Surface decoration method and apparatus for decorating a ceramic printing substrate

Abstract

A surface decoration method and apparatus (1) of a printing substrate (2) advancing on an advancing plane (5) along a given path (P); the decoration apparatus (1) comprises: a printing assembly (8); a lighting unit (11a) for emitting a grazing light with respect to the advancing plane (5) so as to light a portion of a first longitudinal edge (B1) of the printing substrate (2); an optical detection system (12) which is configured to capture images of the first lighted edge (B1) advancing along the path (P) through a detection station (7) and to estimate, based on the captured images, the position and the orientation of said printing substrate (1); and a control system (CU) for adjusting the operation of the printing assembly (8) as a function of the position and the orientation of the printing substrate (2).

Description

[0001] "SURFACE DECORATION METHOD AND APPARATUS FOR DECORATING A CERAMIC PRINTING SUBSTRATE"

[0002] Cross-Reference to Related Applications

[0003] This Patent Application claims priority from Italian Patent Application No . 102024000021106 filed on September 23 , 2024 , the entire disclosure of which is incorporated herein by reference .

[0004] Technical Field

[0005] The present invention relates to a surface decoration method and apparatus for decorating a printing substrate made of a ceramic material .

[0006] Background of the Invention

[0007] In the sector of the production of ceramic products , such as for example ceramic slabs or tiles , the need is increasingly felt to manufacture ceramic products having, on the visible surface , increasingly defined and complex possibly three-dimensional decorations , for example adapted to reproduce the aspect of natural materials , such as wood or natural stones , etc . in an increasingly precise and accurate manner .

[0008] In order to create such decorations , it is known to use typically multi-printing decoration apparatuses , which comprise : a conveyor to convey the printing substrates to be decorated along a given path through one or more printing machines located in series along such given path and which work in a coordinated manner for applying one or more layers of decoration material on the printing substrates so as to create the desired decoration and / or texture on the printing substrate .

[0009] It is evident that such decoration apparatuses , in order to ensure optimal results , require high precision in the positioning of the base substrates entering the various printing machines .

[0010] Exactly for this reason, the known decoration apparatuses generally comprise specially provided orientation systems , typically comprising levellers or centrali zers of the mechanical type , located upstream of the printing assembly along the above-mentioned given path and configured to intercept each printing substrate and orient it , thus rotate it and / or translate it , up to giving it the desired orientation before it is fed towards the subsequent surface treatment stations .

[0011] However, the mechanical orientation always provides for the contact of at least one edge of the printing substrate with a rigid body, which involves the trans fer of sliding stresses and / or tensions which risk compromising the good outcome of the orientation and / or damaging the substrate , especially when it has not yet been fired . Furthermore , the mechanical orientation requires complicated calibration operations , especially in the modern ceramic product production lines which are adapted to operate with substrates of di f ferent formats as the production cycles vary, and in any case requires a certain amount of time during which the advancement of the base substrates is interrupted, with all the related disadvantages in terms of drop in productivity .

[0012] Alternatively, in order to obviate the above-mentioned problems , decoration apparatuses have been developed devoid of mechanical centring systems but equipped with cameras or scanners adapted to detect the pos ition and the orientation of the printing substrate being fed to the printing assembly so as to consequently command the decoration apparatus . An example of decoration apparatus of this type is described in document US2019066267A1 .

[0013] However, even these known solutions have several drawbacks , one of which is the inability to operate with the same level of precision and accuracy required by the modern printing devices , due to the inherent limitations of the detection systems utili zed, which are often very complex, require complex image combination operations for determining position and orientation of the substrate , but also due to possible irregularities of the edge of the substrate which can cause imprecisions and inaccuracies in determining the position and the orientation of the substrate . Furthermore , the known solutions generally provide for the use of a plurality of cameras , each one adapted to capture a part of the printing substrate being fed towards the printing assembly, and thus require complex overlapping and combination operations of the images obtained from the various cameras in order to obtain one single image which can be analysed for deriving the position and the orientation of the printing substrate .

[0014] Furthermore , the systems known for obtaining with a certain degree of accuracy the pos ition and the orientation of the substrate often require the detection and the reconstruction of most of the edges of the printing substrate , with a consequent increase in the processing times and / or in the overall dimensions of the machines .

[0015] The obj ect of the present invention is to provide a surface decoration method and apparatus for decorating a ceramic substrate , which allow overcoming, at least in part , the disadvantages of the prior art , allowing decorating ceramic substrates of di f ferent shapes and dimensions in a simpler, quicker and more ef ficient manner while maintaining the same quality of the final decoration .

[0016] Summary

[0017] In accordance with the present invention, a surface decoration method and apparatus for decorating a ceramic substrate is proposed, according to what is described in the appended independent claims , and preferably, in any one of the claims directly or indirectly dependent on the mentioned independent claims .

[0018] The claims describe preferred embodiments of the present invention, forming integral part of the present description .

