44 there is a lower recirculation inlet 40 of the lower suction branch 30 which is opposite a lower third angular region iii of the cylinder 6 directly adjacent and above the upper recirculation outlet 46 there is an upper recirculation inlet 42 of the upper suction branch 32 for drawing air off from an upper third angular region iii of the cylinder 6 cold air 22 from the blast air openings or nozzles 20 and recirculated air from the recirculation outlets 44 and 46 are deflected in each case on the outer surface of the cylinder 6 around the circumference of the cylinder are thereupon mixed with each other and are then drawn off by the blower 28 through the recirculation inlets 40 and 42 and blown through the blower 28 via the pressure branches 34 and 36 and the outlets 44 and 46 again onto the outer surface 4 of the cylinder 6 excess air is produced in the cold air device 2 as a result of the freshly entering cold air 22 the excess air is drawn back via a suction line 50 from the blower 14 of the cold air generator 8 to its air inlet 12 is cooled by heat exchanger 10 and is again fed by the cold air feed line 16 to the compressed air line 18 in this way an external cooling circuit for the air is formed by the cold air generator 8 its cold air feed line 16 and its suction line 50 through the suction line.