CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from Italian patent application no . 102020000023374 fi led on 05/ 10/2020 , the entire disclosure of which is incorporated herein by reference .

TECHNICAL FIELD

The present invention relates to a detection system and to a method to detect the density of a layer of compacted ceramic powder .

BACKGROUND OF THE INVENTION

In the manufacturing field of ceramic products , in particular ceramic slabs or tiles , ceramic products are manufactured in systems in which semi-dry ceramic powder ( i . e . , with a moisture content of less than 10% , in particular comprised between 5 and 6% ) is fed ( typically substantially continuously) along a given path through a discontinuous compacting machine ( commonly known as press ) or a continuous compacting assembly, which subj ects the ceramic powder to a compacting pressure , so as to obtain a layer of compacted ceramic powder . In detail , when compacting takes place by means of a discontinuous compacting machine , the layer of compacted ceramic powder substantially has the dimensions of a compacted ceramic powder article ( i . e . , the dimensions of a ceramic slab or tile ) to be subj ected to subsequent drying, optional decorating and firing operations so as to obtain a finished ceramic product , in particular a ceramic slab or tile ; instead, when compacting takes place by means of the continuous compacting assembly, the layer of compacted ceramic powder is in the form of a continuous strip of compacted ceramic powder, which is subsequently cut to obtain a plurality of compacted ceramic powder articles (having the dimensions of a ceramic slab or tile ) which will then be dried, optionally decorated, and fired to obtain the finished ceramic products . Compacting of the ceramic powder , both when carried out by means of one or more discontinuous compacting machines and by means of a continuous compacting assembly, requires precision and control in order for the layer of compacted ceramic powder ( and hence the compacted ceramic powder articles ) to have a density that is as homogeneous as possible and at the same time able to ensure correct behaviour during firing . In fact , the more homogeneous the density inside the article of compacted ceramic powder is , the fewer the distortions it will undergo during the subsequent operations , in particular during firing, will be . Moreover, to ensure the reproducibility of production ( i . e . , to produce , in each production cycle , ceramic products that are the same as one another ) , the density value must remain stable throughout the whole of the production cycle , to avoid shrinkage di f ferences (normally comprised between 7 and 8 % ) that would lead to rej ects and/or dimensional deviations .

From the above , it is clear that the density of the layer of compacted ceramic powder is an essential physical parameter to be kept under control during the production of ceramic products . Currently, this parameter is generally detected with mercury or glycerine immersion measuring devices that allow determination of the mass and volume , and consequently calculation of the density, of a speci fically produced sample of compacted ceramic powder . In detail , the known procedure to detect the density of a layer of compacted ceramic powder comprises producing a sample , typically with small dimensions ( in particular, in the order of 1 cm per side ) , immersing this sample in a mercury or glycerine bath so as to determine its weight , using a mercury or glycerine immersion balance , and the volume , measuring the hydrostatic thrust necessary to keep the sample immersed in the bath itsel f .

However, this procedure is particularly laborious and must be conducted by skilled operators in order to minimise the risk of errors and obtain reliable measurements . Another disadvantage of this procedure is linked to the fact that it requires the production of a speci fic sample which is generally obtained from a compacted ceramic powder article , which will then be discarded, with consequent economic drawbacks .

Moreover, in the case of use of mercury immersion measuring devices , there is a further drawback linked to the fact that the use of mercury is potential ly harmful to human health and therefore its use requires compliance with specific safety requirements .

Added to this is the fact that the procedure described above to detect the density cannot be used when the production of ceramic products is carried out in a continuous production line and, more in detail , when compacting the ceramic powder is carried out in a continuous compacting assembly, such as , for example, those described in the patents EP1283097B1 , EP1356909B1 , EP1641607B1 , EP2763827B1 , WO2013050865A1 . In fact , in these cases the ceramic powder is fed and moves on a lower conveyor belt while an upper belt causes it to become gradually thicker until reaching two pressing rollers that apply a final compacting pressure so as to obtain a layer of compacted ceramic powder in the form of continuous strip of compacted ceramic powder, which will then be cut to obtain a plurality of compacted ceramic powder articles . It is clear that the procedure for detecting the density described above (which envisages the production of a speci fic sample and immersion of this sample in a mercury or glycerine bath) would cause discontinuity in the continuous production line , with negative ef fects on its productivity .

Therefore , in these cases , the density is determined through detection systems arranged in line and configured to detect ( in a non-destructive manner ) the density of the layer of compacted ceramic powder (more in particular, in general of compacted ceramic powder articles ) , during movement along the production line . In detail , a known detection system of the density determines the density of each compacted ceramic powder article based on the thickness of the article itsel f and the absorption of X-rays applying the Beer-Lambert law . However, according to the Beer-Lambert law, the density value , in addition to the thickness and to the absorption of X-rays , also depends on an absorption coef ficient that is an intrinsic property of the ceramic material being compacted . Therefore , in order to estimate the density correctly, the detection system must be calibrated, inputting the data relating to thi s absorption coef ficient each time the ceramic material that feeds the production line is changed . Currently, the absorption coef ficient is typically measured using the measuring devices in a mercury or glycerine bath described above , with all the aforesaid drawbacks .

Added to these drawbacks is a slowing of the production cycle of the continuous production line of the ceramic products caused by the calibration operations , the impact of which in terms of machine stoppage , and therefore drops in productivity, becomes increasingly important the more frequently the ceramic material that feeds the production line is changed, hence the more often these calibration operations must be repeated .