[0019] Brief Description of the Drawings

[0020] The invention i s described in the following with reference to the accompanying drawings , which illustrate some non-limiting example embodiments thereof , wherein :

[0021] - Figure 1 is a schematic side view of a plant for manufacturing ceramic products in accordance with an embodiment of the present invention;

[0022] - Figure 2 is a front view of a part of the plant of Figure 1 to better illustrate a detection station of the decoration apparatus , manufactured in accordance with a first variant of the present invention;

[0023] Figure 2A is a schematic representation of what captured by the detection system o f the apparatus o f Figure 2 ;

[0024] - Figure 3 is a front view of a part of the plant of Figure 1 to better illustrate a detection station of the decoration apparatus , manufactured in accordance with a fist variant of the present invention; and

[0025] - Figures 3A and 3B are schematic representations of what captured by the detection system of Figure 3 .

[0026] Detailed Description

[0027] In the accompanying figures , reference numeral 1 indicates , as a whole , a surface decoration apparatus for decorating a printing substrate 2 made of a ceramic material CP .

[0028] More advantageously but not limitedly, in the present discussion, the expression "printing substrate 2" refers , without thereby losing generality, to a basic ceramic article that has not yet been fired, obtained by compacting ( in a manner known per se ) CP ceramic powder and by suitably cutting the ribbon of compacted KP ceramic powder in order to obtain the desired formats . More advantageously but not limitedly, the expression "printing substrate 2" refers to a basic ceramic article that has j ust exited a dryer 3 and is intended, after the decoration, the possible finishing steps and the firing to become a ceramic slab or tile .

[0029] Advantageously, the printing substrate 2 made of a ceramic material has at least one surface S ( in use , oriented upwards ) on which the defined decoration is intended to be formed, a further surface ( in use , oriented downwards and not visible in the accompanying figures ) parallel to and opposite the surface S and at least four edges Bl , B2 , B3 and ( another one parallel to B3 and not visible in the accompanying figures ) connecting the two surfaces .

[0030] Typically but not necessarily, the printing substrate 2 substantially has the shape ( in plan) of a quadrilateral . More precisely, the printing substrate 2 substantially has the shape of a parallelepiped .

[0031] In detail , the printing substrate 2 has at least two longitudinal edges Bl , B2 substantially parallel to each other and substantially parallel to an advancing direction A of the printing substrate 2 , as it will be better explained in the following, a third edge B3 and a fourth transverse edge that j oin the longitudinal edges Bl , B2 to each other extending transverse ( in particular, orthogonal ) to them .

[0032] It is specified that within the scope of the present description the term " second" element does not imply the presence of a " first" element etc . Such terms , in fact , are used as labels for improving clarity and are not to be understood in a limiting manner . Furthermore , the terms such as "upper" , " lower" , " lateral" , "height" , etc . are utili zed with reference to the decoration apparatus 1 arranged on a substantially hori zontal resting plane , for example on the ground or on the floor , on which the conveyor as sembly 4 carrying the printing substrate 2 directly or indirectly rests .

[0033] With particular reference to the accompanying figures , advantageously, the surface decoration apparatus 1 comprises : a conveyor assembly 4 , which defines an advancing plane 5 and is configured to receive the printing substrate 2 and convey it , advantageously but not limitedly with a random orientation, along a given path P , in an advancing direction A, through at least one printing station 6 and a detection station 7 , located upstream of the printing station 6 along the given path P ; and a printing assembly 8 which, in turn, comprises at least one printing unit 9 arranged at the printing station 6 and configured to create a predefined decoration on the printing substrate 2 which, in use , advances through such printing station 6 .

[0034] Advantageously but not limitedly, the conveyor assembly 4 comprises a plurality of transporting devices 10 arranged in sequence and aligned with respect to one another along the given path P . In particular , the advancing plane 5 , advantageously but not limitedly, extends along ( in particular, along at least part of ) the given path P and is adapted to support the printing substrate 2 during the advancement thereof and advantageously consists of the upper surface of the above-mentioned plurality of transporting devices 10 .

[0035] The surface decoration apparatus 1 further comprises : at least one lighting unit I la, which is arranged at the detection station 7 , positioned on a first side of the advancing plane 5 at a defined distance from the longitudinal edge Bl , along a direction B transverse to the advancing direction A and to the longitudinal edge Bl , and is configured to light with a grazing light at least a portion of the longitudinal edge Bl and an optical detection system 12 arranged above the advancing plane 5 for capturing images of the lighted longitudinal edge Bl , advantageously with an adj ustable capturing frequency, for evaluating, based on what captured, the position and the orientation of the printing substrate 2 ( see , in particular, Figures 2 and 3 ) . In particular, the optical detection system 12 is configured to capture images of a capturing area containing at least the zone of the advancing plane 5 that , in use , is occupied by the lighted longitudinal edge Bl advancing through the detection station 7 and evaluate , based on what captured, the position and the orientation of the printing substrate 2 .

[0036] Advantageously, the decoration apparatus 1 further comprises a control system CU ( only schematically illustrated in Figure 1 ) and configured to adj ust the operation of the printing assembly 8 as a function of the position and the orientation of the printing substrate 2 .

[0037] Still more advantageously but not limitedly, the control system CU is configured to rotate and / or translate the above-mentioned predefined decoration intended to be created on the surface S of the printing substrate 2 based on the estimate of the proces sor so as to obtain a manipulated decoration that keeps into account the real position and the real orientation of the printing substrate 2 arriving at the printing station 6 .

