Abstract: A zigzag folding apparatus for a form printing machine has a guiding device for paper feeding disposed in the front end thereof, folding arms for holding paper form blanks in a zigzag along their respective transversely perforated lines through rightward and leftward swing movements thereof effected by crank shafts, and a plurality of rotary spirals for arranging the paper blanks folded by the folding arms in a pile through guiding along the fold lines of the same. Particularly, the crank shafts are connected via a rotating transmission mechanism of gearing to a servo motor for folding drive which is controlled with control signals.

Abstract: A zigzag folding apparatus for a form printing machine, having: a pair of rolls for outfeeding a paper strip being mounted to folding arms for folding the paper strip in a zigzag, one of the folding arms having a swing lever synchronized for swinging motion with the arm, a swing center of the lever coinciding coaxially with the point of contact between both the rolls, so that the rolls can perform an auxiliary folding operation to assist the folding operation of the folding arms under the condition in which the point of outfeeding the paper strip remains stationary; and a swing drive mechanism for activating the swing lever having main shafts on the drive side and out shafts for a swing section disposed in parallel relationship, the main shaft and the output shaft being connected one another by means of a shift transmitting mechanism in which a ratio of transmitting is chaged by operating a screw from the outside, so that the adjustment can be made according to a width of swing on the swing lever and the loca