Patent ID: 7611167

Claim:
In a vehicle having a frame, a vehicle body which fits over the frame, and a plastic fuel tank for storing fuel, where said fuel tank is supported on the frame so as to be elevated above ground level, the improvement comprising configuring said fuel tank with integral noise-suppressing structure for suppressing noise caused by movement of the fuel during vehicle operation, said fuel tank comprising: a substantially flat bottom; front and rear walls rising from the bottom; left and right side walls rising from the bottom; and a substantially flat top wall continuous with upper edges of the front and rear walls and upper edges of the left and right side walls; wherein in a vehicle traveling direction, a length of the substantially flat top wall is more than half of a length of the substantially flat bottom; wherein the vehicle body is configured and arranged to substantially cover the fuel tank; wherein at least one of the front wall and the rear wall of the fuel tank includes a stepped portion comprising a plurality of steps formed integrally thereon, the stepped portion being integrally formed as part of one of the front wall and the rear wall and extending progressively inwardly in a generally inclined direction as the stepped portion extends upwardly, the stepped portion being operable to suppress wave motion on a liquid surface of the fuel, which occurs when the vehicle accelerates or decelerates; and wherein the plurality of steps in the stepped portion includes a first step defining the lowest part of the stepped portion which is inset from one of the front or the rear wall, and the remaining steps rise in sequence such that each respective step is higher than the preceding step.