Abstract: A rotary offset printing press which can be operated either for prime and verso printing or for printing on one side only, with flying plate change in the latter case, is organized so that the common counterpressure roller used with either of the two pairs of printing rollers (plate roller and rubber cloth roller) is used only as a paper feed-out guide during prime and verso printing. The counterpressure cylinder can be shifted to let it assume its normal function in single-side printing. A small shift of the drive gearing makes it possible to use the counterpressure cylinder for one or the other pair of printing rollers selectively while a plate change is performed for the idle pair.

Abstract: To permit relative angular shifting of transmission of rotation between the first gear (1) and a second gear (2), to thereby control the register of a cylinder coupled to the second gear (2) with respect to printing cylinders coupled to the first gear, a third gear (3) is drivingly connected between the first gear (1) and the second gear. The third gear is journalled to rotate about an eccentric portion (6) of a shaft element (9), the shaft element 9 being secured for rocking movement about a central axis (10), from which the eccentric axis (11) is offset. The central axis (10) of the shaft element (9, 6) and the centers of rotation (12, 13) of the first and second gears, respectively, are positioned on a theoretical plane, or line (16) and when the eccentric axis (11) is also located on this theoretical line (16) a normal position is defined.