[0038] According to some advantageous but non-limiting embodiments , such as for example the ones illustrated in the accompanying figures , the decoration apparatus 1 also comprises at least a further lighting unit 11b, arranged at the detection station 7 positioned on a second s ide of the advancing plane 5 , opposite the first side with respect to the advancing direction A, always at a defined distance , along the transverse direction B, from the second longitudinal edge B2 of the printing substrate 2 which, in use , advances along the path P ( see Figures 2 and 3 ) . Such further lighting unit 11b is configured to emit a grazing light ( in particular, a beam o f grazing light ) to the advancing plane 5 so as to light ( exclusively) a portion of the second longitudinal edge B2 . In this case , advantageously but not limitedly, the capturing area of the optical detection system 12 is configured to also contain a zone of such advancing plane 5 that , in use , is occupied by the second lighted longitudinal edge B2 so as to manage also capturing images of such lighted longitudinal edge B2 , as it will be better described in the following .

[0039] In detail , advantageously but not limitedly, the lighting unit I la, or (when more than one , as in the illustrated embodiment ) each one of the lighting units I la, 11b is configured to emit a beam of grazing light with respect to the advancing plane 5 such to light only ( exclusively) the longitudinal edge Bl , B2 to which it is directed, without intercepting and thus lighting the surface S .

[0040] In other words , "beam of grazing light" or "grazing light" means a highly focused light beam which defines a light plane parallel to the advancing plane 5 and intercepts the longitudinal edge Bl , B2 of the printing substrate 2 in a manner substantially parallel to the longitudinal edge Bl , B2 , thus to the advancing direction A, so as to light only an elongated portion ( strip ) of longitudinal edge Bl , B2 , without involving the surface S to be decorated and still more advantageously but not limitedly not even the advancing plane 5 .

[0041] According to some advantageous but non-limiting embodiments , the above-mentioned, or each, lighting unit I la, 11b comprises ( in particular, consists of ) an optical fibre light source 13 configured to emit a light beam and a focal lens 14 for concentrating the light beam so as to obtain a light plane that extends substantially parallel to the advancing plane 5 , defining the above-mentioned grazing light .

[0042] Still more advantageously but not limitedly, the above- mentioned, or each, lighting unit I la, 11b emits a light in the form of light plane substantially parallel to the advancing plane 5 , said light plane involves and lights an elongated portion ( strip ) of the relative longitudinal edge Bl , B2 having an extension of approximately 2mm, along the advancing direction A, and a height , along a direction D perpendicular to the direction A and to the advancing plane 5 , of at least approximately 2mm up to a maximum of approximately the extension of such longitudinal edge Bl , B2 ( thus up to a maximum of approximately the thickness of the smallest of the printing substrates 2 that the decoration apparatus 1 is intended to treat ) . In this manner, it is ensured that the lighting unit I la, 11b involves only the longitudinal edge Bl , B2 , creating a contrast between the lighted longitudinal edge Bl , B2 and the surface S of the printing substrate 2 . In fact , it has been observed that such contrast permits the optical detection system 12 to capture , at every capturing, at least one point of the edge Bl with extreme precision ( see Figures 2A, 3A and 3B ) , allowing obtaining data on the position and on the orientation of the printing substrate 2 with the precision required by the printing assembly 8 ; in particular with a precision of less than approximately ± 0 , 8mm .

[0043] According to some advantageous but non-limiting embodiments , the optical fibre light source 13 is configured to emit a light beam and the focal lens is configured to receive the light beam and focus it so as to obtain the light plane so that this light plane intercepts and lights the relative longitudinal edge along an elongated portion ( strip ) parallel to the advancing direction A.

[0044] Alternatively or additionally, , the above-mentioned, or each, lighting unit I la, 11b comprises ( in particular, consists of ) a stroboscopic lamp focused through a slit and a cylindrical lens for forming a light plane substantially parallel to the advancing plane 5 and arranged to light the above-mentioned portion of lateral longitudinal edge Bl , B2 as the printing substrate 2 advances along the given path P .

[0045] Still according to another advantageous but nonlimiting embodiment , the ( or each) lighting unit I la, 11b comprises an LED light source and a collimation lens for collimating the led light so as to obtain a light plane parallel to the advancing plane 5 .

[0046] Advantageously, the optical detection system 12 comprises a processor (not visible in the accompanying figures ) which is advantageously integrated in the optical detection system 12 and is configured to process the images captured by the optical detection system 12 , advantageously via combination algorithms known per se and not described in detail herein, and to estimate the position of the printing substrate 2 on the advancing plane 5 with respect to a fixed reference system integral with the optical detection system 12 and to estimate the orientation of the printing substrate 2 with respect to the direction A.

[0047] In detail , advantageously but not limitedly, the processor is configured to process the captured images and to determine ( reconstruct ) , based on such captured images , more advantageously by interpolation, the development of the lighted longitudinal edge Bl , B2 , as is schematically illustrated in Figures 2A, 3A and 3B . The processor is further configured to estimate the position and the orientation of the printing substrate 2 as a function of the development at least of the longitudinal edge Bl or, when the decoration apparatus 1 provides for more lighting units I la, 11b, as a function of the development of both edges Bl , B2 .

