US-12623451-B2 - Sheet-fed rotary printing machine comprising an electrode unit

US12623451B2US 12623451 B2US12623451 B2US 12623451B2US-12623451-B2

Abstract

Examples relate to a sheet-fed rotary printing machine including a coating unit, which includes an impression cylinder and a further cylinder forming a contact zone therewith. The coating unit comprises a charging device for electrostatically fixing sheets on the impression cylinder, which includes an electrode unit that is directed toward the outer cylindrical surface of the impression cylinder. A charging core zone includes a region of an outer cylinder surface of the impression cylinder that is located next to the electrode unit. The charging core zone is arranged downstream from the contact zone and upstream from a transfer point leading away from the impression cylinder. An electrode of the electrode unit has a minimum first distance with respect to the impression cylinder of between 4 mm and 13 mm and a minimum second distance with respect to the further cylinder of between 4 mm and n 35 mm.

Inventors

Heinz Michael Koch
Philipp Hoyer
Ulrich Köhler
Wolfgang Schubert
Stefan Singer

Assignees

KOENIG & BAUER AG

Dates

Publication Date: 20260512
Application Date: 20231108
Priority Date: 20230220

Claims (15)

1 . A sheet-fed rotary printing machine, the sheet-fed rotary printing machine comprising at least one coating unit ( 05 ; 06 ; 07 ), which comprises at least one impression cylinder ( 34 ; 61 ) and at least one further cylinder ( 33 ; 63 ) forming a contact zone ( 55 ) with the impression cylinder ( 34 ; 61 ) and designed as a transfer cylinder ( 33 ) or finish coating forme cylinder ( 63 ); and the coating unit ( 05 ; 06 ; 07 ) comprising at least one charging device ( 86 ) for electrostatically fixing sheets (B) on the impression cylinder ( 34 ; 61 ), the charging device comprising at least one electrode unit ( 88 ) that is directed and/or can be directed toward an outer cylindrical surface ( 87 ) of the impression cylinder ( 34 ; 61 ); and a charging core zone ( 89 ) being a region ( 89 ) of an outer cylinder surface ( 92 ), enveloping a cylinder barrel ( 91 ) of the impression cylinder ( 34 ; 61 ), which is located closest to the at least one electrode unit ( 88 ); and the charging core zone ( 89 ) being arranged downstream from the contact zone ( 55 ) and upstream from a transfer point ( 101 ) leading away from the impression cylinder ( 34 ; 61 ), viewed in the direction of rotation (R) of the impression cylinder ( 34 ; 61 ), characterized in that at least one electrode ( 93 ) of the at least one electrode unit ( 88 ) has a minimum first distance ( 94 ) with respect to the impression cylinder ( 34 ; 61 ), which is at least 4 mm and which is no more than 13 mm, and that the at least one electrode ( 93 ) of the at least one electrode unit ( 88 ) has a minimum second distance ( 96 ) with respect to the further cylinder ( 33 ; 63 ), which is at least 4 mm and which is no more than 35 mm.
2 . The sheet-fed rotary printing machine according to claim 1 , characterized in that at least one inspection system ( 97 ) is assigned to the coating unit ( 05 ; 06 ; 07 ), which comprises a camera ( 99 ) that is directed toward an inspection zone ( 98 ) assigned to the impression cylinder ( 34 ; 61 ), and that the inspection zone ( 98 ) is arranged downstream from the contact zone ( 55 ) and upstream from the transfer point ( 101 ) leading away from the impression cylinder ( 34 ; 61 ), viewed in the direction of rotation (R) of the impression cylinder ( 34 ; 61 ).
3 . The sheet-fed rotary printing machine according to claim 2 , characterized in that the charging core zone ( 89 ) is arranged upstream from the inspection zone ( 98 ), viewed in the direction of rotation (R) of the impression cylinder ( 34 ; 61 ).
4 . The sheet-fed rotary printing machine according to claim 1 , characterized in that the minimum first distance ( 94 ) is at least 5 mm or at least 7 mm or at least 9 mm.
5 . The sheet-fed rotary printing machine according to claim 1 , characterized in that the minimum first distance ( 94 ) is no more than 12 mm or no more than 11 mm.
6 . The sheet-fed rotary printing machine according to claim 1 , characterized in that the minimum second distance ( 96 ) is at least 5 mm or at least 7 mm or at least 9 mm.
7 . The sheet-fed rotary printing machine according to claim 1 , characterized in that the minimum second distance ( 96 ) is no more than 30 mm or no more than 20 mm or no more than 15 mm or no more than 12 mm.
8 . The sheet-fed rotary printing machine according to claim 1 , characterized in that a working voltage of the electrode unit ( 88 ), which is applied and/or can be applied during normal operation, is at least 2 kV.
9 . The sheet-fed rotary printing machine according to claim 1 , characterized in that a working voltage of the electrode unit ( 88 ), which is applied and/or can be applied during normal operation, is no more than 20 kV.
10 . The sheet-fed rotary printing machine according to claim 1 , characterized in that the at least one charging device ( 86 ) is connected by circuitry to a higher-level machine control system of the sheet-fed rotary printing machine.
11 . The sheet-fed rotary printing machine according to claim 10 , characterized in that the at least one charging device ( 86 ) is connected by circuitry to the higher-level machine control system of the sheet-fed rotary printing machine in such a way that the working voltage provided during normal operation is only present at the at least one electrode ( 93 ) when sheet travel is activated.
12 . The sheet-fed rotary printing machine according to claim 10 , characterized in that the at least one charging device ( 86 ) is connected by circuitry to the higher-level machine control system of the sheet-fed rotary printing machine in such a way that settings related to this charging device ( 86 ) can be made via a control element of the sheet-fed rotary printing machine.
