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(11) | EP 1 669 176 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Improved pland for forming ceramic tiles or slabs |
| (57) A plant (1) for forming ceramic tiles or slabs comprising a conveyor belt (2) on
which a continuous strip (100) of powdered ceramic material is created, compacting
devices (4, 5) that allow said strip (100) of powders on the belt (2) to be subjected
to continuous pressing to obtain a coherent article of compacted powders, and means
that allow the lateral containment of the material on the belt. Said means comprise
at least one pair of longitudinal parallel containment walls (8, 9), between which
the powdered material is contained, each of said containment walls (8, 9) comprising
a main body (80, 90) with high elastic deformability, and at least one longitudinal
core (81, 91) having a modulus of elasticity of more than 1000 N/mm2 that, associated with said main body, extends substantially for its entire length.
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[0001] The present invention concerns, in general, a plant for manufacturing ceramic tiles or slabs, and in particular a plant for forming the aforementioned slabs.
[0002] Plants for forming ceramic slabs are known that comprise a conveyor belt suitable for making a continuous strip of powdered ceramic material advance through a pressing station, which is equipped with two motorised compacting devices one on top of the other that allow the powders to be continuously pressed on the belt that advances in the station, to obtain an article of coherent material.
[0003] Then, through a suitable cutting station, said article is trimmed at the edges and divided into tesserae that, according to the degree of pressing to which the powders on the belt are subjected, can make the end tiles, or else a group of precompacted slabs that will have to be subjected to a second pressing.
[0004] Such a plant is described in detail in European patent application EP 1 356 909 to the same Applicant, to which we refer for a complete understanding thereof.
[0005] Generally the pressing stations of known plants also comprise means suitable for controlling the spontaneous expansion of the strip of compacted powders, downstream of the compacting devices, to avoid the occurrence of cracks and/or splits, and means suitable for laterally containing the powdered material on the conveyor belt.
[0006] In particular, said lateral containment means consist of two longitudinal walls that, parallel to each other and arranged above the conveyor belt along the advancing direction, accompany the powders during their transportation towards the compacting devices, during the pressing step, in which they are also squashed by said compacting devices, until the end of the expansion step.
[0007] Said containment walls are generally elastically deformable: in the direction perpendicular to the belts, so as not to significantly oppose the action of the compacting devices, ensuring the substantial uniformity of the pressure exerted by them on the entire strip of powdered ceramic material; and in the direction transversal to the belts, to accompany the subsequent linear expansion of the compacted article in the sense of its width, i.e. perpendicular to the direction in which the conveyor belt advances.
[0008] A particularly serious drawback of such containment walls lies in the fact that their deformability is incompatible with the need to make a stable and strong lateral support for the strip of powdered material, both during the transportation step and, in particular, during the pressing step. In this last case, indeed, the containment walls are also subjected to the laterals thrusts caused by the powders being compacted, which they must oppose without deforming or flexing excessively, to ensure a good compacting of the article also at the longitudinal edges.
[0009] The purpose of the present invention is that of overcoming the aforementioned drawback, providing means for laterally containing the powders on the conveyor belt capable of deforming in the direction perpendicular to the belts without offering great resistance and, at the same time, of providing a stable lateral support for the strip of powdered material during transportation and pressing. A further purpose of the invention is to achieve the aforementioned objective with a simple, rational and low-cost solution.
[0010] Such purposes are accomplished through a plant for forming ceramic tiles or slabs comprising at least two containment walls of the powders on the conveyor belt, each of which comprises a main body with high elastic deformability and at least one longitudinal core having modulus of elasticity of over 1000 N/mm2 that, associated with said main body, extends substantially for the entire length thereof.
[0011] Thanks to this solution, said main body allows each containment wall to squash adequately during pressing, whereas the longitudinal core gives them the rigidity necessary for making it a sufficiently stable lateral support for the strip of powdered material.
[0012] In accordance with a preferred embodiment of the invention, said longitudinal core is configured so as to be transversally flexible, and the plant comprises suitable tensioning means to tauten the longitudinal core itself, so as to cause its transversal rigidification and, therefore, the transversal rigidification of the containment wall as a whole.
