MANUFACTURED ARTICLES

Technical Field

The present invention relates to a digital printer for the decoration of slabshaped manufactured articles.

Background Art

In the context of the present disclosure, the expression “slab-shaped manufactured articles” means any product of flattened conformation having two dimensions of spatial extension (i.e. width and length) significantly larger than the third dimension (i.e. thickness), regardless of the material (rigid, soft or flexible) composing it.

By way of non-limiting example only, tiles and slabs made of ceramic material, sheets of paper or cardboard and sheets of cloth are considered slab-shaped manufactured articles which can be decorated by means of the present invention.

In the field of ceramic manufacturing, for example, there has always been a need to decorate the visible face of the slab- shaped manufactured articles for mainly aesthetic purposes.

This practice is also linked to the need of the ceramic industries to produce floor and wall tiles and slabs that are as different as possible from the competition and that best meet the aesthetic standards required by customers.

Specifically, the decoration of slab- shaped manufactured articles consists of applying pigments to the visible face of the tiles, made of unfired or partly fired ceramic material, which are then completely and definitively stabilized by firing in a kiln.

The decoration of the slab- shaped ceramic manufactured articles can be carried out using various methods and, currently, the use of digital printers is widespread.

The decoration of slab- shaped ceramic manufactured articles using digital printers involves the application of special ceramic inks, which consist of mixtures of powdered dyes (mineral oxides, or metal oxides, or metals with complex structures), with a very fine grain size, suspended in a special solvent or other carrier.

The digital printers for the decoration of tiles made of ceramic material of known type usually comprise a plane of forward movement on which the ceramic manufactured articles to be decorated move forward and a plurality of printing heads facing the plane of forward movement and provided with nozzles dispensing the ceramic ink on the visible face of the ceramic manufactured articles.

The plane of forward movement is usually composed of a conveyor belt which is moved along a substantially horizontal direction thanks to pulleys or motor- driven rollers.

In this way, the slab- shaped ceramic manufactured articles are moved underneath the printing heads during ceramic ink dispensing.

The printing heads spray ceramic ink onto the visible face of the slab- shaped ceramic manufactured articles according to a previously established pattern.

The printing heads are mounted on top of the plane of forward movement in a fixed position so as to cover the entire width of the plane of forward movement and be able to decorate the slab- shaped ceramic manufactured articles of any size, according to an operating mode commonly known as “single pass”.

The traditional digital printers do, however, have some drawbacks, comprising the fact that the routine and extraordinary maintenance operations are particularly difficult.

The printing heads are, in fact, usually mounted on a holding bar placed on top of the plane of forward movement at a distance of a few centimeters from the plane itself.

The space to carry out any replacement operations of the heads is therefore very limited and involves a considerable complication also for the execution of capping operations, i.e. the covering of the unused heads with a covering cap designed to prevent the nozzles from drying out.

In this regard, it should be pointed out that the replacement operations of the printing heads and/or the capping operations are quite frequent, since they are to be carried out not only to adjust or clean any heads that are not perfectly functional but also to modify the printing area, i.e. the number and arrangement of the printing heads, which may vary depending on the size of the slab-shaped ceramic manufactured articles to be decorated; therefore, each time the size of the tiles in production is changed, it may be necessary to intervene on the printing heads.

To at least partly overcome these drawbacks, some digital printers have all the printing heads mounted on a sliding drawer; when maintenance/capping operations are required, the drawer is removed from the machine taking the printing heads with it, allowing them to be replaced and/or cleaned and/or capped more easily.

Even in this case, however, the traditional digital printers suffer from serious drawbacks including the fact that the maintenance/capping operations inevitably lead to the shutdown of the printer and therefore of the entire plant for the manufacture of slab-shaped ceramic manufactured articles, with a consequent increase in overall production costs.

In addition, the increase in manufacturing costs is inevitably transferred onto the retail price, with the risk of making the products less attractive to customers. Similar problems for printing on the slab- shaped manufactured articles also occur in sectors other than ceramic manufacturing, such as e.g., in the sector of printing on paper and cardboard and printing on fabric and textiles.

Description of the Invention

The main aim of the present invention is to devise a digital printer for the decoration of slab-shaped manufactured articles, which allows carrying out in a practical, easy and functional manner the maintenance and/or capping operations of the printing heads.

A further object of the present invention is to devise a digital printer for the decoration of slab-shaped manufactured articles which allows avoiding stopping the manufacturing plant or at least reducing the downtime thereof.

Last but not least, the object of the present invention is to devise a digital printer for the decoration of slab-shaped manufactured articles which allows lowering the production costs and the retail price of the finished products.

Another object of the present invention is to devise a digital printer for the decoration of slab-shaped manufactured articles which allows the mentioned drawbacks of the prior art to be overcome within a simple, rational, easy and effective to use as well as affordable solution.

