Abstract:
A fuel tank with a substantially constant tank volume for which the fill capacity varies with the distance at which an end of a fill neck assembly enters the fuel tank. The fill neck assembly may include a fill neck and a fill neck insert.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to vehicular fuel tanks and, in particular, variable capacity vehicular fuel tanks. 
       BACKGROUND OF THE INVENTION 
       [0002]    Optimizing the empty weight of a work vehicle (in this example, an articulated dump truck (“ADT”) is a major concern for off road equipment as extra weight may mean unnecessary fuel consumption; optimization of fuel savings for a given amount of work is a highly prized feature on such a vehicle. Adding significant weight to vehicles powered by fossil fuels are the fuel tanks which are often filled to capacity. Thus, optimization of fuel savings might require limiting the capacity of a fuel tank which has been conventionally accomplished via: (1) tanks sized to a desired capacity, (2) tanks of complex design allowing the operator of the vehicle to measure the amount of fuel in the fuel tank and to stop at certain fuel volumes. Specially sized tanks add to the cost of manufacturing tanks as the tanks must be individually designed and produced for each vehicle model/size. Tanks of complex design are costly to produce yet still require a degree of monitoring by the vehicle operator to optimally fill them. 
       SUMMARY OF THE INVENTION 
       [0003]    A device and method are presented for varying the fuel capacity of a singular tank without extra monitoring by the vehicle operator. The device may be a filler neck assembly which may include a filler neck and a filler neck insert. The method may include the use of filler neck inserts of various lengths or a filler neck insert of adjustable lengths to adjust the fuel capacity of a singular tank by adjusting the length or depth of the filler neck assembly. Conventional fuel tanks do not utilize such filler neck inserts (see  FIG. 6 , “Related Art”). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  illustrates an exemplary embodiment of a work vehicle utilizing the invention; 
           [0005]      FIG. 2  illustrates an exemplary embodiment of a fuel tank utilizing a first embodiment of the invention; 
           [0006]      FIGS. 3   a - 3   c  illustrate schematics of the exemplary embodiment of  FIG. 2  at various stages during a filling of the fuel tank; 
           [0007]      FIG. 4  illustrates an exemplary embodiment of the fuel tank utilizing a second embodiment of the invention; 
           [0008]      FIG. 5  illustrates an exemplary embodiment of the fuel tank utilizing a third embodiment of the invention; and 
           [0009]      FIG. 6  illustrates an exemplary embodiment of a conventional fuel tank which is filled to capacity. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0010]      FIG. 1  illustrates an exemplary embodiment of a work vehicle  10  which could make use of the invention. The particular embodiment illustrated is an articulated dump truck (“ADT”)  10  employing an exemplary embodiment of the invention, i.e., the variable capacity fuel tank  100 . This illustrated ADT  10  includes: a front portion  20  which may have a front chassis (not shown), an engine (not shown), ground engaging front wheels  21 , a cab frame  22 , a roof  22   a,  and a door  22   b;  and a rear portion  30  having a rear chassis (not shown), ground engaging rear wheels  31 , and a dump body  32 ; and an articulation joint  40  allowing angular change between the front portion  20  and the rear portion  30 . 
         [0011]      FIG. 2  illustrates an exemplary embodiment of the invention, i.e., the variable capacity fuel tank  100 , which may include: a fuel tank storage body  110 ; and a filler neck assembly  120  having a filler neck assembly first end  120   a  and a filler neck assembly second end  120   b.  The filler neck assembly  120  may include a filler neck  121  having a filler neck first end  121   a,  a filler neck second end  121   b  and a filler neck inner diameter  121   c;  and a filler neck insert  122  having an insert outer diameter  122   a,  an insert inner diameter  122   b  and a diametrical insert bulge  122   c.  The filler neck assembly first and second ends  120   a,    120   b  may be identical to insert first and second ends  122   d,    122   e.  The variable capacity fuel tank  100  may also include a breather assembly  130  which may include a breather neck  131  and a breather  132 . The breather neck  131  may be merely a hollow tube in communication with, and integral to, the fuel tank storage body  110  and the breather  132 . The breather neck  131  may be considered to be sealed in a manner that allows free airflow only between the breather  132  and the fuel tank storage body  110 . The filler neck  121  may be integral to the fuel tank storage body  110  as illustrated in  FIG. 2 . Some or all of the parts to the variable capacity fuel tank  100  may be plastic, steel or any other material capable of being formed and performing as described herein. Clamped to and, thus, sealing an outer diameter of one or both of the filler neck  121  and the filler neck insert  122  may be a conventional fill tube from an area of the vehicle at which the fuel is pumped in (not shown). To complement  FIG. 2 ,  FIG. 6  illustrates a conventional embodiment of the fuel tank  25 , i.e., a fuel tank without the filler neck insert  122 . 
