DE102015225605A1 - Sheet transport device and method for sheet transport - Google Patents

Abstract

In a method and a device for sheet transport in a digital printing press (1) with inkjet head (13), it is provided that a transfer cylinder (5) upstream of a printing cylinder (12) has trailing edge grippers adjustably arranged in addition to leading edge grippers in order to move the sheet (3 ) at the handover.

Description

The invention relates to a method and a device for sheet transport in a sheet-processing machine, in particular a printing press, with an inkjet printing unit.

State of the art

When transporting sheets by means of rotating cylinders, it is necessary for the sheet to rest smoothly on a lateral surface of the cylinder so that it can be impeccably and accurately printed with a printed image. In particular, when printing with inkjet heads, a constant distance between the inkjet head and the sheet to be printed must be ensured.

By the EP 0 990 518 B1 It is known to arrange suction openings on a lateral surface of the storage drum on a printing cylinder designed as a storage drum of a turning device in order to smooth the sheet.

However, there is the problem that the sheet has too little tension in its transfer to the printing cylinder and then not sucked smoothly on the printing cylinder.

task

The object of the invention is to provide a method and a device for sheet transport, which makes it possible that a sheet on the lateral surface of a printing cylinder of a sheet-processing machine, in particular an inkjet printing cylinder, rests wrinkle-free.

The object is achieved by the features of claims 1 and 5.

It is a particular advantage of the invention that a sheet to be printed rests so smoothly and flat on the outer surface of the inkjet printing cylinder that this maintains a necessary distance from the inkjet head and thus it is excluded that a contact of the inkjet head through the bow takes place. In addition, by maintaining a constant distance of the sheet to the inkjet head, the print quality is increased.

This advantage is achieved in particular by a combination of two transport cylinders, wherein the transfer cylinder upstream of the transfer cylinder has a sheet tensioning device.

The sheet tensioning device consists essentially of trailing edge grippers which are arranged in the circumferential direction and / or lateral direction and / or diagonally, in addition to the sheet leading edge grippers, so that a tension is applied to the sheet held on its leading edge, which draws it smooth while it is being pressed onto the casing surface of the printing cylinder is wound up.

The invention described and the described advantageous developments of the invention are also in combination with each other - as far as is technically feasible - advantageous developments of the invention.

With regard to further advantages and constructive and functional advantageous embodiments of the invention, reference is made to the dependent claims and the description of exemplary embodiments with reference to the accompanying figures.

embodiment

The invention will be explained in more detail with reference to attached figures. Corresponding elements and components are provided in the figures with the same reference numerals. In favor of a better clarity of the figures was waived a true to scale representation.

It show in a schematic representation

1 a digital printing press in section in a schematic representation,

2 the inkjet printing cylinder and an upstream transfer cylinder,

3a -C the effect of the tightening device of the transfer cylinder in detail.

A sheetfed press 1 , in particular a digital printing machine, has a feeder 2 for feeding sheets to the sheet-fed printing machine 1 and a boom 4 for removing the printed sheets from the digital printing press 1 on. It is at least one printing station 6 for printing the sheets 3 intended. The bow is from the investor 2 by means of a feed table to a feed cylinder 8th passed, which preferably the sheet to a double-sized transfer drum 9 transferred. From here the bow arrives 3 by means of a simple big transfer cylinder 11 to a z. B. three-fold pressure cylinder 12 on which the sheet by means of an inkjet printing unit 13 is printed. The printed bow 3 is from the impression cylinder 12 passed to a particular double-sized transfer drum, from where this z. B. simply large transfer drum 16 to a chain gripper 17 of the jib 4 is handed over. In turning mode, the transfer drum works 14 as a storage drum and hands the bow to his Trailing edge to a downstream turning drum 18 from where the bow 3 for printing on its back by means of a transfer drum 19 to the transfer drum 9 is returned, so that this in the printing unit 6 can be printed on the back.

The printing cylinder 12 is designed in particular as an inkjet printing cylinder and has for holding a sheet mechanical or pneumatic gripper devices 22 on to fix the bow on its leading edge. To improve the force acting on the sheet holding force and smooth, wrinkle-free position of the sheet on the impression cylinder 12 is the lateral surface of the printing cylinder 12 with additional suction pads, z. B. in the form of suction openings 24 , Mistake.

