Method for cleaning parts of a printing press

Abstract

The invention relates to a method for cleaning parts of a printing press, in particular rolls, rollers and cylinders of a printing press, for example for printing continuous paper webs or individual sheets in offset printing. The aim of the present invention is to provide a method for cleaning parts of a printing press, in particular rolls, rollers and cylinders of a printing press, by means of which method fast and gentle as well as thorough cleaning of the parts of the printing press, in particular the rolls, rollers and cylinders of a printing press, can be achieved. This aim is a achieved by a method according to claim 1.

Description

[0001] Method for cleaning parts of a printing press

[0002] The invention relates to a method for cleaning parts of a printing press, in particular rollers, rolls and cylinders of a printing press, for example for printing continuous paper webs or single sheets in offset printing.

[0003] Printing presses, especially offset printing presses, operate using the rotary printing process, the web offset printing process, or the sheet-fed offset printing process. The materials to be printed include paper, cardboard, various plastics, as well as metal webs and sheets. What all printing processes have in common is that the printing presses are optimized in terms of throughput quantities, for example of the paper to be printed, and they offer very high productivity. For this purpose, paper webs to be printed, for example, are guided through the printing press via a large number of rollers, rollers, cylinders, and other parts and printed at very high speeds. The trouble-free operation of such printing presses depends in particular on the extremely precise guidance of the materials to be printed via rollers, rollers, cylinders, and other parts of the printing press.Basically, printing machines become dirty during operation depending on the materials used in the parts of the printing machine as well as the materials to be printed on, etc.

[0004] It has been observed that dirt sometimes accumulates more heavily on rollers and cylinders where there is no paper web. If paper is fed over the same spot again at a later time, this accumulation of dirt can appear as a defect in the straight line of the print image. Cleaning must then be carried out at the latest in order to avoid waste and ensure high print quality. Until now, contamination of the printing presses with printing ink was assumed to be the main source of contamination. When cleaning printing presses, paste-like cleaning agents are therefore used which, on the one hand, have a strong cleaning effect through mechanical removal and, on the other hand, are intended to prevent ink from building up again on impression cylinders, transfer rollers and other metal, rubber or plastic parts of the printing press.The paste is therefore applied manually and applied to the relevant part of the printing press, such as an impression cylinder, using a textile. The paste is then polished with another textile.

[0005] This cleaning procedure for parts of the printing press, particularly rollers, cylinders and rolls that become dirty during the printing process, has therefore been very complex and time-consuming up to now. In some cases, machining processes have also been used to remove dirt from rollers, cylinders or rolls of a printing press. All cleaning processes used to date have resulted in a shortened service life of high-precision metal impression cylinders, for example, because the mechanical impact results in small deviations from the nominal dimension of an impression cylinder, for example. The new diameter after mechanical cleaning must be measured with effort and precision and communicated to the printing press control system to prevent an accumulation of malfunctions in the web guide during printing. There is a minimum for each diameter below which the roll in question can no longer be used.Mechanical cleaning, for example by grinding, which leads to a reduction in diameter, therefore inherently contributes to a significant shortening of the service life of such parts of the printing press.

[0006] The object of the present invention is therefore to provide a method for cleaning parts of a printing press, in particular rollers, rolls, and cylinders of a printing press, with which a quick, gentle, and thorough cleaning of the parts of the printing press, in particular the rollers, rolls, and cylinders of a printing press, can be achieved. According to the present invention, the object is achieved by a method for cleaning parts of a printing press, in particular rollers, rolls, and cylinders of a printing press, which comprises the following steps: a] applying an aqueous cleaning solution to a surface of a part of a printing press to be cleaned, which comprises an unbuffered alkaline pickling solution with an initial concentration of sodium hydroxide or potassium hydroxide solution or a mixture thereof, complexing agents, and surfactants of different chain lengths,b] optionally distributing the aqueous cleaning solution over the surface to be cleaned, optionally using distribution means that absorb the aqueous cleaning solution, c] performing steps a] and b) once or several times, wherein at least the initial concentration of sodium hydroxide or potassium hydroxide solution of the aqueous cleaning solution, and preferably also the concentration of the complexing agents and surfactants, is reduced when the steps are performed several times, d] applying water or demineralized water to the surface to be cleaned and optionally distributing the applied water or demineralized water with water-absorbing distribution means, preferably with highly clean water-absorbing distribution means, and e] removing the applied water or demineralized water with water-absorbing distribution means, preferably with highly clean water-absorbing distribution means.

