BE1030975A1 - Process for the production of roof tiles using the rapid firing process - Google Patents

Abstract

According to a first aspect, the invention relates to a method for producing a roof tile from clay (1), comprising the following steps: providing the moist, unprocessed clay (1); producing an aqueous clay suspension (2); separating an oversize fraction from the suspension (2), wherein the oversize fraction comprises grains whose grain diameter exceeds a defined value; granulating the suspension (2) to produce clay granules (3); introducing the clay granules (3) into a press mold (14); pressing the clay granules in the press mold (14), wherein the clay granules (3) are compacted and formed into a roof tile molding; transferring the roof tile molding into a roller kiln; and firing the roof tile molding in a rapid firing process. According to a further aspect, the invention relates to a system (10) for producing a roof tile and to a roof tile.

Description

Process for the manufacture of roof tiles in

Fast firing process

The invention relates to a method for producing a roof tile, a plant for carrying out the method, and a

roof tiles obtained by this process.

State of the art

The production of roof tiles is usually carried out via a

Wet pressing process. In this process, clay and/or loam are mined in a pit, then mixed and prepared for the pressing process. From the prepared clay mixture, an endless clay strand is first extruded through an extrusion press. The clay strand is then cut into so-called lumps. In a turret press, into which a

Plaster molds are inserted, the lump is then given a shape corresponding to the roof tile. After the pressing process, the

Roof tile preform already has a so-called green strength, which allows the roof tile preform to be removed from the plaster mold,

drying frames and thus feed them to the drying process. The

Drying of the roof tile moldings serves to reduce the moisture content of the clay before firing, it usually takes place over a period of 24 hours to 36 hours at a temperature between 80°C and 120°C. After drying, the

Roof tile preforms are placed on ceramic firing cassettes.

Roof tile preforms are placed together with the firing cassettes on

kiln cars and transferred to the tunnel kiln, where the

Roof tile preforms are fired at temperatures between 980°C and 1100°C for a period of at least 24 hours.

Wet pressing processes have the disadvantage that the water bound in the clay mixture must escape from the clay and the press mould. If this does not happen, the water can

leave pores that reduce the weather resistance of the roof tile. The press moulds are therefore made of gypsum, which can absorb water due to its hygroscopic properties. In addition, however, it is still necessary to equip the press moulds made of gypsum with drainage pipes. The

Making plaster molds is labor-intensive and therefore expensive.

Since the gypsum quickly becomes moist, the service life of the press molds is short, which leads to frequent production stops, because the press molds of the turret press have to be replaced regularly.

The moisture remaining in the roof tile moulding must be removed before

The burning process is further reduced if, otherwise, the

Water evaporating during firing creates too many pores in the fired

Roof tiles which reduce the weather resistance of the roof tile.

The pressed roof tile pieces are therefore transferred to drying frames and transferred to the drying process. During transfer, the

Roof tile preforms should not be subjected to mechanical stress, as this may lead to undesirable deformations. The

Roof tile preforms can warp during the drying process or drying cracks can develop. The preforms must therefore be handled with appropriate care, which in turn entails a process-related effort.

The energy consumption in roof tile production is due to the

drying and firing process and the long duration of these two

processes are very high. Since the tunnel kilns are operated with natural gas, high CO: emissions are also generated. From an energy point of view, it is also disadvantageous that a large amount of kiln furniture

(firing cassettes and kiln cars) is introduced into the tunnel kiln. The

Kiln furniture has a high heat capacity, and the

Considerable heat losses occur during heating and subsequent cooling of the kiln furniture.

In order to eliminate some of the disadvantages of the wet pressing process, DE 195 26 849 A1 proposes to produce roof tiles using the dry pressing process. The clay coming from the pit is

The clay is then fed to an intermediate storage facility by a feeder, pan mill, roller mills and mixer. Granules are then produced from this processed, granulated, earth-moist clay by first extruding thin clay strands, which are then broken down into small

The molded bodies are cut up and covered with dry clay dust to create moist clay granules with an enormously large surface area.

In this way, a pre-dried, free-flowing but still plastically deformable granulate is created, which is then pressed into a green

roof tiles are pressed together. However, this theory is very difficult to implement in practice.

Due to the fact that the water withdrawal already occurs before the

pressing process, a large part of the shrinkage already takes place in the

The drying process takes place during the drying of the granulate and not, as is usual with wet pressing, during the drying of the roof tile preforms. This means that there are no more drying errors that can become noticeable when the roof tiles are fired due to warping.

