EP0095652B1 - Device for metering dampening fluid dependent upon the ink profile - Google Patents

Description

The invention relates to a device for ink profile-dependent dampening solution adjustment in an offset printing unit with a ink dampening unit, which supplies a dampening film of the same thickness to the plate cylinder and the inking unit over the width of the printing form, a device separate from the normal dampening unit being provided for changing the portion of the dampening solution in the ink film is.

The correct quantity ratio of dampening fluid and color on the offset printing plate has a significant influence on the print quality that can be achieved with offset printing units. If, for example, the fountain solution requirement exceeds the fountain solution supply, this is noticeable on the printed image by "toning" or "smearing". On the other hand, if the plate is over-moistened, water marks appear. The balanced ratio between ink and fountain solution supply is therefore within this lubrication and water mark limit.

As is well known, the color requirement of a printed image, as seen across the width of the printed image, depends on the respective color area coverage. This fact is taken into account by zonal regulation of the ink supply. On the other hand, the dampening solution is fed across the entire width of the plate using a thin, uniform film. According to the color profile, however, the plate also needs more water locally than in other places. One helps oneself by supplying a quantity of fountain solution averaged over all image areas and builds on the fact that a fountain solution emulsion is formed in the inking unit, which creates the necessary compensation.

Experience has shown that an average supply of dampening water cannot completely compensate for the different needs of the plate for dampening solution according to the color profile. In particular, pressure-free margins cause problems. The composition of the ink-water emulsions forming in the inking unit is so different that printing difficulties arise, although the fountain solution supply should be correct for the continuous printing. The poor adaptability of the fountain solution supply to the color profile, which is dependent on the subject, therefore considerably narrows the tolerance range between the so-called smear limit - too little water - and the water mark limit - too much water.

To remedy this deficiency, DE-A-29 31 579 discloses a device for zonal regulation of the dampening solution guidance over the width of the printing form of an offset printing press with actuators for zone-wise ink metering, the actuators for zone-wise ink metering being assigned corresponding actuators for the dampening agent guidance and these with one another are coupled, with the inclusion of an adapter taking into account in its transmission characteristic the parameters influencing the zonal ink / fountain solution balance. The zonal dimensioning of the dampening solution guidance is thus carried out by a device provided separately from the normal dampening system.

With this known device, the amount of dampening solution supplied is uniquely assigned zonally according to a specific, generally non-linear characteristic of the amount of ink. This coupling of ink and fountain solution supply is of great advantage for production printing, but causes considerable problems when starting up again. After each interruption in printing, the leveled ink / water distribution in the production run collapses immediately. Existing water evaporates on the plate and the inking unit, there is a color balance at least zonally on all rollers, the layer thicknesses are equalized and locally generated emulsions change their structure. It is absolutely necessary to dampen the plate across the entire machine width when restarting the press. Often, even a brief over-moistening of the plate will be necessary to ensure that the non-printing areas run smoothly immediately. In order to create favorable start-up conditions, the coupling of ink and fountain solution would have to be temporarily removed in the known device.

In the known device, the local evaporation which arises is also not compensated for by local overheating.

Also known from EP-A-0 000 689 is a device for monitoring the dampening solution and ink balance in offset printing units, which has a measuring roller arranged between the last dampening roller and the first inking roller, with which the liquid film thickness is measured. The measuring roller is at least partially hydrophilic. Depending on the measuring method used, the measuring roller is constantly in contact with the adjacent application rollers or it is applied alternately to the dampening and inking rollers. With the help of a light source, a measuring photoreceiver, a comparative photoreceiver and a filter in the measuring and comparative beam path, the liquid layer present on the measuring roller can be used to determine the dampening solution and ink balance on the plate. There is no provision for regulating the dampening solution setting process. The dampening solution layer cover is also not measured in sections.

