FUEL TANK

Technical field

The present invention relates to a fuel tank according to the preamble of claim 1.

Background

Vehicles are provided with one or more fuel tanks for storage of vehicle fuel. Ordinary vehicle fuels such as ethanol, gasoline, diesel fuel and the like give off fire hazard gases at ambient temperatures which often occur during refuelling of vehicles. There is thus risk of ignition of the fire hazard gases which propagate around the fuel tank filling orifice during filling of the tank, e.g. by static electricity giving rise to a spark which ignites the gas. In unfortunate circumstances, gas outside the fuel tank may be ignited, followed by flames from outside the fuel tank propagating down into the fuel tank, whereupon the gas in the fuel tank also ignites, which may lead to the fuel tank exploding.

A known practice for preventing the explosion risk is to earth the fuel tank's filling pipe and the filling station's fuel delivery nozzle to the vehicle frame and/or the filling station in order to prevent potential differences and spark formation due to static electricity. Ignitable gases will nevertheless be present around the fuel tank's filling aperture and may be ignited by other causes.

Another known practice for preventing the explosion risk is to provide a flame guard made of mesh material a short distance down in the fuel tank's filling pipe, thereby preventing flames from outside the fuel tank propagating down into the fuel tank. However, the amount of ignitable gases which rise up from the filling aperture during refuelling is only diminished to a very small extent, while at the same time the fuel flow into the fuel tank during refuelling is limited in that it is difficult for liquid to make its way through the mesh material in the filling pipe.

Brief description of the invention

The problem that flames from outside the fuel tank can propagate down into the fuel tank and lead to the gas in the fuel tank igniting and the fuel tank exploding is solved according to the invention by a fuel tank according to the characterising part of claim 1.

A fuel tank according to claim 1 having the characteristics that a liquid seal adapted to separating the gas space in the fuel tank from the surrounding atmosphere is arranged at the lower end of the filling pipe, and that the liquid which separates the gas space in the fuel tank from the surrounding atmosphere is the very fuel with which the fuel tank is intended to be replenished, affords the advantage that flames from outside the fuel tank cannot propagate down into the fuel tank, and hence the ignitable gas in the fuel tank is prevented from igniting and the risk of a fuel tank explosion can be eliminated. Moreover, the amount of ignitable gases which flow out via the fuel tank's filling orifice is limited, and the device is also maintenance-free in that it has no moving parts or wearing parts.

Brief description of the drawing

The invention is explained in more detail below with reference to the attached drawing, in which:

Figure 1 depicts schematically a fuel tank according to an embodiment of the invention.

Description of preferred embodiment

Figure 1 depicts schematically a fuel tank 2 according to an embodiment of the invention, in which the fuel tank 2 comprises a filling pipe 4 and a liquid seal 6 which is adapted to separating the gas space 8 in the fuel tank 2 from the surrounding atmosphere 10, and the liquid 12 which separates the gas space 8 in the fuel tank 2 from the surrounding atmosphere 10 is the very fuel with which the fuel tank 2 is replenished. The presence of the liquid seal 6 means that the filling orifice 14 of the fuel filling pipe 4 will never be in direct communication with the inside of the fuel tank 2, thereby making it impossible for a flame at the mouth of the filling orifice 14 to make its way into the gas space 8 in the fuel tank 2. A flame might make its way into the filling pipe 4 but will be stopped by the fuel in the liquid seal 6, since it is only the gases from the fuel in the liquid seal 6 which can ignite, whereas the fuel as such will not ignite. Moreover, the gas space in the filling pipe 4 is limited, so no imminent explosion risk arises if the gas in the filling pipe 4 is ignited. The largest amounts of fire hazard gases are formed within the actual fuel tank 2 and accumulate in the gas space 8 of the fuel tank 2, from which the gases may be led away through a traditional venting valve 16 arranged on the fuel tank 2.

