Method and device for producing coated, and in particular painted, building boards and associated painted building board

The subject matter of the present invention is a method for producing coated, and in particular painted, building boards (1), preferably for the interior finishing of buildings. First, the respective building board (1) is provided on its longitudinal edges (2) and/or transverse edges with a bevel (4). Then, the respective building board (1) is transferred to a rubber-like transporting belt (7) in such a way that the edges (2) respectively provided with the bevels (4) are arranged transversely in relation to the conveying direction (F) of the transporting belt (7) and the bevels (4) are arranged adjacent to a visible side (6) of the building board (1), facing away from the transporting belt (7). Finally, a coating material, and in particular paint (13), is applied to the visible side (6) of the building board (1) and respective bevel areas (5) of the bevels (4) in one operation with the aid of at least one roller (11) arranged above the transporting belt (7) and rotating substantially transversely in relation to the conveying direction (F).

RELATED APPLICATIONS

This application is a 35 U.S.C. 371 national stage filing from International Application No. PCT/EP2014/064773, filed Jul. 9, 2014, which claims priority to German Application No. 10 2013 108 498.2, filed Aug. 7, 2013, the teachings of which are incorporated herein by reference.

The invention relates to a method for producing coated and in particular painted building boards, preferably for use for the interior finishing of buildings.

Such building boards are generally used for so-called dry construction. This means that the building boards are used for cladding ceilings, walls and in individual cases also floors. Moreover, dry walls can be produced therewith. In the above sense, building board usually means a gypsum fibreboard and in particular a plasterboard. In principle, the building board can however also be a fibre cement board, a timber material board or even a plastic sheet. Moreover, building boards comprising different layers or layer materials are included.

For interior finishing and in particular dry construction with the aid of such building boards, printed surfaces and in particular painted surfaces are increasingly required on the respective visible side of the building board, i.e. the room side. As is known, the paint applied on the visible side is a liquid or powdery coating material. This coating material or paint is applied thin on the visible side of the building board and is built up by chemical and physical processes to form a solid film.

The paint performs essentially two tasks in the case of paints for building boards, in particular for interior finishing. In the first place, the paint is used for decoration, because the building boards often have a surface colour (typically grey) that is scarcely suitable. In addition, there is a protective effect of the paint or the coating produced with the paint against any damage. In principle, the paint can also adjust specific surface properties of the building board, for example change its electrical conductivity in a targeted manner. As a rule, however, it is primarily a matter of providing the building board in question with a specific optical finish.

A printed plasterboard for use in interior finishing is described in the prior art according to EP 2 423 403 A2. A multi-coloured print is applied by means of a multi-coloured ink on the visible side of the plasterboard. Moreover, the known plasterboards are provided with an edge region which can comprise a bevel. The multi-coloured print carried out at this point with the aid of UV ink, which is subsequently cured with UV light, is costly and time-consuming.

For this reason, roller application processes are often used in practice, i.e. procedures with the aid of which paint is applied on building boards by rollers. Use can be made here for example of devices such as are described in DE 299 15 401 U1. The known device is primarily used for flat workpieces, which have an offset at their underside and in particular at transversely running edges. It typically concerns items of furniture here.

If building boards, especially for interior finishing or for producing dry walls, are to be provided for example with the paint coat, the problem arises with the previous procedures that, when paint is applied for example with a device according to DE 299 15 401 U1, the edge regions and the bevels provided there are not reached by the paint. This necessitates upstream or downstream processing steps. As an alternative to this, work is also carried out in practice with adhesive edge strips. This is all relatively expensive, because additional production and processing steps are required. The invention aims to provide a general remedy here.

The technical problem underlying the invention is to develop such a method further in such a way that a coating of the building board on its visible side is also enabled in a quick, problem-free and cost-effective manner in the edge region with a bevel provided there.

