MXPA03003502A

MXPA03003502A - Method and plant for forming ceramic slabs or tiles.

Info

Publication number: MXPA03003502A
Application number: MXPA03003502A
Authority: MX
Inventors: Alessandro Cocquio
Original assignee: Sacmi
Priority date: 2002-04-24
Filing date: 2003-04-22
Publication date: 2005-02-14
Also published as: DE60318645D1; BR0300939A; ITRE20020035A1; ES2298468T3; ATE383932T1; BR0300939B1; CN1332796C; EP1356909B1; ITRE20020035A0; DE60318645T2; EP1356909A3; EP1356909A2; CN1453110A

Abstract

Method for forming ceramic tiles, comprising the following operative steps: creating a continuous layer of powders on a conveyor belt; advancing said belt through a first pressing station of continuous type, with which means for laterally retaining the powders are associated, to effect a first pressing of the powders during the advancement of the belt, and obtain a coherent article of compacted powders; and, by suitable means, controlling and limiting the expansion of said powder article on termination of said first compaction.

Description

METHOD AND PLANT FOR FORMING CERAMIC TILES OR TEXAS This invention relates in general to a method for manufacturing tiles or ceramic tiles, and in particular a method for preforming the tiles and the relative plant for their implementation. Methods of forming ceramic tiles are known, which comprise the following operative steps: depositing a continuous layer of powders in a flexible band with which walls are associated to laterally retain the powders, advancing the band through a station of pre-pressing of the continuous type, which generally consists of at least one roller (or a compactor belt) which effects a first pressing of the powders in the flexible band to obtain a coherent article of compacted powders, and - subjecting the article to a second pressing. According to this method, the article can be decorated with an additional layer of powder before it is fed to the second pressing. The above method and the relative plant for its implementation, are fully described in the international patent application WO 98/23424, the text of which reference must be made for additional information. Tests carried out using the method described in the above patent application have shown that when leaving the first pressing station, the strip of pre-compacted material presents cracks extending to the mass of the strip and are deposited randomly on the entire surface, which are concentrated in the proximity of the longitudinal edges of the article. This is due to the fact that at the end of the compaction, the compressed powders are slightly re-expanded to form this cracks, which is not made good by the second pressing and returns to the useless article or at least disabled, for the subsequent division into pieces Unfinished of small dimensions. The object of the invention is to overcome the disadvantages of the known technique within the assembly of a simple and rational solution. The invention achieves the object by providing a method for forming ceramic tiles or tiles comprising a powder compaction step, at the end of which the subsequent slight expansion of the compacted article is controlled in such a way as to prevent the formation of cracks that affect the products of the prior art. Expansion control refers to both the degree of expansion and its duration, which should be as long as possible, compatible with the production cycle. Specifically, the method of the invention comprises the following operative steps: depositing a continuous layer of powders in a conveyor belt with which walls are associated to laterally retain the powders, advancing the band through the first station of pressing of the continuous type, in such a way as to compact the powders during the advance of the web, to obtain a coherent article of compacted powders that is virtually parallelepiped, - to limit and encourage the expansion of the powder article at the end of the prime. , pressed. According to the invention, the linear expansion of the article after the first pressing must be controlled at least in the direction perpendicular to the upper surface of the article, and also preferably in the directions parallel to this surface. In these latter directions, the linear expansion must preferably be contained within a range of between 0.1 and 1.0% of the width of the article measured in the direction perpendicular to the direction of advance of the band. According to the invention, the first pressing station can be either a first pressing station suitable only for manufacturing the coherent powder layer, which is to be subjected to a second and definitive pressing, or it can be the only press station. pressed and corapactación. In the first case, the pressure to compact the material in the first pressing station, must preferably reach, progressively a maximum value between 30 and 70 kg / cm2. In the second case, the pressure to which the material is subjected must preferably reach a maximum value between 300 and 450 kg / cm2. In certain embodiments, the method of the invention provides the article to be reduced to unfinished pieces of small dimensions. The reduction of the article in pieces without finishing takes lagar after the first pressing even if the first pressing is the only pressing. The invention also includes a plant for implementing the method described above. This plant comprises a conveyor belt in which a continuous strip of powder material is formed, a means for laterally retaining the material in the web, continuous pressing means of the web that allow the strip of the powder in the web to be compacted ( first pressing) to obtain a coherent article of compacted powders, and means to control the expansion of the material at the end of the first pressing. The means for controlling the expansion of the article are preferably associated with the first continuous