A PRODUCTION METHOD, AND A CERAMIC PRODUCT OBTAINED BY SUCH METHOD

A production method is provided. The production method comprises forming material by pressing or pulling ceramic material through a channel of an extrusion die, said channel being at least partly defined by the lateral surface area of at least one rotating die, and heat processing the formed material to form a ceramic product.

TECHNICAL FIELD

The present invention relates to a production method for manufacturing ceramic products, and to ceramic products produced by such method.

BACKGROUND

Ceramic products are vastly used for various applications. One common ceramic product application is structural components, such as bricks, pipes, and wall and floor tiles for interior and exterior decoration. Production of such tiles involves a number of steps. The raw materials, including clay minerals, are prepared by mixing and grinding, and optionally drying. A forming step is thereafter performed. One available forming method is based on dry pressing, where powder material is arranged and compressed in a forming die. Another option requires wetter raw materials, and allows forming of the ceramic product by extrusion and subsequent punching.

Once the article is formed to its desired shape it is normally subject to a post-forming process including drying, glazing and firing.

Existing manufacturing methods for ceramic products require certain properties of the raw materials, and the designs of the final products are limited by the capabilities of the existing production equipment. Typically, if there is need for new ceramic products with new designs there is a large risk that these cannot be made by existing manufacturing processes, thus requiring expensive and time consuming post-processing and process adaptations.

Hence, there is need for an improved manufacturing processes which not only provides a more versatile approach to the production of ceramic products, but also reduces cost and time for ceramic product production.

SUMMARY

It is an object of the invention to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object to provide a manufacturing method where the raw material is continuously formed, and which forming allows for the creating of advanced pattern and structures to the final ceramic product.

To solve these objects a production method is provided, comprising i) forming material by pressing or pulling ceramic material through a channel of an extrusion die, said channel being at least partly defined by the lateral surface area of at least one rotating die, and ii) heat processing the formed material to form a ceramic product.

Preferably, the method is performed by pressing or pulling the ceramic material through bearing surfaces defining the channel. The channel is preferably formed by an extrusion die, whereby the bearing surfaces comprise at least one rotating bearing surface being a surface of a rotating die that defines the cross-section of the formed material such that the channel being at least partly defined by the at least one rotating die.

The rotating die may apply a pattern to the formed material. Preferably, the applied pattern is a repetitive pattern.

The method may further comprise a step of shrinking the formed material such that the dimensions of the pattern of the rotating die are different from the dimensions of the pattern of the ceramic product. Preferably, this shrinking is performed during the heat processing.

The method may further comprise a step of adjusting the flow of the ceramic material upstream the channel. This allows for the control of a correct flow distribution and uniform speed of the ceramic material when it enters the channel.

The method may further comprise a step of driving said rotating die. Such driving may be performed continuously during the manufacturing method.

Driving the rotating die may further comprise synchronizing the rotation of the rotating die with the speed of a downstream conveyor for the ceramic product.

The method may further comprise a step of determining at least one dimension of the ceramic product, and adjusting speed of the rotating die and/or the downstream conveyor based on the determined dimension(s).

The step of heat processing may be performed by firing the formed material. Optionally, heat processing may be a multi-step process also comprising an initial drying step. Typically, such drying step is performed at a temperature which is significantly lower than the temperature of the firing.

The method may further comprise separating an individual product from the formed material before, during, or after heat processing. It should be noted that the steps of separating and heat processing can be performed in any order.

In an embodiment the method further comprises mounting a plurality of individual products to each other before the step of heat processing. By arranging multiple individual products in contact with each other during the heat processing, these will bond mechanically and form a uniform product.

Separating an individual product may be performed by a cutting action of the rotating die. This provides for efficient separation not requiring additional components and cutting or punching stations.

The circumference of the rotating die may be equal to the length of the individual product, or different from the length of the individual product. It is thus possible to determine the periodical match of the pattern of the rotating die with the final individual products in a very flexible manner.

The channel may have a longitudinal extension in a production direction, and the rotational axis of the rotating die may be arranged at an angle relative to said production direction, preferably the rotating die is arranged at an angle of 90°±25° relative to said production direction. It is thus not only possible to have the rotating die perfectly transverse to the production direction, but also to allow the rotating die to “screw” over the material to be formed.

The channel may be defined by a bottom area, an upper area, and two opposing side areas together forming a closed space, wherein at least a part of one of the areas may be formed by the lateral surface area of the at least one rotating die.

In some embodiments, at least a part of at least one further area is defined by the lateral surface area of a further rotating die.

At least one of the bottom area, upper area, and the two opposing side areas may be defined by a bearing surface.

The manufacturing method thus allows for the use of one or more (two, three, four, five, etc.) rotating dies to provide a repetitive pattern to the material to be formed.

The method may further comprise pressing or pulling ceramic material through a pre-bearing passage arranged upstream the rotating die.

The pre-bearing passage may be arranged immediately upstream the rotating die, or the pre-bearing passage may be arranged upstream, but remote from, the rotating die.

The pre-bearing passage may be configured to deform the ceramic material into a master profile, while the channel may be configured to further deform the material into a final profile having a final shape.

The dimensions of the pre-bearing passage may be static.