To solve this technical problem, the subject-matter of the invention is a method for producing coated and in particular painted building boards, preferably for the interior finishing in buildings, with the following process steps:the respective building board is provided on its longitudinal edges and/or transverse edges with a bevel;the respective building board is transferred onto a rubber-like conveyor belt in such a way that the edges respectively provided with the bevels are arranged transversely in relation to the conveying direction of the conveyor belt and the bevels are arranged adjacent to a visible side of the building board and facing away from the conveyor belt;a coating material and in particular a paint is applied to the visible side of the building board and at the same time to the respective bevel areas of the bevels in one operation with the aid of at least one roller arranged above the conveyor belt and rotating essentially transversely in relation to the conveying direction.

The building board is advantageously a plasterboard, although other building boards are also covered by the invention, for example the variants described in the introduction. Such plasterboards are typically produced in such a way that the cardboard forming the visible side of the plasterboard is drawn off from a roll supply. The cardboard is then formed into a flat rectangular tank accommodating the gypsum slurry.

Any turned-up edges of the cardboard are pushed down to the free surface of the gypsum slurry in the so-called calibration of the plasterboard. Finally, a rear-side cardboard is applied. After the start of the setting process of the gypsum slurry, the board strand thus formed is cut to specific lengths and/or widths.

Modern production lines for plasterboards usually produce the building boards in question in such a way that the board strand has a width which corresponds to the length required for the processing of the plasterboards. As soon as the board strand is cut in the transverse direction, therefore, the desired building board is available with the correspondingly cut longitudinal edges. Due to the cut edge, there is no cardboard present at the longitudinal edges, so that an edge protection profile is usually applied here in practice. According to the invention, however, such an edge protection profile is dispensed with, but on the contrary the edges in question are tapered, i.e. receive a bevel.

Since the plasterboards in question are fixed edge to edge on a frame or framework, for example in the production of dry walls, step changes in the evenness and/or possibly material thickness from one plasterboard to the following plasterboard are observed in plan view in the abutting region in the absence of post-processing. This is visually disturbing and is not accepted by the market. For this reason, work is carried out in practice with, for example, rounded rebates on the longitudinal edges, in order to level out the abutting region with filler and to provide a smooth transition.

Within the scope of the invention, such an expensive post-processing step on the cut edges is not (no longer) required. This is because the cut edges in question—as already described—are tapered or provided with the already mentioned bevel. According to an advantageous embodiment, the building boards are in fact provided with the bevels at both their longitudinal edges, and more precisely observing in each case a bevel angle between 20° and 40°, preferably between 30° and 35°. The bevel angle generally denotes the angle of an associated bevel or bevel area at the edge in question that is enclosed with a horizontal or more precisely the visible side.

In addition, it has proved beneficial if the bevel is provided with a flat level area or at any rate a bevel area curved slightly outwards in a convex manner. Moreover, the rotating roller for applying the coating material or the paint on the building board is advantageously provided with a flexible surface and for example a rubber coating.

The possibility thus exists for the rotating roller in question on the one hand and the rubber-like conveyor belt on the other hand to have comparable elasticities. In this connection, the layout is usually selected such that the roller in question and the conveyor belt lie opposite one another, wherein the building board to be coated is passed through the gap between the roller and the conveyor belt. A counter-roller can also be provided beneath the conveyor belt in this region to support the conveyor belt.

In any case, the comparable elasticities of, on the one hand, the rotating roller for the application of the coating material and, on the other hand, of the rubber-like conveyor belt ensure that the building board passing as it were transversely through the gap with its bevels orientated transversely to the conveying direction is coated, and also can be coated in one operation, on the visible side and at the longitudinal edges. This takes place by means of the special roller application process. The respective flexibility between the roller or application roller on the one hand, i.e. its rubber coating, and the rubber-like conveyor belt on the other hand enables an all-over coating of the respective bevel areas of the longitudinal edges as well as of the visible side of the building board located in between, and in one operation.

The building board can thus be provided with the desired coating in a particularly cost-effective manner, said coating being for example a paint or paint application. It can in principle be any kind of paint, i.e. those which are cured by evaporation of solvents or also those which are irradiated with UV light for the curing.

The rubber coating of the rotating roller for the application of the paint and the rubber-like conveyor belt have—as already described—comparable elasticities. A respective modulus of elasticity in the range from 0.01 to 0.1·109N/m2has proved to be beneficial here. The conveyor belt on the one hand and the rotating roller for the application of the coating material on the other hand thus yield and can assume the shape both of the bevel area in the region of the bevel and also of the visible side between the two bevels, so that the all-over application of the coating material is successfully carried out in one operation.