pressing means and placed downstream thereof. According to a preferred embodiment of the invention, the means for controlling the expansion of the compacted article comprise two flat, opposite, roller tables, one of which is placed below the band and the other above by a distance from it. which can be adjusted based on the physical and dimensional characteristics of the article. The upper roller table is inclined at an adjustable, predetermined angle that deviates from the direction of web advance. It should be noted that the means for controlling the expansion of the material at the end of the first pressing may also comprise, for example, at least one fixed plate inclined towards the direction of advance of the strip of compacted material, or any other medium suitable for the purpose , for example, a compaction belt, the axis of which is inclined to the direction of advance of the compacted strip of material. In the claims, additional features of the invention are defined. In order to better understand the operation of the method of the invention and the construction characteristics and merits of the relative means for its implementation, reference is made hereinafter to the attached drawings which show by way of example a preferred embodiment, particularly in the plant to implement the method described above. Figure 1 is a schematic side section through the plant of the invention. Figure 2 is a view in the direction II of the Figure 1. Figure 3 is an enlarged view of a detail of the invention. Figures 4 and 5 are a cross section through the lateral retention means with which the invention is provided, shown under different working conditions, respectively. The figures show the plant 1, comprising a lower, motorized conveyor belt 2, in which a continuous strip of powders is deposited by usual devices, not shown since they are of the known type. The web passes through a pre-compaction station 3, or first press station, the purpose of which is to compact the powders into strip to obtain an article, substantially parallelepiped, of coherent material. This item can then be decorated, if required, and then divided into unfinished pieces of adequate dimensions depending on the final size of the product to be obtained. The first pressing station 3 comprises two mutually superimposed motorized and compacting devices 4, 5, one of which is placed below the band 2 and the other above by a distance from the band 2 which can be adjusted based on the thickness of the powder strip to be compacted and the pressure at which the first pressing will be carried out. In general, this pressure is between 20 and 100 kg / cm2. Each of the compactors 4 and 5 comprises a motorized roller and a free roller, indicated respectively by reference numbers 40, 41 and 50, 51, around which a respective band 42 and j2 passes. Between each pair of rollers 40, 41 and 50, 51, a roller table 43 and 53 is placed, consisting of a plurality of free rollers 430 and 530. The purpose of the two roller tables 43 and 53 is to maintain the webs. 42 and 52 pressed to compact the strip of powder material. The roller board 53 can also be tilted in the advance direction of the belt 2 to gradually compact the powders of the strip. The roller tables 43 and 53 delimit the compaction zone (or first pressing zone) 100 of the dust strip, downstream from which a decompression zone 6 is provided in which the powder strip is expanded, under of a suitable means, in a controlled manner to prevent the formation of cracks in the compacted article. In the illustrated modality, the. Decompression zone 6 comprises two overlapping rolls 44 and 54 placed below the roller tables 43 and 53, respectively. With reference to Figure 3, it can be seen that the roller table 44 is fixed and horizontal, while the roller table 54 is supported by a frame 55 via two actuators 56 of the hydraulic or mechanical type that allow the table The roller is adjusted in level and also inclined to band 2 to allow the compacted mass of powder to expand with a very low deformation gradient compatible with the intrinsic characteristics of the powders. In other embodiments, the means present in the decompression zone 6 may comprise, for example, at least one rigid plate, not shown, inclined to the advancing plane of the compacted strip of powder. In this case, the plate keeps the band 52 pressed against the compacted article. The first pressing station or pre-compaction station also comprises a means for laterally retaining the powders, this means in the illustrated embodiment which is in the form of two belts 8 and 9 associated with the compaction device 5.

In this regard, each of the two belts passes partially around the compaction device 5 and around two diverting wheels 101 and 102. It should be noted that the diverting wheels are of adjustable distance, in order to allow to vary the dimension of the strip in the powders compacted in the direction perpendicular to the direction of advance of the band according to the format to be obtained. The two strips T and 9 are formed from a mixture of elastomeric material of high friction coefficient so that they get squeezed into the compaction zone between the compactors 4 and 5 and then contract laterally and increase their height in the decompression zone, to then return to its rest position not deformed in the other portions. The lateral contraction of the belts in the decompression zones allows the expansion of the compacted article to be controlled in the direction of the width of the article, that is, in a direction perpendicular to the direction of advance of the band 2. It should be noted that the The mixture of elastic material with which the two belts are formed, and their particular profile, are such as to counteract the lateral thrusts exerted by the material on the inner side of the belts during the pressing.

