EP2527149B1 - Colour deck of a printing press with a cleaning device for an ink roller and cleaning process for a colour deck - Google Patents

Description

The invention relates to an inking unit of an offset printing machine having a plurality of mutually-working rollers, which process ink supplied from a paint reservoir, wherein the inking unit comprises a cleaning device with at least one doctor blade and a doctor box, and wherein the doctor blade can be applied to at least one roller of the inking unit, to remove paint adhering to the roller and feed it to the doctor box.

The inking unit of a printing machine is known to be used for the preparation of the printing ink which is supplied from the ink reservoir via the inking unit to the printing area of the printing press, for example a blanket cylinder, a printing plate or the like. The inking unit produces a homogeneous color film prepared for the printing process in order to produce the best possible or efficient printing result.

Often it is necessary to change the ink, for example, to use a printing ink of a different color or other other properties to produce another printed product. In particular, if only smaller editions of the respective object such as a booklet to produce, and this a color change is required, creates a considerable cleaning effort. If only smaller runs are printed, then the cleaning effort can make up a considerable proportion of the overall production effort of the print object and the associated downtime of the printing press can be economically very relevant. This is especially true when careful cleaning is required, for example when switching from dark hues to light hues.

To clean the inking unit, the squeegee of the cleaning device is applied to a roller of the inking unit in order to completely remove the previously used printing ink, whereby the color bead accumulating on the squeegee is transferred to the squeegee box. Due to the usually very high viscosity of the printing inks, however, the color bead usually adheres very strongly to the squeegee and the gravity acting on the squeegee blade is only limited enough to transfer the paint bead into the squeegee box without any problems. To facilitate the transfer of Farbwulst in the doctor box, it is known to give over the washer of the inking unit, the doctor increased amounts of solvent to reduce the viscosity of the ink. The lowering of the viscosity is limited in this case, so that the cleaning step still requires a relatively high amount of time, on the other hand, the use of solvents for environmental reasons is not always desirable. Furthermore, the doctor blade could be made steeper to promote movement of the Farbwulst towards Rakelkaten out. However, the steeper angle often requires the use of a harder doctor blade material, which results in increased wear and thus reduced life of the doctor blade and the roller to be unrolled.

To make the cleaning process more effective, is already in the EP 590 833 A1 proposed an automatic printing press washing system with a doctor blade assembly, wherein when cleaning the pressure rollers of the inking unit, the doctor blade is provided with a sheath. The sheath material may be a non-woven or other thin material having a relatively low coefficient of friction which surrounds the doctor edge upon contact with the roller during the removal of ink. As a result, in particular, a wear of the doctor blade is to be significantly reduced and its life is increased, as well as contamination of the doctor blade during the washing process can be prevented. Due to the sheathing system, the doctor edge in each case becomes an unused portion of one of a roller feeder fed to the supplied region of an endless casing material. As a result, therefore, the doctor is always by a comparatively unused area z. As the fleece against the roller protected. The sheathing system may for this purpose have a take-up roll in order to remove the consumed portion of the sheath material. By the sheathing material thus removed from the roller Farbwulst is transferred to the doctor box or a suitable collecting device. It is understood that such a system is technically very complex and reducing the wear of the doctor is associated with a significant reduction in the effectiveness of the Abrakelprozesses, in addition to the high technical complexity of such a sheath device.

Furthermore, inking rollers with strongly hydrophobic surfaces and thus very low surface energy have been increasingly used in recent years, for example based on fluororubbers, as used, for example, in US Pat DE 10 2004 054 425 A1 have been described, the surfaces are in principle very easy to clean. The special roll surface fortunately accelerated the cleaning process and significantly reduced waste paper consumption as the ink can be removed very quickly from the roll surface. In traditional inking units with high surface energy rollers, however, the ink provided with the detergent slowly dissolves layer by layer. The abraded material thus has a comparatively high proportion of solvents and is therefore comparatively low-viscosity, so that the ablated printing ink can not be easily transferred from the doctor blade in the direction of the doctor box or a collecting device. However, if the rollers are exposed to the cleaning agent in roller surfaces with highly hydrophobic coatings and thus very low surface energy, then almost the entire color layer of the roller dissolves in the first cleaning agent application, then that then due to the relatively high proportion of printing ink results in a material having a comparatively high viscosity, which is then difficult to remove from the doctor blade. Just then, however, the removal of the removed colorant from the doctor blade to the rate-limiting step of the entire cleaning process. Partially, these rollers are therefore used in inking units also combined with classic rollers, as in the DE 10 2007 053 489 A1 described. Then, although the ink can be removed more quickly from the hydrophobic rollers, for the hydrophilic set roller against which the squeegee works, however, the above problems arise again, again here is the effectiveness of the Abrakelvorganges the rate-limiting step of the entire cleaning process. The cost of these downtime of expensive printing machines are significant.

Such cleaning problems occur in sheet-fed offset printing machines, in which the blanket cylinder is provided with an interruption of the pressure-medium-transmitting portion of the blanket in the circumferential direction, reinforced, especially during the color change. The circumferential interruption of the blanket cylinder (blanket cylinder) is usually formed by the gripping device for the sheet or a receiving this channel of the printing and / or blanket cylinder.

The DE 203 13262 U1 describes a cleaning device for a coating unit of a processing machine, in which by means of blowing air drying of the lateral surface of an applicator roll is made possible. For this purpose, the gas stream is aligned perpendicular to the surface of the application roller by means of a nozzle or spraying device.

The EP 974 462 A2 describes a rotary printing machine with air nozzles to remove excess wash water so that it does not contaminate fresh ink.

The US 5 325 780 A describes an inking unit with cleaning device, wherein washing liquid is sprayed by means of a corresponding device.

The invention has for its object to provide an inking unit of an offset printing machine with a cleaning device by which the duration of the cleaning interval can be shortened and the life of the doctor blade is not adversely affected.