The subject-matter of the invention is also a device, which is particularly suitable for producing coated building boards and is recommended for performing the described method. The device in question is provided with at least one planing unit for providing the respective building board with the bevel at its longitudinal edges and/or transverse edges. Furthermore, the device comprises the rubber-like conveyor belt and the roller disposed above the conveyor belt with the further specifications.

Finally, the subject-matter of the invention is a painted building board, which is provided in each case with a bevel at its longitudinal edges and/or transverse edges. The respective bevel area associated with the bevel and the visible side of the building board have a coating applied in one operation. Moreover, the building board is characterised in that a bevel area is disposed above a base area in the thickness direction. This means that the bevel area follows on from the base area in the direction of the visible side of the building board. Overall, the design is made in such a way that the bevel area has a thickness or material thickness which amounts to less than half the thickness or material thickness of the base area.

It is thus ensured that the elasticities of, on the one hand, the roller for the application of the coating material and, on the other hand, of the rubber-like conveyor belt are overall sufficient to be able reliably to accommodate between them and hold and convey the building board both in the visible region and also in the region of its two longitudinal edges with the bevels and at the same time to ensure the coating in the region of the bevel areas and the visible side located in between.

As a result, a method and an associated device for producing coated and in particular painted building boards are described, which enable a particularly cost-effective application of coating material on the building board in question. As a result of this, the coated building board also belonging to the protected subject-matter can be offered at a favourable cost. Nonetheless, the building board has a flawless decorative finish both on its visible side and also in the region of the bevel areas on the longitudinal edges. The building board according to the invention is thus suitable for direct processing in the production of dry walls.

In this connection, the individual building boards are in fact fixed to the frame with the longitudinal edges of edge to edge. As a result of the bevels in the abutting region, any unevennesses or step changes in plan view are practicably not (no longer) observed. Since, moreover, the respective bevel area together with the visible side has a uniform coating, a flawless all-over wall decoration can be made available, and more precisely without post-processing. The main advantages are to be seen in this.

A device for producing coated and in particular painted building boards1is represented in the figures. Building boards1in the present case are plasterboards1, which have been produced from a board strand. For this purpose, the board strand has been cut in the transverse direction to the representation of respective longitudinal edges2of building board1. No cardboard is consequently present in the region of longitudinal edges2on account of the cut edge there. Since building boards1are arranged edge to edge with their longitudinal edges2, for example in the production of a drywall, the abutting region has to be processed in order to provide a flawless transition.

For this purpose, the device is provided with at least one planing unit3. As can be seen from the representation according toFIG. 1, two planing units3lying opposite one another and assigned to respective longitudinal edge2are in fact provided, said planing units being designed and equipped for providing respective building board1with a bevel4at its longitudinal edges2.

Bevel4is as usual an inclined surface at the edge of a workpiece, in the present case at longitudinal edge2of building board or plasterboard1. With the aid of the two planing units3lying opposite one another, building board is thus tapered at its cut edges defining respective longitudinal edges2. Bevel area5running along the bevel and longitudinal edge2thus arises.

It can be seen that, within the context of the example of embodiment, and particularly preferably, bevel4is provided with a respective bevel angle α between approx. 20° and approx. 40°. Bevel angle α is designed equal at both longitudinal edges2. As usual, bevel angle α is enclosed between bevel area5and a horizontal.

In the example of embodiment, and as can be seen inFIG. 2, the horizontal is a visible side6or a plane of building board or plasterboard1parallel thereto. Bevel area5is constituted flat overall. In principle, bevel area5can however also have a shape curved (slightly) outwards in a convex manner in the represented cross-section according toFIG. 2, as is indicated by the dashed line inFIG. 2. According to a particularly preferred embodiment of the invention, bevel angle α is located between 30° and 35°.

