WO2009044319A2

WO2009044319A2 - Controlling the funtioning of decorating machines

Info

Publication number: WO2009044319A2
Application number: PCT/IB2008/053928
Authority: WO
Inventors: Antonio Maccari
Original assignee: Antonio Maccari
Priority date: 2007-10-03
Filing date: 2008-09-26
Publication date: 2009-04-09
Also published as: WO2009044319A3; ITMO20070302A1

Abstract

A measuring device comprises a plate-shaped support base (10) supporting force sensor means (12), the force sensor means (12) being suitable for measuring a force exerted by a decorating device (2) for decorating ceramic items (4). Furthermore, the are disclosed a test device, a controlled motor- driver pump and a decorating device.

Description

Methods and Devices for Controlling a Functioning of Decorating

Machines

Technical Field

The invention regards methods and devices for controlling a functioning of decorating machines, in particular for measuring the operating parameters of decorating machines for decorating ceramic tiles. Decorating machines, functioning such as to be controllable with the methods and devices of the invention, can exhibit application rollers, for example rollers with an external layer of silicone material. The methods and devices of the invention can be used to correctly set the parameters of a decorating machine before the decorating machine begins operating, or to periodically verify the operation of a decorating machine and, if necessary, implement adjustments that enable high quality decoration to be achieved. Background Art

Known art includes decorating machines for decorating ceramic tiles, comprising a conveyer line including at least one conveyor belt, which advances the tiles in an advance direction. Along the line a plurality of printing units are arranged, each printing unit including an applying roller for applying a ceramic glaze of predefined colour on the ceramic tiles. The applying rollers can operate according to any printing method, but the applying rollers that are most commonly used in the ceramics field function using a gravure printing method. In this case, each applying roller is provided with a plurality of cavities on its external surface, the cavities being designed to receive the ceramic glaze and subsequently transfer it to a ceramic tile. A doctor blade makes it possible to fill each cavity with an appropriate quantity of ceramic glaze and to keep clean the portions of the external surface of the roller inteiposed between two adjacent cavities. Certain conditions have to be maintained during operation in order that the decorating machine can produce high quality and repeatable tile decorations.

In particular, the longitudinal axis of each applying roller should be substantially perpendicular to the advance direction of the conveyor belt.

Furthermore, the longitudinal axis of each applying roller should be substantially parallel to the conveying plane defined by the surface of the conveyor belt whereon the tiles to be decorated are supported.

It is desirable that the applying roller rolls in contact with the tile without dragging.

The pressure exerted on the tile by the applying roller must also be appropriate to the case.

The ceramic glaze must have a viscosity within a predetermined range. The viscosity of the ceramic glaze must remain constant for the entire period of decoration.

Finally, the inclination of the doctor blade relative to the applying roller and the pressure exerted by the doctor blade on the applying roller are also critical and must be maintained within a predetermined ranges.

A defect of the decorating machines of known art is the impossibility of precisely determining whether the operating conditions referred to above are respected with precision. As a consequence, currently operators assess whether the decorating machine is operating well by visually examining the machine and the tiles. When an operator notices that the decorating machine is not operating appropriately, the required adjustment operations are carried out on an entirely empirical basis and by trial and error.

As a consequence relatively long stoppages of the decorating machine are necessaiy while the above mentioned operating parameters are suitably adjusted. This slows productivity and reduces repeatability of results.

Further, while some operators, on the basis of personal experience, are able to correctly adjust a decorating machine and achieve good quality tile decorations, inexpert operators are sometimes incapable of establishing the correct operating conditions. If this occurs, poor quality tiles are produced which then have to be disposed of or sold at a reduced price.

An object of the invention is to improve the apparatuses and methods for decorating ceramic items, in particular ceramic tiles, enabling achievement of high quality decorations.

A further object of the invention is to provide methods and devices that make it possible to measure with precision the operating parameters of decorating machines.

A further object of the invention is to enable adjustment of the operating parameters of decorating machines in a simple and repeatable way, reducing the time required for adjustments. A further object of the invention is to enable inexpert operators to quickly and accurately adjust decorating machines.

Another object of the invention is to monitor the process of decorating ceramic items, in particular ceramic tiles.

In a first aspect of the invention, there is provided a method for measuring at least one operating parameter of a decorating machine for ceramic items, the method comprising the steps of: positioning a measuring device comprising force sensor means in contact with a decorating device; measuring the force exerted by the decorating device on the force sensor means. The method according to the first aspect of the invention enables precise determination of the force exerted by the decorating device on the force sensor means. The force measured in this way enables calculation of the force exerted by the decorating device on the ceramic item during the operation of the decorating machine. In one embodiment, the method comprises a step of comparing the force values measured by two distinct sensor elements of the force sensor means along an axis of the decorating device, thereby determining whether the axis of the decorating device is parallel to a support surface supporting the measuring device. In a second aspect of the invention, there is provided a measuring device comprising a plate-shaped support base supporting force sensor means, the force sensor means being suitable for detecting the force exerted by a decorating device for ceramic items. The first and second aspects of the invention enable precise measurement of the operating parameters of the decorating machine, including the pressure exerted by the decorating device on the ceramic item. It is also possible to determine whether the axis of the decorating device is parallel to, or inclined relative to an underlying support surface, for example the support surface of a conveyor belt. The results obtained with the method and device of the first two aspects of the invention can be used to determine whether the decorating machine can function correctly and, if this is not the case, provide useful information for carrying out adjustments on the decorating device.

Using the results obtained with the method and device of the first two aspects of the invention it is also possible for inexpert operators to carry out adjustment operations quickly and with a high degree of repeatability.

In a third aspect of the invention, there is provided a test device for assessing a possible difference in speed between a conveyor and a decorating device of a machine for decorating ceramic items, the test device comprising a first part suitable for being positioned in contact with the conveyor and a second part suitable for being positioned in contact with the decorating device, the first part and the second part being free to move relative to each other in at least one direction, detector means being interposed between the first part and the second part for detecting if the first part and the second part move relative to each other. In a fourth aspect of the invention, there is provided a method for assessing whether there is a difference in speed between a conveyor and a decorating device of a machine for decorating ceramic items, the method comprising the steps of: positioning a first part of a test device in contact with the conveyor, such that the conveyor moves the first part; positioning a second part of the test device in contact with the decorating device, such that the decorating device moves the second part; detecting whether the first part and the second part move relative to each other. The third and fourth aspects of the invention enable effective and reliable determination of whether the conveyor and the decorating device move at the same speed, or sufficiently similar speed, or whether there is excessive difference between the speeds of the conveyor and decorating device. In the case of excessive difference of speeds, the ceramic items and the decorating device slide relative to each other. This implies that the decorations applied to the ceramic items may exhibit defects including reduced resolution or imperfect superimposition of different glazes.

It is noted that the test device and the method of the third and fourth aspects of the invention enable automatic assessment of whether there is a difference in speed between the conveyor and the decorating device, such as to significantly reduce, or even eliminate, the risk of errors by the operator, even in the case of inexpert operators.

In a fifth aspect of the invention, there is provided an apparatus comprising a pump for conveying a fluid towards an applicator device, the applicator device being suitable for applying the fluid on an object, motor means for supplying power to the pump so as to drive the pump at a driving speed, characterized in that it comprises control means for recording a possible variation in the power required for keeping the driving speed substantially constant. In a sixth aspect of the invention, there is provided a method comprising the steps of: conveying a fluid towards an applicator device by means of a pump, the applicator device being suitable for applying the fluid on an object; supplying power to the pump so as to drive the pump at a driving speed; detecting a possible variation in the power required to maintain the driving speed substantially constant, said possible variation being indicative of a change in viscosity of the fluid. The fifth and sixth aspects of the invention make it possible to establish whether changes occur in the physical properties, in particular the viscosity, of the fluid. If for example the viscosity of the fluid diminishes, the power needed by the pump to maintain the driving speed constant diminishes, this being particularly useful for monitoring the viscosity of a glaze in a decorating machine for decorating ceramic items.

In a seventh aspect of the invention, there is provided a method comprising the steps of: printing a first pair of reference marks on a ceramic item, by means of a first decorating device; applying to the ceramic item a second pair of reference marks, by means of a second decorating device, the reference marks of at least a pair selected from either the first pair or the second pair being asymmetrical relative to each other; comparing, on the ceramic item, the position of each reference mark of the first pair and the position of the corresponding reference mark of the second pair. In an eighth aspect of the invention, there is provided a decorating device for ceramic items, comprising a decorating surface at least partially arranged around a longitudinal axis, the decorating surface having a register mark and a further register mark arranged in sequence along the longitudinal axis for assessing if the decorating device is in register, characterized in that the register mark is asymmetrical relative to the further register mark.

The asymmetric register marks, which print asymmetric reference marks on ceramic items, make it possible to distinguish, without error, the end of the decorating device positioned near the operator, and the end of the decorating device positioned near the machine frame. This reduces the possibility of errors by the operator when assessing print alignment. In a ninth aspect of the invention, there is provided a method comprising the steps of: comparing a first area printed by a decorating device with a second area printed by the decorating device, the second area being printed a period of time after the printing of the first area; assessing whether the second area differs from the first area, in order to determine whether at least one parameter of a decorating process carried out by the decorating device has changed during the period of time.

Establishing that the second area has a different appearance from the first area implies that at least one parameter of the decorating process has changed, for example: the inclination or pressure of a doctor blade of the decorating device, the viscosity of a glaze applied by the decorating device, the colour of a glaze or the base colour of a ceramic item decorated by the decorating device. This is indicative of an operating fault that requires further investigation to determine with precision which parameter has changed. If instead the second area is substantially the same as the first area, the decorating process has remained substantially unchanged and production may continue as normal.