The object is achieved by an inking unit according to claim 1, and / or by a cleaning device adapted for such an inking unit and by a corresponding cleaning method.

According to the invention, the cleaning device here comprises a nozzle which can be connected to or connected to a gas-conducting system which directs the exiting gas flow in the direction of the doctor blade. The alignment of the gas stream on the doctor blade can be done directly, so that the exiting gas stream occurs directly on the doctor blade or on the color bead located on this or indirectly by means of a flow deflection, which is different from a roller of the inking unit. In this case, the flow deflection can align the gas flow emerging from the nozzle with the doctor, wherein the flow deflection device can be part of the cleaning device, ie in particular different from the rollers of the inking unit, for example a flow deflection plate.

According to the invention, the gas flow is also aligned in an angular range of ± 60 ° to the tangent of the working against the doctor roller in contact point of the doctor blade to the roller. This also makes it possible for the gas stream, optionally after a flow deflection on a flow deflection device, including a roller of the inking unit, in particular the directed against the squeegee roller, are aligned on the Farbwulst so that it experiences a force component away from the doctor edge in the direction of the doctor box. Preferably, the gas stream will be oriented in an angular range of ± ≤ 45 °, more preferably ± ≤ 20-30 ° to the tangent, whereby the pressure exerted on the Farbwulst away from the doctor edge more efficient, so that the Farbwulst spaced more quickly from the doctor edge and the cleaning step takes less time. The adjustment of the gas flow to the tangent can be carried out in particular in an angular range of ± ≤ 5 ° to 10 °, but preferably the employment to the tangent is given with an angle of ≥ 3 ° or ≥ 5-10 °.

It is understood that when the gas flow is oriented at an acute angle to the bead, it is preferably directed against a flow deflector (including the roller against which the doctor is applied) so that the ultimately resulting gas flow is from the direction of the doctor blade edge the color bead hits. In particular, the gas flow may be directed towards the gap or throat area between the doctor blade and the roller working against it. Furthermore, it is understood that the angle given above with respect to positive or negative angles of attack can apply independently. Thus, the gas flow can be made in particular in an angular range of -340 ° to + 60 ° to the tangent, particularly preferably in an angular range of -30 ° to + 45 ° or -20 ° to + 30 °, in this case on the doctor arranged on the opposite side.

Optionally, the nozzle may also be oriented such that the ejected gas stream at a region of the inking unit, for example an inking roller, is deflected in the direction of the doctor blade. This air-flow-deflecting roller may be, for example, the roller against which the squeegee of the cleaning device works, for the adhering color abzurakeln. By the measure according to the invention the duration of the cleaning step can be shortened considerably. The gas stream may in particular be an air stream. By the gas flow is applied to the Farbwulst contactless an additional pressure force, so that the Farbwulst is fed to the doctor box quicker, so in practice by the gas flow is additionally pressed in the direction of the doctor box, so that the removal of the Farbwulst of the doctor with respect to a conventional cleaning device considerably simplified without nozzle system. It would be surprisingly found that sometimes already comparatively small air pressures can be sufficient to facilitate movement of the Farbwalst in the direction of the doctor box and / or to set in motion, so that the duration of the cleaning step can be significantly shortened. Furthermore, the cleaning device according to the invention has the advantage that this basically manages without mechanical attack on the doctor, even if such devices could optionally be provided in addition. The cleaning device according to the invention has the advantage that it operates without contact with respect to the printing ink to be removed and therefore is not itself subject to a cleaning step, requires a cleaning agent such as solvent and the like. Instead of the doctor box, it is generally possible within the scope of the invention to provide another suitable collecting device for receiving the ink removed by means of the doctor blade.

Thus, according to an alternative, the cleaning device comprises a nozzle, which is connected to a gas-conducting system and which directs the exiting gas flow directly onto the doctor blade. Alternatively, the cleaning device comprises a nozzle which is connected to a gas-conducting system and which directs the exiting gas flow via a flow deflection on the doctor blade. It can also be provided a switching means by which the nozzle is switchable to optionally configured according to one of the two alternatives mentioned, for example by optionally changing the orientation of the nozzle.

In particular, the inking unit according to the invention is such an offset sheet printing machine, where the invention has proven particularly useful due to the uneven printing medium (color) transport due to the bowing. The unevenness is usually due to a recess, e.g. a channel formed, which receives a gripping device for sheet transport. The gripping device can be guided in the recess or the channel. The recess or the channel may extend by ≥ 10 ° -20 ° or ≥ 20 ° -40 °, for example, ≥ 60 ° -90 ° of the circumference of the Druckzylindres. Irrespective of this, these values also apply to a circumferential extent of the recess in the blanket cylinder. The recess or the channel can extend by 30 ° -210 ° or 45 ° -180 ° or in particular 60 ° -160 ° of the circumference of the printing cylinder. The recess or the channel may extend by 30 ° -210 ° or 45 ° -180 ° or in particular 60 ° -160 ° of the circumference of the blanket cylinder. In these embodiments, the cleaning system according to the invention has proven particularly useful due to the resulting Farbwulstes during cleaning, as apparently due to the interruption of the print image transmitting area of the pressure medium flow is not completely continuous, so that the above problem is increasingly set.

Preferably, the nozzle has one or more outlet openings, which act on the squeegee over the plant length of the inking unit roller or over the entire squeegee length with the gas stream. Preferably, in this case, the doctor is acted upon over the entire length thereof, which can be applied to the inking roller or is applied during the cleaning process, with the gas stream. Optionally, the doctor blade can be acted upon over a greater longitudinal extent of the same gas stream, as this is the contact area of the doctor with the respective associated roller in the cleaning step. As a result, it can be avoided, for example, that printing ink accumulates at the end regions of the doctor blade. In the following, "squeegee length" is understood in particular to mean the contact length of the squeegee on the roller, unless otherwise stated in the context.

