Patent ID: 12194734

With reference to the figures, the printing machine according to the invention, generally designated by the reference numeral1, comprises, on a supporting frame, advancement means for advancing material in sheet form2to be printed, formed by a continuous belt, which are provided with at least one traction drum3, which can rotate about its own axis.

In particular, the traction drum3is designed to receive, at an entry region4, the material in sheet form2to be printed and to convey it toward an exit region5, which is arranged circumferentially spaced apart from the entry region4along the direction of rotation of the traction drum3about its own axis, and at which the material in sheet form2finally leaves the traction drum3.

Analog print stations6are arranged around the traction drum3, between the entry region4and the exit region5.

The peculiarity of the invention consists in that it comprises, between at least two of the analog print stations6, conveyance means7for conveying the material in sheet form2to be printed which arrives from the traction drum3along an advancement path that has at least one advancement portion8for moving forward the material in sheet form2to be printed which extends substantially straight.

Also according to the invention, at least one digital print station9is arranged along such advancement portion8.

This solution makes it possible to position the digital print station9in an appendage of the advancement means for advancing or moving forward the material in sheet form, which extends outside the traction drum3so that the digital print station can operate on a substantially straight advancement portion8, with consequent advantages in terms of print quality, and between two analog print stations6which by contrast are arranged along the peripheral region of the same traction drum, with the consequent advantage of ensuring an optimal print registration.

In more detail, the conveyance means7define, for the advancement path of the material in sheet form2that such means provide, at least one outward leg10, which extends from the traction drum3to at least one redirection assembly11for redirecting the material in sheet form2to be printed, which is located in a position laterally spaced apart with respect to the traction drum3, and at least one inward leg12, which, in turn, extends from the redirection assembly11to the traction drum3.

Preferably, the advancement portion8is defined along the at least one outward leg10and extends, advantageously, along a substantially horizontal direction.

As illustrated, the conveyance means7can, for example, comprise at least one redirection roller7a, which makes it possible to redirect the material in sheet form2which arrives from the traction drum3in order to convey it along the outward leg10defined by said conveyance means, and then send it to the digital print station9.

As shown in particular inFIG.3, the redirection roller7acan be covered externally by a layer70that does not adhere to the material in sheet form2, which can be made, for example, of the material commercially known under the TEFLON trademark or another, similar material.

Alternatively, as shown inFIG.4, the redirection roller7acan also be provided by an air blower bar71, constituted by a hollow cylinder, axially fed with air under pressure and provided with a perforated side wall for the outflow of the air, so as to create a gap between the outer surface of the redirection roller7aand the material in sheet form2.

Optionally, as in the example ofFIG.2, the conveyance means7can also comprise a bend roller7bwhich accompanies the material in sheet form2arriving from the inward leg12of the conveyance means, so it adheres once again to the outer surface of the traction drum3.

Advantageously, the redirection assembly11can be provided by one or more redirection rollers11a,11bwhich take the material in sheet form2and convey it from the outward leg10to the inward leg12.

Conveniently, the digital print station9comprises, along the advancement portion8, one or more digital inkjet print heads13which are arranged facing an upward-facing face of the material in sheet form2to be printed and are mutually laterally adjacent along the advancement direction of the material in sheet form2.

Optionally, it is possible to have, at least along the advancement portion8, a vacuum mat16on which the material in sheet form2rests, which makes it possible to prevent unwanted displacements of the material in sheet form2during the application of the inks by the digital print station9.

Conveniently, along the advancement path defined by the conveyance means7, there can be, downstream of the digital print station9, at least one first drying station or station14for the initial drying of the inks, which is constituted, for example, by a drying tunnel.

Preferably, the first drying station14is arranged along the inward leg12of the conveyance means7which returns the material to be printed2to the transfer drum3.

More preferably, according to the embodiments illustrated, along the outward leg10defined by the conveyance means7there is at least one first advancement portion8awhich extends substantially straight and, along the inward leg12, there is at least one second advancement portion8bwhich extends substantially straight. In this case, the digital print station9is conveniently arranged along the above mentioned first advancement portion8aand the first drying station14is arranged along the second advancement portion8b.

It should be noted that both upstream and downstream of the conveyance means7, with respect to the direction of rotation of the traction drum3about its own axis, there can be one or more analog print stations6.

Conveniently, the analog print stations6arranged about the traction drum3can comprise at least one flexographic print station and/or at least one rotogravure print station and/or at least one print station of the “offset” type.

