Sheet processing machine with a sheet transport drum for redirecting sheets and method for transporting sheets

Abstract

Sheet processing machine with a sheet transport drum (4) for recirculating sheets (17) around a rotating axis, wherein the sheet transport drum (4) has guide segments (5) that can be displaced axially to the rotational axis, wherein the guide segments (5) have arc bearing surfaces concentric to the axis of rotation, wherein the arcs (17) of pressure elements (9) can be fixed on the guide segments (5), wherein the pressure elements (9) are movably fixed to the guide segments (5), wherein a press gap for sheets (17) to the guide segments (5) can be formed with the pressure elements (9) and wherein the sheet transport drum (4) is arranged between printing cylinders (1) of a sheet-fed printing machine and has leading edge clamping grippers or wherein the sheet transport drum (4) is arranged as a delivery drum in a delivery of a sheet-fed printing machine, wherein the pressure elements (9) are designed as grippers (9) that can be pressed against the guide segments (5).

Description

[0001] The invention relates to a sheet processing machine with a sheet transport drum for guiding sheets around a rotation axis and to a method for transporting sheets through a sheet processing machine with a sheet transport drum.

[0002] Especially in sheet-fed printing presses, sheets must be transferred from one printing cylinder to the next. Furthermore, the sheets must be transferred from the last printing cylinder to a delivery.

[0003] For this purpose, at least one transfer drum with gripper systems is located between the printing cylinders. This gripper system grasps the leading edge of the sheet and feeds it to the next printing cylinder. After the last printing cylinder, gripper carriages running around a sprocket main shaft grasp the leading edge and feed it to the delivery pile. Both between the printing cylinders and after the last printing cylinder, the sheets are then transported further by gripping the leading edge and guiding it essentially along a circular path.

[0004] In the delivery, the sheet is guided over sheet guide elements, particularly sheet guide plates, during single-sided printing (front and back printing), which are usually vacuum-operated and suck the sheet in. In double-sided printing (front and back printing), the sheet is usually held in suspension without contact by means of a floating sheet guide, thus only touching its leading edge. However, this type of guidance is highly prone to failure and often only partially successful, as the sheet tends to flutter at high speeds and is also affected by suction devices, dryers, powder sprayers, etc.

[0005] DE-PS 514 098 discloses a sheet delivery device in which a discharge drum removes the printed sheets from a printing cylinder. The discharge drum is formed by two ring disks that are adjustable according to the width of the sheet. The leading edge of the sheet is taken over from the printing cylinder by means of a gripper or suction bar that connects the two ring disks. To ensure that the printed sheet spanning the two ring disks is also held at its circumference, the sheet is pressed onto the ring disks, for example by a belt. The disadvantage of this solution is that the belts must remain precisely aligned with the ring disks, and the holding force of the belts is difficult to adjust and control.

[0006] JP 55022953 A discloses a sheet transport drum with two sheet supports that can be adjusted to the unprinted sheet side edges and guide the sheet fixed at the leading edge. The disadvantage of this solution is that the sheet can sag between the sheet supports after the transfer center to the preceding cylinder and can slip off them.

[0007] DE 100 14 417 A1 discloses a device for transporting a sheet for a rotary printing press. In addition to the sheet supports, a suction gripper is provided to pick up the last free sheet edge, namely the trailing edge. The grippers for the trailing edge of the sheet must be designed as suction grippers in order to secure the trailing edge of the sheet, which lies on a closed surface. The disadvantage of this solution is that the sheets are not held on the sheet supports after the transfer center to the preceding cylinder.

[0008] DE 101 02 080 A1 discloses a device for turning flat copies in half-speed sheet-processing machines, which can have conical support elements. A catcher device presses the side edges of the rigid cardboard against the inclined surfaces of the conical support elements, allowing the more rigid material to be curved to match the curvature of the peripheral surface of the transfer drum. The disadvantage of this solution is that the sheet is only curved but not fixed. If the catcher element is set too far, the sheet is undesirably deformed on the conical support elements.

