GB2297719A - Device for cleaning printing units of a rotary printing machine. - Google Patents

Abstract

The device, for cleaning the surface of printing foil (2) carried by a forme cylinder (1), includes a reelable cloth (9) which is provided on a supply reel (8) and may be unwound onto a take-up reel (7). The cloth passes a press-on element (10) engaging a portion of the cloth (9) at the surface (2) to be cleaned. The device is used to clean a directly imageable printing forme (2) to remove silicone and other residues. A cleaning fluid, supplied from a wetting device (11), may assist with the cleaning.

Description

Device cleaning printing units of a rotary printing machine The invention relates to a device cleaning printing units of a rotary printing machine in which a cover which is wound on a supply reel and may be unwound onto a take-up reel passes a press-on element engaging a portion of the reelable cover at a surface to be cleaned.

DD 203 501, for example, shows a device for cleaning a driven cylinder of a printing machine. By means of a working cylinder an entire unit receiving reels and a contact pressure roller may be respectiwly engaged and disengaged at a driven cylinder of a printing machine.

DE-AS 25 38 105 discloses a washing device of a cylinder of a printing machine. By means of a pawl-locking device a contact-pressure roller and a supply roller are connected to each other such that the angle of rotation of the take-up roller increases with each increment of the pawl-locking device, or at least equals the angle of rotation of the contact-pressure roller A device washing a cylinder of a printing machine is also known from DE 38 10 786 Al in which a supply reel and a take-up reel as well as an adjusting device are supported in a washing segment which is mounted so as to be rotatable and pivotable and features an elastic packing.

Furthermore, DE 42 11 310 discloses a device cleaning ink-carrying surfaces in printing units. Accordig to this solution a reelable cover is transported from a supply reel onto a take-up reel, with the take-up reel being mechanically connectable to a drive element when being inserted into guides.

Furthermore, Fig. 1 shows a prior-art cleaning device.

A belt containing a component, provided on the side facing a printing-forme cylinder and to which pressure may be applied is provided inside a hollow body. Said component presses a portion of said belt against the surface to be cleaned, the outside of said belt being provided with a plurality of individual cleaning plates A suction device is to free the cleaning plates from the residues which have been removed from the surface of the printing forme beforehand.

The silicone particles on the printing forme which have been chemically modified by means of the imaging units such as sources of laser beams plug the cleaning plates of the belt very qt ickly, as the silicone particles cannot be completely remote ed from the cleaning W iates by means of the suction device. As a consequence thr eof, the silicone particles: e reapplied onto the printing forme, thus generating a sili ne film considera f affecting the ink trapping of the printing forme and thus le print quality.

Furthers -e, the sucking of impurities is, to a large extent, ineffective due to the g :ase of the driR gear, ink, or cleaning fluid. This makes it often necessary n change the belt, thus incre ;ing the cost of spare parts, which is not acceptable ifl the .7ng run.

Proceeding from the prior art cited and the outlined technical problerr.s including the already existing solutions to these problems it is the object of the invention to provide a residue-free removal of silicone particles and other residues from a dilectly imageable printing forme.

According to the invention this object is achieved by the features of Claim 1.

The advantages attained with this solution are of diverse nature. Due to the fact that a fresh cleaning medium is continuously supplied, the cleaning device operates independently of the soiling of the cleaning medium. The cleaning medium used is much more inexpensive, and its working life only depends on the length of the reelable cover By applying an additional cleaning agent onto the cleaning medium even the most tenacious residues may be loosened and removed.

According to the invention the cleaning device is preferably located below the printing-forme cylinder, a lateral arrangement of the cleaning device being also conceivable. A wetting device supporting the loosing of a layer of silicone particles provided on the printing forme may be assigned to the contact zone between printing forme and cleaning medium.

A cleaning device according to the invention is now described by way of example with reference to the accompanying drawings, in which: FIGURE 1 shows a prior art cleaning device for a cylinder comprising cleaning belts, movable parallel to the axis of the printing-forme cylinder, and cleaning plates; FIGURE 2 is a front elevational view of the inventive cleaning device; and FIGURE 3 is an enlarged side elevational view of the device according to Figure 2.

