EP0607402B1 - Mould for the production of mouldings containing liquid - Google Patents

Abstract

The invention concerns a mould for the production of mouldings containing liquid, such as roof tiles made from clay or a similar material. The mould is made up of two layers, one of which (the layer which comes in contact with the material being moulded) consists of a fine-grained sintered or foamed ceramic material, while the layer located below it is made of coarse-grained sintered or foamed ceramic material or foamed concrete. The use of foamed ceramic material with pores of various sizes gives a mould which is particularly resistant to wear and whose lifetime is several times longer than that of the gypsum moulds used at present in the production of compression-moulded roof tiles.

Description

Technical field

The invention relates to a mold for the production of liquid-containing pressed parts, such as roof tiles made of clay, a clay-like or similar material.

State of the art

Roof tiles in the form of pressed roof tiles are usually made of clay, clay or similar material with a very specific water content; the clay or the clay-containing material is applied to a negative mold made of gypsum, which is accommodated in a steel frame and serves as the lower mold, and is finally pressed into a raw brick of the desired shape in a press by means of a negative mold made of gypsum which also serves as the upper mold . Here, the top of the plaster mold serving as the lower mold is modeled on the surface of the underside of the bricks to be produced, while the downward-facing upper surface of the negative mold made of plaster serving as the upper mold corresponds to the visible outer surface of a brick.

From FR-A-2 601 895 a porous mold for the pressure casting of ceramic shaped pieces with a porous inner layer and a coarse-porous outer layer covering the back of the porous inner layer is known. The porous inner layer has an average pore diameter of at most 20µm and a thickness of 5 to 40mm. On the back of the porous inner layer an adhesive is applied, on which a porous Is applied outer layer, which consists of liquid resin and a filler with a grain size of 0.1 to 5mm and a thickness of 5 to 30mm and a pore diameter of at least 100 microns. This outer layer is sealed by a resin adhesive layer.

Furthermore, EP-A-0 121 929 discloses a permeable mold for forming three-dimensional moldings, the inner layer of which is made from a mixed slurry which contains metallic grains, ceramic grains and a liquid binder with an evaporating or consumable component. A support layer of unsintered metal and ceramic powder is applied to this layer sintered in an oxidizing atmosphere. Due to the evaporating or consumable component of the liquid binder in the inner layer, openings with a porosity of 5 to 60% are created in the mold.

The two known forms described above have in particular the disadvantage that they do not withstand the high contact pressure which is necessary when producing roof tiles in order to squeeze the liquid contained in the material to be pressed out of the clay, the clay-containing or similar material. Furthermore, the forms described above have the disadvantage that they have only a low resistance to abrasion.

With each pressing, the negative molds made of gypsum used as the upper and lower mold undergo considerable abrasion, so that after an approximately known, not too high number of pressings, the wear, in particular on the negative mold made of gypsum as the upper mold, is so great due to the abrasion that the specified tolerances, in particular with regard to the permissible minimum thickness of the finished brick, can no longer be met. In particular, the plaster mold serving as the upper mold must therefore after about 600 to 800, at best 1000 brick pressings can be exchanged for a new, provided upper mold.

For this purpose, depending on the material to be pressed, the press must be replaced with a new, unused gypsum mold after half an hour at the latest, this process on average 5 to max. Takes 10min. Replacing the plaster mold serving as the upper mold takes 1 to 1.5 hours with a ten-hour shift, so that the brick press stops 10 to 15% of the time per shift.

Furthermore, in preparing and manufacturing new gypsum molds and replacing these gypsum molds, the old used gypsum molds are generally employed by three workers in each shift.

Thus, not only is the preparation and provision of new and perfect plaster molds and their replacement for used plaster molds overall very time-consuming and cost-intensive, but also the cumulative downtimes for replacing used molds and for inserting new molds, as well as the plaster quantities required and the amount used when spraying out the plaster molds Water is a considerable cost factor. Additional costs arise from getting and disposing of the considerable amounts of gypsum.

Presentation of the invention

The object of the invention is therefore to provide a mold for the production of liquid-containing pressed parts, such as clay roof tiles, a clay-containing or similar material, which has a very high wear resistance and durability. According to the invention, this is achieved in a mold for the production of liquid-containing pressed parts, such as roof tiles made of clay, a clay-containing or similar material, by the features in the characterizing part of claim 1 or 15. Advantageous further developments are the subject of to claim 1 or 15 directly or indirectly subordinate claims.

