Rotary stirring device for treating molten metal

A rotary device for treating molten metal, said device comprising a hollow shaft at one end of which is a rotor, said rotor having:—

• a roof and a base, said roof and base being spaced apart and connected by a plurality of dividers;
• a passage being defined between each adjacent pair of dividers and the roof and the base, each passage having an inlet in an inner surface of the rotor and an outlet in a peripheral surface of the rotor, each outlet having a greater cross-sectional area than the respective inlet and being disposed radially outward therefrom;
• a flow path being defined through the shaft into the inlets of the passages and out of the outlets;
• and
• a chamber in which mixing of the molten metal and gas can take place wherein the chamber is located radially inwardly of the inlets and has an opening in the base of the rotor and is in the flowpath between the shaft and the inlets, such that in use when the device rotates, molten metal is drawn into the chamber through the base of the rotor where it is mixed with gas passing into the chamber from the shaft, the metal/gas dispersion then being pumped into the passages through the inlets before being discharged from the rotor through the outlets;
• wherein a plurality of first cut-outs are provided in the roof and a plurality of second cut outs are provided in the base, each of the first and second cut outs being contiguous with one of the passages.