Blow form for shaft furnaces, especially blast furnaces or hot-blast cupola furnaces

A blast tuyere for shaft furnaces, includes a conical hollow main body having inner and outer casings defining a hollow space and interconnected by a tuyere nose. The outer casing is formed by a single-piece base body terminating smoothly in the tuyere nose, and the inner casing is formed by a conical weld-in part. The hollow space is divided in antechamber, adjacent the tuyere nose, and main chamber, completely separated hydraulically and including separate coolant circuits. The coolant circuit for the antechamber includes two parallel passages for supply and return of coolant. The passages terminate in a ring channel, arranged in the tuyere nose in a direction transversely to the passages, and are located in an area of an upper apex of the main body radially outside the main chamber. The coolant circuit for the main chamber includes a helical cooling passageway whose inner wall is formed by the weld-in part.