Inking unit for a printing press

Abstract

Inking unit for a printing press with an ink fountain (02), an anilox roller (04) for taking ink (03) from the ink fountain (02) and a temperature control device (06; 16) for temperature control of the anilox roller (04), wherein the temperature control device (06; 16) is a radiant heater (06; 16), wherein the radiant heater (06; 16) has at least one IR radiator, characterized in that the at least one IR radiator is designed as a light-emitting diode (LED) (07), that the anilox roller (04) is divided into a plurality of zones along its axis, wherein each zone is assigned a section (061; 062; 063; 064; ...) of the temperature control device (06; 16), the thermal output of which is independent of the thermal output of the sections (061; 062; 063; 064; ...) and that each section (061; 062; 063; 064; ...) of the tempering device (06; 16) comprises at least one light-emitting diode (07).

Description

[0001] The invention relates to an inking unit for a printing press according to the preamble of claim 1.

[0002] To prevent locally varying ink consumption on a printing plate from leading to zone-by-zone variations in the thickness of the ink layer on the transfer rollers that transport the printing ink from the inking unit to the plate cylinder, the ink delivery by the inking unit is conventionally controlled zone by zone. For example, DE 101 58 485 A1 describes an inking unit with an anilox roller that rotates adjacent to an ink fountain, drawing ink from the ink fountain in its anilox cups. To control the amount of ink drawn into a anilox cup, a doctor blade with zone-by-zone adjustable pressure is applied to the anilox roller. The smaller the amount of ink to be drawn, the greater the doctor blade pressure must be, and consequently, the greater the frictional wear on the doctor blade and anilox roller.

[0003] The rheological properties of the printing ink are temperature-dependent, which means that the ink dosage on a warmed-up printing press can differ significantly from that at start-up. To achieve a consistent print result, the doctor blade of a conventional inking unit must be adjusted as temperatures change.

[0004] DE 197 36 339 A1 proposes controlling the rheological properties of the printing ink by controlling the temperature of the anilox roller and the doctor blade using a temperature control device. The temperature control device can comprise means for supplying temperature-controlled air to the outer surface of the anilox roller or a heat transfer line running inside the roller. The operation of such a temperature control device, which acts on at least one entire roller, inevitably leads to increased energy consumption during printing.

[0005] WO 2015 / 140756 A1 discloses an inking unit for a printing press having an ink fountain, an anilox roller for taking over ink from the ink fountain and a tempering device for tempering the anilox roller, wherein the tempering device is a radiant heater and wherein the radiant heater has at least one IR radiator.

[0006] DE 41 08 883 A1, DE 199 37 467 A1 and DE 10 2011 112 487 A1 each disclose an inking unit for a printing press with an ink fountain, an anilox roller for taking over ink from the ink fountain and a tempering device for tempering the anilox roller, wherein the tempering device is a radiant heater.

[0007] The invention is based on the object of creating an inking unit for a printing press, whereby the energy consumption can be reduced.

[0008] The object is achieved according to the invention by the features of claim 1.

[0009] The temperature control device is a radiant heater with at least one IR radiator, since this - especially if it does not require a heat transfer fluid - enables, for example, zone-by-zone modulation of the thermal output in a simpler way than a cooling device.

[0010] This at least one IR emitter is designed as a light-emitting diode.

[0011] Zone-by-zone control of the performance of the temperature control device in the inking unit has two advantageous effects. Firstly, by applying thermal power only in those zones whose temperature deviates significantly from a target temperature, the energy consumption of the temperature control device as a whole can be kept low. Secondly, by controlling the temperature of the anilox roller zone-by-zone, ink release can be influenced not only by the doctor blade's contact pressure but also by zone-by-zone modulation of the rheological properties of the printing ink. This reduces the requirements for the range of pressures that can be applied with the doctor blade. By limiting the use of high pressures overall and thus reducing friction between the anilox roller and doctor blade, drive energy consumption can be reduced and the service life of the anilox roller and doctor blade can be extended.

[0012] In order to absorb their radiation efficiently, the anilox roller can be colored black at least on its surface.

[0013] In order to be able to heat with different power levels in different zones, the radiant heating system can comprise a plurality of radiators distributed along the axis of the anilox roller.

