Abstract:
An apparatus and method for the balancing of fuel among tanks in a circulating fuel system. The tanks in the system have both a draw conduit and a return conduit mounted to and extending into the tank. Flow restriction devices are mounted in both the draw and the return conduits and are controlled by a fuel level detection system, which detects the fuel in the tank.

Description:
BACKGROUND OF INVENTION  
         [0001]    The present invention relates to the balancing of fuel among tanks in a circulating fuel system mounted on a vehicle or other fuel consuming systems with multiple tanks. More specifically flow restriction devices on the fuel flow out of and into each tank are used to balance stored fuel among a number of tanks. The level of fuel in a tank controls the flow restriction devices.  
         PRIOR ART  
         [0002]    Circulating fuel supply systems that include multiple fuel tanks are known and are typically used with vehicles. When applied to a vehicle the typical circulating fuel system includes at least two fuel tanks, a fuel pump, and an engine with a fuel supply rail. In operation, the fuel pump draws fuel from the tanks, and pumps the fuel to the fuel supply rail of the engine. The engine consumes some of the fuel. Unconsumed fuel leaves the engine and is returned to the fuel tanks. Thus, fuel is in constant circulation out of and back into the fuel tanks.  
           [0003]    As typically used with vehicles the tanks of a circulating fuel system are initially full of fuel. As the vehicle operates, fuel is drawn from the tanks. An engine consumes some of the fuel and any unconsumed fuel is returned to the tanks. Overall stored fuel decreases; however, if the fuel draw and return are not equal for each tank, then the quantity of fuel in the tanks will vary over time. Geometric or mechanical layout differences in tank, draw conduit, and return conduit, or changes in grade during vehicle operation make equal fuel draw and return practically unrealistic. Premature depletion of fuel in a tank relative to other tanks typically results in fuel starvation and engine operational problems.  
           [0004]    Unequal fuel draw and return results in the problem of one tank emptying before the others. This unequal depletion of fuel in the various tanks leads to erratic engine operation or fuel starvation. Various solutions have been proposed to balance the fuel in the tanks and to avoid the problems associated by unequal depletion of fuel from the multiple tanks. The known solutions in the prior art include the use of equal tank and conduit geometry, the use of one or more crossover lines, a venturi device, multiple pumps, special flow dividers, shuttle valves, a priming fuel line, or a complicated computer control system which requires an on-board computer and a electrical system for operation. The applications of these various solutions are described in a number of patents.  
           [0005]    The present invention balances the fuel in multiple fuel tanks through the use of flow restriction devices in both the draw and return conduits in each tank. As compared with prior inventions, the present invention eliminates the need for similar geometry of the tanks and conduits and their physical layout, crossover lines, more than one fuel pump, a venturi device, special flow dividers, shuttle valves, a priming fuel line, a computer, or an electrical system as needed to operate the computer.  
         SUMMARY OF INVENTION  
         [0006]    An object of the present invention is to provide an apparatus and a method for the balancing of fuel between the various tanks in a multiple tank circulating fuel system. The present invention as applied to vehicles is a circulating fuel system, which includes at least two tanks, a pump which draws fuel from the tank, and an engine which receives fuel from the pump and consumes part of the fuel. Unconsumed fuel is returned to the tanks. The invention satisfies the objective by having a fuel level detection system, a draw conduit restriction device, and a return restriction device for each tank.  
           [0007]    In the method of the present invention, the level of fuel in each tank is balanced by detecting the level of fuel in the tank, and then restricting the flow of fuel out of the tank through the draw conduit and restricting the flow of fuel into the tank through the return conduit based on the detected fuel level. 
       
    
    
     DRAWINGS  
       [0008]    [0008]FIG. 1 illustrates a circulating fuel system with flow restriction devices in both the draw and return conduits.  
         [0009]    [0009]FIG. 2 illustrates a float and a float arm mechanism for the control of both the draw and return flow restriction devices.  
         [0010]    [0010]FIG. 3 illustrates a float and a twisted guide mechanism to control gates which restrict both the draw and return fuel flow.  
         [0011]    [0011]FIG. 4 illustrated the use of a caged floatball device on the draw conduit and a caged floatball device on the return conduit to restrict the fuel draw and fuel return respectively.  
         [0012]    [0012]FIG. 5 illustrates a float and a gear mechanism to control gates which restrict both the draw and return fuel flow.  