Disclosure of Invention The characteristics of the invention will better emerge from with reference to the accompanying drawings, illustrating embodiments of the invention by way of non-limiting examples, in which:

Figure 1 is a schematic lateral view of a decorating machine for decorating ceramic items, in particular ceramic tiles; Figure 2 is a schematic perspective view, enlarged and interrupted, illustrating a measuring device near a first decorating device of the machine of Figure 1; Figure 3 is a schematic plan view of the measuring device of Figure 2, associated to an electronic processor;

Figure 4 is a schematic exploded view of a test device for measuring the difference in speed between a decorating device and a conveyor of the machine of Figure 1;

Figure 4a is a view like that of Figure 4, showing a test device in an alternative embodiment;

Figure 5 is an interrupted schematic lateral view of the test device of Figure 4 during use; Figure 6 is a schematic lateral view of a test device like that of Figure 4, in an alternative embodiment;

Figure 7 is a schematic lateral view of a test device like that of Figure 4, in a further alternative embodiment;

Figure 8 is a schematic plan view of a test device like that of Figure 4, in a still further alternative embodiment;

Figure 9 is a lateral view, partially in cross-section, of the test device of

Figure 8;

Figure 10 is a layout for an apparatus for measuring the viscosity of a ceramic glaze used for decorating ceramic items, for example ceramic tiles; Figure 11 is a graph illustrating variation of the supply voltage to a motor of the apparatus of Figure 10;

Figure 12 is an interrupted schematic view of a portion of decorating machine like that of Figure 1, highlighting a plurality of register marks of two applying rollers of the decorating machine; Figure 13 shows the reference marks printed on a test tile by the register marks of Figure 12 in optimum operating conditions; Figure 14 shows the reference marks printed on a test tile by the register marks of Figure 12 in non optimum operating conditions; Figure 15 shows an applying roller suitable for being fitted on the decorating machine of Figure I₅ provided with a plurality of register marks; Figure 16 shows two zones printed by the applying roller of Figure 15, in two successive operating moments separated in time.

Figure 1 illustrates a decorating machine 1 for applying a decoration on a surface 3 of a ceramic item, for example a ceramic tile 4. The decorating machine 1 comprises a plurality of decorating devices 2 each arranged for applying a decorating substance, for example a ceramic glaze, on the surface 3 of the tile 4. The decorating devices 2 are arranged in sequence along a conveyor 5 which moves the tiles 4 in an advance direction F. Each decorating device 2 comprises an applying roller 6 rotatable around its longitudinal axis so as to interact, during rotation, with the surface 3 of the tile 4 moving on the conveyor 5, and apply a corresponding ceramic glaze on the tile 4, in a predetermined decorative pattern. Each applying roller 6 can comprise a substantially rigid hollow central core, for example made of a metallic material. Outside the central core is an intermediate spongy layer covered by an external layer made of deformable elastic material, for example silicone or polyurethane.

In the illustrated example, the decorating devices 2 are gravure devices of known type. Each applying roller 6 has an external surface 7 on which a plurality of cavities are formed, the cavities being arranged according to the required decorative pattern to be applied to the tile 4. A doctor blade 8 distributes the ceramic glaze inside the cavities and maintains the zones of the external surface 7 between the cavities clean. In a version (not illustrated), the decorating devices 2 might not be of gravure type. For example each decorating device 2 could be flexographic, offset, or screen printing type. Furthermore, in place of the applying roller 6 it is possible to use a belt wound on a pair of pulleys to apply the ceramic glaze to the tiles 4.

During decoration the tiles 4 are moved by the conveyor 5 in the advance direction F so as to interact in succession with all the applying rollers 6, each of which prints a corresponding decorative pattern on the surface 3. The combination of the decorative patterns applied by each applying roller 6 forms the final decoration on the tile 4.

Figures 2 and 3 illustrate a measuring device 9 for measuring at least one operating parameter of the decorating machine 1. The measuring device 9 can be used in particular for measuring the pressure exerted by each applying roller 6 on the tiles 4 and for determining whether the applying rollers 6 exhibit longitudinal axes that are substantially parallel to a plane defined by the conveyor 5.

The measuring device 9 comprises a support base 10 shaped as a plate and having a thickness S. The support base 10 in the majority of cases has a square or rectangular shape, though there might also be other shapes. The support base 10 is made of a metallic material, for example steel or aluminium, previously ground, to ensure high dimensional and geometric precision. Sensor means, comprising at least one force sensor 12, are fitted on an upper surface 11 of the support base 10. In the illustrated example a plurality of force sensors 12 are provided, arranged approximately along a straight line L. The straight line L can be substantially parallel to an edge 13 of the support base 10. The use of at least two force sensors 12 is recommended, positioned in two opposite end zones of the support base 10. The force sensors 12 can be sensors of known type, having, for example, an electrical resistance that varies in relation to the applied force. In particular, the electrical resistance of the force sensors 12 can be inversely proportional to the applied force. In a version, the force sensors 12 can comprise load cells.

The force sensors 12 can be glued to the upper surface 11 of the support base 10, or housed in corresponding seats formed in the support base 10. The seats exhibit a limited depth considering that the force sensors 12 are of very limited thickness, typically in the order of a few tenths of a millimetre. In particular, the force sensors 12 can be substantially flat.

Above the force sensors 12 a layer of protective material may be present, for example in the form of a film, to prevent the force sensors 12 from becoming soiled or damaged during use. Departing from each force sensor 12 is at least one connection wire 14 connected to an electronic board 15 on which a control circuit is mounted. The control circuit receives signals from the force sensors 12 and transmits them, for example through a wireless connection 16, to an electronic processor 17. The wireless connection 16 can be of a radio type, for example Wi-Fi, Bluetooth, ZigBee, or of an optical type, or of another type. The measuring device 9 can be used in either dynamic or static conditions. In the first case the support base 10 is positioned on the decorating machine 1 like a normal tile 4, by resting a lower surface of the support base 10 on the conveyor 5, the lower surface being opposite to the upper surface 11 provided with force sensors 12. The straight line L along which the force sensors 12 are arranged is transverse to the advance direction F. The conveyor 5 enables the support base 10 to be advanced along the advance direction F.

Figure 2 illustrates a configuration in which the support base 10 is about to begin interacting with the applying roller 6a of the first decorating device in the sequence of decorating devices 2 arranged along the conveyor 5. Subsequently the support base 10, moved by the conveyor 5, reaches a measuring position in which the force sensors 12 are located below the applying roller 6a. The applying roller 6a was previously positioned at a distance Dl from the conveyor 5 which distance is less than the thickness S of the support base 10. For example, the distance Dl between the applying roller 6a and the support base 10 can be equal to the thickness S of the support base 10 reduced by a predefined quantity Xl. Thus the applying roller 6a is compressed by the quantity Xl by the support base 10 and exercises on the base a corresponding force. When the support base 10 passes below the applying roller 6a, the force sensors 12 interact with surface zones of the applying roller 6a, the surface zones being arranged parallel to a longitudinal axis X of the roller. The force sensors 12 are thus able to measure the force applied by the applying roller 6a at a plurality of points arranged along a generating line of the applying roller 6a.

The values measured by the force sensors 12 are recorded in a memory of the electronic board 15 or transmitted, by the wireless connection 16, to the electronic processor 17, which, using appropriate software, can calculate the pressure applied by the applying roller 6a to each force sensor 12. This pressure is indicative of the pressure that the applying roller 6a exercises on the tiles 4 during the decorating process. Subsequently, the position of the applying roller 6a relative to the conveyor 5 is modified. For example, the applying roller 6a is positioned at a distance D2 from the conveyor 5 which is equal to the thickness S of the support base 10 reduced by a further predetermined quantity X2, differing from the predetermined quantity Xl. The further predefined quantity X2 corresponds to the compression exerted by the support base 10 on the applying roller 6a in the modified position. By passing the support base 10 under the applying roller 6a again, the force applied by the force sensors 12 is measured when the applying roller 6a is at the distance D2 from the conveyor 5. Using the force values measured, corresponding with the quantities Xl and X2, and possibly corresponding with other different compressions, it is possible to determine a correlation between the quantity that an applying roller 6a is compressed and the force exerted by the roller. This correlation permits, during the operation of the decorating machine, to position the applying roller 6a so as to exert the desired force on the ceramic tiles 4.

In particular, if ceramic tiles 4 of known thickness are to be decorated, and the optimum force that the applying roller 6 should exert on the ceramic tiles 4 is known, the correlation, determined as described above, between the quantity by which the applying roller 6a is compressed and the force exerted by the same applying roller 6a makes it possible to establish the distance from the conveyor 5 at which the applying roller 6a must be positioned to apply the optimum force on the ceramic tiles 4.

The software memorized in the electronic processor 17 can directly calculate the ideal distance between the applying roller 6a and the conveyor 5. The measurement described above with reference to the first applying roller 6a can be repeated for all the applying rollers 6 arranged along the conveyor 5, thereby measuring the respective printing pressures. In this way it is possible to compare the pressure applied by each applying roller 6 in order to ensure that all the applying rollers 6 act on the tiles 4 in a substantially uniform manner.

The processing, by numeric interpolation of the temporal sequence of the readings of the force sensors 12, also permits calculation of the angular position of the applying roller 6a relative to the measuring device 9. The measuring device 9 allows to determine whether the longitudinal axis X of the applying roller 6a, or any other applying roller 6, is parallel to the plane along which the tiles 4 move, this plane being defined by the upper section of the conveyor 5. This can be achieved by comparing the force measured by two force sensors 12 positioned in two opposite end zones of the support base 10.

For example, the force measured by a first sensor 12a arranged near a first longitudinal edge 18 of the support base 10 can be compared with the force measured by a second sensor 12b arranged near a second longitudinal edge 19 of the support base 10. The first longitudinal edge 18 is parallel to the second longitudinal edge 19 and to the advance direction F.

