EP3072689B1 - Rotary printing machine with devices for reducing charging of print substrate - Google Patents

Description

The invention relates to a rotary printing machine with means for reducing a charge of the printing substrate.

In a printing unit of a rotary printing press, printing cylinders (also called "printing form cylinders") and impression cylinders (also called "impression rollers") roll against one another in opposite directions. A distinction is made between roller and sheet-fed presses, depending on whether a web-shaped or sheet-shaped substrate is being processed. In web-fed printing presses, the web-shaped substrate is pulled off a supply roll and, after printing, either wound onto a take-up roll or cut by a punch into web sections or blanks, and the web sections or blanks are stacked. The wound, web-shaped substrate is optionally later cut into sections or blanks. In rotogravure, the impression cylinder picks up ink from a paint pan in cells on its surface. The excess is scraped off. The ink is transferred to the substrate passing through the printing cylinder and impression cylinder.

Electrostatic printing aids improve the ink transfer from the printing cylinder to the substrate and thus increase the print quality. For this purpose, an electric field is generated in the region of the printing gap between the printing cylinder and impression cylinder, which exerts a force on the ink in the cells of the printing cylinder, which intensifies the transition of the ink to the printing material and increases the print quality.

In known electrostatic printing aids, the printing cylinder is made of an electrically conductive material (eg of a metal) to ground. The impression cylinder or impression roller has on the circumference a (semi-) conductive layer on the one High voltage is transmitted, which has a negative polarity in the rule. The layer on the circumference is mostly semi-conductive to minimize electrical currents and to avoid the generation of sparks which, when working with solvent paints, could cause ignition or explosion. In particular, when working with watercolors can also be worked with a higher conductive or highly conductive layer on the circumference of the impression.

A semiconducting layer is understood as meaning a layer with a high electrical resistance, which greatly reduces the electric current but still allows a certain electrical current to pass through. The electrical resistance of the layer is measured, for example with a measuring arrangement with two parallel forks, each holding a taped with tap water (city water) leather strip with a length of about 8 cm and a width of about 1 cm, so that the two parallel leather strips about 10 cm Have distance from each other. The two parallel strips of leather are wrapped around the outside of the layer over a length of 8 cm. A measuring voltage of 1,000 volts is applied. With this measuring arrangement, resistances in the range from about 1 MΩ to 20 MΩ are measured for semiconducting layers which are particularly suitable for the present purpose. For higher-conducting layers, the resistances measured with this measuring arrangement are significantly lower and for highly conductive layers they are still much lower.

To transfer the high voltage to the impression roller, for example, charging electrodes are used, which are directed onto the circumference of the impression roller and deliver the charge to the (semi-) conductive layer on the circumference of the impression roller, which sits on an insulating layer (so-called "top-loading"). , In this case, the resistance of the insulating layer is preferably chosen such that it allows a slow discharge of the impression roller after switching off the printing press. Particularly suitable insulating layers have a resistance in the range of about one to two gigaohms, as measured with a device of the type discussed above, with only one Leather strips are hit around the outside of the layer and the resistance between the leather strips and machine ground is measured.

Other charging electrodes are directed to at least one end face of the impression roller and discharge the charge to a conductive layer below a (semi) conductive layer which is exposed at an end face of the impression roller (so-called "side charging"). Furthermore, arranged on the front side charging electrodes are known, which cooperate with a conductive board on the front side of the impression roller, which is electrically connected to a (highly) conductive layer. The (highly) conductive layer below the (semi) conductive layer ensures a uniform distribution of the charge over the length of the impression roller.

Further known are devices for transmitting the high voltage on a front side of the impression, working on the transformer principle. At the front side a fixed primary coil is arranged and this is associated with a fixed on the front side of the impression roller, co-rotating secondary coil.

A "direct charging" takes place, for example, via wiper contacts or brushes on the circumference or an end face of the impression roller or via electrically conductive rolling bearings which support a shaft of the impression roller or via which the impression roller is mounted on an axle, or via a fluid transmission system according to FIG EP 1 780 011 B1 , Preferably, the impression roller here consists of a metallic, electrically conductive material (eg steel) with a semiconductive layer on the circumference.

The (semi-) conductive layer on the circumference of the impression roller is made, for example, of rubber or polyurethane with embedded electrically conductive particles (eg graphite). A (high) conductive layer can also be made of rubber or polyurethane with a correspondingly higher proportion of electrically conductive particles. This can also be a metallic layer. An insulating layer, for example, also made of rubber or polyurethane, but with a produced according to a small number of electrically conductive particles or without electrically conductive particles. For sleeves, the sleeve sleeve (usually made of GFRP) can also be the insulating layer.