[0048] By lighting only one or both longitudinal edges Bl , B2 , the optical detection system 12 at every capturing, captures an image in which the points of the lighted edge Bl , B2 are clearly visible with respect to the remaining part of the non-lighted printing substrate 2 ( see Figures 2A, 3A and 3B ) . Advantageously but not limitedly, the processor is configured to determine the position of such plurality of lighted points of the longitudinal edge Bl , B2 with respect to a fixed reference system integral with the optical detection system 12 so as to determine , based on the position of such points and on the geometrical data of the printing substrate 2 ( i . e . at least on the width of the printing substrate 2 ) , the position of the printing substrate 2 with respect to the above-mentioned fixed reference system and to evaluate the orientation of the printing substrate 2 with respect to said advancing direction A; in particular, based on the deviation of each point from a fixed direction parallel to the advancing direction A.

[0049] In use , when a printing substrate 2 is transported by the conveyor assembly 4 at the detection station 7 at least a portion of the longitudinal edge Bl ( in particular of the wall / surface of the longitudinal edge Bl ) , and more advantageously o f both longitudinal edges Bl , B2 , it intercepts the grazing light defining a lighted elongated portion ( strip ) along the edge Bl , B2 . The di f ference between the points of the lighted longitudinal edge Bl , B2 and the dark zones of the remaining printing substrate 2 will permit the optical detection system 12 to capture , at every capturing, images that show with high precision one or a series of points of the lighted longitudinal edge Bl , B2 . As the printing substrate 2 advances along the given path P more points are thus detected . Once a certain number of points is detected, the processor, by processing such points with known interpolation techniques , reconstructs the development of the longitudinal edge Bl , B2 ( see Figures 2A, 3A and 3B ) and thus estimates the position and the orientation of the printing substrate 2 , as mentioned above .

[0050] It is further understood that the presence of two identical lighting units I la 11b on the two sides of the advancing plane 5 , each configured to light a respective longitudinal edge Bl , B2 of the printing substrate 2 , although not essential , is advantageous in that it permits the optical detection system 12 to capture a plurality of points of each longitudinal edge Bl , B2 in an independent manner and thus permits , advantageously, the processor to estimate the pos ition and the orientation of the printing substrate 2 with greater precision by averaging the results obtained from the determination of the two longitudinal edges Bl , B2 of the printing substrate 2 .

[0051] It is understood that it is not necessary for the capturing to be performed for the entire extension of the longitudinal edge Bl , B2 of the printing substrate 2 , the capturing could be , for example , performed intermittingly or only at the beginning and end of the printing substrate 2 .

[0052] According to some advantageous but non-limiting embodiments , the decoration apparatus 1 comprises a detection device 16 ( only schematically illustrated in Figure 1 ) , advantageously a photocell or an encoder, configured to detect the presence ( in particular, to detect the passage ) of at least a part of a transverse edge B3 of the printing substrate 2 at the detection station 7 and to actuate , consequently, the optical detection system 12 and the , or each, lighting unit I la, 11b . More advantageously but not limitedly, the detection device 16 is arranged immediately upstream of the detection station 7 along the advancing path P and is connected to the , or each, lighting unit I la, 11b and to the optical detection system 12 for transmitting an actuation signal each time that it detects a printing substrate 2 entering the detection station 7 .

[0053] As mentioned above , according to some advantageous but non-limiting embodiments , the control system CU is configured to command the decoration apparatus 1 for operating the optical detection system 12 and each lighting unit I la, 11b for a certain time interval once the actuation signal has been received from the detection device 16 and such time interval can also be less than the time necessary for the passage of the entire printing substrate 2 . Alternatively or additionally, the control system CU is configured to command the operation of the optical detection system 12 and of each lighting unit I la, 11b with intermittence ( i . e . with even very wide capturing frequencies ) , once the above-mentioned actuation signal has been received, for example in order to capture images of the initial part of the printing substrate 2 and of the images of the final part .

[0054] According to some advantageous but non-limiting embodiments , the , or each, lighting unit I la, 11b is mounted, in a movable manner , on a guide 15 extending above the advancing plane 5 and transverse to the advancing direction A and can be actuated so as to translate in an automatic manner along such guide 15 as a function of the format of the printing substrate 2 , so as to keep the above-mentioned given distance between the lighting unit I la, 11b and the longitudinal edge Bl , B2 constant as the format of said printing substrate 2 varies . More in detail , advantageously but not limitedly, the lighting units I la, 11b are slidingly coupled to the guide 15 and carried cantilevered by the guide 15 . Furthermore , a motor is provided, advantageously controlled by the control assembly CU and configured to actuate in automatic manner the lighting units I la, 11b along the guide 15 as the format of the printing substrate 2 varies .

[0055] Advantageously but not limitedly, such control unit CU is configured to actuate into motion the lighting units I la, 11b along the guide 15 so as to ensure that the above- mentioned given distance between the lighting unit I la, 11b and the longitudinal edge Bl , B2 is at most approximately at 250mm . It is understood that such distance depends on the type of lighting unit I la, 11b adopted .

