a space is formed between each side wall and the radiation source for the passage of the inlet air the cross sectional areas of these spaces are together approximately equal to the cross sectional area of a suction channel positioned opposite the spaces the air flow is controlled by means of two speed regulated fans one at the inlet and one at the outlet of the apparatus application_number US 13821487 A description in fig1 a binding apparatus according to the invention is shown in perspective the apparatus comprises a stand 10 having four strong legs 11 in the stand 10 there are two cassettes 12 facing each other for enclosing the wire on which the nonwoven material has been formed the distance between the cassettes is adjustable for adaptation to the actual thickness of the nonwoven material the adjustment is performed by several hydraulic cylinders 13 and is carried out in such a manner that the material is not squeezed by the cassettes each cassette comprises several ir radiation elements equally distributed along the length of the cassette between the ir elements there are spaces through which the cooling air can pass the cooling air is controlled by means of partition walls or other suitable means so that the desired flow is achieved as described in detail below in connection with fig2 the air is supplied to each cassette through large tubes 14 air distribution members may be arranged inside the cassette for equal distribution of.