EP2990365B1 - Machine for machining a web material - Google Patents

Description

The invention relates to a machine for processing a web material, in particular to a web printing machine or to a machine for web cutting or to a machine for film production (film extrusion) or to a machine for laminating films.

In web printing machines, the printable web material (printing material) is drawn off from an unwinding roll and, after printing, wound up on a take-up roll or cut into web sections or blanks by a punch, which are stacked on top of one another. For printing, the web material is passed between one or more arrangements of a printing cylinder (printing form cylinder) and an impression cylinder (impression roller), which roll in opposite directions on the web material. In rotogravure printing, the printing cylinder picks up ink from its ink tray in its surface and the excess is scraped off. The ink is transferred to the printing material passing between the impression cylinder and the impression cylinder. In flexographic printing, the printing unit also comprises a printing cylinder and an impression cylinder, between which the printing material is passed. Flexographic printing is a high-pressure process in which the raised areas of the printing form on the circumference of the printing cylinder are image-bearing. The printing form is inked via an anilox roller, which runs on the circumference of the printing cylinder and to which the ink is fed from an ink tray by means of an immersion roller or via a chamber doctor blade system.

In rotogravure printing, electrostatic printing aids (ESA) are often used to improve ink transfer from the printing cylinder to the substrate and the print quality. For this purpose, an electrical field is generated in the area of the pressure gap between the pressure cylinder and the impression cylinder, which affects the Color exerts a force in the wells of the printing cylinder, which intensifies the transition of the color to the substrate and increases the print quality.

In known electrostatic printing aids, the printing cylinder made of a metal is grounded. The impression cylinder has a semiconducting layer on the circumference, to which a high voltage is transmitted, which usually has a negative polarity.

Rotogravure printing machines usually have several printing units arranged one behind the other in order to apply different colors to the printing material. It is disadvantageous here that the printing material, as a result of the electrostatic charging by means of electrostatic printing aids or corona pretreatment systems, can assume very high charges which impair subsequent processing. For example, when transporting or cutting a roll that includes the printed substrate, voltage flashovers can occur, which can endanger the printer's workers and damage the substrate. Even if the web-shaped printing material is cut, problems with stacking the web sections and pulling off individual web sections from the stacks, as well as voltage flashovers, which can endanger the printing workers and damage the web material, can occur due to the high loads. This can be observed when using paper as a printing material and increasingly when using plastic films and composite materials, which include plastic, paper and aluminum films, for example.

From the EP 1 914 071 B1 a rotary web printing machine is known which comprises electrostatic printing aids of different polarities, as a result of which excessive charging of the printing material is counteracted.

Corona pretreatment systems are used for flexographic printing. This can also lead to charging of the web material and endangering the printing press workers and damage to the web material, in particular if the web material is plastic film or a composite film comprising a plastic film.

In roll cutting, printed web materials wound on rolls are divided one or more times for further processing. Here, too, undesired charging and endangering of the printing workers can occur.

The US 5,205,212 A describes a printing machine for four-color printing, in which a web is printed from one side in a first station and the web is printed from the opposite side in a second station. The transfer of colors to the substrate is carried out using electrostatic printing aids. The printing units comprise rotogravure cylinders and impression rollers rolling on the periphery of the rotogravure cylinders, which are connected to a high voltage of certain polarity. In one embodiment, the impression roller of the last printing unit is connected to a high voltage of positive polarity for the printing of the black color. In another embodiment, the charge is fed contactlessly behind the last printing unit via a loading bar which is arranged at a distance from a roller over which the web materials run.

Proceeding from this, the object of the invention is to create a machine for processing a web material which better avoids undesirable charging of the web material.

According to the invention, the object is achieved by a machine for processing a web material with the features of claim 1. Advantageous configurations of the machine are specified in the subclaims.

The machine for processing a web material according to the invention has an unwinding roll from which the web material is drawn off, a wind-up roll on which the web material is wound up, or a punch which divides the web material into web sections, at least one device arranged between the unwinding roll and the winding roll or punch Machining of the from the unwind to the reel or punch continuous web material and an arrangement arranged between the last device for processing the web material in the direction of flow of the web material and the take-up roll or punch, consisting of a roller and a counter-roller rolling on the circumference of the roller, the roller at least one outer layer of electrically conductive material

Counter roll, wherein the roll has at least one outer layer made of electrically conductive material, which is connected to ground, the counter roll has an outer layer made of semiconducting material, there is a device for transferring electrical charge to the outer layer of the counter roll, an electrical high-voltage source with a positive polarity is connected to the device for transferring electrical charges in order to supply positive charge to the outer layer of the counter-roller and to reduce a negative charge on the web material before it is wound up on the take-up reel or broken down into web sections.

