Patent ID: 9003971
Filing Date: 2015-04-14
Classification: B41J

Abstract:
1. An apparatus for producing proof prints on a print medium having a front side and a rear side for which correctness of page impositions can be checked, comprising: a) a stand configured to receive a roll of print medium, b) a first printer for printing pages on a front side of the print medium fed from the roll of the print medium, c) a second printer for printing pages on a rear side of the print medium, d) a first optical sensor arranged immediately outside of a print medium exit of the first printer, and configured to detect a code stripe printed by the first printer on the front side of the print medium and encoding an absolute Y position of the print medium along a feed direction of the print medium, e) a second optical sensor arranged between the first optical sensor and a print medium entrance of the second printer, and also configured to detect the code stripe, and f) a control unit configured to halt at least the second printer at least if the first optical sensor detects that a feed velocity of the print medium at the print medium exit of the first printer decreases abruptly, and to control the second printer such that the second printer prints the pages on the rear side of the print medium at a correct Y position of the print medium.