Patent Application
20220204295
The present invention relates to a sheet-processing machine comprising a turning device, to a method for conveying sheets, in particular in a turning device of a sheet-processing machine, and to the use of a sheet guide element containing a deionization device in a sheet-processing machine, in particular a turning device of a sheet-processing machine.
In sheet printing presses, for example, an increased electrostatic charge of the sheets can occur in particular in printing units, especially at high speeds. In the printing units, this causes a printed sheet to be drawn to the succeeding sheet guide plates as a result of the charge, despite air cushions that are introduced, and smearing of the fresh ink to occur on the underside of the sheet guide plates.
Increased electrostatic charging of the sheets can also occur in the turning zone, especially at high speeds. The sheets consequently enter the cylinder gap between the turning drum/impression cylinder or the later printing zone in a rippled manner. The sheet can no longer slide on the impression cylinder surface during a smoothing operation and becomes folded.
A device for conveying sheets through the printing zone of the blanket cylinder and the impression cylinder of a sheet rotary printing press is known from EP 0 306 682 A2, wherein deionization rods are arranged upstream from the two ionization rods that generate opposite charges for neutralizing the sheets, which are directed at the sheet from beneath or from above, wherein both are fed, for example, a suitable alternating voltage. This neutralization of the charges creates unambiguous starting conditions for the later positive charge of the sheet. To eliminate the force fit between the sheets and a cover, a further deionization rod is arranged just upstream from the transfer point of the printed sheet to the gripper systems of the sheet removal drum. The arrangement is relatively complex and increases the adhesion of the sheets on the cylinder.
A device for removing electric charges from flat material is known from EP 1 155 834 A2, wherein the positive charge of a printed material lying on a metal plate is compensated for by means of first ionizing tips. Due to the remaining negative charge on the underside of the printed material, the printed material, with the discharged surface, becomes nestled against a further metal plate, wherein the negative charge is compensated for by the downstream ionization rod. This complex system is not suitable for sheet guide elements in sheet-processing machines, in particular in turning devices of sheet-processing machines.
A sheet guide device comprising an electrically insulated, comb-shaped edge is known from EP 1 679 187 B1 or US 2006/150841 A1, wherein a discharging device for discharging the printing material sheets is arranged in the region of the edge. The arrangement in the edge close to the impression cylinder leads to a decreased effect. The edge made of non-conducting material is subject to increased wear, especially in the critical area of the sheet receiving zone, and causes decreased stability in the event of a crash. Furthermore, the arrangement of the discharging device in the concentric guide path makes it more difficult to maintain the optimal electrode spacing, resulting in a decreased effect.
A device for electrostatically influencing signatures is known from DE 197 55 745 A1, wherein a flat charging electrode is applied to the guide surface of a sheet guide plate. The device is intended to draw the sheets onto the sheet guide plate due to the attraction effect and to hold them in a floating state by way of a blower air stream. In reality, a stable floating height of the sheets cannot be maintained at a constant level by such a device. In addition, the flat charging electrode interferes with the nozzle distribution, which has to be configured in accordance with the need for sheet support.
A fan unit in a printing press is known from DE 100 38 774 A1, which comprises controllable ionic fans. In a sheet turning device as well, a printing substrate sheet can thus be guided adhering to the turning drum and turned through the use of generated negative pressure. For this purpose, ionic fan-containing fan units can be integrated within a cylinder or into its surface. This is a complex process, which is also not sufficiently effective.
A device for turning a sheet, while it is conveyed through a printing press, is known from DE 10 2007 049 643 A1, wherein a deceleration system for a sheet is fixed to the stand. The brake system is composed of a generator for an alternating magnetic field and a pneumatic guide device for the sheet. When the sheet passes the generator, a current is to be induced in the ferromagnetic material of the sheet or the printing ink on the sheet. A magnetic field originating from the eddy current is to counteract the field of the generator, so that the sheet is decelerated. The effect of this principle is questionable. The sheets are also not discharged because the generator does not emit any ions.
A turning device of a sheet printing press is known from DE 10 2010 028 702 A1, wherein an ionization device is assigned to the sheet transport path at or in connection with a storage drum, wherein the sheets that are guided on the storage drum or fed to the storage drum can be supplied with electric charges.
DE 100 56 018 A1 shows a device for supporting sheet guidance and sheet stacking, wherein a sheet guide element blowing blower air in the interior encloses a deionization device.
DE 10 2008 001 165 A1 shows a sheet-guiding cylinder of a processing machine, wherein the cylinder comprises a main body on which a cylinder shell that is electrically insulated with respect thereto is arranged.
It is the object of the present invention to devise an alternative sheet-processing machine and an alternative method for conveying sheets in a sheet-processing machine, and to improve sheet guidance in general in a sheet-processing machine, in particular in a turning device of a sheet-processing machine. In particular, reliable sheet guidance is to be improved, especially in the region of a turning device, in particular in the case of low grammage or foil sheets.
According to the present invention, the object is achieved by the features of an independent claim. Advantageous embodiments result from the dependent claims, the description, and the drawings. At this point, all embodiments of the invention disclosed in the claims of the documents as originally filed are explicitly incorporated by reference in the description.
The invention has the advantage that an alternative sheet-processing machine and an alternative method for conveying sheets in a sheet-processing machine are devised. In particular, sheet guidance is further improved, especially in the region of a turning device, which can advantageously result in a considerable increase in performance of a sheet-processing machine, for example a sheet printing press, in particular a sheet offset printing press.