Roller and counter roller are components of a device for regulating the web tension. Web printing machines, machines for web cutting and other machines for processing a web material are anyway provided with such a device for regulating the web tension in the web material as it passes through the machine. According to the invention, this device for regulating the web tension is additionally used to unload the web material before winding it onto the winding roll. For this purpose, it is basically only necessary to ensure that the roller is carefully grounded and the counter-roller is at least provided with an outer layer of semiconducting material. In the case of a counter roll with a core made of conductive material, additional care must be taken to ensure that the positive charges do not flow away from the counter roll directly to the ground, for example by applying the outer layer to an insulating inner layer or isolating the counter roll or the support of the counter roll from ground will.

Roller and counter roller can also be part of a web guiding device for guiding or deflecting the web material.

The invention is based on the knowledge that web materials in machines for processing a web material tend to accept negative charges. Especially with longer runs of the web material through the machine or with the action of several devices for processing the web material, it can happen that the web material wound or stacked on the take-up reel has a high negative charge, which puts printing workers at risk when handling the web material. The The invention overcomes this disadvantage in that, behind the last device for processing the web material in the direction of travel of the web material, a charge of positive polarity is supplied via an arrangement of roller and counter-roller rolling thereon, which completely or at least partially eliminates the negative charging of the web material. This measure can be used to avoid or reduce to an insignificant extent the risk potential for printing workers from the loaded take-up roll or from the stacked web sections. It is particularly advantageous that the arrangement of roller and counter-roller can be arranged outside the potentially explosive area (Ex zone), in particular in the case of a rotogravure printing machine, which makes it possible to supply high positive direct voltages for unloading the web material. The DC voltage discharge system can work outside the Ex zone with charging voltages of + 10 kV and more (e.g. 60 kV). In the Ex zone of a rotogravure printing machine, on the other hand, it is not possible to work with high DC voltages, since AC discharge electrodes have to be used to avoid dangerous spark discharges. However, AC discharge electrons are often not suitable for sufficiently neutralizing a negative charge on the web material, in particular at high web speeds and if critical web materials are printed on with regard to electrostatic charge.

According to a preferred embodiment there is a drive motor which is connected to the roller or the counter roller. In principle, however, it is also possible for the roller or counter roller to be driven by the continuous web material.

The device for regulating the web tension preferably has a drive motor which drives the roller or the counter-roller and is connected to an electrical control device which controls the drive motor in such a way that a predetermined web tension is established in the web material. The drive motor is preferably controlled in such a way that there is a small amount of slippage between the roller and the counter roller and the continuous web material.

According to a preferred embodiment, the roller consists entirely of metal or of another electrically conductive material. In this embodiment, the roller of a conventional device for regulating the web tension can generally be used unchanged. The invention particularly includes rollers which are made homogeneously from metal and have no distinguishable outer layer.

According to a further embodiment, the electrically semiconducting layer of the counter roll is a layer based on rubber or another elastomer or polyurethane. The substances mentioned are preferably semiconducting by embedding electrically conductive substances. The electrically conductive substances are preferably electrically conductive particles (e.g. graphite).

An outer layer made of semiconducting material is understood to mean a layer with a high electrical resistance which greatly reduces the electrical current but still allows a certain electrical current to pass through. The electrical resistance of the layer is measured, for example, using a measuring arrangement with two parallel forks, each holding a moistened leather strip with a length of approximately 8 cm and a width of approximately 1 cm, so that the two parallel leather strips are approximately 10 cm apart. The two parallel leather strips are wrapped around the outer layer to a length of 8 cm. A measuring voltage of 1000 volts is applied. With this measuring arrangement, resistances in the range of one MΩ to 20 MΩ are measured for the semiconducting outer layers that are particularly suitable for the present purpose.

An outer layer made of electrically conductive material or a roller made of electrically conductive material is understood to mean an outer layer or a roller in which the resistances measured with the above-described measuring arrangement are clearly undercut. The electrically conductive material is preferably a metal. Electrically highly conductive materials are also conductive materials in the sense of the invention.