[0007] The method according to the invention is based on the realization that not only printing ink contributes significantly to the contamination of printing presses, but also abrasion of the offset plates, which are usually made of aluminum and are used in the printing process. By using an unbuffered alkaline pickling solution with an initial concentration of sodium hydroxide or potassium hydroxide solution or a mixture thereof, containing complexing agents and surfactants of different chain lengths as the cleaning solution, aluminum-containing contamination in particular is easily removed from the material, metal, rubber, or plastic thanks to the use of the sodium hydroxide or potassium hydroxide solution. The complexing agents and surfactants ensure that precipitation of metal salts from the solution and thus a reduction in the cleaning effect and the formation of streaks in the cleaning result are prevented.

[0008] By optionally distributing the aqueous cleaning solution over the surface to be cleaned using distribution agents, the cleaning effect of the cleaning solution can be exerted evenly on the surfaces to be cleaned. A surprisingly streak-free cleaning result can be achieved, especially by repeating and reducing the initial concentration of the cleaning solution, including the application and optional distribution and removal of water or demineralized water. Abrasive, mechanical grinding or polishing, as was previously necessary, is no longer required, and the printing press components, especially rollers, rolls, and cylinders, have a significantly longer service life.It has been found that conventional cleaning steps using polishing paste or grinding caused dimensional changes that significantly reduced the service life of printing press parts that are in mechanical contact with the materials to be printed or already printed. The cleaning method according to the invention not only significantly increases the service life of these printing press parts, but it is also completed much more quickly, thus significantly reducing the cleaning effort.

[0009] According to a first embodiment of the method, the application and optional distribution of the cleaning solution during repeated execution according to step c] onto the surface to be cleaned and / or the application and removal of the water or demineralized water from the surface to be cleaned according to steps d] and e) takes place before the previously applied aqueous cleaning solution has at least partially dried or dried in. This can effectively suppress the formation of streaks and improve the cleaning result on the surface to be cleaned. In order to achieve an identical cleaning result even if the cleaning process is interrupted on a surface to be cleaned, the repeated repetition of cleaning steps a] and b] according to step c] is carried out when executed several times with the reuse of the aqueous cleaning solution at the initial concentration.Surprisingly, this procedure removes almost all streaks even when the cleaning solution has dried up, thus enabling a very good cleaning result regardless of process interruptions.

[0010] According to a next embodiment, a significant reduction in the cleaning time can be achieved by increasing the cleaning speed by mechanical action of the distribution means and / or by increasing the temperature and / or the initial concentration of the aqueous cleaning solution.

[0011] The method according to the invention has achieved particularly good cleaning results when the parts of the printing machine are rollers, rolls or cylinders with a surface to be cleaned made of steel, chrome-plated steel, rubber, rubber mixtures or plastic, in particular polyurethane.

[0012] A particularly effective and rapid cleaning of parts of the printing press, which are preferably also in mechanical contact with the material to be printed or with the material already printed, in particular of rollers, rolls or cylinders of a printing press, can be carried out in a frame with a holder for the rotatable mounting of the rollers, rolls or cylinders, wherein a means for collecting used cleaning solution is preferably provided.

[0013] Preferably, the aqueous cleaning solution is applied

[0014] Application agents are used, especially brushes, rollers, or spray nozzles. Brushes and rollers can be used for manual cleaning of printing press parts. Spray nozzles can be used primarily in an automatic cleaning process for applying the aqueous cleaning fluid or water or demineralized water, preferably in a rack. The same applies to rollers for applying the aqueous cleaning fluid.

[0015] If, according to a further embodiment, the means for distributing the aqueous cleaning solution consist at least partially of a plastic foam or textile absorbing the aqueous cleaning solution, mechanical pressure can be exerted simultaneously during the distribution of the aqueous cleaning liquid to improve the cleaning effect.

[0016] A streak-free distribution and removal of water or demineralized water is achieved according to a further embodiment of the method, provided that the means for distributing and removing water consist at least partially of cellulose, paper, textile or fleece.

[0017] If the method is carried out in a cleaning device using application agents for the aqueous cleaning solution, wherein the adjustment of the concentration of sodium hydroxide and / or potassium hydroxide solution of the aqueous cleaning solution for carrying out the cleaning steps according to step c] is carried out automatically by the device and steps a] to e] are carried out automatically, a particularly short cleaning time of the parts of the printing press, in particular in the case of rollers, rolls or cylinders of the printing press, can be achieved.