Preferably, the nozzle is designed as a slot nozzle, for example in the form of a nozzle extending over the entire length of the doctor blade or in the form of a plurality of adjacent slot dies. The slot nozzles can each have a width of the nozzle opening transverse to their longitudinal extent of ≦ 0.5 mm, preferably of ≦ 0.2-0.3 mm or ≦ 0.01, particularly preferably of ≦ 0.08 mm, for example of about 0.05 or 0.03 mm. The smaller the nozzle width, the more focused the gas flow can be, and the more precisely this can be aligned with regard to the color bead to be removed. On the other hand, limits are set in the direction of too small nozzle widths for practical reasons, such as with respect to generated pressure force on the Farbwulst, to be generated gas pressure at the nozzle inlet, noise, etc. Especially suitable is a nozzle width of 0.03-0.1 mm, in particular 0 , 03-0.08 mm proved.

The gas flow directed against the doctor blade can be essentially uniform over the longitudinal extent of the doctor blade, ie at any time with essentially the same overpressure or the same flow velocity over the doctor blade length, the deviation being equal to an average of gas pressure or flow velocity ≤ ± 25%. or preferably ≤ ± 10% or more preferably ≤ ± 5%. In this way, a uniform removal of the color bead and thus a uniform cleaning of the doctor blade during color removal can be ensured.

The gas stream emerging from the nozzle generally has a main flow direction which is the direction of the flow stream or flow region with the greatest flow velocity is (flow velocity with respect to the propagation direction of the gas flow). With lateral distance from this main flow direction, the flow velocity of the gas stream or the gas pressure decreases until it finally passes into the static atmosphere or ambient air, which is intersected by the gas stream. In the following, therefore, refers to the "gas flow" or the "flow direction" on the main gas flow at the highest flow rate, so far from the other statements nothing more.

Preferably, a focused air flow is directed to the roller, which fanning as little as possible, so that the Farbwulst can be targeted acted upon by the air flow to facilitate a transfer into the doctor box or generally away from the doctor edge. Preferably, the gas stream fills only in such a way that starting from the main air flow, ie the region of the gas flow with the highest flow velocity in the propagation direction of the gas, up to an air flow region with 75% of the flow velocity or air pressure of the main flow, the fanning in an angular range of ≤ 20 ° to 30 ° or preferably ≤ 10 ° to 15 °, more preferably <5 ° with respect to the main flow direction (the above-mentioned angle thus corresponds to half the fan angle with respect to the arranged on both sides of the main flow flow areas with 75% of the flow velocity of the main flow).

If the outgoing gas stream is directed onto the doctor by means of a flow deflection, the roller can serve as the flow deflection means, against which the doctor bears in a color-removing manner. In this case, the nozzle is preferably aligned such that the main air flow is aligned with a region of the roller so that it is deflected guided by the roller on the doctor, for which the air flow can be directed grazing or reflective to the roller. Preferably, the gas flow diverted by the roller directed directly to the squeegee.

Preferably, the air flow exiting the nozzle (optionally after or without deflection) is directed to a peripheral portion of the roller with a circumferential extent of ≤ 30 ° to 45 °, based on the full circumference of the roller of 360 °, wherein the peripheral portion of the contact area of the Squeegee connects to the roller and is arranged on the Farbwulstseite the squeegee. In this case, the gas flow is particularly preferably directed to a region of the roll which is spaced apart from the contact area of the doctor blade with the roll by ≦ 15 ° to 20 ° or particularly preferably ≦ 5 ° to 10 ° relative to the full circumference of the roll. In this way, on the one hand given a certain tolerance with respect to the alignment of the nozzle on the doctor blade, on the other hand it is ensured that there is still a sufficient air pressure or a sufficient gas flow, which presses the Farbwulst towards the doctor box and thus their Removal supported by doctor blade edge to speed up roller cleaning. In this case, the gas flow is particularly preferably directed to a region of the roll surface which, relative to the roll circumference, is 0 to 30 mm apart from the contact line of the doctor blade on the roll (this region faces the color bead to be removed), preferably in the range from 1 mm to 20 mm , more preferably in the range of ≤ 10 mm to ≤ 6 mm above the contact line of the doctor blade on the roller, most preferably in the range of 2 to 4 mm spaced from said plant line. The gas stream then also supports the color transition of the Farbwulstes from the roller to the doctor blade. At the same time the squeegee is kept clean by means of the flow deflection.

It is understood that in the above, the gas flow is preferably aligned parallel to the contact line of the doctor blade on the roller.

Preferably, the nozzle is oriented such that the emerging gas stream (in particular main stream) is directed against the area of the doctor edge. The gas flow can be directed precisely against the doctor blade edge, but in particular also at a doctor blade edge which is slightly spaced from the doctor blade edge and which is arranged between the doctor blade edge and the ink bead, in particular between the doctor blade edge and the back of the ink bead, ie the thickest region of the ink bead its height opposite the squeegee. In particular, the gas stream (main stream) may be directed against the foot of the Farbwulst, ie against the squeegee from the rising portion of the Farbwulst, which a height of ≤ 30 to 50% or ≤ 10 to 20% of the maximum height of the Farbwulst opposite the doctor can have. This also makes it much easier to transfer the color bead from the squeegee edge and to promote a transfer of the color bead from the squeegee box.

Particularly preferably, the nozzle is oriented such that the gas flow is at an angle of ± 45 ° to the vertical, in this case vertically downwards, toward the upper side of the doctor blade carrying the ink bead. As a result, the gas stream is in one Aligned angle to the doctor blade and the ink bead, so that upon impact of the gas flow on the doctor blade results in a sufficiently strong deflected partial flow, which pushes the Farbwulst away from the doctor blade edge in the direction of the doctor box. Particularly preferably, the nozzle is oriented such that the gas flow is oriented at an angle of ± ≦ 30 °, more preferably ± ≦ 20 ° to 25 ° or most preferably in the range of ± ≦ 10 ° to 15 ° to the vertical. In particular, the gas flow may be oriented at an angle of ± ≤ 0 ° to 5 ° to the vertical.

