In the pulp and paper industry, logs are debarked before chipping. In part of logs to be used as raw material, the bark is adheres very tightly to the logs or the bark is easily loos- ened as larger pieces so that the normal drum debarking is not fast enough or the discharg- ing of the bark creates a problem. Especially many tropical wood species, such as acacia and eucalyptus, are problematic for the drum debarking method, as the long barks create prob- lems by forming"bark balls"in the drum. The bark of acacia and eucalyptus, in addition, tends to loosen as long strips, so that also the fresh bark requires pretreatment, in order to avoid problems after the drum. The long waste barks are not easily discharged through the bark slots of the drum and tend to come out along with the logs to the feeding conveyor of the chipper. In some cases, the drum debarking has proven to be inefficient also for the de- barking of birch.

Also other types of methods than drum debarking are used for debarking logs. A disad- vantage of those methods is, however, the small capacity that requires several debarking lines and a great number of devices. One known method of this kind is described in patent publication US 4 685 498 of Fuji Kogyo. There the logs are transported through a channel- formed section in longitudinal direction. On the bottom of the trough-formed section, there are rollers in longitudinal direction. When the rollers rotate, their teeth rasp the bark from the surface of the log.

In addition, debarking devices equipped with moving bottom elements have been tested. It has been shown in tests that a debarking apparatus in accordance with patent FI 29866 does not rotate the logs efficiently enough, because the push force of the feed motion of the moving elements transferring the logs is not sufficiently stronger than the correspond- ing force of the reverse motion.

Also periodically operating pretreatment devices are being developed, the biggest dis- advantage thereof being the constant need of supervision.

One method is to break the surface of the bark with a high-pressure water jet. In such a procedure also some further method is required to finally remove the bark. A known pre- treatment method of logs of this type has been described in patent publication US 4 180 109. In order to achieve the required pressure of the water, a strong pump is needed in this method. In addition, there are high requirements for the purity of the water.

The method in accordance with the present invention is characterized in that the debarking blades and the logs are moved in relation to each other, so that part of the time the logs are above the cutting edges of the blades, out of contact with the blades, and part of the time the logs are in contact with the cutting edges of the blades. The blades can be moved and the logs rotated in the transversal direction of the logs back and forth by means of members carrying logs periodically or by means of a stepped bottom. The appara- tus in accordance with the present invention is characterized in that in the bottom there is one or several members carrying the logs, said members being from time to time or all the time higher up than the cutting edges of the blades. The blades are attached to the bottom of the apparatus, said bottom moving back and forth the a transversal direction of the appa- ratus, and carrying and pushing the logs periodically, or to members that form portions of said bottom.

As the logs are part of the time higher up than the blades and out of contact with the blades, they are, during that time, able to move forward in the apparatus without bumping against the blades.

The new apparatus in accordance with the invention is continuously working and op- erates with a high capacity as a pretreatment device of logs to be debarked, and with a low capacity the apparatus can be used for debarking logs. The most important advantages of the apparatus are the efficient operation of the pretreatment or the debarking members and the controllability of the handling process.

In the method in accordance with the invention, the logs to be pretreated move along with the bottom inclined in longitudinal direction towards the moving direction, effected by the back and forth motion of the pretreatment member or the pretreatment members.

In the apparatus in accordance with the invention, the pretreatment device comprises an inclined trough-formed frame and a trough-formed bottom moving back and forth in the transversal direction or pretreatment members moving back and forth in the transversal di- rection.

The drawings from 1 to 7 illustrate the present invention and its embodiments in a de- barking line.

Figure 1 is a side view of a line of debarking equipment, in which the logs are debarked by means of an apparatus 1 in accordance with the invention.

Figure 2 is a side view of an alternative line of debarking equipment, in which logs are pretreated for debarking by means of the apparatus 1 in accordance with the invention.

Figure 3 shows one alternative construction of the apparatus in accordance with the present invention, viewed from one end.

Figure 4 shows an enlarged view of a transfer member of logs.

Figure 5 shows a top view of an apparatus in accordance with the invention, equipped with an integral bottom.

Figure 6 shows section A-A of figure 4, in a larger scale.

Figure 7 shows an enlarged view of a detail of the apparatus.

Figure 8 shows an enlarged view of section B-B of figure 4.

Figure 9 shows a top view of the drive mechanism of the apparatus of figure 4.

Figure 1 shows a debarking line having a low capacity, in which log bundles 5 are loaded into a debarking apparatus 1 in accordance with the invention and transferred by means of debarking members and a longitudinal inclination a of the apparatus 1 towards a roller conveyor 2. The log bundles 5 break up during the debarking and the logs drop one by one or in small groups onto the roller conveyor 2 which feeds the logs 6 to a chipper 3 rotated by a motor 4.

Figure 2 shows a debarking line having a high capacity, by which the debarking is ef- fected after the pretreatment in a drum 8, into which the logs are fed by means of a con- veyor 7. When handling logs that are difficult to debark, such as acacia or eucalyptus, the bark has to be cut into lengths, in order to be discharged through the bark slots of the de- barking drum 8.

The bark is cut by means of a pretreatment apparatus 1, onto which the log bundles 5 are loaded by means of a crane or a log truck. The pretreatment apparatus 1 is equipped with debarking members that cut the bark into certain lengths due to the rotating of the logs and the sliding motion resulting from the inclination a of the apparatus 1. The direction of the cutting movement of the blades is parallel to the direction of the cutting edge of the blades.