The lateral surface area of the rotating die may be provided with a topographic pattern. Said topographic pattern may comprise at least one protrusion, said protrusion being configured to form a separation notch in the ceramic product and/or a significant local reduction of the thickness of the ceramic product.

Such significant reduction of the thickness of the ceramic product may define a removable portion of the ceramic product. Due to the thickness reduction it is possible to allow these removable portions to only require a very small force to actually be removed.

At least one protrusion may extend across the entire width of the rotating die, or across a part of the width of the rotating die. The protrusion may extend in a linear or curved manner across the width of the rotating die.

The method may further comprise adding a further material to the ceramic material. Adding such further material may be performed before, during, or after the ceramic material passes the rotating die.

The further material may be embedded in the ceramic material to form a reinforcement of the extruded article.

The further material may be a fibre material or a web material.

The further material may be added as at least one layer to the ceramic material.

The further material may be a liquid or a solid material in the form or powder or particles.

The further material may comprise a plurality of different ceramic and/or non-ceramic materials.

The ceramic material and the at least one further material may be fed through the channel.

The method may further comprise adjusting the position of the rotating die thereby adjusting the dimensions of the channel.

The method may further comprise providing the channel with at least one die core, said die core forming a hollow portion of said ceramic product.

The ceramic product may be a brick or a plate-like product such as a tile.

The channel may provide one side of the formed material with a first structural surface pattern defined by the lateral surface area of at least one rotating die, and an opposite side of the formed material with a second structural surface pattern defined by the lateral surface area of another rotating die.

The first and second structural surface patterns may provide a matching fit when multiple ceramic products are stacked onto each other.

According to a second aspect a ceramic product is provided. The ceramic product is formed by forming ceramic material by pressing or pulling the ceramic material through a channel at least partly defined by at least one rotating die, and subsequent heat processing to form the ceramic product.

Preferably, the ceramic product is formed by pressing or pulling the ceramic material through bearing surfaces defining the channel. The channel is preferably formed by an extrusion die, whereby the bearing surfaces comprise at least one rotating bearing surface being a surface of a rotating die that defines the cross-section of the formed material such that the channel being at least partly defined by the at least one rotating die.

The ceramic product may be a brick or a plate-like product such as a tile or cladding.

Said ceramic product may comprise a plurality of sides, wherein each side is provided with a contour which matches with a corresponding contour of a side of another ceramic product.

The ceramic product may comprise a structural surface pattern corresponding to a pattern of the rotating die.

The structural surface pattern may be provided on an upper side of the ceramic product during its intended use.

The ceramic product may further comprise a structural surface pattern on a bottom side of the ceramic product during its intended use.

The structural surface pattern on the bottom side of the ceramic product may form mounting structures for the ceramic product.

The respective structural surface patterns may provide a fit when multiple ceramic products are stacked onto each other.

The ceramic product may comprise at least one further material.

According to a third aspect a device is provided, comprising at least one ceramic product according to the second aspect.

The device may be a thermal device and the ceramic product may form part of a heat exchanger, cooling profile, and/or heat element.

The device may be a chemical reactor and the ceramic product may form part of a catalyser or condenser.

The device may be an anti-slip device and the ceramic product may form a surface of said anti-slip device.

Still other objectives, features, aspects and advantages of the invention will appear from the following detailed description as well as from the drawings.

Within this specification some specific terms are used, which are defined in the following.

Extrusion: Procedure in which a material under pressure is pressed through a profile shaping tool (also called die) with hole(s) that defines the outgoing materials cross-section and appearance.

Pultrusion: Procedure in which a material under pressure is pulled through a profile shaping tool (also called die) with hole(s) that defines the outgoing materials cross-section and appearance.

Dynamic extrusion: Procedure in which a material under pressure is pressed through a tool with rotating forming members (dies) that can give the material a diverse cross-section and/or appearance in the form of e.g. patterns on one or more surfaces and dimensional changes in cross-sectional area and/or material thickness.

Dynamic pultrusion: Procedure in which a material under pressure is pulled through a tool with rotating forming members (dies) that can give the material a diverse cross-section and/or appearance in the form of e.g. patterns on one or more surfaces and dimensional changes in cross-sectional area and/or material thickness.

Die: Generally, the name used by professionals for profile forming tools.

Rotating die: Rotating profile-shaping part of the tool for dynamic extrusion/pultrusion.

Bearing surface: The surface of an extrusion die in the smallest cross-section that the extruded material is forced through under pressure and thus constitutes the surface to finally define the cross-section and appearance of the formed material.

Static bearing surface: A solid bearing surface the extruded material is forced to pass at a relative speed of outgoing material speed. Because it is static, there is a speed difference between the static bearing surface and the extruded material, resulting in friction and heat. By regulating the length of the bearing surfaces it is possible to regulate the total amount of friction and thus the pressure, balance, and speed of the outgoing material.

Rotating bearing surface: A rotating bearing surface is a surface of the rotating die that defines the cross-section of the formed material, allowing for pattern generation as well as material thickness variations. A rotating bearing surface in general generates much less resistance and friction against the flowing material than a static bearing surface, which previously has created major problems with the imbalance between the different parts of the cross-section of the formed material, and which is defined by all bearing surfaces of the entire die. This has often resulted in process breakdown at start up.