However, the dry pressing process known from the state of the art has the disadvantage that the granulate production described here is associated with a great deal of process engineering effort. In addition, the many individual steps entail high investment and

Operating costs for the corresponding machines and systems.

Task

The invention is based on the object of creating a method and a plant for producing roof tiles, wherein the method has low energy consumption and the lowest possible CO2 emissions and wherein the plant can be used to produce high-quality roof tiles at low production costs and short production times.

Description of the invention

Main features of the invention are specified in claims 1, 14 and 15. Embodiments are the subject of claims 2 to 13.

According to the invention, the object is achieved by a method for producing a roof tile made of clay, wherein the method comprises the following

Steps: — Providing the moist, unprocessed clay; - Creating an aqueous clay suspension; — Separating an oversize fraction from the suspension, whereby the

Oversize fraction includes grains whose grain diameter exceeds a defined value; — granulating the suspension to produce clay granules; — introducing the clay granules into a press mold; — pressing the clay granules in the press mold, whereby the clay granules are compacted and formed into a roof tile molding, - transferring the roof tile molding into a roller kiln and — firing the roof tile molding in a rapid firing process with reduced CO2 emissions.

In this context, a rapid firing process within the meaning of this disclosure is understood to mean a firing process in which one or more

Roof tile moldings are fired for a maximum of 4 hours at temperatures between 950 ° and 1100 °C. The process 5 according to the invention preferably provides for clay preparation for further processing in

Due to the low moisture content of the clay granules, steel molds with high

downtimes, a time- and energy-consuming

Drying of the roof tile blanks before firing is therefore not necessary. Since the roof tile blanks already have a high degree of dimensional stability after pressing, they can be fired in a roller kiln without any kiln furniture. Consequently, the

Energy losses occurring in tunnel or chamber furnaces due to the

Heating and cooling of the kiln furniture is eliminated. The term “dry pressing” refers to a pressing process step in which the pressed roof tile molding undergoes a

Moisture content of 20% or less, preferably 10% or less and particularly preferably 4% or less

The sound can be provided from a single pit (“single source” sound). A sound mix from several

Toning is due to the reduced

Importance of plastic properties not necessary.

According to the invention, the roof tile preforms are fired in a

Roller kiln in the so-called fast firing process, in which the

Firing times for roof tiles are between one and four hours. The shorter firing times compared to conventional

Burning times lead to a reduced energy requirement and thus to a reduction in CO2 emissions. Furthermore, there are significant

Time and cost savings. Due to the low tonnage in the combustion chamber, it is also possible to start and stop the combustion process at short notice, which allows flexible operating times. This makes it possible, for example, to avoid cost-intensive production times such as weekends or holidays, because the

Roller kiln can be raised and lowered quickly.

Roof tiles are usually fired in tunnel or chamber kilns.

A large number of bricks are stacked on appropriately fireproof cassettes to form a unit and fired in the kiln for a period of at least 16 hours. This process requires a sufficiently large combustion chamber, which in turn leads to poor

heat distribution and also a high

In addition, starting up and shutting down the oven, i.e. heating up and cooling down, takes a lot of time, which makes flexible use of the oven difficult. In contrast,

Roller kilns are single-layer firings. The kiln's firing channel is designed to be as small as possible in order to increase the kiln's burning power and thus to be able to burn the material more quickly. At the same time, the firing chamber should be as small as possible in relation to the required output.

Only the breaking load of the rollers represents a limiting factor here.

The use of a roller oven also has the advantage that

Roller kilns compared to those commonly used in brick kilns

Kilns, such as tunnel or chamber kilns, can be operated in a climate-neutral manner. For example, the roller kiln can be electrically or

Hydrogen-based or operated. Tunnel furnaces can be operated with

Hydrogen or electric power are very difficult to operate.

It is also conceivable that the process after the step of pressing the

Clay granules to form roof tiles include a quality control step.

Faulty or unsatisfactory moldings can be returned to the

The suspension production process can be fed into the suspension production process and reprocessed there. The quality control step can be carried out on a random basis.

