EP2308680A1 - Electrostatic printing aid - Google Patents

Abstract

The electrostatic printing assistance has a roller (1.1) with a core (2.1) that is made of an electrically conductive material and an elastic and electrically semiconducting outer layer (6.1). Rotating bearings (8) are provided in the roller.

Description

The invention relates to an electrostatic printing aid.

Electrostatic printing aids are used in printing technology in rotary printing, especially in rotary gravure printing. In rotary printing, the printing material (e.g., paper, cardboard, or plastic film) is passed at high speed between a pressure roller and a impression roller. Particularly high speeds are achieved in commercial printing. The printing cylinder takes in paint on its surface color from a paint tray with. The excess is scraped off. In order to transmit the ink from the wells of the printing cylinder to the greatest possible extent to the printing material, a limited conductive layer - hereinafter also referred to as "semiconductor layer" - is supplied with a high voltage at the circumference of the impression roller. As a result, an electric field forms between the semiconductor layer and the printing cylinder, which exerts a force on the ink in the cells, which intensifies the transition of the ink to the printing material and increases the print quality.

Various solutions are known for applying the high voltage to the semiconductor layer of the impression roller. When feeding the charge onto the surface or "toploading", charge is applied to the surface of the impression roller via needle electrodes without contact. Conventionally, a press roller for toploading from inside to outside has a metal core, an electrically insulating layer, optionally an electrically highly conductive layer and the outside of the semiconductor layer. The electrical charge is supplied to the semiconductor layer on the circumference of the impression roller. The highly conductive layer causes a distribution of the electrical charge in the axial direction of the impression. If no highly conductive layer is present, the distribution of charge can also be effected by a needle electrode extending over the entire axial length of the impression roller. The insulating one Layer prevents the discharge of the charge to ground. It has an electrical resistance of about one to several gigaohms, so that applied charge does not flow unhindered, but can gradually drain when the impression roller is not loaded.

From the EP 1 640 160 A1 is a needle electrode for toploading with at least one flow channel with an aligned on the portion of at least one needle discharge opening is known, which is connectable to a compressed gas source. The air or gas flow prevents dirt from depositing on the needles of the needle electrode, thereby reducing the cost of maintenance and repair.

When directly feeding the charge to the core of the impression roller ("direct charge"), the metallic core of the impression roller is mounted in an insulated manner and provided with the semiconductor layer on the circumference. The electric charge is supplied to the semiconductor layer via the core. It is known to supply the core with the electrical voltage via electrodes or brush grinding contacts. The US 4,697,514 describes a impression roller of an insulating shaft, the electric charge is supplied via sliding contacts. The US 4,966,555 describes a impression roller with an electrically insulating mounted axis on which a hollow cylindrical core is rotatably mounted. The core is supplied with the electrical charge via sliding contacts, which contact a flange at the end of the hollow cylinder.

From the EP 0 566 463 B1 For example, an impression roller provided with an insulating axle is known, which has a limited conductive covering over a steel jacket. The covering is supplied with the electric charge via the axle, a ball bearing between the axle and the steel jacket and the steel jacket. Furthermore, from this document a impression roller with a shaft and a limited conductive Plating on a steel shell known to which the electric charge via a arranged on the front side of the shaft ball bearing, the shaft and the steel shell is supplied.

The direct charge supply via electrodes, brushes and ball bearings is affected by soiling and wear.

From the EP 1 780 011 A2 It is known to supply the core of the impression roller with the charge via a fluid transmission system comprising a rotor electrode connected to the core and a stator electrode concentric thereto and an electrically conductive fluid in a cavity between the rotor electrode and the stator electrode. By applying the voltage supply to the stator electrode, it is possible to transfer electrical charge via the electrically conductive fluid to the rotor electrode and from there to the electrically conductive region of the cylinder. The transmission via the electrically conductive fluid is virtually wear-free.

