Patent ID: 8225598

Claim:
A metering device for introducing liquid reducing agent into an exhaust gas tract, comprising: a working tank which includes a tank contents; a delivery unit which communicates with the working tank and has a reversible feeding direction; a storage tank that communicates with the delivery unit via a filling line, and the filling line includes a connection/blocking valve which blocks a fluid flow into the storage tank; and a metering valve which communicates with the delivery unit and is supplied with the tank contents by the delivery unit, the metering valve being arranged for dispensing the tank contents in a dispensing direction, wherein the metering valve is in fluidic communication with the filling line, and wherein the metering valve communicates with the delivery unit such that the delivery unit, when the feeding direction is reversed, builds up a negative pressure between the delivery unit and the metering valve and, as a result of the negative pressure build-up, gas originating in the exhaust gas tract is aspirated through the metering valve in a direction opposite to the dispensing direction.