Apparatus for modifying traveling position of paper web in paper web processing machine

An apparatus for modifying a traveling position of a paper web in a paper web processing machine, comprising:

• a traveling position modification means for modifying a position of a side edge of a paper web traveling toward a processing section in a paper web processing machine;
• a detection means for detecting said position of said side edge of said paper web;
• and
• a control means connected to said modification means and said detection means for controlling said modification means based on a value detected at said detection means;
• wherein said detection means has a detectable zone with a larger size in a direction parallel to a width of said paper web than a tolerable region that allows said side edge of said paper web to be contained, said detectable zone corresponding to an originally expected position of said side edge of said paper web;
• said control means comprises a reference registration means for registering said value detected at said detection means as a reference value, when the paper web processing machine starts running and has its running speed reach a pre-determined certain speed, a detection tolerable range setting means for setting a detection tolerable range of said side edge of said paper web based on said reference value registered by said reference registration means, a detected value comparison means for confirming if said value detected at said detection means falls outside said detection tolerable range set by said detection tolerable range setting means, and a modification operating means for operating said modification means if said detected value comparison means confirms that said value detected at said detection means falls outside said detection tolerable range.