side walls 51 and 61 several radiant heaters 52 1 52 2 52 3 and 62 1 to 62 3 are arranged located opposite one another and directed towards the filaments in this connection the radiant heaters 52 1 52 3 and 62 1 62 3 are arranged in the cooling shaft 14 underneath one another parallel to the bundle of filaments 12 subject to a spacing in relation to one another so that an intake of air between the radiant heaters into the cooling shaft 14 becomes possible the radiant heaters preferably have a surface temperature lying above 400 u00b0 c below the radiant heaters the cooling shaft 14 is formed by air permeable side walls 53 and 50 the blower casing 54 and the blower casing 64 are in each instance connected to an air supply 15 the air that is blown in now extends into the cooling shaft 14 via the spaces between the radiant heaters 52 1 52 3 and 62 1 62 3 and through the air permeable blow walls 53 and 50 arranged below the cooling shaft 14 is the preparation roller 13 where the bundle of filaments 12 is combined to form a yarn 1 fig3 illustrates one embodiment for the cross section of the heating zone of a blower chamber 54 in this connection the bundle of filaments 12 passes through the cooling shaft 14 and the cooling shaft 14 is bounded by the side walls 57 and 58 the blower casing 54 includes a wall 53 which is arranged in relation to the bundle of filaments in such a way that the in flowing air in the blower casing 54 flows through the wall 53 and along the side walls 57.