Pre-bearing (surface): The surface area that the extruded material passes before, preferably immediately before, it enters the area of the rotating die and its rotating bearing surface. The pre-bearing brings down the material cross-section so much so that the subsequent rotating die won't have to take up unnecessarily large forces from the formed material. Pre-bearing has in combination with upstream material shaping a central role for control and/or regulation of material flows through the die.

Dynamic extrusion and dynamic pultrusion: The process of forming (ceramic) material by utilising rotating dies integrated in extrusion dies. The extrusion die has one or more rotational dies. The cross-sectional profile of the formed material may optionally be defined upstream of where the material to be formed reaches the rotating die whose outer circumference, i.e. the lateral surface area, defines a rotating bearing surface that finally defines the appearance and cross-section of the formed material in conjunction with other bearing surfaces, rotating and/or static, in the die.

Ceramic material: Within the context of this specification this term is to be interpreted broadly, covering any material that is suitable for forming a ceramic product. Ceramic material comprises any formable inorganic, non-metallic oxide, nitride, or carbide material which, after heat processing preferably causing vitrification at least to some extent, forms a hard, brittle, heat resistant and corrosion resistant ceramic product. While no specific list of compounds or minerals are given here, general properties of ceramic products comprise high melting temperature, high hardness, poor conductivity, high moduli of elasticity, high chemical resistance, and low ductility. Examples of ceramic material include clay minerals such as kaolinite, alumina, and silicon carbide.

Pattern: Any structural configuration being transferrable from a die to a ceramic material. A pattern may be macroscopic, i.e. visible by the human eye, or microscopic. A pattern may further extend across the entire formed material, or across only a very small part of it. Typically, although not required, a pattern is a topographic configuration. Examples of patterns comprised within the context of this specification are thickness variations of the formed material, reinforcement ribs, channels, and macro as well as micro structures. Even an entirely smooth surface is herein considered to define a pattern.

DETAILED DESCRIPTION

Extrusion of ceramic materials is not trivial. Many ceramic materials are very difficult to extrude due to high friction between the extruded material and the bearing surface. This high friction causes slow production speed, and the general approach to address this problem is to add solid or fluid lubricants to the ceramic material. Such lubricants include polyetylen or polypropen when extruding e.g. silicon nitride, and/or liquid lubricants such as water, oil, or other evaporable or combustible lubricant.

The present invention is based on the principle of extruding a ceramic material using at least one rotating die, thus forming a rotating bearing surface. The inventors have surprisingly realized that using this technique, the friction that cause the internal shear in the formed material (i.e. by the friction between the extruded material and the bearing surfaces) is to a large extent eliminated. As the friction is significantly reduced, a number of advantages follow.

First of all, the present invention allows for faster extrusion of ceramic material. Secondly, the present invention makes it possible to reduce the liquid (i.e. water, solvent, and/or lubricant) content of the ceramic material while still obtaining the desired production speed. This also reduces the required cost and time for drying the ceramic material after forming, thereby increasing the throughput of the production method.

As the liquid content can be reduced this leads to additional advantages; the formed material will be more rigid and robust, which leads to possibilities of extruding geometries not possible with the prior art methods. Also, due to less liquid content there will less cost for solvent and/or lubricants, and also less shrinkage of the final ceramic product which makes it easier to design the final ceramic product.

The present invention has also proven to significantly improve the surface quality of the extruded ceramic material. This in turn makes it possible to extrude thinner material and to extrude ceramic material previously not being suitable for extrusion, such as ceramic material containing large solid particles, or ceramic material causing a specifically high friction.

Now starting inFIG.1, equipment100for performing the method of the present invention is schematically shown. The equipment100requires a supply102of ceramic raw material. During operation of the equipment this ceramic material is supplied to an extrusion device1which processes the ceramic material and forms it to a desired shape. After forming the ceramic material it is transported to a heat processing station104, typically comprising driers, kilns, etc. for producing ceramic products from the formed ceramic material. Normally, heat processing comprises exposing the formed material to a temperature of 800° C. or more. The specific heat exposure (i.e. temperature, time, and gradient) is dependent on the particular material as well as the dimensions of the final ceramic product.

It should be noted that the equipment100schematically shown inFIG.1could be further provided with conveyors, feeders, etc. (not shown).

The extrusion device1used for forming the ceramic material will be explained in detail with reference toFIGS.2to10.

Starting inFIG.2, the device1is configured to process (i.e. form) ceramic material in a production direction PD. The ceramic material is a plastically deformable material and/or a viscoelastic material and/or a plastically deformable material with elastic property and/or a viscoplastic material with elastic property.

The device1comprises a rotating die3, extending in a radial R direction and a width direction X, having two opposite first and second side walls5,6and an outer circumferential (lateral) surface area4extending in the width direction X between the side walls5,6. The rotating die3comprises a first side portion23in connection to the first side wall5and a second side portion25in connection to the second side wall6, and a mid-portion22extending between the first and second side portions23,25.

The device1further comprises a material definition zone7having a longitudinal direction Y coinciding with the production direction PD, a height direction Z and a width direction X being perpendicular to the height direction Z. The material definition zone7comprises a channel10. In the device1shown inFIG.1, the channel10is preceded (in the production direction PD) by a passage9.