Known for Toploading and Direct Charge are impressioners with an elastically expandable sleeve or a "sleeve" which is applied to the core or "sleeve dome" and the semiconductor layer comprises. A sleeve for toploading has, for example, a carrier sleeve made of insulating, glass fiber reinforced plastic (GRP), on which a layer of semiconductive rubber is applied. A sleeve for direct charge has, for example, a carrier sleeve or "sleeve sleeve" made of glass fiber reinforced plastic, which is conductive at least in sections from the inside to the outside by embedded, electrically conductive particles or at least one integrated, electrically conductive ring. On the carrier sleeve, a layer of semiconductive rubber is applied. The impression roller can be equipped with a sleeve adapted to the width of the printing material to be printed be fitted. The sleeve can be replaced or reworked if the semiconductive layer is worn. Furthermore, when toploading the sleeve can be replaced by a safety sleeve, if you do not want to work with an electrostatic printing aid. The safety sleeve is conductive from the inside to the outside, so that the charge can flow off via the safety sleeve and the core to the ground. Security sleeves are used in particular for printing on plastic films. In this case, a support by an electrostatic printing aid is only required for the printing of special colors. For other colors no electrostatic printing aid is required and to avoid charging of the impression roller through the film material by means of the safety sleeve ensures a discharge of the charge to the mass. Otherwise, printing of solvent-based inks could cause flashovers or sparking and fire. Voltage flashovers can be promoted in particular by contamination, which reduces the resistance between isolated areas.

The cost of equipping and operating printing presses with electrostatic printing aids, which include sleeves for different web widths, possibly for toploading and direct charge, if necessary with safety sleeves, is high. Standstill times must be taken into account when replacing sleeves with security sleeves and vice versa. Due to the fact that impression rollers for toploading are not stored electrically insulating in the machine frame and impression rollers for Direct Charge are stored in an insulating manner in the machine frame, Topload and Direct Charge systems differ fundamentally. A conversion of a Topload system to a Direct Charge system and vice versa is not easily possible.

On this basis, the invention has for its object to produce an electrostatic printing aid, which facilitates the discharge of electrical charge from the impression roller, if it is not used for supplying electrical charge to the impression roller. The electrostatic printing aid should be able to work both with a charge feed by Topload and with a charge feed by Direct Charge.

The object is achieved by electrostatic printing aid having the features of claim 1. Advantageous embodiments of the electrostatic printing aid are specified in the subclaims.

• einen Presseur mit einem Kern aus einem elektrisch leitfähigen Material und einer elastischen und elektrisch halbleitenden Außenschicht,
• Mittel zum drehbaren Lagern, die den Presseur in einem Maschinenrahmen drehbar lagern,
• Mittel zum Isolieren, die die Mittel zum drehbaren Lagern bezüglich des Maschinenrahmens isolieren,
• eine ein- und ausschaltbare Hochspannungsversorgung,
• Mittel zum Zuführen von der Hochspannungsversorgung bereitgestellter Ladung auf den Presseur,
• Mittel zum Abführen elektrischer Ladung vom Presseur,
• Mittel zum elektrischen Schalten, deren Eingang elektrisch mit den Mitteln zum Abführen von Ladung vom Presseur und deren Ausgang elektrisch mit Masse verbunden ist, und
• Mittel zum Steuern der Mittel zum Schalten von einer Öffnungsstellung, in der der Eingang keine Verbindung mit dem Ausgang hat, in eine Schließstellung, in der der Eingang mit dem Ausgang verbunden ist und/oder umgekehrt.

The electrostatic printing aid according to the invention has

• a pressure roller with a core of an electrically conductive material and an elastic and electrically semiconductive outer layer,
• Rotatable support means for rotatably supporting the impression roller in a machine frame,
• Isolating means isolating the means for rotatably supporting the machine frame,
• an on and off switchable high voltage supply,
• Means for supplying charge provided by the high voltage power supply to the impression roller;
• Means for dissipating electrical charge from the impression roller,
• Electrical switching means whose input is electrically connected to the means for dissipating charge from the impression roller and the output thereof to earth, and
• Means for controlling the means for switching from an open position in which the input has no connection with the output, in a Closed position in which the input is connected to the output and / or vice versa.

In the electrostatic printing aid according to the invention, the impression roller is mounted in an electrically insulated manner. This applies both to a press roller with a shaft and to a press roller with an axle. On the - preferably rigid - core of electrically conductive material of the impression roller, an electrically semiconducting or limited conductive outer layer is arranged, which is also referred to below as "semiconductor layer". The impression roller can be used both for toploading and for direct charge since it is mounted in an electrically insulating manner and the transition of the charge from the core to the outer layer is not hindered by an electrically insulating layer. Regardless of the type of high voltage supply, the same impression roller can be used. When the high voltage power supply is switched on, electrical charge is applied to the outer layer in both types of use in order to support the color transition to the printing substrate. When the high voltage electrical supply is turned off, by controlling the means for switching the core of the impression roller can be electrically connected to ground, so that unwanted charge from the outer layer flows to ground. An undesirable sparking can be avoided in particular when printing substrates made of plastic. The risk of inflammation is thereby greatly reduced.