The pressing process preferably takes place in a press mold, which can have a first mold half and a second mold half. The mold halves can be moved between a pressing position in which the

Mould halves essentially define a receiving space that

shape of the finished roof tile, and a filling position in which the

Mould halves are spaced apart and a plastically deformable

Molding compound can be filled into the first and/or the second mold half, can be designed to be movable relative to one another. The first mold half and/or the second mold half have at least one recess which forms a projection of the finished roof tile molding, wherein a first pressure element is provided in and/or on the recess, which is designed to be movable between a starting position in which the first pressure element is set back with respect to the shape of the finished roof tile molding, and a compaction position in which the first pressure element partially forms the surface of the roof tile molding. The method for pressing the roof tile therefore additionally comprises the following steps: — Providing the press mold, wherein the mold halves are in the

Filling position and the at least one first printing element in the

starting position, — filling the clay granulate into the receiving chamber, — moving the mould halves into the pressing position, whereby

Clay granulate is compacted, — moving the at least one pressure element into the

Compaction position, whereby the clay granulate in the area of the first

pressure element is compressed.

Due to the fact that the first pressure element is moved into its compaction position after the mold is closed, the first pressure element further compacts the clay granules in the

Areas where sufficient compaction is not achieved by simply moving the mold halves, for example in the recesses that

projections of the finished roof tile. This allows the

The strength of the roof tile molding can be increased in these areas so that the roof tile molding has greater strength and resistance to external influences.

During compression, the pressure element presses into the surface of the

roof tile blank, whereby the surface of the roof tile is embossed in the compacted areas. The

Embossing gives the roof tile a characteristic appearance and remains even after the firing process. Depending on the number, size and

Arrangement of the printing elements used therefore arise on the

Surface of the roof tile different embossed patterns.

The above-mentioned projections can be located on the top and/or bottom of the roof tile blank. The roof tile blank can, for example, have a top and side fold on its top and be provided with hooking lugs, stacking points,

be provided with slat protectors and stiffening ribs,

After completion of the pressing process, the first

Pressure element moves into the starting position, whereby the pressed roof tile molding can be released from the respective mold half in the area of the recesses and demolding is made easier.

The mould halves are then moved to the filling position and the

Roof tile molding is removed from the mold. The risk of

Damage to the pressed roof tile when removing it from the

In this way, the risk of roof tile sticking to one half of the mold can be reduced.

Preferably, a guide is provided for the first and/or the second mold half, wherein the guide together with the mold halves

Receiving space is completely limited in the filling position and in the pressing position. The guide can have several guide parts and can be moved into a demolding position before the mold halves are opened.

Clay exhibits a relatively large stretching back of the pressed clay granulate in the dry pressing process. The stretching back is approximately 0.7% to 1.0%. If the press mold is opened to remove the pressed roof tile within the guide that laterally limits the receiving space, the pressed roof tile expands and jams within the guide, which can damage the pressed roof tile or make it more difficult to remove from the press mold. To avoid such problems, the guide is laterally, i.e. parallel to the direction of extension of the mold halves, in a

The mold halves are moved to a demolding position in which the pressed roof tile molding remains in place even if the

Clay granules cannot rest against the guide, so that the

Roof tile molding can expand in the direction of extension essentially parallel to the surface of the mold halves.

At least one second pressure element can be provided on the surface of the first and/or the second mold half, which is arranged between a

Starting position in which the second pressure element protrudes or is recessed with respect to the shape of the finished roof tile molding, and a

Compaction position in which the second pressure element sections the

surface of the shape of the roof tile molding, is designed to be movable, wherein the second pressure element during or after the

Moving the mold halves into the pressing position into the compression position or, after completion of the pressing process, back to the starting position. This second pressure element enables, for example,

Further compaction of the clay material outside the depressions is possible.

Preferably, however, the second pressure element is provided with a

The first pressure element is provided in the recess. The first

The pressure element is forced from the recessed position into the compression position by the movement of the second pressure element from the projecting position into the compression position. The second pressure element is used in this embodiment to move the first pressure element into the compression position. The second pressure element can be used as a control element.

Preferably, however, the first and second pressure elements are hydraulically coupled, so that the pressure acting on the second pressure element causes the first pressure element to move into the

compaction position occurs.

The coupling of first and second pressure elements enables easier control of the movement of the first and second

Pressure elements between the respective starting position and the respective compaction position. By moving the mold halves into the pressing position, the clay material exerts pressure on the second

pressure element, through which the second pressure element is pushed into the

compression position. By moving the second

pressure element into the compression position, the second

The first pressure element coupled to the pressure element is moved into the compression position so that no separate control is required for the first pressure element.