Particularly preferably, deionization of a sheet can be achieved after the sheet has been released from a sheet guide cylinder, in particular from a storage drum in a turning device. The machine can be suitable or configured for processing sheets of low grammage and/or for processing foil sheets. The machine can process, in particular print and/or coat, sheet material having a grammage of more than 250 g/m2, preferably, however, of less than 250 g/m2, particularly preferably of less than 150 g/m2, and most particularly preferably of less than 80 g/m2. Preferably, one, two or more discharge electrodes can be arranged in the region of the sheet guide element, in particular of a sheet guide plate of a turning device. The arrangement can be carried out in the form of a cassette. For example, one or more discharge electrodes can be placed onto the sheet guide plate, or one or more discharge electrodes can be recessed into the sheet guide plate. Electrodes that are recessed are preferably in each case positioned between insulators, whose surfaces terminate in particular tangentially at the sheet guide plate.
The sheet guide element, in particular the sheet guide plate, preferably downwardly delimits the long side of a turning zone of a turning device. The sheet guide element, in particular the sheet guide plate, is preferably spaced apart from the cylinder tangent between a storage drum and a turning drum in such a way that the distance with respect to the sheet corresponds to the optimal electrode spacing. Furthermore, a device, in particular a tautening sucker, can be provided on the storage drum, which additionally tightens or tautens the sheet in the vicinity of the cylinder tangent between the storage drum and the turning drum, so that not only the optimal electrode spacing is preserved across the full sheet length, but also that the sheet can be influenced where, on the upper side and underside, it remains free of ion-binding contact with machine parts with mass, so that the ions are able to transition with little impediment into the activated deionizing ambient air, which ultimately results in a maximally possible discharging of the sheets.
A discharge cassette is preferably introduced into the sheet guide element, in particular the sheet guide plate, while turning the sheets so as to discharge the sheets. A discharged sheet is thus freed from electrostatic force actions and can be smoothed so as to be able to pass a downstream processing station or printing zone without ripples and without creases.
It is useful in machines that include turning devices, especially when processing print substrates having low grammage or made of foil material, to provide deionization devices in further, or preferably all, printing units and possible further units and/or a delivery, in addition to the deionization device in the turning device, since the print substrate is always recharged in a printing zone. Preferably, sheet guide elements that contain deionization devices configured as sheet guide plates are used for this purpose, which, arranged at a suitable distance with respect to the sheet conveyor path, particularly advantageously ensure optimal discharge and guidance of the printing materials at the same time.
The invention shall be described hereafter by way of example. The associated drawings schematic show:
The machine 1 in particular includes at least two or a multiplicity of printing units 2 and/or one or more coating units for processing sheets. Each of the printing units 2 of the machine 1 preferably comprises a transfer cylinder or blanket cylinder 6 and a forme cylinder or plate cylinder, which is not shown in detail. A blanket cylinder 6 of a printing unit 2 cooperates with a respective sheet guide cylinder, in particular an impression cylinder 5. A sheet conveyor system, preferably a sheet conveyor drum 7 or a transfer drum or a transfer cylinder, is provided between two sheet guide cylinders, in particular impression cylinders 5. The impression cylinders 5 and the sheet conveyor drum 7 here have a double-sized configuration, and the blanket cylinders 6 and the plate cylinders have a single-sized configuration. Single-sized cylinders can approximately receive one maximum-format sheet, and double-sized cylinders can approximately receive two maximum-format sheets simultaneously around the circumference. In an alternative embodiment, the sheet guide cylinders, in particular the impression cylinders 5 or the transfer drums, could also have a single-sized, triple-sized or larger configuration.
The double-sized impression cylinders 5 or the sheet conveyor drum 7 here preferably each comprise two gripper systems for fixing sheets to be conveyed, in particular foil sheets. These gripper systems, which are arranged diametrically opposed, for example in gripper channels, hold the sheet to be processed for conveyance. The gripper systems preferably comprise stationary gripper pads, which cooperate with gripper fingers that can be moved, for example, by means of radial cams and cam rollers via roller levers, for clamping the sheets. During their respective rotation, the gripper pads of the impression cylinder 5 and of the sheet conveyor drum 7 describe a gripper pad path, which substantially corresponds to the sheet conveyor path. During conveyance, the sheets can rest on the respective cylinder or the cylinder lateral surface of a sheet guide cylinder, in particular of an impression cylinder 5. The sheets are transferred between the sheet guide cylinders, in particular the impression cylinders 5, and the sheet conveyor systems, in particular the sheet conveyor drums 7, of the printing units 2 of the machine 1, preferably in a gripper closure. A delivery 4 comprising a delivery chain loop is preferably arranged downstream from the last unit of the machine 1, the loop receiving the sheets from the last sheet guide cylinder, in particular an impression cylinder 5, by means of gripper carriages and conveying them to a delivery pile. For example, a last unit of the machine 1 upstream from the delivery 4 can be embodied as a printing, coating, drying, inspection or finishing unit, such as an inline processing unit.
