SI8610254A8 - Apparatus for producing glazed ceramic tiles - Google Patents

Description

CERAMICA FIT.TPPO MARAZZI S.p.A.

APPARATUS FOR THE PRODUCTION OF GLEDOSE CERAMIC TILES

FIELD OF THE INVENTION

The invention belongs to the field of ceramics production, and in particular relates to viewing of clay tiles. Labeling according to the International Patent Classification: C 04 B 33/34.

Technical problem

The invention solves the problem of how to construct a device for the production of tiled ceramic tiles, which will allow to ensure a good adhesion of the gaze to the ceramic body, without leaving the porous gaze porous, with satisfactory mechanical strength of the tiles.

The state of the art

According to current understanding in this field, the production of tile tiles is carried out according to one of two general processes for making ceramic tiles.

The first of the known manufacturing processes involves the formation of the ceramic tile body in the traditional way, drying it and then baking it to produce a baked, unglazed product.

Ceramic bodies are all bodies made up of natural raw materials such as clay, kaolin, feldspar, volastonite, talc, calcium carbonate, dolomite, etc., or synthetic materials such as calcined kaolin (chamotte), pure oxides ( aluminum oxide, silica, corundum), with or without added binders to increase mechanical strength.

Such bodies undergo chemical and structural changes during heat treatment and obtain essential mechanical properties, changing from a state of low toughness in raw materials to a state in which they become hard, tough and brittle after heat treatment.

This is why ceramic bodies are baked here, ”usually the heat treatment that causes the aforementioned essential alteration of the mechanical characteristics of ceramic bodies by chemical reactions, crystal modifications and component melting.

The baked material is looked at and re-baked in order to make a structural change in the look (strictly depending on the type of look component), which, for the sake of simplicity, will be referred to as glazing. This term, however, is not completely correct for all the views used in the ceramic tile industry, which can be almost completely melted during baking, or only slightly smaller, closer to the sinter.

However, since baking in ceramic materials is a well-known process in this field, such linguistic singularity cannot lead to misunderstanding. The code is said to be 4-sided, meaning any mixture that, on heating, develops a glassy, transparent or opaque surface, which can be glossy or matte, either in the fully baked form, ie. previously melted, or crude, or in the form of mixed mixtures.

This double baking process, first of the ceramic body and then looking, has its advantages and disadvantages. First of all, first baking, followed by cooling, and then second baking for glazing, is a process that consumes a lot of heat and a lot of time, requiring devices whose volume is large relative to the volume of the tiles produced.

One might think that with double baking prco baking to produce baked, unglazed ceramic products can, if expertly performed, produce ceramic products of optimal characteristics that would be due solely to the nature of the initial clay mixture. The fact is, however, that the requirements arising from the gouging that follows the first baking, in practice, determine the preparation of baked non-baked ceramic products.

Views are usually prepared by wet crushing, for example, containing between 30 and 60% water.

If dry views are used, a wet treatment is then required to ensure that it is applied to the ceramic body.

- 3 When applied, it is applied to a baked unglazed material of a porous structure, ie. which is not glazed, the large quantities of water available do not represent a source of difficulty, since under such conditions ceramic unglazed ceramic products are easily absorbed and therefore easily adhered to the body.

But when pre-baked ceramics are glazed, special pre-baking treatments are required, and especially overheating to allow rapid evaporation of the water. In any case, in order to achieve acceptable grip, such treatments have proven to be very critical, and it presents considerable difficulties in the implementation of such a procedure.

Because of this, problems with. looking clear I eat. multiple glazed ceramic bodies suppress the freedom of molding the ceramic body in an independent manner, which is the case with double firing, because such an independent treatment: only at the cost of serious complications will allow to obtain tiles with glazed ceramic body, which will have the desired properties of mechanical strength.

Due to the problems caused by the double baking process, over time, her approach suggests that both the clay mixture and the baking mixture be baked in a single work operation - the so-called a one-time baking process. According to this process, the raw ceramic bodies are dried, preheated and viewed when warm enough to allow the water contained in the view to evaporate. Preheating, however, does not prevent a certain amount of water from being absorbed by the clay mixture in an uneven manner, so that in practice the absorption is greater at the edges of the product as the edges cool faster.