Advantageously, the rotogravure print station can, for example, be arranged directly upstream of the exit region5of the material in sheet form2from the traction drum3, preferably providing, thereat, for the separation of the material in sheet form2to be printed from the traction drum3, in order to allow the passage of the material in sheet form2between the cylinders of the rotogravure print station, as shown inFIGS.1and2.

Advantageously, the analog print stations6can further comprise at least one station for applying at least one layer for the pretreatment of the material in sheet form to be printed, which is arranged upstream of the conveyance means7along the direction of rotation of the traction drum3about its rotation axis. For example, such pretreatment layer can be a primer or a coating adapted to improve the adhesion of the inks that will be applied on the material in sheet form2by the digital print station and/or by the subsequent analog print stations6.

It should be noted that the inks used in the analog print stations6and in the digital print station9can be of the water-based, biological, or solventless type.

Advantageously, along the advancement means of the material in sheet form2, preferably downstream of the exit region5of the material in sheet form2from the transfer drum3, there can be at least one second drying station or station15for the final drying of the inks, which can also be provided by a drying tunnel.

It must be noted that, around the traction drum3and downstream of each analog print station6, preferably between one analog print station6and the subsequent analog print station, in the direction of rotation of the traction drum3, there can optionally be at least one respective hood18for drying the inks. It should be noted that at least one drying hood18can also be provided downstream of the conveyance means7.

The operation of the printing machine, according to the invention, is the following.

The material in sheet form2to be printed is fed by the advancement means to the traction drum3through the entry region4and proceeds, while adhering to the outer surface of the transfer drum3, passing through at least one analog print station6, which can conveniently apply at least one layer of pretreatment on the material in sheet form2that is transiting on the transfer drum3or execute, in general, an analog print, such as for example a flexographic print or a rotogravure print.

Subsequently, the material in sheet form2is picked up from the transfer drum3by the conveyance means7, by way of the redirection roller7a, so as to be conveyed along the outward leg10of the advancement path defined by the conveyance means7in order to be sent to the digital print station9arranged outside the transfer drum3.

In particular, by proceeding along the outward leg10, the material in sheet form2travels the first advancement portion8a, passing through the digital print station9, where it is subjected to a digital printing process.

Once it has exited from the digital print station9, the material in sheet form2arrives at the redirection assembly11which conducts it toward the inward leg12, where it travels the second advancement portion8b, passing through the first drying station14, which makes it possible to execute an initial drying of the inks applied on the material in sheet form to be printed.

Downstream of the drying station14, the material in sheet form2then reaches the traction drum3once again, so as to continue its advancement, while adhering to the outer surface of the traction drum3.

At this point, proceeding in its advancement on the traction drum3, the material in sheet form2passes through the analog print stations6, located downstream of the conveyance means7, which each apply inks of a respective color on the material in sheet form2.

Once it reaches the exit region5, the material in sheet form2is finally removed from the traction drum3to be sent to the second drying station15which carries out the final drying of the inks applied on the material in sheet form2during its advancement from the entry region4to the exit region5of the traction drum3.

In practice it has been found that the invention fully achieves the intended aim and objects by providing a printing machine that is very compact, with respect to traditional hybrid printing machines, by virtue of the presence of the traction drum, and capable of ensuring an optimal quality of digital printing, by virtue of the presence of the conveyance means interposed between the entry region and the exit region of the material in sheet form onto and off the traction drum, which make it possible to execute the digital print on a substantially straight advancement portion of the material in sheet form.

Another advantage of the invention is that it ensures an optimal print registration, with respect to conventional hybrid machines, thanks to the presence of analog print stations arranged in sequence about the traction drum.

Also, the advantage of having analog print stations downstream of the digital print station is that of being able to apply layers of inks or paints or adhesives (cold seal, heat seal and the like) of great thickness at high speed, something that is much more difficult to do using digital technology, in which the inks or paints or adhesives need to be applied with very low viscosity and very long drying ovens are needed in order to reach the same speeds enabled by the invention.

Another advantage of having analog print stations downstream of the digital print station is the uniformity and colorimetry of solid colors, since they can be printed with analog technology in a single print station, unlike digital technology which uses multiple heads to superimpose multiple colors in order to achieve a spot color, with consequent reduction in the times and costs of color matching.

The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

Thus for example, the digital print station9can, alternatively, be implemented with devices using toner or using stream inkjet technology.

It must further be noted that, if EB/UV inks are used, the drying station or stations will be adapted to carry out the polymerization of the inks using the emission of electron beams or UV rays, depending on the type of ink.

In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to the requirements and to the state of the art.

The disclosures in Italian Patent Application No. 102021000024722 from which this application claims priority are incorporated herein by reference.