Method and apparatus for verification of impositions for printing plates

A method for performing an imposition verification on sheets of paper or another material of impositions prepared by means of digital data and comprising several print pages consisting of text and/or images using a printing unit) in the form or a plotter/printer having a magazine for paper or another sheet formed material and means feeding one sheet of paper at the time into the printing unit, whereby a test print sheet is introduced through a feeding/turning unit of the printing unit and is printed on one side of the sheet based on digital information which has been received in a control unit of the printing unit, and the sheet of paper is turned upside down after the first page has been printed and the sheet is printed on the opposite side thereof based on digital information which has been received in the control unit or said printing unit, and a visual or another verification is made to determine that the print pages of the impositions for the two print sides are located exactly as determined and that the impositions of the front and rear sides of the print sheet exactly coincide with each other, and, in case any lack of exactness is observed, corrections are made in the computer unit for preparing text and/or images, whereupon a renewed verification printing is made as mentioned above, characterized in that

• in that the sheet of paper is fed, with the front edge thereof, to a position against a stop edge at the printing unit,
• in that the sheet of paper, from a place spaced rearwardly from said front edge is moved inwards a further little distance by means of secondary feeder rolls, whereby the sheet of paper becomes buckled and the front edge of the paper is straightened up,
• whereupon the feeding of the sheet of paper is stopped, the printing roll and the counter press rolls are rotated slowly so that the front edge of the sheet, which is now straightened up, is pulled forwards and is kept secured by the printing roll and the counter press rolls of the printing unit,
• and the rear (secondary) feeder rolls are released so that the sheet of paper is given the possibility, in case said sheet happens to be positioned obliquely, of being rotated and being straightened out to enter an exactly correct position.