The above-described "orientation" of the gas flow in each case relates directly to the orientation with respect to the outflow direction from the nozzle, i. without additional flow deflection. The "alignment" of the gas stream described above can also refer to the orientation after deflection by means of a flow deflection, which is then different from a roller of the inking unit.

Particularly preferably, the cleaning device is configured and / or configured such that the gas stream is ejected as a continuous gas stream, d. H. changes in the flow velocity over time are ≤ to 25% of the maximum flow velocity (in each case based on the main flow). Thus, the cleaning step can be uniform and controlled.

According to a variant, the pressure generating device of the cleaning device may be configured or configurable such that the gas stream is ejected discontinuously in time, so the gas stream may, for example, have a time-increasing and decreasing pressure curve, for example as a pulsating gas flow. The gas flow can also be intermittent, so temporarily suspend. Due to the time phases maximum flow velocity, the material of the Farbwulst can be set in motion, in which case by the time phases lower flow rate, a movement of the Farbwulst is maintained. Thus, a movement of the Farbwulstes can be initiated by these flow peaks, without permanently a gas flow with maximum flow velocity must be generated, which may be economically advantageous. In particular, the gas stream for a period of time at the beginning of the cleaning process, in the middle area and at the end of the cleaning process to remove the Farbwulst or - each independently - to an increased value (increased flow rate) are set, and in between with lower flow rate (eg. in each case to values of less than 75% or less than 50% of the value of the maximum flow, more preferably less than 25% of the value of the maximum flow or to 0%) or to elimination. The gas flow can be adjusted according to a further variant (in any case or only) at the beginning and end of the cleaning interval or according to a further variant (in any case or only) in the middle time range and at the end of the cleaning interval (again for the intermediate periods) above). It is understood that the gas flow can also be essentially constant or modulated in each of these time ranges. The duration of each of the flow intervals may independently of each other in the range of 2-60 sec, preferably in the range of 3-40 sec or preferably in the range of 5-20 sec last, for example, about 10 sec. The interim period of reduced flow rate can be longer than the admission period of the doctor blade with gas flow.

The orientation of the nozzle during the cleaning step may be fixed. Alternatively, the orientation of the nozzle during the cleaning step can be changed, for example, oscillated oscillating from the doctor edge in the direction of or to the back of the Farbwulst. This control can be preprogrammed or carried out as a function of a change in position of the Farbwulst, for example by an optical System are monitored as a camera with evaluation, which detects the location and / or height of the Farbwulst. The direction of application of the gas stream can be changed manually or controlled depending on the position of the Farbwulst, for example, to the effect that the gas stream always in the foot of the Farbwulst (as described above) impinges. Alternatively or additionally, the flow velocity of the gas can also be effected as a function of a change in position of the color bead. If the speed of movement of the ink bead away from the blade edge slowed down, the flow rate of the gas of the cleaning device can be further increased, if necessary, be also lowered with sufficient movement of the Farbwulstes. As a result, a particularly efficient operation of the cleaning device is possible. Alternatively or additionally, if appropriate, too

Particularly preferably, the pressure-generating device and the nozzle are designed such that a laminar gas flow is generated. If appropriate, the gas stream may also be quasi-laminar, but preferably laminar. This refers in each case to the gas stream emerging from the nozzle, if appropriate to the gas stream directly at the nozzle outlet. The gas flow at the nozzle outlet may have a Reynolds number of ≤ 10,000 or ≤ 6,000-8,000, for example ≤ 4,000-5,000. The same can apply to the gas flow at the place of impact on the doctor blade. At high flow velocities and Reynolds numbers, a limit is set by the fact that the color bead erosive gas flow does not lead to splashes of Farbwulstmaterials which is removed. Minor spills that do not delay the cleaning process may still be acceptable. The flow rate of the gas stream can easily be so high that at the nozzle outlet and / or on the doctor blade, a gas flow with a Reynolds number ≥ 250-500 or ≥ 1,000-1,500 results, for example ≥ 2,000 or 2,500. As a result, a targeted pressure on the Farbwulst allows and loss of effect due to Whirling avoided.

Preferably, furthermore, the pressure-generating device can be transferred in an operating state or in an operating state, so that the gas is supplied to the cleaning device at an overpressure of ≥ 0.005 to 0.0075 bar / EL of the nozzle or with an overpressure of ≥ 0.01 to 0.015 bar / EL, preferably with an overpressure of ≥ 0.02 to 0.03 bar / EL, more preferably ≥ 0.03 to 0.05 bar / EL (in each case measured at the nozzle inlet based on static ambient air or normal pressure of 1 bar has proven to be sufficient in many cases to exert sufficient pressure on the color bead to set this away from the doctor blade edge in motion, since often only has to be caused by the gas pressure that the color bead sets in motion so the adhesive and / or cohesive forces are overcome, in which case the color bead can be moved in the direction of the doctor box The gas pressure is usually in a range ≦ 1.5 to 2 b ar / EL (overpressure), particularly preferably ≤ 0.75 to 1 bar / EL (gauge pressure) or else ≤ 0.4 to 0.5 bar / EL, optionally also ≤ 0.2 to 0.3 bar / EL or ≤ 0.15 to 0.1 bar / EL. "Overpressure" here means a correspondingly increased pressure compared with normal pressure of 1 bar. "EL" is called "unit length" and refers to a length of the nozzle (length of the slit nozzle or length of the nozzle assembly) of 50 mm, the nozzle being arranged parallel to the squeegee's seating line on the roller. For longer nozzles then there is a corresponding multiple. In this case, "fed to the nozzle" means that the determination of the gas pressure takes place at the inlet area of the nozzle (nozzle inlet). This is usually sufficient to achieve the effect described, with higher pressures are economically inefficient and can also lead to uncontrolled movements of the Farbwulst. Furthermore, an upper limit of the gas pressure / EL is given by the fact that splashes of ink, for example, removed color of the Farbwulstes be avoided by the impinging gas flow, at least in one such extent, which delays the cleaning process. The abovementioned gas pressure / EL may in each case relate to a nozzle with a nozzle opening in the range of 0.03-0.1 mm, in particular scaled to 0.05 mm nozzle width. However, the above-mentioned information on the gas pressure can also apply independently thereof, ie also apply to other nozzle sizes, for example, in each case as "absolute size". For the nozzle widths deviating from the range of 0.03-0.1 mm, in particular scaled to 0.05 mm nozzle width, the gas pressure should be adjusted such that in the main flow path, ie in the region of maximum gas flow, a correspondingly high pressure force of the gas on the color bead exercisable, with the limit of avoiding splashes of the color bead material, at least avoiding to such an extent that would prolong the unacceptable cleaning process.

