Device for limiting the filling level in a fuel tank

An overfill prevention device for a fuel tank comprises a flap valve 31 with a crank arm 32, and a coupling rod 25 mounted for relative movement in a float 21. As a fuel stream flows into the tank via a filler neck 2, the float rises without moving the coupling rod until a portion of the float contacts a stop member 26 on the coupling rod. As the float rises further, the coupling rod and crank arm are lifted and the flap of the valve is moved through at least one-fifth of its pivoting range into the inflowing fuel stream. The flap valve is fully closed by the fuel stream, thus causing a fuel build up in the filler neck which switches off the fuel supply. Fuel remaining in the filler neck can drain into the tank through a leakage gap, and the weight of the coupling rod on the crank arm reopens the flap valve. The centre line of the float may be offset from the centre line of the filler neck, which may have a U-shaped cross-section in the region of the flap valve. The device ensures that the filler neck is unobstructed until the filling operation is completed.