This phenomenon can lead to thin cracks at the edges of the product, reducing its strength.

Another inevitable difficulty that occurs with a one-time baking process is that it requires a fairly complex movement of raw tiles, which must be viewed in this state and whose sensitivity is knownJ

- 4 In a one-time baking process, unbaked viewed plates are baked in a single cycle to the temperature at which the body-made mixture is baked and watched (glazed to look).

Since it requires only one kiln and only one baking operation, a single baking process is certainly a significant improvement over traditional double baking: the device may be cheaper, and the thermal energy lost between annealing unglazed material and baking is thus preserved. .

If the reactions occurring during baking are sufficiently known, single baking can also achieve almost all the phenomena that are typical of baking twice, the honey may resemble the limitation that a mixture of clay with a baking temperature compatible with the characteristics of the batch must be obtained. which is glazed during the same firing, with the corresponding loss of operational independence inherent in double firing.

The greatest difficulty, however, is the tendency of the gas, which is liberated during the firing of the ceramic body, to disturb the smoothness and compactness of the look.

The importance of this phenomenon can easily be seen if it is known that a 1 kg plate made of a mixture containing 10% calcium carbonate and brought to a temperature of 1000 ° C emits carbon dioxide in an amount of about 9θ liters.

The gas liberated by the yen from the ceramic body passes through the gaze, in which small bubbles remain, which, to some extent, leave it in a porous state.

Thus, although single firing eliminates adhesion problems between the gaze and the ceramic body, which exist in double firing in the case of glazed ceramic bodies, it gives rise to gases which, although having executive adhesion properties, have a pelletically porous structure.

- 9 It is also proposed to apply an insulating layer known as a decorative ceramic coating, between the gaze and the ceramic body, in a single baking process, in order to reduce the possibility of interaction between the two. baking time, similar application of said coating reduces satisfactory adhesion to the eye, which is a characteristic of single baking.

In short, double firing leads to tiles with a transparent ceramic body, which therefore have a lower mechanical strength but a well-received and very compact look, while single firing gives tiles with a glazed ceramic body, high mechanical strength and with views that are satisfactory but fit relatively porous.

The aim of the present invention is to overcome the difficulties of the aforementioned tile baking processes, and with the help of an improved apparatus ^ for viewing and baking tiles, - .... ... - _w ··

Description of solution to a technical problem

The inventive prancer utilizes the Improved Process for Bleeding the Looked-off Ceramic Tiles, which, starting from the raw ceramic body, comprises the phases of placing the ceramic body in the furnace, as the first stages of heat treatment, the completion of which of the reaction of firing the ceramic material is substantially complete, and the second phase of thermal of the treatment, which comprises a gradual final cooling, characterized in that it comprises, between the first two stages of thermal treatment, one phase of distribution to said ceramic body, substantially at the final temperature experienced by the first and second stages of heat treatment, dry dry in progress the initial part of the second phase, whereby the ceramic body is brought to a temperature sufficient to be viewed by melting at least one of its components.

According to the invention, a ceramic tile baking and viewing device comprises a baking furnace in which the raw ceramic bodies are placed, and containing the first portion of the oven in cm cm for heating the body until the entire baking reaction is complete, and a second portion of the furnace comprising a temperature regulator for keeping the tiles at a regulated temperature which decreases, for the gradual cooling of said tiles, and a device for moving the body gradually along said first and. the second part of the furnace. The said device is characterized by the fact that a viewing station is provided between the first and second parts of the furnace, equipped with a device for transferring the tiles from the outlet of the first part of the furnace to the inlet of the second part of the furnace, and containing a device for applying dry. said device

The invention. will be described by way of one embodiment with reference to one embodiment of the baking apparatus of the invention shown in the appended drawings, where:

- Figure 1 shows a general schematic of an apparatus according to the invention,

- Figure 2 shows the details of the device in Figure 1,

- Figure 3 shows a typical diagram of the temperatures existing in the device of Figure 1.