Furthermore, the roof tile can be easily removed from the mould. For example, the second pressure element is in the

The mould is moved from its initial position over the shape of the finished roof tile and is moved into the compaction position by the pressure that increases when the mould halves are moved into the pressing position.

Coupling of the first and second pressure elements, the first

Pressure element moves into the compaction position. When the mold is opened, i.e. when the mold halves move into the filling position, the pressure on the second pressure elements is reduced so that they can move back into the protruding position, whereby the pressed

Roof tile blank is lifted and released from the surface of the mold. The first pressure element coupled to the second pressure element is simultaneously moved back to the initial position offset with respect to the shape of the roof tile, whereby the

Roof tile molding also in the area of the recess from the respective

The roof tile then adheres little or not at all to the respective half of the mould, so that the

The risk of damage when removing the roof tile can be reduced.

Preferably, several first pressure elements and/or several second pressure elements are provided, wherein the first pressure elements and/or the second pressure elements are coupled to one another and/or to each other. Sufficient compaction of the clay material can be achieved with one pressure element. If several, preferably small-area pressure elements are used, the compaction can be better controlled, or the pressing process can be controlled in such a way that the compaction takes place in a defined area with a defined pressure on the clay material.

According to a preferred embodiment, the pressure elements are designed in such a way that they can achieve a compaction of the clay granulate of approximately 2:1. This means that the

Initial volume of the clay granulate using the preferred

printing elements can be reduced by half. For this purpose, the

Printing elements must be made of a suitably hard and resilient material, which also has the same

should have expansion properties like the material of the

Press mold halves. The pressure elements can preferably be made of steel, for example.

After filling the clay granulate, the mould halves can be placed in a

Venting position between the filling position and the pressing position, in which air contained in the receiving space is removed from the

recording room can escape.

During the production of the suspension and thus at the beginning of the process according to the invention, it can also be provided that the separation of the undersize fraction and the oversize fraction is carried out with a

sieve or a filter. In particular, it is intended that the separation takes place via a wet sieving process. A

Wet sieving process makes it possible to remove unwanted grain sizes from the

suspension without having to dry it first. Wet sieving can also prevent clogging of the

Sieve meshes can be prevented, which can occur with small grain sizes in dry sieving processes. Alternatively, the separation can be carried out using a centrifuge or a cyclone separator.

According to a further aspect of the invention, a system for

Production of a roof tile using the inventive

The system includes in particular a

Feeding device for feeding unprocessed clay, a

Mill for producing a suspension, a granulating device for

Production of clay granules, a press mould for dry pressing of the

Clay granules to form a roof tile molding and a roller kiln to

Carrying out a rapid firing procedure.

In addition, a crushing device can be provided for pre-crushing the unprocessed clay material into clay pieces of a defined size, whereby the crushing device can be installed upstream of the mill or can also be part of the mill. The mill can have a

Pendulum mill, a roller mill or a

Agitator ball mill. Optionally, the mill can have a

Sorting device for separating out excess material (for example undersize and oversize fractions), wherein the

Sorting device can primarily comprise a sieve.

Preferably, the system also comprises a glazing device which is suitable for processing the surfaces of the roof tile moldings. The moldings can be glazed, embossed, coated or engobed in the glazing device.

According to a further aspect, the invention relates to a roof tile made of

Clay produced using the process described here.

Character description

Further features, details and advantages of the invention emerge from the wording of the claims and from the following description of embodiments with reference to the drawings. They show:

Fig. 1 shows a schematic representation of a plant for producing a roof tile from clay;

Fig. 2 is a flow chart of a process for producing a

Clay roof tile according to a first embodiment;

Fig. 3 is a flow chart of a process for producing a

Clay roof tile according to a second embodiment;

Fig. 4a shows a press mold for producing a roof tile according to a preferred embodiment in a filling position;

Fig. 4b the pressing mold from Fig. 4a in closed pressing position.

Fig. 1 shows a system 10 for producing a roof tile from clay 1 in a schematic representation. The system 10 shown is particularly suitable for carrying out the method according to the invention. The exemplary system 10 from Fig. 1 comprises a feeding device 11 which feeds the untreated pit clay to a mill 12. In the

Mill 12 produces a suspension 2 from the clay. According to the process described here, the lower and upper

Oversize fraction is removed.