         [0013]    [0013]FIG. 6 illustrates a vehicle with dual fuel tanks of a circulating fuel system mounted to the main rail of the chassis.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    The present invention uses flow restriction devices attached to both the draw and the return conduits of individual fuel tanks to balance the quantity of fuel in the fuel tanks of a circulating fuel system. The explanation of this invention begins with a description of the circulating fuel system with multiple fuel tanks. As shown in FIG. 1, a typical circulating fuel system includes a first tank  30  and a second tank  31 . The first and second tanks  30  and  31  contain draw conduits  40  and  41 , respectively. The draw conduits  40  and  41  combine into an inlet  42  of the fuel pump  20 . The fuel pump discharge  15  connects the fuel pump  20  to the engine  10 . In a typical engine the fuel flows through a fuel rail (not shown). A fuel conduit  52  connected to the engine  10  splits into return conduits  50  and  51  which in turn are connected to tanks  30  and  31 , respectively.  
         [0015]    The draw conduit  40  in the first tank  30  contains a draw restriction device  90 . Similarly, the return conduit  50  in the first tank  30  contains a return restriction device  100 . Restriction devices,  90  and  100 , connect to a float  70  through a float arm mechanism  60 . Similarly, the draw conduit  41  and the return conduit  51  in the second tank  31  contain corresponding restriction devices  91  and  101 . These flow restriction devices are connected to a float  71  through a float arm mechanism  61 .  
         [0016]    In operation, fuel in tanks  30  and  31  is drawn into the draw conduits  50  and  51 , respectively. The fuel flows past the draw restriction devices,  90  and  91 , which control the relative, flow of fuel out of fuel tanks  30  and  31 , respectively. The draw restriction devices  90  and  91  are controlled based on fuel levels  80  and  81  through respective float arm mechanisms  60  and  61  and floats  70  and  71 . At a low fuel level in either tank  30  or  31  the draw restriction devices  90  or  91 , which are respectively controlled through float arm mechanisms  60  and  61 , restrict the flow of fuel from the corresponding fuel tank  30  or  31 . The restriction of fuel flow from tanks  30  and  31  decreases as the fuel level in the tank increases.  
         [0017]    Once past the draw restriction devices  90  and  91 , the fuel flows out of the draw conduits  50  and  51  and combines in the fuel pump inlet  42 . The combined fuel is drawn into the fuel pump  20 , which provides the suction to draw the fuel from the fuel tanks  30  and  31 . From the fuel pump  20  the fuel flows under pressure to the engine  10  via the fuel pump discharge  15 . In a typical vehicle engine the fuel flows through a fuel rail in the engine from which some of the fuel is consumed by the engine  10 . Fuel that is not consumed exits the engine  10 , and flows into a fuel return conduit  52 . From the fuel return conduit  52 , the return fuel splits between the return conduits  50  and  51 .  
         [0018]    The return fuel in return conduits  50  and  51  flows past the return restriction devices  100  and  101  which control the relative flow of return fuel into fuel tanks  30  and  31 , respectively. The return restriction devices  100  and  101  are controlled based on fuel levels  80  and  81  through the respective float arm mechanisms  60  and  61  and floats  70  and  71 . At a high fuel level in a tank, the return restriction devices  100  or  101 , which are respectively controlled through float arm mechanisms  60  and  61 , restrict the flow of return fuel into the corresponding fuel tanks  30  or  31 . The restriction of return fuel flow into tanks  30  and  31  decreases as the fuel level in the tank decreases.  
         [0019]    The restriction devices  90 ,  91 ,  100 , and  101  operate to balance fuel among tanks  30  and  31  by providing a varying degrees of restriction to fuel flow from and into tanks  30  and  31  based on the relative fuel levels  80  and  81 . For example, if the fuel level in tank  30  is greater than the fuel in tank  31 , then the draw restriction device  90  will be open to a greater degree than the draw restriction device  91 . This allows fuel to be preferentially drawn from tank  30  as opposed to tank  31 . Similarly, if the fuel level in tank  30  is greater than the fuel level in tank  31 , then the return restriction device  100  will close to a greater degree than the return restriction device  101 . Thus, fuel preferentially returns to tank  31  as opposed to tank  30 . With more fuel being drawn from and less fuel being returned to tank  30  relative to tank  31 , the fuel quantities in tanks  30  and  31  eventually become equal and the tanks are considered balanced.  
         [0020]    In an embodiment of the invention as shown in FIG. 2, the flow restriction devices are butterfly valve  150 , which is mounted inside draw conduit  40 , and butterfly valve  160 , which is mounted inside return conduit  50 . The butterfly valves  150  and  160  are supported on opposite ends of a shaft  110 . The shaft  110  is moveable mounted through both a draw conduit hole  120  in the draw conduit  40  and a return conduit hole  130  in the return conduit  50 . The butterfly valves  150  and  160  are supported perpendicular to each other when viewed form either end of the shaft  110 . The float arm mechanism  60  is attached to the support shaft  110 , and is designed to move the support shaft  110  through a 90-degree rotation from the full tank position to the empty tank position.  
