EP0970810A1 - Method and device for cleaning the ink transport system of a printing press - Google Patents

Abstract

The printer has an ink compartment (14) formed by a doctor blade (12) placed against the periphery of the applicator roller (10). A gaseous printing medium atomizing the cleaning fluid is blown through the ink compartment through attached supply (24) and return-flow (28) pipes containing a pump (26,30). A blocking appliance has a guide sloping towards the direction in which the doctor blade moves in relation to the applicator roller. A slide piece moves along the guide and has a support surface.

Description

The invention relates to a method for cleaning the color system Printing machine, for example a flexographic printing machine with an ink chamber, by a chambered doctor blade that can be adjusted to the circumference of an application roller is formed.

Flexographic printing machines have, for example, one with a roller Cup grid provided with the liquid, with solvent diluted ink is applied to an impression cylinder. While of the printing operation, the chambered doctor blade is pneumatically attached to the circumference of the application roller turned on so that the ink cups with each revolution of the Applicator roller after applying its ink to the printing parts of the Have released printing cylinders, as they pass through the ink chamber filled with paint again. The color system also includes one Conveying device with a feed pump arranged in a feed line, with which the printing ink from an ink container into the chamber doctor blade is conveyed, and a return pump arranged in a return line, with which the ink is removed from the doctor blade and again is returned to the paint container. This way the printing ink circulated continuously in a closed circuit during printing.

When changing colors, the same conveyor is used instead the printing ink a cleaning liquid, such as water, soapy water or solvent to pump through the doctor blade to do this Flush and clean the color system.

If the ink is drained from the ink chamber before rinsing certain color residues inevitably remain in the color chamber. Since the application roller must be movable against the printing cylinder, are the supply line and the return line usually as flexible hoses educated. Even in the sagging sections of these hoses therefore, ink may remain. Subsequent rinsing with solvent the remaining color residues are greatly diluted and then mostly derived together with the solvent. Even the solvent cannot be completely removed from the color system, so that usually several successive rinsing phases are required in which the color concentration in the remaining liquid residues gradually decreases. The repeated rinsing processes therefore result So far, a high consumption of solvents and a corresponding high environmental impact and high disposal costs for the used solvents. Some reduction in solvent use is possible because some of the rinsing processes with used, Already carried out to a certain degree contaminated solvent become.

The object of the invention is a faster and more thorough cleaning of the To enable color system with reduced solvent use.

This object is achieved in that the ink chamber is blown out with a gaseous pressure medium.

The gaseous pressure medium, for example compressed air, becomes relatively high Flow velocity through the ink chamber so that liquid residues, that wet the walls of the paint chamber or in recesses collected, are carried away by the air flow. On in this way the liquid residues can be considerably reduced, so that the number of rinses and thus the consumption of solvent can be reduced without impairing the cleaning success can.

Advantageous refinements of the invention result from the subclaims.

Blowing out with compressed air can occur at various stages in the cleaning process and possibly also take place several times, for example immediately after draining the ink after pre-cleaning with a cleaning fluid and after every rinse during the main cleaning. By blowing out after the last rinsing process, the in Color system remaining residues of cleaning fluid or solvent reduce considerably so that when filling with new printing ink an uncontrolled one Dilution of the printing ink is avoided. That is why of particular advantage because the correct solvent concentration and the correct viscosity of the printing ink is a crucial parameter for the print quality is.

The supply and discharge of the compressed air can be via the supply line and the return line of the color system, so that the entire color system is blown out in one go. In this way, the in the sagging sections of the tubing collected liquid residues remove.

According to a particularly expedient development of the invention, a Cleaning liquid with the help of compressed air in the ink chamber or in entire color system fogged. In this case, not all of it needs Color system to be flooded with cleaning fluid, but through the Liquid mist only becomes the walls of the paint chamber and possibly the Wet hoses with the cleaning liquid. This allows the Reduce the use of cleaning fluid considerably. A part of sprayed liquid, the paint system through the return line again leave without coming into contact with the walls of the color system to be. This liquid is practically not contaminated with the paint residues and can be recovered in a liquid separator so that you get back a high-purity liquid. After the liquid has been nebulized in the color system, the color system will be used again "Dry" compressed air blown out, so that it is heavily contaminated with paint residues Liquid is removed from the system.