Furthermore, by electrically connecting the core to ground, it can be ensured that the pressure roller is safely discharged before and during maintenance and installation work. In addition, it is possible to unload the impression roller in a set-up phase when the synchronous operation of the various printing units is set without the electrostatic printing aid being switched on.

In toploading, no more security sleeves are required, since the discharge of unwanted charge is done solely by controlling the means for switching.

The impression rollers are suitable for toploading as well as direct charge. The storage of the impression roller in the machine frame is independent of the type of high voltage supply. The printing press manufacturer can standardize the constructions of the printing presses and the impression rollers. The costs of production, warehousing and operation can be reduced.

The impression rollers can be provided with a permanently applied outer layer. According to one embodiment of the invention, the outer layer is arranged on a sleeve sleeve and the core is a sleeve mandrel. The effort for the sleeve can be reduced because the insulating layer is eliminated. As a result, the semiconductive layer of the sleeve can be made thicker, so that the sleeve can be reworked more often and has a longer life than conventional sleeves. The sleeve sleeve is electrically conductive at least in a portion from the inside to the outside. For this purpose, the sleeve sleeve may at least partially consist of electrically conductive material or of a material (eg GRP) in which electrically conductive particles (eg graphite, carbon black, iron or carbon fiber particles) are embedded or may be in the sleeve sleeve be integrated at least one electrically conductive ring.

According to a further embodiment, the means for rotatably supporting a rotatably connected to the core shaft and the shaft with respect to the machine housing rotatably overlapping pivot bearing. According to a further embodiment, the means for isolating between bearing receivers used in the machine frame and in the bearing receptacles pivot bearings which store a shaft of the impression roller, arranged. But it is also possible, the means for Isolate between the shaft and the pivot bearings to arrange. Furthermore, it is possible to equip the impression roller with a shaft of electrically insulating material, which forms means for insulating.

According to another embodiment, the means for rotatably supporting an axis and the core on the axis rotatably superimposed pivot bearing. According to a further embodiment, the means for isolating between bearing receptacles in the machine frame and portions of the axis, is mounted on the pivot bearing of the core. In this embodiment, the means for supplying and / or discharging electric charge may be electrical connections to the fixed axis. However, the means for insulating can also be arranged between the pivot bearings and the axle or between the core and the pivot bearings. Furthermore, the axle may be made of an electrically insulating material. In the last-mentioned embodiments, the means for supplying and / or discharging electrical charge may be a charging electrode and / or a fluid transfer system arranged laterally on the core and / or electrical sliding contact and / or electrical brush contact.

According to one embodiment, the means for insulating comprise cylindrical bearing shells made of an insulating material. The bearings can be made in one piece or split.

The means for supplying electrical charge on the impression roller can be designed differently. According to one embodiment, they have at least one charging electrode and / or fluid transfer system and / or electrical sliding contact and / or electrical brush contact and / or electrical connection to an outer bearing part of a rotary bearing for supporting a shaft of the impression roller or on an axis of the impression roller. All suitable means for Supplying electrical charge are included. In particular, the means for supplying an electric charge mentioned in the description of the prior art can be used within the scope of the invention. Preferably, a fluid transfer system is used.

According to one embodiment, the means for discharging electrical charge from the impression roller on at least one fluid transfer system and / or electrical sliding contact and / or electrical brush contact and / or electrical connection to an outer bearing part of a pivot bearing for supporting a shaft of the impression or on an axis of the impression. All suitable means for dissipating electrical charge are included. In particular, the means for supplying an electric charge mentioned in the introduction to the prior art can be used according to the invention as means for discharging an electric charge. Preferably, a fluid transfer system is used.

The means for supplying and discharging electric charge may be the same means.

According to one embodiment, the means for electrical switching are integrated in the housing of the high-voltage power supply or arranged in a separate housing. The integration into the housing of the high-voltage supply is particularly advantageous if the means for supplying the electrical charge are at the same time the means for discharging the electrical charge. Over the same connection with the impression roller then the electrical charge can be supplied and removed. The means for switching can be arranged in particular in a separate housing from the high voltage power supply, if the electrostatic printing aid is prepared by retrofitting a conventional electrostatic printing aid or if a Toploading system with High voltage supply is available. A toploading electrode can not be used to dissipate electrical charge from the impression roller.