[0009] DE 10 2004 031 171 A1 discloses a sheet processing machine in which the delivery drum is configured with vacuum-actuated discs. The discs can be positioned on the sheet side edges. Preferably, only the angular range of the discs that comes into contact with the sheet is subjected to suction air. DE-PS 517 004 already discloses equipping a sheet discharge device with suction discs that can be moved according to the width of the printed sheet and positioned on the pressure-free side edges. Here, too, only the suction openings required for suctioning the sheet side edges are subjected to suction air. A disadvantage of suction discs is that they must be relatively wide to generate sufficient holding force, resulting in pressure-free areas on the order of 10 mm. Another disadvantage is the complex adjustment of the suction angular range of suction discs.

[0010] DE 10 2006 019 029 A1 discloses a processing machine for sheet material in which all transfer cylinders have suction bars for securing the leading edges of the sheets and cylindrical discs with peripherally arranged means for gripping each side edge of the sheet material. The means can be vacuum-operated openings or protruding support elements. The disadvantage of this solution is that the suction bars do not hold the leading edges of the sheets securely enough, and the suction discs require a wide contact surface, or the sheet is damaged by the protruding support elements.

[0011] DE 10 2005 002 509 A1 discloses a machine for processing sheets from printing substrates. Guide rollers are assigned to the sheet supports, which can be adjusted to the sheet side edges. The guide rollers can be arranged in a diverging arrangement with the sheet supports to ensure cross-sheet tension. The guide rollers are pressed against the sheet supports, so that the sheet is clamped between the sheet supports and the guide rollers and cannot flutter. Disadvantages of this solution are the complex positioning of the guide rollers relative to the sheet supports and the wear caused by the diverging arrangement.

[0012] DE 10 2008 025 392 A1 discloses a sheet guiding device for a transfer cylinder, in which a right and a left sheet support bracket for the sheet side edges each interact with a stationary guide roller device to guide the sheets. A disadvantage of this solution is that the guide rollers must be set and adjusted separately. A particularly disadvantageous feature is the need to maintain a distance from the transfer center of the upstream cylinder, which is determined by the roller geometry, and this distance can cause a change in the position of the sheet on the sheet support brackets.

[0013] DE 10 2011 012 808 A1 shows a device for conveying a sheet through a printing machine, wherein a transfer drum has support wheels for guiding the sheet and wherein elastic support strips are arranged on the support wheels.

[0014] The invention is therefore based on the object of creating an alternative possibility for sheet transport in a sheet processing machine.

[0015] 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.

[0016] The invention has the advantage of creating an alternative possibility for sheet transport in a sheet processing machine.

[0017] According to one embodiment of the invention, the side edges of the sheets are pressed onto the axially adjustable guide segments by pressure elements rotating with the guide segments. The pressure elements make it particularly advantageous to guide the sheets along their side edges in such a way that the required pressure-free area is as small as possible. Furthermore, a press nip between the pressure elements and the guide segments securely holds and transports even pliable material from the sheet transport drum. Thus, every material being processed is kept precisely on the ideal trajectory, even under high centrifugal forces, allowing for higher machine speeds.

[0018] In a cost-effective design, the guide segments are designed as guide discs carrying the pressure elements. In a preferred embodiment of the invention, the guide discs are assigned pressure elements designed as grippers, which are moved against the guide discs by a suitable drive. An actuator or, preferably, a gear is used as the drive. The gripper forces generated by the grippers ensure that the sheet side edges are securely held on the guide discs. According to the invention, only a very narrow unprinted side margin is possible. Advantageously, the sheet side edges are quickly gripped, so that the sheet is fixed to the guide discs immediately after the transfer center from the preceding sheet conveyor system.

[0019] A pneumatic or fluid drive for gears or, alternatively, an electric drive for the gears is proposed as the drive for moving the pressure elements. An electromagnetic or permanent magnetic drive is also proposed. The electromagnetic drive (lifting magnet) can rotate with the gear. Another suggestion is the possibility of having an armature rotate with the gear and switching the gear using a non-rotating electromagnet or permanent magnet; this operating principle can also be reversed so that the magnet rotates and the armature is stationary. However, the pressure elements, in particular grippers, are particularly preferably driven by a cam control. Another solution consists of a sliding block with a cam roller, which is moved (driven by a cam) and in the process actuates a gripper.