The aforementioned objects are achieved by the present digital printer for the decoration of slab-shaped manufactured articles having the characteristics of claim 1.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of a digital printer for the decoration of slab-shaped manufactured articles, illustrated by way of an indicative, yet non-limiting example, in the accompanying tables of drawings wherein:

Figure 1 is an axonometric view of the printer according to the invention;

Figure 2 is a side view of the printer according to the invention;

Figure 3 is an axonometric view, on an enlarged scale, of a detail of the printer according to the invention;

Figure 4 is a plan view of a detail of the printer according to the invention, working according to a first operating mode;

Figure 5 is a plan view of a detail of the printer according to the invention, working according to a second operating mode.

Embodiments of the Invention

With particular reference to such figures, reference numeral 1 globally indicates a digital printer for the decoration of slab-shaped manufactured articles.

The digital printer 1 is particularly configured to decorate large- size slab- shaped manufactured articles M (e.g. with sides longer than 2 m), but can also be used to work with smaller sizes.

The digital printer 1 comprises at least one basic frame 2, for the support onto the ground, with which at least one line of forward movement 3 of the slabshaped manufactured articles M is associated.

The line of forward movement 3 is adapted to move the slab- shaped manufactured articles M along a direction of forward movement A.

Advantageously, the line of forward movement 3 defines a substantially horizontal plane of forward movement on which the slab- shaped manufactured articles M rest and move forward along the direction of forward movement A, which is also substantially horizontal.

In more detail, the line of forward movement 3 consists, e.g., of a conveyor belt. The digital printer 1 comprises at least one supporting set 4 associated with the basic frame 2 in a liftable and lowerable manner with respect to said line of forward movement 3.

For this purpose, the basic frame 2 comprises a pair of vertical uprights 5 along which the supporting set 4 is engaged in a sliding manner.

Conveniently, the digital printer 1 comprises automatic means of fine adjustment, not shown in detail in the figures, which adjust the lifting and lowering of the supporting set 4 depending on the thickness of the slab-shaped manufactured articles M.

In actual facts, for the decoration of particularly thin slab-shaped manufactured articles M (e.g. with a thickness of 4 mm), the supporting set 4 is placed in the proximity of the line of forward movement 3; for the decoration of thick slabshaped manufactured articles M (e.g. with a thickness of 2 cm), on the other hand, the supporting set 4 is placed at a greater distance from the line of forward movement 3.

The automatic means of fine adjustment consist, e.g., of a micrometer- controlled electric motor or other similar system.

The supporting set 4 is associated with at least one guidance unit 6 arranged at least partly on top of the line of forward movement 3 and defining a movement path Pl, P2, P3, P4.

A plurality of printing sets 7 is mounted on the guidance unit 6, which printing sets are movable in a sliding manner along the movement path Pl, P2, P3, P4, individually and independently of each other, between at least one working position, wherein the printing sets 7 are arranged on top of the line of forward movement 3 for the dispensing of ink on the slab- shaped manufactured articles M, and at least one home position.

Advantageously, the guidance unit 6 is shaped in a closed loop, the printing sets 7 being movable on the guidance unit 6 in a circular pattern.

In other words, the printing sets 7 may move along the movement path Pl, P2, P3, P4, which is also shaped in a closed loop, either in one direction of travel or in the opposite direction.

This conformation is particularly advantageous to allow the printing sets 7 to be rotated in the working position.

Since, in fact, each printing set 7 is movable individually and independently of the others, it is possible to place in the working position all and only the printing sets 7 necessary to cover the printing area determined by the size of the slab-shaped manufactured articles M being processed, as will be described in more detail below.

In the particular embodiment shown in the figures, the movement path Pl, P2, P3, P4 is shaped like an “O” and extends along a first straight stretch Pl and a second straight stretch P2, arranged along horizontal directions which are parallel to each other and orthogonal to the direction of forward movement A, and along a first curvilinear stretch P3 and a second curvilinear stretch P4, which join together the straight stretches Pl, P2.

Both straight stretches Pl, P2 are arranged on top of the line of forward movement 3 and both curvilinear stretches P3, P4 protrude beyond the line of forward movement 3.

In the working position, the printing sets 7 are placed at the first straight stretch Pl.

The guidance unit 6 comprises at least one linear magnetic motor device 8 provided with a plurality of movable sliders 9 on which the printing sets 7 are mounted.

The linear magnetic motor 8, in actual facts, consists of an electric motor wherein the rotor and the stator, instead of being circular, are deployed along a linear direction and, instead of generating a mechanical torque, produce a force. The linear magnetic motor device 8 is, e.g., integrated along the guidance unit 6 and the movable sliders 9 to produce a magnetic field capable of setting the movable sliders 9 in motion, as well as the printing sets 7 mounted thereon, along the guidance unit 6 and blocking them in the desired positions.