Finally, from US Pat. No. 4,151,796 a device for automatically compensating for fluctuations in the ink and dampening liquid guidance on a sheetfed offset machine is known, in which the Color and the components of the dampening liquid layer of the plate cylinder is illuminated with at least one radiation source. Filters can optionally be introduced into the beam path, which select the wavelengths that are most strongly absorbed by the color or the dampening liquid in question. In the event of a quantitative deviation of the ink layer or of the individual components of the dampening fluid from a predetermined target value, the corresponding reflection deviation sets in motion a control circuit which controls the guidance of the ink and dampening fluid. A regulation of the dampening solution supply in sections is not provided.

The object of the invention is to achieve the same ink-water emulsion as possible, regardless of the color profile and local heating, seen across the machine width. However, this should not make the start-up conditions unnecessarily difficult, but should have a positive impact.

The solution to this problem is, according to the invention, that a hydrophilic measuring roller is provided, which is connected to one of the inking rollers, that a measuring device is arranged in the area of the measuring roller, which determines the wetting of the measuring roller shell in sections over the entire width of the measuring roller, and that a special device for changing the portion of the dampening solution in the ink film is provided, and that a control part converts the measurement signals of the measuring device into control commands and gives up the separate device for adjusting the portion of the dampening solution in the ink film.

The idea of the invention can be realized in two ways. Once you can drive little water, i.e. cover the minimum requirement and supply enough dampening water that the lubrication limit is not reached under normal circumstances. With this dampening method, ink acceptance will occur in such sections on the hydrophilic measuring roller and will then be measured by the sensors of the measuring device, in which too little dampening water is supplied locally due to the highest elevations of the color profile. The additional dampening then takes place automatically at these points.

The other way to realize the idea of the invention is to drive a lot of water, i.e. to move just below the water mark limit with the fountain solution supply. In such a case, dampening water will accumulate on the hydrophilic measuring roller, the lateral surface of which has the same conditions as the plate, in those sections in which over-humidification has occurred due to the valleys of the color profile. This over-moistening can be eliminated by doctoring. If the hydrophilic measuring roller is also cooled, the sectional imbalance between the ink and fountain solution supply will show up faster than on the plate and can thus be eliminated in good time.

The device according to the invention considerably increases the tolerance range between the lubrication and the watermark limit by adapting the dampening solution supply to the color profile. The starting conditions are improved. The optimal continuation printing conditions can be brought about with the device according to the invention in an extremely short time because, for example, with the aid of the additional dampening device, a very rapid saturation of the inking unit with fountain solution can be carried out. It is therefore only necessary to pre-moisten the plate in order to be able to press the machine. Likewise, when using a squeegee device, an ink-water balance can be established very quickly by using the means of over-humidification, which is harmless because the possibly occurring oversaturation of the inking unit with dampening water can be made harmless in all sections by doctoring. The invention therefore not only extends the tolerance range between the lubrication and water mark limits, but also noticeably improves the starting conditions.

The invention is explained in more detail below with reference to the drawing.

• Fig. 1 ein Farbfeuchtwerk nach der Erfindung mit einem Zusatzfeuchtwerk,
• Fig. 2 ein Farbfeuchtwerk nach der Erfindung mit einem auf eine Farbwerkswalze abschnittsweise einwirkenden Feuchtwasserrakel und
• Fig. 3 die Ausbildung der Rakelabschnitte als anstellbare Saugflächen.

It shows schematically:

• 1 is a paint dampening system according to the invention with an additional dampening system,
• Fig. 2 shows a dampening system according to the invention with a dampening doctor blade acting in sections on an inking roller and
• Fig. 3 shows the formation of the doctor sections as adjustable suction surfaces.