The angle of attack of the squeegee with respect to the roller at which the color removal occurs can be in the range of 5 ° -45 ° to horizontal, without being limited thereto. The angle of attack may in particular be in the range of 5 ° -30 ° or 10 ° -20 ° relative to the horizontal. The angle of attack can be ≥ 2 ° and / or ≤ 25 °.

Preferably, the gas stream aligned with the doctor blade is not additionally loaded with other additives such as water for moistening, solvents or the like but an at least essentially pure gas stream which contains ≦ 5 to 10 wt.% Or preferably ≦ 3 to 6 wt particularly preferably ≦ 1 to 2 wt .-% of at standard conditions (20 ° C, 1013 hPa) non-gaseous components such as water, solvents or the like (a possible humidity of the gas stream is taken of this, depending on the application conditions in the range of 2% to 95% relative humidity at the respective temperature and pressure of the gas, or in the range of 10 to 80% relative humidity, Preferably, the gas flow is an air flow, for example from a Compressed air tank, generated by a compressor or the like.

Preferably, the gas stream at room temperature or a temperature in the range thereof, for example 10 ° C to 45 ° C or 10 ° C to 35 ° C, in particular 15 ° to 28 ° C or 18 ° to 25 ° C, wherein a possible increase in temperature due to the working heat in the printing press is taken into account here. Preferably, the supplied gas stream is not preconditioned, if appropriate, except for filtering, for example against dust or the like, in particular not separately tempered. Optionally, however, the gas stream may also be deliberately tempered, in particular heated, for example in order thereby to heat the color bead and to lower its viscosity in order to facilitate a movement in the direction of the squeegee box.

The cleaning device may comprise a washing device, by means of which the inking rollers are charged with a solvent, for example sprayed. As a result, the viscosity of the printing ink can be lowered, so that it is easier to remove from the rollers during the cleaning process by means of the doctor blade.

The term "printing ink" in the context of the invention is not limited to colored printing materials but is to be understood any coating materials in which are applied to the print object by means of the printing press, including transparent coatings that modify the surface properties of the print object as paints, electrically conductive Coatings or the like.

The inking unit according to the invention is not limited to offset printing presses but can generally be used in inking units, in which for color change the previously used ink by means of a mechanical device how a stripping device is removed from a moving element of the inking unit such as a roller. However, the inking unit according to the invention is particularly preferably usable on offset printing machines, in which an inking roller is freed from the printing ink used by means of a doctor blade applied in order to carry out a color change.

In the inking unit according to the invention, the roller subjected to the gas flow works in particular against a distributor roller which has a hard-elastic coating with a hardness greater than or equal to 25 Shore D or greater than 30-50 Shore D, or a non-elastomeric coating, such as e.g. of a synthetic resin or polyamide (eg Rilsan), if a polymeric coating is present (also then preferably with a hardness of greater than or equal to 25 Shore D or greater / equal to 30-50 Shore D), or has a metallic or ceramic surface, optionally each may be coated to modify the surface properties. The hardness of the cover of the distributor roller here is higher than the hardness of the rollers of the inking unit with elastomeric cover, which work against the distributor roller (s). The distributor roller usually performs a traversing movement in the longitudinal direction. The reference of the distributor roller of a polymeric material is preferably applied directly to the roller core, which is usually made of a metallic material such as steel, or on a hard elastic intermediate layer having a hardness of greater than 10 Shore D. The layer thickness of the cover of the distributor roller may be in the range of 20-500 microns.

The roller against which the squeegee works to assist in color removal with the aid of the gas stream used according to the invention can, in particular, be a roller firmly installed in the inking unit. The roller may be independently driven therefrom or in combination therewith by means of a drive on the machine side. The roller may have at least about the same surface speed as the impression cylinder, for example, with a deviation of ≤ 30-50% or ≤ 10-20% or preferably ≤ 3-7% based on the surface speed of the printing cylinder. The roller against which the squeegee for color removal works within the scope of the invention is preferably one which operates directly against one or more inking rollers, which in turn works directly against the impression cylinder. Working in relation to the rollers is understood in the sense of "concerns". The inking rollers each have a rubber coating, preferably having a hardness of ≦ 10-15 Shore D or more preferably having ≦ 50-100 Shore A or ≦ 30-40 Shore A. The invention has proven particularly useful in particular with such inking units.

The invention further comprises a cleaning device with nozzle and compressed gas generating device, which can be used in an inking unit according to the invention.

