CALIBRATION UNIT FOR A ROTARY PRINTING PRESS

A calibration unit (24) for a rotary printing press having a central impression cylinder (10) and a number of colour decks (12a - 12h) disposed around the periphery of the central impression cylinder, each colour deck comprising a rotatable printing cylinder (14; 14') which carries a position mark (22) and is adapted to be set against the periphery of the central impression cylinder, the arrangement of the colour decks being symmetric with respect to at least one axis of symmetry (V, H), the calibration unit (24) having a number of sensor arms (30a-30h) each carrying a sensor (32) for detecting the position mark (22) of one of the printing cylinders, the calibration unit being adapted to be mounted on a frame (20) of the printing press such that the sensor arms project radially from the axis of rotation of the central impression cylinder (10) and are pivotable about that axis independently of the central impression cylinder, characterized in that at least two of the sensor arms (30a-30h; 30b, 30c) are interconnected by a drive mechanism (34; 36) configured for controlling a symmetric pivotal movement of the sensor arms (30d, 30e; 30b, 30c) with respect to a reference axis which, when the unit is mounted to the frame (20) is aligned with said axis of symmetry (V; H).