The prepared suspension 2 is then fed to the granulating device 13, which converts the suspension 2 into clay granules 3 with a defined

moisture content. As shown in Fig. 1, the

Granulating device 13 can be, for example, a spray dryer.

The system 10 from Fig. 1 also comprises an intermediate storage facility 14, which is designed to store and dry the clay granulate 3. The intermediate storage facility 14 is preferably one or more silos.

As a further machine section, the system 10 comprises a press mold 14 for dry pressing the clay granulate 3 into a roof tile molding.

Finally, the pressed roof tile pieces are sent to a

Roller kiln 16, which is suitable for firing the bricks in a rapid firing process, i.e. in less than 4 hours.

As shown in Fig. 1, the system 10 can also have a

Glazing device 15. There, the moldings can be glazed, embossed, coated or printed (e.g. “digital printing”) and/or engobed, for example, before they are fired in the roller kiln 16.

Fig. 2 shows in a flow chart the steps S1-S8 of the inventive method for producing a roof tile from

Tone 1 according to a first embodiment.

First, step S1 takes place: providing the moist, unprocessed

Tone 1. Tone 1 is preferably taken from a nearby

Pit to plant 10. In this way, long

Transport routes and the associated costs can be avoided or reduced. Coordinating the clay mixture from several clays is not necessary due to the lesser importance of plastic properties.

Once it has arrived at the plant 10, the untreated pit clay 1 can be processed directly into an aqueous suspension 2 in the mill 12 according to step S2. The suspension 2 can be homogenized better than dry clay granulate 3. In addition, the subsequent separation processes can be carried out better than conventional processes if the clay 1 is present as an aqueous suspension 2. The conditioning of the

Starting material to a suspension 2 is preferably carried out with the addition of water and using dissolvers and agitators, which can be integrated in the mill 12. At the end of step S2, the

Suspension 2 preferably has a solids content of 55% to 65%.

This is followed by step S3: separating an oversize fraction from the suspension 2, wherein the oversize fraction comprises grains whose

Grain diameter exceeds a defined value. Ideally, the grain size of the subsequent granulate 3 should be between 120 um and 1000 um. To ensure this, grains with a diameter of more than 1000 um are separated from the suspension 2. In a further step S3.1 (see Fig. 3), grains can also be separated from the

Suspension 2 whose diameter is smaller than 120 µm.

After separating out oversize and/or undersize fractions from the

Suspension 2 follows step S4: Granulation of suspension 2 to

Production of clay granulate 3. In order to achieve the best possible pressing result, the clay granulate 3 should have a residual moisture content of 2% to 6%. This prevents the roof tile moldings from shrinking during the pressing process. The granulation process S2 can be carried out, for example, by means of spray or atomization drying in a suitable granulation device 13.

Next comes step S5: Insert the clay granulate 3 into a

Press mold 14. To produce the roof tile molds, the

Clay granulate 3 obtained in step S4 is preferably injected under pressure into the

Press mold 14 of the system. Immediately after this,

Step S6: Pressing the clay granulate 3 in the press mold 14, whereby the

Clay granulate 3 is compacted and formed into a roof tile.

Once the desired amount of clay granulate 3 has been introduced into the press mold 14, the mold halves of the press mold 14 are removed from the

filling position into the pressing position, in which the pressing mold 14

Shape of the finished roof tile.

The next step S7 includes the following: Transferring the

Roof tile blanks into a roller kiln 16 for firing the

Roof tile blank. In the last step S8, the roof tile blank is then fired into a roof tile using the rapid firing process. The

Firing process according to S8 is preferably carried out in a single layer setting.

This allows the highest possible proportion of the radiation energy of the

Oven 16 can be used for heat transfer to the roof tiles.

Fig. 3 shows a flow chart comprising steps S1-S8 of the

Method for producing a clay roof tile 1 according to a second embodiment. The method shown in Fig. 3 differs from the method in Fig. 2 in that the

Method according to Fig. 3 the additional intermediate steps S1.1, S2.1,

S3.1 and S4.1.

Step S1.1 follows step S1 and includes the following:

Breaking of clay slabs contained in clay 1 into clay pieces, whereby the

Clay pieces have an average diameter of 5 cm or less.

The breaking or grinding of larger clay slabs into pieces of clay, which

Medium smaller than 5 cm, can be carried out, for example, in mill 12 and serves to prepare the unprocessed material coming from the stockpile for the subsequent steps.

