Abstract:
A vehicle fuel utilization system for a truck having multiple tanks, an above-tank crossover line coupling the two tanks, a draw line coupled only to a primary tank, and a return line coupled to the crossover line or to either of the tanks separately.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a vehicle utilization fuel system for use primarily in internal-combustion road vehicles. 
     Multiple-tank fuel systems heretofore known employ a plurality of tanks, with the fuel from one tank being passed to another tank through crossover lines coupled to the bottom walls of the tanks. These crossover lines are generally the lowest parts of the vehicle, since flow between the tanks depends upon gravitational forces, and are generally more susceptible to accidental breakage due to debris on the highway or other obstructions which may impact against the below-tank crossover line. 
     Fuel tank utilization systems, such as shown in U.S. Pat. No. 3,981,321, were developed in which an above-tank crossover line was employed. This patented system requires feed lines of about equal length, about equal inner diameters, and about equal fuel flow restrictions, and requires return lines separate from the feed lines, also each having about equal length, about equal inner diameters, and about equal fuel flow restrictions. This system also removes fuel simultaneously from all of the tanks. 
     Other systems involve expensive mechanical parts, such as selector valves, for selecting the return and draw from the tanks independently. Each time a fitting or valve is added to a fuel tank system, the possibility of creating an air leak increases. An air leak in a vehicle fuel system, particularly a diesel-powered, internal-combustion system, creates considerable difficulty for the operator to seal the air leak and reinitiate suction and flow of fuel to the diesel engine. If the engine on a large truck, such as a tractor-trailer truck, for example, is deprived of fuel while under way, it will stop the engine and damage the fuel pump. 
     The same stoppage of the engine and damage to the fuel pump can also occur for any of the fuel utilization systems which draw simultaneously from the multiple tanks. By drawing simultaneously from the multiple tanks, air can be drawn when the higher tank is running low in fuel. If one tank is at a lower elevation than the other, the fuel in the higher tank will be depleted prior to the fuel in the lower tank, allowing the draw tube to suck air, thus depriving the engine and pump of fuel. Tractor-trailer trucks, for example, are frequently driven on crowned or cambered roads, or the engines are idling while the truck is resting on a shoulder. In the United States road system, at least, the right-hand tank, if the tanks are transversely spaced on the vehicle, will thus generally be at a lower elevation than the left-hand tank. In foreign countries such as England, where the vehicles are driven on the left side of the road, the left-hand tank will frequently be below the right-hand tank. 
     Hereinafter, the term &#34;primary tank&#34; will refer to the tank which is on the lower elevation, the right-hand tank in a U.S. road vehicle and the left-hand tank on a vehicle driven in a country where the vehicle operates on the left-hand side of the road. The other tank will be termed a &#34;secondary tank.&#34; 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a fuel tank utilization system for optimizing the draw and minimizing the risk of insufficient fuel being supplied to the engine. An above-tank crossover line is used with crossover tubes being connected to the line and terminating at their lower ends at the bottoms of the tanks. A separate draw line is coupled to a draw tube in the primary tank. The draw tube in the primary tank terminates at the bottom of the primary tank. By utilizing a separate draw line, the draw tube can be placed in the primary tank, which is the lower tank of two transversely spaced tanks. This will always insure that the tank with the most fuel will be the one being utilized to supply the engine. Thus, even though the secondary tank becomes depleted of fuel, there may still be sufficient fuel left in the primary tank to feed the engine. A fuel gauge will be provided in the primary tank and will be the only fuel gauge necessary. The return line can be connected to the crossover line or direct to either the secondary tank or the primary tank. 
     Utilizing this type of system provides the minimum number of connections which could be the source of air leaks. Only one fuel gauge is necessary. The return line does not have to be of any particular length or diameter relative to its connection to either or both tanks. Furthermore, both the return line and the draw line can be connected to the vehicle frame adjacent their respective tanks, making the connection to the frame and tanks easier. It is recognized that this system can be used also with a three or four tank arrangement using two or three crossover lines to the secondary tanks with a single draw line to the primary tank. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of one embodiment of the invention. 
     FIG. 2 is a schematic illustration of a second embodiment of the invention. 
     FIG. 3 is a schematic illustration of a third embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As best shown in the drawings, the vehicle fuel system will include an auxiliary or secondary tank 1 and a primary or main tank 2. These tanks are each provided with a conventional filler cap 3 fitted with a vent to allow the tank to breathe. A crossover tube 11 is connected to the top of the tank and terminates at its lower end at the bottom of the tank. Approximately a 11/4-inch clearance between the bottom of the crossover tube 11 and the bottom of the tank is a suitable clearance. A second crossover tube 12 of similar construction is positioned in the primary tank. A crossover line 10 is coupled to the top ends of the crossover tubes 11 and 12. A return line 18 returns fuel from the diesel engine to the common crossover line 10. 
     The primary tank is provided with a draw tube 16 having its lower end terminating at the bottom of the primary tank. A draw line 14 is coupled to the top end of the draw tube and connects to the pump for the diesel engine. A conventional float-type fuel gauge unit 20 is provided in the primary tank only. Obviously, a fuel gauge can be positioned in the secondary tank, but is generally unnecessary. 
     With this type of system, there is a minimum of connections in the critical draw line between the primary tank and the fuel pump. As is well known to those skilled in the art, and shown for example in the aforementioned Pat. No. 3,981,321 the draw line and the return fuel line of a diesel-powered, internal-combustion engine are connected directly to the combustion chamber injectors, and the opposite end of the return line connects to the fuel tank as shown in the figures. The return line, however, can go either to the crossover line, as shown in FIG. 1, or to the primary tank, as shown in FIG. 2, or only to the secondary tank, as shown in FIG. 3. 
     The fittings may be of any conventional type which provide a good mechanical connection and a tight seal, or, in the alternative, the pipes may be welded or otherwise joined to upper portions of each tank and extend down into the tanks, as illustrated. 
     The return lines and draw lines need not be of any critical diameter. The only requirement is that the lines be sufficient to handle the flow of fuel anticipated in the draw system and in the return system. The draw lines and return lines do not have to be located symmetrically or equidistantly between the tanks, but can be located adjacent to one of the tanks for ease of assembly with the vehicle frame. 
     With this system, the secondary tank can operate at the same level as the primary tank or at a higher level having less fuel in it for a vehicle which is driving on a cambered or crowned road surface or otherwise operated in any instance on an angle. With this system, the fuel is drawn exclusively from one tank, relying on the crossover lines to maintain the levels in the tanks. As is well known to those skilled in the art, the transfer of fuel from one tank to another in the fuel tank systems shown in FIGS. 1-3 necessarily results from different fuel levels in the two tanks. When fuel is drawn from the primary tank 2, the fuel level in the primary tank is lowered below the fuel level of the secondary tank 1, which causes a pressure differential between the crossover line opening in the primary tank and the opening in the secondary tank. Atmospheric pressure forces the fuel in the secondary tank up through crossover tube 11, through the crossover line 10, down crossover tube 11, and into the primary tank until the fuel levels in the two tanks are equalized. This method of transferring liquid is commonly known as siphoning, with the crossover tube being the siphon. That is, the higher level of fuel will automatically force the fuel up out of one tank through the sealed crossover line into the tank whose fuel is at a lower level to maintain the fuel in each tank at the same horizontal plane. 
     While the preferred embodiments of the invention have been illustrated and described, it should be understood that variations will be apparent to those skilled in the art. Accordingly, the invention is not to be limited to the specific embodiments illustrated in the drawings.