the air flow nozzles only at the end of a relatively long free trajectory where the air flow has already lost approximately two thirds of its exit velocity in order to accelerate the tobacco stream to a predetermined value the flow speed of the air flow must therefore be increased by an increase in the blower output which negatively affects the overall power economy of the system referring to fig3 there is shown an arrangement in accordance with the invention in fig3 the generatrix of the guide track 21 or more accurately the guide surface 21 a is based on a uniform generating curve so that individual segments 38 of the guide track adjoin each other continuously air flow nozzles 23 designed as air jets extending vertically in respect to the drawing plan are formed at the respective joints of the individual segments 38 whose downstream wall 38 a in relation to the conveying direction arrow 36 of the fiber stream makes a transition into the concave sliding surface 21 a of the guide track 21 in a steady convex curvature so that an unbroken continuous wall flow of blown air and tobacco is formed on sliding surface 21 individual segments 38 have an upstream wall 38 b in relation to the conveying direction which forms the opposing wall of each flow nozzle or air jet 23 the tobacco stream and the air flow meet directly in the area of the outlet openings of.