Digital printing system

摘要

A digital printing system is disclosed having two independently operable printing towers arranged in series such that a substrate sheet passes sequentially through both printing towers, and in which a perfecting mechanism is provided between the two towers to reverse each substrate sheet during transfer from the first printing tower to the second printing tower, the perfecting mechanism being selectively operable to enable the second tower to print either on the same side of each substrate sheet as the first tower or on the opposite side of each substrate sheet. As well as allowing a duplex mode, the system provides a higher speed simplex mode during which different separations of the same image are printed by the two towers.

主权项

1. A digital printing system having two independently operable printing towers each having an endless intermediate transfer member, an image forming system serving under digital control to deposit ink onto the intermediate transfer member to form an ink image, and an impression station at which the residue film is impressed onto a sheet substrate, wherein the two printing towers are arranged in series such that each substrate sheet passes sequentially through both printing towers, and wherein a selectively operable perfecting mechanism is provided between the two towers to reverse each substrate sheet during transfer from the first printing tower to the second printing tower, the perfecting mechanism selectively enabling the second tower to print either on the same side of each substrate sheet as the first tower or on the opposite side of each substrate sheet, wherein, when the perfecting system acts to reverse the substrate sheets during transfer between the two towers, each tower is operative to impress a complete image onto a respective side of the substrate, and when the perfecting system is inoperative, the on first printing tower serves to impress at least one selected separation of an image onto each substrate sheet to form a partial image and the second printing tower is operative to impress the remaining separations of the same image onto the same side of the substrate sheet in register with the partial image formed by the first printing tower wherein:
i. each printing tower comprises four sequentially disposed print bars and the colors of the print bars are arranged in different sequences in the two printing towers, the colors of the two inner print bars in each printing tower being matched to the colors of the two outer print bars in the second printing tower; and ii. the digital printing system further comprises a print bar positioning system for transferring print bars from one tower to the other, the print bar positioning system including a carriage movable between the two towers and having lifting arms for engaging and raising the print bars.