Rotary printing machines usually have several successively arranged printing units in order to apply different colors to the substrate. The disadvantage is that the substrate can assume very high charges due to the electrostatic charge by electrostatic printing aids that affect subsequent processing. For example, when transporting or cutting a roll comprising the printed substrate, flashovers can occur which endanger print shop workers. If the sheet-like substrate is cut and when working with sheets, it may be due to the high loads problems when stacking the blanks or sheets and removing individual blanks or sheets from the stacks as well as flashovers that endanger printmakers. This is observed when using paper as a substrate and reinforced when using plastic film and composites comprising, for example, plastic, paper and aluminum foils.

EP 1 914 071A describes a rotary printing press with several, in the direction of passage of the printing material successively arranged printing units, each having a printing cylinder and an associated electrostatic printing aid, wherein the electrostatic printing assistance at least two printing units have different polarities. Characterized in that at least one electrostatic printing aid with negative and at least one electrostatic printing aid with positive polarity is present, an excessive charging of the printing material is counteracted and unwanted discharges of the printed substrate and threats to the printing workers are avoided.

Unwanted loading of rolls of electrically substantially insulating web material can also occur in roll cutters in which films are unwound from parent rolls, cut and wound onto daughter rolls. This can also occur when winding films in film extrusion machines and laminating machines.

Based on this, the object of the invention is to provide a rotary printing machine which reduces unwanted charges of the printing material even further.

Furthermore, a method for operating the rotary printing machine is to be made available.

The object is achieved by a rotary printing press with the features of claim 1. Advantageous embodiments of the invention are specified in subclaims.

The rotary printing machine according to the invention comprises an electrically substantially insulating substrate on an unwinding roll from which the printing material is fed to a plurality of printing units arranged one behind the other in the direction of passage of the printing material, each of which a printing cylinder and a impression roller, which roll in opposite directions, and means for generating an electrical Have field in the nip between the impression cylinder and impression roller, wherein the means for generating the electric field of various printing units are connected to high voltage sources having different polarities, and with a take-up reel, on which the printing material is guided behind the printing units, characterized in that each device for generating an electric field via a switching device is connected to a high voltage source of positive polarity and a high voltage source negative polarity, so that by switching d he switching device optional
a high voltage positive polarity or a high voltage negative polarity to the means for generating the electric field can be applied.

An electrically substantially insulating substrate is e.g. a plastic film or a composite film containing a plastic. The composite film contains the plastic, for example in the form of a plastic film or in the form of an extruded layer or in the form of applied plastic particles. In addition, the composite foil comprises e.g. a metal foil or a paper web or a board web or another plastic film. In addition, the composite film may comprise any of the aforementioned components in combination.

The invention is based on the finding that the charges of the printing material are the lowest when a positive voltage is applied to the last printing unit. Apparently, this is due to the fact that plastic film tends to accept negative charges. In a conventional rotary printing press, it is not ensured that the device for generating an electric field of the last used in the direction of passage of the web material (passage direction) printing unit, a high voltage of positive polarity is supplied. This is because the means for generating the electric field are hardwired to the high voltage sources, so that the device for generating the electric field of the last printing unit in the direction of passage is permanently wired to a high voltage source of positive or negative polarity. In many jobs, however, only a part of the printing units of the rotary printing machine is used and the high voltage sources of the other printing units are turned off, for example, in a three-color printing on a rotary printing press with four printing units. As a result, the web material on the take-up roll may still have a high charge, which impairs the handling and further processing of the take-up roll and endangers printing workers. In the rotary printing machine according to the invention is by the connection of each device for generating an electrical
Field via a switching device with a high voltage source of positive polarity and a high voltage negative polarity source achieved that at each print job by simply switching each means for generating an electric field, a voltage is supplied with a polarity, which best possible disturbing charges of the printing material behind the last in the direction of passage printing unit decreases. In particular, a high voltage of positive polarity can be supplied to each print job of the device for generating an electric field of the last used in the direction of passage printing unit. The devices for generating an electric field of upstream in the feed direction upstream printing units used high voltage can be supplied with different polarities, so that the polarity in the direction of passage changes from printing unit to printing unit and / or changes from one group of printing units to another group of printing units.

According to a preferred embodiment, each printing unit has a high-voltage source of positive polarity and a high-voltage source of negative polarity and a switching device connecting the high-voltage sources to the device for generating an electric field. In this embodiment, each printing unit two high voltage sources are assigned Thus, the rotary printing machine has an equal number of high voltage sources of positive and negative polarity. But included in the scope of the invention are also alternative embodiments in which the number of high voltage sources of one polarity is greater than the number of high voltage sources of the other polarity. Preferably, a larger number of high voltage sources of positive polarity than negative polarity is present because the plastic film tends to accept negative charges.