If the force measured by the first sensor 12a is equal or similar to the force measured by the second sensor 12b, the longitudinal axis X of the applying roller 6a is substantially parallel to the plane along which the tiles 4 are conveyed.

If instead there is a substantial difference between the force measured by the first sensor 12a and the force measured by the second sensor 12b, then the longitudinal axis X is not parallel to the plane along which the tiles 4 are conveyed. In the latter case, the quality of decoration obtainable is not constant along the longitudinal axis X, and it is necessary to increase the distance from the conveyor 5 of the end of the applying roller 6a near which the higher pressure reading was measured.

The measuring device 9 can be provided with means for memorizing the measurements taken for the corresponding decorating devices 2. In a version, the operator may remove the measuring device 9 from the conveyor 5 after the measuring device 9 has interacted with all the decorating devices 2. The operator can then move the measuring device 9 to a check point where the memorized data is downloaded and saved, for example in an electronic processor. At the check point the measuring device 9 can be connected to the electronic processor with a connection cable and batteries or other forms of electrical supply incorporated in the measuring device 9 can be recharged.

The measuring device 9 can also function in static conditions. In this case instead of using the conveyor 5 for conveying the support base 10 along the advance direction F, the support base 10 can be manually positioned in the measuring position under the applying roller 6a, or any other applying roller 6 of the decorating machine 1. If the measuring device 9 indicates that adjustments are required to establish the correct pressure of the applying roller 6a, or to render the longitudinal axis X parallel to the plane on which the tiles 4 are conveyed, the adjustments can be made while maintaining the support base 10 in the measuring position under the applying roller 6a. This enables real time verification of how the force measured by the force sensors 12 varies, until the applying roller 6a is positioned correctly relative to the conveyor 5. For this purpose an appropriate software program run by the electronic processor 17 can be used, the processor 17 receiving, by means of any form of connection with or without wires, the value readings of the force sensors 12, elaborating the data, and displaying (for the operator) the measured force values together with the operative instructions necessary to correctly position the applying roller 6a.

In a version, the measuring device 9 can comprise means for signalling, for example LEDs of different colours, controlled by a suitable software program executed by the electronic board 15, such as to provide the operator with immediate information regarding the position of the applying roller 6a. In a version it is possible to use a green LED, a red LED, and an orange LED. The measuring device 9 can also be used in a calibration procedure that enables the positioning of one or more of the applying rollers 6 at a required distance, or at a required height, relative to the plane defined by the conveyor 5. For this purpose, the support base 10 is positioned below an applying roller 6 in a position where the applying roller 6 exerts, on the support base 10, a force other than zero, which is measured by the force sensors 12. The applying roller 6 is then gradually moved away from the conveyor 5. Consequently the force measured by the force sensors 12 diminishes progressively. When the force sensors 12 no longer detect any applied force, the applying roller 6 has reached a reference position or calibration position in which there is no interference between the applying roller 6 and the support base 10. If the applying roller 6 is further moved away from the conveyor 5, the applying roller 6 becomes increasingly detached from the support base 10, on which no force is applied.

The calibration procedure described above enables precise identification of the reference position, in which the distance between the applying roller 6 and the conveyor 5 is known, this distance being equal to the thickness S of the support base 10. During the decoration of the tiles 4, this enables the distance between the applying roller 6 and the conveyor 5 to be adjusted, starting from a precisely determined reference position. In this way errors are reduced; errors which currently are committed when positioning the applying roller 6 at a predetermined height above the conveyor 5.

The measuring device 9 can be used for correctly positioning the components of the decorating machine 1 before these begin operation, or to periodically check the operation of the decorating machine 1 and conduct any necessary adjustments.

As illustrated with the dashed line in Figure 1 , the decorating machine 1 can comprise a reference element, for example a reference roller 58, fitted upstream of the decorating devices 2 relative to the advance direction F. The reference roller 58 can be a freely rotatable roller, possibly of different diameter from the applying rollers 6. The reference roller 58 is positioned such that a longitudinal axis of the reference roller 58 is perpendicular to the advance direction F, with a high degree of precision. When the support base 10 of the measuring device 9 is positioned on the conveyor 5 to be conveyed in the advance direction F, the force sensors 12 interact with the reference roller 58 before interacting with the applying rollers 6. The reference roller 58 interacts with the force sensors 12 arranged along the straight line L according to a sequence that depends on how the support base 10 is positioned on the conveyor 5. In other words, if the support base 10 is positioned on the conveyor 5 such that the straight line L is perpendicular to the advance direction F, and parallel to the longitudinal axis of the reference roller 58, all the force sensors 12 simultaneously detect the application of a force by the reference roller 58. If instead the support base 10 is positioned on the conveyor 5 such that the straight line L is slightly inclined relative to the longitudinal axis of the reference roller 58, as happens in the majority of cases, some force sensors 12 will detect the application of force by the reference roller 58 before the other force sensors 12, according to a sequence that depends on how the support base 10 is positioned relative to the conveyor 5. By detecting this sequence by means of the reference roller 58, it is possible to univocally determine the position of the support base 10 relative to the reference roller 58 and thus relative to the advance direction F. The support base 10 subsequently passes under the first applying roller 6a, the first applying roller 6a interacting with the force sensors 12 arranged along the straight line L according to a succession that depends on both how the support base 10 is positioned on the conveyor 5, and how the longitudinal axis X of the first applying roller 6a is arranged relative to the advance direction F. Since the position of the support base 10 on the conveyor 5, previously determined using the reference roller 58, is known, by detecting the succession in which the force sensors 12 are activated by the first applying roller 6a it is possible to determine the position of the longitudinal axis X of the roller relative to the advance direction F. Otherwise stated, it is possible to determine whether the longitudinal axis X of the first applying roller 6a, in plan view, is perpendicular to the advance direction F, or whether the longitudinal axis X is inclined relative to the advance direction F. In the latter case, the succession of activation of the force sensors 12 makes it possible to establish whether the longitudinal axis X is inclined forwards or backwards relative to the advance direction F and the entity of the inclination. Proceeding in this way, the position of the longitudinal axes of all the applying rollers 6 relative to the advance direction F can be established and the inclinations adjusted if required. It is noted that the reference element, for example the reference roller 58, can be located at any desired position along the conveyor 5, not necessarily upstream of the first applying roller 6a. Figure 4 illustrates, in an exploded view, a test device 20 for assessing the differences of speed between the conveyor 5 and any applying roller 6 of the decorating machine 1. The test device 20 comprises a first part 21 suitable for being positioned in contact with the conveyor 5 such as to be moved by the conveyor 5. The first part 21 can be a flat rectangular or square plate, made for example of a ground metal material. The first part 21 is delimited by a lower flat surface 23 suitable for being positioned on the conveyor 5. The first part 21 is provided with detector means which can comprise a plurality of detectors 24, which could be of the same type as the force sensors 12 described previously with reference to Figures 2 and 3.

For example, the detector means can comprise a pair of detectors 24, positioned at opposite ends of a lateral face 25 of the first part 21 and a further pair of detectors 24, positioned at opposite ends of a further lateral face 26 of the first portion 21. The lateral face 25 and the further lateral face 26 are opposite each other and can be substantially perpendicular to the lower flat surface 23. The test device 20 further comprises a second part 22 suitable for being positioned in contact with an applying roller 6. The second part 22 comprises a flat upper surface 27 suitable for interacting with the applying roller 6. The second part 22 can be made of a metal material, possibly ground. The second part 22 comprises a first lateral appendage 28 and a second lateral appendage 29, projecting from a side that is opposite to the flat upper surface 27. In particular, the first lateral appendage 28 and the second lateral appendage 29 can be substantially orthogonal to the flat upper surface 27. The first lateral appendage 28 and the second lateral appendage 29 are located opposite each other, such as to interact respectively with the pair of detectors 24 fitted on the lateral face 25 of the first part 21 and with a further pair of detectors 24 fitted on the further lateral face 26 of the first part 21.

The first part 21 and the second part 22 are free to move relative to each other with at least one degree of freedom. In particular, the first part 21 and the second part 22 are free to slide relative to each other along a sliding direction A, such that the first lateral appendage 28 and the second lateral appendage 29 can approach, or move away from, the lateral face 25 and the further lateral face 26 respectively. In a rest configuration, between the first lateral appendage 28 and the pair of detectors 24 fitted on the lateral face 25, there is a small clearance, or in any case there is no interference, such that the detectors do not detect any force. A similar situation exists between the second lateral appendage 29 and the further pair of detectors 24 fitted on the further lateral face 26. Interposed between the first part 21 and the second part 22 are means for reducing friction 30 for reducing the friction generated when the first part 21 is moved relative to the second part 22 or vice versa. In the illustrated version, the means for reducing friction 30 comprises a thin sheet of plastic material 31 exhibiting a low frictional coefficient or non-adhesion properties, for example polytetrafluorethylene (PTFE). In an alternative version, the means for reducing friction 30 can comprise rolling elements, for example balls or rollers.

During use, the test device 20 is positioned on the conveyor 5 such as to interact sequentially with one or more of the applying rollers 6. Figure 5 illustrates, by way of example, the first applying roller 6a under which the test device 20 is transiting.

The test device 20 is positioned such that the first lateral appendage 28, the lateral face 25, the second lateral appendage 29, and the further lateral face 26 are transverse relative to the advance direction F. The lower flat surface 23 of the first part 21 is supported on the conveyor 5 which transports it in the advance direction F. Consequently, the first part 21 moves with a linear speed v equal to the linear speed of the upper section of the conveyor 5. The upper flat surface 27 of the second part 22 is in contact with the external surface 7 of the applying roller 6a, which tends to move the second part 22 at a peripheral speed vp dependant on the angular speed ω of the applying roller 6a and on its radius R. If the linear speed v is substantially the same as the peripheral speed vp, i.e. if the applying roller 6a rolls without sliding on the flat upper surface 27, the first part 21 and the second part 22 do not move relative to each other. Consequently the detectors 24 do not detect any force.