Examples of known detection methods and systems of the type described above , which allow determination of the density of each compacted ceramic powder article based on the absorption of radiation of di f ferent types , for example X-rays or laser rays , are described in the documents WO2018051257 , ES2208120 and W02020058933 .

The obj ect of the present invention is to provide a detection system and a method to detect the density of compacted ceramic powder articles , said detection system and method allowing to at least partially overcome the drawbacks of the known art and which at the same time are simple and inexpensive to produce . SUMMARY

In accordance with the present invention, a detection system and a method to detect the density of a layer of compacted ceramic powder are provided according to the annexed independent claims , and preferably, any one of the claims directly or indirectly dependent on the aforesaid independent claims .

The claims describe preferred embodiments of the present invention forming an integral part of the present description .

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the attached drawings , which show some non-limiting embodiments thereof , wherein :

- Fig . 1 is a side and schematic view of a detection system to detect the density of a layer of compacted ceramic powder ;

- Fig . 2 is a schematic side view on an enlarged scale of a part of the detection system of Fig . 1 ;

- Fig . 3 is a schematic and side view of a further part of the detection system of Fig . 1 in accordance with a first embodiment of the invention; and

- Figs . 4 and 5 are schematic and side views of the same part of the detection system depicted in Fig . 3 in accordance with a further embodiment of the invention, in two di f ferent operating configurations .

DETAILED DESCRIPTION

In Fig . 1 the number 1 indicates as a whole a detection system to detect the density of a layer o f compacted ceramic powder KP .

In the present description, the expression " layer of compacted ceramic powder" refers generically to a quantity ( i . e . , to a mass ) of ceramic powder CP after it has been compacted . In other words , the expres sion " layer of compacted ceramic powder" refers both to a continuous strip of compacted ceramic powder coming out of a continuous compacting assembly 2 ( as , for example , illustrated in Fig. 1) , and to a compacted ceramic powder article MCP formed following cutting of the aforesaid continuous strip of compacted ceramic powder or (in accordance with further embodiments, not illustrated) formed directly by compacting a dosed quantity of (uncompacted) ceramic powder CP inside a discontinuous compacting machine (i.e., a press) .

According to some advantageous, but non-exclusive, embodiments (such as the one illustrated in Fig. 1) , the detection system 1 comprises a conveyor assembly 3 configured to convey the (uncompacted) ceramic powder CP along a given path P that extends in a moving direction A from an inlet station 4, at which a feeding assembly 5 feeds a given quantity (i.e. a mass) of (uncompacted) ceramic powder CP, to an outlet station 6, passing through at least one compacting station 7, where this (uncompacted) ceramic powder CP is compacted by a compacting device 8 (which is also part of the detection system 1) , and through a detection station 11, where the density of the layer of compacted ceramic powder KP is detected.

According to some advantageous, but non-exclusive, embodiments (such as the one illustrated in Fig. 1) , the conveyor assembly 3 comprises a conveyor device 9 configured to receive the given quantity (i.e., the mass) of (uncompacted) ceramic powder CP and convey it (substantially continuously) from the inlet station 4 to the (end of the) compacting station 7 along a segment PA of the given path P; and a further conveyor device 10 arranged and configured to receive (in particular, from the conveyor device 9) the layer of compacted ceramic powder KP, or a part thereof, and convey it (substantially continuously) from the compacting station 7 to the outlet station 6, passing through the detection station 11, along a further segment PB of the given path P.

Advantageously, but without limitation, the given path P that goes from the inlet station 4 to the outlet station 6 comprises (in particular, consists of) segments PA and PB that follow one another continuously, i . e . , without the interposition of other segments .

According to some advantageous , but non-limiting, embodiments , the feeding assembly 5 comprises at least one dispensing device 12 ( for example , in the non-limiting embodiment illustrated in Fig . 1 , three dispensing devices 12 arranged one after another along the segment PA of the given path P and each) configured to produce a variable loading profile both along the moving direction A and crosswise to the moving direction A.

Advantageously, but without limitation, the compacting device 8 is arranged at the compacting station 7 downstream of the feeding assembly 5 along the segment PA of the given path P and is configured to apply a controlled compacting pressure on the (uncompacted) ceramic powder CP itsel f so as to compact the ceramic powder CP and obtain the layer of compacted ceramic powder KP .

In particular, according to some advantageous , but non-limiting, embodiments ( such as the one illustrated in Fig . 1 ) , the compacting device 8 comprises ( in particular, consists of ) a continuous compacting assembly 2 arranged along the segment PA of the given path P . In this case , advantageously, but without limitation, the conveyor device 9 comprises ( in particular, consists of ) a conveyor belt 13 that extends ( and is configured to move ) from the inlet station 4 to the ( and through the ) compacting station 7 along the segment PA of the aforesaid given path P and the compacting device 8 (more in particular, the continuous compacting assembly 2 ) comprises at least two compression rollers 14 arranged on opposite sides of the ( in particular, one above and one below the ) conveyor belt 13 to exert a pressure on the (uncompacted) ceramic powder CP so as to compact the (uncompacted) ceramic powder CP itsel f and obtain the layer of compacted ceramic powder KP . Moreover, advantageously but not necessarily, (as illustrated, for example, in Fig. 1) , the compacting device 8 (in particular, the continuous compacting assembly 2) comprises a pressure belt 15, arranged between the feeding assembly 5 and the aforesaid compression rollers 14, said pressure belt 15 converging toward the conveyor belt 13 in the moving direction A so as to exert a (downward) pressure that gradually increases in the direction A on the ceramic powder CP so as to compact it while it moves along the segment PA of the given path P. In particular, the pressure belt 15 is (mainly) made of metal (steel) so that it cannot be substantially deformed while pressure is exerted on the ceramic powder.

