METHOD AND DEVICE FOR SPLITTING CHIPBOARD

This invention relates to a method for splitting chipboard so as to obtain two sections, each having the same area as the original board. The board is split in such a way that the surface texture of each section is determined by the manner in which the glued fibres are torn apart from one another. In addition, this invention relates to a device which allows this splitting to be effected in accordance with this method. The latest developments in design for interior and exterior cladding and panelling materials for houses and buildings show a clear tendency towards the choice of natural products such as stone or timber and wood. This has in turn affected the amount of selection and varieties available in surface texture and aspect. Clients are no longer satisfied with plain wood panelling or painted chipboard.

Many clients now want textured surfaces such as various forms of surface structuring. This is especially used on solid wood panelling. Another method is the use of decorative film glued onto chipboard. Various types of chipboard now seriously compete with solid wood panelling. One of the reasons for this is that chipboard does not shrink to the same extent when drying.

Another alternative to decorative film and painted surfaces is the mechanical imprint of patterns on the board surface to obtain a decorative effect. This method is described in

US-3.726.328 where a board or a solid wood panel can be given a rustic appearance by means of this mechanical imprint.

US-3.554.250 presents a method and a device for feeding a board or a piece of solid wood against a saw blade and thus divide the board into two parts, each part having a sloping surface.

Their cross-section is then a right-angled triangle. As the tool used is a saw blade which moves in one plane only, the cut surfaces will therefore be smooth.

The present method and device make it possible to split chipboard into two sections in such a way that the split surfaces will have an irregular texture. The splitting is effected more by tearing than by cutting. The surfaces separate according to the weaknesses in fibre bonds.

This is done by means of a wedge-shaped knife having an edge which is neither straight, nor has the same setting angle at the outer edge as further inwards. The knife does not move perpendicularly like an ordinary saw blade, but with a rotating motion in the plane of the knife's surface.

The splitting method and a performance example of the device used to put this method into practice are illustrated in figures 1 to 5.

Figure 1. Wedge-shaped knife which splits a piece of chipboard, and rollers which feed the board towards the knife.

Figure 2. This shows the design of the knife itself, its edge and how it is held between jaws.

Figure 3. The knife is driven into the edge of the board.

Figure 4. This figure shows the movement effected by the knife.

Figure 5. Jaws set in a tilted position.

Figure 1 shows how a set of rollers (3) feed a piece of chipboard (2) towards a wedge-shaped knife (1) so that the feeding speed remains even and the board can be directed at a correct angle against the knife (1). These rollers exert a constant pressure on the board (2), thus preventing the formation of cracks. The board (2) is split into two sections, not by a cutting action but by a wedging action. The surface texture of those two sections will depend on how the fibres, which are glued together, will tear away from one another to give a rough and uneven surface.

The knife (1) is sharpened with a constantly increasing angle towards the blade edge. This is meant to give a wedge effect. See figure 1.

The knife is undulated in both the horizontal and vertical planes. It is fixed between a set of jaws (4). These are connected to vibrators which impart a rotating motion to the knife(1) in its main plane. Figure 4 shows how this rotating motion is imparted to the knife (1) .

Figure 3 illustrates how the knife (1) positioned against the edge of the board (2) starts its splitting action as the wavy edge is directed into the board. When the knife (1) has reached so far into the board that its back edge also reaches between the two sections of the board, these are then wedged apart from one another.

If one tilts the jaws (4) at an angle to the main plane of the knife (l), the knife will then respond with an undulatory tension between the jaws (4). This increases the splitting effectiveness and reduces the risks of planing the split surfaces down.