US Patent 9057376 Tube pump for transferring molten metal while preventing overflow

A tube pump for transferring molten metal includes a refractory tube having upper and lower end portions. A motor is disposed near the upper end portion of the refractory tube. A refractory shaft extends in the refractory tube and is connected to the motor near the upper end portion of the refractory tube. A refractory impeller is connected to the shaft in the lower end portion of the refractory tube. An upper outlet extends from upper end portion of the refractory tube through which molten metal flows upon rotation of the impeller. The refractory tube is enclosed at its upper end portion. A gas source flows gas into the refractory tube at or near its upper end portion under a pressure which prevents overflow of the molten metal above the outlet. Flux may be directed into the refractory tube alone or with gas.