According to specific embodiments (such as the one illustrated in Fig. 1) , in this case the compacting device 8 (in particular, continuous compacting assembly 2) also comprises a counterpressure belt 15' arranged on the opposite side of the conveyor belt 13 (in particular, made of rubber or a similar material) relative to the pressure belt 15 to cooperate with the conveyor belt 13 to provide a suitable opposition to the downward force exerted by the pressure belt 15. In these cases, in particular, the counter-pressure belt 15' is (mainly) made of metal (steel) so that it cannot be substantially deformed while pressure is exerted on the ceramic powder.

According to some embodiments, not illustrated, the counterpressure belt 15' and the conveyor belt 13 coincide. In other words, the conveyor belt 13 is (mainly) made of metal (steel) and the counter-pressure belt 15' is absent.

In these cases, i.e., when the compacting device 8 comprises a continuous compacting assembly 2, the detection system 1 also comprises a cutting device 16 (schematically illustrated in Fig. 1) which is arranged downstream of the continuous compacting assembly 2 (in particular, at the compacting station 7 but downstream of the compacting device 8) along the first segment PA of the given path P and configured to cut the layer of compacted ceramic powder KP generated by the continuous compacting assembly 2 (while thi s layer of compacted ceramic powder KP moves continuously along the segment PA) crosswise , so as to obtain at least one first portion Pl and one second portion P2 . In particular ( advantageously, but without limitation) , the cutting device 16 cuts the layer of compacted ceramic powder KP crosswise so as to obtain a plurality of compacted ceramic powder articles MCP, each of which comprises ( in particular, has ; even more in particular, consists of ) a respective portion Pl , P2 of the layer of compacted ceramic powder KP . Even more in particular, each of the compacted ceramic powder articles MCP coincides with a portion Pl , P2 of the layer of compacted ceramic powder KP .

According to some advantageous , but non-limiting, embodiments , the cutting device 16 comprises at least one cutting blade (not illustrated) configured to come into contact with the layer of compacted ceramic powder KP and to cut it , in particular during cutting this blade is operated to move along a transverse traj ectory relative to the moving direction A so as to provide the compacted ceramic powder articles MCP with end edges substantially perpendicular to the direction A.

According to alternative embodiments , not illustrated, the compacting device 8 comprises ( in particular, consists of ) at least one discontinuous compacting machine ( commonly known as press - known per se and therefore not described in further detail ) , arranged immediately downstream of the feeding assembly 5 along the segment PA of the given path P and configured to compact a dosed quantity of (uncompacted) ceramic powder CP, which in this case , advantageously, but not necessarily, will be fed by the feeding assembly 5 directly to the discontinuous compacting machine to generate the layer of compacted ceramic powder KP, and in particular at least the aforesaid first portion Pl of the layer of compacted ceramic powder . In these cases ( i . e . , when the compacting device 8 comprises a discontinuous compacting machine ) , advantageously, but without limitation, the detection system 1 comprises at least a further compacting device (not illustrated) which also comprises ( in particular, consists of ) a further discontinuous compacting machine configured to compact a further dosed quantity of (uncompacted) ceramic powder CP (which, also in this case , advantageously, but not necessarily, will be fed by the feeding assembly 5 directly to the further discontinuous compacting machine ) to generate a further layer of compacted ceramic powder and, in particular, to generate the aforesaid second portion P2 ( of the further layer of compacted ceramic powder ) .

Alternatively, advantageously, but without limitation, the compacting device 8 and the further compacting device can coincide with one another, i . e . , the detection system 1 can comprise a single discontinuous compacting machine that generates in several subsequent processing ( i . e . , pressing) cycles , the aforesaid first portion Pl and second portion P2 ; in particular, several compacted ceramic powder articles MCP .

According to some advantageous , but non-exclusive , embodiments , the detection system 1 furthermore comprises a measuring device 17 configured to measure at least a thickness of at least one cross section of the layer of compacted ceramic powder KP . Advantageously, in order to improve the precision of this measurement , the measuring device 17 is configured to carry out at least two , in particular at least three , measurements ( at the aforesaid cross section of the layer of compacted ceramic powder KP ) to determine the aforesaid thickness . Alternatively, or in combination, the measuring device 17 is , advantageously, but without limitation, configured to measure the thickness of at least two cross sections , more in particular of at least three cross sections , of the layer of compacted ceramic powder KP, so as to also take into account any variations of thickness along the transverse extension of the layer of compacted ceramic powder KP .

According to some non-exclusive embodiments (such as the one illustrated in Fig. 1) , the measuring device 17 is arranged along the segment PA of the given path P (in particular at the compacting station 7 and) downstream of the compacting device 8, even more in particular between the compacting device 8 and the cutting device 16, when present.

Alternatively, or in combination (according to other embodiments such as the one illustrated - see Figs. 1 and 2) , the detection system 1 (also) comprises a (further) measuring device 17' , similar to the measuring device 17, arranged along the segment PB of the given path P and forming part of a detection device 18, which will be described in more detail in the following.