The adjustment of the movement and of the blocking of the movable sliders 9 is micrometric, i.e. the linear magnetic motor device 8 is adapted to position the movable sliders 9 and the printing sets 7 along the guidance unit 6 with precision.

Conveniently, a printing set 7 is provided for each movable slider 9.

Each movable slider 9 comprises lifting and lowering means 10 of a respective printing set 7.

In actual facts, each printing set 7 can be individually lifted with respect to the guidance unit 6.

The lifting and lowering means 10 comprise, e.g., a pneumatic actuator mounted on each movable slider 9 and associated with the respective printing set 7.

Each pneumatic actuator is adapted to move the respective printing set 7 between two extreme positions, namely a lowered position and a lifted position. At least one of the printing sets 7 comprises a plurality of printing heads 11 provided with nozzles 12 oriented along a printing direction B substantially orthogonal to the direction of forward movement A.

This first type of printing sets 7 allows the digital printer 1 to operate according to a first operating mode of the “single pass” type shown in Figure 4, wherein a plurality of printing sets 7 made according to the first type and intended to remain stationary during the passage of the slab-shaped manufactured articles M are placed in the working position.

The number of printing sets 7 placed in the working position depends on the size of the slab- shaped manufactured articles M, so that a printing area covering the entire extent of the slab- shaped manufactured articles M is defined.

In combination with, or as an alternative to the first type of printing sets 7 just described, a second type may be provided wherein at least one of the printing sets 7 comprises a plurality of printing heads 11 provided with nozzles 12 oriented along a printing direction C substantially parallel to the direction of forward movement A.

This second type of printing sets 7 allows the digital printer 1 to operate according to a second operating mode of the “scanning” type shown in Figure 5, wherein a single printing set 7 made according to the second type and intended to be moved back and forth along the guidance unit 6 during the passage of the slab-shaped manufactured articles M is placed in the working position.

By means of the first operating mode (“single pass”) it is possible to obtain faster printing.

By means of the second operating mode (“scanning”), prints with higher resolution and image quality can be obtained.

Regardless of the type and mode of operation, the nozzles 12 of the printing heads 11 are electronically controlled to dispense ink only when and where it is necessary.

The printing sets 7 are mounted cantilevered with respect to the movable sliders 9 and have all the nozzles 12 facing downwards.

Advantageously, the home position comprises a capping station 13.

In combinations with, or as an alternative to the capping station 13, the home position comprises a maintenance station 14.

Preferably, the digital printer 1 comprises at least two home positions, wherein at least one of the home positions comprises a capping station 13 and at least one of the home positions comprises a maintenance station 14.

In the particular embodiment shown in the figures, the digital printer 1 comprises two home positions, with a capping station 13 and a maintenance station 14.

Alternative embodiments of the present invention cannot however be ruled out wherein only one home position is present or three or more home positions are present.

The capping station 13 consists, e.g., of a bedplate 15 mounted cantilevered on the supporting set 4 on top of the line of forward movement 3 and vertically movable together with the guidance unit 6.

The bedplate 15 has a substantially horizontal conformation and defines a supporting plane for the printing sets 7.

Since the nozzles 12 of the printing heads 11 are facing downwards, when a printing set 7 rests on the bedplate 15, the nozzles 12 thereof are automatically closed and they are prevented from drying out.

The bedplate 15 is arranged at a higher height (i.e., at a distance from the line of forward movement 3) than the height of the printing sets 7 when in the lowered position and lower than the height of the printing sets 7 when in the lifted position.

In actual facts, when the printing sets 7 are placed in the working position, the lifting and lowering means 10 are lowered to arrange the printing heads 11 in the proximity of the line of forward movement 3 (e.g. a few mm away) and to improve the quality of the printing.

When, on the other hand, the printing sets 7 are to be placed in the capping station 13, then the lifting and lowering means 10 are raised, to enable the printing sets 7 to be raised above the height of the bedplate 15, then the printing sets 7 are moved along the guidance unit 6 until they are placed on top of the bedplate 15, and finally the lifting and lowering means 10 are lowered until the printing sets 7 are placed on the bedplate 15.

Advantageously, the capping station 13 is arranged at the second straight stretch P2 of the movement path Pl, P2, P3, P4.

The maintenance station 14 consists, e.g., of an equipped workstation 16 associated with the basic frame 2, at which an operator O may carry out maintenance operations, when required.

At the equipped workstation, the lifting and lowering means 10 are useful to place the printing sets 7 in the raised position (e.g. at man height) and to facilitate the interventions by the operator O.

Advantageously, the maintenance station 14 is arranged at the first curvilinear stretch P3 of the movement path Pl, P2, P3, P4.