According to a further embodiment, the switching device comprises means for delayed switching, so that when switching from a high voltage source of one priority to a high voltage source of the other polarity no
Voltages of unequal polarity simultaneously applied to the means for generating an electric field.

According to a further embodiment, a field strength measuring device is provided at least behind the last printing unit in the direction of passage, which determines the charge that has the printing material behind the last printing unit, wherein the field strength measuring device is connected to at least one control device, which is connected to the switching devices in order from the measured by the field strength measuring charge of the printing material to the device for generating an electric field of the various printing units high voltages of specific polarity and / or height to create. The field strength measuring device is arranged such that the printing material passes through the detection range of the field strength measuring device, so that the charging of the printing material is detected by the field strength measuring device. This design favors the automatic control of the degradation of the charge of the wound on the take-up reel printing material. For this purpose, a field strength measuring device is preferably present behind the last printing unit. According to a further embodiment, one or more further field strength measuring devices are provided behind one or more printing units located further forward in the direction of passage of the printing material.

According to a preferred embodiment, a field strength measuring device is arranged on the circumference or at least one end face of the take-up roll. According to a further embodiment, a further field strength measuring device is arranged on a deflection roller of at least one printing unit. Preferably, the further field intensity measuring device is arranged on the circumference of the deflection roller or in the direction of passage of the printing material in front of or behind the deflection roller on the pressure side and / or the opposite side of the printing material.

According to a further embodiment, the control device is designed such that it applies to the means for generating an electric field of the various printing units high voltages with a polarity and / or height, which minimizes the charge of the printing material behind the last printing unit in the direction of passage. According to a further embodiment, the control device is designed such that it applies to the device for generating an electric field of at least one printing unit a high voltage with a polarity which minimizes the charge of the printing material behind the printing unit. By this configuration, an automatic minimization of the charge of the printing material is achieved on the take-up reel. According to a further embodiment, the control device is designed so that for each combination of printing units used a preferred connection of the high voltage sources of different polarity to the various devices for generating an electric field of the printing units used is deposited and the switching devices are switched accordingly or starting from the stored combination the Connections of high voltage sources of different polarity can be optimized.

According to a preferred embodiment, the control device is designed such that a high voltage of positive polarity applies to the device for generating an electric field of the last in the feed direction of the printing material switched-printing unit. The last connected printing unit is the last printing unit in the direction of travel of the web material which actively prints and in which the ESA is switched on. This automatically ensures the application of a positive polarity to the device for generating an electric field of the last printing unit.

According to a further embodiment, each device for generating an electric field via a further switching device is connected to ground and can be applied by switching the other switching device to ground, if
the printing unit is not switched on for a print job. By this configuration, a quick discharge of unused printing units is achieved. The further switching device may be a switchover device of the same printing unit separate switching device or be formed together with this. Preferably, the switching device and the further switching device are structurally combined into a single switching device with a plurality of switching functions.

According to a further embodiment, the means for generating an electric field comprise a pressure roller provided with an electrically semiconductive or conductive layer and means for transferring electrical charge to the semiconductive or conductive layer of the impression roller and are each the means for transmitting the electrical charge Switching connected. According to a further embodiment, the device for transferring electrical charge to the outer layer of the impression roller is a top loading system, a side loading system or a core charging system.

The rotary printing press has at least two printing units arranged one behind the other. Preferably, it has at least three successively arranged printing units, for example for the three-color printing or decorative printing. According to a further embodiment, the rotary printing press has at least four printing units arranged one behind the other, for example for four-color printing. In accordance with a further embodiment, the rotary printing press has six, twelve or more printing units arranged one behind the other. The printing units of the rotary printing press according to the invention are preferably color printing units. Furthermore, the invention comprises rotary printing machines in which one or more printing units for embossing the printing material or for applying a luster or a protective layer or for any other treatment of the printing material are present.

According to one embodiment, the rotary printing press has a take-up device which has a take-up roll. Further, the take-up device comprises means for transferring electrical charge to the web material on the take-up roll and / or deflecting onto the take-up roll, and the means for transferring electrical charge to the web material is connected to at least one positive or negative polarity electrical high voltage source.

This embodiment is based on the recognition that charging of the roll from the web material can best be avoided or minimized if the charging of the web material by supplying charge of opposite polarity by means of a device for transferring electrical charge to the web material on the take-up roll and / /. or compensated for deflection on the take-up roll, so that the web material is almost or completely discharged. By supplying the compensating charge to the web material on the take-up roll and / or deflecting onto the take-up roll, the web material is prevented from undergoing a travel path prior to winding in which it recharges after the compensating charge delivery and a wound roll with undesirable charges is produced.

According to a preferred embodiment, the means for transmitting electrical charge is connected to a high voltage electrical source of positive polarity. As a result, the mostly negative charging of the web material is compensated prior to winding on the take-up reel. However, the invention also includes embodiments in which a high voltage electrical source of negative polarity is connected to the means for transferring electrical charge to the web material.