Step S2.1 follows step S2 and includes the following:

Addition of additives to the suspension 2. The additives facilitate the

Homogenization of the suspension 2 and serve primarily to

To give roof tiles their desired properties, for example to keep the solid content in the suspension as high as possible.

Step S3.1 follows step S3 and includes the following:

Separating a sub-grain fraction from the suspension 2, whereby the

Undersize fraction includes grains whose grain diameter exceeds a defined value. Ideally, the grain size of the subsequent granulate 3 should be between 120 um and 1000 um. To ensure this, grains are separated from the suspension 2 whose

diameter is smaller than 120 um. Step S3.1 can be performed simultaneously with

Step S3 must be carried out.

Step S4.1 follows step S4 and includes the following:

Storing the clay granulate 3 in at least one suitable

Intermediate storage 14. The intermediate storage 14 is preferably a silo.

Storage in an interim storage facility 14 contributes to a further

Homogenization of the granulate 3, whereby in this phase, for example, a compensation of small moisture differences within the granulate 3 can take place. The process of

Intermediate storage can last between a few hours and a few days — depending on production requirements.

According to one embodiment, it is provided that the

Advantageously, the combustion channel of the furnace should be as small as possible in order to increase the combustion power of the furnace and the

This allows the fuel to burn faster. This is another

The advantage of the described method is that the obtained

Roof tile preforms without the usual kiln furniture (e.g. H- or U-

cassettes) because they already have a sufficient

The dimensional stability comes from the dry pressing step. Accordingly, kiln furniture can be dispensed with, which saves space and

This leads to cost savings which also increases the kiln’s firing efficiency. The use of a roller kiln also has the advantage that

Roller kilns compared to those commonly used in brick kilns

Kilns can be operated in a climate-neutral manner. For example, the roller kiln can be operated electrically or on a hydrogen basis.

In Fig. 4a, the mold 14 is shown in a filling position in which the

The mold halves 22, 24 are spaced apart from one another and a clay material can be filled into the receiving space. A filling device 42 is provided for filling the mold 14, which fills the clay material by means of

Compressed air with overpressure can be injected into the receiving chamber 30. The

Injection takes place in an injection direction E essentially parallel to the

Surface 34, 38 of the first and second mold halves 22, 24, respectively.

From the filling position shown in Fig. 4a, the mold halves 22, 24 can be moved in a pressing direction P towards each other into the position shown in Fig. 4b.

Press position in which the receiving space 30 in the

Essentially the shape of the roof tile 18. One of the mold halves 22, 24 can be fixed in place so that only the other mold half 22, 24 is moved. However, it is also possible that both mold halves 22, 24 can be moved and are moved towards each other during the pressing process of the roof tile 18. The guide elements 28 are in a

Essentially perpendicular to the pressing direction P_

Removal direction R into a removal position in which the

Guide elements 28 are spaced from the mold halves 22, 24. The

Mould halves 22, 24 each have a base body 44, 46 made of steel, preferably tool steel. Furthermore, the

Surfaces 34, 38 each have a coating 48, 50, which in the embodiment shown here is each formed from a PU layer.

The coating 48, 50 ensures that the filled

Clay material on the surfaces 34, 38 of the mold halves 22, 24 is reduced.

A first pressure element 52 is provided on or in the recess 40, which is formed by a pressure pad having a pressure chamber 58 filled with an incompressible pressure medium 56. The first pressure element 52 has a pressure line 60 through which the

Pressure medium 56, for example oil, can flow into or out of the pressure chamber 58. The first pressure element 52 is provided at the foot of the depressions 40, i.e. at the transition to the surface 38 of the second mold half 24 facing the first mold half 22.

Furthermore, a second pressure element 62 is provided on the surface 38 of the second mold half 24, the structure of which essentially corresponds to the structure of the first pressure element 52. The second

Pressure element 62 has a pressure chamber 64 and a pressure line 66 which are filled with the pressure medium 56.

The pressure line 66 of the second pressure element 62 is connected to the pressure line 58 of the first pressure element 52 so that the pressure medium 56 can flow between the first and the second pressure element 52, 62. Furthermore, the pressure lines 60, 66 are connected to a

Pressure generating device 68, which provides the pressure medium 56 and/or the pressure in the pressure lines 60, 66 or the

pressure elements 52, 62. Preferably, the

Pressure medium 56 has an overpressure of approximately 5 Pa to 7 Pa. The

Pressure elements 52, 62 are each formed by a recess 70, 72 in the

Base body 46 of the second mold half 24 and the coating 50 designed as a membrane are formed.

