This invention relates to a refiner segment for a disc refiner to disintegrate lignocellulose-containing fiber material.

The disc refiner comprises two opposed refining discs, one or both of which can be rotated. A plurality of refiner segments arranged on the discs are formed with a pattern of bars and intermediate grooves. The refining discs are so arranged that the refiner segments form a refining gap, through which the fiber material is passed whereby it is disintegrated by the bars on the segments.

The bars and grooves of the segments normally extend substantially radially, but can also be arranged more or less oblique in relat¬ ion to the radius. The pattern can be divided into zones located outside each other and having different types of bars.

It was found advantageous, especially at disintegration of fiber material with high concentration, to place flow restrict¬ ions, so-called dams, across the grooves in the refiner segments in order to prevent untreated material from passing out through the refining gap. The dams force the material upward out of the grooves, so that it is subjected to treatment between the bars on the refiner segments on the opposite refining discs.

In plants where the fiber raw material contains great amounts of sand and other impurities, the bars on the refiner segments are worn out prematurely. This applies especially to plants for the manufacture of fiberboard.

When the refiner segments are provided with dams, the wear con¬ centrates on the bars about these dams. It was also found, that the dams are not worn to the same degree as the bars about them. The dams thereby will project up above the bars on the refiner

segment, which implies that they get into contact with and wear down the bars on the refiner segments on the opposed re¬ fining disc. The refiner segments are thereby subjected to much stronger wear, which results in an unacceptably short service life of the refiner segments.

In order to overcome these problems, it has been necessary in certain cases to install expensive equipment, which removes the sand before the disc refiner to the greatest possible extent.

Alternatively, refiner segments without dams had to be used. In such cases some other steps have to be taken about the reduced quality of the finely-distributed material, for ex¬ ample refining in several steps.

The present invention offers a solution for the aforesaid problems, without giving rise to other drawbacks. According to the invention, the dams are so arranged in the grooves that their angle in relation to the radius of the refiner segment is smaller than 30°, preferably smaller than 15°.

Due to this arrangement of the dams, the wear will be more uniform, and the service life of the refiner segment increases.

The invention is described in greater detail in the following, with reference to the accompanying Figure showing an embodim¬ ent of the invention.

The refiner segment 1 is formed with a pattern of bars 2 and grooves 3, which are arranged obliquely in relation to the radius of the refiner segment. In certain places in the grooves dams 4 are provided and arranged substantially radially.

The deviation of the dams from the radius should be less than 15°_ but depending on the configuration of the pattern of the

refiner segment also slightly greater deviations can be imagined.

Suitable dimensions of the pattern of the refiner segment can be a bar width of 1-4 mm, a groove width of 2-12 mm and a bar height of 4-15 mm. The dams should extend upward to the level of the bar tops.

The invention is not restricted to the embodiment shown and de¬ scribed, but can be varied within the scope of the invention idea.