Printing – Antismut device – Anti-offset material application
Patent
1996-02-06
1997-07-08
Hilten, John S.
Printing
Antismut device
Anti-offset material application
101425, B41F 3500
Patent
active
056449860
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method for automatic cleaning of a cylinder, especially a cylinder of a printing machine, in which the cylinder is provided with plates and used for printing on a print carrier made of e.g. paper, plastic film, or metal film, and in which the cylinders become smudged, during printing, with printing ink, particles detached from said print carrier such as dust or fibres, and other foreign objects, wherein an area of the cylinder surface is cleaned by exposing said area to a pressurized flow of fluid so that the foreign objects inside the area on the cylinder surface are detached, and wherein said area is exposed to a vacuum to remove said detached foreign objects and any other material originating from said flow of fluid.
So-called flexographic printing on a print carrier of paper, plastic film or metal film uses a system consisting of a first cylinder, around which a web of the print carrier runs, a second cylinder performing the actual printing and being provided with plates for this purpose, and a third cylinder transmitting ink to the second cylinder.
When the printing process has continued for a certain time, there will normally arise problems with the printing quality. This is because the second cylinder, the printing cylinder, has become smudged with dust, fibres or other particles from the web of paper, plastic film or metal film. When this occurs, it is necessary to halt the printing process, displace the cylinder from its bearing and then manually brush or wash impurities off the second cylinder. This is a serious inconvenience since it means that the stoppage periods may amount to as much as 30 per cent of the total time in which the machine is in use. This means that the operation time in which printing takes place may risk being reduced to 70 per cent of the time in which the machine is in use. Out of those 30 per cent of time in which the machine is halted, up to 90 per cent is due to cleaning the printing cylinder. Furthermore, the waste of paper, plastic film or metal film is substantial because there is a certain running-in period after a stoppage and the web of paper or film being printed during this period does not have a sufficient quality and must be discarded.
EP-0,369,565 describes a cleaner for automatic cleaning of a cylinder by pressing or otherwise discarding impurities from the surface of the cylinder. The cylinder cleaner comprises a brush extending along the total length of the cylinder or, in another embodiment, a bar for applying pressurized air or ultrasound. The cleaning takes place by rotating or displacing the brush along the entire length of the cylinder or by applying pressurized air or ultrasound along the entire length of the bar. This cleaner, however, has the great inconvenience that the efficiency of the cleaning is strongly reduced. Firstly, cleaning by using a brush quickly results in the brush being worn up together with the surface of the cylinder being worn. Secondly, cleaning by using pressurized air or ultrasound being applied to the total length of the cylinder has the effect that the efficiency of the cleaning is not the same over the total length of the cylinder. The pressurized air or the ultrasound is applied at one end of the bar and, therefore, the efficiency of the cleaning will be highest at the first end of the bar and lowest at a second end of the bar opposite the end at which the pressurized air or the ultrasound is applied.
WO 94/12349, a document published after the priority of the present invention, describes an apparatus also for cleaning the surface of a cylinder. The apparatus comprises a jet nozzle being located inside a suction nozzle. The jet nozzle emits a single jet of liquid, and the liquid together with impuries detached from the surface of the cylinder are evacuated through the suction nozzle. The jet nozzle is arranged in the centre of the suction nozzle, and at the opening of the suction nozzle a means for supplying compressed air into the chamber of the suction nozzle
Hilten John S.
Maskinfabriken Tresu A/S
Nguyen Anthony H.
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