In the printing units 2 of the machine 1, the blanket cylinders 6 are functionally connected to the plate cylinders and known inking or inking and dampening units are arranged, which apply the corresponding printing ink onto a printing plate that is clamped on the respective plate cylinder. During its rotation, a plate cylinder is inked by at least one roller, but preferably multiple rollers of the assigned inking unit or inking and dampening unit. When the plate cylinder carries out a rolling motion on the blanket cylinder 6, the printing ink is transferred to the blanket cylinder 6 containing a rubber printing blanket in accordance with the motif. A press nip or a printing zone is formed between a blanket cylinder 6 and an impression cylinder 5, through which the sheet to be printed is conveyed from the impression cylinder 5 by means of the gripper systems. In the press nip, the printing ink is transferred from the blanket cylinder 6 to the sheet in accordance with the motif. The impression cylinder 5 in particular has a lateral surface, extending over the entire surface area, for supporting the sheets to be conveyed, which forms the press nip with the rubber printing blanket of the blanket cylinder 6. A plate cylinder and a blanket cylinder 6 of a respective printing unit 2 of the machine 1 preferably comprise a respective cylinder pin on each side, by way of which the cylinders are rotatably mounted in the stand of the respective printing unit 2. Both the plate cylinders and the blanket cylinders 6 preferably each have bearer rings, which are arranged on both sides and not shown. The plate cylinder bearer rings are in contact with the blanket cylinder bearer rings during the printing process and carry out a rolling motion on one another under pressure. The bearer rings are preferably dimensioned in such a way that, during printing operation, no noteworthy transfer of moment occurs between the cylinders, i.e., no predetermined moment is transferred via the bearer rings.
The machine 1 preferably comprises a drive wheel train, which particularly preferably, as a continuous drive gear wheel train, drives the sheet guide cylinders, in particular the impression cylinders 5 of the printing units 2. The sheet conveyor systems, in particular the sheet conveyor drums 7 or transfer drums, are preferably also driven by the drive wheel train. For this purpose, the impression cylinders 5 and the sheet conveyor drums 7 in each case comprise gear wheels that mesh with one another and form the drive wheel train. The drive wheel train is driven by at least one main drive motor, which provides the drive input centrally or preferably in the region of the forward units of the machine 1. For example, the drive input of the main drive motor can take place in the first printing unit 2 directly following the infeed unit in the sheet conveyor direction BFR, in particular to the gear wheel that is assigned to the shaft of the first impression cylinder 5. The cylinders or drums are driven about their respective axis of rotation by the continuous drive wheel train. The blanket cylinders 6 of the printing units 2 are also preferably driven starting from the drive wheel train. Further rotary bodies or rollers of the machine 1 or of the printing units 2 can likewise be at least temporarily driven by the drive wheel train, wherein these can also be designed to be couplable to the drive wheel train.
For example, a dedicated drive, in particular a plate cylinder direct drive, can be assigned to one or each plate cylinder of a printing unit 2. Direct drives are in particular dedicated drives whose rotors are attached so as to be aligned and concentric, preferably directly with respect to the assigned cylinders. During printing, the plate cylinder in question can then trail the blanket cylinder 6, which is preferably driven by the main drive motor via the drive wheel train, in an electronically synchronized manner. For this purpose, a rotary encoder, which can be connected to a quality control device, a control unit of the printing unit 2 and/or the machine controller, can be assigned to the plate cylinder and/or the blanket cylinder 6. As an alternative, the plate cylinder or plate cylinders, however, can also be driven via the drive wheel train starting from the main drive motor, for example by way of couplings.
In the case of a foil sheet-processing machine 1, foil material-containing sheet substrate or sheet substrate made of foil material is processed, in particular printed and/or coated. The sheet-processing machine 1 comprises in particular suitable equipment for processing foil sheets. The foil sheet-processing machine is preferably embodied as a foil sheet printing press, at least for printing foil sheets. In particular, the machine 1 can comprise a foil sheet processing package, which is specifically matched to the foil material. For example, the machine 1 can comprise at least one primer unit arranged upstream from the printing units 2, for example, and/or a special double-sheet detector unit and/or the gripper systems of the machine 1 can be matched to the thin nature of the foil sheet material and/or printing inks and/or coating materials or dryers that are used can be matched to the foil material. Foil material can be foils made of PVC, PP, PS, PET, for example. Furthermore, however, specialty papers, laminated papers or paperboards could also be processed by a machine 1.
In particular during foil printing, the foil sheets are charged in every active printing unit 2 of the machine 1. The foil sheets in particular undergo renewed extreme static re-charging with each printing process. In particular, deionization devices 8 are therefore provided at least in the printing units 2 and/or coating units of the machine 1, which are arranged downstream from the press nip of the first printing units 2 of the machine 1 with respect to the sheet conveyor direction BFR. Deionization devices 8 are preferably provided in all units of the machine 1 that are arranged downstream from the first printing unit 2. However, in a refinement, it is also possible for a deionization device 8 to be assigned to an infeed unit and/or the first printing unit 2 of the machine 1. The deionization devices 8 are in particular provided in each printing unit 2 and/or coating unit of the machine 1, wherein in particular one deionization device 8 is exclusively arranged in each printing unit 2 and/or coating unit. More preferably, such a deionization device 8 is also provided in each case in one or each additional unit, such as a coating, drying, inspection or finishing unit. Charging devices for deliberately charging cylinders or sheets are in particular not provided.