During a blow-out process, the compressed air throughput is preferably so high that that a turbulent gas flow forms in the color system. Hereby a particularly efficient removal of the liquid residues is achieved. Between the turbulent gas flow and the liquid that flows through the walls of the ink system, there is high friction, with the result that that the liquid "creeps" along the walls of the paint system and is finally discharged through the return line. Optionally, it goes without saying also possible to blow out in the opposite direction perform so that the compressed air is fed into the return line and the liquid residues are blown out via the feed line.

During the entire cleaning process and preferably also during blowing out with compressed air, the applicator roller can be rotated, so that the surface of the applicator roller is thoroughly cleaned and after each Rinsing process is freed of liquid residues.

During the printing process, the chamber doctor blade is usually used with the help of pneumatic cylinders with limited pressing force against the scope of the Application roller biased so that on the one hand an adequate seal the ink chamber is guaranteed, but on the other hand an excessive Wear on the doctor blades and seals that delimit the ink chamber is avoided. During blowing with high air flow however, a considerable overpressure can develop in the ink chamber, because the downstream pipe system inevitably unites has a certain flow resistance. This overpressure in the ink chamber can cause the doctor blade against the force of the pneumatic cylinder is pushed away from the application roller. According to further training the invention is therefore provided that the doctor blade during of the blow-out process self-locking in their employed on the applicator roller Position is blocked, so that despite the prevailing in the ink chamber Overpressure remains attached to the circumference of the application roller. A suitable one Blocking device for the chamber doctor blade is the subject of the claim 6 and the claims dependent thereon.

Figur 1

zeigt eine schematische Darstellung des Farbsystems einer Druckmaschine; und

Figuren 2 und 3

zeigen schematische Stirnansichten einer Auftragwalze, einer Kammerrakel und einer Blockiereinrichtung in unterschiedlichen Betriebsstellungen.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawing.

Figure 1

shows a schematic representation of the color system of a printing press; and

Figures 2 and 3

show schematic end views of an applicator roller, a chamber doctor blade and a blocking device in different operating positions.

In Figures 1 and 2 is a side view and an end view, respectively an application roller 10 of a flexographic printing machine is shown. To the The scope of the application roller 10 is a chamber doctor blade 12 adjustable, the one Ink chamber 14 forms. According to Figure 2, the ink chamber 14 by doctor blade 16, 18 limited, which doctor the circumference of the rotating applicator roller 10. The applicator roller 10 is in turn on the circumference of a not shown Adjustable printing cylinder and gives the in the printing operation Ink chamber 14 received ink to the printing parts of the Clichés on the impression cylinder.

In Figure 1, a conveyor 20 is also shown schematically, which is used during printing to be diluted with solvent Ink continuously between the ink chamber 14 of the doctor blade and to circulate a paint container, not shown. Figure 1 shows the color system however during a cleaning process. Here is the paint container replaced by a storage container 22, the used, so already contains cleaning fluid contaminated with printing ink to a certain degree. The conveyor 20 includes a feed line 24 which from the Storage container 22 leads to the ink chamber 14 and contains a feed pump 26, and one returning from the ink chamber 14 to the reservoir 22 Return line 28 with a return pump 30.

The feed pump 26 and the return pump 30 are driven by compressed air Diaphragm pumps formed, which with compressed air lines 32, 34 Compressed air can be supplied from a compressed air source, not shown. To the Supply line 24 and to the return line 28 is in each case between the ink chamber 14 and the relevant pump, an expansion tank 36 is connected, which in a known manner to compensate for pressure fluctuations serves the pulsating diaphragm pumps.

The feed pump 26 is connected to the associated compressed air line 32 via a metering valve 38 connected to the adjustable delivery rate of this pump is. The delivery rate of the return pump 30 is correspondingly changeable with the aid of a metering valve 40.