[0020] In addition to the guide segments with pressure elements, further guide segments which do not have pressure elements are conceivable, which guide the sheet in the area of ​​further pressure-free corridors, i.e. within the sheet format.

[0021] In a further development, the guide segments are designed with a suitable sheet contact surface that protects the sheet support surface, compensates for gripper tolerances, and offers secure hold. The guide segments can have elastic elements (rubber profiles, plastic parts, etc.) for this purpose. The sheet contact surface of guide discs is preferably designed to be elastic. Particularly preferably, a plastic or rubber hose is arranged along the surface of the guide discs, which simultaneously ensures a narrow, pressure-free side edge. The guide discs can be arranged in such a way that they press the sheet against the outer surface of a cylinder, e.g., a printing cylinder, in the transfer center, or they can also be positioned at a certain distance from the outer surface.

[0022] In a further development, the pressure elements designed as grippers are also designed with a suitable shape and / or material selection to securely fix the sheet side edges to the guide discs. The grippers can be designed similarly to the leading edge clamping grippers of sheet guiding cylinders in sheet-fed offset rotary printing presses.

[0023] Further developments include the use of a sensor system to detect the sheet position on the sheet transport drum. After evaluating the sheet position, further control of the gripper actuators can be carried out to improve the sheet position on the guide discs, particularly for sheet transverse tensioning.

[0024] The sheet transport drum can be used individually or in multiples in any sheet-processing machine. However, the sheet transport drum is preferably used in printing presses, where it can be arranged between two printing units for sheet transport and / or in a delivery as a delivery drum. However, the sheet transport drum can also be used in conjunction with a turning device. Several sheet transport drums according to the invention can also be arranged one behind the other.

[0025] The invention will be explained below by way of example. The accompanying drawings illustrate this schematically: Fig. 1: Sheet transport drum between two printing cylinders of a sheet-fed printing press; Fig. 2: Sheet transport drum as delivery drum after the last printing cylinder of a sheet-fed printing press; Fig. 3: Perspective view of a further development of a guide disk with a cam-controlled gripper finger and a hose as a curved contact element; Fig. 4: Simple embodiment of a cam-controlled drive mechanism for a gripper of a gripper system; Fig. 5: Alternative embodiment of a drive mechanism via a four-bar linkage for a gripper of a gripper system.

[0026] The Fig. 1 shows, in one embodiment of the invention, two printing units of a sheet-fed printing press, for example a sheet-fed offset printing press. Each printing unit contains, for example, a double-sized printing cylinder 1 with gripper systems (not shown) arranged in gripper channels for transporting the sheets to be printed. For sheet transport, the sheets are clamped at the leading edge by the gripper systems and transported through the printing unit while the printing cylinder 1 rotates. Each printing cylinder 1 interacts with a single-sized blanket cylinder 2, and this with a single-sized plate cylinder 3 in the respective printing unit. Alternatively, other cylinder sizes and a different number of cylinders can of course also be used. The printing press is preferably designed in series and comprises further printing, varnishing and / or finishing units (not shown).

[0027] In each printing unit, an inking unit or inking and dampening unit (not shown) is assigned to the plate cylinder 3. The plate cylinder 3 is covered with a printing plate (also not shown), which is inked with the corresponding printing ink by the inking unit. As the plate cylinder 3 rolls onto the blanket cylinder 2, the printing ink is transferred according to the motif onto the blanket cylinder 2, which is covered with a rubber blanket. A printing zone is formed between the blanket cylinder 2 and the impression cylinder 1, through which the substrate to be printed, for example a sheet, is conveyed by the impression cylinder 1. In the printing zone, the printing ink is in turn transferred from the blanket cylinder 2 to the sheet according to the motif.

[0028] Between the two printing units, the sheets are guided and transferred by one or more sheet guide drums. At least one of the sheet guide drums in the press is designed as a sheet transport drum 4 according to the invention. Shown here is a double-sized sheet transport drum 4 between the printing units, which has leading edge clamps for transporting the sheets. The sheet transport drum 4 receives the sheets at the leading edge in a transfer center from the preceding printing cylinder 1 and then transfers them to the downstream cylinder.