The passage9is circumferentially delimited by one or more walls11to form a closed circumference for the ceramic material. The channel10, arranged immediately downstream the passage9, is at least partly defined by the lateral surface area4of the rotating die3. In the shown example the channel10is further defined by a counter-bearing14, arranged opposite the rotating die3, and opposing first and second channel portion side walls extending between the rotating die3and the counter-bearing14.

Rotating die3is rotatable about an axis extending across the production direction PD and arranged to allow the lateral surface area4to, while the rotating die3rotates, exert a pressure onto a surface of the ceramic material when fed through the material definition zone7.

According to the embodiment shown inFIG.2, the passage9is configured to deform the ceramic material into a master profile36having a maximum height H1at a predetermined feeding rate dependent on the ceramic material and minimum cross-sectional area with a first maximum height D1when exiting the passage9.

The channel10is configured to further deform the ceramic material into a final shape37having a minimum height H2by the rotating die3being configured to apply increasing pressure on the master profile36against the counter-bearing14. For this, the rotating die3is configured at a minimum distance D2from the counter bearing14dependent on a maximum allowable pressure applied by the rotating die3at the position of that minimum distance D2. The maximum allowable pressure corresponds to the maximum difference in height of the master profile36and the final profile37and depending on a specific pattern on the lateral surface area4of the rotating die3. The maximum allowable pressure is also dependent on the viscoelastic and viscoplastic properties of the ceramic material and thus a difference between the final height H3of the formed material and the height H2immediately after the channel10, due to the elasticity of the material.

According to one example, the passage9is formed between at least two side walls11; a top pre-bearing and an opposing bottom pre-bearing, wherein the top pre-bearing is arranged above the opposing bottom pre-bearing in the height direction Z. The top pre-bearing and/or the bottom pre-bearing may comprise a wake element.

Typically, the wake element protrudes in a direction from the side wall into the passage9. According to one example, the wake element protrudes in the height direction from the side wall into the passage. The wake element can be designed depending on ceramic material elasticity giving the correct height of the master profile when entering the channel10. Here, elasticity refers to the material swelling after having been pressed into shape in the passage9. The wake element creates a wave form in the ceramic material when having passed the wake element

One advantage of the device1is that maximum load is controlled in both the passage9and in the channel10which gives the possibility to design the extrusion device1dependent on the ceramic material to be processed, as well as on the desired process speed. Controlling the maximum load dependent on ceramic material to be processed allows for a production rate with high quality output and reduces risk for e.g. rupture due to a too high stress on the ceramic material.

According to the example shown inFIG.2, the extrusion device1receives ceramic material; this ceramic material is formed in the passage9into the shape of a master profile36and directly thereafter the ceramic material is formed in the channel10into the shape of the final profile37.FIG.2also shows that the final profile37has a lesser height H1than the height H2of the master profile36due to further pressure on the master profile36in the channel10.FIG.2also shows that the formed material2may have a lesser height H3than the height H1of the final profile36due to shrinking when cooling down from the final profile37to the product profile2, if the forming is performed at elevated temperatures.

FIG.3schematically shows a cross-sectional side view of an extrusion device1according to an embodiment. Here, the rotating die3is shown in a rotational position where the part of the rotating die3pressing against the ceramic material against the counter-bearing14does not comprise any local pattern or indentation38.

FIG.3schematically shows an initial zone A where the ceramic material is pressed by a device (not shown) into the passage9either by a device (not shown) exerting an external pressure in the production direction PD, i.e. extrusion, and/or by the ceramic material being dragged through the passage9by a device (not shown) dragging the material in the production direction PD, i.e. pultrusion.

Zone A of the device1comprises a funnel shaped opening43where the ceramic material changes from an initial form having a larger cross-section than the passage9. The shape of the opening can, however, vary depending on the type of ceramic material, temperature and device pressing the material.

A zone B is arranged directly after zone A, wherein zone B corresponds to the longitudinal extension of the passage9and where the formation of the master profile36takes place, as a result of the ceramic material changing form due to the pressure exerted on the ceramic material from the side walls11of the passage9when the ceramic material moves through the passage9.

A zone C is arranged directly after zone B, wherein zone C corresponds to the longitudinal extension of the channel10and where the formation of the final profile36takes place, as a result of the ceramic material changing form due to the pressure exerted on the ceramic material from at least the rotating die3and the opposing counter bearing14of the channel10.

A zone D is arranged directly after zone C, wherein zone D corresponds to a section of the production line after channel10and where the ceramic material optionally starts to cool down (if the extrusion process is performed using elevated temperature). In such case the final profile36starts to change form due to shrinking as a consequence of the temperature drop. It should be noted that shrinkage can also occur due to drying of the formed material. In zone D, the final profile37can be subject to various production measures for achieving desired properties of the formed material, such as cooling, heating, stretching, compressing, etc. in order to change the final profile37into a desired shape with desired material properties.

The length of zone D typically depends on material properties and a working environment surrounding the ceramic material in zone D. The material properties are e.g. heat dissipation and the mass of the ceramic material to be cooled down. For example, a thinner material cools down faster than a thicker material. The working environment refers e.g. to ambient temperature and humidity. For example, a warmer environment slows down the cooling process compared to a cooler environment.

