EP1316423B1 - Engraved roller and method for its production and reprocessing - Google Patents

Description

The invention relates to a method for producing an anilox roller, in particular for flexographic printing machines, having a cylindrical core and a sleeve detachably held on the core, which has on its surface a grid layer with a cell grid. Furthermore, the invention relates to an anilox roller produced by this method and a method for reprocessing the same.

In flexographic printing, the ink is applied to the printing cylinder using an anilox roller. The surface of the anilox roller passes through a chamber doctor blade, in which the fine cells of the cell grid fill with ink. If the anilox roller then comes into contact with the printing cylinder at another peripheral location, the ink is transferred to the printing parts of the printing cylinder.

Known anilox rollers usually have a dimensionally stable cylindrical core made of metal, which is provided at both ends with stub axles or releasably secured on a continuous axis, so that it can be stored rotatably drivable in the frame of the printing press. During production, the surface of the cylindrical core is provided with a primer layer, on which the ceramic layer consisting of a ceramic material is directly applied. The individual wells are finally formed by means of a laser in the surface of the grid layer.

If the anilox roller to be recycled after prolonged use, because the grid layer is damaged or worn, the entire grid layer and possibly also the primer layer must be sanded before after new primer again a new grid layer can be applied and provided by laser processing with the cell grid , This reprocessing process is very complicated and expensive.

From EP-A-1 132 209 an anilox roller is known in which the cylindrical core is not made of metal, but of carbon fiber reinforced plastic and thus has a lower weight with the same stability. As a result, although the handling of the anilox roller is facilitated and improves the smoothness, but The reprocessing of the anilox roller is similarly costly as with anilox rollers made of metal.

On the other hand, for example from EP 0 791 477 A2. Anilox rollers of the type mentioned above, which are based on the so-called "sleeve technique". In these anilox rollers, the grid layer is not mounted directly on the cylindrical core, but on a hollow cylindrical sleeve, which is then pushed onto the cylindrical core. With this technique it is possible to remove the sleeve from the core and replace it with a new sleeve.

Often, the core has a compressed air system that allows compressed air to be delivered to areas distributed on the surface of the core, thus expanding the sleeve to make it easier to slide open and peel off. However, this procedure requires a special and relatively complicated structure of the sleeve. In compressed air, namely, if possible, only the inner diameter of the sleeve should increase, while the outer diameter should remain as unchanged as possible, otherwise the grid layer consisting of ceramic material may crack and / or flake off. Consequently, the sleeve on the inside of a dimensionally stable as possible layer, for example made of glass fiber reinforced plastic, a compressible layer which can be compressed when expanding the inner diameter. In order for the pneumatic pressure to be evenly distributed on the inner surface of the sleeve, a very thin inner layer of stiffer material should again be provided under the compressible layer.

For a perfect print quality, it is necessary that the sleeve has very good concentricity properties. However, this requirement is difficult to meet for sleeves having the structure described above, because the direct support of the more rigid outer layer on the dimensionally stable core is lost by the presence of the compressible layer. The outer layer of the sleeve must therefore have a high intrinsic stability. This can be achieved only by correspondingly large layer thicknesses, so that there is an increased material consumption and increased costs. The large wall thickness of the sleeve, for example, in the order of 25 mm or more, especially difficult for larger printing widths, the handling of the sleeve and increases the inertial mass of the sleeve and thus the risk of imbalance, so that the desired smoothness is difficult to achieve. The big wall thickness of the Sleeves also makes it difficult to comply with the framework conditions for the outer diameter of the anilox roller and for its inner diameter, ie for the outer diameter of the core. The outer diameter of the anilox roller must take into account the installation conditions in the inking unit of the printing machine as well as considerations related to the printing process, such as the drying time of the ink. Centrifugal force on the circumference of the anilox roller, construction of the chamber doctor blade, etc. On the other hand, with a reduction of the inner diameter increased costs for the core, which must then meet the same stability requirements with smaller outer diameter.

Another disadvantage of the sleeve technique is that when the sleeve is slid onto the core, the grid layer at the ends of the sleeve frequently becomes damaged.

If the grid layer is damaged or worn, replacement of the complete sleeve is uneconomical because of the relatively high cost of the sleeve. The removal of the old raster on the sleeve and the construction of a new grid layer is similar consuming as in the conventional anilox rollers, in which the grid layer is mounted directly on the core.

The object of the invention is to provide a method which enables a simple and cost-effective production and recycling of the anilox rollers

This object is achieved in a method of the type mentioned above in that the sleeve consists of a substantially incompressible material, which is supported directly on the core, that first the sleeve is mounted on the core and only then formed the grid layer on the sleeve is, so that the sleeve with the grid layer is expandable only under temporary enlargement of the outer diameter of the sleeve and thus removable while destroying the Rasterschiebt.

