The present invention relates to a method for decorating surfaces of PVC products. A number of furnishings of buildings and dwellings, in particular furnishings in the field of building carpentry, and components of such products are made of plastic. External texture of such elements is a characteristic surface resulting from the physical properties of the material from which it is made, and the manner of treatment or additives and impurities of the base material. That texture can be smooth, rough, wavy, not uniform, wrinkled. Often said texture is also described by comparison to other materials with generally recognizable and distinctive surface, such as velvet, leathery, canvas texture.

In the search for attractive design and an appropriate surface texture of products, consumers like to use wood products, which surface is antiqued by a rustic appearance. To achieve such of appearance a technological process of the surface of wood treatment called structuring is used, said treatment aim is to give aged (rustic) look to the wood by exposing the natural grain of the wood.

With respect to the wooden elements, the structuring is a known process. It involves using the appropriate brushes, usually wire-made, by means of which, abrasion of the soft parts of the wood occurs, at the same time revealing the harder ones. After performing of aging, the surface gives the impression of intensely used for years and achieves a specific rustic look of a spatial structure. The next step of said process is grinding, by using the appropriate brushes, for example brushing by a tynex head, the aim of which is to remove the torn fibers from the surface of the wood and smoothing the sharp edges of the pores caused by the action of the wire brush. The third step uses a head with replaceable abrasive brushes, which appropriately selected guarantee the final smoothing of the surface and its preparation for staining and varnishing. Shown above the process of wood structuring, as it is apparent from the name, is applied to the wood, that is, such a material, that has both hard and soft grain. Used in the process brushes, essentially brush-out only a soft layer of wood, and therefore in this case the process runs according to a predetermined objective. There are also known plastic products having wooden decoration on the surface obtained by veneering them with PVC films, with patterns that imitate the surface of the wood product.

Imitation of the grain of the wood, on the PVC films, which are glued to the products, is achieved through a method of printing or gentle embossing wood-grain pattern with printed color scheme on the surface of a film. For this reason, they are usually flat imitation or ones with a very little depth. The disadvantages of this solution are the high costs of implementation of this decoration and the high vulnerability to mechanical damage of the film, and difficult to repair damages.

Yet another known method for obtaining a structure imitating the wood grain on the surface of the PVC is technology called calendering. It involves stamping a pattern on the surface of the hot PVC profile, which exits the casting die, by profiled rollers. The disadvantage of this system is the ability to decorate only the full profiles - the ones without cavities inside.

The aim of the invention is to provide such a method for decorating PVC surfaces, in particular the chambered elements, where after conducting of said method, the surface of the element will have a high-quality appearance of the structured surface of the wood element.

A method according invention lies in that:

in a first step, using a machine equipped with a mechanical sliding table with adjustable feed speed, and a variable speed spindle whose axis is perpendicular to the direction of slide of the table and said spindle has ability to approach, with adjustable down force, to the workpiece, there is a pattern cut in the surface of an element in the form of elongated irregular lines imitating aged wood, using a wire brush roller, and in the next step, the surface with obtained pattern is treated in order to blunt sharp edges and to remove burrs.

The brush implemented for cutting the pattern is formed from steel or brass wires with a diameter of 0.2 to 0.5 mm and said brush has shape of a cylinder with an outer diameter dimension of 80 to 400 mm. This brush is mounted on the machine spindle in such a way that the axis of the cylinder is inclined to the spindle axis at an angle of 1 to 3 degrees. Through such brush mounting on the machine spindle, successive ends of the brush's wires, move sideways back and forth during rotation. In addition, the wires are pushed deeper or shallower against the work surface. The shape of the cut pattern, similar to that of a natural aged wood is obtained with combined rotational speed of the brush in the range of 100 to 800 rev/min and the table feed speed of 0.7 to 1.2 m/min.

The surface with obtained pattern is treated in order to blunt sharp edges and to remove burrs by brushing using tynex head. This operation can also be carried by hand or mechanical deburring using abrasives or by sandblasting.

The method according to the invention has a number of valuable advantages. Mainly that, the pattern imitating natural wood grain cut on the surface of the element, is the same as wood grain, unique at any part of the surface. Uniqueness is achieved by the fact, that the brush roller's ends of the wires, where said roller is mounted at an angle on a rotating spindle, carry out a swiveling sideways movement and at the same time ends of the wires travel more or less move towards the element's surface, and also the wires are subject to elastic flexure. The grain that is cut could be shallower or deeper, which depends on the extent of movement of the cylindrical brush towards the work surface. An important advantage is also that, the decorating according to the invention is less expensive than other processes, in particular the process of applying films simulating wood grain pattern on the PVC products. To illustrate the effect which is achieved by the method according to the invention, there is a fragment of the doorframe is a perspective view, with a visible partem on its side surfaces shown in drawing.

An embodiment of a method

In an exemplary embodiment, a pattern is made to an elongated element having spatial cross-section constituting the frame of the door. The surfaces of the frame profiles, which are to be patterned, are produced during the extrusion process as smooth. The element is fixed to a machine table, then in the first step there is aged wood pattern cut in the smooth, flat surface of said element with a wire brush roller mounted on a machine spindle. The roller brush formed of steel wire having a diameter of 0.4 mm, with said roller outer diameter of 120 mm was used. The roller brush was mounted on a spindle with an angle of inclination of 1.2 degrees with respect to the spindle axis. The following operating parameters of the machine were applied: the spindle speed with the attached brush - 200 rev/min, feed rate of the table with fixed to it element - 0.8 m/min. After the pattern is made, in the next step, the surface of the element is treated in order to blunt sharp edges and to remove burrs by brushing using tynex head. This is done on the same, or similar machine equipped with a table with a mechanical drive and on said machine's spindle there is mounted tynex head or cylindrical brush made of sanding fleece. Operating parameters, during performing this step, are set according to recommendations for a particular head. In the final stage, the surface is degreased and coated with lacquer using patina. In an alternative embodiment, the surface with obtained pattern is treated in order to blunt sharp edges and to remove burrs by sandblasting or manual deburring using sanding fleece with suitable granulation.