[0014] Such radiators are preferably arranged outside the anilox roller and oriented to emit radiation radially to the axis onto the anilox roller.

[0015] As a - preferably - source of the radiant power, each section of the tempering device can comprise at least one light-emitting diode.

[0016] The tempering device can be arranged on a circumferential section of the anilox roller moving from the ink fountain to a transfer roller in order to heat the ink, in particular printing ink, after it has been removed from the ink fountain and thus to achieve rheological properties for its transfer to a transfer roller which differ from those during removal.

[0017] The temperature control device can also be arranged on a peripheral section of the anilox roller moving from the transfer roller to the ink fountain, in order to heat its surface immediately before it reaches the ink fountain. Since in this case, the heat radiated into the surface of the anilox roller is distributed throughout the ink and into the deeper layers of the anilox roller during its movement through the ink fountain and to the transfer roller, the ink is usually cooler at the time of transfer to the transfer roller than during removal from the ink fountain.

[0018] The doctor blade can be equipped with actuators in a conventional manner to control the ink delivery from the ink fountain to the anilox roller in zones. The zones of the anilox roller defined by these actuators should correspond to those defined by the sections of the temperature control device.

[0019] An embodiment of the invention is illustrated in the drawings and is described in more detail below.

[0020] It shows Fig. 1 a schematic cross-section through a printing unit of a sheet-fed printing press with an inking unit; Fig. 2 a top view of a section of an ink fountain and a temperature control device of the printing unit.

[0021] Fig. 1 shows a schematic cross-section through a printing unit of a printing press, in particular a sheet-fed printing press. An inking unit 01 of a printing unit comprises an ink fountain 02 which contains a viscous ink 03, in particular printing ink 03. An anilox roller 04 is mounted adjacent to the ink fountain 02, so that the ink 03 accumulated in the ink fountain 02 touches roller 04, e.g. the anilox roller 04, and penetrates into cells of the anilox roller 04 (not visible in the figure). A doctor blade 05 extending from the ink fountain 02 to the anilox roller 04 limits the accumulation space of the ink 03 downwards and, during the rotation of the anilox roller 04, holds back ink 03 adhering to its outer surface outside the cells, so that when the anilox roller 04 rotates, only in the cells a pressure exerted by the doctor blade 05, e.g. B Working doctor blade 05 to the anilox roller 04 dependent ink quantity leaves the ink fountain 02.Preferably, a chamber doctor blade with a chamber, a closing doctor blade and a working doctor blade 05 is arranged on the anilox roller 04.

[0022] Fig. 2 shows a view of a part of the ink fountain 02, seen from the direction of the anilox roller 04. The doctor blade 05 is divided into a plurality of zones along the axis of the anilox roller 04, wherein the zone is divided into sections 051; 052; 053; 054; ..., the contact pressure of which on the anilox roller 04 can be individually controlled in a manner known per se in order to adapt the amount of printing ink 03 transferred from each section 051; 052; 053; 054; ... to the anilox roller 04 to the locally different ink consumption of successive zones of a printing plate along the axis and thus to prevent excessive accumulation of ink 03 or depletion in individual zones.

[0023] On the circumference of the anilox roller 04, a first temperature control device 06 follows the ink fountain 02 in the direction of its rotation. The temperature control device 06 is a radiant heater 06. This radiant heater 06 has at least one IR radiator. The IR radiator is preferably designed as an LED 07. The temperature control device 06 is preferably divided into several sections in the direction of the axis of the anilox roller 04, each section containing one or more infrared-emitting light-emitting diodes 07, for example LEDs 07. The LEDs 07 are aligned to illuminate the circumference of the anilox roller 04. The radiation from the LEDs 07 heats the printing ink 03 held in the cells of the anilox roller 04. Areas of the circumference of the anilox roller 04 from which the printing ink 03 has been wiped off by the doctor blade 05 are directly hit by the radiation from the LEDs 07.In order to make the absorption of radiation by these free areas more effective, the anilox roller 04 can be colored black at least on the surface.