According to a preferred embodiment, the deflection of the web material takes place on the take-up roll by a pressure roller, which on the circumference of the take-up roll unwinds and over which the web material is deflected onto the take-up reel.

According to a further embodiment, the deflection takes place by a deflection roller, which is arranged at a distance from the take-up roll parallel to this and over which the web material is directed onto the take-up roll and / or on the pressure roller.

The means for transferring electrical charge to the web material in the take-up device can be implemented in various ways. According to a preferred embodiment of the invention, the device for transferring electrical charge to the web material comprises a pressure roller, which abuts the web material on the circumference of the take-up roll to unwind in opposite directions to the take-up roll, wherein the pressure roller has an electrically semiconductive or conductive layer on the periphery There is provided means for transferring electrical charge to the electrically semiconductive or conductive layer of the nip roll and the means for transferring electrical charge to the semiconductive or conductive layer is connected to the high voltage electrical source. Here, a pressure roller for applying the electric charge is used on the web material on the take-up roll. This may be an existing for the tight winding of the web material on the take-up reel already present. Furthermore, this may be a separate pressure roller, which serves to supply the electrical charge to the web material and is positioned at a location on the circumference of the take-up roll on which the web material already fits tightly against the take-up roll, for which a further pressure roll may be present.

According to one embodiment, the pressure roller is designed like a pressure roller with a (semi-) conductive layer on the circumference. The statements on impression rollers at the beginning of this description apply accordingly to the pressure roller of the take-up. Furthermore, the known devices for transferring electrical charge to impression rollers can also be used for the transfer of electrical charge to the pressure roller. Accordingly, the statements at the beginning of this description on the transfer of electrical charge on the outer layer of the impression taken by a top-loading system, a side charging system (side loading) or a core charging system (core charging) accordingly apply to the charging of the pressure roller.

According to another embodiment, the means for transferring electrical charge to the sheet material is a charging electrode, which is directed onto the web material on the circumference of the take-up roll and / or deflecting onto the take-up roll, as in the case of the "top loading" described above.

According to another embodiment, the means for transferring electrical charge to the web material is a direct charging device having at least one electrically conductive brush or flexible, electrically semiconducting or conductive tab on the web material on the take-up roll and / or deflecting onto the take-up roll electrical high voltage source is connected. This transfer of electrical charge takes place as in the known direct charging on the circumference of a impression.

According to a further embodiment, the pressure roller or the charging electrode or the direct charging device is held on a displaceable holding device, which is designed to displace the pressure roller or needle electrode or direct charging in the radial direction to the take-up roll, so that the distance of the pressure roller or the charging electrode or the direct charging device to the pressure roller regardless of the diameter of the wound web material remains constant. This promotes uniform unloading of the web material on the take-up roll. The holding device is preferably in a device for transmitting electrical charge to the web material by means of a Pressure roller available. Alternatively, the variable circumference of the take-up roll can be compensated by a pressure roller having an elastic layer at least on the circumference. In particular, when the charge is supplied via a charging electrode or a direct charger to the web material on the take-up roll, a displaceable holding device can be dispensed with. The varying circumference of the take-up roll may eventually be compensated by a variable voltage on the charging electrode or the flexibility of the brushes, cloths or other direct charging device.

According to another embodiment, the device for transferring electrical charge is a deflection roller, via which the web material is fed to the winding roller, the deflection roller has an electrically (semi-) conductive layer on the circumference, is a device for transferring electrical charge to the electrically semiconducting or conductive layer of the deflection roller present and the means for transmitting electrical charge to the semiconductive or conductive layer of the deflection roller connected to the high voltage source. In this embodiment, the deflection roller may be formed as a described at the beginning of the description of the impression roller. The means for transferring electrical charge to the semiconductive or conductive layer of the diverting pulley may be configured as a top-loading system, side-loading system or core-loading system for a compression roller as described at the beginning of the description.

According to a further embodiment, the take-up device has a deflection roller which is arranged at a distance from the take-up roll with its axis of rotation parallel to the rotation axis, the web material is deflected via the deflection roller to the pressure roller and pressed by the pressure roller against the circumference of the take-up roll. In this embodiment, a particularly large part of the circumference of the pressure roller is looped around by the web material. Preferably, the electrical charge is applied to compensate for the charge of the web material via the nip roll. But you can also applied over the pulley become. Due to the large wrap, the application of the compensating charge is particularly effective.

According to a further embodiment, the device for transmitting electrical charge to the web material is connected via a switching device with a high voltage source of positive polarity and a high voltage source of negative polarity. In this embodiment, compensating charge of positive polarity or negative polarity may be supplied depending on the charging of the web material.

