Turning device and method for turning sheets

Abstract

Turning device for a sheet processing machine with a storage drum (2) and a turning drum (3) arranged downstream of the storage drum (2), wherein the storage drum (2) has a gripper system (2.1) for the leading edge of the sheet and a sheet contact element which is movably mounted relative to the outer surface of the storage drum (2) during sheet transport, wherein the sheet contact element is movable and / or moved in a rotation angle range of the storage drum (2) in which the sheet (8) contacted by the sheet contact element is already gripped by the turning drum (3), characterized by that the arc contact element is designed as a ring rotating around a rotation axis or as a band rotating around several rotation axes.

Description

[0001] The invention relates to a turning device for a sheet processing machine with a storage drum and a turning drum arranged downstream of the storage drum according to the preamble of the first claim and to a method for turning sheets in a turning device of a sheet processing machine.

[0002] DE 10 2006 032 922 B3 discloses a device for supporting sheet guidance in printing presses. A sheet stripping element connected to a suction device is arranged in the cylinder channel of a storage drum. The disadvantage of this solution is that the relative movement under frictional contact can cause more or less visible abrasion marks on the substrate surface.

[0003] DE 10 2007 049 643 A1 discloses a method and device for turning a sheet during conveyance through a printing press. In this method, the trailing edge suction grippers are reapplied with suction air after the transfer center. The disadvantage of this solution is that the suction grippers cause grinding marks, and cross-sheet tightening cannot occur at all.

[0004] DE 10 2010 001 685 A1 discloses a turning device for a sheet-fed printing press in which the sheet lying on the storage drum can be taut by suction bar parts in the circumferential direction and, if necessary, in the axial direction of the storage drum before being transferred to the turning drum. The disadvantage of this solution is that the sheet is no longer taut after being transferred to the turning drum. This leads to sheet travel difficulties when the sheet is pulled through the turning drum.

[0005] The invention is therefore based on the object of further improving the turning process in sheet processing machines.

[0006] According to the invention, this object is achieved by a device having the features of the independent device claim and a method having the features of the independent method claim. Advantageous embodiments emerge from the subclaims, the description, and the drawings.

[0007] The invention has the advantage that the turning process in sheet processing machines is further improved.

[0008] Preferably, the sheets are taut in the turning area without leaving marks, so that they can be transferred to the turning drum without creases. In particular, the damaging relative movement is shifted away from the contact point on the sheet.

[0009] The movable sheet contact element is, for example, designed to be rotationally movable or to rotate, and can preferably be subjected to suction air. A ring rotating about a rotational axis or a belt rotating about several rotational axes can be used as the sheet contact element. The movable sheet contact element is integrated into the outer surface of the storage drum, preferably near stretching suction cups between the tines of the comb-shaped storage drum. Alternatively or additionally, the movable sheet contact element can be arranged in the gripper channel of the storage drum. In a further development, the at least one rotational axis of the movable sheet contact element is designed to be oblique to the rotational axis of the storage drum, so that an axial tension component is also established. At least two sheet contact elements are arranged diverging from one another in the pull-off direction.The inclination of the sheet contact elements can be adjustable or controlled or regulated based on sensor values. This allows the sheets to be easily taut lengthwise and / or crosswise.

[0010] In a preferred embodiment, the sheet contact element is designed as a brake belt without a drive, wherein the belt surface and the coefficient of friction on the top and bottom of the belt are coordinated so that the frictional force on the sheet is greater than on the bottom of the belt. Furthermore, the brake belt can be subjected to suction air. This creates a new tightening contact point between a suction plate and the suction belt connected to the suction plate. The sheet drives the suction belt, while the suction belt is braked by the suction contact between the suction plate and the underside of the suction belt. In this case, there is preferably a frictional contact between the suction belt and the sheet without relative movement. By eliminating relative movement between the suction belt and the sheet, damage to the sheets is reduced.

[0011] In an alternative embodiment, a drive, particularly a dynamic drive, is assigned to the sheet contact element. The drive can be controlled such that the driven sheet contact element tracks the accelerated sheet movement. The same speed or a slight slippage can be generated between the sheet contact element and the sheet. In particular, here too, there is a frictional contact between the movable sheet contact element and the sheet with no or almost no relative movement. The sheet can be taut longitudinally and / or transversely by the drive and the position of several sheet contact elements.

[0012] In a further preferred embodiment, the movable sheet contact element can simultaneously be pivoted out of the periphery of the storage drum at the end of a preferably driven rocker, so that it functions as an ejector to bring the sheet into a take-off plane that is sufficiently spaced from the feed plane of the following sheet so that a sheet encounter is avoided.