[0056] According to some advantageous but non-limiting embodiments such as for example the one illustrated in Figure 3 , the optical detection system 12 comprises ( in particular, consists of ) at least a pair of optical detection devices 17 ; each one configured to capture images of a respective capturing area which contains ( involves ) the advancing plane 5 at least at the zone which, in use , is occupied, respectively, by the lighted longitudinal edge Bl , B2 of the printing substrate 2 . More advantageously but not limitedly, each one of such optical detection devices 17 comprises ( in particular, consists of ) a matrix camera .

[0057] Advantageously but not limitedly, in this case , each optical detection device 17 is mounted, in a movable manner, on a further guide (not visible in the accompanying figures ) extending transverse to the advancing direction A along the direction B and can be actuated so as to translate along the further guide for adj usting the position of each optical detection device 17 as a function of the format of the printing substrate 2 . Still according to other advantageous but non-limiting embodiments not illustrated, the further guide coincides with the guide 15 .

[0058] Alternatively or additionally, advantageously but not limitedly, the optical detection system 12 comprises ( in particular, consists of ) at least one CIS (Contact Image Sensor ) contact sensor or at least one CCD ( Charged Coupled Device ) sensor or at least one CMOS ( Complementary metal- oxide Semiconductor ) sensor .

[0059] Still more advantageously but not limitedly, the optical detection system 12 has a resolution of at least 180 PPI ( Pixels Per Inch ) ; in particular, comprised between approximately 300 PPI and approximately 600 PPI ; still more advantageously equal to approximately 600 PPI . It is speci fied that the acronym "PPI" i . e . "Pixels Per Inch" indicates a measurement unit of the resolution of a digital image commonly utili zed for quanti fying the density of pixels distributed on a given area .

[0060] Advantageously but not limitedly, in order to improve the quality of the images captured by the optical detection system 12 , the decoration apparatus 1 comprises a covering portal (not visible in the accompanying figures ) , which surrounds the advancing plane 5 at the detection station 7 to shield the ambient light coming from the outside at least at the above-mentioned capturing area . This enables , advantageously, increasing the contrast between the zone of the longitudinal edge Bl , B2 lighted by the grazing light and the remaining part of the printing substrate 2 , improving the precision and the quality of the capturing and thus enabling obtaining more precise data on the position and on the orientation of the printing substrate 2 .

[0061] According to some advantageous but non-limiting embodiments , such as for example the one illustrated in Figures 1 and 2 , the printing assembly 8 comprises a plurality of printing units , in the illustrated case two printing units 9 , 9 ' all arranged in sequence along the printing station 6 and each configured to apply a certain substance according to a certain pattern on the surface S of the printing substrate 2 . For example according to some advantageous but non-limiting embodiments , the printing assembly 8 compri ses ( in particular, consists of ) a digital inkj et printer 9 configured to apply a first material on the printing substrate 2 according to ( in particular, following; namely defining) a first pattern; and at least a further printing unit 9 ' comprising ( in particular , consisting of ) a digital deposition assembly ( known per se and not described in detail herein ) which is configured to deposit in a controlled manner a second material on the printing substrate 2 according to ( in particular, following ; namely defining) a further pattern, so that the first material applied according to the first pattern and the second material together define the above-mentioned defined decoration . More advantageously but not limitedly, the deposition assembly is as described in patent application W02009118611 (by the same Applicant ) and / or in patent IT1314623 .

[0062] Alternatively or additionally, the printing assembly 8 comprises ( in particular, also consists of ) a spray application unit , for example an airless booth for sprayapplying a covering material ( in particular, a liquid material ; more in particular, comprising enamel ) on the printing substrate 2 . It is understood that the printing assembly 8 could consist of any number of printing units 9 , 9 ' of the types described above or of other types .

[0063] In this case , advantageously but not limitedly, the control assembly CU is configured to command each printing unit 9 , 9 ' as a function of the position and of the orientation of the printing substrate 2 estimated by the optical detection system 12 , as explained above . Alternatively, the decoration apparatus 1 could comprise an optical detection system 12 and at least one lighting unit I la, advantageously a pair of lighting units I la, 11b before every printing unit 9 , 9 ' so as to detect with precision the position and the orientation of the printing substrate 2 entering every printing unit 9 , 9 ' .

[0064] According to another aspect of the present invention, a surface decoration method is proposed, for decorating a printing substrate 2 made of a ceramic material , advantageously of the same type described above .

[0065] Advantageously, the decoration method of the present invention comprises : a conveying step, during which a conveyor assembly 4 , advantageously but not limitedly of the type described above , which defines an advancing plane 5 , conveys at least one printing substrate 2 along a given path P, in an advancing direction A, through at least one printing station 6 and a detection station 7 , located upstream of the printing station 6 along the given path P ; and a printing step, advantageously ( at least partially) simultaneous with the conveying step , during which a printing assembly 8 , advantageously but not limitedly of the type described above and comprising at least one printing unit 9 , 9 ' , creates a predefined decoration on the printing substrate 2 while this advances at the printing station 6 .

[0066] The decoration method further comprises : a lighting step, ( at least partially) prior to the printing step, during which a lighting unit I la, advantageously of the type described above , which is arranged at the detection station 7 , positioned on a first side of the advancing plane 5 at a defined distance from the longitudinal edge Bl , along the direction B, emits a grazing light ( in particular, a beam of grazing light ) with respect to the advancing plane 5 , of the type described above in relation to the decoration apparatus 1 , and lights ( exclusively, without involving the surface S ) a portion of such longitudinal edge Bl .

