reversing or turning assembly of a sheet-processing machine

#Field of the Invention

#The invention relates to a reversing or turning assembly of a sheet-processing machine, in particular a sheet-fed rotary printing press, having an impression cylinder. Sheets which are transported on a circumferential surface of an impression cylinder and printed in an associated printing nip formed between the impression cylinder and a blanket cylinder are gripped at a trailing edge thereof and lifted off the impression cylinder for the purpose of being reversed or turned.

#In sheet-fed rotary printing presses, the paper sheets to be printed are taken from a sheet pile and, with the aid of grippers disposed on rotating cylinders, are transported through individual printing units of the printing press, wherein they are printed with one, two or several colors in respective printing nips of the printing units. In that regard, as noted hereinabove, the printing nips are respectively formed between blanket cylinders, which transfer the printing images for the individual colors, and respective impression cylinders, which are set with great pressure against the blanket cylinders.

#FIG. 1 is a diagrammatic, partly-sectional, side-elevational view of a sheet-fed rotary printing press having an impression cylinder, constructed in accordance with the invention;

#FIG. 2 is an enlarged, fragmentary view of FIG. 1, showing the impression cylinder according to the invention provided with removable closure elements, and a reversing or turning drum disposed downstream from the impression cylinder, as viewed in sheet travel direction through the printing press;

#FIG. 3 is a further enlarged, fragmentary view of a different embodiment of the impression cylinder of FIG. 2, wherein the closure elements are fixed to chains which, in the vicinity of grippers for gripping the sheet leading edge, are guided into the interior of the impression cylinder;

#Referring now in detail to the figures of the drawings and first, particularly to FIG. 1 thereof, there is seen a sheet-fed rotary printing press 1 according to the invention, which includes a first printing unit 2 having an impression cylinder 10 according to the invention which, with a blanket cylinder 12 associated therewith, forms a printing nip 14 for printing the top or front side of a sheet 4 which is transported on the impression cylinder 10 and which is held at a leading edge thereof by gripper devices 6 on the impression cylinder 10 as it passes the printing nip 14. Between the first printing unit 2 and a second printing unit 8 disposed downstream from the first printing unit 2, as viewed in the sheet transport direction, a reversing or turning device 16 is disposed, which has a reversing or turning drum 18 with gripper devices 20 which grip the sheet 4 at the trailing edge thereof, in order to lift the sheet off the impression cylinder 10 and feed it in reversed or turned condition, with the trailing edge thereof leading, to the second printing unit 8.

#According to FIG. 2, the impression cylinder 10 according to the invention has recesses 24 formed in the circumferential surface 22 thereof, into which the gripper devices 20 for gripping the trailing edge of the sheet 4 dip or penetrate when the gripper devices 20 are located preferably in the vicinity of the gripper center line 26, which forms an imaginary connecting line between the rotational centers of the impression cylinder 10 and the reversing or turning drum 18.

#As is shown further in detail in FIG. 2, the recesses 24 are closable by closure elements 28, which are accommodated in grooves 30 extending in the circumferential direction of the impression cylinder 10.