Sheet-fed printing press with screen-printing cylinder

#The present invention is directed to a printing unit with a screen-printing cylinder. The screen printing cylinder has a movable doctor blade device. Two directly cooperating screen-printing cylinders, each with at least one working doctor blade, may also be provided.

#EP 07 23 864 B1 has disclosed a printing unit for a rotary printing press. A first screen-printing cylinder, together with a second cylinder, forms a printing nip, in which a print stock is printed.

#This known printing unit is only suitable for one-sided printing.

#Preferred embodiments of the present invention are shown in the drawings and will be described in detail below.

#FIG. 1 is a schematic representation of a printing press with a printing unit in accordance with the present invention;

#FIG. 2 shows a schematic section through the printing unit of the machine of FIG. 1;

#Referring initially to FIG. 1, there is shown a schematic view, e.g. of a sheet-fed rotary printing press in which a printing unit 4, in accordance with the present invention, is used. The printing press has a sheet feeder 1 with a sheet stacker 2, from whose top, which is automatically kept at a constant height, sheets to be printed are fed individually or in a continuous stream by a belt conveyor 3 to the printing unit 4. The printing unit 4 takes the sheets, one at a time, prints them, and outputs them to a second chain conveyor 6, which, in the case of multicolor printing, feeds them to other printing units like the printing unit 4 or, as shown here, feeds them directly to an output stack 5.

#The sheets pass through the printing unit 4 from top to bottom. The printing unit can be seen more clearly in FIG. 2 which gives a larger scale depiction of its structure.

#Two transport cylinders 7, the upper of which is shown only partially in FIG. 2, are each provided with sheet gripping mechanisms, each in a respective section 8 of their circumferences, in order to grip the leading edges of sheets, which are to be printed, from the first belt conveyor 3 in a register-matching manner. The lower of the two transport cylinders 7 rolls in contact with a first screen-printing cylinder 12, which is likewise equipped with a sheet leading edge gripping mechanism 29 in a section 11 of its circumference. In particular, this sheet leading edge gripping mechanism 29 may be a rotatable shaft with sheet gripper fingers, as seen in FIG. 3a and which is adapted for taking the sheets from the lower transport cylinder 7. The first screen-printing cylinder 12, together with a second screen-printing cylinder 17, forms a printing nip 14 through which the sheets held by the sheet leading edge gripper 29 of the first screen-printing cylinder 12 are conveyed. The two screen-printing cylinders 12 and 17 can be rotated in unison in such a way that with each pass through the printing nip 14, the sheet gripper 29 of the first screen-printing cylinder 12 coincides with, or is aligned with, a channel-like indented section 18 of the second screen-printing cylinder 17.