Patent ID: 7364690

Claim:
Device for injecting a treatment gas into a molten metal contained in a tank, the device being constructed and arranged to be fixed to a wall of the tank and comprising: a tubular housing passing through the wall of the tank and extending from an upstream end external to the tank and attached to the wall of the tank, to a downstream end within the tank to which an injection nozzle is attached for injection of gas therein through an end hole, the upstream end of the tubular housing comprising a closure generally opposite to the injection nozzle and means for connection to a source of gas for injection, a rod which is disposed within the tubular housing and slidable therein, the rod having a diameter which decreases in steps from an upstream end disposed within the upstream end of the tubular housing to a downstream end disposed adjacent the nozzle, the upstream end of the rod having an outer diameter sufficiently close to an inner diameter of the upstream end of the tubular housing to provide a leaktight seal therebetween, and the downstream end of the rod having a diameter dimensioned for unblocking the end hole, and control means for linearly moving the rod through the tubular housing in a back and forth manner, comprising a rod extension from the upstream end through the closure by a predetermined length, and terminating in a control device, wherein the rod is linearly movable by the predetermined length from a first position in which the downstream end of the rod is adjacent the downstream end but set back from the end hole so as to enable passage of the treatment gas, to a second position in which the rod unblocks the end hole, the upstream ends of the rod and the tubular housing maintaining leaktightness throughout the back and forth movement.