In the production of the grid layer thus the sleeve is already firmly seated on the core, so that the sleeve no longer needs to be expanded and pushed onto the core and thus there is no risk of damage to the grid layer. Consequently, since the sleeve does not need to have a compressive layer, its wall thickness can be significantly reduced, saving material and cost. In addition, the relatively stiff material of the sleeve can directly supported on the rigid core, so that even with a very thin sleeve a perfect concentricity of the anilox roller can be guaranteed. In that regard, according to the inventive method produced anilox roller similar advantages as conventional anilox rollers without sleeve. The main advantage over the sleevelose anilox rollers is that a reprocessing of the grid layer caused by damage or wear much less effort and lower costs. Namely, since the sleeve is detachably held on the core, if reprocessing is required, the old sleeve with the grid layer thereon can be easily removed and disposed of. Instead of the old sleeve then a new sleeve is mounted, which causes only a small cost because of the small wall thickness and the simple structure of the sleeve, and on the new sleeve, when it sits firmly back on the core, built the new grid layer. This eliminates the costly grinding of the old grid layer, so that the time and effort required for the reprocessing of the anilox roller is significantly reduced.

Advantageous embodiments of the invention will become apparent from the dependent claims.

The core can, as in the known sleeve technology have a compressed air system that facilitates the sliding of the sleeve on the core and the subsequent removal of the sleeve from the core. Since the sleeve still carries no grid layer when pushed onto the core, it is harmless if the outer diameter of the sleeve is temporarily increased by the compressed air. Since the sleeve according to the invention is only withdrawn from the core again, if in any case a reconstruction of the grid layer is required, destruction of the grid layer when removing the old sleeve can be accepted.

The wall thickness and the material of the sleeve are preferably coordinated so that the inherent elasticity of the sleeve pushing on the core - possibly supported by the compressed air system - allows and then ensures a tight fit of the sleeve on the core. Any initial run-out or slippage of the sleeve upon sliding onto the core may then be eliminated by twisting or otherwise finishing the sleeve on the core before applying the grid coat. The application of the screen layer can be carried out in a manner similar to conventional sleeveless screen rollers by first applying a primer layer and then a ceramic layer which is applied by application or by post-processing receives a very uniform thickness and then on the surface of which the cells of the wells grid are formed with the help of a laser. If necessary, post-processing can improve the top finish.

In the case of the anilox roller according to the invention, the sleeve preferably has a thickness of only 2-5 mm, and apart from the ceramic layer and possibly the primer layer, it consists only of a single material layer, preferably of glass-fiber reinforced plastic.

In the following an embodiment of the invention will be explained in more detail with reference to the drawing.

Fig. 1

eine Ansicht eines Kerns und, teilweise aufgebrochen, eines Sleeves in einer Anfangsphase bei der Herstellung einer Rasterwalze;

Fig. 2

eine Teilansicht der Rasterwalze nach dem Aufschieben des Sleeves auf den Kern;

Fig. 3 bis 6

vergrößerte Darstellungen des Schichtaufbaus der Rasterwalze in verschiedenen Stadien der Herstellung; und

Fig. 7

eine teilweise aufgebrochene Ansicht der nach dem erfindungsgemäßen Verfahren hergestellten Rasterwalze.

Show it:

Fig. 1

a view of a core and, partially broken, a sleeve in an initial phase in the production of an anilox roller;

Fig. 2

a partial view of the anilox roller after pushing the sleeve on the core;

Fig. 3 to 6

enlarged views of the layer structure of the anilox roller in various stages of production; and

Fig. 7

a partially broken view of the screen roller produced by the process according to the invention.

Figure 1 shows (not to scale) a view of a core 10 of an anilox roller. The core 10 has the shape of a hollow cylinder and consists of a dimensionally stable and as light as possible material, such as steel. Aluminum or preferably made of carbon fiber reinforced plastic. At both ends of the core 10 stub axles 12 are formed, which serve to support the anilox roller in a printing press, not shown. Alternatively, instead of the stub axle 12, a continuous axle may be provided, on which the core 10 is releasably mounted by means of a hydraulic system, not shown. Inside the core 10 and in one of the stub axles 12 is a per se known, not shown in detail compressed air system accommodated, can be supplied via the compressed air, which exits via a plurality of distributed on the surface of the core 10 openings 14. The openings 14 form at least one ring 16 which encircles the circumference of the core 10 and is located at a small distance from the end of the core 10 (on the right in FIG. 1), from which a sleeve 18 is pushed onto the core.