13 . The sheet-fed rotary printing machine according to claim 1 , characterized in that the impression cylinder ( 34 ; 61 ) is grounded via at least one carbon brush ( 112 ).
14 . The sheet-fed rotary printing machine according to claim 1 , characterized in that the at least one electrode unit ( 88 ) is arranged so as to be movable between at least two positions, and that one of the at least two positions is a working position and another of the at least two positions is a backed-away position, and that at least one first holding element ( 102 ) is provided for holding the electrode unit ( 88 ) in the working position.
15 . The sheet-fed rotary printing machine according to claim 14 , characterized in that an evasive force (K) shall be understood to mean a force (K) that is exerted, directly or indirectly, by the at least one electrode unit ( 88 ) on this at least one first holding element ( 102 ), and that the at least one first holding element ( 102 ) only allows a movement of the at least one electrode unit ( 88 ) out of the working position effectuated by such an evasive force when this evasive force exceeds a first threshold value.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS This application is the US national phase, under 35 USC § 371, of PCT/EP2023/081146, filed on Nov. 8, 2023, published as WO 2024/175224 A1 on Aug. 29, 2024, and claiming priority to DE 10 2023 104 095.2 filed on Feb. 20, 2023, and all of which are incorporated by reference herein in their entireties. TECHNICAL FIELD Some examples herein relate to a sheet-fed rotary printing machine comprising an electrode unit. For example, the sheet-fed rotary printing machine may include at least one coating unit, which includes at least one impression cylinder and at least one further cylinder forming a contact zone with the impression cylinder and configured as a transfer cylinder or finish coating forme cylinder. The coating unit includes at least one charging device for electrostatically fixing sheets on the impression cylinder, the charging device comprising at least one electrode unit that is directed and/or can be directed toward an outer cylindrical surface of the impression cylinder. A charging core zone includes a region of an outer cylinder surface, enveloping a cylinder barrel of the impression cylinder, which is located closest to the at least one electrode unit. The charging core zone is arranged downstream from the contact zone and upstream from a transfer point leading away from the impression cylinder, viewed in the direction of rotation of the impression cylinder. BACKGROUND In sheet-fed offset printing machines, sheets are provided with coating agent, for example with printing ink, in a contact zone between a transfer cylinder and an impression cylinder. Other coating units are known as well, for example flexographic coating units, in which the sheets cooperate directly with a plate cylinder and an impression cylinder. These are employed, for example, as printing units or as coating units. Depending on the properties of the coating agent and the sheets, it is possible for the sheets to adhere to the transfer cylinder or the plate cylinder. While a movement of the leading sheet edge is decisively determined by the grippers of the impression cylinder, the sheet can thus expand significantly in the rear area and/or detach from the impression cylinder. As soon as the trailing edge of the particular sheet leaves the contact zone, an abrupt relaxation movement of this sheet may occur. The trailing edge of the sheet can even at times surpass the target position thereof on the cylinder circumference. This can adversely affect the further transport of sheets. In particular, however, it is problematic when an inspection system is provided, which the sheets situated on the impression cylinder pass so as to be inspected. The expansion and the abrupt change in the position of the sheets makes an evaluation difficult or impossible, in particular in the rear area of the particular sheet. Devices are known which, by means of blower air and/or electrostatic charge, are intended to fix the sheets in the correct position on the impression cylinder. A sheet-fed rotary printing machine is known from U.S. Pat. No. 3,346,253 A, which comprises an electrode unit in the region downstream from the contact zone between the transfer cylinder and the impression cylinder, wherein the position of this electrode unit can be set by means of adjusting screws and this electrode unit should preferably be arranged approximately two inches (5.08 cm) away from the impression cylinder. A sheet-fed rotary printing machine is known both from U.S. Pat. Nos. 3,342,129 A and 3,174,748 A, comprising an electrode unit in the region downstream from the contact zone between the transfer cylinder and the impression cylinder so as to prevent smudging of the printing ink. A sheet-fed rotary printing machine is known from DE 10 2008 001 165 A1, in which sheets are electrostatically charged upstream from the contact zone between the transfer cylinder and the impression cylinder to facilitate an inspection downstream from this contact zone. A sheet-fed rotary printing machine is known from DE 10 2010 003 046 A1, which comprises a blower device in the region downstream from the contact zone between the transfer cylinder and the impression cylinder to facilitate an inspection downstream from this contact zone. A sheet-fed rotary printing machine is known from EP 2 982 510 A1, comprising an ink jet module that is arranged in the region downstream from the contact zone between the transfer cylinder and the impression cylinder and that, within a housing of this module, comprises an electrostatic sheet guide device to facilitate ink jet printing and an inspection within this module. A sheet-fed printing machine is known from DE 100 33 839 A1, which can comprise a respective drying device at various points, wherein an electrode is provided to support the drying process, the distance of which in relation to an impression cylinder can be varied so as to be able to prevent a collision with a gripper system. A sheet-fed printin