In the form according to the invention, a layer which comes into contact with the material to be pressed consists of fine-pored, sintered or foamed ceramic material, while the layer below is coarse-pored, sintered or foamed ceramic material or foamed concrete.

The fine-pored, sintered or foamed ceramic material has a porosity of the order of 10 Å (10. 10 ^-10 m) to 30 µm and the proportion of porosity is between 5 and 60% depending on the material to be pressed.

According to a further advantageous development of the invention, additives such as corundum, mullite, silicon carbide, silicon nitride, zirconium dioxide and the like are added to the fine-pored, sintered or foamed ceramic material. added. Furthermore, the fine-pored, sintered or foamed ceramic material consists of corundum, mullite, silicon carbide, silicon nitride or zirconium dioxide. Since zirconium dioxide is electrically conductive, if zirconium dioxide is added to the fine-pored, sintered or foamed ceramic material, demolding can be carried out more easily, or the adhesion between the mold and the pressed material is considerably reduced by the application of direct current. The same effect can also be achieved in that the surface of the layer of fine-pored, sintered or foamed material has a metallized or an oxidation layer. Furthermore, according to a further advantageous development of the invention, metal particles can be embedded in the fine-pored, sintered or foamed ceramic material to increase the conductivity.

Furthermore, the layer of foamed ceramic material preferably has a thickness on the order of 0.1 to 2.0 mm. To reinforce the thin layer of fine-pored, sintered or foamed ceramic material, a Stainless steel mesh can be introduced. In particular, such a fabric made of stainless steel is accommodated in an area corresponding to the sealing labyrinth of the finished brick in the form of strip-shaped or web-like projections running in the longitudinal direction of a brick, which protrude outwards from the layer of fine-pored ceramic material; this largely prevents the web-like or strip-like projections in the layer of fine-pored, sintered or foamed material from breaking off.

Because of the high abrasion resistance of fine-pored, sintered or foamed ceramic material, its wear during pressing is minimal compared to the abrasion with the plaster molds commonly used, so that a mold according to the invention has a service life of one depending on the material used for the production of roof tiles can have half to a year and more. When using the mold according to the invention, the daily downtimes of the press in the order of 1 hour to 1.5 hours, which were previously required for spraying out used plaster molds and for inserting new, provided plaster molds, are thus eliminated. This means that the personnel involved in the manufacture, provision and spraying of new gypsum molds are no longer required, and the entire cost of gypsum is also eliminated.

According to a further advantageous embodiment of the mold according to the invention, the layer consists of coarse-pored, sintered or foamed ceramic material, preferably of silicon carbide or corundum and, in order to enable backwashing with solvents or water, has a porosity that is 3 to 20 times greater than the porosity of the layer of fine-pored, sintered or foamed ceramic material. Furthermore, in an advantageous development, the layer of the layer arranged below is preferably made in the region facing away from the layer of fine-pored, sintered or foamed ceramic material coarse-pored, sintered or foamed ceramic material or foamed concrete a number of tubular channels for draining the liquid in the form of water are formed.

According to an advantageous embodiment of the mold according to the invention, cavities are formed in the layer of coarse-pore ceramic material or foamed concrete with supporting intermediate webs left between them. The cavities in the layer of large-pore, sintered or foamed ceramic material preferably have a cross-sectional area of the order of magnitude of 100 mm ² , while the supporting intermediate webs have a thickness of 4 to 5 mm.

The formation of the cavities in the layer of large-pore material saves a considerable amount of material, at the same time the distance and thus the time required for the liquid to be pressed out of the material to be processed in the form of water is reduced in order to keep the relatively thin layer thickness above the penetrate numerous cavities in the layer of coarse-pored, sintered or foamed ceramic material. Liquid entering the cavities can be sucked off through tubular channels running transversely thereto or, as was previously the case, by means of negative pressure.

Furthermore, a porous connecting layer can be provided between the layer of fine-pored, sintered or foamed ceramic material and the layer of coarse-pored, sintered or foamed ceramic material to increase the adhesion.

Advantageously, the mold according to the invention can also be used for slip casting or metal casting with and without vacuum application.

