PURPOSE: To prevent the quality of spun yarn from deteriorating without causing a rise in equipment cost by preventing fly wastes from depositing.

CONSTITUTION: In spinning machinery equipped with a cotton collecting duct 4 having an intermittent damper 8, opened and closed at an interval of a prescribed time with an air cylinder 7 and cylindrical units through which a sliver 14 delivered in a prescribed direction slides and passes in the system, blowoff nozzles 27, communicating with the discharge side of the air cylinder 7 and blowing off compressed air corresponding to the opening and closing of the intermittent damper 8 are arranged and directed toward the periphery or the vicinity of the inlets of the cylindrical units so as not to deposit fly wastes 29 scattering from the sliver 14 on the vicinity of the cylindrical units.