If instead the linear speed v is different from the peripheral speed vp, i.e. if the applying roller 6a rotates and slides on the flat upper surface 27, the first part 21 and the second part 22 move relative to each other and the movement is detected by the detectors 24.

For example, if the linear speed v is less than the peripheral speed vp, the first part 21 moves more slowly than the second part 22. Consequently the first part 21 remains behind relative to the second part 22 and the distance between the second lateral appendage 29 and the further lateral face 26 diminishes. The corresponding detectors 24 detect a compressive force, the intensity of which is proportional to the relative displacement between the first part 21 and the second part 22 and thus proportional to the difference in speed between the conveyor 5 and the applying roller 6a. Vice versa, if the linear speed v is greater than the peripheral speed vp, the first part 21 advances in the advance direction F more rapidly than the second part 22. This results in the distance between the first lateral appendage 28 and the lateral face 25 diminishing. The corresponding detectors 24 thus measure a compressive force proportional to the difference in speed between the conveyor 5 and the applying roller 6a.

The test device 20 comprises a control circuit, positioned on the first part 21 or on the second part 22, which can be connected to an electronic processor, for example the same electronic processor 17 illustrated in Figure 3, by wireless connection. The wireless connection can be of the same type as the connection 16 described previously with reference to Figure 3. The electronic processor can memorize the force readings of the detectors 24, convert them into speed differences and display the values thus calculated to inform the operator on the operating conditions of the decorating machine 1. In an alternative version, the test device 20 can comprise means for memorizing the values detected by the detectors 24. This data can subsequently be downloaded to a control station. In an alternative version, illustrated in Figure 4a, the detectors 24 can comprise optical detectors capable of detecting the relative displacement between the first portion and the second portion. The optical detectors can be, for example of the type currently used in optical mouse devices for personal computers. Figure 4a illustrates a test device 420 having a first part 421 of a similar shape to the first part 21 illustrated in Figure 4 and a second part 22 substantially the same as that illustrated in Figure 4. The first part 421 has an upper face 77 on which at least one optical detector 424 is located, of the type mentioned above, enabling detection of the relative movement between the first part 421 and the second part 22 in the sliding direction A. Between the first part 421 and the second part 22 means for reducing friction 30 are interposed, which in this case can comprise a sheet of plastics 431 having a low frictional coefficient, provided with a through slot 78. The slot 78 permits the optical detector 424 to directly face an inferior face 79 of the first part 21, such that the optical detector 424 can detect whether the first part 421 and the second part 22 move relative to each other, without interfering with the sheet of plastics 431. Between the lateral face 25 of the first part 421 and the first lateral appendage 28 of the second part 22, and also between the further lateral face 26 and the second lateral appendage 29, elastic means can be interposed, for example springs 80. The springs 80 ensure that, in the absence of applied external forces, the first part 421 is centred relative to the second part 22, i.e. that there is a certain clearance between the lateral face 25 and the first lateral appendage 28, as well as between the further lateral face 26 and the second lateral appendage 29. During operation, the test device 420 is positioned on the conveyor 5, similarly to the description referring to Figure 5, to measure whether the first part 421 and the second part 22 move relative to each other. The data supplied by the test device 420 is processed in the same way and used for the same purposes as previously described with reference to Figures 4 and 5.

Figure 6 illustrates a test device 120 in an alternative version, obtained substantially by inverting the test device 20 of Figures 4 and 5. The test device 120 comprises a first part 121 exhibiting similar geometry to the second part 22 of Figure 4 and a second part 122 exhibiting similar geometry to that of the first part 21 of Figure 4. Otherwise stated, the first part 121 is provided with a first lateral appendage 128 and a second lateral appendage 129 projecting from the lower flat surface 23. The second part 122 exhibits instead the form of a quadrangular slab. Detectors 24 are interposed between the first lateral appendage 128 and the second part 122, and also between the second lateral appendage 129 and the second part 122. Means for reducing friction are also provided, but not illustrated, positioned between the first part 121 and the second part 122. The test device 120 illustrated in Figure 6 operates in a manner entirely similar to the test device 20 illustrated in Figures 4 and 5.

Figure 7 illustrates a test device 220 in another alternative version. The test device 220 comprises a first part 221 in an upper area of which a housing 33 is formed, the housing 33 being thereby delimited by inclined lateral surfaces 32. The housing 33 houses a second part 222 which is delimited by the flat upper surface 27 and also by two oblique surfaces 34, which can be parallel to the inclined lateral surfaces 32. The means for reducing friction (not illustrated) and the detector means 24 are interposed between the inclined lateral surfaces 32 and the oblique surfaces 34. The detector means 24 can be fixed alternatively to the first part 221 or to the second part 222. The first part 221 and the second part 222 are free to move relative to each other in the sliding direction A, transversally to the inclined lateral surfaces 32 and to the oblique surfaces 34, such that at least one, or a pair, of detectors 24 are activated if the speed of the applying roller 6a differs from the speed of the conveyor 5.

The test device 220 also functions similarly to the test device 20 illustrated in Figures 4 and 5. Figures 8 and 9 illustrate a test device 320 in another alternative version.

The test device 320 comprises a first part 321, the flat lower surface 23 thereof is suitable for being rested on the conveyor 5. The first part 321 is delimited by four side walls 35 arranged such as to form a parallelepiped. In an upper area of the first part 321 a seat is formed 36, delimited by two front faces 37 and by two rear faces 38. The front faces 37 and the rear faces 38 are inclined relative to the side walls 35, such that, in plan view, the forward faces 37 and the rear faces 38 define a quadrilateral, for example, a square rotated by approximately 45° relative to another quadrilateral defined by the side walls 35.

The test device 320 also comprises a second part 322 positioned above the first part 321. The second part 322 comprises a plate-shaped body 39 delimited by the flat upper surface 27 and a lower surface 40. From the lower surface 40 extends a projecting body 41, suitable for being received in the seat 36. The projecting body 41 has the same plan shape as the seat 36, but the dimensions of the projecting body 41 are slightly smaller than the dimensions of the seat 36, such that between the seat 36 and the projecting body 41 housed therein there is a clearance G. This clearance G enables a pair of detectors 24 to be located between the front faces 37 and corresponding further front faces 42 that delimit the projecting body 41. A further pair of detectors 24 can be provided between the rear faces 38 of the seat 36 and the corresponding further rear faces 43 of the projecting body 41. In the example illustrated in Figure 9, the detectors 24 are fitted on the projecting body 41. In an alternative version the detectors 24 could be fixed to the seat 36. The test device 320 further comprises a plurality of force sensors 312, which can be entirely similar to the force sensors 12 described with reference to Figures 2 and 3. The force sensors 312 can be interposed between the first part 321 and the second part 322, for example fixed to an upper surface zone 44 of the first part 321 which surrounds the seat 36. Above the force sensors 312 means for reducing friction 30 can be provided, for example fixed to the lower surface 40 of the second part 322. In a version which is not illustrated, the force sensors 312 can be fixed to the second part 322 rather than to the first part 321. The force sensors 312 can also be mounted on the flat upper surface 27, but are preferably interposed between the first part 321 and the second part 322 thereby offering the sensors more protection from dirt and the risk of damage. The test device 320 enables implementation both of the test functions of the test device 20 illustrated in Figures 4 and 5, and of the functions of the measuring device 9 illustrated in Figures 2 and 3. When the test device 320 passes below one or more decorating devices 2, moving in the advance direction F, the detectors 24 establish whether the speed of the conveyor 5 differs from the speed of the applying roller 6. This is possible as a consequence of the pair of detectors 24 interposed between the front faces 37 and the further front faces 42, which detect a force if the speed of the conveyor 5 is less than the speed of the applying roller 6, as already described with reference to Figure 5. Similarly, the further pair of detectors 24 interposed between the rear faces 38 and the further rear faces 43 detect a force if the speed of the applying roller 6 is less than the speed of the conveyor 5.

Furthermore, the force sensors 312 enable measurement of the pressure exerted by the applying roller 6 on the flat upper surface 27. By comparing the forces measured by the two force sensors 312 arranged in proximity to a forward edge 45 of the first portion 321, or by comparing the force measured by the two force sensors 312 arranged in proximity to a rear edge 46 of the first portion 321, it is possible to determine whether the longitudinal axis X of the applying roller 6 is parallel to the flat upper surface 27. The test devices 20, 120, and 220 illustrated in Figures from 4 to 7 can also be provided with force sensors for measuring the pressure exerted by the applying roller 6, or for determining whether the longitudinal axis X of the applying roller 6 is parallel to the plane defined by the upper section of the conveyor 5. In this case, the force sensors can be interposed between the first part and the second part of the test device, or fixed to the flat upper surface of the second part.

Vice versa, the test device 320 illustrated in Figure 9 could be devoid of force sensors 312 and comprise only the detectors 24. In this case, the test device 320 could be used solely to determine whether the applying roller 6 and the conveyor 5 have the same speed.

Figure 10 illustrates a portion of an apparatus for decorating items, in particular ceramic tiles, of a similar type to the decorating machine illustrated in figure 1.

The apparatus of figure 10 comprises a reservoir 50 containing a fluid, for example a ceramic glaze 51 in a liquid state intended to be applied on a ceramic tile 4. A supply duct 52 connects the reservoir 50 to a decorating device 2 of the decorating machine 1. A pump P is installed along the supply duct 52 to pump the ceramic glaze 51 arriving from the reservoir 50 towards the applying roller 6 of the decorating device 2. In particular, the ceramic glaze 51 is made to drop above the doctor blade 8, such as to create an accumulation 53 of ceramic glaze 51 between the doctor blade 8 and the applying roller 6. The pump P, which can be of a peristaltic type, is provided with a shaft 54 connected to a further shaft 55 of a motor M, for example through a joint 56. The motor M, which can be a continuous current electrical motor, rotates the shaft 54 at a predefined speed, expressed for example in rotations per minute. The device further comprises control means 57 which control the speed of the motor M and thus of the shaft 54. The control means 57 comprise, for example, a pulse width modulation (PWM) circuit. The PWM circuit enables variation of the time during which the supply voltage is applied to the motor M. Otherwise stated, the supply voltage is applied to the motor M not constantly and continuously, but according to a square wave signal of the type shown in Figure 11, in which an interval of time tl, during which the motor M is powered with a predefined voltage, is followed by an interval of time t2 during which no voltage is supplied to the motor M.