[0013] A technical advantage of the device arises in particular from the fact that, while shifting the relative movement away from the sheet does not reduce local compressive stress, it does reduce or eliminate sliding friction, thus preventing scratching of the sheet. The braking energy required for tensioning no longer damages the sheet surface but is converted, for example, into heat at a later stage in the element chain. The conversion of frictional energy into heat in subsequent machine components is advantageously uncritical at the storage drum location.

[0014] A further advantage can be the reliability of the tensioning process. In previous systems with rigid tensioning elements in the periphery of the storage drum, the constantly changing fluctuations in the friction parameters require operator actions, even within a single job. A balance of forces due to sliding friction occurs, and adjustments to the vacuum are necessary. If the tension is too much, the sheet "snaps." If the tension is too little, it hits the sheet guide plate. With an advanced system, it is possible to reliably adjust the balance of forces to static friction conditions and keep it constant by eliminating sliding friction. This has the advantage of eliminating marks on the sheet and ensuring reliable sheet travel by reducing operating effort and avoiding smearing.

[0015] The invention will be explained below by way of example. The accompanying drawings illustrate this schematically: Fig. 1: Turning device of a sheet-fed printing press comprising a storage drum and a turning drum; Fig. 2: Detailed view of the storage drum; Fig. 3: Rear shell segment of the storage drum with a suction belt as a sheet tightener; Fig. 4: Movable dynamically driven suction element in the cylinder channel of the storage drum.

[0016] The Fig. 1 shows, in one embodiment, a section of a sheet-processing machine, here a sheet-fed printing press, for example a sheet-fed offset rotary printing press in unit and in-line design with a turning device. The turning device is designed here as a three-drum turning device and contains a transfer drum 1, a storage drum 2, and a turning drum 3. The turning device is arranged between printing units of the machine, with an impression cylinder 4 of the following printing unit arranged downstream of the turning drum 3. The impression cylinder 4 is operatively connected to a blanket cylinder 5, and this further connects to a plate cylinder (not shown) in the printing unit. Known inking units or inking and dampening units are arranged in the printing units of the machine, which apply the corresponding printing ink to a printing plate clamped on the respective plate cylinder. The machine can be switched between straight printing and perfecting modes.

[0017] The transfer drum 1 and the turning drum 3 of the turning device are single-sized, and the storage drum 2 is double-sized. For sheet transport, the transfer drum 1 has a gripper system 1.1 arranged in a gripper channel for clamping the sheets 8 at the leading edge. The sheets 8 are transferred at the gripper closure to a gripper system 2.1 of the storage drum 2 arranged in a gripper channel. From the storage drum 2, the sheets 8 are clamped at the leading edge and fed to the turning drum 3 while the storage drum 2 rotates. The turning drum 3 contains a gripper system 3.1 for sheet transport, in particular grippers and / or suction cups, which are pivotably mounted in the turning drum 3. Single-sized cylinders can hold at least one sheet 8 of the maximum format circumferentially. Alternatively, a different number of cylinders and different cylinder sizes can of course also be used in the turning device.

[0018] In straight printing mode, the sheets 8 are taken over by the gripper system 3.1 of the turning drum 3 in a transfer center at the leading edge from a gripper system 2.1 of the storage drum 2. In particular, the transfer center is the contact line between the storage drum 2 and the turning drum 3. When the sheet 8 is turned in perfecting printing, the storage drum 2 guides the sheet 8 past the transfer center and gripped at the trailing edge by the gripper system 3.1 of the turning drum 3. The gripped sheet 8 is then turned as the turning drum 3 rotates according to the trailing edge turning principle, so that its old trailing edge becomes the new leading edge upon its reversal of movement, and the old leading edge lying on the storage drum 2 becomes the new trailing edge. A sheet guide plate 6 is arranged below the storage drum 2 and the turning drum 3 to assist in sheet guidance.

[0019] The storage drum 2 has format-adjustable casing segments that interlock like a comb when the format is adjusted and form the sheet-supporting casing surface. The two gripper systems 2.1 of the double-sized storage drum 2 for the leading edges of the sheets are preferably arranged on fixed front casing segments. Suction cups 2.2 are provided on the rear casing segments, which are adjustable relative to the front casing segments, for taking over and guiding the trailing edges of the sheets. The suction cups 2.2 allow the sheets 8 to be stretched lengthwise and / or crosswise while lying on the storage drum 2 during sheet transport from the transfer drum 1 to the turning drum 3. In the area of ​​the transfer centers, the suction air supply to the suction cups 2.2 is reduced and preferably interrupted so that the gripper system 3.1 of the turning drum 3 can take over the trailing edge of the sheet.