The sheets, in particular the foil sheets, are conveyed or transported along a sheet conveyor path by the sheet guide cylinders, in particular the impression cylinders 5, and the sheet conveyor systems, in particular the sheet conveyor drums 7, of the machine 1. In the process, in particular beneath and along the sheet conveyor path, a sheet guide element, which begins in the region of the sheet guide cylinder, in particular of the impression cylinder 5, is provided in one or all printing units 2. Such a sheet guide element is preferably configured as an in particular metallic sheet guide plate 9, which extends in particular across the machine width. In particular, such a sheet guide plate 9 comprises comb fingers 10 in the region facing the sheet guide cylinder, in particular the impression cylinder 5. With respect to the sheet conveyor direction BFR, in particular a respective deionization device 8 adjoins the comb fingers 10, wherein the comb fingers 10 of the sheet guide plate 9 are made in particular partially or completely of metallic material. Furthermore, the comb-shaped regions of the sheet guide elements could be provided with blower air openings and, in particular, be switchable to blower air, so that a force that acts pneumatically on the sheets can be generated in these regions. In particular, the sheets, in particular the foil sheets, could thus be peeled off the lateral surface of the upstream sheet guide cylinder, in particular the impression cylinder 5, by the pneumatically acting comb fingers 10. The sheet guide surfaces of the comb fingers 10 are thus assigned to blower air openings to which overpressure can be applied. In particular, a blower air action is exerted by the overpressure, which exceeds the ambient pressure, on the sheets that are conveyed along the sheet conveyor path.
A sheet guide element, in particular a sheet guide plate 9, beneath a sheet conveyor system, in particular a sheet conveyor drum 7, can be composed of a single-piece metal sheet or of multiple segments. For example, an upstream guide piece can form a first region, and a downstream guide piece can form a second region for sheet guidance. In the process, for example, a first segment or partial plate can extend from the shell of the sheet guide cylinder, in particular of the impression cylinder 5, to perpendicularly beneath the axis of rotation of the sheet conveyor drum 7. A second segment or partial plate can adjoin in the sheet conveyor direction BFR and extend to the lateral surface of the downstream sheet guide cylinder, in particular the impression cylinder 5. A deionization device 8 is in particular assigned to the first segment of the sheet guide element. In particular, the deionization device 8 is assigned to the sheet guide element, or the sheet guide surface of the sheet guide element, in the region of the upstream sheet guide cylinder, in particular the impression cylinder 5. Particularly preferably, the deionization device 8 forms the sheet guide surface in its arrangement region.
In particular, the segment arranged downstream with respect to the sheet conveyor direction BFR, or a second region of the sheet guide element, in particular of the sheet guide plate 9, is concentrically configured with respect to the axis of rotation of the sheet conveyor system, in particular the sheet conveyor drum 7. In particular, the sheet guide surface of the second segment of the sheet guide element, in particular of the sheet guide plate 9, is concentrically configured about the axis of rotation or the gripper pad path of the sheet conveyor drum 7. The first segment of the sheet guide element, in particular of the sheet guide plate 9, can include a sheet guide surface that steadily approaches the axis of rotation of the sheet conveyor system, in particular of the sheet conveyor drum 7, in or starting in the region of the sheet guide cylinder, in particular of the impression cylinder 5. The sheet guide element thus has a spiral-shaped configuration. The first segment can also be concentrically configured about an axis that is spaced apart from the axis of rotation of the sheet conveyor drum 7.
In particular, at least one fan 14, which can in particular be activated for generating blower and/or suction air, can be assigned to a sheet guide element, in particular a sheet guide plate 9. A fan 14 is preferably arranged at the sheet guide element, in particular at a sheet guide plate 9, so as to generate blower and/or suction air in the region of the sheet guide surface of the sheet guide element, in particular of the sheet guide plate 9. In particular, corresponding openings, for example Venturi nozzles, facing the sheet conveyor path, are assigned to the sheet guide element, in particular to the sheet guide plate 9. Outside potentially provided openings, however, the sheet guide element, in particular the sheet guide plate 9, preferably has a closed sheet guide surface.
In particular, a sheet guide element, in particular a sheet guide plate 9, can be configured in such a way that a sheet guide surface extends, starting in the region of the lateral surface of the sheet guide cylinder, in particular of the impression cylinder 5, to the downstream sheet guide cylinder, in particular the impression cylinder 5, beneath the sheet conveyor system, in particular the sheet conveyor drum 7. A first region of the sheet guide element, in particular of the sheet guide plate 9, which starts in the region of the upstream sheet guide cylinder, in particular of the impression cylinder 5, can comprise the comb fingers 10 and be spaced further apart from the axis of rotation of the sheet conveyor system, in particular of the sheet conveyor drum 7, than a succeeding second region of the sheet guide element, in particular of the sheet guide plate 9. The comb fingers 10 and the first region of the sheet guide plate 9 preferably form a substantially closed sheet guide surface for the sheets.
The first region of the sheet guide plate 9 can start in an angle of rotation range of the sheet conveyor drum 7 that is spaced between 15° and 25°, in particular approximately 20°, apart from the transfer center line formed by the gripper closure between the upstream impression cylinder 5 and the sheet conveyor drum 7. The sheet guide plate 9 or the comb fingers 10 can be arranged at a distance of, for example, 2 mm to 50 mm, in particular between 25 mm and 30 mm, from the sheet conveyor path formed by gripper pads of the sheet conveyor drum 7. The first region of the sheet guide plate 9 preferably steadily approaches the axis of rotation of the sheet conveyor drum 7 or the sheet conveyor path.