The control means 57 are designed such that the speed of the motor M, measured for example by using means for measuring of known type, and thus the speed of the shaft 54, is maintained constant. If the viscosity of the ceramic glaze 51 increases for any reason, it becomes more difficult for the pump P to convey the ceramic glaze 51 through the supply duct 52 as a consequence of the increased internal friction that develops in the ceramic glaze 51 when the glaze 51 is processed by the pump P. Consequently, there is an increase in the power that the motor M must supply to the pump P to maintain the speed of the shaft 54 constant. In order to adjust the power supply, the control means 57 increase the duty cycle of the square wave whereby the supply voltage is supplied to the motor M. Otherwise stated, the duration of the interval tl is increased, while the duration of the interval t2 diminishes. The opposite happens if the viscosity of the ceramic glaze 51 diminishes, whereby the ceramic glaze 51 becomes more fluid and thus more easily pumped by the pump P.

The PWM circuit is connected to an electronic processor 117, which could be the same electronic processor 17 illustrated in Figure 3, through a wireless connection 116 which can be entirely similar to the wireless connection 16 described with reference to Figure 3. An appropriate software program is memorized in the electronic processor 117 and, on the basis of the duty cycle of the square wave according to which the voltage is supplied to the motor M, the program calculates the viscosity of the ceramic glaze 51. Naturally, the system has been suitably previously calibrated. If the viscosity exits from a predefined range, an alarm message is generated such that the operator can intervene and restore the required viscosity.

During the operation of the ceramics machine I₅ the control means 57 and the electronic processor 117 enable continuous monitoring of the viscosity of the ceramic glaze 51, such that the operator is warned immediately if the viscosity level goes out of the predefined range, so the operator can intervene before serious drawbacks develop. It is noted that the control means 57 can be mounted not only on new decorating machines, but also on existing decorating machines with the aim of improving performance. Existing decorating machines generally comprise a motor M and a pump P, to which it is sufficient to connect a box housing the PWM circuit and the necessary electronics for measuring variations in the duty cycle and transmit the readings to the electronic processor 117. In an alternative version, the control means 57 can control the intensity of the current supplying the motor M instead of the electrical tension. In this alternative version, an electronic circuit implements variation of the time during which a predetermined intensity of current is supplied to the motor M. Figure 12 illustrates a portion of a decorating machine 201, of similar type to the decorating machine 1 of Figure 1 , depicting a first applying roller 106a and a second applying roller 106b, arranged in sequence along the advance direction F. The first applying roller 106a extends along a first longitudinal axis Xl, while the second applying roller 106b extends along a second longitudinal axis X2. On the first applying roller 106a a first pair 59 of register marks is defined, illustrated in detail in the enlargements of Figure 12. The register marks of the first pair 59 can comprise a first register mark 60 and a further first register mark 61 arranged in sequence along the direction of the first longitudinal axis Xl. The register marks of the first pair 59 can be located at opposite ends of the first applying roller 106a, such as not to interact with the ceramic tiles during normal production. In particular the first register mark 60 can be located in an end zone 62 of the first applying roller 106a near a frame 80 of the decorating machine 201. The further first register mark 61 can instead be located in a further end zone 63 of the first applying roller 106a located on a side of the decorating machine 201 accessible to operators. As illustrated in the enlarged detail views of Figure 12, the first register mark 60 and the further register mark 61 exhibit the shape of portions of a frame, for example of a square frame. The first register mark 60 and the further register mark 61 are asymmetrical relative to each other. For example, the first register mark 60 can comprise an "L" shaped section 64, while the second register mark 61 can comprise a reversed "L" section 65. On the second applying roller 106b a second pair 66 of register marks is formed, comprising a second register mark 61 and a further second register mark 68 arranged in sequence along the second longitudinal axis X2. The second register mark 61 can be positioned in an end region 69 of the second applying roller 106b, near the frame 80 of the decorating machine 201. The further second register mark 68 can instead be located in a further end region 70 of the second applying roller 106b, on the side of the decorating machine 201 towards the operator. The second register mark 61 and the further second register mark 68 can have the same shape. For example, the second register mark 61 and the further second register mark 68 can both be cross-shaped. The applying rollers arranged downstream of the second applying roller 106b are provided with respective pairs of register marks which can be entirely similar to the second pair 66 of register marks. Before the decorating machine 201 starts decorating ceramic tiles, at least one test tile is passed under the applying rollers 106a and 106b, such as to interact with the respective end zones. If the first applying roller 106a and the second applying roller 106b are correctly positioned relative to each other, and in particular if the first longitudinal axis Xl is parallel to the second longitudinal axis X2, the second register mark 67 prints on the tile a second reference mark 71 centred relative to a first reference mark 72 generated by the first register mark 60. In the present example, as illustrated in Figure 13, the cross produced by the second register mark 67 is located inside, and more precisely in the centre, of the portion of frame generated by the first register mark 60. Similarly, the further first register mark 61 of the first applying roller 106a produces on the test tile a further reference mark 73, for example a portion of frame, inside which, in a centred position, there is a further second reference mark 74, for example a cross, generated by the further second register mark 68.

If the operator, possibly assisted by a machine for acquiring the images of the register marks printed on the test tile and assessing their reciprocal positions, notes a result as illustrated in Figure 13, then the decorating machine 201 is ready for production and adjustments are not required on the relative positions of the first applying roller 106a and second applying roller 106b. If instead the second longitudinal axis X2 is not parallel to the first longitudinal axis Xl, then at least one of the crosses printed by the second register mark 67 or by the further second register mark 68 will not be centred relative to corresponding section of frame. It is possible, for example, that a situation of the type illustrated in Figure 14 might occur, in which the cross generated by the first register mark 60 is displaced to the right by a distance dl relative to the corresponding portion of frame, while the cross generated by the further first register mark 61 is displaced towards the left by a distance d2 relative to the corresponding portion of frame. The measurements of the distances dl and d2 and the direction whereby the corresponding crosses are decentred relative to the respective frames enable calculation of the inclination between the first longitudinal axis Xl and the second longitudinal axis X2, and determination of how and by how much the first applying roller 106a or the second applying roller 106b must be repositioned such that the respective longitudinal axes are restored to a parallel arrangement. In an entirely similar way, it is possible to verify whether the first longitudinal axis Xl is parallel to the longitudinal axes of the applying rollers subsequent to the second applying roller 106b, and modify their position as required.

It is noted that, since the first register mark 60 is asymmetrical relative to the further first register mark 61, on the test tile corresponding non symmetrical reference marks are produced, permitting the operator, or a machine capable of acquiring and processing the images of the register marks 60 and 61, to easily identify which marks are printed by the end of the roller near the machine frame and which marks are printed by the end of the roller near the operator. This reduces errors that can occur in the identification whether, for example, the second longitudinal axis X2 is inclined towards right or left relative to the first longitudinal axis Xl.

Figure 15 illustrates an applying roller 306 which, in addition to being provided with the first register mark 60 and the further first register mark 61, is also provided with a print area 75 in an end zone of the roller. The print area 75 is positioned on the applying roller 306 such as not to interact with the ceramic tiles during normal production. The print area 75 can have any shape, for example the shape can be square or rectangular. The print area 75 is capable of printing on a test tile a printed area 76, as illustrated in Figure 16, shaped according to the shape of the print area 75 and filled with ceramic glaze. For example, the print area 75 can comprise a plurality of cavities, designed to contain ceramic glaze, according to a predetermined print density. In a version not illustrated, the applying roller 306 can have only the print area 75 and be without register marks.

When the decorating machine is correctly adjusted, a first test is conducted and a printed area 76 is printed on a test tile. The printed area 76 is then acquired by a video camera, for example an RGB video camera, and the relative colour is measured and converted, for example into LAB values. In this way at least one numeric parameter is determined for the characterization of the printed area 76.

As an alternative to the RGB video camera, it is possible to use other means for measuring the colour, for example a black and white video camera or a spectrophotometer.

In order to check whether the decorating machine continues to function correctly, such as to produce the same decoration every time that the applying roller 306 is used, the applying roller 306 prints a successive printed area 76' on a test tile, as illustrated in Figure 16. The successive printed area 76' is printed after a period of time, of arbitrary length, from the moment of printing of the printed area 76. The colour of the successive printed area 76' is also measured. A comparison of the colour measurement for the printed area 76 with the colour measurement for the successive printed area 76' determines whether the decorating process actuated by the decorating machine changed during the period between the two successive test prints.

If the result is negative, the decorating process remained unchanged and no further tests are required. If the result is positive, such that the colour of the successive printed area 76' is different from the colour of the printed area 76, at least one parameter of the decorating process has changed. For example, the viscosity of the ceramic glaze might have changed. It is also possible that the pressure exerted on the applying roller 306 by the corresponding doctor blade has changed. For example, if the pressure exerted by the doctor blade on the external surface of the applying roller 306 has increased, the doctor blade would remove an increased quantity of ink from the external surface of the applying roller 306. Consequently the quantity of ink transferred to the tile is less, resulting in the printed area 76 appearing darker than the successive printed area 76'.