The inking unit according to FIG. 1 consists of an ink fountain 1 with ink fountain roller 2, the subsequent ink lifter 3, which supplies 2 ink to a first ink rubbing cylinder 4 from the ink fountain roller. The first ink rubbing cylinder 4 is connected to a second ink rubbing cylinder 6 via a rubber roller 5. This latter also has contact with the distributor roller 7 and the inking unit roller 8. Both of the latter inking unit rollers 7 and 8 are in contact with the third inking cylinder 9, which feeds the first two inking rollers 10 and 11 with ink. The second strand of the inking unit branches off from the distributor roller 7 in the form of four inking unit rollers 12, the last of which rests in the chain on the fourth inking cylinder 13, which feeds the last two inking rollers 14 and 15 with ink. The inking rollers 11 and 14 are connected via a rider roller 16. An intermediate roller 17 also forms a bridge between the first pure inking roller 10 and the fountain solution inking roller 18, which dips into the fountain solution tank 20 via a metering roller 19 Dip roller 21 is supplied with fountain solution. A fountain roller 22 which converges with the ink fountain roller 18 ensures that the fountain film is uniform.

A hydrophilic measuring roller, namely a chrome measuring roller 23, has contact with the inking unit roller 8 connecting the second and third ink rubbing cylinders 6 and 9. Parallel to this chrome measuring roller 23, a number of sensors 24 of a measuring device 29 are arranged at regular intervals from one another. They are electrically connected to an electronic control part 25. A series of dampening water application units 26 of an additional dampening unit 33 are also provided parallel to the second ink rubbing cylinder 6 at equal distances from one another. These fountain solution application units 26 can be designed as ultrasonic atomizers. They are electrically connected to the electronic control part 25 mentioned above. The fountain solution application units 26 of the additional fountain arrangement 33 are supplied with fountain solution by a pump 27 which removes the fountain solution from the fountain case 20.

The five application rollers 18, 10, 11, 14 and 15 are arranged so that they can be removed from the plate cylinder 28. On the one hand, dampening water is conveyed directly into the inking unit 34 by the intermediate roller 17, and on the other hand, ink is also supplied to the ink dampening roller 18.

During production, the dampening unit 35 promotes a uniform dampening film on the plate and in the inking unit 34 in such a way that certain critical points on the printed image, for example non-printing edges, are close to the smear limit with regard to the composition of the ink / water emulsion. While the chrome measuring roller 23 normally runs bare due to the hydrophilic character of its surface with sufficient water supply of the inking roller 8, it will take on color at the points where the ink / water emulsion contains too little water. However, as soon as the surface of the chrome measuring roller 23 is smeared in sections during the printing process, the sensors 24 of the measuring device 29 measuring at these points detect a surface fault and send a corresponding measuring signal to the electronic control unit 25, which converts this measuring signal into an actuating command and the assigned or the assigned dampening water application units 26 of the additional dampening unit 33 cause 6 dampening water to be sprayed onto the lateral surface of the second inking cylinder as long as the control unit 25 issues corresponding control commands. The pump 27 ensures that the working wet water application units 26, e.g. Ultrasonic atomizers are constantly supplied with fountain solution. If the chrome measuring roller 23 runs completely bare again at the smeared points, the control unit 25 no longer sends control commands to the corresponding dampening water application units 26, and the spraying of dampening water in sections is stopped. This spraying of dampening water in sections can be carried out continuously or periodically, depending on how the sensors 24 report the need to the measuring device. In this way it can be achieved that, seen across the entire width of the machine, the fountain solution emulsion which forms in the inking unit always has approximately the same composition. A section-wise lack of dampening water will show up earlier on the inking roller 8 and thus on the chrome measuring roller 23 than on the plate of the plate cylinder 28 because the dampening water is fed directly to the former. In addition, the evaporation caused by heat in the inking unit ensures that too little dampening water on the chrome measuring roller 23 causes "smearing" earlier than on the plate. Therefore, because of the plate-like surface conditions on the chrome measuring roller 23, it can be recognized prematurely where the smear limit would be reached on the plate if dampening water was not immediately supplied to the inking unit 34 at the endangered sections.

