Sheet-fed rotary printing machine for single-side multicolor printing and perfector printing

#The invention relates to a sheet-fed rotary printing machine for single-side multicolor printing or perfector printing having an in-line type of construction with at least one sheet-turning device as well as devices for processing both paper as well as cardboard, and respective printing units each having in addition to a plate cylinder and a rubber-covered or blanket cylinder of equal given diameter, an impression cylinder having a diameter at least double the given diameter, as well as a sheet transfer drum.

#A multicolor sheet-fed rotary printing press of the foregoing general type has become known heretofore from German Published Non-Prosecuted Application (DE-OS) No. 24 52 167. The impression cylinder of each printing unit of this printing machine and the turning cylinder, which is disposed between two printing units, have diameters which are double the diameter of the plate cylinder or blanket cylinder of the printing units. At the tangent point between the impression and turning cylinders, a suction system provided on the turning cylinder grips the trailing edge of the freshly printed sheet which is lying on the smooth sheet-guiding surface of the impression cylinder. After swinging within the circumference or periphery of the turning cylinder, the suction system transfers the gripped trailing edge of the sheet to a gripper system which then swings out again during a further rotational movement of the turning cylinder and transfers the sheet with the trailing edge first to the gripper system of the succeeding impression cylinder. To achieve an in-register sheet transfer, the suction system is constructed as part of a connecting rod or couple of a double rocker or compensating lever.

#Due to the relatively large diameters of the sheet-carrying cylinders, the heretofore known multicolor sheet-fed rotary printing machine is basically suitable for processing cardboard. Because the removal of the leading edge of the sheet from the smooth back-pressure or impression surface of the impression cylinder must take place by means of a suction system, it is inevitable, despite the use of a double rocker, that a rear or trailing section of the sheet will be bent during transfer of the trailing edge of the sheet to the gripper system of the turning cylinder. A consequence thereof is that the processing of thick cardboard is possible, if at all, only within very low speed ranges. Due to the stiffness of the carboard, the aforementioned bending of the trailing edge of the sheet causes the sheet to break away from the suction system particularly at high printing-machine speeds. In addition, with such a turning system, print-free areas for proofing segments must be provided.

#The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying single FIGURE of the drawing which is a diagrammatic side elevational view of a four-color cardboard printing machine which is convertible to a two/two perfector printing machine i.e. such a printing machine which prints in two colors on either side of the sheet.

#Referring now to the drawing, there is shown therein a cardboard printing machine having four printing units 1, 2, 3, 4 wherein a lower part of a printing unit 5 equipped with parts of a turning device is disposed between the first printing unit 1 and the pair of printing units 3 and 4. From a sheet feeder 6, sheets are fed via a feed table 7 to a feeding cylinder 8 of the printing unit 1. The feeding cylinder 8 accelerates the aligned sheet and transfers it to an impression cylinder 9 of the first printing unit 1. The sheet receives its first impression or print by means of a plate cylinder 10 and a rubber-covered or blanket cylinder 11 both of which have the same given diameter. Because the impression cylinder 9 has double the diameter of either the plate cylinder 10 or the blanket cylinder 11, it has two sheet-carrying surfaces. It transfers the printed sheet to the sheet transfer drum 12 of a second printing unit 2, the sheet transfer drum 12 having triple the diameter of either the plate cylinder 10 or the blanket cylinder 11. Then the impression cylinder 9 of the printing unit 2 receives the sheet. The second color is then printed on the sheet by means of the plate cylinder 10 and the rubber-covered cylinder or blanket 11 of the second printing unit 2.

#The second printing unit 2 is followed by a lower part of a printing unit 5 which accommodates a sheet transfer drum 12 of so-called triple diameter and a storage drum 13 of so-called double diameter. The storage drum 13 is provided in the place of an impression cylinder 9 which normally appears in its location in the other printing units of the machine. An ultraviolet or infra-red drying device 14 may be provided above the storage drum 13. The twice-printed sheet is thus taken over by the sheet transfer drum 12 of the lower printing-unit part 5 and is fed to the storage drum 13 whereon the printed side of the sheet faces upwardly and can thus be dried by the drying device 14 as the sheet passes the latter. In the set-up of the cardboard printing machine illustrated in the FIGURE of the drawing, after the twice-printed and dried sheet has been transferred, and following previous smoothing in circumferential and lateral directions by rotary suction pads or suckers of the storage drum 13, the sheet is turned with the aid of the turning cylinder 15 which is housed in the third printing unit 3 in place of the sheet transfer drum 12 which customarily appears in its location in the other printing units of the machine. The turning cylinder 15 also has a so-called triple diameter and therefore is provided with three pincer-type gripper systems 16 symmetrically distributed over the circumference thereof. As shown in the FIGURE of the drawing, with the cardboard printing machine set for first forme and perfector printing, the pincer-type gripper system 16 grips the sheet by the trailing edge thereof and then guides it with the trailing edge first to the impression cylinder 9 of the printing unit 3. The first perfector impression or print is made thereat with the aid of the plate cylinder 10 and the rubber-covered or blanket cylinder 11 of the printing unit 3. The turning device of the invention is, thus, actually distributed over two normal lower printing-unit parts.

#Because the fourth printing unit 4 has precisely the same construction as that of the second printing unit 2, having a sheet transfer drum 12 of triple diameter, an impression cylinder 9 of double diameter as well as a plate cylinder 10 and a rubber-covered or blanket cylinder 11 both of a given so-called single diameter, the sheet experiences its second perfector impression or printing in this fourth printing unit 4. Thereafter, the sheet which is printed twice on both sides thereof is transferred by the impression cylinder 9 to the delivery drum 17 which likewise has a double diameter. A chain delivery 18 thereupon feeds the printed sheet of paper or cardboard to the delivery pile 19 of the sheet delivery 20.