According to other advantageous, and non-limiting, embodiments, the measuring device 17 and the further measuring device 17' coincide with one another, i.e., the detection system 1 is provided with a single measuring device 17, 17' (which can be part of the detection device 18 or be separate from the detection device 18 and which is) configured to detect the thickness of the layer of compacted ceramic powder KP or of a portion Pl, P2 thereof. These thicknesses (of the layer of compacted ceramic powder KP or of a portion Pl, P2 thereof) are, in fact, substantially coincident with one another. In other words, according to some advantageous, but non-limiting, embodiments, the thickness of the layer of compacted ceramic powder KP is substantially homogeneous along the whole of its extension; in particular (even more advantageously, but without limitation) , the thickness of the first portion Pl is substantially the same as (i.e., coincides with) the thickness of the second portion P2.

Even more in particular, advantageously, but without limitation, the aforesaid at least one cross section of the layer of compacted ceramic powder KP the thickness of which is measured by the measuring device 17 is comprised in the first portion Pl (i.e., is a cross section of the first portion Pl) .

According to some advantageous, but non-exclusive, embodiments (such as the one illustrated in Fig. 2) the (each) measuring device 17' (17) comprises (in particular, consists of) a pair of feelers.

Alternatively, the (each) measuring device 17' (17) comprises (in particular, consists of) at least one sensor capable of measuring, advantageously with a precision below around 0.02 mm, the thickness of the layer of compacted ceramic powder KP .

Advantageously, but without limitation, the conveyor device 9 ends in the area of (the end of) the compacting station 7, and is arranged and configured (in particular, is aligned with the conveyor device 10) to transfer at least the first portion Pl and the second portion P2 (in particular the plurality of compacted ceramic powder articles MCP) formed by cutting the layer of compacted ceramic powder KP (when compacting takes place by means of a continuous compacting assembly 2) or by compressing several dosed quantities of ceramic powder CP (when compacting takes place by means of a discontinuous compacting machine) along the segment PB of the given path P.

In particular, advantageously, but without limitation, the conveyor device 10 moves the first portion Pl and the second portion P2 (in particular the plurality of compacted ceramic powder articles MCP) at a speed different to the speed with which the conveyor device 9 conveys the (uncompacted) ceramic powder CP to the (and through the) compacting station 7. More precisely, the speed of the conveyor device 10 adapts to the speed with which the compacted ceramic powder articles MCP move coming out of the segment PA of the given path P so as to always ensure correct distancing between the compacted ceramic powder articles MCP that move along the second segment PB of the given path P . The correct distancing between the compacted ceramic powder articles MCP ( together, as will be explained in the following, with the arrangement in line and with the configuration of the detection station 11 ) advantageously allows detecting of the properties ( in particular, at least the weight and a quantity correlated with the density) of each compacted ceramic powder article MCP independently from the other compacted ceramic powder articles MCP and without blocking the movement of the compacted ceramic powder articles MCP along the segment PB of the given path P , with clear advantages in terms of production continuity and ef ficiency .

Advantageously, but without limitation, the detection system 1 comprises a detection device 18 , which is arranged along the given path P, advantageously, but without limitation, along the segment PB of the given path P , in particular at the detection station 11 , and is configured to detect at least one quantity correlated with the density of at least an area of the first portion Pl of the layer of compacted ceramic powder KP, in particular when this ( first portion Pl ) is at the detection station 11 . In detail , advantageously, this first portion Pl has a given width and a given length and is comprised in ( in particular, coincides with) one ( even more in particular with the first - among those moved coming out of the segment PA of the given path P ) of the aforesaid compacted ceramic powder articles MCP .

According to some advantageous , but non-limiting, embodiments , the detection device 18 is configured to detect at least one quantity correlated with the density ( in particular, of the whole ) of the first portion Pl of the layer of compacted ceramic powder KP . In other words , according to some advantageous , but non-limiting, embodiments , the quantity correlated with the density of the first portion Pl of the layer of compacted ceramic powder KP remains the same along the whole of the extension of this first portion Pl . In this case , the aforesaid area of the first portion Pl of the layer of compacted ceramic powder KP coincides with the whole ( of the extension) of the first portion Pl .

Even more advantageously, but without limitation, the detection device 18 is configured to detect the quantity correlated with the density of the first portion Pl of the layer of compacted ceramic powder KP in proximity of ( even more in particular, in the area of ) the aforesaid cross section that the measuring device 17 , 17 ' measures the thickness of .

Advantageously, but without limitation, the detection device 18 is arranged ( immediately) adj acent to the measuring device 17 , 17 ' . According to yet other advantageous , but non-limiting, embodiments ( as already mentioned above ) , the detection device 18 comprises the measuring device 17 , 17 ' .

Advantageously, but without limitation, the detection device 18 is configured to ( also ) detect a quantity correlated with the density also of at least one second first portion P2 of the layer of compacted ceramic powder KP ( in particular, of at least an area of the second portion P2 ) or of a further layer of compacted ceramic powder (not illustrated) , in particular when this ( the second portion P2 ) is at the detection station 11 . Advantageously, also this second portion P2 has a given width and a given length and is comprised in ( in particular, coincides with) one ( even more in particular with the second - among those moved coming out of the segment PA of the given path P ) of the aforesaid compacted ceramic powder articles MCP . Also in this case , according to some advantageous , but non-limiting, embodiments , the quantity correlated with the density of the second portion P2 of the layer of compacted ceramic powder KP remains the same along the whole o f the extension o f this second portion P2 , so that the aforesaid area of the second portion P2 of the layer of compacted ceramic powder KP coincides with the whole ( of the extension) of the second portion P2 .