According to a further embodiment, the switching means comprises means for delayed switching, so that when switching from a high voltage source of one priority to a high voltage source of the other polarity no voltages of unequal polarity simultaneously applied to the means for transmitting electrical charge to the web material.

According to a further embodiment, the high-voltage source supplies an adjustable high voltage to the device for transmitting electrical charge to the web material. In this embodiment, depending on the charging of the web material, the height of the high voltage can be adjusted to better neutralize the charge of the web material.

According to a further embodiment, at least one field strength measuring device is provided, through the detection region of which the web material is displaced on the take-up roll and / or deflected onto the take-up roll, the field strength measuring device determining the charge comprising the web material which is connected to at least one control device. which is connected to the high voltage source and / or the switching device, in response to the measured by the field strength measuring device charging of the web material to the means for transmitting electrical charge
to apply to the web material a high voltage of certain height and / or polarity. In this embodiment, the height and / or the polarity of the high voltage for compensating the charging of the web material are automatically adjusted. In a preferred embodiment, the controller is adapted to apply to the electrical charge transfer device a high voltage having a magnitude and / or polarity that causes minimal charging of the web material wound on the take-up roll.

According to a preferred embodiment, a field strength measuring device is arranged on the circumference or at least one end face of the take-up roll.

According to a preferred embodiment, the same control device controls the level and / or polarity of the voltages applied to the means for generating an electric field of the various pressure rollers and the means for transmitting electrical charge to the web material on the take-up roll and / or deflecting onto the take-up roll applied voltage.

According to a further embodiment, the winding device is an exchangeable winding roll device. In an exchange reel device, there are two take-up positions in which the web material is alternately wound on a take-up reel. An alternate roll device is designed so that upon complete winding of a take-up roll, the subsequent web material is cut and wound on the other take-up roll. For this purpose, the finished wound take-up roll is pivoted out of the winding position and removed from the take-up device and wound a newly wound take-up reel in the winding position.

According to a preferred embodiment, the rotary printing press is a rotogravure printing machine. Furthermore, the invention relates to rotary printing machines, which are designed as high-pressure, planographic or screen printing machines.

Furthermore, the object is achieved by a method having the features of claim 14. Advantageous embodiments of the method are specified in subclaims.

In the method according to the invention for operating a rotary printing press according to one of claims 1 to 13, a high voltage of positive polarity is applied by switching switching devices to the device for generating an electric field of the printing unit last switched on in the direction of passage of the printing material.

This allows the best possible discharge of the printing material behind the last printing unit.

According to one embodiment of the method, high voltages of one polarity are applied to the devices for generating an electric field of different printing units by switching the switching devices, which effects a minimal charging of the printing material in the printing direction behind the last printing unit.

According to a further embodiment, high voltages of different polarities are applied by switching the switching devices to the devices for generating an electric field in the direction of passage of the printing material of successive printing units and / or to the devices for generating an electric field in the direction of passage of the printing material of successive groups of printing units high voltages of different polarities created. By changing in the passage direction of high voltages of different polarities for generating electric fields, the charging of the printing material is reduced behind the printing units.

Fig. 1

eine Rotationsdruckmaschine mit mehreren Druckwerken und diesen umschaltbar zugeordneten Hochspannungsquellen unterschiedlicher Polarität in einer grobschematischen Ansicht;

Fig. 2

Hochspannungsgeneratoren unterschiedlicher Polarität mit Umschalteinrichtungen und Presseuren mit verschiedenen Aufladesystemen in grobschematischer Ansicht;

Fig. 3

eine alternative Rotationsdruckmaschine in grobschematischer Ansicht;

Fig. 4

eine Wickelvorrichtung mit einer Anpresswalze mit Top-Loading-System in einer grobschematischen Ansicht;

Fig. 5

eine alternative Aufwickelvorrichtung mit Aufwickelwalze mit Kernaufladungs-System.

The invention will be explained in more detail with reference to the accompanying drawings of exemplary embodiments. In the drawings show:

Fig. 1

a rotary printing machine with multiple printing units and these switchable associated high voltage sources of different polarity in a rough schematic view;

Fig. 2

High voltage generators of different polarity with switching devices and impression rollers with different charging systems in a rough schematic view;

Fig. 3

an alternative rotary printing machine in a rough schematic view;

Fig. 4

a winding device with a pressure roller with top loading system in a rough schematic view;

Fig. 5

an alternative winding device with winding roller core charging system.

In the following explanation of various exemplary embodiments, components identified by the same name are given the same reference numerals.

According to Fig. 1 has a rotary printing machine four successively arranged printing units 1.1 to 1.4. Each printing unit 1.1 to 1.4 has a metallic, electrically conductive printing cylinder 2.1 to 2.4, which rests on electrically conductive bearings to ground. Furthermore, each printing unit 1.1 to 1.4 has an electrostatic printing aid 3.1 to 3.4.