[0024] How Fig. 2 shows, the division of the temperature control device 06 into sections 061; 062; 063; 064; etc. corresponds exactly to the section division of the doctor blade 05, i.e. the boundaries of the sections 051; 052; 053; 054; ... of the doctor blade 05 and 061; 062; 063; 064; ... of the temperature control device 06 coincide. Thus, each section 061; 062; 063; 064; ... of the temperature control device 06 enables the temperature of a surface area of ​​the anilox roller 04 to be controlled, which is supplied with ink 03 via exactly one section 051; 052; 053; 054; ... of the doctor blade 05, and the settings of the doctor blade 05 and the temperature control device 06 can be optimized section by section.

[0025] Following the tempering device 06 along the circumference of the anilox roller 04 is a gap 09, e.g., a transfer gap 09, at which the anilox roller 04 and a roller 08, e.g., a transfer roller 08, touch each other. Upon this contact, ink 03 is transferred from the anilox roller 04 to the transfer roller 08. The splitting ratio between the ink 03 transferring to the transfer roller 08 and the ink remaining on the anilox roller 04 depends on the temperature of the ink 03 and consequently on the amount of heat that the ink 03 has absorbed on its way past the tempering device 06. Generally, the reduced viscosity of the ink at elevated temperatures promotes a more rapid transfer to the transfer roller 08.

[0026] The transfer roller 08 transfers the absorbed ink 03 to a cylinder 10, e.g., plate cylinder 10, which it contacts at a nip 17. This cylinder absorbs the ink 03 in a known manner, locally selectively, corresponding to a print image formed on printing plates of the plate cylinder 10. The print image is transferred to a blanket cylinder 11 and from there to a printing substrate, which passes through a nip 12 between the blanket cylinder 11 and an impression cylinder 13.

[0027] The amount of ink 03 that flows from the transfer roller 08 onto the plate cylinder 10 varies from zone to zone, depending on the density of the ink 03 in the print image of the corresponding zone. In order for an ink 03 to be printed with the same saturation in all zones, its layer thickness should be the same in all zones of the transfer roller 08, despite the zone-by-zone variation in outflow. For this to happen, the ink 03 must be recharged from the ink fountain 02 to the transfer roller 08 in a varying amount from zone to zone. By controlling the heating of the ink 03 in sections by the temperature control device 06, such zone-by-zone variation in recharging can be achieved even when a doctor blade that cannot be adjusted zone-by-zone is used on the ink fountain 02.If the squeegee 05 is adjustable zone by zone as described above, even greater differences between the reloading rates of the individual zones can be generated by appropriately controlling the tempering device 06 than with the squeegee 05 alone, so that printing with the same saturation is possible even with greatly differing ink consumption in the individual zones.

[0028] An electronic control unit 14 therefore controls, based on image data of the print image, not only actuators 15 of the individual sections 051; 052; 053; 054; ... of the doctor blade 05 in a manner known per se, but also the power of the LEDs 07 in the sections 061; 062; 063; 064; ... of the tempering device 06, so that in a zone n with low ink consumption, not only the section 05 nthe doctor blade is pressed firmly against the anilox roller 04 in order to minimize the ink release, but also the power of the LEDs 07 is minimal in order to keep the transition of the ink 03 from the anilox roller 04 to the transfer roller 08 low, while in another zone n' with high ink consumption the section 05 n , the squeegee 05 is pressed loosely and at the same time the power of the LEDs 07 is high.

[0029] With a chamber doctor blade, there is no control of the actuators 15 of the sections 051; 052; 053; 054; ..., but the color control is carried out via the line of the LEDs 07.

[0030] To enable even greater differences in ink dosing between the zones, according to a further development, a second temperature control device 16, e.g., a radiant heater 16, is arranged on a peripheral region of the anilox roller 04, which moves from the gap 09 to the ink fountain 02. Preferably, the second temperature control device 16 is mounted directly adjacent to the ink fountain 02 in order to minimize the time that elapses between the heating of a surface point of the anilox roller 04 by the temperature control device 16 and the contact of this surface point with the ink 03 of the ink fountain 02. The warm surface of the anilox roller 04 increases the outflow of the ink 03 from the ink fountain 02 by also reducing the viscosity of the ink 03 and thereby promoting the penetration of the ink 03 into the cells of the anilox roller 04.