[0013] Thanks to this solution, it is advantageously possible to make said containment wall in the form of a belt that, wound in a closed loop on suitable pulleys, can be made to run at the same speed as the conveyor belt, avoiding sliding between the powdered material that advances and the containment wall itself.
[0014] According to a further preferred embodiment of the invention, the plant in object is also equipped with means suitable for ensuring that, during operation, the containment walls always remain parallel to each other and spaced apart by the same amount, so that the width of the article going out is constant.
[0015] Further characteristics and advantages of the invention shall become clear from reading the following description provided as an example and not for limiting purposes, with the help of the figures illustrated in the attached tables, in which:
- figure 1 shows a schematic side section view of a plant according to the invention;
- figure 2 is the cross section II-II indicated in figure 1;
- figures 3 to 8 show the cross sections of one of the containment walls, each in accordance with a different embodiment of the finding.
[0016] From the mentioned figures (see especially fig. 1) the plant 1 can be seen, which comprises a motorised conveyor belt 2 on which, through normal devices, not illustrated since they are per se known, a continuous strip 100 of powders is deposited.
[0017] The belt 2 crosses a pressing station 3 that has the function of pressing the powders of the strip 100 to obtain an article, substantially parallelepiped in shape, of coherent material. Such an article can possibly then be decorated and then divided into tesserae of suitable size according to the size of end product that one wishes to obtain, said tesserae being able to be subsequently subjected to a second pressing step.
[0018] The pressing station 3 comprises two compacting devices 4 and 5, motorised and opposite one another, the first of which is arranged below the belt 2, and the second above it at a height from the belt 2 that can be adjusted according to the thickness of the strip 100 of powders to be compacted, as well as the pressure value at which one wishes to carry out the pressing.
[0019] Each of the compactors 4 and 5 is provided with a motorised roller and an idle roller, respectively indicated with reference numerals 40, 41 and 50, 51, on which a respective belt 42, 52 is wound. Between the pairs of rollers 40, 50, and 41, 51 two roller conveyors 43, 53 are arranged, consisting of a plurality of idle rollers, downstream of which there are two opposite rollers 6 and 7 that have the function of keeping the belts 42 and 52 pressed to press the strip 100 of powdered material. In the illustrated embodiment, the roller conveyor 53 is inclined in the direction in which the belt 2 advances so as to make the compacting of the powders of the strip 100 gradual.
[0020] The rollers 6 and 7 define the pressing area of the strip 100 of powders, downstream of which there are two overlapping plates 16 and 17, the bottom one of which 17 is arranged below the belt 2 and the top one of which 16 is arranged above the belt 2, and in greater detail in contact with the belt 52, said plates 16 and 17 being suitable for controlling the expansion of the strip 100 of powders, to avoid the occurrence of cracks or splits in the compacted article.
[0021] The pressing station 3 also comprises lateral containment means of the strip 100 of powders, which, in the illustrated embodiment, are made through two belts 8 and 9 in a closed loop that, wound on the compacting device 5 and on idler wheels 101, 102 and 103, are suitable for running at the same speed as the conveyor belt 2 (see also fig. 2).
[0022] In detail, as can be seen in figures 1 and 2, said belts 8 and 9 have two respective bottom portions in contact with the conveyor belt 2, which make a pair of containment walls that, parallel to each other and arranged along the direction in which the belt 2 itself advances, are suitable for laterally containing the powders of the strip 100, following it from the deposition on the belt up until the end of the expansion step and passing through the pressing step, during which said bottom portions are squashed by the compactors 4 and 5 together with said strip 100 of powdered material (see fig. 2).
[0023] As clearly illustrated in figure 2, each of said belts 8 and 9 is crossed, for its entire extension, by a longitudinal recess, 83 and 93 respectively, which is suitable for coupling with an annular ribbing 104 projecting from the idler wheels 101, 102, 103, with them making a shape coupling of the male/female type that forces the belt to always rotate in the same vertical plane (in the figures just the ribbing 104 of the wheel 101 can be seen, the others being analogous).