Each electrostatic printing aid 3.1 to 3.4 has a impression roller 4.1 to 4.4, which is an impression cylinder, which rolls on the printing cylinder 2.1 to 2.4. Furthermore, each electrostatic printing aid 3.1 to 3.4 has a high voltage source of positive polarity 5.1 to 5.4 and a high voltage source of negative polarity 6.1 to 6.4.

The high voltage of each high voltage source 5.1 to 5.4 and 6.1 to 6.4 is preferably adjustable.

Each printing unit 1.1 to 1.4 comprises a switching device 7.1 to 7.4, wherein each switching device 7.1 to 7.4 is connected to a high voltage source of positive polarity 5.1 to 5.4 and a high voltage source of negative polarity 6.1 to 6.4.

Each switching device 7.1 to 7.4 is connected via a device for transmitting electrical charge 8.1 to 8.4 a (semi) conductive layer of the impression 4.1 to 4.4 the same printing unit 1.1 to 1.4. Each impression roller 4.1 to 4.4, together with the device for transmitting an electrical charge 8.1 to 8.4, a device for generating an electric field 9.1 to 9.4 in the pressure gap 10.1 to 10.4 between pressure cylinder 2.1 to 2.4 and impression roller 4.1 to 4.4.

From a take-off roll 11, a printing material 12 between the printing cylinders 2.1 to 2.4 and impression rollers 4.1 to 4.4 successive printing units 1.1 to 1.4 passed. In this case, deflecting and / or compensating rollers 13.1 to 13.4 and 14.1 to 14.4 are present between the printing units 1.1 to 1.4, via which the printing material 12 is carried away. Behind the printing units 1.1 to 1.4, the printing material 12 is guided onto a take-up reel 15.

A field strength sensor 16 is arranged next to the printing material 12 immediately before emergence onto the take-up reel 15.

Furthermore, a further field strength sensor 17.1 to 17.4 is arranged behind each printing unit, which is assigned to the printing material 12 on a deflection roller 14.1 to 14.4.

Each printing unit 1.1 to 1.4 has a control device 18.1 to 18.4 for controlling the electrostatic printing aid 3.1 to 3.4. The control devices 1.1 to 1.4 are interconnected via a data bus 19.

Furthermore, the control devices 18.1 to 18.4 are connected via the data bus 19 to a main controller 18.5.

The field strength sensor 16 is connected via the data bus 19 to the control devices 18.1 to 18.5.

Each further field strength sensor 17.1 to 17.4 is connected to the control device 18.1 to 18.4 of the same printing unit 1.1 to 1.4 and / or to the data bus 19.

During operation of the rotary printing machine, the printing substrate 12 is unwound from the unwinding roll 11, passed through the printing units 1.1 to 1.4 and wound onto the take-up reel 15. In the printing units 1.1 to 1.4 it is printed with different colors.

The switching devices 7.1 to 7.4 are controlled by the control devices 18.1 to 18.4 so that a high voltage of positive polarity is applied to the printing unit 1.4 used last in the direction of passage. The polarities of the upstream in the feed direction used printing units 1.1 to 1.3 supplied high voltages are set by the controllers 18.1 to 18.4 so that the field strength sensor 16 measures a minimum charge of the printing material 12 before the take-up roll 15. For this purpose, for example, the printing units 1.1 and 1.3 high voltages negative and supplied in the printing unit 1.2 a high voltage positive polarity.

According to Fig. 2 For example, the device for transferring electrical charge 8.1 to 8.4 to the (semi-) conductive layer of the impression roller 4.1 to 4.4 may be designed differently. All embodiments have a impression roller 4.1 to 4.4 with a metallic core 20. In the remarks of Fig. 2a to c the core has a rotating shaft 21 which is mounted in roller bearings 22.1, 22.2. In the remarks of Fig. 2a and b are the bearings 22.1, 22.2 grounded. In the execution according to Fig. 2c are the bearings 22.1, 22.2 separated by insulation from ground.

In the remarks of Fig. 2d to f the metallic core 20 is mounted on a fixed axle 24 via roller bearings 22.1, 22.2. The axis 24 is held in insulating elements 23.1, 23.2 and insulated from ground.

In the execution of Fig. 2a is outside of the outer periphery of the metallic core 20, an insulating layer 25 is arranged. Outside on the insulating layer 25 sits directly a (semi) conductive layer 26 of the impression 4.1 to 4.4.