[0020] The Fig. Figure 2 shows the storage drum 2 in a more detailed view. The cam-controlled gripper systems 2.1 of the storage drum 2, arranged in the gripper channel, are used to clamp the sheets 8 at the leading edge. These gripper systems 2.1 are located on the front, fixed shell segments of the storage drum 2. The format-adjustable shell segments house the stretching suction cups 2.2, which are adjusted to the respective sheet trailing edges using the format setting. The stretching suction cups 2.2 can be moved circumferentially and / or axially for longitudinal sheet tightening and / or transverse sheet tightening. A sheet tightener 9 is arranged between a gripper system 2.1 and the corresponding stretching suction cups 2.2. The sheet tightener 9 has at least one sheet contact element movable relative to the shell surface of the storage drum 2. A deflector plate 10 is also provided here, projecting into the gripper channel. The gripper systems 2.1 and the sheet tensioners 9 with the sheet contact elements of the storage drum 2 rotate together around the rotation axis of the storage drum 2.

[0021] The Fig. 3 shows a detailed view of a rear casing segment of the storage drum 2 with a stretching suction device 2.2. The rear casing segment is assigned the sheet contact element, which is movable relative to the casing surface and is preferably arranged between comb segments of the rear casing segment. Alternatively, the sheet contact element could also be integrated into a comb segment of the casing segment. The sheet contact element is provided in the sheet-carrying casing surface of the storage drum 2, spaced from the stretching suction device 2.2 in the direction of rotation 7. The sheet contact element is adjusted accordingly with the rear casing segment during format setting. In a further development, the sheet contact element could also take over the function of the stretching suction device 2.2. At least two such sheet contact elements are arranged across the sheet width here. However, a plurality of sheet contact elements are preferably arranged across the sheet width.

[0022] In the illustrated embodiment, the sheet tightener 9 contains a suction plate 11 over which a suction belt 12 sweeps. The suction belt 12 is guided by deflection rollers 13 and has suction openings that temporarily communicate with a suction channel of the suction plate 11. An adjustable negative pressure is applied to the suction plate 11, which acts on the sheet 8 when the suction openings of the suction belt 12 are positioned opposite each other at the suction channel of the suction plate 11. The suction belt 12 is driven here via a drive wheel 14 by a preferably dynamic drive. Alternatively, the suction belt 12 can also be guided over a brake roller, which exerts an adjustable braking torque on the suction belt 12. Further alternatively, the suction belt 12 can be braked via the dimensioned friction on the suction plate 11. Furthermore, a rotating suction ring could also be used instead of a rotating suction belt 12.The rotation axes of the deflection rollers 13 and the drive wheel 14 are parallel to the rotation axis of the storage drum 2. In a further development, these rotation axes can be arranged obliquely to the rotation axis of the storage drum 2 and the suction belts 12 or suction rings can be arranged diverging from one another.

[0023] The tightening of the sheet 8 on the storage drum 2 at the moment of its reversal of movement occurs by mechanically applying the new trailing edge of the sheet 8 to the respectively inserted sheet contact element of the sheet tightener 9. The contact of the sheet 8 against the sheet contact element is preferably increased and ensured by suction air. The tightening is achieved by drive via the drive, by friction of the sheet contact element against its guide, e.g., the suction plate 11, or by a braking element or similar. This keeps the sheet 8 fixed at the new trailing edge taut while it is pulled off the new leading edge by the gripper system 3.1 of the turning drum 3. By simply diverging the alignment of the sheet contact elements, transverse tightening can be easily achieved. The sheet 8 is thus optimally tightened lengthwise and / or crosswise before being guided by the sheet guide plate 6 or a gripper system to the turning drum 3.

[0024] The Fig. 4 shows another embodiment with a movably mounted sheet contact element in the gripper channel of the storage drum 2. The sheet contact element is designed here as a dynamically driven suction element and acts as an ejector to move the sheet 8 into a take-off plane that is sufficiently spaced from the feed plane of the following sheet to avoid sheet contact. Alternatively, the sheet contact element can also be designed as a braking band and / or braked via frictional engagement or a braking element. This rotating or rotating sheet contact element arranged in the gripper channel can also be arranged in addition to a rotating or rotating sheet contact element arranged in the periphery of the storage drum 2. In a further development, this sheet contact element arranged in the gripper channel can also be designed with an adjustable inclination.