[0031] The rollers 04; 08 or cylinder 10 used can have different diameters, so that over the course of several revolutions of the transfer roller 08, a point on its surface successively comes into contact with different points on the surfaces of the anilox roller 04 and plate cylinder 10, and as a result, the ink migrates and is distributed within a zone in the circumferential direction of the rollers 04, 08 or cylinder 10. To support this distribution, friction rollers can also be provided on at least one of the rollers 04; 08. In Fig. In the example shown in Figure 1, the diameters of these rollers 04; 08 and cylinders 10 are identical. As a result, a point on the transfer roller 08 always comes into contact with the same point on the anilox roller 04 and the plate cylinder 10 over the course of several revolutions, and transport of ink 03 in the circumferential direction of the rollers 04; 08 and cylinder 10 is prevented.

[0032] The radiation output of the LEDs 07 can be modulated with a high frequency, which exceeds the rotational frequency of the rollers 04; 08 or cylinder 10 by several times. By performing such a modulation periodically in time with the rotation of the anilox roller 04, a circumferentially uneven distribution of the surface temperature can be established on the surface of the anilox roller 04 with the aid of the tempering device 06 and / or 16. Since the diameters of the rollers 04; 08 or cylinder 10 are in an integer ratio to one another and preferably as in Fig.1 are identical, it is possible in this way not only to control the rate of ink transfer zone by zone, as described above, but also to modulate it within a zone across the circumference of the anilox roller 04. As a result, within a zone, those circumferential sections of the transfer roller 08 can be preferably supplied with ink 03 from which the ink 03 is later passed on to highly ink-consuming circumferential sections of the plate cylinder 10, while an accumulation of ink 03 is avoided in circumferential sections of the transfer cylinder 08 that interact with non-ink-consuming circumferential sections of the plate cylinder 10. List of reference symbols 01 Inking unit 02 Paint box 03 Color, printing ink 04 Roller, anilox roller 05 Squeegee, working squeegee 06 Temperature control device, radiant heating 07 Light-emitting diode, LED 08 Roller, transfer roller 09 Gap, transmission gap 10 cylinders, plate cylinder 11 blanket cylinders 12 gap 13 impression cylinders 14 Control unit 15 Actuator 16 Temperature control device, radiant heating 17 gap 051 Section (05) 052 Section (05) 053 Section (05) 054 Section (05) 061 Section (06) 062 Section (06) 063 Section (06) 064 Section (06)

Claims

[1] Inking unit for a printing press with an ink fountain (02), an anilox roller (04) for taking over ink (03) from the ink fountain (02) and a tempering device (06; 16) for tempering the anilox roller (04), wherein the tempering device (06; 16) is a radiant heater (06; 16), wherein the radiant heater (06; 16) has at least one IR radiator, characterized by that the at least one IR radiator is designed as a light-emitting diode (LED) (07), that the anilox roller (04) is divided into a plurality of zones along its axis, each zone being assigned a section (061; 062; 063; 064; ...) of the temperature control device (06; 16), the thermal output of which can be controlled independently of the thermal output of the sections (061; 062; 063; 064; ...) assigned to the other zones, and that each section (061; 062; 063; 064; ...) of the temperature control device (06; 16) comprises at least one light-emitting diode (07). [2] Inking unit according to claim 1, characterized bythat the thermal power of a section (061; 062; 063; 064; ...) of the tempering device (06; 16) can be modulated during one revolution of the anilox roller (04). [3] Inking unit according to claim 1 or 2, characterized by that the anilox roller (04) is colored black at least on its surface. [4] Inking unit according to one of claims 1 to 3, characterized by that the radiant heater (06; 16) comprises a plurality of radiators which are arranged outside the anilox roller (04) and emit radiation radially to the axis onto the anilox roller (04). [5] Inking unit according to claim 1, characterized by that the tempering device (06) is arranged on a circumferential section of the anilox roller (04) moving from the ink fountain (02) to a transfer roller (08). [6] Inking unit according to claim 5, characterized bya second tempering device (16) which is arranged on a circumferential section of the anilox roller (04) moving from the transfer roller (08) to the ink fountain (02). [7] Inking unit according to one of the preceding claims, characterized by that a doctor blade (05) is provided on the ink fountain (02), on which an actuator (15) controlling the ink supply to the zone is arranged for each zone of the anilox roller (04).

Images