[0067] According to an advantageous but non-limiting embodiment , during the lighting step a further lighting unit 11b, arranged at the detection station 7 on a second side of the advancing plane 5 , opposite the first side with respect to the advancing direction A, at a defined distance , along the direction B, from the second longitudinal edge B2 of the printing substrate 2 , emits a grazing light ( in particular, a beam of grazing light ) with respect to the advancing plane 5 and lights ( exclusively, without involving the surface S ) a portion of the second longitudinal edge B2 .

[0068] Advantageously but not limitedly, the decoration method also comprises a positioning step , ( at least partially) prior to the lighting step, during which the position of the lighting unit I la , or, when more than one , of each lighting unit I la, 11b, is adj usted as a function of the format of the printing substrate 2 , so as to keep the distance between the lighting unit I la, 11b and the longitudinal edge Bl , B2 that this is intended to light constant as the format of the printing substrate 2 varies . Advantageously, the decoration method further comprises : a detection step , ( at least partially) simultaneous with the lighting step and with the conveying step and prior to the printing step, during which an optical detection system 12 ( advantageously but not limitedly of the type described above ) arranged above the advancing plane 5 at the detection station 7 , captures , advantageously with an adj ustable frequency, images of a capturing area containing the zone of the advancing plane 5 that , in use , is occupied by the above-mentioned longitudinal edge Bl lighted by the lighting unit I la advancing through the detection station 7 and, based on the captured images , estimates the position and the orientation of the printing substrate 2 .

[0069] More advantageously but not limitedly, the detection step comprises a processing sub-step, during which a processor comprised in the optical detection system 12 determines ( reconstructs ) the development of the longitudinal edge Bl based on the captured images and estimates , based on such development , the position of the printing substrate 2 with respect to a fixed reference system integral with the optical detection system 12 and the orientation of the printing substrate 2 with respect to the advancing direction A, as is better explained above .

[0070] According to some advantageous but non-limiting embodiments , when the lighting step provides for lighting both longitudinal edges Bl , B2 of the printing substrate 2 , during the detection step, the optical detection system 12 also detects images of the zone of the advancing plane 5 that , in use , is occupied by the second longitudinal edge B2 advancing through the detection station 7 , so as to also estimate the development of the second longitudinal edge B2 . In this case , advantageously but not limitedly, during the processing sub-step, the processor also estimates the position and the orientation of the printing substrate 2 based on the development of the second longitudinal edge B2 , improving the precision and the quality of the estimate .

[0071] The decoration method further comprises a control step, at least partial ly subsequent to the detection step and simultaneous with the printing step, during which a control system CU control s the operation of the printing assembly 8 based on the estimate in such detection step .

[0072] In detail , according to some advantageous but nonlimiting embodiments , the control step comprises a manipulation sub-step, during which the above-mentioned predefined decoration to be created on the printing substrate 2 is rotated and / or moved based on the estimate of the detection step so as to obtain a manipulated decoration ; and during the printing step, the printing assembly 8 applies the manipulated decoration on the printing substrate 2 .

[0073] According to some advantageous but non-limiting embodiments , the decoration method comprises an operation step, ( at least partially) prior to the lighting step and the detection step, during which a detection device 16 , which is located upstream of the detection station 7 along said given path P, detects the presence ( in particular, of at least a part of a transverse edge B3 ) of the printing substrate 2 and transmits an actuation signal to each lighting unit I la , 11b, and to the optical detection system 12 .

[0074] Advantageously but not limitedly, the lighting step is at least partially simultaneous with the conveying step and provides for lighting at least one section of the longitudinal edge Bl while thi s advances through the detection station 7 ; and during the detection step, the optical detection system 12 captures images at adj ustable time intervals . In detail , advantageously but not limitedly, considering the high precision with which the optical detection system 12 manages at every capturing to determine the position of one or more points of the longitudinal edge Bl , B2 , it is not necessary to light and detect the entire edge Bl , B2 of the printing substrate 2 for deriving position and orientation, as better explained above in relation to the decoration apparatus 1 .

[0075] According to some advantageous but non-limiting embodiments , the surface decoration method is carried out by utili zing a decoration apparatus 1 manufactured in accordance with any one of the embodiments described above .

[0076] The decoration method and apparatus 1 of the present invention have numerous advantages , among which the following are mentioned .

[0077] The decoration method and apparatus 1 allow positioning in a precise and accurate manner the predefined decoration to be created on the printing substrate 2 regardless of the actual position and of the actual orientation with which such printing substrate 2 arrives at the printing station 6 , thanks to the precise , quick and accurate evaluation of the real position and orientation of the printing substrate 2 . The decoration method and apparatus 1 permit obtaining in a simple manner but with high precision the position of a plurality of points of at least one longitudinal edge Bl of the printing substrate 2 exploiting the high contrast between the lighted edge Bl and the dark surface S , and thus determining with j ust as much precision data concerning the position and the orientation of the printing substrate 2 so as to be able to adj ust with extreme precision the operation of the printing assembly 8 , rotating and / or translating the predefined decoration as a function of the real position and orientation of the printing substrate 2 entering the printing station 6 .

