It is known that the use of diaphragm carburetors can result in problems with regard to the evacuation or venting of air from fuel lines. The problem on vibratory rammers occurs when the machine is operated until the fuel runs out completely and is then refueled. The small difference in height between the fuel tank and the diaphragm carburetor causes air to be trapped inside the fuel lines with little chance of rising and being evacuated via normal venting of the fuel tank. The air trapped inside prevents fuel from reaching the diaphragm carburetor. The vibratory rammer may therefore be extremely difficult to start and requires an unacceptable number of attempts before the machine actually starts.
FIG. 7 of U.S. Pat. No. 6,874,482 shows how a fuel system is provided with complementary venting. A venting line for air extends from a branch connection on the fuel line, just before the diaphragm carburetor, and continues on to the fuel tank. The routing of the venting line continues up to the fuel tank and the venting line exits above the level of the fuel in the tank. In this way, a complementary venting of the fuel system is achieved under favorable conditions. There is, however, considerable risk that small amounts of fuel remaining in the venting line prevent the passage of air through the line. While refueling, there is also the risk of small amounts of fuel being led in the reverse direction in the venting line thus preventing the passage of air through the line.
In U.S. Pat. No. 6,419,420, a completely sealable fuel tank is shown. All tank connections can be closed by valves. The risk of leakage during transportation of the machine is minimized. The tank venting valve and the fuel valve are integrated with the fuel tank and are operable by a coordinated action as shown in U.S. Pat. No. 6,419,420 incorporated herein by reference. Introduction of a venting line for air, as in U.S. Pat. No. 6,874,482, would in itself provide a possibility for some complementary venting but at the same time would require an additional valve integrated with the fuel tank and integration in the coordinated action.