According to the invention, the ceramic bodies, formed by conventional technologies, are transferred crude, after proper drying, to the inlet of 10 baking furnaces.

The baking furnace comprises a first section 11 in which the temperature is gradually raised to a value sufficient to / enter the plates moving on suitable known transport elements until the baking temperature is reached, that is, the temperature at which the firing reactions of the raw ceramic material may to consider essentially completed.

At the end of this section 11 of the furnace, the tile transfer apparatus transfers the same to the viewing area, generally designated 12.

This zone, which is of particular importance for the invention, is shown in Figure 2. The number 13 indicates the outlet for the tiles from section 11 of the furnace to the conveyor, schematically shown in the form of rollers 14. The roller conveyor extends almost to zone 12, in which creates an environment in which the temperature can be regulated, for example, by means of panels 15 which can be opened jointly so that the temperature in zone 12 remains at a predetermined value, which is typically lower than the temperature of hatch 11 near its outlet 13 , to facilitate tile temperature control.

A zone, generally designated 20, is installed in zone 12 for uniform application of dry eyes in bulk, either as granules or as powder, over tiles which move below it through a wave of strong 14.

In the interest of a direct description of its function and overall structural principle, it may be considered that this apparatus consists of a viewing tank 21 which is guided to a distribution device 22 which is uniformly spread over the tiles which are being transported below it, in any number rows, rollers 14.

A dispenser 23 was installed below the dispenser 20, which did not stay on the tiles-j especially for the gaze that fell into the spaces between the tiles transferred by the rollers 14. The view from the dispenser 23 returns back to the tank 21.

The schematized structure of the device 20 is given as an indication only, since it can have any known form of embodiment: with a barrier, with a vibrating force, a spray or something else, requiring only a correct and continuous arrangement, in the form of granules or powder, here tiles that are carried in its vicinity.

The tile bringing device in zone 12 may also be of a different type, as shown in the diagram in Figure 2 as rollers 14, and for this purpose there are known mechanisms for transferring clay products.

Tile napuštaju ONU 12 and the entrance to the Entrance orifice 16 and the following sections 17 of the furnace Where ostaju the temperature dovoljnoj with _a Fully ostakljavanje and baking gledji transactions, Gang is & lade on an adequately gradual manner like defeating nedozvoljivih enteric tension of blade being javljaju with them, and, jade , the tiles are drawn from the final outlet of the furnace 18, /

The design details of the furnace will not be described here, as both sections 11 and 17 are very close to traditional furnaces, annealing furnaces or heating chambers for baking ceramic bodies for the production of baked unglazed products * which are formed by a double process. According to Torn, these two sections can still be constructed using all the knowledge of traditional technology in this field.

In particular, the inlet openings 10, 13, 16 and 18 of the furnace will be constructed with structural details already known in the art, so as to allow a controlled atmosphere to be maintained in each of the furnace sections to achieve the desired reaction during the thermal processing of ceramic body and watch.

The solution of the present invention is based on the knowledge that it is possible to briefly interrupt the firing of the ceramic body, that is, it is possible, at least at one stage of firing, to expose the ceramic body to a relatively cold surrounding environment, i.e. the middle of which the temperature difference with the ceramic body is much greater than that in the oven during the baking and cooling phase of the ceramic body.

In fact, it has been found that the thermal shock suffered by the tiles due to exposure to such an environment can be tolerated without problems by the material if in any case it remains in a state which is plastic and not in a solid state. Such a plastic state occurs when the ceramic body is in a white-hot state, ie. at a temperature not lower than 700 ° C, for the vast majority of the body-making mixtures used today to make ceramic tiles.

According to the invention, the temperature in the zone 12 is maintained at a size not sufficient to cause the apparatus 20 and its distribution parts to overheat, which could cause melting or at least thickening of the view contained therein. This means that these parts will not be congested and there will be no uneven distribution by looking at the tiles.