[0078] Furthermore , the decoration method and apparatus 1 allow eliminating every need for mechanical orientation of the printing substrate 2 upstream of or at the printing station 6 , avoiding the risk of damaging the printing substrates 2 .

Claims

CLAIMS1. A surface decoration apparatus (1) for decorating a printing substrate (2) made of a ceramic material and having at least a first and a second edge (Bl, B2) substantially parallel to each other, a third edge (B3) and a fourth edge, which join said first and second edges (Bl, B2) to each other extending transverse (in particular, orthogonal) to them; the surface decoration apparatus (1) comprises: a conveyor assembly (4) , which defines an advancing plane (5) for receiving said printing substrate (2) and advancing it along a given path (P) , in an advancing direction (A) , through at least one printing station (6) and a detection station (7) , located upstream of said at least one printing station (6) along said given path (P) ; a printing assembly (8) comprising at least one printing unit (9) arranged at said printing station (6) and configured to create a predefined decoration (D) on said printing substrate ( 2 ) ; at least one lighting unit (Ila) , which is arranged at said detection station (7) , positioned on a first side of said advancing plane (5) at a defined distance from said first edge (Bl) , along a direction (B) transverse to said advancing direction (A) and to said first edge (Bl) , and is configured to emit a grazing light (in particular, a beam of grazing light) with respect to the advancing plane (5) so as to light exclusively a portion of said first edge (Bl) ; an optical detection system (12) , which is arranged above said advancing plane (5) at said detection station (7) , is configured to capture images of a capturing area containing at least the zone of said advancing plane (5) that, in use, is occupied by said first lighted edge (Bl)advancing through said detection station (7) and comprises at least one processor configured to estimate, based on the captured images, the position and the orientation of said printing substrate (2) ; and a control system (CU) configured to adjust the operation of said printing assembly (8) as a function of the position and the orientation of the printing substrate (2) estimated by said processor.

2. The surface decoration apparatus (1) according to claim 1, wherein said processor is configured to process said captured images and to determine, based on said captured images, the development of said first edge (Bl) and to estimate the position and the orientation of said printing substrate (2) as a function of the development of said first edge (Bl ) .

3. The surface decoration apparatus (1) according to claim 1 or 2, comprising at least one further lighting unit (11b) , which is arranged at said detection station (7) positioned on a second side of said advancing plane (5) , opposite the first side with respect to said advancing direction (A) , at a defined distance, along said transverse direction (B) , from said second edge (B2) of said printing substrate (2) that, in use, advances along said path (P) , and is configured to emit a grazing light with respect to said advancing plane (5) so as to light (in particular, exclusively) a portion of said second edge (B2) ; said capturing area of said optical detection system (12) being configured to also contain a zone of said advancing plane (5) that, in use, is occupied by said second lighted edge (B2) of the printing substrate (2) advancing through said detection station (7) , so as to also captureimages of said second lighted edge (B2) ; and said processor being configured to process said captured images and to also determine, based on said captured images, the development of said second edge (B2) and to estimate the position and the orientation of said printing substrate (2) as a function of the development of said first edge (Bl) and of said second edge (B2) .

4. The surface decoration apparatus (1) according to any one of the preceding claims, wherein said at least one lighting unit (Ila) or (when provided) each one of the lighting units (Ila, 11b) comprises (in particular, consists of) an optical fibre light source (13) configured to emit a light beam and a focal lens (14) to concentrate said light beam so as to obtain a light plane that extends substantially parallel to said advancing plane (5) , defining said grazing light .

5. The surface decoration apparatus (1) according to any one of the preceding claims, wherein said at least one lighting unit (Ila) , or (when provided) each one of the lighting units (Ila, 11b) , is mounted, in a movable manner, on a guide (15) extending transverse to said advancing direction (A) along said transverse direction (B) and can be operated so as to translate along said guide (15) , as a function of the format of the printing substrate (2) , so as to keep said given distance between said at least one lighting unit (Ila) and the first edge (Bl) , or between each one of said lighting units (Ila, 11b) and the first or second edge (Bl, B2) constant as the format of said printing substrate (2) varies.

6. The surface decoration apparatus (1) according to any one of claims from 3 to 5, wherein:said optical detection system (12) comprises (in particular, consists of) at least one pair of optical detection devices (17) ; and each one of said optical detection devices (17) is configured to capture images of a respective capturing area that involves said advancing plane (5) at least at the zone that, in use, is occupied by the first lighted edge (Bl) and by the second lighted edge (B2) , respectively, of the printing substrate (2) advancing through said detection station ( 7 ) ; in particular, each one of said optical detection devices (17) is mounted, in a movable manner, on a further guide extending along said transverse direction (B) and can be operated so as to translate along said further guide in order to adjust the position of each optical detection device (17) as a function of the format of the printing substrate (2) .

7. The surface decoration apparatus (1) according to claim 6, wherein each one of said optical detection devices (17) comprises (in particular, consists of) a matrix camera.

8. The surface decoration apparatus (1) according to any one of the preceding claims, wherein said optical detection system (12) comprises (in particular, consists of) at least one CIS (Contact Image Sensor) sensor or at least one CCD (Charged Coupled Device) sensor or at least one CMOS (Complementary metal-oxide Semiconductor) sensor.

