slightly experienced in the relevant art can readily ascertain the causes of malfunctions and can immediately undertake the necessary steps without slowing down or arresting the machine for example an attendant can detect the tendency of the web 6 to pile up in front of the nip 61 as well as actual pileups in front of the nip 61 i e the inability of the leader 6a to enter the path between the neighboring reaches of the flexible elements 7a and 8a such tendency can be counteracted by rotating the hand wheel 37 so as to move the entire upper conveyor unit 7 in a direction to the right as viewed in the drawing i e away from the severing station 5 if the web 6 its leader 6a and or the discrete sheets 106 exhibit a pronounced tendency to fluctuate in their respective paths an attendant will rotate the input element 17 in a direction to move the entire catcher assembly 9 downwardly and away from the severing station 5 i e at the acute angle to the horizontal path for the sheets 106 such tendency of the web 6 and or sheets 106 can be attributed to development of eddy currents as a result of orbital movement of the knives about the axes of the respective knife holders 2 and 3 furthermore the web 6 and or the sheets 106 are likely to vibrate or depart from their prescribed paths owing to a pronounced tendency of a web 6 to curl the operator can also decide to connect the suction.