Furthermore, the successive printed area 76' might differ from the printed area 76 as a consequence of a change in the angle of the doctor blade relative to the external surface of the applying roller 306. Again this leads to a change in the quantity of ink transferred to the tile surface. It is also possible that differences between the successive printed area 76' and the printed area 76 are the consequence of variation in background colour printed on the ceramic tiles and onto which the decoration is transferred. Consequently, on identification of differences between the successive printed area 76' and the printed area 76, further investigation is required in order to establish the cause of the print variations.

It is noted that the colour properties of the printed area 76 and of the successive printed area 76' can also be measured on unfired test tiles, i.e. tiles not yet fired in a kiln. This provides an especially rapid means for testing for print changes. All the applying rollers of the decorating machine are provided with print areas similar to that illustrated in Figure 15, such that it is possible to test, for all the applying rollers, whether the decorating process parameters are unaltered relative to the initial values.

The measuring device 9 illustrated in Figures 2 and 3, the test devices 20, 120, 220, 320, and 420 illustrated in Figures from 4 to 9, the control means 57 illustrated in Figure 10, the device for acquiring the reference marks illustrated in Figures 13 and 14 and the printed zones illustrated in Figure 16 can be connected to a single electronic processor, which operates as a control station, memorizing and processing a plurality of data relative to the operation of the decorating machine, and enabling control and adjustment of the decorating machine in a simple and repeatable manner, even by inexpert operators.

Claims

Claims.

1. A measuring device comprising a plate-shaped support base (10) supporting force sensor means (12), said force sensor means (12) being suitable for measuring a force exerted by a decorating device (2) for decorating ceramic items (4).

2. The device of claim 1, wherein the support base (10) exhibits a substantially quadrangular plan shape.

3. The device of claim 1 or 2, wherein the support base (10) exhibits a shape of a ceramic tile.

4. The device of one of the claims from 1 to 3, wherein the support base (10) is made of a metallic material.

5. The device of claim 4, wherein the metallic material is ground.

6. The device of one of the preceding claims, wherein the force sensor means (12) are glued to a surface (11) of the support base (10), said surface (11) being intended to come into contact with the decorating device (6, 6a).

7. The device of one of the claims from 1 to 5, wherein the force sensor means (12) are housed in relative seats formed on a surface (11) of the support base (10), the surface (11) being intended to come into contact with the decorating device (6, 6a).

8. The device of claim 6 or 7, wherein the surface is an upper surface (11) of the support base (10).

9. The device of one of the preceding claims, wherein the force sensor means (12) have an electrical resistance which is variable in accordance with an applied force.

10. The device of one of the preceding claims, wherein the force sensor means (12) comprise at least one load cell.

11. The device of one of the preceding claims, wherein the force sensor means (12) are substantially flat.

12. The device of one of the preceding claims, wherein the force sensor means comprise a plurality of force sensors (12).

13. The device of claim 12, wherein the plurality of force sensors (12) are arranged along a straight line (L).

14. The device of claim 13, wherein the straight line (L) is substantially parallel to an edge (13) of the support base (10).

15. The device of one of the claims from 12 to 14, wherein said plurality comprises at least two force sensors (12a, 12b) positioned at opposite end zones of the support base (10).

16. The device of claim 12, wherein the force sensors (12) of said plurality are positioned near the ends of the support base (10).

17. The device of one of the preceding claims, and further comprising a layer of protective material covering the force sensor means (12) for protecting the force sensor means (12).

18. The device of one of the preceding claims, wherein the support base (10) supports a control circuit (15) connected to the force sensor means (12) so as to receive a signal from the force sensor means (12).

19. The device of claim 18, and further comprising wireless connection means (16) for connecting the control circuit (15) to an electronic processor (17).

20. The device of claim 19, wherein the wireless connection means (16) are selected from a group comprising: radio connection means, optical connection means.

21. The device of one of the preceding claims, wherein the support base comprises a first part (21; 121; 221; 321; 421) suitable for being positioned in contact with a conveyor (5) transporting the ceramic items (4), and a second part (22; 122; 222; 322) suitable for being positioned in contact with the decorating device (2), the first part (21; 121; 221; 321; 421) and the second part (22; 122; 222; 322) being free to move relative to each other at least in one direction.

22. The device of claim 21 , wherein between the first part (21; 121; 221; 321 ; 421) and the second part (22; 122; 222; 322) detector means (24; 424) are interposed for detecting whether the first part (21; 121; 221; 321; 421) and the second part (22; 122; 222; 322) move relative to each other.

23. The device of claim 22, wherein the detector means (24; 424) comprise force detector means (24) activatable when a part, selected from either the first part (21; 121; 221; 321) or the second part (22; 122; 222; 322), moves relative to, and applies a force to, a further part selected from either the second part (22; 122; 222; 322) or the first part (21; 121; 221; 321).

24. The device of claim 23, wherein the force detector means (24) are of the same type as the force sensor means (12).

25. The device of claim 22, wherein the detector means (24; 424) comprise optical detector means (424).

26. The device of one of the claims from 22 to 25, wherein the detector means (24; 424) comprise first detector means activatable when a part selected from either the first part (21; 121; 221; 321; 421) or the second part (22; 122; 222; 322) moves relative to a further part selected from either the second part (22; 122; 222; 322) or the first part (21; 121; 221; 321; 421).

27. The device of claim 26, wherein the detector means (24; 424) comprise second detector means activating when the further part moves relative to the part.

28. The device of claim 27, wherein the first detector means are arranged in a position opposite the second detector means.

29. The device of one of the claims from 23 to 28, wherein the first part (21; 121; 221 ; 321; 421) is delimited by a first flat surface (23) suitable for being positioned on the conveyor (5), and the second part (22; 122; 222; 322) is delimited by a second flat surface (27) suitable for contacting the decorating device (2).

30. The device of claim 29, wherein the first flat surface (23) is substantially parallel to the second flat surface (27).

31. The device of claim 29 or 30, wherein the detector means (24) are fixed to a lateral surface (25, 26; 32, 33; 42, 43) of a part selected from either the first part (21; 121; 221; 321) or the second part (22; 122; 222; 322), the lateral surface (25, 26; 32, 33; 42, 43) being arranged transversally relative to the first flat surface (23) and the second flat surface (27).

32. The device of claim 31, wherein the lateral surface (25, 26; 32, 33; 42, 43) is substantially perpendicular to the first flat surface (23) and the second flat surface (27).

33. The device of one of the claims from 23 to 32, wherein a part selected from either the first part (21; 121; 221; 321) or second part (22; 122; 222; 322) is housed at least partially in a seat formed in another part selected from either the second part (22; 122; 222; 322) or the first part (21; 121; 221; 321), the detector means (24) being housed in the seat such as to be interposed between the first part (21; 121; 221; 321) and the second part (22; 122; 222; 322).

34. The device of claim 33, wherein the second part (22) is "U" shaped, the seat being defined by two lateral appendages (28, 29) of the second part (22).

35. The device of claim 34, wherein the first part (21) exhibits a parallelepiped shape.

36. The device of claim 33, wherein the first part (121) is "'U" shaped, the seat being defined between two lateral appendages (128, 129) of the first part (121).

37. The device of claim 36, wherein the second part (122) exhibits a parallelepiped shape.

38. The device of claim 33, wherein the second part (322) comprises a plate body (39) from which a projecting body (41) projects, the projecting body (41) being received in the seat (36), the projecting body (41) having smaller plan view dimensions than the plate body (39).

39. The device of claim 38, wherein the projecting body (41) is shaped as a parallelepiped rotated relative to the plate body (39), such that the projecting body (41) exhibits lateral faces (42, 43) which are rotated relative to edge faces (45, 46) of the plate body (39).

40. The device of claim 39, wherein the projecting body (41) is rotated by 45° relative to the plate body (39).

41. The device of one of the claims from 21 to 40, wherein the force sensor means (12) are interposed between an upper surface zone (44) of the first part (321) and a lower surface (40) of the second part (322).

42. A method for measuring at least one operating parameter of a decorating machine (1) for ceramic items (4), the method comprising the steps of:

- positioning a measuring device (9) comprising force sensor means (12) in contact with a decorating device (2);

- detecting the force exerted by the decorating device (2) on the force sensor means (12).

43. The method of claim 42, wherein the force is detected when the measuring device (9) is located below the decorating device (2).

44. The method of claim 42 or 43, wherein the at least one operating parameter is the pressure exerted by the decorating device (2) on the ceramic items (4), said pressure being calculated on the basis of the force.

45. The method of one of the claims from 42 to 44, wherein the force is calculated in different mutual positions of the decorating device (2) and the measuring device (9), such as to determine how pressure applied by the decorating device (2) varies when interference between the decorating device (2) and the measuring device (9) varies.

46. The method of one of the claims from 42 to 45, wherein the decorating machine (1) comprises a conveyor (5) for conveying the ceramic items

(4) in an advance direction (F).

47. The method of claim 46, wherein the at least one operating parameter is the distance between the conveyor (5) and the decorating device (2).

48. The method of claim 46 or 47, further comprising the step of progressively moving the decorating device (2) away from the conveyor

(5) until a reference position is reached at which a force applied by the decorating device (2) on the measuring device (9) is substantially zero.

49. The method of claim 48, wherein the reference position serves as a starting point for adjusting a distance between the decorating device (2) and the conveyor (5) when the ceramic items (4) are decorated.

50. The method of claim 46, wherein the at least one parameter is a parallelism between a longitudinal axis (X) around which the decorating device (2) extends at least partially, and a plane of transport defined by a section of the conveyor (5) transporting the ceramic items (4).

51. The method of claim 50, wherein the parallelism is measured by detecting forces applied to the force sensor means (12) by two distinct zones of the decorating device (2).

52. The method of claim 51, wherein the two distinct zones are arranged in sequence along a direction that is parallel to the longitudinal axis (X).