At the end of a printing process, the supply line 24 and the return line are 28 still connected to the paint container, not shown. To do that To empty the paint system, the supply line 24 is separated from the paint container, and the color still contained in the color chamber is over the Return line 28 conveyed into the paint container. Then there is one Pre-cleaning with used cleaning fluid, e.g. with solvent, Water or soapy water. For this purpose, the supply line 24 and the return line 28 connected to the reservoir 22, as shown in Fig. 1 in dash-dotted lines. With the help of Conveyor system, the cleaning fluid is in a closed circuit circulated so that the ink chamber 14 rinsed with the cleaning liquid becomes. Finally, the cleaning liquid is put back into the reservoir 22 is drained and the ink chamber is supplied via the supply line 24 ventilated.

To the remains of cleaning liquid still contained in the color system remove, the paint system is blown through with compressed air. To this For this purpose, the supply line 24 is connected to the outlet of a valve 42 (dashed lines in Fig. 1). The valve 42 is with compressed air from the Compressed air line 32 is fed and preferably contains an adjustable throttle to control the air flow. The return line 28 is also separated from the storage container 22 and via a liquid separator 44 associated with the atmosphere.

The pumps 26 and 30 each contain two permeable in the conveying direction Check valves that are in operation with the diaphragm pumps during pump operation open and close. During the blow-out process, the Flow of compressed air through these check valves is not impeded. The Compressed air therefore flows from the outlet of the valve 42 through the entire length the supply line 24, through the ink chamber 14 and through the entire length the return line 28 to the liquid separator 44. In this way the entire color system can be blown out thoroughly. The diaphragm pumps can continue to run, but they can also be switched off become. The liquid residues still contained in the color system are entrained by the compressed air and finally in the liquid separator 44 deposited. The required pressure of the compressed air depends on the flow resistance dependent on the color system and is typically in the On the order of 400 to 600 kPa (4 to 6 bar).

After doing this, the liquid remains largely from the color system removed, one or more additional rinse cycles can follow. You can choose to replace the used cleaning fluid also fresh cleaning liquid is supplied from a storage container 22 ' are, as indicated by dash-dotted lines in Fig. 1.

A feed pump 46 connects the reservoir 22 or 22 'to the Outlet of the valve 42. When the feed pump 46 is in operation, thus Cleaning fluid fed into the compressed air flow and through the compressed air nebulized in the supply line 24. Instead of the color system during a rinsing process It is therefore also completely flooded with cleaning liquid possible to clean the cleaning system with a liquid mist that is reflected on the walls of the color system and then through the Compressed air is entrained to the liquid separator 44. In this way the color system can use a much lower amount of cleaning fluid to be cleaned. The supply of the cleaning liquid can possibly also self-priming according to the jet pump principle, so that under certain circumstances, the additional feed pump 46 can be dispensed with can.

While in the example shown, the cleaning liquid is directly at the outlet of the valve 42 is supplied, it is in modified embodiments also possible, the cleaning liquid or at least part of the same downstream of the feed pump 26 or only immediately before or in the Feed ink chamber 14.

After the last rinse cycle, the color system is preferably used again blown out with compressed air, without supply of cleaning fluid, so that the refilling with printing ink no residues of cleaning liquid are more contained in the color system.

2 schematically shows one of two or more pneumatic cylinders 48 shown with which the doctor blade 12 against during the printing operation the scope of the application roller 10 is biased. If during the blowing process a relatively high pressure inside the ink chamber 14 prevails, acts on the relatively large floor area of the ink chamber 14 a force that has the tendency to counteract the doctor blade 12 Force the pneumatic cylinder 48 away from the applicator roller 10. This is in the embodiment shown by one or more blocking devices 50 prevented, which are assigned to the pneumatic cylinders 48.