Furthermore, the invention comprises a method for cleaning an inking unit, using an inking unit designed or operated according to the invention, described above. On the above, in particular for the operation of the cleaning device or the inking unit, reference is also made in full to the method. In particular, the invention relates to a method for cleaning the inking unit of a printing press, in particular offset printing machine, wherein an inking roller is cleaned by means of a working against this doctor blade adhering to the roller paint, wherein the doctor forms a Farbwulst, and wherein a doctor box is provided which ink is absorbed by the squeegee. In general, a gas stream is generated by means of the method according to the invention using an inking unit to the invention described and directed from a nozzle directly or by means of a flow deflection on the doctor. The gas flow is generated at a flow rate so as to be a distance one during the cleaning process supported on the squeegee resulting Farbwulstes away from the blade edge, namely preferably in the direction of the squeegee box for color pickup, or causes. The effect can be done in combination with the gravitational effect on the color bead. According to the invention, the squeegee is acted upon by a gas stream to remove the color bead. The gas stream is preferably aligned with the doctor edge. The gas stream preferably has an overpressure of ≥ 0.05 bar / EL (based on a unit length of the nozzle of 50 mm), on the above statements, moreover, is fully incorporated by reference. The gas flow is adjusted in relation to the overpressure, so that no color splashes occur when the gas flow hits the ink bead. The width of the gas flow preferably corresponds to the contact length of the doctor blade on the corresponding roller.

The flow rate of the gas flow at the nozzle exit and / or upon impact with the doctor blade or the area of the inking unit roller adjacent thereto may be ≥ 0.5-1 m / sec or ≥ 2-3 m / sec, preferably ≥ 5-8 m / sec, optionally also ≥ 10-15 m / sec. The upper limit is given by the fact that color splashes are avoided by hitting the gas flow on the Farbwulst, at least as far as they would extend the cleaning process unacceptable. An unacceptable extension is generally within the scope of the invention (also with respect to the above description of the nozzle width, etc.), if the cleaning process by ≥ 5-10% or even possibly ≥ 15-20% in its duration by the sharpening would extend , compared with cleaning at maximum gas flow without spattering.

Figur 1

eine schematische Darstellung eines Farbwerkes mit erfindungsgemäßer Reinigungseinrichtung,

Figur 2

eine alternative Ausführungsform des Farbwerkes nach Figur 1,

The invention will be explained by way of example and described with reference to the figures. Show it:

FIG. 1

a schematic representation of an inking unit with inventive cleaning device,

FIG. 2

an alternative embodiment of the inking unit after FIG. 1 .

FIG. 1 shows a printing machine 1, in particular offset printing machine, in particular sheetfed offset printing machine, with an inking unit 10. The inking unit has a plurality of mutually opposed rollers 11, 12, which prepare from a color reservoir 14 supplied color (generally printing means), wherein the distributor rollers 11 and non-distributor rollers with usually elastomeric coating are provided, which work against each other. Furthermore, the inking unit 10 comprises a cleaning device 20 which has at least one squeegee 21 and a squeegee box 22 associated therewith.

The sheet-fed offset printing press has, as is customary, a printing cylinder and a blanket cylinder (not shown), one of which (printing cylinder or blanket cylinder) or both having an interruption of the pressure-transmitting region in the circumferential direction. This interruption is effected by an axial recess, such as a channel in the outer periphery of blanket cylinder, which has a sheet transport means such as a gripper with a gripper (e.g., gripping jaws) to assist or ensure the sheet transport. This gripping device can be guided in the recess.

If a cleaning of the inking unit 10 is carried out, for example in a color change, the doctor blade 21 is applied by means of a suitable device to at least one roller of the inking unit, here against a distributor roller 11 to abzurakeln adhering to the roller paint and the doctor box 22. In the present example, the doctor blade is held on the doctor box 22 and the doctor box can be transferred to a first position, in which the doctor blade is spaced from the roller 11 to be cleaned, and to a second position, in which the doctor blade 21 on the roller is attached to remove this adherent paint (see Figure 3). It should be emphasized, however, that this is not generally necessary in the context of the invention, for example, the doctor blade 21 may be positionally changed and applied to the roller and / or spaced therefrom independently of the doctor box. The change in position of the doctor box is done here by pivoting about its longitudinal axis. Furthermore, a "squeegee" within the meaning of the invention is generally understood to mean a collecting device for the ink accumulating on the squeegee 21, regardless of its structural design and / or attachment to the squeegee and / or whether the collecting device is coupled or uncoupled with the squeegee can be changed.

The inking unit of the sheet-fed offset printing press has more than 10-12 rolls, which generally also applies within the scope of the invention, usually 14-16 or more rolls, for example 12-26 rolls or 14-24 rolls, mostly 16-20 rolls. The rolls can each "store" the ink or printing medium, namely by being picked up on the roll surface. The said number of rolls is usually necessary or at least expedient in order to be able to distribute a sufficient amount of the pressure medium within the inking unit in order to be able to even out the uneven pressure medium transport from the pressure medium reservoir to the printing or blanket cylinder. It should be noted that the pressure medium decrease of the blanket cylinder due to the circumferential recess such. a channel is uneven. The recess in this case takes on a gripping device to support the sheet transport or allow.

If the squeegee is applied to the roller 11 for the removal of ink, a color bead 25 is produced on the squeegee (squeegee side) which forms a squeegee-facing foot 25a, at which the color bead rises starting from the squeegee surface, and a bulge 25b, which is the bead height h, has ( Fig. 1b , enlarged view). The foot of the bead For example, it can be considered to be within the range of ≦ 50% or preferably ≦ 25% of the bead height above the squeegee surface.

The roller 11 against which the squeegee works for color removal under support with the gas stream used according to the invention is permanently installed in the inking unit and is driven on the machine side by means of a drive. The roller 11 has about the same surface speed as the impression cylinder. The roller 11 works against inking rollers (rubber rollers), which in turn preferably work directly against the printing cylinder.

