Abstract:
A liquid tank such as a liquid fuel tank, as well as a method of operating such a tank and a structure for implementation in such a tank, are disclosed. In at least one embodiment, the liquid tank is a liquid fuel tank that includes a housing have an inner chamber capable of containing liquid fuel as well as an air space above an upper surface of the liquid fuel, and a floating member included within the inner chamber, where the floating member is configured to float proximate the upper surface of the liquid fuel when the liquid fuel is present within the inner chamber. The floating member includes at least one tapered surface, and the floating member covers a majority of the upper surface of the liquid fuel, whereby the liquid fuel evaporates to a lesser degree than would occur if the floating member was absent.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     FIELD OF THE INVENTION 
       [0001]    The present invention relates to internal combustion engines and, more particularly, relates to fuel storage and delivery systems and methods for use in internal combustion engines. 
       BACKGROUND OF THE INVENTION 
       [0002]    Fuel tanks are typically employed in internal combustion engines to store fuels such as gasoline, diesel fuel and other types of liquid fuels that are used by the engines. When situated within a fuel tank, certain amounts of a liquid fuel typically become vaporized, particularly when temperatures within the tanks rise, when the tanks experience high levels of jostling, and/or when the volume within the tank unoccupied by fuel (and filled with air) becomes large. The vaporization of fuel continues even during the normal course of storage of the fuel within the fuel tank. 
         [0003]    Fuel vapors emanating from the fuel tanks of internal combustion engines are one of the main contributors to evaporative emissions from such engines. Such emissions from fuel tanks can occur particularly when passage(s) are formed that link the interior of the fuel tank with the outside atmosphere, for example, for venting purposes as well as when refueling occurs. Because fuel vapors can contribute to ozone and urban smog and otherwise negatively impact the environment, increasingly it is desired that these evaporative emissions from fuel tanks be entirely eliminated or at least reduced. In particular, legislation has recently been enacted (or is in the process of being enacted) in various jurisdictions such as California placing restrictions on the evaporative emissions of Small Off Road Engines (SORE), such as those employed in various small off-road vehicles and other small vehicles that are used to perform various functions in relation to the environment, for example, lawn mowers and snow blowers. 
         [0004]    For at least these reasons, therefore, it would be advantageous if an improved system/device and/or method could be created to prevent or reduce evaporative emissions from fuel tanks, such as the fuel tanks of internal combustion engines including, for example, SORE engines. 
       SUMMARY OF THE INVENTION 
       [0005]    The present inventors have recognized the desirability of reducing evaporative emissions from fuel tanks and further have recognized that such emissions can be reduced by reducing the surface area of the fuel within a fuel tank that is exposed to air within the fuel tank, so as to reduce the amount of fuel that is vaporized within fuel tanks. Further, the present inventors have recognized that, in at least some embodiments, such goals can be achieved by employing one or more cone-shaped or double-cone-shaped structures that float within the fuel and at the same time reduce the overall surface area of the fuel that is exposed to air within the fuel tank. Such structures can be particularly advantageous in that the structures naturally orient themselves in a manner that results in maximum reduction of the exposed fuel surface. 
         [0006]    In at least some embodiments, the present invention relates to a liquid fuel tank that includes a housing have an inner chamber capable of containing liquid fuel as well as an air space above an upper surface of the liquid fuel. The liquid fuel tank further includes a floating member included within the inner chamber, where the floating member is configured to float proximate the upper surface of the liquid fuel when the liquid fuel is present within the inner chamber. Additionally, the floating member includes at least one tapered surface, where the floating member covers a majority of the upper surface of the liquid fuel, whereby the liquid fuel evaporates to a lesser degree than would occur if the floating member was absent. 
         [0007]    Further, in at least some embodiments, the present invention relates to a liquid tank. The liquid tank includes a portion of a liquid capable of evaporation, and an interior region within which the portion of the liquid is positioned, and further within which is located an air space above an upper surface of the portion of the liquid. The liquid tank also includes means for covering at least a majority of the upper surface, where a covered part of the upper surface is separated from the air space, whereby the evaporation of the liquid occurs at a reduced level due to the means for covering. 
         [0008]    Additionally, in at least some embodiments, the present invention relates to a method of operating a fuel tank. The method includes filling the fuel tank with an amount of a liquid fuel, where an air space remains above an upper surface of the liquid fuel, and floating a structure within the fuel tank. The structure floats proximate the upper surface of the liquid fuel and extends upward out of the liquid fuel above the upper surface, the structure includes a tapered surface such that a cross-sectional area of the structure becomes increasingly smaller as one proceeds upward along the structure away from the upper surface, and a portion of the upper surface is separated from the air space due to the structure. 