A zone E is arranged directly after zone D, wherein zone E corresponds to a section of the production line where the ceramic material has dried or has cooled down to a predetermined temperature representing a temperature establishing the final form of the formed material and where no, or only an infinitesimal change of form will continue. The formed material has a height H3in zone E being optionally less than the height H2of the final profile37. In the same manner, the pattern39of the final profile37may shrink to a pattern40in zone E due to the drying/evaporation cooling.

For example, the method may be used with a ceramic material that will shrink in the range of 0-50%, such as between 0 and 20%. The shrinkage process may occur during any of the steps of cooling, drying, or heat processing (e.g. firing and/or glazing).

It should be noted that for some ceramic materials it is possible to run the extrusion device1at room temperature, whereby little or no cooling is needed and where the majority of the shrinkage that is taking place in general as a result of drying and heat processing. Zones D and E will in such embodiment be very short, if at all necessary.

InFIG.3the extrusion device1comprises a pulling and stretching device54arranged downstream the channel10and being configured to pull the ceramic material in the production direction PD when exiting the channel10. One advantage is that the pulling and stretching device54dynamically can stretch the ceramic material during its forming, e.g. in order to obtain an equidistant pattern in the production direction PD of the formed material. The pulling and stretching device54can further be used to guide the formed material in the width and/or height direction.

According to one example, the distance between indentations38in the pattern38on the rotating die3is less than a distance between elevations40in the corresponding pattern38in the production direction PD on the formed material2, wherein the pulling and stretching device54is configured to stretch the formed material so that high precision in distance between features on the formed material can be achieved by adjustment stretching.

The pulling and stretching device54can be any type of device that comprises means for gripping the formed material and means for pulling. According to one example, the pulling and stretching device54comprises controlling means55for controlling the pulling force applied to the formed material. The controlling means55may comprise sensor(s) and/or may be connected to sensor(s)56that supervises the state of the formed material. The sensor(s) comprises means for sending analog and/or digital information to the controlling means. The information relates to the state of the formed material and the controlling means55is configured to process the information for controlling the pulling and stretching device.

In one embodiment the rotating die3and/or the counter-bearing14comprises a cooling device57that cools down the ceramic material during forming. This has the advantage that a predetermined temperature of the ceramic material is achieved for optimum material properties of the formed material. The material temperature when extruding and/or pultruding can for certain ceramic materials be crucial for the quality of the final ceramic product. The temperature is also important due to frictional properties between the ceramic material and the rotating die3and/or the counter-bearing14. The cooling device57can, for example, be arranged in the form of cooling circuits with gas or liquid fluid conductors arranged within the rotating die3and/or the counter-bearing14; and/or external devices cooling down the rotating die3and/or the counter-bearing14; and/or liquids or gaseous fluids added to the rotating die3and/or the counter-bearing14, or a combination of such devices or any other suitable cooling devices. It should be noted that the rotating die3can be configured to operate without the cooling device57.

According to one example, the rotating die3is configured to be cooled on the surface so that the temperature of the lateral surface area of the rotating die3is below a predetermined allowed temperature of the ceramic material.

FIG.3schematically show that the rotating die3comprises a pattern38comprising at least one indentation38in the lateral surface area4. The number of indentations is here only an illustrative example and there may be more or less indentation or protrusions in a pattern spread over the rotating die3in a predetermined design depending on the desired features of the formed material. The indentations or protrusions can have any shape suitable, for example oval, round, polygon or a mixture of such or other shapes. The indentations38have a bottom44at a maximum depth of the indentation and the indentations may have different or similar depths. Between the indentations38the rotating die3comprises portions that have a default distance D2between the rotating die3and the counter bearing14when facing the counter-bearing14. It should be noted that any protrusion should not have a height larger than the default distance D2.

According to one example, the minimum distance D2in the height direction Z between the lateral surface area4and the counter-bearing14is less than a maximum distance D1, i.e. the height of the passage9.

InFIGS.2and3the channel10is formed between the lateral surface area4of a rotating die3and a counter-bearing14arranged opposite the rotating die3. These two parts form the upper and bottom area of the channel10. In order to define the channel laterally the channel10has side areas as well, thus closing the boundaries of the channel10.

As seen inFIG.4it is possible to replace one or more of the static areas of the channel10, i.e. the counter-bearing14and the side areas, by one or more additional rotating dies.

FIG.4schematically shows an assembly of rotary dies including four rotary dies. The channel10is here defined by the first rotating die3, a second rotating die33arranged opposite the first rotating die3and replacing the counter-bearing14, a third rotating die34replacing one of the side areas and a fourth rotating die35arranged opposite the third rotating die34.

FIG.4is one example only. It would be possible to define the channel10by one more rotating dies3,33,34,35. For example, the channel10could be defined by two rotating dies3,33,34,35while the remaining areas defining the channel10are static. As another example there is no need for the channel10to have a rectangular cross-section; the channel10could be defined by three areas forming a triangular cross-section, by six areas forming a hexagonal cross-section, etc. One or more, possibly all, areas of the channel10may be defined by a specific rotating die3,33,34,35. Each one of the rotating dies3,33,34,35may have a specific pattern on its lateral surface area, for imprinting a side of the formed material with such pattern.