[0018] If the cleaning device includes means for continuously reducing the concentration of sodium hydroxide and / or potassium hydroxide solution to enable repeated cleaning steps, cleaning steps a] and b] can be carried out with a continuously decreasing concentration of sodium hydroxide and / or potassium hydroxide solution, which leads to particularly good cleaning results. Finally, it has been shown that a preferred initial concentration of sodium hydroxide and / or potassium hydroxide solution in the aqueous cleaning solution is 2 to 5 wt.%. With this initial concentration, sufficient cleaning results were achieved in the first cleaning step, while simultaneously using as little sodium hydroxide or potassium hydroxide solution as possible.

[0019] The invention will be explained in more detail below using exemplary embodiments in conjunction with the drawing. The drawing shows in

[0020] Fig. 1 shows an embodiment of the method according to the invention in a schematic flow diagram and in

[0021] Fig. 2 shows a schematic sectional view of the application of an aqueous cleaning solution in a device for carrying out an embodiment of the method.

[0022] The flow diagram of Fig. 1 schematically shows steps a] to e] of an embodiment of the method according to the invention, in which in step a] an aqueous cleaning solution is applied to a surface to be cleaned of a part of a printing press, which cleaning solution comprises an unbuffered alkaline pickling solution with an initial concentration of sodium hydroxide or potassium hydroxide solution or a mixture thereof, complexing agents and surfactants of different chain lengths.

[0023] Optionally, this cleaning solution is distributed over the surface to be cleaned according to step b], optionally using distribution means that absorb the aqueous cleaning solution. The distribution means for distributing the aqueous cleaning solution preferably consist at least partially of a plastic foam or a textile that absorbs the aqueous cleaning solution. For example, brushes or paint rollers can also be used for manual application. Generally, according to one embodiment of the method for applying the aqueous cleaning solution, application means, in particular brushes, rollers, or spray nozzles, can be used to simplify application.

[0024] According to step c], the steps of applying an aqueous cleaning solution and optionally distributing the cleaning solution are repeated, whereby, as shown in Fig. 1 with block v, the initial concentration of at least sodium hydroxide and / or potassium hydroxide solution in the aqueous cleaning solution is reduced upon repeated application of the cleaning solution, in particular the cleaning solution is continuously diluted. This achieves a streak-free cleaning result, which is particularly important for the cleaning effect. As also shown in step c] in Fig. 1, the repetition of step a] can also be repeated with the initial concentration, for example, once.

[0025] Preferably, the repetition of steps a] and b] according to step c] is carried out before the previously applied aqueous cleaning solution has at least partially dried or dried in. Using a so-called wet-on-wet process, streaking in the cleaning result can be significantly suppressed and the cleaning result significantly improved.

[0026] This applies in particular if step d), the application of water or demineralised water to the surface to be cleaned, the optional distribution of the applied water or demineralised water with water-absorbing distribution means and step e), the removal of the applied water or demineralised water with water-absorbing distribution means are carried out before the cleaning solution on the surface to be cleaned has at least partially dried or dried out.

[0027] The use of water or demineralized water in steps d) and e) of the process results in particularly high levels of cleanability of the cleaned surfaces. The means for distributing and removing water or demineralized water are preferably made at least partially of cellulose, paper, textile, or nonwoven fabric. These can absorb water and any dirt particles remaining with the water to a high degree from a cleaned surface and can immediately leave surfaces dry and cleaned. Preference is given to using high-purity cellulose, high-purity and / or lint-free paper, textile, or nonwoven fabric in order to also suppress contamination by foreign substances from the means for distributing and removing water, if necessary.

[0028] The time required for steps a] to d] can be significantly reduced by mechanical action via the distribution means. Mechanical action here does not mean that material is removed, but rather that the loosening of dirt is mechanically assisted by the cleaning solution. An increase in the cleaning speed of the cleaning process can also be achieved by increasing the temperature and / or the initial concentration of the aqueous cleaning solution. In particular, the degree of contamination of the parts of the printing press, for example the rollers, rolls, and cylinders, can influence the choice of the aforementioned parameters or the mechanical action on the surfaces to be cleaned with regard to an adequate cleaning time requirement.

[0029] Fig. 2 shows, for example, in a sectional view the cleaning of a part of a printing press in the form of a roller, roll or cylinder 1 in a device for cleaning parts of a printing press 2. Rollers, rolls or cylinders often have a surface to be cleaned made of steel, chrome-plated steel, rubber, rubber mixtures or plastic, in particular polyurethane.