The piston rod 52 of the pneumatic cylinder 48 occurs on the chamber doctor 12 opposite side from the pneumatic cylinder and can with Locked mechanically in one position with the aid of the blocking device 50 be in which the doctor blades 16, 18 rest on the circumference of the applicator roller 10.

The blocking device 50 has a guide 54 which is connected to the piston rod 52 forms an angle of approximately 80 ° and in which a slide 56 is guided is. Fig. 2 shows the blocking device in the unlocked state. In this The condition is a bore 58 of the slide 56 with the piston rod 52 aligned so that the free end of the piston rod 52 is not through the Slider 56 is supported. The chamber doctor blade is thus in this state 12 solely by the force of the pneumatic cylinder 48 with the applicator roller 10 kept in investment.

The slide 56 has a support surface 60 adjacent to the bore 58, which is perpendicular to the piston rod 52 and consequently with the longitudinal axis the guide 54 forms an angle of approximately 10 °. With help of a pneumatic actuating cylinder 62 is the slide 56 along the guide 54 between the unlocking position shown in FIG. 2 and one shown in FIG. 3 Locking position adjustable. Supports in the locked position the free end of the piston rod 52 on the support surface 60. The actuator cylinder 62 exerts an upward force in FIG. 3 on the slide 56 on, so that the piston rod 52 and the chambered doctor blade 12 by wedge action be pressed against the applicator roller 10. If the chamber squeegee due of the air pressure prevailing in the ink chamber 14 tends to to shift to the right in Fig. 3, the piston rod 52 through blocked the slide 56 in position. The slider 56 is supported frictionally on the guide 54. Because of the small angle of attack The guide has the force exerted by the piston rod 52 on the slide 56 only a small component that counteracts the force of the actuating cylinder 62, and a much larger component that the friction between Slider and guide increased. This way the piston rod and held the chambered doctor blade in its self-locking position.

After completion of the blowing process, the slide 56 is by means of the Actuating cylinder 62 is returned to the unlocking position shown in FIG. 2.

Claims (10)

Method for cleaning the ink system of a printing press with an ink chamber (14) which is formed by a chamber doctor (12) which can be adjusted to the circumference of an application roller (10), characterized in that the ink chamber (14) is blown out with a gaseous pressure medium. Method according to claim 1, characterized in that a supply line (24) connected to the ink chamber (14) and a return line (28) connected to the ink chamber are blown out in one pass with the ink chamber (14). Method according to claim 2, characterized in that the gaseous pressure medium is also allowed to flow through a pump (26, 30) contained in the feed line (24) and / or the return line (28). Method according to one of the preceding claims, characterized in that a cleaning liquid is atomized with the aid of the gaseous pressure medium in the ink chamber (14) and / or the inlet or return line (24, 28). Method according to one of the preceding claims, characterized in that the chamber doctor blade (12) is blocked during the blow-out process in a position set on the applicator roller (10). Apparatus for carrying out the method according to claim 5, characterized by a blocking device (50) with a guide (54) which extends obliquely to the direction in which the chambered doctor blade (12) is movable relative to the application roller (10), and with one the guide (54) guided and supported slide (56), which is adjustable along the guide between a locking position, in which it self-lockingly supports a component (52) connected to the chamber doctor (12), and an unlocking position, in which it supports the component (52) releases. Device according to claim 6, characterized in that the slide (56) has a support surface (60) which forms an angle of less than approximately 30 ° with the guide (54) and on which the component (52) is supported. Apparatus according to claim 7, characterized in that the component (52) connected to the chambered doctor blade (12) is rod-shaped and in that the slide (56) has a bore (58) which opens into the support surface (60) and in the unlocking position the rod-shaped component (52) is aligned. Device according to one of claims 6 to 8, characterized by a pneumatic actuating cylinder (62) for adjusting the slide (56) between the locking position and the unlocking position. Device according to one of claims 6 to 9, characterized in that a pneumatic cylinder (48) is provided for positioning the chamber doctor blade (12) against the applicator roller (10), and in that the component supported by the slide (56) has the free end of a piston rod (52) of the pneumatic cylinder (48).

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