The expression "quantity correlated with the density" means a quantity based on the density of these portions Pl , P2 , in particular that i s the same as the density of these portions Pl , P2 except for a constant that depends on the quality of the ceramic material , i . e . , on the type ( for example , on the composition) of the ceramic powder CP used to produce the layer of compacted ceramic powder KP .

Advantageously, but without limitation, the expression "quantity correlated with the density" of the layer of compacted ceramic powder KP means a quantity proportional to the density of the layer of compacted ceramic powder KP . More in particular ( in this case ) , advantageously, but without limitation, the coef ficient of proportionality between the "quantity correlated with the density" and the density of the layer of compacted ceramic powder KP itsel f is a constant value that is based on the quality of the ceramic material , i . e . , on the type ( for example , on the composition ) of the ceramic powder CP used to produce the layer of compacted ceramic powder KP .

In detail , according to some advantageous but non-limiting embodiments of the invention, such as the one i llustrated in Fig . 2 , the detection device 18 comprises : an emission device 19 , which is arranged along the given path P at the detection station 11 and is configured to emit an X-ray beam having a given emission intensity towards a first side LI of the first portion Pl , when this is at the detection station 11 , so that said X-ray beam goes through it and goes out from a second side L2 of this first portion Pl , opposite the first side LI ; an acquisition device 20 , which is arranged along the given path P at the detection station 11 and is configured to detect an output intensity of the X-ray beam going out from the second side L2 of the first portion Pl ; and a processing unit 21 , configured to determine the aforesaid quantity correlated with the density of the first portion Pl based on the emission intensity, on the output intensity and on the thickness of this first portion Pl .

In particular, advantageously, the emission device 19 is configured to emit an X-ray beam of given intensity, as described above , on each portion Pl , P2 ( i . e . , on each compacted ceramic powder article MCP ) at the detection station 11 , and similarly the acquisition device 20 is configured to detect an output intensity of the X-ray beam going out from the second side L2 of each portion Pl , P2 ( i . e . , of each compacted ceramic powder article MCP ) so as to evaluate this quantity correlated with the density for each portion Pl , P2 ( i . e . , for each compacted ceramic powder article MCP ) .

According to some embodiments , the "quantity correlated with the density" of a layer of compacted ceramic powder KP is a relative density . Even more in particular, advantageously, but without limitation, this "quantity correlated with the density" ( or relative density) of a layer of compacted ceramic powder KP is a density value estimated ( only) based on the emission intensity and on the output intensity of the aforesaid X-ray beam emitted by the emission device 19 on the layer of compacted ceramic powder KP ; in particular, on the respective portion Pl and/or P2 of the layer of compacted ceramic powder KP . Even more advantageously, but without limitation, the expression "quantity correlated with the density" of a layer of compacted ceramic powder KP refers to a measurement of the capacity of this layer of compacted ceramic powder KP to absorb X-rays .

In detail , advantageously, but not necessarily, the processing unit 21 is configured to determine this quantity correlated with the density by means of the Beer-Lambert law .

When the compacting device 8 is a continuous compacting assembly 2 , advantageously, but without limitation, the detection station 11 is located along the segment PB of the given path P, in particular downstream of the cutting device 16 , and the quantity correlated with the density of the first portion Pl and of the second portion P2 is detected after these have been separated ( i . e . , cut ) from the layer of compacted ceramic powder KP . Alternatively, the detection station 11 can be upstream of the cutting device 16 and the quantity correlated with the density can be detected before the first portion Pl and the second portion P2 are separated from the layer of compacted ceramic powder KP .

According to some non-limiting embodiments ( such as the one illustrated) , the detection system 1 also comprises a weighing device 22 , arranged along the segment PB of the given path P and configured to determine a weight of at least the first portion Pl of the layer of compacted ceramic powder KP . In particular, when the compacting device 8 comprises a continuous compacting assembly 2 and a cutting device 16 , the weighing device 22 is advantageously arranged downstream of the cutting device 16 to measure the weight of the aforesaid first portion Pl of the layer of compacted ceramic powder KP independently from the others , i . e . , to detect the weight of a single compacted ceramic powder article MCP, independently from the others .

Advantageously, but without limitation, the detection system 1 furthermore comprises a control assembly 23 , which is connected to the weighing device 22 , to the measuring device 17 and/or 17 ' and to the detection device 18 and is designed to estimate an actual density of at least the aforesaid second portion P2 of the layer of compacted ceramic powder KP or of a further layer of compacted ceramic powder (not illustrated in the attached figures ) based on the data detected by the detection device 18 , by the weighing device 22 and by the measuring device 17 and/or 17 ' , and in particular also based on the given width and on the given length of at least the first portion Pl .

In detail , advantageously, but without limitation, the control assembly 23 is configured to : determine an absolute density of at least the first portion Pl based on the weight , the thickness , the given width and the given length of this first portion Pl ; estimate a correction coef ficient based on comparison between the absolute density and the aforesaid quantity correlated with the density of the first portion Pl ; and to determine the actual density of the second portion P2 of the layer of compacted ceramic powder KP, or of the further layer of compacted ceramic powder KP, based on the quantity correlated with the density of this second portion P2 and on the previously estimated correction coef ficient .