[0025] How it works: In perfecting mode, the sheet 8 to be turned is guided by the turning device, with its leading edge first, onto the storage drum 2 into a storage space downstream of the transfer center. Its trailing edge is grasped by grippers and / or suction cups of the turning drum 3, which are pivotally mounted in the rotating turning drum 3 and, together with the grasped trailing edge, turn the sheet 8 through an additional pivoting motion as the turning drum 3 continues to rotate, so that its trailing edge becomes the new leading edge upon reversal of its movement, and the leading edge lying on the storage drum 2 becomes the new trailing edge.

[0026] When the sheet 8 to be turned or turned is pulled off by the turning drum 3, the sheet 8 is guided, for example, on a sheet guide plate 6 and the rear area of ​​the sheet 8 is tightened by the sheet contact elements of the storage drum 2. To tighten the sheet, the sheet contact element from which the sheet 8 is pulled off after the transfer center is moved. This movement of the sheet contact element therefore takes place in a rotation angle range of the storage drum 2 which, viewed from the side (as shown), is in the third quadrant. The range begins in a position in which the sheet 8 is just gripped by the turning drum 3 - i.e. the stretching suction cups 2.2, if present, are located in the transfer center - and ends in a format-dependent position in which the sheet 8 is released by the last sheet contact element of the storage drum 2.

[0027] The sheet contact elements arranged in the periphery of the storage drum 2 are preferably designed as suction elements and generate their tightening tensile force on the sheet 8 via frictional contact, wherein the tightening is brought about by the counter-rotating movement of the storage drum 2.

[0028] Due to the sheet contact element arranged in the gripper channel, the exposure time to the withdrawn sheet 8 is further extended and thus an even better longitudinal and / or transverse tightening of the sheet 8 is achieved. List of reference symbols used 1 transfer drum 1.1 Gripper system 2 storage drums 2.1 Gripper system 2.2 Stretch suction cups 3 turning drum 3.1 Gripper system 4 printing cylinders 5 rubber cylinders 6 sheet guide plate 7 Direction of rotation 8 sheets 9 Bow tighteners 10 Deflector plate 11 Suction plate 12 suction belt 13 pulleys 14 Drive wheel

Claims

[1] Turning device for a sheet processing machine with a storage drum (2) and a turning drum (3) arranged downstream of the storage drum (2), wherein the storage drum (2) has a gripper system (2.1) for the leading edge of the sheet and a sheet contact element which is movably mounted relative to the outer surface of the storage drum (2) during sheet transport, wherein the sheet contact element is movable and / or moved in a rotation angle range of the storage drum (2) in which the sheet (8) contacted by the sheet contact element is already gripped by the turning drum (3), characterized by , that the arc contact element is designed as a ring rotating around a rotation axis or as a band rotating around several rotation axes. [2] Device according to claim 1, characterized bythat the sheet contact element rotates or revolves about at least one axis mounted parallel or obliquely to the axis of rotation of the storage drum (2). [3] Device according to claim 1 or 2, characterized by that a suction plate (11) is assigned to the sheet contact element and the sheet contact element is designed as a suction ring or suction belt (12) which is in operative connection with the suction plate (11). [4] Device according to at least one of the preceding claims, characterized by that the sheet contact element is and / or is movable in a perfecting printing mode and / or after a transfer center to the turning drum (3). [5] Device according to at least one of the preceding claims, characterized by that the contact surface of the sheet contact element is movable and / or moved with at least one component in the circumferential direction relative to the outer surface of the storage drum (2). [6] Device according to at least one of the preceding claims, characterized by that the arc contact element is connected to a drive and / or a braking device is assigned to the arc contact element. [7] Device according to at least one of the preceding claims, characterized by , that the storage drum (2) has a stretching suction device (2.2) for the sheet trailing edge and the sheet contact element is arranged between the gripper system (2.1) for the sheet leading edge and the stretching suction device (2.2) or that the sheet contact element is arranged in a gripper channel of the storage drum (2). [8] Method for turning sheets (8) in a turning device of a sheet-processing machine, wherein the sheets (8) are guided on a storage drum (2) and wherein the trailing edges of the sheets are taken over by a turning drum (3), characterized bythat the sheets (8) gripped by the turning drum (3) are tightened by at least one sheet contact element of the storage drum (2) by movement relative to the outer surface of the storage drum (2). [9] Method according to claim 8, characterized by that the sheets (8) are tightened by a rotating or circulating sheet contact element in the circumferential direction of the storage drum (2) and / or transversely to the circumferential direction of the storage drum (2).

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