and its upper edge 44 thus it does not completely enclose the spinning unit but since suitable suction manifolds are provided the initial portion whereof is indicated at 45 in fig1 air is drawn from the room and the escape of harmful vapours from the yarn treatment zone into the room is not permitted other suction means are of course provided in a known manner for drawing off the vapour which evolves in the yarn drying zone the troughs 46 into which the liquors are conveyed by pipes 24 and from which they are conveyed in a known manner onto the processing roller are also seen in fig1 and parts of the several yarns f are illustrated therein which yarns leave the treatment roller at different tangential positions and pass onto yarn guides 51 and then are guided to the cops 22 by guide means known per se generally indicated at 52 fig3 5 and 8 particularly illustrate the structure of a spinning unit 10 the support arm 30 is particularly illustrated in fig3 it comprises a first part 50 which comprises a cylindrical portion 50 39 and a portion 50 34 which extends along the ends of the advancing rollers an upper head generally indicated at 51 and a plate 52 which is removable to permit the inner mechanisms to be maintained the described elements constitute the part 30 39 of the arm which is connected e g by means of a bracket.