[0030] Fig. 2 also shows a spray nozzle 3 as an application means, which applies the aqueous cleaning solution or the water or preferably demineralized water to the roller, cylinder or roll 1. The applied medium can be distributed by rotation. Optionally, distribution means, for example painting rollers, can be used here. As shown in Fig. 2, the cleaning device has a means for collecting the cleaning solution or the water or demineralized water, here in the form of a tub 4. The collected cleaning solution can then be diluted, for example using means not shown, according to block v and used again according to steps a] and b] of the method according to the invention.

[0031] It has been shown that the initial concentration of sodium hydroxide and / or potassium hydroxide in the aqueous cleaning solution can preferably be 2 to 5 wt.% to achieve good cleaning results. The complexing agents and surfactants contained in the aqueous cleaning solution further enhance the cleaning effect.

[0032] Cleaning the parts of a printing press using the method according to the invention results in a high degree of cleanliness of the surfaces of the printing press parts, especially rollers, rolls, or cylinders, and, moreover, in no damage or abrasion of the surfaces due to polishing or other mechanical influences. Thus, the method according to the invention ensures a particularly long service life for the parts of a printing press cleaned in this way and significantly reduces the costs of operating the printing press.

Claims

Patent claims 1. A method for cleaning parts of a printing press, in particular rollers, rolls and cylinders (1) of a printing press, the method comprising the following steps: a] applying an aqueous cleaning solution to a surface of a part of a printing press to be cleaned (block a), which comprises an unbuffered alkaline pickling solution with an initial concentration of sodium hydroxide or potassium hydroxide solution or a mixture thereof, complexing agents and surfactants of different chain lengths, b] optionally distributing the aqueous cleaning solution on the surface to be cleaned (block b), optionally using distribution means that absorb the aqueous cleaning solution, c] performing steps a] and b once or several times, wherein at least the initial concentration of sodium hydroxide or potassium hydroxide solution of the aqueous cleaning solution is reduced when performing steps (block v) several times,d] Applying water or demineralised water to the surface to be cleaned and optionally distributing the applied water or demineralised water with water-absorbing distribution means, preferably with highly clean, water-absorbing distribution means, and e] Removing the applied water or demineralised water with water-absorbing distribution means, preferably with highly clean water-absorbing distribution means.

2. Method according to claim 1, characterized in that the application and optional distribution of the cleaning solutions during repeated execution according to step c] on the surface to be cleaned and the application and removal of the water or demineralized water from the surface to be cleaned according to steps d] and e] takes place before the previously applied aqueous cleaning solution has at least partially dried or dried out. Method according to claim 1 or 2, characterized in that the cleaning speed is increased by mechanical action of the distribution means and / or by increasing the temperature and / or the initial concentration of the aqueous cleaning solution. Method according to one of claims 1 to 3, characterized in that the parts of the printing press are rollers, rolls or cylinders with a surface to be cleaned made of steel, chrome-plated steel, rubber, rubber mixtures or plastic, in particular polyurethane.Method according to one of claims 1 to 4, characterized in that the cleaning of the rollers, rolls, or cylinders takes place in a frame with a holder for rotatably supporting the rollers, rolls, or cylinders, wherein a means for collecting used cleaning solution is preferably provided. Method according to one of claims 1 to 5, characterized in that. Step c] begins with the reuse of the aqueous cleaning solution with the initial concentration when repeated several times. Method according to one of claims 1 to 6, characterized in that application means, preferably brushes, rollers, or spray nozzles (3), are used to apply the aqueous cleaning solution. Method according to one of claims 1 to 7, characterized in that the means for distributing the aqueous cleaning solution consist at least partially of a plastic foam or a textile that absorbs the aqueous cleaning solution. Method according to one of claims 1 to 8, characterized in that the means for distributing or removing water or demineralized water consist at least partially of cellulose, paper, textile, or nonwoven.Method according to one of claims 1 to 9, characterized in that the method is carried out in a cleaning device using application means for the aqueous cleaning solution, wherein the adjustment of the concentration of sodium hydroxide and / or potassium hydroxide solution of the aqueous cleaning solution for implementing the cleaning steps according to step c] is carried out automatically by the device, and steps a] to e] are carried out automatically. Method according to one of claims 1 to 10, characterized in that means for reducing the concentration of sodium hydroxide and / or potassium hydroxide solution are provided in the cleaning device for carrying out the repeated execution of the cleaning steps. Method according to one of claims 1 to 11, characterized in that the initial concentration of sodium hydroxide and / or potassium hydroxide solution in the aqueous cleaning solution is 2 to 5 wt.%.

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