Furthermore, the cleaning device 20 comprises a nozzle device 30, which has at least one nozzle 31, here in the form of a slot nozzle, and a gas-carrying system 32 such as a compressed gas line, through which the nozzle 31 compressed gas from a compressed gas generating device 33 can be supplied or fed in carrying out the cleaning process becomes. In this case, the nozzle 31 is aligned in relation to the doctor 21 in such a way that the gas flow emerging from the nozzle occurs in the area of the ink bead on the nozzle. The gas stream can in this case directly from the nozzle on the Farbwulst and / or the Farbwulst upstream portion of the doctor blade edge (ie between blade edge and Farbwulst) occur, or on a flow deflection, which then the air flow just the Farbwulst or the range of the doctor edge , which is upstream of the Farbwulst, is supplied. In particular, the peripheral region 11a of the roller 11 adjacent to the doctor blade edge or adjoining the doctor blade edge can also serve as the flow deflection device, so that the impinging gas flow is then deflected by the roller and directed toward the ink bead.

By applying pressure to the bead 25 with the gas flow emerging from the nozzle 31, the color bead can be pushed away from the doctor blade edge 21 a, so that a gas flow through the gas flow Removal of the color bead 25 is facilitated by the doctor blade edge in the direction of the doctor box or a receptacle for the ink (see Farbwulst 25 '). The gas pressure can be used to assist in this, so that the color bead is moved in the direction of the doctor box under the combined action of gravity and by the gas flow. Optionally, however, the gas flow can also be set so strong that it alone transfers the colored bead in the direction of the doctor box or into it, wherein the doctor blade can also be arranged only with a slight inclination or even horizontally.

The nozzle 31 is designed here as a slot nozzle, so that the nozzle opening extends over the entire length thereof. In this case, the nozzle opening extends over the entire contact area of the doctor blade with respect to the roller 11, possibly also beyond.

During the cleaning process, a temporally and spatially continuous gas flow is generated by the pressure generating device 33, which is connected to the gas-carrying system 32, in the simplest case. Optionally, however, a pulsating gas flow can also be generated (possibly also by modifying the nozzle). In particular, according to the embodiment, a gas flow for removing the Farbwulst generated, which is set at the beginning, in the middle and at the end of the cleaning process, for example, for about 10 seconds, and is switched off or set to less than 50% of the maximum value ,

Furthermore, the pressure generating device 33 is operated such that a laminar gas flow exits from the nozzle 31. The gas flow is adjusted with a pressure such that - normalized to a nozzle length of 50 mm - the nozzle inlet has an overpressure of 0.05 bar, ie with a squeegee length of 1 meter a pressure of 1 bar overpressure (ie absolute pressure of 2 bar). The nozzle can in this case have a width of 0.05 mm. The exiting laminar gas stream can - regardless of the above - for example, have a Reynolds number in the range of 5,000-6,000.

The nozzle 31 is according to FIG. 1 now aligned so that the exiting gas flow occurs in the blade edge on the doctor. In particular, the gas flow in this case in the area between the doctor edge and the foot of the Farbwulst (include the foot area) on the doctor blade, or - most preferably - the gas stream is directed to a region of the roll surface, which relative to the roll circumference 2 to 4 mm above the contact line of the doctor blade on the roller, so that the transfer of the ink bead is supported by the roller on the doctor. Upon impact with the doctor blade, the gas flow is deflected so that a sufficiently strong partial flow results, which pressurizes the ink bead sufficiently to remove it from the doctor blade edge. Even very high-viscosity printing inks can be effectively removed from the blade edge, so that the cleaning process can be accelerated or at least but can be carried out more targeted, if the color bead should not have a sufficient slope due to their high viscosity to move away from the doctor edge. On the other hand, the arrangement of the nozzle device may also require a lower solvent or cleaning agent consumption when washing the inking unit with a solvent during the cleaning process.

Furthermore, the gas flow (main gas flow H) after FIG. 1 in an angular range of ± 10-20 ° to the tangent T of the working against the doctor blade 21 roller 11 in contact point A of the doctor blade aligned with the roller. The gas stream is hereby aligned grazing to the roller, so that a stronger flow deflection and thus reducing the pressure force of the gas stream is avoided.

Still goes out FIG. 1 shown that the nozzle 31 is aligned so that the gas flow is aligned vertically on the doctor blade.

In general, the gas flow can also be oriented, for example, in the direction of the narrowing gap S between the roller and the doctor blade ( Fig. 1c ), so that by the flow deflection in the gap S, a backward gas stream impinges on the Farbwulst 25 and removes them from the doctor edge.

The doctor is set in the embodiment at about 25 ° to the horizontal, when the doctor rests against the roller 11 to remove ink. In this way, on the one hand, the removal of the color bead from the doctor blade edge is supported by the action of gravity, on the other hand limited by the relatively shallow angle of attack (compared to an operation of the cleaning device without gas flow) wear of the doctor.

Furthermore, the inking unit 10 comprises a washing device 50, by means of which the inking rollers 11, 12 applied with a solvent, for example, sprayed, and can be washed, which may be missing if necessary.

In particular, the doctor blade can be a plastic doctor blade. The squeegee may have an elastomeric lip which can be applied to the roller without this being absolutely necessary. The roller 11, to which the doctor blade can be applied, may be a distributor roller having a metallic surface (including metal oxide) or a surface of a non-elastomeric plastic having a hardness of ≥ 50 Shore D. This can generally be considered within the scope of the invention.

According to the further embodiment according to FIG. 2 a separate flow deflection device 40 is provided, which deflects the gas flow in the direction of the color bead and / or the upstream region of the doctor blade. As a result, the arrangement of the nozzle can be handled more flexibly, to ensure that the Farbwulst still strikes a sufficiently strong gas stream. Incidentally, the above is fully referenced.

In particular, the roller against which the squeegee works may have a highly hydrophobic surface, that is, a lower surface energy surface than a surface of a polyamide such as Rysan and / or a polyolefin such as a polyvinyl compound, polybutadiene or natural rubber. In particular, the roll surface can consist partially or completely of halogenated polymers, in particular partially or completely fluorinated polymers, for example perfluorinated hydrocarbons. In particular, the rollers which work against the doctor blade can be designed as in US Pat DE 10 2004 054 425 A1 and the DE 10 2007 053 489 A1 described.