After respective longitudinal edges2of building board or plasterboard1have been tapered as described with the aid of the at least one or the two planing units3, building board1is transferred onto a conveyor belt7or placed onto respective conveyor belt7. Respective building board1is in fact transferred onto rubber-like conveyor belt7in such a way that the edges each provided with bevels4and in particular longitudinal edges2are arranged, according to the example of embodiment, transversely in relation to conveying direction F of conveyor belt7. Moreover, the design is made such that building board1with its bevels4at visible side6or adjacent to visible side6of building board1are arranged facing away from conveyor belt7. In the example of embodiment, the two bevels4of building board1running adjacent to visible side6each point upwards. In contrast, rear side10of building board1lies on conveyor belt7.

It can be seen that conveyor belt7is tensioned by two deflection rollers8,9and is driven with the aid of deflection rollers8,9. As a result of this, building board or plasterboard1is transported in conveying direction F. At least one roller11, which is arranged above conveyor belt7, belongs to the further basic structure. In the example of embodiment, two rollers11,12are in fact provided, which in the present case are constituted as application roller11and metering roller12upstream thereof and have an arrangement above conveyor belt7. The two rollers11,12form an upper gusset-like space filled with paint13. A narrow gap between the two rollers11,12ensures that paint13passes in the desired quantity onto paint application roller11and from there onto building board1.

Roller or application roller11rotates just like metering roller12in each case about an axis orientated essentially transversely in relation to conveying direction F, as corresponding arrows inFIG. 1indicate. Moreover, the design is made in such a way that roller or application roller11and conveyor belt7together define between them a gap14, through which building board of plasterboard1is passed for the purpose of coating. In the example of embodiment represented, a counter-roller15is also provided opposite application roller11and beneath conveyor belt7, with the aid of which counter-roller conveyor belt7together with building board1conveyed through gap14is supported against the contact pressure on the part of the application roller11.

In the example of embodiment, with the aid of roller or application roller11arranged above conveyor belt7and rotating essentially transversely in relation to conveying direction F, paint13is applied in gap14not only on visible side6of building board1, but also on respective bevel areas5of bevels4at longitudinal edges2, and indeed in one operation. As a result of this, building board1thus provided with the respective coating has, after passing through gap14, a paint coat or generally the coating applied in one operation on respective bevel4or its bevel area5and visible side6.

In order to enable this in detail, rotating roller or application roller11for the application of paint13is provided with a flexible surface16indicated inFIG. 1. This flexible surface16is a rubber coating of roller or application roller11in question. Conveyor belt7, for its part, is constituted rubber-like. It has proved generally to be beneficial if rotating roller or application roller11on the one hand and conveyor belt7on the other hand have comparable elasticities. In the example of embodiment, the respective modulus of elasticity of rubber coating16as well as that of the material of conveyor belt7is located in the range from 0.01 to 0.01·109N/m2. This applies of course only by way of example and is in general not imperative.

It can be seen on the basis ofFIG. 2that building board1is provided in the thickness direction with a base area1aand a bevel area1barranged above base area1a. Base area1ahas a material thickness or thickness A. Bevel area1bis provided with a material thickness or thickness B.

The design is made overall in such a way that thickness B of bevel area1bis less than half compared to thickness A of base area1a. That is to say that the following applies:
B≤0.5 A.

Usually, even the relationship B≤0.4 is met.

It is thus ensured that bevel4of building board1extends only over a thickness region of building board1which amounts to 50% and less, in particular even 40% and less, of the thickness. The “step” associated with this can consequently be accommodated and compensated for without problem during the passage of building board1through gap14by, on the one hand, rubber coating16of roller or application roller11and, on the other hand, rubber-like conveyor belt7. As a consequence of this, building board1is coated in one operation with paint13during the passage through gap14with the aid of rotating roller or application roller11both on visible side6and also in the region of its respective bevel areas5of bevels4at respective longitudinal edges2. Any post-processing of bevel areas5is therefore not (no longer) necessary.

In addition, there is the fact that respectively tapered longitudinal edges2, when they are joined edge to edge to form a drywall for example, convey an optically uniform overall impression without any step changes or unevennesses. This is because the two bevels4or their bevel areas5accommodate visible side6located in between. Bevels4and visible side6have all been coated together and in one operation and have a coating of paint13applied in one operation. The main advantages are to be seen in this.