In the execution of Fig. 2b On the outer circumference of the metallic core 20, an insulating layer 25 is disposed and on the outer circumference of the insulating layer 25 is an electrically highly conductive layer 27, on whose outer circumference in turn sits the (semi) conductive layer 26 of the impression 4.1 to 4.4. In the execution of FIG. 2f is disposed on the outer circumference of the metallic core 20, an electrically highly conductive layer 27, on the outer periphery of the (semi) conductive layer 26 of the impression 4.1 to 4.4 sits.

In the execution of Fig. 2a the electric charge is fed via a needle electrode 28 from the outside of the layer 26 of the impression roller 4.1 to 4.4 (Top Loading). The insulating layer 25 prevents the charge from draining to ground.

at Fig. 2b the charge is fed via the one charging electrode 29 to an end face of the impression roller 4.1 to 4.4 of the electrically highly conductive layer 27 (side loading) and distributed uniformly inwardly over the layer 26. Again, the insulating layer 25 prevents flow to the ground.

at Fig. 2c the high voltage is supplied via the shaft 21 (Core Charge Loading), for example by means of a fluid transmission system 30 according to FIG EP 1 780 011 B1 or by brushing. The charge is uniformly distributed to the inside of the layer 26 via the metallic core 20. The insulating elements 23.1, 23.2 prevent leakage to the ground.

In the execution of Fig. 2d the charge is fed via the fixed axle 24 and the roller bearings 22.1, 22.2 to the metallic core 20 (core charge loading). The charge is distributed evenly over the outer circumference of the layer 26. The insulating elements 23.1, 23.2 prevent also here an outflow of the charge to the mass.

at Fig. 2e the charge of the layer 26 is again supplied via a needle electrode 28 (Top Loading). Here, the insulating prevent 23.1, 23.2 outflow to the ground.

According to Fig. 2f the charge is in turn fed via a charging electrode 29 at one end face of the highly conductive layer 27 (side loading). Here, the insulating prevent 23.1, 23.2 a discharge of the charge to ground. In this version can be dispensed with one of the insulation.

According to Fig. 1 are the impression rollers 4.1 to 4.4 and the device for transferring the electrical charge 8.1 to 8.4 as in Fig. 2c or d educated.

The rotary printing machine of Fig. 3 is different from that of Fig. 1 in that the impression rollers 4.1 to 4.4 and the means for transmitting the electric charge 8.1 to 8.4 as in Fig. 2a or 2e are formed.

According to further embodiments, the winding devices of the above-described rotary printing presses are formed as in Fig. 4 or 5 ,

According to Fig. 4 For example, a take-up device has a deflection roller 30, by means of which the web material (printing material) 12 is deflected to form a pressure roller 31. Via the pressure roller 31, the web material 12 is fed to a take-up roll 15.

The pressure roller 31 has an insulating layer 32 on the periphery and a (semi) conductive layer 33 on the circumference of the insulating layer 32. Thus, the pressure roller 31 is corresponding to the impression roller of Fig. 2a built up.

A charging electrode 28, e.g. is formed as a needle electrode is arranged at a distance from the pressure roller 31 parallel to the axis of rotation. The charging electrode 28 is connected to a positive and a negative high voltage generator via an electric wire and a switching device.

About the guide roller 30 and the pressure roller 31, the web material 12 of the take-up roller 15 is supplied. The pressure roller 31 presses the web material 12 against the take-up roll 15. In this case, the (semi-) conductive layer 33 of the pressure roller 31 is charged by the charging electrode 28 in such a way that existing charges on the web material 12 are compensated or the web material 12 is discharged. Consequently, the web material 12 on the take-up roll 15 without unwanted charges wound up.

The embodiment of Fig. 5 differs from that described above in that the pressure roller 31 has an electrically conductive core 34 and a (semi) conductive layer 33 on the periphery. Electric charge is supplied to the core 34 via a core charging system. As a result of this measure, charges on the web material 12 are likewise compensated or unloaded and the result is that the web material on the take-up reel 15 contains no unwanted charges.

Claims (15)