In a second region of the sheet guide plate 9 adjoining the first region of the sheet guide plate 9 in the sheet conveyor direction BFR, the sheets are preferably concentrically guided with respect to the axis of rotation of the sheet conveyor drum 7, or they are guided parallel to the gripper pad path of the sheet conveyor drum 7 or parallel to the sheet conveyor path. The second region of the sheet guide plate 9 can, for example, be configured to be spaced 5 mm to 10 mm apart from the sheet conveyor path. The second region of the sheet guide plate 9 can, for example, start in an angle of rotation range of 60° to 90° spaced apart from the transfer center line between the impression cylinder 5 and the sheet conveyor drum 7. The sheet guide element, in particular the sheet guide plate 9, can thus be configured in such a way that a distance between its first upstream region with respect to the sheet conveyor direction BFR and the gripper pad path or the sheet conveyor path is several times, for example twice or three times, as large compared to that of the downstream second region.
A deionization device 8 is preferably arranged in the first region of the sheet guide plate 9, wherein it is arranged downstream from the comb fingers 10 in the sheet conveyor direction BFR if comb fingers 10 are provided. Comb fingers 10 can, for example, extend over an angle of rotation range of the sheet conveyor drum 7 of approximately 5°. A deionization device 8 can directly adjoin the comb fingers 10 or extend over an angle of rotation range of the sheet conveyor drum 7 of at least approximately 10°. The sheet guide surface of the sheet guide plate 9 formed by the comb fingers 10 and/or the deionization device 8 approaches, in particular steadily, the axis of rotation of the sheet conveyor drum 7, or its gripper pad path, or the sheet conveyor path, as viewed in the sheet conveyor direction BFR. For example, the first region of the sheet guide plate 9 can transition into the second region, which is configured to be substantially concentric with respect to the sheet conveyor path, within an angle of rotation range of the sheet conveyor drum 7 of, for example, approximately 60°. The machine 1 can comprise further units or printing units 2, wherein some, or preferably all, of the units or printing units 2 include or contain sheet guide elements, in particular sheet guide plates 9, for guiding sheets. The sheet guide elements, in particular the sheet guide plates 9, of the machine 1 are in particular configured to be identical.
The sheet guide element, in particular the sheet guide plate 9, preferably surrounds the sheet conveyor system, in particular the sheet conveyor drum 7, for example a transfer drum without lateral surface, in a spiral shape. This means that the forward portion of the sheet guide element, in particular of the sheet guide plate 9, is held spaced further apart from an axis of rotation of the sheet conveyor system, in particular of the sheet conveyor drum 7, than the succeeding portion of the sheet guide element, in particular of the sheet guide plate 9. Thereafter, the sheet guide element, in particular the sheet guide plate 9, transitions preferably tangentially into a concentric radius with respect to the sheet conveyor system, in particular the sheet conveyor drum 7, so as to implement the optimal electrode spacing in the regions of the furthest distance of the guide plate spiral, excluding the comb fingers 10. This means that the guide surface of the sheet guide element 9 in the sheet conveyor direction BFR approaches the radius of the sheet conveyor drum 7, and thereafter leads around the same, concentrically with respect to the radius of the sheet conveyor drum 7.
The insulators 11 of the deionization device 8 are in each case arranged transversely to the sheet conveyor direction BFR, preferably across the entire width of the sheet guide plate 9, and include surfaces arranged perpendicularly to the sheet conveyor path or to the sheet guide surface of the sheet guide plate 9. Each discharge electrode 12 here is in particular arranged between two insulators 11. A forward insulator 11, with respect to the sheet conveyor direction BFR, adjoins the, in particular metallic, comb fingers 10 with its perpendicular or tangential surface. Downstream from the deionization device 8, the sheet guide plate 9 preferably directly adjoins a perpendicular or tangential surface of a rear insulator 11, or a last insulator with respect to the sheet conveyor direction BF.
The mechanism of action involves disruptions that are caused by the extreme adhesion forces resulting from the printing pressure between the sheet, in particular the foil sheet, and the sheet guide cylinder, in particular the impression cylinder 5. When the sheet is transferred from the sheet guide cylinder, in particular the impression cylinder 5, to the sheet conveyor system, in particular to the sheet conveyor drum 7, the sheet is difficult to release because the pull-off forces only act tangentially. As the movement progresses further, the sheet, as a secant, intersects the sheet conveyor drum radius due to the pull-off forces in the sheet, and the “excess” of unwound sheet length created thereby allows the sheet adhering to the impression cylinder surface to further follow the impression cylinder 5. Even though the only truly releasing radial components of the previously only tangentially acting pull-off force are increased as a result, these are still low, and the sheet continues to follow the impression cylinder surface until the release loop of the sheet is peeled off by the pneumatically acting forces of the comb plate, in particular without making mechanical contact. The air cushion generated by the Venturi nozzles cannot contribute to the sheet being pulled off the impression cylinder 5, since the suction potential of the air cushion does not act on the regular sheet path or the balanced floating height.