The second, third and/or the fourth rotating die(s)33,34,35can be arranged in a similar way as the above described first rotating die3to create same or different patterns on two sides of the formed material. The second, third and/or fourth rotating dies33,34,35can comprise annular recesses and/or flange portions that can be arranged to cooperate with annular recesses and/or flange portions of the first rotating die3.

One or more of the rotating dies3,33,34,35may be driven. According to one example, two or more rotating dies3,33,34,35are synchronised. This has the advantage of feeding the ceramic material at the same speed through the channel10. However, it could be possible to also use non-synchronous rotating dies3,33,34,35in order to create friction and/or a special pattern and/or to compensate for material differences.

The extrusion device1can be arranged with a combination of textured and non-textured rotating dies3,33,34,35.

FIGS.5-10schematically show a co-extrusion device1, and/or an on-extrusion device1. Such extrusion device comprises an extrusion and/or pultrusion device1, according to any one of the examples discussed above, wherein the device1comprises at least two inlet channels45,46,47that connects directly or indirectly to the channel10. Each of the at least two inlet channels45,46,47is configured to feed one or more materials, at least one material being a ceramic material, at a predetermined distance upstream from the channel10or to a marriage point for the at least two inlet channels45,46,47in connection to where the passage9transitions into the channel10.

Here, co-extrusion refers to where at least two material streams are together processed and formed into the master profile and then into the final profile or where the at least two material streams are together processed and formed into the final profile.

Here, on-extrusion refers to where the at least two material streams are positioned in a layered fashion either by being together processed and formed into the master profile and then into the final profile or by bringing together the at least two material streams into the master profile at the marriage point and thereafter together processing and forming the joint at least two material streams into the final profile in the channel10.

FIG.5schematically shows a cross-sectional side view of an extrusion device1. The profile definition zone7comprises a first inlet channel45in the form of the passage9and a second inlet channel46in the form of a second passage connected to the profile definition zone7upstream the channel10. The second passage feeds an additional material to the channel10for forming a layered profile product2with ceramic material from the passage9.

According to one example, the second passage46is an extrusion- or pultrusion channel similar to the passage9arranged to work the material. According to one example, the second passage46is a passage that is configured as a conveyer unit for conveying a material to the profile definition zone7.

The device1further comprises an additional channel46barranged to guide a further material to ceramic material. Such channel46bmay be arranged to guide the further material to the lateral surface area4of the rotating die3upstream where the lateral surface area4defines the channel10. As the rotating die3rotates, the lateral surface area4will carry the further material to the channel10where the further material is added to the ceramic material extrusion process. As one example, the further material may be a glazing material that distributes on the surface of the formed material.

The same device1is shown schematically inFIGS.6and7, however in these figures the additional channel46bhas been left out. As already explained, the device1comprises one rotating device3as described above and two material streams that are brought together via the passages9,46.

FIG.8schematically shows a cross-sectional side view of a device1comprising two opposing rotating dies3,33.FIG.8further shows that the device1comprises a passage9and a second passage46connected to the profile definition zone7upstream the channel10for feeding an additional material to the channel10, thereby forming a layered profile product2with material from the passage9.FIG.8further shows that the device1comprises a third passage47for feeding a third material to the profile definition zone7.

According to one example, the third passage47is an extrusion- or pultrusion passage similar to the passage9arranged to work the material. According to one example, the passage47is a passage that is configured as a conveyer unit for conveying a material to the profile definition zone7.

FIG.9schematically shows a cross-sectional side view of a device1that comprises one rotating die3and a three passages9,45,46for feeding three different materials to the profile definition zone7according to what is discussed in connection toFIG.8.

FIG.9further shows an example where the passage45conveys a solid material50, e.g. a wire, mesh, or the like, to the passage9and where the passages46,47introduce one or more materials to be extruded or pultruded in the passage9and in the channel10. The one or more materials may be layered onto the solid material50or may surround the solid material50.

FIG.10schematically shows an example where the passage45conveys a continuous solid material50in the form of a wire, mesh, or the like, and a ceramic material to be extruded or pultruded in the passage9and channel10. InFIG.10the passages45,46are arranged such that the material from the passage46surrounds the solid material50and embeds the solid material50. InFIG.10, the passage46comprises a pressurized chamber51upstream the passage9for forming the ceramic material around the solid material50. The pressurized chamber51comprises a back wall52delimiting the pressurized chamber51.

The passage46comprises a feeding channel53to the pressurized chamber51for feeding the material to the chamber51. The back wall52comprises the passage45that conveys the solid material50and acts as a stop for the ceramic material in the chamber to leak through the passage45. Here, “pressurized” means that the ceramic material in the passage46is subject to pressure by the ceramic material being forced into the passage46and deformed in a similar way as described above with relation to the passage9.

InFIG.10the passage9and channel10plastically deforms the material in a similar manner as described above. Plastic deformation may take place also in the pressurized chamber51, but is not limited to such deformation. Hence, the material in the pressurized chamber51may be formed to surround the solid material50without being plastically deformed.

Here, “solid material” refers to a material that does not undergo any deformation in the profile definition zone7. A non-exhaustive list of examples of solid materials are; bendable wire, stiff rod-like element, mesh of metal and/or fabric and/or composite and/or other suitable materials, a combination of such solid materials, etc.

