Sheet transfer cylinder in a sheet processing machine

Abstract

Sheet transfer cylinder in a sheet-processing machine, wherein the sheet transfer cylinder (9) is provided with at least one detection unit (10) guiding the leading edge of a sheet (27), a holding unit (23) fixing the trailing edge of this sheet (27), and a cylinder jacket (18) having elements arranged one behind the other in the circumferential direction for supporting the sheet (27), wherein the sheet transfer cylinder (9) consists of a first cylinder segment (14) carrying a first element (17) and a second cylinder segment (26) carrying a second element (21), and the second element (21) is designed to be windable, characterized in that the first element (17) is connected to first prongs (19) which are received in a base body (15) of the sheet transfer cylinder (9) in a rotationally fixed manner and spaced from one another across the width.

Description

[0001] The invention relates to sheet transfer cylinders in a sheet processing machine, wherein the sheet transfer cylinder is provided with at least one detection unit guiding the leading edge of a sheet, a holding unit fixing the trailing edge of this sheet and with a cylinder jacket having elements arranged one behind the other in the circumferential direction for transporting the sheet.

[0002] In sheet-fed presses with a unit design, it is common to connect printing units, coating units, and other processing stations such as drying units, inkjet printing units, and the sheet delivery with one or three sheet transfer cylinders each. The sheet transfer cylinders receive the sheets from the printing cylinder of an upstream printing unit and transport them to the printing cylinder of a downstream printing unit or coating unit, or to the sheet delivery. It is possible for the sheet transfer cylinders to guide the sheets in a drying unit, or for inkjet heads to be assigned to a sheet transfer cylinder, thus forming an inkjet printing unit.

[0003] Sheet-fed machines process sheet-shaped printing materials of varying flexural rigidity. In the printing or coating unit, high radial contact forces prevail in the printing nip between the impression and blanket cylinders or the coating cylinder. These contact forces are released after the sheet leaves the printing nip, so that the free ends of the sheets held at the leading edge by the impression cylinder's registration unit return to their original shape. This tendency continues after the sheets are transferred to the registration unit of the sheet transfer cylinders, with the free ends being reset depending on the mass and flexural rigidity of the sheet-shaped material, as well as the speed of the transfer cylinders. In order to avoid damage to the sheet-shaped material being processed, it is known to provide guide devices that prevent the sheets from lifting too far off the outer surfaces of the sheet transfer cylinders.With these guidance devices, it is not possible to keep the entire surface of the sheet material being processed on the jacket of the sheet transfer cylinder. However, this is absolutely necessary in order to carry out certain work operations in a sheet-fed machine. For example, automatic inspection of the sheets using a camera and image analysis based on specific quality criteria is only possible with precise focus on the entire image or image area captured by the camera. Even when using inkjet printers, in order to apply a high-quality subject to the printing substrate, a specified distance must be maintained between the inkjet print heads. Furthermore, the print heads must not come into contact with the printing substrate, as this can lead to mechanical wear or even destruction of the print heads.It is also necessary to ensure that in drying systems consisting of a sheet transfer cylinder and associated dryers, the sheets rest fully on the sheet in order to achieve effective drying and prevent damage to the dryers.

[0004] In DE 35 35 621 C2, three sheet transfer cylinders are provided for transporting sheets from an upstream printing unit to a downstream printing unit. In order to avoid smearing of the print image during perfecting in a perfecting press, the entire cylinder surface of the middle sheet transfer cylinder consists of a number of sheet-supporting elements arranged in the cylinder's circumferential direction, and at the end of this sequence there is a suction device that grips the trailing edge of the sheet. The sheet-supporting elements are received at the front in a guide channel of the sheet transfer cylinder, which has a radially outer section directed in the drum's circumferential direction and a further inner section connected to this via a connecting channel, wherein at least the radially outer section corresponds approximately to the maximum sheet format to be processed.The sheet-supporting elements and the suction device are connected to each other via connecting elements and guided in the guide and connecting channels. Electric motors are provided to adjust the suction device holding the trailing edge to the sheet format being processed, which move the suction device in the circumferential direction of the cylinder.

[0005] The disadvantage is the high technical effort required to implement this cylinder, whereby due to the large number of sub-elements supporting the sheets, it is not possible for the sheets to lie fully on the outer surface of the transfer cylinder, thus making it impossible to carry out certain work operations.