According to some advantageous , but non-limiting, embodiments ( such as the one illustrated in Fig . 1 ) the control assembly 23 comprises , in turn : a processing unit 24 connected to the measuring device 17 and/or 17 ' , and to the weighing device 22 and configured to determine an absolute density of at least the first portion Pl based on the weight , the thickness , the given width and the given length of this first portion Pl ; and a processing unit 25 connected at least to the detection device 18 and to said processing unit 24 and configured to compare the absolute density and the aforesaid quantity correlated with the density of the first portion Pl so as to determine a correction coef ficient . In this case , advantageously, but without limitation, one between the processing unit 24 and the processing unit 25 is configured to determine the actual density of the second portion P2 based on the quantity correlated with the density of this second portion P2 and of the correction coef ficient .

Even more advantageously, this control assembly 23 , advantageously produced as described above , is configured to estimate an actual density of all the compacted ceramic powder articles MCP that arrive at the detection station 11 , based on data detected by the detection device 18 ( in particular, on the quantity correlated with the density of each compacted ceramic powder article MCP ) , by the weighing device 22 ( in particular, on the weight of at least the first portion Pl ) and by the measuring device 17 and/or 17 ' ( in particular, on the thickness of the layer of compacted ceramic powder KP, even more in particular of at least the first portion Pl ) , and even more in particular also based on the given width and the given length of at least the first portion Pl .

It is understood that advantageously, but not necessarily, the processing unit 24 and/or the processing unit 25 and/or the processing unit 21 can coincide with one another, i . e . , there can be a single processing unit , which can optionally coincide with the processing unit of the whole production line of ceramic products , in particular of ceramic slabs or tiles , when the detection system 1 is part of ( is arranged along) the production line of ceramic products .

Advantageously, but without limitation, the control assembly 23 is also configured to control the feeding assembly 5 so as to vary ( over time ) the quantity of ceramic powder CP fed to the inlet station 4 based on the actual density of the layer of compacted ceramic powder KP detected . In particular, the control assembly 23 is configured to control the feeding assembly 5 so that the quantity of ceramic powder CP fed increases where a density below a ( desired) reference density is detected and decreases where a density above a ( desired) reference density is detected . Moreover, advantageously, but without limitation, in particular, the control assembly 23 is ( also ) configured to control the compacting device 8 so as to adj ust the compacting pressure exerted by the compacting device 8 on the ceramic powder CP based on the actual density of the layer of compacted ceramic powder KP detected .

According to some advantageous , but non-limiting, embodiments ( such as the one illustrated in Fig . 1 ) , the conveyor device 9 comprises ( in particular, consists of ) a plurality of rollers 26 , which are arranged beside one another along the second segment PB of the given path P and are oriented crosswise relative to the moving direction A to define a moving plane on which at least the first portion Pl and the second portion P2, and even more in particular all the compacted ceramic powder articles MCP, move.

In this case, according to some advantageous but non-limiting variants of the detection system 1 (such as the one illustrated partially and schematically in Fig. 3) , the weighing device 22 comprises (in particular, consists of) a plurality of load cells 27, which are arranged below the aforesaid moving plane, in particular at least in the area of a part of the segment PB of the given path P and are configured to determine the weight of at least the first portion Pl while this moves on the moving plane, in particular when it (the first portion Pl) is in the area of, even more in particular above, the load cells 27.

Alternatively, according to further advantageous, but nonlimiting, variants of the detection system 1 (such as the one illustrated schematically in Figs. 4 and 5) , the plurality of rollers 26 of the conveyor device 9 comprises vertically movable rollers 26' to lift the first portion Pl (see Fig. 5) ; and the weighing device 22 comprises (in particular, consists of) a plurality of load cells 27, each connected to a movable roller 26' and configured to determine said weight of the first portion Pl when the first portion Pl is arranged in the area of, in particular above, its movable rollers 26' and these movable rollers 26' are operated to lift the first portion Pl.

Alternatively, according to further non-limiting embodiments not illustrated, the conveyor device 10 comprises (in particular, consists of) a conveyor belt that extends along the second segment PB of the given path P and defines a moving plane and the weighing device 22 comprises (in particular, consists of) a plurality of load cells arranged below the moving plane (in particular in contact with, or in any case connected to, the conveyor belt ) and configured to determine the weight of at least the first portion Pl while this moves on the moving plane , in particular when it is in the area of , even more in particular above , the load cells 27 .

It is also understood that the weighing device 22 could be produced in any other way that allows detection of the weight of at least the first portion Pl of the layer of compacted ceramic powder KP with suf ficient precision to allow correct evaluation of the aforesaid correction coef ficient .

In this regard, according to some advantageous , but non-limiting embodiments , the detection system 1 could be configured to form a first portion Pl speci fically si zed to ensure greater precision in evaluating the weight ( also ) with weighing devices 22 of a known type . In particular, the control assembly 23 could be configured to ( in particular, control the cutting device 16 , when present , or the discontinuous compacting machine so as to ) form a first portion Pl having a length and a width suf ficient to ensure , taking account of the thickness of the layer of compacted ceramic powder KP and of the measurement precision achievable by the weighing device 22 used, a correct and precise evaluation of the weight and consequently of the absolute density of the first portion Pl and therefore the correction coef ficient . Even more in particular, in this case the control assembly 23 could be configured to reduce the length ( and optionally the width) of the first portion Pl when the thickness of this first portion Pl increases so as to minimi ze the variation of weight to be evaluated also when the thickness of the layer of compacted ceramic powder KP varies .

