Printing – Processes
Reexamination Certificate
2001-02-14
2002-06-11
Hirshfeld, Andrew H. (Department: 2854)
Printing
Processes
C101S424000
Reexamination Certificate
active
06401619
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a method for cleaning the guide rollers of a web printing press comprising a printing material web, guided by a number of guide rollers, and a corresponding device.
Automated cleaning devices have been known for some time for cleaning the cylinders of a web printing press which are directly involved in the printing process, e.g. rubber blanket cylinders and impression cylinders. Such a cleaning device comprises e.g. a brush roller which is moistened with cleaning liquids and introduced in a rotating fashion to the cylinder to be cleaned to dissolve and remove soiling therefrom, such as printing ink residues, loose paper fibers and paper dust.
With today's conventional printing speeds and increased requirements with regard to printing quality, it is absolutely necessary that those guide rollers which come into contact with the freshly printed printing material web are also regularly cleaned from impurities which accumulate on the guide roller surfaces, in particular, as adhering printing ink residues, paper dust and loose paper fibers, which would otherwise increasingly deteriorate the printing quality.
Since access to the guide rollers is usually difficult and since the number of guide rollers is very large compared to the number of cylinders directly involved in the printing process, it is usually not possible, in practice, to have one conventional automated cleaning device for each guide roller. The guide rollers are therefore conventionally cleaned by hand, with an operator spraying cleaning liquid onto the printing material web and initiating slow movement of the printing material web through the printing machine, wherein he/she manually decelerates a guide roller when the moistened portion of the printing material web moves over this guide roller to thereby generate slippage between the guide roller surface and the printing material web. The cleaning agent supplied, together with the printing material web, to the guide roller surface removes the soiling and the printing material web wipes over the respective guide roller to clean it.
U.S. Pat. No. 4,781,116 discloses a device which automates this long practiced approach for printing machines having paper webs. The system comprises an application device disposed in front of the guide rollers to be cleaned, which removes cleaning liquid from a basin using a dipping roller and applies same to a transfer roller, similar to the printing process, and which in turn contacts the paper web to which the entrained cleaning liquid is transferred. The paper web transports the applied cleaning liquid to the guide rollers to be cleaned, the guide rollers having driving motors which are coupled to the corresponding guide roller for generating a slippage between the paper web and the guide roller surface. This prior art has the associated problem that the transfer roller passes not only cleaning liquid onto the paper web but also impurities, in particular, paper dust, from the paper web back into the cleaning liquid container. This eventually leads to sludge deposits in the cleaning liquid container which have to be removed at regular intervals by hand.
U.S. Pat. No. 5,080,015 discloses a system for cleaning guide rollers of a web printing press based on the same conventional principle, wherein the guide rollers are simply decelerated for producing the required slippage and the cleaning liquid is applied to the paper web using spraying nozzles. The spraying nozzles eliminate the above-mentioned disadvantage of prior art according to U.S. Pat. No. 4,781,116 but there are still problems: Spraying always produces some atomization which causes undesirable operation risks. The risk to the workers breathing in the vapor is only one aspect. The cleaning liquids used e.g. for printing papers usually contain an oily component and thus the atomization precipitation on stairs and scaffoldings causes serious problems with respect to working safety. A further problem consists in spraying the optimum amount of cleaning liquids for each kind of paper web, the quality of which can rapidly change. Excessive cleaning liquid causes dripping. Too little cleaning liquid produces unsatisfactory cleaning results.
Departing from the above mentioned prior art, it is the underlying purpose of the invention to propose a method and a corresponding device, on the basis of the described principle, for cleaning the guide rollers of a web printing press which ensures reliable, safe, low-maintenance, automated cleaning of the guide rollers.
SUMMARY OF THE INVENTION
This object is achieved by a method and device comprising the features of the accompanying independent claims. Advantages further developments of the method and device can be extracted from the dependent claims.
The inventive method and the corresponding device are based on the known principle of applying cleaning liquid onto the printing material web and transporting it, using the printing material web, to the guide rollers to be cleaned, wherein the guide rollers to be cleaned are decelerated or accelerated while the printing material web is running to generate slippage between the printing material web and the surface of the respective guide roller such that soiling of the guide roller surface is wiped off and removed by the printing material web which is either charged with cleaning liquid and/or is dry. Depending on the printing material used, an optimum cleaning result can be achieved when slippage between the guide roller and the printing material web is produced while the moistened web contacts the guide roller. It may also be advantageous to move the moistened web over the guide rollers without slippage such that the printing ink residues adhering thereto are dissolved and the dissolved soiling is wiped off with a subsequent dry portion of the printing material web, i.e. slippage is produced only when the moistened web portion terminates.
In accordance with the invention, the cleaning liquid is neither applied to the printing material web using a transfer roller nor with spraying nozzles. For application of cleaning liquid, the printing material web is guided along a container holding cleaning liquid in such a fashion that it comes into direct contact with the cleaning liquid held in the container to thereby accept the cleaning liquid.
In accordance with the invention, optimum application of cleaning liquid onto the printing material web is achieved when the web accepts the cleaning liquid itself by soaking up the cleaning liquid—depending on the type of printing material web used—or by accepting a liquid film adhering to its surface due to adhesion forces and surface tension effects. The charging of the printing material web with cleaning liquid thus adapts automatically to the maximum or nearly maximum absorption capacity of the printing material web, without requiring any regulating measures. When the printing material is changed, no changes are required in the application of the cleaning liquid. At the same time, the surroundings of the application device are not influenced by the application of the cleaning liquid, in particular there is no disadvantageous atomization. Soiling of the stored cleaning liquid in the container is also unlikely since the printing material web only accepts cleaning liquid and the cleaning liquid does not flow back into the container. Finally, the application, in accordance with the invention, of liquid onto the printing material web is not negatively effected when printing material webs of different widths are used in the same machine. For application of liquid according to prior art, in particular using spraying nozzles, e.g. half of the spraying nozzles must be switched off when working with a printing material web which is only half as wide. This switching off must be coupled with information concerning which “half” of the printing material web is to be covered. In contrast thereto, in accordance with the invention, liquid is applied only when a printing material web is present. Application of liquid in accord
Lundin Kjell E.
Mattis Björn
Nguyen Anthony H.
Oxy-Dry Maschinen GmbH
Volpe and Koenig P.C.
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