         [0012]    In the exemplary embodiment of  FIG. 2 , the diametrical bulge  122   c  in the filler neck insert  122  may serve as a seal between the filler neck insert  122  and the filler neck  121 . In this exemplary embodiment, the filler neck assembly  120  may be held together by frictional forces via an interference fit between the bulge  122   c  and the filler neck inner diameter  121 . However, the filler neck assembly  120  may be held together via sundry arrangements, including, but not limited to screw on arrangements as in the exemplary alternative filler neck assembly  220  of  FIG. 4  and snap on arrangements as in the exemplary alternative filler neck assembly  320  of which could be used for filler neck assemblies having lengths that are adjustable without the necessity of insert change outs. 
         [0013]    In the exemplary embodiments of  FIGS. 2 ,  4  and  5  as well as schematic  FIGS. 3   a - 3   c,  the breather  132  may be designed to allow a volumetric flow rate of air V A1  of approximately twice the rate of fuel injected into the engine per hour. The rate of injection in this particular example is 12 liters/hour, thus, rendering a maximum design volumetric flow rate for the breather (V bmax ) of approximately 24 liters per hour. A design of this sort optimizes the benefits of two features which are somewhat at odds with each other, those features being: (1) the ability of the tank to breathe and thus avoid pressure changes as fuel is injected into the engine; and (2) the ability to prevent or significantly reduce fuel contamination by blocking debris from entering the fuel tank  100 . It should be noted here, that the storage body volume may be 634 liters in this exemplary embodiment and that, currently, this volume may be completely filled in approximately 20 minutes, the approximate conventional fill time for a storage body volume of this size. Thus, the filler neck may be designed to accommodate a V F  of at least 1921 liters/hour (the expected V F ), i.e., the fill rate required to transfer a fuel volume of 634 liters in 20 minutes. 
         [0014]    The exemplary schematics of  FIGS. 3   a  and  3   b  illustrate flow rates of air and fuel during a fueling of the vehicle. As illustrated in  FIG. 3   a , as the fuel tank  100  is being filled, i.e., when the fuel level in the tank  100  is below the second end  120   b,  V A1 +V A2 ≧V F  and P A ≈P T , where V A1  represents a volumetric rate for air flowing out of the fuel tank storage body  110  and through the breather  132 , V A2  represents a volumetric rate for air flowing out of the fuel tank storage body  110  and through the filler neck assembly  120 , V F  represents a volumetric rate for fuel flowing through the filler neck assembly  120  and into the fuel tank storage body  110 , P A  represents atmospheric pressure, and P T  represents fuel tank pressure. Fuel may continue to freely flow into the tank storage body  110  as long as such a condition exists. However, once P T  exceeds P A , the entrance of unpressurized fuel into the storage body  110  may be disallowed or significantly restricted. 
         [0015]    However, once the fuel level in the storage body  110  has completely covered the second end  120   b,  any rate change in fuel volume in the tank V T  must be less than or equal to V bmax  or the tank pressure P T  may quickly exceed the atmospheric pressure P A  disallowing or significantly restricting the entrance of fuel into the tank from the filling process and filling the filler neck assembly  120  as well as the filler tube (not shown), if present, as illustrated in  FIG. 3   b . The following relationships apply once the second end is completely covered: V F &gt;V A1 ; V A2 ≈0; and P T &gt;P A . To reiterate, air tends to not exit the tank storage body  110  through the filler neck assembly  120  as the second end  120   b  is closed. Therefore, pressure may build up in the tank storage body  110  as V F  exceeds V bmax  and, thus, V A1 . In this particular example, P T  quickly builds up as V F  far exceeds V A1  and, in fact, is approximately 80 times greater than V A1 . Once the fuel tops out the filler neck assembly  120  or the filler tube (not shown), if present, the operator may cease fueling the vehicle to avoid fuel waste via overflow and the fuel remaining in the filler neck and/or the filler tube  100   a  may gradually enter the storage body  110  as P T  gradually equalizes with P A  until the fuel level in the filler neck assembly  120  is approximately equal to the fuel level in the overall storage body  110  as illustrated in  FIG. 3   c . It should be noted here that the breather  132  may be designed to allow volumetric flow rates of less than or even greater than twice the rate of fuel injected per hour. As is apparent above, regardless of the capacity of the breather  132 , P T  may rapidly build up in the tank storage body  110  once the second end  120   b  is covered to disallow or significantly restrict the flow of fuel to the tank storage body  110 . 
