This invention relates to the continuous manufacture of board according to the dry method, using as starting material lignocellulosic material such as wood, straw, bagasse and the like. The invention, more precisely, relates to a device for compressing and processing a mat of lignocellulosic material at the manufacture of board .

Manufacture of this type of board comprises the steps of disintegrating the raw material to particles and/or fibers of a suitable size, drying them to a definite moisture quotient, glueing the material prior or subsequent to the drying, forming the glued material to a mat, and compressing and hot pressing the mat to a complete board.

The continuous compressing and pressing of the material mats to board can be affected positively by injecting a suitable processing medium in the form of gas or liquid, whereby also the properties of the complete board can be improved. An example of such process¬ ing medium is vapour, which heats and moistens the fibers in the material and thereby facilitates the pressing operation and/or accelerates the hardening process. Other possibilities are the injection of a hardening agent or accelerating agent to the already pre- glued mat.

For the injection of vapour or another gas into the material mats, normally an injection box is used, against which the mat or a wire support of the mat slides. The box is provided with a large number of injection holes or slots and an edge sealing to the mat/wire. The box can be formed, for example, as a tube package or in some other way. All strongly varying configurations of the box have in common that they must be constructed ^or the mat/wire to slide against the box.

In certain cases an injection box is located on one side of the mat, and a suction box on the opposite side, directly in front or offset. The injection and suction boxes usually are given similar shape.

The sliding between the mat/wire and the injection and, respectively, suction boxes gives rise to considerable wear, which implies that at least the slide surfaces must be exchanged. Furthermore, the sliding between the mat/wire and the boxes often causes problems with the edge sealing.

The afore-said problems are eliminated by the present invention, according to which the processing medium is added via a compression roll whereby sliding is avoided. The characterizing features of the invention are apparent from the attached claims.

The invention is described in greater detail in the following, with reference to the ac¬ companying drawings illustrating examples of different embodiments of the invention.

Fig. 1 shows the principle of the configuration of the device;

Figs. 2-5 show in a schematic way different arrangements for applying the invention;

Fig. 6 shows a detail of the end wall of the compression roll;

Fig. 7 is a cross-section of a configuration for the supply of processing medium.

At the compression and processing of a material mat 1 at the manufacture of board, the compression is carried out with a compression roll 2 (Fig. 1). This roll suitably can operate in pair with a counter-roll 3, whereby the compression takes place symmetrically from both sides of the mat 1 (Figs. 2-5). The processing medium can be injected through the rolls 2,3 symmetrically from both sides (Figs. 2-3). This implies uniform processing of the mat as well as optimum air removal from the mat to the inlet. Alternatively, a roll 2 can be formed for injection, while the counter-roll 3 consists only of a supporting roll (Fig. 4) or a suction roll (Fig. 5). According to Figs. 2, 4 and 5, wires 4 with rolls 5 are used as support for the mat 1 , while Fig. 3 shows an embodiment without wire.

The compression and injection roll 2 shown in Fig. 6 has a perforated shell surface 6 for the supply of processing medium to the mat 1. About the roll 2 inside of the shell surface 6 an axial duct system 7 is arranged for the distribution of the processing medium across the width of the roll 2 and thereby of the mat 1. An adjustable slide shoe 8 (Fig. 7) sealingly abuts the end wall of the roll 2 for the supply of processing medium to the duct system 7. The supply takes place to a restricted sector 9 of the roll 2 where the mat 1 is compressed. This restricted sector 9 is enclosed on both sides, counted in the circumferential direction, by sealing zones 10 where the roll 2 is in contact with the mat

1. The duct system 7 can be closed at the opposite end wall of the roll 2. Alternatively, a slide shoe 8 can be provided at each end wall.

The slide shoe 8 is held in place by means of an adjustable stand, so that the slide shoe can be moved in the circumferential direction. It is thereby possible to vary the position of the injection sector 9. The slide shoe 8 preferably is formed with an exchangeable wear portion 14 of a low-friction material, which abuts a worked surface on the end wall of roll

2. The slide shoe 8 is held pressed against the end wall of the roll, for example by means of springs, compressed air or hydraulically, so that leakage in the sealing surface is minimized.

The slide shoe can be formed with one or several channels 11, 12, 13 which can have different areas. Exchangeable wear portions 14 with different hole area can also be used, for example a slide plate with variable hole opening. It is hereby possible to vary the size of the injection sector 9. In different parts of the injection sector 9 different flows and pressures can be maintained. The channels of the slide shoe 8 can also be used for blow cleaning and suction.

In Fig. 6 the contact surface of the slide shoe 8 against the end wall of the roll 2 is shown schematically. The slide shoe 8 is provided with injection channels 11 for processing medium, blow cleaning channel 12 and suction channel 13. The processing medium can be, for example, low-pressure steam in the first injection channel 11 , seen in the feed direction, and high-pressure steam in the second injection channel 11.

The perforated shell surface 6 on the roll 2 can consist of a punched or drilled hollow metal sheet, which in the form of rings is firmly shrunk on the roll. Axial support strips 15 for the hollow metal sheet can be formed in a shell metal sheet 16 on the roll by milling or casting, or they consist of separate strips attached in recesses in the shell metal sheet 16. These strips 15 can simultaneously define the duct system 7 inside of the shell surface 6.

The transverse distribution of the processing medium to the mat can be varied as desired in that the form of the ducts in the duct system 7 is varied axially, for example with an area reduced in transverse direction.

The openings in the duct system 7 which in the end wall of the roll 2 are not covered by the slide shoe 8, can be sealed by means of an adjustable slide ring of a low-friction material which is held pressed against the end wall.

In order to prevent condensation in the duct system 7, the roll 2 can be heated. This can be brought about preferably by grooves 17 extending all about, preferably arranged helically in the roll 2 inside of the duct system 7. These grooves can be arranged in a heat groove metal sheet 18 inside of the shell metal sheet 16. In these grooves 17, steam, oil or hot water is circulated so that uniform heat is supplied to the shell metal sheet 16.

The invention, of course, is not restricted to the embodiments shown, but can be varied within the scope of the invention idea.