         [0009]    Further, in at least some embodiments, the present invention relates to a structure for implementation in a liquid fuel tank. The structure includes at least one tapered surface, where the structure is configured to float along an upper surface of liquid fuel within the liquid fuel tank and reduce an exposed area of the upper surface so as to reduce evaporation of the liquid fuel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a side elevation view of a simplified fuel tank that for convenience of illustration is shown to be transparent where the fuel tank is semi-filled with fuel and employs a first exemplary floating member in accordance with one embodiment of the present invention; 
           [0011]      FIG. 2  is a side elevation view of the fuel tank of  FIG. 1 , wherein the fuel tank employs a second exemplary floating member in accordance with another embodiment of the present invention; and 
           [0012]      FIG. 3  is a cross-sectional view of the fuel tank of  FIG. 2 , taken along a line  3 - 3  of that figure 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    Referring to  FIG. 1 , a side elevation view of an exemplary fuel tank  2 , in accordance with at least some embodiments of the present invention, is shown. For simplicity of illustration, the fuel tank  2  is a container or housing formed from a transparent material (e.g., a transparent plastic) so that the contents within the fuel tank are visible through the wall of the fuel tank. It will be understood, however, that in other embodiments the fuel tank  2  can be made of a variety of materials, which need not be transparent. Also for simplicity, the fuel tank  2  can be assumed to have a cylindrical or substantially cylindrical shape, with a central axis of the cylindrical fuel tank extending vertically or substantially vertically. However, in alternate embodiments, the fuel tank  2  can take on other shapes, including shapes that are asymmetrical. 
         [0014]    As shown, the fuel tank  2  is partially filled with fuel  6 , up to a level indicated by a surface  8 . An air space  10  is formed within the fuel tank  2  above the surface  8 , within which evaporative emissions from the fuel  6  ordinarily collect. As fuel is drained from the fuel tank  2  by way of an output passage  4  (which can be assumed to be connected by way of a hose or other channel to a carburetor, fuel injectors, etc.), the surface  8  moves downward toward the bottom of the fuel tank and the air space  10  increases in volume. Fuel can be added to the fuel tank  2  by way of an input orifice  5 , which is sealed in the present embodiment by way of a cap  15 . The fuel  6  in the present embodiment is intended to be representative of a wide variety of volatile fluids (e.g., fluids capable of evaporation at normal temperatures and pressures) including, for example, gasoline, diesel fuel, kerosene, crude oil, other petroleum-based fuels, mineral oils, ethanol blends etc. In other embodiments, the fuel  6  can be an organic fluid such as acetone and benzene or another type of volatile fluid other than those mentioned above. 
         [0015]    To minimize or possibly even completely eliminate evaporative emissions, the fuel  6  has located thereon a floating member  12 . The floating member  12  is configured to stay afloat at the surface  8  of the fuel  6 . In the present embodiment, the floating member  12  is made of a buoyant plastic although, in other embodiments, it can be made of other non-metallic materials or potentially of metallic materials as well. In the present embodiment, the fuel tank  2  only includes the single floating member  12 , which is formed as a single piece, albeit in alternate embodiments multiple floating members can be employed. It is believed, however, that the use of a single floating member of appropriate physical shape and size as discussed below is advantageous relative to the use of multiple such members, both in terms of providing robustness as well as limiting the overall amount of evaporative emissions that occur. 
         [0016]    Depending upon the embodiment, the floating member  12  can have various shapes and sizes. Nevertheless, in the present embodiment of  FIG. 1 , the floating member  12  is designed to be conical (or substantially conical).  FIG. 1  in particular shows the floating member  12  to be conical in shape and to be tilted slightly, such that a top  13  of the floating member is tipped away from the viewer, and such that a base surface  17  of the floating member is visible. It will be understood that, in practice, the floating member  12 , while generally tending to be upright in position, will also rock and bob as the fuel  6  within the fuel tank  2  is jostled or otherwise moves about. Further as shown, the shape of the base surface  17  is configured to generally correspond to the inner perimeter of the fuel tank  2 . Thus, in the present exemplary embodiment of  FIG. 1  in which the fuel tank  2  is cylindrical or substantially cylindrical, the floating member  12  is a cone having with the circular (or substantially circular) base surface  17  that generally tracks the inner circular perimeter of the fuel tank. 