[0024] In this way, the belts 8 and 9, which define the lateral containment walls of the powders on the belt 2, are substantially parallel to each other and spaced apart by the same amount, so that the width of the strip 100 of compacted powders remains constant during production.
[0025] However, it should be specified that the idler wheels 101, 102 and 103 are with adjustable gage, so as to be able to vary the size of the strip of compacted powders in the direction perpendicular to that in which the belt 2 advances according to the format that one wishes to obtain, and so that the relative position of the idler wheels can be adjusted to compensate possible permanent stretching of the belts 8 and 9.
[0026] From the structural point of view, as clearly illustrated in figure 2 and in all of figures 3 to 8, the belts 8 and 9 consist of an elastically deformable main body, 80 and 90 respectively, and at least one rigid longitudinal core, 81 and 91, which, associated with said main body, extends for the entire length of the belt. In particular, said longitudinal cores 81 and 91 are fixed to the respective main bodies 80 and 90 with means that do not alloy mutual longitudinal sliding, for example through a glue.
preferably, the main bodies 80 and 90 must be able to reduce its initial size by at least 30% without permanent deformations and, for this reason, must be made from a material having a high elastic working range; moreover, they must also be sufficiently yielding so as not to hinder the compacting means 4 and 5 during pressing and, therefore, the aforementioned material must have a low modulus of elasticity: less than 100 N/mm2 and, preferably, less than 10 N/mm2.
[0027] On the other hand, the longitudinal cores 81 and 91 must be made from a material having a high modulus of elasticity so as not to deform from the lateral thrusts generated by the powders being compacted, said modulus of elasticity being greater than 1000 N/mm2 and, preferably, greater than 10,000 N/mm2.
[0028] In greater detail, said longitudinal cores 81 and 91 are configured so as to be transversally flexible (see figs. 3 to 8), so that the belts 8 and 9 are sufficiently flexible to be wound around the compacting device 5 and the idler wheels 101, 102, 103 describing a closed loop path.
[0029] At the same time, as can be seen in figure 1, the plant 1 comprises a jack device 104 that, associated with the idler rollers 101, acts as tensioning means suitable for sufficiently tautening the belts 8 and 9 to rigidify the cores 81 and 91.
[0030] In particular, said device 104 is able to adjust the position of the idler rollers 101 to compensate possible permanent stretching of the belts 8 and 9, automatically controlling the tensioning force to which the longitudinal cores 81 and 91 are subjected.
[0031] With reference to figures 3 to 8, the belt 8 (although the same considerations are also valid for the belt 9) can comprise just one longitudinal core 81 (figs. 3, 4, 7 and 8), or else it can comprise a plurality of longitudinal cores 81 (figs. 5 and 6).
[0032] Moreover, the longitudinal core 81 can be enclosed inside the main body 80 (fig. 7), or else housed in corresponding seats formed in the outer profile of the main body 80 itself.
[0033] Finally, it is worth noting that the cross section of the belts is configured so as to ensure that, during the expansion step, they do not interfere in any way with the longitudinal edges of the compacted article but, instead, help their expansion avoiding the occurrence of cracks or splits.
[0034] For such a purpose (see figs. 2 to 8), the opposite faces 82 and 92, respectively of the belt 8 and 9, are inclined with respect to the plane of the conveyor belt 2, so that the tangent to their transversal profile, at any point thereof, forms an acute angle α with the plane of the conveyor belt facing towards the strip of powdered material, said angle being preferably between 40° and 89°.
In particular, said transversal profile of the opposite faces 82 and 92 can be a rectilinear segment (as illustrated in the figures), or else it can alternatively consist of a curvilinear portion, a succession of rectilinear portions, or a combination of curvilinear and rectilinear portions.