9. The surface decoration apparatus (1) according to any one of the preceding claims, comprising a detection device (16) , which is configured to detect the presence of said printing substrate (2) at the detection station (7) and is connected to said at least one lighting unit (Ila) (inparticular, to each lighting unit (Ila, 11b) ) and to said optical detection system (12) so as to transmit an actuation signal every time it detects a printing substrate (2) entering said detection station (7) .

10. The surface decoration apparatus (1) according to any one of the preceding claims, comprising a covering portal, which surrounds said advancing plane (5) at said detection station (7) to shield the ambient light coming from the outside at least at said capturing area.

11. The surface decoration apparatus (1) according to any one of the preceding claims, wherein the control system (CU) is configured to rotate and / or translate said predefined decoration intended to be created on said printing substrate (2) based on the estimate of said processor so as to obtain a manipulated decoration to be applied to said printing substrate ( 2 ) .

12. A surface decoration method for decorating a printing substrate (2) made of a ceramic material and having at least a first and a second edge (Bl, B2) substantially parallel to each other and a third edge (B3) and a fourth edge, which join said first and second edges (Bl, B2) to each other extending transverse (in particular, orthogonal) to them; the decoration method comprises: a conveying step, during which a conveyor assembly (4) , which defines an advancing plane (5) , conveys at least one printing substrate (2) along a given path (P) , in an advancing direction (A) , through at least one printing station (6) and a detection station (7) , located upstream of said at least one printing station (6) along said given path (P) ; a printing step, during which a printing assembly (8)comprising at least one printing unit (9, 9' ) arranged at said printing station (6) creates a predefined decoration on said printing substrate (2) ; a lighting step, which is at least partially prior to said printing step and during which a lighting unit (Ila) , which is arranged at said detection station (7) , positioned on a first side of said advancing plane (5) at a defined distance from said first edge (Bl) , along a direction (B) transverse to said advancing direction (A) and to said first edge (Bl) , emits a grazing light (in particular, a beam of grazing light) with respect to the advancing plane (5) and lights exclusively a portion of said first edge (Bl) ; a detection step, which is at least partially simultaneous with said lighting step and with said conveying step and prior to said printing step and during which an optical detection system (12) , arranged above said advancing plane (5) at said detection station (7) , captures, with a given frequency, images of a capturing area containing the zone of said advancing plane (5) that, in use, is occupied by said first lighted edge (Bl) advancing through said detection station (7) and, based on the captured images, estimates the position of the printing substrate (2) and the orientation of said printing substrate (2) with respect to the advancing direction (A) ; and a control step, which is at least partially subsequent to said detection step and simultaneous with the printing step and during which a control system (CU) controls the actuation of said printing assembly (8) based on the estimate of the detection step.

13. The surface decoration method according to claim 12, wherein: said detection step comprises a processing sub-step, during which a processor comprised in the optical detection system (12) determines, based on the captured images, the development of said first edge (Bl) and estimates, based on such development, the position of the printing substrate (2) with respect to a fixed reference system and the orientation of the printing substrate (2) with respect to said advancing direction (A) .

14. The surface decoration method according to claim 12 or 13, wherein, during said lighting step, a further lighting unit (11b) , which is arranged at said detection station (7) on a second side of said advancing plane (5) , opposite the first side with respect to said advancing direction (A) , at a defined distance, along said transverse direction (B) , from said second edge (B2) of said printing substrate (2) , emits a grazing light with respect to the advancing plane (5) and lights (in particular, exclusively) a portion of said second edge (B2) ; and during said detection step, the optical detection system (12) also detects images of the zone of said advancing plane (5) that, in use, is occupied by said second lighted edge (B2) of the printing substrate (2) advancing through said detection station (7) , so as to also estimate the development of said second edge (B2) ; in particular, in this case, during the processing substep, said processor also determines, based on said captured images, the development of said second edge (B2) and estimates the position and the orientation of said printing substrate (2) as a function of the development of said first edge (Bl) and of said second edge (B2) .

15. The surface decoration method according to any one of the claims from 12 to 14, comprising an operation step,which is at least partially prior to said lighting step and to said detection step and during which a detection device (16) , which is located upstream of said detection station (7) along said given path (P) , detects the presence of said printing substrate (2) and transmits an actuation signal to said at least one lighting unit (Ila) or to each lighting unit (Ila, 11b) and to said optical detection system (12) .

16. The surface decoration method according to any one of the claims from 12 to 15, wherein said control step comprises a manipulation sub-step, during which said predefined decoration to be created on said printing substrate (2) is rotated and / or moved based on the estimate of said detection step so as to obtain a manipulated decoration; and, during said printing step, said printing assembly (8) applies said manipulated decoration on said printing substrate (2) .

17. The surface decoration method according to any one of the claims from 12 to 16, comprising a positioning step, which is at least partially prior to said lighting step and during which the position of said at least one lighting unit (Ila) or, when there is more than one, of each lighting unit (Ila, 11b) is adjusted as a function of the format of the printing substrate (2) , so as to keep said given distance between said at least one lighting unit (Ila) and the first edge (Bl) or between each one of said lighting units (Ila, 11b) and the first or second edge (Bl, B2) constant as the format of said printing substrate (2) varies.

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