[0006] DE 199 20 371 A1 describes a turning device in a sheet-fed printing press in which a sheet guided on a printing cylinder of an upstream printing unit is taken over at the trailing edge by a gripping device of a transfer cylinder arranged downstream of the printing cylinder and fed to the printing cylinder of the downstream printing unit. Between the upstream printing cylinder and the downstream transfer cylinder, an oscillating gripper system is provided, which grips the trailing edge of the sheet guided on the upstream printing cylinder and transfers it to the gripping device of the transfer cylinder. The trailing edge of the sheet is held on the printing cylinder by adhesive, by suction of the sheet by means of suction holes formed in the outer surface, by applied electrostatic charges, or by blast air directed from the outside against the outer surface of the printing cylinder.There is no provision for adapting the means holding the trailing edge on the outer surface of the printing cylinder to the different sheet lengths being processed within a format range of the sheet-fed printing press.

[0007] DE 35 42 649 A1 describes a sheet turning device for in-line rotary printing presses with double-sized printing cylinders connected to a single double-sized transfer drum or turning drum. To enable gripping of the sheet end with gripping devices, the printing cylinder located in front of the turning drum is equipped with an adjustable covering, preferably a roller shutter with a film covering above it, which determines the actual diameter of the printing cylinder.

[0008] DE 10 2009 016 685 A1 discloses a flat, substrate-guiding packing for an impression cylinder of a coating unit of a sheet-fed perfecting press. The packing has a first region with a first pattern and a second region, different from the first region, with a second pattern different from the first pattern.

[0009] The object of the invention is to design a sheet transfer cylinder of a sheet-processing machine using simple means in such a way that the sheets to be processed within a format range of the sheet-processing machine rest completely on the cylinder jacket and thus increase the universality and effectiveness of the sheet-processing machine.

[0010] According to the invention, the object is achieved by a sheet transfer cylinder according to the features of claim 1.

[0011] The inventive solution has the advantage that all sheets being processed within a sheet format typical for a sheet-processing machine are transported resting fully on the cylinder surface of the sheet transfer cylinder. This allows for additional work operations to be carried out without any problems, and the sheet transfer cylinders can also be easily adapted to the sheet format being processed.

[0012] The invention is explained in more detail using an exemplary embodiment. The accompanying drawings show: Fig. 1 a schematic side view of a sheet processing machine, Fig. 2 the schematic side view of a sheet transfer cylinder, Fig. 3 a spatial representation of the sheet transfer cylinder according to Fig. 2.

[0013] The sheet processing machine according to Fig. 1 consists of a sheet feeder 1, a sheet system 2, three printing units 3, a drying unit 4, and a sheet delivery 5. In addition to the printing units 3, further printing and coating units as well as, in addition to the drying unit 4, further processing stations such as inkjet printing units, sheet turning units, creasing and / or punching units, etc. can be provided.

[0014] Each printing unit 3 has a double-sized printing cylinder 6, a single-sized transfer cylinder 7, and a printing form cylinder 8 of the same size. A sheet transfer cylinder 9 is arranged between each printing unit 3 and the drying unit 4. The sheet transfer cylinders 9 are also double-sized. They each have two detection units 10, consisting of grippers 11, which are spaced apart and connected in a rotationally fixed manner to a gripper shaft 12, which can be rotated by means not shown, whereby the grippers 11 can be pivoted between an open position and a clamping position, in which the grippers 11 correspond to a gripper bar 13 ( Fig. 2). The detection units 10 are diametrically opposed and are each assigned to a first cylinder segment 14, which is rotationally fixedly connected to a base body 15 arranged on a central shaft 16. The sheet transfer cylinder 9 is mounted in the side walls (not shown) of the sheet-processing machine by means of the central shaft 16.

[0015] Each first cylinder segment 14 is assigned a rigid first element 17, which forms a section of the cylinder jacket 18 of the sheet transfer cylinder 9. The first cylinder segment 14 advantageously consists of first prongs 19 arranged at a distance from one another across the width of the sheet transfer cylinder 9, which support the first element 17, which extends from the gripper bar 13 against a sheet transport direction 20. At the ends of the first elements 17 facing away from the detection units 10, second elements 21 are articulated, thus forming a further section of the cylinder jacket 18, such that the surfaces of the elements 17, 21 are parallel and thus form a continuous cylinder jacket 18. The second element 21 is windable and is designed, for example, as a roller blind.At the free end of the second element 21, a storage container 22 is provided which winds up or unwinds the second element 21 and to which a holding unit 23 is assigned, which in the exemplary embodiment is designed as a suction unit 24.

