The device includes a pneumatic cylinder (20) whose piston rod (21) has a rod or roller (22) extending across the width of the foil web (S) and movable parallel or at an acute angle to the conveyor plane of the suction belt conveyor (1). The conveyor has an intermittent drive (23) which at least during the return of the piston rod reduces the speed of or stops the conveyor. A web store (24) for the excess length of the web is connected in front of the conveyor to take up the excess when the conveyor speed is reduced. The pneumatic cylinder is mounted for swivel movement against spring force in the machine frame.
