Rotary duplicating machine

In a rotary duplicating machine, a combination comprising rotary printing roller means supporting a printing form provided with first and second triggering indicia associated with respective printing form sections which have different lengths, said printing roller means including means for detecting the respective indicia and for producing respective triggering signals in response to such detection;

• rotary counter-pressure roller means, one of said roller means being movable to and from a printing position in close proximity to the other roller means and defining with said other roller means a printing line through which said sections of said printing form must pass;
• operating means connected to said movable roller means for moving said movable roller means to and from said printing position;
• control means including a selectively associatable first cam and second cam, and means for selectively associating said first cam with said operating means to thereby move said movable roller means to said printing position in response to detection of one of said indicia and for a first time period the length of which depends upon the length of the one printing form section associated with said one indicium and during which first time period said printing roller means turns through a first angle corresponding to the length of said one printing form section, and for selectively associating said second cam with said operating means to thereby move said movable roller means to said printing position in response to detection of the other of said indicia and for a second time period the length of which depends upon the length of the other printing form section associated with said other indicium and during which second time period said printing roller means turns through a different second angle corresponding to the length of said other printing form section;
• cam actuating means associated with said control means and including spring means permanently urging said cams towards association with said operating means, abutment means movable to and from blocking positions blocking the movement of said cams into association with said operating means, and electromagnetic means responsive to said triggering signals to move said abutment means away from said blocking position so as to permit movement of the respective cams into association with said operating means;
• and restoring means for restoring said abutment means to said blocking positions and for moving said cams out of association with said operating means.