Patent ID: 7287964

Claim:
A pumping system for coating powders, comprising at least one powder pump comprising: a metering chamber which is bounded by a chamber housing; and an expelling element which is forward-displaceable relative to the chamber housing during a pressure stroke and backward during a suction stroke; the metering chamber comprising: a powder intake duct associated with a power intake valve, a powder outlet duct associated with a powder outlet valve, and a compressed gas intake duct associated with a compressed gas intake valve, the powder intake valve being opened to aspirate a metered quantity of powder into the metering chamber while the powder outlet valve and the compressed gas intake valve being closed, whereby a movement of the expelling element in the direction of the suction stroke aspirates powder through the powder intake duct into the metering chamber, and the powder intake valve being closed in order to convey the metered quantity of powder out of the metering chamber while the powder outlet valve and the compressed gas intake duct are opened, as a result of which compressed gas flowing from the compressed gas intake duct is able to force the metered quantity of powder from the metering chamber into the powder outlet duct; said pump system further comprising a pump control unit to drive the compressed gas intake valve; wherein the pump control unit comprises a time controller by means of which a predetermined delay time is counted since a predetermined operational point, the compressed gas being introduced at the end of the delay time into the metering chamber and the quantity of powdered metered until the end of the delay time is forced by the compressed gas out of the metering chamber.