It is also advisable to maintain a relatively low temperature throughout the viewing area, in order to prevent the viewing tile from being sublimated, with the accompanying dispersion into the environment, and the soiling of furnaces and appliances in the viewing area.

The tiles that reach zone 12 are in a white-hot state, at the temperature they had during baking in the end portion of zone 11 of the oven, at which time that temperature does not have to be the maximum temperature that the tiles reach in the oven 11 for baking.

If the glazing temperature is lower than the baking temperature, it is advantageous, in fact, for the tile cooling phase to start in said furnace, as this causes the tiles to reach the distribution apparatus at the most suitable temperature, taking into account the lowering of the temperature which may be exhibited in zone 12.

In this way, the control of the temperature of the tiles when they are received can in practice be controlled by regulating the temperature at which they leave the section 11 of the furnace, taking into account the lowering of the temperature to which they may be exposed in zone 12. There is also another possibility of controlling the last mentioned temperature by acting on a temperature maintained in zone 12, provided that, as stated above, that temperature does not become such as to cause a physical or chemical change in the powder to spread over the tiles in a white-hot state.

As well as application of the gaze, other operations associated with the beautiful savannah of the tiles can, if desired, be performed in zone 12, such as, for example, setting up a so-called tile. high-temperature transponders to create ornaments that require one particular distribution of pigments that form the ornament. These copiers can be mounted on tiles using robotic manipulators.

The plate mounted on the tile reaches the maximum temperature and minimum viscosity exactly on the touch surface with the ceramic body, which improves its attachment to that body.

The fact that the retention time of the tiles in zone 12, to be viewed briefly, prevents them from spinning from a white plastic state to a brittle state, in which heat stroke can lead to internal stresses, such as cracks in the clay material.

The application of gaze in the form of bulk powder makes the amount of gaze adhering to the vertical sides of the tile negligible and practically equal to zero, and thus the tile is clean at the edges, which in turn reduces the edge brittleness of the gaze coating, as well as the possibility of her crowns are fragile.

If more than one gaze is to be applied, each of which requires a certain temperature of the ceramic body for its application, as well as a temperature for their hardening, other gaze application cells may be placed at part 17 of the furnace in which the end of the tile is gradually cooled.

The features of the process of the invention will be clearer from the study of the following description of some embodiments thereof.

Example 1

Production of wall tiles with the following characteristics:

Size: thickness: Porosity: Break modulus x 20 cm 7 mm 12%

200 kg / cm ^

The mat looks with the influence of bluish milled material.

Characteristic of the mixture:

A mixture of natural sand and clay in the following relationships:

Major clay 60%

Grčs clay 25%

Peldspathic sand 15% (Table 1 gives the composition).

The mixture was prepared by dry milling in a pendulum crusher and moistened to 5% humidity.

The molding is done by dry pressing in hydraulic 2 presses, with a specific pressure of 220 kg / cm with a fivefold mold.

Direct placement in rows of 8, facing 20 cm apart, on a single-layer kiln with rollers, having the following characteristics:

The length of the drying part?

Preheating and baking:

13820 mm 24747 mm

Chamber width: 1465 mm

Maximum baking temperature: 1O6O ° C

Cycle duration: 25 min, approx

Figure 3 shows the firing curve ^, where the ordinance of the titemperaur of the gases from the furnace, and the abscess time, is proportionally related to the longitudinal dimensions of the furnace with respect to the velocity of transport of the tiles therein.

Watching:

See made of a mixture of three-particle matter, glasses (composition given in Table l).

Glass 1: 70%

Glass 2: 20%

Glass 3: 10%

The particle size is between 0.2 and 1 mm

Glazing temperature = 95 ° C

Watching with a roller distributor

Viewing zone length: 1000 mm

Apply 30 g per plate

Passing time: 30 seconds.

After passing through the viewing area, the tiles, still at approximately 9θ0 ° 0, enter the second section of the 17 ovens, which has the following characteristics:

Length: 23311 mm

Width: 1465 mm

This section is maintained in its initial zone at 1000 ° C, and the tiles extend through it in about 4 minutes, which is sufficient for a complex curing of the view.