         [0017]    The conical shape of the floating member  12  more particularly is configured to achieve certain goals. First, the floating member  12  is designed to maximize the extent to which, when the floating member is floating within the fuel  6 , the floating member displaces and covers the fuel so as to reduce the overall extent of the surface  8  of the fuel that is exposed to the air space  10 , thus reducing fuel evaporation. The presence of the floating member  12  within the fuel tank  2  serves to reduce the exposed surface area of the fuel  6  without changing the volume, dimensions or any other characteristics of the fuel tank  2 . As a result of the floating member  12 , the surface  8  of the fuel  6  in the present embodiment is reduced to an annular region  9  around the edge/perimeter of the floating member  12  existing between that edge/perimeter and the inner surface of the fuel tank  2 , and evaporation of the fuel for the most part only occurs from that annular region portion. In the present embodiment the floating member  12  reduces the overall size of the exposed surface by at least a half, or even more (e.g., by three-quarters, seven-eights or even more), although any amount of reduction is possible depending upon the embodiment. 
         [0018]    Second, the configuration of the floating member  12  is selected so as to limit or minimize the height of the floating member, and/or so as to correspond to the shape of a roof or top portion  19  of the fuel tank. This allows for the exposed area of the surface  8  to remain minimized even while the fuel tank  2  is completely filled with fuel  6 . More particularly in the present embodiment, the roof  19  of the fuel tank  2  is generally conic (albeit with a slightly concave appearance) and thus corresponds generally to the shape of the floating member  12 . Consequently, when fuel  6  is added to the fuel tank  12 , the floating member  12  generally continues to rise upward along with the surface  8  until the floating member encounters the roof  19  of the fuel tank, at which point the fuel tank is completely filled. Assuming such a design, there is generally no circumstance in which, due to a limitation on movement of the floating member  12  upwards within the fuel tank  2 , the surface  8  rises relative to the floating member to such an extent that evaporative emissions are significantly increased. 
         [0019]    In addition, the conical structure of the floating member  12  serves to minimize the condensation of evaporated fuel atop the floating member. Rather, to the extent that fuel condenses atop the conical floating member  12 , it tends to flow off of the sides of the cone back to the surface  8  of the fuel  6 , where it reenters the main store of fuel. Further, since in the present embodiment the input orifice  5  of the fuel tank  2  is directly above the floating member  12 , fuel added to the fuel tank via the orifice likewise, upon impacting the floating member, runs down the sides of the floating member and enters the main store of fuel  6 , without any significant accumulation of fuel atop the floating member. 
         [0020]    The conical floating member  12  can be made as a solid piece or can be hollow as well. Further, the degree to which the floating member  12  extends beneath the surface  8  of the fuel  6  can vary depending upon the buoyancy of the floating member and the particular fuel being used. Notwithstanding the fact that the diameter of the conical floating member  12  is greater than its height in the present embodiment, it is nevertheless intended in other embodiments that the diameter be lesser than the height or potentially be of an equal dimension as well. 
         [0021]    Referring now to  FIG. 2 , an alternate embodiment of the floating member, shown as a floating member  14 , is shown to be located within the fuel tank  2 . In contrast to the floating member  12  of  FIG. 1 , the floating member  14  of  FIG. 2  is a double-side conical member including two cone sections, namely, an upper cone section  16  and a lower cone section  18 , which are attached back-to-back at their respective bases at a junction  20  so as to point in diametrically opposite (upward and downward) directions. Such a double-sided conical floating member  14 , in addition to providing all the advantages of the floating member  12  of  FIG. 1 , can also potentially avoid a situation where the conical floating member flips over (e.g., 180 degrees) in such a manner as to limit its effectiveness in reducing fuel evaporation and/or the amount of fuel sitting atop the floating member. In particular, if the floating member  14  of  FIG. 2  flips end-over-end such that the upper cone section  16  is inverted so as to point downward into the fuel  6 , the lower cone section  18  consequently is inverted (from the position shown) so as to point upward out of the fuel, and thus both before and after the flipping event all of the advantages provided by the floating member  12  continue to be provided. 