In the illustrated embodiment, the belts are formed of expanded, closed-cell EPDM rubber. In addition, the profile of the belts is such that during pressing, the inner side of the belt is practically flat and perpendicular to the conveyor belt 2. This reduces the minimum to the loss of material comprised in the elaboration of the compacted article, perfectly parallelepiped . In this regard, Figure 4 shows that the profile of each of the belts comprises on their two side surfaces, a reduced central portion 103 connected to the ends by a curved portion 104. When the belts are deformed by squeezing, between the corapactadores 4 and 5, the central portion 103 moves outward to make the side surface of the belt substantially flat, as shown in Figure 5. Finally, it should be noted that as a result of this tightening, the height of the cross section decreases through the belt by approximately 50% of its height not deformed. This value however can vary depending on the type of profile used and the material with which the belts are formed.

Claims

CLAIMS 1. A method for forming ceramic tiles, comprising the following operative steps: - creating a continuous layer of powders in a conveyor belt, - advancing the web through a first pressing station of the continuous type, with which they are associated means for laterally retaining the powders, for effecting a first pressing of the powders during the advance of the web, and for obtaining a coherent article of compacted powders. - by suitable means, controlling and limiting the expansion of the powder article at the end of the first compaction. A method according to claim 1, characterized in that, upon completion of the expansion of the article, the latter is reduced to unfinished pieces of suitable dimensions for subsequent processing. 3. A method according to claim 1 or 2, characterized by submitting the unfinished article or part obtained therefrom to a second pressing. 4. A method according to claim 1, characterized in that the compaction of the material in the first pressing station is progressive. A method according to claim 4, characterized in that the maximum pressure of powder compaction in the first pressing station is between 20 and 200 kg / cm2. 6. A method according to claim 1, characterized in that the control of the expansion of the material takes place at least in the direction perpendicular to the main dimension surface of the article. A method according to claim 1, characterized in that the control of the expansion of the material takes place at least in the direction perpendicular to the preceding direction and to the direction of advance of the article. A method according to claim 1, characterized in that the allowable value of the expansion in one direction is proportional to the dimensions of the article of the same direction. 9. A method according to claim 8, characterized in that the allowable value is between 0.1 and 1%. 10. A plant for forming ceramic tiles or tiles, comprising a conveyor belt in which a continuous strip of powder material is formed, means for laterally retaining the material in the web, and continuous first pressing means allowing the strip of powder in the web is subjected to a first pressing to obtain a coherent article and of compacted powders, characterized by comprising means for controlling the expansion of the material at the end of the first pressing. A plant according to claim 10, characterized in that the means of the first continuous pressing are placed at least above the strip at a level that is adjustable based on the thickness of the continuous strip of powder to be compacted and comprise means for laterally retaining the powders. 12. A plant according to claim 10, characterized in that the first continuous pressing means are placed both above the web at a level that is adjusted based on the thickness of the continuous strip of powder to be compacted, and below the band. A plant according to claim 10, characterized in that the first continuous pressing means, placed above the strip, comprise a material compacting zone, downstream of which at least one decompression zone of material in the region is present. which act means to control the expansion of the material at the end of the first pressing. 14. A plant according to claim 10, characterized in that the continuous pressing means comprise at least two motorized rollers around which a flexible band passes. 15. A plant according to claim 14, characterized in that within the compaction zone, the flexible band is inclined at an incident angle in the direction of advance of the strip. 16. A plant according to claim 14, characterized in that the inclination angle of the flexible band is a function of the compaction pressure. 17. A plant according to claim 13, characterized in that in the decompression zone, the flexible band is inclined at an angle divergent to the direction of advance of the strip. 18. A plant according to claim 10, characterized in that the continuous pressing means comprises within the first pressing zone, at least one roll table arranged to keep the flexible band pressed against the powder strip. 19. A plant according to claim 10, characterized in that the means for controlling the expansion of a material are adjustable in level. 20. A plant according to claim 19, characterized in that the level adjustment of the means is achieved by at least one piston unit with cylinder. 21. A plant according to claim 10, characterized in that the means for controlling the expansion of the material are inclined at an angle divergent to the direction of advance of the strip. 22. A plant according to claim 10, characterized in that the means for controlling the expansion of the material comprises a roller table. 23. A plant according to claim 10, characterized in that the means for controlling the expansion of the material comprises a plate. 24. A plant according to claim 11, characterized in that the lateral retention means comprise two parallel belts. 25. A plant according to claim 24, characterized in that the belts pass partially around the pressing means. 26. A plant according to claim 24, characterized in that the belts are formed of elastically deformable material.