During the start-up after a shorter or longer standstill of the machine, a quick ink fountain balance in the inking unit 34 can be achieved by briefly adding 33 dampening water into the inking unit 34 from all fountain unit application units 26 of the additional dampening unit. After a brief pre-wetting of the plate on the plate cylinder 28, the continuous printing condition, i.e. produce the desired even fountain solution very quickly across the entire width of the inking unit.

The inking unit 34 according to the embodiment of the invention according to FIG. 2 differs only slightly from the previously described, apart from the different arrangement of some rider rollers. A striking difference, however, is that the inking roller 8 rests exclusively on the third inking cylinder 9, ie has no contact with the second inking cylinder 6. As a result, this inking roller 8 is fed a fountain solution emulsion which is constantly saturated with fountain solution.

The metering roller 19 is designed here as a lifter and the fountain roller 22 is located directly in the fountain flow. From the dipping roller 21, the metering roller 19, which, as noted above, is a lifter, takes on dampening water and feeds it to the dampening cylinder 22, which delivers the dampening water to the ink fountain solution application roller 18.

The inking roller 8 also works a chrome measuring roller 23 together, which is connected to a cooling device, not shown. Beneath the chrome measuring roller 23, sensors 24 of a measuring device 29 extend parallel thereto. They are electrically connected to the electronic control part 25. The latter, in turn, gives up its control commands to an actuating device 30, which controls a fountain solution doctor 31. It consists of a series of doctor sections 32 which are arranged along the chrome measuring roller 23 in such a way that they can be placed by the adjusting device 30 individually or in groups against the outer surface of the chrome measuring roller 23 or can be switched off by the latter. The individual doctor sections 32 preferably consist of a suction belt.

Each time a squeegee section 32 designed as a suction tape is placed on the lateral surface of the chrome measuring roller 23, the suction tape is advanced by a certain distance, so that a new section of the suction tape touches the lateral surface of the chrome measuring roller 23 with each adjusting movement.

A printing unit with an ink fountain according to Fig. 2 can be operated with a relatively high supply of fountain solution, i.e. the fountain solution can be supplied in such a way that in certain valleys of the color profile the fountain solution emulsion leads to a too high percentage of fountain solution, so that there is a risk of occurrence of water marks in these sections of the printed image. However, before this sectionally excess supply of dampening water becomes noticeable on the pressure plate of the plate cylinder 28, the cooled chrome measuring roller 23 will carry more dampening water in these sections than in other sections, so that the sensors 24 give corresponding measurement signals to the control part 25 and the latter convert converted control commands to the Actuating device 30 sends the doctor blade sections 32 assigned to the reporting sensors 24 against the outer surface of the chrome measuring roller 23 and doctoring off the superfluous fountain solution. The doctoring in sections ensures that the ink / fountain solution emulsion has approximately the same composition in all areas of the ink profile.

A simplified form of Rakeiabschnitten 32 shows Fig. 3. Above the Chromn ⁱ eßwalze 23 of FIG. 2 are provided side by side on an adjusting shaft 36 a plurality of pivoted lever 37, the 23 end facing a suction surface having at its, the shell of the Chrommeßwalze 38th From an adjusting device, not shown, these pivot levers 37 can be set against the chrome measuring roller 23 or pivoted away from the latter. The suction surface 38 is so receptive that it is able to scrape off excess dampening water over a longer period of time. Sensors 24 and associated swivel levers 37 can be arranged to be laterally adjustable. In the best case, only sensors 24 and swivel levers 37 are required for the pressure-free edges because these plate areas are most susceptible to over-moisture. Likewise, of course, the dampening water application units 26 can also be adjustably attached parallel to the inking roller 8, the dampening water profile of which is to be changed in sections if necessary.