Despite the large number of rolls of the inking unit of a sheet-fed offset printing machine, which already bring about a homogenization of the pressure medium flow, it was found that a significant improvement of the cleaning of the inking unit can be achieved by the measures according to the invention, since - it is assumed - apparently also the multiplicity of rolls a complete Equalization does not or not always reliably effect.

Claims (22)

1. Cleaning process for an offset printing machine, particularly a sheet-fed offset printing machine, using a colour deck of an offset printing machine comprising several rollers operating oppositely to each other and preparing printing ink supplied from an ink reservoir, and comprising a cleaning device including at least one doctor blade and a blade box, the doctor blade being applied against at least one roller of the colour deck for removing with said doctor blade and supply to the blade box printing ink adhering to said doctor blade while producing an ink bead at said doctor blade, and the process comprising the production of a gas flow from a nozzle of the cleaning device which is connected to a gas-carrying system, and directing said gas flow onto said doctor blade directly or by means of a flow reversing device forming part of the cleaning device and being different from the rollers of the colour deck, characterized in that said gas flow is oriented and produced at a flow intensity such that it causes the ink bead produced at the doctor blade during the cleaning process to move away from the blade edge.
2. Process according to claim 1, characterized in that the nozzle includes two of more outlet openings that are charged with said gas flow by said doctor blade over the length of its roller contact region.
3. Process according to claim 1 or 2, characterized in that the nozzle is oriented in such a manner as to direct said gas flow against the blade edge region.
4. Process according to one of the claims 1 to 3, characterized in that the doctor blade is oriented at an angular range of ± 60° to the tangent of the roller working against the blade at the lay-on point of the blade against the roller.
5. Process according to one of the claims 1 to 4, characterized in that the nozzle is oriented in such a manner that the gas flow is oriented within an angular range of ± 45° to the vertical, in the vertically downward direction, and/or that the blade is arranged toward the roller at an angle of attack within an angular range of 10°-45° to the horizontal.
6. Process according to one of the claims 1 to 5, characterized in that the pressure-generating device is in an operating condition such that the nozzle inlet is charged with the gas at an excess pressure of ≥ 0.05 bar in relation to a length of the nozzle of 50 mm.
7. Process according to one of the claims 1 to 6, characterized in that the nozzle is configured as slot nozzle having a nozzle width transversely to the longitudinal extension smaller than/equal to 0.5 mm.
8. Process according to one of the claims 1 to 7, characterized in that the pressure-generating device is configured in such a way as to discharge the gas flow in a continuous manner.
9. Process according to one of the claims 1 to 7, characterized in that the pressure generating device is configured in such a way as to discharge the gas flow in a discontinuous manner, including an intermittent manner.
10. Process according to one of the claims 1 to 9, characterized in that the pressure generating device and the nozzle are configured in such a manner that a laminar gas flow exits from said nozzle.
11. Process according to claim 10, characterized in that the laminar flow leaving said nozzle has a Reynolds number of ≥ 250.
12. Process according to one of the claims 1 to 11, characterized in that flow rate of the gas flow at the exit of said nozzle and/or at the time of striking the doctor blade or the region of the colour deck ink roller adjacent to it is ≥ 1 m/sec.
13. Colour deck of an offset printing machine for carrying out the process according to one of the claims 1 to 12, wherein the colour deck includes several rollers operating oppositely to each other and preparing printing ink supplied from an ink reservoir, and comprising a cleaning device including at least one doctor blade and a blade box, the doctor blade being applied against at least one roller of the colour deck for removing with said doctor blade and supply to the blade box printing ink adhering to said doctor blade while producing an ink bead at said doctor blade, and the process comprising the production of a gas flow from a nozzle of the cleaning device which is connected to a gas-carrying system and which is oriented in such a manner as to direct said gas flow onto said doctor blade directly or by means of a flow reversing device forming part of the cleaning device and being different from the rollers of the colour deck, characterized in that said gas flow can be oriented and produced in such a manner as to cause the ink bead produced at the doctor blade during the cleaning process to move away from the blade edge, and that the nozzle includes one or several outlet openings that are charged with said gas flow by said blade over a length of its roller contact region.
14. Colour deck according to claim 13, characterized in that said nozzle is oriented in such a manner as to direct said gas flow against the blade edge region.
15. Colour deck according to claim 13 or 14, characterized in that the doctor blade is oriented at an angular range of ± 60° to the tangent of the roller working against the blade at the lay-on point of the blade against the roller.
16. Colour deck according to one of the claims 13 to 15, characterized in that the nozzle is oriented in such a manner that the gas flow is oriented within an angular range of ± 45° to the vertical, in the vertically downward direction, and/or that the blade is arranged toward the roller at an angle of attack within an angular range of 10°-45° to the horizontal.
17. Colour deck according to one of the claims 13 to 16, characterized in that the pressure-generating device is in an operating condition such that the nozzle inlet is charged with the gas at an excess pressure of ≥ 0.05 bar in relation to a length of the nozzle of 50 mm.
18. Colour deck according to one of the claims 13 to 17, characterized in that the nozzle is configured as slot nozzle having a nozzle width transversely to the longitudinal extension smaller than/equal to 0.5 mm.
19. Colour deck according to one of the claims 13 to 18, characterized in that the pressure-generating device is configured in such a way as to discharge said gas flow in a continuous manner.
20. Colour deck according to one of the claims 13 to 19, characterized in that the pressure-generating device is configured in such a way as to discharge said gas flow in a discontinuous manner, including an intermittent manner.
21. Printing machine, comprising a colour deck according to one of the claims 13 to 20.
22. Printing machine according to claim 21 in the form of a sheet-fed offset printing machine comprising a printing blanket cylinder including an interruption of the printing agent transmitting region of the printing blanket and/or rubber blanket cylinder in the circumferential direction.

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