In the filling position according to Fig. 4a, the second pressure element 62 is in a

In the initial position, the first pressure element 52 is curved in the direction of the receiving space 30, i.e. it protrudes beyond the shape of the finished roof tile 18 (dashed line). In the filling position, the first pressure element 52 is set back in an initial position relative to the shape of the finished roof tile 18.

The first and second pressure elements 52, 62 are connected by the

Pressure lines 60, 66 are coupled together in such a way that the first

Pressure element 52 by moving the second pressure element 62 into a compaction position in which the second pressure element 62 partially reproduces the shape of the finished roof tile, by the pressure flowing out of the second pressure element 62 and into the first

Pressure element 52 inflowing pressure medium 56 outwards into a

Compaction position in which the first pressure element 52 also forms a section of the shape of the roof tile 18 (see Fig. 4b).

The invention is not limited to one of the embodiments described above, but can be modified in many ways.

All features and advantages arising from the claims, the description and the drawing, including constructive

Details, spatial arrangements and process steps can be essential to the invention both individually and in a wide variety of combinations.

List of reference symbols

Sn Step n 1 Clay 2 Suspension 3 Clay granules

Plant 11 Feeding device 12 Mill 13 Granulating device 14 Intermediate storage

Glazing equipment 16 Roller kiln 18 Roof tiles

Press mold 22 First mold half 24 Second mold half 26 Guide 28 Guide elements

Recording room 34, 38 Surface

Recess 42 Filling device 44, 46 Base body 48, 50 Coating 52 First pressure element 56 Pressure medium 58, 64 Pressure chamber 60 Pressure line

62 Second pressure element 70, 72 Recess

Claims (14)

Patent claims 1. Method for producing a roof tile from clay (1), comprising the following steps: (S1) providing the moist, unprocessed clay (1); (S2) producing an aqueous clay suspension (2); (S3) separating an oversize fraction from the suspension (2), wherein the oversize fraction comprises grains whose grain diameter exceeds a defined value; (S4) granulating the suspension (2) to produce clay granules (3); (S5) introducing the clay granules (3) into a press mold (14); (S6) pressing the clay granules in the press mold (14), wherein the clay granules (3) are compacted and formed into a roof tile molding; (S7) transferring the roof tile molding into a roller kiln and (S8) firing the roof tile molding in a rapid firing process. 2. Method according to claim 1, characterized in that the method after step (S1) further comprises the following step: (S1.1)Breaking of clay slabs contained in the clay (1) into clay pieces, the clay pieces having an average diameter of 5 cm. 3. Method according to one of the preceding claims, characterized in that the method after step (S2) further comprises the following step: (S2.1)Addition of additives to the suspension (2). 4. Method according to one of the preceding claims, characterized in that the method before step (S3) further comprises the following step: (S3.1) Separating an undersize fraction from the suspension (2), wherein the undersize fraction comprises grains whose grain diameter is below a defined value. 5. Method according to one of the preceding claims, characterized in that the method after step (S4) further comprises the following step: (S4.1) Storing the clay granulate in at least one suitable intermediate storage facility (15), in particular a silo. 6. Process according to one of the preceding claims, characterized in that the aqueous suspension (2) has a solids content of 20% to 70%, in particular 55% to 65%, before granulation, 7. Process according to one of the preceding claims, characterized in that the grains of the oversize fraction each have a grain diameter which is greater than 1000 µm. 8. Process according to one of claims 4 to 7, characterized in that the grains of the undersize fraction each have a grain diameter which is smaller than 100 µm. 9. Method according to one of the preceding claims, characterized in that the clay granulate (3) after granulation of the suspension (2) has a moisture content of less than 15%, in particular from 1% to 11%. 10. Method according to one of the preceding claims, characterized in that the pressing of the clay granulate (3) is carried out by dry pressing. 11. Method according to one of claims 4 to 10, characterized in that the separation of the undersize fraction and the oversize fraction is each carried out in a sieving process. 12. Method according to one of the preceding claims, characterized in that step (S1.1) takes place in a pendulum mill or in a roller mill. 13. Plant (10) for producing a roof tile using the method according to one of the preceding claims. 14. Clay roof tile, characterized in that the roof tile is produced by a process according to one of claims 1 to 12.