53. The method of claim 51 or 52, wherein the two distinct zones are distanced from each other.

54. The method of one of the claims from 51 to 53, wherein, if the forces applied by the two distinct zones are substantially equal, the longitudinal axis (X) is substantially parallel to the plane of transport.

55. The method of one of the claims from 51 to 54, wherein, if the forces applied by the two distinct zones are different, the longitudinal axis (X) is inclined relative to the plane of transport.

56. The method of claim 46, wherein the at least one operating parameter is a perpendicularity between a longitudinal axis (X), around which the decorating device (2) at least partially extends, and the advance direction (F).

57. The method of claim 56, further comprising a determining step for determining a relative position of the measuring device (9) and the conveyor (5).

58. The method of claim 57, wherein, during the determining step, the measuring device (9) interacts with a reference element (58) which projects from a frame of the decorating machine perpendicularly to the advance direction (F).

59. The method of claim 58, wherein the reference element is a freely rotatable roller (58).

60. The method of claim 58 or 59, wherein the reference element (58) is positioned upstream of the decorating device (2).

61. The method of one of the claims from 57 to 60, wherein, during the determining step, a sequence is acquired in which at least two force sensors (12a, 12b) of the force sensor means (12) interact with the reference element (58).

62. The method of claim 61, further comprising a step of comparing the sequence with a further sequence according to which the at least two force sensors (12a, 12b) interact with the decorating device (2).

63. The method of claim 62, wherein if the sequence is equal to the further sequence, the longitudinal axis (X) is substantially parallel to the reference element (58.).

64. The method of claim 62, wherein if the sequence is different from the further sequence, an axis (X) of the decorating device (2) is inclined relative to the reference element (58).

65. The method of one of the claims from 46 to 64, wherein the force sensor means comprise a plurality of sensors (12) arranged along a line (L) which is transversal to the advance direction (F).

66. The method of one of the claims from 42 to 65, wherein, during the step of detecting, the measuring device (9) is maintained in a static position in contact with the decorating device (2).

67. The method of one of the claims from 42 to 66, wherein the measuring device (9) is transported towards the decorating device (2), such that the step of detecting is carried out while the measuring device (9) is moving.

68. The method of one of the claims from 42 to 67, wherein the ceramic items comprise tiles (4).

69. The method of one of the claims from 42 to 68, wherein the decorating device comprises an applying roller (6, 6a).

70. The method of claim 69, wherein the applying roller (6, 6a) works according to a printing method selected from a group comprising: gravure printing, rotogravure printing, flexographic printing, screen printing, offset printing.

71. The method of one of the claims from 42 to 70, wherein a measuring device is used according to one of the claims from 1 to 41.

72. A test device for assessing a possible difference in speed between a conveyor (5) and a decorating device (2) of a machine (1) for decorating ceramic items (4), the test device (20; 120; 220; 320; 420) comprising a first part (21 ; 121 ; 221 ; 321; 421) suitable for being positioned in contact with the conveyor (5) and a second part (22; 122; 222; 322) suitable for being positioned in contact with the decorating device (2), the first part (21; 121; 221; 321; 421) and the second part (22; 122; 222; 322) being free to move relative to each other in at least one direction, detector means (24; 424) being interposed between the first part (21 ; 121 ; 221 ; 321 ; 421) and the second part for detecting if the first part (21; 121; 221 ; 321 ; 421) and the second part (22; 122; 222; 322) move relative to each other.

73. The device of claim 72, wherein the detector means (24; 424) comprise force detector means (24) activatable when a part, selected from either the first part (21; 121; 221; 321) or the second part (22; 122; 222; 322), moves relative to, and applies a force to, another part, selected from either the second part (22; 122; 222; 322) or the first part (21; 121; 221; 321).

74. The device of claim 73, wherein the force detector means (24) have an electrical resistance which is variable as a function of applied force.

75. The device of claim 73, wherein the force detector means (24) comprise at least one load cell.

76. The device of claim 72, wherein the detector means (24; 424) comprise an optical detector means (424).

77. The device of one of the claims from 72 to 76, wherein the detector means (24; 424) comprise first detector means activatable when a part selected from either the first part (21; 121; 221; 321; 421) or the second part (22; 122; 222; 322) moves relative to a further part selected from either the second part (22; 122; 222; 322) or the first part (21; 121; 221; 321; 421).

78. The device of claim 77, wherein the detector means (24; 424) comprise second detector means activatable when the further part moves relative to the part.

79. The device of claim 78, wherein the first detector means are arranged in a position opposite the second detector means.

80. The device of one of the claims from 72 to 79, wherein the first part (21; 121; 221; 321; 421) is delimited by a first flat surface (23) suitable for being positioned on the conveyor (5) and the second part (22; 122; 222; 322) is delimited by a second flat surface (27) suitable for contacting the decorating device (2).

81. The device of claim 80, wherein the first flat surface (23) is substantially parallel to the second flat surface (27).

82. The device of claim 80 or 81, wherein the detector means (24) are fixed to a lateral surface (25, 26; 32, 33; 42, 43) of a part selected from either the first part (21; 121; 221; 321) or the second part (22; 122; 222; 322), the lateral surface (25, 26; 32, 33; 42, 43) being arranged transversally relative to the first flat surface (23) and the second flat surface (27).

83. The device of claim 82, wherein the lateral surface (25, 26; 32, 33; 42, 43) is substantially perpendicular to the first flat surface (23) and to the second flat surface (27).

84. The device of one of the claims from 72 to 83, wherein a part selected from either the first part (21; 121; 221; 321) or the second part (22; 122; 222; 322) is housed at least partially in a seat formed in another part selected from either the second part (22; 122; 222; 322) or the first part (21; 121; 221; 321), the detector means (24) being housed in the seat such as to be interposed between the first part (21; 121; 221; 321) and the second part (22; 122; 222; 322).

85. The device of claim 84, wherein the second part (22) is "U" shaped, the seat being defined by two lateral appendages (28, 29) of the second part (22).

86. The device of claim 85, wherein the first part (21) exhibits a parallelepiped shape.

87. The device of claim 84, wherein the first part (121) is "U" shaped, the seat being defined between two lateral appendages (128, 129) of the first part (121).

88. The device of claim 87, wherein the second part (122) exhibits a parallelepiped shape.

89. The device of claim 84, wherein the part (322) comprises a plate body (39) from which a projecting body (41) projects, the projecting body (41) being received in the seat (36), the projecting body (41) having smaller plan view dimensions than the plate body (39).

90. The device of claim 89, wherein the projecting body (41) is shaped as a parallelepiped rotated relative to the plate body (39), such that the projecting body (41) exhibits lateral faces (42, 43) rotated relative to edge faces (45, 46) of the plate body (39).

91. The device of claim 90, wherein the projecting body (41) is rotated by 45° relative to the plate body (39).

92. The device of one of the claims from 72 to 91, wherein the detector means (24) are fixed to the first part (21; 121; 221; 321).

93. The device of one of the claims from 72 to 92, wherein the detector means (24) are fixed to the second part (22; 122; 222; 322).

94. The device of one of the claims from 72 to 93, wherein between the first part (21; 121; 221; 321; 421) and the second part (22; 122; 222; 322) means for reducing friction (30) are interposed in order to reduce a friction generated when the first part (21; 121; 221; 321) and the second part (22; 122; 222; 322) move relative to each other.

95. The device of claim 94, wherein the means for reducing friction (30) comprise rolling means.

96. The device of claim 94 or 95, wherein the means for reducing friction (30) are made in an anti-adherent plastic material.

97. The device of one of the claims from 72 to 96, wherein the first part (21; 121; 221; 321; 421) is coupled to the second part (22; 122; 222; 322) such as to form an object shaped like a ceramic tile.

98. The device of one of the claims from 72 to 97, and comprising wireless connection means for connecting the device to an electronic processor.

99. The device of claim 98, wherein the means for wireless connection are selected from a group comprising: radio connection means, optical connection means.

100. A method for assessing whether there is a difference in speed between a conveyor (5) and a decorating device (2) of a machine (1) for decorating ceramic items (4), the method comprising the steps of: positioning a first part (21; 121; 221; 321; 421) of a test device (20; 120; 220; 320; 420) in contact with the conveyor (5), such that the conveyor (5) moves the first part (21; 121; 221; 321; 421); positioning a second part (22; 122; 222; 322) of the test device (20; 120; 220; 320; 420) in contact with the decorating device (2), such that the decorating device (2) moves the second part (22; 122; 222; 322); " - detecting whether the first part (21; 121; 221; 321;^' 421) and the second part (22; 122; 222; 322) move relative to each other.

101. The method of claim 100, wherein the first part (21; 121; 221; 321; 421) and the second part (22; 122; 222; 322) are free to move relative to each other at least along an advance direction (F) of the conveyor (5).

102. The method of claim 100 or 101, wherein, for detecting whether the first part (21; 121 ; 221; 321) and the second part (22; 122; 222; 322) move relative to each other, there is provided measuring the force applied by a part selected from either the first part (21; 121; 221; 321) or the second part (22; 122; 222; 322) on another part selected from either the second part (22; 122; 222; 322) or the first part (21; 121; 221; 321),

103. The method of claim 102, as appended to claim 101, wherein the force is directed along the advance direction (F).

104. The method of claim 102 or 103, wherein, if the conveyor (5) has a speed higher than the decorating device (2), the first part (21; 121; 221; 321) advances more rapidly than the second part (22; 122; 222; 322) and applies a force on force detector means (24) located in a first area of the test device (20; 120; 220; 320).

105. The method of claim 104, as claim 102 is appended to claim 101, wherein, if the decorating device (2) has a speed higher than the conveyor (5), the first part (21; 121 ; 221; 321) advances more slowly than the second part (22; 122; 222; 322) and an applied force is detected, said applied force being applied to force detector means (24) positioned in a second area of the test device (20; 120; 220; 320), the first area and the second area being arranged in sequence along the advance direction

(F).

