The present invention concerns a process for manufacturing a metering roll especially usable in flexographic printing presses, in varnish stations for offset presses and/or in short ink train dry offset presses for example, comprising a central cylindrical core and at least one layer of a hard material peripheral coating.

The present invention concerns also a metering roll, especially usable in flexographic printing presses, in varnish stations for offset presses and/or in short ink train dry offset presses for example, comprising a central cylindrical core and at least one layer of a hard material peripheral coating, obtained by this process.

Background Art

The metering rolls, so-called "anilox rolls" are widely used to bring a metered quantity of ink to the plate roll with which it is in contact. The surface layer of the peripheral coating is usually ceramic or metal or a metallic component or alloy, as a metal oxide or carbonate for example. This layer is engraved, mainly by use of a laser beam. For a new use of an existing used anilox roll, it has to be refurbished and the prior art technology to refurbish such an anilox roll consists in the following steps:

(a) A first step consisting in removing the old coating by mechanical methods, like grinding, blasting. This operation is complicated and time- consuming because the coating is made of a hard material not easy to remove. (b) A second step consisting in applying a new coating on the turned or grinded and corundum-blasted surface of the anilox roll.

(c) A third step of grinding and polishing the new coating with diamond bands or similar to obtain a perfectly cylindrical and smooth surface.

(d) A fourth step of engraving the new coating with a laser or suitable mechanical tools.

This technology is very cost-effective. Disclosure of Invention

The process of the invention offers a new technology permitting to refurbish the anilox rolls much more easily, more quickly and at lower costs.

This invention is preferably based on an idea of improving the usual process for manufacturing a metering roll, so-called "anilox roll". It is also based on the aim to reduce the number of steps and simplify the operations and consequently decrease the cost to refurbish used metering rolls.

Therefore, the process of the present invention such as defined in the preamble is characterized in that it comprises at least a first step of melting superficially at least partially the hard material coating, a second step of solidifying said melted hard material, and a third step of engraving the said solidified layer of hard material. According to a preferred realization the first step consists in melting a superficial layer of a rough coating of hard material located on the cylindrical core of a new metering roll to provide a flat smooth surface without any unevenness ready to be engraved. According to another realization the first step consists in melting at least partially the hard material coating of a used metering roll at a depth sufficient to remove any unevenness of the surface to provide a flat smooth surface without any unevenness ready to be engraved.

The first step may be performed preferably by a laser beam. According to an alternative solution, the first step may be performed by a plasma torch.

Said hard material coating obtained during the second step comprises preferably at least a ceramic, at least a metal or at least a metallic component. The third step is preferably performed with at least one laser beam, or a similar technology.

The metering roll such as defined in the preamble is characterized in that said coating comprises a superficially and at least partially melted and solidified layer presenting a flat surface layer without any unevenness, said flat surface being engraved.

According to a first application, said coating is a rough material deposited on said cylindrical core of a new metering roll.

According to a second application, said coating is a superficial layer of a used metering roll, said layer being obtained by melting at least partially a previously engraved coating at a depth sufficient to remove the existing engraving. Brief Description of Drawings

The invention will now be described, by way of an example, with reference to the accompanying drawings, in which :

Figure 1 is a cut view showing partially the surface of an anilox roll to be refurbished according to the process of the present invention, Figure 2 is a similar view as in figure 1 , showing a layer of the melted hard material according to one step of the process of the present invention, and

Figure 3 is a similar view as in figures 1 and 2, showing a new layer of the hard material engraved according to a further step of the process of the present invention.

Mode for Carrying Out the Invention

The process of the invention may be used as well for manufacturing new metering rolls as for refurbishing used metering or so-called anilox rolls. For the first application, the process permits to modify the properties of the peripheral coating, especially the surface tension, the porosity, the hardness. For the second application the process permits to reduce the costs of a life extension of the used metering rolls. Further it is also possible to modify the properties of the coating like for new rolls.

According to the process of the invention, the steps for refurbishing used anilox rolls are the following :

(1) The existing hard material surface coating in ceramic, hard metal or hard metal components is melted to a depth sufficient to remove the engraving.

This operation may be done with a focused laser beam.

(2) The melted hard material solidifies and forms a flat surface free of engraving.

(3) The hard material coating can be engraved again with a laser beam within the re-melted zone.

Figure 1 shows partially the surface of a so-called anilox roll 10 to be refurbished according to the process of the invention. It comprises a central cylindrical core 11 and at least one layer 12 of a hard material peripheral coating. In the drawing only one layer is shown, but the coating could be formed of a plurality of different layers having each another composition and/or properties. The outer part 13 of the layer 12 is engraved, preferably by use of a laser beam (not shown).

Figure 2 shows the anilox roll 10 with a part 14 of the coating of hard material 12, including the engraved outer part 13, melted by a laser beam 5, on a thickness that is deeper than the depth of the existing textured layer 13.

Figure 3 shows the anilox roll 10 having a melted and solidified layer 16 of a hard material recovering the coating 12 and being provided with a new engraving 17 made by at least one laser beam.

This process according to the invention permits to withdraw the steps (a) to (c) of the prior art technology commonly used for refurbishing anilox rolls. Relating to the manufacture of new metering rolls according to the usual process the hard material structured surface is realized in at least three steps: a first step consisting in applying a rough layer of a hard material, a second step consisting in grinding and polishing the surface of the rough layer of hard material, i.e. by diamond bands, and

- a third step of engraving the polished surface with a laser beam.

According to the process of the invention, the grinding and polishing as a second step should be replaced by laser melting and smoothening of the hard material that solidifies and forms a smooth and flat surface. Jn any case, the steps of grinding and polishing with diamond bands or similar will be saved. The physical properties, i.e. the mechanical resistance or other specifications may be adapted to special applications of the metering rolls by choosing the appropriate hard material and laser parameter settings. Finally the densified and smoothened hard material coating can be engraved with a laser beam.