Claims (12)

1. Device for the ink profile-dependent regulation of dampening solution in an offset printing unit having an inking-dampening unit which, over the width of the type forme, supplies a dampening solution film of uniform thickness to the plate cylinder end to the inking unit, a device (26,30,31,33,38), separated from the regular dampening unit (35), being provided for varying section by section the proportion of the dampening solution in the ink film, wherein a hydrophilic measuring roller (23) is provided in contact with one of the inking unit rollers (8), wherein in the area of the measuring roller (23) a measuring device (29) is arranged which measures section by section the extent of wetting of the outer cylindrical surface of the measuring roller (23) over the entire width thereof, wherein there is further provided a special device (30, 31, 33) for varying section by section the proportion of dampening solution in the ink film, end wherein a control stege (25) converts the measuring signals of the measuring device (29) into adjustment commands end applies them to the separated device (26, 30, 31, 33, 38) for regulating section by section the proportion of dampening solution in the ink film.

2. Device according to Claim 1,

wherein an additional dampening unit (33) is provided which, in accordance with the adjustment commands of the control stage, supplies one of the inking unit rollers (8) with dampening solution the quantity of which differs from section to section.

3. Device according to Claim 1,

wherein at the hydrophilic measuring roller (23), as viewed in the direction of rotation thereof, there is provided a doctor blade device (31) after the contact location with the inking unit roller (8) bearing the inking-dampening solution profile, said doctor blade device being engageable section by section with said inking unit roller.

4. Device according to one or more of the preceding claims, wherein the hydrophilic measuring roller (23) is connected to a cooling device.

5. Device according to Claim 2,

wherein in a combined inking-dampening unit a chrome measuring roller (23) is in contact with the inking unit roller (8) which touches the ink distributor cylinder (9) supplying the first ink forme rollers (10, 11), wherein severel sensors (24) of the measuring device (29) are provided parallel to the chrome measuring roller (23), said sensors measuring the section-bysection change in the wetting of the chrome measuring roller end applying the acquired measuring signals to the electronic control stege (25), wherein the control stage (25) converts the measuring signals into adjustment commands end applies them to the additional dampening unit (33) which is arranged along an inking unit roller (6) which is nearer to the ink fountain (1) in the inking unit train than the inking unit roller (8) with which the chrome measuring roller (23) is engaged, end wherein the additional dampening unit (33) consists of several dampening solution applicator units (26) which can be controlled section by section by the control stage (25) end which, in accordance with the adjustment commands, supply dampening solution to the nearest inking unit roller (6).

6. Device according to Claim 5,

wherein the dampening solution applicator units (26) consist of ultrasonic atomizers which are fed by a pump (27) connected to the dampening solution fountain (20).

7. Device according to Claims 3 and 4,

wherein the chrome measuring roller (23) is in contact with the inking unit rc'ter (8) which touches the ink distributor cylinder (9) supplying the first ink forme rollers (10, 11), wherein, parallel to said inking unit roller (8), there are arranged several sensors (24) of the measuring device (29), the measuring signals of which are applied to the electronic control device (25), wherein, likewise parallel to said inking unit roller (8), there is further provided the dampening solution doctor blade (31) which is engageable section by section, the blade sections (32) of which can be brought into and out of engagement with the chrome measuring roller (23) by the adjustment device (30) in accordance with the adjustment commands of the control stage (25).

8. Device according to Claim 7,

wherein the ink forme roller (8) interacting with the chrome measuring roller (23) is exclusively engaged with the ink distributor cylinder (9) supplying the first ink forme rollers (10, 11).

9. Device according to Claim 7,

wherein the blade sections (32) are designed as, respectively, winding-up and unwinding suction strips.

10. Device according to Claim 7,

wherein the blade sections (32) are designed as pivotto-contact suction surfaces (38).

11. Device according to one or more of the preceding claims,

wherein the sensors (24) of the measuring device (29) are displaceably arranged parallel to the inking unit roller the extent of wetting of which is being measured.

12. Device according to one or more of the preceding claims, wherein the blade sections (32) and the dampening solution applicator units (26) are displaceably arranged parallel to the inking unit roller (8, 23) the dampening solution profile of which is to be varied.

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