         [0016]    Below are some alternate embodiments of the invention. Although the specifics of these embodiments render clear differences, the principles of operation, i.e., varying tank capacity by varying a length of an inlet assembly remain the same. 
         [0017]    In the exemplary screw on arrangement, i.e., the filler neck assembly  220  of  FIG. 4 , the filler neck  221  may include an internal thread  221   b.  As illustrated, the filler neck insert  222  may include an insert top  222   a  and a tube with a mating external thread  222   b  for the internal thread  221   b.  In such an arrangement, the filler neck insert  222  is inserted into the inner diameter  221   a  of the filler neck  221  and secured to the filler neck  221  by screwing the tube  222 ′ into the filler neck  221  and tightening via the internal and external threads  221   b,    222   b.  The second filler neck assembly may include a first assembly end  220   a  and a second assembly end  220   b.  The capacities of the fuel tank storage body  210  and tank storage body  110  may remain equal when the location of their corresponding. The length of the filler neck assembly  220  may be adjusted by substituting filler neck inserts of different lengths in the assembly  220 . This embodiment may also have a bulge (not shown) similar to the bulge  122   a  but, in this particular arrangement, the threads and/or the fit between the insert top  222   a  and the filler neck  221  may provide the necessary seal between the filler neck insert  222  and the filler neck  221 . The capacities of the fuel tanks  200  and  100  may be equal when the locations of their respective filler neck second assembly ends  300   b,    100   b  have equivalent locations. 
         [0018]    Note that the exemplary variable capacity fuel tank  300  of  FIG. 5  includes an alternative filler neck assembly  320  having an assembly first end  320   a  an assembly second end  320   b.  As illustrated in  FIG. 5 , the filler neck assembly  320  may include an adjustable length filler neck insert  322  which may include: a cap or adjuster  322   a  with an insert locking tab  322   c  having a first tab side  322   c ′ and a second tab side  322   c ″, and an external thread  322   a ″and a tube  322   b  having a portion of its length threaded with internal thread  322   a ′ matching the external thread  322   a ″, and a vertical filler neck sliding tab  322   b ′. The filler neck  321  may include a ridge  321   b  having a first side  321   b ′ and a second side  321   b ″. In this snap on arrangement, the exemplary adjustable length filler neck insert  322  may be secured to the filler neck  321  by orienting and aligning it as illustrated and pushing filler neck insert  322  into the inner diameter  321   a  of the filler neck  321  until a resistance between the insert locking tab  322   c  and the ridge  321   b  is overcome and the insert locking tab  322   c  snaps into place on the second side of the ridge  321   b.  The length of the insert  322  is adjusted via a sliding of the tube  322   b  toward and away from the first filler neck assembly end  300   a  as the adjuster  322   a  is turned to the left or right and the insert sliding tab  322   b ′ slides within a filler neck groove  321   c  designed to inhibit rotation of the tube  322   b  within the filler neck assembly  300  when the adjuster  322   a  is being rotated. The capacities of the fuel tanks  300  and  100  may be equal when the locations of their respective filler neck second assembly ends  300   b,    100   b  have equivalent locations. 
         [0019]    As illustrated in  FIG. 6 , conventional tanks  50  may include only the filler neck  51  and not a filler neck insert (not shown). Thus, during a filling procedure, the storage body  52  may be filled to the top wall  52   a.    
         [0020]    Having described the preferred embodiment and a few alternatives, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.