[0029] In addition to the leading edge grippers, the sheet transport drum 4 contains two guide disks 5 or disk segments that are arranged so as to be axially displaceable on a shaft 6 and rotate with the shaft 6. The guide disks 5 are positioned opposite the side edges of the printing material so that the printing material is wound onto the guide disks 5. Winding takes place in such a way that the usually print-free side edges rest on the guide disks 5. The guide disks 5 have a support surface for the sheet that is concentric with the shaft 6. Each guide disk 5 is assigned pressure elements such that these rotate with the guide disk 5 and apply a pressure force in certain areas against the sheet-bearing surface of the guide disk 5. The pressure elements are designed here as gripper systems 7. In a double-sized sheet transport drum 4, each guide disk 5 should have at least four pressure elements.The gripper systems 7 are each arranged on the outside of the guide discs 5 and are format-adjustable with the guide discs 5. The concentric sheet support surfaces of the guide discs 5 and the pressure elements form a press nip for the sheets. The sheets are secured in the press nip by two parallel clamping surfaces.

[0030] The Fig. 2 shows, in a further embodiment of the invention, a delivery of a sheet-processing machine, here a sheet-fed printing press, with a sheet transport drum 4 according to the invention. The delivery contains a chain conveyor system (not further designated) with circumferentially guided gripper carriages for receiving and conveying the printed sheets to a delivery pile (also not further designated). The sheet transport drum 4, designed as a delivery drum, contains guide disks 5 which are adjustable axially to a shaft 6 and which carry the pressure elements. The delivery drum has recesses for the gripper carriages of the chain conveyor system which are guided around the delivery drum. The gripper carriages receive the sheets to be delivered from the last printing cylinder 1 of the machine in a transfer center and guide the sheets around the delivery drum. After being guided around the delivery drum, the sheets are guided by the gripper carriages along the chain circle to the delivery pile and deposited there.

[0031] The sheet transport drum 4, designed as a delivery drum, also contains pressure elements designed as gripper systems 7, which are movably and permanently assigned to the guide discs 5. For sheet transport and the precise guiding of the sheets around a sprocket main shaft, the sheet side edges, after being taken over by a gripper carriage, are pressed by the gripper systems 7 against the sheet support surfaces of the guide discs 5. For this purpose, the guide discs 5 have sheet support surfaces concentric with the shaft 6. The sheet can thus be guided precisely concentrically around the rotational axis of the sheet transport drum 4.

[0032] The Fig. 3 shows a perspective view of a further development of a guide disk 5 of the sheet transport drum 4 with a cam-controlled gripper system 7 and a hose 8 assigned to the sheet contact surface. The gripper system 7 has a gripper finger 9, which, in a closed state, presses the sheet side edge against the hose 8 and, in the open state shown, lies below the sheet support surface. In the closed state of the gripper finger 9 (not shown), the sheet is held by the clamping surface of the gripper finger 9 and the slightly flattened hose 8, which form the press nip. The clamping surface of the gripper finger 9 and the contact surface of the hose 8 ensure play-free fixation.

[0033] The gripper finger 9 is held here by a bearing 10 fixedly arranged on the guide disk 5 and rotates with the rotating guide disk 5. The gripper finger 9 is further connected to a transmission coupling 11 which can move radially to the guide disk 5. The transmission coupling 11 is rotatably connected to a drive rocker 12 which is rotatably mounted on the guide disk 5 via a pivot point 13. The drive rocker 12 carries a rotatable cam roller 14 which is operatively connected to a fixed cam disk 15. A spring 16 holds the cam roller 14 to the cam disk 15. When the cam roller 14 is moved radially outwards, the gripper finger 9 is moved via the transmission coupling 11 into the open position shown here to release the sheet. When the transmission coupling 11 moves in the opposite direction, supported by the spring 16, the gripper finger 9 closes to fix the sheet.

[0034] The Fig. 4 shows a simple embodiment of a cam-controlled drive mechanism for a gripper of a gripper system 7. When force is introduced, for example from a curve, according to the direction of the arrow, the gripper pressing the curved edge 17 against a hose 8 arranged on the guide disk 5 is lifted and the curved edge 17 is thus released.