These can be successively from the gripper 22 be charged for the sheet leading edge towards the end of the sheet with suction, so that a bow 3 plan on the printing cylinder 12 can be sucked. To increase the clamping force of the sheet when placed on the impression cylinder 12 it is envisaged that the pressure cylinder 12 upstream transfer cylinder 11 a bow tensioning device 23 having. This consists essentially of suction pads 26 which the bow in addition to the transport grippers 27 fix for the sheet leading edge to the sheet trailing edge. The suction grippers are in the circumferential direction and / or laterally and / or diagonally on the lateral surface of the transfer cylinder 11 slidably arranged. Thus, a bow 3 after the transfer of its leading edge to the gripper device 22 of the printing cylinder 12 and while winding the bow 3 on the lateral surface of the impression cylinder 12 tensioned.

In 3a is the tightening device 23 the transfer cylinder 11 shown. As is apparent from the additional 3b and 3c indicates the tightening device 23 Suction pads 26 on which of the trailing edge of each arch 3 assigned. The suction pads 26 are opposite to the direction of rotation of the transfer cylinder 11 and also slightly slanted outwards (cf. 3c ), by a pivoting movement about a pivot point (in 3b indicated).

LIST OF REFERENCE NUMBERS

1

Sheetfed

2

investor

3

bow

4

boom

5

./.

6

Printing station (printing unit)

7

./.

8th

feed cylinder

9

Transfer drum

10

./.

11

Transfer drum

12

pressure cylinder

13

Inkjet printing unit

14

Transfer drum (storage drum)

15

16

Transfer drum (double size)

17

chain gripper

18

beater

19

Transfer drum

20

./.

21

22

Gripper device

23

Arch tensioning device

24

suction opening

25

26

Suction gripper (trailing edge, 11 )

27

Gripper (leading edge, 11 )

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0990518 B1 [0003]

Claims (10)

Method for transporting sheets in a printing machine ( 1 ) with a pressure cylinder ( 12 ) and an upstream transfer cylinder ( 11 ), characterized in that a to the upstream transfer cylinder ( 11 ) delivered at its leading edge bow ( 3 ) during winding on the transfer cylinder ( 11 ) on its trailing edge and the bow ( 3 ) streamlined and in the stretched, flat state of the transfer cylinder ( 11 ) to the impression cylinder ( 12 ). Method according to claim 1, characterized in that the sheet ( 3 ) in the circumferential direction and / or lateral direction and / or diagonally tightened. Method according to claim 1 or 2, characterized in that the impression cylinder ( 12 ) additional suction pads ( 24 ) has on its lateral surface, which are successively acted upon in the circumferential direction with suction air. Method according to one of the preceding claims, characterized in that the sheet ( 3 ) when transferring from the transfer cylinder ( 11 ) to the impression cylinder ( 12 ) is tightened at its trailing edge. Device for transporting sheets in a transport direction through a printing press with a gripper device ( 22 ) for a sheet leading edge having printing cylinder ( 12 ), wherein in the region of the impression cylinder ( 12 ) a printing station ( 6 ) is arranged, and with a pressure cylinder ( 12 ) - as seen in the transport direction - directly upstream transfer cylinder ( 11 ), characterized in that the transfer cylinder ( 11 ) a sheet tensioning device ( 23 ), wherein the sheet tensioning device ( 23 ) at a respective sheet trailing edge of a respective sheet ( 3 ) attacks. Apparatus according to claim 5, characterized in that the sheet tensioning device ( 23 ) Suction gripper ( 26 ) owns. Apparatus according to claim 6, characterized in that the suction pads ( 26 ) on the lateral surface of the transfer cylinder ( 11 ) are arranged in and against the circumferential direction and / or laterally and / or diagonally displaceable, for performing a tightening movement. Device according to one of claims 5 to 7, characterized in that the pressure cylinder ( 12 ) by means of an inkjet print head ( 13 ) is cooperating inkjet printing cylinder. Device according to one of claims 5 to 8, characterized in that the pressure cylinder ( 12 ) has additional suction pads on its lateral surface, which are successively acted upon in the circumferential direction with suction air.  Digital printing machine with a device according to one of claims 5 to 9.

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