[0016] The second element 21 is supported by second prongs 25, which are spaced apart from one another across the width of the sheet transfer cylinder 9 such that the second prongs 25 are always positioned at a gap with respect to the first prongs 19. The second prongs 25 are rigidly connected to the storage container 22 and the holding unit 23 / suction unit 24, forming a functional unit. The second prongs 25 are accommodated in the base body 15 so as to be displaceable in or against the sheet transport direction 20 and lockable. The second tines 25, the storage container 22 with the second element 21, the holding unit 23 / suction unit 24, and the means for moving or locking the second tines 25 in or against the sheet transport direction 20 within a positioning range form a second cylinder segment 26. The holding unit 23 / suction unit 24 extends across the width of the second cylinder segment 26.

[0017] In Fig. 2 shows a side view of the sheet transfer cylinder 9, simultaneously guiding two sheets 27 which are held by the gripping units 10 in the area of ​​the leading edge of the sheet. The trailing edges of the sheets are secured by the holding units 23, whereby in the embodiment shown in the upper area of ​​the figure, the holding unit 23 / suction unit 24 is covered by the second element 21. In this embodiment, the windable second element 21 is designed to be permeable to air or has suction openings. The embodiment shown at the bottom of this figure shows that the holding unit 23 / suction unit 24 directly grips the rear area of ​​the sheet 27 and the second element 21 is connected via a deflection roller 28 to a storage roller 29 mounted in the storage container 22, so that an air-permeable design of the second element 21 or the provision of suction openings is unnecessary.

[0018] In Fig.Figure 2 shows the position of the holding units 23 during the processing of sheets 27 with a maximum sheet length within a format range of the sheet-processing machine, wherein the free ends of the sheets 27 are just barely held securely. If sheets 27 arrive for processing within the format range provided for the sheet-processing machine with a sheet length shorter than the maximum sheet length, the means locking the second cylinder segments 26 are released and the second cylinder segments 26 are displaced in the sheet transport direction 20 by adjusting means such that the holding units 23 / suction units 24 can securely grasp the free end of the sheets 27 being processed and are locked in this position.

[0019] When the second cylinder segments 26 are moved in the sheet transport direction 20, the windable second elements 21 are wound onto the storage rollers 29 of the storage containers 22. For this purpose, the storage rollers 29 are provided with preloaded torsion springs or drives are assigned to the storage rollers 29, which forcibly wind or release the second elements 21 depending on the realized travel path of the second cylinder segments 26. When the second cylinder segments 26 are moved in the sheet transport direction 20, the second prongs 25 engage the gaps formed by the first prongs 19 of the first cylinder segments 14.The length of the first elements 17 of the cylinder segments 14 is dimensioned such that, when a maximum travel path is realized through the second cylinder segments 26, the holding units 23 are then positioned directly at the end of the first cylinder segments 14, the free ends of the sheets 27 with a minimum sheet length can just be fixed by the holding units 23. The length of the first elements 17 must therefore be smaller than the minimum sheet length to be processed.

[0020] The positioning of the holding units 23 on the sheet transfer cylinder 9 is performed by the machine control system of the sheet-processing machine by entering the length of the sheets 27 to be processed. Depending on the length of the sheets 27, it is advantageous to adjust the time of deactivation of the holding units 23 or their activation within a work cycle to the sheet length. Within a work cycle, the time of activation and deactivation of the detection units 10—in the exemplary embodiment, the closing and opening of the grippers 11—is fixed.In order to ensure trouble-free operation of the sheet processing machine, it is advantageous to deactivate the holding units 23 - in the exemplary embodiment these are designed as suction units 24 - and thus to release the sheets 27 in the area of ​​the trailing edge of the sheet only when the sheets 27 are gripped in the area of ​​the leading edge by a holding system of the transport system downstream of the sheet transfer cylinder 9 and are pulled away from the sheet transfer cylinder 9 far enough that the then free end of the sheet can be transported without problems. This means that when processing sheets 27 with a maximum sheet length, the holding units 23 are deactivated later in relation to the deactivation of the detection units 10 than when processing sheets 27 with a minimum sheet length. The setting of the deactivation time orThe activation time of the holding units 23 can thus also be realized as a function of the length of the sheets 27 to be processed after entering the sheet length via the machine control.