The fact only that a small portion of the volume of ignitable gas flows out through the filling aperture 14 during refuelling reduces the risk of this gas being ignited as compared with the previous situation whereby a large amount of ignitable gas flowed out through the filling aperture 14 during refuelling. In order in addition to prevent the risk of ignition of the smaller volumes of ignitable gases present around the mouth of the filling aperture 14 during refuelling, the filling pipe 4 of the fuel tank 2 is preferably earthingly connected via an earth connection 18 to the frame 22 of the vehicle 20, and a further earth connection 24 is provided for connecting the fuel delivery nozzle 28 of the filling station 26 to the frame 22 of the vehicle 20 to prevent potential differences between the filling pipe 4 and the delivery nozzle 28 and spark formation due to static electricity. The earth connection 24 for connecting the delivery nozzle 28 of the filling station 26 to the frame 22 of the vehicle 20 may for example comprise a resilient cover 25 earthed to the filling pipe 4 and closing the mouth of the filling pipe 4, thereby earthing the delivery nozzle 28 to the cover 25 before the delivery nozzle 28 is introduced downwards into the filling pipe 4.

The fact that only small volumes of ignitable gases flow out through the filling aperture 14 during refuelling means that the person refuelling the vehicle is exposed to a smaller amount of these gases than previously, thereby reducing the health risks during refuelling.

The liquid seal 6 comprises a container 30 with at least one aperture 32 in its upper end 34, which container 30 is filled with fuel during refuelling, since the lower end 36 of the filling pipe 4 leads into the container 30 at a position below the aperture 32 in the upper end 34 of the container 30 as viewed in a vertical direction, and the liquid which passes through the container 30 overflows into the fuel tank 2 via the aperture 32. The fact that the lower end 36 of the filling pipe 4 leads into the container 30 below the surface of the liquid with which the container is filled means that these features constitute a liquid seal 6 in which the liquid 12 which separates the gas space 8 in the fuel tank 2 from the surrounding atmosphere 10 is the very fuel with which the fuel tank 2 is replenished.

The filling pipe 4 is preferably fastened to the fuel tank 2 at the point where the filling pipe 4 enters the fuel tank 2. The container 30 is preferably fastened to the filling pipe 4 by, for example, rods 38, 40 (depicted in dotted lines in the diagram). The container 30 is preferably made of the same material as the filling pipe 4 to make it easy for them to be joined together.

The filling pipe 4 is preferably cylindrical and the container 30 is preferably provided with planar bottom 29 and cylindrical sidewall 31. The container 30 is preferably provided with at least one splash bulkhead 42 on its inner side at the aperture 32 in its upper end 34 in order to keep as much liquid as possible in the liquid seal 6. At least one further splash bulkhead 44 may be arranged on the outside of the filling pipe 4 at the lower end 36 of the filling pipe 4, and the two splash bulkheads 42, 44 are preferably so arranged that they overlap one another in the vertical direction, thereby providing a passage 46 for fuel between the splash bulkheads 42, 44.

Refuelling involves a fuel delivery nozzle 28 being brought towards the filling orifice 14 and fuel thereafter being poured into the filling pipe 4. At the lower end 36 of the filling pipe 4, the fuel flows down into the container 30 and up along the sides of the container, preferably via a passage 46 between two splash bulkheads 42, 44, and proceeds to an aperture 32 in the upper end 34 of the container 30, via which the fuel flows into the fuel tank 2. If the fuel tank 2 is relatively empty at the time of refuelling, as depicted in the diagram, the fuel runs downwards from the upper end 34 of the container 30 along the outer sides of the container 30, but if the fuel tank 2 is relatively full the fuel proceeds into the fuel tank 2 along only the outside of the filling pipe 4.

To ensure that the liquid seal 6 will not reduce the possible fuel flow through the filling pipe 4 during refuelling, the liquid seal is preferably provided with a large diameter. The further down in the fuel tank 2 the liquid seal 6 is situated, the higher the fuel column may reach in the filling pipe 4, thereby increasing the possible fuel replenishment rate.