1. A rotary printing machine with a substantially electrically insulating printing substrate (12) on an unwinding roller (11) from which the printing substrate (12) is guided to a plurality of print units (1.1 to 1.4) that are arranged sequentially in the throughput direction of the printing cylinder and each have a printing cylinder (2.1 to 2.4) and an impression roller (4.1 to 4.4), that roll on each other in opposite directions, and a device for generating an electrical field (9.1 to 9.4) in the printing nip (10.1 to 10.4) between the printing cylinder and impression roller, wherein the devices for generating an electrical field (9.1 to 9.4) of various print units (1.1 to 1.4) are connected to high voltages sources (5.1 to 6.4) that have different polarities, and with a winding roller (15) on which the printing substrate (12) is guided behind the print units (1.1 to 1.4), characterized in that each device for generating an electrical field (9.1 to 9.4) is connected by a switching device (7.1 to 7.4) to a high-voltage source with positive polarity (5.1 to 5.4) and a high voltage source with negative polarity (6.1 to 6.4) such that, by switching the switching device (7.1 to 7.4), a high-voltage with positive polarity or a high-voltage with negative polarity can be applied to the device for generating the electrical field (9.1 to 9.4).
2. The rotary printing machine according to claim 1, wherein each print unit (1.1 to 1.4) has a high-voltage source with positive polarity (5.1 to 5.4) and a high-voltage a source with negative polarity (6.1 to 6.4) and a switching device (7.1 to 7.4) that connects the high-voltage sources to the device for generating an electrical field (9.1 to 9.4).
3. The rotary printing machine according to claim 1 or 2 with high voltage sources (5.1 to 6.4) that supply an adjustable high-voltage.
4. The rotary printing machine according to one of claims 1 to 3, wherein at least after the last print unit (1.4) in the throughput direction of the printing substrate (12), there is a field strength measuring apparatus (16) that determines the charge that the printing substrate (12) has after the last print unit (1.4), wherein the field strength measuring apparatus (16) is connected to at least one control device (18.1 to 18.4) that is connected to the switching devices (7.1 to 7.4) in order to apply high voltages of a specific polarity to the devices for generating an electrical field (9.1 to 9.4) of the various print units (1.1 to 1.4) depending on the charge of the printing substrate (12) measured by the field strength measuring apparatus (16).
5. The rotary printing machine according to claim 4, wherein the field strength measuring apparatus (16) is arranged on the circumference of the winding roller (15) and/or on at least one face of the winding roller (15), and/or wherein another field strength measuring apparatus (17.1 to 17.4) is arranged on a deflection roller (14.1 to 14.4) of at least one print unit (1.1 to 1.4).
6. The rotary printing machine according to one of claims 4 to 5, wherein the control device (18.1 to 18.4) is designed such that it applies high voltages with a polarity to the devices for generating an electrical field (9.1 to 9.4) of the different print units (1.1 to 1.4) that causes a minimum charging of the printing substrate after the last print unit (1.4) in the throughput direction.
7. The rotary printing machine according to one of claims 4 to 6, wherein the control device (18.4) is designed such that it applies a high voltage with positive polarity to the device for generating an electrical field (9.4) for the last connected print unit (1.4) in the throughput direction of the printing substrate.
8. The rotary printing machine according to one of claims 1 to 7, wherein each device for generating an electrical field (9.1 to 9.4) is connected by another switching device to ground and can be grounded by switching the other switching device when the device for generating an electric field (9.1 to 9.4) is not connected by the switching device (7.1 to 7.4) to an electrical high voltage source (5.1 to 6.4).
9. The rotary printing machine according to one of claims 1 to 8, wherein the respective devices for generating an electrical field (9.1 to 9.4) have an impression roller (4.1 to 4.6) provided with an electrically semiconductive or conductive layer (26) and a device for transmitting an electrical charge (8.1 to 8.4) to the semiconductive or conductive layer (26) of the impression roller, and each of the devices for transmitting an electrical charge (8.1 to 8.6) is connected to a switching device (7.1 to 7.4).
10. The rotary printing machine according to one of claims 1 to 9, comprising a winding apparatus that has the winding roller and a device (31, 32, 33, 28) for transmitting an electrical charge to the web material (12) on the winding roller (15) and/or to the winding roller during deflection, wherein the device (31, 32, 33, 28) for transmitting an electrical charge is connected to at least one electrical high-voltage source with a positive or negative polarity.
11. A rotary printing machine according to claim 10, wherein the device (31, 32, 33, 28) for transferring an electric charge to the web material (12) is connected by a switching apparatus (7.1 to 7.4) to a high-voltage source with a positive polarity, and a high-voltage source with a negative polarity.
12. The rotary printing machine according to claim 4 and 11, wherein the control device is connected to the high voltage source and/or the switching apparatus that applies a high voltage of a specific level and/or polarity to the impression roller (4.1 to 4.6; 31, 32, 33) depending on the charge of the web material measured by the field strength measuring apparatus.
13. The rotary printing machine according to one of claims 1 to 12 that is a rotogravure printing machine.
14. A method for operating a rotary printing machine according to one of claims 1 to 13, wherein by switching the switching device (7.4), a high voltage with positive polarity is applied to the device for generating an electrical field (9.4) for the last connected print unit (4.1) in the throughput direction of the printing substrate (12).
15. The method according to claim 14, wherein by switching the switching devices (7.1 to 7.4), high voltages with a polarity are applied to the devices for generating an electrical field (9.1 to 9.4) of various print units (1.1 to 1.4) that cause a minimum charging of the printing substrate (12) in the throughput direction of the printing substrate after the last print unit (1.4).

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