According to a further embodiment, the counter roll has a core made of metal, from the periphery of which an insulating inner layer is arranged, on which the electrically semiconducting outer layer is arranged. The insulating inner layer prevents the positive charges from flowing off to the ground.

According to a further embodiment, an electrically conductive intermediate layer is arranged between the outer layer and the inner layer. The intermediate layer ensures a quick and even distribution of the positive ones Loads over the entire outer circumference of the counter roller. According to a further embodiment, the counter roll has electrical insulation of its bearings in the machine frame or frame. The insulation prevents the positive charges from flowing off to ground. The insulations can be formed by insulating bodies (e.g. insulating shells), which roller bearings (e.g. ball bearings) of a shaft of the counter-roller support in bearing mounts of a frame or frame of the machine. Alternatively, the insulations are bearing bodies, which support an axle made of electrically conductive material, which supports the counter-roller via roller bearings, in bearing mounts of a frame or frame of the machine.

The outer layer and optionally the inner layer and the intermediate layer can be firmly and permanently attached to a core of the counter roll. According to another embodiment, the outer layer and possibly the intermediate layer or inner layer are interchangeably attached to the core of the counter roll. The core of the counter roll can be used as a slightly conical mandrel z. B. be made of metal, which is provided with a connection for compressed air and has outlet openings for the compressed air on the outer circumference. The outer layer can be a semiconducting layer on a support e.g. B. of GRP, which is slightly conical on the inside, matched to the conical shape of the mandrel. By applying compressed air to the mandrel, the outer layer or the carrier can be expanded so that it can be detached from the mandrel. Conversely, when compressed air is applied to the mandrel, the outer layer or the carrier can be expanded so that it can be pushed onto the mandrel. After the compressed air has been extracted, the outer layer or the support settles on the mandrel. In this respect, the design of the counter roller corresponds to the design of impression rollers, which are designed as a sleeve system.

According to a further embodiment, the device for transferring electrical charge is selected from one or more of the following devices: charging electrode, which is directed towards the outer circumference of the counter-roller and releases the charge to the semiconducting layer on the circumference of the counter-roller (top-loading system), Charging electrodes, which are directed to the front side of the counter roller and transfer the charge to a conductive layer below the semiconducting layer, which is exposed on the front side of the impression roller (side charging system), charging electrodes, which are arranged on the front side of the counter roller and with a conductive circuit board interact on the end face of the counter roll, which is electrically connected to a conductive layer below the semiconductive outer layer, transformer devices which have a fixed primary coil next to the end face of the counter roll and a rotating secondary coil fixed to the end face of the counter roll, Slider contacts or brushes on the circumference or on an end face of the counter-roller, which contact a slip ring on the counter-roller, or electrically conductive roller bearings, which support a shaft of the counter-roller or which support the counter-roller on a fixed axis, fluid transmission systems that charge the charge via an electrically conductive Feed fluid between a fixed stator and a rotor rotating with the counter roller.

According to a further embodiment, a field strength sensor is arranged between the arrangement of roller and counter-roller and the take-up reel or punch, which is connected to an electrical control device which is connected to the high-voltage generator, the control device being set up so that the high voltage supplied by the high-voltage generator is dependent on to regulate the field strength of the continuous web material measured by the field strength sensor. As a result, a web material with fluctuating charging can be continuously discharged to a harmless level.

According to a preferred embodiment, the machine is a web printing machine. In the case of a web-fed printing press, the at least one device for processing the web material passing through from the unwinding reel to the take-up reel or punch is a printing unit which consists of a printing cylinder (printing form cylinder) and an impression cylinder (impression roller). A web printing press preferably has 3 to 18 printing units. According to a preferred embodiment, the web printing press is a rotogravure or a flexographic printing press.

According to another embodiment, the machine is a machine for roll cutting. In a machine for roll cutting, the at least one device for processing the web material passing through from the unwinding roll to the winding roll or punch is a cutting device.

According to another embodiment, the machine is a machine for film extrusion or another machine for film production.

According to another embodiment, the machine is a machine for laminating foils.

According to a further embodiment, the web material is paper. According to a preferred embodiment, the web material is a plastic film or a composite film comprising a plastic film.