         [0021]    In the operation of this embodiment, the draw butterfly valve  150  in the draw conduit  40  is fully open and the return butterfly valve  160  in the return conduit  50  is fully closed when the fuel level in the tank is high. Conversely, the draw butterfly valve  150  in the draw conduit  40  is fully closed and the return butterfly valve  160  in the return conduit  50  is fully open when the fuel level in the tank is low.  
         [0022]    The embodiment shown in FIG. 2 directly connects the float arm mechanism to the flow restriction devices. However, the float arm mechanism may also be indirectly connected to the float restriction devices through a gear mechanism, as shown in FIG. 5. In this variation a gear device  480  indirectly connects the float arm  60  to the restriction devices, draw gate  450  and return gate  460 . One skilled in the art would further recognize that restriction devices are not limited to butterfly valves but may be blades, balls, other types of valves or gates, etc. In addition, the restriction devices may be located inside the draw and return conduits or proximately close to the respective open ends of the conduits.  
         [0023]    Another embodiment of the present invention as shown in FIG. 3 includes a float  200  slideably mounted to a twisted guide  210  and the draw conduit  40 . A first end  260  and a second end  270  of the twisted guide  210  are rotatably mounted to a support structure  290 , which is mounted inside the tank (not shown). Alternatively, the first and second ends of the twisted guide  210  may be rotatably mounted to the draw conduit  40 , or an inside surface of the tank  30 . The draw restriction device is a draw gate  220 , which is mounted on the twisted guide  210  and is proximately close to the draw conduit inlet  230 . The return restriction device is a return gate  240 , which is mounted to the twisted guide  210  and is proximately close to the return conduit outlet  250 .  
         [0024]    For this embodiment the up and down movement of the float  200  in response to fuel level in the tank causes the twisted guide  210  to rotate around its longitudinal axis. The draw conduit  40  acts to prevent rotation of the float  200 , thus giving rise to rotation of the twisted guide  210  as the float  200  move up and down. The rotation of the twisted guide  210  results in the movement of draw gate  220  and return gate  240 . The draw gate  220  moves to restrict fuel flow into the draw conduit inlet  230  as the fuel level in the tank decreases. Conversely, the return gate  240  moves to restrict fuel flow out of the return conduit outlet  250  as the fuel level increases. Another embodiment of the present invention as shown in FIG. 4 includes a draw floatball  300  contained in a draw cage  310 , and a return floatball  320  contained in a return cage  330 . The draw cage  310  is attached to an end of a draw conduit extension  340 , which is U-shaped and is in close proximity to the bottom of the tank  30 . The second end of the draw conduit extension  340  is attached to the draw conduit  40 . A weep hole  350  in the draw conduit extension is optional. The return cage  330  is attached to the outlet of the return conduit  50 .  
         [0025]    In this embodiment, the return floatball  320  restricts fuel flow out of the return conduit  50  when the tank fuel level is high. When the level of fuel in the tank is low the draw floatball  300  restricts the flow of fuel out of the tank and into the draw conduit  40 . An optional weep hole  350  in the draw conduit extension  340  allows residual fuel in the very bottom of the fuel tank to be drawn into the draw conduit  40 .  
         [0026]    Another embodiment of this invention is a vehicle  500  with chassis  510  to which is mounted a circulating fuel system with at least two tanks. FIG. 6 specifically shows a truck with two tanks,  30  and  31 , mounted to a frame rail  520  of chassis  510  by a number of attachment devices  530 . Although not shown the rest of the circulating system, which includes an engine, a pump, a draw conduit, and a return conduit, are mounted to the vehicle chassis  510  or cab  505 .  
         [0027]    The embodiments disclosed above describe a variety of flow restriction devices which include butterfly valves, gates, and caged floatballs. Flow restriction devices may also include different types of valves such as ball valves, globe valves, check valves, flapper valves, etc. In addition, flow restriction devices may also include a venturi, an orifice, etc. including variations such as a variable venturi, a variable orifice, etc. One skilled in the art would understand that there are many types of flow restriction devices which may be used and the devices are not limited to those in the embodiments or examples given in this disclosure.  
         [0028]    In addition, a fuel level sending device may be provided for use in monitoring the fuel level in an individual tank. The fuel level sending device may be a mechanical device as the sight gauge  125  in FIG. 1 for the monitoring of the fuel level in close proximity to the tank, or an electric rheostat (not shown) connected to either a float or float arm for use in displaying the fuel level inside the cab of a vehicle.  
         [0029]    The present invention is also a method for detecting a fuel level in a tank and controlling both the draw of fuel out of and the return of fuel into a tank based on the detected fuel level. The method also includes the comparing of fuel levels in at least two tanks and determining a differential level which is used to control the fuel drawn and returned to each fuel tank. While the present invention is shown in several embodiments, it is not limited but susceptible to various changes and modifications without departing from the spirit and scope of the invention.