Furthermore, the sheet, due to the electrostatic charge, is attracted by the sheet guide element, in particular the sheet guide plate 9, when pulled off the sheet guide cylinder, in particular the impression cylinder 5, in this way and would make contact therewith. The present air cushion of the sheet guide plate 9, serving as a distributed load against the non-uniformly distributed field forces of the electrostatic charge, would not be able to create balance, and consequently would not create a floating state. Regions of intensive contact with the sheet guide plate 9 would arise. Any intensive contact with the sheet guide plate 9, however, results in visible scratches on the surface of the sheets, in particular of foil sheets, or in smearing, especially on paper sheets. Due to the above-described specific embodiment of the sheet guide element, in particular of a sheet guide plate 9, however, an effective, the distance preserving measure is devised for the scratch-free or non-smearing guidance of sheets, in particular of foil sheets, on the sheet guide surface under a sheet conveyor system, in particular the sheet conveyor drum 7, after the sheet has been released from the sheet guide cylinder, in particular the impression cylinder 5. As a result of the devised solution, contact of the sheet, in particular the foil sheet, with the sheet guide element, in particular the sheet guide plate 9, specifically with the comb and the subsequent guide surface components, and thereby scratches and smearing, are prevented.
Furthermore, a controller or also automatic sensor-controlled closed-loop control of the one, multiple or all discharge electrodes 12 of one, multiple or even all deionization devices 8 of the machine 1 can be provided in the machine 1. For example, individual discharge electrodes 12, or multiple discharge electrodes 12 of a deionization device 8, or multiple or all deionization devices 8 of the machine can be connected to a generator, in particular a high voltage generator. The discharge action can be set by way of an activation of the generator. For example, the intensity of the deionization device 8 can be controlled by closed-loop or open-loop control by way of measuring equipment in such a way that it is possible to control the discharge in a manner that is matched to the static electricity at the sheet, in particular the foil sheet. Furthermore, in particular in the case of exchangeable discharge cassettes, an arrangement thereof in another location of the machine 1 can be provided. In particular, such a cassette or deionization device 8 can be used in the turning zone. The discharge cassettes can thus be configured to be exchangeable among one another in the machine 1 or have a modular configuration.
The transfer drum 15 and the turning drum 17 of the turning device 3 have a single-sized configuration, for example, and the storage drum 16 has a double-sized configuration, for example. For conveying the sheets, the transfer drum 15 comprises a gripper system, which is not shown and arranged in a gripper channel, for clamping the sheets at the leading edge. The sheets are transferred in the gripper closure to a gripper system of the storage drum 16, which is likewise not shown and arranged in a gripper channel. From the storage drum 16, the sheets, being clamped at the leading edge, are fed to the turning drum 17 during the rotation of the storage drum 16. For conveying the sheets, the turning drum 17 comprises a gripper system, which is likewise not shown, in particular grippers and/or suckers that are pivotably mounted in the turning drum 17. As an alternative, the turning drum 17 can also include a pincer gripper system for receiving or conveying the sheets. Other cylinder arrangements or other cylinder sizes can also be used. For example, the transfer drum 15 can also have a double-sized configuration.
In the recto printing operating mode, the sheets are received by the gripper system of the turning drum 17 in a transfer center line at the leading edge by a gripper system of the storage drum 16. When a sheet is turned during recto and verso printing, this sheet is guided past the transfer center line by the storage drum 16 and gripped at the trailing edge by the gripper system of the turning drum 17. This gripped sheet is subsequently turned, as the rotation of the turning drum 17 progresses, according to the principle of trailing edge turning, so that its old trailing edge becomes the new leading edge starting with its motion reversal, and the old leading edge located on the storage drum 16 becomes the new trailing edge. The turning device 3 is assigned a sheet guide element for supporting the sheet travel, in particular in the recto and verso printing operating mode. For example, a sheet guide element, configured in particular as a sheet guide plate 9, for supporting the sheet guidance can be arranged beneath the storage drum 16 and the turning drum 17. The sheet guide element, in particular the sheet guide plate 9, can also be configured, for example, as a sheet guide element, in particular a sheet guide plate 9, that can be displaced as a function of the operating mode. Such a displaceable sheet guide element, in particular sheet guide plate 9, can be supplied to the sheet conveyor path, at least in the recto and verso printing operating mode.
The storage drum 16, which is not shown in detail, can comprise format-settable shell segments, for example, which during format setting mesh with one another in a comb-like manner and form the sheet-supporting lateral surface. The two diametrically opposed gripper systems of the double-sized storage drum 16 for the leading sheet edges are arranged at preferably stationary forward shell segments. At the rear shell segments, which are adjustable with respect to the forward shell segments, fixation systems, in particular suction systems, for example, twisting suckers and/or tautening suckers, can be provided for receiving and guiding the trailing sheet edges. By way of twisting suckers, the sheets, while the sheets are conveyed from the transfer drum 15 to the turning drum 17, can be tautened in particular longitudinally and/or transversely, lying on the storage drum 16. Even when the turned sheet is pulled off the storage drum 16 by the turning drum 17, tautening of the sheet can preferably be carried out by the fixation systems, in particular the suction systems, such as the twisting suckers or also tautening suckers, in the tines of the rear adjustable shell segments of the storage drum 16.
To support the sheet guidance during recto and verso printing, the sheet guide element arranged below the storage drum 16 and the turning drum 17 can be configured to be settable thereagainst, so that its sheet guide surface is at least approximately aligned parallel to the sheet conveyor path. The sheet conveyor path at least approximately corresponds to a surface that is placed tangentially both against the lateral surface of the storage drum 16 and the turning drum 17. The sheet guide surface of the sheet guide element, in particular of the sheet guide plate 9, can also be slightly approaching the turning drum 17. The sheet guide element, in particular the sheet guide plate 9, has a planar guide surface 9.3 at least in some areas, which particularly preferably is located beneath the turning drum 17, in particular beneath the axis of rotation of the turning drum 17. A deionization device 8 is assigned to the sheet guide element, in particular to the planar guide surface 9.3 of the sheet guide plate 9. The deionization device 8 comprises at least one discharge electrode 12 for discharging a sheet. The deionization device 8, in particular the at least one discharge electrode 12, causes a discharged sheet to be freed from electrostatic force actions, so that it can be smoothed so as to be able to pass the succeeding press nip or the printing zone without ripples and without creases.