Behind this section comes the zone of direct and indirect cooling.

According to torn, the total length of the machine is 62878 mm, with a total tile processing cycle of 40 minutes.

Example 2 ³

Production of floor tiles having the following characteristics:

- έ.

Size: 25 x 25 cm

It debuts at: 8 mm

Porosity and 3%

Half-light, light beige look

Characteristics of the mixture:

A mixture of clay and feldspar in the following relationships:

Feldspar: 45%

Clay 1: 30%

Clay 2: 25% (composition is given in Table l).

The mixture was prepared by wet milling with 35% water and spray.

Scattered Humidity: 5%

Formed by dry pressing with hydraulic press at 2 specific pressures of 3θθ kg / cm, and with triple mold.

Direct placement in rows of 5, on a single-layer kiln with rollers, having the following characteristics:

Length of drying compartment: 14548 mm

Preheating and baking Roller diameter:

Width :

Maximum temperature: Cycle time:

32102 mm cm for at least 12700 mm 1465 mm 1150 ° C for 30 minutes

The firing curve, depending on the gas temperature, will be similar in the general flow of the curve in Figure 3, with different values on the ordinate and on the abscissa.

He is glorious

The watch consists of a single material, glass beads, with a grain size between 0.2 and 1 mm,

Glazing temperature = 1050 ° C

The composition of the glasses is indicated in Table 1 (Frit 4). Watching with a roller distributor.

Viewing zone length: 1500 mm

It is applied 45 g in a tile.

Passing time: 30 seconds.

After passing through the viewing area, the tiles, still at about 1000 ° C, enter the second section of the furnace, which has the following characteristics:

Length: 22628 mm

Chamber width: 1465 mm

It is maintained at a temperature of 11 ° C.

The tiles pass through the first zone of the section, which is maintained at 11OO ° C for about 4 minutes, which is sufficient to harden the gaze, and then pass through the zone of direct and indirect cooling.

In this way the length of the machine is 76695 mm and the total cycle duration is 50 mm.

i

- ι4 Table.1. . CHEMICAL ⁴ · COMPOSITION.

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Maiolica gli 1 05 1 5 1 fc &'ω ¹ | o | ? 1 Km i uiaS ¹ gftl σι I TJ ¹ <-ι I <D u. I 1 1 -P '05 | O.. ω | Ό. r-l 1 <υ. in. | Clay 1 1 1 c I 3 1 ° 1 • Glass 1 1 CM | 05 I xd, 05 | rH. 3 -p 1 1 | 05 | > o. 05, r-l and j « 03. + »1 - 1 SiO ₂ 55.3 61.6 81.0 76.4 73.5 64.8 36.5 50.2 43.3 Al 0 2 3 14.8 20.3 9.4 13.4 22.5 28.5 5.0 1 5.0, 5.5 2 3 6.0 8.0 0.9 0.7 1.1 1.8 0.2 1 1 tio ₂ 0.8 1.1 1.1 1 1 1.7 1.7 0.1 9.5 CaO 14.7 0.6 2.8 j 1.0 0.3 0.3 1 4.4, 1 1 7.5 MgO ^3.2 2.3 0.3 0.3 1 1 0.2 0.3 1.5 3.0 K ₂ 0 3.1 3.8 3.4 5.9 0.6 2.1 0.6 0.5 At 0 2 1.2 1.6 2.1 0.8 0.1 0.2 1 0.7, 1 5.1, 3.5 ZnO 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4.5, 1 3.2, 2.0 BaO 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 6.1, CoO 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 10.0 PbO 1 1 1 1 1 1 1 1 1 1 1 1 34.6, 1 8.8, Zr0_ 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 5.4, 1 1 B O 1 1 1 1 1 1 1 1 5.0, 10.4 25.3, 2 3 1 1 1 1 1 1 1

st

65.0

5.6

0.1

6.0

7.5

0.1

0.8

4.0

10.1

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L.O.I. r ⁴ · ⁶ 6.0 2.7 2.3, 1 1 1 1 1 ⁷ · ⁸ 1 ⁸ ' ⁴ 1 1 1 1 CaCO ^ 22. ³ 0.3 h 4.1 1 1 1 1 1 1 1 1 1 1 1 1

The process according to the invention therefore has the following advantages over the known technologies:

- elimination of all movements of the raw tiles, except for their displacement into the oven, avoiding breakage and crunching.