According to a further embodiment, the means for electrical switching comprise a relay or a manual switch or a semiconductor switch, e.g. a thyristor.

According to a further embodiment, the means for controlling the means for switching comprise a signal line which is connected to the high-voltage electrical supply and / or the machine control. The signal line indicates the means for controlling whether the high voltage electrical supply is on or off and / or what operating state the press has, for example whether it is off, running in run mode or operating in print mode. Depending on the switching state, the means for controlling can control the means for switching. With the high voltage supply switched off, they can connect the core of the impression roller to ground and disconnect it when the high voltage supply is switched on. When the machine is off or running in run-in mode, it can connect the core to ground and separate the core from ground when the machine is operating in print mode.

According to one embodiment, the means for controlling the means for switching are connected to means for determining the rotational speed of the impression roller, which emit a signal to the means for controlling when exceeding a predetermined rotational speed, which switches the means for switching. In particular, this configuration enables the core to be connected to ground when the printing press is operating in the run-in mode and separating the core from the ground during the printing operation of the printing press.

Fig. 1

eine elektrostatische Druckhilfe mit Presseur mit einer Welle und Direct Charge-Hochspannungszuführung sowie Hochspannungs- versorgung mit integrierten Mitteln zum Schalten in einer grob schematischen Ansicht;

Fig. 2

Presseur mit einer Welle Topload-Hochspannungszuführung und von der Hochspannungsversorgung getrennt untergebrachten Mitteln zum Schalten in einer grob schematischen Ansicht;

Fig. 3

Presseur mit einer Achse mit Direct Charge- Hochspannungszuführung und Hochspannungsversorgung mit integrierten Mitteln zum Schalten in einer grob schematischen Ansicht;

Fig. 4

Presseur mit einer Achse mit Topload-Hochspannungszuführung und Hochspannungsversorgung und davon getrennt untergebrachten Mitteln zum Schalten in einer grob schematischen Ansicht.

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

Fig. 1

an electrostatic printing aid with a shaft pressure roller and direct charge high voltage supply, as well as a high voltage supply with integrated switching means in a rough schematic view;

Fig. 2

Pressurizer with a shaft Topload high voltage supply and separated from the high voltage power supply means for switching in a rough schematic view;

Fig. 3

Pressurizer with an axis with direct charge high-voltage feeder and high-voltage supply with integrated means for switching in a roughly schematic view;

Fig. 4

Pressurizer with an axis with Topload high voltage supply and high voltage power supply and separated therefor means for switching in a rough schematic view.

In the following explanation of various embodiments, matching components are provided with the same reference numerals. Components with matching designations, which are designed differently, are designated by the same leading reference numeral, a trailing point and a subsequent, special reference numeral.

According to Fig. 1 has a impression roller 1.1 a cylindrical core 2.1 and a rotatable shaft 3, which projects with sections 3.1, 3.2 of the two end faces of the core 2.1. The core 2.1 including the shaft 3 is made of an electrically conductive material, for example of a metal or a metal alloy.

On the circumference of the core 2.1 sits a sleeve 4. The sleeve 4 has inside a hollow cylindrical sleeve sleeve 5 made of electrically conductive material, which is e.g. a made with electrically conductive particles (graphite, carbon black, carbon fiber etc.) made conductive glass fiber reinforced plastic. The sleeve sleeve 5 carries outside a semiconductor layer 6.1 electrically limited conductive and elastic material. This is, for example, rubber rendered conductive by electroconductive particles (e.g., graphite, carbon black, iron or carbon fiber particles).

This impression roller 1.1 is provided with - not shown - compressed air channels, so that it is possible by applying compressed air to the impression roller to build a compressed air cushion between the core 2.1 and the sleeve sleeve 5, which makes it possible to remove the sleeve 4 in the axial direction.

The sections 3.1, 3.2 of the shaft 3 are mounted on rolling bearings 7, 8, which consist of an electrically conductive material. These are e.g. around ball bearings. The rolling bearings 7, 8 are inserted in hollow cylindrical bearing shells 9, 10 of electrically insulating material. The bearing shells 9, 10 are in turn bearing receptacles 11, 12 of a machine frame 13 used.

The electrostatic printing aid has means for supplying and discharging electric charge 14. This is, for example, a fluid transmission system according to EP 1 780 011 A2 ,

An electrical high voltage supply or high voltage generator 15.1 is connected via a connecting line 16.1 to the means 14 for supplying and discharging electrical charge. The electric high-voltage generator 15.1 contains means for switching or an electrical switching device 17.1 connected to ground 18, e.g. the machine frame 13 ("machine mass") is connected.