106. The method of one of the claims from 102 to 105, further comprising a step of obtaining, on a basis of the force, a difference in speed between the decorating device (2) and the conveyor (5).

107. The method of claim 100 or 101, wherein in order to establish whether the first part (421) and the second part (22) move relative to each other, a movement is measured of a part selected from either the first part (421) or the second part (22) relative to another part selected from either the second part (22) or the first part (421).

108. The method of one of the claims from 100 to 107, wherein the ceramic items comprise tiles (4).

109. The method of one of the claims from 100 to 108, wherein the decorating device comprises an applying roller (6, 6a).

110. The method of claim 109, wherein the applying roller (6, 6a) operates according to a printing method selected from a group comprising: gravure printing, rotogravure printing, flexographic printing, screen printing, offset printing.

111. The method of one of the claims from 100 to 110, wherein the test device of one of the claims from 72 to 99 is used.

112. An apparatus comprising a pump (P) for conveying a fluid (51) towards an applicator device (2), the applicator device (2) being suitable for applying the fluid (51) on an object (4), motor means (M) for supplying power to the pump (P) so as to drive the pump (P) at a driving speed, characterized in that it comprises control means (57) for recording a possible variation in the power required for keeping the driving speed substantially constant.

113. The apparatus of claim 112, wherein the control means (57) comprise a pulse width modulation (PWM) circuit for regulating the power of the motor means (M).

114. The apparatus of claim 113, wherein the pulse width modulation circuit is configured such as to regulate an electrical voltage supplied to the motor means (M).

115. The apparatus of claim 114, wherein the control means (57) comprise means for measuring the percentage duration of an interval (tl) during which electrical voltage is supplied to the motor means (M) relative to a further interval (t2) during which the electrical voltage is not supplied to the motor means (M).

116. The apparatus of claim 113, wherein the pulse width modulation circuit is configured such as to regulate the intensity of current supplied to the motor means (M).

117. The apparatus of one of the claims from 112 to 116, wherein the driving speed is the speed of rotation of a shaft (54) of the pump (P). -Si¬

l l 8. The apparatus of claim 117, wherein the shaft (54) is connected to the motor means (M).

119. The apparatus of one of the claims from 112 to 118, wherein the motor means comprise an electrical motor (M).

120. The apparatus of claim 119, wherein the electrical motor is a continuous current electrical motor (M).

121. The apparatus of one of the claims from 112 to 120, wherein the pump is suitable for processing a ceramic glaze (51).

122. The apparatus of one of the claims from 112 to 121, wherein the pump is a peristaltic pump (P).

123. The apparatus of one of the claims from 112 to 122, wherein the applicator device is a decorating device (2) of a decorating machine (1) for ceramic items (4).

124. The apparatus of one of the claims from 112 to 123, and comprising wireless connection means (116) for connecting the control means (57) to an electronic processor (117).

125. The apparatus of claim 124, wherein the wireless connection means (116) are selected from a group comprising: radio connection means, optical connection means.

126. A method comprising the steps of: conveying a fluid (51 ) towards an applicator device (2) by means of a pump (P), the applicator device (2) being suitable for applying the fluid (51) on an object (4); supplying power to the pump (P) so as to drive the pump (P) at a driving speed; detecting a possible variation in the power required to maintain the driving speed substantially constant, said possible variation being indicative of a change in viscosity of the fluid (51).

127. The method of claim 126, wherein the pump (P) is driven by motor means (M).

128. The method of claim 127, and further comprising a step of controlling the motor means (M) by using a technique of pulse width modulation (PWM).

129. The method of claim 127 or 128, wherein the step of supplying power comprises applying a non-constant electrical supply parameter to the motor means (M).

130. The method of claim 129, wherein the electrical supply parameter is applied in an interval (tl), the interval (tl) being followed by a further interval (t2) in which the electrical supply parameter is substantially zero.

131. The method of claim 130, wherein the step of detecting a possible variation in the power comprises determining the percentage duration of the interval (tl) relative to the sum of the interval (tl) and the further interval (t2).

132. The method of claim 131, wherein, if the percentage duration increases, the viscosity of the fluid (51) has increased.

133. The method of claim 131 or 132, wherein, if the percentage duration decreases, the viscosity of the fluid (51) has diminished.

134. The method of one of the claims from 129 to 133, wherein the electrical supply parameter is selected from a group comprising: electrical voltage, intensity of current.

135. The method of one of the claims from 126 to 134, wherein the fluid is a ceramic glaze (51) conveyed by the pump (P) towards a decorating device (2) of a decorating machine (1) for decorating ceramic items (4).

136. The method of claim 135, wherein the ceramic items comprise tiles

(4⁾.

137. A method comprising the steps of: printing a first pair of reference marks (72, 73) on a ceramic item (4), by means of a first decorating device (106a); applying to the ceramic item (4) a second pair of reference marks (71 , 74), by means of a second decorating device (106b), the reference marks of at least a pair selected from either the first pair or the second pair being asymmetrical relative to each other; comparing, on the ceramic item (4), the position of each reference mark (72, 73) of the first pair and the position of the corresponding reference mark (71, 74) of the second pair.

138. The method of claim 137, further comprising the step of assessing the reciprocal position of a first longitudinal axis (Xl) of the first decorating device (106a) and of a second longitudinal axis (X2) of the second decorating device (106b) by means of the steps of comparing.

139. The method of claim 138, wherein the step of assessing the reciprocal position comprises determining whether the first longitudinal axis (Xl) and the second longitudinal axis (X2) are substantially parallel to each other.

140. The method of claim 138 or 139, wherein, if each reference mark (72, 73) of the first pair is substantially centred relative to the corresponding reference mark (71, 74) of the second pair, the first longitudinal axis (Xl) and the second longitudinal axis (X2) are substantially parallel to each other.

141. The method of one of the claims from 138 to 140, wherein the reference marks (72, 73) of the first pair are printed by respective surface zones of the first decorating device (106a), the surface zones being arranged in sequence along the first longitudinal axis (Xl).

142. The method of claim 141, wherein the surface zones are located in opposite end zones of the first decorating device (106a).

143. The method of one of the claims from 138 to 142, wherein the reference marks (71, 74) of the second pair are printed by respective surface regions of the second decorating device (106b), said surface regions being arranged in sequence along the second longitudinal axis (X2).

144. The method of claim 143, wherein said surface regions are located in opposite end regions of the second decorating device (106b).

145. The method of one of the claims from 138 to 144, wherein the first decorating device (106a) and the second decorating device (106b) are arranged in sequence along a conveyor (5) transporting the items (4) in an advance direction (F), the advance direction (F) being transversal to the first longitudinal axis (Xl) and to the second longitudinal axis (X2).

146. The method of one of the claims from 137 to 145, wherein the first decorating device comprises a first applying roller (106a) and the second decorating device comprises a second applying roller (106b).

147. The method of one of the claims from 137 to 146, wherein the ceramic items comprise ceramic tiles (4).

148. A decorating device for ceramic items (4), comprising a decorating surface at least partially arranged around a longitudinal axis (Xl), the decorating surface having a register mark (60) and a further register mark (61) arranged in sequence along the longitudinal axis (Xl) for assessing if the decorating device (106a) is in register, characterized in that the register mark (60) is asymmetrical relative to the further register mark

(61).

149. The device of claim 148, wherein the register mark (60) and the further register mark (61) are located in opposite end zones (62, 63) of the device (106a).

150. The device of claim 148 or 149, wherein the register mark (60) and the further register mark (61) are each shaped like a portion of a frame.

151. The device of one of the claims from 148 to 150, wherein the register mark (60) comprises an "L" shaped portion (64) inverted with respect to a further "L" shaped portion (65) of the further register mark (61).

152. The device of one of the claims from 148 to 151, comprising a decorating roller (106a) delimited by the decorating surface.

153. The device of claim 152, wherein the decorating roller (106a) comprises a hollow and substantially rigid central core.

154. The device of claim 152 or 153, wherein the decorating roller (106a) comprises an external layer of deformable elastic material.

155. The device of claim 154, wherein the deformable elastic material is selected from a group comprising: silicone, polyurethane.

156. The device of one of the claims from 152 to 155, wherein the decorating roller (106a) comprises an intermediate spongy layer.

157. The device of one of the claims from 148 to 156, wherein a plurality of cavities is obtained on the decorating surface, the cavities forming a pattern to be printed on the ceramic items (4).

158. A method comprising the steps of: comparing a first area (76) printed by a decorating device (2) with a second area (76') printed by the decorating device (2), the second area (76') being printed a period of time after the printing of the first area (76); assessing whether the second area (76') differs from the first area (76), in order to determine whether at least one parameter of a decorating process carried out by the decorating device (2) has changed during the period of time.

159. The method of claim 158, wherein the first area (76) and the second area (76') are assessed on an unfired ceramic tile.

160. The method of claim 158 or 159, wherein the at least one parameter is the inclination of a doctor blade (8) of the decorating device (2) relative to an external surface of the decorating device (2).

161. The method of claim 158 or 159, wherein the at least one parameter is the pressure exerted by a doctor blade (8) of the decorating device (2) on an applying element (6) of the decorating device (2).

162. The method of claim 161, wherein the applying element comprises an applying roller.

163. The method of claim 158 or 159, wherein the at least one parameter is the viscosity of a glaze applied by the decorating device (2).

164. The method of claim 158 or 159, wherein the at least one parameter is the background colour of an item (4) decorated by the decorating device (2).

165. The method of claim 158 or 159, wherein the at least one parameter is the colour of a glaze applied by the decorating device (2) on an item (4) to be decorated.

166. The method of one of the claims from 158 to 165, wherein the step of assessing comprises acquiring the first area (76) and the second area (76') using colour detector means.

167. The method of one of the claims from 158 to 166, wherein the step of assessing comprises comparing the colour of the first area (76) with the colour of the second area (76').