[0021] In the exemplary embodiment, the inventive solution was described using a double-sized sheet transfer cylinder 9 with two diametrically opposed detection units 10 and similar holding units 23. It is also possible to implement this solution on a single-sized sheet transfer cylinder 9. List of reference symbols used 1 sheet feeder 2 arch system 3 printing unit 4 Drying plant 5 sheet delivery 6 printing cylinders 7 transfer cylinders 8 printing form cylinders 9 sheet transfer cylinders 10 Recording unit 11 grippers 12 gripper shaft 13 Gripper bar 14 First cylinder segment 15 basic bodies 16 Central shaft 17 First Element 18 Cylinder barrel 19 First prong 20 Sheet transport direction 21 Second Element 22 storage tanks 23 Holding unit 24 suction unit 25 Second prong 26 Second cylinder segment 27 sheets 28 Deflection roller 29 Storage roller

Claims

[1] Sheet transfer cylinder in a sheet-processing machine, wherein the sheet transfer cylinder (9) is provided with at least one detection unit (10) guiding the leading edge of a sheet (27), a holding unit (23) fixing the trailing edge of this sheet (27), and a cylinder jacket (18) having elements arranged one behind the other in the circumferential direction for supporting the sheet (27), wherein the sheet transfer cylinder (9) consists of a first cylinder segment (14) carrying a first element (17) and a second cylinder segment (26) carrying a second element (21), and the second element (21) is designed to be windable, characterized by that the first element (17) is connected to first prongs (19) which are accommodated in a base body (15) of the sheet transfer cylinder (9) in a rotationally fixed manner and spaced apart from one another across the width. [2] Sheet transfer cylinder according to claim 1, characterized byin that in a sheet transport direction (20) the detection unit (10) connected to the first cylinder segment (14) is provided in front of the latter and the holding unit (23) is provided at the end of the second cylinder segment (26) arranged downstream of the first cylinder segment (14). [3] Sheet transfer cylinder according to claim 2, characterized by that the detection unit (10) consists of grippers (11) which are operatively connected to a gripper bar (13). [4] Sheet transfer cylinder according to claim 2, characterized by that the holding unit (23) is designed as a suction unit (24). [5] Sheet transfer cylinder according to claim 1 and 2, characterized by that a storage container (22) receiving the second element (21) is provided at the end of the second cylinder segment (26). [6] Sheet transfer cylinder according to claim 2 and 5, characterized by that the holding unit (23) and the storage container (22) are designed as a functional unit. [7] Sheet transfer cylinder according to claim 1, characterized by that the second element (21) is connected to the first element (17) to form a continuous cylinder jacket (18). [8] Sheet transfer cylinder according to claim 1, characterized by that the second element (21) is supported against second prongs (25) which are arranged at a distance from one another across the width of the sheet transfer cylinder (9) and are accommodated in their entirety in the base body (15) of the sheet transfer cylinder (9) so as to be displaceable in or against the sheet transport direction (20). [9] Sheet transfer cylinder according to claim 8, characterized by that the second prong (25) is assigned an adjusting and locking means. [10] Sheet transfer cylinder according to claim 9, characterized by that the adjusting means is connected to a machine control which detects the length of the sheets (27) to be processed. [11] Sheet transfer cylinder according to claim 10, characterized bythat the suction unit (24) can be adjusted by the adjusting means within an adjustment range which is determined by the minimum and maximum length of the sheets (27) to be processed. [12] Sheet transfer cylinder according to claim 11, characterized by that the deactivation and activation of the suction unit (24) is adjustable within a working cycle depending on the length of the sheets (27) to be processed. [13] Sheet transfer cylinder according to claim 8, characterized by that the second element (21) is designed to be air-impermeable and the suction unit (24) is arranged to directly grasp the sheet (27). [14] Sheet transfer cylinder according to claim 8, characterized by that the second element (21) is designed to be permeable to air and the suction unit (24) is arranged covered by the second element (21).

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