The high voltage generator 15.1 is connected via a control line 19.1 with a machine control 20.

The electrostatic printing aid is used within a rotary printing system as follows:

If electrical charge is to be transferred to the impression roller 1, the high voltage generator 15.1 is switched on via the machine controller 10 and the switching device 17.1 is opened. As a result, an electrical high voltage is applied to the fluid transmitter 14 via the connecting line 16.1. The electrical high voltage passes through the core 2 and the electrically conductive sleeve sleeve 5 on the semiconductor layer 6 and acts through the substrate between impression roller 1 and impression cylinder through the color in the wells of the printing cylinder.

Since the rolling bearings 7, 8 are insulated from the machine frame 13 by the bearing shells 9, 10, the high tension applied to the impression roller 1.1 can not flow away from the machine frame 13.

If no high voltage supply is required, the high voltage generator 15.1 is switched off via the machine control 20 and the switching device 17.1 is closed. As a result, the fluid transmitter 14 with Mass connected. The electrical charge can flow off the periphery of the semiconductor layer 6 via the sleeve sleeve 5 and the core 2 and the fluid transmitter 14 to ground 18. Unwanted electrical discharges are avoided.

The execution of Fig. 2 differs from the above-described characterized in that the high voltage generator 15.2 is connected via the connecting line 16.2 with a needle electrode 21. The needle electrode 21 is aligned parallel to the impression roller 1.1 and spaced by a small gap from the semiconductor layer 6.1.

Further, the switching device 17.2 is housed in a, separate from the high voltage generator 15.2 housing. The switching device 17.2 is connected to the impression roller 1.1 for discharging electrical charge via the connection line 16.1, wherein it is e.g. is a fluid transfer system.

If charge is to be applied to a printing material via the impression roller 1.1, the high-voltage generator 15.2 is switched on via the machine controller 20 and the control line 19.1. From the needle electrode 2.1 electrical charge is transferred to the semiconductor layer 6.1 via the air gap. Since the roller bearings 8 of the impression roller 1.2 are insulated by the bearing shells 9, 10 from the machine frame 12, the applied electric charge can not drain to ground.

The switching device 17.2 has a high-impedance resistor 22, via which the impression roller 1.1 is permanently connected to ground 18. Excessive voltages can flow away via this resistor 2.2, and the impression roller 1.1 can be gradually discharged after the high-voltage generator 15.2 has been switched off. In addition, the machine control 20 is connected via the control line 19.2 directly or via the high voltage generator 15 and the control line 19.3 with the switching device 17.2. The machine control 20 controls the switching device 17.2 so that it is open when the high voltage generator 15.2 and closed when the high voltage generator 15.2 is off. As a result, a charge from the circumference of the impression roller 1.1 when the high voltage generator 15.2 is switched off quickly to ground 18.

The execution of Fig. 3 is different from the execution of Fig. 1 first, characterized in that the impression roller 1.2 has a hollow cylindrical core 2.2, which is mounted on a fixed axis 23 via the roller bearings 7, 8. The axis is mounted on insulating bearing shells in bearing mounts 11, 12 of a machine frame 13.

The core 2.2 carries on the outer circumference a semiconductive outer layer 6.2. It sits in the example directly on the circumference of the core 2.2. This may be, for example, a vulcanized rubber layer containing electrically conductive particles (e.g., iron particles, graphite particles, carbon particles, carbon fibers).

The high voltage generator 15.1 is connected via the connecting line 16.1 directly electrically connected to the axis 23 of electrically conductive material. When the high voltage generator 15.1 is on the axis 23 and the electrically conductive bearings 7, 8 and the core 2.2 electrical charge transferred to the semiconductor layer 6.2 and passes from there to the substrate in the gap between impression 1.2 and impression cylinder. The insulating mounting of the axle 23 in the machine frame 13 prevents charge from flowing off. The Switching device 17.1 is open, so that the high voltage can not flow through the switching device 17.1 to ground.

The machine controller 20 can switch off the high voltage generator 15.1 via the control line 19.1 and close the switching device 17.1, so that the axis 23 is connected to ground 18 via the switching device 17.1. As a result, charge can flow from the circumference of the impression roller 1.2 to the axis 23 and from there via the connecting line 16.1 and the switching device 17.1 to the mass 16.