         [0022]    Although the two conical sections  16  and  18  forming the double-sided conical floating member  14  are shown to be of equal height and diameter, the present invention is also intended to encompass alternate embodiments of floating members having different heights and diameters of the two cone sections. For example, the cone section  18  can have a height that is larger than its diameter while the cone section  16  has a height that is less than its diameter, or vice-versa. It is, however, typically (albeit not necessarily) the case that at least the diameters of the cone sections  16  and  18  be of the same dimension to maximize the advantages of the floating member  14  in minimizing evaporative emissions. Also, while typically the conical floating member  14  is designed as two cone sections  16  and  18  that are attached back-to-back, both of which are made of the same material, in alternate embodiments the two cones can be integrally formed as a single piece or made of different materials. In addition, the double-sided conical floating member  14  can be made as a solid or hollow structure. As with respect to the floating member  12 , the height of the floating member  14  within the fuel  6  can vary depending upon the buoyancy of the floating member, the characteristics of the fuel, etc. 
         [0023]    Turning now to  FIG. 3 , a cross-sectional view taken along a line  3 - 3  of  FIG. 2  is provided, showing the fuel tank  2  with the conical floating member  14  partially immersed within the fuel  6 . As shown, the upper conical section  16  of the floating member  14  in particular is visible, with a rim  22  of the junction  20  between the conical sections  16 ,  18  of the floating member being visible beneath the fuel surface  8  and an additional junction  24  illustrating where the surface of the fuel  6  meets the conical section  16 . A tip  26  of the floating member  14  typically remains outside the surface of the fuel  6  at all times. An identical or similar cross-sectional view would be provided assuming a similar cut across the fuel tank of  FIG. 1  employing the floating member  12 . As is evident from  FIG. 3 , fuel is capable of evaporating only from the annular region  9  between the additional Junction  24  and the wall of the fuel tank  2 . 
         [0024]    Notwithstanding the above-described embodiments, the present invention is intended to encompass a variety of other arrangements of floating members and fuel tanks. For example, although the present embodiments of  FIGS. 1 and 2  do not illustrate the floating members  12  and  14  as touching the sides of the fuel tank  2 , the present invention is nevertheless intended to include such embodiments as well in which the floating member is in contact with or in close proximity with the sides of the fuel tank  2 . Further, as already noted, the exact shapes and sizes of the floating members and/or fuel tanks can vary with the embodiment. For example, the fuel tank could have an oval cross-section (rather than circular cross-section as shown in  FIG. 3 ), or could be box-like. The floating members can also take additional forms to complement different fuel tank shapes and sizes. In at least some embodiments, more than one floating member (e.g., two half-cones) can be employed within a given fuel tank. 
         [0025]    The present invention relates to a variety of embodiments of fuel tanks and floating members as can be employed in a variety of applications and for a variety of purposes. For example, embodiments of the present invention can be employed in conjunction with a variety of different internal combustion engines used in vehicles or for a variety of other purposes. Embodiments of the present invention can be particularly beneficial insofar as they reduce or even eliminate evaporative emissions from the fuel. 
         [0026]    Among other purposes, some embodiments of the present invention can be employed in conjunction with SORE engines including Class 1 and Class 2 small off-road engines such as those implemented in various machinery and vehicles, including, for example, lawn movers, snow mobiles and the like. Indeed, in at least some such embodiments, the present invention is intended to be applicable to “non-road engines” as defined in 40 C.F.R. §90.3, which states in pertinent part as follows: “Non-road engine means . . . any internal combustion engine: (i) in or on a piece of equipment that is self-propelled or serves a dual purpose by both propelling itself and performing another function (such as garden tractors, off-highway mobile cranes, and bulldozers); or (ii) in or on a piece of equipment that is intended to be propelled while performing its function (such as lawnmowers and string trimmers); or (iii) that, by itself or in or on a piece of equipment, is portable or transportable, meaning designed to be and capable of being carried or moved from one location to another. Indicia of transportability include, but are not limited to, wheels, skids, carrying handles, dolly, trailer, or platform.” 
         [0027]    Also, in at least some additional embodiments, embodiments of the present invention are applicable to engines that have less than one liter in displacement, or engines that both have less than one liter in displacement and fit within the guidelines specified by the above-mentioned regulations. In still further embodiments, the present invention is intended to encompass other small engines, large spark ignition (LSI) engines, and/or other larger (mid-size or even large) engines. In additional embodiments, the present invention is intended to be used with containers or storage tanks other than fuel tanks holding volatile fluids, which are producers of volatile organic compounds (VOC) or evaporative emissions. 
         [0028]    It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.