[0035] The Fig.Figure 5 shows an alternative embodiment of a drive mechanism via a gear for a gripper of a gripper system 7. In particular, a gear based on a four-link gear is proposed. This solution is exemplary of a multitude of arrangements based on four-bar gears. An advantage of this embodiment is that the gripper track extends only slightly above the guide disk 5, which allows the gripper to close shortly after passing the transfer center, i.e., at a point where a circumferential surface of the transferring cylinder would still collide with a higher gripper track. As an alternative, six-link gears (not shown) could be used to drive the grippers, which advantageously require a relatively small drive angle. It is further proposed that the drive cranks of the four- and six-link gears shown be designed as pinions and driven via racks.

[0036] How it works: To secure the sheet to the guide discs 5, a number of grippers are provided that rotate with the guide discs 5 and are attached to the outside of the guide discs 5. To avoid a collision with the printing cylinder 1, the grippers must be pivoted away in the area of ​​the printing cylinder 1, usually to below the active surfaces, i.e., the sheet support surfaces, of the guide discs 5.

[0037] After passing the transfer center between the printing cylinder 1 arranged upstream in the sheet transport direction and the sheet transport drum 4 during the sheet transfer, the grippers close and thus fix the sheet on the guide discs 5. To release the sheet for transfer to the downstream cylinder or after passing the area of ​​the sprocket main shaft in the delivery, the grippers are opened.

[0038] The exemplary drive solution consists of grippers controlled by cam discs 15. These cam discs 15 are mounted on the shaft 6 and do not rotate with it, but are axially movable together with the guide discs 5 and the grippers mounted thereon. List of reference symbols used 1 printing cylinder 2 rubber cylinders 3 plate cylinders 4 sheet transport drum 5 guide discs 6 Wave 7 gripper system 8 hose 9 gripper fingers 10 Storage 11 Transmission coupling 12 drive swing arm 13 Pivot point 14 Cam roller 15 cam disc 16 spring 17 Sheet edge

Claims

[1] Sheet processing machine with a sheet transport drum (4) for guiding sheets (17) around a rotating axis, wherein the sheet transport drum (4) has guide segments (5) which can be displaced axially to the rotation axis, wherein the guide segments (5) have arc support surfaces concentric with the rotation axis, wherein the sheets (17) can be fixed by pressure elements (9) on the guide segments (5), wherein the pressing elements (9) are movably and fixedly assigned to the guide segments (5), wherein a press gap for sheets (17) to the guide segments (5) can be formed with the pressing elements (9) and wherein the sheet transport drum (4) is arranged between printing cylinders (1) of a sheet-fed printing press and has leading edge clamping grippers or wherein the sheet transport drum (4) is arranged as a delivery drum in a delivery of a sheet-fed printing press, wherein the pressing elements (9) are designed as grippers (9) which can be pressed against the guide segments (5). [2] Sheet processing machine according to claim 1, characterized by that the guide segments (5) are designed as guide discs (5) carrying the pressure elements (9). [3] Sheet processing machine according to claim 1 or 2, characterized by that the guide segments (5) have elastic arc contact elements (8). [4] Sheet processing machine according to claim 1, 2 or 3, characterized by that the guide segments (5) have hoses (8). [5] Sheet processing machine according to claim 1, characterized by that the grippers (9) interact with a four- or six-bar linkage. [6] Sheet processing machine according to at least one of the preceding claims, characterized by that the pressure elements (9) can be moved in a cam-controlled manner. [7] Sheet processing machine according to at least one of the preceding claims, characterized by that non-rotating cam discs (15) are provided which are designed to be displaceable with the guide segments (5). [8] Method for transporting sheets (17) through a sheet processing machine with a sheet transport drum (4), wherein the sheet transport drum (4) guides the sheets (17) fixed on guide segments (5) around a rotation axis, wherein the sheets (17) are pressed onto the guide segments (5) for transport by pressure elements (9) arranged on the guide segments (5) and rotating together with the guide segments (5), and wherein the pressing elements (9) are movable in a cam-controlled manner.

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