With reference toFIGS.5to10, the different materials are brought together before the channel10and is then worked in the channel10as described above. The invention is not limited to three passages9,45,46,47but further passages are possible in order to produce a ceramic product with same or different materials in different layers.

According to any one of the preceding examples, the ceramic material that is fed into the device1to form the final ceramic product is either one homogenous material or a mixture of two or more materials that are blended and or layered. The materials can be blended in different ratios and may be blended into a homogeneous mix or a mix with gradients within the material. One material can be a solid and another material can be moldable, e.g. stone bits and clay, wherein the clay forms the ceramic material. The material can also be a layered material comprising two or more layers of same or different materials. The material may comprise one or more strings of solid material that follow through the entire extrusion or pultrusion process, e.g. a wire or another reinforcement material being surrounded by the deformable material. It is also possible to use fibers are reinforcement material.

According to one example, the maximum allowable pressure applied by the rotating die3at the position of the minimum distance D2is dependent on friction between the ceramic material and the counter bearing14in the channel10.

According to one example, the device1is configured to feed a friction material between the counter-bearing14and the formed material and/or configured to feed a friction material between the rotating die3and the formed material.

According to one example, the friction material is conveyed by any of the passages45,46,47at least during start-up of the device1in order to control friction in connection to the rotating die3and/or the counter bearing14.

According to one example, the friction material is conveyed by any of the passages45,46,47during a part of or during the entire production process in order to control friction in connection to the rotating die3and/or the counter bearing14.

According to one example, the friction material is fed directly to the rotating die3such that the friction material rotates with the rotating die3from a position upstream the channel10. A friction material feeding device can be either one of the passages45,46,47. Furthermore, the friction material may be a solid material, a liquid or a gas, or a combination thereof.

Now turning toFIGS.11and12some examples of ceramic products being manufactured by a method according to an embodiment will be described.

Generally, the present invention allows for a continuous forming of ceramic material which, upon suitable heat processing, forms ceramic products. Most preferably the methods described herein are used to produce a continuous profile of formed material, which is subjected to a separation action, such as cutting, in order to form a series of identical or at least similar products. For example, the method may produce a profile which is cut at specific positions to produce products of that specific length, while another portion of the profile is cut at other positions to produce products of a different length. Such products are consequently not identical, but similar as they are cut from the same profile.

The ceramic products shown inFIGS.11and12are subjected to heat processing. Hence, these illustrations also represent the shape of the formed material, at least after being separated from the continuous profile exiting the extrusion device1.

FIG.11shows a plate-like ceramic product60produced by forming a ceramic material using at least one rotating die3, and subsequent heat processing. The ceramic product60has an upper side61, a bottom side62, and two opposite sides63,64. Each side61-64is provided with a repetitive pattern61x,62x,63x,64xformed by an associated rotating die3,33,34,35. In order to produce the ceramic product60, it is thus necessary to make use of four rotating dies3,33,34,35in line with the example shown inFIG.4.

The pattern61xof the upper side61comprises parallel transverse wave-like protrusions, formed by corresponding depressions of the rotating die3. The pattern62xof the bottom side62comprises parallel longitudinal grooves, formed by correspond protrusions of the rotating die33. A first side63comprises a pattern63xof equally spaced-apart protrusions, and the opposite side63comprises a pattern64xof equally spaced-apart depressions. The patterns63x,64xof the opposing sides are matching, such that the protrusions of pattern63xfit in the depressions of pattern64x.

Hence, the ceramic product60can be used in an assembly requiring several ceramic products60, as the fit of the sides63,64makes it very easy to fit multiple products60to each other. For example, the ceramic product60may be a floor tile where the pattern61xof the upper side61provides an anti-slip surface.

Another example of a ceramic product70is shown inFIG.12. Here the ceramic product70is brick-like rather than plate-like, but produced in a similar way by forming a ceramic material using at least one rotating die3, and subsequent heat processing.

The ceramic product70has an upper side71, a bottom side72, and two opposite sides73,74. Each side71-74may be provided with a repetitive pattern71x,72x,73x,74xformed by an associated rotating die3,33,34,35. In order to produce the ceramic product70, it is thus necessary to make use of four rotating dies3,33,34,35in line with the example shown inFIG.4.

The pattern71xof the upper side71comprises repetitive protrusions, arranged in rows and columns and being formed by corresponding depressions of the rotating die3. The pattern72xof the bottom side72may be entirely planar, or it may comprise recesses matching the protrusions of the upper side71.

A first side73comprises a pattern73xof parallel wave-like protrusions, and the opposite side73may be entirely planar of comprise a pattern74xof any protruding or depressed kind.

The ceramic product70can be used in an assembly requiring several ceramic products70, as the fit of the sides71,72makes it very easy to fit multiple products70onto each other. For example, the ceramic product70may be a brick where the pattern73xof the side71provides improved aesthetics to the resulting construction.

The ceramic product70is partially hollow, as a result of multiple channels75extending through the entire ceramic product70in the longitudinal direction.

According to the above description, a ceramic product60,70is formed by pressing or pulling ceramic material through a channel at least partly defined by at least one rotating die, and subsequent heat processing to form the ceramic product.

Examples of ceramic products are brick or a plate-like products such as a tile or cladding.