Referring to Figure 1, a printing-forme cylinder 1 is supported on each side thereof by journals 4 in side walls of a printing unit. On the circumference of the printingforme cylinder 1, a printing forme or printing foil 2 is provided which may be directly imaged inside the machine.

The printing foil 2 may be transported on the circumference of the printing-forme cylinder 1, both its leading end and its trailing end being received in exchangeable reels.

After completion of a print job, the printing forme or printing foil 2 may be reeled off further after having been cleaned, then the new portion of the printing forme or printing foil 2 may be directly imaged by means of sources of laser beams. This is, however, not the subject of the present invention.

So far attempts have been made to clean the printing forme or printing foil 2 by means of a belt 23 on which are provided individual cleaning plates. The cleaning plates are pressed, by means of a bellows 22, against the printing forme 2. By connecting the bellows 22 to a vacuum source 21, one tries to free the residues from the cleaning plates.

The cleaning device of the invention illustrated in Figures 2 and 3 is located below the printing forme cylinder and has a reelable cleaning medium such as a cleaning cloth 9 which is led from a supply reel 8 onto a take-up reel 7. The cylinder 1 has a printing forme or foil 2 which is directly imageable supported thereon. The reels 7 and 8 are driven in a timed manner, i.e. according to a cycle of, for example, one or two revolutions of the printing-forme cylinder in order to ensure that there is always a fresh cleaning cloth 9 available, and that already removed silicone residues are prevented from being returned. Cores 14, 15 of the reels 7, 8 are supported in side walls of a reservoir 6, and a press-on element 10 including a forming body 17 is provided to which pressure may be applied.The forming body 17 may also be engaged at the surface of the printing forme or printing foil 2 mechanically or via an electroniotor.

The press-on element 10 may be controlled via cams or valves such that the press-on element is lifted from the surface of the printing-forme cylinder 1 when passing a gap in the foil 2 on the printing forme cylinder 1.

In the case of a unit to which pressure may be applied, the forming body 17, which extends over the width 13 of the printing forme or printing foil 2, is supplied with pressure via a supply line 18. Alternatively, the supply line may be a line being connected to a motor drive. Inching of the reels 7, 8 may be effected via an electromotor, mechanically via a pawl-type drive, or hydraulically or pneumatically.

When the forming body 17 is supplied with pressure, a strip of the reelable cover 9 is engaged at the printing foil 2.

The rotation of the printing-forme cylinder 1 causes a relative motion between printing foil 2 and engaged cleaning cloth 9, as a result of which the silicone layer may be eroded. The loosening effect may be reinforced by using a cleaning fluid which, via a wetting device 11, is applied onto the cleaning cloth 9.

As, when engaging a strip of the cleaning cloth 9 at the printing forme or printing foil 2, the strips engaged first are soiled the most, the strips engaged later on according to the timing, are soiled less, the less soiled strips of the cleaning cloth 9 may be rewound and, in the following cleaning cycle, may be used to remove the coarsest residues and impurities from the printing forme or printing foil 2 so as fully to exploit the cleaning cloth 9.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims (4)

CLAIMS:

1. Cleaning apparatus for cleaning printing units of a rotary printing machine in which a reelable cloth which is wound on a supply reel and which may be unwound onto a takeup reel, passes a press-on element for engaging a portion of said reelable cloth at a surface to be cleaned, wherein said cleaning device is used in a printing machine to clean a directly imageable printing forme, to remove silicone and other residues.

2. Cleaning apparatus according to claim 1, wherein a wetting station is provided upstream of a contact zone formed by the reelable cloth and the directly imageable printing forme.

3. Cleaning apparatus according to claim 1 or 2, wherein the directly imageable printing forme may be conveyed further on the circumference of a printing-forme cylinder.

4. Cleaning apparatus, substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.