1. Plant (1) for forming ceramic tiles or slabs comprising a conveyor belt (2) on which
a continuous strip (100) of powdered ceramic material is created, compacting devices
(4, 5) that allow said strip (100) of powders on the belt (2) to be subjected to continuous
pressing to obtain a coherent article of compacted powders, and means that allow the
lateral containment of the material on the belt, said means comprising at least one
pair of longitudinal parallel containment walls (8, 9), between which the powdered
material is contained,
characterised in that each of said containment walls (8, 9) comprises a main body (80, 90) with high elastic deformability, and at least one longitudinal core (81, 91) having a modulus of elasticity of more than 1000 N/mm2 that, associated with said main body, extends substantially for its entire length.
characterised in that each of said containment walls (8, 9) comprises a main body (80, 90) with high elastic deformability, and at least one longitudinal core (81, 91) having a modulus of elasticity of more than 1000 N/mm2 that, associated with said main body, extends substantially for its entire length.
2. Plant (1) according to claim 1, characterised in that said main body (80, 90) and longitudinal core (81, 91) are fixed together through
means that do not allow mutual longitudinal sliding.
3. Plant (1) according to claim 1, characterised in that said main body (80, 90) is made with a material having a high elastic range, so as
to be able to reduce its initial size by at least 30% without permanent plastic deformations.
4. Plant (1) according to claim 1, characterised in that said main body (80, 90) is made from a material having modulus of elasticity of less
than 100 N/mm2.
5. Plant (1) according to claim 4, characterised in that said modulus of elasticity of less than 10 N/mm2.
6. Plant (1) according to claim 1, characterised in that said longitudinal core (81, 91) is made from a material having a modulus of elasticity
greater than 10,000 N/mm2.
7. Plant (1) according to claim 1, characterised in that said longitudinal core (81, 91) is enclosed inside the main body (80, 90).
8. Plant (1) according to claim 1, characterised in that said longitudinal core (81, 91) is housed in a corresponding seat formed in the outer
profile of the main body (80, 90).
9. Plant (1) according to claim 1, characterised in that, when not deformed, the opposite faces (82, 92) of said containment walls (8, 9)
are inclined with respect to the plane of the conveyor belt (2) so that the tangent
to the transversal profile of each of them, at any point thereof, forms an acute angle
(α) with the plane of the conveyor belt (2) facing towards the strip (100) of powdered
material.
10. Plant (1) according to claim 9, characterised in that said angle (α) is always between 40° and 89°.
11. Plant (1) according to claim 1, characterised in that it comprises tensioning means (101, 104) to bias under traction the longitudinal
core (81, 91) so as to transversally rigidify it, and therefore to transversally rigidify
the entire containment wall (8, 9).
12. Plant (1) according to claim 11, characterised in that said tensioning means (101, 104) are adjustable so as to be able to compensate possible
permanent stretching of the longitudinal core (81, 91).
13. Plant (1) according to claim 12, characterised in that said adjustment is carried out with a device (104) capable of automatically controlling
the tensioning force on said longitudinal core (81, 91).
14. Plant (1) according to claim 1, characterised in that said containment walls are made in the form of belts (8, 9) that are able to slide
and parallel to each other.
15. Plant (1) according to claim 14, characterised in that it comprises means (83, 93, 104) suitable for ensuring that said belts (8, 9) always
remain parallel to each other and spaced apart by the same amount during the operation
of the plant (1).
16. Plant (1) according to claim 15, characterised in that each of said belts is wound on a group of pulleys (50, 101, 102, 103), with at least
one of which it is suitable for making a shape coupling of the male/female type that
constrains it in the transversal direction with respect to the direction of sliding.
17. Plant (1) according to claim 16, characterised in that said belt (8, 9) is provided with a longitudinal recess (83, 93) formed in its outer
profile, and said pulley (101) is provided with a projecting annular ribbing (104)
suitable for engaging inside said longitudinal recess.
18. Plant (1) according to claim 14, characterised in that each compacting device (4, 5) comprises at least one motorised roller (40 and 50),
and the belts (8, 9) are partially wound on at least one of said motorised rollers
(40 or 50), running at the same speed as the conveyor belt (2).