According to a modification of the invention, the layer that comes into contact with the material to be pressed is a metal plate that has a large number of the finest Holes are penetrated, a layer of large-pore, sintered or foamed ceramic material or foamed concrete is again provided under this plate. The holes in the metal plate are flared to the underlying layer of coarse-pored, sintered or foamed ceramic material or foamed concrete, so that the water squeezed out of the clay reaches the underlying layer of foamed concrete or of coarse-pored, sintered or foamed ceramic material more quickly .

The holes that widen conically to form a layer of coarse-pored, sintered or foamed ceramic material or foamed concrete run approximately perpendicular to the surface of the metal plate. If necessary, the holes are arranged in a different distribution density and / or with different diameters in different areas according to a further advantageous development of the invention. The conically widening holes are produced, for example, by means of laser or electron beam processes.

Fig.1

schematisch in einer stark vergrößerten, unmaßstäblichen Darstellung einen Teil einer Schnittansicht durch eine Form gemäß der Erfindung;

Fig.2

eine ebenfalls schematische, unmaßstäbliche Darstellung einer Schnittansicht eines anderen Teilbereichs der Ausführungsform nach Fig.1, und

Fig.3

ebenfalls wieder schematisch in einer unmaßstäblichen Darstellung einen Teil einer Schnittansicht einer modifizierten Ausführung der erfindungsgemäßen Form.

The invention is explained in detail below on the basis of preferred embodiments with reference to the attached drawing. Show it:

Fig. 1

schematically in a greatly enlarged, scale representation, part of a sectional view through a mold according to the invention;

Fig. 2

a likewise schematic, not to scale representation of a sectional view of another partial area of the embodiment according to FIG. 1, and

Fig. 3

again schematically in an out of scale Representation of part of a sectional view of a modified embodiment of the mold according to the invention.

A first exemplary embodiment of a mold 1 according to the invention is shown schematically and to scale in FIG. An upper layer 10 in FIG. 1 consists of fine-pored, sintered or foamed ceramic material, while underneath another layer 11 of coarse-pored, sintered or foamed ceramic material or foamed concrete is provided. In the lower region of the layer 11 in FIG. 1, tubular channels 110 are provided, via which the liquid is drained from the clay, clayey or similar material in the form of water during the production of pressed roof tiles.

Layer 10 preferably has a thickness of 1.5 mm. Furthermore, both layers 10 and 11 are preferably colored continuously, so that the appearance of the color of the underlying layer 11 alone is an indication that the layer 10 made of fine-pored, sintered or foamed ceramic material is used.

In FIG. 2, in contrast to FIG. 1, protrusions 100 are shown on the upper side of the layer 10 made of fine-pored, sintered or foamed ceramic material in section outwards (upwards in FIG. 2), which in a direction perpendicular to the plane of the drawing are strip-shaped or web-like projections running parallel to one another, which in the negative form correspond to the sealing labyrinth provided in the lateral region of each roof tile.

In order to increase the fracture resistance of these projections 100, which consist of fine-pored, sintered or foamed ceramic material, or to substantially rule out breaking, a steel mesh 20 made of preferably stainless steel is accommodated in the region of such projections 100 the sectional view of Figures 1 and 2 can only be seen as points. As can be seen from FIG. 1, the steel mesh 20 is expediently also provided in the entire layer of fine-pored, sintered or foamed ceramic material.

As can be seen from FIG. 2, cavities 111 are formed in the layer 11 from coarse-pored, sintered or foamed ceramic material or from foamed concrete, between which supporting webs 112 have been left. The cavities 111 have a cross-sectional area on the order of 100 mm ² , while the supporting intermediate webs 112 have a thickness on the order of preferably 4 to 5 mm. The provision of the cavities 111 in the layer 11 achieves considerable material savings and, at the same time, the liquid emerging from the layer 10 generally only has to penetrate a considerably thinner layer above the individual cavities in the form of water. The liquid which has escaped into the cavities can be drained from these, for example, through corresponding channels through the tubular channels 110 in FIG.

3 shows a modification of a mold 1 'according to the invention. In this embodiment, a steel plate 30 is arranged over the layer 11 made of coarse-pored, sintered or foamed ceramic material or made of foamed concrete, which are penetrated by a large number of holes 300. In FIG. 3, the holes 300 shown in section are flared to the layer 11 provided there, made of foamed concrete or of coarse-pored, sintered or foamed ceramic material. The respective center axes are indicated by dash-dotted lines in the individual holes 300. The conical holes 300 have a diameter of 10 μm to 400 μm.