In accordance with a further aspect of the present invention, a method to detect the density of a layer of compacted ceramic powder KP is provided . In particular, the method is advantageously, but without limitation, implemented by the detection system 1 described above . Advantageously, but without limitation, the method comprises a first compacting step, during which (uncompacted) ceramic powder CP is compacted by a compacting device 8 ( advantageously, but without limitation, produced in accordance with one of the embodiments described above ) that applies a compacting pressure on the (uncompacted) ceramic powder CP so as to obtain a layer of compacted ceramic powder KP ; and a moving step, during which the layer of compacted ceramic powder KP is conveyed along a given path P in a moving direction A by a conveyor assembly 3 ( advantageously, but without limitation, of the type described above ) .

Advantageously, but without limitation, at least when the compacting device 8 comprises a continuous compacting assembly 2 , the first compacting step is simultaneous with the moving step, i . e . , as better described above with reference to the detection system 1 , compacting of the ceramic powder CP takes place while it moves along the segment PA of the given path P . Moreover, in this case ( advantageously, but without limitation) the method also comprises a cutting step, at least partially subsequent to the first compacting step , during which a cutting device 16 ( advantageously, but without limitation, of the type described above ) cuts the layer of compacted ceramic powder KP crosswise so as to obtain at least the first portion Pl and the second portion P2 , in particular a plurality of compacted ceramic powder articles MCP, each having a respective first portion Pl , P2 of the layer of compacted ceramic powder KP which has a given width and a given length .

According to some non-limiting variants , not illustrated, when the compacting device 8 comprises ( in particular, consists of ) a discontinuous compacting machine , the layer of compacted ceramic powder KP generated during the first compacting step ( advantageously) comprises , in particular coincides with, the first portion Pl and the method also comprises a second compacting step, similar to the first compacting step, during which the (uncompacted) ceramic powder CP is compacted so as to obtain a further layer of compacted ceramic powder , which ( advantageously) comprises , in particular coincides with, the second portion P2 . In this case ( i . e . , when the second compacting step is provided) , during the moving step the further layer of compacted ceramic powder is conveyed by the conveyor device 9 out of the segment PA of the given path P so that the first portion Pl of the layer of compacted ceramic powder KP, generated during the first compacting step, and the second portion P2 of the further layer of compacted ceramic powder KP, generated during the second compacting step, are conveyed along the segment PB of the given path P arranged one after the other .

Advantageously, the method furthermore comprises a measuring step during which a measuring device 17 and/or 17 ' ( advantageously, but without limitation, of the type described above ) arranged along the given path P carries out at least one measurement , advantageously at least two measurements , even more advantageously at least three measurements , of a thickness of at least one cross section of the layer of compacted ceramic powder KP ; and a first detection step, during which the aforesaid quantity correlated with the density of the first portion Pl ( in particular, of at least an area of this first portion Pl ) is detected .

As already mentioned above with reference to the detection system 1 , according to some advantageous and non-limiting embodiments , the thickness of the layer of compacted ceramic powder KP is substantially homogenous along the whole of its extension; in particular ( even more advantageously, but not necessarily) the thickness of the first portion Pl is substantially the same as ( i . e . , coincides with) the thickness of the second portion P2 .

Even more in particular, advantageously, but without limitation, during the aforesaid measuring step, the measuring device 17 and/or 17 ' carries out at least one measurement of a thickness of the first portion Pl . In other words , advantageously but without limitation, the aforesaid at least one cross section of the layer of compacted ceramic powder KP the thickness of which is measured during the aforesaid measuring step is comprised in the first portion Pl ( i . e . , is a cross section of the first portion Pl ) .

Advantageously, the method also envisages a weighing step , during which a weighing device 22 ( advantageously, but without limitation, of the type described above ) , arranged along said given path P, in particular along the segment PB of the given path P, determines a weight of at least the first portion Pl ; a first processing step, at least partially subsequent to the measuring step and to the weighing step, during which a processing unit 24 determines an absolute density of at least the first portion Pl based on the weight , the thickness , the given width and the given length of this first portion Pl ; and a comparison step, which is at least partially subsequent to the first processing step and to the first detection step and during which a processing unit 25 compares the absolute density and the quantity correlated with the density of the first portion Pl so as to determine a correction coef ficient . In other words , the processing unit 25 determines the deviation between the absolute density and the quantity correlated with the density of the first portion Pl , this deviation being based on ( in particular, coinciding with) the correction coef ficient .

Advantageously, but without limitation, the measuring step, the weighing step, the first processing step and the comparison step can be repeated several times ( i . e . , for di f ferent compacted ceramic powder articles MCP ) , so as to evaluate with greater precision the correction coef ficient and/or veri fy that there are no variations in the value of this correction coef ficient . The method also envisages at least a second detection step during which the aforesaid quantity is detected for at least the aforesaid second portion P2 of the layer of compacted ceramic powder KP or of a further layer of compacted ceramic powder KP; and a calculation step, at least partially subsequent to the comparison step and to the second detection step, during which an actual density of the second portion P2 is estimated based on the quantity detected during the second detection step and on the correction coefficient.