For improving usability of the ceramic products, each or any side of the ceramic product may be provided with a contour which matches with a corresponding contour of a side of another ceramic product. This means that two or more ceramic products60,70may be joined in a puzzle-like manner, providing new and improved ways of aligning and fitting ceramic products to each other as well as to adjoining structures.

Due to the versatility of the rotating die3, the ceramic products may comprise a structural surface pattern corresponding to a pattern of the rotating die.

Typically, the structural surface pattern is provided on an upper side of the ceramic product60,70during its intended use, and/or on a bottom side of the ceramic product60,70during its intended use.

As described above the structural surface pattern on the bottom side60,70of the ceramic product can form mounting structures for the ceramic product. For example, the ceramic product may be a façade tile or cladding wherein hangers are integrally formed on the bottom side of the ceramic product already during the extrusion process using a rotating die33acting on the underside of the formed material.

A ceramic product60,70may be included in different types of devices. For example, a ceramic product60,70may form part of a thermal device such as a heat exchanger, cooling profile, and/or heat element. For example, a ceramic product60,70may form part of a chemical reactor such as a catalyser or a condenser. For example, a ceramic product60,70may form part of an anti-slip device, such as forming a surface of said anti-slip device.

Now turning toFIG.13, a method200for manufacturing a ceramic product60,70will be explained further. In general, the method200comprises two main steps210,250, and a number of optional step (marked with dashed lines inFIG.13) which may be performed in accordance with specific embodiments.

Most generally, the method200comprises a step210of forming material by pressing or pulling ceramic material through a channel10of an extrusion device1, where the channel10is at least partly defined by the lateral surface area4of at least one rotating die1. In a subsequent step250, the formed material is heat processed to form a ceramic product.

As explained above, the rotating die3is preferably applying a pattern, which may be repetitive, to the formed material.

Depending on the type of ceramic material used for the method, the method200may further comprise a step252of shrinking the formed material such that the dimensions of the pattern of the rotating die3are different from the dimensions of the pattern of the ceramic product60,70. Preferably, shrinking is caused after the step of forming the material, preferably during heat processing of the formed material.

During operation of the extrusion device1, the method may perform a step208of adjusting the flow of the ceramic material upstream the channel10, and/or a step212of driving the rotating die3. Step212is preferably performed such the rotation of the rotating die3is synchronized with the speed of a downstream conveyor for the ceramic product.

Another optional step214can be performed, during which at least one dimension of the ceramic product is determined, and the speed of the rotating die3and/or the downstream conveyor is adjusted based on the determined dimension(s).

The step250of heat processing may be performed in one or more sub-steps. For example, the step may comprise firing the ceramic material, but it may also comprises an initial drying step. Typically, the drying step may be performed at room temperature or at a relatively modest temperature, while firing is performed using much higher temperatures (such as 800-1500° C.). As is readily understood, the exact design of the heat processing step250must be selected based on the ceramic material used, as well as on the desired properties of the final ceramic product.

Another optional step240of separating an individual product from the formed material may be performed either before, during, or after the step250of heat processing. Optionally, a step248may be performed in which a plurality of individual products are mounted to each other before the step250of heat processing.

Step240may be performed by a cutting action of the rotating die3, or by using a separate cutting station.

The method200may further comprise a step216of adding a further material to the ceramic material. Step216may be performed before, during, or after the ceramic material passes the rotating die3.

The further material is e.g. embedded in the ceramic material to form a reinforcement of the ceramic product. The further material may be a fibre material or a web material. The further material may be added as at least one layer to the ceramic material. The further material may be a liquid or a solid material in the form or powder or particles. The further material may comprise a plurality of different ceramic and/or non-ceramic materials.

Step216may be performed by feeding the ceramic material and the at least one further material through the channel.

The method200may further comprise a step218of adjusting the position of the rotating die3thereby adjusting the dimensions of the channel10, and consequently also the dimensions of the ceramic product. This step218may be performed by altering the position of the rotating die3relative the other areas of the channel10, may they be defined by static bearing-surfaces or other rotating dies. Optionally, step218is performed by arranging the rotational axis of the rotating die3at an angle relative to the production direction, preferably the rotating die is arranged at an angle of 90°+25° relative to said production direction.

An optional step220may also be performed, which comprises providing the channel10with at least one die core, said die core forming a hollow portion75of said ceramic product60,70.

A step222may be further performed in which the channel10provides one side of the formed material with a first structural surface pattern defined by the lateral surface area of at least one rotating die3, and an opposite side of the formed material with a second structural surface pattern defined by the lateral surface area of another rotating die33,34,35. Possibly, the first and second structural surface patterns will provide a matching fit when multiple ceramic products are stacked onto each other.

It should be noted while the method200has been described as a series of performed steps, these steps could be performed in any suitable order, or even simultaneously. Especially the extrusion part of the method200is preferably performed continuously, which means that many of the above-described steps are performed at the same time and repeatedly.

To summarize, the present disclosure presents improved methods for processing ceramic material in order to form ceramic products. The ceramic material is fed through a passage9where it is formed into a master profile36, and feeding the ceramic material further to a channel defined at least partly by at least one rotating die3, where the master profile37transforms into a final profile37. By heat processing the final profile37is transformed to a ceramic product60,70.

From the description above follows that, although various embodiments of the invention have been described and shown, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subject-matter defined in the following claims.