Figure 3 describes the construction of an apparatus 1 in accordance with the invention, whereby the log bundle to be handled"lives"or rotates efficiently. The apparatus comprises stationary sides 11 and 12 and between them a set of bottom beams 13. Between the bot- tom beams 13 there are arranged movable handling beams 14, into which members 15 for

transferring logs are attached, said members also cutting the bark surface of the logs. The handling beams are supported at their one end by means of rocking arms 16. The supporting of the other end is arranged by a crankshaft 20 described schematically in the figure, said crankshaft rotating the handling beams 14 through a link 19, so that the handling beams carry the logs and transfer them by means of the transfer members, in other words, teeth 15 "uphill"and the beams 14 make their reverse motion below the bottom beams 13, so that the beams 14 and the teeth 15 do not draw the logs backwards. Both the bottom beams and the handling beams have been supported so that their one end equipped with the crankshaft 20 is higher than the other end. Thus, the bottom is inclined sideways. Due to the inclina- tion, the logs on the surface roll towards the other, lower side. The teeth 15 of the handling beams 14 are formed so that when the beams move towards the higher side 12 of the bot- tom, the front edges 48 of the teeth transfer the logs to be handled towards that side (figures 3 and 4). The reverse motion of the teeth is arranged along a lower path so that their less indined, sharp-edged, cutting rear side 49 does not meet the logs until closer to the lower side 11. The motion of the beams 14 is controlled by the positions of the joint pins 17 and 18 and the operation radius R of the link 19 of the crankshaft 20. The motions of the apparatus and the log bundle 5 are indicated by arrows in figure 3.

Figures from 5 to 9 show an other constructional solution in accordance with the pres- ent invention. The apparatus comprises a trough-formed frame 21 and an integral plate bottom 22 moving back and forth and formed as part of a cylinder and provided with a stepped elevation 27. Figure 6 shows how efficient motion of the logs can be accomplished by means of the stepped bottom. The bottom 22 is carried by supporting rollers 23 attached to the frame 21 (figures 6 and 7). The cross section of the bottom 22 has the form of a cir- cular arc or nearly that. The back and forth motion of the bottom 22 indicated by arrow N1 occurs around the center 24 of the part of the cylinder. The bottom is divided into two parallel portions by a stationary longitudinal center bracket 25 supported to the frame 21 at the ends of the apparatus, thus not being in contact with the bottom 22.

The logs are divided into two separate piles by the center bracket 25 and the handling of the logs is effected on both side portions of the bottom. When the bottom moves to the other side 26 of the apparatus, the longitudinal stepped elevation 27 moving along with the bottom under the center bracket and arranged into the middle portion of the bottom, pushes the logs 28, situated longitudinaliy on the bottom of the trough upwards along the side and

the uppermost logs of the log pile roll, due to the cylindrical form of the bottom, towards the center bracket 25 as shown by the arrow N3. When the stepped elevation 27 moves un- der the center bracket, the logs on the other side of the center bracket fall onto the bottom 27 or on top of"pushers"30. When the bottom moves to the opposite direction, towards the other side 29, the logs on the bottom of the trough tend to return along with the bottom towards the center bracket. The return is prevented by stationary"pushers"30 and by the center bracket 25 (figure 7). The"pushers"are transversal stoppers arranged at certain longitudinal distances of the device from each other, projecting from below the center bracket to the two sides of the bracket. The"pushers"are lower than the elevation 27 of the bottom, and right by them, on both sides of the elevation, there are openings 31, through which the stationary"pushers"come out from under the elevation when the elevation is moving back and forth along with the bottom.

Attached to the bottom 22, there are, at certain longitudinal distances of the device from each other, transversal blades 32 (figure 6) for cutting the bark of the logs, and those blades, when moving back and forth with the bottom, cut the bark into lengths, as the "pushers"30 and the center bracket 25 prevent the return motion of the log when the bot- tom 22 slides under the log pile to be handled. Due to the rolling of the log pile, all the logs are at some stage in contact with the blades 32. Effected by the back and forth motion of the bottom and the cutting motion of the blades, the logs also roll around their own axis, so that the bark will be cut all over the log. Because of the living of the log pile and the incli- nation a of the pretreatment apparatus, the direction of the forward motion of the logs fol- lows the arrow N2 (figure 8). As the apparatus of figures 4-8 can be constructed with an almost solid plate bottom, it has a considrable advantage in, that there is no need of any collecting means for loose bark and rubbish under the apparatus.

The back and'forth motion of the bottom 22 is effected by the crank 34 of the crank- shaft 33 and an articulated rod 35. The motion of the crank 34 is shown by arrow N5. The crankshaft 33 is connected to a gearing 37 (figure 9) through a coupling device 36. The gearing is driven by an electric motor 38. One end of the articulated rod 35 is connected with a bearing to the bottom 22 through a link 39. The bottom is also connected through links 39 and 39'to cranks 41 of a synchronizing shaft 40. The synchronizing shaft 40 pre- vents the bottom from twisting, so that both ends of the bottom remain synchronous. The synchronizing shaft 40, effected by the motion of the bottom 22, also moves vertically along

a low gradient curve, supported by cranks 41,41'and supports 44,45 (arrow N4),. The supports 44,45 prevent the synchronizing shaft 40 from moving in the direction of the hori- zontal radius of the shaft 40. The supports 44,45 are supported with bearings at their one end to the synchronizing shaft 40 and at their other end to the frame 21 of the apparatus through links 46,47.

Naturally, instead of the gearing 37 and the electric motor 38, also a hydraulic motor can be used.

In this connection, a sideways inclination means an inclination around the longitudinal axis of the apparatus and the longitudinal inclination means an inclination around the trans- versal axis of the apparatus.