Fig. 1

eine Rollendruckmaschine mit mehreren Druckwerken und einer erfindungsgemäßen Bahnspannungsregelung mit Aufladeelektrode und alternativ mit Direktaufladung in einer grobschematischen Seitenansicht;

Fig. 2a) und b)

die Bahnspannungsregelung derselben Rotllendruckmaschine mit Aufladeelektrode in Vorderansicht (Fig. 2a) und in Seitenansicht (Fig. 2b);

Fig. 3a) und b)

die Bahnspannungsregelung derselben Rotationsdruckmaschine mit Direktaufladung in einer Vorderansicht (Fig. 3a) und in Seitenansicht (Fig. 3b).

The invention is explained in more detail below with reference to the attached drawings of exemplary embodiments. The drawings show:

Fig. 1

a web printing machine with several printing units and a web tension control according to the invention with charging electrode and alternatively with direct charging in a rough schematic side view;

2a) and b)

the web tension control of the same rotary printing machine with charging electrode in front view ( Fig. 2a ) and in side view ( Fig. 2b );

3a) and b)

the web tension control of the same rotary printing machine with direct charging in a front view ( Fig. 3a ) and in side view ( Fig. 3b ).

According to Fig. 1 The web printing machine comprises an unwinding roll 1 and a winding roll 2 and four printer units 3.1 to 3.4 arranged between them. Each printing unit 3.1 to 3.4 has a metallic, electrically conductive printing cylinder 4.1 to 4.4, which is electrically grounded via electrically conductive bearings. Furthermore, each printing unit 3.1 to 3.4 has an impression cylinder 5.1 to 5.4, which rolls on one of the printing cylinders 4.1 to 4.4.

The web printing machine can also have a smaller or larger number of printing units than shown.

When the web-fed printing press is designed as a rotogravure printing press, each printing unit 3.1 to 3.4 preferably has an electrostatic printing aid with a device for transferring electrical charge to an impression cylinder and a high-voltage source for feeding the device for transferring electrical charge.

The printing cylinders 4.1 to 4.4 are located in the Ex area 6, in which solvent-based inks are used.

The printable web material 7 is fed from the unwinding roller 1 via deflection rollers 9.1 to 9.4 to the printing units 3.1 to 3.4 in succession. There is a drying section in each case between the adjacent printing units 3.1, 3.2, etc., in which the printed web material 7 can dry.

A web tension control 10.1 is present between the last printing unit 3.4 and the take-up roll 2. The web tension control 10.1 (device for regulating the web tension) comprises a roller 11.1 and a counter roller 12.1 rolling thereon. The web material 7 is passed between the roller 11.1 and the counter roller 12.1. The web material 7 is fed to and guided away from the web tension control 10.1 via deflection rollers 9.11 and 9.12.

According to Fig. 2 the roller 11.1 including the shaft 11.3 is made of metal and is connected to the machine frame 13 made of metal by means of electrically conductive roller bearings.

The counter roll 12.1 has a core 14 made of metal, on which an inner layer 15 made of insulating material is arranged. An outer layer 16 made of semiconducting material is arranged on the inner layer 15. A device for transferring electrical charge 17, which is designed as a charging electrode 17, is arranged at a distance from the outer layer 16. The charging electrode has a plurality of needles 18 which are directed onto the circumference of the counter roller 12.1 and have a small distance from it. A suitable charging electrode 17 is e.g. B. in the EP 1 640 160 A1 described.

The charging electrode 17 is connected to a high voltage generator 19 with positive polarity.

Conventional discharge electrodes 20.1, 20.2 are arranged upstream and downstream of the roller 11.1. These are connected to a discharge generator 21, which supplies an AC voltage or a DC voltage.

A field strength sensor 22 is arranged between the web tension control 10.1 and the take-up roll 2, in the detection area of which the web material 7 passes. The field strength sensor 22 is connected to a switching and control device 23, which in turn is connected to the high-voltage generator 19 and the discharge generator 21.

The voltages of the high voltage generator 19 and the discharge generator 21 are controlled as a function of the field strength measured by the field strength sensor 22. Due to the positive polarity of the high-voltage generator 19, the preferably negative charges of the continuous web material 7 are neutralized to a more or less harmless level for the printing workers.

The alternative version of the web tension control10.2 from Fig. 1 and Fig. 3 differs from the prescribed web tension control 10.1 in that the counter-roller 12.2 is mounted in insulating bearings 24.1, 24.2 in the machine frame 13. The semiconducting outer layer 16 is arranged directly on the core 14 made of metal of the counter-roller 12.2. The positive voltage of the high-voltage generator 19 is supplied to the counter-roller 12.2 via the shaft 12.4. The facility To transfer the electrical charge to the shaft is, for example, a fluid transmission system, as in the EP 2 363 287 B1 described.

