprising the dissolved additive and the fuel diffuses through diffusion tube  48  and diffusion orifice  44  that defines a restricted opening for the migration of the higher concentration solution out of the inner chamber  40  and mixes with fuel in filter chamber  14 .  
     33. The fuel additives for use in this invention can be of liquid or solid form. Two or more fuel additives can be combined to form a fuel additive composition. The fuel additive(s) can be compounded with a suitable polymer either for providing a solid or semisolid material such as tablet  42  or form for providing a matrix to control the rate of release of the additive into the fuel. The fuel additive can further include a wide variety of binders, compounding agents and mold release agents. When the additive is provided in liquid form, it is preferable, but not required, to combine the liquid fuel additive with a suitable agent to form a solid or semisolid material. As used herein, the term fuel additive includes any commercially known and/or commonly used fuel additive that imparts beneficial properties to the fuel and/or the engine and related fuel-handling components. Common classes of fuel additives include: antioxidants, antiwear agents, cetane improvers, corrosion inhibitors, demulsifiers, detergents, dispersants, flow improvers, lubricity agents, and metal deactivators.  
     34. Tablets  42  of fuel additive include an outer hydrocarbon insoluble coating  47 , which encases the fuel additive composition tablet  42 . The hydrocarbon insoluble coating is selected to be substantially insoluble in hydrocarbon fuel mixtures, yet be permeable to the fuel to allow the fuel to penetrate the coating and contact the fuel additive. A portion of the fuel additive dissolves in the fuel to provide a fuel composition that includes the dissolved fuel additive. The coating may be a hard coating or a soft pliable coating. In general, any coating material can be used with this invention, provided the coating allows fuel access to the fuel additive composition and does not harm downstream fuel systems, fuel injectors, valves and related engine components.  
     35. Typical and preferred coating materials are commercial available polymers co-polymers and block copolymers including, but not limited to: polyethylene glycol or polyvinyl acetate and mixtures thereof. Preferably the coating is selected to provide an effective rate of release of the additive into the fuel. By effective rate of release, it will be understood that the additive is released at a concentration sufficient to provide beneficial properties to the fuel and related fuel-handling components.  
     36. In other embodiments, the fuel additive can be embedded within a solid matrix. The matrix can be either hydrocarbon soluble or hydrocarbon insoluble. If the matrix material is hydrocarbon insoluble, the fuel must be able to penetrate the matrix and contact the fuel additive. It is particularly advantageous to embed a liquid fuel additive in a solid matrix. This provides one means of controlling the rate the additive is released into fuel.  
     37. One alternative design of FIG. 1 includes replacing the plurality of coated tablets  42  with a fewer number of much larger pellets or tablets. By reducing the total surface area of the fuel additive for a specific mass of fuel additive composition, the additive composition dissolves at a slower rate.  
     38. Referring now to FIG. 3, an alternative embodiment of the present invention is illustrated. As has been previously mentioned, the basic filter components of filter  110  are the same as those of filter  10 , and accordingly, the same reference numbers have been used for the basic components. Alternative and additional components are referenced with a one hundred prefix designation. Located within filter I  10  is cap  136  and base plate  34 . Cap  136  includes opening  144  formed therethrough. Opening  144  can be provided in the form of a diffusion orifice that is defined by a diffusion tube  148 . Thermostat  164  is provided in opening  144 . Thermostat  164  is adapted to control the flow of fuel into inner chamber  40  and can be selected from a wide variety of commercially available thermostats. For example, a wax type thermostat can be adapted for use in the present invention. In preferred operation, the thermostat opens in response to a temperature level of fuel in filter  110 . When opened, the thermostat allows passage of fuel into inner chamber  40 . The thermostat  164  can be adapted to open in response to either fuel that is sufficiently warm or fuel that is sufficiently cool.  
     39. In one preferred embodiment, thermostat  164  opens in response to fuel that is sufficiently warm. Fuel additives providing additional benefits to warm fuel can be released on an as-needed release basis. For example, antioxidants and dispersants can be added to the warm fuel to inhibit the deposition of resinous material on filter element  16 . Dispersions can be provided to suspend or dissolve the resinous material, which are eventually burned in an engine (not shown). In alternative embodiments, the thermostat  164  opens when fuel in filter  110  is sufficiently cool. Cool fuel can be indicative of a recently filled tank or of fuel that has not been recirculated through the fuel filter. In either case, the cool fuel may require additional additives to enhance engine performance and/or fuel efficiency. Under certain conditions fuel is circulated through the fuel injection where it becomes heated. The heated fuel can be recirculated through the fuel filter. Since the fuel has already been through the fuel filter, no additional additive may be needed. Thus, when the fuel is sufficiently warm, thermostat  164  can close and prevent the addition of the fuel additive to the heated fuel.  
     40. As an additional benefit, tablets  42  can include an anti-gelling agent for diesel fuel. Thermostat  164  can operate to open in response to cool or cold fuel. The anti-gelling additives can be released on a need-release basis into the fuel to enhance engine performance in cold weather.  
     41. Fuel filter  110  can also include, but is not required to include, one or more baffle plates  150 . Similar to the design of fuel filter  10 , baffle plates  150  are positioned in inner chamber  40  adjacent to opening  144  in upper wall  162 .  