The sleeve 18 is shown in Figure 1 right next to the core 10 and consists of a thin-walled, single-layer tube made of glass fiber reinforced plastic, which has a wall thickness of, for example, 2 mm and the inner diameter coincides with the outer diameter of the core 10. When the sleeve 18 is pushed onto the core 10, the compressed air system is activated so that compressed air exits the openings 14 and the sleeve 18 widens once it has been pushed onto one end of the core. After the sleeve 18 has been pushed completely onto the core 10, the compressed air system is switched off so that the sleeve 18 elastically shrinks and then sits firmly on the core 10. This condition is shown in FIG.

FIG. 3 shows, in an enlarged detail relative to FIG. 2, the single-layer wall of the sleeve 18, which is supported directly on the peripheral surface of the core 10. If necessary, the peripheral surface of the seated on the core 10 sleeves 18, for example, on a lathe, be reworked, so that an exactly cylindrical and centered on the axis of the core 10 shape of the peripheral surface of the sleeve 18 is achieved. Any slight deformations of the sleeve, which may have occurred when pushed onto the core 10, are eliminated in this way.

Subsequently, a primer layer 20 is applied to the peripheral surface of the sleeve 18 (FIG. 4), to which a ceramic layer 22 (FIG. 5) is then applied by known methods, the thickness of which is set very precisely, so that the peripheral surface of the ceramic layer 22 is exactly cylindrical is.

With the aid of a laser, a fine grid of cells 24 is then burned into the peripheral surface of the ceramic layer 22, as shown in FIG.

In this way, the screen roller shown in FIG. 7 is obtained as the end product 26. As in this anilox roller provided with the cell grid 26 ceramic layer 22 directly on the relatively thin and substantially incompressible layer of glass fiber reinforced plastic, which forms the sleeve 18, supported on the rigid core 10, excellent running characteristics of the anilox roller 26 result which for a given stability has a low weight and a correspondingly low moment of inertia and in which there is a very favorable ratio between the outer diameter and the diameter of the core 10.

The existing only a single plastic layer sleeve 18 can be produced inexpensively with little use of materials.

When the ceramic layer 22 (screen layer) forming the well grid 24 is worn or damaged, the sleeve 18 is released from the core 10 and disposed of. For this purpose, the compressed air system is temporarily activated again, so that the sleeve can be easily removed from the core 10. Subsequently, a new sleeve 18 is pushed in the same manner as in Figure 1, and the steps shown in Figures 3 to 6 are repeated, so that one obtains a new-value anilox roller with little effort.

Claims (8)

1. A method of manufacturing an anilox roller, in particular for a flexographic printing press, the anilox roller comprising a cylindrical core (10) and a sleeve (18) detachably held on the core and having at its surface an anilox layer (22) with a grid pattern (24) of pits, characterised in that the sleeve (18) consists of an essentially incompressible material which is supported directly on the core (10), that, at first, the sleeve (18) is mounted on the core (10), and only then the anilox layer (22) is formed on the sleeve (18), so that the sleeve (18) can be expanded only with temporary increase of the outer diameter of the sleeve (18) and can thus be removed while the anilox layer (22) is destroyed.
2. The method of claim 1, characterised in that the sleeve (18) is axially thrust onto the core (10), while preliminarily widening the sleeve by means of compressed air discharged through openings (14) in the peripheral surface of the core (10).
3. An anilox roller, in particular for a flexographic printing press, comprising a cylindrical core (10) and a sleeve (18) which is detachably held on the core and has at its surface an anilox layer (22) with a grid pattern of pits (24), characterised in that the sleeve consists of an essentially incompressible material which is supported directly on the core (10), and that the sleeve (18) having the anilox layer (22) is removable only with temporary increase of the outer diameter of the sleeve (18) and hence with destruction of the anilox layer (22).
4. The anilox roller of claim 3, characterised in that the sleeve (18) is made of glass fibre-reinforced synthetic resin.
5. The anilox roller of claim 3 or 4, characterised in that the sleeve (18) consists of a single layer of material carrying the anilox layer (22) and, optionally, a primer layer (20) interposed between said single layer and said anilox layer.
6. The anilox roller of any of the claims 3 to 5, characterised in that the wall thickness of the sleeve (18), including the anilox layer (22), is not larger than 10 mm, for a printing width of the anilox roller of 1.5 to 2 m or more.
7. The anilox roller of any of the claims 3 to 6, characterised in that the core (10) is made of carbon fibre-reinforced synthetic resin.
8. A method of recycling an anilox roller obtained by the method according to claim 1 or 2, or an anilox roller of any of the claims 3 to 7, characterised in that the sleeve (18) is withdrawn from the core (10) and, in its place, a new sleeve (18) without anilox layer is thrust onto the core (10), the sleeve (18) consisting of an essentially incompressible material which is supported directly on the core (10), and that, then, a new anilox layer (22) is formed on the new sleeve (18), so that the new sleeve (18) having the new anilox layer (22) can be expanded only with temporary increase of the outer diameter of the sleeve (18) and can thus be removed while the anilox layer (22) is destroyed.

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