In this embodiment too, the level of the positive polarity voltage supplied by the high-voltage generator 19 is determined on the basis of the field strength measurement on the web material 7 by means of the field strength sensor 22 and the extent of the discharge of the web material 7 is controlled.

Claims (15)

1. A machine for processing a web material having: An unwinding roller (1) from which the web material (7) is pulled off; a winding roller (2) on which the web material (7) is wound, or a punch that divides the web material (7) into web sections; at least one apparatus, arranged between the unwinding roller (1) and winding roller (2) or punch, for processing (3.1 to 3.4) the web material (7) passing from the unwinding roller (1) to the winding roller (2) or punch, wherein before the winding roller (2) or punch, there is an arrangement consisting of a roller (11) and a counter roller (12) rolling on the circumference of the roller, wherein the roller (11) has at least one outer layer consisting of electrically conductive material that is connected to ground, the counter roller (12) has an outer layer (16) consisting of semiconductor material, there is an apparatus for transmitting an electrical charge (17) to the outer layer (16) of the counter roller (12), an electrical high voltage source (19) with a positive polarity is connected to the apparatus for transmitting an electrical charge in order to supply the positive charge to the outer layer (16) of the counter roller (12) and to dissipate a negative charge of the web material (7) before being wound on the winding roller (2) or cut up into web sections, characterized in that the arrangement consisting of the roller (11) and counter roller (12) is arranged between the last apparatus in the throughput direction of the web material (7) for processing (3, 4) the web material (7) and the winding roller (2) or punch.
2. The machine according to claim 1 that has a drive motor which is connected to the roller (11) or the counter roller (12).
3. The machine according to claim 1 or 2, wherein the roller (11) and counter roller (12) are components of an apparatus for regulating the web voltage (10) in the web material (7).
4. The machine according to claim 3, wherein the apparatus for regulating the web voltage (10) has a drive motor that drives the roller (11) or counter roller (12) and is connected to an electric control apparatus which controls the drive motor so that a predetermined web voltage arises in the web material (7).
5. The machine according to one of claims 1 to 4, wherein the roller (11) consists entirely of metal or another electrically conductive material.
6. The machine according to one of claims 1 to 5, wherein the electrical semiconductive outer layer of the counter roller (12) is an outer layer based on rubber, or another elastomer or polyurethane (16).
7. The machine according to one of claims 1 to 6, wherein the counter roller (12) has a core (14) consisting of metal, on the circumference of which an insulating inner layer (15) is arranged on which the electrically semiconductive outer layer (16) is arranged.
8. The machine according to claim 7, wherein an electrically conductive intermediate layer is arranged between the outer layer (16) and the inner layer (15).
9. The machine according to one of claims 1 to 8, wherein the counter roller (12) has electrical insulations (24.1, 24.2) of its bearings in a machine frame or stand (13).
10. The machine according to one of claims 1 to 9, wherein the apparatus for transmitting an electrical charge is selected from one or more of the following apparatuses: Charging electrode (17) that is directed toward the outer circumference of the counter roller, charging electrode that is directed toward an end face of the counter roller, charging electrode that is arranged on an end face of the counter roller and interacts with a plate on the end face, transformer apparatus on an end face of the counter roller, wiper contacts or brushes, electrically conductive roller bearing, and liquid transfer system.
11. The machine according to one of claims 1 to 10, wherein a field strength sensor (22) is arranged between the arrangement, that consists of the roller (11) and counter roller (12), and the winding roller (2) or punch, and is connected to an electronic regulating apparatus that is connected to the high-voltage generator (19), wherein the control apparatus is configured to regulate the high-voltage supplied from the high-voltage generator (19) depending on the field strength of the web material passing through measured by the field strength sensor (22).
12. The machine according to one of claims 1 to 11 that is a web-fed press, which is preferably a rotogravure or a flexographic printing press.
13. The machine according to one of claims 1 to 10 that is a machine for slitting rolls.
14. The machine according to one of claims 1 to 11 that is a machine for film extrusion or another machine for film production, or that is a machine for laminating.
15. The machine according to one of claims 1 to 14, wherein the web material (7) is a paper, or a plastic film, or a compound film comprising a plastic film.

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