Claims (19)

1. Mould for producing liquid-containing moulded articles, such as roof tiles of clay, a loamy or similar material, characterized in that a layer (10) of the mould (1) coming into contact with the material to be pressed consists of fine-pore, sintered or foamed ceramic material having a porosity of the order of magnitude of 10 Å (10 · 10^-10 m) to 30µm, a porosity proportion between 5 to 60% depending on the material to be pressed and a layer thickness of the order of magnitude of 0.1 to 2.0mm, and
   that the layer (11) therebelow is coarse-pore, sintered or foamed ceramic material or foamed concrete, having a porosity which is a factor of 3 to 20 times greater than the porosity of the fine-pore layer (10).
2. Mould according to claim 1, characterized in that the fine-pore, sintered or foamed ceramic material of the layer (10) consists of corundum, mullite, silicon carbide, silicon nitride or zirconium dioxide.
3. Mould according to claim 1, characterized in that additives such as corundum, mullite, silicon carbide, silicon nitride, zirconium dioxide, are added to the fine-pore sintered or foamed ceramic material of the layer (10).
4. Mould according to any one of claims 1 to 3, characterized in that the surface of the layer (10) of fine-pore, sintered or foamed ceramic material has a metallized layer.
5. Mould according to any one of claims 1 to 3, characterized in that the surface of the layer (10) of fine-pore, sintered or foam material has an oxidation layer.
6. Mould according to any one of claims 1 to 3, characterized in that to increase the conductivity metal particles are intercalated into the fine-pore, sintered or foamed ceramic material.
7. Mould according to any one of the preceding claims, characterized in that for reinforcement a fabric of stainless steel is inserted into the thin layer (10) of fine-pore, sintered or foamed ceramic material.
8. Mould according to claim 7, characterized in that in particular strip-like or web-like projections (100) extending parallel to each other and projecting outwardly from the layer (10) of fine-pore sintered or foamed ceramic material are reinforced by the steel fabric (20) of stainless steel.
9. Mould according to any one of the preceding claims characterized in that the layer (11) of coarse-pore, sintered or foamed ceramic material consists of silicon carbide or corundum.
10. Mould according to any one of the preceding claims, characterized in that a plurality of tubular passages (110) for draining the liquid are formed in the region of the layer (11) of coarse-pore sintered or foamed ceramic material or foamed concrete remote from the layer (10) of fine-pore, sintered or foamed ceramic material.
11. Mould according to any one of the preceding claims, characterized in that in the layer (11) of coarse-pore, sintered or foamed ceramic material or foamed concrete cavities (111) having supporting intermediate webs (112) are formed.
12. Mould according to claim 11, characterized in that the cavities (111) in the layer (11) have a cross-sectional area of the order of magnitude of 100mm² and the supporting intermediate webs (112) a thickness of the order of magnitude of 4 to 5 mm,
13. Mould according to claim 1, characterized in that to increase the bonding a porous bonding layer in provided between the layer (10) of fine-pore, sintered or foamed ceramic material and the layer (11) of coarse-pore sintered or foamed ceramic material.
14. Use of the mould according to claims 1 to 13 in slip casting or metal casting with or without vacuum,
15. Mould for producing liquid-containing press moulded articles, such as roof tiles of clay, a loamy or similar material, characterized in that a layer (10) of the mould (1) coming into contact with the material to be pressed is a metal plate (30) which is perforated by a large number of extremely fine holes (300) having a diameter between 10µm and 400µm, and that the layer (11) therebelow is coarse-pore, sintered or foamed ceramic material or foamed concrete.
16. Mould according to claim 15 characterized in that the holes (300) in the metal plate (30) are conically widened.
17. Mould according to any one of claims 15 or 16, characterized in that the holes (300) extend substantially perpendicularly to the metal plate surface (30a).
18. Mould according to any one of claims 15 to 17, characterized in that the holes (300) are arranged in various regions in a different distribution density and/or with different diameters.
19. Mould according to any one of claims 15 to 18, characterized in that the holes (300) are made by laser or electron beam methods.

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