Apparatus for severing sections from a web by transverse severing cuts at locations related to printed marks on the web

Apparatus for severing web sections from a moving web by transverse severing cuts at locations related to printed marks on the web, said apparatus comprising:

• feed roll means for feeding a web in a web movement direction;
• cutter means for cutting the web transverse to the web movement direction and spaced from said feed roll means in the web movement direction;
• main drive means for driving said cutter means and said feed roll means;
• differential transmission means for operatively connecting the feed roll means to said main drive means;
• servomotor means for imparting a correcting rotation to the differential transmission means;
• detector means for detecting printed marks on the web and for providing a mark signal;
• sensor means for sensing the position of a cutter knife on said cutter means and for providing a knife position signal;
• controller means responsive to the mark signal and to the knife position signal for providing a control signal for controlling the servomotor means in dependence on a deviation of the spacing of successive printed marks for a theoretical web section length, wherein the servomotor means includes a stepping motor operative in response to said control signal, which represents the difference between the theoretical length of each web section corresponding to that distance which would be obtained between a cut and the next following cut if the servomotor was arrested, and the distance between the printed marks associated with said cuts, and shift register means having a plurality of register sections in a number corresponding to the number of printed marks disposed between said cutting means and said detector means for shifting in step with the movement of the printed marks past the mark detector and providing pulses in a number corresponding to said deviation detected for two consecutive printed marks, the pulses being stored in each register section, and wherein stepping pulses in the same number are delivered to the stepping motor when the preceding web section has been severed.