The execution of Fig. 4 is different from the execution of Fig. 2 in that the impression roller 1.2 is designed as in the embodiment of Fig. 3 , Further, the switching device 17.2 is as in FIG. 3 connected directly to the axis 23 via the connecting line 16.1.

The printing aid can be switched via the machine controller 20 in such a way that the high-voltage generator 15.2 supplies charge to the semiconductor layer 6.2 via the needle electrode 21. At the same time, the switching device 17.2 is opened, so that only charge can flow through the resistor 22. Furthermore, the machine controller 20 can switch off the high-voltage generator 15.2 and at the same time close the switching device 17.2, so that the connecting line 16.1 is connected to ground. As a result, excess charge from the shell of the impression roller 1.2 on the core 2.2, the bearings 7, 8 and the axis 23 to flow to ground.

Claims (13)

Electrostatic printing aid with - A impression roller (1) having a core (2) made of an electrically conductive material and an elastic and electrically semiconductive outer layer (6), - means for rotatable bearings (7, 8) which rotatably support the impression roller (1) in a machine frame (13), - means for insulating (9, 10), which isolate the means for rotatably supporting (7, 8) with respect to the machine frame (13), - a high voltage power supply (15) which can be switched on and off, - means for supplying the high voltage supply (15) provided charge on the impression roller (1), Means for removing electrical charge from the impression roller (1), - means for electrical switching (17) whose input is electrically connected to the means for discharging charge (14) from the impression roller (1) and whose output is electrically connected to ground (18), and - means for controlling (20) the means for switching (17) from an open position in which the input has no connection with the output, in a closed position in which the input is connected to the output and / or vice versa. Electrostatic printing aid, in which the outer layer (6) on a sleeve sleeve (5) is arranged and core (2) is a sleeve mandrel. Electrostatic printing aid according to claim 1 or 2, wherein the means for rotatably supporting a non-rotatably connected to the core (2) shaft (3) and the shaft (3) with respect to the machine housing (13) rotatably mounted rotary bearing (7, 8). Electrostatic printing aid according to claim 1 or 2, wherein the means for rotatably supporting (7, 8) an axis (23) and the core (2) on the axis (23) rotatably supporting pivot bearing (7, 8). Apparatus according to claim 3 or 4, wherein the means for isolating (9, 10) between bearing receptacles (11, 12) in the machine frame (13) and in the bearing receivers (11, 12) used rotary bearings (7, 8), the one shaft (3) of the impression roller (1) store, or portions of an axis (23) on which via pivot bearings (7, 8) of the core (2) is mounted, are arranged. Electrostatic printing aid according to one of claims 1 to 5, wherein the means for insulating (9, 10) comprise cylindrical bearing shells made of an electrically insulating material. Electrostatic printing aid according to one of Claims 3 to 6, in which the rotary bearings (7, 8) are roller bearings. Electrostatic printing aid according to one of Claims 1 to 7, in which the means for feeding electrical charge (14) onto the impression roller comprise at least one charging electrode and / or fluid transfer system and / or electrical sliding contact and / or electrical brush contact and / or electrical connection on an outer bearing part of a rotary bearing (7, 8) for supporting a shaft (3) of the impression roller or on an axis (22) of the impression roller (1). Electrostatic printing aid according to one of Claims 1 to 8, in which the means for discharging (14) electrical charge from the impression roller comprise at least one fluid transmission system and / or electrical sliding contact and / or electrical brush contact and / or electrical connection to an outer bearing part of a Rotary bearing (7, 8) for supporting a shaft (3) of the impression roller (1) or on an axis (23) of the impression roller (1). Electrostatic printing aid according to one of claims 1 to 9, wherein the means for electrical switching (17) in the housing of the high voltage power supply (15) integrated or arranged in a separate housing from this. Electrostatic printing aid according to one of claims 1 to 10, wherein the means for electrical switching (17) comprise a relay or a manual switch or a semiconductor switch. An electrostatic printing aid according to any one of claims 1 to 11, wherein the means for controlling the means for switching (17) comprises a signal line (19) connected to the high voltage electrical supply (15) and / or the machine control (20). Electrostatic printing aid according to one of claims 1 to 12, wherein the means for controlling the means for switching (17) are connected to means for determining the speed of rotation of the impression roller, which emit a signal to the means for controlling when exceeding a predetermined rotational speed, the the means for switching switches.

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