     42. Referring now to FIG. 4, another embodiment of the present invention is illustrated. The basic filter components of filter  210  are the same as those of filter  10 , and accordingly, the same reference numbers have been used for the basic components. Alternative and additional components are referenced with a two hundred prefix designation. Located within filter  210  is a cap  236  and base plate  34 . Cap  236  includes a double wall structure  267  that includes a semi-permeable membrane wafer sandwiched therebetween.  
     43. Cap  236  includes inner surface  252 . Inner surface  252  includes a unitary upper wall  262 , which defines centrally therein an orifice  263 . The inner surface  252  includes molded thereon a small annular lip  264  which serves as a retainer for circular plate  265 . Plate  265  functions as a second wall in cooperation with upper wall  262  to hold in position therebetween a substantially cylindrical diffusion or osmotic wafer  248 . The preferred material for diffusion wafer  248  is a microporous polymer, co-polymer or block copolymer including, but not limited to: polyethylene glycol or polyvinyl acetate and mixtures thereof. Plate  265  defines centrally therein an opening  266 , which is aligned with opening orifice  263 . This combination permits the gradual migration of fuel into inner chamber  240  to contact tablets  42 . Osmotic wafer  248  is positioned between the fuel additive and the outlet aperture  30  through which the filtered fuel containing the fuel additive flows on toward the engine (not shown). Use of the semi-permeable membrane in the form of membrane  248  permits only a gradual migration of a portion of fuel in filter chamber  14  into inner chamber  240 . This provides a slow release of the fuel additive composition into the fuel to maintain a substantially constant level of fuel additive in the fuel system.  
     44. In FIG. 5 there is illustrated yet another embodiment of the present invention. The basic filter components of filter  310  are the same as those of filter  10 , and accordingly, the same reference numbers have been used for the basic components. Alternative and additional components are referenced with a three hundred prefix designation. Filter  310  includes base plate  334  having a lower wall portion  338 . Lower wall portion  338  includes orifice  344  formed therethrough which provides fluid communication between inner chamber  340  and filter chamber  314 . Lower wall  338  also can include an axially protruding tapered diffusion tube  348 . Diffusion tube  348  defines a tapered diffusion passageway for orifice  344  that extends therethrough and establishes a passageway of fluid communication between the inner chamber  340  and filter chamber  314 .  
     45. Preferably upper wall  362  of cap  336  includes at least one air vent opening  346 . In one alternative form, outlet endplate  332  can include a substantially circular, hollow vent tube  372  extending obliquely therefrom and adapted to extend from outlet endplate  332  through air vent opening  346  to provide fluid communication between region  370  that is proximate to inlet  328  and inner chamber  340 . In an alternative form, the outlet end plates does not include vent tube  372 , and air vent opening  346  can vent into the interior region  337  of filter chamber  14 . In operation after all the air in inner chamber  340  has escaped through air vent opening  346 , a portion of the fuel mixture in inner chamber  340  could flow out air vent opening  346  into interior region  337  and out outlet  30 , preferably at a substantially lower flow rate than fuel flows from annular space  35  through filter element  16  and out outlet  30 .  
     46. In FIG. 6 there is illustrated an alternative embodiment of a fuel filter  410  for use with the present invention. Fuel filter  410  includes a fuel additive in a single large tablet or cartridge  442 . While it is possible to include fuel additive cartridge  442  in either of FIG. 1 or FIGS. 3-5, the use of smaller coated tablets is preferred. By the use of smaller tablets, a larger mass of the fuel additive can be loaded into the inner chamber without any particular regard to the size or shape of the chamber.  
     47. While the foregoing description provided several embodiments for controlling the release of a fuel additive composition into fuel, it will be understood that the inner housing assembly can be formed to include a variety of structures and openings to allow migration of fuel into the inner chamber. In preferred embodiments, the inner chamber provides a quiescent region inside filter chamber where a source of a fuel additive surrounded by a portion of the fuel flowing through the fuel filter is protected from the typical fluid forces acting on the fuel in the filter.  
     48. The present invention provides a method of enhancing the operation of an internal combustion engine. In one form, the enhancement is provided by controlling the release of a fuel additive into fuel. The controlled released of the additive maintains a constant, uniform concentration of additive in the fuel. In preferred embodiments, the additive is released in a controlled manner to maintain a substantially uniform concentration of additive in the fuel despite the varying amount of fuel that is recirculated through the fuel filter. Use of the present invention decreases the maintenance time and costs, enhances engine performance and increases fuel efficiency. In another form, the invention enhances the usable and/or effective lifespan of fuel filters by providing fuel additives that effectively inhibit the formation of resinous material such as vanishes and asphaltenes and help breakup or disperse such material that has been deposited on fuel handling components.  
     49. According to the present invention, a diffusion tube, diffusion orifice, and baffles may be used to slow the release of the fuel additive into the fuel. The coating on the fuel additive also limits the rate of additive that is dissolved in the fuel. These mechanical and chemical arrangements may be used with a plurality of smaller fuel additive pellets, with a larger tablet, or with a singular, large cartridge of fuel additive. In an alternative embodiment of the present invention, a semipermeable membrane wafer is sandwiched between an upper wall and a retaining plate to provide a slow release means for the mechanism due to the composition of the wafer. This mechanical arrangement may be used with a plurality of smaller tablets or larger tablets or some other form of fuel additives. Further, a thermostat can be included with the openings for each embodiment to provide a need-release feature for the present invention. The thermostat opens in response to fuel that exhibits a temperature level within a predetermined temperature range and permits migration of fuel into the inner chamber.  
     50. While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is considered to be illustrative and not restrictive in character, it is understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.