a device for manufacturing , filling and sealing thermoplastic sacks comprises a station , which comprises a forward draw unit for intermittently pulling forward a web of thermoplastic blown film and for its suspended feed in a vertical direction through a cross welding and cross severing mechanism , which provides the leading end of the blown film web with a cross weld and severs from said web a tubular segment above a gripping and transport mechanism . in order to pass the leading end of the blown film web quickly and without limply withdrawing to one side through the cross weld and cross severing mechanism into a stretched hanging position , there is a wall parallel to the feed path of the blown film web , and above the wall there are in its top region blowing air nozzles , facing the feed direction , between the wall and the feed path .