One of the described sheet guide elements, in particular such a sheet guide plate 9, is assigned to the transfer region between the storage drum 16 and the turning drum 17 in the machine 1. A sheet guide plate 9 in particular downwardly delimits the long side of the turning zone and is spaced apart from the cylinder tangent between the storage drum 16 and the turning drum 17 in such a way that the distance with respect to the sheet corresponds to the optimal electrode spacing. Furthermore, a fixation of the sheet lying on the storage drum 16 can be provided by the fixation systems, in particular the suction systems, for example twisting suckers and/or tautening suckers, of the storage drum 16, so that the sheet is additionally tightened or tautened in the vicinity of the cylinder tangent between the storage drum 16 and the turning drum 17. In this way, it can in particular be achieved that not only the optimal electrode spacing is preserved across the entire sheet length, but also that the sheet can be influenced where, on the upper side and underside, it remains free of ion-binding contact with machine parts with mass. This advantageously causes the ions to be able to transition with little impediment into the activated deionizing ambient air.
In the delivery 4, the gripper carriages are guided by the delivery chains on a gripper carriage track in the sheet conveyor direction BFR to beyond the delivery pile, where the gripper carriages release the substrates for stacking. For releasing the sheets, the clamped leading sheet edges are released in that the gripper fingers are lifted off the gripper pads fixedly arranged at the gripper carriage. The gripper fingers can be moved by way of radial cams and control levers via a gripper shaft at which the gripper fingers are fixedly arranged. With respect to the sheet conveyor direction BFR, a sheet brake is preferably arranged upstream from the delivery pile, which decelerates the sheets to be deposited from the machine speed to the stacking speed after they have been released. After having been decelerated by the sheet brake, the sheets are, for example, aligned at leading, trailing and/or side edge stops and neatly deposited on the delivery pile. The delivery pile is lowered by a pile lifting drive during the sheet stacking process in such a way that the delivery pile surface forms an at least approximately constant stacking level for the arriving sheets.
On the sheet conveyor path to the delivery pile, at least one mechanical sheet guide element is arranged in the delivery 4 beneath the sheet conveyor path, which guides the sheets downstream from the last sheet guide cylinder on the path to the delivery pile. The sheets, which, for example, have been fully printed on both sides in the machine 1, are conveyed by the continuously revolving gripper carriage of the chain conveyor system from the last sheet guide cylinder to the delivery pile. The gripper pads revolving together with the gripper carriages thus describe a gripper pad path, which substantially corresponds to the sheet conveyor path or delimits it on one side, and thereby defines it. The last sheet guide cylinder of the machine 1 is in particular an impression cylinder 5 of the last printing, coating, drying, inspection or finishing unit, which in particular has an at least approximately closed lateral surface. The impression cylinder 5 preferably has a double-sized configuration and comprises two gripper systems that are arranged diametrically opposed in gripper channels, as described above. These gripper systems in particular likewise comprise movable gripper fingers that correspond to gripper pads delimiting or defining the sheet conveyor path. The leading sheet edges are received from these gripper systems by the gripper carriages of the chain conveyor system in the gripper carriage. For receiving the leading sheet edge, the gripper fingers of the impression cylinder 5 are arranged in a staggered layout in relation to the gripper fingers of the gripper carriages. This receiving of the leading sheet edge takes place in a transfer center line in which the leading sheet edge is briefly fixed by both grippers.
The chain conveyor system in the delivery 4 comprises a sprocket wheel shaft, which is arranged adjoining the last sheet guide cylinder, in particular the impression cylinder 5, and includes two sprocket wheels 18 that are arranged coaxially with respect to and spaced apart from one another and that are fixedly connected to the sprocket wheel shaft. The delivery chains run over the sprocket wheels 18 and can be driven by these in a revolving manner. The sprocket wheel shaft can, for example, be driven via the continuous drive wheel train, together with sheet conveyor systems and sheet guide cylinders, in the units or printing units 2 of the machine 1. The sheet guide element, which is preferably configured as a sheet guide plate 9 that preferably extends across the machine width and is arranged between the side walls, is arranged beneath the sprocket wheel shaft between the sprocket wheels 18. This sheet guide plate 9 preferably has an at least approximately closed surface for guiding the sheets in a sliding and/or floating manner. The sheet guide plate 9 can be provided with an ink repellent coating. Furthermore, nozzle openings, in particular Venturi nozzles, for pneumatically guiding the sheets can be assigned to the sheet guide plate 9.
For example, one or more blower modules or fans 14, by way of which blower air nozzles of the sheet guide plate 9 can be supplied with blower air and/or suction air, can be arranged beneath the sheet guide plate 9, which can also be formed of assembled guide segments, so that a supporting air cushion can be formed between the sheet guide plate 9 and the sheets conveyed or transported by the gripper carriages, in particular for recto and verso printing. A preferably deactivatable smoothing device can be assigned to the sheet guide element, in particular the sheet guide plate 9. Such a smoothing device can be deactivated or is not used when sheets containing fresh ink, for example in recto and verso printing, or also foil sheets are transported or guided. The sheet guide elements, in particular the sheet guide plates 9 of the machine 1 are in particular configured to be identical. To be able to avoid that the sheets stick together on the delivery pile, dryers and/or powdering devices, which are not shown in greater detail, can be provided in the delivery 4. It is also possible to integrate a cooling circuit in the sheet guide element to be able to control by open-loop or closed-loop control heating of the sheet guide element.
