Throw-on/throw-off device for a blanket cylinder with a printing speed dependent control system for a sheet-fed offset press

A throw-on and throw-off device for a blanket cylinder in the printing unit of an offset press having a plate cylinder and an impression cylinder, a press frame having bearings mounted thereon for journalling said cylinders and eccentric bushings supporting the ends of the blanket cylinder for throw-on and throw-off movement with respect to the plate cylinder and the impression cylinder each of said blanket, plate and impression cylinder having a printing zone and a gripping zone, and the cylinders being mounted for rotation such that the blanket cylinder engages each of the plate and impression cylinders respectively at a nip and the printing and gripping zones of the blanket cylinder are in registration with the printing and gripping zones of the plate and impression cylinders, comprising in combination,

• a control unit for generating triggering signals;
• actuating means for providing rapid throw-off of said blanket cylinder from both said impression cylinder and said plate cylinder and for providing sequential throw-on of said blanket cylinder on said plate cylinder and on said impression cylinder, said actuating means being responsive to the triggering signals of the control unit for engaging and disengaging the blanket cylinder to/from the plate and impression cylinders for the purpose of beginning/ending a printing cycle when the grinding zones of the blanket cylinder and the plate and impression cylinders are opposite one another;
• a speed sensor for sensing a value of a parameter indicative of the speed of the printing unit and providing the value of the parameter to the control unit;
• and
• means in the control unit responsive to the value of the parameter for adjusting the timing of the trigger signals in order to ensure engagement and disengagement of the blanket cylinder and the plate and impression cylinders occur when the gripping zones of the blanket cylinder and the plate and impression cylinders are immediately adjacent one another for all speeds of the printing unit.