- it simplifies the manufacturing process by removing, if desired, all structures normally required for the storage of raw tiles, provided that the furnace can be filled continuously and directly from the molding section,

- reduction of energy consumption for drying, since there is no water from the view, partially absorbed by the raw tiles,

- greater freedom in the design of patterns and reliefs on the top and back side of the tiles, since there is no problem of differentiated drying caused by different thicknesses or different porosities around the relief on the back side,

- the whole furnace, which contains unglazed tiles, remains clean and requires less maintenance,

- the ceramic body, baked without looking, is free to release gases and can oxidize more easily,

- the baking process is fast and can be done in a short time,

- less pure clay can be used with greater loss in baking, the use of decorative ceramic coatings is completely unnecessary,

- The firing temperature of the ceramic body has nothing to do with the temperature of the burned look, which can vary at any time. Because of this, gl $ dj is baked in a state best suited for perfect fitting and completely porous so that it is applied when the reactions of the ceramic body are complete, making the application of a decorative ceramic coating unnecessary.

- Special gases can be applied, which decompose at the temperatures at which the ceramic body is baked, thus expanding the range of products obtainable.

- glfedj adheres only to the surface of the tile,

- the excess view can be easily returned to the cycle, after being collected in the bus, - _.ό _ multiple consecutive layers of the view can be applied, thereby multiplying the multiple effects,

- As the furnace section behind the viewing section physically separates itself from the furnace for the ceramic body bake, a special atmosphere in it (oxidizing, reducing or inert atmosphere) can be achieved and controlled without altering in any way the characteristics of the baking cycle of the mixture. In this way, great freedom is achieved in achieving the special effects that can be achieved in a controlled atmosphere, which is very difficult to achieve by using traditional technologies,

- can be obtained, it is much more economical, products with glazed ceramic bodies, ie. high mechanical strength, with completely non-porous views, meaning essentially abrasion resistant and with excellent adhesion properties and therefore also have very high impact resistance,

- the area of products that can be used for viewing is significantly expanded, because it has become possible to use low-melting views on glazed ceramic bodies baked at higher temperatures, or views that require very short baking cycles, which is not possible with traditional technologies.

Claims (4)

An apparatus for the production of glazed ceramic tiles, comprising a baking furnace, annealing furnace or chamber into which ceramic bodies are placed, comprising a first section (11) having furnaces for heating ceramic bodies until the firing reactions are substantially completed ,! a second section (17) and a furnace equipped with a temperature control device for keeping the ceramic bodies at a controlled temperature which is lowered for the gradual cooling of said bodies, as well as a device (14) for transporting bodies along the first (11) and second (17) of the furnace section, characterized in that between the first section (11) and the second section (17) there is a conjoined viewing station (12) equipped with a device. (14) for the transport of tiles from the outlet (13) from the first section (11) of the furnace to the inlet (16) of the second section (17) of the furnace, and with the device (20) for the application of dry bulk view to ceramic bodies conveyed by the transport apparatus (14). Apparatus according to claim 1, characterized in that the viewing device (20) is provided with a temperature control device. A device according to claim 1, characterized in that the viewing device (20) is provided over the entire width of the transport device (14) for transferring the tiles. 4-. Apparatus according to claim 3, characterized in that the furnace (11,17) with the rollers (14) is in a single layer. A device according to claim 1, characterized in that the conveyor (14) for the formation of a discontinuous surface support for tiles that are spaced apart and supported on several points is positioned below the coating distribution device (20) over the entire width of the conveyor (14). and having the collecting container (23) look out of the zone between the disconnected tiles positioned below the conveyor (14) and the view dispensing apparatus (20).