The sprocket wheel shaft in the delivery 4 in particular does not include a lateral surface for supporting the sheets. In a refinement, the sprocket wheel shaft can contain two or more support disks or suction disks, or also individual suckers, such as corner suckers, in addition to the sprocket wheels 18 for the revolving delivery chains. For example, the support disks with or without corner suckers or the suction disks can be configured to be axially displaceable so as to be adjustable to the respective sheet side edges. Such disks can also be axially adjusted automatically and/or independently of one another. Such disks in particular include supporting surfaces around the circumference, which have a minimal axial extension. As a result of this extension of the support disks present in the axial direction, a respective sheet can be fixed on the lateral surface of the sheet guide cylinder, in particular of the impression cylinder 5, when receiving the sheets. In this way, a drop of the sheet is avoided as long as the sheet is situated between the disks and the last sheet guide cylinder, in particular the impression cylinder 5. The sheets are preferably pressed against the lateral surface of the impression cylinder 5 by support elements arranged on brackets in small press nips. The support elements can have elastic surfaces. Such disks preferably likewise have a double-sized configuration and can preferably include recesses for the revolving gripper carriages of the chain conveyor system.
Regarding the mechanism of action: The sheets are received from a sheet guide cylinder, in particular a storage drum 16 or an impression cylinder 5 by a sheet conveyor system in the turning device 3 and/or in a unit or printing unit 2, in particular a turning drum 17 or sheet conveyor drum 7 or a gripper carriage in the delivery 4, and are guided past a deionization device 8 along the sheet guide element, in particular the sheet guide plate 9, on the sheet conveyor path. In a refinement, a device can be provided in the region of a transfer drum or of a sprocket wheel shaft, which additionally guides the sheet, held only at the edges, in the vicinity of the gripper pad path in a defined manner so that the optimal electrode spacing is preserved across the full sheet length, and the sheet does not make contact with the sheet guide plate 9 prematurely and drops below said optimal electrode spacing.
The sheets, in particular the foil sheets, are released from the lateral surface of the sheet guide cylinder, in particular of the impression cylinder 5, by the sheet guide element, in particular the sheet guide plate 9, preferably in a spiral shape. In particular the comb fingers 10 of the release loop of the sheet give way at a suitable distance when the sheet is pulled off the lateral surface. Allowing a minimal pull-off loop advantageously increases the releasing radial component of the pull-off forces. By arranging the Venturi nozzles along the guide contour of the sheet guide element in connection with the associated balanced floating height of the sheets beneath the gripper pad path, the suction forces of the air cushion can act on the sheet present on the regular sheet path. In this way, the sheet is held on the outside of the radius of the gripper pad path, and the release loop is kept small.
Due to the at least one discharge electrode 12 that is in particular recessed at the guide plate start, a charge equalization is brought about at the sheet until sufficient charge neutrality is reached, so that the sheet is not subsequently attracted by the sheet guide element, in particular the sheet guide plate 9, as an electrical conductor. Due to the deionization device 8, in particular positive and negative ions are provided to be able to equalize the alternating charge states on the sheet surface. A deionization device 8 is used in particular in each printing unit 2 or unit of the machine 1 since the sheet, in particular the foil sheet, undergoes extreme re-charging during each printing process.
The sheets are in particular optimally discharged by the deionization device 8 of the or each printing unit 2, preferably each unit, of the turning device 3 and/or of the delivery 4. As a result of the discharge, it is possible to feed the sheet in a constantly floating state to the next conveyor system, for example an impression cylinder 5 or a gripper carriage, without the sheet becoming scratched due to contact with the sheet guide element, in particular a sheet guide plate 9. Due to the one or more discharge electrodes 12 of a respective deionization device 8, in particular active discharging is ensured, both with positive and with negative ions. Provided generators preferably operate in a range of 3 to 6 kV, optimally with a high voltage of at least approximately 4.5 kV. The high voltage can also be set as a function of the ascertained electrostatic charge. A respective sheet is discharged by the deionization devices 8, so that the deionized sheets are free of electrostatic forces and rest in a smoothed manner on the sheet guide plate 9 or the air cushion generated by the sheet guide plate 9. The sheets remain deformation-free and smear-free across the entire machine 1.
While a preferred embodiment of a sheet-processing machine comprising a turning device, a method for conveying sheets, and the use of sheet guide elements containing deionization devices, all in accordance with the present invention, has been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that various changes could be made thereto, without departing from the true spirit and scope of the present invention, which is accordingly to be limited only by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 118 568.8 | Jul 2019 | DE | national |
This application is the US national phase, under 35 USC § 371, of PCT/EP2020/065174, filed Jun. 2, 2020; published as WO 2021/004696 A1 on Jan. 14, 2021, and claiming priority to DE 10 2019 118 568.8, filed Jul. 9, 2019, the disclosures of which are expressly incorporated herein, in their entireties, by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/065174 | 6/2/2020 | WO | 00 |