Advantageously, but without limitation, as explained above with reference to the detection system 1, the detection step to detect the quantity and the calculation step are repeated for all the portions Pl, P2 of the layer of compacted ceramic powder KP (i.e., for all the compacted ceramic powder articles MCP) that arrive at the detection station 11, so as to evaluate the actual density of each compacted ceramic powder article MCP.

The first detection step and the second detection step can be carried out before or after the cutting step, when this is provided (i.e., when the compacting device 8 comprises the continuous compacting assembly 2) . In other words, as explained in relation to the detection system 1, the quantity correlated with the density of the first portion Pl and of the second portion P2, can be detected in any area of the first portion Pl and of the second portion P2, respectively, and indifferently before or after these portions Pl and P2 have been separated (i.e., cut) from the layer of compacted ceramic powder KP .

Advantageously, but without limitation, the method furthermore comprises an adjustment step, which is at least partially subsequent to the calculation step and during which the compacting pressure and/or the quantity of (uncompacted) ceramic powder CP fed is adjusted based on the actual density estimated during the calculation step, so as to ensure that the density remains comprised between around 1.5 kg/dm ³ and around 2.5 kg/dm ³ , in particular between around 1.9 kg/dm ³ and around 2.1 kg/dm ³ , even more in particular equal to around 2 kg/dm ³ . In particular, as better explained in relation to the detection system 1 , this adj ustment step is advantageously implemented by acting on the feeding assembly 5 and/or on the compacting device 8 .

Advantageously, but not necessarily, at least the measuring step, the first detection step and the second detection step are simultaneous to the moving step, i . e . , they take place while the conveyor assembly 3 is active and transports the layer of compacted ceramic powder KP and/or the various portions P1 , P2 along the given path P .

According to some advantageous , but non-limiting, embodiments , the first detection step and the second detection step each comprise : a relative irradiation sub-step, during which an emission device 19 ( advantageously, but not necessarily of the type describe above ) , arranged along the given path P ( advantageously, along the segment PB of the given path P ; even more in particular at the detection station 11 ) emits an X-ray beam having a given emission intensity towards one first side LI of the first portion Pl or of the second portion P2 , respectively, so that this X-ray beam goes through the first portion Pl or the second portion P2 , respectively, and goes out from a second side L2 of the relative portion Pl , P2 , opposite said first side LI ; and a relative acquisition sub-step, subsequent to the irradiation step, during which an acquisition device 20 ( advantageously, but not necessarily, of the type described above ) , arranged along the given path P ( in particular along the segment PB of the given path P ; even more in particular at the detection station 11 ) detects an output intensity of the X-ray beam coming out of the second side L2 of the first portion Pl or of the second portion P2 , respectively .

Again according to these advantageous , but non-limiting embodiments , the first detection step and the second detection step furthermore comprise : a relative measuring sub-step during which a further measuring device 17 ' ( advantageously, but not necessarily, of the type described above ) , arranged along the given path P ( advantageously, along the segment PB of the given path P ; even more in particular at the detection station 11 ) , carries out at least one measurement of a thickness of at least one cross section of the first portion Pl or of the second portion P2 , respectively; and a relative processing sub-step during which a processing unit 21 determines said quantity correlated with the density of the first portion Pl or of the second portion P2 , respectively, based on the emission intensity, on the output intensity and on the thickness measured during the measuring sub-step .

According to some advantageous , but non-exclusive , embodiments , when this measuring sub-step is provided, it is simultaneous to , in particular coincides with, the measuring step described above ; and, even more advantageously, the measuring device 17 and the further measuring device 17 ' coincide with one another ( as explained above in relation to the detection system 1 ) .

Moreover, advantageously, but without limitation, in order to improve the precision of this measurement , both during the measuring step and optionally during the relative measuring substep, measurement of a thickness is carried out at least in the area of two ( in particular, at least three ) cross sections of the first portion Pl and/or of the second portion P2 , respectively .

According to other advantageous , but non-exclusive embodiments , when the conveyor device 10 comprises vertically movable rollers 26 ' ( as better explained above in relation to the detection system 1 ) and the weighing device 22 comprises the aforesaid plurality of load cells 27 connected to the movable rollers 26 ' , the weighing step comprises : a standstill sub-step during which at least the first portion Pl stands still in the area of ( in particular above ) the movable rollers 26 ' ; and a li fting sub- step, at least partially simultaneous with the standstill substep, during which the movable rollers 26 ' ( are operated in a known way and) li ft the first portion Pl and the load cells 27 detect the weight thereof .

According to other embodiments ( for example those that provide for a conveyor device 10 in the form of conveyor belt or having a plurality of rollers 26 but without movable rollers 26 ' ) , the weighing step is simultaneous with the moving step, i . e . , takes place while the first portion Pl moves along the given path P, in particular along the segment PB of the given path P .

The present invention has various advantages compared to the state of the art , some of which are set forth in the following .

The detection system 1 and the method to detect the density of the layer of compacted ceramic powder KP described above allow an evaluation of the aforesaid correction coef ficient without interrupting the movement of the conveyor assembly 3 and without the need to create a speci fic sample , thus allowing a rapid and reliable calibration of the detection system 1 , without interrupting the normal production flow, therefore with minimum production downtime .

Moreover, the method and the detection system 1 of the invention allow entirely automated detection of the density and calibration of the detection system 1 , without the need for skilled operators that , for example , evaluate the absolute density of at least one sample and calibrate the detection system 1 accordingly, with consequent advantages both in terms of costs , due to reduction in labour costs , and in terms of precision .